Low-sample flow secondary electrospray ionization: improving vapor ionization efficiency.

PubMed

Vidal-de-Miguel, G; Macía, M; Pinacho, P; Blanco, J

2012-10-16

In secondary electrospray ionization (SESI) systems, gaseous analytes exposed to an elecrospray plume become ionized after charge is transferred from the charging electrosprayed particles to the sample species. Current SESI systems have shown a certain potential. However, their ionization efficiency is limited by space charge repulsion and by the high sample flows required to prevent vapor dilution. As a result, they have a poor conversion ratio of vapor into ions. We have developed and tested a new SESI configuration, termed low-flow SESI, that permits the reduction of the required sample flows. Although the ion to vapor concentration ratio is limited, the ionic flow to sample vapor flow ratio theoretically is not. The new ionizer is coupled to a planar differential mobility analyzer (DMA) and requires only 0.2 lpm of vapor sample flow to produce 3.5 lpm of ionic flow. The achieved ionization efficiency is 1/700 (one ion for every 700 molecules) for TNT and, thus, compared with previous SESI ionizers coupled with atmospheric pressure ionization-mass spectrometry (API-MS) (Mesonero, E.; Sillero, J. A.; Hernández, M.; Fernandez de la Mora, J. Philadelphia PA, 2009) has been improved by a large factor of at least 50-100 (our measurements indicate 70). The new ionizer coupled with the planar DMA and a triple quadrupole mass spectrometer (ABSciex API5000) requires only 20 fg (50 million molecules) to produce a discernible signal after mobility and MS(2) analysis.

Efficient thermoelectric device

NASA Technical Reports Server (NTRS)

Ila, Daryush (Inventor)

2010-01-01

A high efficiency thermo electric device comprising a multi nanolayer structure of alternating insulator and insulator/metal material that is irradiated across the plane of the layer structure with ionizing radiation. The ionizing radiation produces nanocrystals in the layered structure that increase the electrical conductivity and decrease the thermal conductivity thereby increasing the thermoelectric figure of merit. Figures of merit as high as 2.5 have been achieved using layers of co-deposited gold and silicon dioxide interspersed with layers of silicon dioxide. The gold to silicon dioxide ratio was 0.04. 5 MeV silicon ions were used to irradiate the structure. Other metals and insulators may be substituted. Other ionizing radiation sources may be used. The structure tolerates a wide range of metal to insulator ratio.

Applications of High-Resolution Electrospray Ionization Mass Spectrometry to Measurements of Average Oxygen to Carbon Ratios in Secondary Organic Aerosols

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

Bateman, Adam P.; Laskin, Julia; Laskin, Alexander

2012-07-02

The applicability of high resolution electrospray ionization mass spectrometry (HR ESI-MS) to measurements of the average oxygen to carbon ratio (O/C) in organic aerosols was investigated. Solutions with known average O/C containing up to 10 standard compounds representative of secondary organic aerosol (SOA) were analyzed and corresponding electrospray ionization efficiencies were quantified. The assumption of equal ionization efficiency commonly used in estimating O/C ratios of organic aerosols was found to be reasonably accurate. We found that the accuracy of the measured O/C ratios increases by averaging the values obtained from both (+) and (-) modes. A correlation was found betweenmore » the ratio of the ionization efficiencies in the positive and negative ESI modes with the octanol-water partition constant, and more importantly, with the compound's O/C. To demonstrate the utility of this correlation for estimating average O/C values of unknown mixtures, we analyzed the ESI (+) and ESI (-) data for SOA produced by oxidation of limonene and isoprene and compared to online O/C measurements using an aerosol mass spectrometer (AMS). This work demonstrates that the accuracy of the HR ESI-MS methods is comparable to that of the AMS, with the added benefit of molecular identification of the aerosol constituents.« less

High-order harmonic generation in a capillary discharge

DOEpatents

Rocca, Jorge J.; Kapteyn, Henry C.; Mumane, Margaret M.; Gaudiosi, David; Grisham, Michael E.; Popmintchev, Tenio V.; Reagan, Brendan A.

2010-06-01

A pre-ionized medium created by a capillary discharge results in more efficient use of laser energy in high-order harmonic generation (HHG) from ions. It extends the cutoff photon energy, and reduces the distortion of the laser pulse as it propagates down the waveguide. The observed enhancements result from a combination of reduced ionization energy loss and reduced ionization-induced defocusing of the driving laser as well as waveguiding of the driving laser pulse. The discharge plasma also provides a means to spectrally tune the harmonics by tailoring the initial level of ionization of the medium.

Heating of the solar chromosphere by ionization pumping

NASA Technical Reports Server (NTRS)

Lindsey, C. A.

1981-01-01

A new theory is proposed to explain the heating of the solar chromosphere, and possibly the corona, by the dissipation of hydrodynamic compression waves. The basis of the dissipative mechanism, here referred to as ionization pumping, is hysteresis caused by irreversible relaxation of the chromospheric medium to ionization equilibrium following pressure perturbations. In the middle chromosphere, where hydrogen is partially ionized, it is shown that ionization pumping will cause strong dissipation of waves whose periods are 200s or less. This could cause heating of the chromosphere sufficient to compensate for the radiative losses. The mechanism retains a high efficiency for waves of arbitrarily small amplitude and, thus, can be more efficient than shock dissipation for small perturbations in pressure. The formation of shocks therefore is not required for the dissipation of waves whose periods are several minutes or less.

Preliminary Ionization Efficiencies of {sup 11}C and {sup 14}O with the LBNL ECR Ion Sources

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

Xie, Z.Q.; Cerny, J.; Guo, F.Q.

1998-10-05

High charge states, up to fully stripped {sup 11}C and {sup 14}O ion, beams have been produced with the electron cyclotron resonance ion sources (LBNL, ECR and AECR-U) at Lawrence Berkeley National Laboratory. The radioactive atoms of {sup 11}C and {sup 14}O were collected in batch mode with an LN{sub 2} trap and then bled into the ECR ion sources. Ionization efficiency as high as 11% for {sup 11}C{sup 4+} was achieved.

Ionization Efficiency of Doubly Charged Ions Formed from Polyprotic Acids in Electrospray Negative Mode

NASA Astrophysics Data System (ADS)

Liigand, Piia; Kaupmees, Karl; Kruve, Anneli

2016-07-01

The ability of polyprotic acids to give doubly charged ions in negative mode electrospray was studied and related to physicochemical properties of the acids via linear discriminant analysis (LDA). It was discovered that the compound has to be strongly acidic (low p K a1 and p K a2) and to have high hydrophobicity (log P ow) to become multiply charged. Ability to give multiply charged ions in ESI/MS cannot be directly predicted from the solution phase acidities. Therefore, for the first time, a quantitative model to predict the charge state of the analyte in ESI/MS is proposed and validated for small anions. Also, a model to predict ionization efficiencies of these analytes was developed. Results indicate that acidity of the analyte, its octanol-water partition coefficient, and charge delocalization are important factors that influence ionization efficiencies as well as charge states of the analytes. The pH of the solvent was also found to be an important factor influencing the ionization efficiency of doubly charged ions.

Development of high efficiency Versatile Arc Discharge Ion Source at CERN ISOLDE.

PubMed

Penescu, L; Catherall, R; Lettry, J; Stora, T

2010-02-01

We report here recent developments of Forced Electron Beam Induced Arc Discharge (FEBIAD) ion sources at the ISOLDE radioactive ion beam facility, hosted at the European Organization for Nuclear Research (CERN). As a result of the propositions to improve the ionization efficiency, two FEBIAD prototypes have been produced and successfully tested in 2008. Off-line studies showed that the 1+ ionization efficiencies for noble gases are 5-20 times larger than with the standard ISOLDE FEBIAD ion sources and reach 60% for radon, which allowed the identification at ISOLDE of (229)Rn, an isotope that had never previously been observed in the laboratory. A factor of 3 increase is also expected for the ionization efficiency of the other elements. The experimental and theoretical methodology is presented. The theoretical model, which gives precise insights on the processes affecting the ionization, is used to design optimal sources (grouped under the name of VADIS--Versatile Arc Discharge Ion Source) for the different chemical classes of the produced isotopes, as already demonstrated for the noble gases.

Resonance ionization spectroscopy of sodium Rydberg levels using difference frequency generation of high-repetition-rate pulsed Ti:sapphire lasers

NASA Astrophysics Data System (ADS)

Naubereit, P.; Marín-Sáez, J.; Schneider, F.; Hakimi, A.; Franzmann, M.; Kron, T.; Richter, S.; Wendt, K.

2016-05-01

The generation of tunable laser light in the green to orange spectral range has generally been a deficiency of solid-state lasers. Hence, the formalisms of difference frequency generation (DFG) and optical parametric processes are well known, but the DFG of pulsed solid-state lasers was rarely efficient enough for its use in resonance ionization spectroscopy. Difference frequency generation of high-repetition-rate Ti:sapphire lasers was demonstrated for resonance ionization of sodium by efficiently exciting the well-known D1 and D2 lines in the orange spectral range (both ≈589 nm). In order to prove the applicability of the laser system for its use at resonance ionization laser ion sources of radioactive ion beam facilities, the first ionization potential of Na was remeasured by three-step resonance ionization into Rydberg levels and investigating Rydberg convergences. A result of EIP=41449.455 (6) stat(7) syscm-1 was obtained, which is in perfect agreement with the literature value of EIPlit =41449.451(2)cm-1 . A total of 41 level positions for the odd-parity Rydberg series n f 2F5/2,7/2o for principal quantum numbers of 10 ≤n ≤60 were determined experimentally.

Enhancement of ionization efficiency of mass spectrometric analysis from non-electrospray ionization friendly solvents with conventional and novel ionization techniques.

PubMed

Jiang, Ping; Lucy, Charles A

2015-10-15

Electrospray ionization mass spectrometry (ESI-MS) has significantly impacted the analysis of complex biological and petroleum samples. However ESI-MS has limited ionization efficiency for samples in low dielectric and low polarity solvents. Addition of a make-up solvent through a T union or electrospray solvent through continuous flow extractive desorption electrospray ionization (CF-EDESI) enable ionization of analytes in non-ESI friendly solvents. A conventional make-up solvent addition setup was used and a CF-EDESI source was built for ionization of nitrogen-containing standards in hexane or hexane/isopropanol. Factors affecting the performance of both sources have been investigated and optimized. Both the make-up solvent addition and CF-EDESI improve the ionization efficiency for heteroatom compounds in non-ESI friendly solvents. Make-up solvent addition provides higher ionization efficiency than CF-EDESI. Neither the make-up solvent addition nor the CF-EDESI eliminates ionization suppression of nitrogen-containing compounds caused by compounds of the same chemical class. Copyright © 2015 Elsevier B.V. All rights reserved.

The ionization efficiency of aluminum and iron at meteoric velocities

NASA Astrophysics Data System (ADS)

DeLuca, Michael; Munsat, Tobin; Thomas, Evan; Sternovsky, Zoltan

2018-07-01

The ionization efficiency of aluminum was measured in the laboratory over an extended velocity range of 10.8-73.4 km/s and compared to available models. The measurements were made by shooting submicron-sized aluminum dust particles into an air chamber using the University of Colorado's dust accelerator facility. The ionization efficiency, β, is calculated from the total charge generated in the chamber during the complete ablation of particles of known mass. An array of photomultiplier tubes observed the light production by a subset of particles in the chamber to confirm that a moderate deceleration of the ablating particles occurred at low velocities. This information allows the interpretation of the β measurements to be extended to velocities <20 km/s, with the understanding that the low-velocity β measurements are lower limits. Updated β measurements for iron particles are also reported over an extended velocity range compared to previously published data: 10.5-87.3 km/s. The measurements are fit to functions for the ionization efficiency across the entire velocity range, and a semi-empirical function is presented which matches the shape of the measured β curves for aluminum and iron at both high and low velocities.

Laser resonance ionization spectroscopy on lutetium for the MEDICIS project

NASA Astrophysics Data System (ADS)

Gadelshin, V.; Cocolios, T.; Fedoseev, V.; Heinke, R.; Kieck, T.; Marsh, B.; Naubereit, P.; Rothe, S.; Stora, T.; Studer, D.; Van Duppen, P.; Wendt, K.

2017-11-01

The MEDICIS-PROMED Innovative Training Network under the Horizon 2020 EU program aims to establish a network of early stage researchers, involving scientific exchange and active cooperation between leading European research institutions, universities, hospitals, and industry. Primary scientific goal is the purpose of providing and testing novel radioisotopes for nuclear medical imaging and radionuclide therapy. Within a closely linked project at CERN, a dedicated electromagnetic mass separator system is presently under installation for production of innovative radiopharmaceutical isotopes at the new CERN-MEDICIS laboratory, directly adjacent to the existing CERN-ISOLDE radioactive ion beam facility. It is planned to implement a resonance ionization laser ion source (RILIS) to ensure high efficiency and unrivaled purity in the production of radioactive ions. To provide a highly efficient ionization process, identification and characterization of a specific multi-step laser ionization scheme for each individual element with isotopes of interest is required. The element lutetium is of primary relevance, and therefore was considered as first candidate. Three two-step excitation schemes for lutetium atoms are presented in this work, and spectroscopic results are compared with data of other authors.

Novel high power impulse magnetron sputtering enhanced by an auxiliary electrical field

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

Li, Chunwei, E-mail: lcwnefu@126.com, E-mail: xiubotian@163.com; State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001; Tian, Xiubo, E-mail: lcwnefu@126.com, E-mail: xiubotian@163.com

2016-08-15

The high power impulse magnetron sputtering (HIPIMS) technique is a novel highly ionized physical vapor deposition method with a high application potential. However, the electron utilization efficiency during sputtering is rather low and the metal particle ionization rate needs to be considerably improved to allow for a large-scale industrial application. Therefore, we enhanced the HIPIMS technique by simultaneously applying an electric field (EF-HIPIMS). The effect of the electric field on the discharge process was studied using a current sensor and an optical emission spectrometer. Furthermore, the spatial distribution of the electric potential and electric field during the EF-HIPIMS process wasmore » simulated using the ANSYS software. The results indicate that a higher electron utilization efficiency and a higher particle ionization rate could be achieved. The auxiliary anode obviously changed the distribution of the electric potential and the electric field in the discharge region, which increased the plasma density and enhanced the degree of ionization of the vanadium and argon gas. Vanadium films were deposited to further compare both techniques, and the morphology of the prepared films was investigated by scanning electron microscopy. The films showed a smaller crystal grain size and a denser growth structure when the electric field was applied during the discharge process.« less

A combined thermal dissociation and electron impact ionization source for RIB generation

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

Alton, G.D.; Williams, C.

1995-12-31

The probability for simultaneously dissociating and efficiently ionizing the individual atomic constituents of molecular feed materials with conventional, hot-cathode, electron-impact ion sources is low and consequently, the ion beams from these sources often appear as mixtures of several molecular sideband beams. This fragmentation process leads to dilution of the intensity of the species of interest for RIB applications where beam intensity is at a premium. We have conceived an ion source that combines the excellent molecular dissociation properties of a thermal dissociator and the high ionization efficiency characteristics of an electron impact ionization source that will, in principle, overcome thismore » handicap. The source concept will be evaluated as a potential candidate for use for RIB generation at the Holifield Radioactive Ion Beam Facility (HRIBF), now under construction at the Oak Ridge National Laboratory. The design features and principles of operation of the source are described in this article.« less

A singly charged ion source for radioactive {sup 11}C ion acceleration

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

Katagiri, K.; Noda, A.; Nagatsu, K.

2016-02-15

A new singly charged ion source using electron impact ionization has been developed to realize an isotope separation on-line system for simultaneous positron emission tomography imaging and heavy-ion cancer therapy using radioactive {sup 11}C ion beams. Low-energy electron beams are used in the electron impact ion source to produce singly charged ions. Ionization efficiency was calculated in order to decide the geometric parameters of the ion source and to determine the required electron emission current for obtaining high ionization efficiency. Based on these considerations, the singly charged ion source was designed and fabricated. In testing, the fabricated ion source wasmore » found to have favorable performance as a singly charged ion source.« less

A Numerical Simulation of the Energy Conversion Process in Microwave Rocket

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

Shibata, Teppei; Oda, Yasuhisa; Komurasaki, Kimiya

2008-04-28

In Microwave Rocket, a high power microwave beam ionizes atmospheric air inside of the thruster and the ionization front drives a shock wave. In this paper, CFD simulation was conducted using measured propagation velocity of the ionization front to evaluate the engine performance. As a result, maximum cycle efficiency was obtained at the power density of about 200 kW/m{sup 2} which is the transitional beam power condition between Microwave Supported Combustion and Microwave Supported Detonation regimes.

F--Ray: A new algorithm for efficient transport of ionizing radiation

NASA Astrophysics Data System (ADS)

Mao, Yi; Zhang, J.; Wandelt, B. D.; Shapiro, P. R.; Iliev, I. T.

2014-04-01

We present a new algorithm for the 3D transport of ionizing radiation, called F2-Ray (Fast Fourier Ray-tracing method). The transfer of ionizing radiation with long mean free path in diffuse intergalactic gas poses a special challenge to standard numerical methods which transport the radiation in position space. Standard methods usually trace each individual ray until it is fully absorbed by the intervening gas. If the mean free path is long, the computational cost and memory load are likely to be prohibitive. We have developed an algorithm that overcomes these limitations and is, therefore, significantly more efficient. The method calculates the transfer of radiation collectively, using the Fast Fourier Transform to convert radiation between position and Fourier spaces, so the computational cost will not increase with the number of ionizing sources. The method also automatically combines parallel rays with the same frequency at the same grid cell, thereby minimizing the memory requirement. The method is explicitly photon-conserving, i.e. the depletion of ionizing photons is guaranteed to equal the photoionizations they caused, and explicitly obeys the periodic boundary condition, i.e. the escape of ionizing photons from one side of a simulation volume is guaranteed to be compensated by emitting the same amount of photons into the volume through the opposite side. Together, these features make it possible to numerically simulate the transfer of ionizing photons more efficiently than previous methods. Since ionizing radiation such as the X-ray is responsible for heating the intergalactic gas when first stars and quasars form at high redshifts, our method can be applied to simulate thermal distribution, in addition to cosmic reionization, in three-dimensional inhomogeneous cosmological density field.

Electron gyroharmonic effects in ionization and electron acceleration during high-frequency pumping in the ionosphere.

PubMed

Gustavsson, B; Leyser, T B; Kosch, M; Rietveld, M T; Steen, A; Brändström, B U E; Aso, T

2006-11-10

Optical emissions and incoherent scatter radar data obtained during high-frequency electromagnetic pumping of the ionospheric plasma from the ground give data on electron energization in an energy range from 2 to 100 eV. Optical emissions at 4278 A from N2+ that require electrons with energies above the 18 eV ionization energy give the first images ever of pump-induced ionization of the thermosphere. The intensity at 4278 A is asymmetric around the ionospheric electron gyroharmonic, being stronger above the gyroresonance. This contrasts with emissions at 6300 A from O(1D) and of electron temperature enhancements, which have minima at the gyroharmonic but have no apparent asymmetry. This direct evidence of pump-induced ionization contradicts previous indirect evidence, which indicated that ionization is most efficiently produced when the pump frequency was below the gyroharmonic.

Iron oxide nanomatrix facilitating metal ionization in matrix-assisted laser desorption/ionization mass spectrometry.

PubMed

Obena, Rofeamor P; Lin, Po-Chiao; Lu, Ying-Wei; Li, I-Che; del Mundo, Florian; Arco, Susan dR; Nuesca, Guillermo M; Lin, Chung-Chen; Chen, Yu-Ju

2011-12-15

The significance and epidemiological effects of metals to life necessitate the development of direct, efficient, and rapid method of analysis. Taking advantage of its simple, fast, and high-throughput features, we present a novel approach to metal ion detection by matrix-functionalized magnetic nanoparticle (matrix@MNP)-assisted MALDI-MS. Utilizing 21 biologically and environmentally relevant metal ion solutions, the performance of core and matrix@MNP against conventional matrixes in MALDI-MS and laser desorption ionization (LDI) MS were systemically tested to evaluate the versatility of matrix@MNP as ionization element. The matrix@MNPs provided 20- to >100-fold enhancement on detection sensitivity of metal ions and unambiguous identification through characteristic isotope patterns and accurate mass (<5 ppm), which may be attributed to its multifunctional role as metal chelator, preconcentrator, absorber, and reservoir of energy. Together with the comparison on the ionization behaviors of various metals having different ionization potentials (IP), we formulated a metal ionization mechanism model, alluding to the role of exciton pooling in matrix@MNP-assisted MALDI-MS. Moreover, the detection of Cu in spiked tap water demonstrated the practicability of this new approach as an efficient and direct alternative tool for fast, sensitive, and accurate determination of trace metal ions in real samples.

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.,

Three-photon resonance ionization of atomic Mn in a hot-cavity laser ion source using Ti:sapphire lasers

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

Liu, Y.; Gottwald, T.; Mattolat, C.

We have demonstrated three-photon resonance ionization of atomic manganese (Mn) in a hot-cavity ion source using Ti: sapphire lasers. Three-step ionization schemes employing different intermediate levels and Rydberg or autoionizing (AI) states in the final ionization step are established. Strong AI resonances were observed via the 3d 54s5s f 6S 5/2 level at 49 415.35 cm -1, while Rydberg transitions were reached from the 3d 54s4d e 6D 9/2,7/2,5/2) levels at around 47 210 cm -1. Analyses of the strong Rydberg transitions associated with the 3d 54s4d e 6D 7/2 lower level indicate that they belong to the dipole-allowed 4dmore » → nf 6F° 9/2,7/2,5/2 series converging to the 3d 54s 7S 3 ground state of Mn II. From this series, an ionization potential of 59 959.56 ± 0.01 cm -1 is obtained for Mn. At high ion source temperatures the semi-forbidden 4d → nf 8 F°9/2,7/2,5/2 series was also observed. The overall ionization efficiency for Mn has been measured to be about 0.9% when using the strong AI transition in the third excitation step and 0.3% when employing an intense Rydberg transition. Experimental data indicate that the ionization efficiency was limited by the interaction of Mn atoms with ion source materials at high temperatures.« less

Three-photon resonance ionization of atomic Mn in a hot-cavity laser ion source using Ti:sapphire lasers

DOE PAGES

Liu, Y.; Gottwald, T.; Mattolat, C.; ...

2015-05-08

We have demonstrated three-photon resonance ionization of atomic manganese (Mn) in a hot-cavity ion source using Ti: sapphire lasers. Three-step ionization schemes employing different intermediate levels and Rydberg or autoionizing (AI) states in the final ionization step are established. Strong AI resonances were observed via the 3d 54s5s f 6S 5/2 level at 49 415.35 cm -1, while Rydberg transitions were reached from the 3d 54s4d e 6D 9/2,7/2,5/2) levels at around 47 210 cm -1. Analyses of the strong Rydberg transitions associated with the 3d 54s4d e 6D 7/2 lower level indicate that they belong to the dipole-allowed 4dmore » → nf 6F° 9/2,7/2,5/2 series converging to the 3d 54s 7S 3 ground state of Mn II. From this series, an ionization potential of 59 959.56 ± 0.01 cm -1 is obtained for Mn. At high ion source temperatures the semi-forbidden 4d → nf 8 F°9/2,7/2,5/2 series was also observed. The overall ionization efficiency for Mn has been measured to be about 0.9% when using the strong AI transition in the third excitation step and 0.3% when employing an intense Rydberg transition. Experimental data indicate that the ionization efficiency was limited by the interaction of Mn atoms with ion source materials at high temperatures.« less

Nanoengineering of strong field processes in solids

NASA Astrophysics Data System (ADS)

Almalki, S.; Parks, A. M.; Brabec, T.; McDonald, C. R.

2018-04-01

We present a theoretical investigation of the effect of quantum confinement on high harmonic generation in semiconductor materials by systematically varying the confinement width along one or two directions transverse to the laser polarization. Our analysis shows a growth in high harmonic efficiency concurrent with a reduction of ionization. This decrease in ionization comes as a consequence of an increased band gap resulting from the confinement. The increase in harmonic efficiency results from a restriction of wave packet spreading, leading to greater recollision probability. Consequently, nanoengineering of one and two-dimensional nanosystems may prove to be a viable means to increase harmonic yield and photon energy in semiconductor materials driven by intense laser fields.

Multiphoton ionization of many-electron atoms and highly-charged ions in intense laser fields: a relativistic time-dependent density functional theory approach

NASA Astrophysics Data System (ADS)

Tumakov, Dmitry A.; Telnov, Dmitry A.; Maltsev, Ilia A.; Plunien, Günter; Shabaev, Vladimir M.

2017-10-01

We develop an efficient numerical implementation of the relativistic time-dependent density functional theory (RTDDFT) to study multielectron highly-charged ions subject to intense linearly-polarized laser fields. The interaction with the electromagnetic field is described within the electric dipole approximation. The resulting time-dependent relativistic Kohn-Sham (RKS) equations possess an axial symmetry and are solved accurately and efficiently with the help of the time-dependent generalized pseudospectral method. As a case study, we calculate multiphoton ionization probabilities of the neutral argon atom and argon-like xenon ion. Relativistic effects are assessed by comparison of our present results with existing non-relativistic data.

Chemical vapor deposition of aminopropyl silanes in microfluidic channels for highly efficient microchip capillary electrophoresis-electrospray ionization-mass spectrometry.

PubMed

Batz, Nicholas G; Mellors, J Scott; Alarie, Jean Pierre; Ramsey, J Michael

2014-04-01

We describe a chemical vapor deposition (CVD) method for the surface modification of glass microfluidic devices designed to perform electrophoretic separations of cationic species. The microfluidic channel surfaces were modified using aminopropyl silane reagents. Coating homogeneity was inferred by precise measurement of the separation efficiency and electroosmotic mobility for multiple microfluidic devices. Devices coated with (3-aminopropyl)di-isopropylethoxysilane (APDIPES) yielded near diffusion-limited separations and exhibited little change in electroosmotic mobility between pH 2.8 and pH 7.5. We further evaluated the temporal stability of both APDIPES and (3-aminopropyl)triethoxysilane (APTES) coatings when stored for a total of 1 week under vacuum at 4 °C or filled with pH 2.8 background electrolyte at room temperature. Measurements of electroosmotic flow (EOF) and separation efficiency during this time confirmed that both coatings were stable under both conditions. Microfluidic devices with a 23 cm long, serpentine electrophoretic separation channel and integrated nanoelectrospray ionization emitter were CVD coated with APDIPES and used for capillary electrophoresis (CE)-electrospray ionization (ESI)-mass spectrometry (MS) of peptides and proteins. Peptide separations were fast and highly efficient, yielding theoretical plate counts over 600,000 and a peak capacity of 64 in less than 90 s. Intact protein separations using these devices yielded Gaussian peak profiles with separation efficiencies between 100,000 and 400,000 theoretical plates.

Study of Conical Pulsed Inductive Thruster with Multiple Modes of Operation

NASA Technical Reports Server (NTRS)

Miller, Robert; Eskridge, Richard; Martin, Adam; Rose, Frank

2008-01-01

An electrodeless, pulsed, inductively coupled thruster has several advantages over current electric propulsion designs. The efficiency of a pulsed inductive thruster is dependent upon the pulse characteristics of the device. Therefore, these thrusters are throttleable over a wide range of thrust levels by varying the pulse rate without affecting the thruster efficiency. In addition, by controlling the pulse energy and the mass bit together, the ISP of the thruster can also be varied with minimal efficiency loss over a wide range of ISP levels. Pulsed inductive thrusters will work with a multitude of propellants, including ammonia. Thus, a single pulsed inductive thruster could be used to handle a multitude of mission needs from high thrust to high ISP with one propulsion solution that would be variable in flight. A conical pulsed inductive lab thruster has been built to study this form of electric propulsion in detail. This thruster incorporates many advantages that are meant to enable this technology as a viable space propulsion technology. These advantages include incorporation of solid state switch technology for all switching needs of the thruster and pre-ionization of the propellant gas prior to acceleration. Pre-ionizing will significantly improve coupling efficiency between drive and bias fields and the plasma. This enables lower pulse energy levels without efficiency reduction. Pre-ionization can be accomplished at a small fraction of the drive pulse energy.

IONIZED GAS KINEMATICS AT HIGH RESOLUTION. V. [Ne ii], MULTIPLE CLUSTERS, HIGH EFFICIENCY STAR FORMATION, AND BLUE FLOWS IN HE 2–10

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

Beck, Sara; Turner, Jean; Lacy, John

2015-11-20

We measured the 12.8 μm [Ne ii] line in the dwarf starburst galaxy He 2–10 with the high-resolution spectrometer TEXES on the NASA IRTF. The data cube has a diffraction-limited spatial resolution of ∼1″ and a total velocity resolution, including thermal broadening, of ∼5 km s{sup −1}. This makes it possible to compare the kinematics of individual star-forming clumps and molecular clouds in the three dimensions of space and velocity, and allows us to determine star formation efficiencies. The kinematics of the ionized gas confirm that the starburst contains multiple dense clusters. From the M/R of the clusters and themore » ≃30%–40% star formation efficiencies, the clusters are likely to be bound and long lived, like globulars. Non-gravitational features in the line profiles show how the ionized gas flows through the ambient molecular material, as well as a narrow velocity feature, which we identify with the interface of the H ii region and a cold dense clump. These data offer an unprecedented view of the interaction of embedded H ii regions with their environment.« less

A combined thermal dissociation and electron impact ionization source for radioactive ion beam generation{sup a}

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

Alton, G.D.; Williams, C.

1996-04-01

The probability for simultaneously dissociating and efficiently ionizing the individual atomic constituents of molecular feed materials with conventional, hot-cathode, electron-impact ion sources is low and consequently, the ion beams from these sources often appear as mixtures of several molecular sideband beams. This fragmentation process leads to dilution of the intensity of the species of interest for radioactive ion beam (RIB) applications where beam intensity is at a premium. We have conceived an ion source that combines the excellent molecular dissociation properties of a thermal dissociator and the high ionization efficiency characteristics of an electron impact ionization source that will, inmore » principle, overcome this handicap. The source concept will be evaluated as a potential candidate for use for RIB generation at the Holifield Radioactive Ion Beam Facility, now under construction at the Oak Ridge National Laboratory. The design features and principles of operation of the source are described in this article. {copyright} {ital 1996 American Institute of Physics.}« less

A combined thermal dissociation and electron impact ionization source for radioactive ion beam generation (abstract){sup a}

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

Alton, G.D.; Williams, C.

1996-03-01

The probability for simultaneously dissociating and efficiently ionizing the individual atomic constituents of molecular feed materials with conventional, hot-cathode, electron-impact ion sources is low and consequently, the ion beams from these sources often appear as mixtures of several molecular sideband beams. This fragmentation process leads to dilution of the intensity of the species of interest for radioactive ion beam (RIB) applications where beam intensity is at a premium. We have conceived an ion source that combines the excellent molecular dissociation properties of a thermal dissociator and the high ionization efficiency characteristics of an electron impact ionization source that will, inmore » principle, overcome this handicap. The source concept will be evaluated as a potential candidate for use for RIB generation at the Holifield Radioactive Ion Beam Facility, now under construction at the Oak Ridge National Laboratory. The design features and principles of operation of the source are described in this article. {copyright} {ital 1996 American Institute of Physics.}« less

On the Ionization and Ion Transmission Efficiencies of Different ESI-MS Interfaces

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

Cox, Jonathan T.; Marginean, Ioan; Smith, Richard D.

2014-09-30

It is well known that the achievable sensitivity of electrospray ionization mass spectrometry (ESI-MS) is largely determined by the ionization efficiency in the ESI source and ion transmission efficiency through the ESI-MS interface. In this report we systematically study the ion transmission and ionization efficiencies in different ESI-MS interface configurations. The configurations under investigation include a single emitter/single inlet capillary, single emitter/multi-inlet capillary, and a subambient pressure ionization with nanoelectrospray (SPIN) MS interfaces with a single emitter and an emitter array, respectively. We present an effective method to evaluate the overall ion utilization efficiency of an ESI-MS interface by measuringmore » the total gas phase ion current transmitted through the interface and correlating it to the observed ion abundance measured in the corresponding mass spectrum. Our experimental results suggest that the overall ion utilization efficiency in the SPIN-MS interface configurations is better than that in the inlet capillary based ESI-MS interface configurations.« less

Cosmic distribution of highly ionized metals and their physical conditions in the EAGLE simulations

NASA Astrophysics Data System (ADS)

Rahmati, Alireza; Schaye, Joop; Crain, Robert A.; Oppenheimer, Benjamin D.; Schaller, Matthieu; Theuns, Tom

2016-06-01

We study the distribution and evolution of highly ionized intergalactic metals in the Evolution and Assembly of Galaxies and their Environment (EAGLE) cosmological, hydrodynamical simulations. EAGLE has been shown to reproduce a wide range of galaxy properties while its subgrid feedback was calibrated without considering gas properties. We compare the predictions for the column density distribution functions (CDDFs) and cosmic densities of Si IV, C IV, N V, O VI and Ne VIII absorbers with observations at redshift z = 0 to ˜6 and find reasonable agreement, although there are some differences. We show that the typical physical densities of the absorbing gas increase with column density and redshift, but decrease with the ionization energy of the absorbing ion. The typical metallicity increases with both column density and time. The fraction of collisionally ionized metal absorbers increases with time and ionization energy. While our results show little sensitivity to the presence or absence of AGN feedback, increasing/decreasing the efficiency of stellar feedback by a factor of 2 substantially decreases/increases the CDDFs and the cosmic densities of the metal ions. We show that the impact of the efficiency of stellar feedback on the CDDFs and cosmic densities is largely due to its effect on the metal production rate. However, the temperatures of the metal absorbers, particularly those of strong O VI, are directly sensitive to the strength of the feedback.

Cycling excitation process: An ultra efficient and quiet signal amplification mechanism in semiconductor

NASA Astrophysics Data System (ADS)

Liu, Yu-Hsin; Yan, Lujiang; Zhang, Alex Ce; Hall, David; Niaz, Iftikhar Ahmad; Zhou, Yuchun; Sham, L. J.; Lo, Yu-Hwa

2015-08-01

Signal amplification, performed by transistor amplifiers with its merit rated by the efficiency and noise characteristics, is ubiquitous in all electronic systems. Because of transistor thermal noise, an intrinsic signal amplification mechanism, impact ionization was sought after to complement the limits of transistor amplifiers. However, due to the high operation voltage (30-200 V typically), low power efficiency, limited scalability, and, above all, rapidly increasing excess noise with amplification factor, impact ionization has been out of favor for most electronic systems except for a few applications such as avalanche photodetectors and single-photon Geiger detectors. Here, we report an internal signal amplification mechanism based on the principle of the phonon-assisted cycling excitation process (CEP). Si devices using this concept show ultrahigh gain, low operation voltage, CMOS compatibility, and, above all, quantum limit noise performance that is 30 times lower than devices using impact ionization. Established on a unique physical effect of attractive properties, CEP-based devices can potentially revolutionize the fields of semiconductor electronics.

Scattering of hydrogen, nitrogen and water ions from micro pore optic plates for application in spaceborne plasma instrumentation

NASA Astrophysics Data System (ADS)

Stude, Joan; Wieser, Martin; Barabash, Stas

2016-10-01

Time-of-flight mass spectrometers for upcoming space missions into enhanced radiation environments need to be small, light weight and energy efficient. Time-of-flight systems using surface interactions as start-event generation can be smaller than foil-type instruments. Start surfaces for such applications need to provide narrow angular scattering, high ionization yields and high secondary electron emissions to be effective. We measured the angular scattering, energy distribution and positive ionization yield of micro pore optics for incident hydrogen, nitrogen and water ions at 2 keV. Positive ionization yields of 2% for H+ , 0.5% for N+ and 0.2% for H2O+ were detected.

Sensitive screening of abused drugs in dried blood samples using ultra-high-performance liquid chromatography-ion booster-quadrupole time-of-flight mass spectrometry.

PubMed

Chepyala, Divyabharathi; Tsai, I-Lin; Liao, Hsiao-Wei; Chen, Guan-Yuan; Chao, Hsi-Chun; Kuo, Ching-Hua

2017-03-31

An increased rate of drug abuse is a major social problem worldwide. The dried blood spot (DBS) sampling technique offers many advantages over using urine or whole blood sampling techniques. This study developed a simple and efficient ultra-high-performance liquid chromatography-ion booster-quadrupole time-of-flight mass spectrometry (UHPLC-IB-QTOF-MS) method for the analysis of abused drugs and their metabolites using DBS. Fifty-seven compounds covering the most commonly abused drugs, including amphetamines, opioids, cocaine, benzodiazepines, barbiturates, and many other new and emerging abused drugs, were selected as the target analytes of this study. An 80% acetonitrile solvent with a 5-min extraction by Geno grinder was used for sample extraction. A Poroshell column was used to provide efficient separation, and under optimal conditions, the analytical times were 15 and 5min in positive and negative ionization modes, respectively. Ionization parameters of both electrospray ionization source and ion booster (IB) source containing an extra heated zone were optimized to achieve the best ionization efficiency of the investigated abused drugs. In spite of their structural diversity, most of the abused drugs showed an enhanced mass response with the high temperature ionization from an extra heated zone of IB source. Compared to electrospray ionization, the ion booster (IB) greatly improved the detection sensitivity for 86% of the analytes by 1.5-14-fold and allowed the developed method to detect trace amounts of compounds on the DBS cards. The validation results showed that the coefficients of variation of intra-day and inter-day precision in terms of the signal intensity were lower than 19.65%. The extraction recovery of all analytes was between 67.21 and 115.14%. The limits of detection of all analytes were between 0.2 and 35.7ngmL -1 . The stability study indicated that 7% of compounds showed poor stability (below 50%) on the DBS cards after 6 months of storage at room temperature and -80°C. The reported method provides a new direction for abused drug screening using DBS. Copyright © 2017 Elsevier B.V. All rights reserved.

Development of a High Ionization Efficiency Molten Glass Ion Emitter for TIMS

NASA Astrophysics Data System (ADS)

Cheversia, M. B.; Farmer, G.; Koval, C.; David, D.

2006-12-01

Thermal ionization mass spectrometry (TIMS) remains the method of choice for many high precision isotope ratio determinations but is handicapped by the use of low efficiency ion emitters. For example, ionization efficiencies from molten glass emitters (Si-gel) used for such elements as Pb, Cr, Ru, and Ag are in the range of 0.05-2%, which limits the sample size and the precision to which isotope ratio determinations for these elements can be made. Our aim is to improve the ionization efficiency of the molten glass ion emitter using electrochemical methods. This work builds on recent observations indicating that many metals doped in borosilicate glasses (eg. Bi, Ag), are emitted from the liquid glass (in vacuo) primarily as the neutral metal atom. Our goal is to increase the proportion of singly charged metal atoms in metal-doped molten glasses via oxidation induced by electrochemical methods and to assess whether such in situ oxidation of metal atoms leads to an increase in emitted metal ions. Our experiments are performed in a vacuum chamber that mimics conditions in the sample chamber of the TIMS. A borosilicate glass sample is placed in a miniature ceramic crucible. The crucible contains working and reference Pt electrodes, and a Pt thermocouple. The entire apparatus is wrapped with a resistively heated Ta wire until temperatures in the glass reach approximately 1400°C, to ensure that the glass is molten. By this method, we have produced simple cyclic voltammograms that suggest that over a 100°C temperature range, the borosilicate glass undergoes a transition from resistive behavior as a solid, to a conductive electrolyte, as a molten liquid glass, as expected. The change is evident as an order of magnitude decrease in resistivity of the glass, as interpreted from the voltammograms. The voltammograms produced for the pure borosilicate glasses represent the baseline against which we will compare the electrochemical characteristics of Pb doped glasses. These experiments are currently underway and are designed to determine the speciation of lead in the glass, and to determine the voltages required to induce cathodic currents in the glass corresponding to ionization to Pb+ and Pb2+. By generating a cathodic current and an increased concentration of the oxidized species, we hope to ultimately generate a higher intensity ion beam, higher ionization efficiency for low efficiency elements, and higher precision analyses on small sample sizes for the TIMS.

Laser resonance ionization spectroscopy of antimony

NASA Astrophysics Data System (ADS)

Li, R.; Lassen, J.; Ruczkowski, J.; Teigelhöfer, A.; Bricault, P.

2017-02-01

The resonant ionization laser ion source is an element selective, efficient and versatile ion source to generate radioactive ion beams at on-line mass separator facilities. For some elements with complex atomic structures and incomplete spectroscopic data, laser spectroscopic investigations are required for ionization scheme development. Laser resonance ionization spectroscopy using Ti:Sa lasers has been performed on antimony (Sb) at TRIUMF's off-line laser ion source test stand. Laser light of 230.217 nm (vacuum wavelength) as the first excitation step and light from a frequency-doubled Nd:YVO4 laser (532 nm) as the nonresonant ionization step allowed to search for suitable second excitation steps by continuous wavelength scans from 720 nm to 920 nm across the wavelength tuning range of a grating-tuned Ti:Sa laser. Upon the identification of efficient SES, the third excitation steps for resonance ionization were investigated by laser scans across Rydberg states, the ionization potential and autoionizing states. One Rydberg state and six AI states were found to be well suitable for efficient resonance ionization.

Optimization of carrier multiplication for more effcient solar cells: the case of Sn quantum dots.

PubMed

Allan, Guy; Delerue, Christophe

2011-09-27

We present calculations of impact ionization rates, carrier multiplication yields, and solar-power conversion efficiencies in solar cells based on quantum dots (QDs) of a semimetal, α-Sn. Using these results and previous ones on PbSe and PbS QDs, we discuss a strategy to select QDs with the highest carrier multiplication rate for more efficient solar cells. We suggest using QDs of materials with a close to zero band gap and a high multiplicity of the bands in order to favor the relaxation of photoexcited carriers by impact ionization. Even in that case, the improvement of the maximum solar-power conversion efficiency appears to be a challenging task. © 2011 American Chemical Society

Characteristics of light reflected from a dense ionization wave with a tunable velocity.

PubMed

Zhidkov, A; Esirkepov, T; Fujii, T; Nemoto, K; Koga, J; Bulanov, S V

2009-11-20

An optically dense ionization wave (IW) produced by two femtosecond (approximately 10/30 fs) laser pulses focused cylindrically and crossing each other may become an efficient coherent x-ray converter in accordance with the Semenova-Lampe theory. The resulting velocity of a quasiplane IW in the vicinity of pulse intersection changes with the angle between the pulses from the group velocity of ionizing pulses to infinity allowing a tuning of the wavelength of x rays and their bunching. The x-ray spectra after scattering of a lower frequency and long coherent light pulse change from the monochromatic to high order harmoniclike with the duration of the ionizing pulses.

Thrust performance, propellant ionization, and thruster erosion of an external discharge plasma thruster

NASA Astrophysics Data System (ADS)

Karadag, Burak; Cho, Shinatora; Funaki, Ikkoh

2018-04-01

It is quite a challenge to design low power Hall thrusters with a long lifetime and high efficiency because of the large surface area to volume ratio and physical limits to the magnetic circuit miniaturization. As a potential solution to this problem, we experimentally investigated the external discharge plasma thruster (XPT). The XPT produces and sustains a plasma discharge completely in the open space outside of the thruster structure through a magnetic mirror configuration. It eliminates the very fundamental component of Hall thrusters, discharge channel side walls, and its magnetic circuit consists solely of a pair of hollow cylindrical permanent magnets. Thrust, low frequency discharge current oscillation, ion beam current, and plasma property measurements were conducted to characterize the manufactured prototype thruster for the proof of concept. The thrust performance, propellant ionization, and thruster erosion were discussed. Thrust generated by the XPT was on par with conventional Hall thrusters [stationary plasma thruster (SPT) or thruster with anode layer] at the same power level (˜11 mN at 250 W with 25% anode efficiency without any optimization), and discharge current had SPT-level stability (Δ < 0.2). Faraday probe measurements revealed that ion beams are finely collimated, and plumes have Gaussian distributions. Mass utilization efficiencies, beam utilization efficiencies, and plume divergence efficiencies ranged from 28 to 62%, 78 to 99%, and 40 to 48%, respectively. Electron densities and electron temperatures were found to reach 4 × 1018 m-3 ( ∂ n e / n e = ±52%) and 15 eV ( ∂ T e / T e = ±10%-30%), respectively, at 10 mm axial distance from the anode centerline. An ionization mean free path analysis revealed that electron density in the ionization region is substantially higher than the conventional Hall thrusters, which explain why the XPT is as efficient as conventional ones even without a physical ionization chamber. Our findings propose an alternative approach for low power Hall thruster design and provide a successful proof of concept experiment of the XPT.

Gas engineering studies for high pressure self-sustained diffuse discharge closing switches

NASA Astrophysics Data System (ADS)

Hunter, S. R.; Christophorou, L. G.; Carter, J. G.

The operating voltage and discharge stability of diffuse discharges for fast-closing switch applications are critically dependent on the variation of the ionization (alpha/N) and attachment (eta/N) coefficients with E/N (gas density normalized electric field strength). Gases and gas mixtures which possess low (E/N)/sub lim/ values (i.e., the E/N value when anti alpha/N = alpha/N - eta/N = 0) and effective ionization coefficients, anti alpha/N, which vary slowly with E/N near (E/N)(sub lim) lead to lower voltage (i.e., more efficient) operation with increased discharge stability. Several gas mixtures with these characteristics are discussed. It is argued that further improvements in switch efficiency and discharge stability can be obtained by adding a low ionization onset gas additive to these binary mixtures, such that at low E/N, alpha/N is greater than eta/N, while at higher E/N, eta/N is greater than alpha/N over a restricted E/N range. Several low ionization onset gas additives are suggested and the electron attachment and ionization coefficients in selected gas mixtures which possess these desirable characteristics are given.

On the Ionization and Ion Transmission Efficiencies of Different ESI-MS Interfaces

PubMed Central

Cox, Jonathan T.; Marginean, Ioan; Smith, Richard D.; Tang, Keqi

2014-01-01

The achievable sensitivity of electrospray ionization mass spectrometry (ESI-MS) is largely determined by the ionization efficiency in the ESI source and ion transmission efficiency through the ESI-MS interface. These performance characteristics are difficult to evaluate and compare across multiple platforms as it is difficult to correlate electrical current measurements to actual analyte ions reaching the detector of a mass spectrometer. We present an effective method to evaluate the overall ion utilization efficiency of an ESI-MS interface by measuring the total gas phase ion current transmitted through the interface and correlating it to the observed ion abundance measured in the corresponding mass spectrum. Using this method we systematically studied the ion transmission and ionization efficiencies of different ESI-MS interface configurations, including a single emitter/single inlet capillary, single emitter/multi-inlet capillary, and a subambient pressure ionization with nanoelectrospray (SPIN) MS interface with a single emitter and an emitter array, respectively. Our experimental results indicate that the overall ion utilization efficiency of SPIN-MS interface configurations exceeds that of the inlet capillary-based ESI-MS interface configurations. PMID:25267087

On the ionization and ion transmission efficiencies of different ESI-MS interfaces.

PubMed

Cox, Jonathan T; Marginean, Ioan; Smith, Richard D; Tang, Keqi

2015-01-01

The achievable sensitivity of electrospray ionization mass spectrometry (ESI-MS) is largely determined by the ionization efficiency in the ESI source and ion transmission efficiency through the ESI-MS interface. These performance characteristics are difficult to evaluate and compare across multiple platforms as it is difficult to correlate electrical current measurements to actual analyte ions reaching the detector of a mass spectrometer. We present an effective method to evaluate the overall ion utilization efficiency of an ESI-MS interface by measuring the total gas-phase ion current transmitted through the interface and correlating it to the observed ion abundance measured in the corresponding mass spectrum. Using this method, we systematically studied the ion transmission and ionization efficiencies of different ESI-MS interface configurations, including a single emitter/single inlet capillary, single emitter/multi-inlet capillary, and a subambient pressure ionization with nanoelectrospray (SPIN) MS interface with a single emitter and an emitter array, respectively. Our experimental results indicate that the overall ion utilization efficiency of SPIN-MS interface configurations exceeds that of the inlet capillary-based ESI-MS interface configurations.

Reversal electron attachment ionizer for detection of trace species

NASA Technical Reports Server (NTRS)

Bernius, Mark T. (Inventor); Chutjian, Ara (Inventor)

1990-01-01

An in-line reversal electron, high-current ionizer capable of focusing a beam of electrons to a reversal region and executing a reversal of said electrons, such that the electrons possess zero kinetic energy at the point of reversal, may be used to produce both negative and positive ions. A sample gas is introduced at the point of electron reversal for low energy electron-(sample gas) molecule attachment with high efficiency. The attachment process produces negative ions from the sample gas, which includes species present in trace (minute) amounts. These ions are extracted efficiently and directed to a mass analyzer where they may be detected and identified. The generation and detection of positive ions is accomplished in a similar fashion with minimal adjustment to potentials applied to the apparatus.

Reversal electron attachment ionizer for detection of trace species

NASA Technical Reports Server (NTRS)

Bernius, Mark T. (Inventor); Chutjian, Ara (Inventor)

1989-01-01

An in-line reversal electron, high-current ionizer capable of focusing a beam of electrons to a reversal region and executing a reversal of the electrons, such that the electrons possess zero kinetic energy at the point of reversal, may be used to produce both negative and positive ions. A sample gas is introduced at the point of electron reversal for low energy electron-(sample gas) molecule attachment with high efficiency. The attachment process produces negative ions from the sample gas, which includes species present in trace (minute) amounts. These ions are extracted efficiently and directed to a mass analyzer where they may be detected and identified. The generation and detection of positive ions is accomplished in a similar fashion with minimal adjustment to potentials applied to the apparatus.

Graphene oxide membrane as an efficient extraction and ionization substrate for spray-mass spectrometric analysis of malachite green and its metabolite in fish samples.

PubMed

Wei, Shih-Chun; Fan, Shen; Lien, Chia-Wen; Unnikrishnan, Binesh; Wang, Yi-Sheng; Chu, Han-Wei; Huang, Chih-Ching; Hsu, Pang-Hung; Chang, Huan-Tsung

2018-03-20

A graphene oxide (GO) nanosheet-modified N + -nylon membrane (GOM) has been prepared and used as an extraction and spray-ionization substrate for robust mass spectrometric detection of malachite green (MG), a highly toxic disinfectant in liquid samples and fish meat. The GOM is prepared by self-deposition of GO thin film onto an N + -nylon membrane, which has been used for efficient extraction of MG in aquaculture water samples or homogenized fish meat samples. Having a dissociation constant of 2.17 × 10 -9  M -1 , the GOM allows extraction of approximately 98% of 100 nM MG. Coupling of the GOM-spray with an ion-trap mass spectrometer allows quantitation of MG in aquaculture freshwater and seawater samples down to nanomolar levels. Furthermore, the system possesses high selectivity and sensitivity for the quantitation of MG and its metabolite (leucomalachite green) in fish meat samples. With easy extraction and efficient spray ionization properties of GOM, this membrane spray-mass spectrometry technique is relatively simple and fast in comparison to the traditional LC-MS/MS methods for the quantitation of MG and its metabolite in aquaculture products. Copyright © 2017 Elsevier B.V. All rights reserved.

GaN Light-Emitting Triodes (LETs) for High-Efficiency Hole Injection and for Assessment of the Physical Origin of the Efficiency Droop

DTIC Science & Technology

2007-07-06

quantum efficiency . In AlGaN-based UV LEDs, an electron-blocking layer (EBL) is frequently inserted between the p-type cladding layer and the active...me). This limits the hole injection efficiency into the active region, and hence internal quantum efficiency . Figure 1: (a) Schematic band...less efficient than along the lateral direction because most of the holes ionized from the acceptors are localized inside the quantum wells which are

Nuclear microprobe investigation of the effects of ionization and displacement damage in vertical, high voltage GaN diodes

DOE PAGES

Vizkelethy, G.; King, M. P.; Aktas, O.; ...

2016-12-02

Radiation responses of high-voltage, vertical gallium-nitride (GaN) diodes were investigated using Sandia National Laboratories’ nuclear microprobe. Effects of the ionization and the displacement damage were studied using various ion beams. We found that the devices show avalanche effect for heavy ions operated under bias well below the breakdown voltage. Here, the displacement damage experiments showed a surprising effect for moderate damage: the charge collection efficiency demonstrated an increase instead of a decrease for higher bias voltages.

Nuclear microprobe investigation of the effects of ionization and displacement damage in vertical, high voltage GaN diodes

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

Vizkelethy, G.; King, M. P.; Aktas, O.

Radiation responses of high-voltage, vertical gallium-nitride (GaN) diodes were investigated using Sandia National Laboratories’ nuclear microprobe. Effects of the ionization and the displacement damage were studied using various ion beams. We found that the devices show avalanche effect for heavy ions operated under bias well below the breakdown voltage. Here, the displacement damage experiments showed a surprising effect for moderate damage: the charge collection efficiency demonstrated an increase instead of a decrease for higher bias voltages.

Development Status of the Helicon Hall Thruster

DTIC Science & Technology

2009-09-15

Hall thruster , the Helicon Hall Thruster , is presented. The Helicon Hall Thruster combines the efficient ionization mechanism of a helicon source with the favorable plasma acceleration properties of a Hall thruster . Conventional Hall thrusters rely on direct current electron bombardment to ionize the flow in order to generate thrust. Electron bombardment typically results in an ionization cost that can be on the order of ten times the ionization potential, leading to reduced efficiency, particularly at low

Cycling excitation process: An ultra efficient and quiet signal amplification mechanism in semiconductor

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

Liu, Yu-Hsin; Yan, Lujiang; Zhang, Alex Ce

2015-08-03

Signal amplification, performed by transistor amplifiers with its merit rated by the efficiency and noise characteristics, is ubiquitous in all electronic systems. Because of transistor thermal noise, an intrinsic signal amplification mechanism, impact ionization was sought after to complement the limits of transistor amplifiers. However, due to the high operation voltage (30-200 V typically), low power efficiency, limited scalability, and, above all, rapidly increasing excess noise with amplification factor, impact ionization has been out of favor for most electronic systems except for a few applications such as avalanche photodetectors and single-photon Geiger detectors. Here, we report an internal signal amplification mechanismmore » based on the principle of the phonon-assisted cycling excitation process (CEP). Si devices using this concept show ultrahigh gain, low operation voltage, CMOS compatibility, and, above all, quantum limit noise performance that is 30 times lower than devices using impact ionization. Established on a unique physical effect of attractive properties, CEP-based devices can potentially revolutionize the fields of semiconductor electronics.« less

Top-down approach for the direct characterization of low molecular weight heparins using LC-FT-MS.

PubMed

Li, Lingyun; Zhang, Fuming; Zaia, Joseph; Linhardt, Robert J

2012-10-16

Low molecular heparins (LMWHs) are structurally complex, heterogeneous, polydisperse, and highly negatively charged mixtures of polysaccharides. The direct characterization of LMWH is a major challenge for currently available analytical technologies. Electrospray ionization (ESI) liquid chromatography-mass spectrometry (LC-MS) is a powerful tool for the characterization complex biological samples in the fields of proteomics, metabolomics, and glycomics. LC-MS has been applied to the analysis of heparin oligosaccharides, separated by size exclusion, reversed phase ion-pairing chromatography, and chip-based amide hydrophilic interaction chromatography (HILIC). However, there have been limited applications of ESI-LC-MS for the direct characterization of intact LMWHs (top-down analysis) due to their structural complexity, low ionization efficiency, and sulfate loss. Here we present a simple and reliable HILIC-Fourier transform (FT)-ESI-MS platform to characterize and compare two currently marketed LMWH products using the top-down approach requiring no special sample preparation steps. This HILIC system relies on cross-linked diol rather than amide chemistry, affording highly resolved chromatographic separations using a relatively high percentage of acetonitrile in the mobile phase, resulting in stable and high efficiency ionization. Bioinformatics software (GlycReSoft 1.0) was used to automatically assign structures within 5-ppm mass accuracy.

Investigation of Recombination Processes In A Magnetized Plasma

NASA Technical Reports Server (NTRS)

Chavers, Greg; Chang-Diaz, Franklin; Rodgers, Stephen L. (Technical Monitor)

2002-01-01

Interplanetary travel requires propulsion systems that can provide high specific impulse (Isp), while also having sufficient thrust to rapidly accelerate large payloads. One such propulsion system is the Variable Specific Impulse Magneto-plasma Rocket (VASIMR), which creates, heats, and exhausts plasma to provide variable thrust and Isp, optimally meeting the mission requirements. A large fraction of the energy to create the plasma is frozen in the exhaust in the form of ionization energy. This loss mechanism is common to all electromagnetic plasma thrusters and has an impact on their efficiency. When the device operates at high Isp, where the exhaust kinetic energy is high compared to the ionization energy, the frozen flow component is of little consequence; however, at low Isp, the effect of the frozen flow may be important. If some of this energy could be recovered through recombination processes, and re-injected as neutral kinetic energy, the efficiency of VASIMR, in its low Isp/high thrust mode may be improved. In this operating regime, the ionization energy is a large portion of the total plasma energy. An experiment is being conducted to investigate the possibility of recovering some of the energy used to create the plasma. This presentation will cover the progress and status of the experiment involving surface recombination of the plasma.

