VUV photoionization cross sections of HO2, H2O2, and H2CO.

PubMed

Dodson, Leah G; Shen, Linhan; Savee, John D; Eddingsaas, Nathan C; Welz, Oliver; Taatjes, Craig A; Osborn, David L; Sander, Stanley P; Okumura, Mitchio

2015-02-26

The absolute vacuum ultraviolet (VUV) photoionization spectra of the hydroperoxyl radical (HO2), hydrogen peroxide (H2O2), and formaldehyde (H2CO) have been measured from their first ionization thresholds to 12.008 eV. HO2, H2O2, and H2CO were generated from the oxidation of methanol initiated by pulsed-laser-photolysis of Cl2 in a low-pressure slow flow reactor. Reactants, intermediates, and products were detected by time-resolved multiplexed synchrotron photoionization mass spectrometry. Absolute concentrations were obtained from the time-dependent photoion signals by modeling the kinetics of the methanol oxidation chemistry. Photoionization cross sections were determined at several photon energies relative to the cross section of methanol, which was in turn determined relative to that of propene. These measurements were used to place relative photoionization spectra of HO2, H2O2, and H2CO on an absolute scale, resulting in absolute photoionization spectra.

High-Resolution Photoionization, Photoelectron and Photodissociation Studies. Determination of Accurate Energetic and Spectroscopic Database for Combustion Radicals and Molecules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ng, Cheuk-Yiu

2016-04-25

The main goal of this research program was to obtain accurate thermochemical and spectroscopic data, such as ionization energies (IEs), 0 K bond dissociation energies, 0 K heats of formation, and spectroscopic constants for radicals and molecules and their ions of relevance to combustion chemistry. Two unique, generally applicable vacuum ultraviolet (VUV) laser photoion-photoelectron apparatuses have been developed in our group, which have used for high-resolution photoionization, photoelectron, and photodissociation studies for many small molecules of combustion relevance.

VUV-Photoionization CES-Detector of Volatile Bio-Marker Molecules

NASA Astrophysics Data System (ADS)

Mustafaev, Alexander; Luneva, Nataliya; Panasyuk, George; Timofeev, Nikolay; Tsyganov, Alexander

2014-10-01

Energy spectra of characteristic electrons released via photoionization by vacuum ultraviolet (VUV) radiation of admixture molecules in the atmospheric air, not using traditional evacuated energy analyzers, can be determined by Collisional Electron Spectroscopy (CES) method. Some details of CES-photoionization sensor were described in. Our further developments are devoted to application of CES-detectors for a mobile continuous bio-chemical diagnostics. It is known that ``on breathing'' it is possible to find out volatile bio-marker molecules of a lot of diseases (lung cancer, tuberculosis, COPD, asthma, diabetes, kidney disease, mammary cancer, Crohn's disease, ulcerative colitis, etc). But today's weighty and expensive laboratory equipment (like GC MS) provides observation of these bio-markers only during patients' visits to a doctor. In this way we study pocket-size CES-sensor with micro-plasma krypton resonance radiation source (10.6 eV photons) for the photoionization detection of metabolic ammonia, ethanol, acetone and pentane molecules directly in atmospheric air.

Tabletop Femtosecond VUV Photoionization and PEPICO Detection of Microreactor Pyrolysis Products.

PubMed

Couch, David E; Buckingham, Grant T; Baraban, Joshua H; Porterfield, Jessica P; Wooldridge, Laura A; Ellison, G Barney; Kapteyn, Henry C; Murnane, Margaret M; Peters, William K

2017-07-20

We report the combination of tabletop vacuum ultraviolet photoionization with photoion-photoelectron coincidence spectroscopy for sensitive, isomer-specific detection of nascent products from a pyrolysis microreactor. Results on several molecules demonstrate two essential capabilities that are very straightforward to implement: the ability to differentiate isomers and the ability to distinguish thermal products from dissociative ionization. Here, vacuum ultraviolet light is derived from a commercial tabletop femtosecond laser system, allowing data to be collected at 10 kHz; this high repetition rate is critical for coincidence techniques. The photoion-photoelectron coincidence spectrometer uses the momentum of the ion to identify dissociative ionization events and coincidence techniques to provide a photoelectron spectrum specific to each mass, which is used to distinguish different isomers. We have used this spectrometer to detect the pyrolysis products that result from the thermal cracking of acetaldehyde, cyclohexene, and 2-butanol. The photoion-photoelectron spectrometer can detect and identify organic radicals and reactive intermediates that result from pyrolysis. Direct comparison of laboratory and synchrotron data illustrates the advantages and potential of this approach.

Absolute photoionization cross section of the ethyl radical in the range 8-11.5 eV: synchrotron and vacuum ultraviolet laser measurements.

PubMed

Gans, Bérenger; Garcia, Gustavo A; Boyé-Péronne, Séverine; Loison, Jean-Christophe; Douin, Stéphane; Gaie-Levrel, François; Gauyacq, Dolores

2011-06-02

The absolute photoionization cross section of C(2)H(5) has been measured at 10.54 eV using vacuum ultraviolet (VUV) laser photoionization. The C(2)H(5) radical was produced in situ using the rapid C(2)H(6) + F → C(2)H(5) + HF reaction. Its absolute photoionization cross section has been determined in two different ways: first using the C(2)H(5) + NO(2) → C(2)H(5)O + NO reaction in a fast flow reactor, and the known absolute photoionization cross section of NO. In a second experiment, it has been measured relative to the known absolute photoionization cross section of CH(3) as a reference by using the CH(4) + F → CH(3) + HF and C(2)H(6) + F → C(2)H(5) + HF reactions successively. Both methods gave similar results, the second one being more precise and yielding the value: σ(C(2)H(5))(ion) = (5.6 ± 1.4) Mb at 10.54 eV. This value is used to calibrate on an absolute scale the photoionization curve of C(2)H(5) produced in a pyrolytic source from the C(2)H(5)NO(2) precursor, and ionized by the VUV beam of the DESIRS beamline at SOLEIL synchrotron facility. In this latter experiment, a recently developed ion imaging technique is used to discriminate the direct photoionization process from dissociative ionization contributions to the C(2)H(5)(+) signal. The imaging technique applied on the photoelectron signal also allows a slow photoelectron spectrum with a 40 meV resolution to be extracted, indicating that photoionization around the adiabatic ionization threshold involves a complex vibrational overlap between the neutral and cationic ground states, as was previously observed in the literature. Comparison with earlier photoionization studies, in particular with the photoionization yield recorded by Ruscic et al. is also discussed. © 2011 American Chemical Society

A smog chamber study coupling a photoionization aerosol electron/ion spectrometer to VUV synchrotron radiation: organic and inorganic-organic mixed aerosol analysis

NASA Astrophysics Data System (ADS)

Baeza-Romero, María Teresa; Gaie-Levrel, Francois; Mahjoub, Ahmed; López-Arza, Vicente; Garcia, Gustavo A.; Nahon, Laurent

2016-07-01

A reaction chamber was coupled to a photoionization aerosol time-of-flight mass spectrometer based on an electron/ion coincidence scheme and applied for on-line analysis of organic and inorganic-organic mixed aerosols using synchrotron tunable vacuum ultraviolet (VUV) photons as the ionization source. In this proof of principle study, both aerosol and gas phase were detected simultaneously but could be differentiated. Present results and perspectives for improvement for this set-up are shown in the study of ozonolysis ([O3] = 0.13-3 ppm) of α-pinene (2-3 ppm), and the uptake of glyoxal upon ammonium sulphate. In this work the ozone concentration was monitored in real time, together with the particle size distributions and chemical composition, the latter taking advantage of the coincidence spectrometer and the tuneability of the synchrotron radiation as a soft VUV ionization source.

Online characterization of isomeric/isobaric components in the gas phase of mainstream cigarette smoke by tunable synchrotron radiation vacuum ultraviolet photoionization time-of-flight mass spectrometry and photoionization efficiency curve simulation.

PubMed

Pan, Yang; Hu, Yonghua; Wang, Jian; Ye, Lili; Liu, Chengyuan; Zhu, Zhixiang

2013-12-17

A newly developed, qualitative and quantitative method based on tunable synchrotron radiation vacuum ultraviolet photoionization time-of-flight mass spectrometry (SR-VUV-PI-TOFMS) and photoionization efficiency (PIE) curve simulation was applied for the online analysis of isomers and isobaric compounds in the gas phase of mainstream cigarette smoke. After blocking the particulate phase components by the Cambridge filter pad, a puff of fresh gas-phase cigarette smoke was immediately introduced into a vacuum ionization chamber through a heated capillary, then was photoionized, and analyzed by a TOF mass spectrometer. The PIE curves for the mass peaks up to m/z = 106 were measured between 8.0 and 10.7 eV. Some components could be directly identified by their discriminated ionization energies (IEs) on the PIE curve. By simulating the PIE curve with the sum of scaled absolute photoionization cross sections (PICSs), complex isomeric/isobaric compounds along with their mole fractions could be obtained when the best-fitting was realized between experimental and simulated PIE curves. A series of reported toxic compounds for quantification, such as 1,3-butadiene (m/z = 54), 1,3-cyclopentadiene (m/z = 66), benzene (m/z = 78), xylene (m/z = 106), 2-propenal (m/z = 56), acetone and propanal (m/z = 58), crotonaldehyde (m/z = 70), furan and isoprene (m/z = 68), were all found to have other isomers and/or isobaric compounds with considerable abundances. Some isomers have never been reported previously in cigarette smoke, like C5H6 isomers 1-penten-3-yne, 3-penten-1-yne, and 1-penten-4-yne at m/z = 66. Isomeric/isobaric compounds characterization for the mass peaks and mole fraction calculations were discussed in detail below 10.7 eV, an energy value covering several conventional used VUV light sources.

VUV photoionization and dissociative photoionization of the prebiotic molecule acetyl cyanide: Theory and experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bellili, A.; Hochlaf, M., E-mail: hochlaf@univ-mlv.fr, E-mail: martin.schwell@lisa.u-pec.fr; Schwell, M., E-mail: hochlaf@univ-mlv.fr, E-mail: martin.schwell@lisa.u-pec.fr

2014-10-07

The present combined theoretical and experimental investigation concerns the single photoionization of gas-phase acetyl cyanide and the fragmentation pathways of the resulting cation. Acetyl cyanide (AC) is inspired from both the chemistry of cyanoacetylene and the Strecker reaction which are thought to be at the origin of medium sized prebiotic molecules in the interstellar medium. AC can be formed by reaction from cyanoacetylene and water but also from acetaldehyde and HCN or the corresponding radicals. In view of the interpretation of vacuum ultraviolet (VUV) experimental data obtained using synchrotron radiation, we explored the ground potential energy surface (PES) of acetylmore » cyanide and of its cation using standard and recently implemented explicitly correlated methodologies. Our PES covers the regions of tautomerism (between keto and enol forms) and of the lowest fragmentation channels. This allowed us to deduce accurate thermochemical data for this astrobiologically relevant molecule. Unimolecular decomposition of the AC cation turns out to be very complex. The implications for the evolution of prebiotic molecules under VUV irradiation are discussed.« less

Real-time detection of S(1D2) photofragments produced from the 1B2(1Σu+) state of CS2 by vacuum ultraviolet photoelectron imaging using 133 nm probe pulses

NASA Astrophysics Data System (ADS)

Horio, Takuya; Spesyvtsev, Roman; Furumido, Yu; Suzuki, Toshinori

2017-07-01

Ultrafast photodissociation dynamics from the 1B2(1Σu+) state of CS2 are studied by time-resolved photoelectron imaging using the fourth (4ω, 198 nm) and sixth (6ω, 133 nm) harmonics of a femtosecond Ti:sapphire laser. The 1B2 state of CS2 was prepared with the 4ω pulses, and subsequent dynamics were probed using the 6ω vacuum ultraviolet (VUV) pulses. The VUV pulses enabled real-time detection of S(1D2) photofragments, produced via CS2*(1B2(1Σu+)) → CS(X 1Σ+) + S(1D2). The photoionization signal of dissociating CS2*(1B2(1Σu+)) molecules starts to decrease at about 100 fs, while the S(1D2) fragments appear with a finite (ca. 400 fs) delay time after the pump pulse. Also discussed is the configuration interaction of the 1B2(1Σu+) state based on relative photoionization cross-sections to different cationic states.

Laser Desorption 7.87 eV Postionization Mass Spectrometry of Antibiotics in Staphylococcus epidermidis Bacterial Biofilms

PubMed Central

Gasper, Gerald L.; Carlson, Ross; Akhmetov, Artem; Moore, Jerry F.; Hanley, Luke

2010-01-01

This paper describes the development of laser desorption 7.87 eV vacuum ultraviolet postionization mass spectrometry (LDPI-MS) to detect antibiotics within intact bacterial colony biofilms. As >99% of the molecules ejected by laser desorption are neutrals, vacuum ultraviolet (VUV) photoionization of these neutrals can provide significantly increased signal compared to detection of directly emitted ions. Postionization with VUV radiation from the molecular fluorine laser single photon ionizes laser desorbed neutrals with ionization potentials below the 7.87 eV photon energy. Antibiotics with structures indicative of sub-7.87 eV ionization potentials were examined for their ability to be detected by 7.87 eV LDPI-MS. Tetracycline, sulfadiazine, and novobiocin were successfully detected neat as dried films physisorbed on porous silicon oxide substrates. Tetracycline and sulfadiazine were then detected within intact Staphylococcus epidermidis colony biofilms, the former with LOD in the micromolar concentration range. PMID:18704905

Absolute photoionization cross sections of two cyclic ketones: cyclopentanone and cyclohexanone.

PubMed

Price, Chelsea; Fathi, Yasmin; Meloni, Giovanni

2017-05-01

Absolute photoionization cross sections for cyclopentanone and cyclohexanone, as well as partial ionization cross sections for the dissociative ionized fragments, are presented in this investigation. Experiments are performed via a multiplexed photoionization mass spectrometer utilizing vacuum ultraviolet (VUV) synchrotron radiation supplied by the Advanced Light Source of Lawrence Berkeley National Laboratory. These results allow the quantification of these species that is relevant to investigate the kinetics and combustion reactions of potential biofuels. The CBS-QB3 calculated values for the adiabatic ionization energies agree well with the experimental values, and the identification of possible dissociative fragments is discussed for both systems. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Vacuum ultraviolet photoionization of carbohydrates and nucleotides

NASA Astrophysics Data System (ADS)

Shin, Joong-Won; Bernstein, Elliot R.

2014-01-01

Carbohydrates (2-deoxyribose, ribose, and xylose) and nucleotides (adenosine-, cytidine-, guanosine-, and uridine-5'-monophosphate) are generated in the gas phase, and ionized with vacuum ultraviolet photons (VUV, 118.2 nm). The observed time of flight mass spectra of the carbohydrate fragmentation are similar to those observed [J.-W. Shin, F. Dong, M. Grisham, J. J. Rocca, and E. R. Bernstein, Chem. Phys. Lett. 506, 161 (2011)] for 46.9 nm photon ionization, but with more intensity in higher mass fragment ions. The tendency of carbohydrate ions to fragment extensively following ionization seemingly suggests that nucleic acids might undergo radiation damage as a result of carbohydrate, rather than nucleobase fragmentation. VUV photoionization of nucleotides (monophosphate-carbohydrate-nucleobase), however, shows that the carbohydrate-nucleobase bond is the primary fragmentation site for these species. Density functional theory (DFT) calculations indicate that the removed carbohydrate electrons by the 118.2 nm photons are associated with endocyclic C-C and C-O ring centered orbitals: loss of electron density in the ring bonds of the nascent ion can thus account for the observed fragmentation patterns following carbohydrate ionization. DFT calculations also indicate that electrons removed from nucleotides under these same conditions are associated with orbitals involved with the nucleobase-saccharide linkage electron density. The calculations give a general mechanism and explanation of the experimental results.

Vacuum ultraviolet photoionization of carbohydrates and nucleotides.

PubMed

Shin, Joong-Won; Bernstein, Elliot R

2014-01-28

Carbohydrates (2-deoxyribose, ribose, and xylose) and nucleotides (adenosine-, cytidine-, guanosine-, and uridine-5(')-monophosphate) are generated in the gas phase, and ionized with vacuum ultraviolet photons (VUV, 118.2 nm). The observed time of flight mass spectra of the carbohydrate fragmentation are similar to those observed [J.-W. Shin, F. Dong, M. Grisham, J. J. Rocca, and E. R. Bernstein, Chem. Phys. Lett. 506, 161 (2011)] for 46.9 nm photon ionization, but with more intensity in higher mass fragment ions. The tendency of carbohydrate ions to fragment extensively following ionization seemingly suggests that nucleic acids might undergo radiation damage as a result of carbohydrate, rather than nucleobase fragmentation. VUV photoionization of nucleotides (monophosphate-carbohydrate-nucleobase), however, shows that the carbohydrate-nucleobase bond is the primary fragmentation site for these species. Density functional theory (DFT) calculations indicate that the removed carbohydrate electrons by the 118.2 nm photons are associated with endocyclic C-C and C-O ring centered orbitals: loss of electron density in the ring bonds of the nascent ion can thus account for the observed fragmentation patterns following carbohydrate ionization. DFT calculations also indicate that electrons removed from nucleotides under these same conditions are associated with orbitals involved with the nucleobase-saccharide linkage electron density. The calculations give a general mechanism and explanation of the experimental results.

Tabletop Femtosecond VUV Photoionization and PEPICO Detection of Microreactor Pyrolysis Products

DOE Office of Scientific and Technical Information (OSTI.GOV)

Couch, David E.; Buckingham, Grant T.; Baraban, Joshua H.

Here, we report the combination of tabletop vacuum ultraviolet photoionization with photoion--photoelectron coincidence spectroscopy for sensitive, isomer-specific detection of nascent products from a pyrolysis microreactor. Results on several molecules demonstrate two essential capabilities that are very straightforward to implement: the ability to differentiate isomers, and to distinguish thermal products from dissociative ionization. We derive vacuum ultraviolet light is from a commercial tabletop femtosecond laser system, allowing data to be collected at 10 kHz; this high repetition rate is critical for coincidence techniques. The photoion—photoelectron coincidence spectrometer uses the momentum of the ion to identify dissociative ionization events, and coincidence techniquesmore » to provide a photoelectron spectrum specific to each mass, which is used to distinguish different isomers. We also have used this spectrometer to detect the pyrolysis products that result from the thermal cracking of acetaldehyde, cyclohexene, and 2-butanol. The photoion—photoelectron spectrometer can detect and identify organic radicals and reactive intermediates that result from pyrolysis. Direct comparison of laboratory and synchrotron data illustrate the advantages and potential of this approach.« less

Tabletop Femtosecond VUV Photoionization and PEPICO Detection of Microreactor Pyrolysis Products

DOE PAGES

Couch, David E.; Buckingham, Grant T.; Baraban, Joshua H.; ...

2017-06-29

Here, we report the combination of tabletop vacuum ultraviolet photoionization with photoion--photoelectron coincidence spectroscopy for sensitive, isomer-specific detection of nascent products from a pyrolysis microreactor. Results on several molecules demonstrate two essential capabilities that are very straightforward to implement: the ability to differentiate isomers, and to distinguish thermal products from dissociative ionization. We derive vacuum ultraviolet light is from a commercial tabletop femtosecond laser system, allowing data to be collected at 10 kHz; this high repetition rate is critical for coincidence techniques. The photoion—photoelectron coincidence spectrometer uses the momentum of the ion to identify dissociative ionization events, and coincidence techniquesmore » to provide a photoelectron spectrum specific to each mass, which is used to distinguish different isomers. We also have used this spectrometer to detect the pyrolysis products that result from the thermal cracking of acetaldehyde, cyclohexene, and 2-butanol. The photoion—photoelectron spectrometer can detect and identify organic radicals and reactive intermediates that result from pyrolysis. Direct comparison of laboratory and synchrotron data illustrate the advantages and potential of this approach.« less

Identification of combustion intermediates in low-pressure premixed pyridine/oxygen/argon flames.

PubMed

Tian, Zhenyu; Li, Yuyang; Zhang, Taichang; Zhu, Aiguo; Qi, Fei

2008-12-25

Combustion intermediates of two low-pressure premixed pyridine/oxygen flames with respective equivalence ratios of 0.56 (C/O/N = 1:4.83:0.20) and 2.10 (C/O/N = 1:1.29:0.20) have been identified with tunable synchrotron vacuum ultraviolet (VUV) photoionization and molecular-beam mass spectrometry techniques. About 80 intermediates in the rich flame and 60 intermediates in the lean flame, including nitrogenous, oxygenated, and hydrocarbon intermediates, have been identified by measurements of photoionization mass spectra and photoionization efficiency spectra. Some radicals and new nitrogenous intermediates are identified in the present work. The experimental results are useful for studying the conversion of volatile nitrogen compounds and understanding the formation mechanism of NO(x) in flames of nitrogenous fuels.

Online investigations on ozonation products of pyrene and benz[ a]anthracene particles with a vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer

NASA Astrophysics Data System (ADS)

Gao, Shaokai; Zhang, Yang; Meng, Junwang; Shu, Jinian

The reaction products of ozone with pyrene and benz[ a]anthracene absorbed on azelaic acid particles under the pseudo-first-order reaction conditions have been investigated with a vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS). The pyrene and benz[ a]anthracene particles with the initial concentrations of ˜1 mg m -3 are respectively exposed to ˜22 ppm ozone in a reaction chamber with a volume of ˜180 L. The time-of-flight mass spectra of the particulate ozonides are obtained. The assignments of the mass spectra reveal that 4-carboxy-5-phenanthrene-carboxyaldehyde (71%) and hydroxypyrene (23%) are the main solid state ozonides of pyrene, while 2-(2-formyl)phenyl-3-naphthoic acid (35%), hydroxybenz[ a]anthrone (30%), and benz[ a]anthracene-7,12-dione (18%) are the main solid state ozonides of benz[ a]anthracene. The pathways of the ozonations are proposed in the paper.

Vacuum ultraviolet photoionization of carbohydrates and nucleotides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shin, Joong-Won, E-mail: jshin@govst.edu; Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872; Bernstein, Elliot R., E-mail: erb@lamar.colostate.edu

Carbohydrates (2-deoxyribose, ribose, and xylose) and nucleotides (adenosine-, cytidine-, guanosine-, and uridine-5{sup ′}-monophosphate) are generated in the gas phase, and ionized with vacuum ultraviolet photons (VUV, 118.2 nm). The observed time of flight mass spectra of the carbohydrate fragmentation are similar to those observed [J.-W. Shin, F. Dong, M. Grisham, J. J. Rocca, and E. R. Bernstein, Chem. Phys. Lett. 506, 161 (2011)] for 46.9 nm photon ionization, but with more intensity in higher mass fragment ions. The tendency of carbohydrate ions to fragment extensively following ionization seemingly suggests that nucleic acids might undergo radiation damage as a result of carbohydrate,more » rather than nucleobase fragmentation. VUV photoionization of nucleotides (monophosphate-carbohydrate-nucleobase), however, shows that the carbohydrate-nucleobase bond is the primary fragmentation site for these species. Density functional theory (DFT) calculations indicate that the removed carbohydrate electrons by the 118.2 nm photons are associated with endocyclic C–C and C–O ring centered orbitals: loss of electron density in the ring bonds of the nascent ion can thus account for the observed fragmentation patterns following carbohydrate ionization. DFT calculations also indicate that electrons removed from nucleotides under these same conditions are associated with orbitals involved with the nucleobase-saccharide linkage electron density. The calculations give a general mechanism and explanation of the experimental results.« less

Ultra-compact photoionization analyzers. Ecological monitoring application at hazardous production facilities

NASA Astrophysics Data System (ADS)

Mustafaev, Alexander; Rastvorova, Iuliia; Arslanova, Fatima

2017-10-01

It is generally recognized that careful implementation of ecological monitoring should be provided at hazardous production facilities continuously to protect the surrounding environment as well as health and safety of employees. However, the existing devices may not be able to control the environmental situation uninterruptedly due to their technical characteristics or measurement methods. Developed by The Mining University Plasma Research Group ultra-compact photoionization analyzer is proposed as innovative equipment which creates the basis for a new measuring approach. The general operating principle is based on the patented method of stabilization of electric parameters - CES (Collisional Electron Spectroscopy). During the operation at the atmospheric pressure, the vacuum ultraviolet (VUV) photoionization sensor measures the energy of electrons produced by means of ionization with the resonance photons whose wavelength is situated in the VUV. A special software tool was developed to obtain the second-order derivative of the I-U characteristics, taken by the VUV sensor, to construct the characteristic electrons energy spectra. The portable analyzer with a unique set of parameters such as small size (10*10*1 mm), low cost, a wide range of recognizable molecules, great measurement accuracy at the atmospheric pressure can be effectively used both for rapid testing of air pollution load and the study of noxious factors that influence oil and gas industry employees. Dr. Sci., Ph.D, Principal Scientist, Professor.

Photoinduced intermolecular dynamics and subsequent fragmentation in VUV-ionized acetamide clusters

NASA Astrophysics Data System (ADS)

Tarkanovskaja, Marta; Kooser, Kuno; Levola, Helena; Nõmmiste, Ergo; Kukk, Edwin

2016-09-01

Photofragmentation of small gas-phase acetamide clusters (CH3CONH2)n (n ≤ 10) produced by a supersonic expansion source has been studied using time-of-flight ion mass spectroscopy combined with tunable vacuum-ultraviolet (VUV) synchrotron radiation. Fragmentation channels of acetamide clusters under VUV photoionization resulting in protonated and ammoniated clusters formation were identified with the discussion about the preceding intramolecular rearrangements. Acetamide-2,2,2-d3 clusters were also studied in an experiment with a gas discharge lamp as a VUV light source; comparison with the main experiment gave insights into the mechanism of formation of protonated acetamide clusters, indicating that proton transfer from amino group plays a dominant role in that process. Geometry of the acetamide dimer was discussed and the most stable arrangement was concluded to be achieved when subunits of the dimer are connected via two N—H⋯O —C hydrogen bonds. Also, the influence of the photon energy on the stability of the clusters and their fragmentation channels has been examined.

Quantification of isomerically summed hydrocarbon contributions to crude oil by carbon number, double bond equivalent, and aromaticity using gas chromatography with tunable vacuum ultraviolet ionization.

PubMed

Nowak, Jeremy A; Weber, Robert J; Goldstein, Allen H

2018-03-12

The ability to structurally characterize and isomerically quantify crude oil hydrocarbons relevant to refined fuels such as motor oil, diesel, and gasoline represents an extreme challenge for chromatographic and mass spectrometric techniques. This work incorporates two-dimensional gas chromatography coupled to a tunable vacuum ultraviolet soft photoionization source, the Chemical Dynamics Beamline 9.0.2 of the Advanced Light Source at the Lawrence Berkeley National Laboratory, with a time-of-flight mass spectrometer (GC × GC-VUV-TOF) to directly characterize and isomerically sum the contributions of aromatic and aliphatic species to hydrocarbon classes of four crude oils. When the VUV beam is tuned to 10.5 ± 0.2 eV, both aromatic and aliphatic crude oil hydrocarbons are ionized to reveal the complete chemical abundance of C 9 -C 30 hydrocarbons. When the VUV beam is tuned to 9.0 ± 0.2 eV only aromatic hydrocarbons are ionized, allowing separation of the aliphatic and aromatic fractions of the crude oil hydrocarbon chemical classes in an efficient manner while maintaining isomeric quantification. This technique provides an effective tool to determine the isomerically summed aromatic and aliphatic hydrocarbon compositions of crude oil, providing information that goes beyond typical GC × GC separations of the most dominant hydrocarbon isomers.

Harmonium: An Ultrafast Vacuum Ultraviolet Facility.

PubMed

Arrell, Christopher A; Ojeda, José; Longetti, Luca; Crepaldi, Alberto; Roth, Silvan; Gatti, Gianmarco; Clark, Andrew; van Mourik, Frank; Drabbels, Marcel; Grioni, Marco; Chergui, Majed

2017-05-31

Harmonium is a vacuum ultraviolet (VUV) photon source built within the Lausanne Centre for Ultrafast Science (LACUS). Utilising high harmonic generation, photons from 20-110 eV are available to conduct steady-state or ultrafast photoelectron and photoion spectroscopies (PES and PIS). A pulse preserving monochromator provides either high energy resolution (70 meV) or high temporal resolution (40 fs). Three endstations have been commissioned for: a) PES of liquids; b) angular resolved PES (ARPES) of solids and; c) coincidence PES and PIS of gas phase molecules or clusters. The source has several key advantages: high repetition rate (up to 15 kHz) and high photon flux (1011 photons per second at 38 eV). The capabilities of the facility complement the Swiss ultrafast and X-ray community (SwissFEL, SLS, NCCR MUST, etc.) helping to maintain Switzerland's leading role in ultrafast science in the world.

The C( 3P) + NH 3 reaction in interstellar chemistry. I. Investigation of the product formation channels

DOE PAGES

Bourgalais, Jeremy; Capron, Michael; Kailasanathan, Ranjith Kumar Abhinavam; ...

2015-10-13

The product formation channels of ground state carbon atoms, C( 3P), reacting with ammonia, NH3, have been investigated using two complementary experiments and electronic structure calculations. Reaction products are detected in a gas flow tube experiment (330 K, 4 Torr) using tunable vacuum-ultraviolet (VUV) photoionization coupled with time of flight mass spectrometry. Temporal profiles of the species formed and photoionization spectra are used to identify primary products of the C + NH 3 reaction. In addition, H-atom formation is monitored by VUV laser induced fluorescence (LIF) from room temperature to 50 K in a supersonic gas flow generated by themore » Laval nozzle technique. Electronic structure calculations are performed to derive intermediates, transition states, and complexes formed along the reaction coordinate. The combination of photoionization and LIF experiments supported by theoretical calculations indicate that in the temperature and pressure range investigated, the H + H 2CN production channel represents 100% of the product yield for this reaction. As a result, kinetics measurements of the title reaction down to 50 K and the effect of the new rate constants on interstellar nitrogen hydride abundances using a model of dense interstellar clouds are reported in Paper II.« less

Comparison of direct and alternating current vacuum ultraviolet lamps in atmospheric pressure photoionization.

PubMed

Vaikkinen, Anu; Haapala, Markus; Kersten, Hendrik; Benter, Thorsten; Kostiainen, Risto; Kauppila, Tiina J

2012-02-07

A direct current induced vacuum ultraviolet (dc-VUV) krypton discharge lamp and an alternating current, radio frequency (rf) induced VUV lamp that are essentially similar to lamps in commercial atmospheric pressure photoionization (APPI) ion sources were compared. The emission distributions along the diameter of the lamp exit window were measured, and they showed that the beam of the rf lamp is much wider than that of the dc lamp. Thus, the rf lamp has larger efficient ionization area, and it also emits more photons than the dc lamp. The ionization efficiencies of the lamps were compared using identical spray geometries with both lamps in microchip APPI mass spectrometry (μAPPI-MS) and desorption atmospheric pressure photoionization-mass spectrometry (DAPPI-MS). A comprehensive view on the ionization was gained by studying six different μAPPI solvent compositions, five DAPPI spray solvents, and completely solvent-free DAPPI. The observed reactant ions for each solvent composition were very similar with both lamps except for toluene, which showed a higher amount of solvent originating oxidation products with the rf lamp than with the dc lamp in μAPPI. Moreover, the same analyte ions were detected with both lamps, and thus, the ionization mechanisms with both lamps are similar. The rf lamp showed a higher ionization efficiency than the dc lamp in all experiments. The difference between the lamp ionization efficiencies was greatest when high ionization energy (IE) solvent compositions (IEs above 10 eV), i.e., hexane, methanol, and methanol/water, (1:1 v:v) were used. The higher ionization efficiency of the rf lamp is likely due to the larger area of high intensity light emission, and the resulting larger efficient ionization area and higher amount of photons emitted. These result in higher solvent reactant ion production, which in turn enables more efficient analyte ion production. © 2012 American Chemical Society

Bow shock data analysis

NASA Astrophysics Data System (ADS)

Zipf, Edward C.; Erdman, Peeter W.

1994-08-01

The University of Pittsburgh Space Physics Group in collaboration with the Army Research Office (ARO) modeling team has completed a systematic organization of the shock and plume spectral data and the electron temperature and density measurements obtained during the BowShock I and II rocket flights which have been submitted to the AEDC Data Center, has verified the presence of CO Cameron band emission during the Antares engine burn and for an extended period of time in the post-burn plume, and have adapted 3-D radiation entrapment codes developed by the University of Pittsburgh to study aurora and other atmospheric phenomena that involve significant spatial effects to investigate the vacuum ultraviolet (VUV) and extreme ultraviolet (EUV) envelope surrounding the re-entry that create an extensive plasma cloud by photoionization.

Photon-counting array detectors for space and ground-based studies at ultraviolet and vacuum ultraviolet /VUV/ wavelengths

NASA Technical Reports Server (NTRS)

Timothy, J. G.; Bybee, R. L.

1981-01-01

The Multi-Anode Microchannel Arrays (MAMAs) are a family of photoelectric photon-counting array detectors, with formats as large as (256 x 1024)-pixels that can be operated in a windowless configuration at vacuum ultraviolet (VUV) and soft X-ray wavelengths or in a sealed configuration at ultraviolet and visible wavelengths. This paper describes the construction and modes of operation of (1 x 1024)-pixel and (24 x 1024)-pixel MAMA detector systems that are being built and qualified for use in sounding-rocket spectrometers for solar and stellar observations at wavelengths below 1300 A. The performance characteristics of the MAMA detectors at ultraviolet and VUV wavelengths are also described.

VUV Photoionisation of hydrocarbon radicals

NASA Astrophysics Data System (ADS)

Alcaraz, C.; Noller, Bastian; Hemberger, Patrick; Fischer, Ingo; Gans, Bérenger; Boyé-Peronne, Séverine; Douin, Stéphane; Gauyacq, Dolorès; Soldi-Lose, Héloïse; Garcia, Gustavo

2008-09-01

Hydrocarbon radicals CxHy are constituents of various planetary atmospheres, in particular Titan, as a result of the methane photochemistry induced by the solar radiation. They contribute to the neutral chemistry, but are also important for the ionosphere through their photoionisation leading to their cations CxHy +. These cations are also produced by ion-molecule reactions starting from the reaction of the primary ions CH4 + and CH3 + which are created in the non-dissociative and dissociative photoionisation of CH4. This work aims at caracterizing the VUV photoionisation of small hydrocarbon radicals as a function of photon energy. The objective is to provide laboratory data for modelers on the spectroscopy, the thermochemistry, and the reactivity of the radicals and their cations. The hydrocarbon radicals are much less caracterized than stable molecules since they have to be produced in situ in the laboratory experiment. We have adapted at Orsay [1-3] a pyrolysis source (Figure 1) well suited to produce cold beams of hydrocarbon radicals to our experimental setups. Available now at Orsay, we have two new sources of VUV radiation, complementary in terms of tunability and resolution, that can be used for these studies. The first one is the DESIRS beamline [4] at the new french synchrotron, SOLEIL. The second one is the VUV laser developped at the Centre Laser de l'Université Paris-Sud (CLUPS) [5]. At SOLEIL, a photoelectron-photoion coincidence spectrometer is used to monitor the photoionisation on a large photon energy range. At the CLUPS, a pulsedfield ionisation (PFI-ZEKE) spectrometer allows studies at higher resolution on selected photon energies. The first results obtained with these new setups will be presented. References [1] Fischer, I., Schussler, T., Deyerl, H.J., Elhanine, M. & Alcaraz, C., Photoionization and dissociative photoionization of the allyl radical, C3H5. Int. J. Mass Spectrom., 261 (2-3), 227-233 (2007) [2] Schüßler, T., Roth, W., Gerber, T., Alcaraz, C. & Fischer, I., The vacuum ultraviolet photochemistry of radicals: C3H3 and C2H5. Phys. Chem. Chem. Phys., 7 (5), 819-825 (2005) [3] Schüßler, T., Deyerl, H. J., Dummler, S., Fischer, I., Alcaraz, C. & Elhanine, M., The vacuum ultraviolet photochemistry of the allyl radical investigated using synchrotron radiation J. Chem. Phys., 118 (20), 9077-80 (2003) [4] DESIRS, http://www.synchrotronsoleil. fr/portal/page/portal/Recherche/LignesLumiere/ DESIRS [5] CLUPS, http://www.clups.u-psud.fr/

Solvent jet desorption capillary photoionization-mass spectrometry.

PubMed

Haapala, Markus; Teppo, Jaakko; Ollikainen, Elisa; Kiiski, Iiro; Vaikkinen, Anu; Kauppila, Tiina J; Kostiainen, Risto

2015-03-17

A new ambient mass spectrometry method, solvent jet desorption capillary photoionization (DCPI), is described. The method uses a solvent jet generated by a coaxial nebulizer operated at ambient conditions with nitrogen as nebulizer gas. The solvent jet is directed onto a sample surface, from which analytes are extracted into the solvent and ejected from the surface in secondary droplets formed in collisions between the jet and the sample surface. The secondary droplets are directed into the heated capillary photoionization (CPI) device, where the droplets are vaporized and the gaseous analytes are ionized by 10 eV photons generated by a vacuum ultraviolet (VUV) krypton discharge lamp. As the CPI device is directly connected to the extended capillary inlet of the MS, high ion transfer efficiency to the vacuum of MS is achieved. The solvent jet DCPI provides several advantages: high sensitivity for nonpolar and polar compounds with limit of detection down to low fmol levels, capability of analyzing small and large molecules, and good spatial resolution (250 μm). Two ionization mechanisms are involved in DCPI: atmospheric pressure photoionization, capable of ionizing polar and nonpolar compounds, and solvent assisted inlet ionization capable of ionizing larger molecules like peptides. The feasibility of DCPI was successfully tested in the analysis of polar and nonpolar compounds in sage leaves and chili pepper.

Infrared-Vacuum Ultraviolet Pulsed Field Ionization-Photoelectron Study of C₂H₄ + Using a High-Resolution Infrared Laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xing, Xi; Reed, Beth; Bahng, Mi-Kyung

The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. The infrared (IR)-vacuum ultraviolet (VUV)-pulsed field ionization-photoelectron (IR-VUV-PFI-PE) spectrum for C₂H₄(X 1A g, V 11 = 1, N' Ka' Kc'=3₀₃) in the VUV range of 83 000-84 800 cm -1 obtained using a single mode infrared laser revealed 24 rotationally resolved vibrational bands for the ion C₂H₄ +(X 2B 3u) ground state. The frequencies and symmetry of the vibrational bandsmore » thus determined, together with the anharmonic frequency predictions calculated at the CCSD(T)/aug-cc-pVQZ level, have allowed the unambiguous assignment of these vibrational bands. These bands are mostly combination bands. The measured frequencies of these bands yield the fundamental frequencies for V 8 + ) 1103± ( 10 cm -1 and V 10 + ) 813 ( 10 cm -1 of C₂H₄ +(X 2B 3u), which have not been determined previously. The present IR-VUV-PFI-PE study also provides truly rovibrationally selected and resolved state-to-state cross sections for the photoionization transitions C₂H₄(X~ 1A g; V 11, N' Ka' Kc') → C₂H₄ +(X ~ 2B 3u; V i +, N + Ka + Kc +), where N' Ka' Kc' denotes the rotational level of C₂H₄(X ~ 1Ag; V 11), and V i + and N + Ka + Kc + represent the vibrational and rotational states of the cation.« less

Single- and multi-photon ionization studies of organosulfur species

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheung, Yu -San

1999-02-12

Accurate ionization energies (IE`s) for molecular species are used for prediction of chemical reactivity and are of fundamental importance to chemists. The IE of a gaseous molecule can be determined routinely in a photoionization or a photoelectron experiment. IE determinations made in conventional photoionization and photoelectron studies have uncertainties in the range of 3--100 meV (25--250 cm -1). In the past decade, the most exciting development in the field of photoionization and photoelectron spectroscopy has been the availability of high resolution, tunable ultraviolet (UV) and vacuum ultraviolet (VUV) laser sources. The laser pulsed field ionization photoelectron (PFI-PE) scheme is currentlymore » the state-of-the-art photoelectron spectroscopic technique and is capable of providing photoelectron energy resolution close to the optical resolution. The author has focused attention on the photoionization processes of some sulfur-containing species. The studies of the photoionization and photodissociation on sulfur-containing compounds [such as CS 2, CH 3SH, CH 3SSCH 3, CH 3CH 2SCH 2CH 3, HSCH 2CH 2SH and C 4H 4S (thiophene) and sulfur-containing radicals, such as HS, CS, CH 3S, CH 3CH 2S and CH 3SS], have been the major subjects in the group because sulfur is an important species contributing to air pollution in the atmosphere. The modeling of the combustion and oxidation of sulfur compounds represents important steps for the control of both the production and the elimination of sulfur-containing pollutants. Chapter 1 is a general introduction of the thesis. Chapters 2 and 6 contain five papers published in, or accepted for publication in, academic periodicals. In Chapter 7, the progress of the construction in the laboratory of a new vacuum ultraviolet laser system equipped with a reflectron mass spectrometer is presented. Chapters 2 through 7 have been removed for separate processing. A general conclusion of these studies are given in Chapter 8 followed by an appendix.« less

Simulation of the synergistic low Earth orbit effects of vacuum thermal cycling, vacuum UV radiation, and atomic oxygen

NASA Technical Reports Server (NTRS)

Dever, Joyce A.; Degroh, Kim K.; Stidham, Curtis R.; Stueber, Thomas J.; Dever, Therese M.; Rodriguez, Elvin; Terlep, Judith A.

1992-01-01

In order to assess the low Earth orbit (LEO) durability of candidate space materials, it is necessary to use ground laboratory facilities which provide LEO environmental effects. A facility combining vacuum thermal cycling and vacuum ultraviolet (VUV) radiation has been designed and constructed at NASA Lewis Research Center for this purpose. This facility can also be operated without the VUV lamps. An additional facility can be used to provide VUV exposure only. By utilizing these facilities, followed by atomic oxygen exposure in an RF plasma asher, the effects of the individual vacuum thermal cycling and VUV environments can be compared to the effect of the combined vacuum thermal cycling/VUV environment on the atomic oxygen durability of materials. The synergistic effects of simulated LEO environmental conditions on materials were evaluated by first exposing materials to vacuum thermal cycling, VUV, and vacuum thermal cycling/VUV environments followed by exposure to atomic oxygen in an RP plasma asher. Candidate space power materials such as atomic oxygen protected polyimides and solar concentrator mirrors were evaluated using these facilities. Characteristics of the Vacuum Thermal Cycling/VUV Exposure Facility which simulates the temperature sequences and solar ultraviolet radiation exposure that would be experienced by a spacecraft surface in LEO are discussed. Results of durability evaluations of some candidate space power materials to the simulated LEO environmental conditions will also be discussed. Such results have indicated that for some materials, atomic oxygen durability is affected by previous exposure to thermal cycling and/or VUV exposure.

Vacuum ultraviolet photoionization mass spectrometric study of cyclohexene.

PubMed

Chen, Jun; Cao, Maoqi; Wei, Bin; Ding, Mengmeng; Shan, Xiaobin; Liu, Fuyi; Sheng, Liusi

2016-02-01

In this work, photoionization and dissociation of cyclohexene have been studied by means of coupling a reflectron time-of-flight mass spectrometer with the tunable vacuum ultraviolet (VUV) synchrotron radiation. The adiabatic ionization energy of cyclohexene as well as the appearance energies of its fragment ions C6 H9 (+) , C6 H7 (+) , C5 H7 (+) , C5 H5 (+) , C4 H6 (+) , C4 H5 (+) , C3 H5 (+) and C3 H3 (+) were derived from the onset of the photoionization efficiency (PIE) curves. The optimized structures for the transition states and intermediates on the ground state potential energy surfaces related to photodissociation of cyclohexene were characterized at the ωB97X-D/6-31+g(d,p) level. The coupled cluster method, CCSD(T)/cc-pVTZ, was employed to calculate the corresponding energies with the zero-point energy corrections by the ωB97X-D/6-31+g(d,p) approach. Combining experimental and theoretical results, possible formation pathways of the fragment ions were proposed and discussed in detail. The retro-Cope rearrangement was found to play a crucial role in the formation of C4 H6 (+) , C4 H5 (+) and C3 H5 (+) . Intramolecular hydrogen migrations were observed as dominant processes in most of the fragmentation pathways of cyclohexene. The present research provides a clear picture of the photoionization and dissociation processes of cyclohexene in the 8- to 15.5-eV photon energy region. Copyright © 2016 John Wiley & Sons, Ltd.

Dissociative photoionization of isoprene: experiments and calculations.

PubMed

Liu, Xianyun; Zhang, Weijun; Wang, Zhenya; Huang, Mingqiang; Yang, Xibin; Tao, Ling; Sun, Yue; Xu, Yuntao; Shan, Xiaobin; Liu, Fuyi; Sheng, Liusi

2009-03-01

Vacuum ultraviolet (VUV) dissociative photoionization of isoprene in the energy region 8.5-18 eV was investigated with photoionization mass spectroscopy (PIMS) using synchrotron radiation (SR). The ionization energy (IE) of isoprene as well as the appearance energies (AEs) of its fragment ions C(5)H(7) (+), C(5)H(5) (+), C(4)H(5) (+), C(3)H(6) (+), C(3)H(5) (+), C(3)H(4) (+), C(3)H(3) (+) and C(2)H(3) (+) were determined with photoionization efficiency (PIE) curves. The dissociation energies of some possible dissociation channels to produce those fragment ions were also determined experimentally. The total energies of C(5)H(8) and its main fragments were calculated using the Gaussian 03 program and the Gaussian-2 method. The IE of C(5)H(8), the AEs for its fragment ions, and the dissociation energies to produce them were predicted using the high-accuracy energy model. According to our results, the experimental dissociation energies were in reasonable agreement with the calculated values of the proposed photodissociation channels of C(5)H(8). Copyright (c) 2009 John Wiley & Sons, Ltd.

Effects of plasma and vacuum-ultraviolet exposure on the mechanical properties of low-k porous organosilicate glass

Treesearch

X. Guo; J.E. Jakes; S. Banna; Y. Nishi; J.L. Shohet

2014-01-01

The effects of plasma exposure and vacuum-ultraviolet (VUV) irradiation on the mechanical properties of low-k porous organosilicate glass (SiCOH) dielectric films were investigated. Nanoindentation measurements were made on SiCOH films before and after exposure to an electron-cyclotron-resonance plasma or a monochromatic synchrotron VUV beam, to determine the changes...

Nonthermal combined ultraviolet and vacuum-ultraviolet curing process for organosilicate dielectrics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, H.; Guo, X.; Pei, D.

2016-06-13

Porous SiCOH films are of great interest in semiconductor fabrication due to their low-dielectric constant properties. Post-deposition treatments using ultraviolet (UV) light on organosilicate thin films are required to decompose labile pore generators (porogens) and to ensure optimum network formation to improve the electrical and mechanical properties of low-k dielectrics. The goal of this work is to choose the best vacuum-ultraviolet photon energy in conjunction with vacuum ultraviolet (VUV) photons without the need for heating the dielectric to identify those wavelengths that will have the most beneficial effect on improving the dielectric properties and minimizing damage. VUV irradiation between 8.3more » and 8.9 eV was found to increase the hardness and elastic modulus of low-k dielectrics at room temperature. Combined with UV exposures of 6.2 eV, it was found that this “UV/VUV curing” process is improved compared with current UV curing. We show that UV/VUV curing can overcome drawbacks of UV curing and improve the properties of dielectrics more efficiently without the need for high-temperature heating of the dielectric.« less

Vacuum ultraviolet photon fluxes in argon-containing inductively coupled plasmas

NASA Astrophysics Data System (ADS)

Radovanov, S. B.; Persing, H. M.; Wang, S.; Culver, C. L.; Boffard, J. B.; Lin, C. C.; Wendt, A. E.

2013-09-01

Vacuum ultraviolet (VUV) photons emitted from excited atomic states are ubiquitous in material processing plasmas. Damage of materials is induced by energy transfer from the VUV photons to the surface, causing disorder in the surface region, surface reactions, and affecting bonds in the material bulk. Monitoring of the surface flux of VUV photons from inductively coupled plasmas (ICP) and its dependence on discharge parameters is thus highly desirable. Results of non-invasive, direct windowless VUV detection using a photosensitive diode will be presented. Relative VUV fluxes were also obtained using a sodium salicylate coating on the inside of a vacuum window, converting VUV into visible light detected through the vacuum window. The coating is sensitive to wavelengths in the range 80-300 nm, while the photodiode is only sensitive to wavelengths below 120 nm. In argon the VUV emissions are primarily produced by spontaneous decay from 3p5 4 s resonance levels (1s2,1s4) and may be reabsorbed by ground state atoms. Real-time resonance level concentrations were measured and used to predict the VUV photon flux at the detector for a range of different ICP pressures, powers, and for various admixtures of Ar with N2, and H2. This work was supported in part by NSF grant PHY-1068670.

Simulated Space Vacuum Ultraviolet (VUV) Exposure Testing for Polymer Films

NASA Technical Reports Server (NTRS)

Dever, Joyce A.; Pietromica, Anthony J.; Stueber, Thomas J.; Sechkar, Edward A.; Messer, Russell K.

2002-01-01

Vacuum ultraviolet (VUV) radiation of wavelengths between 115 and 200 nm produced by the sun in the space environment can cause degradation to polymer films producing changes in optical, mechanical, and chemical properties. These effects are particularly important for thin polymer films being considered for ultra-lightweight space structures, because, for most polymers, VUV radiation is absorbed in a thin surface layer. NASA Glenn Research Center has developed facilities and methods for long-term ground testing of polymer films to evaluate space environmental VUV radiation effects. VUV exposure can also be used as part of sequential simulated space environmental exposures to determine combined damaging effects. This paper will describe the effects of VUV on polymer films and the necessity for ground testing. Testing practices used at Glenn Research Center for VUV exposure testing will be described including characterization of the VUV radiation source used, calibration procedures traceable to the National Institute of Standards and Technology (NIST), and testing techniques for VUV exposure of polymer surfaces.

Comparison of theory with atomic oxygen 130.4 nm radiation data from the Bow Shock ultraviolet 2 rocket flight

NASA Technical Reports Server (NTRS)

Levin, Deborah A.; Candler, Graham V.; Collins, Robert J.; Howlett, Carl L.; Espy, Patrick; Whiting, Ellis; Park, Chul

1993-01-01

Comparison is made between the results obtained from a state-of-the-art flow and radiative model and bow shock vacuum ultraviolet (VUV) data obtained the recent Bow Shock 2 Flight Experiment. An extensive data set was obtained from onboard rocket measurements at a reentry speed of 5 km/sec between the altitudes of approximately 65-85 km. A description of the NO photoionization cell used, the data, and the interpretation of the data will be presented. The primary purpose of the analyses is to assess the utility of the data and to propose a radiation model appropriate to the flight conditions of Bow Shock 2. Theoretical predictions based on flow modeling discussed in earlier work and a new radiation model are compared with data.

Simultaneous removal of NO and SO2 using vacuum ultraviolet light (VUV)/heat/peroxymonosulfate (PMS).

PubMed

Liu, Yangxian; Wang, Yan; Wang, Qian; Pan, Jianfeng; Zhang, Jun

2018-01-01

Simultaneous removal process of SO 2 and NO from flue gas using vacuum ultraviolet light (VUV)/heat/peroxymonosulfate (PMS) in a VUV spraying reactor was proposed. The key influencing factors, active species, reaction products and mechanism of SO 2 and NO simultaneous removal were investigated. The results show that vacuum ultraviolet light (185 nm) achieves the highest NO removal efficiency and yield of and under the same test conditions. NO removal is enhanced at higher PMS concentration, light intensity and oxygen concentration, and is inhibited at higher NO concentration, SO 2 concentration and solution pH. Solution temperature has a double impact on NO removal. CO 2 concentration has no obvious effect on NO removal. and produced from VUV-activation of PMS play a leading role in NO removal. O 3 and ·O produced from VUV-activation of O 2 also play an important role in NO removal. SO 2 achieves complete removal under all experimental conditions due to its very high solubility in water and good reactivity. The highest simultaneous removal efficiency of SO 2 and NO reaches 100% and 91.3%, respectively. Copyright © 2017 Elsevier Ltd. All rights reserved.

Communication: "Position" does matter: The photofragmentation of the nitroimidazole isomers

NASA Astrophysics Data System (ADS)

Bolognesi, P.; Casavola, A. R.; Cartoni, A.; Richter, R.; Markus, P.; Borocci, S.; Chiarinelli, J.; Tošić, S.; Sa'adeh, H.; Masič, M.; Marinković, B. P.; Prince, K. C.; Avaldi, L.

2016-11-01

A combined experimental and theoretical approach has been used to disentangle the fundamental mechanisms of the fragmentation of the three isomers of nitroimidazole induced by vacuum ultra-violet (VUV) radiation, namely, 4-, 5-, and 2-nitroimidazole. The results of mass spectrometry as well as photoelectron-photoion coincidence spectroscopy display striking differences in the radiation-induced decomposition of the different nitroimidazole radical cations. Based on density functional theory (DFT) calculations, a model is proposed which fully explains such differences, and reveals the subtle fragmentation mechanisms leading to the release of neutral species like NO, CO, and HCN. Such species have a profound impact in biological media and may play a fundamental role in radiosensitising mechanisms during radiotherapy.

Promotion effect of H2 on ethanol oxidation and NOx reduction with ethanol over Ag/Al2O3 catalyst.

PubMed

Yu, Yunbo; Li, Yi; Zhang, Xiuli; Deng, Hua; He, Hong; Li, Yuyang

2015-01-06

The catalytic partial oxidation of ethanol and selective catalytic reduction of NOx with ethanol (ethanol-SCR) over Ag/Al2O3 were studied using synchrotron vacuum ultraviolet (VUV) photoionization mass spectrometry (PIMS). The intermediates were identified by PIMS and their photoionization efficiency (PIE) spectra. The results indicate that H2 promotes the partial oxidation of ethanol to acetaldehyde over Ag/Al2O3, while the simultaneously occurring processes of dehydration and dehydrogenation were inhibited. H2 addition favors the formation of ammonia during ethanol-SCR over Ag/Al2O3, the occurrence of which creates an effective pathway for NOx reduction by direct reaction with NH3. Simultaneously, the enhancement of the formation of ammonia benefits its reaction with surface enolic species, resulting in producing -NCO species again, leading to enhancement of ethanol-SCR over Ag/Al2O3 by H2. Using VUV-PIMS, the reactive vinyloxy radical was observed in the gas phase during the NOx reduction by ethanol for the first time, particularly in the presence of H2. Identification of such a reaction occurring in the gas phase may be crucial for understanding the reaction pathway of HC-SCR over Ag/Al2O3.

Two-dimensional vacuum ultraviolet images in different MHD events on the EAST tokamak

NASA Astrophysics Data System (ADS)

Zhijun, WANG; Xiang, GAO; Tingfeng, MING; Yumin, WANG; Fan, ZHOU; Feifei, LONG; Qing, ZHUANG; EAST Team

2018-02-01

A high-speed vacuum ultraviolet (VUV) imaging telescope system has been developed to measure the edge plasma emission (including the pedestal region) in the Experimental Advanced Superconducting Tokamak (EAST). The key optics of the high-speed VUV imaging system consists of three parts: an inverse Schwarzschild-type telescope, a micro-channel plate (MCP) and a visible imaging high-speed camera. The VUV imaging system has been operated routinely in the 2016 EAST experiment campaign. The dynamics of the two-dimensional (2D) images of magnetohydrodynamic (MHD) instabilities, such as edge localized modes (ELMs), tearing-like modes and disruptions, have been observed using this system. The related VUV images are presented in this paper, and it indicates the VUV imaging system is a potential tool which can be applied successfully in various plasma conditions.

Facility and Methods Developed for Simulated Space Vacuum Ultraviolet Exposure Testing of Polymer Films

NASA Technical Reports Server (NTRS)

Dever, Joyce A.; Pietromica, Anthony J.; Stueber, Thomas J.; Sechkar, Edward A.; Messer, Russell K.

2002-01-01

Vacuum ultraviolet (VUV) radiation of wavelengths between 115 and 200 nm produced by the Sun in the space environment can degrade polymer films, producing changes in their optical, mechanical, and chemical properties. These effects are particularly important for thin polymer films being considered for ultralightweight space structures, because, for most polymers, VUV radiation is absorbed in a thin surface layer. The NASA Glenn Research Center has developed facilities and methods for long-term ground testing of polymer films to evaluate space environmental VUV radiation effects. VUV exposure can also be used as part of combined or sequential simulated space environmental exposures to determine combined damaging effects with other aspects of the space environment, which include solar ultraviolet radiation, solar flare x-rays, electron and proton radiation, atomic oxygen (for low-Earth-orbit missions), and temperature effects. Because the wavelength sensitivity of VUV damage is not well known for most materials, Glenn's VUV facility uses a broad-spectrum deuterium lamp with a magnesium fluoride window that provides output between 115 and 200 nm. Deuterium lamps of this type were characterized by the National Institute of Standards and Technology and through measurements at Glenn. Spectral irradiance measurements show that from approximately 115 to 160 nm, deuterium lamp irradiance can be many times that of air mass zero solar irradiance, and as wavelength increases above approximately 160 nm, deuterium lamp irradiance decreases in comparison to the Sun. The facility is a cryopumped vacuum chamber that achieves a system pressure of approximately 5310(exp -6) torr. It contains four individual VUV-exposure compartments in vacuum, separated by water-cooled copper walls to minimize VUV radiation and any sample contamination cross interactions between compartments. Each VUV-exposure compartment contains a VUV deuterium lamp, a motor-controlled sample stage coupled with a moveable cesium iodide VUV phototube, and two thermocouples for temperature measurement. The vacuum chamber and exterior equipment is shown. Each VUV lamp is located at the top of the chamber with its projection-tube pushed through an O-ring compression fitting. The lamp assemblies are located on ports that can be isolated from the rest of the vacuum chamber, permitting maintenance or replacement of the lamps without breaking vacuum in the main chamber where the samples are located. A view of two of the four interior VUV-exposure compartments, including the moveable sample stages and detector holders is also shown. Glenn is using this facility to support testing of Next Generation Space Telescope sunshield materials that is being led by the NASA Goddard Space Flight Center and to develop an understanding of the wavelength, intensity, and temperature dependence of VUV-induced polymer degradation.

IR + VUV double resonance spectroscopy and extended density functional theory studies of ketone solvation by alcohol: 2-butanone·(methanol)n, n = 1-4 clusters.

PubMed

Shin, Joong-Won; Bernstein, Elliot R

2017-09-28

Infrared plus vacuum ultraviolet (IR + VUV) photoionization vibrational spectroscopy of 2-butanone/methanol clusters [MEK·(MeOH) n , n = 1-4] is performed to explore structures associated with hydrogen bonding of MeOH molecules to the carbonyl functional group of the ketone. IR spectra and X3LYP/6-31++G(d,p) calculations show that multiple isomers of MEK·(MeOH) n are generated in the molecular beam as a result of several hydrogen bonding sites available to the clusters throughout the size range investigated. Isomer interconversion involving solvating MeOH rearrangement should probably occur for n = 1 and 2. The mode energy for a hydrogen bonded OH stretching transition gradually redshifts as the cluster size increases. Calculations suggest that the n = 3 cluster isomers adopt structures in which the MEK molecule is inserted into the cyclic MeOH hydrogen bond network. In larger structures, the cyclic network may be preserved.

Test of prototype ITER vacuum ultraviolet spectrometer and its application to impurity study in KSTAR plasmas.

PubMed

Seon, C R; Hong, J H; Jang, J; Lee, S H; Choe, W; Lee, H H; Cheon, M S; Pak, S; Lee, H G; Biel, W; Barnsley, R

2014-11-01

To optimize the design of ITER vacuum ultraviolet (VUV) spectrometer, a prototype VUV spectrometer was developed. The sensitivity calibration curve of the spectrometer was calculated from the mirror reflectivity, the grating efficiency, and the detector efficiency. The calibration curve was consistent with the calibration points derived in the experiment using the calibrated hollow cathode lamp. For the application of the prototype ITER VUV spectrometer, the prototype spectrometer was installed at KSTAR, and various impurity emission lines could be measured. By analyzing about 100 shots, strong positive correlation between the O VI and the C IV emission intensities could be found.

Measurement of the vacuum-ultraviolet absorption spectrum of low-k dielectrics using X-ray reflectivity

NASA Astrophysics Data System (ADS)

Choudhury, F. A.; Nguyen, H. M.; King, S. W.; Lee, C. H.; Lin, Y. H.; Fung, H. S.; Chen, C. C.; Li, W.; Benjamin, D.; Blatz, J. M.; Nishi, Y.; Shohet, J. L.

2018-02-01

During plasma processing, low-k dielectrics are exposed to high levels of vacuum ultraviolet (VUV) radiation that can cause severe damage to dielectric materials. The degree and nature of VUV-induced damage depend on the VUV photon energies and fluence. In this work, we examine the VUV-absorption spectrum of low-k organosilicate glass using specular X-ray reflectivity (XRR). Low-k SiCOH films were exposed to synchrotron VUV radiation with energies ranging from 7 to 21 eV, and the density vs. depth profile of the VUV-irradiated films was extracted from fitting the XRR experimental data. The results show that the depth of the VUV-induced damage layer is a function of the photon energy. Between 7 and 11 eV, the depth of the damaged layer decreases sharply from 110 nm to 60 nm and then gradually increases to 85 nm at 21 eV. The maximum VUV absorption in low-k films occurs between 11 and 15 eV. The depth of the damaged layer was found to increase with film porosity.

On the absolute photoionization cross section and dissociative photoionization of cyclopropenylidene.

PubMed

Holzmeier, Fabian; Fischer, Ingo; Kiendl, Benjamin; Krueger, Anke; Bodi, Andras; Hemberger, Patrick

2016-04-07

We report the determination of the absolute photoionization cross section of cyclopropenylidene, c-C3H2, and the heat of formation of the C3H radical and ion derived by the dissociative ionization of the carbene. Vacuum ultraviolet (VUV) synchrotron radiation as provided by the Swiss Light Source and imaging photoelectron photoion coincidence (iPEPICO) were employed. Cyclopropenylidene was generated by pyrolysis of a quadricyclane precursor in a 1 : 1 ratio with benzene, which enabled us to derive the carbene's near threshold absolute photoionization cross section from the photoionization yield of the two pyrolysis products and the known cross section of benzene. The cross section at 9.5 eV, for example, was determined to be 4.5 ± 1.4 Mb. Upon dissociative ionization the carbene decomposes by hydrogen atom loss to the linear isomer of C3H(+). The appearance energy for this process was determined to be AE(0K)(c-C3H2; l-C3H(+)) = 13.67 ± 0.10 eV. The heat of formation of neutral and cationic C3H was derived from this value via a thermochemical cycle as Δ(f)H(0K)(C3H) = 725 ± 25 kJ mol(-1) and Δ(f)H(0K)(C3H(+)) = 1604 ± 19 kJ mol(-1), using a previously reported ionization energy of C3H.

Facile Generation and Storage of Polycyclic Aromatic Hydrocarbon Ions in Astrophysical Ices

NASA Technical Reports Server (NTRS)

Gudipati, Murthy S.; Allamandola, Louis J.

2003-01-01

In situ ultraviolet-visible absorption and emission studies of vacuum ultraviolet (VUV) irradiated water-rich, cosmic ice analogs containing polycyclic aromatic hydrocarbons (PAHs) are described. W V irradiation of 12 K water ices containing the PAHs naphthalene (H2O/C10H8 = 200) and 4-methylpyrene (H2O/C17H12 > 500) readily converts the PAHs into their cation form (PAH(+)). Under these conditions, PAH photoionization is the predominant reaction. These ions are trapped and stored in the ices at temperatures between 10 and 50 K, a temperature domain common to ices throughout interstellar clouds and the solar system. Unlike the approx.15% ionization typical after W V irradiation of PAHs isolated in rare-gas matrices, in water ice, PAH photoionization and storage proceed efficiently and almost quantitatively with a greater than 70% ionization yield. As the temperature is increased from 50 to 150 K, the PAH ion bands slowly diminish as the PAH ions ultimately react to form more complex organic species involving the water host. The chemical, spectroscopic, and physical properties of these ion-rich ices can be important in icy objects such as molecular clouds, comets, and planets. Several astrophysical applications are presented.

Space-time resolving vacuum ultraviolet spectrometer based on a rotating polyhedral mirror

NASA Astrophysics Data System (ADS)

Lin, Xiaodong; Xie, Jikang

2000-05-01

Using a rotating polyhedral mirror and a vacuum ultraviolet (VUV) monochromater, a space-time resolving VUV diagnostic system is developed. Measurement of the O VI (103.2 nm) radiation on the HT-6M tokamak shows that the time resolution of the system is better than 4 ms and the space resolution is better than 2 cm. Compared with traditional instruments, this system has improved measurement efficiency, and error from shot-to-shot discharge variations is avoided.

VUV photo-processing of PAH cations: quantitative study on the ionization versus fragmentation processes

PubMed Central

Zhen, Junfeng; Castillo, Sarah Rodriguez; Joblin, Christine; Mulas, Giacomo; Sabbah, Hassan; Giuliani, Alexandre; Nahon, Laurent; Martin, Serge; Champeaux, Jean-Philippe; Mayer, Paul M.

2016-01-01

Interstellar polycyclic aromatic hydrocarbons (PAHs) are strongly affected by the absorption of vacuum ultraviolet (VUV) photons in the interstellar medium (ISM), yet the branching ratio between ionization and fragmentation is poorly studied. This is crucial for the stability and charge state of PAHs in the ISM in different environments, affecting in turn the chemistry, the energy balance, and the contribution of PAHs to the extinction and emission curves. We studied the interaction of PAH cations with VUV photons in the 7 – 20 eV range from the synchrotron SOLEIL beamline, DESIRS. We recorded by action spectroscopy the relative intensities of photo-fragmentation and photo-ionization for a set of eight PAH cations ranging in size from 14 to 24 carbon atoms, with different structures. At photon energies below ~13.6 eV fragmentation dominates for the smaller species, while for larger species ionization is immediately competitive after the second ionization potential (IP). At higher photon energies, all species behave similarly, the ionization yield gradually increases, leveling off between 0.8 and 0.9 at ~18 eV. Among isomers, PAH structure appears to mainly affect the fragmentation cross section, but not the ionization cross section. We also measured the second IP for all species and the third IP for two of them, all are in good agreement with theoretical ones confirming that PAH cations can be further ionized in the diffuse ISM. Determining actual PAH dication abundances in the ISM will require detailed modeling. Our measured photo-ionization yields for several PAH cations provide a necessary ingredient for such models. PMID:27212712

VUV photo-processing of PAH cations: quantitative study on the ionization versus fragmentation processes.

PubMed

Zhen, Junfeng; Castillo, Sarah Rodriguez; Joblin, Christine; Mulas, Giacomo; Sabbah, Hassan; Giuliani, Alexandre; Nahon, Laurent; Martin, Serge; Champeaux, Jean-Philippe; Mayer, Paul M

2016-05-10

Interstellar polycyclic aromatic hydrocarbons (PAHs) are strongly affected by the absorption of vacuum ultraviolet (VUV) photons in the interstellar medium (ISM), yet the branching ratio between ionization and fragmentation is poorly studied. This is crucial for the stability and charge state of PAHs in the ISM in different environments, affecting in turn the chemistry, the energy balance, and the contribution of PAHs to the extinction and emission curves. We studied the interaction of PAH cations with VUV photons in the 7 - 20 eV range from the synchrotron SOLEIL beamline, DESIRS. We recorded by action spectroscopy the relative intensities of photo-fragmentation and photo-ionization for a set of eight PAH cations ranging in size from 14 to 24 carbon atoms, with different structures. At photon energies below ~13.6 eV fragmentation dominates for the smaller species, while for larger species ionization is immediately competitive after the second ionization potential (IP). At higher photon energies, all species behave similarly, the ionization yield gradually increases, leveling off between 0.8 and 0.9 at ~18 eV. Among isomers, PAH structure appears to mainly affect the fragmentation cross section, but not the ionization cross section. We also measured the second IP for all species and the third IP for two of them, all are in good agreement with theoretical ones confirming that PAH cations can be further ionized in the diffuse ISM. Determining actual PAH dication abundances in the ISM will require detailed modeling. Our measured photo-ionization yields for several PAH cations provide a necessary ingredient for such models.

Vacuum ultra-violet damage and damage mitigation for plasma processing of highly porous organosilicate glass dielectrics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marneffe, J.-F. de, E-mail: marneffe@imec.be; Lukaszewicz, M.; Porter, S. B.

2015-10-07

Porous organosilicate glass thin films, with k-value 2.0, were exposed to 147 nm vacuum ultra-violet (VUV) photons emitted in a Xenon capacitive coupled plasma discharge. Strong methyl bond depletion was observed, concomitant with a significant increase of the bulk dielectric constant. This indicates that, besides reactive radical diffusion, photons emitted during plasma processing do impede dielectric properties and therefore need to be tackled appropriately during patterning and integration. The detrimental effect of VUV irradiation can be partly suppressed by stuffing the low-k porous matrix with proper sacrificial polymers showing high VUV absorption together with good thermal and VUV stability. In addition,more » the choice of an appropriate hard-mask, showing high VUV absorption, can minimize VUV damage. Particular processing conditions allow to minimize the fluence of photons to the substrate and lead to negligible VUV damage. For patterned structures, in order to reduce VUV damage in the bulk and on feature sidewalls, the combination of both pore stuffing/material densification and absorbing hard-mask is recommended, and/or the use of low VUV-emitting plasma discharge.« less

Vacuum-Ultraviolet Photovoltaic Detector.

PubMed

Zheng, Wei; Lin, Richeng; Ran, Junxue; Zhang, Zhaojun; Ji, Xu; Huang, Feng

2018-01-23

Over the past two decades, solar- and astrophysicists and material scientists have been researching and developing new-generation semiconductor-based vacuum ultraviolet (VUV) detectors with low power consumption and small size for replacing traditional heavy and high-energy-consuming microchannel-detection systems, to study the formation and evolution of stars. However, the most desirable semiconductor-based VUV photovoltaic detector capable of achieving zero power consumption has not yet been achieved. With high-crystallinity multistep epitaxial grown AlN as a VUV-absorbing layer for photogenerated carriers and p-type graphene (with unexpected VUV transmittance >96%) as a transparent electrode to collect excited holes, we constructed a heterojunction device with photovoltaic detection for VUV light. The device exhibits an encouraging VUV photoresponse, high external quantum efficiency (EQE) and extremely fast tempera response (80 ns, 10 4 -10 6 times faster than that of the currently reported VUV photoconductive devices). This work has provided an idea for developing zero power consumption and integrated VUV photovoltaic detectors with ultrafast and high-sensitivity VUV detection capability, which not only allows future spacecraft to operate with longer service time and lower launching cost but also ensures an ultrafast evolution of interstellar objects.

Evaluation of Low-Earth-Orbit Environmental Effects on International Space Station Thermal Control Materials

NASA Technical Reports Server (NTRS)

Dever, Joyce A.

1998-01-01

Many spacecraft thermal control coatings in low Earth orbit (LEO) can be affected by solar ultraviolet radiation and atomic oxygen. Ultraviolet radiation can darken some polymers and oxides commonly used in thermal control materials. Atomic oxygen can erode polymer materials, but it may reverse the ultraviolet-darkening effect on oxides. Maintaining the desired solar absorptance for thermal control coatings is important to assure the proper operating temperature of the spacecraft. Thermal control coatings to be used on the International Space Station (ISS) were evaluated for their performance after exposure in the NASA Lewis Research Center's Atomic Oxygen-Vacuum Ultraviolet Exposure (AO-VUV) facility. This facility simulated the LEO environments of solar vacuum ultraviolet (VUV) radiation (wavelength range, 115 to 200 nanometers (nm)) and VUV combined with atomic oxygen. Solar absorptance was measured in vacuo to eliminate the "bleaching" effects of ambient oxygen on VUV-induced degradation. The objective of these experiments was to determine solar absorptance increases of various thermal control materials due to exposure to simulated LEO conditions similar to those expected for ISS. Work was done in support of ISS efforts at the requests of Boeing Space and Defense Systems and Lockheed Martin Vought Systems.

In situ measurements of scattering from contaminated optics in the Vacuum Ultraviolet

NASA Astrophysics Data System (ADS)

Herren, Kenneth A.; Linton, Roger C.; Whitaker, Ann F.

1990-07-01

NASA's In Situ Contamination Effects Facility has been used to measure the time dependence of the angular reflectance from molecularly contaminated optical surfaces in the vacuum ultraviolet. The light scattering measurements are accomplished in situ on optical surfaces in real time during deposition of molecular contaminants. The measurements are taken using noncoherent VUV sources with the predominant wavelengths being the krypton resonance lines at 1236 and 1600 angstroms. Detection of the scattered light is accomplished using a set of three solar blind VUV photomultipliers. An in-plane VUV BRDF (bidirectional reflectance distribution function) experiment is described and details of the on-going program to characterize optical materials exposed to the space environment is reported.

In situ measurements of scattering from contaminated optics in the Vacuum Ultraviolet

NASA Technical Reports Server (NTRS)

Herren, Kenneth A.; Linton, Roger C.; Whitaker, Ann F.

1990-01-01

NASA's In Situ Contamination Effects Facility has been used to measure the time dependence of the angular reflectance from molecularly contaminated optical surfaces in the vacuum ultraviolet. The light scattering measurements are accomplished in situ on optical surfaces in real time during deposition of molecular contaminants. The measurements are taken using noncoherent VUV sources with the predominant wavelengths being the krypton resonance lines at 1236 and 1600 angstroms. Detection of the scattered light is accomplished using a set of three solar blind VUV photomultipliers. An in-plane VUV BRDF (bidirectional reflectance distribution function) experiment is described and details of the on-going program to characterize optical materials exposed to the space environment is reported.

Heterogeneous reaction of particulate chlorpyrifos with NO3 radicals: Products, pathways, and kinetics

NASA Astrophysics Data System (ADS)

Li, Nana; Zhang, Peng; Yang, Bo; Shu, Jinian; Wang, Youfeng; Sun, Wanqi

2014-08-01

Chlorpyrifos is a typical chlorinated organophosphorus pesticide. The heterogeneous reaction of chlorpyrifos particles with NO3 radicals was investigated using a vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS) and a real-time atmospheric gas analysis mass spectrometer. Chlorpyrifos oxon, 3,5,6-trichloro-2-pyridinol, O,O-diethyl O-hydrogen phosphorothioate, O,O-diethyl ester thiophosphoric acid, diethyl hydrogen phosphate and a phosphinyl disulfide compound were identified as the main degradation products. The heterogeneous reaction pathways were proposed and their kinetic processes were investigated via a mixed-phase relative rate method. The observed effective rate constant is 3.4 ± 0.2 × 10-12 cm3 molecule-1 s-1.

Possibility of using sources of vacuum ultraviolet irradiation to solve problems of space material science

NASA Technical Reports Server (NTRS)

Verkhoutseva, E. T.; Yaremenko, E. I.

1974-01-01

An urgent problem in space materials science is simulating the interaction of vacuum ultraviolet (VUV) of solar emission with solids in space conditions, that is, producing a light source with a distribution that approximates the distribution of solar energy. Information is presented on the distribution of the energy flux of VUV of solar radiation. Requirements that must be satisfied by the VUV source used for space materials science are formulated, and a critical evaluation is given of the possibilities of using existing sources for space materials science. From this evaluation it was established that none of the sources of VUV satisfies the specific requirements imposed on the simulator of solar radiation. A solution to the problem was found to be in the development of a new type of source based on exciting a supersonic gas jet flowing into vacuum with a sense electron beam. A description of this gas-jet source, along with its spectral and operation characteristics, is presented.

Effect of vacuum-ultraviolet irradiation on the dielectric constant of low-k organosilicate dielectrics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, H.; Shohet, J. L.; Ryan, E. T.

2014-11-17

Vacuum ultraviolet (VUV) irradiation is generated during plasma processing in semiconductor fabrications, while the effect of VUV irradiation on the dielectric constant (k value) of low-k materials is still an open question. To clarify this problem, VUV photons with a range of energies were exposed on low-k organosilicate dielectrics (SiCOH) samples at room temperature. Photon energies equal to or larger than 6.0 eV were found to decrease the k value of SiCOH films. VUV photons with lower energies do not have this effect. This shows the need for thermal heating in traditional ultraviolet (UV) curing since UV light sources do notmore » have sufficient energy to change the dielectric constant of SiCOH and additional energy is required from thermal heating. In addition, 6.2 eV photon irradiation was found to be the most effective in decreasing the dielectric constant of low-k organosilicate films. Fourier Transform Infra-red Spectroscopy shows that these 6.2 eV VUV exposures removed organic porogens. This contributes to the decrease of the dielectric constant. This information provides the range of VUV photon energies that could decrease the dielectric constant of low-k materials most effectively.« less

Vacuum ultraviolet radiation/atomic oxygen synergism in materials reactivity

NASA Technical Reports Server (NTRS)

Koontz, Steven; Leger, Lubert; Albyn, Keith; Cross, Jon

1990-01-01

Experimental results are presented which indicate that low fluxes of vacuum UV (VUV) radiation exert a pronounced influence on the atomic oxygen reactivity of such fluorocarbon and fluorocarbon spacecraft materials as the FEP Teflon and PCTFE that are under consideration for the Space Station Freedom. With simultaneous exposure to VUV fluxes comparable to those experienced in LEO, the reactivity of these materials becomes comparable to that of Kapton; VUV radiation has also been shown to increase the reactivity of Kapton with thermal-energy oxygen atoms.

Printable Top-Gate-Type Polymer Light-Emitting Transistors with Surfaces of Amorphous Fluoropolymer Insulators Modified by Vacuum Ultraviolet Light Treatment

NASA Astrophysics Data System (ADS)

Kajii, Hirotake; Terashima, Daiki; Kusumoto, Yusuke; Ikezoe, Ikuya; Ohmori, Yutaka

2013-04-01

We investigated the fabrication and electrical and optical properties of top-gate-type polymer light-emitting transistors with the surfaces of amorphous fluoropolymer insulators, CYTOP (Asahi Glass) modified by vacuum ultraviolet light (VUV) treatment. The surface energy of CYTOP, which has a good solution barrier property was increased by VUV irradiation, and the gate electrode was fabricated by solution processing on the CYTOP film using the Ag nano-ink. The influence of VUV irradiation on the optical properties of poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) films with various gate insulators was investigated to clarify the passivation effect of gate insulators. It was found that the poly(methyl methacrylate) (PMMA) film prevented the degradation of the F8BT layer under VUV irradiation because the PMMA film can absorb VUV. The solution-processed F8BT device with multilayer PMMA/CYTOP insulators utilizing a gate electrode fabricated using the Ag nano-ink exhibited both the ambipolar characteristics and yellow-green emission.