Ionization Mechanism of Positive-Ion Nitrogen Direct Analysis in Real Time.

PubMed

Song, Liguo; Chuah, Wei Chean; Lu, Xinyi; Remsen, Edward; Bartmess, John E

2018-04-01

Nitrogen can be an inexpensive alternative to helium used by direct analysis in real time (DART), especially in consideration of the looming helium shortage. Therefore, the ionization mechanism of positive-ion N 2 DART has been systematically investigated. Our experiments suggest that a range of metastable nitrogen species with a variety of internal energies existed and all of them were less energetic than metastable helium atoms. However, compounds with ionization energies (IE) equal to or lower than 10.2 eV (all organic compounds except the extremely small ones) can be efficiently ionized. Because N 2 DART was unable to efficiently ionize ambient moisture and common organic solvents such as methanol and acetonitrile, the most important ionization mechanism was direct Penning ionization followed by self-protonation of polar compounds generating [M+H] + ions. On the other hand, N 2 DART was able to efficiently ionize ammonia, which was beneficial in the ionization of hydrogen-bonding compounds with proton affinities (PA) weaker than ammonia generating [M+NH 4 ] + ions and large PAHs generating [M+H] + ions through proton transfer. N 2 DART was also able to efficiently ionize NO, which led to the ionization of nonpolar compounds such as alkanes and small aromatics generating [M-(2m+1)H] + (m=0,1…) ions. Lastly, metastable nitrogen species was also able to produce oxygen atoms, which resulted in increased oxygen adducts as the polarity of organic compounds decreased. In comparison with He DART, N 2 DART was approximately one order of magnitude less sensitive in generating [M+H] + ions, but could be more sensitive in generating [M+NH 4 ] + ions. Graphical Abstract ᅟ.

Ionization Mechanism of Positive-Ion Nitrogen Direct Analysis in Real Time

NASA Astrophysics Data System (ADS)

Song, Liguo; Chuah, Wei Chean; Lu, Xinyi; Remsen, Edward; Bartmess, John E.

2018-02-01

Nitrogen can be an inexpensive alternative to helium used by direct analysis in real time (DART), especially in consideration of the looming helium shortage. Therefore, the ionization mechanism of positive-ion N2 DART has been systematically investigated. Our experiments suggest that a range of metastable nitrogen species with a variety of internal energies existed and all of them were less energetic than metastable helium atoms. However, compounds with ionization energies (IE) equal to or lower than 10.2 eV (all organic compounds except the extremely small ones) can be efficiently ionized. Because N2 DART was unable to efficiently ionize ambient moisture and common organic solvents such as methanol and acetonitrile, the most important ionization mechanism was direct Penning ionization followed by self-protonation of polar compounds generating [M+H]+ ions. On the other hand, N2 DART was able to efficiently ionize ammonia, which was beneficial in the ionization of hydrogen-bonding compounds with proton affinities (PA) weaker than ammonia generating [M+NH4]+ ions and large PAHs generating [M+H]+ ions through proton transfer. N2 DART was also able to efficiently ionize NO, which led to the ionization of nonpolar compounds such as alkanes and small aromatics generating [M-(2m+1)H]+ (m=0,1…) ions. Lastly, metastable nitrogen species was also able to produce oxygen atoms, which resulted in increased oxygen adducts as the polarity of organic compounds decreased. In comparison with He DART, N2 DART was approximately one order of magnitude less sensitive in generating [M+H]+ ions, but could be more sensitive in generating [M+NH4]+ ions. [Figure not available: see fulltext.

Diagnostic studies of ion beam formation in inductively coupled plasma

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

Jacobs, Jenee L.

2015-01-01

This dissertation describes a variety of studies focused on the plasma and the ion beam in inductively coupled plasma mass spectrometry (ICP-MS). The ability to use ICP-MS for measurements of trace elements in samples requires the analytes to be efficiently ionized. Updated ionization efficiency tables are discussed for ionization temperatures of 6500 K and 7000 K with an electron density of 1 x 10 15 cm -3. These values are reflective of the current operating parameters of ICP-MS instruments. Calculations are also discussed for doubly charged (M 2+) ion formation, neutral metal oxide (MO) ionization, and metal oxide (MO +)more » ion dissociation for similar plasma temperature values. Ionization efficiency results for neutral MO molecules in the ICP have not been reported previously.« less

Capillary atmospheric pressure electron capture ionization (cAPECI): a highly efficient ionization method for nitroaromatic compounds.

PubMed

Derpmann, Valerie; Mueller, David; Bejan, Iustinian; Sonderfeld, Hannah; Wilberscheid, Sonja; Koppmann, Ralf; Brockmann, Klaus J; Benter, Thorsten

2014-03-01

We report on a novel method for atmospheric pressure ionization of compounds with elevated electron affinity (e.g., nitroaromatic compounds) or gas phase acidity (e.g., phenols), respectively. The method is based on the generation of thermal electrons by the photo-electric effect, followed by electron capture of oxygen when air is the gas matrix yielding O2(-) or of the analyte directly with nitrogen as matrix. Charge transfer or proton abstraction by O2(-) leads to the ionization of the analytes. The interaction of UV-light with metals is a clean method for the generation of thermal electrons at atmospheric pressure. Furthermore, only negative ions are generated and neutral radical formation is minimized, in contrast to discharge- or dopant assisted methods. Ionization takes place inside the transfer capillary of the mass spectrometer leading to comparably short transfer times of ions to the high vacuum region of the mass spectrometer. This strongly reduces ion transformation processes, resulting in mass spectra that more closely relate to the neutral analyte distribution. cAPECI is thus a soft and selective ionization method with detection limits in the pptV range. In comparison to standard ionization methods (e.g., PTR), cAPECI is superior with respect to both selectivity and achievable detection limits. cAPECI demonstrates to be a promising ionization method for applications in relevant fields as, for example, explosives detection and atmospheric chemistry.

High-field plasma acceleration in a high-ionization-potential gas

DOE PAGES

Corde, S.; Adli, E.; Allen, J. M.; ...

2016-06-17

Plasma accelerators driven by particle beams are a very promising future accelerator technology as they can sustain high accelerating fields over long distances with high energy efficiency. They rely on the excitation of a plasma wave in the wake of a drive beam. To generate the plasma, a neutral gas can be field-ionized by the head of the drive beam, in which case the distance of acceleration and energy gain can be strongly limited by head erosion. In our research, we overcome this limit and demonstrate that electrons in the tail of a drive beam can be accelerated by upmore » to 27 GeV in a high-ionization-potential gas (argon), boosting their initial 20.35 GeV energy by 130%. Particle-in-cell simulations show that the argon plasma is sustaining very high electric fields, of ~150 GV m -1, over ~20 cm. Lastly, the results open new possibilities for the design of particle beam drivers and plasma sources.« less

PHD TUTORIAL: A complete numerical approach to electron hydrogen collisions

NASA Astrophysics Data System (ADS)

Bartlett, Philip L.

2006-11-01

This tutorial presents an extensive computational study of electron-impact scattering and ionization of atomic hydrogen and hydrogenic ions, through the solution of the non-relativistic Schrödinger equation in coordinate space using propagating exterior complex scaling (PECS). It details the complete numerical and computational development of the PECS method, which enables highly computationally-efficient solution of these collision systems. Benchmark results are presented for a complete range of electron-hydrogen collisions, including discrete elastic and inelastic scattering both below and above the ionization threshold energy, very low-energy ionizing collisions through to moderately high-energy ionizing collisions, ground-state and excited-state targets and charged hydrogenic targets with Z <= 4. Total ionization cross sections through to fully differential cross sections, both in-plane and out-of-plane, are given and are found to be in excellent accord with other state-of-the-art methods and measurements, where available. We also review our recent confirmation (Bartlett and Stelbovics 2004 Phys. Rev. Lett. 93 233201) of the Wannier and related threshold laws for e-H collisions.

A Versatile Integrated Ambient Ionization Source Platform.

PubMed

Ai, Wanpeng; Nie, Honggang; Song, Shiyao; Liu, Xiaoyun; Bai, Yu; Liu, Huwei

2018-04-30

The pursuit of high-throughput sample analysis from complex matrix demands development of multiple ionization techniques with complementary specialties. A versatile integrated ambient ionization source (iAmIS) platform is proposed in this work, based on the idea of integrating multiple functions, enhancing the efficiency of current ionization techniques, extending the applications, and decreasing the cost of the instrument. The design of the iAmIS platform combines flowing atmospheric pressure afterglow (FAPA) source/direct analysis in real time (DART), dielectric barrier discharge ionization (DBDI)/low-temperature plasma (LTP), desorption electrospray ionization (DESI), and laser desorption (LD) technique. All individual and combined ionization modes can be easily attained by modulating parameters. In particular, the FAPA/DART&DESI mode can realize the detection of polar and nonpolar compounds at the same time with two different ionization mechanisms: proton transfer and charge transfer. The introduction of LD contributes to the mass spectrometry imaging and the surface-assisted laser desorption (SALDI) under ambient condition. Compared with other individual or multi-mode ion source, the iAmIS platform provides the flexibility of choosing different ionization modes, broadens the scope of the analyte detection, and facilitates the analysis of complex samples. Graphical abstract ᅟ.

A Versatile Integrated Ambient Ionization Source Platform

NASA Astrophysics Data System (ADS)

Ai, Wanpeng; Nie, Honggang; Song, Shiyao; Liu, Xiaoyun; Bai, Yu; Liu, Huwei

2018-04-01

The pursuit of high-throughput sample analysis from complex matrix demands development of multiple ionization techniques with complementary specialties. A versatile integrated ambient ionization source (iAmIS) platform is proposed in this work, based on the idea of integrating multiple functions, enhancing the efficiency of current ionization techniques, extending the applications, and decreasing the cost of the instrument. The design of the iAmIS platform combines flowing atmospheric pressure afterglow (FAPA) source/direct analysis in real time (DART), dielectric barrier discharge ionization (DBDI)/low-temperature plasma (LTP), desorption electrospray ionization (DESI), and laser desorption (LD) technique. All individual and combined ionization modes can be easily attained by modulating parameters. In particular, the FAPA/DART&DESI mode can realize the detection of polar and nonpolar compounds at the same time with two different ionization mechanisms: proton transfer and charge transfer. The introduction of LD contributes to the mass spectrometry imaging and the surface-assisted laser desorption (SALDI) under ambient condition. Compared with other individual or multi-mode ion source, the iAmIS platform provides the flexibility of choosing different ionization modes, broadens the scope of the analyte detection, and facilitates the analysis of complex samples. [Figure not available: see fulltext.

High efficiency direct detection of ions from resonance ionization of sputtered atoms

DOEpatents

Gruen, Dieter M.; Pellin, Michael J.; Young, Charles E.

1986-01-01

A method and apparatus are provided for trace and other quantitative analysis with high efficiency of a component in a sample, with the analysis involving the removal by ion or other bombardment of a small quantity of ion and neutral atom groups from the sample, the conversion of selected neutral atom groups to photoions by laser initiated resonance ionization spectroscopy, the selective deflection of the photoions for separation from original ion group emanating from the sample, and the detection of the photoions as a measure of the quantity of the component. In some embodiments, the original ion group is accelerated prior to the RIS step for separation purposes. Noise and other interference are reduced by shielding the detector from primary and secondary ions and deflecting the photoions sufficiently to avoid the primary and secondary ions.

High efficiency direct detection of ions from resonance ionization of sputtered atoms

DOEpatents

Gruen, D.M.; Pellin, M.J.; Young, C.E.

1985-01-16

A method and apparatus are provided for trace and other quantitative analysis with high efficiency of a component in a sample, with the analysis involving the removal by ion or other bombardment of a small quantity of ion and neutral atom groups from the sample, the conversion of selected neutral atom groups to photoions by laser initiated resonance ionization spectroscopy, the selective deflection of the photoions for separation from original ion group emanating from the sample, and the detection of the photoions as a measure of the quantity of the component. In some embodiments, the original ion group is accelerated prior to the RIS step for separation purposes. Noise and other interference are reduced by shielding the detector from primary and secondary ions and deflecting the photoions sufficiently to avoid the primary and secondary ions.

Creating space plasma from the ground

NASA Astrophysics Data System (ADS)

Carlson, H. C.; Djuth, F. T.; Zhang, L. D.

2017-01-01

We have performed an experiment to compare as directly as realizable the ionization production rate by HF radio wave energy versus by solar EUV. We take advantage of the commonality that ionization production by both ground-based high-power HF radio waves and by solar EUV is driven by primary and secondary suprathermal electrons near and above 20 eV. Incoherent scatter radar (ISR) plasma-line amplitudes are used as a measure of suprathermal electron fluxes for ISR wavelengths near those for 430 MHz and are indeed a clean measure of such for those fluxes sufficiently weak to have negligible self-damping. We present data from an HF heating experiment on November 2015 at Arecibo, which even more directly confirm the only prior midlatitude estimate, of order 10% efficiency for conversion of HF energy to ionospheric ionization. We note the theoretical maximum possible is 1/3, while 1% or less reduces the question to near practical irrelevance. Our measurements explicitly confirm the prediction that radio-frequency production of artificial ionospheres can be practicable, even at midlatitudes. Furthermore, that this midlatitude efficiency is comparable to efficiencies measured at high latitudes (which include enhancements unique to high latitudes including magnetic zenith effect, gyrofrequency multiples, and double resonances) requires reexamination of current theoretical thinking about soft-electron acceleration processes in weakly magnetized plasmas. The implications are that electron acceleration by any of a variety of processes may be a fundamental underpinning to energy redistribution in space plasmas.

Silver nanostructures in laser desorption/ionization mass spectrometry and mass spectrometry imaging.

PubMed

Sekuła, Justyna; Nizioł, Joanna; Rode, Wojciech; Ruman, Tomasz

2015-09-21

Silver nanoparticles have been successfully applied as a matrix replacement for the laser desorption/ionization time-of-flight mass spectrometry (LDI-ToF-MS). Nanoparticles, producing spectra with highly reduced chemical background in the low m/z region, are perfectly suited for low-molecular weight compound analysis and imaging. Silver nanoparticles (AgNPs) can efficiently absorb ultraviolet laser radiation, transfer energy to the analyte and promote analyte desorption, but also constitute a source of silver ions suitable for analyte cationisation. This review provides an overview of the literature on silver nanomaterials as non-conventional desorption and ionization promoters in LDI-MS and mass spectrometry imaging.

Observation of novel photochemistry in the multiphoton ionization of Mo(CO) sub 6 van der Waals clusters

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

Peifer, W.R.; Garvey, J.F.

1989-07-27

van der Waals clusters of Mo(CO){sub 6} generated in the free-jet expansion of a pulsed beam of seeded helium are subjected to multiphoton ionization and the product ions analyzed by quadrupole mass spectrometry. Oxomolybdenum and dioxomolybdenum ions are observed to be produced with high efficiency. This behavior is in striking contrast to that of metal carbonyl monomers and covalently bound cluster carbonyls, which under complete ligand loss prior to ionization. The observed photochemistry is ascribed to reactions between a photoproduced molybdenum atom and the ligands of neighboring Mo(CO){sub 6} solvent molecules within the van der Waals cluster.

Capillary electrophoresis electrospray ionization mass spectrometry interface

DOEpatents

Smith, Richard D.; Severs, Joanne C.

1999-01-01

The present invention is an interface between a capillary electrophoresis separation capillary end and an electrospray ionization mass spectrometry emitter capillary end, for transporting an anolyte sample from a capillary electrophoresis separation capillary to a electrospray ionization mass spectrometry emitter capillary. The interface of the present invention has: (a) a charge transfer fitting enclosing both of the capillary electrophoresis capillary end and the electrospray ionization mass spectrometry emitter capillary end; (b) a reservoir containing an electrolyte surrounding the charge transfer fitting; and (c) an electrode immersed into the electrolyte, the electrode closing a capillary electrophoresis circuit and providing charge transfer across the charge transfer fitting while avoiding substantial bulk fluid transfer across the charge transfer fitting. Advantages of the present invention have been demonstrated as effective in providing high sensitivity and efficient analyses.

Analysis of nonderivatized steroids by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using C70 fullerene as matrix.

PubMed

Montsko, Gergely; Vaczy, Alexandra; Maasz, Gabor; Mernyak, Erzsebet; Frank, Eva; Bay, Csaba; Kadar, Zalan; Ohmacht, Robert; Wolfling, Janos; Mark, Laszlo

2009-10-01

Neutral steroid hormones are currently analyzed by gas or liquid chromatography/mass spectrometry based methods. Most of the steroid compounds, however, lack volatility and do not contain polar groups, which results in inadequate chromatographic behavior and low ionization efficiency. Derivatization of the steroids to form more volatile, thermostable, and charged products solves this difficulty, but the derivatization of compounds with unknown chemical moieties is not an easy task. In this study, a rapid, high-throughput, sensitive matrix-assisted laser desorption/ionization time-of-flight mass spectrometry method is described using C(70) fullerene as a matrix compound. The application of the method is demonstrated for five general sex steroids and for synthetic steroid compounds in both negative and positive ionization modes.

The SPES surface ionization source

NASA Astrophysics Data System (ADS)

Manzolaro, M.; D'Agostini, F.; Monetti, A.; Andrighetto, A.

2017-09-01

Ion sources and target systems play a crucial role in isotope separation on line facilities, determining the main characteristics of the radioactive ion beams available for experiments. In the context of the selective production of exotic species (SPES) facility, a 40 MeV, 200 μA proton beam directly impinges a uranium carbide target, generating approximately 1013 fissions per second. The radioactive isotopes produced by the 238U fissions are delivered to the 1+ ion source by means of a tubular transfer line. Here they can be ionized and subsequently accelerated toward the experimental areas. In this work, the characterization of the surface ionization source currently adopted for the SPES facility is presented, taking as a reference ionization efficiency and transversal emittance measurements. The effects of long term operation at high temperature are also illustrated and discussed.

Effects of ionizing radiation in ginkgo and guarana [rapid communication

NASA Astrophysics Data System (ADS)

Rabelo Soriani, Renata; Cristina Satomi, Lucilia; Pinto, Terezinha de Jesus A.

2005-07-01

Raw plant materials normally carry high bioburden due to their origin, offering potential hazards to consumers. The use of decontamination processes is therefore an important step towards the consumer safety and therapeutical efficiency. Several authors have reported the treatment of medicinal herbs with ionizing radiation. This work evaluated the effects of different radiation doses on the microbial burden and chemical constituents of ginkgo ( Ginkgo biloba L.) and guaraná ( Paullinia cupana H.B.K.).

Was Star Formation Suppressed in High-Redshift Minihalos?

NASA Astrophysics Data System (ADS)

Haiman, Zoltán; Bryan, Greg L.

2006-10-01

The primordial gas in the earliest dark matter halos, collapsing at redshifts z~20, with masses Mhalo~106 Msolar and virial temperatures Tvir<104 K, relied on the presence of molecules for cooling. Several theoretical studies have suggested that gas contraction and star formation in these minihalos was suppressed by radiative, chemical, thermal, and dynamical feedback processes. The recent measurement by the Wilkinson Microwave Anisotropy Probe (WMAP) of the optical depth to electron scattering, τ~0.09+/-0.03, provides the first empirical evidence for this suppression. The new WMAP result is consistent with vanilla models of reionization, in which ionizing sources populate cold dark matter halos down to a virial temperature of Tvir=104 K. On the other hand, we show that in order to avoid overproducing the optical depth, the efficiency for the production of ionizing photons in minihalos must have been about an order of magnitude lower than expected from massive metal-free stars and lower than the efficiency in large halos that can cool via atomic hydrogen (Tvir>104 K). This conclusion is insensitive to assumptions about the efficiency of ionizing photon production in the large halos, as long as reionization ends by z=6, as required by the spectra of bright quasars at z<~6. Our conclusion is strengthened if the clumping of the ionized gas evolves with redshift, as suggested by semianalytical predictions and three-dimensional numerical simulations.

Laser-Induced Ionization Efficiency Enhancement On A Filament For Thermal Ionization Mass Spectrometry

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

Siegfried, M.

2015-10-14

The evaluation of trace Uranium and Plutonium isotope ratios for nanogram to femtogram material quantities is a vital tool for nuclear counter-proliferation and safeguard activities. Thermal Ionization Mass Spectrometry (TIMS) is generally accepted as the state of the art technology for highly accurate and ultra-trace measurements of these actinide ratios. However, the very low TIMS ionization yield (typically less than 1%) leaves much room for improvement. Enhanced ionization of Nd and Sm from a TIMS filament was demonstrated using wavelength resonance with a nanosecond (pulse width) laser operating at 10 Hz when light was directed toward the filament.1 For thismore » study, femtosecond and picosecond laser capabilities were to be employed to study the dissociation and ionization mechanisms of actinides/lanthanides and measure the enhanced ionization of the metal of interest. Since the underlying chemistry of the actinide/lanthanide carbides produced and dissociated on a TIMS filament is not well understood, the experimental parameters affecting the photodissociation and photoionization with one and two laser beams were to be investigated.« less

Atmospheric Gaseous Plasma with Large Dimensions

NASA Astrophysics Data System (ADS)

Korenev, Sergey

2012-10-01

The forming of atmospheric plasma with large dimensions using electrical discharge typically uses the Dielectric Barrier Discharge (DBD). The study of atmospheric DBD was shown some problems related to homogeneous volume plasma. The volume of this plasma determines by cross section and gas gap between electrode and dielectric. The using of electron beam for volume ionization of air molecules by CW relativistic electron beams was shown the high efficiency of this process [1, 2]. The main advantage of this approach consists in the ionization of gas molecules by electrons in longitudinal direction determines by their kinetic energy. A novel method for forming of atmospheric homogeneous plasma with large volume dimensions using ionization of gas molecules by pulsed non-relativistic electron beams is presented in the paper. The results of computer modeling for delivered doses of electron beams in gases and ionization are discussed. The structure of experimental bench with plasma diagnostics is considered. The preliminary results of forming atmospheric plasma with ionization gas molecules by pulsed nanosecond non-relativistic electron beam are given. The analysis of potential applications for atmospheric volume plasma is presented. Reference: [1] S. Korenev. ``The ionization of air by scanning relativistic high power CW electron beam,'' 2002 IEEE International Conference on Plasma Science. May 2002, Alberta, Canada. [2] S. Korenev, I. Korenev. ``The propagation of high power CW scanning electron beam in air.'' BEAMS 2002: 14th International Conference on High-Power Particle Beams, Albuquerque, New Mexico (USA), June 2002, AIP Conference Proceedings Vol. 650(1), pp. 373-376. December 17.

A New Electrospray Aerosol Generator with High Particle Transmission Efficiency

PubMed Central

Fu, Huijing; Patel, Anand C.; Holtzman, Michael J.; Chen, Da-Ren

2012-01-01

A new single-capillary electrospray (ES) aerosol generator has been developed for monodisperse particle production with maximal transmission efficiency. The new generator consists of both a spray chamber in a point-to-orifice-plate configuration and a charge reduction chamber that can hold up to 4 Nuclespot ionizers (Model P-2042, NRD Inc.). The 2 chambers are partitioned by an orifice plate. To optimize the particle transmission efficiency of the prototype, a systematic study was performed on the generator by varying the system setup and operation. Two key dimensions of the generator setup, the orifice diameter and the distance from the capillary tip to the orifice plate, were varied. Fluorescence analysis was applied to characterize the loss of ES-generated particles at different locations of the prototype. It was found that particle loss in the generator could be reduced by either increasing the orifice diameter or decreasing the distance between the capillary tip and the orifice plate. Increasing either the total radioactivity of the ionizers or the flowrate of the particle carrier gas also further decreased the particle loss in the system. The maximum particle transmission efficiency of 88.0% was obtained with the spray chamber fully opened to the charge reduction chamber, the capillary tip at the same level as the orifice plate, and 4 bipolar ionizers installed. PMID:22829715

Interatomic Coulombic decay cascades in multiply excited neon clusters

PubMed Central

Nagaya, K.; Iablonskyi, D.; Golubev, N. V.; Matsunami, K.; Fukuzawa, H.; Motomura, K.; Nishiyama, T.; Sakai, T.; Tachibana, T.; Mondal, S.; Wada, S.; Prince, K. C.; Callegari, C.; Miron, C.; Saito, N.; Yabashi, M.; Demekhin, Ph. V.; Cederbaum, L. S.; Kuleff, A. I.; Yao, M.; Ueda, K.

2016-01-01

In high-intensity laser light, matter can be ionized by direct multiphoton absorption even at photon energies below the ionization threshold. However on tuning the laser to the lowest resonant transition, the system becomes multiply excited, and more efficient, indirect ionization pathways become operative. These mechanisms are known as interatomic Coulombic decay (ICD), where one of the species de-excites to its ground state, transferring its energy to ionize another excited species. Here we show that on tuning to a higher resonant transition, a previously unknown type of interatomic Coulombic decay, intra-Rydberg ICD occurs. In it, de-excitation of an atom to a close-lying Rydberg state leads to electron emission from another neighbouring Rydberg atom. Moreover, systems multiply excited to higher Rydberg states will decay by a cascade of such processes, producing even more ions. The intra-Rydberg ICD and cascades are expected to be ubiquitous in weakly-bound systems exposed to high-intensity resonant radiation. PMID:27917867

Real time analysis of brain tissue by direct combination of ultrasonic surgical aspiration and sonic spray mass spectrometry.

PubMed

Schäfer, Karl-Christian; Balog, Júlia; Szaniszló, Tamás; Szalay, Dániel; Mezey, Géza; Dénes, Júlia; Bognár, László; Oertel, Matthias; Takáts, Zoltán

2011-10-15

Direct combination of cavitron ultrasonic surgical aspirator (CUSA) and sonic spray ionization mass spectrometry is presented. A commercially available ultrasonic surgical device was coupled to a Venturi easy ambient sonic-spray ionization (V-EASI) source by directly introducing liquified tissue debris into the Venturi air jet pump. The Venturi air jet pump was found to efficiently nebulize the suspended tissue material for gas phase ion production. The ionization mechanism involving solely pneumatic spraying was associated with that of sonic spray ionization. Positive and negative ionization spectra were obtained from brain and liver samples reflecting the primary application areas of the surgical device. Mass spectra were found to feature predominantly complex lipid-type constituents of tissues in both ion polarity modes. Multiply charged peptide anions were also detected. The influence of instrumental settings was characterized in detail. Venturi pump geometry and flow parameters were found to be critically important in ionization efficiency. Standard solutions of phospholipids and peptides were analyzed in order to test the dynamic range, sensitivity, and suppression effects. The spectra of the intact tissue specimens were found to be highly specific to the histological tissue type. The principal component analysis (PCA) and linear discriminant analysis (LDA) based data analysis method was developed for real-time tissue identification in a surgical environment. The method has been successfully tested on post-mortem and ex vivo human samples including astrocytomas, meningeomas, metastatic brain tumors, and healthy brain tissue. © 2011 American Chemical Society

High-current fast electron beam propagation in a dielectric target.

PubMed

Klimo, Ondrej; Tikhonchuk, V T; Debayle, A

2007-01-01

Recent experiments demonstrate an efficient transformation of high intensity laser pulse into a relativistic electron beam with a very high current density exceeding 10(12) A cm(-2). The propagation of such a beam inside the target is possible if its current is neutralized. This phenomenon is not well understood, especially in dielectric targets. In this paper, we study the propagation of high current density electron beam in a plastic target using a particle-in-cell simulation code. The code includes both ionization of the plastic and collisions of newborn electrons. The numerical results are compared with a relatively simple analytical model and a reasonable agreement is found. The temporal evolution of the beam velocity distribution, the spatial density profile, and the propagation velocity of the ionization front are analyzed and their dependencies on the beam density and energy are discussed. The beam energy losses are mainly due to the target ionization induced by the self-generated electric field and the return current. For the highest beam density, a two-stream instability is observed to develop in the plasma behind the ionization front and it contributes to the beam energy losses.

A highly sensitive electron spectrometer for crossed-beam collisional ionization: A retarding-type magnetic bottle analyzer and its application to collision-energy resolved Penning ionization electron spectroscopy

NASA Astrophysics Data System (ADS)

Yamakita, Yoshihiro; Tanaka, Hideyasu; Maruyama, Ryo; Yamakado, Hideo; Misaizu, Fuminori; Ohno, Koichi

2000-08-01

A highly sensitive electron energy analyzer which utilizes a "magnetic bottle" combined with a retarding electrostatic field has been developed for Penning ionization electron spectroscopy. A beam of metastable rare-gas atoms is crossed with a continuous supersonic sample beam in the source region of the analyzer. The emitted electrons are collected by an inhomogeneous magnetic field (the magnetic bottle effect) with a high efficiency of nearly 4π solid angle, which is more than 103 times higher than that of a conventional hemispherical analyzer. The kinetic energy of electrons is analyzed by scanning the retarding field in a flight tube of the analyzer in the presence of a weak magnetic field. The velocity of the metastable atoms can also be resolved by a time-of-flight method in the present instrument. Examples of Penning ionization electron energy spectra as a function of collision energy are presented for Ar and N2 with metastable He*(2 3S) atoms. This instrument has opened the possibility for extensive studies of Penning ionization electron spectroscopy for low-density species, such as clusters, ions, electronically excited species, unstable or transient species, and large molecules with low volatility.

Organic–inorganic binary mixture matrix for comprehensive laser-desorption ionization mass spectrometric analysis and imaging of medium-size molecules including phospholipids, glycerolipids, and oligosaccharides

DOE PAGES

Feenstra, Adam D.; Ames Lab., Ames, IA; O'Neill, Kelly C.; ...

2016-10-13

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is a widely adopted, versatile technique, especially in high-throughput analysis and imaging. However, matrix-dependent selectivity of analytes is often a severe limitation. In this work, a mixture of organic 2,5-dihydroxybenzoic acid and inorganic Fe 3O 4 nanoparticles is developed as a binary MALDI matrix to alleviate the well-known issue of triacylglycerol (TG) ion suppression by phosphatidylcholine (PC). In application to lipid standards and maize seed cross-sections, the binary matrix not only dramatically reduced the ion suppression of TG, but also efficiently desorbed and ionized a wide variety of lipids such as cationic PC, anionicmore » phosphatidylethanolamine (PE) and phosphatidylinositol (PI), and neutral digalactosyldiacylglycerol (DGDG). The binary matrix was also very efficient for large polysaccharides, which were not detected by either of the individual matrices. As a result, the usefulness of the binary matrix is demonstrated in MS imaging of maize seed sections, successfully visualizing diverse medium-size molecules and acquiring high-quality MS/MS spectra for these compounds.« less

Quantum mechanical calculations related to ionization and charge transfer in DNA

NASA Astrophysics Data System (ADS)

Cauët, E.; Valiev, M.; Weare, J. H.; Liévin, J.

2012-07-01

Ionization and charge migration in DNA play crucial roles in mechanisms of DNA damage caused by ionizing radiation, oxidizing agents and photo-irradiation. Therefore, an evaluation of the ionization properties of the DNA bases is central to the full interpretation and understanding of the elementary reactive processes that occur at the molecular level during the initial exposure and afterwards. Ab initio quantum mechanical (QM) methods have been successful in providing highly accurate evaluations of key parameters, such as ionization energies (IE) of DNA bases. Hence, in this study, we performed high-level QM calculations to characterize the molecular energy levels and potential energy surfaces, which shed light on ionization and charge migration between DNA bases. In particular, we examined the IEs of guanine, the most easily oxidized base, isolated and embedded in base clusters, and investigated the mechanism of charge migration over two and three stacked guanines. The IE of guanine in the human telomere sequence has also been evaluated. We report a simple molecular orbital analysis to explain how modifications in the base sequence are expected to change the efficiency of the sequence as a hole trap. Finally, the application of a hybrid approach combining quantum mechanics with molecular mechanics brings an interesting discussion as to how the native aqueous DNA environment affects the IE threshold of nucleobases.

Laser ion source for multi-nucleon transfer reaction products

NASA Astrophysics Data System (ADS)

Hirayama, Y.; Watanabe, Y. X.; Imai, N.; Ishiyama, H.; Jeong, S. C.; Miyatake, H.; Oyaizu, M.; Kimura, S.; Mukai, M.; Kim, Y. H.; Sonoda, T.; Wada, M.; Huyse, M.; Kudryavtsev, Yu.; Van Duppen, P.

2015-06-01

We have developed a laser ion source for the target-like fragments (TLFs) produced in multi-nucleon transfer (MNT) reactions. The operation principle of the source is based on the in-gas laser ionization and spectroscopy (IGLIS) approach. In the source TLFs are thermalized and neutralized in high pressure and high purity argon gas, and are extracted after being selectively re-ionized in a multi-step laser resonance ionization process. The laser ion source has been implemented at the KEK Isotope Separation System (KISS) for β-decay spectroscopy of neutron-rich isotopes with N = 126 of nuclear astrophysical interest. The simulations of gas flow and ion-beam optics have been performed to optimize the gas cell for efficient thermalization and fast transporting the TLFs, and the mass-separator for efficient transport with high mass-resolving power, respectively. To confirm the performances expected at the design stage, off-line experiments have been performed by using 56Fe atoms evaporated from a filament in the gas cell. The gas-transport time of 230 ms in the argon cell and the measured KISS mass-resolving power of 900 are consistent with the designed values. The high purity of the gas-cell system, which is extremely important for efficient and highly-selective production of laser ions, was achieved and confirmed from the mass distribution of the extracted ions. After the off-line tests, on-line experiments were conducted by directly injecting energetic 56Fe beam into the gas cell. After thermalization of the injected 56Fe beam, laser-produced singly-charged 56Fe+ ions were extracted. The extraction efficiency and selectivity of the gas cell in the presence of plasma induced by 56Fe beam injection as well as the time profile of the extracted ions were investigated; extraction efficiency of 0.25%, a beam purity of >99% and an extraction time of 270 ms. It has been confirmed that the performance of the KISS laser ion source is satisfactory to start the measurements of lifetimes of the β-decayed nuclei with N = 126 .

Enhanced ionization efficiency in TIMS analyses of plutonium and americium using porous ion emitters

DOE PAGES

Baruzzini, Matthew L.; Hall, Howard L.; Watrous, Matthew G.; ...

2016-12-05

Investigations of enhanced sample utilization in thermal ionization mass spectrometry (TIMS) using porous ion emitter (PIE) techniques for the analyses of trace quantities of americium and plutonium were performed. Repeat ionization efficiency (i.e., the ratio of ions detected to atoms loaded on the filament) measurements were conducted on sample sizes ranging from 10–100 pg for americium and 1–100 pg for plutonium using PIE and traditional (i.e., a single, zone-refined rhenium, flat filament ribbon with a carbon ionization enhancer) TIMS filament sources. When compared to traditional filaments, PIEs exhibited an average boost in ionization efficiency of ~550% for plutonium and ~1100%more » for americium. A maximum average efficiency of 1.09% was observed at a 1 pg plutonium sample loading using PIEs. Supplementary trials were conducted using newly developed platinum PIEs to analyze 10 pg mass loadings of plutonium. As a result, platinum PIEs exhibited an additional ~134% boost in ion yield over standard PIEs and ~736% over traditional filaments at the same sample loading level.« less

Enhanced adsorption of ionizable antibiotics on activated carbon fiber under electrochemical assistance in continuous-flow modes.

PubMed

Wang, Sitan; Li, Xiaona; Zhao, Huimin; Quan, Xie; Chen, Shuo; Yu, Hongtao

2018-05-01

Ionizable antibiotics have attracted serious concerns because of their variable dissociation forms and thereby rendering unique toxicity and microorganism resistance. Developing an efficient and environmentally friendly method for removing these micropollutants from environmental media remains very challenging. Here, electro-assisted adsorption onto activated carbon fiber in continuous-flow mode was used to remove three ionizable antibiotics, sulfadimethoxine (SDM), ciprofloxacin (CIP), and clarithromycin (CLA), from water. Benefiting from strengthened electrostatic interactions, the adsorption capacities for the target antibiotics (10 mg/L) in flow mode (70.9-202.2 mg/g) increased by ∼5 times under a potential of 1.0 V (SDM) or -1.0 V (CIP and CLA) relative to those of open circuit (OC) adsorption. Meanwhile, effluent concentration decreased from >100 μg/L to 9.6 μg/L with removal efficiency increasing from 99.0% to 99.9%. Moreover, high recovery efficiency of ACF up to 96.35 ± 0.65% was achieved by imposing a reverse potential (-1.0 V) relative to that used for SDM adsorption. In addition, trace levels of antibiotics (364-580 ng/L) in surface water could be removed effectively to achieve low effluent concentration (0.4-1.2 ng/L) and high removal efficiency (99.9%) upon treating up to ∼1560 bed volumes (BVs), demonstrating the potential of electro-assisted adsorption for practical application in water treatment. Copyright © 2018 Elsevier Ltd. All rights reserved.

Feasibility of atmospheric pressure desorption/ionization on silicon mass spectrometry in analysis of drugs.

PubMed

Huikko, K; Ostman, P; Sauber, C; Mandel, F; Grigoras, K; Franssila, S; Kotiaho, T; Kostiainen, R

2003-01-01

The feasibility of atmospheric pressure desorption/ionization on silicon mass spectrometry (AP-DIOS-MS) for drug analysis was investigated. It was observed that only compounds with relative high proton affinity are efficiently ionized under AP-DIOS conditions. The limits of detection (LODs) achieved in MS mode with midazolam, propranolol, and angiotensin II were 80 fmol, 20 pmol, and 1 pmol, respectively. In MS/MS mode the LODs for midazolam and propranolol were 10 fmol and 5 pmol, respectively. The good linearity (r(2) > 0.991), linear dynamic range of 3 orders of magnitude, and reasonable repeatability showed that the method is suitable for quantitative analysis. Copyright 2003 John Wiley & Sons, Ltd.

Initiation of air ionization by ultrashort laser pulses: evidence for a role of metastable-state air molecules

NASA Astrophysics Data System (ADS)

Bulgakov, A. V.; Mirza, I.; Bulgakova, N. M.; Zhukov, V. P.; Machulka, R.; Haderka, O.; Campbell, E. E. B.; Mocek, T.

2018-06-01

Transmission measurements for femtosecond laser pulses focused in air with spectral analysis of emission from the focal region have been carried out for various pulse energies and air pressures. The air breakdown threshold and pulse attenuation due to plasma absorption are evaluated and compared with calculations based on the multiphoton ionization model. The plasma absorption is found to depend on the pulse repetition rate and is considerably stronger at 1 kHz than at 1–10 Hz. This suggests that accumulation of metastable states of air molecules plays an important role in initiation of air breakdown, enhancing the ionization efficiency at high repetition rates. Possible channels of metastable-state-assisted air ionization and the role of the observed accumulation effect in laser material processing are discussed.

A theoretical analysis of vacuum arc thruster performance

NASA Technical Reports Server (NTRS)

Polk, James E.; Sekerak, Mike; Ziemer, John K.; Schein, Jochen; Qi, Niansheng; Binder, Robert; Anders, Andre

2001-01-01

In vacuum arc discharges the current is conducted through vapor evaporated from the cathode surface. In these devices very dense, highly ionized plasmas can be created from any metallic or conducting solid used as the cathode. This paper describes theoretical models of performance for several thruster configurations which use vacuum arc plasma sources. This analysis suggests that thrusters using vacuum arc sources can be operated efficiently with a range of propellant options that gives great flexibility in specific impulse. In addition, the efficiency of plasma production in these devices appears to be largely independent of scale because the metal vapor is ionized within a few microns of the cathode electron emission sites, so this approach is well-suited for micropropulsion.

Attachment of chloride anion to sugars: mechanistic investigation and discovery of a new dopant for efficient sugar ionization/detection in mass spectrometers.

PubMed

Boutegrabet, Lemia; Kanawati, Basem; Gebefügi, Istvan; Peyron, Dominique; Cayot, Philippe; Gougeon, Régis D; Schmitt-Kopplin, Philippe

2012-10-08

A new method for efficient ionization of sugars in the negative-ion mode of electrospray mass spectrometry is presented. Instead of using strongly hydrophobic dopants such as dichloromethane or chloroform, efficient ionization of sugars has been achieved by using aqueous HCl solution for the first time. This methodology makes it possible to use hydrophilic dopants, which are more appropriate for chromatographic separation techniques with efficient sugar ionization and detection in mass spectrometry. The interaction between chloride anions and monosaccharides (glucose and galactose) was studied by DFT in the gas phase and by implementing the polarizable continuum model (PCM) for calculations in solution at the high B3LYP/6-31+G(d,p)//B3LYP/6-311+G(2d,p) level of theory. In all optimized geometries of identified [M+Cl](-) anions, a non-covalent interaction exists. Differences were revealed between monodentate and bidentate complex anions, with the latter having noticeably higher binding energies. The calculated affinity of glucose and galactose toward the chloride anion in the gas phase and their chloride anion binding energies in solution are in excellent agreement with glucose and galactose [M+Cl](-) experimental intensity profiles that are represented as a function of the chloride ion concentration. Density functional calculations of gas-phase affinities toward chloride anion were also performed for the studied disaccharides sucrose and gentiobiose. All calculations are in excellent agreement with the experimental data. An example is introduced wherein HCl was used to effectively ionize sugars and form chlorinated adduct anions to detect sugars and glycosylated metabolites (anthocyanins) in real biological systems (Vitis vinifera grape extracts and wines), whereas they would not have been easily detectable under standard infusion electrospray mass spectrometry conditions as deprotonated species. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

GASEOUS DISCHARGE DEVICE

DOEpatents

Gow, J.D.

1961-01-10

An extremely compact two-terminal gaseous discharge device is described that is capable of producing neutrons in copious quantities, relatively high energy ions, intense x rays, and the like. Principal novelty resides in the provision of a crossed electric-magnetic field region in the discharge envelope that traps electrons and accelerates them to very high energies to provide an intense ionizing medium adjacent the anode of the device for ionizing gas therein with extremely high efficiency. In addition, the crossed-field trapping region holds the electrons close to the anode whereby the acceleration of ions to the cathode is not materially effected by the electron sheath and the ions assume substantially the full energy of the anodecathode potential drop. (auth)

Control of nitromethane photoionization efficiency with shaped femtosecond pulses.

PubMed

Roslund, Jonathan; Shir, Ofer M; Dogariu, Arthur; Miles, Richard; Rabitz, Herschel

2011-04-21

The applicability of adaptive femtosecond pulse shaping is studied for achieving selectivity in the photoionization of low-density polyatomic targets. In particular, optimal dynamic discrimination (ODD) techniques exploit intermediate molecular electronic resonances that allow a significant increase in the photoionization efficiency of nitromethane with shaped near-infrared femtosecond pulses. The intensity bias typical of high-photon number, nonresonant ionization is accounted for by reference to a strictly intensity-dependent process. Closed-loop adaptive learning is then able to discover a pulse form that increases the ionization efficiency of nitromethane by ∼150%. The optimally induced molecular dynamics result from entry into a region of parameter space inaccessible with intensity-only control. Finally, the discovered pulse shape is demonstrated to interact with the molecular system in a coherent fashion as assessed from the asymmetry between the response to the optimal field and its time-reversed counterpart.

Alkali metal cation complexation by 1,3-alternate, mono-ionisable calix[4]arene-benzocrown-6 compounds

DOE PAGES

Surowiec, Malgorzata A.; Custelcean, Radu; Surowiec, Kazimierz; ...

2014-04-23

Alkali metal cation extraction behavior for two series of 1,3-alternate, mono-ionizable calix[4]arene-benzocrown-6 compounds is examined. In Series 1, the proton-ionizable group is a substituent on the benzo group of the polyether ring that directs it away from the crown ether cavity. In Series 2, the proton-ionizable group is attached to one para position in the calixarene framework, thus positioning it over the crown ether ring. Competitive solvent extraction of alkali metal cations from aqueous solutions into chloroform shows high Cs+ efficiency and selectivity. Single-species extraction pH profiles of Cs+ for Series 1 and 2 ligands with the same proton-ionizable groupmore » are very similar. Thus, association of Cs+ with the calixcrown ring is more important than the the proton-ionizable group’s position in relation to the crown ether cavity. Solid-state structures are presented for two unionized ligands from Series 2, as is a crystal containing two different ionized ligand–Cs+ complexes.« less

Boosting the power conversion efficiency of perovskite solar cells using self-organized polymeric hole extraction layers with high work function.

PubMed

Lim, Kyung-Geun; Kim, Hak-Beom; Jeong, Jaeki; Kim, Hobeom; Kim, Jin Young; Lee, Tae-Woo

2014-10-08

A self-organized hole extraction layer (SOHEL) with high work function (WF) is designed for energy level alignment with the ionization potential level of CH3 NH3 PbI3 . The SOHEL increases the built-in potential, photocurrent, and power conversion efficiency (PCE) of CH3 NH3 PbI3 perovskite solar cells. Thus, interface engineering of the positive electrode of solution-processed planar heterojunction solar cells using a high-WF SOHEL is a very effective way to achieve high device efficiency (PCE = 11.7% on glass). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ion microscopy with resonant ionization mass spectrometry : time-of-flight depth profiling with improved isotopic precision.

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

Pellin, M. J.; Veryovkin, I. V.; Levine, J.

2010-01-01

There are four generally mutually exclusive requirements that plague many mass spectrometric measurements of trace constituents: (1) the small size (limited by the depth probed) of many interesting materials requires high useful yields to simply detect some trace elements, (2) the low concentrations of interesting elements require efficient discrimination from isobaric interferences, (3) it is often necessary to measure the depth distribution of elements with high surface and low bulk contributions, and (4) many applications require precise isotopic analysis. Resonant ionization mass spectrometry has made dramatic progress in addressing these difficulties over the past five years.

Nanostructured solid substrates for efficient laser desorption/ionization mass spectrometry (LDI-MS) of low molecular weight compounds.

PubMed

Silina, Yuliya E; Volmer, Dietrich A

2013-12-07

Analytical applications often require rapid measurement of compounds from complex sample mixtures. High-speed mass spectrometry approaches frequently utilize techniques based on direct ionization of the sample by laser irradiation, mostly by means of matrix-assisted laser desorption/ionization (MALDI). Compounds of low molecular weight are difficult to analyze by MALDI, however, because of severe interferences in the low m/z range from the organic matrix used for desorption/ionization. In recent years, surface-assisted laser desorption/ionization (SALDI) techniques have shown promise for small molecule analysis, due to the unique properties of nanostructured surfaces, in particular, the lack of a chemical background in the low m/z range and enhanced production of analyte ions by SALDI. This short review article presents a summary of the most promising recent developments in SALDI materials for MS analysis of low molecular weight analytes, with emphasis on nanostructured materials based on metals and semiconductors.

A comparative study of disinfection efficiency and regrowth control of microorganism in secondary wastewater effluent using UV, ozone, and ionizing irradiation process.

PubMed

Lee, O-Mi; Kim, Hyun Young; Park, Wooshin; Kim, Tae-Hun; Yu, Seungho

2015-09-15

Ionizing radiation technology was suggested as an alternative method to disinfection processes, such as chlorine, UV, and ozone. Although many studies have demonstrated the effectiveness of irradiation technology for microbial disinfection, there has been a lack of information on comparison studies of disinfection techniques and a regrowth of each treatment. In the present study, an ionizing radiation was investigated to inactivate microorganisms and to determine the critical dose to prevent the regrowth. As a result, it was observed that the disinfection efficiency using ionizing radiation was not affected by the seasonal changes of wastewater characteristics, such as temperature and turbidity. In terms of bacterial regrowth after disinfection, the ionizing radiation showed a significant resistance of regrowth, whereas, on-site UV treatment is influenced by the suspended solid, temperature, or precipitation. The electric power consumption was also compared for the economic feasibility of each technique at a given value of disinfection efficiency of 90% (1-log), showing 0.12, 36.80, and 96.53 Wh/(L/day) for ionizing radiation, ozone, and UV, respectively. The ionizing radiation requires two or three orders of magnitude lower power consumption than UV and ozone. Consequently, ionizing radiation can be applied as an effective and economical alternative technique to other conventional disinfection processes. Copyright © 2015 Elsevier B.V. All rights reserved.

The MOSDEF Survey: Direct Observational Constraints on the Ionizing Photon Production Efficiency, ξ ion, at z ∼ 2

NASA Astrophysics Data System (ADS)

Shivaei, Irene; Reddy, Naveen A.; Siana, Brian; Shapley, Alice E.; Kriek, Mariska; Mobasher, Bahram; Freeman, William R.; Sanders, Ryan L.; Coil, Alison L.; Price, Sedona H.; Fetherolf, Tara; Azadi, Mojegan; Leung, Gene; Zick, Tom

2018-03-01

We combine Hα and Hβ spectroscopic measurements and UV photometry for a sample of 673 galaxies from the MOSDEF survey to constrain hydrogen-ionizing photon production efficiencies ({ξ }ion}) at z = 1.4–2.6. We find < {log}({ξ }ion}/[{{{s}}}-1/{erg} {{{s}}}-1 {Hz}}-1])> = 25.06 (25.34), assuming the Calzetti (SMC) curve for the UV dust correction and a scatter of 0.28 dex in the {ξ }ion} distribution. After accounting for observational uncertainties and variations in dust attenuation, we conclude that the remaining scatter in {ξ }ion} is likely dominated by galaxy-to-galaxy variations in stellar populations, including the slope and upper-mass cutoff of the initial mass function, stellar metallicity, star formation burstiness, and stellar evolution (e.g., single/binary star evolution). Moreover, {ξ }ion} is elevated in galaxies with high ionization states (high [O III]/[O II]) and low oxygen abundances (low [N II]/Hα and high [O III]/Hβ) in the ionized ISM. However, {ξ }ion} does not correlate with the offset from the z ∼ 0 star-forming locus in the BPT diagram, suggesting no change in the hardness of the ionizing radiation accompanying the offset from the z ∼ 0 sequence. We also find that galaxies with blue UV spectral slopes (< β > =-2.1) have {ξ }ion} elevated by a factor of ∼2 relative to the average {ξ }ion} of the sample (< β > =-1.4). If these blue galaxies are similar to those at z > 6, our results suggest that a lower Lyman-continuum escape fraction is required for galaxies to maintain reionization, compared to the canonical {ξ }ion} predictions from stellar population models. Furthermore, we demonstrate that even with robustly dust-corrected Hα, the UV dust attenuation can cause on average a ∼0.3 dex systematic uncertainty in {ξ }ion} calculations.

Mass Spectrometric Imaging Using Laser Ablation and Solvent Capture by Aspiration (LASCA)

NASA Astrophysics Data System (ADS)

Brauer, Jonathan I.; Beech, Iwona B.; Sunner, Jan

2015-09-01

A novel interface for ambient, laser ablation-based mass spectrometric imaging (MSI) referred to as laser ablation and solvent capture by aspiration (LASCA) is presented and its performance demonstrated using selected, unaltered biological materials. LASCA employs a pulsed 2.94 μm laser beam for specimen ablation. Ablated materials in the laser plumes are collected on a hanging solvent droplet with electric field-enhanced trapping, followed by aspiration of droplets and remaining plume material in the form of a coarse aerosol into a collection capillary. The gas and liquid phases are subsequently separated in a 10 μL-volume separatory funnel, and the solution is analyzed with electrospray ionization in a high mass resolution Q-ToF mass spectrometer. The LASCA system separates the sampling and ionization steps in MSI and combines high efficiencies of laser plume sampling and of electrospray ionization (ESI) with high mass resolution MS. Up to 2000 different compounds are detected from a single ablation spot (pixel). Using the LASCA platform, rapid (6 s per pixel), high sensitivity, high mass-resolution ambient imaging of "as-received" biological material is achieved routinely and reproducibly.

1-(3-aminopropyl)-3-butylimidazolium bromide for carboxyl group derivatization: potential applications in high sensitivity peptide identification by mass spectrometry.

PubMed

Qiao, Xiaoqiang; Zhou, Yuan; Hou, Chunyan; Zhang, Xiaodan; Yang, Kaiguang; Zhang, Lihua; Zhang, Yukui

2013-03-01

The cationic reagent 1-(3-aminopropyl)-3-butylimidazolium bromide (BAPI) was exploited for the derivatization of carboxyl groups on peptides. Nearly 100% derivatization efficiency was achieved with the synthetic peptide RVYVHPI (RI-7). Furthermore, the peptide derivative was stable in a 0.1% TFA/water solution or a 0.1% (v/v) TFA/acetonitrile/water solution for at least one week. The effect of BAPI derivatization on the ionization of the peptide RI-7 was further investigated, and the detection sensitivity was improved >42-fold via matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), thus outperforming the commercial piperazine derivatization approach. Moreover, the charge states of the peptide were largely increased via BAPI derivatization by electrospray ionization (ESI) MS. The results indicate the potential merits of BAPI derivatization for high sensitivity peptide analysis by MS.

Recent progress in microchip electrophoresis-mass spectrometry.

PubMed

Kitagawa, Fumihiko; Otsuka, Koji

2011-06-25

This review highlights the methodological and instrumental developments in microchip electrophoresis (MCE)-mass spectrometry (MS) from 1997. In MCE-MS, the development of ionization interface is one of the most important issues to realize highly sensitive detection and high separation efficiency. Among several interfaces, electrospray ionization (ESI) has been mainly employed to MCE-MS since a simple structure of the ESI interface is suitable for coupling with the microchips. Although the number of publications is still limited, laser desorption ionization (LDI) interface has also been developed for MCE-MS. The characteristics of the ESI and LDI interfaces applied to the electrophoresis microchips are presented in this review. The scope of applications in MCE-MS covers mainly biogenic compounds such as bioactive amines, peptides, tryptic digests and proteins. This review provides a comprehensive table listing the applications in MCE-MS. Copyright © 2010 Elsevier B.V. All rights reserved.

Electron-Atom Ionization Calculations using Propagating Exterior Complex Scaling

NASA Astrophysics Data System (ADS)

Bartlett, Philip

2007-10-01

The exterior complex scaling method (Science 286 (1999) 2474), pioneered by Rescigno, McCurdy and coworkers, provided highly accurate ab initio solutions for electron-hydrogen collisions by directly solving the time-independent Schr"odinger equation in coordinate space. An extension of this method, propagating exterior complex scaling (PECS), was developed by Bartlett and Stelbovics (J. Phys. B 37 (2004) L69, J. Phys. B 39 (2006) R379) and has been demonstrated to provide computationally efficient and accurate calculations of ionization and scattering cross sections over a large range of energies below, above and near the ionization threshold. An overview of the PECS method for three-body collisions and the computational advantages of its propagation and iterative coupling techniques will be presented along with results of: (1) near-threshold ionization of electron-hydrogen collisions and the Wannier threshold laws, (2) scattering cross section resonances below the ionization threshold, and (3) total and differential cross sections for electron collisions with excited targets and hydrogenic ions from low through to high energies. Recently, the PECS method has been extended to solve four-body collisions using time-independent methods in coordinate space and has initially been applied to the s-wave model for electron-helium collisions. A description of the extensions made to the PECS method to facilitate these significantly more computationally demanding calculations will be given, and results will be presented for elastic, single-excitation, double-excitation, single-ionization and double-ionization collisions.

Novel Laser Ignition Technique Using Dual-Pulse Pre-Ionization

NASA Astrophysics Data System (ADS)

Dumitrache, Ciprian

Recent advances in the development of compact high power laser sources and fiber optic delivery of giant pulses have generated a renewed interest in laser ignition. The non-intrusive nature of laser ignition gives it a set of unique characteristics over the well-established capacitive discharge devices (or spark plugs) that are currently used as ignition sources in engines. Overall, the use of laser ignition has been shown to have a positive impact on engine operation leading to a reduction in NOx emission, fuel saving and an increased operational envelope of current engines. Conventionally, laser ignition is achieved by tightly focusing a high-power q-switched laser pulse until the optical intensity at the focus is high enough to breakdown the gas molecules. This leads to the formation of a spark that serves as the ignition source in engines. However, there are certain disadvantages associated with this ignition method. This ionization approach is energetically inefficient as the medium is transparent to the laser radiation until the laser intensity is high enough to cause gas breakdown. As a consequence, very high energies are required for ignition (about an order of magnitude higher energy than capacitive plugs at stoichiometric conditions). Additionally, the fluid flow induced during the plasma recombination generates high vorticity leading to high rates of flame stretching. In this work, we are addressing some of the aforementioned disadvantages of laser ignition by developing a novel approach based on a dual-pulse pre-ionization scheme. The new technique works by decoupling the effect of the two ionization mechanisms governing plasma formation: multiphoton ionization (MPI) and electron avalanche ionization (EAI). An UV nanosecond pulse (lambda = 266 nm) is used to generate initial ionization through MPI. This is followed by an overlapped NIR nanosecond pulse (lambda = 1064 nm) that adds energy into the pre-ionized mixture into a controlled manner until the gas temperature is suitable for combustion (T=2000-3000 K). This technique is demonstrated by attempting ignition of various mixtures of propane-air and it is shown to have distinct advantages when compared to the classical approach: lower ignition energy for given stoichiometry than conventional laser ignition ( 20% lower), extension of the lean limit ( 15% leaner) and improvement in combustion efficiency. Moreover, it is demonstrated that careful alignment of the two pulses influences the fluid dynamics of the early flame kernel growth. This finding has a number of implications for practical uses as it demonstrates that the flame kernel dynamics can be tailored using various combinations of laser pulses and opens the door for implementing such a technique to applications such as: flame holding and flame stabilization in high speed flow combustors (such as ramjet and scramjet engines), reducing flame stretching in highly turbulent combustion devices and increasing combustion efficiency for stationary natural gas engines. As such, the work presented in this dissertation should be of interest to a broad audience including those interested in combustion research, engine operation, chemically reacting flows, plasma dynamics and laser diagnostics.

Collective Autoionization in Multiply-Excited Systems: A novel ionization process observed in Helium Nanodroplets

PubMed Central

LaForge, A. C.; Drabbels, M.; Brauer, N. B.; Coreno, M.; Devetta, M.; Di Fraia, M.; Finetti, P.; Grazioli, C.; Katzy, R.; Lyamayev, V.; Mazza, T.; Mudrich, M.; O'Keeffe, P.; Ovcharenko, Y.; Piseri, P.; Plekan, O.; Prince, K. C.; Richter, R.; Stranges, S.; Callegari, C.; Möller, T.; Stienkemeier, F.

2014-01-01

Free electron lasers (FELs) offer the unprecedented capability to study reaction dynamics and image the structure of complex systems. When multiple photons are absorbed in complex systems, a plasma-like state is formed where many atoms are ionized on a femtosecond timescale. If multiphoton absorption is resonantly-enhanced, the system becomes electronically-excited prior to plasma formation, with subsequent decay paths which have been scarcely investigated to date. Here, we show using helium nanodroplets as an example that these systems can decay by a new type of process, named collective autoionization. In addition, we show that this process is surprisingly efficient, leading to ion abundances much greater than that of direct single-photon ionization. This novel collective ionization process is expected to be important in many other complex systems, e.g. macromolecules and nanoparticles, exposed to high intensity radiation fields. PMID:24406316

Detection of polychlorinated biphenyls in transformer oils in Vietnam by multiphoton ionization mass spectrometry using a far-ultraviolet femtosecond laser as an ionization source.

PubMed

Duong, Vu Thi Thuy; Duong, Vu; Lien, Nghiem Thi Ha; Imasaka, Tomoko; Tang, Yuanyuan; Shibuta, Shinpei; Hamachi, Akifumi; Hoa, Do Quang; Imasaka, Totaro

2016-03-01

Polychlorinated biphenyls (PCBs) in transformer and food oils were measured using gas chromatography combined with multiphoton ionization mass spectroscopy. An ultrashort laser pulse emitting in the far-ultraviolet region was utilized for efficient ionization of the analytes. Numerous signal peaks were clearly observed for a standard sample mixture of PCBs when the third and fourth harmonic emissions (267 and 200nm) of a femtosecond Ti:sapphire laser (800nm) were employed. The signal intensities were found to be greater when measured at 200nm compared with those measured at 267nm, providing lower detection limits especially for highly chlorinated PCBs at shorter wavelengths. After simple pretreatment using disposable columns, PCB congeners were measured and found to be present in the transformer oils used in Vietnam. Copyright © 2015 Elsevier B.V. All rights reserved.

Escape of ionizing radiation from high redshift dwarf galaxies: role of AGN feedback

NASA Astrophysics Data System (ADS)

Trebitsch, Maxime; Volonteri, Marta; Dubois, Yohan; Madau, Piero

2018-05-01

While low mass, star forming galaxies are often considered as the primary driver of reionization, their actual contribution to the cosmic ultraviolet background is still uncertain, mostly because the escape fraction of ionizing photons is only poorly constrained. Theoretical studies have shown that efficient supernova feedback is a necessary condition to create paths through which ionizing radiation can escape into the intergalactic medium. We investigate the possibility that accreting supermassive black holes in early dwarf galaxies may provide additional feedback and enhance the leakage of ionizing radiation. We use a series of high resolution cosmological radiation hydrodynamics simulations where we isolate the different sources of feedback. We find that supernova feedback prevents the growth of the black hole, thus quenching its associated feedback. Even in cases where the black hole can grow, the structure of the interstellar medium is strongly dominated by supernova feedback. We conclude that, in the dwarf galaxy regime, supermassive black holes do not appear to play a significant role in enhancing the escape fraction and in contributing to the early UV background.

Efficient and robust photo-ionization loading of beryllium ions

NASA Astrophysics Data System (ADS)

Wolf, Sebastian; Studer, Dominik; Wendt, Klaus; Schmidt-Kaler, Ferdinand

2018-02-01

We demonstrate the efficient generation of Be^+ ions with a 60 ns and 150 nJ laser pulse near 235 nm for two-step photo-ionization, proven by subsequent counting of the number of ions loaded into a linear Paul trap. The bandwidth and power of the laser pulse are chosen in such a way that a first, resonant step fully saturates the entire velocity distribution of beryllium atoms effusing from a thermal oven. The second excitation step is driven by the same light field causing efficient non-resonant ionization. Our ion-loading scheme has a similar efficiency as compared to former pathways using two-photon continuous wave laser excitation, but with an order of magnitude lower than average UV light power.

Target Plate Material Influence on Fullerene-C60 Laser Desorption/Ionization Efficiency

NASA Astrophysics Data System (ADS)

Zeegers, Guido P.; Günthardt, Barbara F.; Zenobi, Renato

2016-04-01

Systematic laser desorption/ionization (LDI) experiments of fullerene-C60 on a wide range of target plate materials were conducted to gain insight into the initial ion formation in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. The positive and negative ion signal intensities of precursor, fragment, and cluster ions were monitored, varying both the laser fluence (0-3.53 Jcm-2) and the ion extraction delay time (0-950 ns). The resulting species-specific ion signal intensities are an indication for the ionization mechanisms that contribute to LDI and the time frames in which they operate, providing insight in the (MA)LDI primary ionization. An increasing electrical resistivity of the target plate material increases the fullerene-C60 precursor and fragment anion signal intensity. Inconel 625 and Ti90/Al6/V4, both highly electrically resistive, provide the highest anion signal intensities, exceeding the cation signal intensity by a factor ~1.4 for the latter. We present a mechanism based on transient electrical field strength reduction to explain this trend. Fullerene-C60 cluster anion formation is negligible, which could be due to the high extraction potential. Cluster cations, however, are readily formed, although for high laser fluences, the preferred channel is formation of precursor and fragment cations. Ion signal intensity depends greatly on the choice of substrate material, and careful substrate selection could, therefore, allow for more sensitive (MA)LDI measurements.

Selective ionization of dissolved organic nitrogen by positive ion atmospheric pressure photoionization coupled with Fourier transform ion cyclotron resonance mass spectrometry.

PubMed

Podgorski, David C; McKenna, Amy M; Rodgers, Ryan P; Marshall, Alan G; Cooper, William T

2012-06-05

Dissolved organic nitrogen (DON) comprises a heterogeneous family of organic compounds that includes both well-known biomolecules such as urea or amino acids and more complex, less characterized compounds such as humic and fulvic acids. Typically, DON represents only a small fraction of the total dissolved organic carbon pool and therefore presents inherent problems for chemical analysis and characterization. Here, we demonstrate that DON may be selectively ionized by atmospheric pressure photionization (APPI) and characterized at the molecular level by Fourier transform ion cyclotron resonance mass spectrometry. Unlike electrospray ionization (ESI), APPI ionizes polar and nonpolar compounds, and ionization efficiency is not determined by polarity. APPI is tolerant to salts, due to the thermal treatment inherent to nebulization, and thus avoids salt-adduct formation that can complicate ESI mass spectra. Here, for dissolved organic matter from various aquatic environments, we selectively ionize DON species that are not efficiently ionized by other ionization techniques and demonstrate significant signal-to-noise increase for nitrogen species by use of APPI relative to ESI.

Improvement in ionization efficiency of direct analysis in real time-mass spectrometry (DART-MS) by corona discharge.

PubMed

Sekimoto, Kanako; Sakakura, Motoshi; Kawamukai, Takatomo; Hike, Hiroshi; Shiota, Teruhisa; Usui, Fumihiko; Bando, Yasuhiko; Takayama, Mitsuo

2016-08-02

Herein it is shown that a combination of direct analysis in real time (DART) with a corona discharge system consisting of only a needle electrode easily improves DART ionization efficiency. Positive and negative DC corona discharges led to a formation of abundant excited helium atoms as well as the reactant ions H3O(+)(H2O)n and O2˙(-) in the DART analyte ionization area. These phenomena resulted in an increase in the absolute intensities of (de)protonated analytes by a factor of 2-20 over conventional DART. The other analyte ions detected in this corona-DART system (i.e., molecular ions, fragment ions, oxygenated (de)protonated analytes, dehydrogenated deprotonated analytes, and negative ion adducts) were quite similar to those obtained from DART alone. This indicates a lack of side reactions due to the corona discharge. The change in the relative intensities of individual analyte-related ions due to the combination of a corona discharge system with DART suggests that there is no effect of the abundant excited helium in the analyte ionization area on the fragmentation processes or enhancement of oxidation due to hydroxyl radicals HO˙. Furthermore, it was found that the corona-DART combination can be applied to the highly sensitive analysis of n-alkanes, in which the alkanes are ionized as positive ions via hydride abstraction and oxidation, independent of the type of alkane or the mass spectrometer used.

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.

A Radical-Mediated Pathway for the Formation of [M + H](+) in Dielectric Barrier Discharge Ionization.

PubMed

Wolf, Jan-Christoph; Gyr, Luzia; Mirabelli, Mario F; Schaer, Martin; Siegenthaler, Peter; Zenobi, Renato

2016-09-01

Active capillary plasma ionization is a highly efficient ambient ionization method. Its general principle of ion formation is closely related to atmospheric pressure chemical ionization (APCI). The method is based on dielectric barrier discharge ionization (DBDI), and can be constructed in the form of a direct flow-through interface to a mass spectrometer. Protonated species ([M + H](+)) are predominantly formed, although in some cases radical cations are also observed. We investigated the underlying ionization mechanisms and reaction pathways for the formation of protonated analyte ([M + H](+)). We found that ionization occurs in the presence and in the absence of water vapor. Therefore, the mechanism cannot exclusively rely on hydronium clusters, as generally accepted for APCI. Based on isotope labeling experiments, protons were shown to originate from various solvents (other than water) and, to a minor extent, from gaseous impurities and/or self-protonation. By using CO2 instead of air or N2 as plasma gas, additional species like [M + OH](+) and [M - H](+) were observed. These gas-phase reaction products of CO2 with the analyte (tertiary amines) indicate the presence of a radical-mediated ionization pathway, which proceeds by direct reaction of the ionized plasma gas with the analyte. The proposed reaction pathway is supported with density functional theory (DFT) calculations. These findings add a new ionization pathway leading to the protonated species to those currently known for APCI. Graphical Abstract ᅟ.

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.

Ionization of EPA Contaminants in Direct and Dopant-Assisted Atmospheric Pressure Photoionization and Atmospheric Pressure Laser Ionization

NASA Astrophysics Data System (ADS)

Kauppila, Tiina J.; Kersten, Hendrik; Benter, Thorsten

2015-06-01

Seventy-seven EPA priority environmental pollutants were analyzed using gas chromatography-mass spectrometry (GC-MS) equipped with an optimized atmospheric pressure photoionization (APPI) and an atmospheric pressure laser ionization (APLI) interface with and without dopants. The analyzed compounds included e.g., polycyclic aromatic hydrocarbons (PAHs), nitro compounds, halogenated compounds, aromatic compounds with phenolic, acidic, alcohol, and amino groups, phthalate and adipatic esters, and aliphatic ethers. Toluene, anisole, chlorobenzene, and acetone were tested as dopants. The widest range of analytes was ionized using direct APPI (66/77 compounds). The introduction of dopants decreased the amount of compounds ionized in APPI (e.g., 54/77 with toluene), but in many cases the ionization efficiency increased. While in direct APPI the formation of molecular ions via photoionization was the main ionization reaction, dopant-assisted (DA) APPI promoted ionization reactions, such as charge exchange and proton transfer. Direct APLI ionized a much smaller amount of compounds than APPI (41/77 compounds), showing selectivity towards compounds with low ionization energies (IEs) and long-lived resonantly excited intermediate states. DA-APLI, however, was able to ionize a higher amount of compounds (e.g. 51/77 with toluene), as the ionization took place entirely through dopant-assisted ion/molecule reactions similar to those in DA-APPI. Best ionization efficiency in APPI and APLI (both direct and DA) was obtained for PAHs and aromatics with O- and N-functionalities, whereas nitro compounds and aliphatic ethers were the most difficult to ionize. Halogenated aromatics and esters were (mainly) ionized in APPI, but not in APLI.

Mode transition induced by the magnetic field gradient in Hall thrusters

NASA Astrophysics Data System (ADS)

Han, Liang; Wei, Liqiu; Yu, Daren

2016-09-01

A mode transition phenomenon was found in Hall thrusters, which was induced by the increase of the magnetic field gradient. In the transition process, we observed experimentally that there have been obvious changes in the oscillation, the mean value of the discharge current, the thrust, the anode efficiency, and the plume pattern. The shifting and compression of the high magnetic field causes the electron density in the discharge channel to decrease and the ionization zone to move towards the exit plane. This also corresponds to a low atom density in the discharge channel, resulting in a loss of stability of the ionization at a high magnetic field gradient, which presents the transition of the discharge mode.

Physical Conditions in Shocked Interstellar Gas Interacting with the Supernova Remnant IC 443

NASA Astrophysics Data System (ADS)

Ritchey, Adam M.; Federman, Steven Robert; Jenkins, Edward B.; Caprioli, Damiano; Wallerstein, George

2018-06-01

We present the results of a detailed investigation into the physical conditions in interstellar material interacting with the supernova remnant IC 443. Our analysis is based on an examination of high-resolution HST/STIS spectra of two stars probing predominantly neutral gas located both ahead of and behind the supernova shock front. The pre-shock neutral gas is characterized by densities and temperatures typical of diffuse interstellar clouds, while the post-shock material exhibits a range of more extreme physical conditions, including high temperatures (>104 K) in some cases, which may require a sudden heating event to explain. The ionization level is enhanced in the high-temperature post-shock material, which could be the result of enhanced radiation from shocks or from an increase in cosmic-ray ionization. The gas-phase abundances of refractory elements are also enhanced in the high-pressure gas, suggesting efficient destruction of dust grains by shock sputtering. Observations of highly-ionized species at very high velocity indicate a post-shock temperature of 107 K for the hot X-ray emitting plasma of the remnant’s interior, in agreement with studies of thermal X-ray emission from IC 443.

Electrospray Ionization Efficiency Is Dependent on Different Molecular Descriptors with Respect to Solvent pH and Instrumental Configuration

PubMed Central

Kiontke, Andreas; Oliveira-Birkmeier, Ariana; Opitz, Andreas

2016-01-01

Over the past decades, electrospray ionization for mass spectrometry (ESI-MS) has become one of the most commonly employed techniques in analytical chemistry, mainly due to its broad applicability to polar and semipolar compounds and the superior selectivity which is achieved in combination with high resolution separation techniques. However, responsiveness of an analytical method also determines its suitability for the quantitation of chemical compounds; and in electrospray ionization for mass spectrometry, it can vary significantly among different analytes with identical solution concentrations. Therefore, we investigated the ESI-response behavior of 56 nitrogen-containing compounds including aromatic amines and pyridines, two compound classes of high importance to both, synthetic organic chemistry as well as to pharmaceutical sciences. These compounds are increasingly analyzed employing ESI mass spectrometry detection due to their polar, basic character. Signal intensities of the peaks from the protonated molecular ion (MH+) were acquired under different conditions and related to compound properties such as basicity, polarity, volatility and molecular size exploring their quantitative impact on ionization efficiency. As a result, we found that though solution basicity of a compound is the main factor initially determining the ESI response of the protonated molecular ion, other factors such as polarity and vaporability become more important under acidic solvent conditions and may nearly outweigh the importance of basicity under these conditions. Moreover, we show that different molecular descriptors may become important when using different types of instruments for such investigations, a fact not detailed so far in the available literature. PMID:27907110

Test study of boron nitride as a new detector material for dosimetry in high-energy photon beams.

PubMed

Poppinga, D; Halbur, J; Lemmer, S; Delfs, B; Harder, D; Looe, H K; Poppe, B

2017-09-05

The aim of this test study is to check whether boron nitride (BN) might be applied as a detector material in high-energy photon-beam dosimetry. Boron nitride exists in various crystalline forms. Hexagonal boron nitride (h-BN) possesses high mobility of the electrons and holes as well as a high volume resistivity, so that ionizing radiation in the clinical range of the dose rate can be expected to produce a measurable electrical current at low background current. Due to the low atomic numbers of its constituents, its density (2.0 g cm -3 ) similar to silicon and its commercial availability, h-BN appears as possibly suitable for the dosimetry of ionizing radiation. Five h-BN plates were contacted to triaxial cables, and the detector current was measured in a solid-state ionization chamber circuit at an applied voltage of 50 V. Basic dosimetric properties such as formation by pre-irradiation, sensitivity, reproducibility, linearity and temporal resolution were measured with 6 MV photon irradiation. Depth dose curves at quadratic field sizes of 10 cm and 40 cm were measured and compared to ionization chamber measurements. After a pre-irradiation with 6 Gy, the devices show a stable current signal at a given dose rate. The current-voltage characteristic up to 400 V shows an increase in the collection efficiency with the voltage. The time-resolved detector current behavior during beam interrupts is comparable to diamond material, and the background current is negligible. The measured percentage depth dose curves at 10 cm  ×  10 cm field size agreed with the results of ionization chamber measurements within  ±2%. This is a first study of boron nitride as a detector material for high-energy photon radiation. By current measurements on solid ionization chambers made from boron nitride chips we could demonstrate that boron nitride is in principle suitable as a detector material for high-energy photon-beam dosimetry.

Test study of boron nitride as a new detector material for dosimetry in high-energy photon beams

NASA Astrophysics Data System (ADS)

Poppinga, D.; Halbur, J.; Lemmer, S.; Delfs, B.; Harder, D.; Looe, H. K.; Poppe, B.

2017-09-01

The aim of this test study is to check whether boron nitride (BN) might be applied as a detector material in high-energy photon-beam dosimetry. Boron nitride exists in various crystalline forms. Hexagonal boron nitride (h-BN) possesses high mobility of the electrons and holes as well as a high volume resistivity, so that ionizing radiation in the clinical range of the dose rate can be expected to produce a measurable electrical current at low background current. Due to the low atomic numbers of its constituents, its density (2.0 g cm-3) similar to silicon and its commercial availability, h-BN appears as possibly suitable for the dosimetry of ionizing radiation. Five h-BN plates were contacted to triaxial cables, and the detector current was measured in a solid-state ionization chamber circuit at an applied voltage of 50 V. Basic dosimetric properties such as formation by pre-irradiation, sensitivity, reproducibility, linearity and temporal resolution were measured with 6 MV photon irradiation. Depth dose curves at quadratic field sizes of 10 cm and 40 cm were measured and compared to ionization chamber measurements. After a pre-irradiation with 6 Gy, the devices show a stable current signal at a given dose rate. The current-voltage characteristic up to 400 V shows an increase in the collection efficiency with the voltage. The time-resolved detector current behavior during beam interrupts is comparable to diamond material, and the background current is negligible. The measured percentage depth dose curves at 10 cm  ×  10 cm field size agreed with the results of ionization chamber measurements within  ±2%. This is a first study of boron nitride as a detector material for high-energy photon radiation. By current measurements on solid ionization chambers made from boron nitride chips we could demonstrate that boron nitride is in principle suitable as a detector material for high-energy photon-beam dosimetry.

Charge Exchange Reaction in Dopant-Assisted Atmospheric Pressure Chemical Ionization and Atmospheric Pressure Photoionization.

PubMed

Vaikkinen, Anu; Kauppila, Tiina J; Kostiainen, Risto

2016-08-01

The efficiencies of charge exchange reaction in dopant-assisted atmospheric pressure chemical ionization (DA-APCI) and dopant-assisted atmospheric pressure photoionization (DA-APPI) mass spectrometry (MS) were compared by flow injection analysis. Fourteen individual compounds and a commercial mixture of 16 polycyclic aromatic hydrocarbons were chosen as model analytes to cover a wide range of polarities, gas-phase ionization energies, and proton affinities. Chlorobenzene was used as the dopant, and methanol/water (80/20) as the solvent. In both techniques, analytes formed the same ions (radical cations, protonated molecules, and/or fragments). However, in DA-APCI, the relative efficiency of charge exchange versus proton transfer was lower than in DA-APPI. This is suggested to be because in DA-APCI both dopant and solvent clusters can be ionized, and the formed reagent ions can react with the analytes via competing charge exchange and proton transfer reactions. In DA-APPI, on the other hand, the main reagents are dopant-derived radical cations, which favor ionization of analytes via charge exchange. The efficiency of charge exchange in both DA-APPI and DA-APCI was shown to depend heavily on the solvent flow rate, with best efficiency seen at lowest flow rates studied (0.05 and 0.1 mL/min). Both DA-APCI and DA-APPI showed the radical cation of chlorobenzene at 0.05-0.1 mL/min flow rate, but at increasing flow rate, the abundance of chlorobenzene M(+.) decreased and reagent ion populations deriving from different gas-phase chemistry were recorded. The formation of these reagent ions explains the decreasing ionization efficiency and the differences in charge exchange between the techniques. Graphical Abstract ᅟ.

Insight into doping efficiency of organic semiconductors from the analysis of the density of states in n-doped C60 and ZnPc

NASA Astrophysics Data System (ADS)

Gaul, Christopher; Hutsch, Sebastian; Schwarze, Martin; Schellhammer, Karl Sebastian; Bussolotti, Fabio; Kera, Satoshi; Cuniberti, Gianaurelio; Leo, Karl; Ortmann, Frank

2018-05-01

Doping plays a crucial role in semiconductor physics, with n-doping being controlled by the ionization energy of the impurity relative to the conduction band edge. In organic semiconductors, efficient doping is dominated by various effects that are currently not well understood. Here, we simulate and experimentally measure, with direct and inverse photoemission spectroscopy, the density of states and the Fermi level position of the prototypical materials C60 and zinc phthalocyanine n-doped with highly efficient benzimidazoline radicals (2-Cyc-DMBI). We study the role of doping-induced gap states, and, in particular, of the difference Δ1 between the electron affinity of the undoped material and the ionization potential of its doped counterpart. We show that this parameter is critical for the generation of free carriers and influences the conductivity of the doped films. Tuning of Δ1 may provide alternative strategies to optimize the electronic properties of organic semiconductors.

A Sleeping Giant Awakened: Reignition of AGN Activity, Reborn Star Formation, and a Multiphase Outflow in one of the Largest Radio Galaxies Known

NASA Astrophysics Data System (ADS)

Tremblay, Grant; O'Dea, Christopher; Labiano, Alvaro; Baum, Stefi; McDermid, Richard; Combes, Francoise; Garcia-Burillo, Santiago; Davis, Timothy

2014-08-01

3C 236 is the second largest known radio galaxy and one of the largest objects in the known Universe. Its central AGN has recently reignited after a 10 Myr dormancy period, giving rise to a very young and compact radio source and a 1000 km/sec outflow of warm ionized and atomic HI gas. We propose GMOS-N IFU observations to resolve this outflow, determine its driver, and estimate the relative coupling efficiencies between the warm ionized, atomic, and cold molecular gas phases. We will assemble a much-needed spatially resolved Balmer decrement (extinction map) across the dramatic double dust lanes of this source, enabling high spatial resolution star formation rate, efficiency, and gas excitation and velocity maps. These will address several mysteries related to the very high star formation efficiency and the unique nature of the multiphase outflow in this source. 3C 236 is such a remarkable galaxy that whatever the results of the proposed observations, they will have wide-ranging implications for the triggering of star formation and AGN activity, their possibly coupled co-evolution, and the feedback effects of the latter on the former.

Toward single-cell analysis by plume collimation in laser ablation electrospray ionization mass spectrometry.

PubMed

Stolee, Jessica A; Vertes, Akos

2013-04-02

Ambient ionization methods for mass spectrometry have enabled the in situ and in vivo analysis of biological tissues and cells. When an etched optical fiber is used to deliver laser energy to a sample in laser ablation electrospray ionization (LAESI) mass spectrometry, the analysis of large single cells becomes possible. However, because in this arrangement the ablation plume expands in three dimensions, only a small portion of it is ionized by the electrospray. Here we show that sample ablation within a capillary helps to confine the radial expansion of the plume. Plume collimation, due to the altered expansion dynamics, leads to greater interaction with the electrospray plume resulting in increased ionization efficiency, reduced limit of detection (by a factor of ~13, reaching 600 amol for verapamil), and extended dynamic range (6 orders of magnitude) compared to conventional LAESI. This enhanced sensitivity enables the analysis of a range of metabolites from small cell populations and single cells in the ambient environment. This technique has the potential to be integrated with flow cytometry for high-throughput metabolite analysis of sorted cells.

Modeling of metal thin film growth: Linking angstrom-scale molecular dynamics results to micron-scale film topographies

NASA Astrophysics Data System (ADS)

Hansen, U.; Rodgers, S.; Jensen, K. F.

2000-07-01

A general method for modeling ionized physical vapor deposition is presented. As an example, the method is applied to growth of an aluminum film in the presence of an ionized argon flux. Molecular dynamics techniques are used to examine the surface adsorption, reflection, and sputter reactions taking place during ionized physical vapor deposition. We predict their relative probabilities and discuss their dependence on energy and incident angle. Subsequently, we combine the information obtained from molecular dynamics with a line of sight transport model in a two-dimensional feature, incorporating all effects of reemission and resputtering. This provides a complete growth rate model that allows inclusion of energy- and angular-dependent reaction rates. Finally, a level-set approach is used to describe the morphology of the growing film. We thus arrive at a computationally highly efficient and accurate scheme to model the growth of thin films. We demonstrate the capabilities of the model predicting the major differences on Al film topographies between conventional and ionized sputter deposition techniques studying thin film growth under ionized physical vapor deposition conditions with different Ar fluxes.

High-Rate Capable Floating Strip Micromegas

NASA Astrophysics Data System (ADS)

Bortfeldt, Jonathan; Bender, Michael; Biebel, Otmar; Danger, Helge; Flierl, Bernhard; Hertenberger, Ralf; Lösel, Philipp; Moll, Samuel; Parodi, Katia; Rinaldi, Ilaria; Ruschke, Alexander; Zibell, André

2016-04-01

We report on the optimization of discharge insensitive floating strip Micromegas (MICRO-MEsh GASeous) detectors, fit for use in high-energy muon spectrometers. The suitability of these detectors for particle tracking is shown in high-background environments and at very high particle fluxes up to 60 MHz/cm2. Measurement and simulation of the microscopic discharge behavior have demonstrated the excellent discharge tolerance. A floating strip Micromegas with an active area of 48 cm × 50 cm with 1920 copper anode strips exhibits in 120 GeV pion beams a spatial resolution of 50 μm at detection efficiencies above 95%. Pulse height, spatial resolution and detection efficiency are homogeneous over the detector. Reconstruction of particle track inclination in a single detector plane is discussed, optimum angular resolutions below 5° are observed. Systematic deviations of this μTPC-method are fully understood. The reconstruction capabilities for minimum ionizing muons are investigated in a 6.4 cm × 6.4 cm floating strip Micromegas under intense background irradiation of the whole active area with 20 MeV protons at a rate of 550 kHz. The spatial resolution for muons is not distorted by space charge effects. A 6.4 cm × 6.4 cm floating strip Micromegas doublet with low material budget is investigated in highly ionizing proton and carbon ion beams at particle rates between 2 MHz and 2 GHz. Stable operation up to the highest rates is observed, spatial resolution, detection efficiencies, the multi-hit and high-rate capability are discussed.

Surface Desorption Dielectric-Barrier Discharge Ionization Mass Spectrometry.

PubMed

Zhang, Hong; Jiang, Jie; Li, Na; Li, Ming; Wang, Yingying; He, Jing; You, Hong

2017-07-18

A variant of dielectric-barrier discharge named surface desorption dielectric-barrier discharge ionization (SDDBDI) mass spectrometry was developed for high-efficiency ion transmission and high spatial resolution imaging. In SDDBDI, a tungsten nanotip and the inlet of the mass spectrometer are used as electrodes, and a piece of coverslip is used as a sample plate as well as an insulating dielectric barrier, which simplifies the configuration of instrument and thus the operation. Different from volume dielectric-barrier discharge (VDBD), the microdischarges are generated on the surface at SDDBDI, and therefore the plasma density is extremely high. Analyte ions are guided directly into the MS inlet without any deflection. This configuration significantly improves the ion transmission efficiency and thus the sensitivity. The dependence of sensitivity and spatial resolution of the SDDBDI on the operation parameters were systematically investigated. The application of SDDBDI was successfully demonstrated by analysis of multiple species including amino acids, pharmaceuticals, putative cancer biomarkers, and mixtures of both fatty acids and hormones. Limits of detection (S/N = 3) were determined to be 0.84 and 0.18 pmol, respectively, for the analysis of l-alanine and metronidazole. A spatial resolution of 22 μm was obtained for the analysis of an imprinted cyclophosphamide pattern, and imaging of a "T" character was successfully demonstrated under ambient conditions. These results indicate that SDDBDI has high-efficiency ion transmission, high sensitivity, and high spatial resolution, which render it a potential tool for mass spectrometry imaging.

High efficiency carrier multiplication in PbSe nanocrystals: implications for solar energy conversion.

PubMed

Schaller, R D; Klimov, V I

2004-05-07

We demonstrate for the first time that impact ionization (II) (the inverse of Auger recombination) occurs with very high efficiency in semiconductor nanocrystals (NCs). Interband optical excitation of PbSe NCs at low pump intensities, for which less than one exciton is initially generated per NC on average, results in the formation of two or more excitons (carrier multiplication) when pump photon energies are more than 3 times the NC band gap energy. The generation of multiexcitons from a single photon absorption event is observed to take place on an ultrafast (picosecond) time scale and occurs with up to 100% efficiency depending upon the excess energy of the absorbed photon. Efficient II in NCs can be used to considerably increase the power conversion efficiency of NC-based solar cells.

Combination of electrospray ionization, atmospheric pressure photoionization and laser desorption ionization Fourier transform ion cyclotronic resonance mass spectrometry for the investigation of complex mixtures - Application to the petroleomic analysis of bio-oils.

PubMed

Hertzog, Jasmine; Carré, Vincent; Le Brech, Yann; Mackay, Colin Logan; Dufour, Anthony; Mašek, Ondřej; Aubriet, Frédéric

2017-05-29

The comprehensive description of complex mixtures such as bio-oils is required to understand and improve the different processes involved during biological, environmental or industrial operation. In this context, we have to consider how different ionization sources can improve a non-targeted approach. Thus, the Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has been coupled to electrospray ionization (ESI), laser desorption ionization (LDI) and atmospheric pressure photoionization (APPI) to characterize an oak pyrolysis bio-oil. Close to 90% of the all 4500 compound formulae has been attributed to C x H y O z with similar oxygen class compound distribution. Nevertheless, their relative abundance in respect with their double bound equivalent (DBE) value has evidenced significant differences depending on the ion source used. ESI has allowed compounds with low DBE but more oxygen atoms to be ionized. APPI has demonstrated the efficient ionization of less polar compounds (high DBE values and less oxygen atoms). The LDI behavior of bio-oils has been considered intermediate in terms of DBE and oxygen amounts but it has also been demonstrated that a significant part of the features are specifically detected by this ionization method. Thus, the complementarity of three different ionization sources has been successfully demonstrated for the exhaustive characterization by petroleomic approach of a complex mixture. Copyright © 2017 Elsevier B.V. All rights reserved.

An All-Solid-State High Repetiton Rate Titanium:Sapphire Laser System For Resonance Ionization Laser Ion Sources

NASA Astrophysics Data System (ADS)

Mattolat, C.; Rothe, S.; Schwellnus, F.; Gottwald, T.; Raeder, S.; Wendt, K.

2009-03-01

On-line production facilities for radioactive isotopes nowadays heavily rely on resonance ionization laser ion sources due to their demonstrated unsurpassed efficiency and elemental selectivity. Powerful high repetition rate tunable pulsed dye or Ti:sapphire lasers can be used for this purpose. To counteract limitations of short pulse pump lasers, as needed for dye laser pumping, i.e. copper vapor lasers, which include high maintenance and nevertheless often only imperfect reliability, an all-solid-state Nd:YAG pumped Ti:sapphire laser system has been constructed. This could complement or even replace dye laser systems, eliminating their disadvantages but on the other hand introduce shortcomings on the side of the available wavelength range. Pros and cons of these developments will be discussed.

Target Plate Material Influence on Fullerene-C60 Laser Desorption/Ionization Efficiency.

PubMed

Zeegers, Guido P; Günthardt, Barbara F; Zenobi, Renato

2016-04-01

Systematic laser desorption/ionization (LDI) experiments of fullerene-C60 on a wide range of target plate materials were conducted to gain insight into the initial ion formation in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. The positive and negative ion signal intensities of precursor, fragment, and cluster ions were monitored, varying both the laser fluence (0-3.53 Jcm(-2)) and the ion extraction delay time (0-950 ns). The resulting species-specific ion signal intensities are an indication for the ionization mechanisms that contribute to LDI and the time frames in which they operate, providing insight in the (MA)LDI primary ionization. An increasing electrical resistivity of the target plate material increases the fullerene-C60 precursor and fragment anion signal intensity. Inconel 625 and Ti90/Al6/V4, both highly electrically resistive, provide the highest anion signal intensities, exceeding the cation signal intensity by a factor ~1.4 for the latter. We present a mechanism based on transient electrical field strength reduction to explain this trend. Fullerene-C60 cluster anion formation is negligible, which could be due to the high extraction potential. Cluster cations, however, are readily formed, although for high laser fluences, the preferred channel is formation of precursor and fragment cations. Ion signal intensity depends greatly on the choice of substrate material, and careful substrate selection could, therefore, allow for more sensitive (MA)LDI measurements. Graphical Abstract ᅟ.

How does ionizing radiation escape from galaxies?

NASA Astrophysics Data System (ADS)

Orlitova, Ivana

2016-10-01

Search for sources that reionized the Universe from z 15 to z 6 is one of the main drivers of present-day astronomy. Low-mass star-forming galaxies are the most favoured sources of ionizing photons, but the searches of escaping Lyman continuum (LyC) have not been extremely successful. Our team has recently detected prominent LyC escape from five Green Pea galaxies at redshift 0.3, using the HST/COS spectrograph, which represents a significant breakthrough. We propose here to study the LyC escape of the strongest among these leakers, J1152, with spatial resolution. From the comparison of the ionizing and non-ionizing radiation maps, and surface brightness profiles, we will infer the major mode in which LyC is escaping: from the strongest starburst, from the galaxy edge, through a hole along our line-of-sight, through clumpy medium, or directly from all the production sites due to highly ionized medium in the entire galaxy. In parallel, we will test the predictive power of two highly debated indirect indicators of LyC leakage: the [OIII]5007/[OII]3727 ratio, and Lyman-alpha. We predict that their spatial distribution should closely follow that of the ionizing continuum if column densities of the neutral gas are low. This combined study, which relies on the HST unique capabilities, will bring crucial information on the structure of the leaking galaxies, provide constraints for hydrodynamic simulations, and will lead to efficient future searches for LyC leakers across a large range of redshifts.

State-resolved three-dimensional electron-momentum correlation in nonsequential double ionization of benzene

NASA Astrophysics Data System (ADS)

Winney, Alexander H.; Lin, Yun Fei; Lee, Suk Kyoung; Adhikari, Pradip; Li, Wen

2016-03-01

We report state-resolved electron-momentum correlation measurement of strong-field nonsequential double ionization in benzene. With a novel coincidence detection apparatus, highly efficient triple coincidence (electron-electron dication) and quadruple coincidence (electron-electron-cation-cation) are used to resolve the final ionic states and to characterize three-dimensional (3D) electron-momentum correlation. The primary states associated with dissociative and nondissociative dications are assigned. A 3D momentum anticorrelation is observed for the electrons in coincidence with dissociative benzene dication states whereas such a correlation is absent for nondissociative dication states.

Diode-laser-based RIMS measurements of strontium-90

NASA Astrophysics Data System (ADS)

Bushaw, B. A.; Cannon, B. D.

1998-12-01

Double- and triple-resonance excitation schemes for the ionization of strontium are presented. Use of single-mode diode lasers for the resonance excitations provides a high degree of optical isotopic selectivity: with double-resonance, selectivity of >104 for 90Sr against the stable Sr isotopes has been demonstrated. Measurement of lineshapes and stable isotope shifts in the triple-resonance process indicate that optical selectivity should increase to ˜109. When combined with mass spectrometer selectivity this is sufficient for measurement of 90Sr at background environmental levels. Additionally, autoionizing resonances have been investigated for improving ionization efficiency with lower power lasers.

Current developments with TRIUMF's titanium-sapphire laser based resonance ionization laser ion source. An overview

NASA Astrophysics Data System (ADS)

Lassen, J.; Li, R.; Raeder, S.; Zhao, X.; Dekker, T.; Heggen, H.; Kunz, P.; P. Levy, C. D.; Mostanmand, M.; Teigelhöfer, A.; Ames, F.

2017-11-01

Developments at TRIUMF's isotope separator and accelerator (ISAC) resonance ionization laser ion source (RILIS) in the past years have concentrated on increased reliability for on-line beam delivery of radioactive isotopes to experiments, as well as increasing the number of elements available through resonance ionization and searching for ionization schemes with improved efficiency. The current status of these developments is given with a list of two step laser ionization schemes implemented recently.

Fast, low-level detection of strontium-90 and strontium-89 in environmental samples by collinear resonance ionization spectroscopy

NASA Astrophysics Data System (ADS)

Monz, L.; Hohmann, R.; Kluge, H.-J.; Kunze, S.; Lantzsch, J.; Otten, E. W.; Passler, G.; Senne, P.; Stenner, J.; Stratmann, K.; Swendt, K.; Zimmer, K.; Herrmann, G.; Trautmann, N.; Walter, K.

1993-12-01

Environmental assessment in the wake of a nuclear accident requires the rapid determination of the radiotoxic isotopes 89Sr and 90Sr. Useful measurements must be able to detect 10 8 atoms in the presence of about 10 18 atoms of the stable, naturally occurring isotopes. This paper describes a new approach to this problem using resonance ionization spectroscopy in collinear geometry, combined with classical mass separation. After collection and chemical separation, the strontium from a sample is surface-ionized and the ions are accelerated to an energy of about 30 keV. Initially, a magnetic mass separator provides an isotopic selectivity of about 10 6. The ions are then neutralized by charge exchange and the resulting fast strontium atoms are selectively excited into high-lying atomic Rydberg states by narrow-band cw laser light in collinear geometry. The Rydberg atoms are then field-ionized and detected. Thus far, a total isotopic selectivity of S > 10 10 and an overall efficiency of ξ = 5 × 10 -6 have been achieved. The desired detection limit of 10 8 atoms 90Sr has been demonstrated with synthetic samples.

High-efficiency generation of pulsed Lyman-α radiation by resonant laser wave mixing in low pressure Kr-Ar mixture.

PubMed

Saito, Norihito; Oishi, Yu; Miyazaki, Koji; Okamura, Kotaro; Nakamura, Jumpei; Louchev, Oleg A; Iwasaki, Masahiko; Wada, Satoshi

2016-04-04

We report an experimental generation of ns pulsed 121.568 nm Lyman-α radiation by the resonant nonlinear four-wave mixing of 212.556 nm and 845.015 nm radiation pulses providing a high conversion efficiency 1.7x10^-3 with the output pulse energy 3.6 μJ achieved using a low pressure Kr-Ar mixture. Theoretical analysis shows that this efficiency is achieved due to the advantage of using (i) the high input laser intensities in combination with (ii) the low gas pressure allowing us to avoid the onset of full-scale discharge in the laser focus. In particular, under our experimental conditions the main mechanism of photoionization caused by the resonant 2-photon 212.556 nm radiation excitation of Kr atoms followed by the 1-photon ionization leads to ≈17% loss of Kr atoms and efficiency loss only by the end of the pulse. The energy of free electrons, generated by 212.556 nm radiation via (2 + 1)-photon ionization and accelerated mainly by 845.015 nm radiation, remains during the pulse below the level sufficient for the onset of full-scale discharge by the electron avalanche. Our analysis also suggests that ≈30-fold increase of 845.015 nm pulse energy can allow one to scale up the L-α radiation pulse energy towards the level of ≈100 μJ.

High Sensitivity and High Detection Specificity of Gold-Nanoparticle-Grafted Nanostructured Silicon Mass Spectrometry for Glucose Analysis.

PubMed

Tsao, Chia-Wen; Yang, Zhi-Jie

2015-10-14

Desorption/ionization on silicon (DIOS) is a high-performance matrix-free mass spectrometry (MS) analysis method that involves using silicon nanostructures as a matrix for MS desorption/ionization. In this study, gold nanoparticles grafted onto a nanostructured silicon (AuNPs-nSi) surface were demonstrated as a DIOS-MS analysis approach with high sensitivity and high detection specificity for glucose detection. A glucose sample deposited on the AuNPs-nSi surface was directly catalyzed to negatively charged gluconic acid molecules on a single AuNPs-nSi chip for MS analysis. The AuNPs-nSi surface was fabricated using two electroless deposition steps and one electroless etching step. The effects of the electroless fabrication parameters on the glucose detection efficiency were evaluated. Practical application of AuNPs-nSi MS glucose analysis in urine samples was also demonstrated in this study.

Reionization of Hydrogen and Helium by Early Stars and Quasars

NASA Astrophysics Data System (ADS)

Wyithe, J. Stuart B.; Loeb, Abraham

2003-04-01

We compute the reionization histories of hydrogen and helium caused by the ionizing radiation fields produced by stars and quasars. For the quasars we use a model based on halo-merger rates that reproduces all known properties of the quasar luminosity function at high redshifts. The less constrained properties of the ionizing radiation produced by stars are modeled with two free parameters: (i) a transition redshift, ztran, above which the stellar population is dominated by massive, zero-metallicity stars and below which it is dominated by a Scalo mass function; and (ii) the product of the escape fraction of stellar ionizing photons from their host galaxies and the star formation efficiency, fescf*. We constrain the allowed range of these free parameters at high redshifts on the basis of the lack of the H I Gunn-Peterson trough at z<~6 and the upper limit on the total intergalactic optical depth for electron scattering, τes<0.18, from recent cosmic microwave background (CMB) experiments. We find that quasars ionize helium by a redshift z~4, but cannot reionize hydrogen by themselves before z~6. A major fraction of the allowed combinations of fescf* and ztran leads to an early peak in the ionized fraction because of the presence of metal-free stars at high redshifts. This sometimes results in two reionization epochs, namely, an early H II or He III overlap phase followed by recombination and a second overlap phase. Even if early overlap is not achieved, the peak in the visibility function for scattering of the CMB often coincides with the early ionization phase rather than with the actual reionization epoch. Consequently, τes does not correspond directly to the reionization redshift. We generically find values of τes>~7%, which should be detectable by the MAP satellite.

Dustbuster: a New Generation Impact-ionization Time-of-flight Mass Spectrometer for in situ Analysis of Cosmic Dust

NASA Astrophysics Data System (ADS)

Austin, D. E.; Ahrens, T. J.; Beauchamp, J. L.

2000-10-01

We have developed and tested a small impact-ionization time-of-flight mass spectrometer for analysis of cosmic dust, suitable for use on deep space missions. This mass spectrometer, named Dustbuster, incorporates a large target area and a reflectron, simultaneously optimizing mass resolution, sensitivity, and collection efficiency. Dust particles hitting the 65-cm2 target plate are partially ionized. The resulting ions are accelerated through a modified reflectron that focuses the ions in space and time to produce high-resolution spectra. The instrument, shown below, measures 10 x 10 x 20 cm, has a mass of 500 g, and consumes little power. Laser desorption ionization of metal and mineral samples (embedded in the impact plate) simulates particle impacts for instrument performance tests. Mass resolution in these experiments is near 200, permitting resolution of isotopes. The mass spectrometer can be combined with other instrument components to determine dust particle trajectories and sizes. This project was funded by NASA's Planetary Instrument Definition and Development Program.

Photoionization pathways and thresholds in generation of Lyman-α radiation by resonant four-wave mixing in Kr-Ar mixture

NASA Astrophysics Data System (ADS)

Louchev, Oleg A.; Saito, Norihito; Oishi, Yu; Miyazaki, Koji; Okamura, Kotaro; Nakamura, Jumpei; Iwasaki, Masahiko; Wada, Satoshi

2016-09-01

We develop a set of analytical approximations for the estimation of the combined effect of various photoionization processes involved in the resonant four-wave mixing generation of ns pulsed Lyman-α (L-α ) radiation by using 212.556 nm and 820-845 nm laser radiation pulses in Kr-Ar mixture: (i) multi-photon ionization, (ii) step-wise (2+1)-photon ionization via the resonant 2-photon excitation of Kr followed by 1-photon ionization and (iii) laser-induced avalanche ionization produced by generated free electrons. Developed expressions validated by order of magnitude estimations and available experimental data allow us to identify the area for the operation under high input laser intensities avoiding the onset of full-scale discharge, loss of efficiency and inhibition of generated L-α radiation. Calculations made reveal an opportunity for scaling up the output energy of the experimentally generated pulsed L-α radiation without significant enhancement of photoionization.

Efficient pre-ionization by direct X-B mode conversion in VEST

NASA Astrophysics Data System (ADS)

Jo, JongGab; Lee, H. Y.; Kim, S. C.; Kim, S. H.; An, Y. H.; Hwang, Y. S.

2017-01-01

Pre-ionization experiments with pure toroidal field have been carried out in VEST (Versatile Experiment Spherical Torus) to investigate the feasibility of direct XB mode conversion from perpendicular LFS (Low Field Side) injection for efficient pre-ionization. Pre-ionization plasmas are studied by measuring the electron density and temperature profiles with respect to microwave power and toroidal field strength, and 2D full wave cold plasma simulation using the COMSOL Multiphysics is performed for the comparison. It is experimentally figured out that exceeding the threshold microwave power (>3 kW), the parametric decay and localized collisional heating is observed near the UHR (Upper Hybrid Resonance), and the efficient XB mode conversion can be achieved in both short density scale length (Ln) and magnetic scale length (LB) region positioned at outboard and inboard sides, respectively. From the 2D full wave simulations, the reflection and tunneling of X-wave near the R-cutoff layer according to the measured electron density profiles are analyzed with electric field polarization and power flow. Threshold electric field and wave power density for parametric decay are evaluated at least more than 4.8 × 104 V/m and 100 W/cm2, respectively. This study shows that efficient pre-ionization schemes using direct XB mode conversion can be realized by considering the key factors such as Ln, LB, and transmitted wave power at the UHR. Application to Ohmic start-up experiment is carried out to confirm the effect of the pre-ionization schemes on tokamak plasma start-up in VEST.

Filamentation instability of a fast electron beam in a dielectric target.

PubMed

Debayle, A; Tikhonchuk, V T

2008-12-01

High-intensity laser-matter interaction is an efficient method for high-current relativistic electron beam production. At current densities exceeding a several kA microm{-2} , the beam propagation is maintained by an almost complete current neutralization by the target electrons. In such a geometry of two oppositely directed flows, beam instabilities can develop, depending on the target and the beam parameters. The present paper proposes an analytical description of the filamentation instability of an electron beam propagating through an insulator target. It is shown that the collisionless and resistive instabilities enter into competition with the ionization instability. This latter process is dominant in insulator targets where the field ionization by the fast beam provides free electrons for the neutralization current.

Molecular Insights into the pH-Dependent Adsorption and Removal of Ionizable Antibiotic Oxytetracycline by Adsorbent Cyclodextrin Polymers

PubMed Central

Zhang, Yu; Cai, Xiyun; Xiong, Weina; Jiang, Hao; Zhao, Haitong; Yang, Xianhai; Li, Chao; Fu, Zhiqiang; Chen, Jingwen

2014-01-01

Effects of pH on adsorption and removal efficiency of ionizable organic compounds (IOCs) by environmental adsorbents are an area of debate, because of its dual mediation towards adsorbents and adsorbate. Here, we probe the pH-dependent adsorption of ionizable antibiotic oxytetracycline (comprising OTCH2 +, OTCH±, OTC−, and OTC2−) onto cyclodextrin polymers (CDPs) with the nature of molecular recognition and pH inertness. OTCH± commonly has high adsorption affinity, OTC− exhibits moderate affinity, and the other two species have negligible affinity. These species are evidenced to selectively interact with structural units (e.g., CD cavity, pore channel, and network) of the polymers and thus immobilized onto the adsorbents to different extents. The differences in adsorption affinity and mechanisms of the species account for the pH-dependent adsorption of OTC. The mathematical equations are derived from the multiple linear regression (MLR) analysis of quantitatively relating adsorption affinity of OTC at varying pH to adsorbent properties. A combination of the MLR analysis for OTC and molecular recognition of adsorption of the species illustrates the nature of the pH-dependent adsorption of OTC. Based on this finding, γ-HP-CDP is chosen to adsorb and remove OTC at pH 5.0 and 7.0, showing high removal efficiency and strong resistance to the interference of coexisting components. PMID:24465975

An approach toward quantification of organic compounds in complex environmental samples using high-resolution electrospray ionization mass spectrometry

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

Nguyen, Tran B.; Nizkorodov, Sergey; Laskin, Alexander

2013-01-07

Quantitative analysis of individual compounds in complex mixtures using high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) is complicated by differences in the ionization efficiencies of analyte molecules in the mixture, resulting in signal suppression during ionization. However, the ability to obtain concentration estimates of compounds in an environmental sample is important for data interpretation and comparison. We introduce an approach for estimating mass concentrations of analytes observed in a multicomponent mixture by HR-ESI-MS, without prior separation. The approach relies on a calibration of the instrument using appropriate standards added to the mixture of studied analytes. An illustration of how the proposedmore » calibration can be applied in practice is provided for aqueous extracts of isoprene photooxidation organic aerosol, with multifunctional organic acids standards. We show that the observed ion sensitivities in ESI-MS are positively correlated with the “adjusted mass,” defined as a product of the molecular mass and the H/C ratio in the molecule (adjusted mass = H/C x molecular mass). The correlation of the observed ESI sensitivity with adjusted mass is justified by considering trends of the physical and chemical properties of organic compounds that affect ionization in the positive ion mode, i.e., gas-phase basicity, polarizability, and molecular size.« less

Are clusters important in understanding the mechanisms in atmospheric pressure ionization? Part 1: Reagent ion generation and chemical control of ion populations.

PubMed

Klee, Sonja; Derpmann, Valerie; Wißdorf, Walter; Klopotowski, Sebastian; Kersten, Hendrik; Brockmann, Klaus J; Benter, Thorsten; Albrecht, Sascha; Bruins, Andries P; Dousty, Faezeh; Kauppila, Tiina J; Kostiainen, Risto; O'Brien, Rob; Robb, Damon B; Syage, Jack A

2014-08-01

It is well documented since the early days of the development of atmospheric pressure ionization methods, which operate in the gas phase, that cluster ions are ubiquitous. This holds true for atmospheric pressure chemical ionization, as well as for more recent techniques, such as atmospheric pressure photoionization, direct analysis in real time, and many more. In fact, it is well established that cluster ions are the primary carriers of the net charge generated. Nevertheless, cluster ion chemistry has only been sporadically included in the numerous proposed ionization mechanisms leading to charged target analytes, which are often protonated molecules. This paper series, consisting of two parts, attempts to highlight the role of cluster ion chemistry with regard to the generation of analyte ions. In addition, the impact of the changing reaction matrix and the non-thermal collisions of ions en route from the atmospheric pressure ion source to the high vacuum analyzer region are discussed. This work addresses such issues as extent of protonation versus deuteration, the extent of analyte fragmentation, as well as highly variable ionization efficiencies, among others. In Part 1, the nature of the reagent ion generation is examined, as well as the extent of thermodynamic versus kinetic control of the resulting ion population entering the analyzer region.

Luminescence of water or ice as a new detection method for magnetic monopoles

NASA Astrophysics Data System (ADS)

Pollmann, Anna Obertacke

2017-12-01

Cosmic ray detectors use air as a radiator for luminescence. In water and ice, Cherenkov light is the dominant light producing mechanism when the particle's velocity exceeds the Cherenkov threshold, approximately three quarters of the speed of light in vacuum. Luminescence is produced by highly ionizing particles passing through matter due to the electronic excitation of the surrounding molecules. The observables of luminescence, such as the wavelength spectrum and decay times, are highly dependent on the properties of the medium, in particular, temperature and purity. The results for the light yield of luminescence of previous measurements vary by two orders of magnitude. It will be shown that even for the lowest measured light yield, luminescence is an important signature of highly ionizing particles below the Cherenkov threshold. These could be magnetic monopoles or other massive and highly ionizing exotic particles. With the highest observed efficiencies, luminescence may even contribute significantly to the light output of standard model particles such as the PeV IceCube neutrinos. We present analysis techniques to use luminescence in neutrino telescopes and discuss experimental setups to measure the light yield of luminescence for the particular conditions in neutrino detectors.

Zero kinetic energy photoelectron spectroscopy of tryptamine and the dissociation pathway of the singly hydrated cation cluster.

PubMed

Gu, Quanli; Knee, J L

2012-09-14

The relative ionization energies of tryptamine conformations are determined by zero kinetic energy photoelectron spectroscopy and photoionization efficiency measurements. The relative cationic conformational stabilities are compared to the published results for the neutral molecule. In the cation, the interaction strength changes significantly between amino group and either the phenyl or the pyrrole moiety of the indole chromophore where most of the positive charge is located, leading to different conformational structures and relative conformer energies in the cation. In particular, the measured adiabatic ionization potential of isomer B is 60,928 ± 5 cm(-1), at least 400 cm(-1) higher than any of the 6 other tryptamine isomers which all have ionization potentials within 200 cm(-1) of each other. In addition to the monomer, measurements were made on the A conformer of the tryptamine(+)-H(2)O complex including the ionization threshold and cation dissociation energy measured using a threshold photoionization fragmentation method. The water cluster exhibits an unexpectedly high ionization potential of 60,307 ± 100 cm(-1), close to the conformer A monomer of 60 320 ± 100 cm(-1). It also exhibits surprisingly low dissociation energy of 1750 ± 150 cm(-1) compared to other H-bonding involved cation-H(2)O complexes which are typically several thousands of wavenumbers higher. Quantum chemical calculations indicate that upon ionization the structure of the parent molecule in the water complex remains mostly unchanged due to the rigid intermolecular double hydrogen bonded water molecule bridging the monomer backbone and its side chain thus leading to the high ionization potential in the water cluster. The surprisingly low dissociation energy measured in the cationic water complex is attributed to the formation of a much more stable structural isomer H(+) in the exit channel.

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.

Driving Turbulence and Triggering Star Formation by Ionizing Radiation

NASA Astrophysics Data System (ADS)

Gritschneder, Matthias; Naab, Thorsten; Walch, Stefanie; Burkert, Andreas; Heitsch, Fabian

2009-03-01

We present high-resolution simulations on the impact of ionizing radiation of massive O stars on the surrounding turbulent interstellar medium (ISM). The simulations are performed with the newly developed software iVINE which combines ionization with smoothed particle hydrodynamics (SPH) and gravitational forces. We show that radiation from hot stars penetrates the ISM, efficiently heats cold low-density gas and amplifies overdensities seeded by the initial turbulence. The formation of observed pillar-like structures in star-forming regions (e.g. in M16) can be explained by this scenario. At the tip of the pillars gravitational collapse can be induced, eventually leading to the formation of low-mass stars. Detailed analysis of the evolution of the turbulence spectra shows that UV radiation of O stars indeed provides an excellent mechanism to sustain and even drive turbulence in the parental molecular cloud.