Is vacuum ultraviolet detector a concentration or a mass dependent detector?

PubMed

Liu, Huian; Raffin, Guy; Trutt, Guillaume; Randon, Jérôme

2017-12-29

The vacuum ultraviolet detector (VUV) is a very effective tool for chromatogram deconvolution and peak identification, and can also be used for quantification. To avoid quantitative issues in relation to time drift, such as variation of peak area or peak height, the detector response type has to be well defined. Due to the make-up flow and pressure regulation of make-up, the detector response (height of the peak) and peak area appeared to be dependent on experimental conditions such as inlet pressure and make-up pressure. Even if for some experimental conditions, VUV looks like mass-flow sensitive detector, it has been demonstrated that VUV is a concentration sensitive detector. Copyright © 2017 Elsevier B.V. All rights reserved.

Vacuum Ultraviolet (VUV) radiation-induced degradation of Fluorinated Ethylene Propylene (FEP) Teflon aboard the Long Duration Exposure Facility (LDEF)

NASA Technical Reports Server (NTRS)

Brinza, David E.; Stiegman, A. E.; Staszak, Paul R.; Laue, Eric G.; Liang, Ranty H.

1992-01-01

Examination of fluorinated ethylene propylene (FEP) copolymer specimens recovered from the Long Duration Exposure Facility (LDEF) provides evidence for degradation attributed to extended solar vacuum ultraviolet (VUV) irradiation. Scanning electron microscope (SEM) images of sheared FEP film edges reveal the presence of a highly embrittled layer on the exposed surface of specimens obtained from the trailing edge of the LDEF. Similar images obtained for leading edge and control FEP films do not exhibit evidence for such an embrittled layer. Laboratory VUV irradiation of FEP films is found to produce a damage layer similar to that witnessed in the LDEF trailing edge films. Spectroscopic analyses of irradiated films provide data to advance a photochemical mechanism for degradation.

Gas chromatography-vacuum ultraviolet spectroscopy for analysis of fatty acid methyl esters.

PubMed

Fan, Hui; Smuts, Jonathan; Bai, Ling; Walsh, Phillip; Armstrong, Daniel W; Schug, Kevin A

2016-03-01

A new vacuum ultraviolet (VUV) detector for gas chromatography was recently developed and applied to fatty acid methyl ester (FAME) analysis. VUV detection features full spectral acquisition in a wavelength range of 115-240nm, where virtually all chemical species absorb. VUV absorption spectra of 37 FAMEs, including saturated, monounsaturated, and polyunsaturated types were recorded. Unsaturated FAMEs show significantly different gas phase absorption profiles than saturated ones, and these classes can be easily distinguished with the VUV detector. Another advantage includes differentiating cis/trans-isomeric FAMEs (e.g. oleic acid methyl ester and linoleic acid methyl ester isomers) and the ability to use VUV data analysis software for deconvolution of co-eluting signals. As a universal detector, VUV also provides high specificity, sensitivity, and a fast data acquisition rate, making it a powerful tool for fatty acid screening when combined with gas chromatography. The fatty acid profile of several food oil samples (olive, canola, vegetable, corn, sunflower and peanut oils) were analyzed in this study to demonstrate applicability to real world samples. Copyright © 2015 Elsevier Ltd. All rights reserved.

CIV VUV FPI Interferometer for Transition Region Magnetography

NASA Technical Reports Server (NTRS)

Gary, G. A.

2005-01-01

Much in the same way photonics harnesses light for engineering and technology applications, solar physics harnesses light for the remote sensing of the sun. In photonics the vacuum ultraviolet region offers shorter wavelength and higher energies per photon, while in solar physics the VUV allows the remote sensing of the upper levels of the solar atmosphere where magnetic fields dominate the physics. Understanding solar magnetism is a major aim for astrophysics and for understanding solar-terrestrial interaction. The poster is on our instrument development program for a high-spectral-resolution, high-finesse, Vacuum Ultraviolet Fabry-Perot Interferometer (VUV FPI) for obtaining narrow-passband images, magnetograms, and Dopplergrams of the transition region emission line of CIV (155nm). The poster will cover how the V W interferometer will allow us to understand solar magnetism, what is special about the MSFC VUV FPI, and why the University of Toronto F2 eximer has been of particular value to this program.

Vacuum ultraviolet and infrared spectra of condensed methyl acetate on cold astrochemical dust analogs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sivaraman, B.; Nair, B. G.; Mason, N. J.

2013-12-01

Following the recent report of the first identification of methyl acetate (CH{sub 3}COOCH{sub 3}) in the interstellar medium (ISM), we have carried out vacuum ultraviolet (VUV) and infrared (IR) spectroscopy studies on methyl acetate from 10 K until sublimation in an ultrahigh vacuum chamber simulating astrochemical conditions. We present the first VUV and IR spectra of methyl acetate relevant to ISM conditions. Spectral signatures clearly showed molecular reorientation to have started in the ice by annealing the amorphous ice formed at 10 K. An irreversible phase change from amorphous to crystalline methyl acetate ice was found to occur between 110more » K and 120 K.« less

Products and kinetics of the heterogeneous reaction of suspended vinclozolin particles with ozone.

PubMed

Gan, Jie; Yang, Bo; Zhang, Yang; Shu, Xi; Liu, Changgeng; Shu, Jinian

2010-11-25

Vinclozolin is a widely used fungicide that can be released into the atmosphere via application and volatilization. This paper reports an experimental investigation on the heterogeneous ozonation of vinclozolin particles. The ozonation of vinclozolin adsorbed on azelaic acid particles under pseudo-first-order conditions is investigated online with a vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS). The ozonation products are analyzed with a combination of VUV-ATOFMS and GC/MS. Two main ozonation products are observed. The formation of the ozonation products results from addition of O(3) on the C-C double bond of the vinyl group. The heterogeneous reactive rate constant of vinclozolin particles under room temperature is (2.4 ± 0.4) × 10(-17) cm(3) molecules(-1) s(-1), with a corresponding lifetime at 100 ppbv O(3) of 4.3 ± 0.7 h, which is almost comparable with the estimated lifetime due to the reaction with atmospheric OH radicals (∼1.7 h). The reactive uptake coefficient for O(3) on vinclozolin particles is (6.1 ± 1.0) × 10(-4).

Uncovering Highly-Excited State Mixing in Acetone Using Ultrafast VUV Pulses and Coincidence Imaging Techniques

DOE PAGES

Couch, David E.; Kapteyn, Henry C.; Murnane, Margaret M.; ...

2017-03-17

Here, understanding the ultrafast dynamics of highly-excited electronic states of small molecules is critical for a better understanding of atmospheric and astrophysical processes, as well as for designing coherent control strategies for manipulating chemical dynamics. In highly excited states, nonadiabatic coupling, electron-electron interactions, and the high density of states govern dynamics. However, these states are computationally and experimentally challenging to access. Fortunately, new sources of ultrafast vacuum ultraviolet pulses, in combination with electron-ion coincidence spectroscopies, provide new tools to unravel the complex electronic landscape. Here we report time-resolved photoelectron-photoion coincidence experiments using 8 eV pump photons to study the highlymore » excited states of acetone. We uncover for the first time direct evidence that the resulting excited state consists of a mixture of both n y → 3p and π → π* character, which decays with a time constant of 330 fs. In the future, this approach can inform models of VUV photochemistry and aid in designing coherent control strategies for manipulating chemical reactions.« less

Uncovering Highly-Excited State Mixing in Acetone Using Ultrafast VUV Pulses and Coincidence Imaging Techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Couch, David E.; Kapteyn, Henry C.; Murnane, Margaret M.

Here, understanding the ultrafast dynamics of highly-excited electronic states of small molecules is critical for a better understanding of atmospheric and astrophysical processes, as well as for designing coherent control strategies for manipulating chemical dynamics. In highly excited states, nonadiabatic coupling, electron-electron interactions, and the high density of states govern dynamics. However, these states are computationally and experimentally challenging to access. Fortunately, new sources of ultrafast vacuum ultraviolet pulses, in combination with electron-ion coincidence spectroscopies, provide new tools to unravel the complex electronic landscape. Here we report time-resolved photoelectron-photoion coincidence experiments using 8 eV pump photons to study the highlymore » excited states of acetone. We uncover for the first time direct evidence that the resulting excited state consists of a mixture of both n y → 3p and π → π* character, which decays with a time constant of 330 fs. In the future, this approach can inform models of VUV photochemistry and aid in designing coherent control strategies for manipulating chemical reactions.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bréchignac, Philippe, E-mail: philippe.brechignac@u-psud.fr; Falvo, Cyril; Parneix, Pascal

Polycyclic aromatic hydrocarbons (PAHs) are key species encountered in a large variety of environments such as the Interstellar Medium (ISM) and in combustion media. Their UV spectroscopy and photodynamics in neutral and cationic forms are important to investigate in order to learn about their structure, formation mechanisms, and reactivity. Here, we report an experimental photoelectron-photoion coincidence study of a prototypical PAH molecule, coronene, and its small clusters, in a molecular beam using the vacuum ultraviolet (VUV) photons provided by the SOLEIL synchrotron facility. Mass-selected high resolution threshold photoelectron (TPES) and total ion yield spectra were obtained and analyzed in detail.more » Intense series of autoionizing resonances have been characterized as originating from the monomer, dimer, and trimer neutral species, which may be used as spectral fingerprints for their detection in the ISM by VUV absorption spectroscopy. Finally, a full description of the electronic structure of the monomer cation was made and discussed in detail in relation to previous spectroscopic optical absorption data. Tentative vibrational assignments in the near-threshold TPES spectrum of the monomer have been made with the support of a theoretical approach based on density functional theory.« less

VUV PHOTO-PROCESSING OF PAH CATIONS: QUANTITATIVE STUDY ON THE IONIZATION VERSUS FRAGMENTATION PROCESSES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhen, Junfeng; Castillo, Sarah Rodriguez; Joblin, Christine

2016-05-10

Interstellar polycyclic aromatic hydrocarbons (PAHs) are strongly affected by the absorption of vacuum ultraviolet (VUV) photons in the interstellar medium (ISM), yet the branching ratio between ionization and fragmentation is poorly studied. This is crucial for the stability and charge state of PAHs in the ISM in different environments, affecting in turn the chemistry, the energy balance, and the contribution of PAHs to the extinction and emission curves. We studied the interaction of PAH cations with VUV photons in the 7–20 eV range from the synchrotron SOLEIL beamline, DESIRS. We recorded by action spectroscopy the relative intensities of photo-fragmentation andmore » photo-ionization for a set of eight PAH cations ranging in size from 14 to 24 carbon atoms, with different structures. At photon energies below ∼13.6 eV fragmentation dominates for the smaller species, while for larger species ionization is immediately competitive after the second ionization potential (IP). At higher photon energies all species behave similarly; the ionization yield gradually increases, leveling off between 0.8 and 0.9 at ∼18 eV. Among isomers, PAH structure appears to mainly affect the fragmentation cross section but not the ionization cross section. We also measured the second IP for all species and the third IP for two of them; all are in good agreement with theoretical ones, confirming that PAH cations can be further ionized in the diffuse ISM. Determining actual PAH dication abundances in the ISM will require detailed modeling. Our measured photo-ionization yields for several PAH cations provide a necessary ingredient for such models.« less

Research on fluorescence from photoionization, photodissociation, and vacuum, along with bending quantrum study

NASA Technical Reports Server (NTRS)

Judge, D. L.

1975-01-01

Reports of research concerning the fluorescence of CS2 are presented. Fluorescence from fragments of CS2 vapor produced by vacuum ultraviolet radiation, and fluorescence from photoionization of CS2 vapor are discussed along with fluorescence produced by photodissociation of CS2, and fluorescence from photoionization of OCS.

Large area, surface discharge pumped, vacuum ultraviolet light source

DOEpatents

Sze, Robert C.; Quigley, Gerard P.

1996-01-01

Large area, surface discharge pumped, vacuum ultraviolet (VUV) light source. A contamination-free VUV light source having a 225 cm.sup.2 emission area in the 240-340 nm region of the electromagnetic spectrum with an average output power in this band of about 2 J/cm.sup.2 at a wall-plug efficiency of approximately 5% is described. Only ceramics and metal parts are employed in this surface discharge source. Because of the contamination-free, high photon energy and flux, and short pulse characteristics of the source, it is suitable for semiconductor and flat panel display material processing.

CIV Polarization Measurements using a Vacuum Ultraviolet Fabry-Perot Interferometer

NASA Technical Reports Server (NTRS)

West, Edward; Gary, G. Allen; Cirtain, Jonathan; David, John; Kobayashi, Ken; Pietraszewski, Chris

2009-01-01

Marshall Space Flight Center's (MSFC) is developing a Vacuum Ultraviolet (VUV) Fabry-P rot Interferometer that will be launched on a sounding rocket for high throughput, high-cadence, extended field of view CIV (155nm) measurements. These measurements will provide (i) Dopplergrams for studies of waves, oscillations, explosive events, and mass motions through the transition region, and, (ii), polarization measurements to study the magnetic field in the transition region. This paper will describe the scientific goals of the instrument, a brief description of the optics and the polarization characteristics of the VUV Fabry P rot.

Interplanetary survival probability of Aspergillus terreus spores under simulated solar vacuum ultraviolet irradiation

NASA Astrophysics Data System (ADS)

Sarantopoulou, E.; Gomoiu, I.; Kollia, Z.; Cefalas, A. C.

2011-01-01

This work is a part of ESA/EU SURE project aiming to quantify the survival probability of fungal spores in space under solar irradiation in the vacuum ultraviolet (VUV) (110-180 nm) spectral region. The contribution and impact of VUV photons, vacuum, low temperature and their synergies on the survival probability of Aspergillus terreus spores is measured at simulated space conditions on Earth. To simulate the solar VUV irradiation, the spores are irradiated with a continuous discharge VUV hydrogen photon source and a molecular fluorine laser, at low and high photon intensities at 10 15 photon m -2 s -1 and 3.9×10 27 photons pulse -1 m -2 s -1, respectively. The survival probability of spores is independent from the intensity and the fluence of photons, within certain limits, in agreement with previous studies. The spores are shielded from a thin carbon layer, which is formed quickly on the external surface of the proteinaceous membrane at higher photon intensities at the start of the VUV irradiation. Extrapolating the results in space conditions, for an interplanetary direct transfer orbit from Mars to Earth, the spores will be irradiated with 3.3×10 21 solar VUV photons m -2. This photon fluence is equivalent to the irradiation of spores on Earth with 54 laser pulses with an experimental ˜92% survival probability, disregarding the contribution of space vacuum and low temperature, or to continuous solar VUV irradiation for 38 days in space near the Earth with an extrapolated ˜61% survival probability. The experimental results indicate that the damage of spores is mainly from the dehydration stress in vacuum. The high survival probability after 4 days in vacuum (˜34%) is due to the exudation of proteins on the external membrane, thus preventing further dehydration of spores. In addition, the survival probability is increasing to ˜54% at 10 K with 0.12 K/s cooling and heating rates.

Vacuum-ultraviolet lasers and spectroscopy

NASA Astrophysics Data System (ADS)

Hollenstein, U.

2012-01-01

Single-photon ionisation of most atoms and molecules requires short-wavelength radiation, typically in the vacuum-ultraviolet (VUV, λ < 200 nm) or extreme ultraviolet (XUV, λ < 105 nm) region of the electromagnetic spectrum. The first VUV and XUV radiation sources used to study molecular photoabsorption and photoionisation spectra were light sources emitting a broad continuous spectrum, such as high pressure lamps or synchrotrons. Monochromatic VUV and XUV radiation was obtained using diffraction gratings in evacuated monochromators, which resulted in a resolving power ν/Δv of at best 106 (i. e. 0.1 cm-1 at 100 000 cm-1), but more typically in the range 104-105 . The invention of the laser and the development of nonlinear optical frequency-upconversion techniques enabled the development of table-top narrow-bandwidth, coherent VUV and XUV laser sources with which VUV photoabsorption, photoionisation and photoelectron spectra of molecules can be recorded at much higher resolution, the best sources having bandwidths better than 50 MHz. Such laser sources are ideally suited to study the structure and dynamics of electronically excited states of atoms and molecules and molecular photoionisation using photoabsorption, photoionisation and photoelectron spectroscopy. This chapter presents the general principles that are exploited to generate tunable narrow-band laser radiation below 200 nm and describes spectroscopic methods such as photoabsorption spectroscopy, photoionisation spectroscopy and threshold photoelectron spectroscopy that relay on the broad tunability and narrow-bandwidth of VUV radiation sources.

Pyrolysis of the Simplest Carbohydrate, Glycolaldehyde (CHO-CH2OH), and Glyoxal in a Heated Microreactor.

PubMed

Porterfield, Jessica P; Baraban, Joshua H; Troy, Tyler P; Ahmed, Musahid; McCarthy, Michael C; Morgan, Kathleen M; Daily, John W; Nguyen, Thanh Lam; Stanton, John F; Ellison, G Barney

2016-04-14

Both glycolaldehyde and glyoxal were pyrolyzed in a set of flash-pyrolysis microreactors. The pyrolysis products resulting from CHO-CH2OH and HCO-CHO were detected and identified by vacuum ultraviolet (VUV) photoionization mass spectrometry. Complementary product identification was provided by argon matrix infrared absorption spectroscopy. Pyrolysis pressures in the microreactor were about 100 Torr, and contact times with the microreactors were roughly 100 μs. At 1200 K, the products of glycolaldehyde pyrolysis are H atoms, CO, CH2═O, CH2═C═O, and HCO-CHO. Thermal decomposition of HCO-CHO was studied with pulsed 118.2 nm photoionization mass spectrometry and matrix infrared absorption. Under these conditions, glyoxal undergoes pyrolysis to H atoms and CO. Tunable VUV photoionization mass spectrometry provides a lower bound for the ionization energy (IE)(CHO-CH2OH) ≥ 9.95 ± 0.05 eV. The gas-phase heat of formation of glycolaldehyde was established by a sequence of calorimetric experiments. The experimental result is ΔfH298(CHO-CH2OH) = -75.8 ± 1.3 kcal mol(-1). Fully ab initio, coupled cluster calculations predict ΔfH0(CHO-CH2OH) of -73.1 ± 0.5 kcal mol(-1) and ΔfH298(CHO-CH2OH) of -76.1 ± 0.5 kcal mol(-1). The coupled-cluster singles doubles and noniterative triples correction calculations also lead to a revision of the geometry of CHO-CH2OH. We find that the O-H bond length differs substantially from earlier experimental estimates, due to unusual zero-point contributions to the moments of inertia.

Impact of plasma jet vacuum ultraviolet radiation on reactive oxygen species generation in bio-relevant liquids

NASA Astrophysics Data System (ADS)

Jablonowski, H.; Bussiahn, R.; Hammer, M. U.; Weltmann, K.-D.; von Woedtke, Th.; Reuter, S.

2015-12-01

Plasma medicine utilizes the combined interaction of plasma produced reactive components. These are reactive atoms, molecules, ions, metastable species, and radiation. Here, ultraviolet (UV, 100-400 nm) and, in particular, vacuum ultraviolet (VUV, 10-200 nm) radiation generated by an atmospheric pressure argon plasma jet were investigated regarding plasma emission, absorption in a humidified atmosphere and in solutions relevant for plasma medicine. The energy absorption was obtained for simple solutions like distilled water (dH2O) or ultrapure water and sodium chloride (NaCl) solution as well as for more complex ones, for example, Rosewell Park Memorial Institute (RPMI 1640) cell culture media. As moderate stable reactive oxygen species, hydrogen peroxide (H2O2) was studied. Highly reactive oxygen radicals, namely, superoxide anion (O2•-) and hydroxyl radicals (•OH), were investigated by the use of electron paramagnetic resonance spectroscopy. All species amounts were detected for three different treatment cases: Plasma jet generated VUV and UV radiation, plasma jet generated UV radiation without VUV part, and complete plasma jet including all reactive components additionally to VUV and UV radiation. It was found that a considerable amount of radicals are generated by the plasma generated photoemission. From the experiments, estimation on the low hazard potential of plasma generated VUV radiation is discussed.

Vibrational autoionization of state-selective jet-cooled methanethiol (CH 3SH) investigated with infrared + vacuum-ultraviolet photoionization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Min; Shen, Zhitao; Pratt, S. T.

Vibrational autoionization of Rydberg states provides key information about nonadiabatic processes above an ionization threshold. In this work, we employed time-of-flight mass detection of CH 3SH + to record vibrational-state selective photo-ionization efficiency (PIE) spectra of jet-cooled methanethiol (CH 3SH) on exciting CH 3SH to a specific vibrationally excited state with an infrared (IR) laser, followed by excitation with a tunable laser in the vacuum-ultraviolet (VUV) region for ionization. Autoionizing Rydberg states assigned to the ns, np, nd and nf series are identified. When IR light at 2601 (ν 3, SH stretching mode) and 2948 cm -1 (ν 2, CHmore » 3 symmetric stretching mode) was employed, the Rydberg series converged to the respective vibrationally excited (ν 3 and ν 2) states of CH 3SH +. When IR light at 3014 cm -1 (overlapped ν 1/ν 9, CH 3 antisymmetric stretching and CH 2 antisymmetric stretching modes) was employed, Rydberg series converging to two vibrationally excited states (ν 1 and ν 9) of CH 3SH + were observed. When IR light at 2867 cm -1 (2ν 10, overtone of CH 3 deformation mode) and 2892 cm -1 (2ν 4, overtone of CH 2 scissoring mode) was employed, both Δν = -1 and Δν = -2 ionization transitions were observed; there is evidence for direct ionization from the initial state into the CH 3SH + (ν 4 + = 1) continuum. In all observed IR-VUV-PIE spectra, the ns and nd series show intensity greater than the other Rydberg series, which is consistent with the fact that the highest-occupied molecular orbital of CH 3SH is a p-like lone pair orbital on the S atom. Finally, the quantum yields for autoionization of various vibrational excited states are discussed. Values of ν 1 = 3035, ν 2 = 2884, ν 3 = 2514, and ν 9 = 2936 cm -1 for CH 3SH + derived from the converged limits agree satisfactorily with values observed for Ar-tagged CH 3SH + at 3026, 2879, 2502, and 2933 cm -1.« less

Vibrational autoionization of state-selective jet-cooled methanethiol (CH 3SH) investigated with infrared + vacuum-ultraviolet photoionization

DOE PAGES

Xie, Min; Shen, Zhitao; Pratt, S. T.; ...

2017-10-24

Vibrational autoionization of Rydberg states provides key information about nonadiabatic processes above an ionization threshold. In this work, we employed time-of-flight mass detection of CH 3SH + to record vibrational-state selective photo-ionization efficiency (PIE) spectra of jet-cooled methanethiol (CH 3SH) on exciting CH 3SH to a specific vibrationally excited state with an infrared (IR) laser, followed by excitation with a tunable laser in the vacuum-ultraviolet (VUV) region for ionization. Autoionizing Rydberg states assigned to the ns, np, nd and nf series are identified. When IR light at 2601 (ν 3, SH stretching mode) and 2948 cm -1 (ν 2, CHmore » 3 symmetric stretching mode) was employed, the Rydberg series converged to the respective vibrationally excited (ν 3 and ν 2) states of CH 3SH +. When IR light at 3014 cm -1 (overlapped ν 1/ν 9, CH 3 antisymmetric stretching and CH 2 antisymmetric stretching modes) was employed, Rydberg series converging to two vibrationally excited states (ν 1 and ν 9) of CH 3SH + were observed. When IR light at 2867 cm -1 (2ν 10, overtone of CH 3 deformation mode) and 2892 cm -1 (2ν 4, overtone of CH 2 scissoring mode) was employed, both Δν = -1 and Δν = -2 ionization transitions were observed; there is evidence for direct ionization from the initial state into the CH 3SH + (ν 4 + = 1) continuum. In all observed IR-VUV-PIE spectra, the ns and nd series show intensity greater than the other Rydberg series, which is consistent with the fact that the highest-occupied molecular orbital of CH 3SH is a p-like lone pair orbital on the S atom. Finally, the quantum yields for autoionization of various vibrational excited states are discussed. Values of ν 1 = 3035, ν 2 = 2884, ν 3 = 2514, and ν 9 = 2936 cm -1 for CH 3SH + derived from the converged limits agree satisfactorily with values observed for Ar-tagged CH 3SH + at 3026, 2879, 2502, and 2933 cm -1.« less

Competitive fragmentation pathways of acetic acid dimer explored by synchrotron VUV photoionization mass spectrometry and electronic structure calculations.

PubMed

Guan, Jiwen; Hu, Yongjun; Zou, Hao; Cao, Lanlan; Liu, Fuyi; Shan, Xiaobin; Sheng, Liusi

2012-09-28

In present study, photoionization and dissociation of acetic acid dimers have been studied with the synchrotron vacuum ultraviolet photoionization mass spectrometry and theoretical calculations. Besides the intense signal corresponding to protonated cluster ions (CH(3)COOH)(n)·H(+), the feature related to the fragment ions (CH(3)COOH)H(+)·COO (105 amu) via β-carbon-carbon bond cleavage is observed. By scanning photoionization efficiency spectra, appearance energies of the fragments (CH(3)COOH)·H(+) and (CH(3)COOH)H(+)·COO are obtained. With the aid of theoretical calculations, seven fragmentation channels of acetic acid dimer cations were discussed, where five cation isomers of acetic acid dimer are involved. While four of them are found to generate the protonated species, only one of them can dissociate into a C-C bond cleavage product (CH(3)COOH)H(+)·COO. After surmounting the methyl hydrogen-transfer barrier 10.84 ± 0.05 eV, the opening of dissociative channel to produce ions (CH(3)COOH)(+) becomes the most competitive path. When photon energy increases to 12.4 eV, we also found dimer cations can be fragmented and generate new cations (CH(3)COOH)·CH(3)CO(+). Kinetics, thermodynamics, and entropy factors for these competitive dissociation pathways are discussed. The present report provides a clear picture of the photoionization and dissociation processes of the acetic acid dimer in the range of the photon energy 9-15 eV.

Dissociative photoionization of ethyl acrylate: Theoretical and experimental insights

NASA Astrophysics Data System (ADS)

Song, Yanlin; Chen, Jun; Ding, Mengmeng; Wei, Bin; Cao, Maoqi; Shan, Xiaobin; Zhao, Yujie; Huang, Chaoqun; Sheng, Liusi; Liu, Fuyi

2015-08-01

The photoionization and dissociation of ethyl acrylate have been investigated by time-of-flight mass spectrometer with tunable vacuum ultraviolet (VUV) source in the range of 9.0-20.0 eV. The photoionization mass spectrum (PIMS) for ethyl acrylate and photoionization efficiency (PIE) curves for its major fragment ions: C5H7O2+, C4H5O2+, C3H5O2+, C3H4O+, C3H3O+, C2H5O+, C2H3O+, C2H5+ and C2H4+ have been obtained. The formation channels of main fragments are predicted by Gaussian 09 program at G3B3 level and examined via their dissociation energies from experimental results. Based on our analysis, nine main dissociative photoionization channels are proposed: C5H7O2+ + H, C4H5O2+ + CH3, C3H5O2+ + C2H3, C3H4O+ + C2H4O, C3H3O+ + C2H5O, C2H5O+ + C3H3O, C2H3O+ + C3H5O, C2H5+ + C3H3O2, C2H4+ + C3H4O2, respectively. The results of this work lead to a better understanding of photochemistry in the environment.

Attosecond transient absorption of argon atoms in the vacuum ultraviolet region: line energy shifts versus coherent population transfer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, Wei; Warrick, Erika R.; Neumark, Daniel M.

Using attosecond transient absorption, the dipole response of an argon atom in the vacuum ultraviolet (VUV) region is studied when an external electromagnetic field is present. An isolated attosecond VUV pulse populates Rydberg states lying 15 eV above the argon ground state. A synchronized few-cycle near infrared (NIR) pulse modifies the oscillating dipoles of argon impulsively, leading to alterations in the VUV absorption spectra. As the NIR pulse is delayed with respect to the VUV pulse, multiple features in the absorption profile emerge simultaneously including line broadening, sideband structure, sub-cycle fast modulations, and 5-10 fs slow modulations. These features indicatemore » the coexistence of two general processes of the light-matter interaction: the energy shift of individual atomic levels and coherent population transfer between atomic eigenstates, revealing coherent superpositions. Finally, an intuitive formula is derived to treat both effects in a unifying framework, allowing one to identify and quantify the two processes in a single absorption spectrogram.« less

Attosecond transient absorption of argon atoms in the vacuum ultraviolet region: line energy shifts versus coherent population transfer

NASA Astrophysics Data System (ADS)

Cao, Wei; Warrick, Erika R.; Neumark, Daniel M.; Leone, Stephen R.

2016-01-01

Using attosecond transient absorption, the dipole response of an argon atom in the vacuum ultraviolet (VUV) region is studied when an external electromagnetic field is present. An isolated attosecond VUV pulse populates Rydberg states lying 15 eV above the argon ground state. A synchronized few-cycle near infrared (NIR) pulse modifies the oscillating dipoles of argon impulsively, leading to alterations in the VUV absorption spectra. As the NIR pulse is delayed with respect to the VUV pulse, multiple features in the absorption profile emerge simultaneously including line broadening, sideband structure, sub-cycle fast modulations, and 5-10 fs slow modulations. These features indicate the coexistence of two general processes of the light-matter interaction: the energy shift of individual atomic levels and coherent population transfer between atomic eigenstates, revealing coherent superpositions. An intuitive formula is derived to treat both effects in a unifying framework, allowing one to identify and quantify the two processes in a single absorption spectrogram.

Attosecond transient absorption of argon atoms in the vacuum ultraviolet region: line energy shifts versus coherent population transfer

DOE PAGES

Cao, Wei; Warrick, Erika R.; Neumark, Daniel M.; ...

2016-01-18

Using attosecond transient absorption, the dipole response of an argon atom in the vacuum ultraviolet (VUV) region is studied when an external electromagnetic field is present. An isolated attosecond VUV pulse populates Rydberg states lying 15 eV above the argon ground state. A synchronized few-cycle near infrared (NIR) pulse modifies the oscillating dipoles of argon impulsively, leading to alterations in the VUV absorption spectra. As the NIR pulse is delayed with respect to the VUV pulse, multiple features in the absorption profile emerge simultaneously including line broadening, sideband structure, sub-cycle fast modulations, and 5-10 fs slow modulations. These features indicatemore » the coexistence of two general processes of the light-matter interaction: the energy shift of individual atomic levels and coherent population transfer between atomic eigenstates, revealing coherent superpositions. Finally, an intuitive formula is derived to treat both effects in a unifying framework, allowing one to identify and quantify the two processes in a single absorption spectrogram.« less

Vacuum ultraviolet spectropolarimeter design for precise polarization measurements.

PubMed

Narukage, Noriyuki; Auchère, Frédéric; Ishikawa, Ryohko; Kano, Ryouhei; Tsuneta, Saku; Winebarger, Amy R; Kobayashi, Ken

2015-03-10

Precise polarization measurements in the vacuum ultraviolet (VUV) region provide a new means for inferring weak magnetic fields in the upper atmosphere of the Sun and stars. We propose a VUV spectropolarimeter design ideally suited for this purpose. This design is proposed and adopted for the NASA-JAXA chromospheric lyman-alpha spectropolarimeter (CLASP), which will record the linear polarization (Stokes Q and U) of the hydrogen Lyman-α line (121.567 nm) profile. The expected degree of polarization is on the order of 0.1%. Our spectropolarimeter has two optically symmetric channels to simultaneously measure orthogonal linear polarization states with a single concave diffraction grating that serves both as the spectral dispersion element and beam splitter. This design has a minimal number of reflective components with a high VUV throughput. Consequently, these design features allow us to minimize the polarization errors caused by possible time variation of the VUV flux during the polarization modulation and by statistical photon noise.

Comparison of surface vacuum ultraviolet emissions with resonance level number densities. II. Rare-gas plasmas and Ar-molecular gas mixtures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boffard, John B., E-mail: jboffard@wisc.edu; Lin, Chun C.; Wang, Shicong

2015-03-15

Vacuum ultraviolet (VUV) emissions from excited plasma species can play a variety of roles in processing plasmas, including damaging the surface properties of materials used in semiconductor processing. Depending on their wavelength, VUV photons can easily transmit thin upper dielectric layers and affect the electrical characteristics of the devices. Despite their importance, measuring VUV fluxes is complicated by the fact that few materials transmit at VUV wavelengths, and both detectors and windows are easily damaged by plasma exposure. The authors have previously reported on measuring VUV fluxes in pure argon plasmas by monitoring the concentrations of Ar(3p{sup 5}4s) resonance atomsmore » that produce the VUV emissions using noninvasive optical emission spectroscopy in the visible/near-infrared wavelength range [Boffard et al., J. Vac. Sci. Technol., A 32, 021304 (2014)]. Here, the authors extend this technique to other rare-gases (Ne, Kr, and Xe) and argon-molecular gas plasmas (Ar/H{sub 2}, Ar/O{sub 2}, and Ar/N{sub 2}). Results of a model for VUV emissions that couples radiation trapping and the measured rare-gas resonance level densities are compared to measurements made with both a calibrated VUV photodiode and a sodium salicylate fluorescence detection scheme. In these more complicated gas mixtures, VUV emissions from a variety of sources beyond the principal resonance levels of the rare gases are found to contribute to the total VUV flux.« less

Vacuum ultraviolet images of the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Smith, Andrew M.; Cornett, Robert H.; Hill, Robert S.

1987-09-01

Images with 50arcsec resolution of the Large Magellanic Cloud (LMC), obtained with sounding-rocket instrumentation in two vacuum ultraviolet (VUV) bandpasses, are presented. The bandpasses are each ≡200 Å wide and are centered, for hot stars, near 1500 Å and 1900 Å. Photometry was done on the digitized images for all associations in the list of Lucke and Hodge. The authors discuss the results and their relationship to the overall characteristics of star formation in the LMC. They present a simple model for propagating star formation in the LMC whose results closely resemble the distribution of associations as revealed by VUV images.

Generation of vacuum ultraviolet radiation by intracavity high-harmonic generation toward state detection of single trapped ions

NASA Astrophysics Data System (ADS)

Wakui, Kentaro; Hayasaka, Kazuhiro; Ido, Tetsuya

2014-12-01

Vacuum ultraviolet (VUV) radiation around 159 nm is obtained toward direct excitation of a single trapped ion. An efficient fluoride-based VUV output coupler is employed for intracavity high-harmonic generation of a Ti:S oscillator. Using this coupler, where we measured its reflectance to be about 90 %, an average power reaching 6.4 W is coupled out from a modest fundamental power of 650 mW. When a single comb component out of 1.9 10 teeth is resonant to the atomic transition, 100s of fluorescence photons per second will be detectable under a realistic condition.

Large area, surface discharge pumped, vacuum ultraviolet light source

DOEpatents

Sze, R.C.; Quigley, G.P.

1996-12-17

Large area, surface discharge pumped, vacuum ultraviolet (VUV) light source is disclosed. A contamination-free VUV light source having a 225 cm{sup 2} emission area in the 240-340 nm region of the electromagnetic spectrum with an average output power in this band of about 2 J/cm{sup 2} at a wall-plug efficiency of approximately 5% is described. Only ceramics and metal parts are employed in this surface discharge source. Because of the contamination-free, high photon energy and flux, and short pulse characteristics of the source, it is suitable for semiconductor and flat panel display material processing. 3 figs.

Time resolved 3D momentum imaging of ultrafast dynamics by coherent VUV-XUV radiation

DOE PAGES

Sturm, F. P.; Wright, T. W.; Ray, D.; ...

2016-06-14

Have we present a new experimental setup for measuring ultrafast nuclear and electron dynamics of molecules after photo-excitation and ionization. We combine a high flux femtosecond vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) source with an internally cold molecular beam and a 3D momentum imaging particle spectrometer to measure electrons and ions in coincidence. We describe a variety of tools developed to perform pump-probe studies in the VUV-XUV spectrum and to modify and characterize the photon beam. First benchmark experiments are presented to demonstrate the capabilities of the system.

Single photon ionization and chemical ionization combined ion source based on a vacuum ultraviolet lamp for orthogonal acceleration time-of-flight mass spectrometry.

PubMed

Hua, Lei; Wu, Qinghao; Hou, Keyong; Cui, Huapeng; Chen, Ping; Wang, Weiguo; Li, Jinghua; Li, Haiyang

2011-07-01

A novel combined ion source based on a vacuum ultraviolet (VUV) lamp with both single photon ionization (SPI) and chemical ionization (CI) capabilities has been developed for an orthogonal acceleration time-of-flight mass spectrometer (oaTOFMS). The SPI was accomplished using a commercial 10.6 eV krypton discharge lamp with a photon flux of about 10(11) photons s(-1), while the CI was achieved through ion-molecule reactions with O(2)(+) reactant ions generated by photoelectron ionization at medium vacuum pressure (MVP). To achieve high ionization efficiency, the ion source pressure was elevated to 0.3 mbar and the photoionization length was extended to 36 mm. As a result, limits of detection (LODs) down to 3, 4, and 6 ppbv were obtained for benzene, toluene, and p-xylene in MVP-SPI mode, and values of 8 and 10 ppbv were obtained for toluene and chloroform, respectively, in SPI-CI mode. As it is feasible to switch between MVP-SPI mode and SPI-CI mode rapidly, this system is capable of monitoring complex organic mixtures with a wide range of ionization energies (IEs). The analytical capacity of this system was demonstrated by measuring dehydrogenation products of long-chain paraffins to olefins through direct capillary sampling and drinking water disinfection byproducts from chlorine through a membrane interface.

Polarization selection rules and optical transitions in terbium activated yttrium tantalate phosphor under x-ray, vacuum-ultraviolet, and ultraviolet excitations.

PubMed

Nazarov, Mihail; Tsukerblat, Boris; Byeon, Clare Chisu; Arellano, Ivan; Popovici, Elisabeth-Jeanne; Noh, Do Young

2009-01-01

The terbium-activated yttrium tantalite (YTaO(4):Tb(3+)) phosphor is of great interest due to the interesting spectroscopic properties of rare earth ions in crystals and also practical use in x-ray imaging. Using the group-theoretical approach, we analyze the selection rules for the transition between Stark components of Tb(3+) in symmetry of the actual crystal field and the polarization for the allowed transitions. The luminescence upon UV, vacuum-ultraviolet (VUV), and x-ray excitation is presented and discussed. The YTaO(4):Tb(3+) phosphors are found to be efficient VUV-excited luminescent materials that could be used not only in x-ray intensifying screens, but also in mercury-free fluorescent lamps or plasma display panels.

Impact of plasma jet vacuum ultraviolet radiation on reactive oxygen species generation in bio-relevant liquids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jablonowski, H.; Hammer, M. U.; Reuter, S.

Plasma medicine utilizes the combined interaction of plasma produced reactive components. These are reactive atoms, molecules, ions, metastable species, and radiation. Here, ultraviolet (UV, 100–400 nm) and, in particular, vacuum ultraviolet (VUV, 10–200 nm) radiation generated by an atmospheric pressure argon plasma jet were investigated regarding plasma emission, absorption in a humidified atmosphere and in solutions relevant for plasma medicine. The energy absorption was obtained for simple solutions like distilled water (dH{sub 2}O) or ultrapure water and sodium chloride (NaCl) solution as well as for more complex ones, for example, Rosewell Park Memorial Institute (RPMI 1640) cell culture media. As moderate stablemore » reactive oxygen species, hydrogen peroxide (H{sub 2}O{sub 2}) was studied. Highly reactive oxygen radicals, namely, superoxide anion (O{sub 2}{sup •−}) and hydroxyl radicals ({sup •}OH), were investigated by the use of electron paramagnetic resonance spectroscopy. All species amounts were detected for three different treatment cases: Plasma jet generated VUV and UV radiation, plasma jet generated UV radiation without VUV part, and complete plasma jet including all reactive components additionally to VUV and UV radiation. It was found that a considerable amount of radicals are generated by the plasma generated photoemission. From the experiments, estimation on the low hazard potential of plasma generated VUV radiation is discussed.« less

Vacuum ultraviolet trimming of oxygenated functional groups from oxidized self-assembled hexadecyl monolayers in an evacuated environment

NASA Astrophysics Data System (ADS)

Soliman, Ahmed I. A.; Utsunomiya, Toru; Ichii, Takashi; Sugimura, Hiroyuki

2017-09-01

Vacuum ultraviolet light irradiation in dry air generates active oxygen species, which have powerful oxidation abilities. These active oxygen species (O) can oxidize the alkyl moieties of polymers, and generate new oxygenated groups such as OH, CHO and COOH groups. Reducing the oxygen content in the exposure environment decreases the rate of oxidation processes. In this study, we examined the influences of the 172 nm VUV irradiation in a high vacuum (HV, < 10-3 Pa) environment on the chemical constituents, surface properties and morphological structure of well-defined VUV/(O)-modified hexadecyl (HD-) self-assembled monolayer (SAM) prepared on hydrogen-terminated silicon (H-Si) substrate. After VUV light irradiation in a HV environment (HV-VUV), the chemical constituents and surface properties were changed in two distinct stages. At short irradiation time (the first stage), the Csbnd O and COO groups decreased rapidly, while the Cdbnd O groups slightly changed. The dissociation of nonderivatizable groups (such as ether (Csbnd Osbnd C) and ester (Csbnd COOsbnd C) groups) compensated the dissociated OH, CHO, Csbnd COsbnd C and COOH groups. With further irradiation (the second stage), the quantities of the oxygenated groups slightly decreased. The carbon skeleton (Csbnd C) of SAM was scarcely dissociated during the HV-VUV treatment. These chemical changes affected the surface properties, such as wettability and morphology.

Birefringence of magnesium fluoride in the vacuum ultraviolet and application to a half-waveplate.

PubMed

Ishikawa, Ryohko; Kano, Ryouhei; Bando, Takamasa; Suematsu, Yoshinori; Ishikawa, Shin-nosuke; Kubo, Masahito; Narukage, Noriyuki; Hara, Hirohisa; Tsuneta, Saku; Watanabe, Hiroko; Ichimoto, Kiyoshi; Aoki, Kunichika; Miyagawa, Kenta

2013-12-01

Spectro-polarimeteric observations in the vacuum-ultraviolet (VUV) region are expected to be developed as a new astrophysics diagnostic tool for investigating space plasmas with temperatures of >10(4)  K. Precise measurements of the difference in the extraordinary and ordinary refractive indices are required for developing accurate polarimeters, but reliable information on the birefringence in the VUV range is difficult to obtain. We have measured the birefringence of magnesium fluoride (MgF2) with an accuracy of better than ±4×10(-5) around the hydrogen Lyman-α line (121.57 nm). We show that MgF2 can be applied practically as a half-waveplate for the chromospheric Lyman-alpha spectro-polarimeter (CLASP) sounding rocket experiment and that the developed measurement method can be easily applied to other VUV birefringent materials at other wavelengths.

Carrier Conduction and Light Emission by Modification of Poly(alkylfluorene) Interface under Vacuum Ultraviolet Light Irradiation

NASA Astrophysics Data System (ADS)

Ohmori, Yutaka; Kajii, Hirotake; Terashima, Daiki; Kusumoto, Yusuke

2013-03-01

Organic field effect transistors (OFETs) have been extensively studied for flexible electronics. The characteristics of poly(9,9-dioctylfluorenyl-2,7-dyl) (F8) modified by thermal or light are strongly dependent on the carrier transport and optical characteristics. We investigate all solution-processed OFETs with Ag nano-ink as gate electrodes patterned by Vacuum Ultraviolet (VUV) (172 nm). Bi-layer gate insulators of amorphous fluoro-polymer CYTOP (Asahi Glass Corp.) and poly(methylmethacrylate) (PMMA) were used. Top-gate-type OFETs with ITO source/drain electrode utilizing F8 or poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) as an active layer were fabricated, and investigated the carrier conduction and emission characteristic. Without VUV irradiation, both OFETs showed the ambipolar and light-emitting characteristics. On the other hand, F8 devices with VUV exhibited only p-type conduction. The quenching centers were generated in F8 layer by VUV irradiation, which are related to the electron trap sites at the interface. OFETs with F8BT showed both p- and n-type conduction even after VUV. F8BT suffers less damage by VUV and maintain light emission. Light emitting transistors were realized utilizing F8BT patterned by VUV irradiation. This research was partially supported financially by MEXT. The authors thank Harima Chemicals Inc. for providing Ag nano-ink.

AMS+ALS: Kinetic and Product Studies of the Heterogeneous Oxidation of Organic Aerosol at the Advanced Light Source

NASA Astrophysics Data System (ADS)

Kroll, J. H.; Wilson, K. R.; Kessler, S. H.; Browne, E. C.; Nah, T.; Smith, J.; Worsnop, D. R.

2014-12-01

The atmospheric oxidation of condensed-phase organic species can have a major influence on the composition, properties, and impacts of organic aerosol (OA); however the rates and products of such "aging" reactions are poorly constrained. Here we describe a series of laboratory experiments aimed at better understanding one class of aging reactions, the heterogeneous oxidation of OA by gas-phase oxidants. Central to these experiments is the availability of vacuum ultraviolet (VUV) light at the Chemical Dynamics Beamline of the Advanced Light Source at LBNL, which enables the implementation of VUV photoionization aerosol mass spectrometry. This technique allows for the real-time, speciated measurement of OA composition, yielding molecular information that is highly complementary to ensemble data from electron-impact ionization. OA composition is measured with both ionization schemes as a function of oxidant exposure within a flow reactor, providing detailed information on the kinetics and products of heterogeneous oxidation over multiple generations of oxidation. Specific topics investigated include the branching between functionalization and fragmentation of OA components, the formation of secondary organic aerosol from photolytically-generated radical species, and the heterogeneous aging of soot-associated organic species.

Synergistic damage effects of vacuum ultraviolet photons and O2 in SiCOH ultra-low-k dielectric films

NASA Astrophysics Data System (ADS)

Lee, J.; Graves, D. B.

2010-10-01

Damage incurred during plasma processing, leading to increases in dielectric constant k, is a persistent problem with porous ultra-low-k dielectric films, such as SiCOH. Although most of the proposed mechanisms of plasma-induced damage focus on the role of ion bombardment and radical attack, we show that plasma-generated vacuum ultraviolet (VUV) photons can play a role in creating damage leading to increases in the dielectric constant of this material. Using a vacuum beam apparatus with a calibrated VUV lamp, we show that 147 nm VUV photons impacting SiCOH results in post-exposure adsorption and reaction with water vapour from the atmosphere to form silanol bonds, thereby raising the dielectric constant. Furthermore, the level of damage increases synergistically under simultaneous exposure to VUV photons and O2. The vacuum beam photon fluences are representative of typical plasma processes, as measured in a separate plasma tool. Fourier-transform infrared (FTIR) spectroscopy (ex situ) and mass spectrometry (in situ) imply that O2 reacts with methyl radicals formed from scissioned Si-C bonds to create CO2 and H2O, the latter combining with Si dangling bonds to generate more SiOH groups than with photon exposure alone. In addition, sample near-surface diffusivity, manipulated through ion bombardment and sample heating, can be seen to affect this process. These results demonstrate that VUV photo-generated surface reactions can be potent contributors to ultra-low-k dielectric SiCOH film plasma-induced damage, and suggest that they could play analogous roles in other plasma-surface interactions.

Radiative lifetimes in B I using ultraviolet and vacuum-ultraviolet laser-induced fluorescence

NASA Technical Reports Server (NTRS)

O'Brian, T. R.; Lawler, J. E.

1992-01-01

Radiative lifetimes of the eight lowest even parity levels in the doublet system of B I are measured using time-resolved laser-induced fluorescence in the UV and VUV on an atomic beam of boron. The accurate lifetimes provide a base for improved determination of absolute transition probabilities in B I. The techniques described are broadly applicable to measurement of lifetimes of levels with transitions in the visible, UV, and VUV in almost any element.

Nonequilibrium Stagnation-Line Radiative Heating for Fire II

NASA Technical Reports Server (NTRS)

Johnston, Christopher O.; Hollis, Brian R.; Sutton, Kenneth

2007-01-01

This paper presents a detailed analysis of the shock-layer radiative heating to the Fire II vehicle using a new air radiation model and a viscous shock-layer flowfield model. This new air radiation model contains the most up-to-date properties for modeling the atomic-line, atomic photoionization, molecular band, and non-Boltzmann processes. The applied viscous shock-layer flowfield analysis contains the same thermophysical properties and nonequilibrium models as the LAURA Navier-Stokes code. Radiation-flowfield coupling, or radiation cooling, is accounted for in detail in this study. It is shown to reduce the radiative heating by about 30% for the peak radiative heating points, while reducing the convective heating only slightly. A detailed review of past Fire II radiative heating studies is presented. It is observed that the scatter in the radiation predicted by these past studies is mostly a result of the different flowfield chemistry models and the treatment of the electronic state populations. The present predictions provide, on average throughout the trajectory, a better comparison with Fire II flight data than any previous study. The magnitude of the vacuum ultraviolet (VUV) contribution to the radiative flux is estimated from the calorimeter measurements. This is achieved using the radiometer measurements and the predicted convective heating. The VUV radiation predicted by the present model agrees well with the VUV contribution inferred from the Fire II calorimeter measurement, although only when radiation-flowfield coupling is accounted for. This agreement provides evidence that the present model accurately models the VUV radiation, which is shown to contribute significantly to the Fire II radiative heating.

Time-dependent dielectric breakdown of plasma-exposed porous organosilicate glass

NASA Astrophysics Data System (ADS)

Nichols, M. T.; Sinha, H.; Wiltbank, C. A.; Antonelli, G. A.; Nishi, Y.; Shohet, J. L.

2012-03-01

Time-dependent dielectric breakdown (TDDB) is a major concern for low-k organosilicate dielectrics. To examine the effect of plasma exposure on TDDB degradation, time-to-breakdown measurements were made on porous SiCOH before and after exposure to plasma. A capillary-array window was used to separate charged particle and vacuum ultraviolet (VUV) photon bombardment. Samples exposed to VUV photons, and a combination of VUV photons and ion bombardment exhibited significant degradation in breakdown time. The samples exposed to VUV photons and ion bombardment showed more degradation in breakdown time in comparison to samples exposed to VUV photons alone.

Vacuum ultraviolet radiation/atomic oxygen synergism in fluorinated ethylene propylene Teflon erosion

NASA Technical Reports Server (NTRS)

Stiegman, A. E.; Brinza, David E.; Laue, Eric G.; Anderson, Mark S.; Liang, Ranty H.

1992-01-01

A micrographic investigation is reported of samples of the fluorinated ethylene propylene (FEP) Teflon thermal-blanketing materials recovered from the Long-Duration Exposure Facility (LDEF) satellite. The samples are taken from the trailing edge and row 8 which correspond to exposures to vacuum UV (VUV) and VUV + atomic O, respectively. Data are taken from SEM and IR-spectra observations, and the LDEF leading-edge FEP shows a high degree of erosion, roughening, and sharp peaks angled in the direction of the flow of atomic O. The trailing edge sample influenced primarily by VUV shows a hard brittle layer and some cracked mosaic patterns. Comparisons to a reference sample suggest that the brittle layer is related to exposure to VUV and is removed by atomic-O impingement. Polymers that are stable to VUV radiation appear to be more stable in terms of atomic oxygen.

An experimental and kinetic investigation of premixed furan/oxygen/argon flames

PubMed Central

Tian, Zhenyu; Yuan, Tao; Fournet, Rene; Glaude, Pierre-Alexandre; Sirjean, Baptiste; Battin-Leclerc, Frédérique; Zhang, Kuiwen; Qi, Fei

2013-01-01

The detailed chemical structures of three low-pressure (35 Torr) premixed laminar furan/oxygen/argon flames with equivalence ratios of 1.4, 1.8 and 2.2 have been investigated by using tunable synchrotron vacuum ultraviolet (VUV) photoionization and molecular-beam mass spectrometry. About 40 combustion species including hydrocarbons and oxygenated intermediates have been identified by measurements of photoionization efficiency spectra. Mole fraction profiles of the flame species including reactants, intermediates and products have been determined by scanning burner position with some selected photon energies near ionization thresholds. Flame temperatures have been measured by a Pt-6%Rh/Pt-30%Rh thermocouple. A new mechanism involving 206 species and 1368 reactions has been proposed whose predictions are in reasonable agreement with measured species profiles for the three investigated flames. Rate-of-production and sensitivity analyses have been performed to track the key reaction paths governing furan consumption for different equivalence ratios. Both experimental and modeling results indicate that few aromatics could be formed in these flames. Furthermore, the current model has been validated against previous pyrolysis results of the literature obtained behind shock waves and the agreement is reasonable as well. PMID:23814311

An experimental and kinetic investigation of premixed furan/oxygen/argon flames.

PubMed

Tian, Zhenyu; Yuan, Tao; Fournet, Rene; Glaude, Pierre-Alexandre; Sirjean, Baptiste; Battin-Leclerc, Frédérique; Zhang, Kuiwen; Qi, Fei

2011-04-01

The detailed chemical structures of three low-pressure (35 Torr) premixed laminar furan/oxygen/argon flames with equivalence ratios of 1.4, 1.8 and 2.2 have been investigated by using tunable synchrotron vacuum ultraviolet (VUV) photoionization and molecular-beam mass spectrometry. About 40 combustion species including hydrocarbons and oxygenated intermediates have been identified by measurements of photoionization efficiency spectra. Mole fraction profiles of the flame species including reactants, intermediates and products have been determined by scanning burner position with some selected photon energies near ionization thresholds. Flame temperatures have been measured by a Pt-6%Rh/Pt-30%Rh thermocouple. A new mechanism involving 206 species and 1368 reactions has been proposed whose predictions are in reasonable agreement with measured species profiles for the three investigated flames. Rate-of-production and sensitivity analyses have been performed to track the key reaction paths governing furan consumption for different equivalence ratios. Both experimental and modeling results indicate that few aromatics could be formed in these flames. Furthermore, the current model has been validated against previous pyrolysis results of the literature obtained behind shock waves and the agreement is reasonable as well.

VUV photodynamics and chiral asymmetry in the photoionization of gas phase alanine enantiomers.

PubMed

Tia, Maurice; Cunha de Miranda, Barbara; Daly, Steven; Gaie-Levrel, François; Garcia, Gustavo A; Nahon, Laurent; Powis, Ivan

2014-04-17

The valence shell photoionization of the simplest proteinaceous chiral amino acid, alanine, is investigated over the vacuum ultraviolet region from its ionization threshold up to 18 eV. Tunable and variable polarization synchrotron radiation was coupled to a double imaging photoelectron/photoion coincidence (i(2)PEPICO) spectrometer to produce mass-selected threshold photoelectron spectra and derive the state-selected fragmentation channels. The photoelectron circular dichroism (PECD), an orbital-sensitive, conformer-dependent chiroptical effect, was also recorded at various photon energies and compared to continuum multiple scattering calculations. Two complementary vaporization methods-aerosol thermodesorption and a resistively heated sample oven coupled to an adiabatic expansion-were applied to promote pure enantiomers of alanine into the gas phase, yielding neutral alanine with different internal energy distributions. A comparison of the photoelectron spectroscopy, fragmentation, and dichroism measured for each of the vaporization methods was rationalized in terms of internal energy and conformer populations and supported by theoretical calculations. The analytical potential of the so-called PECD-PICO detection technique-where the electron spectroscopy and circular dichroism can be obtained as a function of mass and ion translational energy-is underlined and applied to characterize the origin of the various species found in the experimental mass spectra. Finally, the PECD findings are discussed within an astrochemical context, and possible implications regarding the origin of biomolecular asymmetry are identified.

A rapid detection method for policy-sensitive amines real-time supervision.

PubMed

Zhang, Haixu; Shu, Jinian; Yang, Bo; Zhang, Peng; Ma, Pengkun

2018-02-01

Many organic amines that comprise a benzene ring are policy-sensitive because of their toxicity and links to social harm. However, to date, detection of such compounds mainly relies on offline methods. This study proposes an online pptv (parts per trillion by volume) level of detection method for amines, using the recently-built vacuum ultraviolet photoionization mass spectrometer (VUV-PIMS) combined with a new doping technique. Thus, the dichloromethane doping-assisted photoionization mass spectra of aniline, benzylamine, phenethylamine, amphetamine, and their structural isomers were recorded. The dominant characteristic mass peaks for all amines are those afforded by protonated amines and the amino radical-loss. The signal intensities of the amines were enhanced by 60-130 times compared to those recorded without doping assistance. Under 10s detection time, the sensitivities of aniline and benzylamine in the gas phase were determined as 4.0 and 2.7 countspptv -1 , with limits of detection (LODs) of 36 and 22 pptv, respectively. Notably, the detection efficiency of this method can be tenfold better in future applications since the ion transmission efficiency of the mass spectrometer was intentionally reduced to ~ 10% in this study. Therefore, dichloromethane doping-assisted photoionization mass spectrometry has proven to be a highly promising on-line approach to amine detection in environmental and judicial supervision and shows great potential for application in the biological field. Copyright © 2017 Elsevier B.V. All rights reserved.

Devices useful for vacuum ultraviolet beam characterization including a movable stage with a transmission grating and image detector

DOEpatents

Gessner, Oliver; Kornilov, Oleg A; Wilcox, Russell B

2013-10-29

The invention provides for a device comprising an apparatus comprising (a) a transmission grating capable of diffracting a photon beam into a diffracted photon output, and (b) an image detector capable of detecting the diffracted photon output. The device is useful for measuring the spatial profile and diffraction pattern of a photon beam, such as a vacuum ultraviolet (VUV) beam.

Dependence of absolute photon flux on infrared absorbance alteration and surface roughness on photoresist polymers irradiated with vacuum ultraviolet photons emitted from HBr plasma

NASA Astrophysics Data System (ADS)

Zhang, Yan; Takeuchi, Takuya; Ishikawa, Kenji; Hayashi, Toshio; Takeda, Keigo; Sekine, Makoto; Hori, Masaru

2017-12-01

The absolute fluxes of vacuum ultraviolet (VUV) photons emitted from HBr plasma were analyzed and the effects of VUV photons on a photoresist polymer in ArF-excimer-laser (193 nm) lithography were quantitatively investigated on the basis of the infrared spectra attributed to the C=O region. The spectral peak intensity assigned to the methacrylic acid (MAA) in the photoresist drastically decreased owing to the loss of this monomer caused by the irradiation of VUV photons at dosages below 16 × 1016 photons/cm2. X-ray photoelectron spectroscopy observation showed that the removed monomer moved to the surface and generated volatile products that induced a decrease in film thickness. As a consequence, the surface became rough during the early-stage irradiation at dosages lower than 16 × 1016 photons/cm2 owing to the monomer loss of MAA with volatile product formation and subsequent cross-linking reactions.

Outgassing Measurements for Three Materials, Combined with Vacuum Ultraviolet Radiation Illumination of the Volatile Condensable Materials

NASA Technical Reports Server (NTRS)

Albyn, Keith

2005-01-01

The photolysis of three organic materials, by vacuum ultraviolet (VUV) radiation, has been quantified using 15-MHz temperature-controlled quartz microbalances (TQCM's). The rate at which molecular species, released from the individual samples, condensed on two TQCM s was measured for periods of up to 139.9-hours. The individual samples were heated in an effusion cell and the emitted molecular species collected on a pair of TQCM's which were maintained at -40 degrees Celsius. At several points during the deposition measurement, the deposition surface of one TQCM was illuminated by a 30 Watt deuterium lamp, and the loss of material from that surface was observed. V W illumination of the TQCM, concurrent with condensation, reduced the rate that material was lost from the deposition surface. These measurements present a contrasting picture of molecular deposition, in the presence of VUV, to that presented by other investigators who observed an enhanced rate of molecular deposition, when the deposition surface was illuminated by VUV.

VUV and XUV reflectance of optically coated mirrors for selection of high harmonics

DOE PAGES

Larsen, K. A.; Cryan, J. P.; Shivaram, N.; ...

2016-08-08

We report the reflectance, ~1° from normal incidence, of six different mirrors as a function of photon energy, using monochromatic vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) radiation with energies between 7.5 eV and 24.5 eV. The mirrors examined included both single and multilayer optical coatings, as well as an uncoated substrate. Furthermore, we discuss the performance of each mirror, paying particular attention to the potential application of suppression and selection of high-order harmonics of a Ti:sapphire laser.

The efficacy of post porosity plasma protection against vacuum-ultraviolet damage in porous low-k materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lionti, K.; Volksen, W.; Darnon, M.

2015-03-21

As of today, plasma damage remains as one of the main challenges to the reliable integration of porous low-k materials into microelectronic devices at the most aggressive node. One promising strategy to limit damage of porous low-k materials during plasma processing is an approach we refer to as post porosity plasma protection (P4). In this approach, the pores of the low-k material are filled with a sacrificial agent prior to any plasma treatment, greatly minimizing the total damage by limiting the physical interactions between plasma species and the low-k material. Interestingly, the contribution of the individual plasma species to themore » total plasma damage is not fully understood. In this study, we investigated the specific damaging effect of vacuum-ultraviolet (v-UV) photons on a highly porous, k = 2.0 low-k material and we assessed the P4 protective effect against them. It was found that the impact of the v-UV radiation varied depending upon the v-UV emission lines of the plasma. More importantly, we successfully demonstrated that the P4 process provides excellent protection against v-UV damage.« less

Contamination study

NASA Astrophysics Data System (ADS)

Johnson, R. Barry; Herren, Kenneth A.

1990-09-01

The time dependence of the angular reflectance from molecularly contaminated optical surfaces in the Vacuum Ultraviolet (VUV) is measured. The light scattering measurements are accomplished in situ on optical surfaces in real time during deposition of molecular contaminants. The measurements are taken using non-coherent VUV sources with the predominant wavelengths being the Krypton resonance lines at 1236 and 1600 A. Detection of the scattered light is accomplished using a set of three solar blind VUV photomultipliers. An in-plane VUV BRDF (Bidirectional Reflectance Distribution Functions) experiment is described and details of the ongoing program to characterize optical materials exposed to the space environment is reported.

Vacuum ultraviolet photoabsorption of prime ice analogues of Pluto and Charon

NASA Astrophysics Data System (ADS)

Pavithraa, S.; Lo, J.-I.; Rahul, K.; Raja Sekhar, B. N.; Cheng, B.-M.; Mason, N. J.; Sivaraman, B.

2018-02-01

Here we present the first Vacuum UltraViolet (VUV) photoabsorption spectra of ice analogues of Pluto and Charon ice mixtures. For Pluto the ice analogue is an icy mixture containing nitrogen (N2), carbon monoxide (CO), methane (CH4) and water (H2O) prepared with a 100:1:1:3 ratio, respectively. Photoabsorption of icy mixtures with and without H2O were recorded and no significant changes in the spectra due to presence of H2O were observed. For Charon a VUV photoabsorption spectra of an ice analogue containing ammonia (NH3) and H2O prepared with a 1:1 ratio was recorded, a spectrum of ammonium hydroxide (NH4OH) was also recorded. These spectra may help to interpret the P-Alice data from New Horizons.

Modular Heat Dissipation Technique for a CubeSat

DTIC Science & Technology

2015-07-28

Model TVAC Thermal Vacuum Chamber System xv U.S. United States UV Ultraviolet VUV Vacuum Ultraviolet xvi 1 MODULAR HEAT...failure percentage approaches to 50% in university- led missions [Swartwout, 2013]. It can also be deduced from the analysis that on-orbit failures of...simulator is designed to achieve one sun equivalent illumination with three-degree collimation over a 12 in x 12 in area. A 1.6 kW lamp is used for the

Bidirectional Reflectance Function Measurement of Molecular Contaminant Scattering in the Vacuum Ultraviolet

NASA Technical Reports Server (NTRS)

Herren, Kenneth A.; Gregory, Don A.

2006-01-01

Bi-directional reflectance distribution function (BRDF) measurements of optical surfaces both before and after molecular contamination were done using UV, VUV and visible light. Molecular contamination of optical surfaces from outgassed material has been shown in many cases to proceed from acclimation centers, and to produce many roughly hemispherical "islands" of contamination on the surface. Vacuum Ultraviolet (VW) wavelengths are used here to measure angularly scattered light from optical surfaces.

Competitive fragmentation pathways of acetic acid dimer explored by synchrotron VUV photoionization mass spectrometry and electronic structure calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guan Jiwen; Hu Yongjun; Zou Hao

2012-09-28

In present study, photoionization and dissociation of acetic acid dimers have been studied with the synchrotron vacuum ultraviolet photoionization mass spectrometry and theoretical calculations. Besides the intense signal corresponding to protonated cluster ions (CH{sub 3}COOH){sub n}{center_dot}H{sup +}, the feature related to the fragment ions (CH{sub 3}COOH)H{sup +}{center_dot}COO (105 amu) via {beta}-carbon-carbon bond cleavage is observed. By scanning photoionization efficiency spectra, appearance energies of the fragments (CH{sub 3}COOH){center_dot}H{sup +} and (CH{sub 3}COOH)H{sup +}{center_dot}COO are obtained. With the aid of theoretical calculations, seven fragmentation channels of acetic acid dimer cations were discussed, where five cation isomers of acetic acid dimer are involved.more » While four of them are found to generate the protonated species, only one of them can dissociate into a C-C bond cleavage product (CH{sub 3}COOH)H{sup +}{center_dot}COO. After surmounting the methyl hydrogen-transfer barrier 10.84 {+-} 0.05 eV, the opening of dissociative channel to produce ions (CH{sub 3}COOH){sup +} becomes the most competitive path. When photon energy increases to 12.4 eV, we also found dimer cations can be fragmented and generate new cations (CH{sub 3}COOH){center_dot}CH{sub 3}CO{sup +}. Kinetics, thermodynamics, and entropy factors for these competitive dissociation pathways are discussed. The present report provides a clear picture of the photoionization and dissociation processes of the acetic acid dimer in the range of the photon energy 9-15 eV.« less

Nitration of particle-associated PAHs and their derivatives (nitro-, oxy-, and hydroxy-PAHs) with NO 3 radicals

NASA Astrophysics Data System (ADS)

Zhang, Yang; Yang, Bo; Gan, Jie; Liu, Changgeng; Shu, Xi; Shu, Jinian

2011-05-01

The heterogeneous reactions of typical polycyclic aromatic hydrocarbons (PAHs) and their derivatives (nitro-, oxy-, and hydroxy-PAHs) adsorbed on azelaic acid particles with NO 3 radicals are investigated using a flow-tube reactor coupled to a vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS). The mono-nitro-, di-nitro-, and poly-nitro-products from successive nitro-substitution reactions of PAHs and their derivatives are observed in real time with VUV-ATOFMS. 9-Nitroanthracene, anthraquinone, anthrone, 9,10-dinitroanthracene, 2-, 4-, and 9-nitrophenanthrene, 1-nitropyrene, 1,3-, 1,6-, and 1,8-dinitropyrene, 7-nitrobenzo[ a]anthracene, and benzo[ a]anthracene-7,12-dione are identified by GC/MS analysis of the reaction products of PAHs and their derivatives coated on the inner bottom surface of the conical flasks with NO 3 radicals. Other oxygenated products are tentatively assigned. 1-Nitropyrene is the only mono-nitrated product detected in the reaction of surface-bound pyrene with gas-phase NO 3 radicals. This phenomenon is different from what has been observed in previous studies of the gas-phase pyrene nitration, showing that 2-nitropyrene is the sole nitration product. The experimental results may reveal the discrepancies between the heterogeneous and homogeneous nitrations of pyrene.

Degradation of naproxen by UV, VUV photolysis and their combination.

PubMed

Arany, Eszter; Szabó, Rita Katalin; Apáti, László; Alapi, Tünde; Ilisz, István; Mazellier, Patrick; Dombi, András; Gajda-Schrantz, Krisztina

2013-11-15

Naproxen is a widely used nonsteroidal anti-inflammatory drug. Recently, this medicine was detected both in natural waters (up to 1.5 μg L(-1)) and in sewage treatment plant effluents (up to 5.2 μg L(-1)). Moreover, naproxen is only partly eliminated by classical processes used in sewage treatment plants. Therefore, its degradation is of utmost interest. Advanced oxidation processes proved to be the most suitable methods for the elimination of persistent organic contaminants. In this work ultraviolet (UV, 254 nm), vacuum ultraviolet photolysis (VUV, 172 nm) and their combination (UV/VUV, 254/185 nm) were investigated. The efficiency of the methods increased in the following order: UV < VUV < UV/VUV photolysis. However, VUV irradiation was found to mineralize the contaminant molecule most effectively. The chemical structures of three out of four aromatic by-products and of some aliphatic carboxylic acids were presumed. The effects of dissolved O2 and the initial concentration of naproxen on the degradation were also investigated. Copyright © 2013 Elsevier B.V. All rights reserved.

Ultraviolet Communication for Medical Applications

DTIC Science & Technology

2015-06-01

DEI procured several UVC phosphors and tested them with vacuum UV (VUV) excitation. Available emission peaks include: 226 nm, 230 nm, 234 nm, 242...SUPPLEMENTARY NOTES Report contains color. 14. ABSTRACT Under this Phase II SBIR effort, Directed Energy Inc.’s (DEI) proprietary ultraviolet ( UV ...15. SUBJECT TERMS Non-line-of-sight (NLOS), networking, optical communication, plasma-shells, short range, ultraviolet ( UV ) light 16. SECURITY

Photocatalytic pretreatment of oily wastewater from the restaurant by a vacuum ultraviolet/TiO2 system.

PubMed

Kang, Jian-xiong; Lu, Lu; Zhan, Wei; Li, Bo; Li, Dao-sheng; Ren, Yong-zheng; Liu, Dong-qi

2011-02-15

The present study aims at investigating the performance of a vacuum ultraviolet (VUV, 185 nm) and TiO(2) oxidation system for the pretreatment of oily wastewater from restaurant. The influence of irradiation time, pH, dissolved oxygen (DO), the dosage of TiO(2) and the initial chemical oxygen demand (COD) concentration on COD removal efficiency was ascertained and optimum process conditions for stable and effective operation were determined. Under the optimum conditions of irradiation 10 min, initial COD 3981 mg/L, TiO(2) 150 mg/L, pH 7.0 and flow rate of air 40 L/h, the process of VUV and TiO(2)/VUV achieved removal efficiencies of COD, BOD(5) and oil as 50±3%, 37±2%, 86±3%, and 63±3%, 43±2%, 70±3%, respectively. The biodegradability factor f(B) of the wastewater was determined as 1.56 which indicated that the VUV/TiO(2) process improved the biodegradability of the oily wastewater significantly. Results clearly indicate that VUV/TiO(2) photolysis tends to destruct parts of COD, BOD(5), and ammonia, as well as enhances the biodegradability of the oily wastewater simultaneously. Thus, this technique could be used as a pretreatment step for conventional biological treatment of oily wastewater. Copyright © 2010 Elsevier B.V. All rights reserved.

Vacuum ultraviolet detector for gas chromatography.

PubMed

Schug, Kevin A; Sawicki, Ian; Carlton, Doug D; Fan, Hui; McNair, Harold M; Nimmo, John P; Kroll, Peter; Smuts, Jonathan; Walsh, Phillip; Harrison, Dale

2014-08-19

Analytical performance characteristics of a new vacuum ultraviolet (VUV) detector for gas chromatography (GC) are reported. GC-VUV was applied to hydrocarbons, fixed gases, polyaromatic hydrocarbons, fatty acids, pesticides, drugs, and estrogens. Applications were chosen to feature the sensitivity and universal detection capabilities of the VUV detector, especially for cases where mass spectrometry performance has been limited. Virtually all chemical species absorb and have unique gas phase absorption cross sections in the approximately 120-240 nm wavelength range monitored. Spectra are presented, along with the ability to use software for deconvolution of overlapping signals. Some comparisons with experimental synchrotron data and computed theoretical spectra show good agreement, although more work is needed on appropriate computational methods to match the simultaneous broadband electronic and vibronic excitation initiated by the deuterium lamp. Quantitative analysis is governed by Beer-Lambert Law relationships. Mass on-column detection limits reported for representatives of different classes of analytes ranged from 15 (benzene) to 246 pg (water). Linear range measured at peak absorption for benzene was 3-4 orders of magnitude. Importantly, where absorption cross sections are known for analytes, the VUV detector is capable of absolute determination (without calibration) of the number of molecules present in the flow cell in the absence of chemical interferences. This study sets the stage for application of GC-VUV technology across a wide breadth of research areas.

Contamination effects study

NASA Technical Reports Server (NTRS)

1988-01-01

The in-situ optical surface measurement system is a facility designed to study the deleterious effects of particulate materials on the surface reflectivities of optical materials in the vacuum ultraviolet (VUV). This arrangement is designed to simulate the on-orbit effects of contamination and degradation of optical surfaces. This simulation is accomplished through the use of non-coherent VUV sources illuminating optical surfaces located in a high vacuum chamber. Several sources of contamination are employed. The reflectivity is measured both at the specular reflection as well as at two scattered positions, forward and reverse. The system components are described and an operating procedure is given.

A new broadly tunable (7.4-10.2 eV) laser based VUV light source and its first application to aerosol mass spectrometry

NASA Astrophysics Data System (ADS)

Hanna, S. J.; Campuzano-Jost, P.; Simpson, E. A.; Robb, D. B.; Burak, I.; Blades, M. W.; Hepburn, J. W.; Bertram, A. K.

2009-01-01

A laser based vacuum ultraviolet (VUV) light source using resonance enhanced four wave difference mixing in xenon gas was developed for near threshold ionization of organics in atmospheric aerosol particles. The source delivers high intensity pulses of VUV light (in the range of 1010 to 1013 photons/pulse depending on wavelength, 5 ns FWHM) with a continuously tunable wavelength from 122 nm (10.2 eV) to 168 nm (7.4 eV)E The setup allows for tight (<1 mm2) and precise focusing ([mu]rad pointing angle adjustability), attributes required for single particle detection. The generated VUV is separated from the pump wavelengths by a custom monochromator which ensures high spectral purity and minimizes absorptive losses. The performance of the source was characterized using organic molecules in the gas phase and optimal working conditions are reported. In the gas phase measurements, photoionization efficiency (PIE) curves were collected for seven different organic species with ionization energies spanning the full wavelength range of the VUV source. The measured appearance energies are very close to the literature values of the ionization energies for all seven species. The effectiveness of the source for single particle studies was demonstrated by analysis of individual caffeine aerosols vaporized by a pulsed CO2 laser in an ion trap mass spectrometer. Mass spectra from single particles down to 300 nm in diameter were collected. Excellent signal to noise characteristics for these small particles give a caffeine detection limit of 8 × 105 molecules which is equivalent to a single 75 nm aerosol, or approximately 1.5% of a 300 nm particleE The appearance energy of caffeine originating from the aerosol was also measured and found to be 7.91 ± 0.05 eV, in good agreement with literature values.

Recent Advances in Understanding the Reactivity of Energetic Ionic Liquids in Propulsion Applications

DTIC Science & Technology

2014-08-12

vacuum ultraviolet photoionization of catalytically decomposed aerosols of EILs will be discussed. 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION...45 photoionization , fragmentation: thermal decomposition, photoionization : M06/6-31+G(d,p) AE = 10.37 eV Distribution A:  Approved for public... photoionization , fragmentation: thermal decomposition, photoionization : M06/6-31+G(d,p) Distribution A:  Approved for public release; distribution

Development of two-channel prototype ITER vacuum ultraviolet spectrometer with back-illuminated charge-coupled device and microchannel plate detectors.

PubMed

Seon, C R; Choi, S H; Cheon, M S; Pak, S; Lee, H G; Biel, W; Barnsley, R

2010-10-01

A vacuum ultraviolet (VUV) spectrometer of a five-channel spectral system is designed for ITER main plasma impurity measurement. To develop and verify the system design, a two-channel prototype system is fabricated with No. 3 (14.4-31.8 nm) and No. 4 (29.0-60.0 nm) among the five channels. The optical system consists of a collimating mirror to collect the light from source to slit, two holographic diffraction gratings with toroidal geometry, and two different electronic detectors. For the test of the prototype system, a hollow cathode lamp is used as a light source. To find the appropriate detector for ITER VUV system, two kinds of detectors of the back-illuminated charge-coupled device and the microchannel plate electron multiplier are tested, and their performance has been investigated.

Vacuum ultraviolet photoabsorption of prime ice analogues of Pluto and Charon.

PubMed

Pavithraa, S; Lo, J-I; Rahul, K; Raja Sekhar, B N; Cheng, B-M; Mason, N J; Sivaraman, B

2018-02-05

Here we present the first Vacuum UltraViolet (VUV) photoabsorption spectra of ice analogues of Pluto and Charon ice mixtures. For Pluto the ice analogue is an icy mixture containing nitrogen (N 2 ), carbon monoxide (CO), methane (CH 4 ) and water (H 2 O) prepared with a 100:1:1:3 ratio, respectively. Photoabsorption of icy mixtures with and without H 2 O were recorded and no significant changes in the spectra due to presence of H 2 O were observed. For Charon a VUV photoabsorption spectra of an ice analogue containing ammonia (NH 3 ) and H 2 O prepared with a 1:1 ratio was recorded, a spectrum of ammonium hydroxide (NH 4 OH) was also recorded. These spectra may help to interpret the P-Alice data from New Horizons. Copyright © 2017 Elsevier B.V. All rights reserved.

A straightforward method for Vacuum-Ultraviolet flux measurements: The case of the hydrogen discharge lamp and implications for solid-phase actinometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fulvio, D., E-mail: daniele.fulvio@uni-jena.de, E-mail: dfu@oact.inaf.it; Brieva, A. C.; Jäger, C.