Preliminary Spectroscopic Measurements for a Gallium Electromagnetic (GEM) Thruster

NASA Technical Reports Server (NTRS)

Thomas, Robert E.; Burton, Rodney L.; Glumac, Nick G.; Polzin, Kurt A.

2007-01-01

As a propellant option for electromagnetic thrusters, liquid ,gallium appears to have several advantages relative to other propellants. The merits of using gallium in an electromagnetic thruster (EMT) are discussed and estimates of discharge current levels and mass flow rates yielding efficient operation are given. The gallium atomic weight of 70 predicts high efficiency in the 1500-2000 s specific impulse range, making it ideal for higher-thrust, near-Earth missions. A spatially and temporally broad spectroscopic survey in the 220-520 nm range is used to determine which species are present in the plasma and estimate electron temperature. The spectra show that neutral, singly, and doubly ionized gallium species are present in a 20 J, 1.8 kA (peak) are discharge. With graphite present on the insulator to facilitate breakdown, singly and doubly ionized carbon atoms are also present, and emission is observed from molecular carbon (CZ) radicals. A determination of the electron temperature was attempted using relative emission line data, and while the spatially and temporally averaged, spectra don't fit well to single temperatures, the data and presence of doubly ionized gallium are consistent with distributions in the 1-3 eV range.

Ion Clouds in the Inductively Coupled Plasma Torch: A Closer Look through Computations.

PubMed

Aghaei, Maryam; Lindner, Helmut; Bogaerts, Annemie

2016-08-16

We have computationally investigated the introduction of copper elemental particles in an inductively coupled plasma torch connected to a sampling cone, including for the first time the ionization of the sample. The sample is inserted as liquid particles, which are followed inside the entire torch, i.e., from the injector inlet up to the ionization and reaching the sampler. The spatial position of the ion clouds inside the torch as well as detailed information on the copper species fluxes at the position of the sampler orifice and the exhausts of the torch are provided. The effect of on- and off-axis injection is studied. We clearly show that the ion clouds of on-axis injected material are located closer to the sampler with less radial diffusion. This guarantees a higher transport efficiency through the sampler cone. Moreover, our model reveals the optimum ranges of applied power and flow rates, which ensure the proper position of ion clouds inside the torch, i.e., close enough to the sampler to increase the fraction that can enter the mass spectrometer and with minimum loss of material toward the exhausts as well as a sufficiently high plasma temperature for efficient ionization.

Design of a secondary ionization target for direct production of a C- beam from CO2 pulses for online AMS.

PubMed

Salazar, Gary; Ognibene, Ted

2013-01-01

We designed and optimized a novel device "target" that directs a CO 2 gas pulse onto a Ti surface where a Cs + beam generates C - from the CO 2 . This secondary ionization target enables an accelerator mass spectrometer to ionize pulses of CO 2 in the negative mode to measure 14 C/ 12 C isotopic ratios in real time. The design of the targets were based on computational flow dynamics, ionization mechanism and empirical optimization. As part of the ionization mechanism, the adsorption of CO 2 on the Ti surface was fitted with the Jovanovic-Freundlich isotherm model using empirical and simulation data. The inferred adsorption constants were in good agreement with other works. The empirical optimization showed that amount of injected carbon and the flow speed of the helium carrier gas improve the ionization efficiency and the amount of 12 C - produced until reaching a saturation point. Linear dynamic range between 150 and 1000 ng of C and optimum carrier gas flow speed of around 0.1 mL/min were shown. It was also shown that the ionization depends on the area of the Ti surface and Cs + beam cross-section. A range of ionization efficiency of 1-2.5% was obtained by optimizing the described parameters.

Recombination in liquid-filled ionization chambers beyond the Boag limit

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

Brualla-González, L.; Roselló, J.

Purpose: The high mass density and low mobilities of charge carriers can cause important recombination in liquid-filled ionization chambers (LICs). Saturation correction methods have been proposed for LICs. Correction methods for pulsed irradiation are based on Boag equation. However, Boag equation assumes that the charge ionized by one pulse is fully collected before the arrival of the next pulse. This condition does not hold in many clinical beams where the pulse repetition period may be shorter than the charge collection time, causing overlapping between charge carriers ionized by different pulses, and Boag equation is not applicable there. In this work,more » the authors present an experimental and numerical characterization of collection efficiencies in LICs beyond the Boag limit, with overlapping between charge carriers ionized by different pulses. Methods: The authors have studied recombination in a LIC array for different dose-per-pulse, pulse repetition frequency, and polarization voltage values. Measurements were performed in a Truebeam Linac using FF and FFF modalities. Dose-per-pulse and pulse repetition frequency have been obtained by monitoring the target current with an oscilloscope. Experimental collection efficiencies have been obtained by using a combination of the two-dose-rate method and ratios to the readout of a reference chamber (CC13, IBA). The authors have also used numerical simulation to complement the experimental data. Results: The authors have found that overlap significantly increases recombination in LICs, as expected. However, the functional dependence of collection efficiencies on the dose-per-pulse does not change (a linear dependence has been observed in the near-saturation region for different degrees of overlapping, the same dependence observed in the nonoverlapping scenario). On the other hand, the dependence of collection efficiencies on the polarization voltage changes in the overlapping scenario and does not follow that of Boag equation, the reason being that changing the polarization voltage also affects the charge collection time, thus changing the amount of overlapping. Conclusions: These results have important consequences for saturation correction methods for LICs. On one hand, the two-dose-rate method, which relies on the functional dependence of the collection efficiencies on dose-per-pulse, can also be used in the overlapping situation, provided that the two measurements needed to feed the method are performed at the same pulse repetition frequency (monitor unit rate). This result opens the door to computing collection efficiencies in LICs in many clinical setups where charge overlap in the LIC exists. On the other hand, correction methods based on the voltage-dependence of Boag equation like the three-voltage method or the modified two-voltage method will not work in the overlapping scenario due to the different functional dependence of collection efficiencies on the polarization voltage.« less

Determination of hexabromocyclododecane by flowing atmospheric pressure afterglow mass spectrometry.

PubMed

Smoluch, Marek; Silberring, Jerzy; Reszke, Edward; Kuc, Joanna; Grochowalski, Adam

2014-10-01

The first application of a flowing atmospheric-pressure afterglow ion source for mass spectrometry (FAPA-MS) for the chemical characterization and determination of hexabromocyclododecane (HBCD) is presented. The samples of technical HBCD and expanded polystyrene foam (EPS) containing HBCD as a flame retardant were prepared by dissolving the appropriate solids in dichloromethane. The ionization of HBCD was achieved with a prototype FAPA source. The ions were detected in the negative-ion mode. The ions corresponding to a deprotonated HBCD species (m/z 640.7) as well as chlorine (m/z 676.8), nitrite (m/z 687.8) and nitric (m/z 703.8) adducts were observed in the spectra. The observed isotope pattern is characteristic for a compound containing six bromine atoms. This technique is an effective approach to detect HBCD, which is efficiently ionized in a liquid phase, resulting in high detection efficiency and sensitivity. Copyright © 2014 Elsevier B.V. All rights reserved.

Soft Argon-Propane Dielectric Barrier Discharge Ionization.

PubMed

Schütz, Alexander; Lara-Ortega, Felipe J; Klute, Felix David; Brandt, Sebastian; Schilling, Michael; Michels, Antje; Veza, Damir; Horvatic, Vlasta; García-Reyes, Juan F; Franzke, Joachim

2018-03-06

Dielectric barrier discharges (DBDs) have been used as soft ionization sources (DBDI) for organic mass spectrometry (DBDI-MS) for approximately ten years. Helium-based DBDI is often used because of its good ionization efficiency, low ignition voltage, and homogeneous plasma conditions. Argon needs much higher ignition voltages than helium when the same discharge geometry is used. A filamentary plasma, which is not suitable for soft ionization, may be produced instead of a homogeneous plasma. This difference results in N 2 , present in helium and argon as an impurity, being Penning-ionized by helium but not by metastable argon atoms. In this study, a mixture of argon and propane (C 3 H 8 ) was used as an ignition aid to decrease the ignition and working voltages, because propane can be Penning-ionized by argon metastables. This approach leads to homogeneous argon-based DBDI. Furthermore, operating DBDI in an open environment assumes that many uncharged analyte molecules do not interact with the reactant ions. To overcome this disadvantage, we present a novel approach, where the analyte is introduced in an enclosed system through the discharge capillary itself. This nonambient DBDI-MS arrangement is presented and characterized and could advance the novel connection of DBDI with analytical separation techniques such as gas chromatography (GC) and high-pressure liquid chromatography (HPLC) in the near future.

Fast Magnetoresistive Random-Access Memory

NASA Technical Reports Server (NTRS)

Wu, Jiin-Chuan; Stadler, Henry L.; Katti, Romney R.

1991-01-01

Magnetoresistive binary digital memories of proposed new type expected to feature high speed, nonvolatility, ability to withstand ionizing radiation, high density, and low power. In memory cell, magnetoresistive effect exploited more efficiently by use of ferromagnetic material to store datum and adjacent magnetoresistive material to sense datum for readout. Because relative change in sensed resistance between "zero" and "one" states greater, shorter sampling and readout access times achievable.

Universal strategy for Ohmic hole injection into organic semiconductors with high ionization energies

NASA Astrophysics Data System (ADS)

Kotadiya, Naresh B.; Lu, Hao; Mondal, Anirban; Ie, Yutaka; Andrienko, Denis; Blom, Paul W. M.; Wetzelaer, Gert-Jan A. H.

2018-02-01

Barrier-free (Ohmic) contacts are a key requirement for efficient organic optoelectronic devices, such as organic light-emitting diodes, solar cells, and field-effect transistors. Here, we propose a simple and robust way of forming an Ohmic hole contact on organic semiconductors with a high ionization energy (IE). The injected hole current from high-work-function metal-oxide electrodes is improved by more than an order of magnitude by using an interlayer for which the sole requirement is that it has a higher IE than the organic semiconductor. Insertion of the interlayer results in electrostatic decoupling of the electrode from the semiconductor and realignment of the Fermi level with the IE of the organic semiconductor. The Ohmic-contact formation is illustrated for a number of material combinations and solves the problem of hole injection into organic semiconductors with a high IE of up to 6 eV.

Universal strategy for Ohmic hole injection into organic semiconductors with high ionization energies.

PubMed

Kotadiya, Naresh B; Lu, Hao; Mondal, Anirban; Ie, Yutaka; Andrienko, Denis; Blom, Paul W M; Wetzelaer, Gert-Jan A H

2018-04-01

Barrier-free (Ohmic) contacts are a key requirement for efficient organic optoelectronic devices, such as organic light-emitting diodes, solar cells, and field-effect transistors. Here, we propose a simple and robust way of forming an Ohmic hole contact on organic semiconductors with a high ionization energy (IE). The injected hole current from high-work-function metal-oxide electrodes is improved by more than an order of magnitude by using an interlayer for which the sole requirement is that it has a higher IE than the organic semiconductor. Insertion of the interlayer results in electrostatic decoupling of the electrode from the semiconductor and realignment of the Fermi level with the IE of the organic semiconductor. The Ohmic-contact formation is illustrated for a number of material combinations and solves the problem of hole injection into organic semiconductors with a high IE of up to 6 eV.

Electrochemical Ionization and Analyte Charging in the Array of Micromachined UltraSonic Electrospray (AMUSE) Ion Source

PubMed Central

Forbes, Thomas P.; Degertekin, F. Levent; Fedorov, Andrei G.

2010-01-01

Electrochemistry and ion transport in a planar array of mechanically-driven, droplet-based ion sources are investigated using an approximate time scale analysis and in-depth computational simulations. The ion source is modeled as a controlled-current electrolytic cell, in which the piezoelectric transducer electrode, which mechanically drives the charged droplet generation using ultrasonic atomization, also acts as the oxidizing/corroding anode (positive mode). The interplay between advective and diffusive ion transport of electrochemically generated ions is analyzed as a function of the transducer duty cycle and electrode location. A time scale analysis of the relative importance of advective vs. diffusive ion transport provides valuable insight into optimality, from the ionization prospective, of alternative design and operation modes of the ion source operation. A computational model based on the solution of time-averaged, quasi-steady advection-diffusion equations for electroactive species transport is used to substantiate the conclusions of the time scale analysis. The results show that electrochemical ion generation at the piezoelectric transducer electrodes located at the back-side of the ion source reservoir results in poor ionization efficiency due to insufficient time for the charged analyte to diffuse away from the electrode surface to the ejection location, especially at near 100% duty cycle operation. Reducing the duty cycle of droplet/analyte ejection increases the analyte residence time and, in turn, improves ionization efficiency, but at an expense of the reduced device throughput. For applications where this is undesirable, i.e., multiplexed and disposable device configurations, an alternative electrode location is incorporated. By moving the charging electrode to the nozzle surface, the diffusion length scale is greatly reduced, drastically improving ionization efficiency. The ionization efficiency of all operating conditions considered is expressed as a function of the dimensionless Peclet number, which defines the relative effect of advection as compared to diffusion. This analysis is general enough to elucidate an important role of electrochemistry in ionization efficiency of any arrayed ion sources, be they mechanically-driven or electrosprays, and is vital for determining optimal design and operation conditions. PMID:20607111

Ionization degree measurement in the gain medium of a hydrocarbon-free rubidium vapor laser operating in pulsed and CW modes.

PubMed

Zhao, Xiaofan; Yang, Zining; Hua, Weihong; Wang, Hongyan; Xu, Xiaojun

2017-04-17

Although the diode pumped alkali laser (DPAL) works in a three-level scheme, higher energy-state excitation and ionization processes exist during operation, which may lead to deleterious effects on laser performance. In this paper, we report the ionization degree measurement in the gain medium of an operational hydrocarbon-free Rb DPAL by using the optogalvanic method. The results show that, at the pulsed mode with a duration of ~1 ms, a maximal ionization degree of ~0.06% is obtained at a pump power of 140 W. While in the CW mode, the plasma reaches an ionization degree as high as ~2% at a pump power of 110 W, which is mainly due to the enough time for sufficient plasma development. A comparison with our previous work [Opt. Lett.39, 6501 (2014)] as well as modeling results is made and discussed. The influences of different population transfer channels on laser performance are simulated and analyzed. The results show that, for a typical hydrocarbon-free Rb laser (pump intensity of 15 kW/cm², helium pressure of 10 atm and cell temperature of 438 K), all the high-energy excitation effects give an overall negative influence on laser efficiency of ~3.78%, while the top two influencing channels are the photoionization (~1.8%) and the energy pooling (~1.53%). The work in this paper experimentally reveals the influence of the macroscopic ionization evolution process on an operational DPAL for the first time, which would be helpful for a more comprehensive understanding of the physics in DPALs.

Efficient Ionization Investigation for Flow Control and Energy Extraction

NASA Technical Reports Server (NTRS)

Schneider, Steven J.; Kamhawi, Hani; Blankson, Isaiah M.

2009-01-01

Nonequilibrium ionization of air by nonthermal means is explored for hypersonic vehicle applications. The method selected for evaluation generates a weakly ionized plasma using pulsed nanosecond, high-voltage discharges sustained by a lower dc voltage. These discharges promise to provide a means of energizing and sustaining electrons in the air while maintaining a nearly constant ion/neutral molecule temperature. This paper explores the use of short approx.5 nsec, high-voltage approx.12 to 22 kV, repetitive (40 to 100 kHz) discharges in generating a weakly ionized gas sustained by a 1 kV dc voltage in dry air at pressures from 10 to 80 torr. Demonstrated lifetimes of the sustainer discharge current approx.10 to 25 msec are over three orders of magnitude longer than the 5 nsec pulse that generates the electrons. This life is adequate for many high speed flows, enabling the possibility of exploiting weakly ionized plasma phenomena in flow-fields such as those in hypersonic inlets, combustors, and nozzles. Results to date are obtained in a volume of plasma between electrodes in a bell jar. The buildup and decay of the visible emission from the pulser excited air is photographed on an ICCD camera with nanosecond resolution and the time constants for visible emission decay are observed to be between 10 to 15 nsec decreasing as pressure increases. The application of the sustainer voltage does not change the visible emission decay time constant. Energy consumption as indicated by power output from the power supplies is 194 to 669 W depending on pulse repetition rate.

Extreme gaseous outflows in radio-loud narrow-line Seyfert 1 galaxies

NASA Astrophysics Data System (ADS)

Komossa, S.; Xu, D. W.; Wagner, A. Y.

2018-07-01

We present four radio-loud narrow-line Seyfert 1 (NLS1) galaxies with extreme emission-line shifts, indicating radial outflow velocities of the ionized gas of up to 2450 km s-1, above the escape velocity of the host galaxies. The forbidden lines show strong broadening, up to 2270 km s-1. An ionization stratification (higher line shift at higher ionization potential) implies that we see a large-scale outflow rather than single, localized jet-cloud interactions. Similarly, the paucity of zero-velocity [O III] λ5007 emitting gas implies the absence of a second narrow-line region (NLR) component at rest, and therefore a large part of the high-ionization NLR is affected by the outflow. Given the radio loudness of these NLS1 galaxies, the observations are consistent with a pole on view onto their central engines, so that the effects of polar outflows are maximized. In addition, a very efficient driving mechanism is required to reach the high observed velocities. We explore implications from recent hydrodynamic simulations of the interaction between fast winds or jets with the large-scale NLR. Overall, the best agreement with observations (and especially the high outflow speeds of the [Ne V] emitting gas) can be reached if the NLS1 galaxies are relatively young sources with lifetimes not much exceeding 1 Myr. These systems represent sites of strong feedback at NLR scales at work, well below redshift one.

Extreme Gaseous Outflows in Radio-Loud Narrow-Line Seyfert 1 Galaxies

NASA Astrophysics Data System (ADS)

Komossa, S.; Xu, D. W.; Wagner, A. Y.

2018-04-01

We present four radio-loud NLS1 galaxies with extreme emission-line shifts, indicating radial outflow velocities of the ionized gas of up to 2450 km/s, above the escape velocity of the host galaxies. The forbidden lines show strong broadening, up to 2270 km/s. An ionization stratification (higher line shift at higher ionization potential) implies that we see a large-scale outflow rather than single, localized jet-cloud interactions. Similarly, the paucity of zero-velocity [OIII]λ5007 emitting gas implies the absence of a second narrow-line region (NLR) component at rest, and therefore a large part of the high-ionization NLR is affected by the outflow. Given the radio loudness of these NLS1 galaxies, the observations are consistent with a pole on view onto their central engines, so that the effects of polar outflows are maximized. In addition, a very efficient driving mechanism is required, to reach the high observed velocities. We explore implications from recent hydrodynamic simulations of the interaction between fast winds or jets with the large-scale NLR. Overall, the best agreement with observations (and especially the high outflow speeds of the [NeV] emitting gas) can be reached if the NLS1 galaxies are relatively young sources with lifetimes not much exceeding 1 Myr. These systems represent sites of strong feedback at NLR scales at work, well below redshift one.

Sensitive electrospray mass spectrometry analysis of one-bead-one-compound peptide libraries labeled by quaternary ammonium salts.

PubMed

Bąchor, Remigiusz; Cydzik, Marzena; Rudowska, Magdalena; Kluczyk, Alicja; Stefanowicz, Piotr; Szewczuk, Zbigniew

2012-08-01

A rapid and straightforward method for high-throughput analysis of single resin beads from one-bead-one-compound combinatorial libraries with high resolution electrospray ionization tandem mass spectrometry (HR ESI-MS/MS) is presented. The application of an efficient method of peptide derivatization by quaternary ammonium salts (QAS) formation increases ionization efficiency and reduces the detection limit, allowing analysis of trace amounts of compounds by ESI-MS. Peptides, synthesized on solid support, contain a new cleavable linker composed of a Peg spacer (9-aza-3,6,12,15-tetraoxa-10-on-heptadecanoic acid), lysine with ɛ-amino group marked by the N,N,N-triethylglycine salt, and methionine, which makes possible the selective cleavage by cyanogen bromide. Even a small portion of peptides derivatized by QAS cleaved from a single resin bead is sufficient for sequencing by HR ESI-MS/MS experiments. The developed strategy was applied to a small training library of α chymotrypsin substrates. The obtained results confirm the applicability of the proposed method in combinatorial chemistry.

Implementation of the infinite-range exterior complex scaling to the time-dependent complete-active-space self-consistent-field method

NASA Astrophysics Data System (ADS)

Orimo, Yuki; Sato, Takeshi; Scrinzi, Armin; Ishikawa, Kenichi L.

2018-02-01

We present a numerical implementation of the infinite-range exterior complex scaling [Scrinzi, Phys. Rev. A 81, 053845 (2010), 10.1103/PhysRevA.81.053845] as an efficient absorbing boundary to the time-dependent complete-active-space self-consistent field method [Sato, Ishikawa, Březinová, Lackner, Nagele, and Burgdörfer, Phys. Rev. A 94, 023405 (2016), 10.1103/PhysRevA.94.023405] for multielectron atoms subject to an intense laser pulse. We introduce Gauss-Laguerre-Radau quadrature points to construct discrete variable representation basis functions in the last radial finite element extending to infinity. This implementation is applied to strong-field ionization and high-harmonic generation in He, Be, and Ne atoms. It efficiently prevents unphysical reflection of photoelectron wave packets at the simulation boundary, enabling accurate simulations with substantially reduced computational cost, even under significant (≈50 % ) double ionization. For the case of a simulation of high-harmonic generation from Ne, for example, 80% cost reduction is achieved, compared to a mask-function absorption boundary.

Coupling of metal-organic frameworks-containing monolithic capillary-based selective enrichment with matrix-assisted laser desorption ionization-time-of-flight mass spectrometry for efficient analysis of protein phosphorylation.

PubMed

Li, Daojin; Yin, Danyang; Chen, Yang; Liu, Zhen

2017-05-19

Protein phosphorylation is a major post-translational modification, which plays a vital role in cellular signaling of numerous biological processes. Mass spectrometry (MS) has been an essential tool for the analysis of protein phosphorylation, for which it is a key step to selectively enrich phosphopeptides from complex biological samples. In this study, metal-organic frameworks (MOFs)-based monolithic capillary has been successfully prepared as an effective sorbent for the selective enrichment of phosphopeptides and has been off-line coupled with matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) for efficient analysis of phosphopeptides. Using š-casein as a representative phosphoprotein, efficient phosphorylation analysis by this off-line platform was verified. Phosphorylation analysis of a nonfat milk sample was also demonstrated. Through introducing large surface areas and highly ordered pores of MOFs into monolithic column, the MOFs-based monolithic capillary exhibited several significant advantages, such as excellent selectivity toward phosphopeptides, superb tolerance to interference and simple operation procedure. Because of these highly desirable properties, the MOFs-based monolithic capillary could be a useful tool for protein phosphorylation analysis. Copyright © 2016 Elsevier B.V. All rights reserved.

A DUAL PLATFORM FOR SELECTIVE ANALYTE ENRICHMENT AND IONIZATION IN MASS SPECTROMETRY USING APTAMER-CONJUGATED GRAPHENE OXIDE

PubMed Central

Gulbakan, Basri; Yasun, Emir; Shukoor, M. Ibrahim; Zhu, Zhi; You, Mingxu; Tan, Xiaohong; Sanchez, Hernan; Powell, David H.; Dai, Hongjie; Tan, Weihong

2010-01-01

This study demonstrates the use of aptamer-conjugated graphene oxide as an affinity extraction and detection platform for analytes from complex biological media. We have shown that cocaine and adenosine can be selectively enriched from plasma samples and that direct mass spectrometric readout can be obtained without a matrix and with greatly improved signal-to-noise ratios. The aptamer conjugated graphene oxide has clear advantages in target enrichment and in generating highly efficient ionization of target molecules for mass spectrometry. These results demonstrate the utility of the approach for analysis of small molecules in real biological samples. PMID:21090719

Ceria nanocubic-ultrasonication assisted dispersive liquid-liquid microextraction coupled with matrix assisted laser desorption/ionization mass spectrometry for pathogenic bacteria analysis.

PubMed

Abdelhamid, Hani Nasser; Bhaisare, Mukesh L; Wu, Hui-Fen

2014-03-01

A new ceria (CeO2) nanocubic modified surfactant is used as the basis of a novel nano-based microextraction technique for highly sensitive detection of pathogenic bacteria (Pseudomonas aeruginosa and Staphylococcus aureus). The technique uses ultrasound enhanced surfactant-assisted dispersive liquid-liquid microextraction (UESA-DLLME) with and without ceria (CeO2) followed by matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS). In order to achieve high separation efficiency, we investigated the influential parameters, including extraction time of ultrasonication, type and volume of the extraction solvent and surfactant. Among various surfactants, the cationic surfactants can selectively offer better extraction efficiency on bacteria analysis than that of the anionic surfactants due to the negative charges of bacteria cell membranes. Extractions of the bacteria lysate from aqueous samples via UESA-DLLME-MALDI-MS were successfully achieved by using cetyltrimethyl ammonium bromide (CTAB, 10.0 µL, 1.0×10(-3) M) as surfactants in chlorobenzene (10.0 µL) and chloroform (10.0 µL) as the optimal extracting solvent for P. aeruginosa and S. aureus, respectively. Ceria nanocubic was synthesized, and functionalized with CTAB (CeO2@CTAB) and then characterized using transmission electron microscopy (TEM) and optical spectroscopy (UV and FTIR). CeO2@CTAB demonstrates high extraction efficiency, improve peaks ionization, and enhance resolution. The prime reasons for these improvements are due to the large surface area of nanoparticles, and its absorption that coincides with the wavelength of MALDI laser (337 nm, N2 laser). CeO2@CTAB-based microextraction offers lowest detectable concentrations tenfold lower than that of without nanoceria. The present approach has been successfully applied to detect pathogenic bacteria at low concentrations of 10(4)-10(5) cfu/mL (without ceria) and at 10(3)-10(4) cfu/mL (with ceria) from bacteria suspensions. Finally, the current approach was applied for analyzing the pathogenic bacteria in biological samples (blood and serum). Ceria assist surfactant (CeO2@CTAB) liquid-liquid microextraction (LLME) offers better extraction efficiency than that of using the surfactant in LLME alone. © 2013 Elsevier B.V. All rights reserved.

Peptides Labeled with Pyridinium Salts for Sensitive Detection and Sequencing by Electrospray Tandem Mass Spectrometry

NASA Astrophysics Data System (ADS)

Waliczek, Mateusz; Kijewska, Monika; Rudowska, Magdalena; Setner, Bartosz; Stefanowicz, Piotr; Szewczuk, Zbigniew

2016-11-01

Mass spectrometric analysis of trace amounts of peptides may be problematic due to the insufficient ionization efficiency resulting in limited sensitivity. One of the possible ways to overcome this problem is the application of ionization enhancers. Herein we developed new ionization markers based on 2,4,6-triphenylpyridinium and 2,4,6-trimethylpyridinium salts. Using of inexpensive and commercially available pyrylium salt allows selective derivatization of primary amino groups, especially those sterically unhindered, such as ɛ-amino group of lysine. The 2,4,6-triphenylpyridinium modified peptides generate in MS/MS experiments an abundant protonated 2,4,6-triphenylpyridinium ion. This fragment is a promising reporter ion for the multiple reactions monitoring (MRM) analysis. In addition, the fixed positive charge of the pyridinium group enhances the ionization efficiency. Other advantages of the proposed ionization enhancers are the simplicity of derivatization of peptides and the possibility of convenient incorporation of isotopic labels into derivatized peptides.

Highly Efficient Gluten Degradation by Lactobacilli and Fungal Proteases during Food Processing: New Perspectives for Celiac Disease▿

PubMed Central

Rizzello, Carlo G.; De Angelis, Maria; Di Cagno, Raffaella; Camarca, Alessandra; Silano, Marco; Losito, Ilario; De Vincenzi, Massimo; De Bari, Maria D.; Palmisano, Francesco; Maurano, Francesco; Gianfrani, Carmen; Gobbetti, Marco

2007-01-01

Presently, the only effective treatment for celiac disease is a life-long gluten-free diet. In this work, we used a new mixture of selected sourdough lactobacilli and fungal proteases to eliminate the toxicity of wheat flour during long-time fermentation. Immunological (R5 antibody-based sandwich and competitive enzyme-linked immunosorbent assay [ELISA] and R5 antibody-based Western blot), two-dimensional electrophoresis, and mass spectrometry (matrix-assisted laser desorption ionization-time of flight, strong-cation-exchange-liquid chromatography/capillary liquid chromatography-electrospray ionization-quadrupole-time of flight [SCX-LC/CapLC-ESI-Q-TOF], and high-pressure liquid chromatography-electrospray ionization-ion trap mass spectrometry) analyses were used to determine the gluten concentration. Assays based on the proliferation of peripheral blood mononuclear cells (PBMCs) and gamma interferon production by PBMCs and intestinal T-cell lines (iTCLs) from 12 celiac disease patients were used to determine the protein toxicity of the pepsin-trypsin digests from fermented wheat dough (sourdough). As determined by R5-based sandwich and competitive ELISAs, the residual concentration of gluten in sourdough was 12 ppm. Albumins, globulins, and gliadins were completely hydrolyzed, while ca. 20% of glutenins persisted. Low-molecular-weight epitopes were not detectable by SCX-LC/CapLC-ESI-Q-TOF mass spectrometry and R5-based Western blot analyses. The kinetics of the hydrolysis of the 33-mer by lactobacilli were highly efficient. All proteins extracted from sourdough activated PBMCs and induced gamma interferon production at levels comparable to the negative control. None of the iTCLs demonstrated immunoreactivity towards pepsin-trypsin digests. Bread making was standardized to show the suitability of the detoxified wheat flour. Food processing by selected sourdough lactobacilli and fungal proteases may be considered an efficient approach to eliminate gluten toxicity. PMID:17513580

Characteristics of soft x-ray spectra from ultra-fast micro-capillary discharge plasmas

NASA Astrophysics Data System (ADS)

Li, Jing; Avaria, Gonzalo; Shlyaptsev, Vyacheslav; Tomasel, Fernando; Grisham, Michael; Dawson, Quincy; Rocca, Jorge; NSF CenterExtreme Ultraviolet Science; Technology Collaboration

2013-10-01

The efficient generation of high aspect ratio (e.g. 300:1) plasma columns ionized to very high degrees of ionization (e.g. Ni-like Xenon) by an ultrafast current pulses of moderate amplitude in micro-capillary channels is of interest for fundamental plasma studies and for applications such as the generation of discharge-pumped soft x-ray lasers. Spectra and simulations for plasmas generated in 500 um alumina capillary discharges driven by 35-40 kA current pulses with 4 ns rise time were obtained in Xenon and Neon discharges. The first shows the presence of lines corresponding to ionization stages up to Fe-like Xe. The latter show that Al impurities from the walls and Si (from injected SiH4) are ionized to the H-like and He-like stages. He-like spectra containing the resonance line significantly broaden by opacity, the intercombination line, and Li-like satellites are analyzed and modeled. For Xenon discharges, the spectral lines from the Ni-like transitions the 3d94d(3/2, 3/2)J=0 to the 3d94p(5/2, 3/2)J=1 and to 3d94p(3/2, 1/2)J=1 are observed at gas pressures up to 2.0 Torr. Work supported by NSF Award PHY-1004295.

Efficient ionisation of calcium, strontium and barium by resonant laser pumping

NASA Technical Reports Server (NTRS)

Skinner, C. H.

1980-01-01

Efficient ionization has been observed when an atomic vapor of strontium, barium or calcium was illuminated with a long pulse tunable laser at the frequency of the atomic resonance line. The variation in the degree of ionization with neutral density and laser intensity has been measured using the 'hook' method. The maximum ionization observed was 94%. Excited state populations were measured yielding an excitation temperature (depending on exact experimental conditions) in the region of 0.4 eV. The decay of ion density after the laser pulse was monitored and the recombination coefficients determined. The results are interpreted in terms of an electron heating model.

First Spectroscopic Evidence for High Ionization State and Low Oxygen Abundance in Lyα Emitters

NASA Astrophysics Data System (ADS)

Nakajima, Kimihiko; Ouchi, Masami; Shimasaku, Kazuhiro; Hashimoto, Takuya; Ono, Yoshiaki; Lee, Janice C.

2013-05-01

We present results from Keck/NIRSPEC and Magellan/MMIRS follow-up spectroscopy of Lyα emitters (LAEs) at z = 2.2 identified in our Subaru narrowband survey. We successfully detect Hα emission from seven LAEs, and perform a detailed analysis of six LAEs free from active galactic nucleus activity, two out of which, CDFS-3865 and COSMOS-30679, have [O II] and [O III] line detections. They are the first [O II]-detected LAEs at high-z, and their [O III]/[O II] ratios and R23-indices provide the first simultaneous determinations of ionization parameter and oxygen abundance for LAEs. CDFS-3865 has a very high ionization parameter (q_{ion}=2.5^{+1.7}_{-0.8} \\times 10^8 cm s-1) and a low oxygen abundance (12+log (O/H)=7.84^{+0.24}_{-0.25}) in contrast with moderate values of other high-z galaxies such as Lyman break galaxies (LBGs). COSMOS-30679 also possesses a relatively high ionization parameter (q_{ion}=8^{+10}_{-4} \\times 10^7 cm s-1) and a low oxygen abundance (12+log (O/H)=8.18^{+0.28}_{-0.28}). Both LAEs appear to fall below the mass-metallicity relation of z ~ 2 LBGs. Similarly, a low metallicity of 12 + log (O/H) < 8.4 is independently indicated for typical LAEs from a composite spectrum and the [N II]/Hα index. Such high ionization parameters and low oxygen abundances can be found in local star-forming galaxies, but this extreme local population occupies only ~0.06% of the Sloan Digital Sky Survey spectroscopic galaxy sample with a number density ~100 times smaller than that of LAEs. With their high ionization parameters and low oxygen abundances, LAEs would represent an early stage of galaxy formation dominated by massive stars in compact star-forming regions. High-q ion galaxies like LAEs would produce ionizing photons efficiently with a high escape fraction achieved by density-bounded H II regions, which would significantly contribute to cosmic reionization at z > 6. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

Particle in cell simulation on plasma grating contrast enhancement induced by infrared laser pulse

NASA Astrophysics Data System (ADS)

Li, M.; Yuan, T.; Xu, Y. X.; Wang, J. X.; Luo, S. N.

2018-05-01

The dynamics of plasma grating contrast enhancement (PGCE) irradiated by an infrared laser pulse is investigated with one dimensional particle-in-cell simulation where field ionization and impact ionization are simultaneously considered for the first time. The numeric results show that the impact ionization dominates the PGCE process. Upon the interaction with the laser pulse, abundant free electrons are efficiently accelerated and subsequently triggered massive impact ionizations in the density ridges of the plasma grating for the higher local plasma energy density, which efficiently enhances the grating contrast. Besides the dynamic analysis of PGCE, we explore the parameter space of the incident infrared laser pulse to optimize the PGCE effect, which can provide useful guidance to experiments related to laser-plasma-grating interactions and may find applications in prolonging the duration of the plasma grating.

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

Keyshar, Kunttal; Berg, Morgann; Zhang, Xiang

Here, the values of the ionization energies of transition metal dichalcogenides (TMDs) are needed to assess their potential usefulness in semiconductor heterojunctions for high-performance optoelectronics. Here, we report on the systematic determination of ionization energies for three prototypical TMD monolayers (MoSe 2, WS 2, and MoS 2) on SiO 2 using photoemission electron microscopy with deep ultraviolet illumination. The ionization energy displays a progressive decrease from MoS 2, to WS 2, to MoSe 2, in agreement with predictions of density functional theory calculations. Combined with the measured energy positions of the valence band edge at the Brillouin zone center, wemore » deduce that, in the absence of interlayer coupling, a vertical heterojunction comprising any of the three TMD monolayers would form a staggered (type-II) band alignment. This band alignment could give rise to long-lived interlayer excitons that are potentially useful for valleytronics or efficient electron–hole separation in photovoltaics.« less

A Penning discharge as a dc source for multiply ionized atoms.

NASA Astrophysics Data System (ADS)

Rainer, Kling; Manfred, Kock

1997-10-01

We report upon a specially designed Penning discharge which has been further developed from a source published by Finley et al.(Finley, D. S., Bowyer, S., Paresce, F., Malina, R. F.: Appl. Opt. 18) (1979) 649 towards a radiation standard for the XUV.(Heise, C., Hollandt, J., Kling, R., Kock, M., Kuehne, M.: Appl. Opt. 33) (1994) 5111 The discharge stands out for low buffer gas pressure, high electric power input and a strong superimposed magnetic field. That leads to intense sputtering of the cathodes which can be made of nearly any material. The efficient excitation and ionization of the sputtered atoms permit spectroscopy on multiply ionized spezies. W III and Fe III spectra will be given as examples. We also will present kinetic temperatures of the nonthermal plasma showing that the ionic component is decoupled from the cold neutral gas component.

Heavy component of spent nuclear fuel: Efficiency of model-substance ionization by electron-induced discharge

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

Antonov, N. N., E-mail: antonovnickola@gmail.com; Gavrikov, A. V.; Samokhin, A. A.

The method of plasma separation of spent nuclear fuel can be tested with a model substance which has to be transformed from the condensed to plasma state. For this purpose, electron-induced discharge in lead vapor injected into the interelectrode gap is simulated using the kinetic approach. The ionization efficiency, the electrostatic-potential distribution, and those of the ion and electron densities in the discharge gap are derived as functions of the discharge-current density and concentration of the vapor of the model substance. Given a discharge-current density of 3.5 A/cm{sup 2} and a lead-vapor concentration of 2 × 10{sup 12} cm{sup –3},more » the simulated ionization efficiency proves to be nearly 60%. The discharge in lead vapor is also investigated experimentally.« less

On the SIMS Ionization Probability of Organic Molecules.

PubMed

Popczun, Nicholas J; Breuer, Lars; Wucher, Andreas; Winograd, Nicholas

2017-06-01

The prospect of improved secondary ion yields for secondary ion mass spectrometry (SIMS) experiments drives innovation of new primary ion sources, instrumentation, and post-ionization techniques. The largest factor affecting secondary ion efficiency is believed to be the poor ionization probability (α + ) of sputtered material, a value rarely measured directly, but estimated to be in some cases as low as 10 -5 . Our lab has developed a method for the direct determination of α + in a SIMS experiment using laser post-ionization (LPI) to detect neutral molecular species in the sputtered plume for an organic compound. Here, we apply this method to coronene (C 24 H 12 ), a polyaromatic hydrocarbon that exhibits strong molecular signal during gas-phase photoionization. A two-dimensional spatial distribution of sputtered neutral molecules is measured and presented. It is shown that the ionization probability of molecular coronene desorbed from a clean film under bombardment with 40 keV C 60 cluster projectiles is of the order of 10 -3 , with some remaining uncertainty arising from laser-induced fragmentation and possible differences in the emission velocity distributions of neutral and ionized molecules. In general, this work establishes a method to estimate the ionization efficiency of molecular species sputtered during a single bombardment event. Graphical Abstract .

High-speed upper-airway imaging using full-range optical coherence tomography

NASA Astrophysics Data System (ADS)

Jing, Joseph; Zhang, Jun; Loy, Anthony Chin; Wong, Brian J. F.; Chen, Zhongping

2012-11-01

Obstruction in the upper airway can often cause reductions in breathing or gas exchange efficiency and lead to rest disorders such as sleep apnea. Imaging diagnosis of the obstruction region has been accomplished using computed tomography (CT) and magnetic resonance imaging (MRI). However CT requires the use of ionizing radiation, and MRI typically requires sedation of the patient to prevent motion artifacts. Long-range optical coherence tomography (OCT) has the potential to provide high-speed three-dimensional tomographic images with high resolution and without the use of ionizing radiation. In this paper, we present work on the development of a long-range OCT endoscopic probe with 1.2 mm OD and 20 mm working distance used in conjunction with a modified Fourier domain swept source OCT system to acquire structural and anatomical datasets of the human airway. Imaging from the bottom of the larynx to the end of the nasal cavity is completed within 40 s.

Determination of ionization energies of CnN (n=4-12): Vacuum-ultraviolet (VUV) photoionization experiments and theoretical calculations

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

Kostko, Oleg; Zhou, Jia; Sun, Bian Jian

2010-06-10

Results from single photon vacuum ultraviolet photoionization of astrophysically relevant CnN clusters, n = 4 - 12, in the photon energy range of 8.0 eV to 12.8 eV are presented. The experimental photoionization efficiency curves, combined with electronic structure calculations, provide improved ionization energies of the CnN species. A search through numerous nitrogen-terminated CnN isomers for n=4-9 indicates that the linear isomer has the lowest energy, and therefore should be the most abundant isomer in the molecular beam. Comparison with calculated results also shed light on the energetics of the linear CnN clusters, particularly in the trends of the even-carbonmore » and the odd-carbon series. These results can help guide the search of potential astronomical observations of these neutral molecules together with their cations in highly ionized regions or regions with a high UV/VUV photon flux (ranging from the visible to VUV with flux maxima in the Lyman- region) in the interstellar medium.« less

Determination of ionization energies of CnN (n=4-12): Vacuum-ultraviolet (VUV) photoionization experiments and theoretical calculations

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

Kostko, Oleg; Zhou, Jia; Sun, Bian Jian

2010-03-02

Results from single photon vacuum ultraviolet photoionization of astrophysically relevant CnN clusters, n = 4 - 12, in the photon energy range of 8.0 eV to 12.8 eV are presented. The experimental photoionization efficiency curves, combined with electronic structure calculations, provide improved ionization energies of the CnN species. A search through numerous nitrogen-terminated CnN isomers for n=4-9 indicates that the linear isomer has the lowest energy, and therefore should be the most abundant isomer in the molecular beam. Comparison with calculated results also shed light on the energetics of the linear CnN clusters, particularly in the trends of the even-carbonmore » and the odd-carbon series. These results can help guide the search of potential astronomical observations of these neutral molecules together with their cations in highly ionized regions or regions with a high UV/VUV photon flux (ranging from the visible to VUV with flux maxima in the Lyman-a region) in the interstellar medium.« less

Experimental Determination of the Ionization Energies of MoSe 2, WS 2, and MoS 2 on SiO 2 Using Photoemission Electron Microscopy

DOE PAGES

Keyshar, Kunttal; Berg, Morgann; Zhang, Xiang; ...

2017-07-19

Here, the values of the ionization energies of transition metal dichalcogenides (TMDs) are needed to assess their potential usefulness in semiconductor heterojunctions for high-performance optoelectronics. Here, we report on the systematic determination of ionization energies for three prototypical TMD monolayers (MoSe 2, WS 2, and MoS 2) on SiO 2 using photoemission electron microscopy with deep ultraviolet illumination. The ionization energy displays a progressive decrease from MoS 2, to WS 2, to MoSe 2, in agreement with predictions of density functional theory calculations. Combined with the measured energy positions of the valence band edge at the Brillouin zone center, wemore » deduce that, in the absence of interlayer coupling, a vertical heterojunction comprising any of the three TMD monolayers would form a staggered (type-II) band alignment. This band alignment could give rise to long-lived interlayer excitons that are potentially useful for valleytronics or efficient electron–hole separation in photovoltaics.« less

Calculation of multiphoton ionization processes

NASA Technical Reports Server (NTRS)

Chang, T. N.; Poe, R. T.

1976-01-01

We propose an accurate and efficient procedure in the calculation of multiphoton ionization processes. In addition to the calculational advantage, this procedure also enables us to study the relative contributions of the resonant and nonresonant intermediate states.

Nuclear Forensics: Measurements of Uranium Oxides Using Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS)

DTIC Science & Technology

2010-03-01

Isotope Ratio Analysis of Actinides , Fission Products, and Geolocators by High- efficiency Multi-collector Thermal Ionization Mass Spectrometry...Information, 1999. Hou, Xiaolin, and Per Roos. “ Critical Comparison of radiometric and Mass Spectrometric Methods for the Determination of...NUCLEAR FORENSICS: MEASUREMENTS OF URANIUM OXIDES USING TIME-OF-FLIGHT SECONDARY ION MASS

High sensitive and throughput screening of Aflatoxin using MALDI-TOF-TOF-PSD-MS/MS

USDA-ARS?s Scientific Manuscript database

We have achieved sensitive and efficient detection of aflatoxin B1(AFB1) through matrix-assisted laser desorption/ionization time-of-flight-time-of-flight mass spectrometry (MALDI-TOF-TOF) and post-source decay (PSD) tandem mass spectrometry (MS/MS) using an acetic acid – a-cyano-4-hydroxycinnamic a...

Laser stripping of hydrogen atoms by direct ionization

DOE PAGES

Brunetti, E.; Becker, W.; Bryant, H. C.; ...

2015-05-08

Direct ionization of hydrogen atoms by laser irradiation is investigated as a potential new scheme to generate proton beams without stripping foils. The time-dependent Schrödinger equation describing the atom-radiation interaction is numerically solved obtaining accurate ionization cross-sections for a broad range of laser wavelengths, durations and energies. Parameters are identified where the Doppler frequency up-shift of radiation colliding with relativistic particles can lead to efficient ionization over large volumes and broad bandwidths using currently available lasers.

Laser stripping of hydrogen atoms by direct ionization

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

Brunetti, E.; Becker, W.; Bryant, H. C.

Direct ionization of hydrogen atoms by laser irradiation is investigated as a potential new scheme to generate proton beams without stripping foils. The time-dependent Schrödinger equation describing the atom-radiation interaction is numerically solved obtaining accurate ionization cross-sections for a broad range of laser wavelengths, durations and energies. Parameters are identified where the Doppler frequency up-shift of radiation colliding with relativistic particles can lead to efficient ionization over large volumes and broad bandwidths using currently available lasers.

Graphene as a Novel Matrix for the Analysis of Small Molecules by MALDI-TOF MS

PubMed Central

Dong, Xiaoli; Cheng, Jinsheng; Li, Jinghong; Wang, Yinsheng

2010-01-01

Graphene was utilized for the first time as matrix for the analysis of low-molecular weight compounds using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Polar compounds including amino acids, polyamines, anticancer drugs and nucleosides could be successfully analyzed. Additionally, nonpolar compounds including steroids could be detected with high resolution and sensitivity. Compared with conventional matrix, graphene exhibited high desorption/ionization efficiency for nonpolar compounds. The graphene matrix functions as substrate to trap analytes, and it transfers energy to the analytes upon laser irradiation, which allowed for the analytes to be readily desorbed/ionized and interference of intrinsic matrix ions to be eliminated. The use of graphene as matrix avoided the fragmentation of analytes and provided good reproducibility and high salt tolerance, underscoring the potential application of graphene as matrix for MALDI-MS analysis of practical samples in complex sample matrices. We also demonstrated that the use of graphene as adsorbent for the solid-phase extraction of squalene could improve greatly the detection limit. This work not only opens a new field for applications of graphene, but also offers a new technique for high-speed analysis of low-molecular weight compounds in areas such as metabolism research and natural products characterization. PMID:20565059

High-efficiency, low-temperature cesium diodes with lanthanum-hexaboride electrodes

NASA Technical Reports Server (NTRS)

Morris, J. F.

1974-01-01

Lanthanum hexaboride electrodes in 1700 K cesium diodes may triple power outputs compared with those demonstrated for nuclear thermionic space applications. Still greater relative gains seem possible for emitters below 1700 K. Further improvements in cesium diode performance should result from the lower collector temperatures allowed for earth and low power space duties. Decreased temperatures will lessen thermal transport losses that attend thermionic conversion mechanisms. Such advantages will add to those from collector Carnot and electrode effects. If plasma ignition difficulties impede diode temperature reductions, recycling small fractions of the output power could provide ionization. So high efficiency, low temperature cesium diodes with lanthanum hexaboride electrodes appear feasible.

Enhanced Ionization of Embedded Clusters by Electron-Transfer-Mediated Decay in Helium Nanodroplets.

PubMed

LaForge, A C; Stumpf, V; Gokhberg, K; von Vangerow, J; Stienkemeier, F; Kryzhevoi, N V; O'Keeffe, P; Ciavardini, A; Krishnan, S R; Coreno, M; Prince, K C; Richter, R; Moshammer, R; Pfeifer, T; Cederbaum, L S; Mudrich, M

2016-05-20

We report the observation of electron-transfer-mediated decay (ETMD) involving magnesium (Mg) clusters embedded in helium (He) nanodroplets. ETMD is initiated by the ionization of He followed by removal of two electrons from the Mg clusters of which one is transferred to the He ion while the other electron is emitted into the continuum. The process is shown to be the dominant ionization mechanism for embedded clusters for photon energies above the ionization potential of He. For Mg clusters larger than five atoms we observe stable doubly ionized clusters. Thus, ETMD provides an efficient pathway to the formation of doubly ionized cold species in doped nanodroplets.

Beacons in the dark: using the most distant galaxies to probe cosmic reionization

NASA Astrophysics Data System (ADS)

De Barros, Stephane

2017-08-01

One of the major unresolved problems in modern cosmology is when and how the universe was ionized. The consensus scenario is that ultra-faint, low-mass galaxies contributed most to the UV background at high-redshift and that reionization was an inhomogeneous process, with ionized bubbles created first around galaxy overdensities. The very surprising discovery of Ly-alpha emission lines around a large fraction of the most luminous galaxies at z=7.4-8.7, when we expect the universe to be highly neutral, could thus be explained by the fact that they lie in large HII bubbles which were ionized thanks to yet undetected fainter neighbors. Theoretical models indeed predict a boost of up to 6x larger galaxy counts around the brightest sources compared to the general field, when probing down to luminosities as faint as 0.1L_UV of the central source. Here we propose a direct test of these models by searching for fainter neighbors around three bright z>7.4 galaxies emitting Ly-alpha, including two sources that lie only 9 Mpc from each other and could share the same ionized bubble, as well as the most distant confirmed Ly-alpha emitter EGSY-8p7 at z=8.68. Given the expected overdensities, we have the opportunity to detect 20 (and up to 50) new z 7-9 galaxies with only a modest investment of HST time. These observations are thus maximally efficient at providing a large number of precious high-redshift targets for early JWST spectroscopy to directly study the galaxies that are in the process of ionizing the universe. Our imaging will further enhance the legacy of the CANDELS/EGS field, and we will make the reduced data available to the community immediately for JWST follow-up.

Ionization cross section, pressure shift and isotope shift measurements of osmium

NASA Astrophysics Data System (ADS)

Hirayama, Yoshikazu; Mukai, Momo; Watanabe, Yutaka; Oyaizu, Michihiro; Ahmed, Murad; Kakiguchi, Yutaka; Kimura, Sota; Miyatake, Hiroari; Schury, Peter; Wada, Michiharu; Jeong, Sun-Chan

2017-11-01

In-gas-cell laser resonance ionization spectroscopy of neutral osmium atoms was performed with the use of a two-color two-step laser resonance ionization technique. Saturation curves for the ionization scheme were measured, and the ionization cross section was experimentally determined by solving the rate equations for the ground, intermediate and ionization continuum populations. The pressure shift and pressure broadening in the resonance spectra of the excitation transition were measured. The electronic factor {F}247 for the transition {λ }1=247.7583 nm to the intermediate state was deduced from the measured isotope shifts of stable {}{188,189,{190,192}}Os isotopes. The efficient ionization scheme, pressure shift, nuclear isotope shift and {F}247 are expected to be useful for applications of laser ion sources to unstable nuclei and for nuclear spectroscopy based on laser ionization techniques.

Clinical translation of human microRNA 21 as a potential biomarker for exposure to ionizing radiation.

PubMed

Halimi, Mohammad; Parsian, Hadi; Asghari, S Mohsen; Sariri, Reyhaneh; Moslemi, Dariush; Yeganeh, Farshid; Zabihi, Ebrahim

2014-06-01

This study investigated to what extent the serum microRNA 21 (miR-21) level alters in response to ionizing radiation (IR). Initially, we evaluated the appropriateness of our RNA extraction efficiency and microRNA assay in serum, and then investigated the serum miR-21 level in 4 patients with breast cancer in 4 stages: pre- and postoperation, at the beginning radiotherapy, and after 25 sessions of radiotherapy with a total of 50 Gy irradiation, as well as in 20 healthy volunteers. The initial analysis showed the appropriateness of our RNA extraction efficiency and microRNA assay in serum for identifying people exposed to IR. We then analyzed the serum miR-21 level in another group of 40 patients with breast cancer before and after radiotherapy. During our large-scale analysis, the miR-21 level before radiotherapy was comparable with healthy volunteers (P = 0.10) and increased significantly after radiotherapy (P < 0.001)-an indication that this could discriminate irradiated patients from nonirradiated ones with high specificity (75%) and sensitivity (80%). According to this study, serum miR-21 has the potential to be used as a biomarker for the identification of people exposed to ionizing radiation. Copyright © 2014 Mosby, Inc. All rights reserved.

Using Quasi-3D OSIRIS simulations of LWFA to study generating high brightness electron beams using ionization and density downramp injection

NASA Astrophysics Data System (ADS)

Dalichaouch, Thamine; Davidson, Asher; Xu, Xinlu; Yu, Peicheng; Tsung, Frank; Mori, Warren; Li, Fei; Zhang, Chaojie; Lu, Wei; Vieira, Jorge; Fonseca, Ricardo

2016-10-01

In the past few decades, there has been much progress in theory, simulation, and experiment towards using Laser wakefield acceleration (LWFA) as the basis for designing and building compact x-ray free-electron-lasers (XFEL) as well as a next generation linear collider. Recently, ionization injection and density downramp injection have been proposed and demonstrated as a controllable injection scheme for creating higher quality and ultra-bright relativistic electron beams using LWFA. However, full-3D simulations of plasma-based accelerators are computationally intensive, sometimes taking 100 millions of core-hours on today's computers. A more efficient quasi-3D algorithm was developed and implemented into OSIRIS using a particle-in-cell description with a charge conserving current deposition scheme in r - z and a gridless Fourier expansion in ϕ. Due to the azimuthal symmetry in LWFA, quasi-3D simulations are computationally more efficient than 3D cartesian simulations since only the first few harmonics in are needed ϕ to capture the 3D physics of LWFA. Using the quasi-3D approach, we present preliminary results of ionization and down ramp triggered injection and compare the results against 3D LWFA simulations. This work was supported by DOE and NSF.

Intense laser pulse propagation in ionizing gases

NASA Astrophysics Data System (ADS)

Bian, Zhigang

2003-10-01

There have been considerable technological advances in the development of high intensity, short pulse lasers. However, high intensity laser pulses are subject to various laser-plasma instabilities. In this thesis, a theory is developed to study the scattering instability that occurs when a laser pulse propagates through and ionizes a gas. The instability is due to the intensity dependence of the ionization rate, which leads to a transversely structured free electron density. The instability is convective in the frame of laser pulse, but can have a relatively short growth length scaling as Lg˜k0/k2p where k0 is the laser wave number, k2p=w2p/c 2 and op is the plasma frequency. The most unstable perturbations correspond to a scattering angle for which the transverse wave number is around the plasma wave number, k p. The scattered light is frequency upshifted. The comparison between simple analytic theory and numerical simulation shows good agreement. Instabilities can drastically change the shape of the laser pulse and reduce the propagation distance of the laser pulse. Therefore, we change the propagation conditions and reduce the laser-plasma interaction possibilities in applications which require an interaction length well in excess of the Rayleigh length of the laser beam. One of the methods is to use a capillary to propagate the laser pulse. We studied the propagation of short pulses in a glass capillary. The propagation is simulated using the code WAKE, which has been modified to treat the case in which the simulation boundary is the wall of a capillary. Parameters that were examined include transmission efficiency of the waveguides as a function of gas pressure, laser intensity, and waveguide length, which is up to 40 Rayleigh lengths. The transmission efficiency decreases with waveguide length due to energy loss through the side-walls of the capillary. The loss increases with gas pressure due to ionization of the gas and scattering of the radiation. The intensity on the inner wall of the capillary is monitored to assure realistic simulations, consistent with optical breakdown of the waveguide material. Generally speaking the intensity on the wall increases with gas pressure due to the scattering of the lowest order capillary mode. Finally, the high order harmonic generation (HHG) in a capillary is investigated. The phase matching condition is studied to increase the conversion efficiency for high order harmonics generation. The phase matching occurs as a balance of the dispersion of the neutral gas, plasma and the waveguide.

The study of ionization by electron impact of a substance simulating spent nuclear fuel components

NASA Astrophysics Data System (ADS)

Antonov, N. N.; Bochkarev, E. I.; Gavrikov, A. V.; Samokhin, A. A.; Smirnov, V. P.