2014-07-07

Vacuum-Ultraviolet (VUV) radiation is responsible for the photo-processing of simple and complex molecules in several terrestrial and extraterrestrial environments. In the laboratory such radiation is commonly simulated by inexpensive and easy-to-use microwave-powered hydrogen discharge lamps. However, VUV flux measurements are not trivial and the methods/devices typically used for this purpose, mainly actinometry and calibrated VUV silicon photodiodes, are not very accurate or expensive and lack of general suitability to experimental setups. Here, we present a straightforward method for measuring the VUV photon flux based on the photoelectric effect and using a gold photodetector. This method is easily applicable to mostmore » experimental setups, bypasses the major problems of the other methods, and provides reliable flux measurements. As a case study, the method is applied to a microwave-powered hydrogen discharge lamp. In addition, the comparison of these flux measurements to those obtained by O{sub 2} actinometry experiments allow us to estimate the quantum yield (QY) values QY{sub 122} = 0.44 ± 0.16 and QY{sub 160} = 0.87 ± 0.30 for solid-phase O{sub 2} actinometry.« less

A technique for synergistic atomic oxygen and vacuum ultraviolet radiation durability evaluation of materials for use in LEO

NASA Technical Reports Server (NTRS)

Rutledge, Sharon K.; Banks, Bruce A.

1996-01-01

Material erosion data collected during flight experiments such as the Environmental Oxygen Interaction with Materials (EOIM)-3 and the Long Duration Exposure Facility (LDEF) have raised questions as to the sensitivity of material erosion to levels of atomic oxygen exposure and vacuum ultraviolet (VUV) radiation. The erosion sensitivity of some materials such as FEP Teflon used as a thermal control material on satellites in low Earth orbit (LEO), is particularly important but difficult to determine. This is in large part due to the inability to hold all but one exposure parameter constant during a flight experiment. This is also difficult to perform in a ground based facility, because often the variation of the level of atomic oxygen or VUV radiation also results in a change in the level of the other parameter. A facility has been developed which allows each parameter to be changed almost independently and offer broad area exposure. The resulting samples can be made large enough for mechanical testing. The facility uses an electron cyclotron resonance plasma source to provide the atomic oxygen. A series of glass plates is used to focus the atomic oxygen while filtering the VUV radiation from the plasma source. After filtering, atomic oxygen effective flux levels can still be measured which are as high as 7 x 10(exp 15) atoms/cm(exp 2)-sec which is adequate for accelerated testing. VUV radiation levels after filtering can be as low as 0.3 suns. Additional VUV suns can be added with the use of deuterium lamps which allow the VUV level to be changed while keeping the flux of atomic oxygen constant. This paper discusses the facility, and results from exposure of Kapton and FEP at pre-determined atomic oxygen flux and VUV sun levels.

Degradation of organic pollutants by Vacuum-Ultraviolet (VUV): Kinetic model and efficiency.

PubMed

Xie, Pengchao; Yue, Siyang; Ding, Jiaqi; Wan, Ying; Li, Xuchun; Ma, Jun; Wang, Zongping

2018-04-15

Vacuum-Ultraviolet (VUV), an efficient and green method to produce hydroxyl radical (•OH), is effective in degrading numerous organic contaminants in aqueous solution. Here, we proposed an effective and simple kinetic model to describe the degradation of organic pollutants in VUV system, by taking the •OH scavenging effects of formed organic intermediates as co-existing organic matter in whole. Using benzoic acid (BA) as a •OH probe, •OH was regarded vital for pollutant degradation in VUV system, and the thus developed model successfully predicted its degradation kinetics under different conditions. Effects of typical influencing factors such as BA concentrations and UV intensity were investigated quantitatively by the model. Temperature was found to be an important influencing factor in the VUV system, and the quantum yield of •OH showed a positive linear dependence on temperature. Impacts of humic acid (HA), alkalinity, chloride, and water matrices (realistic waters) on the oxidation efficiency were also examined. BA degradation was significantly inhibited by HA due to its scavenging of •OH, but was influenced much less by the alkalinity and chloride; high oxidation efficiency was still obtained in the realistic water. The degradation kinetics of three other typical micropollutants including bisphenol A (BPA), nitrobenzene (NB) and dimethyl phthalate (DMP), and the mixture of co-existing BA, BPA and DMP were further studied, and the developed model predicted the experimental data well, especially in realistic water. It is expected that this study will provide an effective approach to predict the degradation of organic micropollutants by the promising VUV system, and broaden the application of VUV system in water treatment. Copyright © 2018 Elsevier Ltd. All rights reserved.

Novel Process of Simultaneous Removal of Nitric Oxide and Sulfur Dioxide Using a Vacuum Ultraviolet (VUV)-Activated O2/H2O/H2O2 System in A Wet VUV-Spraying Reactor.

PubMed

Liu, Yangxian; Wang, Qian; Pan, Jianfeng

2016-12-06

A novel process for NO and SO 2 simultaneous removal using a vacuum ultraviolet (VUV, with 185 nm wavelength)-activated O 2 /H 2 O/H 2 O 2 system in a wet VUV-spraying reactor was developed. The influence of different process variables on NO and SO 2 removal was evaluated. Active species (O 3 and ·OH) and liquid products (SO 3 2- , NO 2 - , SO 4 2- , and NO 3 - ) were analyzed. The chemistry and routes of NO and SO 2 removal were investigated. The oxidation removal system exhibits excellent simultaneous removal capacity for NO and SO 2 , and a maximum removal of 96.8% for NO and complete SO 2 removal were obtained under optimized conditions. SO 2 reaches 100% removal efficiency under most of test conditions. NO removal is obviously affected by several process variables. Increasing VUV power, H 2 O 2 concentration, solution pH, liquid-to-gas ratio, and O 2 concentration greatly enhances NO removal. Increasing NO and SO 2 concentration obviously reduces NO removal. Temperature has a dual impact on NO removal, which has an optimal temperature of 318 K. Sulfuric acid and nitric acid are the main removal products of NO and SO 2 . NO removals by oxidation of O 3 , O·, and ·OH are the primary routes. NO removals by H 2 O 2 oxidation and VUV photolysis are the complementary routes. A potential scaled-up removal process was also proposed initially.

Luminescence from Vacuum-Ultraviolet-Irradiated Cosmic Ice Analogs and Residue

NASA Technical Reports Server (NTRS)

Gudipati, Murthy S.; Dworkin, Jason P.; Chillier, Xavier D. F.; Allamandola, Louis J.

2003-01-01

Here we report a study of the optical luminescent properties for a variety of vacuum-ultraviolet (VUV)-irradiated cosmic ice analogs and the complex organic residues produced. Detailed results are presented for the irradiated, mixed molecular ice: H2O: CH3OH:NH3:CO(100:50:1:1), a realistic representation for an interstellar/precometary ice that reproduces all the salient infrared spectral features associated with interstellar ices. The irradiated ices and the room-temperature residues resulting from this energetic processing have remarkable photoluminescent properties in the visible (520-570 nm). The luminescence dependence on temperature, thermal cycling, and VUV exposure is described. It is suggested that this type of luminescent behavior might be applicable to solar system and interstellar observations and processes for various astronomical objects with an ice heritage. Some examples include grain temperature determination and vaporization rates, nebula radiation balance, albedo values, color analysis, and biomarker identification.

Luminescence from Vacuum-Ultraviolet-Irradiated Cosmic Ice Analogs and Residues

NASA Technical Reports Server (NTRS)

Gudipati, Murthy S.; Dworkin, Jason P.; Chillier, Xavier D. F.; Allamandola, Louis J.

2003-01-01

Here we report a study of the optical luminescent properties for a variety of vacuum-ultraviolet (VUV)- irradiated cosmic ice analogs and the complex organic residues produced. Detailed results are presented for the irradiated, mixed molecular ice: H2O:CH3OH:NH3:CO (100:50:1:1), a realistic representation for an interstellar/precometary ice that reproduces all the salient infrared spectral features associated with interstellar ices. The irradiated ices and the room-temperature residues resulting from this energetic processing have remarkable photoluminescent properties in the visible (520-570 nm). The luminescence dependence on temperature, thermal cycling, and VUV exposure is described. It is suggested that this type of luminescent behavior might be applicable to solar system and interstellar observations and processes for various astronomical objects with an ice heritage. Some examples include grain temperature determination and vaporization rates, nebula radiation balance, albedo values, color analysis, and biomarker identification.

Ultra-fast switching of light by absorption saturation in vacuum ultra-violet region.

PubMed

Yoneda, Hitoki; Inubushi, Yuichi; Tanaka, Toshihiro; Yamaguchi, Yuta; Sato, Fumiya; Morimoto, Shunsuke; Kumagai, Taisuke; Nagasono, Mitsuru; Higashiya, Atsushi; Yabashi, Makina; Ishikawa, Tetsuya; Ohashi, Haruhiko; Kimura, Hiroaki; Kitamura, Hikaru; Kodama, Ryosuke

2009-12-21

Advances in free electron lasers producing high energy photons [Nat. Photonics 2(9), 555-559 (2008)] are expected to open up a new science of nonlinear optics of high energy photons. Specifically, lasers of photon energy higher than the plasma frequency of a metal can show new interaction features because they can penetrate deeply into metals without strong reflection. Here we show the observation of ultra-fast switching of vacuum ultra-violet (VUV) light caused by saturable absorption of a solid metal target. A strong gating is observed at energy fluences above 6J/cm2 at wavelength of 51 nm with tin metal thin layers. The ratio of the transmission at high intensity to low intensity is typically greater than 100:1. This means we can design new nonlinear photonic devices such as auto-correlator and pulse slicer for the VUV region.

In situ measurement of VUV/UV radiation from low-pressure microwave-produced plasma in Ar/O2 gas mixtures

NASA Astrophysics Data System (ADS)

Iglesias, E. J.; Mitschker, F.; Fiebrandt, M.; Bibinov, N.; Awakowicz, P.

2017-08-01

Ultraviolet (UV) and vacuum ultraviolet (VUV) spectral irradiance is determined in low-pressure microwave-produced plasma, which is regularly used for polymer surface treatment. The re-emitted fluorescence in the UV/VIS spectral range from a sodium salicylate layer is measured. This fluorescence is related to VUV/UV radiation in different spectral bands based on cut-off filters. The background produced by direct emitted radiation in the fluorescence spectral region is quantified using a specific background filter, thus enabling the use of the whole fluorescence spectral range. A novel procedure is applied to determine the absolute value of the VUV/UV irradiance on a substrate. For that, an independent measurement of the absolute spectral emissivity of the plasma in the UV is performed. The measured irradiances on a substrate from a 25 Pa Ar/O2-produced plasma are in the range of 1015-1016 (photon~ s-1 cm-2). These values include the contribution from impurities present in the discharge.

Xenon excimer emission from pulsed high-pressure capillary microdischarges

NASA Astrophysics Data System (ADS)

Lee, Byung-Joon; Rahaman, Hasibur; Petzenhauser, Isfried; Frank, Klaus; Giapis, Konstantinos P.

2007-06-01

Intense xenon vacuum ultraviolet (VUV) emission is observed from a high-pressure capillary cathode microdischarge in direct current operation, by superimposing a high-voltage pulse of 50ns duration. Under stagnant gas conditions, the total VUV light intensity increases linearly with pressure from 400 to 1013mbar for a fixed voltage pulse. At fixed pressure, however, the VUV light intensity increases superlinearly with voltage pulse height ranging from 08to2.8kV. Gains in emission intensity are obtained by inducing gas flow through the capillary cathode, presumably because of excimer dimer survival due to gas cooling.

Low-temperature direct heterogeneous bonding of polyether ether ketone and platinum.

PubMed

Fu, Weixin; Shigetou, Akitsu; Shoji, Shuichi; Mizuno, Jun

2017-10-01

Direct heterogeneous bonding between polyether ether ketone (PEEK) and Pt was realized at the temperatures lower than 150°C. In order to create sufficient bondability to diverse materials, the surface was modified by vacuum ultraviolet (VUV) irradiation, which formed hydrate bridges. For comparison, direct bonding between surfaces atomically cleaned via Ar fast atom bombardment (FAB) was conducted in a vacuum. The VUV irradiation was found to be effective for creating an ultrathin hydrate bridge layer from the residual water molecules in the chamber. Tight bonds were formed through dehydration of the hydrate bridges by heating at 150°C, which also contributed to enhancing interdiffusion across the interface. The VUV-modified surfaces showed bondability as good as that of the FAB-treated surfaces, and the VUV-modified samples had shear strengths at the same level as those of FAB-treated surfaces. This technology will be of practical use in the packaging of lightweight, flexible biomedical devices. Copyright © 2017 Elsevier B.V. All rights reserved.

Steady-State Vacuum Ultraviolet Exposure Facility With Automated Lamp Calibration and Sample Positioning Fabricated

NASA Technical Reports Server (NTRS)

Sechkar, Edward A.; Steuber, Thomas J.; Banks, Bruce A.; Dever, Joyce A.

2000-01-01

The Next Generation Space Telescope (NGST) will be placed in an orbit that will subject it to constant solar radiation during its planned 10-year mission. A sunshield will be necessary to passively cool the telescope, protecting it from the Sun s energy and assuring proper operating temperatures for the telescope s instruments. This sunshield will be composed of metalized polymer multilayer insulation with an outer polymer membrane (12 to 25 mm in thickness) that will be metalized on the back to assure maximum reflectance of sunlight. The sunshield must maintain mechanical integrity and optical properties for the full 10 years. This durability requirement is most challenging for the outermost, constantly solar-facing polymer membrane of the sunshield. One of the potential threats to the membrane material s durability is from vacuum ultraviolet (VUV) radiation in wavelengths below 200 nm. Such radiation can be absorbed in the bulk of these thin polymer membrane materials and degrade the polymer s optical and mechanical properties. So that a suitable membrane material can be selected that demonstrates durability to solar VUV radiation, ground-based testing of candidate materials must be conducted to simulate the total 10- year VUV exposure expected during the Next Generation Space Telescope mission. The Steady State Vacuum Ultraviolet exposure facility was designed and fabricated at the NASA Glenn Research Center at Lewis Field to provide unattended 24-hr exposure of candidate materials to VUV radiation of 3 to 5 times the Sun s intensity in the wavelength range of 115 to 200 nm. The facility s chamber, which maintains a pressure of approximately 5 10(exp -6) torr, is divided into three individual exposure cells, each with a separate VUV source and sample-positioning mechanism. The three test cells are separated by a water-cooled copper shield plate assembly to minimize thermal effects from adjacent test cells. Part of the interior sample positioning mechanism of one test cell is shown in the illustration. Of primary concern in VUV exposure is the maintenance of constant measured radiation intensity so that the sample s total exposure can be determined in equivalent Sun hours. This is complicated by the fact that a VUV lamp s intensity degrades over time, necessitating a decrease in the distance between the test samples and the lamp. The facility overcomes this challenge by periodically measuring the lamp s intensity with a cesium-iodide phototube and adjusting the sample distance as required to maintain constant exposure intensity. Sample positioning and periodic phototube location under the lamp are both achieved by a single lead-screw assembly. The lamps can be isolated from the main vacuum chamber for cleaning or replacement so that samples are not exposed to the atmosphere during a test.

Note: Hollow cathode lamp with integral, high optical efficiency isolation valve: a modular vacuum ultraviolet source.

PubMed

Roberts, F Sloan; Anderson, Scott L

2013-12-01

The design and operating conditions of a hollow cathode discharge lamp for the generation of vacuum ultraviolet radiation, suitable for ultrahigh vacuum (UHV) application, are described in detail. The design is easily constructed, and modular, allowing it to be adapted to different experimental requirements. A thin isolation valve is built into one of the differential pumping stages, isolating the discharge section from the UHV section, both for vacuum safety and to allow lamp maintenance without venting the UHV chamber. The lamp has been used both for ultraviolet photoelectron spectroscopy of surfaces and as a "soft" photoionization source for gas-phase mass spectrometry.

Exploiting single photon vacuum ultraviolet photoionization to unravel the synthesis of complex organic molecules in interstellar ices

NASA Astrophysics Data System (ADS)

Abplanalp, Matthew J.; Förstel, Marko; Kaiser, Ralf I.

2016-01-01

Complex organic molecules (COM) such as aldehydes, ketones, carboxylic acids, esters, and amides are ubiquitous in the interstellar medium, but traditional gas phase astrochemical models cannot explain their formation routes. By systematically exploiting on line and in situ vacuum ultraviolet photoionization coupled with reflectron time of flight mass spectrometry (PI-ReTOF-MS) and combining these data with infrared spectroscopy (FTIR), we reveal that complex organic molecules can be synthesized within interstellar ices that are condensed on interstellar grains via non-equilibrium reactions involving suprathermal hydrogen atoms at temperatures as low as 5 K. By probing for the first time specific structural isomers without their degradation (fragment-free), the incorporation of tunable vacuum ultraviolet photoionization allows for a much greater understanding of reaction mechanisms that exist in interstellar ices compared to traditional methods, thus eliminating the significant gap between observational and laboratory data that existed for the last decades. With the commission of the Atacama Large Millimeter/Submillimeter Array (ALMA), the number of detections of more complex organic molecules in space will continue to grow ⿿ including biorelevant molecules connected to the Origins of Life theme ⿿ and an understanding of these data will rely on future advances in sophisticated physical chemistry laboratory experiments.

Identification and deconvolution of carbohydrates with gas chromatography-vacuum ultraviolet spectroscopy.

PubMed

Schenk, Jamie; Nagy, Gabe; Pohl, Nicola L B; Leghissa, Allegra; Smuts, Jonathan; Schug, Kevin A

2017-09-01

Methodology for qualitative and quantitative determination of carbohydrates with gas chromatography coupled to vacuum ultraviolet detection (GC-VUV) is presented. Saccharides have been intently studied and are commonly analyzed by gas chromatography-mass spectrometry (GC-MS), but not always effectively. This can be attributed to their high degree of structural complexity: α/β anomers from their axial/equatorial hydroxyl group positioning at the C1-OH and flexible ring structures that lead to the open chain, five-membered ring furanose, and six-membered ring pyranose configurations. This complexity can result in convoluted chromatograms, ambiguous fragmentation patterns and, ultimately, analyte misidentification. In this study, mono-, di, and tri-saccharides were derivatized by two different methods-permethylation and oximation/pertrimethylsilylation-and analyzed by GC-VUV. These two derivatization methods were then compared for their efficiency, ease of use, and robustness. Permethylation proved to be a useful technique for the analysis of ketopentoses and pharmaceuticals soluble in dimethyl sulfoxide (DMSO), while the oximation/pertrimethylsilylation method prevailed as the more promising, overall, derivatization method. VUV spectra have been shown to be distinct and allow for efficient differentiation of isomeric species such as ketopentoses and reducing versus non-reducing sugars. In addition to identification, pharmaceutical samples containing several compounds were derivatized and analyzed for their sugar content with the GC-VUV technique to provide data for qualitative analysis. Copyright © 2017 Elsevier B.V. All rights reserved.

Vacuum ultraviolet emission characteristics from He-Ne-Xe gas discharge in an alternating current plasma display panel cell

NASA Astrophysics Data System (ADS)

Seo, Jeong Hyun; Jeong, Heui Seob; Lee, Joo Yul; Yoon, Cha Keun; Kim, Joong Kyun; Whang, Ki-Woong

2000-08-01

We measured the time integrated vacuum ultraviolet (VUV) emission spectra of He-Ne-Xe gas mixture from a surface type alternating current (ac) plasma display panel cell. The measured emission lines are the resonance line (147 nm) from Xe*(1s4), the first continuum (150 nm) and the second continuum (173 nm) from Xe dimer excited states. The relative intensities of VUV spectral lines from Xe* and Xe2* are dependent on the He/Ne mixing ratio as well as the Xe partial and total pressure. The intensity of 147 nm VUV increases with the Ne content increase and Xe2* molecular emission increases with the He content increase. Infrared (IR) spectra and the time variation of VUV were measured to explain the reaction pathway and the effect of the mixing ratio of He/Ne on the spectral intensity. A detailed study for the decay time shows that the decay time of 147 nm has two time constants and the radiation of 150 and 173 nm results mainly from Xe*(1s5). The IR spectra shows that the contribution from Xe**(>6 s) to Xe*(1s5) and Xe*(1s4) in He-Xe is different from that of Ne-Xe. The change of IR intensity explains the spectral intensity variations of He-Xe and Ne-Xe discharge.

Solid state direct bonding of polymers by vacuum ultraviolet light below 160 nm

NASA Astrophysics Data System (ADS)

Hashimoto, Yuki; Yamamoto, Takatoki

2017-10-01

This work investigated the application of vacuum ultraviolet (VUV) irradiation to the bonding of various substrates, including glass, polycarbonate (PC), cyclic olefin polymer (COP), polydimethylsiloxane (PDMS) and polymethyl methacrylate (PMMA). This method has the advantage of being able to bond various substrates without the application of heat or adhesives, and therefore may be very useful in the fabrication of micro/nanoscale structures composed of polymers. In contrast to previous applications of this technique, the present study used VUV radiation at wavelengths at and below 160 nm so as to take advantage of the higher energy in this range. Bonding was assessed based on measuring the shear stress of various test specimens subjected to VUV irradiation and then pressed together, and a number of analytical methods were also employed to examine the irradiated surfaces in order to elucidate the morphological and chemical changes following VUV treatment. These analyses included water contact angle measurements, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), time of flight secondary ion mass spectrometry (TOF-SIMS) and atomic force microscopy (AFM). Poor bonding was identified between combinations consisting of PMMA/PC, PMMA/COP, PMMA/PMMA, PMMA/glass, and PC/COP, whereas all other combinations resulted in successful bonding with the bonding stress values such as PC/PC = 2.0 MPa, PC/glass = 10.7 MPa and COP/COP = 1.7 MPa, respectively.

Selective Generation of the Radical Cation Isomers [CH3CN](•+) and [CH2CNH](•+) via VUV Photoionization of Different Neutral Precursors and Their Reactivity with C2H4.

PubMed

Polášek, Miroslav; Zins, Emilie-Laure; Alcaraz, Christian; Žabka, Ján; Křížová, Věra; Giacomozzi, Linda; Tosi, Paolo; Ascenzi, Daniela

2016-07-14

Experimental and theoretical studies have been carried out to demonstrate the selective generation of two different C2H3N(+) isomers, namely, the acetonitrile [CH3CN](•+) and the ketenimine [CH2CNH](•+) radical cations. Photoionization and dissociative photoionization experiments from different neutral precursors (acetonitrile and butanenitrile) have been performed using vacuum ultraviolet (VUV) synchrotron radiation in the 10-15 eV energy range, delivered by the DESIRS beamline at the SOLEIL storage ring. For butanenitrile (CH3CH2CH2CN) an experimental ionization threshold of 11.29 ± 0.05 eV is obtained, whereas the appearance energy for the formation of [CH2CNH](•+) fragments is 11.52 ± 0.05 eV. Experimental findings are fully supported by theoretical calculations at the G4 level of theory (ZPVE corrected energies at 0 K), giving a value of 11.33 eV for the adiabatic ionization energy of butanenitrile and an exothermicity of 0.49 for fragmentation into [CH2CNH](•+) plus C2H4, hampered by an energy barrier of 0.29 eV. The energy difference between [CH3CN](•+) and [CH2CNH](•+) is 2.28 eV (with the latter being the lowest energy isomer), and the isomerization barrier is 0.84 eV. Reactive monitoring experiments of the [CH3CN](•+) and [CH2CNH](•+) isomers with C2H4 have been performed using the CERISES guided ion beam tandem mass spectrometer and exploiting the selectivity of ethylene that gives exothermic charge exchange and proton transfer reactions with [CH3CN](•+) but not with [CH2CNH](•+) isomers. In addition, minor reactive channels are observed leading to the formation of new C-C bonds upon reaction of [CH3CN](•+) with C2H4, and their astrochemical implications are briefly discussed.

Effects of Various Wavelength Ranges of Vacuum Ultraviolet Radiation on Teflon FEP Film Investigated

NASA Technical Reports Server (NTRS)

Dever, Joyce A.; McCracken, Cara A.

2004-01-01

Teflon Fluorinated Ethylene Propylene (FTP) films (DuPont) have been widely used for spacecraft thermal control and have been observed to become embrittled and cracked upon exposure to the space environment. This degradation has been attributed to a synergistic combination of radiation and thermal effects. A research study was undertaken at the NASA Glenn Research Center to examine the effects of different wavelength ranges of vacuum ultraviolet (VUV) radiation on the degradation of the mechanical properties of FEP. This will contribute to an overall understanding of space radiation effects on Teflon FEP, and will provide information necessary to determine appropriate techniques for using laboratory tests to estimate space VUV degradation. Research was conducted using inhouse facilities at Glenn and was carried out, in part, through a grant with the Cleveland State University. Samples of Teflon FEP film of 50.8 microns thickness were exposed to radiation from a VUV lamp from beneath different cover windows to provide different exposure wavelength ranges: MgF2 (115 to 400 nm), crystalline quartz (140 to 400 nm), and fused silica (FS, 155 to 400 nm). Following exposure, FEP film specimens were tensile tested to determine the ultimate tensile strength and elongation at failure as a function of the exposure duration for each wavelength range. The graphs show the effect of ultraviolet exposure on the mechanical properties of the FEP samples.

Dynamic photolytical actinometry of the vacuum-ultraviolet radiation produced by multichannel surface discharges of submicrosecond duration.

PubMed

Tcheremiskine, V I; Uteza, O P; Sentis, M L; Mikheev, L D

2007-06-01

Absolute measurements of the vacuum-ultraviolet (VUV) radiation power produced by a planar broadband optical source of submicrosecond light pulse duration are carried out in the transient regime of formation of a photodissociation (bleaching) wave in a photodecomposing absorptive medium. The source is based on a multichannel surface discharge initiated in ArN(2) gas mixtures on the area of approximately 0.1 m(2). The energetic characteristics of the produced VUV radiation are determined on the basis of spatially and temporally resolved observations of the pulsed photolysis of XeF(2) vapors. It is shown that the photon flux intensity produced by the source within the spectral range of 120-200 nm reaches 1.1 x 10(23) photonscm(2) s corresponding to the effective brightness temperature of discharge plasma of 20 kK and to the intrinsic efficiency of the discharge VUV emission of 3.2%. Numerical simulations of the photolysis process show a rather weak sensitivity of the results to the fraction of discharge radiation emitted into the line spectrum, as well as to the angular distribution of emitted radiation. The spectral band of measurements can be selected according to the choice of parent photodecomposing particles.

Vacuum ultraviolet radiation effects on two-dimensional MoS2 field-effect transistors

NASA Astrophysics Data System (ADS)

McMorrow, Julian J.; Cress, Cory D.; Arnold, Heather N.; Sangwan, Vinod K.; Jariwala, Deep; Schmucker, Scott W.; Marks, Tobin J.; Hersam, Mark C.

2017-02-01

Atomically thin MoS2 has generated intense interest for emerging electronics applications. Its two-dimensional nature and potential for low-power electronics are particularly appealing for space-bound electronics, motivating the need for a fundamental understanding of MoS2 electronic device response to the space radiation environment. In this letter, we quantify the response of MoS2 field-effect transistors (FETs) to vacuum ultraviolet (VUV) total ionizing dose radiation. Single-layer (SL) and multilayer (ML) MoS2 FETs are compared to identify differences that arise from thickness and band structure variations. The measured evolution of the FET transport properties is leveraged to identify the nature of VUV-induced trapped charge, isolating the effects of the interface and bulk oxide dielectric. In both the SL and ML cases, oxide trapped holes compete with interface trapped electrons, exhibiting an overall shift toward negative gate bias. Raman spectroscopy shows no variation in the MoS2 signatures as a result of VUV exposure, eliminating significant crystalline damage or oxidation as possible radiation degradation mechanisms. Overall, this work presents avenues for achieving radiation-hard MoS2 devices through dielectric engineering that reduces oxide and interface trapped charge.

Mechanisms of the effect of VUV radiation on the microfungi

NASA Astrophysics Data System (ADS)

Zvereva, Galina; Kirtsideli, Irina; Machs, Eduard; Vangonen, Albert

2018-04-01

The mechanisms of the effect of vacuum ultraviolet (VUV) radiation (λ = 172 nm) on various types of microfungi spores were investigated. It is found that there are several parallel direct and indirect mechanisms, which lead to spores inactivation, including destruction of the cell wall and DNA by means of direct absorption of VUV radiation and by VUV photolysis reactive products. IR transmission spectra indicate the etching of the spore cell wall material with the predominant degradation of the polysaccharides. Electrophoresis of irradiated spores DNA shows heavy (about 20 000 pairs of nucleotides) and light fragments appearance. Experiments using an antioxidant (iodine) indicate the participation of reactive radicals in inactivation, which provide not less than 10% of inactivated cells

Vacuum ultraviolet emission spectrum measurement of a microwave-discharge hydrogen-flow lamp in several configurations: Application to photodesorption of CO ice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Y.-J.; Wu, C.-Y. R.; Chuang, K.-J.

2014-01-20

We report measurements of the vacuum ultraviolet (VUV) emission spectra of a microwave-discharge hydrogen-flow lamp (MDHL), a common tool in astrochemistry laboratories working on ice VUV photoprocessing. The MDHL provides hydrogen Ly-α (121.6 nm) and H{sub 2} molecular emission in the 110-180 nm range. We show that the spectral characteristics of the VUV light emitted in this range, in particular the relative proportion of Ly-α to molecular emission bands, strongly depend on the pressure of H{sub 2} inside the lamp, the lamp geometry (F type versus T type), the gas used (pure H{sub 2} versus H{sub 2} seeded in He),more » and the optical properties of the window used (MgF{sub 2} versus CaF{sub 2}). These different configurations are used to study the VUV irradiation of CO ice at 14 K. In contrast to the majority of studies dedicated to the VUV irradiation of astrophysical ice analogs, which have not taken into consideration the emission spectrum of the MDHL, our results show that the processes induced by photons in CO ice from a broad energy range are different and more complex than the sum of individual processes induced by monochromatic sources spanning the same energy range, as a result of the existence of multistate electronic transitions and discrepancy in absorption cross sections between parent molecules and products in the Ly-α and H{sub 2} molecular emission ranges.« less

Note: Hollow cathode lamp with integral, high optical efficiency isolation valve: A modular vacuum ultraviolet source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sloan Roberts, F.; Anderson, Scott L.

2013-12-15

The design and operating conditions of a hollow cathode discharge lamp for the generation of vacuum ultraviolet radiation, suitable for ultrahigh vacuum (UHV) application, are described in detail. The design is easily constructed, and modular, allowing it to be adapted to different experimental requirements. A thin isolation valve is built into one of the differential pumping stages, isolating the discharge section from the UHV section, both for vacuum safety and to allow lamp maintenance without venting the UHV chamber. The lamp has been used both for ultraviolet photoelectron spectroscopy of surfaces and as a “soft” photoionization source for gas-phase massmore » spectrometry.« less

OH- Initiated Heterogeneous Oxidation of Saturated Organic Aerosols in the Presence of SO2: Uptake Kinetics and Product Identification.

NASA Astrophysics Data System (ADS)

Richards-Henderson, N. K.; Ward, M.; Goldstein, A. H.; Wilson, K. R.

2014-12-01

Gas-phase oxidation mechanisms for organic gases are often used as a starting point to understand heterogeneous oxidation. The reaction of a simple alkane hydrocarbon by OH proceeds through hydrogen abstraction and under ambient conditions leads to peroxy radical (RO2) formation. RO2 can further react to form: (1) smaller molecular weight products (i.e. fragmentation) via alkoxy radical formation and dissociation and/or (2) higher molecular weight products with oxygenated functional groups (i.e. functionalization). The ability to perturb these two pathways (functionalization vs. fragmentation) is critical for understanding the detailed reaction mechanism that control atmospheric aging chemistry of particles. At high temperatures the presence of sulfur dioxide (SO2) during organic-OH gas-phase oxidation enhances the fragmentation pathway leading to increased alkoxy formation. It is unknown if a comparative affect occurs at room temperature during a heterogeneous reaction. We used the heterogeneous reaction of OH radicals with sub-micron squalane particles in the presence and absence of SO2 as a model system to explore changes in individual mechanistic pathways. Detailed kinetic measurements were made in a flow tube reactor using a vacuum ultraviolet (VUV) photoionization aerosol mass spectrometer and oxidation products are identified from samples collected on quartz filters using thermal desorption two-dimensional chromatographic separation and ionization by either VUV (10.5 eV) or electron impact (70 eV), with detection by high resolution time of flight mass spectrometry (GCxGC-VUV/EI-HRTOFMS). In the presence of SO2 the yields of alcohols were enhanced compared to without SO2, suggesting that the alkoxy formation pathway was dominant. The results from this work will provide an experimentally-confirmed kinetic framework that could be used to model atmospheric aging mechanisms.

Characterization of secondary organic aerosol from photo-oxidation of gasoline exhaust and specific sources of major components.

PubMed

Ma, Pengkun; Zhang, Peng; Shu, Jinian; Yang, Bo; Zhang, Haixu

2018-01-01

To further explore the composition and distribution of secondary organic aerosol (SOA) components from the photo-oxidation of light aromatic precursors (toluene, m-xylene, and 1,3,5-trimethylbenzene (1,3,5-TMB)) and idling gasoline exhaust, a vacuum ultraviolet photoionization mass spectrometer (VUV-PIMS) was employed. Peaks of the molecular ions of the SOA components with minimum molecular fragmentation were clearly observed from the mass spectra of SOA, through the application of soft ionization methods in VUV-PIMS. The experiments comparing the exhaust-SOA and light aromatic mixture-SOA showed that the observed distributions of almost all the predominant cluster ions in the exhaust-SOA were similar to that of the mixture-SOA. Based on the characterization experiments of SOA formed from individual light aromatic precursors, the SOA components with molecular weights of 98 and 110 amu observed in the exhaust-SOA resulted from the photo-oxidation of toluene and m-xylene; the components with a molecular weight of 124 amu were derived mainly from m-xylene; and the components with molecular weights of 100, 112, 128, 138, and 156 amu were mainly derived from 1,3,5-TMB. These results suggest that C 7 -C 9 light aromatic hydrocarbons are significant SOA precursors and that major SOA components originate from gasoline exhaust. Additionally, some new light aromatic hydrocarbon-SOA components were observed for the first time using VUV-PIMS. The corresponding reaction mechanisms were also proposed in this study to enrich the knowledge base of the formation mechanisms of light aromatic hydrocarbon-SOA compounds. Copyright © 2017 Elsevier Ltd. All rights reserved.

Variability in the vacuum-ultraviolet transmittance of magnesium fluoride windows. [for Space Telescope Imaging Spectrograph

NASA Technical Reports Server (NTRS)

Herzig, Howard; Fleetwood, Charles M., Jr.; Toft, Albert R.

1992-01-01

Sample window materials tested during the development of a domed magnesium fluoride detector window for the Hubble Space Telescope's Imaging Spectrograph are noted to exhibit wide variability in VUV transmittance; a test program was accordingly instituted to maximize a prototype domed window's transmittance. It is found that VUV transmittance can be maximized if the boule from which the window is fashioned is sufficiently large to allow such a component to be cut from the purest available portion of the boule.

Comparison between UV and VUV photolysis for the pre- and post-treatment of coking wastewater.

PubMed

Xing, Rui; Zheng, Zhongyuan; Wen, Donghui

2015-03-01

In this study, ultraviolet (UV) and vacuum ultraviolet (VUV) photolysis were investigated for the pre-treatment and post-treatment of coking wastewater. First, 6-fold diluted raw coking wastewater was irradiated by UV and VUV. It was found that 15.9%-35.4% total organic carbon (TOC) was removed after 24 hr irradiation. The irradiated effluent could be degraded by the acclimated activated sludge. Even though the VUV photolysis removed more chemical oxygen demand (COD) than UV, the UV-irradiated effluent demonstrated better biodegradability. After 4 hr UV irradiation, the biological oxygen demand BOD5/COD ratio of irradiated coking wastewater increased from 0.163 to 0.224, and its toxicity decreased to the greatest extent. Second, the biologically treated coking wastewater was irradiated by UV and VUV. Both of them were able to remove 37%-47% TOC within 8 hr irradiation. Compared to UV, VUV photolysis could significantly improve the transparency of the bio-treated effluent. VUV also reduced 7% more ammonia nitrogen (NH4+-N), 17% more nitrite nitrogen (NO2--N), and 18% more total nitrogen (TN) than UV, producing 35% less nitrite nitrogen (NO3--N) as a result. In conclusion, UV irradiation was better in improving the biodegradability of coking wastewater, while VUV was more effective at photolyzing the residual organic compounds and inorganic N-species in the bio-treated effluent. Copyright © 2015. Published by Elsevier B.V.

Comprehensive Chemical Characterization of Hydrocarbons in NIST Standard Reference Material 2779 Gulf of Mexico Crude Oil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Worton, David R.; Zhang, Haofei; Isaacman-VanWertz, Gabriel

Comprehensive chemical information is needed to understand the environmental fate and impact of hydrocarbons released during oil spills. However, chemical information remains incomplete because of the limitations of current analytical techniques and the inherent chemical complexity of crude oils. In this study, gas chromatography (GC)-amenable C 9-C 33 hydrocarbons were comprehensively characterized from the National Institute of Standards and Technology Standard Reference Material (NIST SRM) 2779 Gulf of Mexico crude oil by GC coupled to vacuum ultraviolet photoionization mass spectrometry (GC/VUV-MS), with a mass balance of 68 ± 22%. This technique overcomes one important limitation faced by traditional GC andmore » even comprehensive 2D gas chromatography (GC×GC): the necessity for individual compounds to be chromatographically resolved from one another in order to be characterized. VUV photoionization minimizes fragmentation of the molecular ions, facilitating the characterization of the observed hydrocarbons as a function of molecular weight (carbon number, N C), structure (number of double bond equivalents, N DBE), and mass fraction (mg kg -1), which represent important metrics for understanding their fate and environmental impacts. Linear alkanes (8 ± 1%), bran ched alkanes (11 ± 2%), and cycloalkanes (37 ± 12%) dominated the mass with the largest contribution from cycloalkanes containing one or two rings and one or more alkyl side chains (27 ± 9%). Linearity and good agreement with previous work for a subset of >100 components and for the sum of compound classes provided confidence in our measurements and represents the first independent assessment of our analytical approach and calibration methodology. Another crude oil collected from the Marlin platform (35 km northeast of the Macondo well) was shown to be chemically identical within experimental errors to NIST SRM 2779, demonstrating that Marlin crude is an appropriate surrogate oil for researchers conducting laboratory research into impacts of the DeepWater Horizon disaster.« less

Comprehensive Chemical Characterization of Hydrocarbons in NIST Standard Reference Material 2779 Gulf of Mexico Crude Oil

DOE PAGES

Worton, David R.; Zhang, Haofei; Isaacman-VanWertz, Gabriel; ...

2015-10-13

Comprehensive chemical information is needed to understand the environmental fate and impact of hydrocarbons released during oil spills. However, chemical information remains incomplete because of the limitations of current analytical techniques and the inherent chemical complexity of crude oils. In this study, gas chromatography (GC)-amenable C 9-C 33 hydrocarbons were comprehensively characterized from the National Institute of Standards and Technology Standard Reference Material (NIST SRM) 2779 Gulf of Mexico crude oil by GC coupled to vacuum ultraviolet photoionization mass spectrometry (GC/VUV-MS), with a mass balance of 68 ± 22%. This technique overcomes one important limitation faced by traditional GC andmore » even comprehensive 2D gas chromatography (GC×GC): the necessity for individual compounds to be chromatographically resolved from one another in order to be characterized. VUV photoionization minimizes fragmentation of the molecular ions, facilitating the characterization of the observed hydrocarbons as a function of molecular weight (carbon number, N C), structure (number of double bond equivalents, N DBE), and mass fraction (mg kg -1), which represent important metrics for understanding their fate and environmental impacts. Linear alkanes (8 ± 1%), bran ched alkanes (11 ± 2%), and cycloalkanes (37 ± 12%) dominated the mass with the largest contribution from cycloalkanes containing one or two rings and one or more alkyl side chains (27 ± 9%). Linearity and good agreement with previous work for a subset of >100 components and for the sum of compound classes provided confidence in our measurements and represents the first independent assessment of our analytical approach and calibration methodology. Another crude oil collected from the Marlin platform (35 km northeast of the Macondo well) was shown to be chemically identical within experimental errors to NIST SRM 2779, demonstrating that Marlin crude is an appropriate surrogate oil for researchers conducting laboratory research into impacts of the DeepWater Horizon disaster.« less

Comprehensive Chemical Characterization of Hydrocarbons in NIST Standard Reference Material 2779 Gulf of Mexico Crude Oil.

PubMed

Worton, David R; Zhang, Haofei; Isaacman-VanWertz, Gabriel; Chan, Arthur W H; Wilson, Kevin R; Goldstein, Allen H

2015-11-17

Comprehensive chemical information is needed to understand the environmental fate and impact of hydrocarbons released during oil spills. However, chemical information remains incomplete because of the limitations of current analytical techniques and the inherent chemical complexity of crude oils. In this work, gas chromatography (GC)-amenable C9-C33 hydrocarbons were comprehensively characterized from the National Institute of Standards and Technology Standard Reference Material (NIST SRM) 2779 Gulf of Mexico crude oil by GC coupled to vacuum ultraviolet photoionization mass spectrometry (GC/VUV-MS), with a mass balance of 68 ± 22%. This technique overcomes one important limitation faced by traditional GC and even comprehensive 2D gas chromatography (GC×GC): the necessity for individual compounds to be chromatographically resolved from one another in order to be characterized. VUV photoionization minimizes fragmentation of the molecular ions, facilitating the characterization of the observed hydrocarbons as a function of molecular weight (carbon number, NC), structure (number of double bond equivalents, NDBE), and mass fraction (mg kg(-1)), which represent important metrics for understanding their fate and environmental impacts. Linear alkanes (8 ± 1%), branched alkanes (11 ± 2%), and cycloalkanes (37 ± 12%) dominated the mass with the largest contribution from cycloalkanes containing one or two rings and one or more alkyl side chains (27 ± 9%). Linearity and good agreement with previous work for a subset of >100 components and for the sum of compound classes provided confidence in our measurements and represents the first independent assessment of our analytical approach and calibration methodology. Another crude oil collected from the Marlin platform (35 km northeast of the Macondo well) was shown to be chemically identical within experimental errors to NIST SRM 2779, demonstrating that Marlin crude is an appropriate surrogate oil for researchers conducting laboratory research into impacts of the DeepWater Horizon disaster.

VUV spectroscopy in impurity injection experiments at KSTAR using prototype ITER VUV spectrometer.

PubMed

Seon, C R; Hong, J H; Song, I; Jang, J; Lee, H Y; An, Y H; Kim, B S; Jeon, T M; Park, J S; Choe, W; Lee, H G; Pak, S; Cheon, M S; Choi, J H; Kim, H S; Biel, W; Bernascolle, P; Barnsley, R

2017-08-01

The ITER vacuum ultra-violet (VUV) core survey spectrometer has been designed as a 5-channel spectral system so that the high spectral resolving power of 200-500 could be achieved in the wavelength range of 2.4-160 nm. To verify the design of the ITER VUV core survey spectrometer, a two-channel prototype spectrometer was developed. As a subsequent step of the prototype test, the prototype VUV spectrometer has been operated at KSTAR since the 2012 experimental campaign. From impurity injection experiments in the years 2015 and 2016, strong emission lines, such as Kr xxv 15.8 nm, Kr xxvi 17.9 nm, Ne vii 46.5 nm, Ne vi 40.2 nm, and an array of largely unresolved tungsten lines (14-32 nm) could be measured successfully, showing the typical photon number of 10 13 -10 15 photons/cm 2 s.

Infrared absorption of methanol clusters (CH3OH)n with n = 2-6 recorded with a time-of-flight mass spectrometer using infrared depletion and vacuum-ultraviolet ionization.

PubMed

Han, Hui-Ling; Camacho, Cristopher; Witek, Henryk A; Lee, Yuan-Pern

2011-04-14

We investigated IR spectra in the CH- and OH-stretching regions of size-selected methanol clusters, (CH(3)OH)(n) with n = 2-6, in a pulsed supersonic jet by using the IR-VUV (vacuum-ultraviolet) ionization technique. VUV emission at 118 nm served as the source of ionization in a time-of-flight mass spectrometer. The tunable IR laser emission served as a source of predissociation or excitation before ionization. The variations of intensity of protonated methanol cluster ions (CH(3)OH)(n)H(+) and CH(3)OH(+) and (CH(3)OH)(2)(+) were monitored as the IR laser light was tuned across the range 2650-3750 cm(-1). Careful processing of these action spectra based on photoionization efficiencies and the production and loss of each cluster due to photodissociation yielded IR spectra of the size-selected clusters. Spectra of methanol clusters in the OH region have been extensively investigated; our results are consistent with previous reports, except that the band near 3675 cm(-1) is identified as being associated with the proton acceptor of (CH(3)OH)(2). Spectra in the CH region are new. In the region 2800-3050 cm(-1), bands near 2845, 2956, and 3007 cm(-1) for CH(3)OH split into 2823, 2849, 2934, 2955, 2984, and 3006 cm(-1) for (CH(3)OH)(2) that correspond to proton donor and proton acceptor, indicating that the methanol dimer has a preferred open-chain structure. In contrast, for (CH(3)OH)(3), the splitting diminishes and the bands near 2837, 2954, and 2987 cm(-1) become narrower, indicating a preferred cyclic structure. Anharmonic vibrational wavenumbers predicted for the methanol open-chain dimer and the cyclic trimer with the B3LYP∕VPT2∕ANO1 level of theory are consistent with experimental results. For the tetramer and pentamer, the spectral pattern similar to that of the trimer but with greater widths was observed, indicating that the most stable structures are also cyclic.

Coupling a versatile aerosol apparatus to a synchrotron: Vacuum ultraviolet light scattering, photoelectron imaging, and fragment free mass spectrometry

NASA Astrophysics Data System (ADS)

Shu, Jinian; Wilson, Kevin R.; Ahmed, Musahid; Leone, Stephen R.

2006-04-01

An aerosol apparatus has been coupled to the Chemical Dynamics Beamline of the Advanced Light Source at Lawrence Berkeley National Laboratory. This apparatus has multiple capabilities for aerosol studies, including vacuum ultraviolet (VUV) light scattering, photoelectron imaging, and mass spectroscopy of aerosols. By utilizing an inlet system consisting of a 200μm orifice nozzle and aerodynamic lenses, aerosol particles of ˜50nm-˜1μm in diameter can be sampled directly from atmospheric pressure. The machine is versatile and can probe carbonaceous aerosols generated by a laboratory flame, nebulized solutions of biological molecules, hydrocarbon aerosol reaction products, and synthesized inorganic nanoparticles. The sensitivity of this apparatus is demonstrated by the detection of nanoparticles with VUV light scattering, photoelectron imaging, and charged particle detection. In addition to the detection of nanoparticles, the thermal vaporization of aerosols on a heater tip leads to the generation of intact gas phase molecules. This phenomenon coupled to threshold single photon ionization, accessible with tunable VUV light, allows for fragment-free mass spectrometry of complex molecules. The initial experiments with light scattering, photoelectron imaging, and aerosol mass spectrometry reported here serve as a demonstration of the design philosophy and multiple capabilities of the apparatus.

Intensity and Energy Level Analysis of the Vacuum Ultraviolet Spectrum of Four Times Ionize Nickel (Ni V)

NASA Astrophysics Data System (ADS)

Ward, Jacob Wolfgang; Nave, Gillian

2016-01-01

Recent measurements of four times ionized iron and nickel (Fe V & Ni V) wavelengths in the vacuum ultraviolet (VUV) have been taken using the National Institute for Standards and Technology (NIST) Normal Incidence Vacuum Spectrograph (NIVS) with a sliding spark light source with invar electrodes. The wavelengths observed in those measurements make use of high resolution photographic plates with the majority of observed lines having uncertainties of approximately 3mÅ. In addition to observations made with photographic plates, the same wavelength region was observed with phosphor image plates, which have been demonstrated to be accurate as a method of intensity calibration when used with a deuterium light source. This work will evaluate the use of phosphor image plates and deuterium lamps as an intensity calibration method for the Ni V spectrum in the 1200-1600Å region of the VUV. Additionally, by pairing the observed wavelengths of Ni V with accurate line intensities, it is possible to create an energy level optimization for Ni V providing high accuracy Ritz wavelengths. This process has previously been applied to Fe V and produced Ritz wavelengths that agreed with the above experimental observations.

Plasma Jet (V)UV-Radiation Impact on Biologically Relevant Liquids and Cell Suspension

NASA Astrophysics Data System (ADS)

Tresp, H.; Bussiahn, R.; Bundscherer, L.; Monden, A.; Hammer, M. U.; Masur, K.; Weltmann, K.-D.; Woedtke, Th. V.; Reuter, S.

2014-10-01

In this study the generation of radicals in plasma treated liquids has been investigated. To quantify the contribution of plasma vacuum ultraviolet (VUV) and ultraviolet (UV) radiation on the species investigated, three cases have been studied: UV of plasma jet only, UV and VUV of plasma jet combined, and the plasma effluent including all reactive components. The emitted VUV has been observed by optical emission spectroscopy and its effect on radical formation in liquids has been analyzed by electron spin resonance spectroscopy. Radicals have been determined in ultrapure water (dH2O), as well as in more complex, biorelevant solutions like phosphate buffered saline (PBS) solution, and two different cell culture media. Various compositions lead to different reactive species formation, e.g. in PBS superoxide anion and hydroxyl radicals have been detected, in cell suspension also glutathione thiyl radicals have been found. This study highlights that UV has no impact on radical generation, whereas VUV is relevant for producing radicals. VUV treatment of dH2O generates one third of the radical concentration produced by plasma-effluent treatment. It is relevant for plasma medicine because although plasma sources are operated in open air atmosphere, still VUV can lead to formation of biorelevant radicals. This work is funded by German Federal Ministry of Education a Research (BMBF) (Grant # 03Z2DN12+11).

Improved molecular level identification of organic compounds using comprehensive two-dimensional chromatography, dual ionization energies and high resolution mass spectrometry

DOE PAGES

Worton, David R.; Decker, Monika; Isaacman-VanWertz, Gabriel; ...

2017-05-22

A new analytical methodology combining comprehensive two-dimensional gas chromatography (GC×GC), dual ionization energies and high resolution time of flight mass spectrometry has been developed that improves molecular level identification of organic compounds in complex environmental samples. GC×GC maximizes compound separation providing cleaner mass spectra by minimizing erroneous fragments from interferences and co-eluting peaks. Traditional electron ionization (EI, 70 eV) provides MS fragmentation patterns that can be matched to published EI MS libraries while vacuum ultraviolet photoionization (VUV, 10.5 eV) yields MS with reduced fragmentation enhancing the abundance of the molecular ion providing molecular formulas when combined with high resolution massmore » spectrometry. We demonstrate this new approach by applying it to a sample of organic aerosol. In this sample, 238 peaks were matched to EI MS library data with FM ≥ 800 but a fifth (42 compounds) were determined to be incorrectly identified because the molecular formula was not confirmed by the VUV MS data. This highlights the importance of using a complementary technique to confirm compound identifications even for peaks with very good matching statistics. In total, 171 compounds were identified by EI MS matching to library spectra with confirmation of the molecular formula from the high resolution VUV MS data and were not dependent on the matching statistics being above a threshold value. A large number of unidentified peaks were still observed with FM < 800, which in routine analysis would typically be neglected. Where possible, these peaks were assigned molecular formulas from the VUV MS data (211 in total). In total, the combination of EI and VUV MS data provides more than twice as much molecular level peak information than traditional approaches and improves confidence in the identification of individual organic compounds. The molecular formula data from the VUV MS data was used, in conjunction with GC×GC retention times and the observed EI MS, to generate a new, searchable EI MS library compatible with the standard NIST MS search program. This library is deliberately dynamic and editable so that other end users can add new entries and update existing entries as new information becomes available.A new analytical methodology has been developed to improve molecular level identification of organic compounds in complex samples.« less

Chemical compositions of black carbon particle cores and coatings via soot particle aerosol mass spectrometry with photoionization and electron ionization.

PubMed

Canagaratna, Manjula R; Massoli, Paola; Browne, Eleanor C; Franklin, Jonathan P; Wilson, Kevin R; Onasch, Timothy B; Kirchstetter, Thomas W; Fortner, Edward C; Kolb, Charles E; Jayne, John T; Kroll, Jesse H; Worsnop, Douglas R

2015-05-14

Black carbon is an important constituent of atmospheric aerosol particle matter (PM) with significant effects on the global radiation budget and on human health. The soot particle aerosol mass spectrometer (SP-AMS) has been developed and deployed for real-time ambient measurements of refractory carbon particles. In the SP-AMS, black carbon or metallic particles are vaporized through absorption of 1064 nm light from a CW Nd:YAG laser. This scheme allows for continuous "soft" vaporization of both core and coating materials. The main focus of this work is to characterize the extent to which this vaporization scheme provides enhanced chemical composition information about aerosol particles. This information is difficult to extract from standard SP-AMS mass spectra because they are complicated by extensive fragmentation from the harsh 70 eV EI ionization scheme that is typically used in these instruments. Thus, in this work synchotron-generated vacuum ultraviolet (VUV) light in the 8-14 eV range is used to measure VUV-SP-AMS spectra with minimal fragmentation. VUV-SP-AMS spectra of commercially available carbon black, fullerene black, and laboratory generated flame soots were obtained. Small carbon cluster cations (C(+)-C5(+)) were found to dominate the VUV-SP-AMS spectra of all the samples, indicating that the corresponding neutral clusters are key products of the SP vaporization process. Intercomparisons of carbon cluster ratios observed in VUV-SP-AMS and SP-AMS spectra are used to confirm spectral features that could be used to distinguish between different types of refractory carbon particles. VUV-SP-AMS spectra of oxidized organic species adsorbed on absorbing cores are also examined and found to display less thermally induced decomposition and fragmentation than spectra obtained with thermal vaporization at 200 °C (the minimum temperature needed to quantitatively vaporize ambient oxidized organic aerosol with a continuously heated surface). The particle cores tested in these studies include black carbon, silver, gold, and platinum nanoparticles. These results demonstrate that SP vaporization is capable of providing enhanced organic chemical composition information for a wide range of organic coating materials and IR absorbing particle cores. The potential of using this technique to study organic species of interest in seeded laboratory chamber or flow reactor studies is discussed.

Improved molecular level identification of organic compounds using comprehensive two-dimensional chromatography, dual ionization energies and high resolution mass spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Worton, David R.; Decker, Monika; Isaacman-VanWertz, Gabriel

A new analytical methodology combining comprehensive two-dimensional gas chromatography (GC×GC), dual ionization energies and high resolution time of flight mass spectrometry has been developed that improves molecular level identification of organic compounds in complex environmental samples. GC×GC maximizes compound separation providing cleaner mass spectra by minimizing erroneous fragments from interferences and co-eluting peaks. Traditional electron ionization (EI, 70 eV) provides MS fragmentation patterns that can be matched to published EI MS libraries while vacuum ultraviolet photoionization (VUV, 10.5 eV) yields MS with reduced fragmentation enhancing the abundance of the molecular ion providing molecular formulas when combined with high resolution massmore » spectrometry. We demonstrate this new approach by applying it to a sample of organic aerosol. In this sample, 238 peaks were matched to EI MS library data with FM ≥ 800 but a fifth (42 compounds) were determined to be incorrectly identified because the molecular formula was not confirmed by the VUV MS data. This highlights the importance of using a complementary technique to confirm compound identifications even for peaks with very good matching statistics. In total, 171 compounds were identified by EI MS matching to library spectra with confirmation of the molecular formula from the high resolution VUV MS data and were not dependent on the matching statistics being above a threshold value. A large number of unidentified peaks were still observed with FM < 800, which in routine analysis would typically be neglected. Where possible, these peaks were assigned molecular formulas from the VUV MS data (211 in total). In total, the combination of EI and VUV MS data provides more than twice as much molecular level peak information than traditional approaches and improves confidence in the identification of individual organic compounds. The molecular formula data from the VUV MS data was used, in conjunction with GC×GC retention times and the observed EI MS, to generate a new, searchable EI MS library compatible with the standard NIST MS search program. This library is deliberately dynamic and editable so that other end users can add new entries and update existing entries as new information becomes available.A new analytical methodology has been developed to improve molecular level identification of organic compounds in complex samples.« less

Unexpected methyl migrations of ethanol dimer under synchrotron VUV radiation

NASA Astrophysics Data System (ADS)

Xiao, Weizhan; Hu, Yongjun; Li, Weixing; Guan, Jiwen; Liu, Fuyi; Shan, Xiaobin; Sheng, Liusi

2015-01-01

While methyl transfer is well known to occur in the enzyme- and metal-catalyzed reactions, the methyl transfer in the metal-free organic molecules induced by the photon ionization has been less concerned. Herein, vacuum ultraviolet single photon ionization and dissociation of ethanol dimer are investigated with synchrotron radiation photoionization mass spectroscopy and theoretical methods. Besides the protonated clusters cation (C2H5OH) ṡ H+ (m/z = 47) and the β-carbon-carbon bond cleavage fragment CH2O ṡ (C2H5OH)H+ (m/z = 77), the measured mass spectra revealed that a new fragment (C2H5OH) ṡ (CH3)+ (m/z = 61) appeared at the photon energy of 12.1 and 15.0 eV, where the neutral dimer could be vertically ionized to higher ionic state. Thereafter, the generated carbonium ions are followed by a Wagner-Meerwein rearrangement and then dissociate to produce this new fragment, which is considered to generate after surmounting a few barriers including intra- and inter-molecular methyl migrations by the aid of theoretical calculations. The appearance energy of this new fragment is measured as 11.55 ± 0.05 eV by scanning photoionization efficiency curve. While the signal intensity of fragment m/z = 61 starts to increase, the fragments m/z = 47 and 77 tend to slowly incline around 11.55 eV photon energy. This suggests that the additional fragment channels other than (C2H5OH) ṡ H+ and CH2O ṡ (C2H5OH)H+ have also been opened, which consume some dimer cations. The present report provides a clear description of the photoionization and dissociation processes of the ethanol dimer in the range of the photon energy 12-15 eV.

Hydrated electron based decomposition of perfluorooctane sulfonate (PFOS) in the VUV/sulfite system.

PubMed

Gu, Yurong; Liu, Tongzhou; Wang, Hongjie; Han, Huili; Dong, Wenyi

2017-12-31

As one of the most reactive species, hydrated electron (e aq - ) is promising for reductive decomposition of recalcitrant organic pollutants, such as perfluorooctane sulfonate (PFOS). In this study, PFOS decomposition using a vacuum ultraviolet (VUV)/sulfite system was systematically investigated in comparison with sole VUV and ultraviolet (UV)/sulfite systems. A fast and nearly complete (97.3%) PFOS decomposition was observed within 4h from its initial concentration of 37.2μM in the VUV/sulfite system. The observed rate constant (k obs ) for PFOS decomposition in the studied system was 0.87±0.0060h -1 , which was nearly 7.5 and 2 folds faster than that in sole VUV and UV/sulfite systems, respectively. Compared to previously studied UV/sulfite system, VUV/sulfite system enhanced PFOS decomposition in both weak acidic and alkaline pH conditions. In weak acidic condition (pH6.0), PFOS predominantly decomposed via direct VUV photolysis, whereas in alkaline condition (pH>9.0), PFOS decomposition was mainly induced by e aq - generated from both sulfite and VUV photolytic reactions. At a fixed initial solution pH (pH10.0), PFOS decomposition kinetics showed a positive linear dependence with sulfite dosage. The co-presence of humic acid (HA) and NO 3 - obviously suppressed PFOS decomposition, whereas HCO 3 - showed marginal inhibition. A few amount of short chain perfluorocarboxylic acids (PFCAs) were detected in PFOS decomposition process, and a high defluorination efficiency (75.4%) was achieved. These results suggested most fluorine atoms in PFOS molecule ultimately mineralized into fluoride ions, and the mechanisms for PFOS decomposition in the VUV/sulfite system were proposed. Copyright © 2017 Elsevier B.V. All rights reserved.

Ultrafast internal conversion dynamics of highly excited pyrrole studied with VUV/UV pump probe spectroscopy.

PubMed

Horton, Spencer L; Liu, Yusong; Chakraborty, Pratip; Matsika, Spiridoula; Weinacht, Thomas

2017-02-14

We study the relaxation dynamics of pyrrole after excitation with an 8 eV pump pulse to a state just 0.2 eV below the ionization potential using vacuum ultraviolet/ultraviolet pump probe spectroscopy. Our measurements in conjunction with electronic structure calculations indicate that pyrrole undergoes rapid internal conversion to the ground state in less than 300 fs. We find that internal conversion to the ground state dominates over dissociation.

Study of VUV Generation by Coherent Resonant Frequency Mixing in Metal Vapors.

DTIC Science & Technology

1986-04-24

measuroments of coherent two- dye-laser oscillator -2 mplifier system designed for ex- photon aborption in lithium demonstrate that this periments t res(ona-nt...Harmonic Vacuum-Ultraviolet Generation in Metal Vapors," Phys. Rev. A 19, 1589 (1979). 2. ,.-C. Diels. E. W. Van Strvhand. and D. Gold , in Picosecond

VUV action spectroscopy of protonated leucine-enkephalin peptide in the 6-14 eV range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ranković, M. Lj.; Canon, F.; Nahon, L.

2015-12-28

We have studied the Vacuum Ultraviolet (VUV) photodissociation of gas-phase protonated leucine-enkephalin peptide ion in the 5.7 to 14 eV photon energy range by coupling a linear quadrupole ion trap with a synchrotron radiation source. We report VUV activation tandem mass spectra at 6.7, 8.4, and 12.8 eV photon energies and photodissociation yields for a number of selected fragments. The obtained results provide insight into both near VUV radiation damage and electronic properties of a model peptide. We could distinguish several absorption bands and assign them to particular electronic transitions, according to previous theoretical studies. The photodissociation yields appear tomore » be very different for the various observed fragmentation channels, depending on both the types of fragments and their position along the peptide backbone. The present results are discussed in light of recent gas-phase spectroscopic data on peptides.« less

The VUV dimer spectra excited in condensed krypton

NASA Astrophysics Data System (ADS)

Gerasimov, Gennady N.; Krylov, Boris E.; Hallin, Reinhold

2004-05-01

The vacuum ultraviolet (VUV) emission spectra of krypton homonuclear molecules (dimers) were observed in the wavelength range 120-200 nm. The krypton dimers were excited in a DC capillary discharge and the wall of tube could be cooled with liquid nitrogen. The homogeneous DC discharge was a straight channel in the middle of capillary tube. The gas krypton pressure in the discharge channel could be stabilized in the pressure range from 3 hPa to 1000 hPa. The DC discharge current density and the electron concentration were ~ 10 A/cm2 and ~ 2-4 1014 cm-3, respectively. The VUV krypton spectra excited in vicinity of solid krypton were compared with the spectra recorded without condensed krypton. The VUV spectral lines intensities were observed as nonlinear function of the discharge length. This nonlinear increase of intensity with the length of the tube has still to be explained.

Sub-mm Scale Fiber Guided Deep/Vacuum Ultra-Violet Optical Source for Trapped Mercury Ion Clocks

NASA Technical Reports Server (NTRS)

Yi, Lin; Burt, Eric A.; Huang, Shouhua; Tjoelker, Robert L.

2013-01-01

We demonstrate the functionality of a mercury capillary lamp with a diameter in the sub-mm range and deep ultraviolet (DUV)/ vacuum ultraviolet (VUV) radiation delivery via an optical fiber integrated with the capillary. DUV spectrum control is observed by varying the fabrication parameters such as buffer gas type and pressure, capillary diameter, electrical resonator design, and temperature. We also show spectroscopic data of the 199Hg+ hyper-fine transition at 40.5GHz when applying the above fiber optical design. We present efforts toward micro-plasma generation in hollow-core photonic crystal fiber with related optical design and theoretical estimations. This new approach towards a more practical DUV optical interface could benefit trapped ion clock developments for future ultra-stable frequency reference and time-keeping applications.

Photochemistry of polycyclic aromatic hydrocarbons in cosmic water ice. II. Near UV/VIS spectroscopy and ionization rates

NASA Astrophysics Data System (ADS)

Bouwman, J.; Cuppen, H. M.; Steglich, M.; Allamandola, L. J.; Linnartz, H.

2011-05-01

Context. Mid-infrared emission features originating from polycyclic aromatic hydrocarbons (PAHs) are observed towards photon dominated regions in space. Towards dense clouds, however, these emission features are quenched. Observations of dense clouds show that many simple volatile molecules are frozen out on interstellar grains, forming thin layers of ice. Recently, observations have shown that more complex non-volatile species, presumably including PAHs, also freeze out and contribute to the ongoing solid-state chemistry. Aims: The study presented here aims at obtaining reaction rate data that characterize PAH photochemistry upon vacuum ultraviolet (VUV) irradiation in an interstellar H2O ice analogue to explore the potential impact of PAH:H2O ice reactions on overall interstellar ice chemistry. To this end, the experimental results are implemented in a chemical model under simple interstellar cloud conditions. Methods: Time-dependent near-UV/VIS spectroscopy on the VUV photochemistry of anthracene, pyrene, benzo[ghi]perylene and coronene containing interstellar H2O ice analogs is performed at 25 and 125 K, using an optical absorption setup. Results: Near-UV/VIS absorption spectra are presented for these four PAHs and their photoproducts including cationic species trapped in H2O ice. Oscillator strengths of the cation absorption bands are derived relative to the oscillator strength of the neutral parent PAH. The loss of the parent and growth of PAH photoproducts are measured as a function of VUV dose, yielding solid state reaction constants. The rate constants are used in an exploratory astrochemical model, to assess the importance of PAH:H2O ice photoprocessing in UV exposed interstellar environments, compared with the timescales in which PAH molecules are incorporated in interstellar ices. Conclusions: All four PAHs studied here are found to be readily ionized upon VUV photolysis when trapped in H2O ice and exhibit similar rates for ionization at astronomically relevant temperatures. Depending on the relative efficiency of H2O photodesorption and PAH photoionization in H2O ice, the latter may trigger a charge induced aromatic solid state chemistry, in which PAH cations play a central role.

VUV dissociative excitation cross sections of H2O, NH3, and CH4 by electron impact. [Vacuum Ultra-Violet

NASA Technical Reports Server (NTRS)

Morgan, H. D.; Mentall, J. E.

1974-01-01

Absolute excitation functions for excited fragments resulting from electron bombardment of H2O, NH3, and CH4 by low-energy electrons (0 to 300 eV) have been measured in the vacuum ultraviolet (1100 to 1950 A). The predominant emission for each molecule was the H Lyman-alpha line, while the O I, N I, C I, and C II emissions were at least an order of magnitude weaker. Absolute cross sections at 100 eV are given along with the appearance potential of the various processes and the possible dissociative-excitation channels through which such processes proceed.

Luminescence from VUV Irradiated Cosmic Ice Analogs and Organic Residues

NASA Technical Reports Server (NTRS)

Gudipati, Murthy S.; Dworkin, Jason P.; Chillier, Xavier; Allamandola, Louis J.; DeVincenzi, Donald (Technical Monitor)

2002-01-01

The optical luminescent properties for a variety of vacuum-ultraviolet (VUV) irradiated cosmic ice analogs and the complex organic residues produced from irradiation might be applicable to Solar System and interstellar observations and processes for various astronomical objects with an ice heritage. Some examples include grain temperature determination and vaporization rates, nebula radiation balance, albedo values, color analysis, and biomarker identification. Detailed results are presented for the mixed molecular ice: H2O:CH3OH:NH3:CO (100:50:1:1), a realistic representation for an interstellar/precometary ice. The irradiated ices and the room-temperature residues resulting from this energetic processing have remarkable photoluminescent properties in the visible (520-570 nm). The luminescence dependence on temperature, thermal cycling, and VUV exposure of the residue is described.

Strategy for Realizing High-Precision VUV Spectro-Polarimeter

NASA Astrophysics Data System (ADS)

Ishikawa, R.; Narukage, N.; Kubo, M.; Ishikawa, S.; Kano, R.; Tsuneta, S.

2014-12-01

Spectro-polarimetric observations in the vacuum ultraviolet (VUV) range are currently the only means to measure magnetic fields in the upper chromosphere and transition region of the solar atmosphere. The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) aims to measure linear polarization at the hydrogen Lyman- α line (121.6 nm). This measurement requires a polarization sensitivity better than 0.1 %, which is unprecedented in the VUV range. We here present a strategy with which to realize such high-precision spectro-polarimetry. This involves the optimization of instrument design, testing of optical components, extensive analyses of polarization errors, polarization calibration of the instrument, and calibration with onboard data. We expect that this strategy will aid the development of other advanced high-precision polarimeters in the UV as well as in other wavelength ranges.

A simple resonance enhanced laser ionization scheme for CO via the A1Π state

NASA Astrophysics Data System (ADS)

Sun, Z. F.; von Zastrow, A. D.; Parker, D. H.

2017-07-01

We investigate the laser ionization process taking place when the CO molecule is exposed to vacuum ultraviolet (VUV) radiation resonant with the CO A1Π (v = 0) ← X1Σ+ (v = 0) transition around 154 nm, along with the ultraviolet (UV) and visible (Red) radiation used to generate VUV by four-wave difference-frequency mixing. By measuring the CO+ ion recoil and a room temperature gas spectrum, it is possible to assign the ionization process as 1 + 1' + 1'' REMPI where the one-photon steps refer to the VUV, UV, and Red radiation, respectively. Resonance enhanced ionization of rotational states around J = 12 arise due to the overlap of the fixed wavelength UV (˜250 nm) with the R band-head of a transition assigned to CO E1Π (v = 6) ← A1Π (v = 0) with a term value of 104 787.5 cm-1. The REMPI process is efficient and polarization sensitive and should be useful in a wide range of studies involving nascent CO.

The effect of VUV radiation from Ar/O2 plasmas on low-k SiOCH films

NASA Astrophysics Data System (ADS)

Lee, J.; Graves, D. B.

2011-08-01

The degradation of porous low-k materials, like SiOCH, under plasma processing continues to be a problem in the next generation of integrated-circuit fabrication. Due to the exposure of the film to many species during plasma treatment, such as photons, ions, radicals, etc, it is difficult to identify the mechanisms responsible for plasma-induced damage. Using a vacuum beam apparatus with a calibrated Xe vacuum ultraviolet (VUV) lamp, we show that 147 nm VUV photons and molecular O2 alone can damage these low-k materials. Using Fourier-transform infrared (FTIR) spectroscopy, we show that VUV/O2 exposure causes a loss of methylated species, resulting in a hydrophilic, SiOx-like layer that is susceptible to H2O absorption, leading to an increased dielectric constant. The effect of VUV radiation on chemical modification of porous SiOCH films in the vacuum beam apparatus and in Ar and O2 plasma exposure was found to be a significant contributor to dielectric damage. Measurements of dielectric constant change using a mercury probe are consistent with chemical modification inferred from FTIR analysis. Furthermore, the extent of chemical modification appears to be limited by the penetration depth of the VUV photons, which is dependent on wavelength of radiation. The creation of a SiOx-like layer near the surface of the material, which grows deeper as more methyl is extracted, introduces a dynamic change of VUV absorption throughout the material over time. As a result, the rate of methyl loss is continuously changing during the exposure. We present a model that attempts to capture this dynamic behaviour and compare the model predictions to experimental data through a fitting parameter that represents the effective photo-induced methyl removal. While this model accurately simulates the methyl loss through VUV exposure by the Xe lamp and Ar plasma, the methyl loss from VUV photons in O2 plasma are only accurately depicted at longer exposure times. We conclude that other species, such as oxygen radicals or ions, may play a major role in chemical modification at short times near the surface of the material, while VUV photons contribute to the majority of the damage in the bulk.

The Flare Irradiance Spectral Model (FISM) and its Contributions to Space Weather Research, the Flare Energy Budget, and Instrument Design

NASA Technical Reports Server (NTRS)

Chamberlin, Phillip

2008-01-01

The Flare Irradiance Spectral Model (FISM) is an empirical model of the solar irradiance spectrum from 0.1 to 190 nm at 1 nm spectral resolution and on a 1-minute time cadence. The goal of FISM is to provide accurate solar spectral irradiances over the vacuum ultraviolet (VUV: 0-200 nm) range as input for ionospheric and thermospheric models. The seminar will begin with a brief overview of the FISM model, and also how the Solar Dynamics Observatory (SDO) EUV Variability Experiment (EVE) will contribute to improving FISM. Some current studies will then be presented that use FISM estimations of the solar VUV irradiance to quantify the contributions of the increased irradiance from flares to Earth's increased thermospheric and ionospheric densites. Initial results will also be presented from a study looking at the electron density increases in the Martian atmosphere during a solar flare. Results will also be shown quantifying the VUV contributions to the total flare energy budget for both the impulsive and gradual phases of solar flares. Lastly, an example of how FISM can be used to simplify the design of future solar VUV irradiance instruments will be discussed, using the future NOAA GOES-R Extreme Ultraviolet and X-Ray Sensors (EXIS) space weather instrument.

A vacuum ultraviolet photoionization study on the thermal decomposition of ammonium perchlorate

DOE PAGES

Gobi, Sandor; Zhao, Long; Xu, Bo; ...

2017-11-14

Pyrolysis products of ammonium perchlorate (NH 4ClO 4) at 483 K were monitored on line and in situ via single photon photoionization reflectron time-of-flight spectrometry (PI-ReTOF-MS) in the photon energy range of 9.00–17.50 eV. The photoionization efficiency curves (PIE) of the subliming product molecules were collected and allowed for detection of three class of products containing chlorine, nitrogen, and oxygen including atoms and free radicals. The results found suggest a new insight into possible low-temperature decomposition pathways of NH 4ClO 4.

A vacuum ultraviolet photoionization study on the thermal decomposition of ammonium perchlorate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gobi, Sandor; Zhao, Long; Xu, Bo

Pyrolysis products of ammonium perchlorate (NH 4ClO 4) at 483 K were monitored on line and in situ via single photon photoionization reflectron time-of-flight spectrometry (PI-ReTOF-MS) in the photon energy range of 9.00–17.50 eV. The photoionization efficiency curves (PIE) of the subliming product molecules were collected and allowed for detection of three class of products containing chlorine, nitrogen, and oxygen including atoms and free radicals. The results found suggest a new insight into possible low-temperature decomposition pathways of NH 4ClO 4.

A vacuum ultraviolet photoionization study on the thermal decomposition of ammonium perchlorate

NASA Astrophysics Data System (ADS)

Góbi, Sándor; Zhao, Long; Xu, Bo; Ablikim, Utuq; Ahmed, Musahid; Kaiser, Ralf I.

2018-01-01

Pyrolysis products of ammonium perchlorate (NH4ClO4) at 483 K were monitored on line and in situ via single photon photoionization reflectron time-of-flight spectrometry (PI-ReTOF-MS) in the photon energy range of 9.00-17.50 eV. The photoionization efficiency curves (PIE) of the subliming product molecules were collected and allowed for detection of three class of products containing chlorine, nitrogen, and oxygen including atoms and free radicals. These results suggest a new insight into possible low-temperature decomposition pathways of NH4ClO4.

Atomic Oxygen Effects on Seal Leakage

NASA Technical Reports Server (NTRS)

Christensen, John R.; Underwood, Steve D.; Kamenetzky, Rachel R.; Vaughn, Jason A.

1999-01-01

Common Berthing Mechanism (CBM provides the structural interface between separate International Space Station (ISS) elements, such as the Laboratory and Node modules. The CBM consists of an active and a passive half that join together with structural bolts. The seal at this interface is the CBM-to-CBM molded seal. The CBM-to-CBM interface is assembled on orbit, thus the seals can be exposed to the space environment for up to 65 hours. Atomic Oxygen/Vacuum Ultraviolet radiation (AO/VUV) in space is a potential hazard to the seals. Testing was conducted to determine the effect on leakage of the CBM-to-CBM seal material exposed to AO/VUV. The sealing materials were S383 silicone and V835 fluorocarbon material. Control samples, which were not exposed to the AO/VUV environment, were used to ensure that ff any changes in leakage occurred, they could be attributed to the AO/VUV exposure. After exposure to the AO/VUV environment the leakage increase was dramatic for the fluorocarbon. This testing was a major contributing factor in selecting silicone as the CBM-to-CBM seal material.

Ignition of Ionic Liquids. Volume 2

DTIC Science & Technology

2010-09-01

TOFMS time-of-flight-mass-spectrometry TS transition state VUV vacuum ultraviolet ZPE zero-point energy Approved for public...energies ( ZPEs ) were scaled by a factor of 0.9613 and 0.9804, respectively, and when necessary intrinsic reaction coordinate (IRC) calculations were...oscillations in the PE reflect the vibration of the DNB molecule, including ZPE . The trajectory shows three dissociation steps, eliminating NO2 followed

VUV thin films, chapter 7

NASA Technical Reports Server (NTRS)

Zukic, Muamer; Torr, Douglas G.

1993-01-01

The application of thin film technology to the vacuum ultraviolet (VUV) wavelength region from 120 nm to 230 nm has not been fully exploited in the past because of absorption effects which complicate the accurate determination of the optical functions of dielectric materials. The problem therefore reduces to that of determining the real and imaginary parts of a complex optical function, namely the frequency dependent refractive index n and extinction coefficient k. We discuss techniques for the inverse retrieval of n and k for dielectric materials at VUV wavelengths from measurements of their reflectance and transmittance. Suitable substrate and film materials are identified for application in the VUV. Such applications include coatings for the fabrication of narrow and broadband filters and beamsplitters. The availability of such devices open the VUV regime to high resolution photometry, interferometry and polarimetry both for space based and laboratory applications. This chapter deals with the optics of absorbing multilayers, the determination of the optical functions for several useful materials, and the design of VUV multilayer stacks as applied to the design of narrow and broadband reflection and transmission filters and beamsplitters. Experimental techniques are discussed briefly, and several examples of the optical functions derived for selected materials are presented.

Absolute photon-flux measurements in the vacuum ultraviolet

NASA Technical Reports Server (NTRS)

Samson, J. A. R.; Haddad, G. N.

1974-01-01

Absolute photon-flux measurements in the vacuum ultraviolet have extended to short wavelengths by use of rare-gas ionization chambers. The technique involves the measurement of the ion current as a function of the gas pressure in the ion chamber. The true value of the ion current, and hence the absolute photon flux, is obtained by extrapolating the ion current to zero gas pressure. Examples are given at 162 and 266 A. The short-wavelength limit is determined only by the sensitivity of the current-measuring apparatus and by present knowledge of the photoionization processes that occur in the rate gases.