2015-11-01

Plasma sources of model substances are necessary to solve problems associated with development of the spent nuclear fuel (SNF) plasma separation method. Lead was chosen to simulate kinetic and dynamic properties of the heavy SNF components. In this paper we present the results of a study of a lead vapor discharge with a lead concentration of 1012-1013 cm-3. Ionization was carried out by an electron beam (with energy of up to 500 eV per electron) inside a centimeter gap between planar electrodes. The discharge was numerically modeled using the hydrodynamic and single-particle approximation. Current-voltage characteristics and single ionization efficiency were obtained as functions of the vapors concentration and thermoelectric current. An ion current of hundreds of microamperes at the ionization efficiency near tenths of a percent was experimentally obtained. These results are in good agreement with our model.

Note: a novel vacuum ultraviolet light source assembly with aluminum-coated electrodes for enhancing the ionization efficiency of photoionization mass spectrometry.

PubMed

Zhu, Zhixiang; Wang, Jian; Qiu, Keqing; Liu, Chengyuan; Qi, Fei; Pan, Yang

2014-04-01

A novel vacuum ultraviolet (VUV) light source assembly (VUVLSA) for enhancing the ionization efficiency of photoionization mass spectrometer has been described. The VUVLSA composes of a Krypton lamp and a pair of disk electrodes with circular center cavities. The two interior surfaces that face the photoionization region were aluminum-coated. VUV light can be reflected back and forth in the photoionization region between the electrodes, thus the photoionization efficiency can be greatly enhanced. The performances of two different shaped electrodes, the coated double flat electrodes (DFE), and double conical electrodes, were studied. We showed that the signal amplification of coated DFE is around 4 times higher than that of uncoated electrodes without VUV light reflection. The relationship between the pressure of ionization chamber and mass signal enhancement has also been studied.

Time-dependent Cooling in Photoionized Plasma

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

Gnat, Orly, E-mail: orlyg@phys.huji.ac.il

I explore the thermal evolution and ionization states in gas cooling from an initially hot state in the presence of external photoionizing radiation. I compute the equilibrium and nonequilibrium cooling efficiencies, heating rates, and ion fractions for low-density gas cooling while exposed to the ionizing metagalactic background radiation at various redshifts ( z = 0 − 3), for a range of temperatures (10{sup 8}–10{sup 4} K), densities (10{sup −7}–10{sup 3} cm{sup −3}), and metallicities (10{sup −3}–2 times solar). The results indicate the existence of a threshold ionization parameter, above which the cooling efficiencies are very close to those in photoionization equilibriummore » (so that departures from equilibrium may be neglected), and below which the cooling efficiencies resemble those in collisional time-dependent gas cooling with no external radiation (and are thus independent of density).« less

A Simple Sonication Improves Protein Signal in Matrix-Assisted Laser Desorption Ionization Imaging

NASA Astrophysics Data System (ADS)

Lin, Li-En; Su, Pin-Rui; Wu, Hsin-Yi; Hsu, Cheng-Chih

2018-02-01

Proper matrix application is crucial in obtaining high quality matrix-assisted laser desorption ionization (MALDI) mass spectrometry imaging (MSI). Solvent-free sublimation was essentially introduced as an approach of homogeneous coating that gives small crystal size of the organic matrix. However, sublimation has lower extraction efficiency of analytes. Here, we present that a simple sonication step after the hydration in standard sublimation protocol significantly enhances the sensitivity of MALDI MSI. This modified procedure uses a common laboratory ultrasonicator to immobilize the analytes from tissue sections without noticeable delocalization. Improved imaging quality with additional peaks above 10 kDa in the spectra was thus obtained upon sonication treatment. [Figure not available: see fulltext.

Ionization tube simmer current circuit

DOEpatents

Steinkraus, R.F. Jr.

1994-12-13

A highly efficient flash lamp simmer current circuit utilizes a fifty percent duty cycle square wave pulse generator to pass a current over a current limiting inductor to a full wave rectifier. The DC output of the rectifier is then passed over a voltage smoothing capacitor through a reverse current blocking diode to a flash lamp tube to sustain ionization in the tube between discharges via a small simmer current. An alternate embodiment of the circuit combines the pulse generator and inductor in the form of an FET off line square wave generator with an impedance limited step up output transformer which is then applied to the full wave rectifier as before to yield a similar simmer current. 6 figures.

Ionization tube simmer current circuit

DOEpatents

Steinkraus, Jr., Robert F.

1994-01-01

A highly efficient flash lamp simmer current circuit utilizes a fifty percent duty cycle square wave pulse generator to pass a current over a current limiting inductor to a full wave rectifier. The DC output of the rectifier is then passed over a voltage smoothing capacitor through a reverse current blocking diode to a flash lamp tube to sustain ionization in the tube between discharges via a small simmer current. An alternate embodiment of the circuit combines the pulse generator and inductor in the form of an FET off line square wave generator with an impedance limited step up output transformer which is then applied to the full wave rectifier as before to yield a similar simmer current.

Lifetime of inner-shell hole states of Ar (2p) and Kr (3d) using equation-of-motion coupled cluster method

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

Ghosh, Aryya; Vaval, Nayana, E-mail: np.vaval@ncl.res.in; Pal, Sourav

2015-07-14

Auger decay is an efficient ultrafast relaxation process of core-shell or inner-shell excited atom or molecule. Generally, it occurs in femto-second or even atto-second time domain. Direct measurement of lifetimes of Auger process of single ionized and double ionized inner-shell state of an atom or molecule is an extremely difficult task. In this paper, we have applied the highly correlated complex absorbing potential-equation-of-motion coupled cluster (CAP-EOMCC) approach which is a combination of CAP and EOMCC approach to calculate the lifetime of the states arising from 2p inner-shell ionization of an Ar atom and 3d inner-shell ionization of Kr atom. Wemore » have also calculated the lifetime of Ar{sup 2+}(2p{sup −1}3p{sup −1}) {sup 1}D, Ar{sup 2+}(2p{sup −1}3p{sup −1}) {sup 1}S, and Ar{sup 2+}(2p{sup −1}3s{sup −1}) {sup 1}P double ionized states. The predicted results are compared with the other theoretical results as well as experimental results available in the literature.« less

A Systems Approach to Evaluating Ionizing Radiation: Six Focus Areas to Improve Quality, Efficiency, and Patient Safety

PubMed Central

Mower, Laura; Bushe, Chris

2015-01-01

Abstract: Ionizing radiation is an essential component of the care process. However, providers and patients may not be fully aware of the risks involved, the level of ionizing radiation delivered with various procedures, or the potential for harm through incidental overexposure or cumulative dose. Recent high-profile incidents demonstrating the devastating short-term consequences of radiation overexposure have drawn attention to these risks, but applicable solutions are lacking. Although various recommendations and guidelines have been proposed, organizational variability challenges providers to identify their own practical solutions. To identify potential failure modes and develop solutions to preserve patient safety within a large, national healthcare system, we assembled a multidisciplinary team to conduct a comprehensive analysis of practices surrounding the delivery of ionizing radiation. Workgroups were developed to analyze existing culture, processes, and technology to identify deficiencies and propose solutions. Six focus areas were identified: competency and certification; equipment; monitoring and auditing; education; clinical pathways; and communication and marketing. This manuscript summarizes this comprehensive, multidisciplinary, and systemic analysis of risk and provides examples to illustrate how these focus areas can be used to improve the use of ionizing radiation. The proposed solutions, once fully implemented, may advance patient safety and care. PMID:26042626

New developments of the in-source spectroscopy method at RILIS/ISOLDE

NASA Astrophysics Data System (ADS)

Marsh, B. A.; Andel, B.; Andreyev, A. N.; Antalic, S.; Atanasov, D.; Barzakh, A. E.; Bastin, B.; Borgmann, Ch.; Capponi, L.; Cocolios, T. E.; Day Goodacre, T.; Dehairs, M.; Derkx, X.; De Witte, H.; Fedorov, D. V.; Fedosseev, V. N.; Focker, G. J.; Fink, D. A.; Flanagan, K. T.; Franchoo, S.; Ghys, L.; Huyse, M.; Imai, N.; Kalaninova, Z.; Köster, U.; Kreim, S.; Kesteloot, N.; Kudryavtsev, Yu.; Lane, J.; Lecesne, N.; Liberati, V.; Lunney, D.; Lynch, K. M.; Manea, V.; Molkanov, P. L.; Nicol, T.; Pauwels, D.; Popescu, L.; Radulov, D.; Rapisarda, E.; Rosenbusch, M.; Rossel, R. E.; Rothe, S.; Schweikhard, L.; Seliverstov, M. D.; Sels, S.; Sjödin, A. M.; Truesdale, V.; Van Beveren, C.; Van Duppen, P.; Wendt, K.; Wienholtz, F.; Wolf, R. N.; Zemlyanoy, S. G.

2013-12-01

At the CERN ISOLDE facility, long isotope chains of many elements are produced by proton-induced reactions in target materials such as uranium carbide. The Resonance Ionization Laser Ion Source (RILIS) is an efficient and selective means of ionizing the reaction products to produce an ion beam of a chosen isotope. Coupling the RILIS with modern ion detection techniques enables highly sensitive studies of nuclear properties (spins, electromagnetic moments and charge radii) along an isotope chain, provided that the isotope shifts and hyperfine structure splitting of the atomic transitions can be resolved. At ISOLDE the campaign to measure the systematics of isotopes in the lead region (Pb, Bi, Tl and Po) has been extended to include the gold and astatine isotope chains. Several developments were specifically required for the feasibility of the most recent measurements: new ionization schemes (Po, At); a remote controlled narrow line-width mode of operation for the RILIS Ti:sapphire laser (At, Au, Po); isobar free ionization using the Laser Ion Source Trap, LIST (Po); isobar selective particle identification using the multi-reflection time-of-flight mass separator (MR-ToF MS) of ISOLTRAP (Au, At). These are summarized as part of an overview of the current status of the in-source resonance ionization spectroscopy setup at ISOLDE.

New Evidence for Efficient Collisionless Heating of Electrons at the Reverse Shock of a Young Supernova Remnant

NASA Technical Reports Server (NTRS)

Yamaguchi, Hiroya; Eriksen, Kristoffer A.; Badenes, Carles; Hughes, John P.; Brickhouse, Nancy S.; Foster, Adam R.; Patnaude, Daniel J.; Petre, Robert; Slane, Patrick O.; Smith, Randall K.

2013-01-01

Although collisionless shocks are ubiquitous in astrophysics, certain key aspects of them are not well understood. In particular, the process known as collisionless electron heating, whereby electrons are rapidly energized at the shock front, is one of the main open issues in shock physics. Here, we present the first clear evidence for efficient collisionless electron heating at the reverse shock of Tycho's supernova remnant (SNR), revealed by Fe K diagnostics using high-quality X-ray data obtained by the Suzaku satellite. We detect K beta (3p yields 1s) fluorescence emission from low-ionization Fe ejecta excited by energetic thermal electrons at the reverse shock front, which peaks at a smaller radius than Fe K alpha (2p yields 1s) emission dominated by a relatively highly ionized component. Comparisons with our hydrodynamical simulations imply instantaneous electron heating to a temperature 1000 times higher than expected from Coulomb collisions alone. The unique environment of the reverse shock, which is propagating with a high Mach number into rarefied ejecta with a low magnetic field strength, puts strong constraints on the physical mechanism responsible for this heating and favors a cross-shock potential created by charge deflection at the shock front. Our sensitive observation also reveals that the reverse shock radius of this SNR is about 10% smaller than the previous measurement using the Fe K alpha morphology from the Chandra observations. Since strong Fe K beta fluorescence is expected only from low-ionization plasma where Fe ions still have many 3p electrons, this feature is key to diagnosing the plasma state and distribution of the immediate postshock ejecta in a young SNR.

Development of a Computationally Efficient, High Fidelity, Finite Element Based Hall Thruster Model

NASA Technical Reports Server (NTRS)

Jacobson, David (Technical Monitor); Roy, Subrata

2004-01-01

This report documents the development of a two dimensional finite element based numerical model for efficient characterization of the Hall thruster plasma dynamics in the framework of multi-fluid model. Effect of the ionization and the recombination has been included in the present model. Based on the experimental data, a third order polynomial in electron temperature is used to calculate the ionization rate. The neutral dynamics is included only through the neutral continuity equation in the presence of a uniform neutral flow. The electrons are modeled as magnetized and hot, whereas ions are assumed magnetized and cold. The dynamics of Hall thruster is also investigated in the presence of plasma-wall interaction. The plasma-wall interaction is a function of wall potential, which in turn is determined by the secondary electron emission and sputtering yield. The effect of secondary electron emission and sputter yield has been considered simultaneously, Simulation results are interpreted in the light of experimental observations and available numerical solutions in the literature.

Electrochemically Initiated Tagging of Thiols Using an Electrospray Ionization-Based Liquid Microjunction Surface Sampling Probe Two-Electrode Cell

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

Van Berkel, Gary J; Kertesz, Vilmos

2009-01-01

This paper reports on the conversion of a liquid microjunction surface sampling probe (LMJ-SSP) into a two electrode electrochemical cell using a conductive sample surface and the probe as the two electrodes with an appropriate battery powered circuit. With this LMJ-SSP, two-electrode cell arrangement, tagging of analyte thiol functionalities (in this case peptide cysteine residues) with hydroquinone tags was initiated electrochemically using a hydroquinone doped solution when the analyte either was initially in solution or was sampled from a surface. Efficient tagging (~90%), at flow rates of 5-10 L/min, could be achieved for up to at least two cysteines onmore » a peptide. The high tagging efficiency observed was explained with a simple kinetic model. In general, the incorporation of a two-electrode electrochemical cell, or other multiple electrode arrangement, into the LMJ-SSP is expected to add to the versatility of this approach for surface sampling and ionization coupled with mass spectrometric detection.« less

Determination of polycyclic aromatic hydrocarbons and their nitro-, amino-derivatives absorbed on particulate matter 2.5 by multiphoton ionization mass spectrometry using far-, deep-, and near-ultraviolet femtosecond lasers.

PubMed

Tang, Yuanyuan; Imasaka, Tomoko; Yamamoto, Shigekazu; Imasaka, Totaro

2016-06-01

Multiphoton ionization processes of parent-polycyclic aromatic hydrocarbons (PPAHs), nitro-PAHs (NPAHs), and amino-PAHs (APAHs) were examined by gas chromatography combined with time-of-flight mass spectrometry using a femtosecond Ti:sapphire laser as the ionization source. The efficiency of multiphoton ionization was examined using lasers emitting in the far-ultraviolet (200 nm), deep-ultraviolet (267 nm), and near-ultraviolet (345 nm) regions. The largest signal intensities were obtained when the far-ultraviolet laser was employed. This favorable result can be attributed to the fact that these compounds have the largest molar absorptivities in the far-ultraviolet region. On the other hand, APAHs were ionized more efficiently than NPAHs in the near-ultraviolet region because of their low ionization energies. A sample extracted from a real particulate matter 2.5 (PM2.5) sample was measured, and numerous signal peaks arising from PAH and its analogs were observed at 200 nm. On the other hand, only a limited number of signed peaks were observed at 345 nm, some of which were signed to PPAHs, NPAHs, and APAHs. Thus, multiphoton ionization mass spectrometry has potential for the use in comprehensive analysis of toxic environmental pollutants. Copyright © 2016 Elsevier Ltd. All rights reserved.

Theoretical and observational determinations of the ionization coefficient of meteors

NASA Astrophysics Data System (ADS)

Jones, William

1997-07-01

We examine the problem of the determination of the ionization coefficient beta from both the theoretical and observational points of view. In the past, theoretical evaluations of beta in terms of the relevant scattering cross-sections have used the Massey-Sida formula, which we show to give results which are plainly incorrect. We derive an integral equation for beta and compare the results of its application to copper and iron with laboratory simulations. Agreement for the variation of the ionization coefficient with velocity is good. The ionization coefficient has been determined observationally by Verniani & Hawkins from a comparison of radar and visual observations, employing the luminous efficiency tau also obtained observationally by Verniani. However, this determination of tau would appear to be invalidated by fragmentation. There is good evidence that the radiation of cometary meteors is dominated by that of iron in the visual range, and we have accordingly re-analysed the data of Verniani & Hawkins using the luminous efficiency of iron obtained in simulation experiments. However, it is not possible to choose an iron concentration which gives agreement between the determination of the ionization coefficient by this means and its determination from the theoretical equation in terms of either scattering coefficients or simulation methods. The observational ionization coefficients are much lower than predicted by the present theory and we provisionally explain this as a consequence of transfer of charge from the meteoric ion to a molecule of the air. It is now possible for the meteoric atom to be re-ionized, but it is also possible at sufficiently high initial line densities for significant dissociative recombination of the electrons and nitrogen or oxygen to take place. This recombination will not take place in meteor trains simulated in an ionization chamber. We thus conclude that the present theory is limited to faint radio meteors at lower velocities (v<~35 km s^-1), for which no significant secondary ionization or recombination will take place. The theoretical results may be approximated by the analytic form beta~=9.4x10^-6 (v-10)^2v^0.8, where the velocity v is in km s^-1. For visual meteors in the range of about 30 to 60 km s^-1, we propose as a reasonable approximation the result we have obtained from the Verniani-Hawkins observational data using simulation results for the luminosity: beta=4.91x10^-6v^2.25. At present, however, we are unable to propose estimates of beta for slow bright meteors or fast radio meteors.

SU-C-201-03: Ionization Chamber Collection Efficiency in Pulsed Radiation Fields of High Pulse Dose

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

Gotz, M; Karsch, L; Pawelke, J

Purpose: To investigate the reduction of collection efficiency of ionization chambers (IC) by volume recombination and its correction in pulsed fields of very high pulse dose. Methods: Measurements of the collection efficiency of a plane-parallel advanced Markus IC (PTW 34045, 1mm electrode spacing, 300V nominal voltage) were obtained for collection voltages of 100V and 300V by irradiation with a pulsed electron beam (20MeV) of varied pulse dose up to approximately 600mGy (0.8nC liberated charge). A reference measurement was performed with a Faraday cup behind the chamber. It was calibrated for the liberated charge in the IC by a linear fitmore » of IC measurement to reference measurement at low pulse doses. The results were compared to the commonly used two voltage approximation (TVA) and to established theories for volume recombination, with and without considering a fraction of free electrons. In addition, an equation system describing the charge transport and reactions in the chamber was solved numerically. Results: At 100V collection voltage and moderate pulse doses the established theories accurately predict the observed collection efficiency, but at extreme pulse doses a fraction of free electrons needs to be considered. At 300V the observed collection efficiency deviates distinctly from that predicted by any of the established theories, even at low pulse doses. However, the numeric solution of the equation system is able to reproduce the measured collection efficiency across the entire dose range of both voltages with a single set of parameters. Conclusion: At high electric fields (3000V/cm here) the existing theoretical descriptions of collection efficiency, including the TVA, are inadequate to predict pulse dose dependency. Even at low pulse doses they might underestimate collection efficiency. The presented, more accurate numeric solution, which considers additional effects like electric shielding by the charges, might provide a valuable tool for future investigations. This project was funded by the German ministry of research and education (BMBF) under grant number: 03Z1N511 and by the state of Saxony under grant number: B 209.« less

In situ analysis of plant tissue underivatized carbohydrates and on-probe enzymatic degraded starch by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry by using carbon nanotubes as matrix.

PubMed

Gholipour, Yousef; Nonami, Hiroshi; Erra-Balsells, Rosa

2008-12-15

Underivatized carbohydrates of tulip bulb and leaf tissues were characterized in situ by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) by using carbon nanotubes (CNTs) as matrix. Two sample preparation methods--(i) depositing CNTs on the fresh tissue slices placed on the probe and (ii) locating semitransparent tissues on a dried layer of CNTs on the probe--were examined. Furthermore, practicability of in situ starch analysis by MALDI-TOF MS was examined by detection of glucose originated from on-probe amyloglucosidase-catalyzed degradation of starch on the tissue surface. Besides, CNTs could efficiently desorb/ionize natural mono-, di-, and oligosaccharides extracted from tulip bulb tissues as well as glucose resulting from starch enzymatic degradation in vitro. These results were compared with those obtained by in situ MALDI-TOF MS analysis of similar tissues. Positive ion mode showed superior signal reproducibility. CNTs deposited under semitransparent tissue could also desorb/ionize neutral carbohydrates, leading to nearly complete elimination of matrix cluster signals but with an increase in tissue-originated signals. Furthermore, several experiments were carried out to compare the efficiency of 2,5-dihydroxybenzoic acid, nor-harmane, alpha-cyano-4-hydroxycinnamic acid, and CNTs as matrices for MALDI of neutral carbohydrates from the intact plant tissue surface and for enzymatic tissue starch degradation; these results are discussed in brief. Among matrices studied, the lowest laser power was needed to acquire carbohydrate signals with high signal-to-noise ratio and resolution when CNTs were used.

Non-random distribution of DNA double-strand breaks induced by particle irradiation

NASA Technical Reports Server (NTRS)

Lobrich, M.; Cooper, P. K.; Rydberg, B.; Chatterjee, A. (Principal Investigator)

1996-01-01

Induction of DNA double-strand breaks (dsbs) in mammalian cells is dependent on the spatial distribution of energy deposition from the ionizing radiation. For high LET particle radiations the primary ionization sites occur in a correlated manner along the track of the particles, while for X-rays these sites are much more randomly distributed throughout the volume of the cell. It can therefore be expected that the distribution of dsbs linearly along the DNA molecule also varies with the type of radiation and the ionization density. Using pulsed-field gel and conventional gel techniques, we measured the size distribution of DNA molecules from irradiated human fibroblasts in the total range of 0.1 kbp-10 Mbp for X-rays and high LET particles (N ions, 97 keV/microns and Fe ions, 150 keV/microns). On a mega base pair scale we applied conventional pulsed-field gel electrophoresis techniques such as measurement of the fraction of DNA released from the well (FAR) and measurement of breakage within a specific NotI restriction fragment (hybridization assay). The induction rate for widely spaced breaks was found to decrease with LET. However, when the entire distribution of radiation-induced fragments was analysed, we detected an excess of fragments with sizes below about 200 kbp for the particles compared with X-irradiation. X-rays are thus more effective than high LET radiations in producing large DNA fragments but less effective in the production of smaller fragments. We determined the total induction rate of dsbs for the three radiations based on a quantitative analysis of all the measured radiation-induced fragments and found that the high LET particles were more efficient than X-rays at inducing dsbs, indicating an increasing total efficiency with LET. Conventional assays that are based only on the measurement of large fragments are therefore misleading when determining total dsb induction rates of high LET particles. The possible biological significance of this non-randomness for dsb induction is discussed.

X-ray and multiwavelength insights into the inner structure of high-luminosity disc-like emitters

NASA Astrophysics Data System (ADS)

Luo, B.; Brandt, W. N.; Eracleous, M.; Wu, Jian; Hall, P. B.; Rafiee, A.; Schneider, D. P.; Wu, Jianfeng

2013-02-01

We present X-ray and multiwavelength studies of a sample of eight high-luminosity active galactic nuclei (AGN) with disc-like Hβ emission-line profiles selected from the Sloan Digital Sky Survey Data Release 7. These sources have higher redshift (z ≈ 0.6) than the majority of the known disc-like emitters, and they occupy a largely unexplored space in the luminosity-redshift plane. Seven sources have typical AGN X-ray spectra with power-law photon indices of Γ ≈ 1.4-2.0; two of them show some X-ray absorption (column density NH ≈ 1021-1022 cm-2 for neutral gas). The other source, J0850+4451, has only three hard X-ray photons detected and is probably heavily obscured (NH ≳ 3 × 1023 cm-2). This object is also identified as a low-ionization broad absorption line (BAL) quasar based on Mg II λ2799 absorption; it is the first disc-like emitter reported that is also a BAL quasar. The infrared-to-ultraviolet (UV) spectral energy distributions (SEDs) of these eight sources are similar to the mean SEDs of typical quasars with a UV `bump', suggestive of standard accretion discs radiating with high efficiency, which differs from low-luminosity disc-like emitters. Studies of the X-ray-to-optical power-law slope parameters (αOX) indicate that there is no significant excess X-ray emission in these high-luminosity disc-like emitters. Energy budget analysis suggests that for disc-like emitters in general, the inner disc must illuminate and ionize the outer disc efficiently (≈15 per cent of the nuclear ionizing radiation is required on average) via direct illumination and/or scattering. Warped accretion discs are probably needed for direct illumination to work in high-luminosity objects, as their geometrically thin inner discs decrease the amount of direct illumination possible for a flat disc.

Liquid-chromatography thermospray mass-spectrometric study of n-acylamino dilactones and 4-butyrolactones derived from Antimycin-A

USGS Publications Warehouse

Abidi, S.L.; Ha, S.C.; Rosen, R.T.

1990-01-01

Reversed-phase high-performance liquid chromatography—thermospray mass spectrometric (HPLC—MS) characteristics of four sets of lactonic complexes (one 4-butyrolactones and three dilactone complexes) derived from antimycin A were investigated. Three types of 8-hydroxy analogues were also included in the study. Pairs of a–b structures isomeric at the 8-acyloxy ester side-chains were best separated with a high-efficiency octadecylsilica column prior to analysis by HPLC—MS. Mass spectra of the a–b pairs each with identical molecular weights exhibited virtually indistinguishable fragmentation patterns, although their relative intensities were not superimposable. In some cases, HPLC—MS of the title compounds yielded mass chromatograms showing the minor components more easily recognizable than the HPLC—UV counter parts because of the apparent higher ionization efficiency of the minor isomers and increased resolution of subcomponents in the MS system. Under the mobile phase conditions employed, analyte ionization occurred with variable degrees of gas phase ammonolysis depending upon the ammonia concentration of the buffer. Potential applicability of the on-line HPLC—MS technique for the characterization of components in mixtures of antimycin analogues and isomers is demonstrated.

Rapid and selective determination of multi-sulfonamides by high-performance thin layer chromatography coupled to fluorescent densitometry and electrospray ionization mass detection.

PubMed

Chen, Yisheng; Schwack, Wolfgang

2014-02-28

In the European Union (EU), sulfonamides are among the most widely administrated groups of antibiotics in animal husbandry. Therefore, monitoring their residues in edible animal tissues plays an important role in the EU food safety framework. In this work, a simple and efficient method for the rapid screening of twelve prior sulfonamides frequently prescribed as veterinary drugs by high-performance thin-layer chromatography (HPTLC) was established. Sample extracts obtained with acetonitrile were tenfold concentrated and applied to HPTLC without any further cleanup. Following separation and fluram derivatization, sensitive and selective quantitation of the analytes can readily be accomplished with fluorescent densitometry. Limits of detection and quantitation were 15-40 and 35-70μg/kg, respectively. Additionally, a confirmative detection by HPTLC-electrospray ionization mass spectrometry (HPTLC-ESI/MS) was optimized, offering straightforward identification of target zones. Therefore, the risk of potential false positive findings can efficiently be reduced. The method was validated to meet the enforced commission regulation (EU) No. 37/2010, regarding different matrix complexities (bovine milk, porcine liver and kidney). Copyright © 2014 Elsevier B.V. All rights reserved.

Modeling the gain of inner-shell X-ray laser transitions in neon, argon, and copper driven by X-ray free electron laser radiation using photo-ionization and photo-excitation processes

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

Nilsen, Joseph

2015-12-16

Using an X-ray free electron laser (XFEL) at 960 eV to photo-ionize the 1s electron in neutral neon followed by lasing on the 2p-1s transition in singly-ionized neon, an inner-shell X-ray laser was demonstrated at 849 eV in singly-ionized neon gas several years ago. It took decades to demonstrate this scheme, because it required a very strong X-ray source that could photo-ionize the 1s (K shell) electron in neon on a timescale comparable to the intrinsic Auger lifetime in neon of 2 fs. In this paper, we model the neon inner shell X-ray laser under similar conditions to those usedmore » in the XFEL experiments at the SLAC Linac Coherent Light Source (LCLS), and show how we can improve the efficiency of the neon laser and reduce the drive requirements by tuning the XFEL to the 1s-3p transition in neutral neon in order to create gain on the 2p-1s line in neutral neon. We also show how the XFEL could be used to photo-ionize L-shell electrons to drive gain on n = 3–2 transitions in singly-ionized Ar and Cu plasmas. Furthermore, these bright, coherent, and monochromatic X-ray lasers may prove very useful for doing high-resolution spectroscopy and for studying non-linear process in the X-ray regime.« less

Investigation of theoretical efficiency limit of hot carriers solar cells with a bulk indium nitride absorber

NASA Astrophysics Data System (ADS)

Aliberti, P.; Feng, Y.; Takeda, Y.; Shrestha, S. K.; Green, M. A.; Conibeer, G.

2010-11-01

Theoretical efficiencies of a hot carrier solar cell considering indium nitride as the absorber material have been calculated in this work. In a hot carrier solar cell highly energetic carriers are extracted from the device before thermalisation, allowing higher efficiencies in comparison to conventional solar cells. Previous reports on efficiency calculations approached the problem using two different theoretical frameworks, the particle conservation (PC) model or the impact ionization model, which are only valid in particular extreme conditions. In addition an ideal absorber material with the approximation of parabolic bands has always been considered in the past. Such assumptions give an overestimation of the efficiency limits and results can only be considered indicative. In this report the real properties of wurtzite bulk InN absorber have been taken into account for the calculation, including the actual dispersion relation and absorbance. A new hybrid model that considers particle balance and energy balance at the same time has been implemented. Effects of actual impact ionization (II) and Auger recombination (AR) lifetimes have been included in the calculations for the first time, considering the real InN band structure and thermalisation rates. It has been observed that II-AR mechanisms are useful for cell operation in particular conditions, allowing energy redistribution of hot carriers. A maximum efficiency of 43.6% has been found for 1000 suns, assuming thermalisation constants of 100 ps and ideal blackbody absorption. This value of efficiency is considerably lower than values previously calculated adopting PC or II-AR models.

The epoch of cosmic heating by early sources of X-rays

NASA Astrophysics Data System (ADS)

Eide, Marius B.; Graziani, Luca; Ciardi, Benedetta; Feng, Yu; Kakiichi, Koki; Di Matteo, Tiziana

2018-05-01

Observations of the 21 cm line from neutral hydrogen indicate that an epoch of heating (EoH) might have preceded the later epoch of reionization. Here we study the effects on the ionization state and the thermal history of the intergalactic medium (IGM) during the EoH induced by different assumptions on ionizing sources in the high-redshift Universe: (i) stars; (ii) X-ray binaries (XRBs); (iii) thermal bremsstrahlung of the hot interstellar medium (ISM); and (iv) accreting nuclear black holes (BHs). To this aim, we post-process outputs from the (100 h-1 comoving Mpc)3 hydrodynamical simulation MassiveBlack-II with the cosmological 3D radiative transfer code CRASH, which follows the propagation of ultraviolet and X-ray photons, computing the thermal and ionization state of hydrogen and helium through the EoH. We find that stars determine the fully ionized morphology of the IGM, while the spectrally hard XRBs pave way for efficient subsequent heating and ionization by the spectrally softer ISM. With the seeding prescription in MassiveBlack-II, BHs do not contribute significantly to either ionization or heating. With only stars, most of the IGM remains in a cold state (with a median T = 11 K at z = 10), however, the presence of more energetic sources raises the temperature of regions around the brightest and more clustered sources above that of the cosmic microwave background, opening the possibility to observing the 21 cm signal in emission.

Ion energies in high power impulse magnetron sputtering with and without localized ionization zones

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

Yang, Yuchen; Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720; Tanaka, Koichi

2015-03-23

High speed imaging of high power impulse magnetron sputtering discharges has revealed that ionization is localized in moving ionization zones but localization disappears at high currents for high yield targets. This offers an opportunity to study the effect ionization zones have on ion energies. We measure that ions have generally higher energies when ionization zones are present, supporting the concept that these zones are associated with moving potential humps. We propose that the disappearance of ionization zones is caused by an increased supply of atoms from the target which cools electrons and reduces depletion of atoms to be ionized.

Study on the characteristics of a two gap capillary discharge

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

Huang, D.; Yang, L. J., E-mail: yanglj@mail.xjtu.edu.cn; Huo, P.

2015-02-15

The paper presents a new two-gap capillary (TGC) discharge structure. The prominent innovation is the introduction of the middle electrode, which divides the capillary into the trigger gap and the main gap. The discharge circuit of the TGC comprises the trigger circuit and the main circuit. The two circuits are used for the pre-ionization of the trigger gap and providing energy of 450 J for the main gap arc discharging, respectively. When the discharge initiates, the trigger gap is pre-ionized under high voltage pulse produced by trigger circuit, and meanwhile, the weakly ionized plasma is generated. The main circuit then maintainsmore » the expansion of the plasma, which is called soft capillary discharge. Afterwards, the main gap is shorted and discharges under a relatively low voltage. With the optimization of the circuit parameter, both the energy deposition ratio in main gap and the degree of plasma ionization are enhanced. The efficiency of the energy deposition is almost twice higher compared with that of the conventional capillary structure. The life performance test indicates that the erosion of the middle electrode and the trigger gap carbonization are the key factors that limit the life performance of the TGC.« less

Equation of motion coupled cluster methods for electron attachment and ionization potential in polyacenes

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

Bhaskaran-Nair, Kiran; Kowalski, Karol; Jarrell, Mark

2015-11-05

Polyacenes have attracted considerable attention due to their use in organic based optoelectronic materials. Polyacenes are polycyclic aromatic hydrocarbons composed of fused benzene rings. Key to understanding and design of new functional materials is an understanding of their excited state properties starting with their electron affinity (EA) and ionization potential (IP). We have developed a highly accurate and com- putationally e*fficient EA/IP equation of motion coupled cluster singles and doubles (EA/IP-EOMCCSD) method that is capable of treating large systems and large basis set. In this study we employ the EA/IP-EOMCCSD method to calculate the electron affinity and ionization potential ofmore » naphthalene, anthracene, tetracene, pentacene, hex- acene and heptacene. We have compared our results with other previous theoretical studies and experimental data. Our EA/IP results are in very good agreement with experiment and when compared with the other theoretical investigations our results represent the most accurate calculations as compared to experiment.« less

A physics-based model for the ionization of samarium by the MOSC chemical releases in the upper atmosphere

NASA Astrophysics Data System (ADS)

Bernhardt, Paul A.; Siefring, Carl L.; Briczinski, Stanley J.; Viggiano, Albert; Caton, Ronald G.; Pedersen, Todd R.; Holmes, Jeffrey M.; Ard, Shaun; Shuman, Nicholas; Groves, Keith M.

2017-05-01

Atomic samarium has been injected into the neutral atmosphere for production of electron clouds that modify the ionosphere. These electron clouds may be used as high-frequency radio wave reflectors or for control of the electrodynamics of the F region. A self-consistent model for the photochemical reactions of Samarium vapor cloud released into the upper atmosphere has been developed and compared with the Metal Oxide Space Cloud (MOSC) experimental observations. The release initially produces a dense plasma cloud that that is rapidly reduced by dissociative recombination and diffusive expansion. The spectral emissions from the release cover the ultraviolet to the near infrared band with contributions from solar fluorescence of the atomic, molecular, and ionized components of the artificial density cloud. Barium releases in sunlight are more efficient than Samarium releases in sunlight for production of dense ionization clouds. Samarium may be of interest for nighttime releases but the artificial electron cloud is limited by recombination with the samarium oxide ion.

Coulomb-driven energy boost of heavy ions for laser-plasma acceleration.

PubMed

Braenzel, J; Andreev, A A; Platonov, K; Klingsporn, M; Ehrentraut, L; Sandner, W; Schnürer, M

2015-03-27

An unprecedented increase of kinetic energy of laser accelerated heavy ions is demonstrated. Ultrathin gold foils have been irradiated by an ultrashort laser pulse at a peak intensity of 8×10^{19}  W/  cm^{2}. Highly charged gold ions with kinetic energies up to >200  MeV and a bandwidth limited energy distribution have been reached by using 1.3 J laser energy on target. 1D and 2D particle in cell simulations show how a spatial dependence on the ion's ionization leads to an enhancement of the accelerating electrical field. Our theoretical model considers a spatial distribution of the ionization inside the thin target, leading to a field enhancement for the heavy ions by Coulomb explosion. It is capable of explaining the energy boost of highly charged ions, enabling a higher efficiency for the laser-driven heavy ion acceleration.

Resonance-modulated wavelength scaling of high-order-harmonic generation from H2+

NASA Astrophysics Data System (ADS)

Wang, Baoning; He, Lixin; Wang, Feng; Yuan, Hua; Zhu, Xiaosong; Lan, Pengfei; Lu, Peixiang

2018-01-01

Wavelength scaling of high-order harmonic generation (HHG) in a non-Born-Oppenheimer treatment of H2+ is investigated by numerical simulations of the time-dependent Schrödinger equation. The results show that the decrease in the wavelength-dependent HHG yield is reduced compared to that in the fixed-nucleus approximation. This slower wavelength scaling is related to the charge-resonance-enhanced ionization effect, which considerably increases the ionization rate at longer driving laser wavelengths due to the relatively larger nuclear separation. In addition, we find an oscillation structure in the wavelength scaling of HHG from H2+. Upon decreasing the laser intensity or increasing the nuclear mass, the oscillation structure will shift towards a longer wavelength of the laser pulse. These results permit the generation of an efficient harmonic spectrum in the midinfrared regime by manipulating the nuclear dynamics of molecules.

Matrix effects in pesticide multi-residue analysis by liquid chromatography-mass spectrometry.

PubMed

Kruve, Anneli; Künnapas, Allan; Herodes, Koit; Leito, Ivo

2008-04-11

Three sample preparation methods: Luke method (AOAC 985.22), QuEChERS (quick, easy, cheap, effective, rugged and safe) and matrix solid-phase dispersion (MSPD) were applied to different fruits and vegetables for analysis of 14 pesticide residues by high-performance liquid chromatography with electrospray ionization-mass spectrometry (HPLC/ESI/MS). Matrix effect, recovery and process efficiency of the sample preparation methods applied to different fruits and vegetables were compared. The Luke method was found to produce least matrix effect. On an average the best recoveries were obtained with the QuEChERS method. MSPD gave unsatisfactory recoveries for some basic pesticide residues. Comparison of matrix effects for different apple varieties showed high variability for some residues. It was demonstrated that the amount of co-extracting compounds that cause ionization suppression of aldicarb depends on the apple variety as well as on the sample preparation method employed.

High Resolution Separations and Improved Ion Production and Transmission in Metabolomics

PubMed Central

Metz, Thomas O.; Page, Jason S.; Baker, Erin S.; Tang, Keqi; Ding, Jie; Shen, Yufeng; Smith, Richard D.

2008-01-01

The goal of metabolomics analyses is the detection and quantitation of as many sample components as reasonably possible in order to identify compounds or “features” that can be used to characterize the samples under study. When utilizing electrospray ionization to produce ions for analysis by mass spectrometry (MS), it is important that metabolome sample constituents be efficiently separated prior to ion production, in order to minimize ionization suppression and thereby extend the dynamic range of the measurement, as well as the coverage of the metabolome. Similarly, optimization of the MS inlet and interface can lead to increased measurement sensitivity. This perspective review will focus on the role of high resolution liquid chromatography (LC) separations in conjunction with improved ion production and transmission for LC-MS-based metabolomics. Additional emphasis will be placed on the compromise between metabolome coverage and sample analysis throughput. PMID:19255623

Exploring the potential of high resolution mass spectrometry for the investigation of lignin-derived phenol substitutes in phenolic resin syntheses.

PubMed

Dier, Tobias K F; Fleckenstein, Marco; Militz, Holger; Volmer, Dietrich A

2017-05-01

Chemical degradation is an efficient method to obtain bio-oils and other compounds from lignin. Lignin bio-oils are potential substitutes for the phenol component of phenol formaldehyde (PF) resins. Here, we developed an analytical method based on high resolution mass spectrometry that provided structural information for the synthesized lignin-derived resins and supported the prediction of their properties. Different model resins based on typical lignin degradation products were analyzed by electrospray ionization in negative ionization mode. Utilizing enhanced mass defect filter techniques provided detailed structural information of the lignin-based model resins and readily complemented the analytical data from differential scanning calorimetry and thermogravimetric analysis. Relative reactivity and chemical diversity of the phenol substitutes were significant determinants of the outcome of the PF resin synthesis and thus controlled the areas of application of the resulting polymers. Graphical abstract ᅟ.

Coherent control of strong-field two-pulse ionization of Rydberg atoms.

PubMed

Fedorov, M; Poluektov, N

2000-02-28

Strong-field ionization of Rydberg atoms is investigated in its dependence on phase features of the initial coherent population of Rydberg levels. In the case of a resonance between Rydberg levels and some lower-energy atomic level (V-type transitions), this dependence is shown to be very strong: by a proper choice of the initial population an atom can be made either completely or very little ionized by a strong laser pulse. It is shown that phase features of the initial coherent population of Rydberg levels and the ionization yield can be efficiently controlled in a scheme of ionization by two strong laser pulses with a varying delay time between them.

Research on the degradation mechanism of dimethyl phthalate in drinking water by strong ionization discharge

NASA Astrophysics Data System (ADS)

Hong, ZHAO; Chengwu, YI; Rongjie, YI; Huijuan, WANG; Lanlan, YIN; I, N. MUHAMMAD; Zhongfei, MA

2018-03-01

The degradation mechanism of dimethyl phthalate (DMP) in the drinking water was investigated using strong ionization discharge technology in this study. Under the optimized condition, the degradation efficiency of DMP in drinking water was up to 93% in 60 min. A series of analytical techniques including high-performance liquid chromatography, liquid chromatography mass spectrometry, total organic carbon analyzer and ultraviolet-visible spectroscopy were used in the study. It was found that a high concentration of ozone (O3) produced by dielectric barrier discharge reactor was up to 74.4 mg l-1 within 60 min. Tert-butanol, isopropyl alcohol, carbonate ions ({{{{CO}}}3}2-) and bicarbonate ions ({{{{HCO}}}3}-) was added to the sample solution to indirectly prove the presence and effect of hydroxyl radicals (·OH). These analytical findings indicate that mono-methyl phthalate, phthalic acid (PA) and methyl ester PA were detected as the major intermediates in the process of DMP degradation. Finally, DMP and all products were mineralized into carbon dioxide (CO2) and water (H2O) ultimately. Based on these analysis results, the degradation pathway of DMP by strong ionization discharge technology were proposed.

HOW TO FIND YOUNG MASSIVE CLUSTER PROGENITORS

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

Bressert, E.; Longmore, S.; Testi, L.

2012-10-20

We propose that bound, young massive stellar clusters form from dense clouds that have escape speeds greater than the sound speed in photo-ionized gas. In these clumps, radiative feedback in the form of gas ionization is bottled up, enabling star formation to proceed to sufficiently high efficiency so that the resulting star cluster remains bound even after gas removal. We estimate the observable properties of the massive proto-clusters (MPCs) for existing Galactic plane surveys and suggest how they may be sought in recent and upcoming extragalactic observations. These surveys will potentially provide a significant sample of MPC candidates that willmore » allow us to better understand extreme star-formation and massive cluster formation in the Local Universe.« less

High Power Light Gas Helicon Plasma Source For VASMIR

NASA Technical Reports Server (NTRS)

Squire, J. P.; Chang-Diaz, F. R.; Glover, T. W.; Jacobson, V. T.; McCaskill, G. E.; Winter, D. S.; Baity, F. W.; Carter, M. D.; Goulding, R. H.

2004-01-01

The VASIMR space propulsion development effort relies on a high power (greater than 10kW) helicon source to produce a dense flowing plasma (H, D and He) target for ion cyclotron resonance (ICR) acceleration of the ions. Subsequent expansion in an expanding magnetic field (magnetic nozzle) converts ion lunetic energy to directed momentum. This plasma source must have critical features to enable an effective propulsion device. First, it must ionize most of the input neutral flux of gas, thus producing a plasma stream with a high degree of ionization for application of ICR power. This avoids propellant waste and potential power losses due to charge exchange. Next, the plasma stream must flow into a region of high magnetic field (approximately 0.5 T) for efficient ICR acceleration. Third, the ratio of input power to plasma flux must be low, providing an energy per ion-electron pair approaching 100 eV. Lastly, the source must be robust and capable of very long life-times (years). In our helicon experiment (VX-10) we have measured a ratio of input gas to plasma flux near 100%. The plasma flows from the helicon region (B approximately 0.1 T) into a region with a peak magnetic field of 0.8 T. The energy input per ion-electron pair has been measured at 300 plus or minus 100 eV. Recent results at Oak Ridge National Laboratory (ORNL) show an enhanced efficiency mode of operation with a high power density, over 5 kW in a 5 cm diameter tube. Our helicon is presently 9 cm in diameter and operates up to 3.5 kW of input power. An upgrade to a power level of 10 kW is underway. Much of our recent work has been with a Boswell double-saddle antenna design. We are also converting the antenna design to a helical type. With these modifications, we anticipate an improvement in the ionization efficiency. This paper presents the results from scaling the helicon in the VX-10 device from 3.5 to 10 kW. We also compare the operation with a double-saddle to a helical antenna design. Finally, we discuss modeling of these configurations using ORNL's EMIR code.

Laser separation of lithium isotopes by double resonance enhanced multiphoton ionization of Li/sub 2/

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

Balz, J.G.; Bernheim, R.A.; Gold, L.P.

1987-01-01

Multiphoton ionization spectra of /sup 7/Li/sub 2/, /sup 6/Li/sub 2/, and /sup 7/Li/sup 6/Li vapors have been measured in the 570--650 nm region using a single, low resolution, multimode cw dye laser. A number of wavelengths provide selective multiphoton ionization of one isotopic species demonstrating the possibility of efficient laser-driven isotopic separation in lithium in this wavelength region.

The absorption of energetic electrons by molecular hydrogen gas

NASA Technical Reports Server (NTRS)

Cravens, T. E.; Victor, G. A.; Dalgarno, A.

1975-01-01

The processes by which energetic electrons lose energy in a weakly ionized gas of molecular hydrogen are analyzed, and calculations are carried out taking into account the discrete nature of the excitation processes. The excitation, ionization, and heating efficiencies are computed for electrons with energies up to 100 eV absorbed in a gas with fractional ionizations up to 0.01, and the mean energy per pair of neutral hydrogen atoms is calculated.

Electron energy deposition in N2 gas

NASA Technical Reports Server (NTRS)

Fox, J. L.; Victor, G. A.

1988-01-01

The processes by which energetic electrons lose energy in a weakly ionized gas of molecular nitrogen are analyzed and calculations are carried out taking into account the discrete nature of the excitation processes. The excitation, ionization, dissociation and heating efficiencies are computed for energies up to 200 eV absorbed in a gas with fractional ionizations varying from 10(-6) to 10(-2). Individual vibrational excitations up to the seventh vibrational level are presented.

Large-area field-ionization detector for the study of Rydberg atoms.

PubMed

Jones, A C L; Piñeiro, A M; Roeder, E E; Rutbeck-Goldman, H J; Tom, H W K; Mills, A P

2016-11-01

We describe here the development and characterization of a micro-channel plate (MCP) based detector designed for the efficient collection and detection of Rydberg positronium (Ps) atoms for use in a time-of-flight apparatus. The designed detector collects Rydberg atoms over a large area (∼4 times greater than the active area of the MCP), ionizing incident atoms and then collecting and focusing the freed positrons onto the MCP. Here we discuss the function, design, and optimization of the device. The detector has an efficiency for Rydberg Ps that is two times larger than that of the γ-ray scintillation detector based scheme it has been designed to replace, with half the background signal. In principle, detectors of the type described here could be readily employed for the detection of any Rydberg atom species, provided a sufficient field can be applied to achieve an ionization rate of ≥10 8 /s. In such cases, the best time resolution would be achieved by collecting ionized electrons rather than the positive ions.

Resonant ionization spectroscopy of autoionizing Rydberg states in cobalt and redetermination of its ionization potential

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

Liu, Yuan; Gottwald, T.; Mattolat, C.

We obtained multi-step resonance ionization spectroscopy of cobalt using a hot-cavity laser ion source and three Ti:Sapphire lasers. Furthermore, the photoionization spectra revealed members of five new autoionizing Rydberg series that originate from three different lower levels of 3d 74s5s h 4F 9/2, 3d 74s4d f 4G 11/2, and 3d 74s4d f 4H 13/2 and converge to the first four excited states of singly ionized Co. Our analyses of the Rydberg series yield 63564.689 0.036 cm -1 as the first ionization potential of Co, which is an order of magnitude more accurate than the previous estimation. Using a three-step resonancemore » ionization scheme that employs an autoinizing Rydberg state in the last transition, we obtained an overall ionization efficiency of about 18% for Co.« less

Resonant ionization spectroscopy of autoionizing Rydberg states in cobalt and redetermination of its ionization potential

DOE PAGES

Liu, Yuan; Gottwald, T.; Mattolat, C.; ...

2017-03-20

We obtained multi-step resonance ionization spectroscopy of cobalt using a hot-cavity laser ion source and three Ti:Sapphire lasers. Furthermore, the photoionization spectra revealed members of five new autoionizing Rydberg series that originate from three different lower levels of 3d 74s5s h 4F 9/2, 3d 74s4d f 4G 11/2, and 3d 74s4d f 4H 13/2 and converge to the first four excited states of singly ionized Co. Our analyses of the Rydberg series yield 63564.689 0.036 cm -1 as the first ionization potential of Co, which is an order of magnitude more accurate than the previous estimation. Using a three-step resonancemore » ionization scheme that employs an autoinizing Rydberg state in the last transition, we obtained an overall ionization efficiency of about 18% for Co.« less

Evidence for Trivelpiece-Gould modes in a helicon discharge.

PubMed

Blackwell, D D; Madziwa, T G; Arnush, D; Chen, F F

2002-04-08

The high ionization efficiency of helicon discharges has been attributed to Landau damping and mode coupling to Trivelpiece-Gould (TG) modes. Though theory predicts the importance of TG modes, they have rarely been seen. Here they were detected directly by measuring their radiofrequency current with a J-dot probe, thus supporting the contention that TG modes play a role in these enigmatic plasma sources.

Action-FRET of a Gaseous Protein

NASA Astrophysics Data System (ADS)

Daly, Steven; Knight, Geoffrey; Halim, Mohamed Abdul; Kulesza, Alexander; Choi, Chang Min; Chirot, Fabien; MacAleese, Luke; Antoine, Rodolphe; Dugourd, Philippe

2017-01-01

Mass spectrometry is an extremely powerful technique for analysis of biological molecules, in particular proteins. One aspect that has been contentious is how much native solution-phase structure is preserved upon transposition to the gas phase by soft ionization methods such as electrospray ionization. To address this question—and thus further develop mass spectrometry as a tool for structural biology—structure-sensitive techniques must be developed to probe the gas-phase conformations of proteins. Here, we report Förster resonance energy transfer (FRET) measurements on a ubiquitin mutant using specific photofragmentation as a reporter of the FRET efficiency. The FRET data is interpreted in the context of circular dichroism, molecular dynamics simulation, and ion mobility data. Both the dependence of the FRET efficiency on the charge state—where a systematic decrease is observed—and on methanol concentration are considered. In the latter case, a decrease in FRET efficiency with methanol concentration is taken as evidence that the conformational ensemble of gaseous protein cations retains a memory of the solution phase conformational ensemble upon electrospray ionization.

Enhanced one-photon double ionization of atoms and molecules in an environment of different species.

PubMed

Stumpf, V; Kryzhevoi, N V; Gokhberg, K; Cederbaum, L S

2014-05-16

The correlated nature of electronic states in atoms and molecules is manifested in the simultaneous emission of two electrons after absorption of a single photon close to the respective threshold. Numerous observations in atoms and small molecules demonstrate that the double ionization efficiency close to threshold is rather small. In this Letter we show that this efficiency can be dramatically enhanced in the environment. To be specific, we concentrate on the case where the species in question has one or several He atoms as neighbors. The enhancement is achieved by an indirect process, where a He atom of the environment absorbs a photon and the resulting He(+) cation is neutralized fast by a process known as electron transfer mediated decay, producing thereby doubly ionized species. The enhancement of the double ionization is demonstrated in detail for the example of the Mg · He cluster. We show that the double ionization cross section of Mg becomes 3 orders of magnitude larger than the respective cross section of the isolated Mg atom. The impact of more neighbors is discussed and the extension to other species and environments is addressed.

A discharge flow-photoionization mass spectrometric study of the FO(X 2 Pi i) radical. Photoionization efficiency spectrum and ionization energy

NASA Technical Reports Server (NTRS)

Zhang, Zhengyu; Kuo, Szu-Cherng; Klemm, R. Bruce; Monks, Paul S.; Stief, Louis J.

1994-01-01

Photoionization efficiency spectra of FO were measured over the wavelength range 80.0-100.0 nm and in the ionization threshold region, 94.0-100.0 nm, using a discharge flow-photoionization mass spectrometer apparatus coupled to a synchrotron radiation source. FO was generated by the reaction of F2P atoms with NO3 and via a F2O2 discharge. A value of 12.78 +/- 0.03 eV was obtained for the adiabatic ionization energy of FO from photoion thresholds which corresponds to FO(+)(X 3 Sigma -) from FO(X 2 Pi i). These results, which are the first to be obtained by direct Photo-ionization mass spectrometry (PIMS) measurements, corroborate those of a photoelectron spectroscopy (PES) study; however, the ionization energy determined here is free from interferences due to other species which complicated the PES measurement. A value of 109.5 +/- 8.0 kJ/mol for Delta f H 0 298(FO) is computed from the present value of IE(FO) and a previous appearance energy measurement, and a value for the proton affinity of FO is calculated to be 511.5 +/- 10.0 kJ/mol.

New generation of Cherenkov counters

NASA Astrophysics Data System (ADS)

Giomataris, Y.; Charpak, G.; Peskov, V.; Sauli, F.

1992-12-01

Experimental results with a parallel plate avalanche chamber (PPAC) having a CsI photocathode and pad array readout are reported. High gains in excess of 10 5 have been obtained with He gas at atmospheric pressure and traces of CH 4 or CF 4 quencher. Such light gas mixtures extend the transparency for the Cherenkov light to the extreme UV region and allow detector operation with very low sensitivity to the ionization produced by minimum ionizing particles. A hadron blind detector (HBD) is discussed which exploits the broad photon energy bandwidth (≈ 10 eV) and the high Cherenkov threshold ( pπ = 15 GeV). This fast detector, since it has a good spatial resolution, can be used at the future Large Hadron Collider (LHC) or the Superconductivity Super Collider (SSC) either as an efficient electron tagger, rejecting hadrons faking electrons in the calorimeter, or as a pretracker giving fast electron and high-energy muon signature and momentum estimation. Other potential applications in the domain of Cherenkov light detection are also discussed.

High thermal conductivity in electrostatically engineered amorphous polymers

PubMed Central

Shanker, Apoorv; Li, Chen; Kim, Gun-Ho; Gidley, David; Pipe, Kevin P.; Kim, Jinsang

2017-01-01

High thermal conductivity is critical for many applications of polymers (for example, packaging of light-emitting diodes), in which heat must be dissipated efficiently to maintain the functionality and reliability of a system. Whereas uniaxially extended chain morphology has been shown to significantly enhance thermal conductivity in individual polymer chains and fibers, bulk polymers with coiled and entangled chains have low thermal conductivities (0.1 to 0.4 W m−1 K−1). We demonstrate that systematic ionization of a weak anionic polyelectrolyte, polyacrylic acid (PAA), resulting in extended and stiffened polymer chains with superior packing, can significantly enhance its thermal conductivity. Cross-plane thermal conductivity in spin-cast amorphous films steadily grows with PAA degree of ionization, reaching up to ~1.2 W m−1 K−1, which is on par with that of glass and about six times higher than that of most amorphous polymers, suggesting a new unexplored molecular engineering strategy to achieve high thermal conductivities in amorphous bulk polymers. PMID:28782022

AP-MALDI Mass Spectrometry Imaging of Gangliosides Using 2,6-Dihydroxyacetophenone

NASA Astrophysics Data System (ADS)

Jackson, Shelley N.; Muller, Ludovic; Roux, Aurelie; Oktem, Berk; Moskovets, Eugene; Doroshenko, Vladimir M.; Woods, Amina S.