Solar CIV Vacuum-Ultraviolet Fabry-Perot Interferometers

NASA Technical Reports Server (NTRS)

Gary, G. Allen; West, Edward A.; Rees, David; McKay, Jack A.; Zukic, Maumer; Herman, Peter

2006-01-01

Aims: A tunable, high spectral resolution, high effective finesse, vacuum ultraviolet (VUV) Fabry-Perot interferometer (PPI) is designed for obtaining narrow-passband images, magnetograms, and Dopplergrams of the transition region emission line of CIV (155 nm). Methods: The integral part of the CIV narrow passband filter package (with a 2-10 pm FWHM) consists of a multiple etalon system composed of a tunable interferometer that provides high-spectral resolution and a static low-spectral resolution interferometer that allows a large effective free spectral range. The prefilter for the interferometers is provided by a set of four mirrors with dielectric high-reflective coatings. A tunable interferometer, a VUV piezoelectric-control etalon, has undergone testing using the surrogate F2 eximer laser line at 157 nm for the CIV line. We present the results of the tests with a description of the overall concept for a complete narrow-band CIV spectral filter. The static interferometer of the filter is envisioned as being hudt using a set of fixed MgF2 plates. The four-mirror prefilter is designed to have dielectric multilayer n-stacks employing the design concept used in the Ultraviolet Imager of NASA's Polar Spacecraft. A dual etalon system allows the effective free spectral range to be commensurate with the prefilter profile. With an additional etalon, a triple etalon system would allow a spectrographic resolution of 2 pm. The basic strategy has been to combine the expertise of spaceflight etalon manufacturing with VUV coating technology to build a VUV FPI which combines the best attributes of imagers and spectrographs into a single compact instrument. Results. Spectro-polarimetry observations of the transition region CIV emission can be performed to increase the understanding of the magnetic forces, mass motion, evolution, and energy release within the solar atmosphere at the base of the corona where most of the magnetic field is approximately force-free. The 2D imaging of the full vector magnetic field at the height of maximum magnetic influence (minimum plasma beta) can be accomplished, albeit difficult, by measuring the Zeeman splitting of the CIV resonance pair. Designs of multiple VUV FPIs can be developed for integration into future orbiting solar observatories to obtain rapid cadence, spectral imaging of the transition region.

Communication: Direct measurements of nascent O({sup 3}P{sub 0,1,2}) fine-structure distributions and branching ratios of correlated spin-orbit resolved product channels CO(ã{sup 3}Π; v) + O({sup 3}P{sub 0,1,2}) and CO(Χ{sup ~1}Σ{sup +}; v) + O({sup 3}P{sub 0,1,2}) in VUV photodissociation of CO{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Zhou; Chang, Yih Chung; Gao, Hong

2014-06-21

We present a generally applicable experimental method for the direct measurement of nascent spin-orbit state distributions of atomic photofragments based on the detection of vacuum ultraviolet (VUV)-excited autoionizing-Rydberg (VUV-EAR) states. The incorporation of this VUV-EAR method in the application of the newly established VUV-VUV laser velocity-map-imaging-photoion (VMI-PI) apparatus has made possible the branching ratio measurement for correlated spin-orbit state resolved product channels, CO(ã{sup 3}Π; v) + O({sup 3}P{sub 0,1,2}) and CO(Χ{sup ~1}Σ{sup +}; v) + O({sup 3}P{sub 0,1,2}), formed by VUV photoexcitation of CO{sub 2} to the 4s(1{sub 0}{sup 1}) Rydberg state at 97,955.7 cm{sup −1}. The total kinetic energy releasemore » (TKER) spectra obtained from the O{sup +} VMI-PI images of O({sup 3}P{sub 0,1,2}) reveal the formation of correlated CO(ã{sup 3}Π; v = 0–2) with well-resolved v = 0–2 vibrational bands. This observation shows that the dissociation of CO{sub 2} to form the spin-allowed CO(ã{sup 3}Π; v = 0–2) + O({sup 3}P{sub 0,1,2}) channel has no potential energy barrier. The TKER spectra for the spin-forbidden CO(Χ{sup ~1}Σ{sup +}; v) + O({sup 3}P{sub 0,1,2}) channel were found to exhibit broad profiles, indicative of the formation of a broad range of rovibrational states of CO(Χ{sup ~1}Σ{sup +})  with significant vibrational populations for v = 18–26. While the VMI-PI images for the CO(ã{sup 3}Π; v = 0–2) + O({sup 3}P{sub 0,1,2}) channel are anisotropic, indicating that the predissociation of CO{sub 2} 4s(1{sub 0}{sup 1}) occurs via a near linear configuration in a time scale shorter than the rotational period, the angular distributions for the CO(Χ{sup ~1}Σ{sup +}; v) + O({sup 3}P{sub 0,1,2}) channel are close to isotropic, revealing a slower predissociation process, which possibly occurs on a triplet surface via an intersystem crossing mechanism.« less

Direct Analysis of Organic Compounds in Liquid Using a Miniature Photoionization Ion Trap Mass Spectrometer with Pulsed Carrier-Gas Capillary Inlet.

PubMed

Lu, Xinqiong; Yu, Quan; Zhang, Qian; Ni, Kai; Qian, Xiang; Tang, Fei; Wang, Xiaohao

2017-08-01

A miniature ion trap mass spectrometer with capillary direct sampling and vacuum ultraviolet photoionization source was developed to conduct trace analysis of organic compounds in liquids. Self-aspiration sampling is available where the samples are drawn into the vacuum chamber through a capillary with an extremely low flow rate (less than 1 μL/min), which minimizes sample consumption in each analysis to tens of micrograms. A pulsed gas-assisted inlet was designed and optimized to promote sample transmission in the tube and facilitate the cooling of ions, thereby improving instrument sensitivity. A limit of detection of 2 ppb could be achieved for 2,4-dimethylaniline in a methanol solution. The sampling system described in the present study is specifically suitable for a miniature photoionization ion trap mass spectrometer that can perform rapid and online analysis for liquid samples. Graphical Abstract ᅟ.

Direct Analysis of Organic Compounds in Liquid Using a Miniature Photoionization Ion Trap Mass Spectrometer with Pulsed Carrier-Gas Capillary Inlet

NASA Astrophysics Data System (ADS)

Lu, Xinqiong; Yu, Quan; Zhang, Qian; Ni, Kai; Qian, Xiang; Tang, Fei; Wang, Xiaohao

2017-08-01

A miniature ion trap mass spectrometer with capillary direct sampling and vacuum ultraviolet photoionization source was developed to conduct trace analysis of organic compounds in liquids. Self-aspiration sampling is available where the samples are drawn into the vacuum chamber through a capillary with an extremely low flow rate (less than 1 μL/min), which minimizes sample consumption in each analysis to tens of micrograms. A pulsed gas-assisted inlet was designed and optimized to promote sample transmission in the tube and facilitate the cooling of ions, thereby improving instrument sensitivity. A limit of detection of 2 ppb could be achieved for 2,4-dimethylaniline in a methanol solution. The sampling system described in the present study is specifically suitable for a miniature photoionization ion trap mass spectrometer that can perform rapid and online analysis for liquid samples.

HANDBOOK ON ADVANCED PHOTOCHEMICAL OXIDATION ...

EPA Pesticide Factsheets

This handbook summarizes commercial-scale system performance and cost data for advanced photochemical oxidation (APO) treatment of contaminated water, air, and solids. Similar information from pilot- and bench-scale evaluations of APO processes is also included to supplement the commercial-scale data. Performance and cost data is summarized for various APO processes, including vacuum ultraviolet (VUV) photolysis, ultraviolet (UV)/oxidation, photo-Fenton, and dye- or semiconductor-sensitized APO processes. This handbook is intended to assist engineering practitioners in evaluating the applicability of APO processes and in selecting one or more such processes for site-specific evaluation.APO has been shown to be effective in treating contaminated water and air. Regarding contaminated water treatment, UV/oxidation has been evaluated for the most contaminants, while VUV photolysis has been evaluated for the fewest. Regarding contaminated air treatment, the sensitized APO processes have been evaluated for the most contaminants, while VUV photolysis has been evaluated for the fewest.APO processes for treating contaminated solids generally involve treatment of contaminated slurry or leachate generated using an extraction process such as soil washing. APO has been shown to be effective in treating contaminated solids, primarily at the bench-scale level. Information

Molecular Beam Mass Spectrometry With Tunable Vacuum Ultraviolet (VUV) Synchrotron Radiation

PubMed Central

Golan, Amir; Ahmed, Musahid

2012-01-01

Tunable soft ionization coupled to mass spectroscopy is a powerful method to investigate isolated molecules, complexes and clusters and their spectroscopy and dynamics1-4. Fundamental studies of photoionization processes of biomolecules provide information about the electronic structure of these systems. Furthermore determinations of ionization energies and other properties of biomolecules in the gas phase are not trivial, and these experiments provide a platform to generate these data. We have developed a thermal vaporization technique coupled with supersonic molecular beams that provides a gentle way to transport these species into the gas phase. Judicious combination of source gas and temperature allows for formation of dimers and higher clusters of the DNA bases. The focus of this particular work is on the effects of non-covalent interactions, i.e., hydrogen bonding, stacking, and electrostatic interactions, on the ionization energies and proton transfer of individual biomolecules, their complexes and upon micro-hydration by water1, 5-9. We have performed experimental and theoretical characterization of the photoionization dynamics of gas-phase uracil and 1,3-dimethyluracil dimers using molecular beams coupled with synchrotron radiation at the Chemical Dynamics Beamline10 located at the Advanced Light Source and the experimental details are visualized here. This allowed us to observe the proton transfer in 1,3-dimethyluracil dimers, a system with pi stacking geometry and with no hydrogen bonds1. Molecular beams provide a very convenient and efficient way to isolate the sample of interest from environmental perturbations which in return allows accurate comparison with electronic structure calculations11, 12. By tuning the photon energy from the synchrotron, a photoionization efficiency (PIE) curve can be plotted which informs us about the cationic electronic states. These values can then be compared to theoretical models and calculations and in turn, explain in detail the electronic structure and dynamics of the investigated species 1, 3. PMID:23149375

Deuterium Enrichment of PAHs by VUV Irradiation of Interstellar Ices

NASA Technical Reports Server (NTRS)

Bernstein, Max P.; Sandford, Scott A.; Allamandola, Louis J.; Gillette, J. Seb; Zare, Richard N.; DeVincenzi, Donald (Technical Monitor)

1998-01-01

Laboratory results demonstrate that polycyclic aromatic hydrocarbons (PAHs) rapidly exchange their hydrogen atoms with those of nearby molecules when they are frozen into low-temperature ices and exposed to vacuum ultraviolet radiation. As a result, PAHs quickly become deuterium-enriched when VUV irradiated in D-containing ices. This mechanism has important consequences for several astrophysical issues owing to the ubiquitous nature of PAHs in the interstellar medium. For example, this process may explain the deuterium enrichments found in PAHs in meteorites and interplanetary dust particles. These results also provide general predictions about the molecular siting of the deuterium on aromatic materials in meteorites if this process produced a significant fraction of their D-enrichment.

The spectral properties of uranium hexafluoride and its thermal decomposition products

NASA Technical Reports Server (NTRS)

Krascella, N. L.

1976-01-01

This investigation was initiated to provide basic spectral data for gases of interest to the plasma core reactor concept. The attenuation of vacuum ultraviolet (VUV) radiation by helium at pressures up to 20 atm over path lengths of about 61 cm and in the approximate wavelength range between 80 and 300 nm was studied. Measurements were also conducted to provide basic VUV data with respect to UF6 and UF6/argon mixtures in the wavelength range between 80 and 120 nm. Finally, an investigation was initiated to provide basic spectral emission and absorption data for UF6 and possible thermal decomposition products of UF6 at elevated temperatures.

Rapid preparation of solution-processed InGaZnO thin films by microwave annealing and photoirradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheong, Heajeong; Ogura, Shintaro; Ushijima, Hirobumi

We fabricated solution-processed indium–gallium–zinc oxide (IGZO) thin-film transistors (TFTs) by microwave (MW) annealing an IGZO precursor film followed by irradiating with vacuum ultraviolet (VUV) light. MW annealing allows more rapid heating of the precursor film than conventional annealing processes using a hot plate or electric oven and promotes the crystallization of IGZO. VUV irradiation was used to reduce the duration and temperature of the post-annealing step. Consequently, the IGZO TFTs fabricated through MW annealing for 5 min and VUV irradiation for 1 min exhibited an on/off current ratio of 10{sup 8} and a field-effect mobility of 0.3 cm{sup 2} V{sup −1} s{supmore » −1}. These results indicate that MW annealing and photoirradiation is an effective combination for annealing solution processed IGZO precursor films to prepare the semiconductor layers of TFTs.« less

Laboratory Spectroscopy of Planetary Ices in the VUV and THz Spectral Regions

NASA Technical Reports Server (NTRS)

Gerakines, P.; Hilton, D.; Sangala, B.

2010-01-01

I will describe efforts to study the spectroscopy of condenser) films at low temperature (10-150 K) in both the far-infrared/THz (30-3000 microns) and vacuum-ultraviolet (VUV, 100-200 nm.) ranges of the electromagnetic spectrum. In each of these wavelength ranges, there is a general lack of laboratory data for ices relevant to astrophysical environments such as the outer Solar System. These studies are focused on mixtures of candidate species applicable to planets and satellites in the outer solar system, such as those dominated by H2O or N2 with other important species such as CO2, CH4, and NH3. We will discuss our results in relation to analyses of VUV data sets from the UVIS instrument on Cassini, far-infrared data from missions such as Herschel and SOFIA, as well as sub-mm observatories such as ALMA.

Proton-induced degradation of VUV transmission of LiF and MgF2

NASA Technical Reports Server (NTRS)

Reft, C. S.; Becher, J.; Kernell, R. L.

1980-01-01

Proton-induced degradation of vacuum ultraviolet (VUV) transmittance of LiF and MgF2 was measured for 85- and 600-MeV protons for a fluence up to 2.8 x 10 to the 13th p/sq cm. Transmittances were measured from 105 to 210 nm. When the irradiation level for a given material is expressed in terms of absorbed energy per unit of volume of crystal, 85- and 600-MeV protons produce the same degradation. MgF2 is substantially more radiation resistant than LiF in the VUV. Irradiation of LiF with 1.8 x 10 to the 13th p/sq cm at 85 MeV changed the transmittance of the hydrogen Ly-alpha line at 121.6 nm from 55 to 23%. The corresponding change for MgF2 was from 52 to 42% for 2.8 x 10 to the 13th p/sq cm.

The effects of simulated low Earth orbit environments on spacecraft thermal control coatings

NASA Technical Reports Server (NTRS)

Dever, Joyce A.; Rutledge, Sharon K.; Bruckner, Eric J.; Stidham, Curtis R.; Stueber, Thomas J.; Booth, Roy E.

1993-01-01

Candidate Space Station Freedom radiator coatings including Z-93, YB-71, anodized aluminum and SiO(x) coated silvered Teflon have been characterized for optical properties degradation upon exposure to environments containing atomic oxygen, vacuum ultraviolet (VUV) radiation, and/or silicone contamination. YB-71 coating showed a blue-gray discoloration, which has not been observed in space, upon exposure in atomic oxygen facilities which also provide exaggerated VUV radiation. This is evidence that damage mechanisms occur in these ground laboratory facilities which are different from those which occur in space. Radiator coatings exposed to an electron cyclotron resonance (ECR) atomic oxygen source in the presence of silicone-containing samples showed severe darkening from the intense VUV radiation provided by the ECR and from silicone contamination. Samples exposed to atomic oxygen from the ECR source and to VUV lamps, simultaneously, with in situ reflectance measurement, showed that significantly greater degradation occurred when samples received line-of-site ECR beam exposure than when samples were exposed to atomic oxygen scattered off of quartz surfaces without line-of-site view of the ECR beam. For white paints, exposure to air following atomic oxygen/VUV exposure reversed the darkening due to VUV damage. This illustrates the importance of in situ reflectance measurement.

An investigation of the degradation of Fluorinated Ethylene Propylene (FEP) copolymer thermal blanketing materials aboard LDEF in the laboratory

NASA Technical Reports Server (NTRS)

Stiegman, A. E.; Brinza, David E.; Anderson, Mark S.; Minton, Timothy K.; Laue, Eric G.; Liang, Ranty H.

1991-01-01

Samples of fluorinated ethylene propylene copolymer thermal blanketing material, recovered from the Long Duration Exposure Facility (LDEF), were investigated to determine the nature and the extent of degradation due to exposure to the low-Earth-orbit environment. Samples recovered from the ram-facing direction of LDEF, which received vacuum-ultraviolet (VUV) radiation and atomic-oxygen impingement, and samples from the trailing edge, which received almost exclusively VUV exposure, were investigated by scanning electron microscopy and atomic force microscopy. The most significant result of this investigation was found on samples that received only VUV exposure. These samples possessed a hard, embrittled surface layer that was absent from the atomic-oxygen exposed sample and from unexposed control samples. This surface layer is believed to be responsible for the 'synergistic' effect between VUV and atomic oxygen. Overall, the investigation revealed dramatically different morphologies for the two samples. The sample receiving both atomic-oxygen and VUV exposure was deeply eroded and had a characteristic 'rolling' surface morphology, while the sample that received only VUV exposure showed mild erosion and a surface morphology characterized by sharp high-frequency peaks. The morphologies observed in the LDEF samples, including the embrittled surface layer, were successfully duplicated in the laboratory.

Temporal VUV Emission Characteristics Related to Generations and Losses of Metastable Atoms in Xenon Pulsed Barrier Discharge

NASA Astrophysics Data System (ADS)

Motomura, Hideki; Loo, Ka Hong; Ikeda, Yoshihisa; Jinno, Masafumi; Aono, Masaharu

Although xenon pulsed dielectric barrier discharge is one of the most promising substitutes for mercury low-pressure discharge for fluorescent lamps, the efficacy of xenon fluorescent lamp is not enough for practical use for general lighting. To improve the efficacy it is indispensable to clarify mechanisms of vacuum ultraviolet (VUV) emissions, which excite phosphor, from xenon discharge related to plasma characteristics. In this paper emission waveforms and temporal change of metastable atom density are measured and temporal VUV emission characteristics related to generations and losses of metastable atoms in xenon pulsed barrier discharge is investigated. It is shown that the lamp efficacy is improved by about 10% with shorter pulse in which the two VUV emission peaks in a pulse are overlapped. It is also shown that at the lower pressure of 1.3 kPa metastable atoms generated during on-period of the voltage pulse are not efficiently consumed for VUV emissions in the off-period of the voltage pulse because of lower rate of three-body collision and quenching. This fact is thought to be one of the reasons why the lamp efficacy is low at lower pressure.

Wide-field direct CCD observations supporting the Astro-1 Space Shuttle mission's Ultraviolet Imaging Telescope

NASA Technical Reports Server (NTRS)

Hintzen, Paul; Angione, Ron; Talbert, Freddie; Cheng, K.-P.; Smith, Eric; Stecher, Theodore P.

1993-01-01

Wide field direct CCD observations are being obtained to support and complement the vacuum-ultraviolet (VUV) images provided by Astro's Ultraviolet Imaging Telescope (UIT) during a Space Shuttle flight in December 1990. Because of the wide variety of projects addressed by UIT, the fields observed include (1) galactic supernova remnants such as the Cygnus Loop and globular clusters such as Omega Cen and M79; (2) the Magellanic Clouds, M33, M81, and other galaxies in the Local Group; and (3) rich clusters of galaxies, principally the Perseus cluster and Abell 1367. Ground-based observations have been obtained for virtually all of the Astro-1 UIT fields. The optical images allow identification of individual UV sources in each field and provide the long baseline in wavelength necessary for accurate analysis of UV-bright sources. To facilitate use of our optical images for analysis of UIT data and other projects, we plan to archive them, with the UIT images, at the National Space Science Data Center (NSSDC), where they will be universally accessible via anonymous FTP. The UIT, one of three telescopes comprising the Astro spacecraft, is a 38-cm f/9 Ritchey-Chretien telescope on which high quantum efficiency, solar-blind image tubes are used to record VUV images on photographic film. Five filters with passbands centered between 1250A and 2500A provide both VUV colors and a measurement of extinction via the 2200A dust feature. The resulting calibrated VUV pictures are 40 arcminutes in diameter at 2.5 arcseconds resolution. The capabilities of UIT, therefore, complement HST's WFPC: the latter has 40 times greater collecting area, while UIT's usable field has 170 times WFPC's field area.

High-Reflectivity Coatings for a Vacuum Ultraviolet Spectropolarimeter

NASA Astrophysics Data System (ADS)

Narukage, Noriyuki; Kubo, Masahito; Ishikawa, Ryohko; Ishikawa, Shin-nosuke; Katsukawa, Yukio; Kobiki, Toshihiko; Giono, Gabriel; Kano, Ryouhei; Bando, Takamasa; Tsuneta, Saku; Auchère, Frédéric; Kobayashi, Ken; Winebarger, Amy; McCandless, Jim; Chen, Jianrong; Choi, Joanne

2017-03-01

Precise polarization measurements in the vacuum ultraviolet (VUV) region are expected to be a new tool for inferring the magnetic fields in the upper atmosphere of the Sun. High-reflectivity coatings are key elements to achieving high-throughput optics for precise polarization measurements. We fabricated three types of high-reflectivity coatings for a solar spectropolarimeter in the hydrogen Lyman-α (Lyα; 121.567 nm) region and evaluated their performance. The first high-reflectivity mirror coating offers a reflectivity of more than 80 % in Lyα optics. The second is a reflective narrow-band filter coating that has a peak reflectivity of 57 % in Lyα, whereas its reflectivity in the visible light range is lower than 1/10 of the peak reflectivity (˜ 5 % on average). This coating can be used to easily realize a visible light rejection system, which is indispensable for a solar telescope, while maintaining high throughput in the Lyα line. The third is a high-efficiency reflective polarizing coating that almost exclusively reflects an s-polarized beam at its Brewster angle of 68° with a reflectivity of 55 %. This coating achieves both high polarizing power and high throughput. These coatings contributed to the high-throughput solar VUV spectropolarimeter called the Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP), which was launched on 3 September, 2015.

A small porous-plug burner for studies of combustion chemistry and soot formation

NASA Astrophysics Data System (ADS)

Campbell, M. F.; Schrader, P. E.; Catalano, A. L.; Johansson, K. O.; Bohlin, G. A.; Richards-Henderson, N. K.; Kliewer, C. J.; Michelsen, H. A.

2017-12-01

We have developed and built a small porous-plug burner based on the original McKenna burner design. The new burner generates a laminar premixed flat flame for use in studies of combustion chemistry and soot formation. The size is particularly relevant for space-constrained, synchrotron-based X-ray diagnostics. In this paper, we present details of the design, construction, operation, and supporting infrastructure for this burner, including engineering attributes that enable its small size. We also present data for charactering the flames produced by this burner. These data include temperature profiles for three premixed sooting ethylene/air flames (equivalence ratios of 1.5, 1.8, and 2.1); temperatures were recorded using direct one-dimensional coherent Raman imaging. We include calculated temperature profiles, and, for one of these ethylene/air flames, we show the carbon and hydrogen content of heavy hydrocarbon species measured using an aerosol mass spectrometer coupled with vacuum ultraviolet photoionization (VUV-AMS) and soot-volume-fraction measurements obtained using laser-induced incandescence. In addition, we provide calculated mole-fraction profiles of selected gas-phase species and characteristic profiles for seven mass peaks from AMS measurements. Using these experimental and calculated results, we discuss the differences between standard McKenna burners and the new miniature porous-plug burner introduced here.

A small porous-plug burner for studies of combustion chemistry and soot formation.

PubMed

Campbell, M F; Schrader, P E; Catalano, A L; Johansson, K O; Bohlin, G A; Richards-Henderson, N K; Kliewer, C J; Michelsen, H A

2017-12-01

We have developed and built a small porous-plug burner based on the original McKenna burner design. The new burner generates a laminar premixed flat flame for use in studies of combustion chemistry and soot formation. The size is particularly relevant for space-constrained, synchrotron-based X-ray diagnostics. In this paper, we present details of the design, construction, operation, and supporting infrastructure for this burner, including engineering attributes that enable its small size. We also present data for charactering the flames produced by this burner. These data include temperature profiles for three premixed sooting ethylene/air flames (equivalence ratios of 1.5, 1.8, and 2.1); temperatures were recorded using direct one-dimensional coherent Raman imaging. We include calculated temperature profiles, and, for one of these ethylene/air flames, we show the carbon and hydrogen content of heavy hydrocarbon species measured using an aerosol mass spectrometer coupled with vacuum ultraviolet photoionization (VUV-AMS) and soot-volume-fraction measurements obtained using laser-induced incandescence. In addition, we provide calculated mole-fraction profiles of selected gas-phase species and characteristic profiles for seven mass peaks from AMS measurements. Using these experimental and calculated results, we discuss the differences between standard McKenna burners and the new miniature porous-plug burner introduced here.

A Mechanistical Study on the Formation of Dimethyl Ether (CH3OCH3) and Ethanol (CH3CH2OH) in Methanol-containing Ices and Implications for the Chemistry of Star-forming Regions

NASA Astrophysics Data System (ADS)

Bergantini, Alexandre; Góbi, Sándor; Abplanalp, Matthew J.; Kaiser, Ralf I.

2018-01-01

The underlying formation mechanisms of complex organic molecules (COMs)—in particular, structural isomers—in the interstellar medium (ISM) are largely elusive. Here, we report new experimental findings on the role of methanol (CH3OH) and methane (CH4) ices in the synthesis of two C2H6O isomers upon interaction with ionizing radiation: ethanol (CH3CH2OH) and dimethyl ether (CH3OCH3). The present study reproduces the interstellar abundance ratios of both species with ethanol to dimethyl ether branching ratios of (2.33 ± 0.14):1 suggesting that methanol and methane represents the key precursor to both isomers within interstellar ices. Exploiting isotopic labeling combined with reflectron time-of-flight mass spectrometry (Re-TOF-MS) after isomer selective vacuum ultra-violet (VUV) photoionization of the neutral molecules, we also determine the formation mechanisms of both isomers via radical–radical recombination versus carbene (CH2) insertion with the former pathway being predominant. Formation routes to higher molecular weight reaction products such as ethylene glycol (HOCH2CH2OH), dimethyl peroxide (CH3OOCH3), and methoxymethanol (CH3OCH2OH) are discussed briefly as well.

Narrowband NanoSat Scale Photometry for VUV Planetary and Heliophysics missions

NASA Astrophysics Data System (ADS)

Noto, J.; Doe, R. A.; Frey, H. U.

2015-12-01

Remote vacuum ultraviolet (VUV) soundings to support Explorer-class atmospheric research are typically enabled by large aperture, wideband spectrographs carefully pointed to measure a planet's disk and limb regions (i.e. TIMED/GUVI and MAVEN/UVS). An alternate measurement paradigm is to identify key aeronomical emission targets (i.e HI 121.6-nm, OI 135.6-nm, N2 Lyman-Birge-Hopfield band 135 - 155 nm) and create a series of narrowband photometers each with greater in-band sensitivity (relative to a spectrograph) due to enhanced out-of-band rejection and absence of a dispersive element. Recent advances in narrowband VUV coating and PMT miniaturization have enabled design of a dual-channel nanosatellite-scale VUV photometer with flight heritage significantly leveraged from the NASA POLAR UVI imager the Air Force CubeSat Tiny Ionospheric Photometer (CTIP). Herein we present further modeled sensitivity studies and current build status of the dual-channel thermosphere/ionosphere photometer (DTIP) and address notional missions including dayside O/N2 composition, auroral energetics, nightside plasma structuring and peak layer characterization, and hydrogen geocoronal tomographic imaging.

Fast discharge in a plasma gun with hemispherical insulator

NASA Astrophysics Data System (ADS)

Antsiferov, P. S.; Dorokhin, L. A.; Sidelnikov, Yu. V.; Koshelev, K. N.

2009-05-01

A method of creation of hot dense plasma is proposed. It is based on cumulation of a shockwave, which originates on a hemispherical surface of insulator of plasma gun. The results of first experiments are presented. The shock wave is driven by fast electrical discharge (dI /dt>1012 A/s). The inductive storage with semiconductor opening switch is used as a current driver. Time resolved pin-hole images and vacuum ultraviolet (vuv) spectra are studied. Shockwaves from hemispherical insulator with 4 mm radius create plasma with a form of column about 1 mm diameter and 3-4 mm length. vuv spectra contain the lines of Ar ions that corresponds to the electron temperature about 20 eV. Possible practical application is discussed.

Effects of Contamination, UV Radiation, and Atomic Oxygen on ISS Thermal Control Materials

NASA Technical Reports Server (NTRS)

Visentine, Jim; Finckenor, Miria; Zwiener, Jim; Munafo, Paul (Technical Monitor)

2001-01-01

Thermal control surfaces on the International Space Station (ISS) have been tailored for optimum optical properties. The space environment, particularly contamination, ultraviolet (UV) radiation, and atomic oxygen (AO) may have a detrimental effect on these optical properties. These effects must be quantified for modeling and planning. Also of interest was the effect of porosity on the reaction to simulated space environment. Five materials were chosen for this study based on their use on ISS. The thermal control materials were Z-93 white coating, silverized Teflon, chromic acid anodized aluminum, sulfuric acid anodized aluminum, and 7075-T6 aluminum. Some of the samples were exposed to RTV 560 silicone; others were exposed to Tefzel offgassing products. Two samples of Z-93 were not exposed to contamination as clean "controls". VUV radiation was used to photo-fix the contaminant to the material surface, then the samples were exposed to AO. All samples were exposed to 1000 equivalent sun-hours (ESH) of vacuum ultraviolet radiation (VUV) at the AZ Technology facility and a minimum of 1.5 x 10(exp 20) atoms/sq cm of AO at Marshall Space Flight Center. Half of the samples were exposed to an additional 2000 ESH of VUV at Huntington Beach prior to sent to AZ Technology. Darkening of the Z-93 white coating was noted after VUV exposure. AO exposure did bleach the Z-93 but not back to its original brightness. Solar absorptance curves show the degradation due to contamination and VUV and the recovery with AO exposure. More bleaching was noted on the Tefzel-contaminated samples than with the RTV-contaminated samples.

Surface Chemical Conversion of Organosilane Self-Assembled Monolayers with Active Oxygen Species Generated by Vacuum Ultraviolet Irradiation of Atmospheric Oxygen Molecules

NASA Astrophysics Data System (ADS)

Kim, Young-Jong; Lee, Kyung-Hwang; Sano, Hikaru; Han, Jiwon; Ichii, Takashi; Murase, Kuniaki; Sugimura, Hiroyuki

2008-01-01

The chemical conversion of the top surface of n-octadecyltrimethoxy silane self-assembled monolayers (ODS-SAMs) on oxide-covered Si substrates using active oxygen species generated from atmospheric oxygen molecules irradiated with vacuum ultraviolet (VUV) light at 172 nm in wavelength has been studied on the basis of water contact angle measurements, ellipsometry, X-ray photoelectron spectroscopy, and atomic force microscopy. An ODS-SAM whose water contact angle was 104° on average was prepared using chemical vapor deposition with substrate and vapor temperatures of 150 °C. The VUV treatment of an ODS-SAM sample was carried out by placing the sample in air and then irradiating the sample surface with a Xe-excimer lamp. The distance between the lamp and the sample was regulated so that the VUV light emitted from the lamp was almost entirely absorbed by atmospheric oxygen molecules to generate active oxygen species, such as ozone and atomic oxygen before reaching the sample surface. Hence, the surface chemical conversion of the ODS-SAM was primarily promoted through chemical reactions with the active oxygen species. Photochemical changes in the ODS-SAM were found to be the generation of polar functional groups, such as -COOH, -CHO, and -OH, on the surface and the subsequent etching of the monolayer. Irradiation parameters, such as irradiation time, were optimized to achieve a better functionalization of the SAM top surface while minimizing the etching depth of the ODS-SAM. The ability to graft another SAM onto the modified ODS-SAM bearing polar functional groups was demonstrated by the formation of alkylsilane bilayers.

Spectral lines and characteristic of temporal variations in photoionized plasmas induced with laser-produced plasma extreme ultraviolet source

NASA Astrophysics Data System (ADS)

Saber, I.; Bartnik, A.; Wachulak, P.; Skrzeczanowski, W.; Jarocki, R.; Fiedorowicz, H.

2017-11-01

Spectral lines for Kr/Ne/H2 photoionized plasma in the ultraviolet and visible (UV/Vis) wavelength ranges have been created using a laser-produced plasma (LPP) EUV source. The source is based on a double-stream gas puff target irradiated with a commercial Nd:YAG laser. The laser pulses were focused onto a gas stream, injected into a vacuum chamber synchronously with the EUV pulses. Spectral lines from photoionization in neutral Kr/Ne/H2 and up to few charged states were observed. The intense emission lines were associated with the Kr transition lines. Experimental and theoretical investigations on intensity variations for some ionic lines are presented. A decrease in the intensity with the delay time between the laser pulse and the spectrum acquisition was revealed. Electron temperature and electron density in the photoionized plasma have been estimated from the characteristic emission lines. Temperature was obtained using Boltzmann plot method, assuming that the population density of atoms and ions are considered in a local thermodynamic equilibrium (LTE). Electron density was calculated from the Stark broadening profile. The temporal evaluation of the plasma and the way of optimizing the radiation intensity of LPP EUV sources is discussed.

Indium Tin Oxide-Magnesium Fluoride Co-Deposited Films for Spacecraft Applications

NASA Technical Reports Server (NTRS)

Dever, Joycer A.; Rutledge, Sharon K.; Hambourger, Paul D.; Bruckner, Eric; Ferrante, Rhea; Pal, Anna Marie; Mayer, Karen; Pietromica, Anthony J.

1998-01-01

Highly transparent coatings with a maximum sheet resistivity between 10(exp 8) and 10(exp 9) ohms/square are desired to prevent charging of solar arrays for low Earth polar orbit and geosynchronous orbit missions. Indium tin oxide (ITO) and magnesium fluoride (MgF2) were ion beam sputter co-deposited onto fused silica substrates and were evaluated for transmittance, sheet resistivity and the effects of simulated space environments including atomic oxygen (AO) and vacuum ultraviolet (VUV) radiation. Optical properties and sheet resistivity as a function of MgF2 content in the films will be presented. Films containing 8.4 wt.% MgF2 were found to be highly transparent and provided sheet resistivity in the required range. These films maintained a high transmittance upon exposure to AO and to VUV radiation, although exposure to AO in the presence of charged species and intense electromagnetic radiation caused significant degradation in film transmittance. Sheet resistivity of the as-fabricated films increased with time in ambient conditions. Vacuum beat treatment following film deposition caused a reduction in sheet resistivity. However, following vacuum heat treatment, sheet resistivity values remained stable during storage in ambient conditions.

Methyl Radicals in Oxidative Coupling of Methane Directly Confirmed by Synchrotron VUV Photoionization Mass Spectroscopy

PubMed Central

Luo, Liangfeng; Tang, Xiaofeng; Wang, Wendong; Wang, Yu; Sun, Shaobo; Qi, Fei; Huang, Weixin

2013-01-01

Gas-phase methyl radicals have been long proposed as the key intermediate in catalytic oxidative coupling of methane, but the direct experimental evidence still lacks. Here, employing synchrotron VUV photoionization mass spectroscopy, we have directly observed the formation of gas-phase methyl radicals during oxidative coupling of methane catalyzed by Li/MgO catalysts. The concentration of gas-phase methyl radicals correlates well with the yield of ethylene and ethane products. These results lead to an enhanced fundamental understanding of oxidative coupling of methane that will facilitate the exploration of new catalysts with improved performance. PMID:23567985

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsuchiya, Kimichika, E-mail: kimichika.tsuchiya@kek.jp; Adachi, Masahiro; Shioya, Tatsuro

At the 2.5-GeV Photon Factory (PF) storage ring, we recently constructed four new undulators known as U#02-2, U#13, SGU#15, and U#28 for BL02, BL13, BL15, and BL28, respectively. SGU#15 is an in-vacuum undulator with a period length of 17.6 mm. The other three undulators are elliptically polarizing undulators (EPUs) for the vacuum ultraviolet and soft X-ray (VUV-SX) light sources to obtain various polarization states. We constructed these new undulators by fiscal 2013 and step by step installed them in the PF ring. We describe the details of the construction of these new undulators in this report.

INTRODUCTION: The 8th International Conference on Vacuum Ultraviolet Radiation Physics

NASA Astrophysics Data System (ADS)

Nilsson, Per Olof; Hedin, Lars

1987-01-01

The VUV conferences series The international conferences on vacuum ultraviolet radiation physics started in 1962, and are now being held every third year. VUV-8 took place at Lund University, August 4-8, 1986. VUV-9 will be arranged at the University of Hawaii, USA, August 14-18, 1989, with Prof. C S Fadley as conference chairman. Chairman of the international advisory board for the period 1986-89 is Prof. L Hedin. The theme of the series can be summarized as experimental and theoretical progress in research fields utilizing the interaction of VUV radiation with matter. The topics cover broad areas within atomic and molecular physics, solid state physics and VUV instrumentation. The conferences emphasize interdisciplinary aspects. To these belong common experimental techniques as, e.g., synchrotron radiation instrumentation, and common theoretical foundations for the description of photon interactions with matter. The VUV-8 conference The VUV-8 conference in Lund was attended by 300 participants from 26 countries. An address list of the participants is given at the end of this volume. There were 33 invited papers given as plenary or key-note talks. As many as 229 posters were presented; 49 of them were also given orally. These numbers are typical for the VUV conferences, except for the number of posters, which was unusually large. In the conference planning the poster sessions were stressed, and particular care was taken to provide a good atmosphere at these sessions. Thus the posters were kept up during the whole conference, coffee was served in the hail with the posters and there were convenient places to sit down close to the posters. Considering the wide scope of the conference it was necessary to emphasize a limited number of topics of high current interest and importance. Thus besides traditional topics, several rapidly expanding fields were discussed in special sessions. At VUV-8 there were the following sessions. Theory of atoms and molecules photoabsorption and -ionization of atoms and molecules and related phenomena multiphoton and other dynamical processes plasma physics VUV lasers time resolved spectroscopy instrumentation for VUV radiation synchrotron radiation centres solid state spectroscopy dynamical processes involving localized levels fundamental aspects of photoemission spin-polarized photoemission inverse photoemission semiconductors organic materials adsorbates Proceedings of VUV-8 The present volume contains most of the invited papers (28 out of 33). Regarding the contributed papers, over 50 are now being published in regular issues of PHYSICA SCRIPTA. These papers will also appear in a reprint volume, PHYSICA SCRIPTA RS4, which soon will be available. Abstracts of invited and contributed papers appeared in three conference volumes as follows: Volume I: Atomic and molecular physics. Instrumentation. Volume II: Solid state physics. Volume III: Post deadline papers. These books have been registered in an international data base and can thus be cited as published documents. Copies may be received from the conference secretary.* Acknowledgements We would like to thank our sponsors, which are listed on the following page, the members of the international program committee, and all others who helped in the planning of the program. Above all we like to thank those who worked with the local organization. Due to their dedicated efforts the conference ran very smoothly with a pleasant atmosphere.

Laser Desorption Postionization Mass Spectrometry of Antibiotic-Treated Bacterial Biofilms using Tunable Vacuum Ultraviolet Radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gasper, Gerald L; Takahashi, Lynelle K; Zhou, Jia

2010-08-04

Laser desorption postionization mass spectrometry (LDPI-MS) with 8.0 ? 12.5 eV vacuum ultraviolet synchrotron radiation is used to single photon ionize antibiotics andextracellular neutrals that are laser desorbed both neat and from intact bacterial biofilms. Neat antibiotics are optimally detected using 10.5 eV LDPI-MS, but can be ionized using 8.0 eV radiation, in agreement with prior work using 7.87 eV LDPI-MS. Tunable vacuum ultraviolet radiation also postionizes laser desorbed neutrals of antibiotics and extracellular material from within intact bacterial biofilms. Different extracellular material is observed by LDPI-MS in response to rifampicin or trimethoprim antibiotic treatment. Once again, 10.5 eV LDPI-MSmore » displays the optimum trade-off between improved sensitivity and minimum fragmentation. Higher energy photons at 12.5 eV produce significant parent ion signal, but fragment intensity and other low mass ions are also enhanced. No matrix is added to enhance desorption, which is performed at peak power densities insufficient to directly produce ions, thus allowing observation of true VUV postionization mass spectra of antibiotic treated biofilms.« less

VUV spectroscopic study of the ? state of H2

NASA Astrophysics Data System (ADS)

Dickenson, G. D.; Ubachs, W.

2014-04-01

Spectral lines, probing rotational quantum states J‧ = 0, 1, 2 of the inner well vibrations (υ‧ ≤ 8) in the ? state of molecular hydrogen, were recorded in high resolution using a vacuum ultraviolet Fourier transform absorption spectrometer in the wavelength range 73-86 nm. Accurate line positions and predissociation widths are determined from a fit to the absorption spectra. Improved values for the line positions are obtained, while the predissociation widths agree well with previous investigations.

A Miniaturized Linear Wire Ion Trap with Electron Ionization and Single Photon Ionization Sources

NASA Astrophysics Data System (ADS)

Wu, Qinghao; Tian, Yuan; Li, Ailin; Andrews, Derek; Hawkins, Aaron R.; Austin, Daniel E.

2017-05-01

A linear wire ion trap (LWIT) with both electron ionization (EI) and single photon ionization (SPI) sources was built. The SPI was provided by a vacuum ultraviolet (VUV) lamp with the ability to softly ionize organic compounds. The VUV lamp was driven by a pulse amplifier, which was controlled by a pulse generator, to avoid the detection of photons during ion detection. Sample gas was introduced through a leak valve, and the pressure in the system is shown to affect the signal-to-noise ratio and resolving power. Under optimized conditions, the limit of detection (LOD) for benzene was 80 ppbv using SPI, better than the LOD using EI (137 ppbv). System performance was demonstrated by distinguishing compounds in different classes from gasoline.

Integrated experimental setup for angle resolved photoemission spectroscopy of transuranic materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graham, Kevin S.; Joyce, John J.; Durakiewicz, Tomasz

2013-09-15

We have developed the Angle Resolved Photoemission Spectroscopy (ARPES) system for transuranic materials. The ARPES transuranic system is an endstation upgrade to the Laser Plasma Light Source (LPLS) at Los Alamos National Laboratory. The LPLS is a tunable light source for photoemission with a photon energy range covering the vacuum ultraviolet (VUV) and soft x-ray regions (27–140 eV). The LPLS was designed and developed for transuranic materials. Transuranic photoemission is currently not permitted at the public synchrotrons worldwide in the VUV energy range due to sample encapsulation requirements. With the addition of the ARPES capability to the LPLS system theremore » is an excellent opportunity to explore new details centered on the electronic structure of actinide and transuranic materials.« less

Vacuum ultraviolet thin films. I - Optical constants of BaF2, CaF2, LaF3, MgF2, Al2O3, HfO2, and SiO2 thin films. II - Vacuum ultraviolet all-dielectric narrowband filters

NASA Technical Reports Server (NTRS)

Zukic, Muamer; Torr, Douglas G.; Spann, James F.; Torr, Marsha R.

1990-01-01

An iteration process matching calculated and measured reflectance and transmittance values in the 120-230 nm VUV region is presently used to ascertain the optical constants of bulk MgF2, as well as films of BaF2, CaF2, LaF3, MgF2, Al2O3, HfO2, and SiO2 deposited on MgF2 substrates. In the second part of this work, a design concept is demonstrated for two filters, employing rapidly changing extinction coefficients, centered at 135 nm for BaF2 and 141 nm for SiO2. These filters are shown to yield excellent narrowband spectral performance in combination with narrowband reflection filters.

VUV Emission of Microwave Driven Argon Plasma Source

NASA Astrophysics Data System (ADS)

Henriques, Julio; Espinho, Susana; Felizardo, Edgar; Tatarova, Elena; Dias, Francisco; Ferreira, Carlos

2013-09-01

An experimental and kinetic modeling investigation of a low-pressure (0.1-1.2 mbar), surface wave (2.45 GHz) induced Ar plasma as a source vacuum ultraviolet (VUV) light is presented, using visible and VUV optical spectroscopy. The electron density and the relative VUV emission intensities of excited Ar atoms (at 104.8 nm and 106.6 nm) and ions (at 92.0 nm and 93.2 nm) were determined as a function of the microwave power and pressure. The experimental results were analyzed using a 2D self-consistent theoretical model based on a set of coupled equations including the electron Boltzmann equation, the rate balance equations for the most important electronic excited species and for charged particles, the gas thermal balance equation, and the wave electrodynamics. The principal collisional and radiative processes for neutral Ar(3p54s) and Ar(3p54p) and ionized Ar(3s3p6 2S1/2) levels are accounted for. Model predictions are in good agreement with the experimental measurements. This study was funded by the Foundation for Science and Technology, Portuguese Ministry of Education and Science, under the research contract PTDC/FIS/108411/2008.

Emission spectra of photoionized plasmas induced by intense EUV pulses: Experimental and theoretical investigations

NASA Astrophysics Data System (ADS)

Saber, Ismail; Bartnik, Andrzej; Skrzeczanowski, Wojciech; Wachulak, Przemysław; Jarocki, Roman; Fiedorowicz, Henryk

2017-03-01

Experimental measurements and numerical modeling of emission spectra in photoionized plasma in the ultraviolet and visible light (UV/Vis) range for noble gases have been investigated. The photoionized plasmas were created using laser-produced plasma (LPP) extreme ultraviolet (EUV) source. The source was based on a gas puff target; irradiated with 10ns/10J/10Hz Nd:YAG laser. The EUV radiation pulses were collected and focused using grazing incidence multifoil EUV collector. The laser pulses were focused on a gas stream, injected into a vacuum chamber synchronously with the EUV pulses. Irradiation of gases resulted in a formation of low temperature photoionized plasmas emitting radiation in the UV/Vis spectral range. Atomic photoionized plasmas produced this way consisted of atomic and ionic with various ionization states. The most dominated observed spectral lines originated from radiative transitions in singly charged ions. To assist in a theoretical interpretation of the measured spectra, an atomic code based on Cowan's programs and a collisional-radiative PrismSPECT code have been used to calculate the theoretical spectra. A comparison of the calculated spectral lines with experimentally obtained results is presented. Electron temperature in plasma is estimated using the Boltzmann plot method, by an assumption that a local thermodynamic equilibrium (LTE) condition in the plasma is validated in the first few ionization states. A brief discussion for the measured and computed spectra is given.

Spectroscopie d'emission VUV-visible provenant de plasmas basse pression: Applications aux traitements de surfaces polymeriques

NASA Astrophysics Data System (ADS)

Fozza, Alexandru C.

The main objective of this thesis is to make a contribution to the spectroscopic study of low pressure glow discharges in the vacuum ultraviolet and to reveal the effect of this radiation on polymeric materials. This research considers the following important aspects relevant to low pressure glow discharges: (i)characterization of vacuum ultraviolet (VUV) emission of several plasmas in the wavelength range available through crystalline fluoride windows, (ii)analysis of the emission dependence on several external parameters, and (iii)study of the VUV effect, in the accessible range, on polymeric materials of interest with respect to plasma treatments. The plasmas investigated, namely, hydrogen, oxygen and their mixtures with argon, were chosen by taking into consideration the composition of the gases used in technological plasmas, and the conditions needed for polymeric material irradiation. Two separate spectrophotometric instruments, a VUV monochromator (ARC VM-502) and an optical multichannel analyzer (OMA), were used. For the chosen plasmas, we measured the variation of the intensity of the atomic lines for different gas pressures and absorbed power levels. In the case of pure gas plasmas, the pressure dependence of the atomic line intensities was attributed to changes in the electron energy distribution function (EEDF). The argon emission spectra are very sensitive to the presence of impurities. The mixture plasmas we have studied (Ar-H2 and Ar-O2) show a strong emission of atomic fines in the VUV region, stronger than those resulting from the pure molecular gases. The above mixtures show promise as photon sources for the treatment of polymer surfaces. An important external parameter for the characterization of glow discharges is the excitation frequency. The goal of the specific experiments was to directly investigate the frequency-dependence effect. The frequency-related effects on plasma emission were investigated for two plasmas: pure hydrogen and 7% H2 in Ar mixture. In the case of pure hydrogen, we observed a change from a non-stationary to a stationary electron energy distribution function. For the Ar-H2 mixture, we have shown that the EEDF is stationary and that the dissociation rate for hydrogen molecules does not depend on frequency. A difference between the excitation mechanisms of different atomic lines was proven. Among the most sensitive materials with respect to plasma generated UV radiation are polymers. We have optimized the gaseous composition for various types of VUV radiation fluxes for the photochemical treatments of polymers. We have developed a system containing a thermo-stabilized quartz crystal microbalance (QCM) and chambers for sample irradiation and gas absorption measurements. In this way we have separately measured the effects of both the active oxygen species (AO) and the VUV, as well as their synergistic actions. (Abstract shortened by UMI.)

Improved vacuum-UV (VUV)-initiated photomineralization of organic compounds in water with a xenon excimer flow-through photoreactor (Xe2* lamp, 172 nm) containing an axially centered ceramic oxygenator.

PubMed

Oppenländer, Thomas; Walddörfer, Carsten; Burgbacher, Jens; Kiermeier, Martin; Lachner, Klaus; Weinschrott, Helga

2005-07-01

Xenon excimer (Xe2*) lamps can be used for the oxidation and mineralization of organic compounds in aqueous solution. This vacuum-ultraviolet (VUV) photochemical method is mainly based on the photochemically initiated homolysis of water that produces hydrogen atoms and hydroxyl radicals. The efficiency of substrate oxidation and mineralization is limited markedly due to the high absorbance of water at the emission maximum of the Xe2* lamp (lambda(max)=172 nm). This photochemical condition generates an extreme heterogeneity between the irradiated volume V(irr) and the non-irradiated ("dark") bulk solution. During VUV-initiated photomineralization of organic substrates, the fast scavenging of hydrogen atoms and of carbon-centered radicals by dissolved molecular oxygen produces a permanent oxygen deficit within V(irr) and adjacent compartments. Hence, at a constant photon flux the concentration of dissolved molecular oxygen within the zones of photo and thermal radical reactions limits the rate of mineralization, i.e. the rate of TOC diminution. Thus, a simple and convenient technique is presented that overcomes this limitation by injection of molecular oxygen (or air) into the irradiated volume by use of a ceramic oxygenator (aerator). The tube oxygenator was centered axially within the xenon excimer flow-through lamp. Consequently, the oxygen or air bubbles enhanced the transfer of dissolved molecular oxygen into the VUV-irradiated volume leading to an increased rate of mineralization of organic model compounds, e.g. 1-heptanol, benzoic acid and potassium hydrogen phthalate.

LEMUR: Large European Module for Solar Ultraviolet Research

NASA Technical Reports Server (NTRS)

Teriaca, Luca; Vincenzo, Andretta; Auchere, Frederic; Brown, Charles M.; Buchlin, Eric; Cauzzi, Gianna; Culhane, J. Len; Curdt, Werner; Davila, Joseph M.; Del Zanna, Giulio;

Heats of Vaporization of Room Temperature Ionic Liquids by Tunable Vacuum Ultraviolet Photoionization (Preprint)

DTIC Science & Technology

2009-08-31

A.; deyko, A.; Lovelock , K. R. J.; Licence, P.; Jones, R. G. J. Phys. Chem. B 2008, 112, 11734. (19) Armstrong, J. P.; Hurst, C.; Jones, R. G...Licence, P.; Lovelock , K. R. J.; Satterly, C. J.; Villar-Garcia, I. J. PCCP 2007, 9, 982. (20) Gross, J. H. J. Am. Soc. Mass Spectrom. 2008, 19, 1347

Extreme ultraviolet spectroscopy of low pressure helium microwave driven discharges

NASA Astrophysics Data System (ADS)

Espinho, Susana; Felizardo, Edgar; Tatarova, Elena; Alves, Luis Lemos

2016-09-01

Surface wave driven discharges are reliable plasma sources that can produce high levels of vacuum and extreme ultraviolet radiation (VUV and EUV). The richness of the emission spectrum makes this type of discharge a possible alternative source in EUV/VUV radiation assisted applications. However, due to challenging experimental requirements, publications concerning EUV radiation emitted by microwave plasmas are scarce and a deeper understanding of the main mechanisms governing the emission of radiation in this spectral range is required. To this end, the EUV radiation emitted by helium microwave driven plasmas operating at 2.45 GHz has been studied for low pressure conditions. Spectral lines from excited helium atoms and ions were detected via emission spectroscopy in the EUV/VUV regions. Novel data concerning the spectral lines observed in the 23 - 33 nm wavelength range and their intensity behaviour with variation of the discharge operational conditions are presented. The intensity of all the spectral emissions strongly increases with the microwave power delivered to the plasma up to 400 W. Furthermore, the intensity of all the ion spectral emissions in the EUV range decreases by nearly one order of magnitude as the pressure was raised from 0.2 to 0.5 mbar. Work funded by FCT - Fundacao para a Ciencia e a Tecnologia, under Project UID/FIS/50010/2013 and grant SFRH/BD/52412/2013 (PD-F APPLAuSE).

Cavitation induced Becquerel effect.

PubMed

Prevenslik, T V

2003-06-01

The observation of an electrical current upon the ultraviolet (UV) illumination of one of a pair of identical electrodes in liquid water, called the Becquerel effect, was made over 150 years ago. More recently, an electrical current was found if the water surrounding one electrode was made to cavitate by focused acoustic radiation, the phenomenon called the cavitation induced Becquerel effect. Since cavitation is known to produce UV light, the electrode may simply absorb the UV light and produce the current by the photo-emission theory of photoelectrochemistry. But the current was found to be semi-logarithmic with the standard electrode potential which is characteristic of the oxidation of the electrode surface in the photo-decomposition theory, and not the photo-emission theory. High bubble collapse temperatures may oxidize the electrode, but this is unlikely because melting was not observed on the electrode surfaces. At ambient temperature, oxidation may proceed by chemical reaction provided a source of vacuum ultraviolet (VUV) radiation is available to produce the excited OH* states of water to react with the electrode. The source of VUV radiation is shown to be the spontaneous emission of coherent infrared (IR) radiation from water molecules in particles that form in bubbles because of surface tension, the spontaneous IR emission induced by cavity quantum electrodynamics. The excited OH* states are produced as the IR radiation accumulates to VUV levels in the bubble wall molecules.

Test of SensL SiPM coated with NOL-1 wavelength shifter in liquid xenon

NASA Astrophysics Data System (ADS)

Akimov, D. Yu.; Belov, V. A.; Borshchev, O. V.; Burenkov, A. A.; Grishkin, Yu. L.; Karelin, A. K.; Kuchenkov, A. V.; Martemiyanov, A. N.; Ponomarenko, S. A.; Simakov, G. E.; Stekhanov, V. N.; Surin, N. M.; Timoshin, V. S.; Zeldovich, O. Ya.

2017-05-01

A SensL MicroFC-SMT-60035 6×6 mm2 silicon photo-multiplier coated with a NOL-1 wavelength shifter have been tested in the liquid xenon to detect the 175-nm scintillation light. For comparison, a Hamamatsu vacuum ultraviolet sensitive MPPC VUV3 3×3 mm2 was tested under the same conditions. The photodetection efficiency of 13.1 ± 2.5% and 6.0 ± 1.0%, correspondingly, is obtained.

Experimental and theoretical studies on gas-phase reactions of NO3 radicals with three methoxyphenols: Guaiacol, creosol, and syringol

NASA Astrophysics Data System (ADS)

Yang, Bo; Zhang, Haixu; Wang, Youfeng; Zhang, Peng; Shu, Jinian; Sun, Wanqi; Ma, Pengkun

2016-01-01

Methoxyphenols, lignin pyrolysis products, are major biomass combustion components and are considered potential tracers for wood smoke emissions. Their atmospheric reactivity, however, has not been well characterized. Guaiacol, creosol, and syringol are three typical methoxyphenols generated in relatively high concentrations in fresh wood smoke. In this study, the gas-phase reactions of NO3 radicals with these methoxyphenols were investigated using a laboratory-built vacuum ultraviolet photoionization gas time-of-flight mass spectrometer (VUV-GTOFMS) and off-line GC-MS. By combining experimental and theoretical methods, 4-nitroguaiacol, 6-nitroguaiacol, and 4,6-dinitroguaiacol were determined as the primary degradation products for guaiacol; similarly, 6-nitrocreosol and 3-nitrosyringol were identified for creosol and syringol, respectively. Using the relative rate method, rate constants at 298 K and 1 atm for the gas-phase reactions of guaiacol, creosol, and syringol with NO3 radicals were measured to be 3.2 × 10-12, 2.4 × 10-13, and 4.0 × 10-13 cm3 molecule-1 s-1, respectively. At a typical tropospheric concentration of NO3 radicals (5 × 108 molecule cm-3), atmospheric lifetimes for guaiacol, creosol, and syringol toward NO3 radicals were 0.2, 2.3, and 1.4 h, respectively. These results indicate that the reaction with NO3 radicals can be a major sink for methoxyphenols at night.

Use of VUV Radiation to Control Elastomer Seal Adhesion

NASA Technical Reports Server (NTRS)

deGroh, Henry C., III; Puleo, Bernadette J.; Waters, Deborah L.

2013-01-01

Due to their wide operating temperatures and low leakage rates, silicone elastomers are the only class of flight qualified elastomer materials that currently meet NASA's needs for various seal applications, which include docking and hatch seals for future space exploration vehicles. However, silicone elastomers are naturally sticky and exhibit sizeable adhesion when mated against metals and other silicone surfaces. This undesirable adhesion can make undocking spacecraft or opening a hatch problematic. Two approaches that can be used to reduce seal adhesion include use of grease or, application of low doses of atomic oxygen (AO). This paper investigates a third approach: the application of light doses of vacuum ultraviolet (VUV) radiation. Presented are the adhesion and leakage characteristics of S0383-70 silicone elastomer exposed to various VUV doses in the 115 to 200 nm wavelength range. The data indicate that adhesion is expected to be less than the target threshold maximum of 2 lb/in(exp2) after about 1 J/cm(exp2) of VUV exposure for seal-to-metal configurations and after 2 J/cm(exp2) for seal-to-seal configurations with no significant damage, or increase in seal leakage. This paper shows that VUV, without AO or grease, can be an effective means to reduce adhesion to the desired levels necessary for space seals with minimal change in seal leak rates.

Protonation enhancement by dichloromethane doping in low-pressure photoionization

PubMed Central

Shu, Jinian; Zou, Yao; Xu, Ce; Li, Zhen; Sun, Wanqi; Yang, Bo; Zhang, Haixu; Zhang, Peng; Ma, Pengkun

2016-01-01

Doping has been used to enhance the ionization efficiency of analytes in atmospheric pressure photoionization, which is based on charge exchange. Compounds with excellent ionization efficiencies are usually chosen as dopants. In this paper, we report a new phenomenon observed in low-pressure photoionization: Protonation enhancement by dichloromethane (CH2Cl2) doping. CH2Cl2 is not a common dopant due to its high ionization energy (11.33 eV). The low-pressure photoionization source was built using a krypton VUV lamp that emits photons with energies of 10.0 and 10.6 eV and was operated at ~500–1000 Pa. Protonation of water, methanol, ethanol, and acetaldehyde was respectively enhanced by 481.7 ± 122.4, 197.8 ± 18.8, 87.3 ± 7.8, and 93.5 ± 35.5 times after doping 291 ppmv CH2Cl2, meanwhile CH2Cl2 almost does not generate noticeable ions itself. This phenomenon has not been documented in the literature. A new protonation process involving in ion-pair and H-bond formations was proposed to expound the phenomenon. The observed phenomenon opens a new prospect for the improvement of the detection efficiency of VUV photoionization. PMID:27905552

Protonation enhancement by dichloromethane doping in low-pressure photoionization.

PubMed

Shu, Jinian; Zou, Yao; Xu, Ce; Li, Zhen; Sun, Wanqi; Yang, Bo; Zhang, Haixu; Zhang, Peng; Ma, Pengkun

2016-12-01

Doping has been used to enhance the ionization efficiency of analytes in atmospheric pressure photoionization, which is based on charge exchange. Compounds with excellent ionization efficiencies are usually chosen as dopants. In this paper, we report a new phenomenon observed in low-pressure photoionization: Protonation enhancement by dichloromethane (CH 2 Cl 2 ) doping. CH 2 Cl 2 is not a common dopant due to its high ionization energy (11.33 eV). The low-pressure photoionization source was built using a krypton VUV lamp that emits photons with energies of 10.0 and 10.6 eV and was operated at ~500-1000 Pa. Protonation of water, methanol, ethanol, and acetaldehyde was respectively enhanced by 481.7 ± 122.4, 197.8 ± 18.8, 87.3 ± 7.8, and 93.5 ± 35.5 times after doping 291 ppmv CH 2 Cl 2 , meanwhile CH 2 Cl 2 almost does not generate noticeable ions itself. This phenomenon has not been documented in the literature. A new protonation process involving in ion-pair and H-bond formations was proposed to expound the phenomenon. The observed phenomenon opens a new prospect for the improvement of the detection efficiency of VUV photoionization.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kimura, Shin-ichi; Ito, Takahiro; Nakamura, Eiken

A high-energy-resolution angle-resolved photoemission beamline in the vacuum-ultraviolet (VUV) region has been designed for a 750 MeV synchrotron light source UVSOR-II. The beamline equips an APPLE-II-type undulator with the horizontally/vertically linear and right/left circular polarizations, a modified Wadsworth-type monochromator and a high-resolution photoelectron analyzer. The monochromator covers the photon energy range of 6 - 40 eV. The energy resolution (hv/{delta}hv) and the photon flux on samples are expected to be 2 x 104 and 1012 photons/sec at 10 eV, 4 x 104 and 5 x 1011 photons/sec at 20 eV, and 6 x 104 and 1011 photons/sec at 40 eV,more » respectively. The beamline provides the high-resolution angle-resolved photoemission spectroscopy less than 1 meV in the whole VUV energy range.« less

Charging of Basic Structural Shapes in a Simulated Lunar Environment

NASA Technical Reports Server (NTRS)

Craven, P.; Schneider, T.; Vaughn, J.; Wang, J.; Polansky, J.

2012-01-01

In order to understand the effect of the charging environment on and around structures on the lunar surface, we have exposed basic structural shapes to electrons and Vacuum Ultra-Violet (VUV) radiation. The objects were, in separate runs, isolated, grounded, and placed on dielectric surfaces. In this presentation, the effects of electron energy, VUV flux, and sample orientation, on the charging of the objects will be examined. The potential of each of the object surfaces was monitored in order to determine the magnitude of the ram and wake effects under different orientations relative to the incoming beams (solar wind). This is a part of, and complementary to, the study of the group at USC under Dr. J. Wang, the purpose of which is to model the effects of the charging environment on structures on the lunar surface.

Optical transmittance investigation of 1-keV ion-irradiated sapphire crystals as potential VUV to NIR window materials of fusion reactors

NASA Astrophysics Data System (ADS)

Iwano, Keisuke; Yamanoi, Kohei; Iwasa, Yuki; Mori, Kazuyuki; Minami, Yuki; Arita, Ren; Yamanaka, Takuma; Fukuda, Kazuhito; Empizo, Melvin John F.; Takano, Keisuke; Shimizu, Toshihiko; Nakajima, Makoto; Yoshimura, Masashi; Sarukura, Nobuhiko; Norimatsu, Takayoshi; Hangyo, Masanori; Azechi, Hiroshi; Singidas, Bess G.; Sarmago, Roland V.; Oya, Makoto; Ueda, Yoshio

2016-10-01

We investigate the optical transmittances of ion-irradiated sapphire crystals as potential vacuum ultraviolet (VUV) to near-infrared (NIR) window materials of fusion reactors. Under potential conditions in fusion reactors, sapphire crystals are irradiated with hydrogen (H), deuterium (D), and helium (He) ions with 1-keV energy and ˜ 1020-m-2 s-1 flux. Ion irradiation decreases the transmittances from 140 to 260 nm but hardly affects the transmittances from 300 to 1500 nm. H-ion and D-ion irradiation causes optical absorptions near 210 and 260 nm associated with an F-center and an F+-center, respectively. These F-type centers are classified as Schottky defects that can be removed through annealing above 1000 K. In contrast, He-ion irradiation does not cause optical absorptions above 200 nm because He-ions cannot be incorporated in the crystal lattice due to the large ionic radius of He-ions. Moreover, the significant decrease in transmittance of the ion-irradiated sapphire crystals from 140 to 180 nm is related to the light scattering on the crystal surface. Similar to diamond polishing, ion irradiation modifies the crystal surface thereby affecting the optical properties especially at shorter wavelengths. Although the transmittances in the VUV wavelengths decrease after ion irradiation, the transmittances can be improved through annealing above 1000 K. With an optical transmittance in the VUV region that can recover through simple annealing and with a high transparency from the ultraviolet (UV) to the NIR region, sapphire crystals can therefore be used as good optical windows inside modern fusion power reactors in terms of light particle loadings of hydrogen isotopes and helium.

Fourier-transform spectroscopy of HD in the vacuum ultraviolet at λ = 87-112 nm

NASA Astrophysics Data System (ADS)

Ivanov, T. I.; Dickenson, G. D.; Roudjane, M.; de Oliveira, N.; Joyeux, D.; Nahon, L.; Tchang-Brillet, W.-Ü. L.; Ubachs, W.

2010-03-01

Absorption spectroscopy in the vacuum ultraviolet (VUV) domain was performed on the hydrogen-deuteride molecule with a novel Fourier-transform spectrometer based upon wavefront division interferometry. This unique instrument, which is a permanent endstation of the undulator-based beamline DESIRS on the synchrotron SOLEIL facility, opens the way to Fourier-transform spectroscopy in the VUV range. The HD spectral lines in the Lyman and Werner bands were recorded in the 87-112 nm range from a quasi-static gas sample in a windowless configuration and with a Doppler-limited resolution. Line positions of some 268 transitions in the ? Lyman bands and 141 transitions in the ? Werner bands were deduced with uncertainties of 0.04 cm-1 (1σ) which correspond to Δλ/λ ∼ 4 × 10-7. This extensive laboratory database is of relevance for comparison with astronomical observations of H2 and HD spectra from highly redshifted objects, with the goal of extracting a possible variation of the proton-to-electron mass ratio (μ = m p /m e ) on a cosmological time scale. For this reason also calculations of the so-called sensitivity coefficients K i were performed in order to allow for deducing constraints on Δμ/μ. The K i coefficients, associated with the line shift that each spectral line undergoes as a result of a varying value for μ, were derived from calculations as a function of μ solving the Schrödinger equation using ab initio potentials.

Detection of significant differences between absorption spectra of neutral helium and low temperature photoionized helium plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bartnik, A.; Wachulak, P.; Fiedorowicz, H.

2013-11-15

In this work, spectral investigations of photoionized He plasmas were performed. The photoionized plasmas were created by irradiation of helium stream, with intense pulses from laser-plasma extreme ultraviolet (EUV) source. The EUV source was based on a double-stream Xe/Ne gas-puff target irradiated with 10 ns/10 J Nd:YAG laser pulses. The most intense emission from the source spanned a relatively narrow spectral region below 20 nm, however, spectrally integrated intensity at longer wavelengths was also significant. The EUV radiation was focused onto a gas stream, injected into a vacuum chamber synchronously with the EUV pulse. The long-wavelength part of the EUVmore » radiation was used for backlighting of the photoionized plasmas to obtain absorption spectra. Both emission and absorption spectra in the EUV range were investigated. Significant differences between absorption spectra acquired for neutral helium and low temperature photoionized plasmas were demonstrated for the first time. Strong increase of intensities and spectral widths of absorption lines, together with a red shift of the K-edge, was shown.« less

Weak-field few-femtosecond VUV photodissociation dynamics of water isotopologues

NASA Astrophysics Data System (ADS)

Baumann, Arne; Bazzi, Sophia; Rompotis, Dimitrios; Schepp, Oliver; Azima, Armin; Wieland, Marek; Popova-Gorelova, Daria; Vendrell, Oriol; Santra, Robin; Drescher, Markus

2017-07-01

We present a joint experimental and theoretical study of the VUV-induced dynamics of H2O and its deuterated isotopologues in the first excited state (A ˜1B1 ) utilizing a VUV-pump VUV-probe scheme combined with a b initio classical trajectory calculations. 16-fs VUV pulses centered at 161 nm created by fifth-order harmonic generation are employed for single-shot pump-probe measurements. Combined with a precise determination of the VUV pulses' temporal profile, they provide the necessary temporal resolution to elucidate sub-10-fs dissociation dynamics in the 1+1 photon ionization time window. Ionization with a single VUV photon complements established strong-field ionization schemes by disclosing the molecular dynamics under perturbative conditions. Kinetic isotope effects derived from the pump-probe experiment are found to be in agreement with our by ab initio classical trajectory calculations, taking into account photoionization cross sections for the ground and first excited state of the water cation.

Vacuum-ultraviolet photoionization studies of the microhydration of DNA bases (guanine, cytosine, adenine, and thymine).

PubMed

Belau, Leonid; Wilson, Kevin R; Leone, Stephen R; Ahmed, Musahid

2007-08-09

In this work, we report on a photoionization study of the microhydration of the four DNA bases. Gas-phase clusters of water with DNA bases [guanine (G), cytosine (C), adenine (A), and thymine (T)] are generated via thermal vaporization of the bases and expansion of the resultant vapor in a continuous supersonic jet expansion of water seeded in Ar. The resulting clusters are investigated by single-photon ionization with tunable vacuum-ultraviolet synchrotron radiation and mass analyzed using reflectron mass spectrometry. Photoionization efficiency (PIE) curves are recorded for the DNA bases and the following water (W) clusters: G, GWn (n = 1-3); C, CWn (n = 1-3); A, AWn (n = 1,2); and T, TWn (n = 1-3). Appearance energies (AE) are derived from the onset of these PIE curves (all energies in eV): G (8.1 +/- 0.1), GW (8.0 +/- 0.1), GW2 (8.0 +/- 0.1), and GW3 (8.0); C (8.65 +/- 0.05), CW (8.45 +/- 0.05), CW2 (8.4 +/- 0.1), and CW3 (8.3 +/- 0.1); A (8.30 +/- 0.05), AW (8.20 +/- 0.05), and AW2 (8.1 +/- 0.1); T (8.90 +/- 0.05); and TW (8.75 +/- 0.05), TW2 (8.6 +/- 0.1), and TW3 (8.6 +/- 0.1). The AEs of the DNA bases decrease slightly with the addition of water molecules (up to three) but do not converge to values found for photoinduced electron removal from DNA bases in solution.

Evaluation of thermal control coatings for use on solar dynamic radiators in low earth orbit

NASA Technical Reports Server (NTRS)

Dever, Joyce A.; Rodriguez, Elvin; Slemp, Wayne S.; Stoyack, Joseph E.

1991-01-01

Thermal control coatings with high thermal emittance and low solar absorptance are needed for Space Station Freedom (SSF) solar dynamic power module radiator (SDR) surfaces for efficient heat rejection. Additionally, these coatings must be durable to low earth orbital (LEO) environmental effects of atomic oxygen, ultraviolet radiation and deep thermal cycles which occur as a result of start-up and shut-down of the solar dynamic power system. Eleven candidate coatings were characterized for their solar absorptance and emittance before and after exposure to ultraviolet (UV) radiation (200 to 400 nm), vacuum UV (VUV) radiation (100 to 200 nm) and atomic oxygen. Results indicated that the most durable and best performing coatings were white paint thermal control coatings Z-93, zinc oxide pigment in potassium silicate binder, and YB-71, zinc orthotitanate pigment in potassium silicate binder. Optical micrographs of these materials exposed to the individual environmental effects of atomic oxygen and vacuum thermal cycling showed that no surface cracking occurred.

Resonantly enhanced method for generation of tunable, coherent vacuum ultraviolet radiation

DOEpatents

Glownia, James H.; Sander, Robert K.

1985-01-01

Carbon Monoxide vapor is used to generate coherent, tunable vacuum ultraviolet radiation by third-harmonic generation using a single tunable dye laser. The presence of a nearby electronic level resonantly enhances the nonlinear susceptibility of this molecule allowing efficient generation of the vuv light at modest pump laser intensities, thereby reducing the importance of a six-photon multiple-photon ionization process which is also resonantly enhanced by the same electronic level but to higher order. By choosing the pump radiation wavelength to be of shorter wavelength than individual vibronic levels used to extend tunability stepwise from 154.4 to 124.6 nm, and the intensity to be low enough, multiple-photon ionization can be eliminated. Excitation spectra of the third-harmonic emission output exhibit shifts to shorter wavelength and broadening with increasing CO pressure due to phase matching effects. Increasing the carbon monoxide pressure, therefore, allows the substantial filling in of gaps arising from the stepwise tuning thereby providing almost continuous tunability over the quoted range of wavelength emitted.

Resonantly enhanced method for generation of tunable, coherent vacuum-ultraviolet radiation

DOEpatents

Glownia, J.H.; Sander, R.K.

1982-06-29

Carbon Monoxide vapor is used to generate coherent, tunable vacuum ultraviolet radiation by third-harmonic generation using a single tunable dye laser. The presence of a nearby electronic level resonantly enhances the nonlinear susceptibility of this molecule allowing efficient generation of the vuv light at modest pump laser intensities, thereby reducing the importance of a six-photon multiple-photon ionization process which is also resonantly enhanced by the same electronic level but no higher order. By choosing the pump radiation wavelength to be of shorter wavelength than individual vibronic levels used to extend tunability stepwise from 154.4 to 124.6 nm, and the intensity to be low enough, multiple-photon ionization can be eliminated. Excitation spectra of the third-harmonic emission output exhibit shifts to shorter wavelength and broadening with increasing CO pressure due to phase matching effects. Increasing the carbon monoxide pressure, therefore, allows the substantial filling in of gaps arising from the stepwise tuning thereby providing almost continuous tunability over the quoted range of wavelength emitted.

Evaluation of thermal control coatings for use on solar dynamic radiators in low Earth orbit

NASA Technical Reports Server (NTRS)

Dever, Joyce A.; Rodriguez, Elvin; Slemp, Wayne S.; Stoyack, Joseph E.

1991-01-01

Thermal control coatings with high thermal emittance and low solar absorptance are needed for Space Station Freedom (SSF) solar dynamic power module radiator (SDR) surfaces for efficient heat rejection. Additionally, these coatings must be durable to low earth orbital (LEO) environmental effects of atomic oxygen, ultraviolet radiation and deep thermal cycles which occur as a result of start-up and shut-down of the solar dynamic power system. Eleven candidate coatings were characterized for their solar absorptance and emittance before and after exposure to ultraviolet (UV) radiation (200 to 400 nm), vacuum UV (VUV) radiation (100 to 200 nm) and atomic oxygen. Results indicated that the most durable and best performing coatings were white paint thermal control coatings Z-93, zinc oxide pigment in potassium silicate binder, and YB-71, zinc orthotitanate pigment in potassium silicate binder. Optical micrographs of these materials exposed to the individual environmental effects of atomic oxygen and vacuum thermal cycling showed that no surface cracking occurred.

Comparative survival analysis of Deinococcus radiodurans and the haloarchaea Natrialba magadii and Haloferax volcanii exposed to vacuum ultraviolet irradiation.

PubMed

Abrevaya, Ximena C; Paulino-Lima, Ivan G; Galante, Douglas; Rodrigues, Fabio; Mauas, Pablo J D; Cortón, Eduardo; Lage, Claudia de Alencar Santos

2011-12-01

The haloarchaea Natrialba magadii and Haloferax volcanii, as well as the radiation-resistant bacterium Deinococcus radiodurans, were exposed to vacuum UV (VUV) radiation at the Brazilian Synchrotron Light Laboratory. Cell monolayers (containing 10(5) to 10(6) cells per sample) were prepared over polycarbonate filters and irradiated under high vacuum (10(-5) Pa) with polychromatic synchrotron radiation. N. magadii was remarkably resistant to high vacuum with a survival fraction of (3.77±0.76)×10(-2), which was larger than that of D. radiodurans (1.13±0.23)×10(-2). The survival fraction of the haloarchaea H. volcanii, of (3.60±1.80)×10(-4), was much smaller. Radiation resistance profiles were similar between the haloarchaea and D. radiodurans for fluences up to 150 J m(-2). For fluences larger than 150 J m(-2), there was a significant decrease in the survival of haloarchaea, and in particular H. volcanii did not survive. Survival for D. radiodurans was 1% after exposure to the higher VUV fluence (1350 J m(-2)), while N. magadii had a survival lower than 0.1%. Such survival fractions are discussed regarding the possibility of interplanetary transfer of viable microorganisms and the possible existence of microbial life in extraterrestrial salty environments such as the planet Mars and Jupiter's moon Europa. This is the first work to report survival of haloarchaea under simulated interplanetary conditions.

High resolution monochromator for the VUV radiation from the DORIS storage ring

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saile, V.; Gurtler, P.; Koch, E.E.

1976-10-01

The unique properties of the DORIS storage ring at DESY as a synchroton radiation source are exploited for high resolution spectroscopy in the vacuum ultraviolet. We describe a new experimental set up with a 3-m normal incidence monochromator for wavelengths between 3000 A and 300 A (4 < or = h..omega.. < or = 40 eV) using a vertical dispersion plane. The storage ring provides a light flux intense and stable enough for rapid photoelectrical scanning of the spectra with a resolution of 0.03 A in first order. (AIP)

Atmospheric lifetime of SF5CF3

NASA Astrophysics Data System (ADS)

Takahashi, K.; Nakayama, T.; Matsumi, Y.; Solomon, S.; Gejo, T.; Shigemasa, E.; Wallington, T. J.

2002-08-01

The vacuum ultraviolet (VUV) absorption spectrum of SF5CF3 was measured over the range 106-200 nm. At 121.6 nm, σ(base e) = (7.8 +/- 0.6) × 10-18 cm2 molecule-1, in which quoted uncertainty includes two standard deviation from the least-square fit in the Beer-Lambert plot and our estimate of potential systematic errors associated with measurements of the reactant concentrations. The VUV spectrum and literature data for electron attachment and ion-molecule reactions were incorporated into a model of the stratosphere, mesosphere, and lower thermosphere. This information provides better constraints on the atmospheric lifetime and hence on the potential of this highly radiatively-active trace gas to influence the climate system. The atmospheric lifetime of SF5CF3 is dominated by dissociative electron attachment and is estimated to be approximately 950 years. Solar proton events could reduce this to a lower limit of 650 years.

Reflectance of polytetrafluoroethylene for xenon scintillation light

NASA Astrophysics Data System (ADS)

Silva, C.; Pinto da Cunha, J.; Pereira, A.; Chepel, V.; Lopes, M. I.; Solovov, V.; Neves, F.

2010-03-01

Gaseous and liquid xenon particle detectors are being used in a number of applications including dark matter search and neutrino-less double beta decay experiments. Polytetrafluoroethylene (PTFE) is often used in these detectors both as electrical insulator and as a light reflector to improve the efficiency of detection of scintillation photons. However, xenon emits in the vacuum ultraviolet (VUV) wavelength region (λ ≃175 nm) where the reflecting properties of PTFE are not sufficiently known. In this work, we report on measurements of PTFE reflectance, including its angular distribution, for the xenon scintillation light. Various samples of PTFE, manufactured by different processes (extruded, expanded, skived, and pressed) have been studied. The data were interpreted with a physical model comprising both specular and diffuse reflections. The reflectance obtained for these samples ranges from about 47% to 66% for VUV light. Other fluoropolymers, namely, ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), and perfluoro-alkoxyalkane (PFA) were also measured.

Test and Analysis Capabilities of the Space Environment Effects Team at Marshall Space Flight Center

NASA Technical Reports Server (NTRS)

Finckenor, M. M.; Edwards, D. L.; Vaughn, J. A.; Schneider, T. A.; Hovater, M. A.; Hoppe, D. T.

2002-01-01

Marshall Space Flight Center has developed world-class space environmental effects testing facilities to simulate the space environment. The combined environmental effects test system exposes temperature-controlled samples to simultaneous protons, high- and low-energy electrons, vacuum ultraviolet (VUV) radiation, and near-ultraviolet (NUV) radiation. Separate chambers for studying the effects of NUV and VUV at elevated temperatures are also available. The Atomic Oxygen Beam Facility exposes samples to atomic oxygen of 5 eV energy to simulate low-Earth orbit (LEO). The LEO space plasma simulators are used to study current collection to biased spacecraft surfaces, arcing from insulators and electrical conductivity of materials. Plasma propulsion techniques are analyzed using the Marshall magnetic mirror system. The micro light gas gun simulates micrometeoroid and space debris impacts. Candidate materials and hardware for spacecraft can be evaluated for durability in the space environment with a variety of analytical techniques. Mass, solar absorptance, infrared emittance, transmission, reflectance, bidirectional reflectance distribution function, and surface morphology characterization can be performed. The data from the space environmental effects testing facilities, combined with analytical results from flight experiments, enable the Environmental Effects Group to determine optimum materials for use on spacecraft.

Use of radiation in biomaterials science

NASA Astrophysics Data System (ADS)

Benson, Roberto S.

2002-05-01

Radiation is widely used in the biomaterials science for surface modification, sterilization and to improve bulk properties. Radiation is also used to design of biochips, and in situ photopolymerizable of bioadhesives. The energy sources most commonly used in the irradiation of biomaterials are high-energy electrons, gamma radiation, ultraviolet (UV) and visible light. Surface modification involves placement of selective chemical moieties on the surface of a material by chemical reactions to improve biointeraction for cell adhesion and proliferation, hemocompatibility and water absorption. The exposure of a polymer to radiation, especially ionizing radiation, can lead to chain scission or crosslinking with changes in bulk and surface properties. Sterilization by irradiation is designed to inactivate most pathogens from the surface of biomedical devices. An overview of the use of gamma and UV radiation to improve surface tissue compatibility, bulk properties and surface properties for wear resistance, formation of hydrogels and curing dental sealants and bone adhesives is presented. Gamma and vacuum ultraviolet (VUV) irradiated ultrahigh molecular weight polyethylene (UHMWPE) exhibit improvement in surface modulus and hardness. The surface modulus and hardness of UHMWPE showed a dependence on type of radiation, dosage and processing. VUV surface modified e-PTFE vascular grafts exhibit increases in hydrophilicity and improvement towards adhesion of fibrin glue.

Furfural: The Unimolecular Dissociative Photoionization Mechanism of the Simplest Furanic Aldehyde.

PubMed

Winfough, Matthew; Voronova, Krisztina; Muller, Giel; Laguisma, Gabrielle; Sztáray, Bálint; Bodi, Andras; Meloni, Giovanni

2017-05-11

The unimolecular dissociation reactions of energy-selected furfural cations have been studied by imaging photoelectron photoion coincidence spectroscopy at the vacuum-ultraviolet (VUV) beamline of the Swiss Light Source. In the photon energy range of 10.9-14.5 eV, furfural ions decay by numerous fragmentation channels. Modeling the breakdown diagram yielded the 0 K appearance energies of 10.95 ± 0.10, 11.16, and 12.03 eV for the c-C 4 H 3 O-CO + (m/z = 95), c-C 4 H 4 O + (m/z = 68), and c-C 3 H 3 + (m/z = 39) fragment ions, respectively, formed by parallel dissociation channels. An internal conversion from the A″ to the A' electronic state via a conical intersection takes place along the reaction coordinate in the case of the H-loss channel (c-C 4 H 3 O-CO + formation). Quantum chemical calculations and experimental results confirmed a fast conversion to the A' state and that the rate-determining step is a tight transition state on the potential energy surface. Appearance energies were also derived for the sequential dissociation products from the furan cation, c-C 4 H 4 O + , for the formation of CH 2 CO + (m/z = 42), C 3 H 4 + (m/z = 40), and CHO + (m/z = 29) at 12.81, 12.80, and 13.34 eV, respectively. Statistical rate theory modeling of the breakdown diagram can also be used to predict the fractional ion abundances and thermal shifts in mass spectrometric pyrolysis studies to help assigning the m/z channels either to ionization of the neutrals or to dissociative ionization processes, with potential use for combustion diagnostics. The cationic geometry optimizations yielded functional-dependent spurious DFT minima and a deviating planar MP2 optimized geometry, which are briefly discussed.

Thermal decomposition mechanism of 1-ethyl-3-methylimidazolium bromide ionic liquid.

PubMed

Chambreau, Steven D; Boatz, Jerry A; Vaghjiani, Ghanshyam L; Koh, Christine; Kostko, Oleg; Golan, Amir; Leone, Stephen R

2012-06-21

In order to better understand the volatilization process for ionic liquids, the vapor evolved from heating the ionic liquid 1-ethyl-3-methylimidazolium bromide (EMIM(+)Br(-)) was analyzed via tunable vacuum ultraviolet photoionization time-of-flight mass spectrometry (VUV-PI-TOFMS) and thermogravimetric analysis mass spectrometry (TGA-MS). For this ionic liquid, the experimental results indicate that vaporization takes place via the evolution of alkyl bromides and alkylimidazoles, presumably through alkyl abstraction via an S(N)2 type mechanism, and that vaporization of intact ion pairs or the formation of carbenes is negligible. Activation enthalpies for the formation of the methyl and ethyl bromides were evaluated experimentally, ΔH(‡)(CH(3)Br) = 116.1 ± 6.6 kJ/mol and ΔH(‡)(CH(3)CH(2)Br) = 122.9 ± 7.2 kJ/mol, and the results are found to be in agreement with calculated values for the S(N)2 reactions. Comparisons of product photoionization efficiency (PIE) curves with literature data are in good agreement, and ab initio thermodynamics calculations are presented as further evidence for the proposed thermal decomposition mechanism. Estimates for the enthalpy of vaporization of EMIM(+)Br(-) and, by comparison, 1-butyl-3-methylimidazolium bromide (BMIM(+)Br(-)) from molecular dynamics calculations and their gas phase enthalpies of formation obtained by G4 calculations yield estimates for the ionic liquids' enthalpies of formation in the liquid phase: ΔH(vap)(298 K) (EMIM(+)Br(-)) = 168 ± 20 kJ/mol, ΔH(f, gas)(298 K) (EMIM(+)Br(-)) = 38.4 ± 10 kJ/mol, ΔH(f, liq)(298 K) (EMIM(+)Br(-)) = -130 ± 22 kJ/mol, ΔH(f, gas)(298 K) (BMIM(+)Br(-)) = -5.6 ± 10 kJ/mol, and ΔH(f, liq)(298 K) (BMIM(+)Br(-)) = -180 ± 20 kJ/mol.

Protection of Polymers from the Space Environment by Atomic Layer Deposition

NASA Astrophysics Data System (ADS)

Lindholm, Ned F.; Zhang, Jianming; Minton, Timothy K.; O'Patchen, Jennifer; George, Steven M.; Groner, Markus D.

2009-01-01

Polymers in space may be subjected to a barrage of incident atoms, photons, and/or ions. For example, oxygen atoms can etch and oxidize these materials. Photons may act either alone or in combination with oxygen atoms to degrade polymers and paints and thus limit their usefulness. Colors fade under the intense vacuum ultraviolet (VUV) solar radiation. Ions can lead to the build-up of static charge on polymers. Atomic layer deposition (ALD) techniques can provide coatings that could mitigate many challenges for polymers in space. ALD is a gas-phase technique based on two sequential, self-limiting surface reactions, and it can deposit very uniform, conformal, and pinhole-free films with atomic layer control. We have studied the efficacy of various ALD coatings to protect Kapton® polyimide, FEP Teflon®, and poly(methyl methacrylate) films from atomic-oxygen and VUV attack. Atomic-oxygen and VUV studies were conducted with the use of a laser-breakdown source for hyperthermal O atoms and a D2 lamp as a source of VUV light. These studies used a quartz crystal microbalance (QCM) to monitor mass loss in situ, as well as surface profilometry and scanning electron microscopy to study the surface recession and morphology changes ex situ. Al2O3 ALD coatings applied to polyimide and FEP Teflon® films protected the underlying substrates from O-atom attack, and ZnO coatings protected the poly(methyl methacrylate) substrate from VUV-induced damage.

Ab Initio Calculation of Photoionization and Inelastic Photon Scattering Spectra of He below the N=2 Threshold in a dc Electric Field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mihelic, Andrej; Zitnik, Matjaz

2007-06-15

We study the Stark effect on doubly excited states of the helium atom below N=2. We present the ab initio photoionization and total inelastic photon scattering cross sections calculated with the method of complex scaling for field strengths F{<=}100 kV/cm. The calculations are compared to the measurements of the ion [Phys. Rev. Lett. 90, 133002 (2003)] and vacuum ultraviolet fluorescence yields [Phys. Rev. Lett. 96, 093001 (2006)]. For the case of photoionization and for incident photons with polarization vector P parallel to the electric field F, we confirm the propensity rule proposed by Tong and Lin [Phys. Rev. Lett. 92,more » 223003 (2004)]. Furthermore, the rule is also shown to apply for F perpendicular P and for the case of the inelastic scattering in both experimental geometries.« less

Laboratory measurements and modeling of molecular photoabsorption in the ultraviolet for planetary atmospheres applications: diatomic sulfur and sulfur monoxide

NASA Astrophysics Data System (ADS)

Stark, Glenn

2016-07-01

Our research program comprises the measurement and modeling of ultraviolet molecular photoabsorption cross sections with the highest practical resolution. It supports efforts to interpret and model observations of planetary atmospheres. Measurement and modeling efforts on diatomic sulfur (S _{2}) and sulfur monoxide (SO) are in progress. S _{2}: Interpretations of atmospheric (Io, Jupiter, cometary comae) S _{2} absorption features are hindered by a complete lack of laboratory cross section data in the ultraviolet. We are working to quantify the photoabsorption spectrum of S _{2} from 240 to 300 nm based on laboratory measurements and theoretical calculations. We have constructed an experimental apparatus to produce a stable column of S _{2} vapor at a temperature of 800 K. High-resolution measurements of the absorption spectrum of the strong B - X system of S _{2} were completed using the NIST VUV-FTS at Gaithersburg, Maryland. These measurements are currently being incorporated into a coupled-channel model of the absorption spectrum of S _{2} to quantify the contributions from individual band features and to establish the mechanisms responsible for the strong predissociation signature of the B - X system. A successful coupled channels model can then be used to calculate the B - X absorption spectrum at any temperature. SO: There has been a long-standing need for high-resolution cross sections of sulfur monoxide radicals in the ultraviolet and vacuum ultraviolet regions, where the molecule strongly predissociates, for modeling the atmospheres of Io and Venus, and most recently for understanding sulfur isotope effects in the ancient (pre-O _{2}) atmosphere of Earth. We have produced a measurable column of SO in a continuous-flow DC discharge cell, using SO _{2} as a parent molecule. Photoabsorption measurements were recently recorded on the DESIRS beamline of the SOLEIL synchrotron, taking advantage of the high-resolution VUV-FTS on that beamline. A number of strong, predissociated SO bands were measured in the 140 to 200 nm region. Weaker features associated with the SO B - X system were simultaneously recorded, allowing for an approximate determination of the VUV SO band f-values.

Vacuum Ultraviolet Radiation and Atomic Oxygen Durability Evaluation of HST Bi-Stem Thermal Shield Materials

NASA Technical Reports Server (NTRS)

Dever, Joyce; deGroh, Kim K.

2002-01-01

Bellows-type thermal shields were used on the bi-stems of replacement solar arrays installed on the Hubble Space Telescope (HST) during the first HST servicing mission (SMI) in December 1993. These thermal shields helped reduce the problem of thermal gradient- induced jitter observed with the original HST solar arrays during orbital thermal cycling and have been in use on HST for eight years. This paper describes ground testing of the candidate solar array bi-stem thermal shield materials including backside aluminized Teflon(R)FEP (fluorinated ethylene propylene) with and without atomic oxygen (AO) and ultraviolet radiation protective surface coatings for durability to AO and combined AO and vacuum ultraviolet (VOV) radiation. NASA Glenn Research Center (GRC) conducted VUV and AO exposures of samples of candidate thermal shield materials at HST operational temperatures and pre- and post-exposure analyses as part of an overall program coordinated by NASA Goddard Space Flight Center (GSFC) to determine the on-orbit durability of these materials. Coating adhesion problems were observed for samples having the AO- and combined AO/UV-protective coatings. Coating lamination occurred with rapid thermal cycling testing which simulated orbital thermal cycling. This lack of adhesion caused production of coating flakes from the material that would have posed a serious risk to HST optics if the coated materials were used for the bi-stem thermal shields. No serious degradation was observed for the uncoated aluminized Teflon(R) as evaluated by optical microscopy, although atomic force microscopy (AFM) microhardness testing revealed that an embrittled surface layer formed on the uncoated Teflon(R) surface due to vacuum ultraviolet radiation exposure. This embrittled layer was not completely removed by AO erosion, No cracks or particle flakes were produced for the embrittled uncoated material upon exposure to VUV and AO at operational temperatures to an equivalent exposure of approximately five years in the HST environment. Uncoated aluminized FEP Teflon(R) was determined to be the most appropriate thermal shield material and was used on the bi-stems of replacement solar arrays installed on HST during SMI in December 1993. The SMI -installed solar arrays air scheduled to be replaced during MST's fourth servicing mission (SM3B) in early 2002.

A detailed kinetic modeling study of toluene oxidation in a premixed laminar flame

PubMed Central

Tian, Zhenyu; Pitz, William J.; Fournet, René; Glaude, Pierre-Alexander; Battin-Leclerc, Frédérique

2013-01-01

An improved chemical kinetic model for the toluene oxidation based on experimental data obtained in a premixed laminar low-pressure flame with vacuum ultraviolet (VUV) photoionization and molecular beam mass spectrometry (MBMS) techniques has been proposed. The present mechanism consists of 273 species up to chrysene and 1740 reactions. The rate constants of reactions of toluene decomposition, reaction with oxygen, ipso-additions and metatheses with abstraction of phenylic H-atom are updated; new pathways of C4 + C2 species giving benzene and fulvene are added. Based on the experimental observations, combustion intermediates such as fulvenallene, naphtol, methylnaphthalene, acenaphthylene, 2-ethynylnaphthalene, phenanthrene, anthracene, 1-methylphenanthrene, pyrene and chrysene are involved in the present mechanism. The final toluene model leads to an overall satisfactory agreement between the experimentally observed and predicted mole fraction profiles for the major products and most combustion intermediates. The toluene depletion is governed by metathese giving benzyl radicals, ipso-addition forming benzene and metatheses leading to C6H4CH3 radicals. A sensitivity analysis indicates that the unimolecular decomposition via the cleavage of a methyl C-H bond has a strong inhibiting effect, while decomposition via C-C bond breaking, ipso-addition of H-atom to toluene, decomposition of benzyl radicals and reactions related to C6H4CH3 radicals have promoting effect for the consumption of toluene. Moreover, flow rate analysis is performed to illustrate the formation pathways of mono- and polycyclic aromatics. PMID:23762016

Invited Article: High resolution angle resolved photoemission with tabletop 11 eV laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Yu; Vishik, Inna M.; Yi, Ming

2016-01-15

We developed a table-top vacuum ultraviolet (VUV) laser with 113.778 nm wavelength (10.897 eV) and demonstrated its viability as a photon source for high resolution angle-resolved photoemission spectroscopy (ARPES). This sub-nanosecond pulsed VUV laser operates at a repetition rate of 10 MHz, provides a flux of 2 × 10{sup 12} photons/s, and enables photoemission with energy and momentum resolutions better than 2 meV and 0.012 Å{sup −1}, respectively. Space-charge induced energy shifts and spectral broadenings can be reduced below 2 meV. The setup reaches electron momenta up to 1.2 Å{sup −1}, granting full access to the first Brillouin zone ofmore » most materials. Control over the linear polarization, repetition rate, and photon flux of the VUV source facilitates ARPES investigations of a broad range of quantum materials, bridging the application gap between contemporary low energy laser-based ARPES and synchrotron-based ARPES. We describe the principles and operational characteristics of this source and showcase its performance for rare earth metal tritellurides, high temperature cuprate superconductors, and iron-based superconductors.« less

Vacuum-Ultraviolet photoionization studies of the microhydrationof DNA bases (Guanine, Cytosine, Adenine and Thymine)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belau, L.; Wilson, K.R.; Leone, S.R.

2007-01-22

In this work, we report on a photoionization study of the microhydration of the four DNA bases. Gas-phase clusters of water with DNA bases [guanine (G), cytosine (C), adenine (A), and thymine (T)] are generated via thermal vaporization of the bases and expansion of the resultant vapor in a continuous supersonic jet expansion of water seeded in Ar. The resulting clusters are investigated by single-photon ionization with tunable vacuum-ultraviolet synchrotron radiation and mass analyzed using reflectron mass spectrometry. Photoionization efficiency (PIE) curves are recorded for the DNA bases and the following water (W) clusters: G, GW{sub n} (n = 1-3);more » C, CW{sub n} (n = 1-3); A, AW{sub n} (n = 1,2); and T, TW{sub n} (n = 1-3). Appearance energies (AE) are derived from the onset of these PIE curves (all energies in eV): G (8.1 {+-} 0.1), GW (8.0 {+-} 0.1), GW{sub 2} (8.0 {+-} 0.1), and GW{sub 3} (8.0); C (8.65 {+-} 0.05), CW (8.45 {+-} 0.05), CW{sub 2} (8.4 {+-} 0.1), and CW{sub 3} (8.3 {+-} 0.1); A (8.30 {+-} 0.05), AW (8.20 {+-} 0.05), and AW{sub 2} (8.1 {+-} 0.1); T (8.90 {+-} 0.05); and TW (8.75 {+-} 0.05), TW{sub 2} (8.6 {+-} 0.1), and TW{sub 3} (8.6 {+-} 0.1). The AEs of the DNA bases decrease slightly with the addition of water molecules (up to three) but do not converge to values found for photoinduced electron removal from DNA bases in solution.« less

Gas-phase conformation-specific photofragmentation of proline-containing peptide ions.

PubMed

Kim, Tae-Young; Valentine, Stephen J; Clemmer, David E; Reilly, James P

2010-08-01

Singly-protonated proline-containing peptides with N-terminal arginine are photodissociated with vacuum ultraviolet (VUV) light in an ESI linear ion trap/orthogonal-TOF (LIT/o-TOF). When proline is the nth residue from the N-terminus, unusual b(n) + 2 and a(n) + 2 ions are observed. Their formation is explained by homolytic cleavage of the C(alpha)-C bond in conjunction with a rearrangement of electrons and an amide hydrogen. The latter is facilitated by a proline-stabilized gas-phase peptide conformation. Copyright 2010 American Society for Mass Spectrometry. Published by Elsevier Inc. All rights reserved.

The cavitation induced Becquerel effect and the hot spot theory of sonoluminescence.

PubMed

Prevenslik, T V

2003-06-01

Over 150 years ago, Becquerel discovered the ultraviolet illumination of one of a pair of identical electrodes in liquid water produced an electric current, the phenomenon called the Becquerel effect. Recently, a similar effect was observed if the water surrounding one electrode is made to cavitate by focused acoustic radiation, which by similarity is referred to as the cavitation induced Becquerel effect. The current in the cavitation induced Becquerel effect was found to be semi-logarithmic with the standard electrode potential that is consistent with the oxidation of the electrode surface by the photo-decomposition theory of photoelectrochemistry. But oxidation of the electrode surface usually requires high temperatures, say as in cavitation. Absent high bubble temperatures, cavitation may produce vacuum ultraviolet (VUV) light that excites water molecules in the electrode film to higher H(2)O(*) energy states, the excited states oxidizing the electrode surface by chemical reaction. Solutions of the Rayleigh-Plesset equation during bubble collapse that include the condensation of water vapor show any increase in temperature or pressure of the water vapor by compression heating is compensated by the condensation of vapor to the bubble wall, the bubbles collapsing almost isothermally. Hence, the cavitation induced Becquerel effect is likely caused by cavitation induced VUV light at ambient temperature.

International Test Program for Synergistic Atomic Oxygen and Vacuum Ultraviolet Radiation Exposure of Spacecraft Materials

NASA Technical Reports Server (NTRS)

Miller, Sharon K.

2001-01-01

The components and materials of spacecraft in low Earth orbit can degrade in thermal and optical performance through interaction with atomic oxygen and vacuum ultraviolet (VUV) radiation, which are predominant in low Earth orbit. Because of the importance of low Earth orbit durability and performance to manufacturers and users, an international test program for assessing the durability of spacecraft materials and components was initiated. Initial tests at the NASA Glenn Research Center consisted of exposure of samples representing a variety of thermal control paints, multilayer insulation materials, and Sun sensors that have been used in space. Materials donated from various international sources were tested alongside materials whose performance is well known, such as Teflon FEP, Kapton H, or Z-93-P white paint. The optical, thermal, or mass loss data generated during the tests were then provided to the participating material suppliers. Data were not published unless the participant donating the material consented to publication. The test program is intended to give spacecraft builders and users a better understanding of degradation processes and effects so that they can improve their predictions of spacecraft performance.

VUV Testing of Science Cameras at MSFC: QE Measurement of the CLASP Flight Cameras

NASA Technical Reports Server (NTRS)

Champey, Patrick; Kobayashi, Ken; Winebarger, Amy; Cirtain, Jonathan; Hyde, David; Robertson, Bryan; Beabout, Brent; Beabout, Dyana; Stewart, Mike

2015-01-01

The NASA Marshall Space Flight Center (MSFC) has developed a science camera suitable for sub-orbital missions for observations in the UV, EUV and soft X-ray. Six cameras were built and tested for the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP), a joint National Astronomical Observatory of Japan (NAOJ) and MSFC sounding rocket mission. The CLASP camera design includes a frame-transfer e2v CCD57-10 512x512 detector, dual channel analog readout electronics and an internally mounted cold block. At the flight operating temperature of -20 C, the CLASP cameras achieved the low-noise performance requirements (less than or equal to 25 e- read noise and greater than or equal to 10 e-/sec/pix dark current), in addition to maintaining a stable gain of approximately equal to 2.0 e-/DN. The e2v CCD57-10 detectors were coated with Lumogen-E to improve quantum efficiency (QE) at the Lyman- wavelength. A vacuum ultra-violet (VUV) monochromator and a NIST calibrated photodiode were employed to measure the QE of each camera. Four flight-like cameras were tested in a high-vacuum chamber, which was configured to operate several tests intended to verify the QE, gain, read noise, dark current and residual non-linearity of the CCD. We present and discuss the QE measurements performed on the CLASP cameras. We also discuss the high-vacuum system outfitted for testing of UV and EUV science cameras at MSFC.

VUV testing of science cameras at MSFC: QE measurement of the CLASP flight cameras

NASA Astrophysics Data System (ADS)

Champey, P.; Kobayashi, K.; Winebarger, A.; Cirtain, J.; Hyde, D.; Robertson, B.; Beabout, B.; Beabout, D.; Stewart, M.

2015-08-01

The NASA Marshall Space Flight Center (MSFC) has developed a science camera suitable for sub-orbital missions for observations in the UV, EUV and soft X-ray. Six cameras were built and tested for the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP), a joint MSFC, National Astronomical Observatory of Japan (NAOJ), Instituto de Astrofisica de Canarias (IAC) and Institut D'Astrophysique Spatiale (IAS) sounding rocket mission. The CLASP camera design includes a frame-transfer e2v CCD57-10 512 × 512 detector, dual channel analog readout and an internally mounted cold block. At the flight CCD temperature of -20C, the CLASP cameras exceeded the low-noise performance requirements (<= 25 e- read noise and <= 10 e- /sec/pixel dark current), in addition to maintaining a stable gain of ≍ 2.0 e-/DN. The e2v CCD57-10 detectors were coated with Lumogen-E to improve quantum efficiency (QE) at the Lyman- wavelength. A vacuum ultra-violet (VUV) monochromator and a NIST calibrated photodiode were employed to measure the QE of each camera. Three flight cameras and one engineering camera were tested in a high-vacuum chamber, which was configured to operate several tests intended to verify the QE, gain, read noise and dark current of the CCD. We present and discuss the QE measurements performed on the CLASP cameras. We also discuss the high-vacuum system outfitted for testing of UV, EUV and X-ray science cameras at MSFC.

Valence and lowest Rydberg electronic states of phenol investigated by synchrotron radiation and theoretical methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Limão-Vieira, P., E-mail: plimaovieira@fct.unl.pt; Ferreira da Silva, F.; Lange, E.

2016-07-21

We present the experimental high-resolution vacuum ultraviolet (VUV) photoabsorption spectra of phenol covering for the first time the full 4.3–10.8 eV energy-range, with absolute cross sections determined. Theoretical calculations on the vertical excitation energies and oscillator strengths were performed using time-dependent density functional theory and the equation-of-motion coupled cluster method restricted to single and double excitations level. These have been used in the assignment of valence and Rydberg transitions of the phenol molecule. The VUV spectrum reveals several new features not previously reported in the literature, with particular reference to the 6.401 eV transition, which is here assigned to themore » 3sσ/σ{sup ∗}(OH)←3π(3a″) transition. The measured absolute photoabsorption cross sections have been used to calculate the photolysis lifetime of phenol in the earth’s atmosphere (0–50 km).« less

Inactivation of Bacillus atrophaeus by OH radicals

NASA Astrophysics Data System (ADS)

Ono, Ryo; Yonetamari, Kenta; Tokumitsu, Yusuke; Yonemori, Seiya; Yasuda, Hachiro; Mizuno, Akira

2016-08-01

The inactivation of Bacillus atrophaeus by OH radicals is measured. This study aims to evaluate the bactericidal effects of OH radicals produced by atmospheric-pressure nonthermal plasma widely used for plasma medicine; however, in this study, OH radicals are produced by vacuum ultraviolet (VUV) photolysis of water vapor instead of plasma to allow the production of OH radicals with almost no other reactive species. A 172 nm VUV light from a Xe2 excimer lamp irradiates a He-H2O mixture flowing in a quartz tube to photodissociate H2O to produce OH, H, O, HO2, H2O2, and O3. The produced reactive oxygen species (ROS) flow out of the quartz tube nozzle to the bacteria on an agar plate and cause inactivation. The inactivation by OH radicals among the six ROS is observed by properly setting the experimental conditions with the help of simulations calculating the ROS densities. A 30 s treatment with approximately 0.1 ppm OH radicals causes visible inactivation.

Measurements and Modeling of Total Solar Irradiance in X-class Solar Flares

NASA Technical Reports Server (NTRS)

Moore, Christopher S.; Chamberlin, Phillip Clyde; Hock, Rachel

2014-01-01

The Total Irradiance Monitor (TIM) from NASA's SOlar Radiation and Climate Experiment can detect changes in the total solar irradiance (TSI) to a precision of 2 ppm, allowing observations of variations due to the largest X-class solar flares for the first time. Presented here is a robust algorithm for determining the radiative output in the TIM TSI measurements, in both the impulsive and gradual phases, for the four solar flares presented in Woods et al., as well as an additional flare measured on 2006 December 6. The radiative outputs for both phases of these five flares are then compared to the vacuum ultraviolet (VUV) irradiance output from the Flare Irradiance Spectral Model (FISM) in order to derive an empirical relationship between the FISM VUV model and the TIM TSI data output to estimate the TSI radiative output for eight other X-class flares. This model provides the basis for the bolometric energy estimates for the solar flares analyzed in the Emslie et al. study.

Energetics and dynamics through time-resolved measurements in mass spectrometry

NASA Astrophysics Data System (ADS)

Lifshitz, Chava

Results of recent work on time-resolved photoionization and electron ionization mass spectrometry carried out in Jerusalem are reviewed. Time-resolved photoionization mass spectrometry in the vacuum ultraviolet is applied to polycyclic aromatic hydrocarbons, for example naphthalene, pyrene and fluoranthene as well as to some bromo derivatives (bromonaphthalene and bromoanthracene). Time-resolved photoionization efficiency curves are modelled by Rice-Ramsperger-Kassel-Marcus QET rate-energy k ( E ) dependences of the unimolecular dissociative processes and by the rate process infrared radiative relaxation k . Experimental results are augmented by time-resolved photorad dissociation data for the same species, whenever available. Kinetic shifts, conventional and intrinsic (due to competition between dissociative and radiative decay), are evaluated. Activation parameters (activation energies and entropies) are deduced. Thermochemical information is obtained including bond energies and ionic heats of formation. Fullerenes, notably C , are studied by time-resolved electron ionization and a large intrinsic shift, due to competition with black-bodylike radiative decay in the visible is discussed.

Determining the partial photoionization cross-sections of ethyl radicals.

PubMed

FitzPatrick, B L; Maienschein-Cline, M; Butler, L J; Lee, S-H; Lin, J J

2007-12-13

Using a crossed laser-molecular beam scattering apparatus, these experiments photodissociate ethyl chloride at 193 nm and detect the Cl and ethyl products, resolved by their center-of-mass recoil velocities, with vacuum ultraviolet photoionization. The data determine the relative partial cross-sections for the photoionization of ethyl radicals to form C2H5+, C2H4+, and C2H3+ at 12.1 and 13.8 eV. The data also determine the internal energy distribution of the ethyl radical prior to photoionization, so we can assess the internal energy dependence of the photoionization cross-sections. The results show that the C2H4++H and C2H3++H2 dissociative photoionization cross-sections strongly depend on the photoionization energy. Calibrating the ethyl radical partial photoionization cross-sections relative to the bandwidth-averaged photoionization cross-section of Cl atoms near 13.8 eV allows us to use these data in conjunction with literature estimates of the Cl atom photoionization cross-sections to put the present bandwidth-averaged cross-sections on an absolute scale. The resulting bandwidth-averaged cross-section for the photoionization of ethyl radicals to C2H5+ near 13.8 eV is 8+/-2 Mb. Comparison of our 12.1 eV data with high-resolution ethyl radical photoionization spectra allows us to roughly put the high-resolution spectrum on the same absolute scale. Thus, one obtains the photoionization cross-section of ethyl radicals to C2H5+ from threshold to 12.1 eV. The data show that the onset of the C2H4++H dissociative photoionization channel is above 12.1 eV; this result offers a simple way to determine whether the signal observed in photoionization experiments on complex mixtures is due to ethyl radicals. We discuss an application of the results for resolving the product branching in the O+allyl bimolecular reaction.

Vacuum ultraviolet radiation and thermal cycling effects on atomic oxygen protective photovoltaic array blanket materials

NASA Technical Reports Server (NTRS)

Brady, J.; Banks, B.

1990-01-01

The importance of synergistic environmental exposure is demonstrated through the evaluation of DuPont 93-1 in simulated LEO environment. Changes in optical properties, surface condition, and mass loss data are described. The qualitative results indicate the necessity for exposure of materials to a series of simulated LEO environments in order to properly determine synergistic effects and demonstrate the overall LEO durability of candidate materials. It is shown that synergistic effects may occur with vacuum thermal cycling combined with VUV radiation followed by atomic oxygen exposure. Testing the durability of candidate solar array blanket materials in a test sequence with necessary synergistic effects makes it possible to determine the appropriate material for providing structural support and maintaining the proper operating temperature for solar cells in the SSF Photovaltaic Power System.

Fragmentation dynamics of the ethyl bromide and ethyl iodide cations: a velocity-map imaging study.

PubMed

Gardiner, Sara H; Karsili, Tolga N V; Lipciuc, M Laura; Wilman, Edward; Ashfold, Michael N R; Vallance, Claire

2014-02-07

The photodissociation dynamics of ethyl bromide and ethyl iodide cations (C2H5Br(+) and C2H5I(+)) have been studied. Ethyl halide cations were formed through vacuum ultraviolet (VUV) photoionization of the respective neutral parent molecules at 118.2 nm, and were photolysed at a number of ultraviolet (UV) photolysis wavelengths, including 355 nm and wavelengths in the range from 236 to 266 nm. Time-of-flight mass spectra and velocity-map images have been acquired for all fragment ions and for ground (Br) and spin-orbit excited (Br*) bromine atom products, allowing multiple fragmentation pathways to be investigated. The experimental studies are complemented by spin-orbit resolved ab initio calculations of cuts through the potential energy surfaces (along the RC-Br/I stretch coordinate) for the ground and first few excited states of the respective cations. Analysis of the velocity-map images indicates that photoexcited C2H5Br(+) cations undergo prompt C-Br bond fission to form predominantly C2H5(+) + Br* products with a near-limiting 'parallel' recoil velocity distribution. The observed C2H3(+) + H2 + Br product channel is thought to arise via unimolecular decay of highly internally excited C2H5(+) products formed following radiationless transfer from the initial excited state populated by photon absorption. Broadly similar behaviour is observed in the case of C2H5I(+), along with an additional energetically accessible C-I bond fission channel to form C2H5 + I(+) products. HX (X = Br, I) elimination from the highly internally excited C2H5X(+) cation is deemed the most probable route to forming the C2H4(+) fragment ions observed from both cations. Finally, both ethyl halide cations also show evidence of a minor C-C bond fission process to form CH2X(+) + CH3 products.

Mechanisms involved in HBr and Ar cure plasma treatments applied to 193 nm photoresists

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pargon, E.; Menguelti, K.; Martin, M.

2009-05-01

In this article, we have performed detailed investigations of the 193 nm photoresist transformations after exposure to the so-called HBr and Ar plasma cure treatments using various characterization techniques (x-ray photoelectron spectroscopy, Fourier transformed infrared, Raman analyses, and ellipsometry). By using windows with different cutoff wavelengths patched on the photoresist film, the role of the plasma vacuum ultraviolet (VUV) light on the resist modifications is clearly outlined and distinguished from the role of radicals and ions from the plasma. The analyses reveal that both plasma cure treatments induce severe surface and bulk chemical modifications of the resist films. The synergisticmore » effects of low energetic ion bombardment and VUV plasma light lead to surface graphitization or cross-linking (on the order of 10 nm), while the plasma VUV light (110-210 nm) is clearly identified as being responsible for ester and lactone group removal from the resist bulk. As the resist modification depth depends strongly on the wavelength penetration into the material, it is found that HBr plasma cure that emits near 160-170 nm can chemically modify the photoresist through its entire thickness (240 nm), while the impact of Ar plasmas emitting near 100 nm is more limited. In the case of HBr cure treatment, Raman and ellipsometry analyses reveal the formation of sp{sup 2} carbon atoms in the resist bulk, certainly thanks to hydrogen diffusion through the resist film assisted by the VUV plasma light.« less

Dissociative photoionization of 1,3-butadiene: experimental and theoretical insights.

PubMed

Fang, Wenzheng; Gong, Lei; Zhang, Qiang; Shan, Xiaobin; Liu, Fuyi; Wang, Zhenya; Sheng, Liusi

2011-05-07

The vacuum-ultraviolet photoionization and dissociative photoionization of 1,3-butadiene in a region ∼8.5-17 eV have been investigated with time-of-flight photoionization mass spectrometry using tunable synchrotron radiation. The adiabatic ionization energy of 1,3-butadiene and appearance energies for its fragment ions, C(4)H(5)(+), C(4)H(4)(+), C(4)H(3)(+), C(3)H(3)(+), C(2)H(4)(+), C(2)H(3)(+), and C(2)H(2)(+), are determined to be 9.09, 11.72, 13.11, 15.20, 11.50, 12.44, 15.15, and 15.14 eV, respectively, by measurements of photoionization efficiency spectra. Ab initio molecular orbital calculations have been performed to investigate the reaction mechanism of dissociative photoionization of 1,3-butadiene. On the basis of experimental and theoretical results, seven dissociative photoionization channels are proposed: C(4)H(5)(+) + H, C(4)H(4)(+) + H(2), C(4)H(3)(+) + H(2) + H, C(3)H(3)(+) + CH(3), C(2)H(4)(+) + C(2)H(2), C(2)H(3)(+) + C(2)H(2) + H, and C(2)H(2)(+) + C(2)H(2) + H(2). Channel C(3)H(3)(+) + CH(3) is found to be the dominant one, followed by C(4)H(5)(+) + H and C(2)H(4)(+) + C(2)H(2). The majority of these channels occur via isomerization prior to dissociation. Transition structures and intermediates for those isomerization processes were also determined.

Radiation Durability of Candidate Polymer Films for the Next Generation Space Telescope Sunshield

NASA Technical Reports Server (NTRS)

Dever, Joyce; Semmel, Charles; Edwards, David; Messer, Russell; Peters, Wanda; Carter, Amani; Puckett, David

2002-01-01

The Next Generation Space Telescope (NGST), anticipated to be launched in 2009 for a 10-year mission, will make observations in the infrared portion of the spectrum to examine the origins and evolution of our universe. Because it must operate at cold temperatures in order to make these sensitive measurements, it will use a large, lightweight, deployable sunshield, comprised of several polymer film layers, to block heat and stray light. This paper describes laboratory radiation durability testing of candidate NGST sunshield polymer film materials. Samples of fluorinated polyimides CP1 and CP2, and a polvarylene ether benzimidazole. TOR-LM(TM), were exposed to 40 keV electron and 40 keV proton radiation followed by exposure to vacuum ultraviolet (VUV) radiation in the 115 to 200 nm wavelength range. Samples of these materials were also exposed to VUV without prior electron and proton exposure. Samples of polyimides Kapton HN, Kapton E, and Upilex-S were exposed to electrons and protons only, due to limited available exposure area in the VUV facility. Exposed samples were evaluated for changes in solar absorptance and thermal emittance and mechanical properties of ultimate tensile strength and elongation at failure. Data obtained are compared with previously published data for radiation durability testing of these polymer film materials.

Catalytic oxidation of VOCs over Mn/TiO2/activated carbon under 185 nm VUV irradiation.

PubMed

Shu, Yajie; Xu, Yin; Huang, Haibao; Ji, Jian; Liang, Shimin; Wu, Muyan; Leung, Dennis Y C

2018-06-04

Volatile organic compounds (VOCs) are regarded as the major contributors to air pollution, and should be strictly regulated. Photocatalytic oxidation (PCO) is of great interest for the removal of VOCs owing to its strong oxidation capability. However, its application is greatly limited by catalytic deactivation. Vacuum Ultraviolet (VUV) irradiation provides a novel way to improve the photocatalytic activity while much O 3 will be generated which may cause secondary pollution. In this study, a multi-functional catalyst of Mn/TiO 2 /activated carbon (AC) was developed to eliminate and utilize O 3 , as well as enhance catalytic oxidation of VOC degradation via ozone-assisted catalytic oxidation (OZCO). The results indicate that Mn modified TiO 2 /AC (i.e. 0.1%Mn/20%TiO 2 /AC) achieved a toluene removal efficiency of nearly 86% with 100% elimination rate of O 3 . With the help of Mn/TiO 2 /AC catalyst, O 3 was catalytically decomposed and transformed into active species of O ( 1 D) and OH, thus enhancing toluene removal. The combination of VUV irradiation with multi-functional catalyst provides a novel and efficient way for the degradation of VOCs. Copyright © 2018 Elsevier Ltd. All rights reserved.

Mapping and controlling ultrafast dynamics of highly excited H 2 molecules by VUV-IR pump-probe schemes

DOE PAGES

Sturm, F. P.; Tong, X. M.; Palacios, A.; ...

2017-01-09

Here, we used ultrashort femtosecond vacuum ultraviolet (VUV) and infrared (IR) pulses in a pump-probe scheme to map the dynamics and nonequilibrium dissociation channels of excited neutral H 2 molecules. A nuclear wave packet is created in the B 1Σmore » $$+\\atop{u}$$ state of the neutral H 2 molecule by absorption of the ninth harmonic of the driving infrared laser field. Due to the large stretching amplitude of the molecule excited in the B 1Σ$$+\\atop{u}$$ electronic state, the effective H 2 + ionization potential changes significantly as the nuclear wave packet vibrates in the bound, highly electronically and vibrationally excited B potential-energy curve. We probed such dynamics by ionizing the excited neutral molecule using time-delayed VUV-or-IR radiation. We identified the nonequilibrium dissociation channels by utilizing three-dimensional momentum imaging of the ion fragments. We also found that different dissociation channels can be controlled, to some extent, by changing the IR laser intensity and by choosing the wavelength of the probe laser light. Furthermore, we concluded that even in a benchmark molecular system such as H 2*, the interpretation of the nonequilibrium multiphoton and multicolor ionization processes is still a challenging task, requiring intricate theoretical analysis.« less

Kr photoionized plasma induced by intense extreme ultraviolet pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bartnik, A., E-mail: andrzej.bartnik@wat.edu.pl; Wachulak, P.; Fiedorowicz, H.

Irradiation of any gas with an intense EUV (extreme ultraviolet) radiation beam can result in creation of photoionized plasmas. The parameters of such plasmas can be significantly different when compared with those of the laser produced plasmas (LPP) or discharge plasmas. In this work, the photoionized plasmas were created in a krypton gas irradiated using an LPP EUV source operating at a 10 Hz repetition rate. The Kr gas was injected into the vacuum chamber synchronously with the EUV radiation pulses. The EUV beam was focused onto a Kr gas stream using an axisymmetrical ellipsoidal collector. The resulting low temperature Krmore » plasmas emitted electromagnetic radiation in the wide spectral range. The emission spectra were measured either in the EUV or an optical range. The EUV spectrum was dominated by emission lines originating from Kr III and Kr IV ions, and the UV/VIS spectra were composed from Kr II and Kr I lines. The spectral lines recorded in EUV, UV, and VIS ranges were used for the construction of Boltzmann plots to be used for the estimation of the electron temperature. It was shown that for the lowest Kr III and Kr IV levels, the local thermodynamic equilibrium (LTE) conditions were not fulfilled. The electron temperature was thus estimated based on Kr II and Kr I species where the partial LTE conditions could be expected.« less

Kr photoionized plasma induced by intense extreme ultraviolet pulses

NASA Astrophysics Data System (ADS)

Bartnik, A.; Wachulak, P.; Fiedorowicz, H.; Skrzeczanowski, W.

2016-04-01

Irradiation of any gas with an intense EUV (extreme ultraviolet) radiation beam can result in creation of photoionized plasmas. The parameters of such plasmas can be significantly different when compared with those of the laser produced plasmas (LPP) or discharge plasmas. In this work, the photoionized plasmas were created in a krypton gas irradiated using an LPP EUV source operating at a 10 Hz repetition rate. The Kr gas was injected into the vacuum chamber synchronously with the EUV radiation pulses. The EUV beam was focused onto a Kr gas stream using an axisymmetrical ellipsoidal collector. The resulting low temperature Kr plasmas emitted electromagnetic radiation in the wide spectral range. The emission spectra were measured either in the EUV or an optical range. The EUV spectrum was dominated by emission lines originating from Kr III and Kr IV ions, and the UV/VIS spectra were composed from Kr II and Kr I lines. The spectral lines recorded in EUV, UV, and VIS ranges were used for the construction of Boltzmann plots to be used for the estimation of the electron temperature. It was shown that for the lowest Kr III and Kr IV levels, the local thermodynamic equilibrium (LTE) conditions were not fulfilled. The electron temperature was thus estimated based on Kr II and Kr I species where the partial LTE conditions could be expected.

Surface analysis of anodized aluminum clamps from NASA-LDEF satellite

NASA Technical Reports Server (NTRS)

Grammer, H. L.; Wightman, J. P.; Young, Philip R.

1992-01-01

Surface analysis results of selected anodized aluminum clamps containing black (Z306) and white (A276) paints which received nearly six years of Low Earth Orbit (LEO) exposure on the Long Duration Exposure Facility are reported. Surface analytical techniques, including x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and scanning electron microscopy/energy dispersive analysis by x-ray (SEM/EDAX), showed significant differences in the surface composition of these materials depending upon the position on the LDEF. Differences in the surface composition are attributed to varying amounts of atomic oxygen and vacuum ultraviolet radiation (VUV). Silicon containing compounds were the primary contaminant detected on the materials.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koivisto, H., E-mail: hannu.koivisto@phys.jyu.fi; Kalvas, T.; Tarvainen, O.

Several ion source related research and development projects are in progress at the Department of Physics, University of Jyväskylä (JYFL). The work can be divided into investigation of the ion source plasma and development of ion sources, ion beams, and diagnostics. The investigation covers the Electron Cyclotron Resonance Ion Source (ECRIS) plasma instabilities, vacuum ultraviolet (VUV) and visible light emission, photon induced electron emission, and the development of plasma diagnostics. The ion source development covers the work performed for radiofrequency-driven negative ion source, RADIS, beam line upgrade of the JYFL 14 GHz ECRIS, and the development of a new room-temperature-magnetmore » 18 GHz ECRIS, HIISI.« less

Time-resolved photoelectron spectroscopy of polyatomic molecules using 42-nm vacuum ultraviolet laser based on high harmonics generation

NASA Astrophysics Data System (ADS)

Nishitani, Junichi; West, Christopher W.; Higashimura, Chika; Suzuki, Toshinori

2017-09-01

Time-resolved photoelectron spectroscopy (TRPES) of gaseous polyatomic molecules using 266-nm (4.7 eV) pump and 42-nm (29.5 eV) probe pulses is presented. A 1-kHz Ti:sapphire laser with a 35 fs pulse duration is employed to generate high harmonics in Kr gas, and the 19th harmonic (42-nm) was selected using two SiC/Mg mirrors. Clear observation of the ultrafast electronic dephasing in pyrazine and photoisomerization of 1,3-cyclohexadiene demonstrates the feasibility of TRPES with the UV pump and VUV probe pulses under weak excitation conditions in the perturbation regime.

Dissociative Excitation of Adenine by Electron Impact

NASA Astrophysics Data System (ADS)

McConkey, J. William; Trocchi, Joshuah; Dech, Jeffery; Kedzierski, Wladek

2017-04-01

Dissociative excitation of adenine (C6H5NH2) into excited atomic fragments has been studied in the electron impact energy range from threshold to 300 eV. A crossed beam system coupled to a vacuum ultraviolet (VUV) monochromator is used to study emissions in the wavelength range from 110 to 200 nm. The beam of adenine vapor from a stainless steel oven is crossed at right angles by the electron beam and the resultant UV radiation is detected in a mutually orthogonal direction. The strongest feature in the spectrum is H Lyman- α. Financial support from NSERC and CFI, Canada, is gratefully acknowledged.

Measurement of free radical kinetics in pulsed plasmas by UV and VUV absorption spectroscopy and by modulated beam mass spectrometry

NASA Astrophysics Data System (ADS)

Cunge, G.; Bodart, P.; Brihoum, M.; Boulard, F.; Chevolleau, T.; Sadeghi, N.

2012-04-01

This paper reviews recent progress in the development of time-resolved diagnostics to probe high-density pulsed plasma sources. We focus on time-resolved measurements of radicals' densities in the afterglow of pulsed discharges to provide useful information on production and loss mechanisms of free radicals. We show that broad-band absorption spectroscopy in the ultraviolet and vacuum ultraviolet spectral domain and threshold ionization modulated beam mass spectrometry are powerful techniques for the determination of the time variation of the radicals' densities in pulsed plasmas. The combination of these complementary techniques allows detection of most of the reactive species present in industrial etching plasmas, giving insights into the physico-chemistry reactions involving these species. As an example, we discuss briefly the radicals' kinetics in the afterglow of a SiCl4/Cl2/Ar discharge.

Skylab ultraviolet stellar spectra - A new white dwarf, HD 149499 B

NASA Technical Reports Server (NTRS)

Parsons, S. B.; Wray, J. D.; Benedict, G. F.; Henize, K. G.; Laget, M.

1976-01-01

The letter reports the discovery of a cool star with excess brightness in the vacuum ultraviolet on an objective-prism photograph obtained during the second Skylab mission. This star, HD 149499, is of type K0 V and has a companion with an apparent magnitude of about 11.8; the relatively flat UV spectrum observed at the position of HD 149499 is characteristic of a 10th or 11th magnitude unreddened O- or early B-type star. It is shown that the excess VUV brightness is due to the companion, HD 149499B, which probably lies in the region of the H-R diagram occupied by the hot white dwarfs. Inspection of white dwarf lists indicates that this star is the sixth or seventh brightest white dwarf known. A maximum orbital motion of 0.025 arcsec/yr is estimated along with a period of just under 500 yr.

Dependence of nanomechanical modification of polymers on plasma-induced cross-linking

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tajima, S.; Komvopoulos, K.

2007-01-01

The nanomechanical properties of low-density polyethylene (LDPE) modified by inductively coupled, radio-frequency Ar plasma were investigated by surface force microscopy. The polymer surface was modified under plasma conditions of different ion energy fluences and radiation intensities obtained by varying the sample distance from the plasma power source. Nanoindentation results of the surface stiffness versus maximum penetration depth did not reveal discernible differences between untreated and plasma-treated LDPE, presumably due to the small thickness of the modified surface layer that resulted in a substrate effect. On the contrary, nanoscratching experiments demonstrated a significant increase in the surface shear resistance of plasma-modifiedmore » LDPE due to chain cross-linking. These experiments revealed an enhancement of cross-linking with increasing ion energy fluence and radiation intensity, and a tip size effect on the friction force and dominant friction mechanisms (adhesion, plowing, and microcutting). In addition, LDPE samples with a LiF crystal shield were exposed to identical plasma conditions to determine the role of vacuum ultraviolet (VUV) and ultraviolet (UV) radiation in the cross-linking process. The cross-linked layer of plasma-treated LDPE exhibited much higher shear strength than that of VUV/UV-treated LDPE. Plasma-induced surface modification of the nanomechanical properties of LDPE is interpreted in the context of molecular models of the untreated and cross-linked polymer surfaces derived from experimental findings.« less

Heats of Vaporization of Room Temperature Ionic Liquids by Tunable Vacuum Ultraviolet Photoionization

DTIC Science & Technology

2009-12-07

18) Emel’yanenko, V. N.; Verevkin, S. P.; Heintz, A.; Corfield, J.-A.; deyko, A.; Lovelock , K. R. J.; Licence, P.; Jones, R. G. J. Phys. Chem. B 2008...112, 11734. (19) Armstrong, J. P.; Hurst, C.; Jones, R. G.; Licence, P.; Lovelock , K. R. J.; Satterly, C. J.; Villar-Garcia, I. J. Phys. Chem. Chem...Phys. 2007, 9, 982. (20) Lovelock , K. R. J.; Deyko, A.; Corfield, J.-A.; Gooden, P. N.; Licence, P.; Jones, R. G. ChemPhysChem 2009, 10, 337. (21

Spectroscopy of N,N-dimethylformamide in the VUV and IR regions: Experimental and computational studies

NASA Astrophysics Data System (ADS)

Shastri, Aparna; Das, Asim Kumar; Krishnakumar, Sunanda; Singh, Param Jeet; Raja Sekhar, B. N.

2017-12-01

The electronic absorption spectrum of N,N-dimethylformamide (DMF) is studied in the 45 000-80 000 cm-1 (5.6-9.9 eV) region using synchrotron radiation. The vacuum ultraviolet (VUV) spectrum comprises mostly of Rydberg series of ns, np, and nd types converging to the first two ionization potentials (IPs). Quantum defect values obtained are consistent with excitation of an electron from the highest occupied molecular orbitals localized on nitrogen (4a″) and oxygen (16a'); in addition, the 3s Rydberg transition converging to the third IP (3a″) is observed at 8.95 eV. A reinvestigation of the infrared spectrum of DMF in the 500-4000 cm-1 region with the help of density functional theory (DFT) calculations establishes the planarity of the ground state and leads to revision of several vibrational assignments. Vertical excited state energies and their valence/Rydberg character are predicted using time dependent DFT calculations; excellent correlation is achieved between theoretical results and experimentally observed spectral features. Potential energy curves of the first few excited states give additional insights into the nature of the excited states and their role in photodissociation dynamics. The absorption spectrum of DMF in the region >63 400 cm-1 (7.85 eV) as well as a complete set of spectral assignments in the VUV region (45 000-80 000 cm-1) is reported for the first time. This work represents a comprehensive study of the absorption spectra of DMF in the VUV and infrared regions.

Photoelectron angular distributions from rotationally resolved autoionizing states of N 2

DOE PAGES

Chartrand, A. M.; McCormack, E. F.; Jacovella, U.; ...

2017-12-08

The single-photon, photoelectron-photoion coincidence spectrum of N 2 has been recorded at high (~1.5 cm -1) resolution in the region between the N 2 + X 2Σ g +, v + = 0 and 1 ionization thresholds by using a double imaging spectrometer and intense vacuum-ultraviolet light from the Synchrotron SOLEIL. This approach provides the relative photoionization cross section, the photoelectron energy distribution, and the photoelectron angular distribution as a function of photon energy. The region of interest contains autoionizing valence states, vibrationally autoionizing Rydberg states converging to vibrationally excited levels of the N 2 + X 2Σ g +more » ground state, and electronically autoionizing states converging to the N 2 + A 2Π and B 2Σ u + states. The wavelength resolution is sufficient to resolve rotational structure in the autoionizing states, but the electron energy resolution is insufficient to resolve rotational structure in the photoion spectrum. Here, a simplified approach based on multichannel quantum defect theory is used to predict the photoelectron angular distribution parameters, β, and the results are in reasonably good agreement with experiment.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chartrand, A. M.; McCormack, E. F.; Jacovella, U.

The single-photon, photoelectron-photoion coincidence spectrum of N 2 has been recorded at high (~1.5 cm -1) resolution in the region between the N 2 + X 2Σ g +, v + = 0 and 1 ionization thresholds by using a double imaging spectrometer and intense vacuum-ultraviolet light from the Synchrotron SOLEIL. This approach provides the relative photoionization cross section, the photoelectron energy distribution, and the photoelectron angular distribution as a function of photon energy. The region of interest contains autoionizing valence states, vibrationally autoionizing Rydberg states converging to vibrationally excited levels of the N 2 + X 2Σ g +more » ground state, and electronically autoionizing states converging to the N 2 + A 2Π and B 2Σ u + states. The wavelength resolution is sufficient to resolve rotational structure in the autoionizing states, but the electron energy resolution is insufficient to resolve rotational structure in the photoion spectrum. Here, a simplified approach based on multichannel quantum defect theory is used to predict the photoelectron angular distribution parameters, β, and the results are in reasonably good agreement with experiment.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kimura, Shin-Ichi; Ito, Takahiro; Hosaka, Masahito

A novel variably polarized angle-resolved photoemission spectroscopy beamline in the vacuum-ultraviolet (VUV) region has been installed at the UVSOR-II 750 MeV synchrotron light source. The beamline is equipped with a 3 m long APPLE-II type undulator with horizontally/vertically linear and right/left circular polarizations, a 10 m Wadsworth type monochromator covering a photon energy range of 6-43 eV, and a 200 mm radius hemispherical photoelectron analyzer with an electron lens of a {+-}18 deg. acceptance angle. Due to the low emittance of the UVSOR-II storage ring, the light source is regarded as an entrance slit, and the undulator light is directlymore » led to a grating by two plane mirrors in the monochromator while maintaining a balance between high-energy resolution and high photon flux. The energy resolving power (h{nu}/{Delta}h{nu}) and photon flux of the monochromator are typically 1x10{sup 4} and 10{sup 12} photons/s, respectively, with a 100 {mu}m exit slit. The beamline is used for angle-resolved photoemission spectroscopy with an energy resolution of a few meV covering the UV-to-VUV energy range.« less

The Gaseous Phase as a Probe of the Astrophysical Solid Phase Chemistry

NASA Astrophysics Data System (ADS)

Abou Mrad, Ninette; Duvernay, Fabrice; Isnard, Robin; Chiavassa, Thierry; Danger, Grégoire

2017-09-01

In support of space missions and spectroscopic observations, laboratory experiments on ice analogs enable a better understanding of organic matter formation and evolution in astrophysical environments. Herein, we report the monitoring of the gaseous phase of processed astrophysical ice analogs to determine if the gaseous phase can elucidate the chemical mechanisms and dominant reaction pathways occurring in the solid ice subjected to vacuum ultra-violet (VUV) irradiation at low temperature and subsequently warmed. Simple (CH3OH), binary (H2O:CH3OH, CH3OH:NH3), and ternary ice analogs (H2O:CH3OH:NH3) were VUV-processed and warmed. The evolution of volatile organic compounds in the gaseous phase shows a direct link between their relative abundances in the gaseous phase, and the radical and thermal chemistries modifying the initial ice composition. The correlation between the gaseous and solid phases may play a crucial role in deciphering the organic composition of astrophysical objects. As an example, possible solid compositions of the comet Lovejoy are suggested using the abundances of organics in its comae.

229Thorium-doped calcium fluoride for nuclear laser spectroscopy.

PubMed

Dessovic, P; Mohn, P; Jackson, R A; Winkler, G; Schreitl, M; Kazakov, G; Schumm, T

2014-03-12

The (229)thorium isotope presents an extremely low-energy isomer state of the nucleus which is expected around 7.8 eV, in the vacuum ultraviolet (VUV) regime. This unique system may bridge between atomic and nuclear physics, enabling coherent manipulation and precision spectroscopy of nuclear quantum states using laser light. It has been proposed to implant (229)thorium into VUV transparent crystal matrices to facilitate laser spectroscopy and possibly realize a solid-state nuclear clock. In this work, we validate the feasibility of this approach by computer modelling of thorium doping into calcium fluoride single crystals. Using atomistic modelling and full electronic structure calculations, we find a persistent large band gap and no additional electronic levels emerging in the middle of the gap due to the presence of the dopant, which should allow direct optical interrogation of the nuclear transition.Based on the electronic structure, we estimate the thorium nuclear quantum levels within the solid-state environment. Precision laser spectroscopy of these levels will allow the study of a broad range of crystal field effects, transferring Mössbauer spectroscopy into the optical regime.

Research of green emitting rare-earth doped materials as potential quantum-cutter

NASA Astrophysics Data System (ADS)

Moine, Bernard; Beauzamy, Lena; Gredin, Patrick; Wallez, Gilles; Labeguerie, Jessica

2008-03-01

Because the energy of vacuum ultraviolet (VUV) photons emitted by xenon plasma discharge is more than twice that of visible photons, quantum cutting appears to be a promising process in rare-earth doped materials in order to obtain efficient phosphors for mercury free lighting devices as well as for plasma display panels. With an aim of application, it is important to take into account the emitting color of the developed new phosphors. Most of the time, this leads to use systems with at least two kinds of rare earth ions: one of them playing the role of energy sensitizer, and the other one being in charge of emitting the light of the suitable color. We focus our attention on green rare-earth doped materials. In order to get very efficient phosphors, it is not only necessary to get the highest possible quantum yield, but also to have a material characterized by a strong absorption in the VUV range. Borate and fluoride matrices doped with Dy 3+/Tb 3+ couples of ions are selected according to the position of the 5d band of dysprosium as green emitters.

Report on the search for atmospheric holes using airs image data

NASA Technical Reports Server (NTRS)

Reinleitner, Lee A.

1991-01-01

Frank et al (1986) presented a very controversial hypothesis which states that the Earth is being bombarded by water-vapor clouds resulting from the disruption and vaporization of small comets. This hypothesis was based on single-pixel intensity decreases in the images of the earth's dayglow emissions at vacuum-ultraviolet (VUV) wavelengths using the DE-1 imager. These dark spots, or atmospheric holes, are hypothesized to be the result of VUV absorption by a water-vapor cloud between the imager and the dayglow-emitting region. Examined here is the VUV data set from the Auroral Ionospheric Remote Sensor (AIRS) instrument that was flown on the Polar BEAR satellite. AIRS was uniquely situated to test this hypothesis. Due to the altitude of the sensor, the holes should show multi-pixel intensity decreases in a scan line. A statistical estimate indicated that sufficient 130.4-nm data from AIRS existed to detect eight to nine such holes, but none was detected. The probability of this occurring is less than 1.0 x 10(exp -4). A statistical estimate indicated that sufficient 135.6-nm data from AIRS existed to detect approx. 2 holes, and two ambiguous cases are shown. In spite of the two ambiguous cases, the 135.6-nm data did not show clear support for the small-comet hypothesis. The 130.4-nm data clearly do not support the small-comet hypothesis.

Ultraviolet /UV/ sensitive phosphors for silicon imaging detectors

NASA Technical Reports Server (NTRS)

Viehmann, W.; Cowens, M. W.; Butner, C. L.

1981-01-01

The fluorescence properties of UV sensitive organic phosphors and the radiometric properties of phosphor coated silicon detectors in the VUV, UV, and visible wavelengths are described. With evaporated films of coronene and liumogen, effective quantum efficiencies of up to 20% have been achieved on silicon photodiodes in the vacuum UV. With thin films of methylmethacrylate (acrylic), which are doped with organic laser dyes and deposited from solution, detector quantum efficiencies of the order of 15% for wavelengths of 120-165 nm and of 40% for wavelengths above 190 nm have been obtained. The phosphor coatings also act as antireflection coatings and thereby enhance the response of coated devices throughout the visible and near IR.

Excitation of vacuum ultraviolet spectra of krypton in a cooled gas discharge

NASA Astrophysics Data System (ADS)

Gerasimov, Gennadii N.; Krylov, Boris E.; Hallin, Reinhold

1995-08-01

Results are presented on the experimental study of VUV spectra of krypton excited by a dc discharge in a capillary tube with the wall cooled to the temperature of liquid nitrogen. We studied the 120-200 nm spectral region corresponding to the transitions between the dimer lowest excited states and the weakly bound ground state, 1u, 0u+ yields 0g+. Electron impact, transferring dimers from the ground state into the excited state, is shown to be an efficient excitation mechanism in the 50-650 Torr and the 10-50 mA pressure and current ranges. The spectra obtained and the calculations made corroborate the high rate of this process.

VUV Fourier-Transform absorption study of the npπ1 Πu-, v, N ←X1 Σg+, v″ = 0,N″ transitions in D2

NASA Astrophysics Data System (ADS)

Glass-Maujean, M.; Jungen, Ch.; Dickenson, G. D.; Ubachs, W.; de Oliveira, N.; Joyeux, D.; Nahon, L.

2015-09-01

The DESIRS beamline of the SOLEIL synchrotron facility, equipped with a vacuum ultraviolet Fourier-Transform spectrometer has been used to measure Q (N″) (N -N″ = 0) absorption transitions of the D2 molecule. Some 212 Q-lines were assigned and their transition frequencies determined up to excitation energies of 137 000 cm-1 above the ground state, thereby extending the earlier work by various authors, and considerably improving the spectral accuracy (<0.1 cm-1). The assignments have been aided by first principles multichannel quantum defect theory (MQDT) calculations which also provide predictions of the autoionization widths of the upper levels.

Radical Anions of Oxidized vs. Reduced Oxytocin: Influence of Disulfide Bridges on CID and Vacuum UV Photo-Fragmentation

NASA Astrophysics Data System (ADS)

MacAleese, Luke; Girod, Marion; Nahon, Laurent; Giuliani, Alexandre; Antoine, Rodolphe; Dugourd, Philippe

2018-06-01

The nonapeptide oxytocin (OT) is used as a model sulfur-containing peptide to study the damage induced by vacuum UV (VUV) radiations. In particular, the effect of the presence (or absence in reduced OT) of oxytocin's internal disulfide bridge is evaluated in terms of photo-fragmentation yield and nature of the photo-fragments. Intact, as well as reduced, OT is studied as dianions and radical anions. Radical anions are prepared and photo-fragmented in two-color experiments (UV + VUV) in a linear ion trap. VUV photo-fragmentation patterns are analyzed and compared, and radical-induced mechanisms are proposed. The effect of VUV is principally to ionize but secondary fragmentation is also observed. This secondary fragmentation seems to be considerably enabled by the initial position of the radical on the molecule. In particular, the possibility to form a radical on free cysteines seems to increase the susceptibility to VUV fragmentation. Interestingly, disulfide bridges, which are fundamental for protein structure, could also be responsible for an increased resistance to ionizing radiations. [Figure not available: see fulltext.

Characterization of an ultraviolet imaging detector with high event rate ROIC (HEROIC) readout

NASA Astrophysics Data System (ADS)

Nell, Nicholas; France, Kevin; Harwit, Alex; Bradley, Scott; Franka, Steve; Freymiller, Ed; Ebbets, Dennis

2016-07-01

We present characterization results from a photon counting imaging detector consisting of one microchannel plate (MCP) and an array of two readout integrated circuits (ROIC) that record photon position. The ROICs used in the position readout are the high event rate ROIC (HEROIC) devices designed to handle event rates up to 1 MHz per pixel, recently developed by the Ball Aerospace and Technologies Corporation in collaboration with the University of Colorado. An opaque cesium iodide (CsI) photocathode sensitive in the far-ultraviolet (FUV; 122-200 nm), is deposited on the upper surface of the MCP. The detector is characterized in a chamber developed by CU Boulder that is capable of illumination with vacuum-ultraviolet (VUV) monochromatic light and measurement of absolute ux with a calibrated photodiode. Testing includes investigation of the effects of adjustment of internal settings of the HEROIC devices including charge threshold, gain, and amplifier bias. The detector response to high count rates is tested. We report initial results including background, uniformity, and quantum detection efficiency (QDE) as a function of wavelength.

Rovibrational photoionization dynamics of methyl and its isotopomers studied by high-resolution photoionization and photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Schulenburg, A. M.; Alcaraz, Ch.; Grassi, G.; Merkt, F.

2006-09-01

High-resolution photoionization and pulsed-field-ionization zero-kinetic-energy photoelectron spectra of CH3, CH2D, CHD2, and CD3 have been recorded in the vicinity of the first adiabatic ionization threshold following single-photon excitation from the ground neutral state using a narrow-bandwidth vacuum-ultraviolet laser. The radicals were produced from the precursor molecules methyl-bromide, methyl-iodide, dimethyl-thioether, acetone, and nitromethane by 193nm excimer photolysis in a quartz capillary and were subsequently cooled to a rotational temperature Trot≈30K in a supersonic expansion. Nitromethane was identified as a particularly suitable photolytic precursor of methyl for studies by photoionization and threshold photoelectron spectroscopy. Thanks to the cold rotational temperature reached in the supersonic expansion, the rotational structure of the threshold ionization spectra could be resolved, and the photoionization dynamics investigated. Rydberg series converging on excited rotational levels of CH3+ could be observed in the range of principal quantum number n =30-50, and both rotational autoionization and predissociation were identified as decay processes in the threshold region. The observed photoionization transitions can be understood in the realm of an orbital model for direct ionization but the intensity distributions can only be fully accounted for if the rotational channel interactions mediated by the quadrupole of the cation are considered. Improved values of the adiabatic ionization thresholds were derived for all isotopomers [CH3: 79356.2(15)cm-1, CH2D: 79338.8(15)cm-1, CHD2: 79319.1(15)cm-1, and CD3: 79296.4(15)cm-1].

Complex mixture analysis by photoionization mass spectrometry with a VUV hydrogen laser source

NASA Astrophysics Data System (ADS)

Huth, T. C.; Denton, M. B.

1985-12-01

Trace organic analysis in complex matrix presents one of the most challenging problems in analytical mass spectrometry. When ionization is accomplished non-selectively using electron impact, extensive sample clean-up is often necessary in order to isolate the analyte from the matrix. Sample preparation can be greatly reduced when the VUV H2 laser is used to selectively photoionize only a small fraction of compounds introduced into the ion source. This device produces parent ions only for all compounds whose ionization potentials lie below a threshold value determined by the photon energy of 7.8 eV. The only observed interference arises from electron impact ionization, when scattered laser radiation interacts with metal surfaces, producing electrons which are then accelerated by potential fields inside the source. These can be suppressed to levels acceptable for practical analysis through proper instrumental design. Results are presented which indicate the ability of this ion source to discriminate against interfering matrix components, in simple extracts from a variety of complex real world matrices, such as brewed coffee, beer, and urine.

The VUV instrument SPICE for Solar Orbiter: performance ground testing

NASA Astrophysics Data System (ADS)

Caldwell, Martin E.; Morris, Nigel; Griffin, Douglas K.; Eccleston, Paul; Anderson, Mark; Pastor Santos, Carmen; Bruzzi, Davide; Tustain, Samuel; Howe, Chris; Davenne, Jenny; Grundy, Timothy; Speight, Roisin; Sidher, Sunil D.; Giunta, Alessandra; Fludra, Andrzej; Philippon, Anne; Auchere, Frederic; Hassler, Don; Davila, Joseph M.; Thompson, William T.; Schuehle, Udo H.; Meining, Stefan; Walls, Buddy; Phelan, P.; Dunn, Greg; Klein, Roman M.; Reichel, Thomas; Gyo, Manfred; Munro, Grant J.; Holmes, William; Doyle, Peter

2017-08-01

SPICE is an imaging spectrometer operating at vacuum ultraviolet (VUV) wavelengths, 70.4 - 79.0 nm and 97.3 - 104.9 nm. It is a facility instrument on the Solar Orbiter mission, which carries 10 science instruments in all, to make observations of the Sun's atmosphere and heliosphere, at close proximity to the Sun, i.e to 0.28 A.U. at perihelion. SPICE's role is to make VUV measurements of plasma in the solar atmosphere. SPICE is designed to achieve spectral imaging at spectral resolution >1500, spatial resolution of several arcsec, and two-dimensional FOV of 11 x16arcmins. The many strong constraints on the instrument design imposed by the mission requirements prevent the imaging performance from exceeding those of previous instruments, but by being closer to the sun there is a gain in spatial resolution. The price which is paid is the harsher environment, particularly thermal. This leads to some novel features in the design, which needed to be proven by ground test programs. These include a dichroic solar-transmitting primary mirror to dump the solar heat, a high in-flight temperature (60deg.C) and gradients in the optics box, and a bespoke variable-line-spacing grating to minimise the number of reflective components used. The tests culminate in the systemlevel test of VUV imaging performance and pointing stability. We will describe how our dedicated facility with heritage from previous solar instruments, is used to make these tests, and show the results, firstly on the Engineering Model of the optics unit, and more recently on the Flight Model. For the keywords, select up to 8 key terms for a search on your manuscript's subject.

Plasma ignition thresholds in UV laser ablation plumes

NASA Astrophysics Data System (ADS)

Clarke, P.; Dyer, P. E.; Key, P. H.; Snelling, H. V.

Ultraviolet (UV) laser thresholds for plasma ignition on solid targets predicted from electron-neutral collisional heating are generally much higher than those observed experimentally. This inconsistency was reconciled by Rosen, et al. [2], who showed that excited-state photoionization played a key role in long-pulse UV laser breakdown. Here we develop a related model but with emphasis on pulses of 10 ns duration. Experimental results are also reported for titanium, copper, silicon, and ferulic acid targets in vacuum, irradiated with combinations of the XeF, KrF, and ArF lasers for comparison with predictions.

Highly Resolved Studies of Vacuum Ultraviolet Photoionization Dynamics

NASA Astrophysics Data System (ADS)

Kakar, Sandeep

We use measurements of dispersed fluorescence from electronically excited photoions to study fundamental aspects of intramolecular dynamics. Our experimental innovations make it possible to obtain highly resolved photoionization data that offer qualitative insights into molecular scattering. In particular, we obtain vibrationally resolved data to probe coupling between the electronic and nuclear degrees of freedom by studying the distribution of vibrational energy among photoions. Vibrationally resolved branching ratios are measured over a broad spectral range of excitation energy and their non-Franck-Condon behavior is used as a tool to investigate two diverse aspects of shape resonant photoionization. First, vibrational branching ratios are obtained for the SiF_4 5a _1^{-1} and CS_2 5sigma_{rm u} ^{-1} photoionization channels to help elucidate the microscopic aspects of shape resonant wavefunction for polyatomic molecules. It is shown that in such molecules the shape resonant wavefunction is not necessarily attributable to a specific bond in the molecule. Second, the multichannel aspect of shape resonant photoionization dynamics, reflected in continuum channel coupling, is investigated by obtaining vibrational branching ratios for the 2 sigma_{rm u}^{ -1} and 4sigma^{ -1} photoionization of the isoelectronic molecules N_2 and CO, respectively. These data indicate that effects of continuum coupling may be widespread. We also present the first set of rotationally resolved data over a wide energy range for the 2 sigma_{rm u}^{ -1} photoionization of N_2. These data probe the partitioning of the angular momentum between the photoelectron and photoion, and highlight the multicenter nature of the molecular potential. These case studies illustrate the utility of dispersed fluorescence measurements as a complement to photoelectron spectroscopy for obtaining highly resolved data for molecular photoionization. These measurements makes it possible to probe intrinsically molecular aspects, such as the vibration and rotation, of photoionization dynamics over an extended spectral range when used in conjunction with synchrotron radiation as the exciting source. Furthermore, the high resolution made possible by this technique provides high selectivity for accessing weaker ionization channels which are the ones strongly affected by resonant activity, and the present study repeatedly stresses the importance of this capability in discovering and deciphering new trends in resonant molecular ionization dynamics.

The translational, rotational, and vibrational energy effects on the chemical reactivity of water cation H2O+(X 2B1) in the collision with deuterium molecule D2

NASA Astrophysics Data System (ADS)

Xu, Yuntao; Xiong, Bo; Chang, Yih Chung; Ng, C. Y.

2013-07-01

By employing the newly established vacuum ultraviolet (VUV) laser pulsed field ionization-photoion (PFI-PI) double quadrupole-double octopole ion guide apparatus, we have examined the translational, rotational, and vibrational energy effects on the chemical reactivity of water cation H2O+(X2B1) in the collision with deuterium molecule D2. The application of a novel electric-field pulsing scheme to the VUV laser PFI-PI ion source has enabled the preparation of a rovibrationally selected H2O+(X2B1; v_1^ + v_2^ + v_3^ +; N+Ka+Kc+) ion beam with not only high internal-state selectivity and high intensity but also high translational energy resolution. Despite the unfavorable Franck-Condon factors, we are able to prepare the excited vibrational states (v_1^ + v_2^ + v_3^ +) = (100) and (020) along with the (000) ground vibrational state, for collisional studies, where v_1^ +, v_2^ +, and v_3^ + represent the symmetric stretching, bending, and asymmetric stretching modes of H2O+(X2B1). We show that a range of rotational levels from N+Ka+Kc+ = 000 to 322, covering a rotational energy range of 0-200 cm-1 of these vibrational states, can also be generated for absolute integral cross section (σ) measurements at center-of-mass collision energies (Ecms) from thermal energies to 10.00 eV. The Ecm dependences of the σ values are consistent with the prediction of the orbiting model, indicating that translational energy significantly hinders the chemical reactivity of H2O+(X2B1). Rotational enhancements are observed at Ecm < 0.30 eV for all the three vibrational states, (000), (100), and (020). While the σ values for (100) are found to be only slightly below those for (000), the σ values for (020) are lower than those for (000) and (100) by up to 20% at Ecm ≤ 0.20 eV, indicative of vibrational inhibition at low Ecm by excitation of the (020) mode. Rationalizations are proposed for the observed rotational enhancements and the bending vibrational inhibition. Rigorous theoretical calculations are needed to interpret the wealth of rovibrationally selected cross sections obtained in the present study.

Molecular alignment dependent electron interference in attosecond ultraviolet photoionization

PubMed Central

Yuan, Kai-Jun; Bandrauk, André D.

2015-01-01

We present molecular photoionization processes by intense attosecond ultraviolet laser pulses from numerical solutions of time-dependent Schrödinger equations. Simulations preformed on a single electron diatomic H2+ show minima in molecular photoelectron energy spectra resulting from two center interference effects which depend strongly on molecular alignment. We attribute such sensitivity to the spatial orientation asymmetry of the photoionization process from the two nuclei. A similar influence on photoelectron kinetic energies is also presented. PMID:26798785

Near-Infrared Scintillation of Liquid Argon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tilly, Elizabeth; Escobar, Carlos

2017-01-01

Liquid argon is well known to scintillate in the vacuum ultraviolet (VUV) range which is inherently difficult to detect. There has been recent evidence to suggest that it also emits near infrared (NIR) light. If this is the case, many large-scale time projection chambers and other similar detectors will be able to maximize light collection while minimizing cost. The goal of this project is to confirm and quantify this NIR emission. In order to accomplish this, an α-source was placed in a volume of highly purified liquid argon and observed using an infrared PMT with a filter excluding light withmore » wavelength <715 nm. Performing a simple counting experiment, there were indications of NIR scintillation. Further analysis is in progress.« less

Ion source research and development at University of Jyväskylä: Studies of different plasma processes and towards the higher beam intensities.