2018-03-01

Matrix-assisted laser/desorption ionization (MALDI) mass spectrometry imaging (MSI) is widely used as a unique tool to record the distribution of a large range of biomolecules in tissues. 2,6-Dihydroxyacetophenone (DHA) matrix has been shown to provide efficient ionization of lipids, especially gangliosides. The major drawback for DHA as it applies to MS imaging is that it sublimes under vacuum (low pressure) at the extended time necessary to complete both high spatial and mass resolution MSI studies of whole organs. To overcome the problem of sublimation, we used an atmospheric pressure (AP)-MALDI source to obtain high spatial resolution images of lipids in the brain using a high mass resolution mass spectrometer. Additionally, the advantages of atmospheric pressure and DHA for imaging gangliosides are highlighted. The imaging of [M-H]- and [M-H2O-H]- mass peaks for GD1 gangliosides showed different distribution, most likely reflecting the different spatial distribution of GD1a and GD1b species in the brain. [Figure not available: see fulltext.

Detection of the barium daughter in 136Xe -->136Ba + 2e- by in situ single-molecule fluorescence imaging

NASA Astrophysics Data System (ADS)

Nygren, David

2015-10-01

To proceed toward effective ``discovery class'' ton-scale detectors in the search for neutrino-less double beta decay, a robust technique for rejection of all radioactivity-induced backgrounds is urgently needed. An efficient technique for detection of the barium daughter in the decay 136Xe -->136Ba + 2e- would provide a long-sought pathway toward this goal. Single-molecule fluorescent imaging appears to offer a new way to detect the barium daughter atom, which emerges naturally in an ionized state in pure xenon. A doubly charged barium ion can initiate a chelation process with a non-fluorescent precursor molecule, leading to a highly fluorescent complex. Repeated photo-excitation of the complex can reveal both presence and location of a single ionized atom with high precision and selectivity. Detection within the active volume of a xenon gas Time Projection Chamber operating at high pressure would be automatic, and with a capability for redundant confirmation.

[High-performance liquid-liquid chromatography in beverage analysis].

PubMed

Bricout, J; Koziet, Y; de Carpentrie, B

1978-01-01

Liquid liquid chromatography was performed with columns packed with stationary phases chemically bonded to silica microparticules. These columns show a high efficiency and are used very easily. Flavouring compounds like aromatic aldehydes which have a low volatility were analyzed in brandy using a polar phase alkylnitrile. Sapid substances like amarogentin in Gentiana lutea or glyryrrhizin in Glycyrrhiza glabra were determined by reversed phase chromatography. Finally ionizable substances like synthetic dyes can be analyzed by paired ion chromatography witha non polar stationary phase.

Commentary: Ethical Issues of Current Health-Protection Policies on Low-Dose Ionizing Radiation

PubMed Central

Socol, Yehoshua; Dobrzyński, Ludwik; Doss, Mohan; Feinendegen, Ludwig E.; Janiak, Marek K.; Miller, Mark L.; Sanders, Charles L.; Scott, Bobby R.; Ulsh, Brant; Vaiserman, Alexander

2014-01-01

The linear no-threshold (LNT) model of ionizing-radiation-induced cancer is based on the assumption that every radiation dose increment constitutes increased cancer risk for humans. The risk is hypothesized to increase linearly as the total dose increases. While this model is the basis for radiation safety regulations, its scientific validity has been questioned and debated for many decades. The recent memorandum of the International Commission on Radiological Protection admits that the LNT-model predictions at low doses are “speculative, unproven, undetectable and ‘phantom’.” Moreover, numerous experimental, ecological, and epidemiological studies show that low doses of sparsely-ionizing or sparsely-ionizing plus highly-ionizing radiation may be beneficial to human health (hormesis/adaptive response). The present LNT-model-based regulations impose excessive costs on the society. For example, the median-cost medical program is 5000 times more cost-efficient in saving lives than controlling radiation emissions. There are also lives lost: e.g., following Fukushima accident, more than 1000 disaster-related yet non-radiogenic premature deaths were officially registered among the population evacuated due to radiation concerns. Additional negative impacts of LNT-model-inspired radiophobia include: refusal of some patients to undergo potentially life-saving medical imaging; discouragement of the study of low-dose radiation therapies; motivation for radiological terrorism and promotion of nuclear proliferation. PMID:24910586

Optimizing the ionization and energy absorption of laser-irradiated clusters

NASA Astrophysics Data System (ADS)

Kundu, M.; Bauer, D.

2008-03-01

It is known that rare-gas or metal clusters absorb incident laser energy very efficiently. However, due to the intricate dependencies on all the laser and cluster parameters, it is difficult to predict under which circumstances ionization and energy absorption are optimal. With the help of three-dimensional particle-in-cell simulations of xenon clusters (up to 17256 atoms), it is shown that for a given laser pulse energy and cluster, an optimum wavelength exists that corresponds to the approximate wavelength of the transient, linear Mie-resonance of the ionizing cluster at an early stage of negligible expansion. In a single ultrashort laser pulse, the linear resonance at this optimum wavelength yields much higher absorption efficiency than in the conventional, dual-pulse pump-probe setup of linear resonance during cluster expansion.

Measurement of the ionization produced by sub-keV silicon nuclear recoils in a CCD dark matter detector

DOE PAGES

Chavarria, A. E.; Collar, J. I.; Peña, J. R.; ...

2016-10-15

We report a measurement of the ionization efficiency of silicon nuclei recoiling with sub-keV kinetic energy in the bulk silicon of a charge-coupled device (CCD). Nuclear recoils are produced by low-energy neutrons (<24 keV) from a 124Sb– 9Be photoneutron source, and their ionization signal is measured down to 60 eV electron equivalent. This energy range, previously unexplored, is relevant for the detection of low-mass dark matter particles. The measured efficiency is found to deviate from the extrapolation to low energies of the Lindhard model. Furthermore, this measurement also demonstrates the sensitivity to nuclear recoils of CCDs employed by DAMIC, amore » dark matter direct detection experiment located in the SNOLAB underground laboratory.« less

Mass analyzer ``MASHA'' high temperature target and plasma ion source

NASA Astrophysics Data System (ADS)

Semchenkov, A. G.; Rassadov, D. N.; Bekhterev, V. V.; Bystrov, V. A.; Chizov, A. Yu.; Dmitriev, S. N.; Efremov, A. A.; Guljaev, A. V.; Kozulin, E. M.; Oganessian, Yu. Ts.; Starodub, G. Ya.; Voskresensky, V. M.; Bogomolov, S. L.; Paschenko, S. V.; Zelenak, A.; Tikhonov, V. I.

2004-05-01

A new separator and mass analyzer of super heavy atoms (MASHA) has been created at the FLNR JINR Dubna to separate and measure masses of nuclei and molecules with precision better than 10-3. First experiments with the FEBIAD plasma ion source have been done and give an efficiency of ionization of up to 20% for Kr with a low flow test leak (6 particle μA). We suppose a magnetic field optimization, using the additional electrode (einzel lens type) in the extracting system, and an improving of the vacuum conditions in order to increase the ion source efficiency.

Absorption and dissociative photoionization cross sections of NH3 from 80 to 1120 A

NASA Technical Reports Server (NTRS)

Samson, James A. R.; Haddad, G. N.; Kilcoyne, L. D.

1987-01-01

The total absorption, photoionization, and dissociative photoionization cross sections of ammonia have been measured from 80 to 1120 A. All possible fragment ions have been observed including doubly ionized ammonia. The absolute ionization efficiencies have also been measured in this spectral range. The appearance potentials of the fragment ions have been measured and are compared with the calculated appearance potentials derived from published heats of formation and ionization potentials of the fragments.

Cross sections for direct and dissociative ionization of NH3 and CS2 by electron impact

NASA Technical Reports Server (NTRS)

Rao, M. V. V. S.; Srivastava, S. K.

1991-01-01

A crossed electron beam-molecular beam collision geometry is used to measure cross sections for the production of positive ions by electron impact on NH3 and CS2. Ionization cross-section data for NH3 and the values of various cross sections are presented, as well as ionization efficiency curves for CS2. Considerable differences are found between the various results on NH3. The present values are close to the data of Djuric et al. (1981). The semiempirical calculations of Hare and Meath (1987) differ considerably in the absolute values of cross sections. Discrepancies were observed in comparisons of cross sections of other fragment ions resulting from the ionization and dissociate ionization of NH3.

Magnetic field configurations on thruster performance in accordance with ion beam characteristics in cylindrical Hall thruster plasmas

NASA Astrophysics Data System (ADS)

Kim, Holak; Choe, Wonho; Lim, Youbong; Lee, Seunghun; Park, Sanghoo

2017-03-01

Magnetic field configuration is critical in Hall thrusters for achieving high performance, particularly in thrust, specific impulse, efficiency, etc. Ion beam features are also significantly influenced by magnetic field configurations. In two typical magnetic field configurations (i.e., co-current and counter-current configurations) of a cylindrical Hall thruster, ion beam characteristics are compared in relation to multiply charged ions. Our study shows that the co-current configuration brings about high ion current (or low electron current), high ionization rate, and small plume angle that lead to high thruster performance.

Octanol/water partitioning simulation by RP-HPLC for structurally diverse acidic drugs: comparison of three columns in the presence and absence of n-octanol as the mobile phase additive.

PubMed

Giaginis, Costas; Theocharis, Stamatios; Tsantili-Kakoulidou, Anna

2013-12-01

The advantageous effect of n-octanol as a mobile phase additive for lipophilicity assessment of structurally diverse acidic drugs both in the neutral and ionized form was explored. Two RP C18 columns, ABZ+ and Aquasil, were used for the determination of logkw indices, and the results were compared with those previously reported on a base-deactivated silica column. At pH 2.5, the use of n-octanol-saturated buffer as the mobile phase aqueous component led to high-quality 1:1 correlation between logkw and logP for the ABZ+ column, while inferior statistics were obtained for Aquasil. At physiological pH, the correlations were significantly improved if strongly ionized acidic drugs were treated separately from weakly ionized ones. In the latter case, 1:1 correlations between logD7.4 and logkw(oct) indices were obtained in the presence of 0.25% n-octanol. Concerning strongly ionized compounds, adequate correlations were established under the same conditions; however, slopes were significantly lower than unity, while large negative intercepts were obtained. According to the absolute difference (diff = logD7.4 – logkw) pattern, base-deactivated silica showed a better performance than ABZ+, however, the latter seems more efficient for the lipophilicity assessment of highly lipophilic acidic compounds. Aquasil may be the column of choice if logD7.4<3 with the limitation, however, that very hydrophilic compounds cannot be measured.

Desorption atmospheric pressure photoionization and direct analysis in real time coupled with travelling wave ion mobility mass spectrometry.

PubMed

Räsänen, Riikka-Marjaana; Dwivedi, Prabha; Fernández, Facundo M; Kauppila, Tiina J

2014-11-15

Ambient mass spectrometry (MS) is a tool for screening analytes directly from sample surfaces. However, background impurities may complicate the spectra and therefore fast separation techniques are needed. Here, we demonstrate the use of travelling wave ion mobility spectrometry in a comparative study of two ambient MS techniques. Desorption atmospheric pressure photoionization (DAPPI) and direct analysis in real time (DART) were coupled with travelling wave ion mobility mass spectrometry (TWIM-MS) for highly selective surface analysis. The ionization efficiencies of DAPPI and DART were compared. Test compounds were: bisphenol A, benzo[a]pyrene, ranitidine, cortisol and α-tocopherol. DAPPI-MS and DART-TWIM-MS were also applied to the analysis of chloroquine from dried blood spots, and α-tocopherol from almond surface, and DAPPI-TWIM-MS was applied to analysis of pharmaceuticals and multivitamin tablets. DAPPI was approximately 100 times more sensitive than DART for bisphenol A and 10-20 times more sensitive for the other compounds. The limits of detection were between 30-290 and 330-8200 fmol for DAPPI and DART, respectively. Also, from the authentic samples, DAPPI ionized chloroquine and α-tocopherol more efficiently than DART. The mobility separation enabled the detection of species with low signal intensities, e.g. thiamine and cholecalciferol, in the DAPPI-TWIM-MS analysis of multivitamin tablets. DAPPI ionized the studied compounds of interest more efficiently than DART. For both DAPPI and DART, the mobility separation prior to MS analysis reduced the amount of chemical noise in the mass spectrum and significantly increased the signal-to-noise ratio for the analytes. Copyright © 2014 John Wiley & Sons, Ltd.

Quantitative Profiling of Major Neutral Lipid Classes in Human Meibum by Direct Infusion Electrospray Ionization Mass Spectrometry

PubMed Central

Chen, Jianzhong; Green, Kari B.; Nichols, Kelly K.

2013-01-01

Purpose. The purpose of this investigation was to better understand lipid composition in human meibum. Methods. Intact lipids in meibum samples were detected by direct infusion electrospray ionization mass spectrometry (ESI-MS) analysis in positive detection mode using sodium iodide (NaI) as an additive. The peak intensities of all major types of lipid species, that is, wax esters (WEs), cholesteryl esters (CEs), and diesters (DEs) were corrected for peak overlapping and isotopic distribution; an additional ionization efficiency correction was performed for WEs and CEs, which was simplified by the observation that the corresponding ionization efficiency was primarily dependent on the specific lipid class and saturation degree of the lipids while independent of the carbon chain length. A set of WE and CE standards was spiked in meibum samples for ionization efficiency determination and absolute quantitation. Results. The absolute amount (μmol/mg) for each of 51 WEs and 31 CEs in meibum samples was determined. The summed masses for 51 WEs and 31 CEs accounted for 48 ± 4% and 40 ± 2%, respectively, of the total meibum lipids. The mass percentages of saturated and unsaturated species were determined to be 75 ± 2% and 25 ± 1% for CEs and 14 ± 1% and 86 ± 1% for WEs. The profiles for two types of DEs were also obtained, which include 42 α,ω Type II DEs, and 21 ω Type I-St DEs. Conclusions. Major neutral lipid classes in meibum samples were quantitatively profiled by ESI-MS analysis with NaI additive. PMID:23847307

Topological signature in the NEXT high pressure xenon TPC

NASA Astrophysics Data System (ADS)

Ferrario, Paola; NEXT Collaboration

2017-09-01

The NEXT experiment aims to observe the neutrinoless double beta decay of 136Xe in a high-pressure xenon gas TPC using electroluminescence to amplify the signal from ionization. One of the main advantages of this technology is the possibility to use the topology of events with energies close to Qββ as an extra tool to reject background. In these proceedings we show with data from prototypes that an extra background rejection factor of 24.3 ± 1.4 (stat.)% can be achieved, while maintaining an efficiency of 66.7 ± 1.% for signal events. The performance expected in NEW, the next stage of the experiment, is to improve to 12.9% ± 0.6% background acceptance for 66.9% ± 0.6% signal efficiency.

Ultraviolet surprise: Efficient soft x-ray high-harmonic generation in multiply ionized plasmas.

PubMed

Popmintchev, Dimitar; Hernández-García, Carlos; Dollar, Franklin; Mancuso, Christopher; Pérez-Hernández, Jose A; Chen, Ming-Chang; Hankla, Amelia; Gao, Xiaohui; Shim, Bonggu; Gaeta, Alexander L; Tarazkar, Maryam; Romanov, Dmitri A; Levis, Robert J; Gaffney, Jim A; Foord, Mark; Libby, Stephen B; Jaron-Becker, Agnieszka; Becker, Andreas; Plaja, Luis; Murnane, Margaret M; Kapteyn, Henry C; Popmintchev, Tenio

2015-12-04

High-harmonic generation is a universal response of matter to strong femtosecond laser fields, coherently upconverting light to much shorter wavelengths. Optimizing the conversion of laser light into soft x-rays typically demands a trade-off between two competing factors. Because of reduced quantum diffusion of the radiating electron wave function, the emission from each species is highest when a short-wavelength ultraviolet driving laser is used. However, phase matching--the constructive addition of x-ray waves from a large number of atoms--favors longer-wavelength mid-infrared lasers. We identified a regime of high-harmonic generation driven by 40-cycle ultraviolet lasers in waveguides that can generate bright beams in the soft x-ray region of the spectrum, up to photon energies of 280 electron volts. Surprisingly, the high ultraviolet refractive indices of both neutral atoms and ions enabled effective phase matching, even in a multiply ionized plasma. We observed harmonics with very narrow linewidths, while calculations show that the x-rays emerge as nearly time-bandwidth-limited pulse trains of ~100 attoseconds. Copyright © 2015, American Association for the Advancement of Science.

The Ultraviolet Surprise. Efficient Soft X-Ray High Harmonic Generation in Multiply-Ionized Plasmas

DOE PAGES

Popmintchev, Dimitar; Hernandez-Garcia, Carlos; Dollar, Franklin; ...

2015-12-04

High-harmonic generation is a universal response of matter to strong femtosecond laser fields, coherently upconverting light to much shorter wavelengths. Optimizing the conversion of laser light into soft x-rays typically demands a trade-off between two competing factors. Reduced quantum diffusion of the radiating electron wave function results in emission from each species which is highest when a short-wavelength ultraviolet driving laser is used. But, phase matching—the constructive addition of x-ray waves from a large number of atoms—favors longer-wavelength mid-infrared lasers. We identified a regime of high-harmonic generation driven by 40-cycle ultraviolet lasers in waveguides that can generate bright beams inmore » the soft x-ray region of the spectrum, up to photon energies of 280 electron volts. Surprisingly, the high ultraviolet refractive indices of both neutral atoms and ions enabled effective phase matching, even in a multiply ionized plasma. We observed harmonics with very narrow linewidths, while calculations show that the x-rays emerge as nearly time-bandwidth–limited pulse trains of ~100 attoseconds.« less

Multiply charged ion generation according to magnetic field configurations in Hall thruster plasmas

NASA Astrophysics Data System (ADS)

Kim, Holak; Lee, Seunghun; Kim, Junbum; Lim, Youbong; Choe, Wonho; KIMS Collaboration

2016-09-01

Plasma propulsion is the most promising techniques to operate satellites for low earth orbit as well as deep space exploration. A typical plasma propulsion system is Hall thruster (HT) that uses crossed electromagnetic fields to ionize a propellant gas and to accelerate the ionized gas. In HT the tailoring of magnetic fields is significant due to that the electron confinement in the electromagnetic fields affects thruster performances such as thrust force, specific impulse, power efficiency, and life time. We designed an anode layer HT (TAL) with the magnetic field tailoring. The TAL is possible to keep discharge in 1 2 kilovolts, which voltage is useful to obtain high specific impulse The magnetic field tailoring is adapted to minimize undesirable heat dissipations and secondary electron emissions at a wall surrounding plasma In presentation, we will report TAL performances including thrust force, specific impulse, and anode efficiency measured by a pendulum thrust stand. This mechanical measurement will be compared to the plasma diagnostics conducted by angular Faraday probe, retarding potential analyzer, and ExB probe Grant No. 2014M1A3A3A02034510.

Bismuth- and lithium-loaded plastic scintillators for gamma and neutron detection (Conference Presentation)

NASA Astrophysics Data System (ADS)

Martinez, H. Paul; Cherepy, Nerine J.; Sanner, Robert D.; Beck, Patrick R.; Swanberg, Eric L.; Payne, Stephen A.

2016-09-01

Plastic scintillators are widely deployed for ionizing radiation detection, as they can be fabricated in large sizes, for high detection efficiency. However commercial plastics are limited in use for gamma spectroscopy, since their photopeak is too weak, due to low Z, and they are also limited in use for neutron detection, since proton recoils are indistinguishable from other ionizing radiation absorption events in standard plastics. We are working on scale up and production of transparent plastic scintillators based on polystyrene (PS) with high loading of bismuth metallorganics for gamma spectroscopy, and with lithium metallorganics for neutron detection. When activated with standard organic fluors, PS scintillators containing 8 wt% bismuth provide energy resolution of 11% at 662 keV. A PS plastic formulation including 1.3 wt% lithium-6 provides a neutron capture peak at 525 keVee, with 11% resolution for the capture peak and 90% efficiency for thermal neutron capture in 2mm thickness. Acknowledgements This work was performed under the auspices of the U.S. DOE by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344, and has been supported by the US DOE National Nuclear Security Administration, Defense Nuclear Nonproliferation Research and Development under Contract No. DE-AC03-76SF00098

Determination of drugs and drug-like compounds in different samples with direct analysis in real time mass spectrometry.

PubMed

Chernetsova, Elena S; Morlock, Gertrud E

2011-01-01

Direct analysis in real time (DART), a relatively new ionization source for mass spectrometry, ionizes small-molecule components from different kinds of samples without any sample preparation and chromatographic separation. The current paper reviews the published data available on the determination of drugs and drug-like compounds in different matrices with DART-MS, including identification and quantitation issues. Parameters that affect ionization efficiency and mass spectra composition are also discussed. Copyright © 2011 Wiley Periodicals, Inc.

Multi-MW Closed Cycle MHD Nuclear Space Power Via Nonequilibrium He/Xe Working Plasma

NASA Technical Reports Server (NTRS)

Litchford, Ron J.; Harada, Nobuhiro

2011-01-01

Prospects for a low specific mass multi-megawatt nuclear space power plant were examined assuming closed cycle coupling of a high-temperature fission reactor with magnetohydrodynamic (MHD) energy conversion and utilization of a nonequilibrium helium/xenon frozen inert plasma (FIP). Critical evaluation of performance attributes and specific mass characteristics was based on a comprehensive systems analysis assuming a reactor operating temperature of 1800 K for a range of subsystem mass properties. Total plant efficiency was expected to be 55.2% including plasma pre-ionization power, and the effects of compressor stage number, regenerator efficiency and radiation cooler temperature on plant efficiency were assessed. Optimal specific mass characteristics were found to be dependent on overall power plant scale with 3 kg/kWe being potentially achievable at a net electrical power output of 1-MWe. This figure drops to less than 2 kg/kWe when power output exceeds 3 MWe. Key technical issues include identification of effective methods for non-equilibrium pre-ionization and achievement of frozen inert plasma conditions within the MHD generator channel. A three-phase research and development strategy is proposed encompassing Phase-I Proof of Principle Experiments, a Phase-II Subscale Power Generation Experiment, and a Phase-III Closed-Loop Prototypical Laboratory Demonstration Test.

Modeling of plasma chemical processes in the artificial ionized layer in the upper atmosphere by the nanosecond corona discharge

NASA Astrophysics Data System (ADS)

Vikharev, A. L.; Gorbachev, A. M.; Ivanov, O. A.; Kolisko, A. L.; Litvak, A. G.

1993-08-01

The plasma chemical processes in the corona discharge formed in air by a series of high voltage pulses of nanosecond duration are investigated experimentally. The experimental conditions (reduced electric field, duration and repetition frequency of the pulses, gas pressure in the chamber) modeled the regime of creation of the artificial ionized layer (AIL) in the upper atmosphere by a nanosecond microwave discharge. It was found that in a nanosecond microwave discharge predominantly generation of ozone occurs, and that the production of nitrogen dioxide is not large. The energy expenditures for the generation of one O 3 molecule were about 15 eV. On the basis of the experimental results the prognosis of the efficiency of ozone generation in AIL was made.

Using microwave heating to improve the desorption efficiency of high molecular weight VOC from beaded activated carbon.

PubMed

Fayaz, Mohammadreza; Shariaty, Pooya; Atkinson, John D; Hashisho, Zaher; Phillips, John H; Anderson, James E; Nichols, Mark

2015-04-07

Incomplete regeneration of activated carbon loaded with organic compounds results in heel build-up that reduces the useful life of the adsorbent. In this study, microwave heating was tested as a regeneration method for beaded activated carbon (BAC) loaded with n-dodecane, a high molecular weight volatile organic compound. Energy consumption and desorption efficiency for microwave-heating regeneration were compared with conductive-heating regeneration. The minimum energy needed to completely regenerate the adsorbent (100% desorption efficiency) using microwave regeneration was 6% of that needed with conductive heating regeneration, owing to more rapid heating rates and lower heat loss. Analyses of adsorbent pore size distribution and surface chemistry confirmed that neither heating method altered the physical/chemical properties of the BAC. Additionally, gas chromatography (with flame ionization detector) confirmed that neither regeneration method detectably altered the adsorbate composition during desorption. By demonstrating improvements in energy consumption and desorption efficiency and showing stable adsorbate and adsorbent properties, this paper suggests that microwave heating is an attractive method for activated carbon regeneration particularly when high-affinity VOC adsorbates are present.

Study of solid-conversion gaseous detector based on GEM for high energy X-ray industrial CT.

PubMed

Zhou, Rifeng; Zhou, Yaling

2014-01-01

The general gaseous ionization detectors are not suitable for high energy X-ray industrial computed tomography (HEICT) because of their inherent limitations, especially low detective efficiency and large volume. The goal of this study was to investigate a new type of gaseous detector to solve these problems. The novel detector was made by a metal foil as X-ray convertor to improve the conversion efficiency, and the Gas Electron Multiplier (hereinafter "GEM") was used as electron amplifier to lessen its volume. The detective mechanism and signal formation of the detector was discussed in detail. The conversion efficiency was calculated by using EGSnrc Monte Carlo code, and the transport course of photon and secondary electron avalanche in the detector was simulated with the Maxwell and Garfield codes. The result indicated that this detector has higher conversion efficiency as well as less volume. Theoretically this kind of detector could be a perfect candidate for replacing the conventional detector in HEICT.

Localized traveling ionization zones and their importance for the high power impulse magnetron sputtering process

NASA Astrophysics Data System (ADS)

Maszl, Christian

2016-09-01

High power impulse magnetron sputtering (HiPIMS) is a technique to deposit thin films with superior quality. A high ionization degree up to 90% and the natural occurence of high energetic metal ions are the reason why HiPIMS exceeds direct current magnetron sputtering in terms of coating quality. On the other hand HiPIMS suffers from a reduced efficiency, especially if metal films are produced. Therefore, a lot of research is done by experimentalists and theoreticians to clarify the transport mechanisms from target to substrate and to identify the energy source of the energetic metal ions. Magnetron plasmas are prone to a wide range of wave phenomena and instabilities. Especially, during HiPIMS at elevated power/current densities, symmetry breaks and self-organization in the plasma torus are observed. In this scenario localized travelling ionization zones with certain quasi-mode numbers are present which are commonly referred to as spokes. Because of their high rotation speed compared to typical process times of minutes their importance for thin film deposition was underestimated at first. Recent investigations show that spokes have a strong impact on particle transport, are probably the source of the high energetic metal ions and are therefore the essence of HiPIMS plasmas. In this contribution we will describe the current understanding of spokes, discuss implications for thin film synthesis and highlight open questions. This project is supported by the DFG (German Science Foundation) within the framework of the Coordinated Research Center SFB-TR 87 and the Research Department ``Plasmas with Complex Interactions'' at Ruhr-University Bochum.

A rapid and sensitive method for the simultaneous analysis of aliphatic and polar molecules containing free carboxyl groups in plant extracts by LC-MS/MS

PubMed Central

2009-01-01

Background Aliphatic molecules containing free carboxyl groups are important intermediates in many metabolic and signalling reactions, however, they accumulate to low levels in tissues and are not efficiently ionized by electrospray ionization (ESI) compared to more polar substances. Quantification of aliphatic molecules becomes therefore difficult when small amounts of tissue are available for analysis. Traditional methods for analysis of these molecules require purification or enrichment steps, which are onerous when multiple samples need to be analyzed. In contrast to aliphatic molecules, more polar substances containing free carboxyl groups such as some phytohormones are efficiently ionized by ESI and suitable for analysis by LC-MS/MS. Thus, the development of a method with which aliphatic and polar molecules -which their unmodified forms differ dramatically in their efficiencies of ionization by ESI- can be simultaneously detected with similar sensitivities would substantially simplify the analysis of complex biological matrices. Results A simple, rapid, specific and sensitive method for the simultaneous detection and quantification of free aliphatic molecules (e.g., free fatty acids (FFA)) and small polar molecules (e.g., jasmonic acid (JA), salicylic acid (SA)) containing free carboxyl groups by direct derivatization of leaf extracts with Picolinyl reagent followed by LC-MS/MS analysis is presented. The presence of the N atom in the esterified pyridine moiety allowed the efficient ionization of 25 compounds tested irrespective of their chemical structure. The method was validated by comparing the results obtained after analysis of Nicotiana attenuata leaf material with previously described analytical methods. Conclusion The method presented was used to detect 16 compounds in leaf extracts of N. attenuata plants. Importantly, the method can be adapted based on the specific analytes of interest with the only consideration that the molecules must contain at least one free carboxyl group. PMID:19939243

Extending semi-numeric reionization models to the first stars and galaxies

NASA Astrophysics Data System (ADS)

Koh, Daegene; Wise, John H.

2018-03-01

Semi-numeric methods have made it possible to efficiently model the epoch of reionization (EoR). While most implementations involve a reduction to a simple three-parameter model, we introduce a new mass-dependent ionizing efficiency parameter that folds in physical parameters that are constrained by the latest numerical simulations. This new parametrization enables the effective modelling of a broad range of host halo masses containing ionizing sources, extending from the smallest Population III host haloes with M ˜ 106 M⊙, which are often ignored, to the rarest cosmic peaks with M ˜ 1012 M⊙ during EoR. We compare the resulting ionizing histories with a typical three-parameter model and also compare with the latest constraints from the Planck mission. Our model results in an optical depth due to Thomson scattering, τe = 0.057, that is consistent with Planck. The largest difference in our model is shown in the resulting bubble size distributions that peak at lower characteristic sizes and are broadened. We also consider the uncertainties of the various physical parameters, and comparing the resulting ionizing histories broadly disfavours a small contribution from galaxies. The smallest haloes cease a meaningful contribution to the ionizing photon budget after z = 10, implying that they play a role in determining the start of EoR and little else.

An evaluation of krypton propellant in Hall thrusters

NASA Astrophysics Data System (ADS)

Linnell, Jesse Allen

Due to its high specific impulse and low price, krypton has long sparked interest as an alternate Hall thruster propellant. Unfortunately at the moment, krypton's relatively poor performance precludes it as a legitimate option. This thesis presents a detailed investigation into krypton operation in Hall thrusters. These findings suggest that the performance gap can be decreased to 4% and krypton can finally become a realistic propellant option. Although krypton has demonstrated superior specific impulse, the xenon-krypton absolute efficiency gap ranges between 2 and 15%. A phenomenological performance model indicates that the main contributors to the efficiency gap are propellant utilization and beam divergence. Propellant utilization and beam divergence have relative efficiency deficits of 5 and 8%, respectively. A detailed characterization of internal phenomena is conducted to better understand the xenon-krypton efficiency gap. Krypton's large beam divergence is found to be related to a defocusing equipotential structure and a weaker magnetic field topology. Ionization processes are shown to be linked to the Hall current, the magnetic mirror topology, and the perpendicular gradient of the magnetic field. Several thruster design and operational suggestions are made to optimize krypton efficiency. Krypton performance is optimized for discharge voltages above 500 V and flow rates corresponding to an a greater than 0.015 mg/(mm-s), where alpha is a function of flow rate and discharge channel dimensions (alpha = m˙alphab/Ach). Performance can be further improved by increasing channel length or decreasing channel width for a given flow rate. Also, several magnetic field design suggestions are made to enhance ionization and beam focusing. Several findings are presented that improve the understanding of general Hall thruster physics. Excellent agreement is shown between equipotential lines and magnetic field lines. The trim coil is shown to enhance beam focusing, ionization processes, and electron dynamics. Electron mobility and the Hall parameter are studied and compared to different mobility models. Azimuthal electron current is studied using a fluid and particle drift approach. Analyses of several magnetic field features are conducted and simple tools are suggested for the development of future Hall thrusters. These findings have strong implications for future Hall thruster design, lifetimes, and modeling.

Laser desorption ionization of small molecules assisted by tungsten oxide and rhenium oxide particles.

PubMed

Bernier, Matthew C; Wysocki, Vicki H; Dagan, Shai

2015-07-01

Inorganic metal oxides have shown potential as matrices for assisting in laser desorption ionization with advantages over the aromatic acids typically used. Rhenium and tungsten oxides are attractive options due to their high work functions and relative chemical inertness. In this work, it is shown that ReO3 and WO3 , in microparticle (μP) powder forms, can efficiently facilitate ionization of various types of small molecules and provide minimized background contamination at analyte concentrations below 1 ng/µL. This study shows that untreated inorganic WO3 and ReO3 particles are valid matrix options for detection of protonatable, radical, and precharged species under laser desorption ionization. Qualitatively, the WO3 μP showed improved detection of apigenin, sodiated glucose, and precharged analyte choline, while the ReO3 μP allowed better detection of protonated cocaine, quinuclidine, ametryn, and radical ions of polyaromatic hydrocarbons at detection levels as low as 50 pg/µL. For thermometer ion survival yield experiments, it was also shown that the ReO3 powder was significantly softer than α-cyano-4-hydroxycinnaminic acid. Furthermore, it provided higher intensities of cocaine and polyaromatic hydrocarbons, at laser flux values equal to those used with α-cyano-4-hydroxycinnaminic acid. Copyright © 2015 John Wiley & Sons, Ltd.

Toward advanced gamma rays radiation resistance and shielding efficiency with phthalonitrile resins and composites

NASA Astrophysics Data System (ADS)

Derradji, Mehdi; Zegaoui, Abdeldjalil; Xu, Yi-Le; Wang, An-ran; Dayo, Abdul Qadeer; Wang, Jun; Liu, Wen-bin; Liu, Yu-Guang; Khiari, Karim

2018-04-01

The phthalonitrile resins have claimed the leading place in the field of high performance polymers thanks to their combination of outstanding properties. The present work explores for the first time the gamma rays radiation resistance and shielding efficiency of the phthalonitrile resins and its related tungsten-reinforced nanocomposites. The primary goal of this research is to define the basic behavior of the phthalonitrile resins under highly ionizing gamma rays. The obtained results confirmed that the neat phthalonitrile resins can resist absorbed doses as high as 200 kGy. Meanwhile, the remarkable shielding efficiency of the phthalonitrile polymers was confirmed to be easily improved by preparing lead-free nanocomposites. In fact, the gamma rays screening ratio reached the exceptional value of 42% for the nanocomposites of 50 wt% of nano-tungsten loading. Thus, this study confirms that the remarkable performances of the phthalonitrile resins are not limited to the thermal and mechanical properties and can be extended to the gamma rays radiation and shielding resistances.

Evaluation of species-dependent detection efficiencies in the aerosol mass spectrometer

USDA-ARS?s Scientific Manuscript database

Mass concentrations of chemical species calculated from the aerosol mass spectrometer (AMS) depend on two factors: particle collection efficiency (CE) and relative ionization efficiency (RIE, relative to the primary calibrant ammonium nitrate). While previous studies have characterized CE, RIE is re...

Carbon Nanotube Fiber Ionization Mass Spectrometry: A Fundamental Study of a Multi-Walled Carbon Nanotube Functionalized Corona Discharge Pin for Polycyclic Aromatic Hydrocarbons Analysis.

PubMed

Nahan, Keaton S; Alvarez, Noe; Shanov, Vesselin; Vonderheide, Anne

2017-11-01

Mass spectrometry continues to tackle many complicated tasks, and ongoing research seeks to simplify its instrumentation as well as sampling. The desorption electrospray ionization (DESI) source was the first ambient ionization source to function without extensive gas requirements and chromatography. Electrospray techniques generally have low efficiency for ionization of nonpolar analytes and some researchers have resorted to methods such as direct analysis in real time (DART) or desorption atmospheric pressure chemical ionization (DAPCI) for their analysis. In this work, a carbon nanotube fiber ionization (nanoCFI) source was developed and was found to be capable of solid phase microextraction (SPME) of nonpolar analytes as well as ionization and sampling similar to that of direct probe atmospheric pressure chemical ionization (DP-APCI). Conductivity and adsorption were maintained by utilizing a corona pin functionalized with a multi-walled carbon nanotube (MWCNT) thread. Quantitative work with the nanoCFI source with a designed corona discharge pin insert demonstrated linearity up to 0.97 (R 2 ) of three target PAHs with phenanthrene internal standard. Graphical Abstract ᅟ.

Carbon Nanotube Fiber Ionization Mass Spectrometry: A Fundamental Study of a Multi-Walled Carbon Nanotube Functionalized Corona Discharge Pin for Polycyclic Aromatic Hydrocarbons Analysis

NASA Astrophysics Data System (ADS)

Nahan, Keaton S.; Alvarez, Noe; Shanov, Vesselin; Vonderheide, Anne

2017-09-01

Mass spectrometry continues to tackle many complicated tasks, and ongoing research seeks to simplify its instrumentation as well as sampling. The desorption electrospray ionization (DESI) source was the first ambient ionization source to function without extensive gas requirements and chromatography. Electrospray techniques generally have low efficiency for ionization of nonpolar analytes and some researchers have resorted to methods such as direct analysis in real time (DART) or desorption atmospheric pressure chemical ionization (DAPCI) for their analysis. In this work, a carbon nanotube fiber ionization (nanoCFI) source was developed and was found to be capable of solid phase microextraction (SPME) of nonpolar analytes as well as ionization and sampling similar to that of direct probe atmospheric pressure chemical ionization (DP-APCI). Conductivity and adsorption were maintained by utilizing a corona pin functionalized with a multi-walled carbon nanotube (MWCNT) thread. Quantitative work with the nanoCFI source with a designed corona discharge pin insert demonstrated linearity up to 0.97 (R2) of three target PAHs with phenanthrene internal standard. [Figure not available: see fulltext.

Energy Conversion Alternatives Study (ECAS), Westinghouse phase 1. Volume 9: Closed-cycle MHD. [energy conversion efficiency of electric power plants using magnetohydrodynamics

NASA Technical Reports Server (NTRS)

Tsu, T. C.

1976-01-01

A closed-cycle MHD system for an electric power plant was studied. It consists of 3 interlocking loops, an external heating loop, a closed-cycle cesium seeded argon nonequilibrium ionization MHD loop, and a steam bottomer. A MHD duct maximum temperature of 2366 K (3800 F), a pressure of 0.939 MPa (9.27 atm) and a Mach number of 0.9 are found to give a topping cycle efficiency of 59.3%; however when combined with an integrated gasifier and optimistic steam bottomer the coal to bus bar efficiency drops to 45.5%. A 1978 K (3100 F) cycle has an efficiency of 55.1% and a power plant efficiency of 42.2%. The high cost of the external heating loop components results in a cost of electricity of 21.41 mills/MJ (77.07 mills/kWh) for the high temperature system and 19.0 mills/MJ (68.5 mills/kWh) for the lower temperature system. It is, therefore, thought that this cycle may be more applicable to internally heated systems such as some futuristic high temperature gas cooled reactor.

Ion Voltage Diagnostics in the Far-Field Plume of a High-Specific Impulse Hall Thruster

NASA Technical Reports Server (NTRS)

Hofer, Richard R.; Haas, James M.; Gallimore, Alec D.

2003-01-01

The effects of the magnetic field and discharge voltage on the far-field plume of the NASA 173Mv2 laboratory-model Hall thruster were investigated. A cylindrical Langmuir probe was used to measure the plasma potential and a retarding potential analyzer was employed to measure the ion voltage distribution. The plasma potential was affected by relatively small changes in the external magnetic field, which suggested a means to control the plasma surrounding the thruster. As the discharge voltage increased, the ion voltage distribution showed that the acceleration efficiency increased and the dispersion efficiency decreased. This implied that the ionization zone was growing axially and moving closer to the anode, which could have affected thruster efficiency and lifetime due to higher wall losses. However, wall losses may have been reduced by improved focusing efficiency since the total efficiency increased and the plume divergence decreased with discharge voltage.

Increasing Polyaromatic Hydrocarbon (PAH) Molecular Coverage during Fossil Oil Analysis by Combining Gas Chromatography and Atmospheric-Pressure Laser Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS)

PubMed Central

Benigni, Paolo; DeBord, J. Daniel; Thompson, Christopher J.; Gardinali, Piero; Fernandez-Lima, Francisco

2016-01-01

Thousands of chemically distinct compounds are encountered in fossil oil samples that require rapid screening and accurate identification. In the present paper, we show for the first time, the advantages of gas chromatography (GC) separation in combination with atmospheric-pressure laser ionization (APLI) and ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) for the screening of polyaromatic hydrocarbons (PAHs) in fossil oils. In particular, reference standards of organics in shale oil, petroleum crude oil, and heavy sweet crude oil were characterized by GC-APLI-FT-ICR MS and APLI-FT-ICR MS. Results showed that, while APLI increases the ionization efficiency of PAHs, when compared to other ionization sources, the complexity of the fossil oils reduces the probability of ionizing lower-concentration compounds during direct infusion. When gas chromatography precedes APLI-FT-ICR MS, an increase (more than 2-fold) in the ionization efficiency and an increase in the signal-to-noise ratio of lower-concentration fractions are observed, giving better molecular coverage in the m/z 100–450 range. That is, the use of GC prior to APLI-FT-ICR MS resulted in higher molecular coverage, higher sensitivity, and the ability to separate and characterize molecular isomers, while maintaining the ultrahigh resolution and mass accuracy of the FT-ICR MS separation. PMID:27212790

Signal enhancement of carboxylic acids by inclusion with β-cyclodextrin in negative high-voltage-assisted laser desorption ionization mass spectrometry.

PubMed

Ren, Xinxin; Liu, Jia; Zhang, Chengsen; Sun, Jiamu; Luo, Hai

2014-01-15

It is difficult to directly analyze carboxylic acids in complex mixtures by ambient high-voltage-assisted laser desorption ionization mass spectrometry (HALDI-MS) in negative ion mode due to the low ionization efficiency of carboxylic acids. A method for the rapid detection of carboxylic acids in negative HALDI-MS has been developed based on their inclusion with β-cyclodextrin (β-CD). The negative HALDI-MS signal-to-noise ratios (S/Ns) of aliphatic, aromatic and hetero atom-containing carboxylic acids can all be significantly improved by forming 1:1 complexes with β-CD. These complexes are mainly formed by specific inclusion interactions which are verified by their collision-induced dissociation behaviors in comparison with that of their corresponding maltoheptaose complexes. A HALDI-MS/MS method has been successfully developed for the detection of α-lipoic acid in complex cosmetics and ibuprofen in a viscous drug suspension. The negative HALDI-MS S/Ns of carboxylic acids can be improved up to 30 times via forming non-covalent complexes with β-CD. The developed method shows the advantages of being rapid and simple, and is promising for rapid detection of active ingredients in complex samples or fast screening of drugs and cosmetics. Copyright © 2013 John Wiley & Sons, Ltd.

Hydrodynamic and shock heating instabilities of liquid metal strippers for RIA

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

Hassanein, Ahmed

2013-05-24

Stripping of accelerated ions is a key problem for the design of RIA to obtain high efficiency. Thin liquid Lithium film flow is currently considered as stripper for RIA ion beams to obtain higher Z for following acceleration: in extreme case of Uranium from Z=29 to Z=60-70 (first stripper) and from Z=70 till full stripping Z=92 (second stripper). Ionization of ion occurs due to the interaction of the ion with electrons of target material (Lithium) with the loss of parts of the energy due to ionization, Q{sub U}, which is also accompanied with ionization energy losses, Q{sub Li} of themore » lithium. The resulting heat is so high that can be removed not by heat conduction but mainly by convection, i.e., flowing of liquid metal across beam spot area. The interaction of the beam with the liquid metal generates shock wave propagating along direction perpendicular to the beam as well as excites oscillations along beam direction. We studied the dynamics of these excited waves to determine conditions for film stability at the required velocities for heat removal. It will allow optimizing jet nozzle shapes and flow parameters to prevent film fragmentation and to ensure stable device operation.« less

KrF laser pumping by electron beam discharge

NASA Astrophysics Data System (ADS)

Bonnet, J.; Fournier, G.; Pigache, D.

1981-09-01

The pumping of excimer lasers used in nuclear fusion and isotope separation is considered. Homogeneous ionization with an electron beam permitted discharge pumping of a KrF laser with a discharge-energy/beam-energy ratio 5. This high value is obtained to the detriment of an energy density and an efficiency which are about half the best values obtained under other conditions. This result does not modify a recent conclusion indicating that an electron beam controlled discharge has no significant advantage over a pure electron beam as regards pumping high energy KrF lasers at high repetition rate.

A laser-based FAIMS detector for detection of ultra-low concentrations of explosives

NASA Astrophysics Data System (ADS)

Akmalov, Artem E.; Chistyakov, Alexander A.; Kotkovskii, Gennadii E.; Sychev, Alexey V.; Tugaenko, Anton V.; Bogdanov, Artem S.; Perederiy, Anatoly N.; Spitsyn, Eugene M.

2014-06-01

A non-contact method for analyzing of explosives traces from surfaces was developed. The method is based on the laser desorption of analyzed molecules from the surveyed surfaces followed by the laser ionization of air sample combined with the field asymmetric ion mobility spectrometry (FAIMS). The pulsed radiation of the fourth harmonic of a portable GSGG: Cr3+ :Nd3+ laser (λ = 266 nm) is used. The laser desorption FAIMS analyzer have been developed. The detection limit of the analyzer equals 40 pg for TNT. The results of detection of trinitrotoluene (TNT), cyclotrimethylenetrinitramine (RDX) and cyclotetramethylenetetranitramine (HMX) are presented. It is shown that laser desorption of nitro-compounds from metals is accompanied by their surface decomposition. A method for detecting and analyzing of small concentrations of explosives in air based on the laser ionization and the FAIMS was developed. The method includes a highly efficient multipass optical scheme of the intracavity fourthharmonic generation of pulsed laser radiation (λ = 266 nm) and the field asymmetric ion mobility (FAIM) spectrometer disposed within a resonator. The ions formation and detection proceed inside a resonant cavity. The laser ion source based on the multi-passage of radiation at λ = 266 nm through the ionization region was elaborated. On the basis of the method the laser FAIMS analyzer has been created. The analyzer provides efficient detection of low concentrations of nitro-compounds in air and shows a detection limit of 10-14 - 10-15 g/cm3 both for RDX and TNT.

Momentum and Heat Flux Measurements in the Exhaust of VASIMR Using Helium Propellant

NASA Technical Reports Server (NTRS)

Chavers, D. Gregory

2002-01-01

Electromagnetic thrusters typically use electric and magnetic fields to accelerate and exhaust plasma through interactions with the charged particles in the plasma. The energy required to create the plasma, i.e. ionization energy, is potential energy between the electron and ion. This potential energy is typically lost since it is not recovered as the plasma is exhausted and is known as frozen flow loss. If the frozen flow energy is a small fraction of the total plasma energy, this frozen flow loss may be negligible. However, if the frozen flow energy is a major fraction of the total plasma energy, this loss can severely reduce the energy efficiency of the thruster. Recovery and utilization of this frozen flow energy can improve the energy efficiency of a thruster during low specific impulse operating regimes when the ionization energy is a large fraction of the total plasma energy. This paper quantifies the recovery of the frozen flow energy, i.e. recombination energy, via the process of surface recombination for helium. To accomplish this task the momentum flux and heat flux of the plasma flow were measured and compared to calculated values from electrostatic probe data. This information was used to deduce the contribution of recombination energy to the total heat flux on a flat plate as well as to characterize the plasma conditions. Helium propellant was investigated initially due to its high ionization potential and hence available recombination energy.

Past Exposure to Densely Ionizing Radiation Leaves a Unique Permanent Signature in the Genome

PubMed Central

Hande, M. Prakash; Azizova, Tamara V.; Geard, Charles R.; Burak, Ludmilla E.; Mitchell, Catherine R.; Khokhryakov, Valentin F.; Vasilenko, Evgeny K.; Brenner, David J.

2003-01-01

Speculation has long surrounded the question of whether past exposure to ionizing radiation leaves a unique permanent signature in the genome. Intrachromosomal rearrangements or deletions are produced much more efficiently by densely ionizing radiation than by chemical mutagens, x-rays, or endogenous aging processes. Until recently, such stable intrachromosomal aberrations have been very hard to detect, but a new chromosome band painting technique has made their detection practical. We report the detection and quantification of stable intrachromosomal aberrations in lymphocytes of healthy former nuclear-weapons workers who were exposed to plutonium many years ago. Even many years after occupational exposure, more than half the blood cells of the healthy plutonium workers contain large (>6 Mb) intrachromosomal rearrangements. The yield of these aberrations was highly correlated with plutonium dose to the bone marrow. The control groups contained very few such intrachromosomal aberrations. Quantification of this large-scale chromosomal damage in human populations exposed many years earlier will lead to new insights into the mechanisms and risks of cytogenetic damage. PMID:12679897

Fragmentation of neutral amino acids and small peptides by intense, femtosecond laser pulses.

PubMed

Duffy, Martin J; Kelly, Orla; Calvert, Christopher R; King, Raymond B; Belshaw, Louise; Kelly, Thomas J; Costello, John T; Timson, David J; Bryan, William A; Kierspel, Thomas; Turcu, I C Edmond; Cacho, Cephise M; Springate, Emma; Williams, Ian D; Greenwood, Jason B

2013-09-01

High power femtosecond laser pulses have unique properties that could lead to their application as ionization or activation sources in mass spectrometry. By concentrating many photons into pulse lengths approaching the timescales associated with atomic motion, very strong electric field strengths are generated, which can efficiently ionize and fragment molecules without the need for resonant absorption. However, the complex interaction between these pulses and biomolecular species is not well understood. To address this issue, we have studied the interaction of intense, femtosecond pulses with a number of amino acids and small peptides. Unlike previous studies, we have used neutral forms of these molecular targets, which allowed us to investigate dissociation of radical cations without the spectra being complicated by the action of mobile protons. We found fragmentation was dominated by fast, radical-initiated dissociation close to the charge site generated by the initial ionization or from subsequent ultrafast migration of this charge. Fragments with lower yields, which are useful for structural determinations, were also observed and attributed to radical migration caused by hydrogen atom transfer within the molecule.

Development of a High-Throughput Microwave Imaging System for Concealed Weapons Detection

DTIC Science & Technology

2016-07-15

hardware. Index Terms—Microwave imaging, multistatic radar, Fast Fourier Transform (FFT). I. INTRODUCTION Near-field microwave imaging is a non-ionizing...configuration, but its computational demands are extreme. Fast Fourier Transform (FFT) imaging has long been used to efficiently construct images sampled with...Simulated image of 25 point scatterers imaged at range 1.5m, with array layout depicted in Fig. 3. Left: image formed with Equation (5) ( Fourier

Threshold ionization spectroscopic investigation of supersonic jet-cooled, laser-desorbed Tryptophan

NASA Astrophysics Data System (ADS)

Taherkhani, Mehran; Armentano, Antonio; Černý, Jiří; Müller-Dethlefs, Klaus

2016-07-01

Tryptophan (Trp) was studied by two-colour Photoionization Efficiency (PIE) and Mass Analysed Threshold Ionization (MATI) spectroscopy using a laser desorption apparatus. Conformer A of Trp was excited into the S1 state (34,878 cm-1) and the second laser was scanned around the D0 cation ground and the D1 excited state. No ionization signal into the D0 state could be found, but a clear threshold was observed for the D1 state with an ionization energy of 66,704 ± 3 cm-1 (8.27 eV). This observation is explained in terms of the electronic configurations of the S1 and cationic states.

Ionization of biomolecular targets by ion impact: input data for radiobiological applications

NASA Astrophysics Data System (ADS)

de Vera, Pablo; Abril, Isabel; Garcia-Molina, Rafael; Solov'yov, Andrey V.

2013-06-01

In this work we review and further develop a semiempirical model recently proposed for the ion impact ionization of complex biological media. The model is based on the dielectric formalism, and makes use of a semiempirical parametrization of the optical energy-loss function of bioorganic compounds, allowing the calculation of single and total ionization cross sections and related quantities for condensed biological targets, such as liquid water, DNA and its components, proteins, lipids, carbohydrates or cell constituents. The model shows a very good agreement with experimental data for water, adenine and uracil, and allows the comparison of the ionization efficiency of different biological targets, and also the average kinetic energy of the ejected secondary electrons.

Ionization imaging—A new method to search for 0- ν ββ decay

NASA Astrophysics Data System (ADS)

Chinowski, W.; Goldschmidt, A.; Nygren, D.; Bernstein, A.; Heffner, M.; Millaud, J.

2007-10-01

We present a new method to search for 0- ν ββ decay in 136Xe, the Ionization Imaging Chamber. This concept is based on 3-D track reconstruction by detection of ionization, without avalanche gain, in a novel time projection chamber (TPC) geometry. The rejection efficiency of external charged particle backgrounds is optimized by the realization of a maximal, fully active, closed, and ex post facto variable fiducial surface. Event localization within the fiducial volume and detailed event reconstruction mitigate external neutral particle backgrounds; larger detectors offer higher rejection efficiencies. Energy resolution at the Q-value of 2.5 MeV is expected to be better than 1% FWHM, reducing the potential impact of allowed 2- ν ββ decays. Scaling from ˜25 kg prototype to 1000+ kg target mass is graceful. A new possible methodology for the identification of the daughter barium nucleus is also described.

Application of flowerlike MgO for highly sensitive determination of lead via matrix-assisted laser desorption/ionization mass spectrometry.

PubMed

Hou, Jian; Chen, Suming; Cao, Changyan; Liu, Huihui; Xiong, Caiqiao; Zhang, Ning; He, Qing; Song, Weiguo; Nie, Zongxiu

2016-08-01

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) is a high-throughput method to achieve fast and accurate identification of lead (Pb) exposure, but is seldom used because of low ionization efficiency and insufficient sensitivity. Nanomaterials applied in MS are a promising technique to overcome the obstacles of MALDI. Flowerlike MgO nanostructures are applied for highly sensitive lead profiling in real samples. They can be used in two ways: (a) MgO is mixed with N-naphthylethylenediamine dihydrochloride (NEDC) as a novel matrix MgO/NEDC; (b) MgO is applied as an absorbent to enrich Pb ions in very dilute solution. The signal intensities of lead by MgO/NEDC were ten times higher than the NEDC matrix. It also shows superior anti-interference ability when analyzing 10 μmol/L Pb ions in the presence of organic substances or interfering metal ions. By applying MgO as adsorbent, the LOD of lead before enrichment is 1 nmol/L. Blood lead test can be achieved using this enrichment process. Besides, MgO can play the role of internal standard to achieve quantitative analysis. Flowerlike MgO nanostructures were applied for highly sensitive lead profiling in real samples. The method is helpful to prevent Pb contamination in a wide range. Further, the combination of MgO with MALDI MS could inspire more nanomaterials being applied in highly sensitive profiling of pollutants. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Investigation of a Light Gas Helicon Plasma Source for the VASIMR Space Propulsion System

NASA Technical Reports Server (NTRS)

Squire, J. P.; Chang-Diaz, F. R.; Jacobson, V. T.; Glover, T. W.; Baity, F. W.; Carter, M. D.; Goulding, R. H.; Bengtson, R. D.; Bering, E. A., III

2003-01-01

An efficient plasma source producing a high-density (approx.10(exp 19/cu m) light gas (e.g. H, D, or He) flowing plasma with a high degree of ionization is a critical component of the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) concept. We are developing an antenna to apply ICRF power near the fundamental ion cyclotron resonance to further accelerate the plasma ions to velocities appropriate for space propulsion applications. The high degree of ionization and a low vacuum background pressure are important to eliminate the problem of radial losses due to charge exchange. We have performed parametric (e.g. gas flow, power (0.5 - 3 kW), magnetic field , frequency (25 and 50 MHz)) studies of a helicon operating with gas (H2 D2, He, N2 and Ar) injected at one end with a high magnetic mirror downstream of the antenna. We have explored operation with a cusp and a mirror field upstream. Plasma flows into a low background vacuum (<10(exp -4) torr) at velocities higher than the ion sound speed. High densities (approx. 10(exp 19/cu m) have been achieved at the location where ICRF will be applied, just downstream of the magnetic mirror.

Comparison of free radicals formation induced by cold atmospheric plasma, ultrasound, and ionizing radiation.

PubMed

Rehman, Mati Ur; Jawaid, Paras; Uchiyama, Hidefumi; Kondo, Takashi

2016-09-01

Plasma medicine is increasingly recognized interdisciplinary field combining engineering, physics, biochemistry and life sciences. Plasma is classified into two categories based on the temperature applied, namely "thermal" and "non-thermal" (i.e., cold atmospheric plasma). Non-thermal or cold atmospheric plasma (CAP) is produced by applying high voltage electric field at low pressures and power. The chemical effects of cold atmospheric plasma in aqueous solution are attributed to high voltage discharge and gas flow, which is transported rapidly on the liquid surface. The argon-cold atmospheric plasma (Ar-CAP) induces efficient reactive oxygen species (ROS) in aqueous solutions without thermal decomposition. Their formation has been confirmed by electron paramagnetic resonance (EPR) spin trapping, which is reviewed here. The similarities and differences between the plasma chemistry, sonochemistry, and radiation chemistry are explained. Further, the evidence for free radical formation in the liquid phase and their role in the biological effects induced by cold atmospheric plasma, ultrasound and ionizing radiation are discussed. Copyright © 2016 Elsevier Inc. All rights reserved.