PubMed

Koivisto, H; Kalvas, T; Tarvainen, O; Komppula, J; Laulainen, J; Kronholm, R; Ranttila, K; Tuunanen, J; Thuillier, T; Xie, D; Machicoane, G

2016-02-01

Several ion source related research and development projects are in progress at the Department of Physics, University of Jyväskylä (JYFL). The work can be divided into investigation of the ion source plasma and development of ion sources, ion beams, and diagnostics. The investigation covers the Electron Cyclotron Resonance Ion Source (ECRIS) plasma instabilities, vacuum ultraviolet (VUV) and visible light emission, photon induced electron emission, and the development of plasma diagnostics. The ion source development covers the work performed for radiofrequency-driven negative ion source, RADIS, beam line upgrade of the JYFL 14 GHz ECRIS, and the development of a new room-temperature-magnet 18 GHz ECRIS, HIISI.

Study of the Synchrotron Photoionization Oxidation of 2-Methylfuran Initiated by O(3P) under Low-Temperature Conditions at 550 and 650 K.

PubMed

Fathi, Yasmin; Meloni, Giovanni

2017-09-21

The O-( 3 P)-initiated oxidation of 2-methylfuran (2-MF) was investigated using vacuum-ultraviolet synchrotron radiation from the Advanced Light Source at Lawrence Berkeley National Laboratory. Reaction species were studied by multiplexed photoionization mass spectrometry at 550 and 650 K. The oxygen addition pathway is favored in this reaction, forming four triplet diradicals that undergo intersystem crossing into singlet epoxide species that lead to the formation of products at m/z 30 (formaldehyde), 42 (propene), 54 (1-butyne, 1,3-butadiene, and 2-butyne), and 70 (2-butenal, methyl vinyl ketone, and 3-butenal). Mass-to-charge ratios, photoionization spectra, and adiabatic ionization energies for each primary reaction species were obtained and used to characterize their identities. In addition, by means of electronic structure calculations, potential energy surface scans of the different species produced throughout the oxidation were examined to further validate the primary chemistry occurring. Branching fractions for the formation of the primary products were calculated at the two temperatures and contribute 81.0 ± 21.4% at 550 K and 92.1 ± 25.5% at 650 K.

Atomic Processes for XUV Lasers: Alkali Atoms and Ions

NASA Astrophysics Data System (ADS)

Dimiduk, David Paul

The development of extreme ultraviolet (XUV) lasers is dependent upon knowledge of processes in highly excited atoms. Described here are spectroscopy experiments which have identified and characterized certain autoionizing energy levels in core-excited alkali atoms and ions. Such levels, termed quasi-metastable, have desirable characteristics as upper levels for efficient, powerful XUV lasers. Quasi -metastable levels are among the most intense emission lines in the XUV spectra of core-excited alkalis. Laser experiments utilizing these levels have proved to be useful in characterizing other core-excited levels. Three experiments to study quasi-metastable levels are reported. The first experiment is vacuum ultraviolet (VUV) absorption spectroscopy on the Cs 109 nm transitions using high-resolution laser techniques. This experiment confirms the identification of transitions to a quasi-metastable level, estimates transition oscillator strengths, and estimates the hyperfine splitting of the quasi-metastable level. The second experiment, XUV emission spectroscopy of Ca II and Sr II in a microwave-heated plasma, identifies transitions from quasi-metastable levels in these ions, and provides confirming evidence of their radiative, rather than autoionizing, character. In the third experiment, core-excited Ca II ions are produced by inner-shell photoionization of Ca with soft x-rays from a laser-produced plasma. This preliminary experiment demonstrated a method of creating large numbers of these highly-excited ions for future spectroscopic experiments. Experimental and theoretical evidence suggests the CA II 3{ rm p}^5 3d4s ^4 {rm F}^circ_{3/2 } quasi-metastable level may be directly pumped via a dipole ionization process from the Ca I ground state. The direct process is permitted by J conservation, and occurs due to configuration mixing in the final state and possibly the initial state as well. The experiments identifying and characterizing quasi-metastable levels are compared to calculations using the Hartree-Fock code RCN/RCG. Calculated parameters include energy levels, wavefunctions, and transition rates. Based on an extension of this code, earlier unexplained experiments showing strong two-electron radiative transitions from quasi-metastable levels are now understood.

Brominated Tyrosine and Polyelectrolyte Multilayer Analysis by Laser Desorption VUV Postionization and Secondary Ion Mass Spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

University of Illinois at Chicago; Blaze, Melvin M. T.; Takahashi, Lynelle

2011-03-14

The small molecular analyte 3,5-dibromotyrosine (Br2Y) and chitosan-alginate polyelectrolyte multilayers (PEM) with and without adsorbed Br2Y were analyzed by laser desorption postionization mass spectrometry (LDPI-MS). LDPI-MS using 7.87 eV laser and tunable 8 ? 12.5 eV synchrotron vacuum ultraviolet (VUV) radiation found that desorption of clusters from Br2Y films allowed detection by≤8 eV single photon ionization. Thermal desorption and electronic structure calculations determined the ionization energy of Br2Y to be ~;;8.3?0.1 eV and further indicated that the lower ionization energies of clusters permitted their detection at≤8 eV photon energies. However, single photon ionization could only detect Br2Y adsorbed within PEMsmore » when using either higher photon energies or matrix addition to the sample. All samples were also analyzed by 25 keV Bi3 + secondary ion mass spectrometry (SIMS), with the negative ion spectra showing strong parent ion signal which complemented that observed by LDPI-MS. The negative ion SIMS depended strongly on the high electron affinity of this specific analyte and the analyte?s condensed phase environment.« less

The Gaseous Phase as a Probe of the Astrophysical Solid Phase Chemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abou Mrad, Ninette; Duvernay, Fabrice; Isnard, Robin

2017-09-10

In support of space missions and spectroscopic observations, laboratory experiments on ice analogs enable a better understanding of organic matter formation and evolution in astrophysical environments. Herein, we report the monitoring of the gaseous phase of processed astrophysical ice analogs to determine if the gaseous phase can elucidate the chemical mechanisms and dominant reaction pathways occurring in the solid ice subjected to vacuum ultra-violet (VUV) irradiation at low temperature and subsequently warmed. Simple (CH{sub 3}OH), binary (H{sub 2}O:CH{sub 3}OH, CH{sub 3}OH:NH{sub 3}), and ternary ice analogs (H{sub 2}O:CH{sub 3}OH:NH{sub 3}) were VUV-processed and warmed. The evolution of volatile organic compoundsmore » in the gaseous phase shows a direct link between their relative abundances in the gaseous phase, and the radical and thermal chemistries modifying the initial ice composition. The correlation between the gaseous and solid phases may play a crucial role in deciphering the organic composition of astrophysical objects. As an example, possible solid compositions of the comet Lovejoy are suggested using the abundances of organics in its comae.« less

UV + V UV double-resonance studies of autoionizing Rydberg states of the hydroxyl radical

DOE Office of Scientific and Technical Information (OSTI.GOV)

Green, Amy M.; Liu, Fang; Lester, Marsha I., E-mail: milester@sas.upenn.edu

2016-05-14

The hydroxyl radical (OH) is a key oxidant in atmospheric and combustion chemistry. Recently, a sensitive and state-selective ionization method has been developed for detection of the OH radical that utilizes UV excitation on the A{sup 2}Σ{sup +}–X{sup 2}Π transition followed by fixed 118 nm vacuum ultraviolet (VUV) radiation to access autoionizing Rydberg states [J. M. Beames et al., J. Chem. Phys. 134, 241102 (2011)]. The present study uses tunable VUV radiation generated by four-wave mixing to examine the origin of the enhanced ionization efficiency observed for OH radicals prepared in specific A{sup 2}Σ{sup +} intermediate levels. The enhancement ismore » shown to arise from resonant excitation to distinct rotational and fine structure levels of two newly identified {sup 2}Π Rydberg states with an A{sup 3}Π cationic core and a 3d electron followed by ionization. Spectroscopic constants are derived and effects due to uncoupling of the Rydberg electron are revealed for the OH {sup 2}Π Rydberg states. The linewidths indicate a Rydberg state lifetime due to autoionization on the order of a picosecond.« less

High-resolution one-photon absorption spectroscopy of the D2Σ- ← X2 Π system of radical OH and OD

NASA Astrophysics Data System (ADS)

Heays, A. N.; de Oliveira, N.; Gans, B.; Ito, K.; Boyé-Péronne, S.; Douin, S.; Hickson, K. M.; Nahon, L.; Loison, J. C.

2018-01-01

Vacuum-ultraviolet (VUV) photoabsorption spectra were recorded of the A2Σ+(v‧ = 0) ← X2 Π(v‧‧ = 0) , D2Σ-(v‧ = 0) ← X2 Π(v‧‧ = 0) and D2Σ-(v‧ = 1) ← X2 Π(v‧‧ = 0) bands of the OH and OD radicals generated in a plasma-discharge source using synchrotron radiation as a background continuum coupled with the VUV Fourier-transform spectrometer on the DESIRS beamline of synchrotron SOLEIL. High-resolution spectra permitted the quantification of transition frequencies, relative f-values, and natural line broadening. The f-values were absolutely calibrated with respect to a previous measurement of A2Σ+(v‧ = 0) ← X2 Π(v‧‧ = 0) (Wang et al., 1979). Lifetime broadening of the excited D2Σ-(v = 0) and D2Σ-(v = 1) levels is measured for the first time and compared with previous experimental limits, and implies a lifetime 5 times shorter than a theoretical prediction (van der Loo and Groenenboom, 2005). A local perturbation of the D2Σ-(v = 0) level in OH was found.

Time-resolved multi-mass ion imaging: Femtosecond UV-VUV pump-probe spectroscopy with the PImMS camera.

PubMed

Forbes, Ruaridh; Makhija, Varun; Veyrinas, Kévin; Stolow, Albert; Lee, Jason W L; Burt, Michael; Brouard, Mark; Vallance, Claire; Wilkinson, Iain; Lausten, Rune; Hockett, Paul

2017-07-07

The Pixel-Imaging Mass Spectrometry (PImMS) camera allows for 3D charged particle imaging measurements, in which the particle time-of-flight is recorded along with (x, y) position. Coupling the PImMS camera to an ultrafast pump-probe velocity-map imaging spectroscopy apparatus therefore provides a route to time-resolved multi-mass ion imaging, with both high count rates and large dynamic range, thus allowing for rapid measurements of complex photofragmentation dynamics. Furthermore, the use of vacuum ultraviolet wavelengths for the probe pulse allows for an enhanced observation window for the study of excited state molecular dynamics in small polyatomic molecules having relatively high ionization potentials. Herein, preliminary time-resolved multi-mass imaging results from C 2 F 3 I photolysis are presented. The experiments utilized femtosecond VUV and UV (160.8 nm and 267 nm) pump and probe laser pulses in order to demonstrate and explore this new time-resolved experimental ion imaging configuration. The data indicate the depth and power of this measurement modality, with a range of photofragments readily observed, and many indications of complex underlying wavepacket dynamics on the excited state(s) prepared.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sturm, F. P.; Tong, X. M.; Palacios, A.

Here, we used ultrashort femtosecond vacuum ultraviolet (VUV) and infrared (IR) pulses in a pump-probe scheme to map the dynamics and nonequilibrium dissociation channels of excited neutral H 2 molecules. A nuclear wave packet is created in the B 1Σmore » $$+\\atop{u}$$ state of the neutral H 2 molecule by absorption of the ninth harmonic of the driving infrared laser field. Due to the large stretching amplitude of the molecule excited in the B 1Σ$$+\\atop{u}$$ electronic state, the effective H 2 + ionization potential changes significantly as the nuclear wave packet vibrates in the bound, highly electronically and vibrationally excited B potential-energy curve. We probed such dynamics by ionizing the excited neutral molecule using time-delayed VUV-or-IR radiation. We identified the nonequilibrium dissociation channels by utilizing three-dimensional momentum imaging of the ion fragments. We also found that different dissociation channels can be controlled, to some extent, by changing the IR laser intensity and by choosing the wavelength of the probe laser light. Furthermore, we concluded that even in a benchmark molecular system such as H 2*, the interpretation of the nonequilibrium multiphoton and multicolor ionization processes is still a challenging task, requiring intricate theoretical analysis.« less

Liquid xenon calorimeter for MEG II experiment with VUV-sensitive MPPCs

NASA Astrophysics Data System (ADS)

Ogawa, Shinji; MEG II Collaboration

2017-02-01

The MEG II experiment is an upgrade of the MEG experiment to search for the charged lepton flavor violating decay of muon, μ+ →e+ γ . The MEG II experiment is expected to reach a branching ratio sensitivity of 4 ×10-14 , which is one order of magnitude better than the sensitivity of the current MEG experiment. The performance of the liquid xenon (LXe) γ-ray detector will be greatly improved with a highly granular scintillation readout realized by replacing 216 photomultiplier tubes (PMTs) on the γ-ray entrance face with 4092 Multi-Pixel Photon Counters (MPPCs). For this purpose, we have developed a new type of MPPC which is sensitive to the LXe scintillation light in vacuum ultraviolet (VUV) range, in collaboration with Hamamatsu Photonics K.K. We have measured the performance of the MPPC in LXe, and an excellent performance has been confirmed including high photon detection efficiency (> 15 %) for LXe scintillation light. An excellent performance of the LXe detector has been confirmed by Monte Carlo simulations based on the measured properties of the MPPC. The construction of the detector is in progress, aiming to start physics data taking in 2017.

Communication: Protonation process of formic acid from the ionization and fragmentation of dimers induced by synchrotron radiation in the valence region

NASA Astrophysics Data System (ADS)

Arruda, Manuela S.; Medina, Aline; Sousa, Josenilton N.; Mendes, Luiz A. V.; Marinho, Ricardo R. T.; Prudente, Frederico V.

2016-04-01

The ionization and fragmentation of monomers of organic molecules have been extensively studied in the gas phase using mass spectroscopy. In the spectra of these molecules it is possible to identify the presence of protonated cations, which have a mass-to-charge ratio one unit larger than the parent ion. In this work, we investigate this protonation process as a result of dimers photofragmentation. Experimental photoionization and photofragmentation results of doubly deuterated formic acid (DCOOD) in the gas phase by photons in the vacuum ultraviolet region are presented. The experiment was performed by using a time-of-flight mass spectrometer installed at the Brazilian Synchrotron Light Laboratory and spectra for different pressure values in the experimental chamber were obtained. The coupled cluster approach with single and double substitutions was employed to assist the experimental analysis. Results indicate that protonated formic acid ions are originated from dimer dissociation, and the threshold photoionization of (DCOOD)ṡD+ is also determined.

SiC-based Photo-detectors for UV, VUV, EUV and Soft X-ray Detection

NASA Technical Reports Server (NTRS)

Yan, Feng

2006-01-01

A viewgraph presentation describing an ideal Silicon Carbide detector for ultraviolet, vacuum ultraviolet, extreme ultraviolet and soft x-ray detection is shown. The topics include: 1) An ideal photo-detector; 2) Dark current density of SiC photodiodes at room temperature; 3) Dark current in SiC detectors; 4) Resistive and capacitive feedback trans-impedance amplifier; 5) Avalanche gain; 6) Excess noise; 7) SNR in single photon counting mode; 8) Structure of SiC single photon counting APD and testing structure; 9) Single photon counting waveform and testing circuit; 10) Amplitude of SiC single photon counter; 11) Dark count of SiC APD photon counters; 12) Temperature-dependence of dark count rate; 13) Reduce the dark count rate by reducing the breakdown electric field; 14) Spectrum range for SiC detectors; 15) QE curves of Pt/4H-SiC photodiodes; 16) QE curve of SiC; 17) QE curves of SiC photodiode vs. penetration depth; 18) Visible rejection of SiC photodiodes; 19) Advantages of SiC photodiodes; 20) Competitors of SiC detectors; 21) Extraterrestrial solar spectra; 22) Visible-blind EUV detection; 23) Terrestrial solar spectra; and 24) Less than 1KeV soft x-ray detection.

Absolute vacuum ultraviolet photoabsorption cross section studies of atomic and molecular species: Techniques and observational data

NASA Technical Reports Server (NTRS)

Judge, D. L.; Wu, C. Y. R.

1990-01-01

Absorption of a high energy photon (greater than 6 eV) by an isolated molecule results in the formation of highly excited quasi-discrete or continuum states which evolve through a wide range of direct and indirect photochemical processes. These are: photoionization and autoionization, photodissociation and predissociation, and fluorescence. The ultimate goal is to understand the dynamics of the excitation and decay processes and to quantitatively measure the absolute partial cross sections for all processes which occur in photoabsorption. Typical experimental techniques and the status of observational results of particular interest to solar system observations are presented.

VUV Dissociative Photoionization of Quinoline in the 7-26 eV Photon Energy Range

NASA Astrophysics Data System (ADS)

Leach, Sydney; Jochims, Hans-Werner; Baumgärtel, Helmut; Champion, Norbert

2018-05-01

The dissociative photoionization of quinoline was studied by photoionization mass spectrometry and ion yield measurements over a synchrotron photon excitation energy range 7-26 eV. The ionic and neutral products were identified with the aid of thermochemical calculations that, in some cases, led to deeper understanding of photodissociation pathways and the determination of upper limits of heats of formation of ionic and neutral dissociation products. A detailed comparison between the 20 eV photon excitation and 70 eV electron impact mass spectra, coupled with estimation of thermochemical appearance energies, leads to assignment of the dissociative ionization cation and neutral products for each detected ion. Reaction schemes for formation of these products are proposed in a number of cases. Ion intensities in the photon and electron impact mass spectra were used to consider extending a rule of charge retention in simple bond cleavage to more complex cases of dissociative ionization.

An ESR study of the UV degradation of FEP

NASA Technical Reports Server (NTRS)

George, G. A.; Hill, D. J. T.; Odonnell, J. H.; Pomery, P. J.; Rasoul, F.

1992-01-01

Spacecraft in low earth orbit are subjected to significant levels of high energy radiation, including ultraviolet (UV) and visible ultraviolet (VUV) wavelengths. The effects of UV radiation are enhanced over those at the surface of the earth, where the only incident wavelengths are greater than 290 nm. In low earth orbit the incident UV wavelengths extend below 290 nm into the VUV region, where the Lyman alpha-emissions of atomic hydrogen occur at 121 nm. In addition to electromagnetic radiation, in low earth orbit polymer materials may also be subjected to atomic oxygen particle radiation, which will result in direct oxidation of the polymer.

A new membrane inlet interface of a vacuum ultraviolet lamp ionization miniature mass spectrometer for on-line rapid measurement of volatile organic compounds in air.

PubMed

Hou, Keyong; Wang, Junde; Li, Haiyang

2007-01-01

A novel membrane inlet interface coupled to a single-photon ionization (SPI) miniature time-of-flight mass spectrometer has been developed for on-line rapid measurement of volatile organic compounds (VOCs). The vacuum ultraviolet (VUV) light source for SPI was a commercial krypton discharge lamp with photon energy of 10.6 eV and photon flux of 10(10) photons/s. The experimental results showed that the sensitivity was 5 times as high as obtained with the traditional membrane inlet. The enrichment efficiency could be adjusted in the range of 10 to 20 times for different VOCs when a buffer cell was added to the inlet interface, and the memory effect was effectively eliminated. A detection limit as low as 25 parts-per-billion by volume (ppbv) for benzene has been achieved, with a linear dynamic range of three orders of magnitude. The rise times were 6 s, 10 s and 15 s for benzene, toluene and p-xylene, respectively, and the fall time was only 6 s for all of these compounds. The analytical capacity of this system was demonstrated by the on-line analysis of VOCs in single puff mainstream cigarette smoke, in which more than 50 compounds were detected in 2 s. Copyright 2007 John Wiley & Sons, Ltd.

Ultraviolet spectrophotometry of three LINERs

NASA Technical Reports Server (NTRS)

Goodrich, R. W.; Keel, W. C.

1986-01-01

Three galaxies known to be LINERs were observed spectroscopically in the ultraviolet in an attempt to detect the presumed nonthermal continuum source thought to be the source of photoionization in the nuclei. NGC 4501 was found to be too faint for study with the IUE spectrographs, while NGC 5005 had an extended ultraviolet light profile. Comparison with the optical light profile of NGC 5005 indicates that the ultraviolet source is distributed spatially in the same manner as the optical starlight, probably indicating that the ultraviolet excess is due to a component of hot stars in the nucleus. These stars contribute detectable absorption features longward of 2500 A; together with optical data, the IUE spectra suggest a burst of star formation about 1 billion yr ago, with a lower rate continuing to produce a few OB stars. In NGC 4579, a point source contributing most of the ultraviolet excess is found that is much different than the optical light distribution. Furthermore, the ultraviolet to X-ray spectral index in NGC 4579 is 1.4, compatible with the UV to X-ray indices found for samples of Seyfert galaxies. This provides compelling evidence for the detection of the photoionizing continuum in NGC 4579 and draws the research fields of normal galaxies and active galactic nuclei closer together. The emission-line spectrum of NGC 4579 is compared with calculations from a photoionization code, CLOUDY, and several shock models. The photoionization code is found to give superior results, adding to the increasing weight of evidence that the LINER phenomenon is essentially a scaled-down version of the Seyfert phenomenon.

Differentiation of Microbial Species and Strains in Coculture Biofilms by Multivariate Analysis of Laser Desorption Postionization Mass Spectra

DOE Office of Scientific and Technical Information (OSTI.GOV)

University of Illinois at Chicago; Montana State University; Bhardwaj, Chhavi

2013-04-01

7.87 to 10.5 eV vacuum ultraviolet (VUV) photon energies were used in laser desorption postionization mass spectrometry (LDPI-MS) to analyze biofilms comprised of binary cultures of interacting microorganisms. The effect of photon energy was examined using both tunable synchrotron and laser sources of VUV radiation. Principal components analysis (PCA) was applied to the MS data to differentiate species in Escherichia coli-Saccharomyces cerevisiae coculture biofilms. PCA of LDPI-MS also differentiated individual E. coli strains in a biofilm comprised of two interacting gene deletion strains, even though these strains differed from the wild type K-12 strain by no more than four genemore » deletions each out of approximately 2000 genes. PCA treatment of 7.87 eV LDPI-MS data separated the E. coli strains into three distinct groups two ?pure? groups and a mixed region. Furthermore, the ?pure? regions of the E. coli cocultures showed greater variance by PCA when analyzed by 7.87 eV photon energies than by 10.5 eV radiation. Comparison of the 7.87 and 10.5 eV data is consistent with the expectation that the lower photon energy selects a subset of low ionization energy analytes while 10.5 eV is more inclusive, detecting a wider range of analytes. These two VUV photon energies therefore give different spreads via PCA and their respective use in LDPI-MS constitute an additional experimental parameter to differentiate strains and species.« less

A Comparison of Space and Ground Based Facility Environmental Effects for FEP Teflon. Revised

NASA Technical Reports Server (NTRS)

Rutledge, Sharon K.; Banks, Bruce A.; Kitral, Michael

1998-01-01

Fluorinated Ethylene Propylene (FEP) Teflon is widely used as a thermal control material for spacecraft, however, it is susceptible to erosion, cracking, and subsequent mechanical failure in low Earth orbit. One of the difficulties in determining whether FEP Teflon will survive during a mission is the wide disparity of erosion rates observed for this material in space and in ground based facilities. Each environment contains different levels of atomic oxygen, ions, and vacuum ultraviolet (VUV) radiation in addition to parameters such as the energy of the arriving species and temperature. These variations make it difficult to determine what is causing the observed differences in erosion rates. This paper attempts to narrow down which factors affect the erosion rate of FEP Teflon through attempting to change only one environmental constituent at a time. This was attempted through the use of a single simulation facility (plasma asher) environment with a variety of Faraday cages and VUV transparent windows. Isolating one factor inside of a radio frequency (RF) plasma proved to be very difficult. Two observations could be made. First, it appears that the erosion yield of FEP Teflon with respect to that of polyimide Kapton is not greatly affected by the presence or lack of VUV radiation present in the RF plasma and the relative erosion yield for the FEP Teflon may decrease with increasing fluence. Second, shielding from charged particles appears to lower the relative erosion yield of the FEP to approximately that observed in space, however it is difficult to determine for sure whether ions, electrons, or some other components are causing the enhanced erosion.

Photoionization and Photofragmentation of Carbon Fullerene Molecular Ions

NASA Astrophysics Data System (ADS)

Baral, Kiran Kumar

Cross sections are reported for single and double photoionization accompanied by the loss of as many as seven pairs of C atoms of C60 + and C70+ fullerene molecular ions in the photon energy range 18 eV to 150 eV. These measurements were performed at the Advanced Light Source (ALS) by merging a mass-selected ion beam with a beam of monochromatized synchrotron radiation. Threshold energies were determined for the formation of doubly and triply charged fragment ions from parent ions C60+ and C70+. The energy dependences of cross-sections for direct photoionization yielding C60 2+ and C702+ are compared with those for forming different doubly and triply charged fullerene fragment ions. Two-dimensional product ion scans were measured and quantified at four discrete photon energies: 35 eV, 65 eV, 105 eV and 140 eV, in the vacuum ultraviolet region, providing a comprehensive mapping of the product channels involving single ionization of fullerene ions C60+ and C 70+ accompanied by fragmentation. Since fullerenes are composed of even numbers of carbon atoms, the fragmentation occurs by the loss of differing numbers of carbon atom pairs. In addition to pure ionization, fragmentation product channels become relatively more important at higher photon energies.

Interfacial electronic structure and full spectral Hamaker constants of Si{sub 3}N{sub 4} intergranular films from VUV and SR-VEEL spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

French, R.H.; Scheu, C.; Duscher, G.

1995-09-01

The interfacial electronic structure, presented as the interband transition strength J{sub cv}({omega}) of the interatomic bonds, can be determined by Kramers Kronig (KK) analysis of vacuum ultraviolet (VUV) reflectance or spatially resolved valence electron energy loss (SR-VEEL) spectra. For the wetted interfaces in Si{sub 3}N{sub 4}, equilibrium thin glass films are formed whose thickness is determined by a force balance between attractive and repulsive force terms KK analysis of J{sub cv}({omega}) to yield {var_epsilon}{sub 2}({xi}) for the phases present, permits the direct calculation of the configuration-dependent Hamaker constants for the attractive vdW forces from the interfacial electronic structure. Interband transitionmore » strengths and full spectral Hamaker constants for Si{sub 3}N{sub 4}samples containing a SiYAlON glass have been determined using SR-VEELS from grains and grain boundaries and compared with results from bulk VUV spectroscopy on separate samples of glass and nitride. The A{sub 121}Hamaker constant for Si{sub 3}N{sub 4} with glass of the bulk composition is 8 zJ (zJ = 10{sup {minus}21}J) from the more established optical method. The EELS method permits the determination of vdW forces based upon actual local compositions and structure, which may differ noticeably from bulk standards. Current results show that full spectral Hamaker constants determined from VUV and SR-VEEL measurements of uniform bulk samples agree, but care must be take in the single scattering and zero loss subtraction corrections, and more work is ongoing in this area. Still the results show that for the grain boundary films present in these polycrystalline Si{sub 3}N{sub 4} samples the glass composition is of lower index of refraction. This can arise from increased oxygen content in determined in situ from the SR-VEELS of a particular grain boundary film. 45 refs.« less

Optical Characterization of Molecular Contaminant Films

NASA Technical Reports Server (NTRS)

Visentine, James T.

2007-01-01

A semi-empirical method of optical characterization of thin contaminant films on surfaces of optical components has been conceived. The method was originally intended for application to films that become photochemically deposited on such optical components as science windows, lenses, prisms, thinfilm radiators, and glass solar-cell covers aboard spacecraft and satellites in orbit. The method should also be applicable, with suitable modifications, to thin optical films (whether deposited deliberately or formed as contaminants) on optical components used on Earth in the computer microchip laser communications and thin-film industries. The method is expected to satisfy the need for a means of understanding and predicting the reductions in spectral transmittance caused by contaminant films and the consequent deterioration of performances of sensitive optical systems. After further development, this method could become part of the basis of a method of designing optical systems to minimize or compensate for the deleterious effects of contaminant films. In the original outer-space application, these deleterious effects are especially pronounced because after photochemical deposition, the films become darkened by further exposure to solar vacuum ultraviolet (VUV) radiation. In this method, thin contaminant films are theoretically modeled as thin optical films, characterized by known or assumed values of thickness, index of refraction, and absorption coefficient, that form on the outer surfaces of the original antireflection coating on affected optical components. The assumed values are adjusted as needed to make actual spectral transmittance values approximate observed ones as closely as possible and to correlate these values with amounts of VUV radiation to which the optical components have been exposed. In an initial study, the method was applied in correlating measured changes in transmittance of high-purity fused silica photochemically coated with silicone films of various measured thicknesses and exposed to various measured amounts of VUV radiation. In each case, it was found to be possible to select an index of refraction and absorption coefficient that made the ultraviolet, visible, and infrared transmittance changes predicted by the model match the corresponding measured transmittance changes almost exactly.

Luminescence of Tb-doped Ca 3Y 2(Si 3O 9) 2 oxide upon UV and VUV synchrotron radiation excitation

NASA Astrophysics Data System (ADS)

Dobrowolska, Anna; Zych, Eugeniusz

2011-07-01

Powders of calcium yttrium silicate, Ca 3Y 2(Si 3O 9) 2, containing 0.1-3% Tb 3+ were prepared using a sol-gel method and characterized with XRD, IR, UV-vis and UV-VUV spectroscopies at room temperature and 10 K. Structural analysis revealed pure monoclinic phase of Ca 3Y 2(Si 3O 9) 2 after heat-treatment at 1000 °C. Infrared spectroscopy showed that between 800 and 900 °C a short-range structural organization of the components proceeded, yet without crystallization. A strong emission of Tb 3+ had been observed both in the green part of the spectrum due to the 5D4→ 7FJ transitions and in the blue-violet region owing to the 5D3→ 7FJ radiative relaxation. The color of the light could be tuned from yellowish-green to bluish-white both by means of the dopant content and the temperature of synthesis. Efficient luminescence of Tb 3+-doped Ca 3Y 2(Si 3O 9) 2 phosphors could also be obtained upon stimulation with vacuum ultraviolet synchrotron radiation demonstrating that an energy transfer from the host to the Tb 3+ ions takes place.

Luminescence optimization of MBO 3:Eu 3+ (M=Y, Gd, Al) red phosphor by spray pyrolysis using combinatorial chemistry

NASA Astrophysics Data System (ADS)

Youl Jung, Kyeong

2010-08-01

Conventional solution-based combinatorial chemistry was combined with spray pyrolysis and applied to optimize the luminescence properties of (Y x, Gd y, Al z)BO 3:Eu 3+ red phosphor under vacuum ultraviolet (VUV) excitation. For the Y-Gd-Al ternary system, a compositional library was established to seek the optimal composition at which the highest luminescence under VUV (147 nm) excitation could be achieved. The Al content was found to mainly control the relative peak ratio (R/O) of red and orange colors due to the 5D 0→ 7F 2 to 5D 0→ 7F 1 transitions of Eu 3+. The substitution of Gd atoms in the place of Y sites did not contribute to change the R/O ratio, but was helpful to enhance the emission intensity. As a result, the 613 nm emission peak due to the 5D 0→ 7F 2 transitions of Eu 3+ was intensified by increasing the Al/Gd ratio at a fixed Y content, resulting in the improvement of the color coordinate. Finally, the optimized host composition was (Y 0.11, Gd 0.10, Al 0.79)BO 3 in terms of the emission intensity at 613 nm and the color coordinate.

Infrared Spectroscopic Investigation on CH Bond Acidity in Cationic Alkanes

NASA Astrophysics Data System (ADS)

Matsuda, Yoshiyuki; Xie, Min; Fujii, Asuka

2016-06-01

We have demonstrated large enhancements of CH bond acidities in alcohol, ether, and amine cations through infrared predissociation spectroscopy based on the vacuum ultraviolet photoionization detection. In this study, we investigate for the cationic alkanes (pentane, hexane, and heptane) with different alkyl chain lengths. The σ electrons are ejected in the ionization of alkanes, while nonbonding electrons are ejected in ionization of alcohols, ethers, and amines. Nevertheless, the acidity enhancements of CH in these cationic alkanes have also been demonstrated by infrared spectroscopy. The correlations of their CH bond acidities with the alkyl chain lengths as well as the mechanisms of their acidity enhancements will be discussed by comparison of infrared spectra and theoretical calculations.

Calibration of a high harmonic spectrometer by laser induced plasma emission.

PubMed

Farrell, J P; McFarland, B K; Bucksbaum, P H; Gühr, M

2009-08-17

We present a method that allows for a convenient switching between high harmonic generation (HHG) and accurate calibration of the vacuum ultraviolet (VUV) spectrometer used to analyze the harmonic spectrum. The accurate calibration of HHG spectra is becoming increasingly important for the determination of electronic structures. The wavelength of the laser harmonics themselves depend on the details of the harmonic geometry and phase matching, making them unsuitable for calibration purposes. In our calibration mode, the target resides directly at the focus of the laser, thereby enhancing plasma emission and suppressing harmonic generation. In HHG mode, the source medium resides in front or after the focus, showing enhanced HHG and no plasma emission lines. We analyze the plasma emission and use it for a direct calibration of our HHG spectra. (c) 2009 Optical Society of America

Accurate VUV Laboratory Measurements of Fe III Transitions for Astrophysical Applications

NASA Technical Reports Server (NTRS)

Blackwell-Whitehead, R. J.; Pickering, J. C.; Smillie, D.; Nave, G.; Szabo, C. I.; Smith, Peter L.; Nielsen, K. E.; Peters, G.

2006-01-01

We report preliminary measurements of Fe III spectra in the 1150 to 2500 A wavelength interval. Spectra have been recorded with an iron-neon Penning discharge lamp (PDL) between 1600 and 2500 A at Imperial College (IC) using high resolution Fourier (FT) transform spectroscopy. These FT spectrometer measurements were extended beyond 1600 A to 1150 A using high-resolution grating spectroscopy at the National Institute of Standards and Technology (NIST). These recorded spectra represent the first radiometrically calibrated measurements of a doubly-ionized iron-group element spectrum combining the techniques of vacuum ultraviolet FT and grating spectroscopy. The spectral range of the new laboratory measurements corresponds to recent HST/STIS observations of sharp-lined B stars and of Eta Carinae. The new improved atomic data can be applied to abundance studies and diagnostics of astrophysical plasmas.

The valence and Rydberg states of difluoromethane: A combined experimental vacuum ultraviolet spectrum absorption and theoretical study by ab initio configuration interaction and density functional computations

NASA Astrophysics Data System (ADS)

Palmer, Michael H.; Vrønning Hoffmann, Søren; Jones, Nykola C.; Coreno, Marcello; de Simone, Monica; Grazioli, Cesare

2018-06-01

The vacuum ultraviolet (VUV) spectrum for CH2F2 from a new synchrotron study has been combined with earlier data and subjected to detailed scrutiny. The onset of absorption, band I and also band IV, is resolved into broad vibrational peaks, which contrast with the continuous absorption previously claimed. A new theoretical analysis, using a combination of time dependent density functional theory (TDDFT) calculations and complete active space self-consistent field, leads to a major new interpretation. Adiabatic excitation energies (AEEs) and vertical excitation energies, evaluated by these methods, are used to interpret the spectra in unprecedented detail using theoretical vibronic analysis. This includes both Franck-Condon (FC) and Herzberg-Teller (HT) effects on cold and hot bands. These results lead to the re-assignment of several known excited states and the identification of new ones. The lowest calculated AEE sequence for singlet states is 11B1 ˜ 11A2 < 21B1 < 11A1 < 21A1 < 11B2 < 31A1 < 31B1. These, together with calculated higher energy states, give a satisfactory account of the principal maxima observed in the VUV spectrum. Basis sets up to quadruple zeta valence with extensive polarization are used. The diffuse functions within this type of basis generate both valence and low-lying Rydberg excited states. The optimum position for the site of further diffuse functions in the calculations of Rydberg states is shown to lie on the H-atoms. The routine choice on the F-atoms is shown to be inadequate for both CHF3 and CH2F2. The lowest excitation energy region has mixed valence and Rydberg character. TDDFT calculations show that the unusual structure of the onset arises from the near degeneracy of 11B1 and 11A2 valence states, which mix in symmetric and antisymmetric combinations. The absence of fluorescence in the 10.8-11 eV region contrasts with strong absorption. This is interpreted by the 21B1 and 11A1 states where no fluorescence is calculated for these two states, which are only active in absorption. The nature of the two states, 11B1 and 21B1, is fundamentally different, but both are complex owing to the presence of FC and HT effects occurring in different ways. The two most intense bands, close to 12.5 and 15.5 eV, contain valence states as expected; the onset of the 15.5 eV band shows a set of vibrational peaks, but the vibration frequency does not correspond to any of the photoelectron spectral (PES) structure and is clearly valence in nature. The routine use of PES footprints to detect Rydberg states in VUV spectra is shown to be inadequate. The combined effects of FC and HT in the VUV spectral bands lead to additional vibrations when compared with the PES.

Online study on the co-pyrolysis of coal and corn with vacuum ultraviolet photoionization mass spectrometry.

PubMed

Weng, Jun-Jie; Liu, Yue-Xi; Zhu, Ya-Nan; Pan, Yang; Tian, Zhen-Yu

2017-11-01

With the aim to support the experimental tests in a circulating fluidized bed pilot plant, the pyrolysis processes of coal, corn, and coal-corn blend have been studied with an online pyrolysis photoionization time-of-flight mass spectrometry (Py-PI-TOFMS). The mass spectra at different temperatures (300-800°C) as well as time-evolved profiles of selected species were measured. The pyrolysis products such as alkanes, alkenes, phenols, aromatics, as well as nitrogen- and sulfur-containing species were detected. As temperature rises, the relative ion intensities of high molecular weight products tend to decrease, while those of aromatics increase significantly. During the co-pyrolysis, coal can promote the reaction temperature of cellulose in corn. Time-evolved profiles demonstrate that coal can affect pyrolysis rate of cellulose, hemicellulose, and lignin of corn in blend. This work shows that Py-PI-TOFMS is a powerful approach to permit a better understanding of the mechanisms underlying the co-pyrolysis of coal and biomass. Copyright © 2017 Elsevier Ltd. All rights reserved.

A Fourier transform spectrometer without a beam splitter for the vacuum ultraviolet range: From the optical design to the first UV spectrum.

PubMed

de Oliveira, N; Joyeux, D; Phalippou, D; Rodier, J C; Polack, F; Vervloet, M; Nahon, L

2009-04-01

We describe a Fourier transform (FT) spectrometer designed to operate down to 60 nm (20 eV) on a synchrotron radiation beamline for high resolution absorption spectrometry. As far as we know, such an instrument is not available below 140 nm mainly because manufacturing accurate and efficient beam splitters remains a major problem at these wavelengths, especially if a wide bandwidth operation is desired. In order to overcome this difficulty, we developed an interferometer based on wave front division instead of amplitude division. It relies on a modified Fresnel bimirror configuration that requires only flat mirrors. The instrument provides path difference scanning through the translation of one reflector. During the scanning, the moving reflector is controlled by an optical system that keeps its direction constant within a tolerable value and provides an accurate interferometric measurement of the path difference variation. Therefore, a regular interferogram sampling is obtained, producing a nominal spectral impulse response and an accurate spectral calibration. The first results presented in this paper show a measured spectral resolution of delta(sigma)=0.33 cm-1 (interval between spectral samples). This was obtained with a sampling interval of 29 nm (path difference) and 512 K samples from a one-sided interferogram using a cosine FT. Such a sampling interval should allow the recording of large bandwidth spectra down to lambda=58 nm with an ultimate resolving power of 500,000 at this wavelength. In order to check the instrument performances, we first recorded an interferogram from a He-Ne stabilized laser. This provided the actual spectral impulse function, which was found to be fully satisfactory. The determination of the impulse response distortion and of the noise on the vacuum ultraviolet (VUV) spectral range provided accurate information in the sampling error profile over a typical scan. Finally, the instrument has been moved to the SU5 undulator-based synchrotron radiation beamline (Super-ACO facility, LURE, Orsay, France). A high resolution spectrum of O2 (the Schumann-Runge absorption bands, 185-200 nm) was computed from recorded interferograms using the beamline monochromator at the zeroth order to feed the instrument with an 11% relative bandwidth "white" beam (2003). These UV measurements are very close to those found in the literature, showing nominal performances of the FT spectrometer that should translate into an unprecedented resolving power at shortest VUV wavelengths. A recent upgrade (2007) and future developments will be discussed in light of the current installation of the upgraded FT spectrometer as a permanent endstation for ultrahigh resolution absorption spectrometry on the VUV beamline DESIRS at SOLEIL, the new French third generation synchrotron facility.

An investigation of electronic states of some molecules and molecular cations using mass analyzed threshold ionization and photoinduced Rydberg ionization spectroscopy

NASA Astrophysics Data System (ADS)

Hofstein, Jason David

1999-11-01

Mass analyzed threshold ionization (MATI) experiments have enabled mapping of the n-dependent Rydberg state survival probability for a series of molecules. Utilizing vacuum and extreme ultraviolet (VUV/XUV) photons, one photon Rydberg manifold spectra of argon, hydrogen chloride, nitrogen, benzene, and oxygen were produced, and the prospects of photoinduced Rydberg ionization (PIRI) experiments examined. It was found that the widths of Rydberg manifolds for the molecules studied are quite different. Hydrogen chloride and nitrogen have the narrowest manifold width, followed by benzene, and then oxygen. These varying widths are most strongly correlated with the angular momentum (i.e., quantum defect) of the initially prepared Rydberg orbital. PIRI experiments required the use of a static cell, rather than a molecular jet assembly, for the more efficient production of higher amounts of VUV/XUV radiation, and hence more Rydberg signal needed to observe PIRI. Armed with the ability to produce tunable VUV/XUV radiation, and to determine the feasibility of a PIRI experiment, the MATI and fragment PIRI spectra of trans-1,3-butadiene (BD) were recorded. The MATI spectrum is vibrationally resolved and was analyzed with the help of ab initio calculations and other published results. The fragment PIRI spectrum of the A<==X transition of BD+ is not vibrationally resolved, but information regarding the wavelength dependence of fragmentation pathways has been gathered and interpreted. It was found that at low photodissociation photon energies, production of C3H3+ dominates, but at higher photon energies, C2H4 + is also produced. The production of each fragment showed a definite PIRI wavelength dependence.

Oxygen isotope fractionation in the vacuum ultraviolet photodissociation of carbon monoxide: Wavelength, pressure and temperature dependency.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chakraborty, Subrata; Davis, Ryan; Ahmed, Musahid

Several absorption bands exist in the VUV region of Carbon monoxide (CO). Emission spectra indicate that these bands are all predissociative. An experimental investigation of CO photodissociation by vacuum ultraviolet photons (90 to 108 nm; ~13 to 11 eV) from the Advanced Light Source Synchrotron and direct measurement of the associated oxygen isotopic composition of the products are presented here. A wavelength dependency of the oxygen isotopic composition in the photodissociation product was observed. Slope values (δ'{sup 18}O/ δ'{sup 17}O) ranging from 0.76 to 1.32 were observed in oxygen three-isotope space (δ'{sup 18}O vs. δ'{sup 17}O) which correlated with increasingmore » synchrotron photon energy, and indicate a dependency of the upper electronic state specific dissociation dynamics (e.g., perturbation and coupling associated with a particular state). An unprecedented magnitude in isotope separation was observed for photodissociation at the 105 and 107 nm synchrotron bands and are found to be associated with accidental predissociation of the vibrational states ({nu} = 0 and 1) of the upper electronic state E{sup 1}Π. For each synchrotron band, a large (few hundred per mil) extent of isotopic fractionation was observed and the range of fractionation is a combination of column density and exposure time. A significant temperature dependency in oxygen isotopic fractionation was observed, indicating a rotational level dependency in the predissociation process.« less

High-resolution study of oscillator strengths and predissociation rates for 13C18O . W-X bands and Rydberg complexes between 92.9 and 93.5 nm

NASA Astrophysics Data System (ADS)

Eidelsberg, M.; Lemaire, J. L.; Federman, S. R.; Heays, A. N.; Stark, G.; Lyons, J. R.; Gavilan, L.; de Oliveira, N.

2017-06-01

We carried out experiments at the SOLEIL synchrotron facility to acquire data for modelling CO photochemistry in the vacuum ultraviolet. We report oscillator strengths and predissociation rates for four vibrational bands associated with transitions from the v = 0 level of the X1Σ+ ground state to the v = 0-3 vibrational levels of the core excited W1Π Rydberg state, and for three overlapping bands associated with the 4pπ, 5pπ, and 5pσ Rydberg states between 92.9 and 93.4 nm in 13C18O. These results complete those obtained in the same conditions for 12C16O, 13C16O, and 12C18O recently published by us, and extend the development of a comprehensive database of line positions, oscillator strengths, and linewidths of photodissociating transitions for CO isotopologues. Absorption spectra were recorded using the Vacuum UltraViolet Fourier Transform Spectrometer (VUV-FTS) installed on the Dichroïsme Et Spectroscopie par Interaction avec le Rayonnement Synchrotron (DESIRS) beamline at SOLEIL. The resolving power of the measurements, R = 300 000 to 400 000, allows the analysis of individual line strengths and widths within the bands. Gas column densities in the differentially pumped system were calibrated using the B-X (0-0) band at 115.1 nm in 13C18O.

Photoionization of three isomers of the C9H7 radical.

PubMed

Hemberger, Patrick; Steinbauer, Michael; Schneider, Michael; Fischer, Ingo; Johnson, Melanie; Bodi, Andras; Gerber, Thomas

2010-04-15

Three resonance-stabilized radicals, 1-indenyl (Ind), 1-phenylpropargyl (1PPR), and 3-phenylpropargyl (3PPR), all isomers of the composition C(9)H(7), were generated by jet flash pyrolysis. Their photoionization was examined by VUV synchrotron radiation. The mass spectra show a clean and efficient radical generation when the pyrolysis is turned on. To study the photoionization, photoion yield measurements and threshold photoionization spectroscopy techniques were applied. We determined adiabatic ionization energies (IE(ad)) of 7.53 eV for Ind, 7.20 eV for 3PPR, and 7.4 eV for 1PPR. Ab initio calculations show no major change in geometry upon ionization, in agreement with ionization from a nonbonding molecular orbital. The IEs were also computed and are in agreement with the measured ones. The difference in the IE might allow a distinction of the three isomers in flames. In the indenyl spectrum, an excited a(+) (3)B(2) state of the cation was identified at 8.10 eV, which shows a low-energy vibrational progression of 61 meV. Furthermore, we have examined the dissociative photoionization of the precursors. The indenyl precursor, 1-indenyl bromide, undergoes dissociative photoionization to Ind(+). An appearance energy (AE(0K)) of 10.2 eV was obtained from fitting the experimental breakdown diagram. A binding energy of 1.8 eV can thus be determined for the C-Br bond in 1-indenyl bromide. The phenylpropargyl precursors 1PPBr (1-phenylpropargyl bromide/3-phenyl-3-bromopropyne) and 3PPBr (3-phenylpropargyl bromide/1-phenyl-3-bromopropyne) also lose a bromine atom upon dissociative photoionization. Approximate appearance energies of 9.8 eV for 3PPBr and 9.3 eV for 1PPBr have been determined.

Evaluation of Oxygen Interactions with Materials 3: Mission and induced environments

NASA Technical Reports Server (NTRS)

Koontz, Steven L.; Leger, Lubert J.; Rickman, Steven L.; Hakes, Charles L.; Bui, David T.; Hunton, Donald; Cross, Jon B.

1995-01-01

The Evaluation of Oxygen Interactions with Materials 3 (EOIM-3) flight experiment was developed to obtain benchmark atomic oxygen/material reactivity data. The experiment was conducted during Space Shuttle mission 46 (STS-46), which flew July 31 to August 7, 1992. Quantitative interpretation of the materials reactivity measurements requires a complete and accurate definition of the space environment exposure, including the thermal history of the payload, the solar ultraviolet exposure, the atomic oxygen fluence, and any spacecraft outgassing contamination effects. The thermal history of the payload was measured using twelve thermocouple sensors placed behind selected samples and on the EOIM-3 payload structure. The solar ultraviolet exposure history of the EOIM-3 payload was determined by analysis of the as-flown orbit and vehicle attitude combined with daily average solar ultraviolet and vacuum ultraviolet (UV/VUV) fluxes. The atomic oxygen fluence was assessed in three different ways. First, the O-atom fluence was calculated using a program that incorporates the MSIS-86 atmospheric model, the as-flown Space Shuttle trajectory, and solar activity parameters. Second, the oxygen atom fluence was estimated directly from Kapton film erosion. Third, ambient oxygen atom measurements were made using the quadrupole mass spectrometer on the EOIM-3 payload. Our best estimate of the oxygen atom fluence as of this writing is 2.3 +/- 0.3 x 10(exp 20) atoms/sq cm. Finally, results of post-flight X-ray photoelectron spectroscopy (XPS) surface analyses of selected samples indicate low levels of contamination on the payload surface.

Application of I-structure though-glass interconnect filled with submicron gold particles to a hermetic sealing device

NASA Astrophysics Data System (ADS)

Nomura, Kazuya; Okada, Akiko; Shoji, Shuichi; Ogashiwa, Toshinori; Mizuno, Jun

2016-10-01

We propose hermetic sealing of a glass-to-glass structure with an I-structure through-glass interconnect via (TGV) filled with submicron Au particles. The top and bottom bumps and the TGV were formed by a simple filling process with a bump-patterned dry film resist. The sealing devices consisting of two glass substrates were bonded via Au interlayers. Vacuum ultraviolet irradiation in the presence of oxygen gas (VUV/O3) pretreatment was used for low-temperature Au-Au bonding at 200 °C. The bonded samples showed He leakage rates of less than 1.3  ×  10-9 Pa m3 s-1. The cross-sectional scanning electron microscope images of the fabricated I-structure TGV showed perfect adhesion between the I-structure TGV and glass substrate. These results indicate that the proposed I-structure TGV is suitable for hermetic sealing devices.

The vacuum ultraviolet spectrum of krypton and xenon excimers excited in a cooled dc discharge

NASA Astrophysics Data System (ADS)

Gerasimov, G.; Krylov, B.; Loginov, A.; Zvereva, G.; Hallin, R.; Arnesen, A.; Heijkenskjöld, F.

1998-01-01

We present results of an experimental and theoretical study of the VUV spectra of krypton and xenon excimers excited by a dc discharge in a capillary tube cooled by liquid nitrogen. The studied spectral regions of 115-170 nm and 140-195 nm for krypton and xenon respectively correspond to transitions between the lowest excited dimer states 1u, 0u+ and the weakly bound ground state 0g+. A semiempirical method was suggested and applied to describe the experimental spectra and to estimate the temperature of the radiating plasma volume. Electron impact, transferring dimers from the ground state to the excited states, is shown to be an efficient excitation mechanism in the 100-850 hPa and the 10-50 mA pressure and discharge current ranges. The spectra obtained as well as the results of calculations corroborate the high rate of this mechanism.

Vibrational structure of vinyl chloride cation studied by using one-photon zero-kinetic energy photoelectron spectroscopy.

PubMed

Zhang, Ping; Li, Juan; Mo, Yuxiang

2007-09-06

The vibrational structure of vinyl chloride cation, CH(2)CHCl+ (X(2)A' '), has been studied by vacuum ultraviolet (VUV) zero-kinetic energy (ZEKE) photoelectron spectroscopy. Among nine symmetric vibrational modes, the fundamental frequencies of six modes have been determined. The first overtone of the out-of-plane CH(2) twist vibrational mode has been also measured. In addition to these, the combination and overtone bands of the above vibrational modes about 4500 cm(-1) above the ground state have been observed in the ZEKE spectrum. The vibrational band intensities of the ZEKE spectrum can be described approximately by the Franck-Condon factors with harmonic approximation. The ZEKE spectrum has been assigned based on the harmonic frequencies and Franck-Condon factors from theoretical calculations. The ionization energy (IE) of CH(2)CHCl is determined as 80705.5 +/- 2.5 (cm(-1)) or 10.0062 +/- 0.0003 (eV).

X-Ray Radiation Measurements With Photodiodes In Plasmas Generated By 1017 W/Cm2 Intensity Krf Excimer Laser Pulses

NASA Astrophysics Data System (ADS)

Rácz, E.; Földes, I. B.; Ryć, L.

2006-01-01

Experiments were carried out using a prepulse-free hybrid KrF excimer-dye laser system (700fs pulse duration, 248nm wavelength, 15mJ pulse energy). The intensity of the p-polarized, focused laser beam was 1.5ṡ1017 W/cm2. Vacuum ultraviolet (VUV) and x-rays from solid state laser plasmas were generated in the laser-plasma interaction of subpicosecond laser pulses of nonrelativistic laser intensities. An x-ray sensitive FLM photodiode (ITE, Warsaw) was used to detect x-rays between 1-19 keV in front of the targets. The diode was filtered by a 4μm Al foil. The dependence of the x-ray flux on laser intensity and the angular distribution of x-rays for aluminum and copper targets in the half space of the front side of the targets were investigated.

Toluene Valence and Rydberg Excitations as Studied by ab initio Calculations and Vacuum Ultraviolet (VUV) Synchrotron Radiation.

PubMed

Serralheiro, C; Duflot, D; da Silva, F Ferreira; Hoffmann, S V; Jones, N C; Mason, N J; Mendes, B; Limão-Vieira, P

2015-08-27

The electronic spectroscopy of isolated toluene in the gas phase has been investigated using high-resolution photoabsorption spectroscopy in the 4.0-10.8 eV energy range, with absolute cross-section measurements derived. We present the first set of ab initio calculations (vertical energies and oscillator strengths), which we use in the assignment of valence and Rydberg transitions of the toluene molecule. The spectrum reveals several new features not previously reported in the literature, with particular relevance to 7.989 and 8.958 eV, which are here tentatively assigned to the π*(17a') ← σ(15a') and 1π*(10a″) ← 1π(14a') transitions, respectively. The measured absolute photoabsorption cross sections have been used to calculate the photolysis lifetime of toluene in the upper stratosphere (20-50 km).

A multifunctional setup to record FTIR and UV-vis spectra of organic molecules and their photoproducts in astronomical ices.

PubMed

Kofman, V; Witlox, M J A; Bouwman, J; Ten Kate, I L; Linnartz, H

2018-05-01

This article describes a new, multi-functional, high-vacuum ice setup that allows to record the in situ and real-time spectra of vacuum UV (VUV)-irradiated non-volatile molecules embedded in a low-temperature (10 K) amorphous solid water environment. Three complementary diagnostic tools-UV-visible (UV-vis) and Fourier Transform Infrared (FTIR) spectroscopy and temperature-programmed desorption quadrupole mass spectrometry-can be used to simultaneously study the physical and chemical behavior of the organic molecules in the ice upon VUV irradiation. The setup is equipped with a temperature-controlled sublimation oven that enables the controlled homogeneous deposition of solid species such as amino acids, nucleobases, and polycyclic aromatic hydrocarbons (PAHs) in ice mixtures prepared from precursor gases and/or liquids. The resulting ice is photo-processed with a microwave discharge hydrogen lamp, generating VUV radiation with a spectral energy distribution representative for the interstellar medium. The characteristics, performance, and future potential of the system are discussed by describing three different applications. First, a new method is introduced, which uses broadband interference transmission fringes recorded during ice deposition, to determine the wavelength-dependent refractive index, n λ , of amorphous solid water. This approach is also applicable to other solids, pure and mixed. Second, the UV-vis and FTIR spectroscopy of an VUV-irradiated triphenylene:water ice mixture is discussed, monitoring the ionization efficiency of PAHs in interstellar ice environments. The third and final example investigates the stability of solid glycine upon VUV irradiation by monitoring the formation of dissociation products in real time.

A multifunctional setup to record FTIR and UV-vis spectra of organic molecules and their photoproducts in astronomical ices

NASA Astrophysics Data System (ADS)

Kofman, V.; Witlox, M. J. A.; Bouwman, J.; ten Kate, I. L.; Linnartz, H.

2018-05-01

This article describes a new, multi-functional, high-vacuum ice setup that allows to record the in situ and real-time spectra of vacuum UV (VUV)-irradiated non-volatile molecules embedded in a low-temperature (10 K) amorphous solid water environment. Three complementary diagnostic tools—UV-visible (UV-vis) and Fourier Transform Infrared (FTIR) spectroscopy and temperature-programmed desorption quadrupole mass spectrometry—can be used to simultaneously study the physical and chemical behavior of the organic molecules in the ice upon VUV irradiation. The setup is equipped with a temperature-controlled sublimation oven that enables the controlled homogeneous deposition of solid species such as amino acids, nucleobases, and polycyclic aromatic hydrocarbons (PAHs) in ice mixtures prepared from precursor gases and/or liquids. The resulting ice is photo-processed with a microwave discharge hydrogen lamp, generating VUV radiation with a spectral energy distribution representative for the interstellar medium. The characteristics, performance, and future potential of the system are discussed by describing three different applications. First, a new method is introduced, which uses broadband interference transmission fringes recorded during ice deposition, to determine the wavelength-dependent refractive index, nλ, of amorphous solid water. This approach is also applicable to other solids, pure and mixed. Second, the UV-vis and FTIR spectroscopy of an VUV-irradiated triphenylene:water ice mixture is discussed, monitoring the ionization efficiency of PAHs in interstellar ice environments. The third and final example investigates the stability of solid glycine upon VUV irradiation by monitoring the formation of dissociation products in real time.

Low Earth orbital atomic oxygen environmental simulation facility for space materials evaluation

NASA Technical Reports Server (NTRS)

Stidham, Curtis R.; Banks, Bruce A.; Stueber, Thomas J.; Dever, Joyce A.; Rutledge, Sharon K.; Bruckner, Eric J.

1993-01-01

Simulation of low Earth orbit atomic oxygen for accelerated exposure in ground-based facilities is necessary for the durability evaluation of space power system component materials for Space Station Freedom (SSF) and future missions. A facility developed at the National Aeronautics and Space Administrations's (NASA) Lewis Research Center provides accelerated rates of exposure to a directed or scattered oxygen beam, vacuum ultraviolet (VUV) radiation, and offers in-situ optical characterization. The facility utilizes an electron-cyclotron resonance (ECR) plasma source to generate a low energy oxygen beam. Total hemispherical spectral reflectance of samples can be measured in situ over the wavelength range of 250 to 2500 nm. Deuterium lamps provide VUV radiation intensity levels in the 115 to 200 nm range of three to five equivalent suns. Retarding potential analyses show distributed ion energies below 30 electron volts (eV) for the operating conditions most suited for high flux, low energy testing. Peak ion energies are below the sputter threshold energy (approximately 30 eV) of the protective coatings on polymers that are evaluated in the facility, thus allowing long duration exposure without sputter erosion. Neutral species are expected to be at thermal energies of approximately .04 eV to .1 eV. The maximum effective flux level based on polyimide Kapton mass loss is 4.4 x 10 exp 6 atoms/((sq. cm)*s), thus providing a highly accelerated testing capability.

High Abundance of Ions in Cosmic Ices

NASA Technical Reports Server (NTRS)

Gudipati, Murthy S.; Allamandola, Louis J.; Fonda, Mark (Technical Monitor)

2002-01-01

Water-rich, mixed molecular ices and polycyclic aromatic hydrocarbons (PAHs) are common throughout interstellar molecular clouds and the Solar System. Vacuum ultraviolet (VUV) irradiation and particle bombardment of these abiotic ices produces complex organic species, including important biogenic molecules such as amino acids and functionalized PAHs which may have played a role in the origin of life. This ability of such water-rich, oxygen dominated ices to promote production of complex organic species is surprising and points to an important, unusual, but previously overlooked mechanism at play within the ice. Here we report the nature of this mechanism using electronic spectroscopy. VUV-irradiation of PAH/H2O ices leads to an unprecedented and efficient (greater than 70 %) conversion of the neutral PAHs to their cation form (PAH+). Further, these H2O/PAH+ ices are stabile at temperatures below 50 K, a temperature domain common throughout interstellar clouds and the Solar System. Between 50 and 125 K they react to form the complex organics. In view of this, we conclude that charged PAHs and other molecular ions should be common and abundant in many cosmic ices. The chemical, spectroscopic and physical properties of these ion-rich ices can be of fundamental importance for objects as diverse as comets, planets, and molecular clouds and may account for several poorly understood phenomena associated with each of these object classes.

Ab initio dynamics and photoionization mass spectrometry reveal ion-molecule pathways from ionized acetylene clusters to benzene cation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stein, Tamar; Bandyopadhyay, Biswajit; Troy, Tyler P.

The growth mechanism of hydrocarbons in ionizing environments, such as the interstellar medium (ISM), and some combustion conditions remains incompletely understood. Ab initio molecular dynamics (AIMD) simulations and molecular beam vacuum-UV (VUV) photoionization mass spectrometry experiments were performed to understand the ion-molecule growth mechanism of small acetylene clusters (up to hexamers). A dramatic dependence of product distribution on the ionization conditions is demonstrated experimentally and understood from simulations. The products change from reactive fragmentation products in a higher temperature, higher density gas regime toward a very cold collision-free cluster regime that is dominated by products whose empirical formula is (Cmore » 2H 2) n +, just like ionized acetylene clusters. The fragmentation products result from reactive ion- molecule collisions in a comparatively higher pressure and temperature regime followed by unimolecular decomposition. The isolated ionized clusters display rich dynamics that contain bonded C 4H 4 + and C 6H 6 + structures solvated with one or more neutral acetylene molecules. Such species contain large amounts ( > 2 eV) of excess internal energy. The role of the solvent acetylene molecules is to affect the barrier crossing dynamics in the potential energy surface (PES) between (C 2H 2) n + isomers and provide evaporative cooling to dissipate the excess internal energy and stabilize products including the aromatic ring of the benzene cation. Formation of the benzene cation is demonstrated in AIMD simulations of acetylene clusters with n > 3, as well as other metastable C 6H 6 + isomers. Lastly, these results suggest a path for aromatic ring formation in cold acetylene-rich environments such as parts of the ISM.« less

Ab initio dynamics and photoionization mass spectrometry reveal ion–molecule pathways from ionized acetylene clusters to benzene cation

PubMed Central

Stein, Tamar; Bandyopadhyay, Biswajit; Troy, Tyler P.; Fang, Yigang; Kostko, Oleg

2017-01-01

The growth mechanism of hydrocarbons in ionizing environments, such as the interstellar medium (ISM), and some combustion conditions remains incompletely understood. Ab initio molecular dynamics (AIMD) simulations and molecular beam vacuum-UV (VUV) photoionization mass spectrometry experiments were performed to understand the ion–molecule growth mechanism of small acetylene clusters (up to hexamers). A dramatic dependence of product distribution on the ionization conditions is demonstrated experimentally and understood from simulations. The products change from reactive fragmentation products in a higher temperature, higher density gas regime toward a very cold collision-free cluster regime that is dominated by products whose empirical formula is (C2H2)n+, just like ionized acetylene clusters. The fragmentation products result from reactive ion–molecule collisions in a comparatively higher pressure and temperature regime followed by unimolecular decomposition. The isolated ionized clusters display rich dynamics that contain bonded C4H4+ and C6H6+ structures solvated with one or more neutral acetylene molecules. Such species contain large amounts (>2 eV) of excess internal energy. The role of the solvent acetylene molecules is to affect the barrier crossing dynamics in the potential energy surface (PES) between (C2H2)n+ isomers and provide evaporative cooling to dissipate the excess internal energy and stabilize products including the aromatic ring of the benzene cation. Formation of the benzene cation is demonstrated in AIMD simulations of acetylene clusters with n > 3, as well as other metastable C6H6+ isomers. These results suggest a path for aromatic ring formation in cold acetylene-rich environments such as parts of the ISM. PMID:28484019

Ab initio dynamics and photoionization mass spectrometry reveal ion-molecule pathways from ionized acetylene clusters to benzene cation.

PubMed

Stein, Tamar; Bandyopadhyay, Biswajit; Troy, Tyler P; Fang, Yigang; Kostko, Oleg; Ahmed, Musahid; Head-Gordon, Martin

2017-05-23

The growth mechanism of hydrocarbons in ionizing environments, such as the interstellar medium (ISM), and some combustion conditions remains incompletely understood. Ab initio molecular dynamics (AIMD) simulations and molecular beam vacuum-UV (VUV) photoionization mass spectrometry experiments were performed to understand the ion-molecule growth mechanism of small acetylene clusters (up to hexamers). A dramatic dependence of product distribution on the ionization conditions is demonstrated experimentally and understood from simulations. The products change from reactive fragmentation products in a higher temperature, higher density gas regime toward a very cold collision-free cluster regime that is dominated by products whose empirical formula is (C 2 H 2 ) n + , just like ionized acetylene clusters. The fragmentation products result from reactive ion-molecule collisions in a comparatively higher pressure and temperature regime followed by unimolecular decomposition. The isolated ionized clusters display rich dynamics that contain bonded C 4 H 4 + and C 6 H 6 + structures solvated with one or more neutral acetylene molecules. Such species contain large amounts (>2 eV) of excess internal energy. The role of the solvent acetylene molecules is to affect the barrier crossing dynamics in the potential energy surface (PES) between (C 2 H 2 ) n + isomers and provide evaporative cooling to dissipate the excess internal energy and stabilize products including the aromatic ring of the benzene cation. Formation of the benzene cation is demonstrated in AIMD simulations of acetylene clusters with n > 3, as well as other metastable C 6 H 6 + isomers. These results suggest a path for aromatic ring formation in cold acetylene-rich environments such as parts of the ISM.

Ab initio dynamics and photoionization mass spectrometry reveal ion-molecule pathways from ionized acetylene clusters to benzene cation

DOE PAGES

Stein, Tamar; Bandyopadhyay, Biswajit; Troy, Tyler P.; ...

2017-05-08

The growth mechanism of hydrocarbons in ionizing environments, such as the interstellar medium (ISM), and some combustion conditions remains incompletely understood. Ab initio molecular dynamics (AIMD) simulations and molecular beam vacuum-UV (VUV) photoionization mass spectrometry experiments were performed to understand the ion-molecule growth mechanism of small acetylene clusters (up to hexamers). A dramatic dependence of product distribution on the ionization conditions is demonstrated experimentally and understood from simulations. The products change from reactive fragmentation products in a higher temperature, higher density gas regime toward a very cold collision-free cluster regime that is dominated by products whose empirical formula is (Cmore » 2H 2) n +, just like ionized acetylene clusters. The fragmentation products result from reactive ion- molecule collisions in a comparatively higher pressure and temperature regime followed by unimolecular decomposition. The isolated ionized clusters display rich dynamics that contain bonded C 4H 4 + and C 6H 6 + structures solvated with one or more neutral acetylene molecules. Such species contain large amounts ( > 2 eV) of excess internal energy. The role of the solvent acetylene molecules is to affect the barrier crossing dynamics in the potential energy surface (PES) between (C 2H 2) n + isomers and provide evaporative cooling to dissipate the excess internal energy and stabilize products including the aromatic ring of the benzene cation. Formation of the benzene cation is demonstrated in AIMD simulations of acetylene clusters with n > 3, as well as other metastable C 6H 6 + isomers. Lastly, these results suggest a path for aromatic ring formation in cold acetylene-rich environments such as parts of the ISM.« less

Treatment to Control Adhesion of Silicone-Based Elastomers

NASA Technical Reports Server (NTRS)

deGroh, Henry C., III; Puleo, Bernadette J.; Waters, Deborah L.

2013-01-01

Seals are used to facilitate the joining of two items, usually temporarily. At some point in the future, it is expected that the items will need to be separated. This innovation enables control of the adhesive properties of silicone-based elastomers. The innovation may also be effective on elastomers other than the silicone-based ones. A technique has been discovered that decreases the level of adhesion of silicone- based elastomers to negligible levels. The new technique causes less damage to the material compared to alternative adhesion mitigation techniques. Silicone-based elastomers are the only class of rubber-like materials that currently meet NASA s needs for various seal applications. However, silicone-based elastomers have natural inherent adhesive properties. This stickiness can be helpful, but it can frequently cause problems as well, such as when trying to get items apart. In the past, seal adhesion was not always adequately addressed, and has caused in-flight failures where seals were actually pulled from their grooves, preventing subsequent spacecraft docking until the seal was physically removed from the flange via an extravehicular activity (EVA). The primary method used in the past to lower elastomer seal adhesion has been the application of some type of lubricant or grease to the surface of the seal. A newer method uses ultraviolet (UV) radiation a mixture of UV wavelengths in the range of near ultraviolet (NUV) and vacuum ultraviolet (VUV) wavelengths.

Photo-thermal processing of semiconductor fibers and thin films

NASA Astrophysics Data System (ADS)

Gupta, Nishant

Furnace processing and rapid thermal processing (RTP) have been an integral part of several processing steps in semiconductor manufacturing. The performance of RTP techniques can be improved many times by exploiting quantum photo-effects of UV and vacuum ultraviolet (VUV) photons in thermal processing and this technique is known as rapid photo-thermal processing (RPP). As compared to furnace processing and RTP, RPP provides higher diffusion coefficient, lower stress and lower microscopic defects. In this work, a custom designed automated photo assisted processing system was built from individual parts and an incoherent light source. This photo-assisted processing system is used to anneal silica clad silicon fibers and deposit thin-films. To the best of our knowledge, incoherent light source based rapid photo-thermal processing (RPP) was used for the first time to anneal glass-clad silicon core optical fibers. X-ray diffraction examination, Raman spectroscopy and electrical measurements showed a considerable enhancement of structural and crystalline properties of RPP treated silicon fibers. Photons in UV and vacuum ultraviolet (VUV) regions play a very important role in improving the bulk and carrier transport properties of RPP-treated silicon optical fibers, and the resultant annealing permits a path forward to in situ enhancement of the structure and properties of these new crystalline core optical fibers. To explore further applications of RPP, thin-films of Calcium Copper Titanate (CaCu3Ti4O12) or CCTO and Copper (I) Oxide (Cu2O) were also deposited using photo-assisted metal-organic chemical vapor deposition (MOCVD) on Si/SiO2 and n-Si substrate respectively. CCTO is one of the most researched giant dielectric constant materials in recent years. The given photo-assisted MOCVD approach provided polycrystalline CCTO growth on a SiO2 surface with grain sizes as large as 410 nm. Copper (I) oxide (Cu2O) is a direct band gap semiconductor with p-type conductivity and is a potential candidate for multi-junction solar cells. X-ray diffraction study revealed a preferred orientation, as (200) oriented crystals of Cu2O are grown on both substrates. Also, electrical characterization of Cu2O/n-Si devices showed the lowest saturation current density of 1.5x10-12 A/cm 2 at zero bias. As a result, photo-assisted thermal processing has the potential of making the process more effective with enhanced device performance.

Flow-Tube Investigations of Hypergolic Reactions of a Dicyanamide Ionic Liquid Via Tunable Vacuum Ultraviolet Aerosol Mass Spectrometry.

PubMed

Chambreau, Steven D; Koh, Christine J; Popolan-Vaida, Denisia M; Gallegos, Christopher J; Hooper, Justin B; Bedrov, Dmitry; Vaghjiani, Ghanshyam L; Leone, Stephen R

2016-10-07

The unusually high heats of vaporization of room-temperature ionic liquids (RTILs) complicate the utilization of thermal evaporation to study ionic liquid reactivity. Although effusion of RTILs into a reaction flow-tube or mass spectrometer is possible, competition between vaporization and thermal decomposition of the RTIL can greatly increase the complexity of the observed reaction products. In order to investigate the reaction kinetics of a hypergolic RTIL, 1-butyl-3-methylimidazolium dicyanamide (BMIM + DCA - ) was aerosolized and reacted with gaseous nitric acid, and the products were monitored via tunable vacuum ultraviolet photoionization time-of-flight mass spectrometry at the Chemical Dynamics Beamline 9.0.2 at the Advanced Light Source. Reaction product formation at m/z 42, 43, 44, 67, 85, 126, and higher masses was observed as a function of HNO 3 exposure. The identities of the product species were assigned to the masses on the basis of their ionization energies. The observed exposure profile of the m/z 67 signal suggests that the excess gaseous HNO 3 initiates rapid reactions near the surface of the RTIL aerosol. Nonreactive molecular dynamics simulations support this observation, suggesting that diffusion within the particle may be a limiting step. The mechanism is consistent with previous reports that nitric acid forms protonated dicyanamide species in the first step of the reaction.

Laser-Induced Acoustic Desorption Atmospheric Pressure Photoionization via VUV-Generating Microplasmas.

PubMed

Benham, Kevin; Hodyss, Robert; Fernández, Facundo M; Orlando, Thomas M

2016-11-01

We demonstrate the first application of laser-induced acoustic desorption (LIAD) and atmospheric pressure photoionization (APPI) as a mass spectrometric method for detecting low-polarity organics. This was accomplished using a Lyman-α (10.2 eV) photon generating microhollow cathode discharge (MHCD) microplasma photon source in conjunction with the addition of a gas-phase molecular dopant. This combination provided a soft desorption and a relatively soft ionization technique. Selected compounds analyzed include α-tocopherol, perylene, cholesterol, phenanthrene, phylloquinone, and squalene. Detectable surface concentrations as low as a few pmol per spot sampled were achievable using test molecules. The combination of LIAD and APPI provided a soft desorption and ionization technique that can allow detection of labile, low-polarity, structurally complex molecules over a wide mass range with minimal fragmentation. Graphical Abstract ᅟ.

Space Environmental Effects Testing Capability at the Marshall Space Flight Center

NASA Technical Reports Server (NTRS)

DeWittBurns, H.; Craven, Paul; Finckenor, Miria; Nehls, Mary; Schneider, Todd; Vaughn, Jason

2012-01-01

Understanding the effects of the space environment on materials and systems is fundamental and essential for mission success. If not properly understood and designed for, the effects of the environment can lead to degradation of materials, reduction of functional lifetime, and system failure. In response to this need, the Marshall Space Flight Center has developed world class Space Environmental Effects (SEE) expertise and test facilities to simulate the space environment. Capabilities include multiple unique test systems comprising the most complete SEE testing capability available. These test capabilities include charged particle radiation (electrons, protons, ions), ultraviolet radiation (UV), vacuum ultraviolet radiation (VUV), atomic oxygen, plasma effects, space craft charging, lunar surface and planetary effects, vacuum effects, and hypervelocity impacts as well as the combination of these capabilities. In addition to the uniqueness of the individual test capabilities, MSFC is the only NASA facility where the effects of the different space environments can be tested in one location. Combined with additional analytical capabilities for pre- and post-test evaluation, MSFC is a one-stop shop for materials testing and analysis. The SEE testing and analysis are performed by a team of award winning experts nationally recognized for their contributions in the study of the effects of the space environment on materials and systems. With this broad expertise in space environmental effects and the variety of test systems and equipment available, MSFC is able to customize tests with a demonstrated ability to rapidly adapt and reconfigure systems to meet customers needs. Extensive flight experiment experience bolsters this simulation and analysis capability with a comprehensive understanding of space environmental effects.

Optical spectroscopy of molecular positronium.

PubMed

Cassidy, D B; Hisakado, T H; Tom, H W K; Mills, A P

2012-03-30

We report optical spectroscopic measurements of molecular positronium (Ps(2)), performed via a previously unobserved L=1 excited state. Ps(2) molecules created in a porous silica film, and also in vacuum from an Al(111) crystal, were resonantly excited and then photoionized by pulsed lasers, providing conclusive evidence for the production of this molecular matter-antimatter system and its excited state. Future experiments making use of the photoionized vacuum L=1 Ps(2) could provide a source of Ps(+) ions, as well as other multipositronic systems, such as Ps(2)H(-) or Ps(2)O.

Up-conversion media on basis single crystals BaY2F8 for UV and VUV solid state lasers

NASA Astrophysics Data System (ADS)

Pushkar, A. A.; Ouvarova, T. V.; Molchanov, V. N.

2007-04-01

Crystal BaY IIF 8 represents the big interest as the perspective active media for lasers ultra-violet (UV) and vacuumultra- violet (VUV) regions. For the decision of problems with solarization this media and a choice of sources pump it is offered to use up-conversion mechanisms pump with activators from rare-earth elements (RE). We have developed technology of grown of oriented monocrystals BaY IIF 8, have defined influence of orientation on growth rate and quality ofthe received monocrystals.

Photoabsorption and photoionization cross sections of NH3, PH3, H2S, C2H2, and C2H4 in the VUV region

NASA Technical Reports Server (NTRS)

Xia, T. J.; Chien, T. S.; Wu, C. Y. Robert; Judge, D. L.

1991-01-01

Using synchrotron radiation as a continuum light source, the photoabsorption and photoionization cross sections of NH3, PH3, H2S, C2H2, and C2H4 have been measured from their respective ionization thresholds to 1060 A. The vibrational constants associated with the nu(2) totally symmetric, out-of-plane bending vibration of the ground electronic state of PH3(+) have been obtained. The cross sections and quantum yields for producing neutral products through photoexcitation of these molecules in the given spectral regions have also been determined. In the present work, autoionization processes were found to be less important than dissociation and predissociation processes in NH3, PH3, and C2H4. Several experimental techniques have been employed in order to examine the various possible systematic errors critically.

VUV photo-oxidation of gaseous benzene combined with ozone-assisted catalytic oxidation: Effect on transition metal catalyst

NASA Astrophysics Data System (ADS)

Huang, Haibao; Lu, Haoxian; Zhan, Yujie; Liu, Gaoyuan; Feng, Qiuyu; Huang, Huiling; Wu, Muyan; Ye, Xinguo

2017-01-01

Volatile organic compounds (VOCs) cause the major air pollution concern. In this study, a series of ZSM-5 supported transition metals were prepared by impregnation method. They were combined with vacuum UV (VUV) photo-oxidation in a continuous-flow packed-bed reactor and used for the degradation of benzene, a typical toxic VOCs. Compared with VUV photo-oxidation alone, the introduction of catalysts can greatly enhance benzene oxidation under the help of O3, the by-products from VUV irradiation, via ozone-assisted catalytic oxidation (OZCO). The catalytic activity of transition metals towards benzene oxidation followed the order: Mn > Co > Cu > Ni > Fe. Mn achieved the best catalytic activity due to the strongest capability for O3 catalytic decomposition and utilization. Benzene and O3 removal efficiency reached as high as 97% and 100% after 360 min, respectively. O3 was catalytically decomposed, generating highly reactive oxidants such as rad OH and rad O for benzene oxidation.

Infrared absorption of methanethiol clusters (CH3SH)n, n = 2-5, recorded with a time-of-flight mass spectrometer using IR depletion and VUV ionization

NASA Astrophysics Data System (ADS)

Fu, Lung; Han, Hui-Ling; Lee, Yuan-Pern

2012-12-01

We investigated IR spectra in the CH- and SH-stretching regions of size-selected methanethiol clusters, (CH3SH)n with n = 2-5, in a pulsed supersonic jet using infrared (IR)-vacuum ultraviolet (VUV) ionization. VUV emission at 132.50 nm served as the source of ionization in a time-of-flight mass spectrometer. Clusters were dissociated with light from a tunable IR laser before ionization. The variations in intensity of methanethiol cluster ions (CH3SH)n+ were monitored as the IR laser light was tuned across the range 2470-3100 cm-1. In the SH-stretching region, the spectrum of (CH3SH)2 shows a weak band near 2601 cm-1, red-shifted only 7 cm-1 from that of the monomer. In contrast, all spectra of (CH3SH)n, n = 3-5, show a broad band near 2567 cm-1 with much greater intensity. In the CH-stretching region, absorption bands of (CH3SH)2 are located near 2865, 2890, 2944, and 3010 cm-1, red-shifted by 3-5 cm-1 from those of CH3SH. These red shifts increase slightly for larger clusters and bands near 2856, 2884, 2938, and 3005 cm-1 were observed for (CH3SH)5. These spectral results indicate that the S-H...S hydrogen bond plays an important role in clusters with n = 3-5, but not in (CH3SH)2, in agreement with theoretical predictions. The absence of a band near 2608 cm-1 that corresponds to absorption of the non-hydrogen-bonded SH moiety and the large width of observed feature near 2567 cm-1 indicate that the dominant stable structures of (CH3SH)n, n = 3-5, have a cyclic hydrogen-bonded framework.

Ground-based simulation of LEO environment: Investigations of a select LDEF material: FEP Teflon (trademark)

NASA Technical Reports Server (NTRS)

Cross, Jon B.; Koontz, Steven L.

1993-01-01

The Long Duration Exposure Facility (LDEF) has produced a wealth of data on materials degradation in the low earth orbit (LEO) space environment and has conclusively shown that surface chemistry (as opposed to surface physics-sputtering) is the key to understanding and predicting the degradation of materials in the LEO environment. It is also clear that materials degradation and spacecraft contamination are closely linked and that the fundamental mechanisms responsible for this linking are in general not well understood especially in the area of synergistic effects. The study of the fundamental mechanisms underlying materials degradation in LEO is hampered by the fact that the degradation process itself is not observed during the actual exposure to the environment. Rather the aftermath of the degradation process is studied, i.e., the material that remains after exposure is observed and mechanisms are proposed to explain the observed results. The EOIM-3 flight experiment is an attempt to bring sophisticated diagnostic equipment into the space environment and monitor the degradation process in real time through the use of mass spectrometry. More experiments of this nature which would include surface sensitive diagnostics (Auger and photoelectron spectroscopes) are needed to truly unravel the basic chemical mechanisms involved in the materials degradation process. Since these in-space capabilities will most likely not be available in the near future, ground-based LEO simulation facilities employing sophisticated diagnostics are needed to further advance the basic understanding of the materials degradation mechanisms. The LEO simulation facility developed at Los Alamos National Laboratory has been used to investigate the atomic oxygen/vacuum ultraviolet (AO/VUV) enhanced degradation of FEP Teflon. The results show that photo-ejection of polymer fragments occur at elevated temperature (200 C), that VUV synergistic rare gas sputtering of polymer fragments occur even at 25 C, and that combined OA/VUV interaction produces a wide variety of gas phase reaction products.

Infrared Absorption of Methanol-Water Clusters Mn(H2O), n = 1-4, Recorded with the Vuv-Ionization Techniques

NASA Astrophysics Data System (ADS)

Lee, Yu-Fang; Lee, Yuan-Pern

2016-06-01

We investigated IR spectra in the CH- and OH-stretching regions of size-selected methanol-water clusters, Mn(H_2O) with M representing CH_3OH and n = 1-4, in a pulsed supersonic jet by using the VUV (vacuum-ultraviolet)-ionization/IR-depletion technique. The VUV light at 118 nm served as the source of ionization in a time-of-flight mass spectrometer. The tunable IR laser served as a source of dissociation for clusters before ionization. Spectra of methanol-water clusters in the OH region show significant variations as the number of methanol molecules increase, whereas spectra in the CH region are similar. For M(H_2O), absorption of a structure with H_2O as a proton donor was observed at 3570, 3682, and 3722 wn, whereas that of methanol as a proton donor was observed at 3611 and 3753 wn. For M2(H_2O), the OH-stretching band of the dangling OH of H_2O was observed at 3721 wn, whereas overlapped bands near 3425, 3472, and 3536 wn correspond to the OH-stretching modes of three hydrogen-bonded OH in a cyclic structure. For M3(H_2O), the dangling OH shifts to 3715 wn, and the hydrogen-bonded OH-stretching bands become much broader, with a band near 3179 wn having the smallest wavenumber. Scaled harmonic vibrational wavenumbers and relative IR intensities predicted for the methanol-water clusters with the M06-2X/aug-cc-pVTZ method are consistent with our experimental results. For M4(H_2O), observed spectrum agree less with theoretical predictions, indicating the presence of isomers other than the most stable cyclic one. Spectra of Mn(H_2O) and Mn+1 are compared and the cooperative hydrogen-bonding is discussed.

Directional Degradation of Spectralon Diffuser Under Ionizing Radiation for Calibration of Space-Based Sensors

NASA Technical Reports Server (NTRS)

Georgiev, G. T.; Butler, J. J.; Kowalewski, M. G.; Ding, L.

2012-01-01

Assessment of the effect of Vacuum Ultra Violet (VUV) irradiation on the Bidirectional Reflectance Distribution Function (BRDF) of Spectralon is presented in this paper. The sample was a 99% white Spectralon calibration standard irradiated with VUV source positioned at 60o off the irradiation direction for a total of 20 hours. The BRDF before and after VUV irradiation was measured and compared at number of wavelengths in the UV, VIS and IR. Non-isotropic directional degradation of Spectralon diffuser under ionizing radiation was detected at different BRDF measurement geometries primarily at UV spectral range. The 8o directional/hemispherical reflectance of the same sample was also measured and compared from 200nm to 2500nm. Index Terms BRDF, Reflectance, Multiangular, Spectralon, Remote Sensing

Hot filament-dissociation of (CH3)3SiH and (CH3)4Si, probed by vacuum ultra violet laser time of flight mass spectroscopy.

PubMed

Sharma, Ramesh C; Koshi, Mitsuo

2006-11-01

The decomposition of trimethylsilane and tetramethylsilane has been investigated for the first time, using hot wire (catalytic) at various temperatures. Trimethylsilane is catalytic-dissociated in these species SiH(2), CH(3)SiH, CH(3), CH(2)Si. Time of flight mass spectroscopy signal of these species are linearly increasing with increasing catalytic-temperature. Time of flight mass spectroscopy (TOFMS) signals of (CH(3))(3)SiH and photodissociated into (CH(3))(2)SiH are decreasing with increasing hot filament temperature. TOFMS signal of (CH(3))(4)Si is decreasing with increasing hot wire temperature, but (CH(3))(3)Si signal is almost constant with increasing the temperature. We calculated activation energies of dissociated species of the parental molecules for fundamental information of reaction kinetics for the first time. Catalytic-dissociation of trimethylsilane, and tetramethylsilane single source time of flight coupled single photon VUV (118 nm) photoionization collisionless radicals at temperature range of tungsten filament 800-2360 K. The study is focused to understand the fundamental information on reaction kinetics of these molecules at hot wire temperature, and processes of catalytic-chemical vapour deposition (Cat-CVD) technique which could be implemented in amorphous and crystalline SiC semiconductors thin films.

MgII Linear Polarization Measurements Using the MSFC Solar Ultraviolet Magnetograph

NASA Technical Reports Server (NTRS)

West, Edward; Cirtain, Jonathan; Kobayahsi, Ken; Davis, John; Gary, Allen; Adams, Mitzi

2011-01-01

This paper will describe the Marshall Space Flight Center's Solar Ultraviolet Magnetograph (SUMI) sounding rocket program, with emphasis on the polarization characteristics of the VUV optics and their spectral, spatial and polarization resolution. SUMI's first flight (7/30/2010) met all of its mission success criteria and this paper will describe the data that was acquired with emphasis on the MgII linear polarization measurements.

Simulated Space Environmental Effects on Thin Film Solar Array Components

NASA Technical Reports Server (NTRS)

Finckenor, Miria; Carr, John; SanSoucie, Michael; Boyd, Darren; Phillips, Brandon

2017-01-01

The Lightweight Integrated Solar Array and Transceiver (LISA-T) experiment consists of thin-film, low mass, low volume solar panels. Given the variety of thin solar cells and cover materials and the lack of environmental protection typically afforded by thick coverglasses, a series of tests were conducted in Marshall Space Flight Center's Space Environmental Effects Facility to evaluate the performance of these materials. Candidate thin polymeric films and nitinol wires used for deployment were also exposed. Simulated space environment exposures were selected based on SSP 30425 rev. B, "Space Station Program Natural Environment Definition for Design" or AIAA Standard S-111A-2014, "Qualification and Quality Requirements for Space Solar Cells." One set of candidate materials were exposed to 5 eV atomic oxygen and concurrent vacuum ultraviolet (VUV) radiation for low Earth orbit simulation. A second set of materials were exposed to 1 MeV electrons. A third set of samples were exposed to 50, 100, 500, and 700 keV energy protons, and a fourth set were exposed to >2,000 hours of near ultraviolet (NUV) radiation. A final set was rapidly thermal cycled between -55 and +125 C. This test series provides data on enhanced power generation, particularly for small satellites with reduced mass and volume resources. Performance versus mass and cost per Watt is discussed.

Simulated Space Environmental Effects on Thin Film Solar Array Components

NASA Technical Reports Server (NTRS)

Finckenor, Miria; Carr, John; SanSoucie, Michael; Boyd, Darren; Phillips, Brandon

2017-01-01

The Lightweight Integrated Solar Array and Transceiver (LISA-T) experiment consists of thin-film, low mass, low volume solar panels. Given the variety of thin solar cells and cover materials and the lack of environmental protection typically afforded by thick coverglasses, a series of tests were conducted in Marshall Space Flight Center's Space Environmental Effects Facility to evaluate the performance of these materials. Candidate thin polymeric films and nitinol wires used for deployment were also exposed. Simulated space environment exposures were selected based on SSP 30425 rev. B, "Space Station Program Natural Environment Definition for Design" or AIAA Standard S-111A-2014, "Qualification and Quality Requirements for Space Solar Cells." One set of candidate materials were exposed to 5 eV atomic oxygen and concurrent vacuum ultraviolet (VUV) radiation for low Earth orbit simulation. A second set of materials were exposed to 1 MeV electrons. A third set of samples were exposed to 50, 100, 500, and 700 keV energy protons, and a fourth set were exposed to >2,000 hours of near ultraviolet (NUV) radiation. A final set was rapidly thermal cycled between -55 and +125degC. This test series provides data on enhanced power generation, particularly for small satellites with reduced mass and volume resources. Performance versus mass and cost per Watt is discussed.

Simulated Space Environmental Effects on Thin Film Solar Array Components

NASA Technical Reports Server (NTRS)

Finckenor, Miria; Carr, John; SanSoucie, Michael; Boyd, Darren; Phillips, Brandon

2017-01-01

The Lightweight Integrated Solar Array and Transceiver (LISA-T) experiment consists of thin-film, low mass, low volume solar panels. Given the variety of thin solar cells and cover materials and the lack of environmental protection afforded by typical thick coverglasses, a series of tests were conducted in Marshall Space Flight Center's Space Environmental Effects Facility to evaluate the performance of these materials. Candidate thin polymeric films and nitinol wires used for deployment were also exposed. Simulated space environment exposures were selected based on SSP 30425 rev. B, "Space Station Program Natural Environment Definition for Design" or AIAA Standard S-111A-2014, "Qualification and Quality Requirements for Space Solar Cells." One set of candidate materials were exposed to 5 eV atomic oxygen and concurrent vacuum ultraviolet (VUV) radiation for low Earth orbit simulation. A second set of materials were exposed to 1 MeV electrons. A third set of samples were exposed to 50, 500, and 750 keV energy protons, and a fourth set were exposed to >2,000 hours of ultraviolet radiation. A final set was rapidly thermal cycled between -50 and +120 C. This test series provides data on enhanced power generation, particularly for small satellites with reduced mass and volume resources. Performance versus mass and cost per Watt is discussed.

An isomer-specific study of solid nitromethane decomposition pathways - Detection of aci-nitromethane (H2CNO(OH)) and nitrosomethanol (HOCH2NO) intermediates

NASA Astrophysics Data System (ADS)

Maksyutenko, Pavlo; Förstel, Marko; Crandall, Parker; Sun, Bing-Jian; Wu, Mei-Hung; Chang, Agnes H. H.; Kaiser, Ralf I.

2016-08-01

An isomer specific study of energetic electron exposed nitromethane ices was performed via photoionization - reflectron time of flight mass spectrometry (PI-ReTOF-MS) of the subliming products employing tunable vacuum ultraviolet light for ionization. Supported by electronic structure calculations, nitromethane (CH3NO2) was found to isomerize to methyl nitrite (CH3ONO) and also via hydrogen migration to the hitherto elusive aci-nitromethane isomer (H2CNO(OH)). The latter isomerizes to nitrosomethanol (HOCH2NO) through hydroxyl group (OH) migration, and, probably, ring closure to the cyclic 2-hydroxy-oxaziridine isomer (c-H2CON(OH)) as well. The importance of hydrogen migrations was also verified via the nitrosomethane (CH3NO) - formaldehyde oxime isomer (CH2NOH) pair.

LABORATORY PHOTO-CHEMISTRY OF PAHS: IONIZATION VERSUS FRAGMENTATION

PubMed Central

Zhen, Junfeng; Castellanos, Pablo; Paardekooper, Daniel M.; Ligterink, Niels; Linnartz, Harold; Nahon, Laurent; Joblin, Christine; Tielens, Alexander G. G. M.

2015-01-01

Interstellar Polycyclic Aromatic Hydrocarbons (PAH) are expected to be strongly processed by Vacuum Ultra-Violet (VUV) photons. Here, we report experimental studies on the ionization and fragmentation of coronene (C24H12), ovalene (C32H14) and hexa-peri-hexabenzocoronene (HBC; C42H18) cations by exposure to synchrotron radiation in the range of 8–40 eV. The results show that for small PAH cations such as coronene, fragmentation (H-loss) is more important than ionization. However, as the size increases, ionization becomes more and more important and for the HBC cation, ionization dominates. These results are discussed and it is concluded that, for large PAHs, fragmentation only becomes important when the photon energy has reached the highest ionization potential accessible. This implies that PAHs are even more photo-stable than previously thought. The implications of this experimental study for the photo-chemical evolution of PAHs in the interstellar medium (ISM) are briefly discussed. PMID:26688710

Flash Pyrolysis of t-Butyl Hydroperoxide and Di-t-butyl Peroxide: Evidence of Roaming in the Decomposition of Organic Hydroperoxides.

PubMed

Jones, Paul J; Riser, Blake; Zhang, Jingsong

2017-10-19

Thermal decomposition of t-butyl hydroperoxide and di-t-butyl peroxide was investigated using flash pyrolysis (in a short reaction time of <100 μs) and vacuum-ultraviolet (λ = 118.2 nm) single-photon ionization time-of-flight mass spectrometry (VUV-SPI-TOFMS) at temperatures up to 1120 K and quantum computational methods. Acetone and methyl radical were detected as the predominant products in the initial decomposition of di-t-butyl peroxide via O-O bond fission. In the initial dissociation of t-butyl hydroperoxide, acetone, methyl radical, isobutylene, and isobutylene oxide products were identified. The novel detection of the unimolecular formation of isobutylene oxide, as supported by the computational study, was found to proceed via a roaming hydroxyl radical facilitated by a hydrogen-bonded intermediate. This new pathway could provide a new class of reactions to consider in the modeling of the low temperature oxidation of alkanes.

Determination of Spectroscopic Properties of Atmospheric Molecules from High Resolution Vacuum Ultraviolet Cross Section and Wavelength Measurements

NASA Technical Reports Server (NTRS)

Parkinson, W. H.; Yoshino, K.

1999-01-01

We have studied the spectroscopy and the cross sections of the simple molecules of atmospheric interest such as oxygen, nitric oxide, carbon dioxide, and water. We have made cross section measurements on an absolute base without the effects from the limited instrumental resolution. We have used the following different instruments- the grating spectrometer (6.65-m at CfA, 3-m at Photon Factory), VUV Fourier transform spectrometer at Imperial College, and then moved the same one to the Photon Factory. Selection of the instruments depend on the appearance of molecular bands, and their wavelength region. For example, the cross section measurements of Doppler limited bands can been done with the Fourier transform spectrometer at the very high resolution (0.025/ cm resolution). All of these spectroscopic measurements are needed for accurate calculations of the production of atomic oxygen penetration of solar radiation into the Earth's atmosphere, and photochemistry of minor molecules.

Boron nitride nanotubes matrix for signal enhancement in infrared laser desorption postionization mass spectrometry.

PubMed

Lu, Qiao; Hu, Yongjun; Chen, Jiaxin; Li, Yujian; Song, Wentao; Jin, Shan; Liu, Fuyi; Sheng, Liusi

2018-09-01

The nanomaterials function as the substrate to trap analytes, absorb energy from the laser irradiation and transfer energy to the analytes to facilitate the laser desorption process. In this work, the signal intensity and reproducibility of analytes with nanomaterials as matrices were explored by laser desorption postionization mass spectrometry (LDPI-MS). Herein, the desorbed neutral species were further ionized by vacuum ultraviolet (VUV, 118 nm) and analyzed by mass spectrometer. Compared with other nanomaterial matrices such as graphene and carbon nanotubes (CNTs), boron nitride nanotubes (BNNTs) exhibited much higher desorption efficiency under infrared (IR) light and produced no background signal in the whole mass range by LDPI-MS. Additionally, this method was successfully and firstly exploited to in situ detection and imaging for drugs of low concentration in intact tissues, which proved the utility, facility and convenience of this method applied in drug discovery and biomedical research. Copyright © 2018 Elsevier B.V. All rights reserved.

Polymeric materials in Space

NASA Astrophysics Data System (ADS)

Skurat, Vladimir

Paper of short review type. It is the continuation of and addition to previous review papers "V. E. Skurat. Polymers in Space. In: Encyclopedia of aerospace engineering, vol. 4, Wiley and sons, 2010; Ibid., 2012 (on line)". Following topics are considered: (1) Destruction of polymers by solar radiation with various wavelengths in different spectral regions (visible-UV, vacuum UV (VUV), deep UV, soft and hard X-rays) are discussed. In difference with common polymer photochemistry induced by UV radiation, directions of various routs of polymer phototransformations and their relative yields are greatly dependent on wavelength of light (photon energy) during illuminations in VUV, deep UV and X-ray regions. During last twenty years, intensive spacecraft investigations of solar spectrum show great periodic and spontaneous variations of radiation intensities in short-wavelengths regions - up to one - two decimal orders of magnitude for X-rays. As a result, during solar flares the absorbed dose on the polymer surfaces from X-rays can be compared with absorbed dose from VUV radiation. (2) Some new approaches to predictions of reaction efficiencies of fast orbital atomic oxygen in their interaction with polymeric materials are considered. (3) Some aspects of photocatalitic destruction of polymers in vacuum conditions by full-spectrum solar radiation are discussed. This process can take place in enamels containing semiconducting particles (TiO2, ZnO) as pigments. (4) Contamination of spacecraft surfaces from intrinsic outer atmosphere play important role not only from the point of view of deterioration of optical and thermophysical properties. Layers of SiO2 contaminations with nanometer thicknesses can greatly diminish mass losses from perfluorinated polymers under VUV irradiation.

The Distant Double Bond Determines the Fate of the Carboxylic Group in the Dissociative Photoionization of Oleic Acid.

PubMed

Heringa, Maarten F; Slowik, Jay G; Goldmann, Maximilian; Signorell, Ruth; Hemberger, Patrick; Bodi, Andras

2017-12-15

The valence threshold photoionization of oleic acid has been studied using synchrotron VUV radiation and imaging photoelectron photoion coincidence (iPEPICO) spectroscopy. An oleic acid aerosol beam was impacted on a copper thermodesorber, heated to 130 °C, to evaporate the particles quantitatively. Upon threshold photoionization, oleic acid produces the intact parent ion first, followed by dehydration at higher energies. Starting at ca. 10 eV, a large number of fragment ions slowly rise suggesting several fragmentation coordinates with quasi-degenerate activation energies. However, water loss is the dominant low-energy dissociation channel, and it is shown to be closely related to the unsaturated carbon chain. In the lowest-barrier process, one of the four allylic hydrogen atoms is transferred to the carboxyl group to form the leaving water molecule and a cyclic ketone fragment ion. A statistical model to analyze the breakdown diagram and measured rate constants yields a 0 K appearance energy of 9.77 eV, which can be compared with the density functional theory result of 9.19 eV. Alternative H-transfer steps yielding a terminal C=O group are ruled out based on energetics and kinetics arguments. Some of the previous photoionization mass spectrometric studies also reported 2 amu and 26 amu loss fragment ions, corresponding to hydrogen and acetylene loss. We could not identify such peaks in the mass spectrum of oleic acid. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

APPI-MS: Effects of mobile phases and VUV lamps on the detection of PAH compounds

PubMed Central

Short, Luke Chandler; Cai, Sheng-Suan; Syage, Jack A.

2009-01-01

The technique of atmospheric pressure photoionization (APPI) has several advantages over electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI), including efficient ionization of non-polar or low charge affinity compounds, reduced susceptibility to ion suppression, high sensitivity, and large linear dynamic range. These benefits are greatest at low flow rates (i.e., ≤100 μL/min), while at a higher flow, photon absorption and ion-molecule reactions become significant. Under certain circumstances, APPI signal and S/N have been observed to excel at higher flow, which may be due to a non-photoionzation mechanism. To better understand APPI at higher flow rates, we have selected three lamps (Xe, Kr and Ar) and four mobile phases typical for reverse-phase, high-pressure liquid chromatography: acetonitrile, methanol, (1:1) acetonitrile:water and (1:1) methanol:water. As test compounds, three polyaromatic hydrocarbons are studied: benzo[a]pyrene, indeno[1,2,3-c,d]pyrene and benz[a]anthracene. We find that solvent photoabsorption cross-section is not the only parameter in explaining relative signal intensity, but that solvent photo-ion chemistry can also play a significant role. Three conclusions from this investigation are: (i) Methanol photoionization leads to protonated methanol clusters that can result in chemical ionization of analyte molecule; (ii) Use of the Ar lamp often results in greater signal and S/N; (iii) Acetonitrile photoionization is less efficient and resulting clusters are too strongly bound to efficiently chemically ionize the analyte, so that analyte ion formation is dominated by direct photoionization. PMID:17188507

APPI-MS: effects of mobile phases and VUV lamps on the detection of PAH compounds.

PubMed

Short, Luke Chandler; Cai, Sheng-Suan; Syage, Jack A

2007-04-01

The technique of atmospheric pressure photoionization (APPI) has several advantages over electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI), including efficient ionization of nonpolar or low charge affinity compounds, reduced susceptibility to ion suppression, high sensitivity, and large linear dynamic range. These benefits are greatest at low flow rates (i.e.,

Development of ultraviolet lasers

NASA Technical Reports Server (NTRS)

Walters, G. K.

1974-01-01

The pulsed electron accelerator selected for use in the development of ultraviolet laser capability suitable for use in photoexcitation and photoionization studies of the upper atmosphere is reported. Performance figures, installation specifications, and total cost of the equipment are briefly shown, and plans for further studies are outlined.

Dissociative Photoionization of 1-Halogenated Silacyclohexanes: Silicon Traps the Halogen.

PubMed

Bodi, Andras; Sigurdardottir, Katrin Lilja; Kvaran, Ágúst; Bjornsson, Ragnar; Arnason, Ingvar

2016-11-23

The threshold photoelectron spectra and threshold photoionization mass spectra of 1-halogenated-1-silacyclohexanes, for the halogens X = F, Cl, Br, and I, have been obtained using synchrotron vacuum ultraviolet radiation and photoelectron photoion coincidence spectroscopy. As confirmed by a similar ionization onset and density functional theory molecular orbitals, the ionization to the ground state is dominated by electron removal from the silacyclohexane ring for X = F, Cl, and Br, and from the halogen lone pair for X = I. The breakdown diagrams show that the dissociative photoionization mechanism is also different for X = I. Whereas the parent ions decay by ethylene loss for X = F to Br in the low-energy regime, the iodine atom is lost for X = I. The first step is followed by a sequential ethylene loss at higher internal energies in each of the compounds. It is argued that the tendency of silicon to lower bond angles stabilizes the complex cation in which C 2 H 4 is η 2 -coordinated to it, and which precedes ethylene loss. Together with the relatively strong silicon-halogen bonds and the increased inductive effect of the silacyclohexane ring in stabilizing the cation, this explains the main differences observed in the fragmentation of the halogenated silacyclohexane and halogenated cyclohexane ions. The breakdown diagrams have been modeled taking into account slow dissociations at threshold and the resulting kinetic shift. The 0 K appearance energies have been obtained to within 0.08 eV for the ethylene loss for X = F to Br (10.56, 10.51, and 10.51 eV, respectively), the iodine atom loss for X = I (10.11 eV), the sequential ethylene loss for X = F to I (12.29, 12.01, 11.94, and 11.86 eV, respectively), and the minor channels of H loss for X = F (10.56 eV) and propylene loss in X = Cl (also at 10.56 eV). The appearance energies for the major channels likely correspond to the dissociative photoionization reaction energy.

Laboratory Measurements and Modeling of Molecular Photoabsorption Cross Sections in the Ultraviolet: Diatomic Sulfur (S2) and Sulfur Monoxide (SO)

NASA Astrophysics Data System (ADS)

Stark, Glenn; Lyons, James; Herde, Hannah; Nave, Gillian; de Oliveira, Nelson

2015-11-01

Our research program comprises the measurement and modeling of ultraviolet molecular photoabsorption cross sections with the highest practical resolution. It supports efforts to interpret and model observations of planetary atmospheres. Measurement and modeling efforts on diatomic sulfur (S2) and sulfur monoxide (SO) are in progress.S2: Interpretations of atmospheric (Io, Jupiter, cometary comae) S2 absorption features are hindered by a complete lack of laboratory cross section data in the ultraviolet. We are working to quantify the photoabsorption spectrum of S2 from 240 to 300 nm based on laboratory measurements and theoretical calculations. We have constructed an experimental apparatus to produce a stable column of S2 vapor at a temperature of 800 K. High-resolution measurements of the absorption spectrum of the strong B - X system of S2 were completed using the NIST VUV-FTS at Gaithersburg, MD. These measurements are being incorporated into a coupled-channel model of the absorption spectrum of S2 to quantify the contributions from individual bands and to establish the mechanisms responsible for the strong predissociation signature of the B - X system. A successful coupled channels model can then be used to calculate the B - X absorption spectrum at any temperature.SO: There has been a long-standing need for high-resolution cross sections of SO radicals in the UV and VUV regions, where the molecule strongly predissociates, for modeling the atmospheres of Io and Venus, and for understanding sulfur isotope effects in the ancient (pre-O2) atmosphere of Earth. We have produced a measurable column of SO in a continuous-flow DC discharge cell, using SO2 as a parent molecule. Photoabsorption measurements were recently recorded with the high-resolution VUV-FTS on the DESIRS beamline of the SOLEIL synchrotron. A number of strong, predissociated SO bands were measured in the 140 to 200 nm region. Weaker features associated with the SO B - X system were simultaneously recorded, allowing for an approximate determination of the VUV SO band f-values.

UV and VUV photolysis vs. UV/H2O2 and VUV/H2O2, treatment for removal of clofibric acid from aqueous solution.

PubMed

Li, Wenzhen; Lu, Shuguang; Qiu, Zhaofu; Lin, Kuangfei

2011-07-01

Clofibric acid (CA), a metabolite of lipid regulators, was investigated in ultra-pure water and sewage treatment plant (STP) effluent at 10 degrees C under UV, vacuum UV (VUV), UV/H2O2 and VUV/H2O2 processes. The influences of NO3-, HCO3- and humic acid (HA) on CA photolysis in all processes were examined. The results showed that all the experimental data well fitted the pseudo-first-order kinetic model, and the apparent rate constant (k(ap)) and half-life time (t(1/2)) were calculated accordingly. Direct photolysis of CA through UV irradiation was the main process, compared with the indirect oxidation of CA due to the slight generation of hydroxyl radicals dissociated from water molecules under UV irradiation below 200 nm monochromatic wavelength emission. In contrast, indirect oxidation was the main CA degradation mechanism in UV/H2O2 and VUV/H2O2, and VUV/H2O2 was the most effective process for CA degradation. The addition of 20 mg L(-1) HA could significantly inhibit CA degradation, whereas, except for UV irradiation, the inhibitive effects of NO3- and HCO3- (1.0 x 10(-3) and 0.1 mol L(-1), respectively) on CA degradation were observed in all processes, and their adverse effects were more significant in UV/H2O2 and VUV/H2O2 processes, particularly at the high NO3- and HCO3- concentrations. The degradation rate decreased 1.8-4.9-fold when these processes were applied to a real STP effluent owing to the presence of complex constituents. Of the four processes, VUV/H2O2 was the most effective, and the CA removal efficiency reached over 99% after 40 min in contrast to 80 min in both the UV/H2O2 and VUV processes and 240 min in the UV process.

Making Ultraviolet Spectro-Polarimetry Polarization Measurements with the MSFC Solar Ultraviolet Magnetograph Sounding Rocket

NASA Technical Reports Server (NTRS)

West, Edward; Cirtain, Jonathan; Kobayashi, Ken; Davis, John; Gary, Allen

2011-01-01

This paper will describe the Marshall Space Flight Center's Solar Ultraviolet Magnetograph Investigation (SUMI) sounding rocket program. This paper will concentrate on SUMI's VUV optics, and discuss their spectral, spatial and polarization characteristics. While SUMI's first flight (7/30/2010) met all of its mission success criteria, there are several areas that will be improved for its second and third flights. This paper will emphasize the MgII linear polarization measurements and describe the changes that will be made to the sounding rocket and how those changes will improve the scientific data acquired by SUMI.

Catalytic Decomposition of Hydroxylammonium Nitrate Ionic Liquid: Enhancement of NO Formation.

PubMed

Chambreau, Steven D; Popolan-Vaida, Denisia M; Vaghjiani, Ghanshyam L; Leone, Stephen R

2017-05-18

Hydroxylammonium nitrate (HAN) is a promising candidate to replace highly toxic hydrazine in monopropellant thruster space applications. The reactivity of HAN aerosols on heated copper and iridium targets was investigated using tunable vacuum ultraviolet photoionization time-of-flight aerosol mass spectrometry. The reaction products were identified by their mass-to-charge ratios and their ionization energies. Products include NH 3 , H 2 O, NO, hydroxylamine (HA), HNO 3 , and a small amount of NO 2 at high temperature. No N 2 O was detected under these experimental conditions, despite the fact that N 2 O is one of the expected products according to the generally accepted thermal decomposition mechanism of HAN. Upon introduction of iridium catalyst, a significant enhancement of the NO/HA ratio was observed. This observation indicates that the formation of NO via decomposition of HA is an important pathway in the catalytic decomposition of HAN.

NEW EXPERIMENTAL EVIDENCES ABOUT THE FORMATION AND CONSUMPTION OF KETOHYDROPEROXIDES

PubMed Central

Battin-Leclerc, Frédérique; Herbinet, Olivier; Glaude, Pierre-Alexandre; Fournet, René; Zhou, Zhongyue; Deng, Liulin; Guo, Huijun; Xie, Mingfeng; Qi, Fei

2013-01-01

The formation of hydroperoxides postulated in all the kinetic models for the low temperature oxidation of alkanes have been experimentally proved thanks to a new type of apparatus associating a quartz jet-stirred reactor through a molecular-beam sampling system to a reflectron time-of-flight mass spectrometer combined with tunable synchrotron vacuum ultraviolet photoionization. This apparatus has been used to investigate the low-temperature oxidation of n-butane and has allowed demonstrating the formation of different types of alkylhydroperoxides, namely methylhydroperoxide, ethylhydroperoxide and butylhydroperoxide, and of C4 alkylhydroperoxides including a carbonyl function (ketohydroperoxides). In addition, the formation of products deriving from these ketohydroperoxides, such as C4 molecules including either two carbonyl groups or one carbonyl and one alcohol functions, has been observed. Simulations using a detailed kinetic model have been performed to support some of the assumptions made in this work. PMID:23700382

Rapid comprehensive characterization of crude oils by thermogravimetry coupled to fast modulated gas chromatography-single photon ionization time-of-flight mass spectrometry.

PubMed

Wohlfahrt, S; Fischer, M; Saraji-Bozorgzad, M; Matuschek, G; Streibel, T; Post, E; Denner, T; Zimmermann, R

2013-09-01

Comprehensive multi-dimensional hyphenation of a thermogravimetry device (i.e. a thermobalance) to gas chromatography and single photon ionization-time-of-flight mass spectrometry (TG-GC×SPI-MS) has been used to investigate two crude oil samples of different geographical origin. The source of the applied vacuum ultraviolet radiation is an electron beam pumped rare gas excimer lamp (EBEL). The soft photoionization favors the formation of molecular ions. Introduction of a fast, rapidly modulated gas chromatographic separation step in comparison with solely TG-SPI-MS enables strongly enhanced detection especially with such highly complex organic matrices as crude oil. In contrast with former TG-SPI-MS measurements, separation and identification of overlying substances is possible because of different GC retention times. The specific contribution of isobaric compounds to one mass signal is determined for alkanes, naphthalenes, alkylated benzenes, and other compounds.

Photodissociation of ethylbenzene and n-propylbenzene in a molecular beam

NASA Astrophysics Data System (ADS)

Huang, Cheng-Liang; Jiang, Jyh-Chiang; Lee, Yuan T.; Ni, Chi-Kung

2002-10-01

The photodissociation of jet-cooled ethylbenzene and n-propylbenzene at both 193 and 248 nm was studied using vacuum ultraviolet photoionization/multimass ion imaging techniques. The photofragment translational energy distributions from both the molecules obtained at 193 nm show that the probability of portioning energy to product translational energy decreases monotonically with increasing translational energy. They indicate that the dissociation occurs from the ground electronic state. However, the photofragment translational energy distributions from both molecules obtained at 248 nm contain a fast and a slow component. 75% of ethylbenzene and 80% of n-propylbenzene following the 248 nm photoexcitation dissociate from electronic excited state, resulting in the fast component. The remaining 25% of ethylbenzene and 20% of n-propylbenzene dissociate through the ground electronic state, giving rise to the slow component. A comparison with an ab initio calculation suggests that the dissociation from the first triplet state corresponds to the fast component in translational energy distribution.

Far-ultraviolet and optical spectrophotometry of X-ray selected Seyfert galaxies

NASA Technical Reports Server (NTRS)

Clarke, J. T.; Bowyer, S.; Grewing, M.

1986-01-01

Five X-ray selected Seyfert galaxies were examined via near-simultaneous far-ultraviolet and optical spectrophotometry in an effort to test models for excitation of emission lines by X-ray and ultraviolet continuum photoionization. The observed Ly-alpha/H-beta ratio in the present sample averages 22, with an increase found toward the high-velocity wings of the H lines in the spectrum of at least one of the Seyfert I nuclei. It is suggested that Seyfert galaxies with the most high-velocity gas exhibit the highest Ly-alpha/H-beta ratios at all velocities in the line profiles, and that sometimes this ratio may be highest for the highest velocity material in the broad-line clouds. Since broad-lined objects are least affected by Ly-alpha trapping effects, they have Ly-alpha/H-beta ratios much closer to those predicted by early photoionization calculations.

Correlated proton-electron hole dynamics in protonated water clusters upon extreme ultraviolet photoionization

PubMed Central

Li, Zheng; Vendrell, Oriol

2016-01-01

The ultrafast nuclear and electronic dynamics of protonated water clusters H+(H2O)n after extreme ultraviolet photoionization is investigated. In particular, we focus on cluster cations with n = 3, 6, and 21. Upon ionization, two positive charges are present in the cluster related to the excess proton and the missing electron, respectively. A correlation is found between the cluster's geometrical conformation and initial electronic energy with the size of the final fragments produced. For situations in which the electron hole and proton are initially spatially close, the two entities become correlated and separate in a time-scale of 20 to 40 fs driven by strong non-adiabatic effects. PMID:26798842

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palmer, Michael H., E-mail: m.h.palmer@ed.ac.uk; Ridley, Trevor, E-mail: t.ridley@ed.ac.uk, E-mail: vronning@phys.au.dk, E-mail: nykj@phys.au.dk, E-mail: marcello.coreno@elettra.eu, E-mail: desimone@iom.cnr.it, E-mail: malgorzata.biczysko@sns.it, E-mail: kipeters@wsu.edu; Hoffmann, Søren Vrønning, E-mail: t.ridley@ed.ac.uk, E-mail: vronning@phys.au.dk, E-mail: nykj@phys.au.dk, E-mail: marcello.coreno@elettra.eu, E-mail: desimone@iom.cnr.it, E-mail: malgorzata.biczysko@sns.it, E-mail: kipeters@wsu.edu

New photoelectron, ultraviolet (UV), and vacuum UV (VUV) spectra have been obtained for bromobenzene by synchrotron study with higher sensitivity and resolution than previous work. This, together with use of ab initio calculations with both configuration interaction and time dependent density functional theoretical methods, has led to major advances in interpretation. The VUV spectrum has led to identification of a considerable number of Rydberg states for the first time. The Franck-Condon (FC) analyses including both hot and cold bands lead to identification of the vibrational structure of both ionic and electronically excited states including two Rydberg states. The UV onsetmore » has been interpreted in some detail, and an interpretation based on the superposition of FC and Herzberg-Teller contributions has been performed. In a similar way, the 6 eV absorption band which is poorly resolved is analysed in terms of the presence of two ππ* states of {sup 1}A{sub 1} (higher oscillator strength) and {sup 1}B{sub 2} (lower oscillator strength) symmetries, respectively. The detailed analysis of the vibrational structure of the 2{sup 2}B{sub 1} ionic state is particularly challenging, and the best interpretation is based on equation-of-motion-coupled cluster with singles and doubles computations. A number of equilibrium structures of the ionic and singlet excited states show that the molecular structure is less subject to variation than corresponding studies for iodobenzene. The equilibrium structures of the 3b{sub 1}3s and 6b{sub 2}3s (valence shell numbering) Rydberg states have been obtained and compared with the corresponding ionic limit structures.« less

Vacuum ultraviolet molecular nitrogen photoabsorption cross sections for planetary atmospheric transmission models

NASA Astrophysics Data System (ADS)

Stark, G.; Smith, P. L.; Yoshino, K.; Rufus, J.; Huber, K. P.

2001-11-01

The analyses of VUV occultation measurements of the N2-rich atmospheres of Titan and Triton are hampered by the lack of fundamental spectroscopic data for N2. In particular, there is a need for reliable photoabsorption f-values and line widths for the ~ 100 electronic bands of N2 in the 80 to 100 nm wavelength region. As part of our continuing program of laboratory measurements and analyses of the N2 VUV absorption spectrum, we present the results of new measurements of individual line strengths and widths in selected bands. These results indicate that within a number of individual bands there are significant departures from the predicted line strength distributions based on isolated band models. New line width measurements in the 95 to 100 nm region are also presented and compared to other values found in the literature. We have continued to compile on-line molecular spectroscopic atlas based on our N2 laboratory data: http://cfa-www.harvard.edu/amdata/ampdata/N2ARCHIVE/n2home.html. The archive includes published and unpublished 14N2, 14N15N, and 15N2 line lists and spectroscopic identifications, excited state energy levels, band and line f-values, a summary of published band f-value and line width measurements, and a cross-referenced summary of the relevant N2 literature. The listings are searchable by wavelength interval or band identification and are suitable for down-loading in a convenient format. We gratefully acknowledge funding support from NASA grant NAG5-9059 and the Smithsonian Institution Atherton-Seidel grant program.

High-resolution threshold photoionization of N2O

NASA Technical Reports Server (NTRS)

Wiedmann, R. T.; Grant, E. R.; Tonkyn, R. G.; White, M. G.

1991-01-01

Pulsed field ionization (PFI) has been used in conjunction with a coherent VUV source to obtain high-resolution threshold photoelectron spectra for the (000), (010), (020), and (100) vibrational states of the N2O(+) cation. Simulations for the rotational profiles of each vibronic level were obtained by fitting the Buckingham-Orr-Sichel equations using accurate spectroscopic constants for the ground states of the neutral and the ion. The relative branch intensities are interpreted in terms of the partial waves of the outgoing photoelectron to which the ionic core is coupled and in terms of the angular momentum transferred to the core.

Temporal variations of electron density and temperature in Kr/Ne/H2 photoionized plasma induced by nanosecond pulses from extreme ultraviolet source

NASA Astrophysics Data System (ADS)

Saber, I.; Bartnik, A.; Wachulak, P.; Skrzeczanowski, W.; Jarocki, R.; Fiedorowicz, H.

2017-06-01

Spectral investigations of low-temperature photoionized plasmas created in a Kr/Ne/H2 gas mixture were performed. The low-temperature plasmas were generated by gas mixture irradiation using extreme ultraviolet pulses from a laser-plasma source. Emission spectra in the ultraviolet/visible range from the photoionized plasmas contained lines that mainly corresponded to neutral atoms and singly charged ions. Temporal variations in the plasma electron temperature and electron density were studied using different characteristic emission lines at various delay times. Results, based on Kr II lines, showed that the electron temperature decreased from 1.7 to 0.9 eV. The electron densities were estimated using different spectral lines at each delay time. In general, except for the Hβ line, in which the electron density decreased from 3.78 × 1016 cm-3 at 200 ns to 5.77 × 1015 cm-3 at 2000 ns, most of the electron density values measured from the different lines were of the order of 1015 cm-3 and decreased slightly while maintaining the same order when the delay time increased. The time dependences of the measured and simulated intensities of a spectral line of interest were also investigated. The validity of the partial or full local thermodynamic equilibrium (LTE) conditions in plasma was explained based on time-resolved electron density measurements. The partial LTE condition was satisfied for delay times in the 200 ns to 1500 ns range. The results are summarized, and the dominant basic atomic processes in the gas mixture photoionized plasma are discussed.

Laboratory Studies of Thermal Energy Charge Transfer of Multiply Charged Ions in Astrophysical Plasmas

NASA Technical Reports Server (NTRS)

Kwong, Victor H. S.

2003-01-01

The laser ablation/ion storage facility at the UNLV Physics Department has been dedicated to the study of atomic and molecular processes in low temperature plasmas. Our program focuses on the charge transfer (electron capture) of multiply charged ions and neutrals important in astrophysics. The electron transfer reactions with atoms and molecules is crucial to the ionization condition of neutral rich photoionized plasmas. With the successful deployment of the Far Ultraviolet Spectroscopic Explorer (FUSE) and the Chandra X-ray Observatory by NASA high resolution VUV and X-ray emission spectra fiom various astrophysical objects have been collected. These spectra will be analyzed to determine the source of the emission and the chemical and physical environment of the source. The proper interpretation of these spectra will require complete knowledge of all the atomic processes in these plasmas. In a neutral rich environment, charge transfer can be the dominant process. The rate coefficients need to be known accurately. We have also extended our charge transfer measurements to KeV region with a pulsed ion beam. The inclusion of this facility into our current program provides flexibility in extending the measurement to higher energies (KeV) if needed. This flexibility enables us to address issues of immediate interest to the astrophysical community as new observations are made by high resolution space based observatories.

ABSOLUTE INTEGRAL CROSS SECTIONS AND PRODUCT BRANCHING RATIOS FOR THE VIBRATIONALLY SELECTED ION-MOLECULE REACTIONS: N{sub 2}{sup +}(X {sup 2}{Sigma}{sub g}{sup +}; v {sup +} = 0-2) + CH{sub 4}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu Yuntao; Chang, Yih Chung; Lu Zhou

Absolute vibrationally selected integral cross sections ({sigma}{sub v+}'s) for the ion-molecule reaction N{sub 2}{sup +}(X {sup 2}{Sigma}{sub g}{sup +}; v {sup +} = 0-2) + CH{sub 4} have been measured by using the newly developed vacuum ultraviolet (VUV) laser pulsed field ionization-photoion (PFI-PI) double-quadrupole-double-octopole ion guide apparatus. By employing a novel electric field pulsing scheme to the VUV laser PFI-PI source, we have been able to prepare reactant N{sub 2}{sup +} ions in single-vibrational quantum states with not only high intensity and high purity but also high kinetic energy resolution, allowing integral cross section measurements to be conducted in themore » center-of-mass kinetic energies (E{sub cm}'s) from 0.05 to 10.00 eV. Three primary product channels corresponding to the formations of CH{sub 3}{sup +}, CH{sub 2}{sup +}, and N{sub 2}H{sup +} were identified. After correcting for the secondary reactions involving CH{sub 3}{sup +} and CH{sub 2}{sup +}, we have determined the {sigma}{sub v+} values of the formation of these primary product ions, {sigma}{sub v+}(CH{sub 3}{sup +}), {sigma}{sub v+}(CH{sub 2}{sup +}), and {sigma}{sub v+}(N{sub 2}H{sup +}), and their branching ratios, [{sigma}{sub v+}(CH{sub 3}{sup +}): {sigma}{sub v+}(CH{sub 2}{sup +}): {sigma}{sub v+}(N{sub 2}H{sup +})]/{sigma}{sub v+}(CH{sub 3}{sup +} + CH{sub 2}{sup +} + N{sub 2}H{sup +}), v {sup +} = 0-2, in the E{sub cm} range of 0.05-10.00 eV, where {sigma}{sub v+}(CH{sub 3}{sup +} + CH{sub 2}{sup +} + N{sub 2}H{sup +}) = {sigma}{sub v+}(CH{sub 3}{sup +}) + {sigma}{sub v+}(CH{sub 2}{sup +}) + {sigma}{sub v+}(N{sub 2}H{sup +}). The branching ratios are found to be nearly independent of the v {sup +} state and E{sub cm}. Complex v {sup +}-state and E{sub cm} dependences for {sigma}{sub v+}(CH{sub 3}{sup +}), {sigma}{sub v+}(CH{sub 2}{sup +}), and {sigma}{sub v+}(N{sub 2}H{sup +}) along with vibrational inhibition for the formation of these product ions are observed. The vibrational effects on the {sigma}{sub v+} values are sufficiently large to warrant the inclusion of the vibrationally excited reactions N{sub 2}{sup +}(X {sup 2}{Sigma}{sub g}{sup +}; v {sup +} {>=} 1) + CH{sub 4} for a more realistic modeling of the ion and neutral densities observed in the atmosphere of Titan. The cross-sectional data obtained in the present study are also useful for benchmarking theoretical calculations on ion-neutral collision dynamics.« less

Laser excitation of the n =3 level of positronium for antihydrogen production

NASA Astrophysics Data System (ADS)

Aghion, S.; Amsler, C.; Ariga, A.; Ariga, T.; Bonomi, G.; Bräunig, P.; Bremer, J.; Brusa, R. S.; Cabaret, L.; Caccia, M.; Caravita, R.; Castelli, F.; Cerchiari, G.; Chlouba, K.; Cialdi, S.; Comparat, D.; Consolati, G.; Demetrio, A.; Di Noto, L.; Doser, M.; Dudarev, A.; Ereditato, A.; Evans, C.; Ferragut, R.; Fesel, J.; Fontana, A.; Forslund, O. K.; Gerber, S.; Giammarchi, M.; Gligorova, A.; Gninenko, S.; Guatieri, F.; Haider, S.; Holmestad, H.; Huse, T.; Jernelv, I. L.; Jordan, E.; Kellerbauer, A.; Kimura, M.; Koettig, T.; Krasnicky, D.; Lagomarsino, V.; Lansonneur, P.; Lebrun, P.; Lehner, S.; Liberadzka, J.; Malbrunot, C.; Mariazzi, S.; Marx, L.; Matveev, V.; Mazzotta, Z.; Nebbia, G.; Nedelec, P.; Oberthaler, M.; Pacifico, N.; Pagano, D.; Penasa, L.; Petracek, V.; Pistillo, C.; Prelz, F.; Prevedelli, M.; Ravelli, L.; Resch, L.; Rienäcker, B.; Røhne, O. M.; Rotondi, A.; Sacerdoti, M.; Sandaker, H.; Santoro, R.; Scampoli, P.; Smestad, L.; Sorrentino, F.; Spacek, M.; Storey, J.; Strojek, I. M.; Testera, G.; Tietje, I.; Vamosi, S.; Widmann, E.; Yzombard, P.; Zmeskal, J.; Zurlo, N.; AEgIS Collaboration

2016-07-01

We demonstrate the laser excitation of the n =3 state of positronium (Ps) in vacuum. A combination of a specially designed pulsed slow positron beam and a high-efficiency converter target was used to produce Ps. Its annihilation was recorded by single-shot positronium annihilation lifetime spectroscopy. Pulsed laser excitation of the n =3 level at a wavelength λ ≈205 nm was monitored via Ps photoionization induced by a second intense laser pulse at λ =1064 nm. About 15% of the overall positronium emitted into vacuum was excited to n =3 and photoionized. Saturation of both the n =3 excitation and the following photoionization was observed and explained by a simple rate equation model. The positronium's transverse temperature was extracted by measuring the width of the Doppler-broadened absorption line. Moreover, excitation to Rydberg states n =15 and 16 using n =3 as the intermediate level was observed, giving an independent confirmation of excitation to the 3 3P state.

Microfocusing at the PG1 beamline at FLASH

DOE PAGES

Dziarzhytski, Siarhei; Gerasimova, Natalia; Goderich, Rene; ...

2016-01-01

The Kirkpatrick–Baez (KB) refocusing mirror system installed at the PG1 branch of the plane-grating monochromator beamline at the soft X-ray/XUV free-electron laser in Hamburg (FLASH) is designed to provide tight aberration-free focusing down to 4 µm × 6 µm full width at half-maximum (FWHM) on the sample. Such a focal spot size is mandatory to achieve ultimate resolution and to guarantee best performance of the vacuum-ultraviolet (VUV) off-axis parabolic double-monochromator Raman spectrometer permanently installed at the PG1 beamline as an experimental end-station. The vertical beam size on the sample of the Raman spectrometer, which operates without entrance slit, defines andmore » limits the energy resolution of the instrument which has an unprecedented design value of 2 meV for photon energies below 70 eV and about 15 meV for higher energies up to 200 eV. In order to reach the designed focal spot size of 4 µm FWHM (vertically) and to hold the highest spectrometer resolution, special fully motorized in-vacuum manipulators for the KB mirror holders have been developed and the optics have been aligned employing wavefront-sensing techniques as well as ablative imprints analysis. Lastly, aberrations like astigmatism were minimized. In this article the design and layout of the KB mirror manipulators, the alignment procedure as well as microfocus optimization results are presented.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dziarzhytski, Siarhei; Gerasimova, Natalia; Goderich, Rene

The Kirkpatrick–Baez (KB) refocusing mirror system installed at the PG1 branch of the plane-grating monochromator beamline at the soft X-ray/XUV free-electron laser in Hamburg (FLASH) is designed to provide tight aberration-free focusing down to 4 µm × 6 µm full width at half-maximum (FWHM) on the sample. Such a focal spot size is mandatory to achieve ultimate resolution and to guarantee best performance of the vacuum-ultraviolet (VUV) off-axis parabolic double-monochromator Raman spectrometer permanently installed at the PG1 beamline as an experimental end-station. The vertical beam size on the sample of the Raman spectrometer, which operates without entrance slit, defines andmore » limits the energy resolution of the instrument which has an unprecedented design value of 2 meV for photon energies below 70 eV and about 15 meV for higher energies up to 200 eV. In order to reach the designed focal spot size of 4 µm FWHM (vertically) and to hold the highest spectrometer resolution, special fully motorized in-vacuum manipulators for the KB mirror holders have been developed and the optics have been aligned employing wavefront-sensing techniques as well as ablative imprints analysis. Lastly, aberrations like astigmatism were minimized. In this article the design and layout of the KB mirror manipulators, the alignment procedure as well as microfocus optimization results are presented.« less

Correlated proton-electron hole dynamics in protonated water clusters upon extreme ultraviolet photoionization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Zheng; Vendrell, Oriol

2016-01-13

The ultrafast nuclear and electronic dynamics of protonated water clusters H+(H2O)n after extreme ultraviolet photoionization is investigated. In particular, we focus on cluster cations with n = 3, 6, and 21. Upon ionization, two positive charges are present in the cluster related to the excess proton and the missing electron, respectively. A correlation is found between the cluster's geometrical conformation and initial electronic energy with the size of the final fragments produced. As a result, for situations in which the electron hole and proton are initially spatially close, the two entities become correlated and separate in a time-scale of 20more » to 40 fs driven by strong non-adiabatic effects.« less

Viability of Cladosporium herbarum spores under 157 nm laser and vacuum ultraviolet irradiation, low temperature (10 K) and vacuum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarantopoulou, E., E-mail: esarant@eie.gr; Stefi, A.; Kollia, Z.

Ultraviolet photons can damage microorganisms, which rarely survive prolonged irradiation. In addition to the need for intact DNA, cell viability is directly linked to the functionality of the cell wall and membrane. In this work, Cladosporium herbarum spore monolayers exhibit high viability (7%) when exposed to 157 nm laser irradiation (412 kJm⁻²) or vacuum-ultraviolet irradiation (110–180 nm) under standard pressure and temperature in a nitrogen atmosphere. Spore viability can be determined by atomic-force microscopy, nano-indentation, mass, μ-Raman and attenuated reflectance Fourier-transform far-infrared spectroscopies and DNA electrophoresis. Vacuum ultraviolet photons cause molecular damage to the cell wall, but radiation resistance inmore » spores arises from the activation of a photon-triggered signaling reaction, expressed via the exudation of intracellular substances, which, in combination with the low penetration depth of vacuum-ultraviolet photons, shields DNA from radiation. Resistance to phototoxicity under standard conditions was assessed, as was resistance to additional environmental stresses, including exposure in a vacuum, under different rates of change of pressure during pumping time and low (10 K) temperatures. Vacuum conditions were far more destructive to spores than vacuum-ultraviolet irradiation, and UV-B photons were two orders of magnitude more damaging than vacuum-ultraviolet photons. The viability of irradiated spores was also enhanced at 10 K. This work, in addition to contributing to the photonic control of the viability of microorganisms exposed under extreme conditions, including decontamination of biological warfare agents, outlines the basis for identifying bio-signaling in vivo using physical methodologies.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Plogmaker, Stefan; Johansson, Erik M. J.; Rensmo, Haakan

A novel light chopper system for fast timing experiments in the vacuum-ultraviolet (VUV) and x-ray spectral region has been developed. It can be phase-locked and synchronized with a synchrotron radiation storage ring, accommodating repetition rates in the range of {approx}8 to {approx}120 kHz by choosing different sets of apertures and subharmonics of the ring frequency (MHz range). Also the opening time of the system can be varied from some nanoseconds to several microseconds to meet the needs of a broad range of applications. Adjusting these parameters, the device can be used either for the generation of single light pulses ormore » pulse packages from a microwave driven, continuous He gas discharge lamp or from storage rings which are otherwise often considered as quasi-continuous light sources. This chopper can be utilized for many different kinds of experiments enabling, for example, unambiguous time-of-flight (TOF) multi-electron coincidence studies of atoms and molecules excited by a single light pulse as well as time-resolved visible laser pump x-ray probe electron spectroscopy of condensed matter in the valence and core level region.« less

Evaluation of Low Earth Orbit Environmental Effects on International Space Station Thermal Control Materials

NASA Technical Reports Server (NTRS)

Dever, Joyce A.; Rutledge, Sharon K.; Hasegawa, Mark M.; Reed, Charles K.

1998-01-01

Samples of International Space Station (ISS) thermal control coatings were exposed to simulated low Earth orbit (LEO) environmental conditions to determine effects on optical properties. In one test, samples of the white paint coating Z-93P were coated with outgassed products from Tefzel(R) (ethylene tetrafluoroethylene copolymer) power cable insulation as-may occur on ISS. These samples were then exposed, along with an uncontaminated Z-93P witness sample, to vacuum ultraviolet (VUV) radiation to determine solar absorptance degradation. The Z-93P samples coated with Tefzel(R) outgassing products experienced greater increases in solar absorptance than witness samples not coated with Tefzel(R) outgassing products. In another test, samples of second surface silvered Teflon(R) FEP (fluorinated ethylene propylene), SiO. (where x=2)-coated silvered Teflon(R) FEP, and Z-93P witness samples were exposed to the combined environments of atomic oxygen and VLTV radiation to determine optical properties changes due to these simulated ISS environmental effects. This test verified the durability of these materials in the absence of contaminants.

Enhanced scintillation of Ba3In(B3O6)3 based on nitrogen doping

NASA Astrophysics Data System (ADS)

Wang, Z. X.; Pei, H.; Tao, X. M.; Cai, G. M.; Mao, R. H.; Jin, Z. P.

2018-02-01

Scintillating materials, as a class of luminescent materials, are highly demanded for practical use in the high-energy detection. However, the applications are often hampered by their low light yield (LY) or long decay time for many traditional scintillators. In this work, upon nitrogen anion doping, scintillation performance in layered borate Ba3In(B3O6)3 (BIB) has been excellently enhanced with high XEL intensity of ～3 times as large as that of commercial Bi4Ge3O12 (BGO) and ultra-fast fluorescent decay time of ～1.25 ns. To shed light on origins of the intrinsic violet-blue emission, we measured the in-situ vacuum ultraviolet excited (VUV) emission spectra of N-BIB ceramic. Combined with experiments and first principles calculations, the band-gap reduction and donor-acceptor density increasing by nitrogen (N) doping is responsible for the enhancement of scintillation performance for N-doped Ba3In(B3O6)3. Moreover, nitrogen anion doping rather than conventional cation doping is found to be also applicable to other intrinsic luminescent materials for enhancing performance.

Swift heavy ion irradiation of interstellar dust analogues. Small carbonaceous species released by cosmic rays

NASA Astrophysics Data System (ADS)

Dartois, E.; Chabot, M.; Pino, T.; Béroff, K.; Godard, M.; Severin, D.; Bender, M.; Trautmann, C.

2017-03-01

Context. Interstellar dust grain particles are immersed in vacuum ultraviolet (VUV) and cosmic ray radiation environments influencing their physicochemical composition. Owing to the energetic ionizing interactions, carbonaceous dust particles release fragments that have direct impact on the gas phase chemistry. Aims: The exposure of carbonaceous dust analogues to cosmic rays is simulated in the laboratory by irradiating films of hydrogenated amorphous carbon interstellar analogues with energetic ions. New species formed and released into the gas phase are explored. Methods: Thin carbonaceous interstellar dust analogues were irradiated with gold (950 MeV), xenon (630 MeV), and carbon (43 MeV) ions at the GSI UNILAC accelerator. The evolution of the dust analogues is monitored in situ as a function of fluence at 40, 100, and 300 K. Effects on the solid phase are studied by means of infrared spectroscopy complemented by simultaneously recording mass spectrometry of species released into the gas phase. Results: Specific species produced and released under the ion beam are analyzed. Cross sections derived from ion-solid interaction processes are implemented in an astrophysical context.

Experimental and ab initio characterization of HC3N+ vibronic structure. II. High-resolution VUV PFI-ZEKE spectroscopy.

PubMed

Gans, Bérenger; Lamarre, Nicolas; Broquier, Michel; Liévin, Jacques; Boyé-Péronne, Séverine

2016-12-21

Vacuum-ultraviolet pulsed-field-ionization zero-kinetic-energy photoelectron spectra of X + Π2←XΣ+1 and B + Π2←XΣ+1 transitions of the HC 3 14 N and HC 3 15 N isotopologues of cyanoacetylene have been recorded. The resolution of the photoelectron spectra allowed us to resolve the vibrational structures and the spin-orbit splittings in the cation. Accurate values of the adiabatic ionization potentials of the two isotopologues (E I /hc(HC 3 14 N)=93 909(2) cm -1 and E I /hc(HC 3 15 N)=93 912(2) cm -1 ), the vibrational frequencies of the ν 2 , ν 6 , and ν 7 vibrational modes, and the spin-orbit coupling constant (A SO = -44(2) cm -1 ) of the X + Π2 cationic ground state have been derived from the measurements. Using ab initio calculations, the unexpected structure of the B + Π2←XΣ+1 transition is tentatively attributed to a conical intersection between the A + and B + electronic states of the cation.

Current status of BL-2B at photon factory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nambu, Akira, E-mail: akia.nambu.tw@hitachi.com; Ueda, Kazuhiro; Horiba, Koji

A new soft x-ray beamline BL-2B at Photon Factory of High Energy Accelerator Research Organization (KEK-PF) covers energy range from vacuum ultraviolet (30 eV) to soft x-ray (4000 eV). This wide energy range could be achieved by employing two undulators and two monochromators. Two different energy range undulators were installed tandem to a 9-meter straight section of PF storage ring. The 1{sup st} undulator is for VUV (30 eV) to SX (280 eV), while the other one is for SX (280 eV) to HX (4000 eV). It is also necessary to be equipped with two different monochrometors for energy abovemore » and under 2000 eV; grating monochrometor and double crystal monochrometor. One of the main purposes of this bemaline is spectroscopic study of light elements contained in several functional materials. The beamline is designed for photoemission spectroscopy (PES), X-ray absorption fine structure (XAFS) and other types of experiments. The performance of the new beamline is reported and typical examples of its application to material science are demonstrated.« less

Effect of attochirp on attosecond streaking time delay in photoionization of atoms

NASA Astrophysics Data System (ADS)

Goldsmith, C.; Jaroń-Becker, A.; Becker, A.

2018-01-01

We present a theoretical analysis of the effect of the attochirp on the streaking time delay, intrinsic to photoionization of an atom by an attosecond laser pulse at extreme ultraviolet wavelengths superposed by a femtosecond streaking pulse. To this end, we determine the expectation value of the delay in a chirped pulse using a recently developed model formula. Results of our calculations show that the attochirp can be relevant for photoemission from the 3p shell in argon atom at frequencies near the Cooper minimum, while it is negligible if the photoionization cross section as a function of frequency varies smoothly.

An XUV/VUV free-electron laser oscillator

NASA Astrophysics Data System (ADS)

Goldstein, J. C.; Newnam, B. E.; Cooper, R. K.; Comly, J. C., Jr.

Problems regarding the extension of free-electron laser technology from the visible and near infrared region, where such devices are currently operating, to the ultraviolet have recently been extensively discussed. It was found that significant technical problems must be overcome before free-electron lasers (FELs) can be operated in the VUV (100-200 nm) and the XUV (50-100). However, the present lack of other intense and tunable sources of coherent radiation at these wavelengths together with the intrinsic properties of FELs make the development of such devices potentially very rewarding. The properties of FELs include continuous tunability in wavelength and output in the form of a train of picosecond pulses. An investigation is conducted regarding the feasibility of an operation of a FEL in the XUV/VUV regions, taking into account a theoretical model. It is found that modest improvements in electron beam and optical mirror technologies will make the design of a FEL for operation in the 50-200-nm range of optical wavelength possible.

Prediction of the size distributions of methanol-ethanol clusters detected in VUV laser/time-of-flight mass spectrometry.

PubMed

Liu, Yi; Consta, Styliani; Shi, Yujun; Lipson, R H; Goddard, William A

2009-06-25

The size distributions and geometries of vapor clusters equilibrated with methanol-ethanol (Me-Et) liquid mixtures were recently studied by vacuum ultraviolet (VUV) laser time-of-flight (TOF) mass spectrometry and density functional theory (DFT) calculations (Liu, Y.; Consta, S.; Ogeer, F.; Shi, Y. J.; Lipson, R. H. Can. J. Chem. 2007, 85, 843-852). On the basis of the mass spectra recorded, it was concluded that the formation of neutral tetramers is particularly prominent. Here we develop grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) frameworks to compute cluster size distributions in vapor mixtures that allow a direct comparison with experimental mass spectra. Using the all-atom optimized potential for liquid simulations (OPLS-AA) force field, we systematically examined the neutral cluster size distributions as functions of pressure and temperature. These neutral cluster distributions were then used to derive ionized cluster distributions to compare directly with the experiments. The simulations suggest that supersaturation at 12 to 16 times the equilibrium vapor pressure at 298 K or supercooling at temperature 240 to 260 K at the equilibrium vapor pressure can lead to the relatively abundant tetramer population observed in the experiments. Our simulations capture the most distinct features observed in the experimental TOF mass spectra: Et(3)H(+) at m/z = 139 in the vapor corresponding to 10:90% Me-Et liquid mixture and Me(3)H(+) at m/z = 97 in the vapors corresponding to 50:50% and 90:10% Me-Et liquid mixtures. The hybrid GCMC scheme developed in this work extends the capability of studying the size distributions of neat clusters to mixed species and provides a useful tool for studying environmentally important systems such as atmospheric aerosols.

Elucidating the Chemical Complexity of Organic Aerosol Constituents Measured During the Southeastern Oxidant and Aerosol Study (SOAS)

NASA Astrophysics Data System (ADS)

Yee, L.; Isaacman, G. A.; Spielman, S. R.; Worton, D. R.; Zhang, H.; Kreisberg, N. M.; Wilson, K. R.; Hering, S. V.; Goldstein, A. H.

2013-12-01

Thousands of volatile organic compounds are uniquely created in the atmosphere, many of which undergo chemical transformations that result in more highly-oxidized and often lower vapor pressure species. These species can contribute to secondary organic aerosol, a complex mixture of organic compounds that is still not chemically well-resolved. Organic aerosol collected on filters taken during the Southeastern Oxidant and Aerosol Study (SOAS) constitute hundreds of unique chemical compounds. Some of these include known anthropogenic and biogenic tracers characterized using standardized analytical techniques (e.g. GC-MS, UPLC, LC-MS), but the majority of the chemical diversity has yet to be explored. By employing analytical techniques involving sample derivatization and comprehensive two-dimensional gas chromatography (GC x GC) with high-resolution-time-of-flight mass spectrometry (HR-ToF-MS), we elucidate the chemical complexity of the organic aerosol matrix along the volatility and polarity grids. Further, by utilizing both electron impact (EI) and novel soft vacuum ultraviolet (VUV) ionization mass spectrometry, a greater fraction of the organic mass is fully speciated. The GC x GC-HR-ToF-MS with EI/VUV technique efficiently provides an unprecedented level of speciation for complex ambient samples. We present an extensive chemical characterization and quantification of organic species that goes beyond typical atmospheric tracers in the SOAS samples. We further demonstrate that complex organic mixtures can be chemically deconvoluted by elucidation of chemical formulae, volatility, functionality, and polarity. These parameters provide insight into the sources (anthropogenic vs. biogenic), chemical processes (oxidation pathways), and environmental factors (temperature, humidity), controlling organic aerosol growth in the Southeastern United States.

Photoionization of Benzene and Small Polycyclic Aromatic Hydrocarbons in Ultraviolet-Processed Astrophysical Ices: A Computational Study

NASA Technical Reports Server (NTRS)

Woon, D. E.; Park, J.-Y.

2004-01-01

We employed density functional theory (DFT) calculations to model the photoionization behavior of benzene and small polycyclic aromatic hydrocarbons when they are embedded in a matrix of water ice in order to investigate issues raised by recent experimental work by Gudipati and Allamandola. The ionization energies of benzene, naphthalene, anthracene, and pyrene were found to be lowered by 1.5-2.1 eV in water ice. Low-lying vertical electronic excitation energies were computed with time-dependent DFT for both neutral and ionized species and are found in both cases to be remarkably unaffected by the ice matrix. Chemical behavior in ultraviolet-photoprocessed ices is also discussed, with a focus on electron recombination and pathways leading to phenol and analogous products.

Ionization heating in rare-gas clusters under intense XUV laser pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arbeiter, Mathias; Fennel, Thomas

The interaction of intense extreme ultraviolet (XUV) laser pulses ({lambda}=32 nm, I=10{sup 11}-10{sup 14} W/cm{sup 2}) with small rare-gas clusters (Ar{sub 147}) is studied by quasiclassical molecular dynamics simulations. Our analysis supports a very general picture of the charging and heating dynamics in finite samples under short-wavelength radiation that is of relevance for several applications of free-electron lasers. First, up to a certain photon flux, ionization proceeds as a series of direct photoemission events producing a jellium-like cluster potential and a characteristic plateau in the photoelectron spectrum as observed in Bostedt et al. [Phys. Rev. Lett. 100, 133401 (2008)]. Second,more » beyond the onset of photoelectron trapping, nanoplasma formation leads to evaporative electron emission with a characteristic thermal tail in the electron spectrum. A detailed analysis of this transition is presented. Third, in contrast to the behavior in the infrared or low vacuum ultraviolet range, the nanoplasma energy capture proceeds via ionization heating, i.e., inner photoionization of localized electrons, whereas collisional heating of conduction electrons is negligible up to high laser intensities. A direct consequence of the latter is a surprising evolution of the mean energy of emitted electrons as function of laser intensity.« less

Photoionization in Ultraviolet Processing of Astrophysical Ice Analogs at Cryogenic Temperatures

NASA Technical Reports Server (NTRS)

Woon, David E.

2004-01-01

Two recent experimental studies have demonstrated that amino acids or amino acid precursors are generated when astrophysical ice analogs are subjected to ultraviolet (UV) irradiation at cryogenic temperatures. Understanding the complete phenomenology of photoprocessing is critical to elucidating chemical reaction mechanisms that can function within an ice matrix under very cold conditions. Pushing beyond the much better characterized study of photolytic dissociation of chemical bonds through electronic excitation, this work explored the ability of UV radiation present in the interstellar medium to ionize small molecules embedded in ices. Quantum chemical calculations, including bulk solvation effects, were used to study the ionization of hydrogen (H2), water, and methanol (CH3OH) bound in small clusters of water. Ionization potentials were found to be much smaller in the condensed phase than in the gas phase; even a small cluster can account for large changes in the ionization potentials in ice, as well as the known formation of an OH--H3O+ pair in the case of H2O photoionization. To gauge the impact of photoionization on subsequent grain chemistry, the reaction between OH and CO in the presence of H3O+ was studied and compared with the potential energy surface without hydronium present, which is relevant to chemistry following photolysis. The differences indicate that the reaction is somewhat more likely to proceed to products (H + CO2) in the case of photoionization.

The PUR Experiment on the EXPOSE-R facility: biological dosimetry of solar extraterrestrial UV radiation

NASA Astrophysics Data System (ADS)

Bérces, A.; Egyeki, M.; Fekete, A.; Horneck, G.; Kovács, G.; Panitz, C.

2015-01-01

The aim of our experiment Phage and Uracil Response was to extend the use of bacteriophage T7 and uracil biological dosimeters for measuring the biologically effective ultraviolet (UV) dose in the harsh extraterrestrial radiation conditions. The biological detectors were exposed in vacuum-tightly cases in the European Space Agency (ESA) astrobiological exposure facility attached to the external platform of Zvezda (EXPOSE-R). EXPOSE-R took off to the International Space Station (ISS) in November 2008 and was installed on the External platform of the Russian module Zvezda of the ISS in March 2009. Our goal was to determine the dose-effect relation for the formation of photoproducts (i.e. damage to phage DNA and uracil, respectively). The extraterrestrial solar UV radiation ranges over the whole spectrum from vacuum-UV (λ<200 nm) to UVA (315 nm<λ<400 nm), which causes photolesions (photoproducts) in the nucleic acids/their components either by photoionization or excitation. However, these wavelengths cause not only photolesions but in a wavelength-dependent efficiency the reversion of some photolesions, too. Our biological detectors measured in situ conditions the resultant of both reactions induced by the extraterrestrial UV radiation. From this aspect the role of the photoreversion in the extension of the biological UV dosimetry are discussed.

Gage measures total radiation, including vacuum UV, from ionized high-temperature gases

NASA Technical Reports Server (NTRS)

Wood, A. D.

1969-01-01

Transient-heat transfer gage measures the total radiation intensity from vacuum ultraviolet and ionized high temperature gases. The gage includes a sensitive piezoelectric crystal that is completely isolated from any ionized flow and vacuum ultraviolet irradiation.

Infrared absorption of methanol-water clusters (CH3OH)n(H2O), n = 1-4, recorded with the VUV-ionization/IR-depletion technique

NASA Astrophysics Data System (ADS)

Lee, Yu-Fang; Kelterer, Anne-Marie; Matisz, Gergely; Kunsági-Máté, Sándor; Chung, Chao-Yu; Lee, Yuan-Pern

2017-04-01

We recorded infrared (IR) spectra in the CH- and OH-stretching regions of size-selected clusters of methanol (M) with one water molecule (W), represented as MnW, n = 1-4, in a pulsed supersonic jet using the photoionization/IR-depletion technique. Vacuum ultraviolet emission at 118 nm served as the source of ionization in a time-of-flight mass spectrometer to detect clusters MnW as protonated forms Mn-1WH+. The variations in intensities of Mn-1WH+ were monitored as the wavelength of the IR laser light was tuned across the range 2700-3800 cm-1. IR spectra of size-selected clusters were obtained on processing of the observed action spectra of the related cluster-ions according to a mechanism that takes into account the production and loss of each cluster due to IR photodissociation. Spectra of methanol-water clusters in the OH region show significant variations as the number of methanol molecules increases, whereas those in the CH region are similar for all clusters. Scaled harmonic vibrational wavenumbers and relative IR intensities predicted with the M06-2X/aug-cc-pVTZ method for the methanol-water clusters are consistent with our experimental results. For dimers, absorption bands of a structure WM with H2O as a hydrogen-bond donor were observed at 3570, 3682, and 3722 cm-1, whereas weak bands of MW with methanol as a hydrogen-bond donor were observed at 3611 and 3753 cm-1. For M2W, the free OH band of H2O was observed at 3721 cm-1, whereas a broad feature was deconvoluted to three bands near 3425, 3472, and 3536 cm-1, corresponding to the three hydrogen-bonded OH-stretching modes in a cyclic structure. For M3W, the free OH shifted to 3715 cm-1, and the hydrogen-bonded OH-stretching bands became much broader, with a weak feature near 3179 cm-1 corresponding to the symmetric OH-stretching mode of a cyclic structure. For M4W, the observed spectrum agrees unsatisfactorily with predictions for the most stable cyclic structure, indicating significant contributions from branched isomers, which is distinctly different from M5 of which the cyclic form dominates.

Infrared absorption of methanol-water clusters (CH3OH)n(H2O), n = 1-4, recorded with the VUV-ionization/IR-depletion technique.

PubMed

Lee, Yu-Fang; Kelterer, Anne-Marie; Matisz, Gergely; Kunsági-Máté, Sándor; Chung, Chao-Yu; Lee, Yuan-Pern

2017-04-14

We recorded infrared (IR) spectra in the CH- and OH-stretching regions of size-selected clusters of methanol (M) with one water molecule (W), represented as M n W, n = 1-4, in a pulsed supersonic jet using the photoionization/IR-depletion technique. Vacuum ultraviolet emission at 118 nm served as the source of ionization in a time-of-flight mass spectrometer to detect clusters M n W as protonated forms M n-1 WH + . The variations in intensities of M n-1 WH + were monitored as the wavelength of the IR laser light was tuned across the range 2700-3800 cm -1 . IR spectra of size-selected clusters were obtained on processing of the observed action spectra of the related cluster-ions according to a mechanism that takes into account the production and loss of each cluster due to IR photodissociation. Spectra of methanol-water clusters in the OH region show significant variations as the number of methanol molecules increases, whereas those in the CH region are similar for all clusters. Scaled harmonic vibrational wavenumbers and relative IR intensities predicted with the M06-2X/aug-cc-pVTZ method for the methanol-water clusters are consistent with our experimental results. For dimers, absorption bands of a structure WM with H 2 O as a hydrogen-bond donor were observed at 3570, 3682, and 3722 cm -1 , whereas weak bands of MW with methanol as a hydrogen-bond donor were observed at 3611 and 3753 cm -1 . For M 2 W, the free OH band of H 2 O was observed at 3721 cm -1 , whereas a broad feature was deconvoluted to three bands near 3425, 3472, and 3536 cm -1 , corresponding to the three hydrogen-bonded OH-stretching modes in a cyclic structure. For M 3 W, the free OH shifted to 3715 cm -1 , and the hydrogen-bonded OH-stretching bands became much broader, with a weak feature near 3179 cm -1 corresponding to the symmetric OH-stretching mode of a cyclic structure. For M 4 W, the observed spectrum agrees unsatisfactorily with predictions for the most stable cyclic structure, indicating significant contributions from branched isomers, which is distinctly different from M 5 of which the cyclic form dominates.

High Sensitivity Absorption Spectroscopy on Ti II VUV Resonance Lines of Astrophysical Interest

NASA Astrophysics Data System (ADS)

Wiese, Lm; Fedchak, Ja; Lawler, Je

2000-06-01

The neutral hydrogen regions of the Interstellar Medium (ISM) of our Galaxy and distant galaxies produce simple absorption spectra because most metals are singly ionized and in their ground fine structure level. Elemental abundance measurements and other studies of the ISM rely on accurate atomic oscillator strengths (f-values) for a few key lines in the second spectra of Ti and other metals. The Ti II VUV resonance lines at 1910.6 and 1910.9 Åare important in absorption line systems in which quasars provide the continuum and the ISM of intervening galaxies is observed. Some of these absorption line systems are redshifted to the visible and observed with ground based telescopes. We report the first laboratory measurement of these Ti II VUV resonance lines. Using High Sensitivity Absorption Spectroscopy, we determined f-values for the 1910 Ålines relative to well-known Ti II resonance lines at 3067 and 3384 ÅContinuum radiation from an Aladdin Storage Ring bending magnet at the Synchrotron Radiation Center (SRC) is passed through a discharge plasma containing Ti^+. The transmitted light is analyzed by our 3m vacuum echelle spectrometer equipped with VUV sensitive CCD array. The resolving power of our spectrometer/detector array is 300,000. F-values are determined to within 10%.