Dissolution and ionization of sodium superoxide in sodium–oxygen batteries

PubMed Central

Kim, Jinsoo; Park, Hyeokjun; Lee, Byungju; Seong, Won Mo; Lim, Hee-Dae; Bae, Youngjoon; Kim, Haegyeom; Kim, Won Keun; Ryu, Kyoung Han; Kang, Kisuk

2016-01-01

With the demand for high-energy-storage devices, the rechargeable metal–oxygen battery has attracted attention recently. Sodium–oxygen batteries have been regarded as the most promising candidates because of their lower-charge overpotential compared with that of lithium–oxygen system. However, conflicting observations with different discharge products have inhibited the understanding of precise reactions in the battery. Here we demonstrate that the competition between the electrochemical and chemical reactions in sodium–oxygen batteries leads to the dissolution and ionization of sodium superoxide, liberating superoxide anion and triggering the formation of sodium peroxide dihydrate (Na2O2·2H2O). On the formation of Na2O2·2H2O, the charge overpotential of sodium–oxygen cells significantly increases. This verification addresses the origin of conflicting discharge products and overpotentials observed in sodium–oxygen systems. Our proposed model provides guidelines to help direct the reactions in sodium–oxygen batteries to achieve high efficiency and rechargeability. PMID:26892931

Dissolution and ionization of sodium superoxide in sodium-oxygen batteries.

PubMed

Kim, Jinsoo; Park, Hyeokjun; Lee, Byungju; Seong, Won Mo; Lim, Hee-Dae; Bae, Youngjoon; Kim, Haegyeom; Kim, Won Keun; Ryu, Kyoung Han; Kang, Kisuk

2016-02-19

With the demand for high-energy-storage devices, the rechargeable metal-oxygen battery has attracted attention recently. Sodium-oxygen batteries have been regarded as the most promising candidates because of their lower-charge overpotential compared with that of lithium-oxygen system. However, conflicting observations with different discharge products have inhibited the understanding of precise reactions in the battery. Here we demonstrate that the competition between the electrochemical and chemical reactions in sodium-oxygen batteries leads to the dissolution and ionization of sodium superoxide, liberating superoxide anion and triggering the formation of sodium peroxide dihydrate (Na2O2·2H2O). On the formation of Na2O2·2H2O, the charge overpotential of sodium-oxygen cells significantly increases. This verification addresses the origin of conflicting discharge products and overpotentials observed in sodium-oxygen systems. Our proposed model provides guidelines to help direct the reactions in sodium-oxygen batteries to achieve high efficiency and rechargeability.

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

Phipps, Arran T.J.

Determining the composition of dark matter is at the forefront of modern scientific research. There is compelling evidence for the existence of vast quantities of dark matter throughout the universe, however it has so-far eluded all direct detection efforts and its identity remains a mystery. Weakly interacting massive particles (WIMPs) are a favored dark matter candidate and have been the primary focus of direct detection for several decades. The Cryogenic Dark Matter Search (CDMS) has developed the Z-dependent Ionization and Phonon (ZIP) detector to search for such particles. Typically made from germanium, these detectors are capable of distinguishing between electromagneticmore » background and a putative WIMP signal through the simultaneous measurement of ionization and phonons produced by scattering events. CDMS has operated several arrays of these detectors at the Soudan Underground Laboratory (Soudan, MN, USA) resulting in many competitive (often world-leading) WIMP exclusion limits. This dissertation focuses on ionization collection in these detectors under the sub-Kelvin, low electric field, and high crystal purity conditions unique to CDMS. The design and performance of a fully cryogenic HEMT-based amplifier capable of achieving the SuperCDMS SNOLAB ionization energy resolution goal of 100 eVee is presented. The experimental apparatus which has been used to record electron and hole properties under CDMS conditions is described. Measurements of charge transport, trapping, and impact ionization as a function of electric field in two CDMS detectors are shown, and the ionization collection efficiency is determined. The data is used to predict the error in the nuclear recoil energy scale under both CDMSlite and iZIP operating modes. A two species, two state model is developed to describe how ionization collection and space charge generation in CDMS detectors are controlled by the presence of “overcharged” D- donor and A+ acceptor impurity states. The thermal stability of these states is exclusive to sub-Kelvin operation, explaining why ionization collection in CDMS detectors differs from similar semiconductor detectors operating at higher temperature. This work represents a solid foundation for the understanding ionization collection in CDMS detectors.« less

Derivatization reagents in liquid chromatography/electrospray ionization tandem mass spectrometry.

PubMed

Santa, Tomofumi

2011-01-01

Liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) is one of the most prominent analytical techniques owing to its inherent selectivity and sensitivity. In LC/ESI-MS/MS, chemical derivatization is often used to enhance the detection sensitivity. Derivatization improves the chromatographic separation, and enhances the mass spectrometric ionization efficiency and MS/MS detectability. In this review, an overview of the derivatization reagents which have been applied to LC/ESI-MS/MS is presented, focusing on the applications to low molecular weight compounds. 2010 John Wiley & Sons, Ltd.

Modelling massive star feedback with Monte Carlo radiation hydrodynamics: photoionization and radiation pressure in a turbulent cloud

NASA Astrophysics Data System (ADS)

Ali, Ahmad; Harries, Tim J.; Douglas, Thomas A.

2018-07-01

We simulate a self-gravitating, turbulent cloud of 1000 M⊙ with photoionization and radiation pressure feedback from a 34 M⊙ star. We use a detailed Monte Carlo radiative transfer scheme alongside the hydrodynamics to compute photoionization and thermal equilibrium with dust grains and multiple atomic species. Using these gas temperatures, dust temperatures, and ionization fractions, we produce self-consistent synthetic observations of line and continuum emission. We find that all material is dispersed from the (15.5 pc)3 grid within 1.6 Myr or 0.74 free-fall times. Mass exits with a peak flux of 2 × 10-3 M⊙ yr-1, showing efficient gas dispersal. The model without radiation pressure has a slight delay in the breakthrough of ionization, but overall its effects are negligible. 85 per cent of the volume, and 40 per cent of the mass, become ionized - dense filaments resist ionization and are swept up into spherical cores with pillars that point radially away from the ionizing star. We use free-free emission at 20 cm to estimate the production rate of ionizing photons. This is almost always underestimated: by a factor of a few at early stages, then by orders of magnitude as mass leaves the volume. We also test the ratio of dust continuum surface brightnesses at 450 and 850 µm to probe dust temperatures. This underestimates the actual temperature by more than a factor of 2 in areas of low column density or high line-of-sight temperature dispersion; the H II region cavity is particularly prone to this discrepancy. However, the probe is accurate in dense locations such as filaments.

Low- and high-LET radiation drives clonal expansion of lung progenitor cells in vivo

PubMed Central

Farin, Alicia M.; Manzo, Nicholas D.; Kirsch, David G.; Stripp, Barry R.

2015-01-01

Abundant populations of epithelial progenitor cells maintain the epithelium along the proximal-to-distal axis of the airway. Exposure of lung tissue to ionizing radiation leads to tissue remodeling and potential cancer initiation or progression. However, little is known about the effects of ionizing radiation on airway epithelial progenitor cells. We hypothesized that ionizing radiation exposure will alter the behavior of airway epithelial progenitor cells in a radiation dose- and quality-dependent manner. To address this hypothesis, we cultured primary airway epithelial cells isolated from mice exposed to various doses of 320 kVp X-ray or 600 MeV/nucleon 56Fe ions in a 3D epithelial-fibroblast co-culture system. Colony-forming efficiency of the airway epithelial progenitor cells was assessed at culture day 14. In vivo clonogenic and proliferative potentials of airway epithelial progenitor cells were measured after exposure to ionizing radiation by lineage tracing and IdU incorporation. Exposure to both X-rays and 56Fe resulted in a dose dependent decrease in the ability of epithelial progenitors to form colonies in vitro. In vivo evidence for increased clonogenic expansion of epithelial progenitors was observed after exposure to both X-rays and 56Fe. Interestingly, we found no significant increase in the epithelial proliferative index, indicating that ionizing radiation does not promote increased turnover of the airway epithelium. Therefore, we propose a model in which radiation induces a dose-dependent decrease in the pool of available progenitor cells, leaving fewer progenitors able to maintain the airway long-term. This work provides novel insights into the effects of ionizing radiation exposure on airway epithelial progenitor cell behavior. PMID:25564721

Modelling massive-star feedback with Monte Carlo radiation hydrodynamics: photoionization and radiation pressure in a turbulent cloud

NASA Astrophysics Data System (ADS)

Ali, Ahmad; Harries, Tim J.; Douglas, Thomas A.

2018-04-01

We simulate a self-gravitating, turbulent cloud of 1000M⊙ with photoionization and radiation pressure feedback from a 34M⊙ star. We use a detailed Monte Carlo radiative transfer scheme alongside the hydrodynamics to compute photoionization and thermal equilibrium with dust grains and multiple atomic species. Using these gas temperatures, dust temperatures, and ionization fractions, we produce self-consistent synthetic observations of line and continuum emission. We find that all material is dispersed from the (15.5pc)3 grid within 1.6Myr or 0.74 free-fall times. Mass exits with a peak flux of 2× 10-3M⊙yr-1, showing efficient gas dispersal. The model without radiation pressure has a slight delay in the breakthrough of ionization, but overall its effects are negligible. 85 per cent of the volume, and 40 per cent of the mass, become ionized - dense filaments resist ionization and are swept up into spherical cores with pillars that point radially away from the ionizing star. We use free-free emission at 20cm to estimate the production rate of ionizing photons. This is almost always underestimated: by a factor of a few at early stages, then by orders of magnitude as mass leaves the volume. We also test the ratio of dust continuum surface brightnesses at 450 and 850μ to probe dust temperatures. This underestimates the actual temperature by more than a factor of 2 in areas of low column density or high line-of-sight temperature dispersion; the HII region cavity is particularly prone to this discrepancy. However, the probe is accurate in dense locations such as filaments.

HV discharge acceleration by sequences of UV laser filaments with visible and near-infrared pulses

NASA Astrophysics Data System (ADS)

Schubert, Elise; Rastegari, Ali; Feng, Chengyong; Mongin, Denis; Kamer, Brian; Kasparian, Jérôme; Wolf, Jean-Pierre; Arissian, Ladan; Diels, Jean-Claude

2017-12-01

We investigate the triggering and guiding of DC high-voltage discharges over a distance of 37 cm by filaments produced by ultraviolet (266 nm) laser pulses of 200 ps duration. The latter reduce the breakdown electric field by half and allow up to 80% discharge probability in an electric field of 920 kV m–1. This high efficiency is not further increased by adding nanosecond pulses in the Joule range at 532 and at 1064 nm. However, the latter statistically increases the guiding length, thereby accelerating the discharge by a factor of 2. This effect is due both to photodetachment and to the heating of the plasma channel, that increases the efficiency of avalanche ionization and reduces electron attachment and recombination.

Ionization Waves of Arbitrary Velocity

NASA Astrophysics Data System (ADS)

Turnbull, D.; Franke, P.; Katz, J.; Palastro, J. P.; Begishev, I. A.; Boni, R.; Bromage, J.; Milder, A. L.; Shaw, J. L.; Froula, D. H.

2018-06-01

Flying focus is a technique that uses a chirped laser beam focused by a highly chromatic lens to produce an extended focal region within which the peak laser intensity can propagate at any velocity. When that intensity is high enough to ionize a background gas, an ionization wave will track the intensity isosurface corresponding to the ionization threshold. We report on the demonstration of such ionization waves of arbitrary velocity. Subluminal and superluminal ionization fronts were produced that propagated both forward and backward relative to the ionizing laser. All backward and all superluminal cases mitigated the issue of ionization-induced refraction that typically inhibits the formation of long, contiguous plasma channels.

Instantaneous and efficient surface wave excitation of a low pressure gas or gases

DOEpatents

Levy, Donald J.; Berman, Samuel M.

1988-01-01

A system for instantaneously ionizing and continuously delivering energy in the form of surface waves to a low pressure gas or mixture of low pressure gases, comprising a source of rf energy, a discharge container, (such as a fluorescent lamp discharge tube), an rf shield, and a coupling device responsive to rf energy from the source to couple rf energy directly and efficiently to the gas or mixture of gases to ionize at least a portion of the gas or gases and to provide energy to the gas or gases in the form of surface waves. The majority of the rf power is transferred to the gas or gases near the inner surface of the discharge container to efficiently transfer rf energy as excitation energy for at least one of the gases. The most important use of the invention is to provide more efficient fluorescent and/or ultraviolet lamps.

(E)-Propyl α-Cyano-4-Hydroxyl Cinnamylate: A High Sensitive and Salt Tolerant Matrix for Intact Protein Profiling by MALDI Mass Spectrometry

NASA Astrophysics Data System (ADS)

Wang, Sheng; Xiao, Zhaohui; Xiao, Chunsheng; Wang, Huixin; Wang, Bing; Li, Ying; Chen, Xuesi; Guo, Xinhua

2016-04-01

Low-abundance samples and salt interference are always of great challenges for the practical protein profiling by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Herein, a series of carboxyl-esterified derivatives of α-cyano-4-hydroxycinnamic acid (CHCA) were synthesized and evaluated as matrices for MALDI-MS analysis of protein. Among them, (E)-propyl α-cyano-4-hydroxyl cinnamylate (CHCA-C3) was found to exhibit excellent assay performance for intact proteins by improving the detection sensitivity 10 folds compared with the traditional matrices [i.e., super2,5-dihydroxybenzoic acid (superDHB), sinapic acid (SA), and CHCA]. In addition, CHCA-C3 was shown to have high tolerance to salts, the ion signal of myoglobin was readily detected even in the presence of urea (8 M), NH4HCO3 (2 M), and KH2PO4 (500 mM), meanwhile sample washability was robust. These achievements were mainly attributed to improved ablation ability and increased hydrophobicity or affinity of CHCA-C3 to proteins in comparison with hydrophilic matrixes, leading to more efficient ionization of analyte. Furthermore, direct analysis of proteins from crude egg white demonstrated that CHCA-C3 was a highly efficient matrix for the analysis of low-abundance proteins in complex biological samples. These outstanding performances indicate the tremendous potential use of CHCA-C3 in protein profiling by MALDI-MS.

Removal of nonylphenol from industrial sludge by using an electron beam

NASA Astrophysics Data System (ADS)

Choi, Jang-Seung; Park, Jun-Hyun; Kim, Yuri; Kim, JinKyu; Jung, SeungTae; Han, Bumsoo; Alkhuraiji, Turki S.

2016-09-01

Endocrine disrupting chemicals (EDCs) and potential EDCs are mostly man-made, found in various materials such as pesticides, additives or contaminants in food, and personal care products. EDCs have been suspected to be associated with altered reproductive function in males and females increased incidence of breast cancer, abnormal growth patterns and neuro-developmental delays in children and changes in immune function. A number of processes were investigated regarding their potential for removing of endocrine disrupters. Those processes are ferric chloride coagulation, powdered activated carbon, magnetic ion exchange combined with microfiltration or ultrafiltration, as well as nanofiltration, and reverse osmosis. They show some good removal of EDCs in aqueous solution, but do not show good efficiency when EDCs are in sludge. High energy ionizing radiation has the ability to remove the EDCs with a very high degree of reliability and in a clean and efficient manner. The ionizing radiation interacts with EDCs both directly and indirectly. Direct interaction takes place with EDCs, and the structure of EDCs is destroyed or changed. During indirect interaction, radiolysis products of water result in the formation of highly reactive intermediates which then react with the target molecules, culminating in structural changes. For confirmation of radiation reduction of EDCs in industrial sludge, a pilot scale experiment up to 50 kGy of electron beam was conducted with samples from the textile dyeing industries. The experimental result showed over a 90% reduction of nonylphenol (NP) at absorbed doses of around 10 kGy.

Joint neutron crystallographic and NMR solution studies of Tyr residue ionization and hydrogen bonding: Implications for enzyme-mediated proton transfer

DOE PAGES

Michalczyk, Ryszard; Unkefer, Clifford J.; Bacik, John -Paul; ...

2015-05-05

Proton transfer is a fundamental mechanism at the core of many enzyme-catalyzed reactions. It is also exquisitely sensitive to a number of factors, including pH, electrostatics, proper active-site geometry, and chemistry. Carbonic anhydrase has evolved a fast and efficient way to conduct protons through a combination of hydrophilic amino acid side chains that coordinate a highly ordered H-bonded water network. This study uses a powerful approach, combining NMR solution studies with neutron protein crystallography, to determine the effect of pH and divalent cations on key residues involved in proton transfer in human carbonic anhydrase. Lastly, the results have broad implicationsmore » for our understanding of proton transfer and how subtle changes in ionization and H-bonding interactions can modulate enzyme catalysis.« less

Solid-Phase Microextraction Coupled to Capillary Atmospheric Pressure Photoionization-Mass Spectrometry for Direct Analysis of Polar and Nonpolar Compounds.

PubMed

Mirabelli, Mario F; Zenobi, Renato

2018-04-17

A novel capillary ionization source based on atmospheric pressure photoionization (cAPPI) was developed and used for the direct interfacing between solid-phase microextraction (SPME) and mass spectrometry (MS). The efficiency of the source was evaluated for direct and dopant-assisted photoionization, analyzing both polar (e.g., triazines and organophosphorus pesticides) and nonpolar (polycyclic aromatic hydrocarbons, PAHs) compounds. The results show that the range of compound polarity, which can be addressed by direct SPME-MS can be substantially extended by using cAPPI, compared to other sensitive techniques like direct analysis in real time (DART) and dielectric barrier discharge ionization (DBDI). The new source delivers a very high sensitivity, down to sub parts-per-trillion (ppt), making it a viable alternative when compared to previously reported and less comprehensive direct approaches.

Propagation direction reversal of ionization zones in the transition between high and low current magnetron sputtering

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

School of Materials Science and Engineering, State Key Lab for Materials Processing and Die & Mold Technology, Huazhong University of Science and Technology, Wuhan 430074, China; Department of Physics, University of California Berkeley, Berkeley, California 94720, USA; Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA

2014-12-11

Past research has revealed the propagation of dense, asymmetric ionization zones in both high and low current magnetron discharges. Here we report about the direction reversal of ionization zone propagation as observed with fast cameras. At high currents, zones move in the E B direction with velocities of 103 to 104 m/s. However at lower currents, ionization zones are observed to move in the opposite, the -E B direction, with velocities ~;; 103 m/s. It is proposed that the direction reversal is associated with the local balance of ionization and supply of neutrals in the ionization zone.

A Corona Discharge Initiated Electrochemical Electrospray Ionization Technique

PubMed Central

Lloyd, John R.; Hess, Sonja

2009-01-01

We report here the development of a corona discharge (CD) initiated electrochemical (EC) electrospray ionization (ESI) technique using a standard electrospray ion source. This is a new ionization technique distinct from ESI, electrochemistry inherent to ESI, APCI, and techniques using hydroxyl radicals produced under atmospheric pressure conditions. By maximizing the observable CD at the tip of a stainless steel ESI capillary, efficient electrochemical oxidation of electrochemically active compounds is observed. For electrochemical oxidation to be observed, the ionization potential of the analyte must be lower than Fe. Ferrocene labeled compounds were chosen as the electrochemically active moiety. The electrochemical cell in the ESI source was robust and generated ions with selectivity according to the ionization potential of the analytes and up to zeptomolar sensitivity. Our results indicate that CD initiated electrochemical ionization has the potential to become a powerful technique to increase the dynamic range, sensitivity and selectivity of ESI experiments. Synopsis Using a standard ESI source a corona discharge initiated electrochemical ionization technique was established resulting from the electrochemistry occurring at the CD electrode surface. PMID:19747843

First results on Ge resonant laser photoionization in hollow cathode lamp

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

Scarpa, Daniele, E-mail: daniele.scarpa@lnl.infn.it; Andrighetto, Alberto; Barzakh, Anatoly

2016-02-15

In the framework of the research and development activities of the SPES project regarding the optimization of the radioactive beam production, a dedicated experimental study has been recently started in order to investigate the possibility of in-source ionization of germanium using a set of tunable dye lasers. Germanium is one of the beams to be accelerated by the SPES ISOL facility, which is under construction at Legnaro INFN Laboratories. The three-step, two color ionization schemes have been tested using a Ge hollow cathode lamp. The slow and the fast optogalvanic signals were detected and averaged by an oscilloscope as amore » proof of the laser ionization inside the lamp. As a result, several wavelength scans across the resonances of ionization schemes were collected with the fast optogalvanic signal. Some comparisons of ionization efficiency for different ionization schemes were made. Furthermore, saturation curves of the first excitation transitions have been obtained. This investigation method and the setup built in the laser laboratory of the SPES project can be applied for the photo-ionization scheme studies also for the other possible radioactive elements.« less

Spectroscopy of the UO+2 cation and the delayed ionization of UO2.

PubMed

Merritt, Jeremy M; Han, Jiande; Heaven, Michael C

2008-02-28

Vibronically resolved spectra for the UO+2 cation have been recorded using the pulsed field ionization zero electron kinetic energy (PFI-ZEKE) technique. For the ground state, long progressions in both the bending and symmetric stretch vibrations were observed. Bend and stretch progressions of the first electronically excited state were also observed, and the origin was found at an energy of 2678 cm(-1) above the ground state zero-point level. This observation is consistent with a recent theoretical prediction [Infante et al., J. Chem. Phys. 127, 124308 (2007)]. The ionization energy for UO2, derived from the PFI-ZEKE spectrum, namely, 6.127(1) eV, is in excellent agreement with the value obtained from an earlier photoionization efficiency measurement. Delayed ionization of UO2 in the gas phase has been reported previously [Han et al., J. Chem. Phys. 120, 5155 (2004)]. Here, we extend the characterization of the delayed ionization process by performing a quantitative study of the ionization rate as a function of the energy above the ionization threshold. The ionization rate was found to be 5 x 10(6) s(-1) at threshold, and increased linearly with increasing energy in the range investigated (0-1200 cm(-1)).

Matrix Assisted Ionization Vacuum (MAIV), a New Ionization Method for Biological Materials Analysis Using Mass Spectrometry*

PubMed Central

Inutan, Ellen D.; Trimpin, Sarah

2013-01-01

The introduction of electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) for the mass spectrometric analysis of peptides and proteins had a dramatic impact on biological science. We now report that a wide variety of compounds, including peptides, proteins, and protein complexes, are transported directly from a solid-state small molecule matrix to gas-phase ions when placed into the vacuum of a mass spectrometer without the use of high voltage, a laser, or added heat. This ionization process produces ions having charge states similar to ESI, making the method applicable for high performance mass spectrometers designed for atmospheric pressure ionization. We demonstrate highly sensitive ionization using intermediate pressure MALDI and modified ESI sources. This matrix and vacuum assisted soft ionization method is suitable for the direct surface analysis of biological materials, including tissue, via mass spectrometry. PMID:23242551

Evaluation of the influence of ionization states and spacers in the thermotropic phase behaviour of amino acid-based cationic lipids and the transfection efficiency of their assemblies.

PubMed

Sarker, Satya Ranjan; Arai, Satoshi; Murate, Motohide; Takahashi, Hiroshi; Takata, Masaki; Kobayashi, Toshihide; Takeoka, Shinji

2012-01-17

The influence of both the ionization states and the hydrocarbon chain spacer of a series of amino acid-based cationic lipids was evaluated in terms of gene delivery efficiency and cytotoxicity to the COS-7 cell line and compared with that of Lipofectamine 2000. We synthesized a series of amino acid-based cationic lipids with different ionization states (i.e., -NH(2), -NH(3)(+)Cl(-) or -NH(3)(+)TFA(-)) in the lysine head group and different hydrocarbon chain spacers (i.e., 0, 3, 5 or 7 carbon atoms) between the hydrophilic head group and hydrophobic moieties. In the 3-carbon series, the cationic assemblies formed a micellar structure in the presence of -NH(3)(+)Cl(-) and a vesicular structure both in the presence of -NH(2) and -NH(3)(+)TFA(-). Differential scanning calorimetry (DSC) data revealed a significantly lower (8.1°C) gel-to-liquid crystalline phase transition temperature for cationic assemblies bearing -NH(3)(+)TFA(-) when compared to their -NH(2) counterparts. Furthermore, the zeta potential of cationic assemblies having -NH(3)(+)TFA(-) in the hydrophilic head group was maximum followed by -NH(3)(+)Cl(-) and -NH(2) irrespective of their hydrocarbon chain spacer length. The gene delivery efficiency in relation to the ionization states of the hydrophilic head group was as follows: -NH(3)(+)TFA(-)>-NH(3)(+)Cl(-)>-NH(2). Copyright © 2011 Elsevier B.V. All rights reserved.

High-frequency, high-intensity photoionization

NASA Astrophysics Data System (ADS)

Reiss, H. R.

1996-02-01

Two analytical methods for computing ionization by high-frequency fields are compared. Predicted ionization rates compare well, but energy predictions for the onset of ionization differ radically. The difference is shown to arise from the use of a transformation in one of the methods that alters the zero from which energy is measured. This alteration leads to an apparent energy threshold for ionization that can, especially in the stabilization regime, differ strongly from the laboratory measurement. It is concluded that channel closings in intense-field ionization can occur at high as well as low frequencies. It is also found that the stabilization phenomenon at high frequencies, very prominent for hydrogen, is absent in a short-range potential.

Status of Pulsed Inductive Thruster Research

NASA Technical Reports Server (NTRS)

Hrbud, Ivana; LaPointe, Michael; Vondra, Robert; Lovberg, Ralph; Dailey, C. Lee; Schafer, Charles (Technical Monitor)

2002-01-01

The TRW Pulsed Inductive Thruster (PIT) is an electromagnetic propulsion system that can provide high thrust efficiency over a wide range of specific impulse values. In its basic form, the PIT consists of a flat spiral coil covered by a thin dielectric plate. A pulsed gas injection nozzle distributes a thin layer of gas propellant across the plate surface at the same time that a pulsed high current discharge is sent through the coil. The rising current creates a time varying magnetic field, which in turn induces a strong azimuthal electric field above the coil. The electric field ionizes the gas propellant and generates an azimuthal current flow in the resulting plasma. The current in the plasma and the current in the coil flow in opposite directions, providing a mutual repulsion that rapidly blows the ionized propellant away from the plate to provide thrust. The thrust and specific impulse can be tailored by adjusting the discharge power, pulse repetition rate, and propellant mass flow, and there is minimal if any erosion due to the electrodeless nature of the discharge. Prior single-shot experiment,; performed with a Diameter diameter version of the PIT at TRW demonstrated specific impulse values between 2,000 seconds and 8,000 seconds, with thruster efficiencies of about 52% for ammonia. This paper outlines current and planned activities to transition the single shot device into a multiple repetition rate thruster capable of supporting NASA strategic enterprise missions.

Fabrication of Nanostructured Mesoporous Germanium for Application in Laser Desorption Ionization Mass Spectrometry.

PubMed

Abdelmaksoud, Hazem H; Guinan, Taryn M; Voelcker, Nicolas H

2017-02-15

Surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) is a high-throughput analytical technique ideally suited for small-molecule detection from different bodily fluids (e.g., saliva, urine, and blood plasma). Many SALDI-MS substrates require complex fabrication processes and further surface modifications. Furthermore, some substrates show instability upon exposure to ambient conditions and need to be kept under special inert conditions. We have successfully optimized mesoporous germanium (meso-pGe) using bipolar electrochemical etching and efficiently applied meso-pGe as a SALDI-MS substrate for the detection of illicit drugs such as in the context of workplace, roadside, and antiaddictive drug compliance. Argon plasma treatment improved the meso-pGe efficiency as a SALDI-MS substrate and eliminated the need for surface functionalization. The resulting substrate showed a precise surface geometry tuning by altering the etching parameters, and an outstanding performance for illicit drug detection with a limit of detection in Milli-Q water of 1.7 ng/mL and in spiked saliva as low as 5.3 ng/mL for cocaine. The meso-pGe substrate had a demonstrated stability over 56 days stored in ambient conditions. This proof-of-principle study demonstrates that meso-pGe can be reproducibly fabricated and applied as an analytical SALDI-MS substrate which opens the door for further analytical and forensic high-throughput applications.

Palladium modified porous silicon as multi-functional MALDI chip for serum peptide detection.

PubMed

Li, Xiao; Chen, Xiaoming; Tan, Jie; Liang, Xiao; Wu, Jianmin

2017-02-14

Interest in using mesoporous materials for peptidomic research has increased recently. The present study reports a new type of matrix assisted laser desorption/ionization (MALDI) plate derived from electrochemically etched porous silicon (PSi) whose surface was modified with palladium nanoparticles (PdNPs). Owing to the well-tailored pore size and the molecular filtration effect of the PSi, peptides in serum samples can be selectively captured and enriched in the pore channel, thereby eliminating the interference from large proteins in subsequent MALDI-MS detection. On the other hand, the PdNPs with localized surface plasmon resonance (LSPR) effect can help to enhance the efficiency of energy absorption in the UV region. Meanwhile, the charge separation effect between the PSi semiconductor and PdNPs also can be applied to promote the accumulation of positive charges on PdNPs, resulting in an improvement in laser desorption/ionization (LDI) efficiency under positive linear detection mode. The interplay among these unique properties of PSi and PdNPs can synergistically increase the overall sensitivity in serum peptide detection. Using this technology, serum sample can be directly detected on the PSi-PdNPs chip without complicated pretreatment process. Therefore, a high fidelity serum peptide fingerprint can be acquired in a high throughput way. With the assistance of statistical analysis, colorectal cancer patients and healthy people can be accurately distinguished based on the serum peptide fingerprints.

Pulsed discharges produced by high-power surface waves

NASA Astrophysics Data System (ADS)

Böhle, A.; Ivanov, O.; Kolisko, A.; Kortshagen, U.; Schlüter, H.; Vikharev, A.

1996-02-01

The mechanisms of the ionization front advance in surface-wave-produced discharges are investigated using two experimental set-ups. The high-power surface waves are excited in a 3 cm wavelength band by a surfaguide and a novel type of launcher (an E-plane junction). The ionization front velocity of the surface wave is measured for a wide range of gas pressures, incident microwave power and initial pre-ionization. The experimental results are compared with theoretical ones based on three different models. The comparison between theory and experiment allows one to suggest a new interpretation of the ionization front's advance. The ionization front velocity is determined by a breakdown wave or an ionization wave in the electric field of a high-power surface wave in the zone near the ionization front.

Enabling Efficient and Confident Annotation of LC−MS Metabolomics Data through MS1 Spectrum and Time Prediction

DOE PAGES

Broeckling, Corey D.; Ganna, Andrea; Layer, Mark; ...

2016-09-08

Liquid chromatography coupled to electrospray ionization-mass spectrometry (LC–ESI-MS) is a versatile and robust platform for metabolomic analysis. However, while ESI is a soft ionization technique, in-source phenomena including multimerization, nonproton cation adduction, and in-source fragmentation complicate interpretation of MS data. Here, we report chromatographic and mass spectrometric behavior of 904 authentic standards collected under conditions identical to a typical nontargeted profiling experiment. The data illustrate that the often high level of complexity in MS spectra is likely to result in misinterpretation during the annotation phase of the experiment and a large overestimation of the number of compounds detected. However, ourmore » analysis of this MS spectral library data indicates that in-source phenomena are not random but depend at least in part on chemical structure. These nonrandom patterns enabled predictions to be made as to which in-source signals are likely to be observed for a given compound. Using the authentic standard spectra as a training set, we modeled the in-source phenomena for all compounds in the Human Metabolome Database to generate a theoretical in-source spectrum and retention time library. A novel spectral similarity matching platform was developed to facilitate efficient spectral searching for nontargeted profiling applications. Taken together, this collection of experimental spectral data, predictive modeling, and informatic tools enables more efficient, reliable, and transparent metabolite annotation.« less

Enabling Efficient and Confident Annotation of LC-MS Metabolomics Data through MS1 Spectrum and Time Prediction

DOE PAGES

Broeckling, Corey D.; Ganna, Andrea; Layer, Mark; ...

2016-08-25

Liquid chromatography coupled to electrospray ionization-mass spectrometry (LC–ESI-MS) is a versatile and robust platform for metabolomic analysis. However, while ESI is a soft ionization technique, in-source phenomena including multimerization, nonproton cation adduction, and in-source fragmentation complicate interpretation of MS data. Here, we report chromatographic and mass spectrometric behavior of 904 authentic standards collected under conditions identical to a typical nontargeted profiling experiment. The data illustrate that the often high level of complexity in MS spectra is likely to result in misinterpretation during the annotation phase of the experiment and a large overestimation of the number of compounds detected. However, ourmore » analysis of this MS spectral library data indicates that in-source phenomena are not random but depend at least in part on chemical structure. These nonrandom patterns enabled predictions to be made as to which in-source signals are likely to be observed for a given compound. Using the authentic standard spectra as a training set, we modeled the in-source phenomena for all compounds in the Human Metabolome Database to generate a theoretical in-source spectrum and retention time library. A novel spectral similarity matching platform was developed to facilitate efficient spectral searching for nontargeted profiling applications. Taken together, this collection of experimental spectral data, predictive modeling, and informatic tools enables more efficient, reliable, and transparent metabolite annotation.« less

Gas chromatographic quadrupole time-of-flight full scan high resolution mass spectrometric screening of human urine in antidoping analysis.

PubMed

Abushareeda, Wadha; Lyris, Emmanouil; Kraiem, Suhail; Wahaibi, Aisha Al; Alyazidi, Sameera; Dbes, Najib; Lommen, Arjen; Nielen, Michel; Horvatovich, Peter L; Alsayrafi, Mohammed; Georgakopoulos, Costas

2017-09-15

This paper presents the development and validation of a high-resolution full scan (FS) electron impact ionization (EI) gas chromatography coupled to quadrupole Time-of-Flight mass spectrometry (GC/QTOF) platform for screening anabolic androgenic steroids (AAS) in human urine samples. The World Antidoping Agency (WADA) enlists AAS as prohibited doping agents in sports, and our method has been developed to comply with the qualitative specifications of WADA to be applied for the detection of sports antidoping prohibited substances, mainly for AAS. The method also comprises of the quantitative analysis of the WADA's Athlete Biological Passport (ABP) endogenous steroidal parameters. The applied preparation of urine samples includes enzymatic hydrolysis for the cleavage of the Phase II glucuronide conjugates, generic liquid-liquid extraction and trimethylsilyl (TMS) derivatization steps. Tandem mass spectrometry (MS/MS) acquisition was applied on few selected ions to enhance the specificity and sensitivity of GC/TOF signal of few compounds. The full scan high resolution acquisition of analytical signal, for known and unknown TMS derivatives of AAS provides the antidoping system with a new analytical tool for the detection designer drugs and novel metabolites, which prolongs the AAS detection, after electronic data files' reprocessing. The current method is complementary to the respective liquid chromatography coupled to mass spectrometry (LC/MS) methodology widely used to detect prohibited molecules in sport, which cannot be efficiently ionized with atmospheric pressure ionization interface. Copyright © 2017 Elsevier B.V. All rights reserved.

Model study of modern oil-based paint media by triacylglycerol profiling in positive and negative ionization modes.

PubMed

Degano, Ilaria; La Nasa, Jacopo; Ghelardi, Elisa; Modugno, Francesca; Colombini, Maria Perla

2016-12-01

Lipid binders have traditionally been determined in paintings by using gas chromatography/mass spectrometry (GC/MS) to identify the characteristic profiles and ratios of fatty acids . However, the presence of mixtures in contemporary and modern oil paints makes the GC/MS determination of fatty acids insufficient to fully characterize the lipid binding media. In this study we prove that triacylglycerol (TAG) profiling by high-performance liquid chromatography with high-resolution tandem mass spectrometry, using ESI in positive and negative ionization modes is highly effective. We exploited this analytical approach to study the curing and degradation processes undergone by six plant oils used in the formulation of media in modern paints, using both natural and artificial ageing experiments. We believe that is the first time that a negative ionization mode has been applied for this purpose and that a survey with HPLC-ESI-Q-ToF has been carried out to study the ageing kinetics of plant oils. TAG profiling enabled us to study the evolution over time of the constituents of modern oils, with respect to curing and ageing. The data analyzed in this study demonstrate that our approach is efficient to study the oxidation of TAGs during ageing. The data also improve current knowledge on the properties of vegetable oils, which could lead to the development of new paint materials and conservation treatments for modern and contemporary works of art. Copyright © 2016 Elsevier B.V. All rights reserved.

The Pulsed Cylindrical Magnetron for Deposition

NASA Astrophysics Data System (ADS)

Korenev, Sergey

2012-10-01

The magnetron sputtering deposition of films and coatings broadly uses in microelectronics, material science, environmental applications and etc. The rate of target evaporation and time for deposition of films and coatings depends on magnetic field. These parameters link with efficiency of gas molecules ionization by electrons. The cylindrical magnetrons use for deposition of films and coatings on inside of pipes for different protective films and coatings in oil, chemical, environmental applications. The classical forming of magnetic field by permanent magnets or coils for big and long cylindrical magnetrons is complicated. The new concept of pulsed cylindrical magnetron for high rate deposition of films and coating for big and long pipes is presented in this paper. The proposed cylindrical magnetron has azimuthally pulsed high magnetic field, which allows forming the high ionized plasma and receiving high rate of evaporation material of target (central electrode). The structure of proposed pulsed cylindrical magnetron sputtering system is given. The main requirements to deposition system are presented. The preliminary data for forming of plasma and deposition of Ta films and coatings on the metal pipers are discussed. The comparison of classical and proposed cylindrical magnetrons is given. The analysis of potential applications is considered.

Asymmetric soft-error resistant memory

NASA Technical Reports Server (NTRS)

Buehler, Martin G. (Inventor); Perlman, Marvin (Inventor)

1991-01-01

A memory system is provided, of the type that includes an error-correcting circuit that detects and corrects, that more efficiently utilizes the capacity of a memory formed of groups of binary cells whose states can be inadvertently switched by ionizing radiation. Each memory cell has an asymmetric geometry, so that ionizing radiation causes a significantly greater probability of errors in one state than in the opposite state (e.g., an erroneous switch from '1' to '0' is far more likely than a switch from '0' to'1'. An asymmetric error correcting coding circuit can be used with the asymmetric memory cells, which requires fewer bits than an efficient symmetric error correcting code.

Lower hybrid wave edge power loss quantification on the Alcator C-Mod tokamak

NASA Astrophysics Data System (ADS)

Faust, I. C.; Brunner, D.; LaBombard, B.; Parker, R. R.; Terry, J. L.; Whyte, D. G.; Baek, S. G.; Edlund, E.; Hubbard, A. E.; Hughes, J. W.; Kuang, A. Q.; Reinke, M. L.; Shiraiwa, S.; Wallace, G. M.; Walk, J. R.

2016-05-01

For the first time, the power deposition of lower hybrid RF waves into the edge plasma of a diverted tokamak has been systematically quantified. Edge deposition represents a parasitic loss of power that can greatly impact the use and efficiency of Lower Hybrid Current Drive (LHCD) at reactor-relevant densities. Through the use of a unique set of fast time resolution edge diagnostics, including innovative fast-thermocouples, an extensive set of Langmuir probes, and a Lyα ionization camera, the toroidal, poloidal, and radial structure of the power deposition has been simultaneously determined. Power modulation was used to directly isolate the RF effects due to the prompt ( t < τ E ) response of the scrape-off-layer (SOL) plasma to Lower Hybrid Radiofrequency (LHRF) power. LHRF power was found to absorb more strongly in the edge at higher densities. It is found that a majority of this edge-deposited power is promptly conducted to the divertor. This correlates with the loss of current drive efficiency at high density previously observed on Alcator C-Mod, and displaying characteristics that contrast with the local RF edge absorption seen on other tokamaks. Measurements of ionization in the active divertor show dramatic changes due to LHRF power, implying that divertor region can be a key for the LHRF edge power deposition physics. These observations support the existence of a loss mechanism near the edge for LHRF at high density ( n e > 1.0 × 10 20 (m-3)). Results will be shown addressing the distribution of power within the SOL, including the toroidal symmetry and radial distribution. These characteristics are important for deducing the cause of the reduced LHCD efficiency at high density and motivate the tailoring of wave propagation to minimize SOL interaction, for example, through the use of high-field-side launch.

Lower Hybrid wave edge power loss quantification on the Alcator C-Mod tokamak

NASA Astrophysics Data System (ADS)

Faust, I. C.

2015-11-01

For the first time, the power deposition of Lower Hybrid RF waves into the edge plasma of a diverted tokamak has been systematically quantified. Edge deposition represents a parasitic loss of power that can greatly impact the use and efficiency of Lower Hybrid Current Drive (LHCD) at reactor-relevant densities. Through the use of a unique set of fast time resolution edge diagnostics, including innovative fast-thermocouples, an extensive set of Langmuir probes, and a Lyα ionization camera, the toroidal, poloidal and radial structure of the power deposition has been simultaneously determined. Power modulation was used to directly isolate the RF effects due to the prompt (t <τE) response of the scrape-off-layer (SOL) plasma to LHRF power. LHRF power was found to absorb more strongly in the edge at higher densities. It is found that a majority of this edge-deposited power is promptly conducted to the divertor. This correlates with the loss of current drive efficiency at high density previously observed on Alcator C-Mod, and displaying characteristics that contrast with the local RF edge absorption seen on other tokamaks. Measurements of ionization in the active divertor show dramatic changes due to LHRF power, implying that divertor region can be key for the LHRF edge power deposition physics. These observations support the existence a loss mechanism near the edge for LHRF at high density (ne > 1 . 0 .1020 [m-3]). Results will be shown addressing the distribution of power within the SOL, including the toroidal symmetry and radial distribution. These characteristics are important for deducing the cause of the reduced LHCD efficiency at high density and motivates the tailoring of wave propagation to minimize SOL interaction, for example, through the use of high-field-side launch. This work was performed on the Alcator C-Mod tokamak, a DoE Office of Science user facility, and is supported by USDoE award DE-FC02-99ER54512.

SONTRAC: A High Efficiency Solar Neutron Telescope

NASA Astrophysics Data System (ADS)

Wunderer, C. B.; Macri, J.; McConnell, M. L.; Ryan, J. M.; Baltgalvis, J.; Holslin, D.; Polichar, A.; Jenkins, T.

1997-05-01

Solar flare neutron emission between 20 and 100 MeV comes from a portion of the energetic proton spectrum that is poorly sampled by both nuclear-line and pion- decay gamma rays. SONTRAC is a new generation solar neutron telescope/spectrometer consisting of densely packed, alternating orthogonal layers of scintillating plastic fibers. The fibers in both dimensions are viewed by image intensifiers and CCD cameras. Incident neutrons scatter off hydrogen in the plastic scintillator. The resulting ionizing proton tracks can be reconstructed in three dimensions using the two planar CCD track images. Two neutron-proton scatters provide sufficient information to reconstruct the energy and direction of the incident neutron. Photomultiplier tubes view the other sides of the fiber scintillator array. The signals from the PMTs are used to give an additional measure of the proton energies and to provide a trigger for the CCD cameras. Recent technological advances have allowed us to construct an affordable working prototype instrument that consists of all the essential technical elements mentioned above. We will present images of tracks produced by minimum ionizing muons and energetic neutrons. We will also present efficiency estimates for SONTRAC's ability to detect and measure gamma rays above 10 MeV.

Study of EHD flow generator's efficiencies utilizing pin to single ring and multi-concentric rings electrodes

NASA Astrophysics Data System (ADS)

Sumariyah; Kusminart; Hermanto, A.; Nuswantoro, P.

2016-11-01

EHD flow or ionic wind yield corona discharge is a stream coming from the ionized gas. EHD is generated by a strong electric field and its direction follows the electric field lines. In this study, the efficiency of the EHD flow generators utilizing pin-multi concentric rings electrodes (P-MRE) and the EHD pin-single ring electrode (P-SRE) have been measured. The comparison of efficiencies two types of the generator has been done. EHD flow was generated by using a high-voltage DC 0-10 KV on the electrode pin with a positive polarity and electrode ring/ multi-concentric rings of negative polarity. The efficiency was calculated by comparison between the mechanical power of flow to the electrical power that consumed. We obtained that the maximum efficiency of EHD flow generator utilizing pin-multi concentric rings electrodes was 0.54% and the maximum efficiency of EHD flow generator utilizing a pin-single ring electrode was 0.23%. Efficiency of EHD with P-MRE 2.34 times Efficiency of EHD with P-SRE

STARLIFE-An International Campaign to Study the Role of Galactic Cosmic Radiation in Astrobiological Model Systems.

PubMed

Moeller, Ralf; Raguse, Marina; Leuko, Stefan; Berger, Thomas; Hellweg, Christine Elisabeth; Fujimori, Akira; Okayasu, Ryuichi; Horneck, Gerda

2017-02-01

In-depth knowledge regarding the biological effects of the radiation field in space is required for assessing the radiation risks in space. To obtain this knowledge, a set of different astrobiological model systems has been studied within the STARLIFE radiation campaign during six irradiation campaigns (2013-2015). The STARLIFE group is an international consortium with the aim to investigate the responses of different astrobiological model systems to the different types of ionizing radiation (X-rays, γ rays, heavy ions) representing major parts of the galactic cosmic radiation spectrum. Low- and high-energy charged particle radiation experiments have been conducted at the Heavy Ion Medical Accelerator in Chiba (HIMAC) facility at the National Institute of Radiological Sciences (NIRS) in Chiba, Japan. X-rays or γ rays were used as reference radiation at the German Aerospace Center (DLR, Cologne, Germany) or Beta-Gamma-Service GmbH (BGS, Wiehl, Germany) to derive the biological efficiency of different radiation qualities. All samples were exposed under identical conditions to the same dose and qualities of ionizing radiation (i) allowing a direct comparison between the tested specimens and (ii) providing information on the impact of the space radiation environment on currently used astrobiological model organisms. Key Words: Space radiation environment-Sparsely ionizing radiation-Densely ionizing radiation-Heavy ions-Gamma radiation-Astrobiological model systems. Astrobiology 17, 101-109.

Influence of Triply-Charged Ions and Ionization Cross-Sections in a Hybrid-PIC Model of a Hall Thruster Discharge

NASA Technical Reports Server (NTRS)

Smith, Brandon D.; Boyd, Iain D.; Kamhawi, Hani

2014-01-01

The sensitivity of xenon ionization rates to collision cross-sections is studied within the framework of a hybrid-PIC model of a Hall thruster discharge. A revised curve fit based on the Drawin form is proposed and is shown to better reproduce the measured crosssections at high electron energies, with differences in the integrated rate coefficients being on the order of 10% for electron temperatures between 20 eV and 30 eV. The revised fit is implemented into HPHall and the updated model is used to simulate NASA's HiVHAc EDU2 Hall thruster at discharge voltages of 300, 400, and 500 V. For all three operating points, the revised cross-sections result in an increase in the predicted thrust and anode efficiency, reducing the error relative to experimental performance measurements. Electron temperature and ionization reaction rates are shown to follow the trends expected based on the integrated rate coefficients. The effects of triply-charged xenon are also assessed. The predicted thruster performance is found to have little or no dependence on the presence of triply-charged ions. The fraction of ion current carried by triply-charged ions is found to be on the order of 1% and increases slightly with increasing discharge voltage. The reaction rates for the 0?III, I?III, and II?III ionization reactions are found to be of similar order of magnitude and are about one order of magnitude smaller than the rate of 0?II ionization in the discharge channel.

Assessment of ionization chamber correction factors in photon beams using a time saving strategy with PENELOPE code.

PubMed

Reis, C Q M; Nicolucci, P

2016-02-01

The purpose of this study was to investigate Monte Carlo-based perturbation and beam quality correction factors for ionization chambers in photon beams using a saving time strategy with PENELOPE code. Simulations for calculating absorbed doses to water using full spectra of photon beams impinging the whole water phantom and those using a phase-space file previously stored around the point of interest were performed and compared. The widely used NE2571 ionization chamber was modeled with PENELOPE using data from the literature in order to calculate absorbed doses to the air cavity of the chamber. Absorbed doses to water at reference depth were also calculated for providing the perturbation and beam quality correction factors for that chamber in high energy photon beams. Results obtained in this study show that simulations with phase-space files appropriately stored can be up to ten times shorter than using a full spectrum of photon beams in the input-file. Values of kQ and its components for the NE2571 ionization chamber showed good agreement with published values in the literature and are provided with typical statistical uncertainties of 0.2%. Comparisons to kQ values published in current dosimetry protocols such as the AAPM TG-51 and IAEA TRS-398 showed maximum percentage differences of 0.1% and 0.6% respectively. The proposed strategy presented a significant efficiency gain and can be applied for a variety of ionization chambers and clinical photon beams. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Population Studies of Intact Vitamin D Binding Protein by Affinity Capture ESI-TOF-MS

PubMed Central

Borges, Chad R.; Jarvis, Jason W.; Oran, Paul E.; Rogers, Stephen P.; Nelson, Randall W.

2008-01-01

Blood plasma proteins with molecular weights greater than approximately 30 kDa are refractory to comprehensive, high-throughput qualitative characterization of microheterogeneity across human populations. Analytical techniques for obtaining high mass resolution for targeted, intact protein characterization and, separately, high sample throughput exist, but efficient means of coupling these assay characteristics remain rather limited. This article discusses the impetus for analyzing intact proteins in a targeted manner across populations and describes the methodology required to couple mass spectrometric immunoassay with electrospray ionization mass spectrometry for the purpose of qualitatively characterizing a prototypical large plasma protein, vitamin D binding protein, across populations. PMID:19137103

A vacuum ultraviolet laser pulsed field ionization-photoion study of methane (CH 4): Determination of the appearance energy of methylium from methane with unprecedented precision and the resulting impact on the bond dissociation energies of CH 4 and CH 4 +

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

Chang, Yih -Chung; Xiong, Bo; Bross, David H.

Here, we report on the successful implementation of a high-resolution vacuum ultraviolet (VUV) laser pulsed field ionization-photoion (PFI-PI) detection method for the study of unimolecular dissociation of quantum-state- or energy-selected molecular ions. As a test case, we have determined the 0 K appearance energy (AE 0) for the formation of methylium, CH 3 +, from methane, CH 4, as AE 0 (CH 3 +/CH 4) = 14.32271 ± 0.00013 eV. This value has a significantly smaller error limit, but is otherwise consistent with previous laboratory and/or synchrotron-based studies of this dissociative photoionization onset. Furthermore, the sum of the VUV lasermore » PFI-PI spectra obtained for the parent CH 4 + ion and the fragment CH 3 + ions of methane is found to agree with the earlier VUV pulsed field ionization-photoelectron (VUV-PFI-PE) spectrum of methane, providing unambiguous validation of the previous interpretation that the sharp VUV-PFI-PE step observed at the AE 0 (CH 3 +/CH 4) threshold ensues because of higher PFI detection efficiency for fragment CH 3 + than for parent CH 4 +. This, in turn, is a consequence of the underlying high- n Rydberg dissociation mechanism for the dissociative photoionization of CH 4, which was proposed in previous synchrotron-based VUV-PFI-PE and VUV-PFI-PEPICO studies of CH 4. The present highly accurate 0 K dissociative ionization threshold for CH 4 can be utilized to derive accurate values for the bond dissociation energies of methane and methane cation. For methane, the straightforward application of sequential thermochemistry via the positive ion cycle leads to some ambiguity because of two competing VUV-PFI-PE literature values for the ionization energy of methyl radical. The ambiguity is successfully resolved by applying the Active Thermochemical Tables (ATcT) approach, resulting in D 0 (H-CH 3) = 432.463 ± 0.027 kJ/mol and D 0(H-CH 3 +) = 164.701 ± 0.038 kJ/mol.« less

A vacuum ultraviolet laser pulsed field ionization-photoion study of methane (CH 4): Determination of the appearance energy of methylium from methane with unprecedented precision and the resulting impact on the bond dissociation energies of CH 4 and CH 4 +

DOE PAGES

Chang, Yih -Chung; Xiong, Bo; Bross, David H.; ...

2017-03-27

Here, we report on the successful implementation of a high-resolution vacuum ultraviolet (VUV) laser pulsed field ionization-photoion (PFI-PI) detection method for the study of unimolecular dissociation of quantum-state- or energy-selected molecular ions. As a test case, we have determined the 0 K appearance energy (AE 0) for the formation of methylium, CH 3 +, from methane, CH 4, as AE 0 (CH 3 +/CH 4) = 14.32271 ± 0.00013 eV. This value has a significantly smaller error limit, but is otherwise consistent with previous laboratory and/or synchrotron-based studies of this dissociative photoionization onset. Furthermore, the sum of the VUV lasermore » PFI-PI spectra obtained for the parent CH 4 + ion and the fragment CH 3 + ions of methane is found to agree with the earlier VUV pulsed field ionization-photoelectron (VUV-PFI-PE) spectrum of methane, providing unambiguous validation of the previous interpretation that the sharp VUV-PFI-PE step observed at the AE 0 (CH 3 +/CH 4) threshold ensues because of higher PFI detection efficiency for fragment CH 3 + than for parent CH 4 +. This, in turn, is a consequence of the underlying high- n Rydberg dissociation mechanism for the dissociative photoionization of CH 4, which was proposed in previous synchrotron-based VUV-PFI-PE and VUV-PFI-PEPICO studies of CH 4. The present highly accurate 0 K dissociative ionization threshold for CH 4 can be utilized to derive accurate values for the bond dissociation energies of methane and methane cation. For methane, the straightforward application of sequential thermochemistry via the positive ion cycle leads to some ambiguity because of two competing VUV-PFI-PE literature values for the ionization energy of methyl radical. The ambiguity is successfully resolved by applying the Active Thermochemical Tables (ATcT) approach, resulting in D 0 (H-CH 3) = 432.463 ± 0.027 kJ/mol and D 0(H-CH 3 +) = 164.701 ± 0.038 kJ/mol.« less

Organic solar cells based on high dielectric constant materials: An approach to increase efficiency

NASA Astrophysics Data System (ADS)

Hamam, Khalil Jumah Tawfiq

The efficiency of organic solar cells still lags behind inorganic solar cells due to their low dielectric constant which results in a weakly screened columbic attraction between the photogenerated electron-hole system, therefore the probability of charge separating is low. Having an organic material with a high dielectric constant could be the solution to get separated charges or at least weakly bounded electron-hole pairs. Therefore, high dielectric constant materials have been investigated and studied by measuring modified metal-phthalocyanine (MePc) and polyaniline in pellets and thin films. The dielectric constant was investigated as a function of temperature and frequency in the range of 20Hz to1MHz. For MePc we found that the high dielectric constant was an extrinsic property due to water absorption and the formation of hydronuim ion allowed by the ionization of the functional groups such as sulphonated and carboxylic groups. The dielectric constant was high at low frequencies and decreasing as the frequency increase. Investigated materials were applied in fabricated bilayer heterojunction organic solar cells. The application of these materials in an organic solar cells show a significant stability under room conditions rather than improvement in their efficiency.

Measurement of scintillation and ionization yield with high-pressure gaseous mixtures of Xe and TMA for improved neutrinoless double beta decay and dark matter searches

DOE PAGES

Nakajima, Y.; Goldschmidt, A.; Matis, H. S.; ...

2016-03-18

The gaseous Xenon(Xe) time projection chamber (TPC) is an attractive detector technique for neutrinoless double beta decay and WIMP dark matter searches. While it is less dense compared to Liquid Xe detectors, it has intrinsic advantages in tracking capability and better energy resolution. The performance of gaseous Xe can be further improved by molecular additives such as trimethylamine(TMA), which is expected to (1) cool down the ionization electrons, (2) convert Xe excitation energy to TMA ionizations through Penning transfer, and (3) produce scintillation and electroluminescence light in a more easily detectable wavelength (300 nm). In order to test the feasibilitymore » of the performance improvements with TMA, in this paper we made the first direct measurement of Penning and fluorescence transfer efficiency with gaseous mixtures of Xe and TMA. While we observed a Penning transfer efficiency up to ~35%, we found strong suppression of primary scintillation light with TMA. We also found that the primary scintillation light with Xe and TMA mixture can be well characterized by ~3% fluorescence transfer from Xe to TMA, with further suppression due to TMA self-quenching. No evidence of the scintillation light produced by recombination of TMA ions was found. This strong suppression of scintillation light makes dark matter searches quite challenging, while the possibility of improved neutrinoless double beta decay searches remains open. Finally, this work has been carried out within the context of the NEXT collaboration.« less

Plasma catalytic reforming of methane

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

Bromberg, L.; Cohn, D.R.; Rabinovich, A.