Direct evidence for radiative charge transfer after inner-shell excitation and ionization of large clusters

NASA Astrophysics Data System (ADS)

Hans, Andreas; Stumpf, Vasili; Holzapfel, Xaver; Wiegandt, Florian; Schmidt, Philipp; Ozga, Christian; Reiß, Philipp; Ben Ltaief, Ltaief; Küstner-Wetekam, Catmarna; Jahnke, Till; Ehresmann, Arno; Demekhin, Philipp V.; Gokhberg, Kirill; Knie, André

2018-01-01

We directly observe radiative charge transfer (RCT) in Ne clusters by dispersed vacuum-ultraviolet photon detection. The doubly ionized Ne2+-{{{N}}{{e}}}n-1 initial states of RCT are populated after resonant 1s-3p photoexcitation or 1s photoionization of Ne n clusters with < n> ≈ 2800. These states relax further producing Ne+-Ne+-{{{N}}{{e}}}n-2 final states, and the RCT photon is emitted. Ab initio calculations assign the observed RCT signal to the{}{{{N}}{{e}}}2+(2{{{p}}}-2{[}1{{D}}]){--}{{{N}}{{e}}}n-1 initial state, while transitions from other possible initial states are proposed to be quenched by competing relaxation processes. The present results are in agreement with the commonly discussed scenario, where the doubly ionized atom in a noble gas cluster forms a dimer which dissipates its vibrational energy on a picosecond timescale. Our study complements the picture of the RCT process in weakly bound clusters, providing information which is inaccessible by charged particle detection techniques.

Theoretical and Experimental Photoelectron Spectroscopy Characterization of the Ground State of Thymine Cation.

PubMed

Majdi, Youssef; Hochlaf, Majdi; Pan, Yi; Lau, Kai-Chung; Poisson, Lionel; Garcia, Gustavo A; Nahon, Laurent; Al-Mogren, Muneerah Mogren; Schwell, Martin

2015-06-11

We report on the vibronic structure of the ground state X̃(2)A″ of the thymine cation, which has been measured using a threshold photoelectron photoion coincidence technique and vacuum ultraviolet synchrotron radiation. The threshold photoelectron spectrum, recorded over ∼0.7 eV above the ionization potential (i.e., covering the whole ground state of the cation) shows rich vibrational structure that has been assigned with the help of calculated anharmonic modes of the ground electronic cation state at the PBE0/aug-cc-pVDZ level of theory. The adiabatic ionization energy has been experimentally determined as AIE = 8.913 ± 0.005 eV, in very good agreement with previous high resolution results. The corresponding theoretical value of AIE = 8.917 eV has been calculated in this work with the explicitly correlated method/basis set (R)CCSD(T)-F12/cc-pVTZ-F12, which validates the theoretical approach and benchmarks its accuracy for future studies of medium-sized biological molecules.

Products from the Oxidation of Linear Isomers of Hexene

PubMed Central

Battin-Leclerc, Frédérique; Rodriguez, Anne; Husson, Benoit; Herbinet, Olivier; Glaude, Pierre-Alexandre; Wang, Zhandong; Cheng, Zhanjun; Qi, Fei

2014-01-01

The experimental study of the oxidation of the three linear isomers of hexene was performed in a quartz isothermal jet-stirred reactor (JSR) at temperatures ranging from 500 to 1100 K including the negative temperature coefficient (NTC) zone, at quasi-atmospheric pressure (1.07 bar), at a residence time of 2 s and with dilute stoichiometric mixtures. The fuel and reaction product mole fractions were measured using online gas chromatography. In the case of 1-hexene, the JSR has also been coupled through a molecular-beam sampling system to a reflectron time-of-flight mass spectrometer combined with tunable synchrotron vacuum ultraviolet photoionization. A difference of reactivity between the three fuels which varies with the temperature range has been observed and is discussed according to the changes in the possible reaction pathways when the double bond is displaced. An enhanced importance of the reactions via the Waddington mechanism and of those of allylic radicals with HO2 radicals can be noted for 2- and 3-hexenes compared to 1-hexene. PMID:24400665

Photon-assisted Beam Probes for Low Temperature Plasmas and Installation of Neutral Beam Probe in Helimak

NASA Astrophysics Data System (ADS)

Garcia de Gorordo, Alvaro; Hallock, Gary A.; Kandadai, Nirmala

2008-11-01

The Heavy Ion Beam Probe (HIBP) diagnostic has successfully measured the electric potential in a number of major plasma devices in the fusion community. In contrast to a Langmuir probe, the HIBP measures the exact electric potential rather than the floating potential. It is also has the advantage of being a very nonperturbing diagnostic. We propose a new photon-assisted beam probe technique that would extend the HIBP type of diagnostics into the low temperature plasma regime. We expect this method to probe plasmas colder than 10 eV. The novelty of the proposed diagnostic is a VUV laser that ionizes the probing particle. Excimer lasers produce the pulsed VUV radiation needed. The lasers on the market don't have a short enough wavelength too ionize any ion directly and so we calculate the population density of excited states in a NLTE plasma. These new photo-ionization techniques can take an instantaneous one-dimensional potential measurement of a plasma and are ideal for nonmagnitized plasmas where continuous time resolution is not required. Also the status of the Neutral Beam Probe installation on the Helimak experiment will be presented.

New design for a microwave discharge lamp.

PubMed

Glangetas, A

1980-03-01

A simple discharge lamp with a microwave cavity fitting inside provides an intense source of VUV resonance radiation for photochemical work inside a vacuum chamber. Good coupling and minimum reabsorption result in better efficiency ( greater, similar1%) and more intense output power (up to 2.5x10(16) quanta s(-1)) than have been achieved previously.

Scintillation properties of Nd 3+, Tm 3+, and Er 3+ doped LuF 3 scintillators in the vacuum ultra violet region

NASA Astrophysics Data System (ADS)

Yanagida, Takayuki; Kawaguchi, Noriaki; Fukuda, Kentaro; Kurosawa, Shunsuke; Fujimoto, Yutaka; Futami, Yoshisuke; Yokota, Yuui; Taniue, Kojiro; Sekiya, Hiroyuki; Kubo, Hidetoshi; Yoshikawa, Akira; Tanimori, Toru

2011-12-01

In order to develop novel vacuum ultra violet (VUV) emitting scintillators, we grew Nd 0.5%, Tm 0.5%, and Er 0.5% doped LuF3 scintillators by the μ-pulling down method, because LuF3 has a very wide band gap and Nd3+, Tm3+, and Er3+ luminescence centers show fast and intense 5d-4f emission in VUV region. Transmittance and X-ray induced radioluminescence were studied in these three samples using our original spectrometer made by Bunkou-Keiki company. In the VUV region, transmittance of 20-60% was achieved for all the samples. The emission peaks appeared at approximately 180, 165, and 164 nm for Nd3+, Tm3+, and Er3+ doped LuF3, respectively. Using PMT R8778 (Hamamatsu), we measured their light yields under 241Am α-ray excitation. Compared with Nd:LaF3 scintillator, which has 33 photoelectrons/5.5 MeV α, Nd:LuF3 and Tm:LuF3 showed 900±90 and 170±20 ph/5.5 MeV-α, respectively. Only for the Nd doped one, we can detect 137Cs 662 keV γ-ray photoabsorption peak and the light yield of 1200±120 ph/MeV was measured. We also investigated their decay time profiles by picosecond pulse X-ray equipped streak camera, and the main decay component of Nd:LuF3 turned out to be 7.63 ns.

Polarization Calibration of the Chromospheric Lyman-Alpha SpectroPolarimeter for a 0.1% Polarization Sensitivity in the VUV Range. Part II: In-Flight Calibration

NASA Astrophysics Data System (ADS)

Giono, G.; Ishikawa, R.; Narukage, N.; Kano, R.; Katsukawa, Y.; Kubo, M.; Ishikawa, S.; Bando, T.; Hara, H.; Suematsu, Y.; Winebarger, A.; Kobayashi, K.; Auchère, F.; Trujillo Bueno, J.; Tsuneta, S.; Shimizu, T.; Sakao, T.; Cirtain, J.; Champey, P.; Asensio Ramos, A.; Štěpán, J.; Belluzzi, L.; Manso Sainz, R.; De Pontieu, B.; Ichimoto, K.; Carlsson, M.; Casini, R.; Goto, M.

2017-04-01

The Chromospheric Lyman-Alpha SpectroPolarimeter is a sounding rocket instrument designed to measure for the first time the linear polarization of the hydrogen Lyman-{α} line (121.6 nm). The instrument was successfully launched on 3 September 2015 and observations were conducted at the solar disc center and close to the limb during the five-minutes flight. In this article, the disc center observations are used to provide an in-flight calibration of the instrument spurious polarization. The derived in-flight spurious polarization is consistent with the spurious polarization levels determined during the pre-flight calibration and a statistical analysis of the polarization fluctuations from solar origin is conducted to ensure a 0.014% precision on the spurious polarization. The combination of the pre-flight and the in-flight polarization calibrations provides a complete picture of the instrument response matrix, and a proper error transfer method is used to confirm the achieved polarization accuracy. As a result, the unprecedented 0.1% polarization accuracy of the instrument in the vacuum ultraviolet is ensured by the polarization calibration.

Slow Photoelectron Spectroscopy and State-Selected Unimolecular Decomposition of Ionized DNA Bases Analogues

NASA Astrophysics Data System (ADS)

Mahjoub, Ahmed; Hochlaf, Majdi; Poisson, Lionel; Garcia, Gustavo A.; Nahon, Laurent

2013-06-01

We studied the single-photon ionization of gas-phase 2-Piperidone (DNA basis analogue) and of its dimer using vacuum-ultraviolet (VUV) synchrotron radiation coupled to a velocity map imaging electron/ion coincidence spectrometer The slow photoelectron spectrum (SPES) of the monomer is dominated by the vibrational transitions to the ground state. These spectra are assigned with the help of theoretical calculations dealing with the equilibrium geometries, electronic-state patterns and evolutions, harmonic and anharmonic wavenumbers. After its formation, dimer is subject of intramolecular isomerization, H transfer and then unimolecular fragmentation processes. The near threshold photofragmentation pattern of the cationic 2-Piperidone cation and its dimer has been recorded. The experimental method yields the fragment intensity as a function of the internal energy deposited into the parent cation. In parallel, ab initio studies on ionic and neutral fragmentation products have been performed with the aim of determining the isomers of the ionic products observed experimentally as well as of their neutral counterparts. L. Nahon, N. De Oliveria,J. F. Gil,B. Pilette,O. Marcouillé, B. La garde and F. Polack Journal of Synchrotron Radiation {19}(4), 508-520; 2012

Acrylonitrile characterization and high energetic photochemistry at Titan temperatures

NASA Astrophysics Data System (ADS)

Toumi, A.; Piétri, N.; Chiavassa, T.; Couturier-Tamburelli, I.

2016-05-01

Laboratory infrared spectra of amorphous and crystalline acrylonitrile (C2H3CN) ices were recorded between 4000 and 650 cm-1. Heating up the acrylonitrile sample to 160 K shows details on the transition between amorphous and crystalline ice at ∼94 K. This molecule can be used as an indicator of the surface temperature of Titan since it is known also to be ∼94 K. The desorption energy of acrylonitrile was determined using two methods (IRTF and mass spectrometries) to be around 35 kJ mol-1. Solid phase acrylonitrile was irradiated with vacuum ultraviolet (VUV) light at low temperatures (20, 70, 95 and 130 K) using a microwave-discharge hydrogen flow lamp. Isoacrylonitrile, cyanoacetylene (HC3N), isocyanoacetylene (HC2NC), acetylene (C2H2) and hydrogen cyanide (HCN) were identified as photoproducts by using FTIR spectroscopy. The branching ratio of each pathway has been calculated for the different temperatures. We have estimated the acrylonitrile, HCN and HC3N νCtbnd N stretching band strengths to be respectively A = 3.98 ×10-18 , A = 1.38 ×10-18 and A = 2.92 ×10-18cmmolecule-1 .

Improved wavelengths for Fe V and Ni V for analysis of spectra of white dwarf stellar stars

NASA Astrophysics Data System (ADS)

Ward, Jacob; Nave, Gillian

2015-08-01

A recent paper by J.C. Berengut et al. tests for a potential variation in the fine-structure constant, α, in the presence of a high gravitational field through spectral analysis of white-dwarf stars. The spectrum of G191-B2B has prominent Fe V and Ni V lines in the vacuum ultraviolet (VUV) region that were used to determine any variation in α via observed shifts in their wavelengths. Although no strong evidence for a variation was found, the authors did find a difference between values obtained for Fe V and Ni V that were indicative of a problem with the laboratory wavelengths. The laboratory wavelengths dominate the uncertainty of the measured variation, so improved values would tighten the constraints on the variation of α.We have re-measured the spectra of Fe V and Ni V spectra in the VUV in order to reduce the wavelength uncertainties and put the two spectra on a consistent wavelength scale. The spectra were produced by a sliding spark light source with electrodes made of invar, an iron nickel alloy. Spectra of Fe V and Ni V were obtained using peak currents of 750-2000 A. The spectra were recorded using the NIST Normal Incidence Vacuum Spectrograph with phosphor image plates and photographic plates as detectors. Wavelengths from 1100 Å to 1800 Å were covered in a single exposure. A spectrum of a Pt/Ne hollow cathode lamp was also recorded for wavelength calibration.The spectra recorded on photographic plates are better resolved than the phosphor image plate spectra and are being measured in two ways. The first measures the positions of the spectral lines on a comparator, traditionally used to measure many archival spectra at NIST. The second uses a commercial image scanner to obtain a digital image of the plate that can be analyzed using line fitting software. Preliminary analysis of these spectra indicates that the literature values of the Fe V and Ni V wavelengths are not on the same scale and differ from our new measurements by up to 0.02 Å in some wavelength regions. We shall present improved analyses of the spectra using both methods and summarize their advantages and disadvantages.

Isomerization and Fragmentation of Cyclohexanone in a Heated Micro-Reactor

NASA Astrophysics Data System (ADS)

Porterfield, Jessica P.; Nguyen, Thanh Lam; Baraban, Joshua H.; Buckingham, Grant; Troy, Tyler; Kostko, Oleg; Ahmed, Musahid; Stanton, John F.; Daily, John W.; Ellison, Barney

2016-06-01

he thermal decomposition of cyclohexanone (C_6H10=O) has been studied in a set of flash-pyrolysis micro-reactors. Samples of C_6H10=O were first observed to decompose at 1200 K. Short residence times of 100 μsec and dilution of samples (<0.1%) isolate unimolecular decomposition. Products were identified by tunable VUV photoionization mass spectroscopy, photoionization appearance thresholds, and complementary matrix infrared absorption spectroscopy. Thermal cracking of cyclohexanone appeared to result from a variety of competing pathways pictured to the right. Isomerization of cyclohexanone to the enol, cyclohexen-1-ol (C_6H_9OH), is followed by retro-Diels-Alder cleavage to CH_2=CH_2 and CH_2=C(OH)-CH=CH_2. Further isomerization of CH_2=C(OH)CH=CH_2 to methyl vinyl ketone (CH_3COCH=CH_2, MVK) was also observed. Photoionization spectra identified both enols, C_6H_9OH and CH=C(OH)CH=CH_2, and the ionization threshold of C_6H_9OH was measured to be 8.2 ± 0.1 eV. At 1200 K, the products of cyclohexanone pyrolysis were found to be: C_6H_9OH, CH_2=C(OH)CH=CH_2, MVK, CH_2CHCH_2, CO, CH_2=C=O, CH_3, CH_2=C=CH_2, CH_2=CH-CH=CH_2, CH_2=CHCH_2CH_3, CH_2=CH_2, and HCCH.

VUV-absorption cross section of carbon dioxide from 150 to 800 K and applications to warm exoplanetary atmospheres

NASA Astrophysics Data System (ADS)

Venot, O.; Bénilan, Y.; Fray, N.; Gazeau, M.-C.; Lefèvre, F.; Es-sebbar, Et.; Hébrard, E.; Schwell, M.; Bahrini, C.; Montmessin, F.; Lefèvre, M.; Waldmann, I. P.

2018-01-01

Context. Most exoplanets detected so far have atmospheric temperatures significantly higher than 300 K. Often close to their star, they receive an intense UV photons flux that triggers important photodissociation processes. The temperature dependency of vacuum ultraviolet (VUV) absorption cross sections are poorly known, leading to an undefined uncertainty in atmospheric models. Similarly, data measured at low temperatures similar to those of the high atmosphere of Mars, Venus, and Titan are often lacking. Aims: Our aim is to quantify the temperature dependency of the VUV absorption cross sections of important molecules in planetary atmospheres. We want to provide high-resolution data at temperatures prevailing in these media, and a simple parameterisation of the absorption in order to simplify its use in photochemical models. This study focuses on carbon dioxide (CO2). Methods: We performed experimental measurements of CO2 absorption cross sections with synchrotron radiation for the wavelength range (115-200 nm). For longer wavelengths (195-230 nm), we used a deuterium lamp and a 1.5 m Jobin-Yvon spectrometer. We used these data in our one-dimensional (1D) thermo-photochemical model in order to study their impact on the predicted atmospheric compositions. Results: The VUV absorption cross section of CO2 increases with the temperature. The absorption we measured at 150 K seems to be close to the absorption of CO2 in the fundamental ground state. The absorption cross section can be separated into two parts: a continuum and a fine structure superimposed on the continuum. The variation in the continuum of absorption can be represented by the sum of three Gaussian functions. Using data at high temperature in thermo-photochemical models significantly modifies the abundance and the photodissociation rates of many species in addition to CO2, such as methane and ammonia. These deviations have an impact on synthetic transmission spectra, leading to variations of up to 5 ppm. Conclusions: We present a full set of high-resolution (Δλ = 0.03 nm) absorption cross sections of CO2 from 115 to 230 nm for temperatures ranging from 150 to 800 K. A parameterisation allows us to calculate the continuum of absorption in this wavelength range. Extrapolation at higher temperature has not been validated experimentally and therefore should be used with caution. Similar studies on other major species are necessary to improve our understanding of planetary atmospheres. The data presented in Fig. 1 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/609/A34

Effects of space vacuum and solar ultraviolet irradiation (254 nanometers) on the colony forming ability of Bacillus subtilis spores

NASA Technical Reports Server (NTRS)

Buecker, H.; Horneck, G.; Wollenhaupt, H.

1973-01-01

Bacillus subtilis spores are highly resistant to harsh environments. Therefore, in the Apollo 16 Microbial Response to Space Environment Experiment (M191), these spores were exposed to space vacuum or solar ultraviolet irradiation, or both, to estimate the change of survival for terrestrial organisms in space. The survival of the spores was determined in terms of colony-forming ability. Comparison of the flight results with results of simulation experiments on earth applying high vacuum or ultraviolet irradiation, or both, revealed no remarkable difference. Simultaneous exposure to both these space factors resulted in a synergistic effect (that is, an ultraviolet supersensitivity). Therefore, the change of survival in space is assumed to depend on the degree of protection against solar ultraviolet irradiation.

Electron impact ionization in the vicinity of comets

NASA Astrophysics Data System (ADS)

Cravens, T. E.; Kozyra, J. U.; Nagy, A. F.; Gombosi, T. I.; Kurtz, M.

1987-07-01

The solar wind interacts very strongly with the extensive cometary coma, and the various interaction processes are initiated by the ionization of cometary neutrals. The main ionization mechanism far outside the cometary bow shock is photoionization by solar extreme ultraviolet radiation.Electron distributions measured in the vicinity of comets Halley and Giacobini-Zinner by instruments on the VEGA and ICE spacecraft, respectively, are used to calculate electron impact ionization frequencies. Ionization by electrons is of comparable importance to photoionization in the magnetosheaths of Comets Halley and Giacobini-Zinner. The ionization frequency in the inner part of the cometary plasma region of comet Halley is several times greater than the photoionization value. Tables of ionization frequencies as functions of electron temperature are presented for H2O, CO2, CO, O, N2, and H.

Fast temporal correlation between hard X-ray and ultraviolet continuum brightenings

NASA Technical Reports Server (NTRS)

Machado, Marcos E.; Mauas, Pablo J.

1986-01-01

Recent Solar Maximum Mission (SMM) observations have shown fast and simultaneous increases in hard X-rays (HXR, E25 keV) and ultraviolet continuum (UVC, lambda lambda approx. equals 1600 and 1388 A) radiation. A simple and natural explanation is given for this phenomenon to happen, which does not involve extreme conditions for energy transport processes, and confirms earlier results on the effect of XUV photoionization in the solar atmosphere.

Resonances in the Photoionization Cross Sections of Atomic Nitrogen Shape the Far-ultraviolet Spectrum of the Bright Star in 47 Tucanae

NASA Astrophysics Data System (ADS)

Dixon, William V.; Chayer, Pierre

2013-08-01

The far-ultraviolet spectrum of the Bright Star (B8 III) in 47 Tuc (NGC 104) shows a remarkable pattern: it is well fit by local thermodynamic equilibrium models at wavelengths longer than Lyβ, but at shorter wavelengths it is fainter than the models by a factor of two. A spectrum of this star obtained with the Far Ultraviolet Spectroscopic Explorer shows broad absorption troughs with sharp edges at 995 and 1010 Å and a deep absorption feature at 1072 Å none of which are predicted by the models. We find that these features are caused by resonances in the photoionization cross sections of the first and second excited states of atomic nitrogen (2s 2 2p 3 2 D 0 and 2 P 0). Using cross sections from the Opacity Project, we can reproduce these features, but only if we use the cross sections at their full resolution, rather than the resonance-averaged cross sections usually employed to model stellar atmospheres. These resonances are strongest in stellar atmospheres with enhanced nitrogen and depleted carbon abundances, a pattern typical of post-asymptotic giant branch stars.

Multiplexed photoionization mass spectrometry investigation of the O( 3P) + propyne reaction

DOE PAGES

Savee, John D.; Borkar, Sampada; Welz, Oliver; ...

2015-05-18

Here, the reaction of O( 3P) + propyne (C 3H 4) was investigated at 298 K and 4 Torr using time-resolved multiplexed photoionization mass spectrometry and a synchrotron-generated tunable vacuum ultraviolet light source. The time-resolved mass spectra of the observed products suggest five major channels under our conditions: C 2H 3 + HCO, CH 3 + HCCO, H + CH 3CCO, C 2H 4 + CO, and C 2H 2 + H 2 + CO. The relative branching ratios for these channels were found to be 1.00, (0.35 ± 0.11), (0.18 ± 0.10), (0.73 ± 0.27), and (1.31 ± 0.62).more » In addition, we observed signals consistent with minor production of C 3H 3 + OH and H 2 + CH 2CCO, although we cannot conclusively assign them as direct product channels from O( 3P) + propyne. The direct abstraction mechanism plays only a minor role (≤1%), and we estimate that O( 3P) addition to the central carbon of propyne accounts for 10% of products, with addition to the terminal carbon accounting for the remaining 89%. The isotopologues observed in experiments using d1-propyne (CH 3CCD) and analysis of product branching in light of previously computed stationary points on the singlet and triplet potential energy surfaces (PESs) relevant to O( 3P) + propyne suggest that, under our conditions, (84 ± 14)% of the observed product channels from O( 3P) + propyne result from intersystem crossing from the initial triplet PES to the lower-lying singlet PES.« less

Fragmentation of mercury compounds under ultraviolet light irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kokkonen, E.; Hautala, L.; Jänkälä, K.

2015-08-21

Ultraviolet light induced photofragmentation of mercury compounds is studied experimentally with electron energy resolved photoelectron-photoion coincidence techniques and theoretically with computational quantum chemical methods. A high resolution photoelectron spectrum using synchrotron radiation is presented. Fragmentation of the molecule is studied subsequent to ionization to the atomic-mercury-like d orbitals. State dependent fragmentation behaviour is presented and specific reactions for dissociation pathways are given. The fragmentation is found to differ distinctly in similar orbitals of different mercury compounds.

Corona And Ultraviolet Equipment For Testing Materials

NASA Technical Reports Server (NTRS)

Laue, Eric G.

1993-01-01

Two assemblies of laboratory equipment developed for use in testing abilities of polymers, paints, and other materials to withstand ultraviolet radiation and charged particles. One is vacuum ultraviolet source built around commercial deuterium lamp. Other exposes specimen in partial vacuum to both ultraviolet radiation and brush corona discharge. Either or both assemblies used separately or together to simulate approximately combination of solar radiation and charged particles encountered by materials aboard spacecraft in orbit around Earth. Also used to provide rigorous environmental tests of materials exposed to artificial ultraviolet radiation and charged particles in industrial and scientific settings or to natural ultraviolet radiation and charged particles aboard aircraft at high altitudes.

Electron Spectroscopy: Ultraviolet and X-Ray Excitation.

ERIC Educational Resources Information Center

Baker, A. D.; And Others

1980-01-01

Reviews recent growth in electron spectroscopy (54 papers cited). Emphasizes advances in instrumentation and interpretation (52); photoionization, cross-sections and angular distributions (22); studies of atoms and small molecules (35); transition, lanthanide and actinide metal complexes (50); organometallic (12) and inorganic compounds (2);…

Atomic Oscillator Strengths in the Vacuum Ultraviolet

NASA Technical Reports Server (NTRS)

Nave, Gillian; Sansonetti, Craig J.; Szabo, Csilla I.

2006-01-01

We have developed techniques to measure branching fractions in the vacuum ultraviolet using diffraction grating spectroscopy and phosphor image plates as detectors. These techniques have been used to measure branching fractions in Fe II that give prominent emission lines in astrophysical objects.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fu, H.B.; Hu, Y.J.; Bernstein, E.R.

Small methanol clusters are formed by expanding a mixture of methanol vapor seeded in helium and are detected using vacuum UV (vuv) (118 nm) single-photon ionization/linear time-of-flight mass spectrometer (TOFMS). Protonated cluster ions, (CH{sub 3}OH){sub n-1}H{sup +} (n=2-8), formed through intracluster ion-molecule reactions following ionization, essentially correlate to the neutral clusters, (CH{sub 3}OH){sub n}, in the present study using 118 nm light as the ionization source. Both experimental and Born-Haber calculational results clarify that not enough excess energy is released into protonated cluster ions to initiate further fragmentation in the time scale appropriate for linear TOFMS. Size-specific spectra for (CH{submore » 3}OH){sub n} (n=4 to 8) clusters in the OH stretch fundamental region are recorded by IR+vuv (118 nm) nonresonant ion-dip spectroscopy through the detection chain of IR multiphoton predissociation and subsequent vuv single-photon ionization. The general structures and gross features of these cluster spectra are consistent with previous theoretical calculations. The lowest-energy peak contributed to each cluster spectrum is redshifted with increasing cluster size from n=4 to 8, and limits near {approx}3220 cm{sup -1} in the heptamer and octamer. Moreover, IR+vuv nonresonant ionization detected spectroscopy is employed to study the OH stretch first overtone of the methanol monomer. The rotational temperature of the clusters is estimated to be at least 50 K based on the simulation of the monomer rotational envelope under clustering conditions.« less

Detailed product analysis during the low temperature oxidation of n-butane

PubMed Central

Herbinet, Olivier; Battin-Leclerc, Frédérique; Bax, Sarah; Le Gall, Hervé; Glaude, Pierre-Alexandre; Fournet, René; Zhou, Zhongyue; Deng, Liulin; Guo, Huijun; Xie, Mingfeng; Qi, Fei

2013-01-01

The products obtained from the low-temperature oxidation of n-butane in a jet-stirred reactor (JSR) have been analysed using two methods: gas chromatography analysis of the outlet gas and reflectron time-of-flight mass spectrometry. The mass spectrometer was combined with tunable synchrotron vacuum ultraviolet photoionization and coupled with a JSR via a molecular-beam sampling system. Experiments were performed under quasi-atmospheric pressure, for temperatures between 550 and 800 K, at a mean residence time of 6s and with a stoichiometric n-butane/oxygen/argon mixture (composition = 4/26/70 in mol %). 36 reaction products have been quantified, including addition to the usual oxidation products, acetic acid, hydrogen peroxide, C1, C2 and C4 alkylhydroperoxides and C4 ketohydroperoxides. Evidence of the possible formation of products (dihydrofuranes, furanones) derived from cyclic ethers has also been found. The performance of a detailed kinetic model of the literature has been assessed with the simulation of the formation of this extended range of species. These simulations have also allowed the analysis of possible pathways for the formation of some obtained products. PMID:21031192

ON THE FORMATION OF AMIDE POLYMERS VIA CARBONYL–AMINO GROUP LINKAGES IN ENERGETICALLY PROCESSED ICES OF ASTROPHYSICAL RELEVANCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Förstel, Marko; Maksyutenko, Pavlo; Jones, Brant M.

2016-04-01

We report on the formation of organic amide polymers via carbonyl–amino group linkages in carbon monoxide and ammonia bearing energetically processed ices of astrophysical relevance. The first group comprises molecules with one carboxyl group and an increasing number of amine moieties starting with formamide (45 u), urea (60 u), and hydrazine carboxamide (75 u). The second group consists of species with two carboxyl (58 u) and up to three amine groups (73 u, 88 u, and 103 u). The formation and polymerization of these linkages from simple inorganic molecules via formamide und urea toward amide polymers is discussed in anmore » astrophysical and astrobiological context. Our results show that long chain molecules, which are closely related to polypeptides, easily form by energetically processing simple, inorganic ices at very low temperatures and can be released into the gas phase by sublimation of the ices in star-forming regions. Our experimental results were obtained by employing reflectron time-of-flight mass spectroscopy, coupled with soft, single photon vacuum ultraviolet photoionization; they are complemented by theoretical calculations.« less

Study of the Low Temperature Oxidation of Propane

PubMed Central

Cord, Maximilien; Husson, Benoit; Huerta, Juan Carlos Lizardo; Herbinet, Olivier; Glaude, Pierre-Alexandre; Fournet, René; Sirjean, Baptiste; Battin-Leclerc, Frédérique; Ruiz-Lopez, Manuel; Wang, Zhandong; Xie, Mingfeng; Cheng, Zhanjun; Qi, Fei

2013-01-01

The low-temperature oxidation of propane was investigated using a jet-stirred reactor at atmospheric pressure and two methods of analysis: gas chromatography and synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) with direct sampling through a molecular jet. The second method allowed the identification of products, such as molecules with hydroperoxy functions, which are not stable enough to be detected by gas chromatography. Mole fractions of the reactants and reaction products were measured as a function of the temperature (530-730 K), with a particular attention to reaction products involved in the low temperature oxidation, such as cyclic ethers, aldehydes, alcohols, ketones, and hydroperoxides. A new model has been obtained from an automatically generated one, which was used as a starting point, with a large number of re-estimated thermochemical and kinetic data. The kinetic data of the most sensitive reactions, i.e., isomerizations of alkylperoxy radicals and the subsequent decompositions, have been calculated at the CBS-QB3 level of theory. The model allows a satisfactory prediction of the experimental data. A flow rate analysis has allowed highlighting the important reaction channels. PMID:23181456

Flame experiments at the advanced light source: new insights into soot formation processes.

PubMed

Hansen, Nils; Skeen, Scott A; Michelsen, Hope A; Wilson, Kevin R; Kohse-Höinghaus, Katharina

2014-05-26

The following experimental protocols and the accompanying video are concerned with the flame experiments that are performed at the Chemical Dynamics Beamline of the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory(1-4). This video demonstrates how the complex chemical structures of laboratory-based model flames are analyzed using flame-sampling mass spectrometry with tunable synchrotron-generated vacuum-ultraviolet (VUV) radiation. This experimental approach combines isomer-resolving capabilities with high sensitivity and a large dynamic range(5,6). The first part of the video describes experiments involving burner-stabilized, reduced-pressure (20-80 mbar) laminar premixed flames. A small hydrocarbon fuel was used for the selected flame to demonstrate the general experimental approach. It is shown how species' profiles are acquired as a function of distance from the burner surface and how the tunability of the VUV photon energy is used advantageously to identify many combustion intermediates based on their ionization energies. For example, this technique has been used to study gas-phase aspects of the soot-formation processes, and the video shows how the resonance-stabilized radicals, such as C3H3, C3H5, and i-C4H5, are identified as important intermediates(7). The work has been focused on soot formation processes, and, from the chemical point of view, this process is very intriguing because chemical structures containing millions of carbon atoms are assembled from a fuel molecule possessing only a few carbon atoms in just milliseconds. The second part of the video highlights a new experiment, in which an opposed-flow diffusion flame and synchrotron-based aerosol mass spectrometry are used to study the chemical composition of the combustion-generated soot particles(4). The experimental results indicate that the widely accepted H-abstraction-C2H2-addition (HACA) mechanism is not the sole molecular growth process responsible for the formation of the observed large polycyclic aromatic hydrocarbons (PAHs).

Flame Experiments at the Advanced Light Source: New Insights into Soot Formation Processes

PubMed Central

Hansen, Nils; Skeen, Scott A.; Michelsen, Hope A.; Wilson, Kevin R.; Kohse-Höinghaus, Katharina

2014-01-01

The following experimental protocols and the accompanying video are concerned with the flame experiments that are performed at the Chemical Dynamics Beamline of the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory1-4. This video demonstrates how the complex chemical structures of laboratory-based model flames are analyzed using flame-sampling mass spectrometry with tunable synchrotron-generated vacuum-ultraviolet (VUV) radiation. This experimental approach combines isomer-resolving capabilities with high sensitivity and a large dynamic range5,6. The first part of the video describes experiments involving burner-stabilized, reduced-pressure (20-80 mbar) laminar premixed flames. A small hydrocarbon fuel was used for the selected flame to demonstrate the general experimental approach. It is shown how species’ profiles are acquired as a function of distance from the burner surface and how the tunability of the VUV photon energy is used advantageously to identify many combustion intermediates based on their ionization energies. For example, this technique has been used to study gas-phase aspects of the soot-formation processes, and the video shows how the resonance-stabilized radicals, such as C3H3, C3H5, and i-C4H5, are identified as important intermediates7. The work has been focused on soot formation processes, and, from the chemical point of view, this process is very intriguing because chemical structures containing millions of carbon atoms are assembled from a fuel molecule possessing only a few carbon atoms in just milliseconds. The second part of the video highlights a new experiment, in which an opposed-flow diffusion flame and synchrotron-based aerosol mass spectrometry are used to study the chemical composition of the combustion-generated soot particles4. The experimental results indicate that the widely accepted H-abstraction-C2H2-addition (HACA) mechanism is not the sole molecular growth process responsible for the formation of the observed large polycyclic aromatic hydrocarbons (PAHs). PMID:24894694

Window contamination on Expose-R

NASA Astrophysics Data System (ADS)

Demets, R.; Bertrand, M.; Bolkhovitinov, A.; Bryson, K.; Colas, C.; Cottin, H.; Dettmann, J.; Ehrenfreund, P.; Elsaesser, A.; Jaramillo, E.; Lebert, M.; van Papendrecht, G.; Pereira, C.; Rohr, T.; Saiagh, K.

2015-01-01

Expose is a multi-user instrument for astrobiological and astrochemical experiments in space. Installed at the outer surface of the International Space Station, it enables investigators to study the impact of the open space environment on biological and biochemical test samples. Two Expose missions have been completed so far, designated as Expose-E (Rabbow et al. 2012) and Expose-R (Rabbow et al. this issue). One of the space-unique environmental factors offered by Expose is full-spectrum, ultraviolet (UV)-rich electromagnetic radiation from the Sun. This paper describes and analyses how on Expose-R, access of the test samples to Solar radiation degraded during space exposure in an unpredicted way. Several windows in front of the Sun-exposed test samples acquired a brown shade, resulting in a reduced transparency in visible light, UV and vacuum UV (VUV). Post-flight investigations revealed the discolouration to be caused by a homogenous film of cross-linked organic polymers at the inside of the windows. The chemical signature varied per sample carrier. No such films were found on windows from sealed, pressurized compartments, or on windows that had been kept out of the Sun. This suggests that volatile compounds originating from the interior of the Expose facility were cross-linked and photo-fixed by Solar irradiation at the rear side of the windows. The origin of the volatiles was not fully identified; most probably there was a variety of sources involved including the biological test samples, adhesives, plastics and printed circuit boards. The outer surface of the windows (pointing into space) was chemically impacted as well, with a probable effect on the transparency in VUV. The reported analysis of the window contamination on Expose-R is expected to help the interpretation of the scientific results and offers possibilities to mitigate this problem on future missions - in particular Expose-R2, the direct successor of Expose-R.

Vacuum ultraviolet photoabsorption spectroscopy of CH2Cl2 and CD2Cl2 in the energy region 50,000-95,000 cm-1

NASA Astrophysics Data System (ADS)

Mandal, Anuvab; Singh, Param Jeet; Shastri, Aparna; Jagatap, B. N.

2014-12-01

A consolidated study of the VUV absorption spectra of CH2Cl2 and CD2Cl2 in the 50,000-95,000 cm-1 region using synchrotron radiation is presented. Rydberg series and vibronic analysis are carried out and supported by quantum chemical calculations. The broad absorption band of CH2Cl2 in the region 50,000-60,000 cm-1 is attributed to the valence states 11B2, 11B1 and 11A1. Most of the bands in the 60,000-95,000 cm-1 region are fitted to Rydberg series of ns, np and nd type converging to the first four ionization potentials 11.320, 11.357, 12.152 and 12.271 eV of CH2Cl2 arising from excitation of an electron from one of the four outermost Cl non-bonding orbitals (2b1, 3b2, 1a2 and 4a1). Vertical excited states of CH2Cl2 calculated using TDDFT are correlated with experimentally observed electronic states based on the symmetries of the initial and final MOs involved in a transition. A few Rydberg transitions viz. 2b1→5s, 4p, 5p, 6p; 3b2→4p, 5p; 1a2→4p are accompanied by vibronic features. Observed vibronic bands are assigned mainly to the CCl symmetric stretch (ν3‧) mode with smaller contributions from the CH symmetric stretch (ν1‧), CH2 bend (ν2‧) and CH2 wag (ν8‧) modes. Assignments are corroborated by comparison with the VUV absorption spectrum of the deuterated isotopologue CD2Cl2, reported here for the first time. The high underlying intensities seen in several sub-regions are explained by valence or valence-Rydberg mixed type transitions predicted with high oscillator strengths by the TDDFT calculations.

Toroidal Variable-Line-Space Gratings: The Good, the Bad and The Ugly

NASA Technical Reports Server (NTRS)

West, Edward A.; Kobayashi, Ken; Cirtain, Jonathan; Gary, Allen; Davis, John; Reader, Joseph

2009-01-01

Toroidal variable-line-space (VLS) gratings are an important factor in the design of an efficient VUV solar telescope that will measure the CIV (155nm) and MgII (280nm) emissions lines in the Sun's transition region. In 1983 Kita and Harada described spherical VLS gratings but the technology to commercially fabricate these devices is a recent development, especially for toroidal surfaces. This paper will describe why this technology is important in the development of the Solar Ultraviolet Magnetograph Investigation (SUMI) sounding rocket program (the good), the delays due to the conversion between the TVLS grating design and the optical fabrication (the bad), and finally the optical testing, alignment and tolerancing of the gratings (the ugly). The Solar Ultraviolet Magnetograph Investigation, SUMI, has been reported in several papers since this program began in 2000. The emphasis of this paper is to describe SUMI's Toroidal Variable-Line-Space (TVLS) gratings. These gratings help SUMI meet its scientific goals which require both high spectral resolution and high optical efficiency for magnetic field measurements in the vacuum ultraviolet wavelength band of the solar spectrum (the good). Unfortunately, the technology readiness level of these gratings has made their implementation difficult, especially for a sounding rocket payload (the bad). Therefore, this paper emphasizes the problems and solutions that were developed to use these gratings in SUMI (the ugly). Section 2 contains a short review of the scientific goals of SUMI and why this mission is important in the understanding of the 3D structure of the magnetic field on the Sun. The flight hardware that makes up the SUMI payload is described in Section 3 with emphasis on those components that affect the TVLS gratings. Section 4 emphasizes the alignment, testing and optical modeling that were developed to optimize the performance of these gratings.

Characterization of combustion-generated carbonaceous nanoparticles by size-dependent ultraviolet laser photoionization.

PubMed

Commodo, Mario; Sgro, Lee Anne; Minutolo, Patrizia; D'Anna, Andrea

2013-05-16

Photoelectric charging of particles is a powerful tool for online characterization of submicrometer aerosol particles. Indeed photoionization based techniques have high sensitivity and chemical selectivity. Moreover, they yield information on electronic properties of the material and are sensitive to the state of the surface. In the present study the photoionization charging efficiency, i.e., the ratio between the generated positive ions and the corresponding neutral ones, for different classes of flame-generated carbonaceous nanoparticles was measured. The fifth harmonics of a Nd:YAG laser, 213 nm (5.82 eV), was used as an ionization source for the combustion generated nanoparticles, whereas a differential mobility analyzer (DMA) coupled to a Faraday cup electrometer was used for particle classification and detection. Carbonaceous nanoparticles in the nucleation mode, i.e., sizes ranging from 1 to 10 nm, show a photoionization charging efficiency clearly dependent on the flame conditions. In particular, we observed that the richer the flame is, i.e., the higher the equivalent ratio is, the higher the photon charging efficiency is. We hypothesized that such an increase in the photoionization propensity of the carbonaceous nanoparticles from richer flame condition is associated to the presence within the particles of larger aromatic moieties. The results clearly show that photoionization is a powerful diagnostic tool for the physical-chemical characterization of combustion aerosol, and it may lead to further insights into the soot formation mechanism.

Application of Laser Plasma Sources of Soft X-rays and Extreme Ultraviolet (EUV) in Imaging, Processing Materials and Photoionization Studies

NASA Astrophysics Data System (ADS)

Fiedorowicz, H.; Bartnik, A.; Wachulak, P. W.; Jarocki, R.; Kostecki, J.; Szczurek, M.; Ahad, I. U.; Fok, T.; Szczurek, A.; Wȩgrzyński, Ł.

In the paper we present new applications of laser plasma sources of soft X-rays and extreme ultraviolet (EUV) in various areas of plasma physics, nanotechnology and biomedical engineering. The sources are based on a gas puff target irradiated with nanosecond laser pulses from commercial Nd: YAG lasers, generating pulses with time duration from 1 to 10 ns and energies from 0.5 to 10 J at a 10 Hz repetition rate. The targets are produced with the use of a double valve system equipped with a special nozzle to form a double-stream gas puff target which allows for high conversion efficiency of laser energy into soft X-rays and EUV without degradation of the nozzle. The sources are equipped with various optical systems to collect soft X-ray and EUV radiation and form the radiation beam. New applications of these sources in imaging, including EUV tomography and soft X-ray microscopy, processing of materials and photoionization studies are presented.

Charge Transfer Dissociation of Complex Oligosaccharides: Comparison with Collision-Induced Dissociation and Extreme Ultraviolet Dissociative Photoionization

NASA Astrophysics Data System (ADS)

Ropartz, David; Li, Pengfei; Fanuel, Mathieu; Giuliani, Alexandre; Rogniaux, Hélène; Jackson, Glen P.

2016-10-01

The structural characterization of oligosaccharides still challenges the field of analytical chemistry. Tandem mass spectrometry offers many advantages toward this aim, although the generic fragmentation method (low-energy collision-induced dissociation) shows clear limitations and is often insufficient to retrieve some essential structural information on these molecules. In this work, we present the first application of helium charge transfer dissociation (He-CTD) to characterize the structure of complex oligosaccharides. We compare this method with low-energy collision-induced dissociation and extreme-ultraviolet dissociative photoionization (XUV-DPI), which was shown previously to ensure the successful characterization of complex glycans. Similarly to what could be obtained by XUV-DPI, He-CTD provides a complete description of the investigated structures by producing many informative cross-ring fragments and no ambiguous fragmentation. Unlike XUV-DPI, which is performed at a synchrotron source, He-CTD has the undeniable advantage of being implementable in a conventional benchtop ion trap in a conventional laboratory setting.

Examination of Laser Microprobe Vacuum Ultraviolet Ionization Mass Spectrometry with Application to Mapping Mars Returned Samples

NASA Astrophysics Data System (ADS)

Burton, A. S.; Berger, E. L.; Locke, D. R.; Lewis, E. K.; Moore, J. F.

2018-04-01

Laser microprobe of surfaces utilizing a two laser setup whereby the desorption laser threshold is lowered below ionization, and the resulting neutral plume is examined using 157nm Vacuum Ultraviolet laser light for mass spec surface mapping.

The use of isoprene as a novel dopant in negative ion atmospheric pressure photoionization mass spectrometry coupled to high-performance liquid chromatography.

PubMed

Dousty, Faezeh; O'Brien, Rob

2015-06-15

As in the case with positive ion atmospheric pressure photoionization (PI-APPI), the addition of dopants significantly improves the sensitivity of negative ion APPI (NI-APPI). However, the research on dopant-assisted-NI-APPI has been quite limited compared to the studies on dopant-assisted PI-APPI. This work presents the potential of isoprene as a novel dopant for NI-APPI. Thirteen compounds, possessing suitable gas-phase ion energetic properties in order to make stable negative ions, were selected. Dopants were continuously introduced into a tee junction prior to the ion source through a fused-silica capillary, while analytes were directly injected into the same tee. Then both were mixed with the continuous solvent from high-performance liquid chromatography (HPLC), nebulized, and entered the source. The nebulized stream was analyzed by APPI tandem quadrupole mass spectrometry in the negative ion mode. The results obtained using isoprene were compared with those obtained by using toluene as a dopant and dopant-free NI-APPI. Isoprene enhanced the ionization intensities of the studied compounds, which were found to be comparable and, in some cases, more effective than toluene. The mechanisms leading to the observed set of negative analyte ions were also discussed. Because in NI-APPI, thermal electrons, which are produced during the photoionization of a dopant, are considered the main reagent ions, both isoprene and toluene promoted the ionization of analytes through the same mechanisms, as expected. Isoprene was shown to perform well as a novel dopant for NI-APPI. Isoprene has a high photoabsorption cross section in the VUV region; therefore, its photoionization leads to a highly effective production of thermal electrons, which further promotes the ionization of analytes. In addition, isoprene is environmentally benign and less toxic compared to currently used dopants. Copyright © 2015 John Wiley & Sons, Ltd.

Determination of Ionospheric Electron Density Profiles from Satellite UV (Ultraviolet) Emission Measurements, Fiscal Year 1984.

DTIC Science & Technology

1985-04-26

distribution function. It is from the calculated distribution function that the photoelectron flux can be derived. The VUV daytime emissions that we are...OECLASSIPICATIONUOOWNdGRADING SCHEDULE Apoe o ulcrlae N/A distribution unlimited .PE RPORMING ORGANIZATION REPORT NUMBER41S( 5. MONITORING ORGANIZATION REPORT...EDP for systems users. This report considers the following ionospheric subregions: (a) the daytime mid- latitude ionosphere from, 90 to 1000 km, (b

Combined Experimental and Computational Study on the Unimolecular Decomposition of JP-8 Jet Fuel Surrogates. I. n-Decane (n-C10H22).

PubMed

Zhao, Long; Yang, Tao; Kaiser, Ralf I; Troy, Tyler P; Ahmed, Musahid; Belisario-Lara, Daniel; Ribeiro, Joao Marcelo; Mebel, Alexander M

2017-02-16

Exploiting a high temperature chemical reactor, we explored the pyrolysis of helium-seeded n-decane as a surrogate of the n-alkane fraction of Jet Propellant-8 (JP-8) over a temperature range of 1100-1600 K at a pressure of 600 Torr. The nascent products were identified in situ in a supersonic molecular beam via single photon vacuum ultraviolet (VUV) photoionization coupled with a mass spectroscopic analysis of the ions in a reflectron time-of-flight mass spectrometer (ReTOF). Our studies probe, for the first time, the initial reaction products formed in the decomposition of n-decane-including radicals and thermally labile closed-shell species effectively excluding mass growth processes. The present study identified 18 products: molecular hydrogen (H 2 ), C2 to C7 1-alkenes [ethylene (C 2 H 4 ) to 1-heptene (C 7 H 14 )], C1-C3 radicals [methyl (CH 3 ), vinyl (C 2 H 3 ), ethyl (C 2 H 5 ), propargyl (C 3 H 3 ), allyl (C 3 H 5 )], small C1-C3 hydrocarbons [methane (CH 4 ), acetylene (C 2 H 2 ), allene (C 3 H 4 ), methylacetylene (C 3 H 4 )], along with higher-order reaction products [1,3-butadiene (C 4 H 6 ), 2-butene (C 4 H 8 )]. On the basis of electronic structure calculations, n-decane decomposes initially by C-C bond cleavage (excluding the terminal C-C bonds) producing a mixture of alkyl radicals from ethyl to octyl. These alkyl radicals are unstable under the experimental conditions and rapidly dissociate by C-C bond β-scission to split ethylene (C 2 H 4 ) plus a 1-alkyl radical with the number of carbon atoms reduced by two and 1,4-, 1,5-, 1,6-, or 1,7-H shifts followed by C-C β-scission producing alkenes from propene to 1-octene in combination with smaller 1-alkyl radicals. The higher alkenes become increasingly unstable with rising temperature. When the C-C β-scission continues all the way to the propyl radical (C 3 H 7 ), it dissociates producing methyl (CH 3 ) plus ethylene (C 2 H 4 ). Also, at higher temperatures, hydrogen atoms can abstract hydrogen from C 10 H 22 to yield n-decyl radicals, while methyl (CH 3 ) can also abstract hydrogen or recombine with hydrogen to form methane. These n-decyl radicals can decompose via C-C-bond β-scission to C3 to C9 alkenes.

Cleaning Spectralon(TM) To Maintain Reflectance Properties

NASA Technical Reports Server (NTRS)

Stiegman, Albert; Bruegge, Carl; Plett, Gary

1996-01-01

Hydrocarbon impurities removed and stability of Spectralon(TM) towards ultraviolet and vacuum-ultraviolet radiation greatly enhanced by baking material at 90 degrees C for 24 h in vacuum of 10 to negative 5th power torr. After vacuum bake, material handled with white cotton, lint-free gloves in clean environment (preferably cleanroom). As material has tendency to reabsorb volatile organic compounds, stored and transported only in clean, air-tight (preferably glass or oil-free metal) containers.

Surface exciton emission of MgO crystals

NASA Astrophysics Data System (ADS)

Kuang, Wen-Jian; Li, Qing; Chen, Yu-Xiang; Hu, Kai; Wang, Ning-Hui; Xing, Fang-Li; Yan, Qun; Sun, Shuai-Shuai; Huang, Yan; Tao, Ye; Tolner, Harm

2013-09-01

MgO crystals have been exposed to vacuum ultraviolet (VUV) radiation from a synchrotron, with energies up to 9 eV, and the emitted light, at wavelengths above 200 nm, was observed. It is concluded that bulk excitons, play an important role in the diffusion of energy inside MgO crystals, resulting in 5.85 eV (212 nm) emission from the MgO terraces of large (0.2-2 µm) MgO : F crystals. In the case of aliovalent impurity doping, then the bulk exciton energy is also transferred to the Vk centres and 5.3 eV (235 nm) light is emitted. Both fluorine and silicon doping appear to promote UV surface emission, acting similarly to an ns2 ion inside MgO, while strong scandium doping is killing the surface emission completely. The 212 nm surface UV emission and the 235 nm bulk UV emission can be excited only at the bandgap edge. Broadband visible light, centred around 400 nm, is also emitted. Contrary to the UV emission, this is not generated when excited at the bandgap edge; instead, we find that it is only excited at sub-bandgap energies, with a maximum at the 5C surface excitation energy of 5.71 eV (217 nm) for the MgO terraces.

Secondary organic aerosol formation from ozone-initiated reactions with nicotine and secondhand tobacco smoke

NASA Astrophysics Data System (ADS)

Sleiman, Mohamad; Destaillats, Hugo; Smith, Jared D.; Liu, Chen-Lin; Ahmed, Musahid; Wilson, Kevin R.; Gundel, Lara A.

2010-11-01

We used controlled laboratory experiments to evaluate the aerosol-forming potential of ozone reactions with nicotine and secondhand smoke. Special attention was devoted to real-time monitoring of the particle size distribution and chemical composition of SOA as they are believed to be key factors determining the toxicity of SOA. The experimental approach was based on using a vacuum ultraviolet photon ionization time-of-flight aerosol mass spectrometer (VUV-AMS), a scanning mobility particle sizer (SMPS) and off-line thermal desorption coupled to mass spectrometry (TD-GC-MS) for gas-phase byproducts analysis. Results showed that exposure of SHS to ozone induced the formation of ultrafine particles (<100 nm) that contained high molecular weight nitrogenated species ( m/ z 400-500), which can be due to accretion/acid-base reactions and formation of oligomers. In addition, nicotine was found to contribute significantly (with yields 4-9%) to the formation of secondary organic aerosol through reaction with ozone. The main constituents of the resulting SOA were tentatively identified and a reaction mechanism was proposed to elucidate their formation. These findings identify a new component of thirdhand smoke that is associated with the formation of ultrafine particles (UFP) through oxidative aging of secondhand smoke. The significance of this chemistry for indoor exposure and health effects is highlighted.

International Test Program for Synergistic Atomic Oxygen and VUV Exposure of Spacecraft Materials

NASA Technical Reports Server (NTRS)

Rutledge, Sharon; Banks, Bruce; Dever, Joyce; Savage, William

2000-01-01

Spacecraft in low Earth orbit (LEO) are subject to degradation in thermal and optical performance of components and materials through interaction with atomic oxygen and vacuum ultraviolet radiation which are predominant in LEO. Due to the importance of LEO durability and performance to manufacturers and users, an international test program for assessing the durability of spacecraft materials and components was initiated. Initial tests consisted of exposure of samples representing a variety of thermal control paints and multilayer insulation materials that have been used in space. Materials donated from various international sources were tested alongside a material whose performance is well known such as Teflon FEP or Kapton H for multilayer insulation, or Z-93-P for white thermal control paints. The optical, thermal or mass loss data generated during the test was then provided to the participating material supplier. Data was not published unless the participant donating the material consented to publication. This paper presents a description of the types of tests and facilities that have been used for the test program as well as some examples of data that have been generated. The test program is intended to give spacecraft builders and users a better understanding of degradation processes and effects to enable improved prediction of spacecraft performance.

Generation of multicolor vacuum ultraviolet pulses through four-wave sum-frequency mixing in argon

NASA Astrophysics Data System (ADS)

Shi, Liping; Li, Wenxue; Zhou, Hui; Wang, Di; Ding, Liang'en; Zeng, Heping

2013-11-01

We demonstrate efficient generation of multicolor vacuum ultraviolet pulses with excellent mode quality through χ(3)-based four-wave sum-frequency mixing and third-order harmonic generation of 400- and 267-nm femtosecond laser pulses in argon gas. The χ(3)-based nonlinear optical processes were optimized with appropriate control of gas pressure and group velocity delay between the driving pulses. Furthermore, the pulse breakup effects were observed for tightly focused ultraviolet pulses.

Theoretical and experimental studies relevant to interpretation of auroral emissions

NASA Technical Reports Server (NTRS)

Keffer, Charles E.

1991-01-01

The accomplishments achieved over the past year are detailed with emphasis on the interpretation or auroral emissions and studies of potential spacecraft-induced contamination effects. Accordingly, the research was divided into two tasks. The first task is designed to add to the understanding of space vehicle induced external contamination. An experimental facility for simulation of the external environment for a spacecraft in low earth orbit was developed. The facility was used to make laboratory measurements of important phenomena required for improving the understanding of the space vehicle induced external environment and its effect on measurement of auroral emissions from space-based platforms. A workshop was sponsored to provide a forum for presentation of the latest research by nationally recognized experts on space vehicle contamination and to discuss the impact of this research on future missions involving space-based platforms. The second task is to add an ab initio auroral calculation to the extant ionospheric/thermospheric global modeling capabilities. Once the addition of the code was complete, the combined model was to be used to compare the relative intensities and behavior of various emission sources (dayglow, aurora, etc.). Such studies are essential to an understanding of the types of vacuum ultraviolet (VUV) auroral images which are expected to be available within two years with the successful deployment of the Ultraviolet Imager (UVI) on the ISTP POLAR spacecraft. In anticipation of this, the second task includes support for meetings of the science working group for the UVI to discuss operational and data analysis needs. Taken together, the proposed tasks outline a course of study designed to make significant contributions to the field of space-based auroral imaging.

TIMED solar EUV experiment: preflight calibration results for the XUV photometer system

NASA Astrophysics Data System (ADS)

Woods, Thomas N.; Rodgers, Erica M.; Bailey, Scott M.; Eparvier, Francis G.; Ucker, Gregory J.

1999-10-01

The Solar EUV Experiment (SEE) on the NASA Thermosphere, Ionosphere, and Mesosphere Energetics and Dynamics (TIMED) mission will measure the solar vacuum ultraviolet (VUV) spectral irradiance from 0.1 to 200 nm. To cover this wide spectral range two different types of instruments are used: a grating spectrograph for spectra between 25 and 200 nm with a spectral resolution of 0.4 nm and a set of silicon soft x-ray (XUV) photodiodes with thin film filters as broadband photometers between 0.1 and 35 nm with individual bandpasses of about 5 nm. The grating spectrograph is called the EUV Grating Spectrograph (EGS), and it consists of a normal- incidence, concave diffraction grating used in a Rowland spectrograph configuration with a 64 X 1024 array CODACON detector. The primary calibrations for the EGS are done using the National Institute for Standards and Technology (NIST) Synchrotron Ultraviolet Radiation Facility (SURF-III) in Gaithersburg, Maryland. In addition, detector sensitivity and image quality, the grating scattered light, the grating higher order contributions, and the sun sensor field of view are characterized in the LASP calibration laboratory. The XUV photodiodes are called the XUV Photometer System (XPS), and the XPS includes 12 photodiodes with thin film filters deposited directly on the silicon photodiodes' top surface. The sensitivities of the XUV photodiodes are calibrated at both the NIST SURF-III and the Physikalisch-Technische Bundesanstalt (PTB) electron storage ring called BESSY. The other XPS calibrations, namely the electronics linearity and field of view maps, are performed in the LASP calibration laboratory. The XPS and solar sensor pre-flight calibration results are primarily discussed as the EGS calibrations at SURF-III have not yet been performed.

Ultralow Energy Electron Attachment at Sub-Millielectron Volt Resolution

NASA Astrophysics Data System (ADS)

Chutjian, Ara

1999-10-01

The technique of rare-gas photoionization(J. M. Ajello and A. Chutjian, J. Chem. Phys. 65), 5524 (1976). has been extended(A. Kortyna, M. Darrach and A. Chutjian, Bull. Am. Phys. Soc. 43), 1336 (1998). by use of direct laser ionization to electron energies ɛ in the range 0-100 meV, with a resolution Δɛ of 0.4-0.5 meV (FWHM). Tunable UV light at λ276 nm is produced using a pulsed Nd:YAG laser and nonlinear mixing techniques. The beam is frequency tripled in a pulsed jet of xenon. The VUV radiation, tunable at λ92 nm, is then used to photoionize Xe at its ^2P_1/2 threshold (single-photon ionization). The photoelectrons produced interact with admixed target gas to generate negative ions through the s-wave capture process. Recent results in electron attachment to SF6 will be reported which show resonance structure at the opening of the ground-state vibrational channels.^3,(H. Hotop et al., AIP Conf. Proc. Ser. 360 (AIP, New York, 1995), and private communication.) This structure corresponds to the process of vibrational excitation + attachment, which is superimposed on the underlying s-wave (direct) capture process. It should be a general phenomenon, present in a wide variety of zero-energy electron attaching molecules.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Turner, Andrew M.; Abplanalp, Matthew J.; Kaiser, Ralf I.

Phosphine, which has now been confirmed around the carbon-rich star IRC+10216, provides the first example of a phosphorus-containing single bond in interstellar or circumstellar media. While four compounds containing both phosphorus and carbon have been discovered, none contain a carbon–phosphorus single bond. Here, we show that this moiety is plausible from the reaction of phosphine with methane in electron-irradiated interstellar ice analogues. Fractional sublimation allows for detection of individual products at distinct temperatures using reflectron time-of-flight mass spectrometry (ReTOF) coupled with vacuum ultraviolet photoionization. This method produced phosphanes and methylphosphanes as large as P{sub 8}H{sub 10} and CH{sub 3}P{sub 8}H{submore » 9}, which demonstrates that a phosphorus–carbon bond can readily form and that methylphosphanes sublime at 12–17 K higher temperatures than the non-organic phosphanes. Also, irradiated ices of phosphine with deuterated-methane untangle the reaction pathways through which these methylphosphanes were formed and identified radical recombination to be preferred over carbene/phosphinidene insertion reactions. In addition, these ReTOF results confirm that CH{sub 3}PH{sub 2} and CH{sub 6}P{sub 2} can form via insertion of carbene and phosphinidene and that the methylenediphosphine (PH{sub 2}CH{sub 2}PH{sub 2}) isomer forms in the ices, although methylphosphine (CH{sub 3}P{sub 2}H{sub 3}) is likely the more abundant isomer and that phosphanes and organophosphanes preferentially fragment via the loss of a phosphino group when photoionized. While the formation of methylphosphine is overall endoergic, the intermediates produced by interactions with energetic electrons proceed toward methylphosphine favorably and barrierlessly and provide plausible mechanisms toward hitherto unidentified interstellar compounds.« less

Desorption atmospheric pressure photoionization high-resolution mass spectrometry: a complementary approach for the chemical analysis of atmospheric aerosols.

PubMed

Parshintsev, Jevgeni; Vaikkinen, Anu; Lipponen, Katriina; Vrkoslav, Vladimir; Cvačka, Josef; Kostiainen, Risto; Kotiaho, Tapio; Hartonen, Kari; Riekkola, Marja-Liisa; Kauppila, Tiina J

2015-07-15

On-line chemical characterization methods of atmospheric aerosols are essential to increase our understanding of physicochemical processes in the atmosphere, and to study biosphere-atmosphere interactions. Several techniques, including aerosol mass spectrometry, are nowadays available, but they all suffer from some disadvantages. In this research, desorption atmospheric pressure photoionization high-resolution (Orbitrap) mass spectrometry (DAPPI-HRMS) is introduced as a complementary technique for the fast analysis of aerosol chemical composition without the need for sample preparation. Atmospheric aerosols from city air were collected on a filter, desorbed in a DAPPI source with a hot stream of toluene and nitrogen, and ionized using a vacuum ultraviolet lamp at atmospheric pressure. To study the applicability of the technique for ambient aerosol analysis, several samples were collected onto filters and analyzed, with the focus being on selected organic acids. To compare the DAPPI-HRMS data with results obtained by an established method, each filter sample was divided into two equal parts, and the second half of the filter was extracted and analyzed by liquid chromatography/mass spectrometry (LC/MS). The DAPPI results agreed with the measured aerosol particle number. In addition to the targeted acids, the LC/MS and DAPPI-HRMS methods were found to detect different compounds, thus providing complementary information about the aerosol samples. DAPPI-HRMS showed several important oxidation products of terpenes, and numerous compounds were tentatively identified. Thanks to the soft ionization, high mass resolution, fast analysis, simplicity and on-line applicability, the proposed methodology has high potential in the field of atmospheric research. Copyright © 2015 John Wiley & Sons, Ltd.

Recent advances and applications of gas chromatography vacuum ultraviolet spectroscopy.

PubMed

Santos, Inês C; Schug, Kevin A

2017-01-01

The vacuum ultraviolet spectrophotometer was developed recently as an alternative to existing gas chromatography detectors. This detector measures the absorption of gas-phase chemical species in the range of 120-240 nm, where all chemical compounds present unique absorption spectra. Therefore, qualitative analysis can be performed and quantification follows standard Beer-Lambert law principles. Different fields of application, such as petrochemical, food, and environmental analysis have been explored. Commonly demonstrated is the capability for facile deconvolution of co-eluting analytes. The concept of additive absorption for co-eluting analytes has also been advanced for classification and speciation of complex mixtures using a data treatment procedure termed time interval deconvolution. Furthermore, pseudo-absolute quantitation can be performed for system diagnosis, as well as potentially calibrationless quantitation. In this manuscript an overview of these features, the vacuum ultraviolet spectrophotometer instrumentation, and performance capabilities are given. A discussion of the applications of the vacuum ultraviolet detector is provided by describing and discussing the papers published thus far since 2014. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Resolution of isomeric new designer stimulants using gas chromatography - Vacuum ultraviolet spectroscopy and theoretical computations.

PubMed

Skultety, Ludovit; Frycak, Petr; Qiu, Changling; Smuts, Jonathan; Shear-Laude, Lindsey; Lemr, Karel; Mao, James X; Kroll, Peter; Schug, Kevin A; Szewczak, Angelica; Vaught, Cory; Lurie, Ira; Havlicek, Vladimir

2017-06-08

Distinguishing isomeric representatives of "bath salts", "plant food", "spice", or "legal high" remains a challenge for analytical chemistry. In this work, we used vacuum ultraviolet spectroscopy combined with gas chromatography to address this issue on a set of forty-three designer drugs. All compounds, including many isomers, returned differentiable vacuum ultraviolet/ultraviolet spectra. The pair of 3- and 4-fluoromethcathinones (m/z 181.0903), as well as the methoxetamine/meperidine/ethylphenidate (m/z 247.1572) triad, provided very distinctive vacuum ultraviolet spectral features. On the contrary, spectra of 4-methylethcathinone, 4-ethylmethcathinone, 3,4-dimethylmethcathinone triad (m/z 191.1310) displayed much higher similarities. Their resolution was possible only if pure standards were probed. A similar situation occurred with the ethylone and butylone pair (m/z 221.1052). On the other hand, majority of forty-three drugs was successfully separated by gas chromatography. The detection limits for all the drug standards were in the 2-4 ng range (on-column amount), which is sufficient for determinations of seized drugs during forensics analysis. Further, state-of-the-art time-dependent density functional theory was evaluated for computation of theoretical absorption spectra in the 125-240 nm range as a complementary tool. Copyright © 2017 Elsevier B.V. All rights reserved.

Ultrafast photodynamics of pyrazine in the vacuum ultraviolet region studied by time-resolved photoelectron imaging using 7.8-eV pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Horio, Takuya; Suzuki, Yoshi-ichi; Suzuki, Toshinori, E-mail: suzuki@kuchem.kyoto-u.ac.jp

The ultrafast electronic dynamics of pyrazine (C{sub 4}N{sub 2}H{sub 4}) were studied by time-resolved photoelectron imaging (TRPEI) using the third (3ω, 4.7 eV) and fifth harmonics (5ω, 7.8 eV) of a femtosecond Ti:sapphire laser (ω). Although the photoionization signals due to the 5ω − 3ω and 3ω − 5ω pulse sequences overlapped near the time origin, we have successfully extracted their individual TRPEI signals using least squares fitting of the observed electron kinetic energy distributions. When the 5ω pulses preceded the 3ω pulses, the 5ω pulses predominantly excited the S{sub 4} (ππ{sup *}, {sup 1}B{sub 1u}+{sup 1}B{sub 2u}) state. Themore » photoionization signal from the S{sub 4} state generated by the time-delayed 3ω pulses was dominated by the D{sub 3}({sup 2}B{sub 2g})←S{sub 4} photoionization process and exhibited a broad electron kinetic energy distribution, which rapidly downshifted in energy within 100 fs. Also observed were the photoionization signals for the 3s, 3p{sub z}, and 3p{sub y} members of the Rydberg series converging to D{sub 0}({sup 2}A{sub g}). The Rydberg signals appeared immediately within our instrumental time resolution of 27 fs, indicating that these states are directly photoexcited from the ground state or populated from S{sub 4} within 27 fs. The 3s, 3p{sub z}, and 3p{sub y} states exhibited single exponential decay with lifetimes of 94 ± 2, 89 ± 2, and 58 ± 1 fs, respectively. With the reverse pulse sequence of 3ω − 5ω, the ultrafast internal conversion (IC) from S{sub 2}(ππ{sup *}) to S{sub 1}(nπ{sup *}) was observed. The decay associated spectrum of S{sub 2} exhibited multiple bands ascribed to D{sub 0}, D{sub 1}, and D{sub 3}, in agreement with the 3ω-pump and 6ω-probe experiment described in our preceding paper [T. Horio et al., J. Chem. Phys. 145, 044306 (2016)]. The electron kinetic energy and angular distributions from S{sub 1} populated by IC from S{sub 2} are also discussed.« less

Electronic Properties of Free-Standing Surfactant-Capped Lead Halide Perovskite Nanocrystals Isolated in Vacuo.

PubMed

Milosavljevic, Aleksandar R; Bozanic, Dusan; Sadhu, Subha; Vukmirovic, Nenad; Dojcilovic, Radovan; Sapkota, Pitambar; Huang, Weixin; Bozek, John D; Nicolas, Christophe; Nahon, Laurent; Ptasinska, Sylwia

2018-06-14

We report an investigation of lead halide perovskite CH3NH3PbBr3 nanocrystals and associated ligand molecules, by combining several different state-of-the-art experimental techniques, including synchrotron radiation based XPS and VUV PES of free-standing nanocrystals isolated in vacuum. By using this novel approach for perovskite materials we could directly obtain a complete band alignment to vacuum of both CH3NH3PbBr3 nanocrystals and the ligands widely used in their preparation. We discuss possible influence of the ligand molecules to apparent perovskite properties, and we compare the electronic properties of nanocrystals to that of bulk material. The experimental results were supported by DFT calculations.

Extreme ultraviolet (EUV) and FUV calibration facility for special sensor ultraviolet limb imager (SSULI)

NASA Astrophysics Data System (ADS)

Boyer, Craig N.; Osterman, Steven N.; Thonnard, Stefan E.; McCoy, Robert P.; Williams, J. Z.; Parker, S. E.

1994-09-01

A facility for calibrating far ultraviolet and extreme ultraviolet instruments has recently been completed at the Naval Research Laboratory. Our vacuum calibration vessel is 2-m in length, 1.67-m in diameter, and can accommodate optical test benches up to 1.2-m wide by 1.5-m in length. A kinematically positioned frame with four axis precision pointing capability of 10 microns for linear translation and .01 degrees for rotation is presently used during vacuum optical calibration of SSULI. The chamber was fabricated from 304 stainless steel and polished internally to reduce surface outgassing. A dust-free environment is maintained at the rear of the vacuum chamber by enclosing the 2-m hinged vacuum access door in an 8 ft. by 8 ft. class 100 clean room. Every effort was made to obtain an oil-free environment within the vacuum vessel. Outgassing products are continually monitored with a 1 - 200 amu residual gas analyzer. An oil-free claw and vane pump evacuates the chamber to 10-2 torr through 4 in. diameter stainless steel roughing lines. High vacuum is achieved and maintained with a magnetically levitated 480 l/s turbo pump and a 3000 l/s He4 cryopump. Either of two vacuum monochrometers, a 1-m f/10.4 or a 0.2-m f/4.5 are coaxially aligned with the optical axis of the chamber and are used to select single UV atomic resonance lines from a windowless capillary or penning discharge UV light source. A calibrated channeltron detector is coaxially mounted with the SSULI detector during calibration. All vacuum valves, the cooling system for the cryopump compressor, and the roughing pump are controlled through optical fibers which are interfaced to a computer through a VME board. Optical fibers were chosen to ensure that complete electrical isolation is maintained between the computer and the vacuum system valves-solenoids and relays.

Photoelectron spectroscopy of a series of acetate and propionate esters

NASA Astrophysics Data System (ADS)

Śmiałek, Małgorzata A.; Guthmuller, Julien; MacDonald, Michael A.; Zuin, Lucia; Delwiche, Jacques; Hubin-Franskin, Marie-Jeanne; Lesniewski, Tadeusz; Mason, Nigel J.; Limão-Vieira, Paulo

2017-10-01

The electronic state and photoionization spectroscopy of a series of acetate esters: methyl acetate, isopropyl acetate, butyl acetate and pentyl acetate as well as two propionates: methyl propionate and ethyl propionate, have been determined using vacuum-ultraviolet photoelectron spectroscopy. These experimental investigations are complemented by ab initio calculations. The measured first adiabatic and vertical ionization energies were determined as: 10.21 and 10.45 eV for methyl acetate, 9.99 and 10.22 eV for isopropyl acetate, 10.07 and 10.26 eV for butyl acetate, 10.01 and 10.22 eV for pentyl acetate, 10.16 and 10.36 eV for methyl propionate and 9.99 and 10.18 eV for ethyl propionate. For the four smaller esters vibrational transitions were calculated and compared with those identified in the photoelectron spectrum, revealing the most distinctive ones to be a Csbnd O stretch combined with a Cdbnd O stretch. The ionization energies of methyl and ethyl esters as well as for a series of formates and acetates were compared showing a clear dependence of the value of the ionization energy on the size of the molecule with very little influence of its conformation.

Photoionization in the Precursor of Laser Supported Detonation by Ultraviolet Radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shimamura, Kohei; Michigami, Keisuke; Wang, Bin

The propagation mechanism of laser-supported detonation (LSD) is important for designing laser propulsion for a detonation type thruster. The purpose of this work to was to confirm that photo-ionization in precursor is the predominant LSD sustainment mechanism. First of all, we tried to investigate the dependency of LSD duration on ambient gas species, air and argon. We took a series of high-speed images using the laser shadow-graphy. Besides, to estimate the UV photons emitted from the plasma, we used plasma emission spectroscopy and determined the electron temperature and density. As a result, the LSD duration of argon plasma and airmore » plasma are 0.7 {mu}s and 0.3 {mu}s, resp. Besides, argon plasma emitted 10{sup 10} to 10{sup 14} photons/seconds, which was higher than air plasma. These results reveal that LSD propagation depends on the photon-contributing photoionization. The threshold photon-emission rate of LSD termination gives the elucidation of the LSD termination condition.« less

Fluoride coatings for vacuum ultraviolet reflection filters.

PubMed

Guo, Chun; Kong, Mingdong; Lin, Dawei; Li, Bincheng

2015-12-10

LaF3/MgF2 reflection filters with a high spectral-discrimination capacity of the atomic-oxygen lines at 130.4 and 135.6 nm, which were employed in vacuum ultraviolet imagers, were prepared by molybdenum-boat thermal evaporation. The optical properties of reflection filters were characterized by a high-precision vacuum ultraviolet spectrophotometer. The vulnerability of the filter's microstructures to environmental contamination and the recovery of the optical properties of the stored filter samples with ultraviolet ozone cleaning were experimentally demonstrated. For reflection filters with the optimized nonquarter-wave multilayer structures, the reflectance ratios R135.6 nm/R130.4 nm of 92.7 and 20.6 were achieved for 7° and 45° angles of incidence, respectively. On the contrary, R135.6 nm/R130.4 nm ratio of 12.4 was obtained for a reflection filter with a standard π-stack multilayer structure with H/L=1/4 at 7° AOI.

The discontinuity near 1600 A in the spectra of DA white dwarfs

NASA Technical Reports Server (NTRS)

Wegner, G.

1984-01-01

Ultraviolet spectroscopic observations of two relatively cool DA white dwarfs, L481 - 60 (= WD 1544 - 37) and BPM 1266 ( = WD 2105 - 82), with the International Ultraviolet Explorer (IUE) satellite show a strong drop in their spectral energy distributions below 1600 A. Published model atmospheres and thier visual spectra suggest that these two stars have effective temperatures in the vicinity of 9,000-10,000 K, and it is proposed that the 1600 A feature could be due to the 342(1S) 3s2(1S) photoionization edge of Mg I.

Extreme ultraviolet photoionization of aldoses and ketoses

NASA Astrophysics Data System (ADS)

Shin, Joong-Won; Dong, Feng; Grisham, Michael E.; Rocca, Jorge J.; Bernstein, Elliot R.

2011-04-01

Gas phase monosaccharides (2-deoxyribose, ribose, arabinose, xylose, lyxose, glucose galactose, fructose, and tagatose), generated by laser desorption of solid sample pellets, are ionized with extreme ultraviolet photons (EUV, 46.9 nm, 26.44 eV). The resulting fragment ions are analyzed using a time of flight mass spectrometer. All aldoses yield identical fragment ions regardless of size, and ketoses, while also generating same ions as aldoses, yields additional features. Extensive fragmentation of the monosaccharides is the result the EUV photons ionizing various inner valence orbitals. The observed fragmentation patterns are not dependent upon hydrogen bonding structure or OH group orientation.

Photophysical and photochemical effects of UV and VUV photo-oxidation and photolysis on PET and PEN

NASA Astrophysics Data System (ADS)

Morgan, Andrew

Polyethylene Terephthalate (PET) is a widely used polymer in the bottling, packaging, and clothing industry. In recent years an increasing global demand for PET has taken place due to the Solar Disinfection (SODIS) process. SODIS is a method of sterilizing fresh water into drinkable water. The PET bottles are used in the process to contain the water during solar irradiation due to its highly transparent optical property. Alongside PET, polyethylene 2,6-napthalate (PEN) is used in bottling and flexible electronic applications. The surface of PEN would need to be modified to control the hydrophilicity and the interaction it exudes as a substrate. The UV light absorption properties of PET and PEN are of great importance for many applications, and thus needs to be studied along with its photochemical resistance. The optical and chemical nature of PET was studied as it was treated by UV photo-oxidation, photo-ozonation, and photolysis under atmospheric pressure. Another investigation was also used to study PEN and PET as they are treated by vacuum UV (VUV) photo-oxidation, VUV photolysis, and remote oxygen reactions. The extent of the photoreactions' effect into the depth of the polymers is examined as treatment conditions are changed. The different experimental methods established the rate of several competing photoreactions on PET and PEN during irradiance, and their effect on the optical quality of the polymers.

The ultraviolet variations of iota Cas

NASA Technical Reports Server (NTRS)

Molnar, M. R.; Mallama, A. D.; Soskey, D. G.; Holm, A. V.

1976-01-01

The Ap variable star iota Cas was observed with the photometers on OAO-2 covering the spectral range 1430-4250 A. The ultraviolet light curves show a double wave with primary minimum and maximum at phase ? 0.00 and 0.35, respectively. Secondary minimum light is at phase ? 0.65 with secondary maximum at phase ? 0.85. The light curves longward of 3150 A vary in opposition to those shortward of this 'null region'. Ground-based coude spectra show that the Fe II and Cr II line strengths have a double-wave variation such that maximum strength occurs at minimum ultraviolet light. We suggest that the strong ultraviolet opacities due to photoionization and line blanketing by these metals may cause the observed photometric variations. We have also constructed an oblique-rotator model which shows iron and chromium lying in a great circle band rather than in circular spots.