1998-08-01

Thermal plasma technology can be efficiently used in the production of hydrogen and hydrogen-rich gases from methane and a variety of fuels. This paper describes progress in plasma reforming experiments and calculations of high temperature conversion of methane using heterogeneous processes. The thermal plasma is a highly energetic state of matter that is characterized by extremely high temperatures (several thousand degrees Celsius) and high degree of dissociation and substantial degree of ionization. The high temperatures accelerate the reactions involved in the reforming process. Hydrogen-rich gas (50% H{sub 2}, 17% CO and 33% N{sub 2}, for partial oxidation/water shifting) can bemore » efficiently made in compact plasma reformers. Experiments have been carried out in a small device (2--3 kW) and without the use of efficient heat regeneration. For partial oxidation/water shifting, it was determined that the specific energy consumption in the plasma reforming processes is 16 MJ/kg H{sub 2} with high conversion efficiencies. Larger plasmatrons, better reactor thermal insulation, efficient heat regeneration and improved plasma catalysis could also play a major role in specific energy consumption reduction and increasing the methane conversion. A system has been demonstrated for hydrogen production with low CO content ({approximately} 1.5%) with power densities of {approximately} 30 kW (H{sub 2} HHV)/liter of reactor, or {approximately} 10 m{sup 3}/hr H{sub 2} per liter of reactor. Power density should further increase with increased power and improved design.« less

Modeling photoionization of aqueous DNA and its components.

PubMed

Pluhařová, Eva; Slavíček, Petr; Jungwirth, Pavel

2015-05-19

Radiation damage to DNA is usually considered in terms of UVA and UVB radiation. These ultraviolet rays, which are part of the solar spectrum, can indeed cause chemical lesions in DNA, triggered by photoexcitation particularly in the UVB range. Damage can, however, be also caused by higher energy radiation, which can ionize directly the DNA or its immediate surroundings, leading to indirect damage. Thanks to absorption in the atmosphere, the intensity of such ionizing radiation is negligible in the solar spectrum at the surface of Earth. Nevertheless, such an ionizing scenario can become dangerously plausible for astronauts or flight personnel, as well as for persons present at nuclear power plant accidents. On the beneficial side, ionizing radiation is employed as means for destroying the DNA of cancer cells during radiation therapy. Quantitative information about ionization of DNA and its components is important not only for DNA radiation damage, but also for understanding redox properties of DNA in redox sensing or labeling, as well as charge migration along the double helix in nanoelectronics applications. Until recently, the vast majority of experimental and computational data on DNA ionization was pertinent to its components in the gas phase, which is far from its native aqueous environment. The situation has, however, changed for the better due to the advent of photoelectron spectroscopy in liquid microjets and its most recent application to photoionization of aqueous nucleosides, nucleotides, and larger DNA fragments. Here, we present a consistent and efficient computational methodology, which allows to accurately evaluate ionization energies and model photoelectron spectra of aqueous DNA and its individual components. After careful benchmarking, the method based on density functional theory and its time-dependent variant with properly chosen hybrid functionals and polarizable continuum solvent model provides ionization energies with accuracy of 0.2-0.3 eV, allowing for faithful modeling and interpretation of DNA photoionization. The key finding is that the aqueous medium is remarkably efficient in screening the interactions within DNA such that, unlike in the gas phase, ionization of a base, nucleoside, or nucleotide depends only very weakly on the particular DNA context. An exception is the electronic interaction between neighboring bases which can lead to sequence-specific effects, such as a partial delocalization of the cationic hole upon ionization enabled by presence of adjacent bases of the same type.

CMOS-Compatible SOI MESFETS for Radiation-Hardened DC-to-DC Converters

NASA Technical Reports Server (NTRS)

Thornton, Trevor; Lepkowski, William; Wilk, Seth

2013-01-01

A radiation-tolerant transistor switch has been developed that can operate between 196 and +150 C for DC-to-DC power conversion applications. A prototype buck regulator component was demonstrated to be performing well after a total ionizing dose of 300 krad(Si). The prototype buck converters showed good efficiencies at ultra-high switching speeds in the range of 1 to 10 MHz. Such high switching frequency will enable smaller, lighter buck converters to be developed as part of the next project. Switching regulators are widely used in commercial applications including portable consumer electronics.

Fused dithienogermolodithiophene low band gap polymers for high-performance organic solar cells without processing additives.

PubMed

Zhong, Hongliang; Li, Zhe; Deledalle, Florent; Fregoso, Elisa Collado; Shahid, Munazza; Fei, Zhuping; Nielsen, Christian B; Yaacobi-Gross, Nir; Rossbauer, Stephan; Anthopoulos, Thomas D; Durrant, James R; Heeney, Martin

2013-02-13

We report the synthesis of a novel ladder-type fused ring donor, dithienogermolodithiophene, in which two thieno[3,2-b]thiophene units are held coplanar by a bridging dialkyl germanium. Polymerization of this extended monomer with N-octylthienopyrrolodione by Stille polycondensation afforded a polymer, pDTTG-TPD, with an optical band gap of 1.75 eV combined with a high ionization potential. Bulk heterojunction solar cells based upon pDTTG-TPD:PC(71)BM blends afforded efficiencies up to 7.2% without the need for thermal annealing or processing additives.

Are the argon metastables important in high power impulse magnetron sputtering discharges?

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

Gudmundsson, J. T., E-mail: tumi@hi.is; Science Institute, University of Iceland, Dunhaga 3, IS-107 Reykjavik; Lundin, D.

2015-11-15

We use an ionization region model to explore the ionization processes in the high power impulse magnetron sputtering (HiPIMS) discharge in argon with a titanium target. In conventional dc magnetron sputtering (dcMS), stepwise ionization can be an important route for ionization of the argon gas. However, in the HiPIMS discharge stepwise ionization is found to be negligible during the breakdown phase of the HiPIMS pulse and becomes significant (but never dominating) only later in the pulse. For the sputtered species, Penning ionization can be a significant ionization mechanism in the dcMS discharges, while in the HiPIMS discharge Penning ionization ismore » always negligible as compared to electron impact ionization. The main reasons for these differences are a higher plasma density in the HiPIMS discharge, and a higher electron temperature. Furthermore, we explore the ionization fraction and the ionized flux fraction of the sputtered vapor and compare with recent experimental work.« less

Radiation hard pixel sensors using high-resistive wafers in a 150 nm CMOS processing line

NASA Astrophysics Data System (ADS)

Pohl, D.-L.; Hemperek, T.; Caicedo, I.; Gonella, L.; Hügging, F.; Janssen, J.; Krüger, H.; Macchiolo, A.; Owtscharenko, N.; Vigani, L.; Wermes, N.

2017-06-01

Pixel sensors using 8'' CMOS processing technology have been designed and characterized offering the benefits of industrial sensor fabrication, including large wafers, high throughput and yield, as well as low cost. The pixel sensors are produced using a 150 nm CMOS technology offered by LFoundry in Avezzano. The technology provides multiple metal and polysilicon layers, as well as metal-insulator-metal capacitors that can be employed for AC-coupling and redistribution layers. Several prototypes were fabricated and are characterized with minimum ionizing particles before and after irradiation to fluences up to 1.1 × 1015 neq cm-2. The CMOS-fabricated sensors perform equally well as standard pixel sensors in terms of noise and hit detection efficiency. AC-coupled sensors even reach 100% hit efficiency in a 3.2 GeV electron beam before irradiation.

Effect of low-frequency oscillation on performance of Hall thrusters

NASA Astrophysics Data System (ADS)

Liqiu, WEI; Wenbo, LI; Yongjie, DING; Daren, YU

2018-07-01

In this paper, a direct connection between the discharge current amplitude and the thruster performance is established by varying solely the capacitance of the filter unit of the Hall thrusters. To be precise, the variation characteristics of ion current, propellant utilization efficiency, and divergence angle of plume at different low-frequency oscillation amplitudes are measured. The findings demonstrate that in the case of the propellant in the discharge channel just meets or falls below the full ionization condition, the increase of low-frequency oscillation amplitude can significantly enhance the ionization degree of the neutral gas in the channel and increase the thrust and anode efficiency of thruster. On the contrary, the increase in the amplitude of low-frequency oscillation will lead to increase the loss of plume divergence, therefore the thrust and anode efficiency of thruster decrease.

Effect of an InxGa1-xAs-GaAs blocking heterocathode metal contact on the GaAs TED operation

NASA Astrophysics Data System (ADS)

Arkusha, Yu. V.; Prokhorov, E. D.; Storozhenko, I. P.

2004-09-01

The frequency dependence of the generation efficiency of an mm- -nn:In:InxGaGa1-1-xAs- As-nn:GaAs-:GaAs-nn++:GaAs TED with the 2.5-mm long active region is calculated. The optimum values - which yield the diode maximum generation efficiency - for the :GaAs TED with the 2.5-mm long active region is calculated. The optimum values - which yield the diode maximum generation efficiency - for the nn:In:InxGaGa1-1-xAs cathode length, the cathode concentration of ionized impurities, and the height of the potential barrier on metal contact are determined.As cathode length, the cathode concentration of ionized impurities, and the height of the potential barrier on metal contact are determined.

Highly informative multiclass profiling of lipids by ultra-high performance liquid chromatography - Low resolution (quadrupole) mass spectrometry by using electrospray ionization and atmospheric pressure chemical ionization interfaces.

PubMed

Beccaria, Marco; Inferrera, Veronica; Rigano, Francesca; Gorynski, Krzysztof; Purcaro, Giorgia; Pawliszyn, Janusz; Dugo, Paola; Mondello, Luigi

2017-08-04

A simple, fast, and versatile method, using an ultra-high performance liquid chromatography system coupled with a low resolution (single quadrupole) mass spectrometer was optimized to perform multiclass lipid profiling of human plasma. Particular attention was made to develop a method suitable for both electrospray ionization and atmospheric pressure chemical ionization interfaces (sequentially in positive- and negative-ion mode), without any modification of the chromatographic conditions (mobile phase, flow-rate, gradient, etc.). Emphasis was given to the extrapolation of the structural information based on the fragmentation pattern obtained using atmospheric pressure chemical ionization interface, under each different ionization condition, highlighting the complementary information obtained using the electrospray ionization interface, of support for related molecule ions identification. Furthermore, mass spectra of phosphatidylserine and phosphatidylinositol obtained using the atmospheric pressure chemical ionization interface are reported and discussed for the first time. Copyright © 2017 Elsevier B.V. All rights reserved.

Characterization of extreme ultraviolet laser ablation mass spectrometry for actinide trace analysis and nanoscale isotopic imaging

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

Green, Tyler; Kuznetsov, Ilya; Willingham, David

The purpose of this research was to characterize Extreme Ultraviolet Time-of-Flight (EUV TOF) Laser Ablation Mass Spectrometry for high spatial resolution elemental and isotopic analysis. We compare EUV TOF results with Secondary Ionization Mass Spectrometry (SIMS) to orient the EUV TOF method within the overall field of analytical mass spectrometry. Using the well-characterized NIST 61x glasses, we show that the EUV ionization approach produces relatively few molecular ion interferences in comparison to TOF SIMS. We demonstrate that the ratio of element ion to element oxide ion is adjustable with EUV laser pulse energy and that the EUV TOF instrument hasmore » a sample utilization efficiency of 0.014%. The EUV TOF system also achieves a lateral resolution of 80 nm and we demonstrate this lateral resolution with isotopic imaging of closely spaced particles or uranium isotopic standard materials.« less

Degradation of fluoroquinolone antibiotics during ionizing radiation treatment and assessment of antibacterial activity, toxicity and biodegradability of the products

NASA Astrophysics Data System (ADS)

Tegze, Anna; Sági, Gyuri; Kovács, Krisztina; Homlok, Renáta; Tóth, Tünde; Mohácsi-Farkas, Csilla; Wojnárovits, László; Takács, Erzsébet

2018-06-01

This work aimed at investigating the ionizing radiation induced degradation of two fluoroquinolone antibiotics: norfloxacin and ciprofloxacin. At 0.1 mmol dm-3 concentration a low dose, 2 kGy was sufficient to degrade the initial molecules. However, despite of the high removal efficiency the degrees of both the mineralization and the oxidation were low, ∼10% and ∼25%, respectively. (The difference between the results obtained in norfloxacin and ciprofloxacin solutions was not statistically significant.) Broth microdilution tests carried out on Staphylococcus aureus evidenced removal of antibacterial activity in samples irradiated with 2 kGy. Acute toxicity determined on Vibrio fischeri bacteria showed increased toxicity at low doses indicating that the early degradation products were more toxic than the initial molecules. The results of biodegradation experiments performed in activated sludge have shown that the degradation products have become available to the metabolic processes of the microorganisms.

Optimal control of the strong-field ionization of silver clusters in helium droplets

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

Truong, N. X.; Goede, S.; Przystawik, A.

Optimal control techniques combined with femtosecond laser pulse shaping are applied to steer and enhance the strong-field induced emission of highly charged atomic ions from silver clusters embedded in helium nanodroplets. With light fields shaped in amplitude and phase we observe a substantial increase of the Ag{sup q+} yield for q>10 when compared to bandwidth-limited and optimally stretched pulses. A remarkably simple double-pulse structure, containing a low-intensity prepulse and a stronger main pulse, turns out to produce the highest atomic charge states up to Ag{sup 20+}. A negative chirp during the main pulse hints at dynamic frequency locking to themore » cluster plasmon. A numerical optimal control study on pure silver clusters with a nanoplasma model converges to a similar pulse structure and corroborates that the optimal light field adapts to the resonant excitation of cluster surface plasmons for efficient ionization.« less

Cometary particulate analyzer. [mass spectrometry of laser plasmas

NASA Technical Reports Server (NTRS)

Friichtenicht, J. F.; Miller, D. J.; Utterback, N. G.

1979-01-01

A concept for determining the relative abundance of elements contained in cometary particulates was evaluated. The technique utilizes a short, high intensity burst of laser radiation to vaporize and ionize collected particulate material. Ions extracted from this laser produced plasma are analyzed in a time of flight mass spectrometer to yield an atomic mass spectrum representative of the relative abundance of elements in the particulates. Critical aspects of the development of this system are determining the ionization efficiencies for various atomic species and achieving adequate mass resolution. A technique called energy-time focus, which utilizes static electric fields to alter the length of the ion flight path in proportion to the ion initial energy, was used which results in a corresponding compression to the range of ion flight times which effectively improves the inherent resolution. Sufficient data were acquired to develop preliminary specifications for a flight experiment.

Optimization of laser-plasma injector via beam loading effects using ionization-induced injection

NASA Astrophysics Data System (ADS)

Lee, P.; Maynard, G.; Audet, T. L.; Cros, B.; Lehe, R.; Vay, J.-L.

2018-05-01

Simulations of ionization-induced injection in a laser driven plasma wakefield show that high-quality electron injectors in the 50-200 MeV range can be achieved in a gas cell with a tailored density profile. Using the PIC code Warp with parameters close to existing experimental conditions, we show that the concentration of N2 in a hydrogen plasma with a tailored density profile is an efficient parameter to tune electron beam properties through the control of the interplay between beam loading effects and varying accelerating field in the density profile. For a given laser plasma configuration, with moderate normalized laser amplitude, a0=1.6 and maximum electron plasma density, ne 0=4 ×1018 cm-3 , the optimum concentration results in a robust configuration to generate electrons at 150 MeV with a rms energy spread of 4% and a spectral charge density of 1.8 pC /MeV .

Irradiation of wastewater with electron beam is a key to sustainable smart/green cities: a review

NASA Astrophysics Data System (ADS)

Hossain, Kaizar; Maruthi, Y. Avasn; Das, N. Lakshmana; Rawat, K. P.; Sarma, K. S. S.

2018-03-01

Remediation of wastewater, sludge and removal of objectionable substances from our environment using radiation technology is neglected. Hardly, a couple of decades ago, application of electron beam (EB) technology has gained attention for waste management. When wastewater is irradiated with electron beam, the beam can alter the physico-chemical properties of irradiated aqueous material and also transform wastewater chemicals due to the excitation or ionization of chemical molecules. Thus, chemical reactions may be capable of producing new compounds. The beam of electrons initiates primary reactions to induce the excitation or ionization of molecules at varied rates. This review paper will help to a budding researcher how to optimize the irradiation process to achieve high efficiency with low electron beam energy which is economically viable/feasible. Application of E-beam radiation for wastewater treatment may ensure future smart cities with sustainable water resources management.

Power matching between plasma generation and electrostatic acceleration in helicon electrostatic thruster

NASA Astrophysics Data System (ADS)

Ichihara, D.; Nakagawa, Y.; Uchigashima, A.; Iwakawa, A.; Sasoh, A.; Yamazaki, T.

2017-10-01

The effects of a radio-frequency (RF) power on the ion generation and electrostatic acceleration in a helicon electrostatic thruster were investigated with a constant discharge voltage of 300 V using argon as the working gas at a flow rate either of 0.5 Aeq (Ampere equivalent) or 1.0 Aeq. A RF power that was even smaller than a direct-current (DC) discharge power enhanced the ionization of the working gas, thereby both the ion beam current and energy were increased. However, an excessively high RF power input resulted in their saturation, leading to an unfavorable increase in an ionization cost with doubly charged ion production being accompanied. From the tradeoff between the ion production by the RF power and the electrostatic acceleration made by the direct current discharge power, the thrust efficiency has a maximum value at an optimal RF to DC discharge power ratio of 0.6 - 1.0.

A review of reaction rates and thermodynamic and transport properties for an 11-species air model for chemical and thermal nonequilibrium calculations to 30000 K

NASA Technical Reports Server (NTRS)

Gupta, Roop N.; Yos, Jerrold M.; Thompson, Richard A.; Lee, Kam-Pui

1990-01-01

Reaction rate coefficients and thermodynamic and transport properties are reviewed and supplemented for the 11-species air model which can be used for analyzing flows in chemical and thermal nonequilibrium up to temperatures of 3000 K. Such flows will likely occur around currently planned and future hypersonic vehicles. Guidelines for determining the state of the surrounding environment are provided. Curve fits are given for the various species properties for their efficient computation in flowfield codes. Approximate and more exact formulas are provided for computing the properties of partially ionized air mixtures in a high energy environment. Limitations of the approximate mixing laws are discussed for a mixture of ionized species. An electron number-density correction for the transport properties of the charged species is obtained. This correction has been generally ignored in the literature.

MULTIPLE ELECTRON BEAM ION PUMP AND SOURCE

DOEpatents

Ellis, R.E.

1962-02-27

A vacuum pump is designed which operates by ionizing incoming air and by withdrawing the ions from the system by means of electrical fields. The apparatus comprises a cylindrical housing communicable with the vessel to be evacuated and having a thin wall section in one end. Suitable coils provide a longitudinal magnetic field within the cylinder. A broad cathode and an anode structure is provided to establish a plurality of adjacent electron beams which are parallel to the cylinder axis. Electron reflector means are provided so that each of the beams constitutes a PIG or reflex discharge. Such structure provides a large region in which incoming gas molecules may be ionized by electron bombardment. A charged electrode assembly accelerates the ions through the thin window, thereby removing the gas from the system. The invention may also be utilized as a highly efficient ion source. (AEC)

Investigation of ionizing radiation shielding effectiveness of decorative building materials used in Bangladeshi dwellings

NASA Astrophysics Data System (ADS)

Yesmin, Sabina; Sonker Barua, Bijoy; Uddin Khandaker, Mayeen; Tareque Chowdhury, Mohammed; Kamal, Masud; Rashid, M. A.; Miah, M. M. H.; Bradley, D. A.

2017-11-01

Following the rapid growing per capita income, a major portion of Bangladeshi dwellers is upgrading their non-brick houses by rod-cement-concrete materials and simultaneously curious to decorate the houses using luxurious marble stones. Present study was undertaken to investigate the gamma-ray attenuation co-efficient of decorative marble materials leading to their suitability as shielding of ionizing radiation. A number of commercial grades decorative marble stones were collected from home and abroad following their large-scale uses. A well-shielded HPGe γ-ray spectrometer combined with associated electronics was used to evaluate the mass attenuation coefficients of the studied materials for high energy photons. Some allied parameters such as half-value layer and radiation protection efficacy of the investigated marbles were calculated. The results showed that among the studied samples, the marble 'Carrara' imported from Italy is suitable to be used as radiation shielding material.

Annotation of the human serum metabolome by coupling three liquid chromatography methods to high-resolution mass spectrometry.

PubMed

Boudah, Samia; Olivier, Marie-Françoise; Aros-Calt, Sandrine; Oliveira, Lydie; Fenaille, François; Tabet, Jean-Claude; Junot, Christophe

2014-09-01

This work aims at evaluating the relevance and versatility of liquid chromatography coupled to high resolution mass spectrometry (LC/HRMS) for performing a qualitative and comprehensive study of the human serum metabolome. To this end, three different chromatographic systems based on a reversed phase (RP), hydrophilic interaction chromatography (HILIC) and a pentafluorophenylpropyl (PFPP) stationary phase were used, with detection in both positive and negative electrospray modes. LC/HRMS platforms were first assessed for their ability to detect, retain and separate 657 metabolite standards representative of the chemical families occurring in biological fluids. More than 75% were efficiently retained in either one LC-condition and less than 5% were exclusively retained by the RP column. These three LC/HRMS systems were then evaluated for their coverage of serum metabolome. The combination of RP, HILIC and PFPP based LC/HRMS methods resulted in the annotation of about 1328 features in the negative ionization mode, and 1358 in the positive ionization mode on the basis of their accurate mass and precise retention time in at least one chromatographic condition. Less than 12% of these annotations were shared by the three LC systems, which highlights their complementarity. HILIC column ensured the greatest metabolome coverage in the negative ionization mode, whereas PFPP column was the most effective in the positive ionization mode. Altogether, 192 annotations were confirmed using our spectral database and 74 others by performing MS/MS experiments. This resulted in the formal or putative identification of 266 metabolites, among which 59 are reported for the first time in human serum. Copyright © 2014 Elsevier B.V. All rights reserved.

Desorption electrospray ionization mass spectrometry for the analysis of pharmaceuticals and metabolites.

PubMed

Kauppila, Tiina J; Wiseman, Justin M; Ketola, Raimo A; Kotiaho, Tapio; Cooks, R Graham; Kostiainen, Risto

2006-01-01

The performance of desorption electrospray ionization (DESI) in the analysis of a group of pharmaceuticals and their glucuronic acid conjugates is reported. The suitability of different sprayer solvents and different surfaces was examined. In the positive ion mode, water/methanol/trifluoroacetic acid performed best, whereas, in the negative ion mode, water/methanol/ammonium hydroxide was found to be the most suitable spray solvent. Of the surfaces investigated, polymethylmethacrylate (PMMA) was found to give the best performance in terms of sensitivity. Spray solution flow rate and the distance of the sprayer tip from the surface were also found to have significant effects on the signal intensity. Analytes with basic groups efficiently formed the corresponding protonated molecules in the positive ion mode, whereas acidic analytes, such as the glucuronic acid conjugates, formed intense signals due to the deprotonated molecules in the negative ion mode. Ionization of neutral compounds was less efficient and in many cases it was achieved through adduct formation with simple anions or cations. Copyright (c) 2005 John Wiley & Sons, Ltd.

Direct evidence of two interatomic relaxation mechanisms in argon dimers ionized by electron impact

PubMed Central

Ren, Xueguang; Jabbour Al Maalouf, Elias; Dorn, Alexander; Denifl, Stephan

2016-01-01

In weakly bound systems like liquids and clusters electronically excited states can relax in inter-particle reactions via the interplay of electronic and nuclear dynamics. Here we report on the identification of two prominent examples, interatomic Coulombic decay (ICD) and radiative charge transfer (RCT), which are induced in argon dimers by electron collisions. After initial ionization of one dimer constituent ICD and RCT lead to the ionization of its neighbour either by energy transfer to or by electron transfer from the neighbour, respectively. By full quintuple-coincidence measurements, we unambiguously identify ICD and RCT, and trace the relaxation dynamics as function of the collisional excited state energies. Such interatomic processes multiply the number of electrons and shift their energies down to the critical 1–10 eV range, which can efficiently cause chemical degradation of biomolecules. Therefore, the observed relaxation channels might contribute to cause efficient radiation damage in biological systems. PMID:27000407

Measurement of X-ray emission efficiency for K-lines.

PubMed

Procop, M

2004-08-01

Results for the X-ray emission efficiency (counts per C per sr) of K-lines for selected elements (C, Al, Si, Ti, Cu, Ge) and for the first time also for compounds and alloys (SiC, GaP, AlCu, TiAlC) are presented. An energy dispersive X-ray spectrometer (EDS) of known detection efficiency (counts per photon) has been used to record the spectra at a takeoff angle of 25 degrees determined by the geometry of the secondary electron microscope's specimen chamber. Overall uncertainty in measurement could be reduced to 5 to 10% in dependence on the line intensity and energy. Measured emission efficiencies have been compared with calculated efficiencies based on models applied in standardless analysis. The widespread XPP and PROZA models give somewhat too low emission efficiencies. The best agreement between measured and calculated efficiencies could be achieved by replacing in the modular PROZA96 model the original expression for the ionization cross section by the formula given by Casnati et al. (1982) A discrepancy remains for carbon, probably due to the high overvoltage ratio.

Time-resolved quantitative-phase microscopy of laser-material interactions using a wavefront sensor.

PubMed

Gallais, Laurent; Monneret, Serge

2016-07-15

We report on a simple and efficient technique based on a wavefront sensor to obtain time-resolved amplitude and phase images of laser-material interactions. The main interest of the technique is to obtain quantitative self-calibrated phase measurements in one shot at the femtosecond time-scale, with high spatial resolution. The technique is used for direct observation and quantitative measurement of the Kerr effect in a fused silica substrate and free electron generation by photo-ionization processes in an optical coating.

Binary and ternary gas mixtures for use in glow discharge closing switches

DOEpatents

Hunter, Scott R.; Christophorou, Loucas G.

1990-01-01

Highly efficient binary and ternary gas mixtures for use in diffuse glow discharge closing switches are disclosed. The binary mixtures are combinations of helium or neon and selected perfluorides. The ternary mixtures are combinations of helium, neon, or argon, a selected perfluoride, and a small amount of gas that exhibits enhanced ionization characteristics. These mixtures are shown to be the optimum choices for use in diffuse glow discharge closing switches by virtue of the combined physio-electric properties of the mixture components.

What are the current solutions for interfacing supercritical fluid chromatography and mass spectrometry?

PubMed

Guillarme, Davy; Desfontaine, Vincent; Heinisch, Sabine; Veuthey, Jean-Luc

2018-04-15

Mass spectrometry (MS) is considered today as one of the most popular detection methods, due to its high selectivity and sensitivity. In particular, this detector has become the gold standard for the analysis of complex mixtures such as biological samples. The first successful SFC-MS hyphenation was reported in the 80's, and since then, several ionization sources, mass analyzers and interfacing technologies have been combined. Due to the specific physicochemical properties and compressibility of the SFC mobile phase, directing the column effluent into the ionization source is more challenging than in LC. Therefore, some specific interfaces have to be employed in SFC-MS, to i) avoid (or at least limit) analytes precipitation due to CO 2 decompression, when the SFC mobile phase is not anymore under backpressure control, ii) achieve adequate ionization yield, even with a low proportion of MeOH in the mobile phase and iii) preserve the chromatographic integrity (i.e. maintaining retention, selectivity, and efficiency). The goal of this review is to describe the various SFC-MS interfaces and highlight the most favorable ones in terms of reliability, flexibility, sensitivity and user-friendliness. Copyright © 2018 Elsevier B.V. All rights reserved.

Signal enhancement for peptide analysis in liquid chromatography-electrospray ionization mass spectrometry with trifluoroacetic acid containing mobile phase by postcolumn electrophoretic mobility control.

PubMed

Wang, Nan-Hsuan; Lee, Wan-Li; Her, Guor-Rong

2011-08-15

A strategy based on postcolumn electrophoretic mobility control (EMC) was developed to alleviate the adverse effect of trifluoroacetic acid (TFA) on the liquid chromatography-mass spectrometry (LC-MS) analysis of peptides. The device created to achieve this goal consisted of a poly(dimethylsiloxane) (PDMS)-based junction reservoir, a short connecting capillary, and an electrospray ionization (ESI) sprayer connected to the outlet of the high-performance liquid chromatography (HPLC) column. By apply different voltages to the junction reservoir and the ESI emitter, an electric field was created across the connecting capillary. Due to the electric field, positively charged peptides migrated toward the ESI sprayer, whereas TFA anions remained in the junction reservoir and were removed from the ionization process. Because TFA did not enter the ESI source, ion suppression from TFA was alleviated. Operation of the postcolumn device was optimized using a peptide standard mixture. Under optimized conditions, signals for the peptides were enhanced 9-35-fold without a compromise in separation efficiency. The optimized conditions were also applied to the LC-MS analysis of a tryptic digest of bovine serum albumin.

Microhydration of LiOH: Insight from electronic decays of core-ionized states

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

Kryzhevoi, Nikolai V., E-mail: nikolai.kryzhevoi@pci.uni-heidelberg.de

2016-06-28

We compute and compare the autoionization spectra of a core-ionized LiOH molecule both in its isolated and microhydrated states. Stepwise microhydration of LiOH leads to gradual elongation of the Li–OH bond length and finally to molecular dissociation. The accompanying changes in the local environment of the OH{sup −} and Li{sup +} counterions are reflected in the computed O 1s and Li 1s spectra. The role of solvent water molecules and the counterion in the spectral shape formation is assessed. Electronic decays of the microhydrated LiOH are found to be mostly intermolecular since the majority of the populated final states havemore » at least one outer-valence vacancy outside the initially core-ionized ion, mainly on a neighboring water molecule. The charge delocalization occurs through the intermolecular Coulombic and electron transfer mediated decays. Both mechanisms are highly efficient that is partly attributed to hybridization of molecular orbitals. The computed spectral shapes are sensitive to the counterion separation as well as to the number and arrangement of solvent molecules. These sensitivities can be used for studying the local hydration structure of solvated ions in aqueous solutions.« less

GAS-PHASE SYNTHESIS OF PRECURSORS OF INTERSTELLAR GLYCINE: A COMPUTATIONAL STUDY OF THE REACTIONS OF ACETIC ACID WITH HYDROXYLAMINE AND ITS IONIZED AND PROTONATED DERIVATIVES

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

Barrientos, Carmen; Redondo, Pilar; Largo, Laura

2012-04-01

A computational study of the reactions of hydroxylamine and its ionized and protonated derivatives with acetic acid is provided. The reaction of neutral hydroxylamine with acetic acid, despite being clearly exothermic, involves a very large energy barrier. The reaction of ionized hydroxylamine with acetic acid is also clearly exothermic, but again a significant energy barrier is found (around 24 kcal mol{sup -1} at the CCSD(T) level). The reaction of the most stable protonated isomer of hydroxylamine, NH{sub 3}OH{sup +}, with acetic acid also involves a high barrier (more than 27 kcal mol{sup -1} at the CCSD(T) level). Only the highermore » energy isomer, NH{sub 2}OH{sup +}{sub 2}, leads to a sensibly lower energy barrier (about 2.3 kcal mol{sup -1} at the CCSD(T) level). Nevertheless, an estimate of the reaction coefficient at low temperatures such as those reigning in the interstellar medium gives very low values. Therefore, it seems that precursors of interstellar glycine could not be efficiently produced from the reactions of hydroxylamine-derived ions with acetic acid.« less

Measurements of trap dynamics of cold OH molecules using resonance-enhanced multiphoton ionization

NASA Astrophysics Data System (ADS)

Gray, John M.; Bossert, Jason A.; Shyur, Yomay; Lewandowski, H. J.

2017-08-01

Trapping cold, chemically important molecules with electromagnetic fields is a useful technique to study small molecules and their interactions. Traps provide long interaction times, which are needed to precisely examine these low-density molecular samples. However, the trapping fields lead to nonuniform molecular density distributions in these systems. Therefore, it is important to be able to experimentally characterize the spatial density distribution in the trap. Ionizing molecules at different locations in the trap using resonance-enhanced multiphoton ionization (REMPI) and detecting the resulting ions can be used to probe the density distribution even at the low density present in these experiments because of the extremely high efficiency of detection. Until recently, one of the most chemically important molecules, OH, did not have a convenient REMPI scheme identified. Here, we use a newly developed 1 +1' REMPI scheme to detect trapped cold OH molecules. We use this capability to measure the trap dynamics of the central density of the cloud and the density distribution. These types of measurements can be used to optimize loading of molecules into traps, as well as to help characterize the energy distribution, which is critical knowledge for interpreting molecular collision experiments.

Short communication: Identification of subclinical cow mastitis pathogens in milk by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

PubMed

Barreiro, J R; Ferreira, C R; Sanvido, G B; Kostrzewa, M; Maier, T; Wegemann, B; Böttcher, V; Eberlin, M N; dos Santos, M V

2010-12-01

Subclinical mastitis is a common and easily disseminated disease in dairy herds. Its routine diagnosis via bacterial culture and biochemical identification is a difficult and time-consuming process. In this work, we show that matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) allows bacterial identification with high confidence and speed (1 d for bacterial growth and analysis). With the use of MALDI-TOF MS, 33 bacterial culture isolates from milk of different dairy cows from several farms were analyzed, and the results were compared with those obtained by classical biochemical methods. This proof-of-concept case demonstrates the reliability of MALDI-TOF MS bacterial identification, and its increased selectivity as illustrated by the additional identification of coagulase-negative Staphylococcus species and mixed bacterial cultures. Matrix-assisted laser desorption-ionization mass spectrometry considerably accelerates the diagnosis of mastitis pathogens, especially in cases of subclinical mastitis. More immediate and efficient animal management strategies for mastitis and milk quality control in the dairy industry can therefore be applied. Copyright © 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Laser-induced dissociation processes of protonated glucose: dehydration reactions vs cross-ring dissociation

NASA Astrophysics Data System (ADS)

Dyakov, Y. A.; Kazaryan, M. A.; Golubkov, M. G.; Gubanova, D. P.; Bulychev, N. A.; Kazaryan, S. M.

2018-04-01

Studying the processes occurring in biological systems under irradiation is critically important for understanding the principles of working of biological systems. One of the main problems, which stimulate interest to the processes of photo-induced excitation and ionization of biomolecules, is the necessity of their identification by various mass spectrometry (MS) methods. While simple analysis of small molecules became a standard MS technique long time ago, recognition of large molecules, especially carbohydrates, is still a difficult problem, and requires sophisticated techniques and complicated computer analysis. Due to the large variety of substances in the samples, as far as the complexity of the processes occurring after excitation/ionization of the molecules, the recognition efficiency of MS technique in terms of carbohydrates is still not high enough. Additional theoretical and experimental analysis of ionization and dissociation processes in various kinds of polysaccharides, beginning from the simplest ones, is necessary. In our work, we extent previous theoretical and experimental studies of saccharides, and concentrate our attention to protonated glucose. In this article we paid the most attention to the cross-ring dissociation and water loss reactions due to their importance for identification of various isomers of hydrocarbon molecules (for example, distinguish α- and β-glucose).

Direct Impact Corona Ionization of Bacteria for Rapid, Reproducible Identification via Spectral Pattern Recognition

NASA Astrophysics Data System (ADS)

Alusta, Pierre; Buzatu, Dan; Tarasenko, Olga; Wilkes, Jon; Darsey, Jerry

2011-06-01

A novel atmospheric pressure ionization process, Direct Impact Corona Ionization (DICI), is described here. In this process, a corona impinges onto the flat surface of a stainless steel pin carrying a thin film of dried bacterial suspension, the analyte. Two electrodes—a corona electrode and the sample pin—are immersed in hot inert He gas flux, flowing past them towards a 0.4 mm orifice leading to a mass spectrometer analyzer. An electric potential of 1.5-3.0 kV is placed between the two. At distances less than 1 cm, an intermittent arc is formed. At approximately 4 mm, the arc becomes a continuous corona discharge (plasma). The plasma is hot enough to: A) locally melt the impact zone on the steel pin, and B) ablate the dry thin bacterial film deposited on the metal pin. Biomolecular ions as heavy as 790 m/z are generated. Mass spectral fingerprints of bacteria are obtained with a high degree of reproducibility by selecting the highest intensity of an "indicator ion", 560.5 m/z or another relatively heavy ion whose appearance signals efficient vaporization of low volatility components.

Photoionization Modeling and the K Lines of Iron

NASA Technical Reports Server (NTRS)

Kallman, T. R.; Palmeri, P.; Bautista, M. A.; Mendoza, C.; Krolik, J. H.

2004-01-01

We calculate the efficiency of iron K line emission and iron K absorption in photoionized models using a new set of atomic data. These data are more comprehensive than those previously applied to the modeling of iron K lines from photoionized gases, and allow us to systematically examine the behavior of the properties of line emission and absorption as a function of the ionization parameter, density and column density of model constant density clouds. We show that, for example, the net fluorescence yield for the highly charged ions is sensitive to the level population distribution produced by photoionization, and these yields are generally smaller than those predicted assuming the population is according to statistical weight. We demonstrate that the effects of the many strongly damped resonances below the K ionization thresholds conspire to smear the edge, thereby potentially affecting the astrophysical interpretation of absorption features in the 7-9 keV energy band. We show that the centroid of the ensemble of K(alpha) lines, the K(beta) energy, and the ratio of the K(alpha(sub 1)) to K(alpha(sub 2)) components are all diagnostics of the ionization parameter of our model slabs.

Laser Desorption Ionization of small molecules assisted by Tungsten oxide and Rhenium oxide particles

PubMed Central

Bernier, Matthew; Wysocki, Vicki; Dagan, Shai

2015-01-01

Inorganic metal oxides have shown potential as matrices for assisting in laser desorption ionization (LDI) with advantages over the aromatic acids typically used. Rhenium and tungsten oxides are an attractive option due to their high work functions and relative chemical inertness. In this work, it is shown that ReO3 and WO3, in microparticle (μP) powder forms, can efficiently ionize various types of small molecules and provide minimized background contamination at analyte concentrations below 1 ng/μL. This study shows that untreated inorganic WO3 and ReO3 particles are valid matrix options for detection of protonatable, radical, and precharged species under LDI. Qualitatively, the WO3 μP showed an improved detection of apigenin, sodiated glucose, and the precharged analyte choline, while the ReO3 μP allowed detection of protonated cocaine, quinuclidine, ametryn, and radical ions of polyaromatic hydrocarbons at detection levels as low as 50 pg/μL. For thermometer ion survival yield experiments, it was also shown that the ReO3 powder was significantly softer than CCA. Furthermore, it provided higher intensities of cocaine and polyaromatic hydrocarbons, at laser flux values equal to that used with CCA. PMID:26349643

Ionized gas at the edge of the central molecular zone

NASA Astrophysics Data System (ADS)

Langer, W. D.; Goldsmith, P. F.; Pineda, J. L.; Velusamy, T.; Requena-Torres, M. A.; Wiesemeyer, H.

2015-04-01

Context. The edge of the central molecular zone (CMZ) is the location where massive dense molecular clouds with large internal velocity dispersions transition to the surrounding more quiescent and lower CO emissivity region of the Galaxy. Little is known about the ionized gas surrounding the molecular clouds and in the transition region. Aims: We determine the properties of the ionized gas at the edge of the CMZ near Sgr E using observations of N+ and C+. Methods: We observed a small portion of the edge of the CMZ near Sgr E with spectrally resolved [C ii] 158 μm and [N ii] 205 μm fine structure lines at six positions with the GREAT instrument on SOFIA and in [C ii] using Herschel HIFI on-the-fly strip maps. We use the [N ii] spectra along with a radiative transfer model to calculate the electron density of the gas and the [C ii] maps to illuminate the morphology of the ionized gas and model the column density of CO-dark H2. Results: We detect two [C ii] and [N ii] velocity components, one along the line of sight to a CO molecular cloud at - 207 km s-1 associated with Sgr E and the other at -174 km s-1 outside the edge of another CO cloud. From the [N ii] emission we find that the average electron density is in the range of ~5 to 21 cm-3 for these features. This electron density is much higher than that of the disk's warm ionized medium, but is consistent with densities determined for bright diffuse H ii nebula. The column density of the CO-dark H2 layer in the -207 km s-1 cloud is ~1-2 × 1021 cm-2 in agreement with theoretical models. The CMZ extends further out in Galactic radius by ~7 to 14 pc in ionized gas than it does in molecular gas traced by CO. Conclusions: The edge of the CMZ likely contains dense hot ionized gas surrounding the neutral molecular material. The high fractional abundance of N+ and high electron density require an intense EUV field with a photon flux of order 106 to 107 photons cm-2 s-1, and/or efficient proton charge exchange with nitrogen, at temperatures of order 104 K, and/or a large flux of X-rays. Sgr E is a region of massive star formation as indicated by the presence of numerous compact H ii regions. The massive stars are potential sources of the EUV radiation that ionizes and heat the gas. In addition, X-ray sources and the diffuse X-ray emission in the CMZ are candidates for ionizing nitrogen.

Synthetic oligomer analysis using atmospheric pressure photoionization mass spectrometry at different photon energies.

PubMed

Desmazières, Bernard; Legros, Véronique; Giuliani, Alexandre; Buchmann, William

2014-01-15

Atmospheric pressure photoionization (APPI) followed by mass spectrometric detection was used to ionize a variety of polymers: polyethylene glycol, polymethyl methacrylate, polystyrene, and polysiloxane. In most cases, whatever the polymer or the solvent used (dichloromethane, tetrahydrofuran, hexane, acetone or toluene), only negative ion mode produced intact ions such as chlorinated adducts, with no or few fragmentations, in contrast to the positive ion mode that frequently led to important in-source fragmentations. In addition, it was shown that optimal detection of polymer distributions require a fine tuning of other source parameters such as temperature and ion transfer voltage. Series of mass spectra were recorded in the negative mode, in various solvents (dichloromethane, tetrahydrofuran, hexane, toluene, and acetone), by varying the photon energy from 8eV up to 10.6eV using synchrotron radiation. To these solvents, addition of a classical APPI dopant (toluene or acetone) was not necessary. Courtesy of the synchrotron radiation, it was demonstrated that the photon energy required for an efficient ionization of the polymer was correlated to the ionization energy of the solvent. As commercial APPI sources typically use krypton lamps with energy fixed at 10eV and 10.6eV, the study of the ionization of polymers over a wavelength range allowed to confirm and refine the previously proposed ionization mechanisms. Moreover, the APPI source can efficiently be used as an interface between size exclusion chromatography or reverse phase liquid chromatography and MS for the study of synthetic oligomers. However, the photoionization at fixed wavelength of polymer standards with different molecular weights showed that it was difficult to obtain intact ionized oligomers with molecular weights above a few thousands. Copyright © 2013 Elsevier B.V. All rights reserved.

Effect of oblique channel on discharge characteristics of 200-W Hall thruster

NASA Astrophysics Data System (ADS)

Ding, Yongjie; Peng, Wuji; Sun, Hezhi; Xu, Yu; Wei, Liqiu; Li, Hong; Zeng, Ming; Wang, Fufeng; Yu, Daren

2017-02-01

In an experiment involving a 200-W Hall thruster, partial ionization occurs in the plume area because of the extrapolation of the magnetic field. To improve the thruster performance, the concept of an oblique channel is proposed for improving the ionization degree in the plume area. Calculations performed using a Particle-in-cell (PIC) simulator and the experimental results both show that an oblique channel structure can reduce the wall loss. Compared with a straight channel under similar conditions of the discharge voltage and current, the ionization degree in the plume area, thrust, specific impulse, propellant utilization, and anode efficiency are improved by ˜20%. The oblique channel is an important design consideration for improving the partial ionization of the plume area in the thruster.

The different origins of high- and low-ionization broad emission lines revealed by gravitational microlensing in the Einstein cross

NASA Astrophysics Data System (ADS)

Braibant, L.; Hutsemékers, D.; Sluse, D.; Anguita, T.

2016-07-01

We investigate the kinematics and ionization structure of the broad emission line region of the gravitationally lensed quasar QSO2237+0305 (the Einstein cross) using differential microlensing in the high- and low-ionization broad emission lines. We combine visible and near-infrared spectra of the four images of the lensed quasar and detect a large-amplitude microlensing effect distorting the high-ionization CIV and low-ionization Hα line profiles in image A. While microlensing only magnifies the red wing of the Balmer line, it symmetrically magnifies the wings of the CIV emission line. Given that the same microlensing pattern magnifies both the high- and low-ionization broad emission line regions, these dissimilar distortions of the line profiles suggest that the high- and low-ionization regions are governed by different kinematics. Since this quasar is likely viewed at intermediate inclination, we argue that the differential magnification of the blue and red wings of Hα favors a flattened, virialized, low-ionization region whereas the symmetric microlensing effect measured in CIV can be reproduced by an emission line formed in a polar wind, without the need of fine-tuned caustic configurations. Based on observations made with the ESO-VLT, Paranal, Chile; Proposals 076.B-0197 and 076.B-0607 (PI: Courbin).

Eu2+-Doped Sr2B2-2xSi2+3xAl2-xN8+x: A Boron-Containing Orange-Emitting Nitridosilicate with Interesting Composition-Dependent Photoluminescence Properties.

PubMed

Ten Kate, Otmar M; Xie, Rong-Jun; Wang, Chun-Yun; Funahashi, Shiro; Hirosaki, Naoto

2016-11-07

Novel Sr 2-y Eu y B 2-2x Si 2+3x Al 2-x N 8+x phosphors were investigated as a function of the boron and aluminum over silicon ratio and as a function of the Eu 2+ concentration. Samples were prepared via solid-state reaction synthesis by carefully controlling the synthesis conditions and composition. At high boron and aluminum content, that is, x = 0, a Eu 2+ 5d-4f emission is observed of which the maximum shifts from 595 nm for low Eu concentrations (y = 0.005) toward 623 nm for high Eu concentrations (y = 0.5). The samples can be excited by UV or blue light up to ∼475 nm. Substitution of [B 2 Al] 9+ units by [Si 3 N] 9+ units, increasing x up to 0.15, greatly improves the luminescence efficiency up to 46% and shows a very large redshift of the excitation bands with ∼100 nm, while the emission band shifts with ∼10 nm. The shifts are attributed to the lowering of the 5d level as a result of the decreased Eu-N distance upon substitution. Temperature-dependent measurements show that the Eu 2+ 5d-4f emission is largely thermally quenched at room temperature for x = 0 due to thermal ionization toward the conduction band, explaining the low luminescence efficiency. The lowering of the 5d level at larger values of x reduces the thermal ionization and consequently increases the thermal stability and quantum efficiency, resulting in strongly luminescent blue-to-orange conversion phosphors that are interesting for light-emitting diode applications.

Comparison of Internal Energy Distributions of Ions Created by Electrospray Ionization and Laser Ablation-Liquid Vortex Capture-Electrospray Ionization

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

Cahill, John F.; Kertesz, Vilmos; Ovchinnikova, Olga S.

2015-06-27

Recently a number of techniques have combined laser ablation with liquid capture for mass spectrometry spot sampling and imaging applications. The newly developed non-contact liquid-vortex capture probe has been used to efficiently collect 355 nm UV laser ablated material in a continuous flow solvent stream in which the captured material dissolves and then undergoes electrospray ionization. This sampling and ionization approach has produced what appear to be classic electrospray ionization spectra; however, the softness of this sampling/ionization process versus simple electrospray ionization has not been definitely determined. A series of benzlypyridinium salts, known as thermometer ions, were used to comparemore » internal energy distributions between electrospray ionization and the UV laser ablation liquid-vortex capture probe electrospray combination. Measured internal energy distributions were identical between the two techniques, even with differences in laser fluence (0.7-3.1 J cm-2) and when using UV-absorbing or non-UV-absorbing sample substrates. This data indicates ions formed directly by UV laser ablation, if any, are likely an extremely small constituent of the total ion signal observed. Instead, neutral molecules, clusters or particulates ejected from the surface during laser ablation, subsequently captured and dissolved in the flowing solvent stream then electrosprayed are the predominant source of ion signal observed. The electrospray ionization process used controls the softness of the technique.« less

Improving low-level plasma protein mass spectrometry-based detection for candidate biomarker discovery and validation

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

Page, Jason S.; Kelly, Ryan T.; Camp, David G.

2008-09-01

Methods. To improve the detection of low abundance protein candidate biomarker discovery and validation, particularly in complex biological fluids such as blood plasma, increased sensitivity is desired using mass spectrometry (MS)-based instrumentation. A key current limitation on the sensitivity of electrospray ionization (ESI) MS is due to the fact that many sample molecules in solution are never ionized, and the vast majority of the ions that are created are lost during transmission from atmospheric pressure to the low pressure region of the mass analyzer. Two key technologies, multi-nanoelectrospray emitters and the electrodynamic ion funnel have recently been developed and refinedmore » at Pacific Northwest National Laboratory (PNNL) to greatly improve the ionization and transmission efficiency of ESI MS based analyses. Multi-emitter based ESI enables the flow from a single source (typically a liquid chromatography [LC] column) to be divided among an array of emitters (Figure 1). The flow rate delivered to each emitter is thus reduced, allowing the well-documented benefits of nanoelectrospray 1 for both sensitivity and quantitation to be realized for higher flow rate separations. To complement the increased ionization efficiency afforded by multi-ESI, tandem electrodynamic ion funnels have also been developed at PNNL, and shown to greatly improve ion transmission efficiency in the ion source interface.2, 3 These technologies have been integrated into a triple quadrupole mass spectrometer for multiple reaction monitoring (MRM) of probable biomarker candidates in blood plasma and show promise for the identification of new species even at low level concentrations.« less

Highly sensitive derivatization reagents possessing positively charged structures for the determination of oligosaccharides in glycoproteins by high-performance liquid chromatography electrospray ionization tandem mass spectrometry.

PubMed

Min, Jun Zhe; Nagai, Keisuke; Shi, Qing; Zhou, Wenjun; Todoroki, Kenichiro; Inoue, Koichi; Lee, Yong-Ill; Toyo'oka, Toshimasa

2016-09-23

We have developed three kinds of novel derivatization reagents (4-CEBTPP, 4-CBBTPP, 5-COTPP) with triphenylphosphine (TPP) as a basic structure carrying a permanent positive charge for resolution of the oligosaccharides in glycoprotein using high-performance liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). The synthesized reagents reacted with the sialylglycosylamine of the sialylglycopeptide after treatment by PNGase F. The final derivatives were analyzed by ESI-MS and sensitively detected in the selected reaction monitoring (SRM) mode. Furthermore, the limits of detection (S/N=3) on the SRM chromatograms were at the fmol level (30fmol). Therefore, we used the limit of detection of the reagent products detected by the SRM and evaluated the utility of each reagent. Among the reagents, the positively charged 4-CEBTPP derivative's peak area was the highest; 4-CEBTPP with a positively charged structure showed about a 20 times greater sensitivity for the glycosylamine of the SGP product compared to the conventional fluorescence reagent, Fmoc-Cl. In addition, various fragment ions based on the carbohydrate units also appeared in the MS/MS spectra. Among the fragment ions, m/z 627.37 (CE=40eV) corresponding to 4-CEBTPP-GlcNAc and m/z 120.09 (CE=100eV) corresponding to 4-CEBTPP are the most important ones for identifying the oligosaccharide. 4-CEBTPP-SGA was easily identified by the selected-ion chromatogram in the product ion scan (m/z 120.09) and in the precursor ion scan (m/z 627.37) by MS/MS detection. The derivatized analytes have a high ionization efficiency and they are detected with a high sensitivity in the electrospray ionization. The novel derivatization reagent with a multi-function provided a higher sensitivity for the oligosaccharide analysis, as well as a better specificity and feasibility. Furthermore, several oligosaccharides in fetuin and ribonuclease B were successfully identified by the proposed procedure. Copyright © 2016 Elsevier B.V. All rights reserved.

Synergistic effect of ozonation and ionizing radiation for PVA decomposition.

PubMed

Sun, Weihua; Chen, Lujun; Zhang, Yongming; Wang, Jianlong

2015-08-01

Ozonation and ionizing radiation are both advanced oxidation processes (AOPs) without chemical addition and secondary pollution. Also, the two processes' efficiency is determined by different pH conditions, which creates more possibilities for their combination. Importantly, the combined process of ozonation and ionizing radiation could be suitable for treating wastewaters with extreme pH values, i.e., textile wastewater. To find synergistic effects, the combined process of ozonation and ionizing radiation mineralization was investigated for degradation of polyvinyl alcohol (PVA) at different pH levels. A synergistic effect was found at initial pH in the range 3.0-9.4. When the initial pH was 3.0, the combined process of ozonation and ionizing radiation gave a PVA mineralization degree of 17%. This was 2.7 times the sum achieved by the two individual processes, and factors of 2.1 and 1.7 were achieved at initial pH of 7.0 and 9.4, respectively. The combined process of ozonation and ionizing radiation was demonstrated to be a feasible strategy for treatment of PVA-containing wastewater. Copyright © 2015. Published by Elsevier B.V.

Sensitive ion detection device and method for analysis of compounds as vapors in gases

DOEpatents

Denton, M. Bonner; Sperline, Roger P.

2015-09-15

An ion mobility spectrometer (IMS) for the detection of trace gaseous molecular compounds dissolved or suspended in a carrier gas, particularly in ambient air, without preconcentration or the trapping of analyte particles. The IMS of the invention comprises an ionization volume of greater than 5 cm.sup.3 and preferably greater than 100 cm.sup.3. The larger size ionizers of this invention enable analysis of trace (<1 ppb) of sample compounds in the gas phase. To facilitate efficient ion motion through the large volume ionization and reaction regions of the IMS, an electric field gradient can be provided in the ionization region or in both the ionization and reaction regions. The systems can be implemented with radioactive ionization sources, corona discharge ion sources or ions can be formed by photoionization. In specific embodiments, particularly when the sample gas is ambient air, the sample gas is heater prior to entry into the instrument, the instrument is run at temperatures above ambient, and the instrument can be heated by contact with heated sample gas exiting the instrument.

Sensitive ion detection device and method for analysis of compounds as vapors in gases

DOEpatents

Denton, M. Bonner; Sperline, Roger P

2014-02-18

An ion mobility spectrometer (IMS) for the detection of trace gaseous molecular compounds dissolved or suspended in a carrier gas, particularly in ambient air, without preconcentration or the trapping of analyte particles. The IMS of the invention comprises an ionization volume of greater than 5 cm.sup.3 and preferably greater than 100 cm.sup.3. The larger size ionizers of this invention enable analysis of trace (<1 ppb) of sample compounds in the gas phase. To facilitate efficient ion motion through the large volume ionization and reaction regions of the IMS, an electric field gradient can be provided in the ionization region or in both the ionization and reaction regions. The systems can be implemented with radioactive ionization sources, corona discharge ion sources or ions can be formed by photoionization. In specific embodiments, particularly when the sample gas is ambient air, the sample gas is heater prior to entry into the instrument, the instrument is run at temperatures above ambient, and the instrument can be heated by contact with heated sample gas exiting the instrument.

Study of the ionization rate of the released deuterium in vacuum arc discharges with metal deuteride cathodes

NASA Astrophysics Data System (ADS)

Liu, Fei-Xiang; Long, Ji-Dong; Zheng, Le; Dong, Pan; Li, Chen; Chen, Wei

2018-02-01

The ionization rate of the released deuterium from a metal deuteride cathode in vacuum arc discharges is investigated by both experiments and modeling analysis. Experimental results show that the deuterium ionization rate increases from 2% to 30% with the increasing arc current in the range of 2-100 A. Thus the full ionization assumption, as is widely used in arc plasma simulations, is not satisfied for the released deuterium at low discharge current. According to the modeling results, the neutral-to-ion conversion efficiency for the deuterium traveling across the cathodic spot region can be significantly less than one, due to the fast plasma expansion and rarefaction in the vacuum. In addition, the model also reveals that, unlike the metal atoms which are mainly ionized in the sheath region and flow back to the cathode, the deuterium ionization primarily occurs in the quasi-neutral region and moves towards the anode. Consequently, the cathodic sheath layer acts like a filter that increases the deuterium fraction beyond the sheath region.

Efficiencies for production of atomic nitrogen and oxygen by relativistic proton impact in air

NASA Technical Reports Server (NTRS)

Porter, H. S.; Jackman, C. H.; Green, A. E. S.

1976-01-01

Relativistic electron and proton impact cross sections are obtained and represented by analytic forms which span the energy range from threshold to 1 GeV. For ionization processes, the Massey-Mohr continuum generalized oscillator strength surface is parameterized. Parameters are determined by simultaneous fitting to (1) empirical data, (2) the Bethe sum rule, and (3) doubly differential cross sections for ionization. Branching ratios for dissociation and predissociation from important states of N2 and O2 are determined. The efficiency for the production of atomic nitrogen and oxygen by protons with kinetic energy less than 1 GeV is determined using these branching ratio and cross section assignments.

Electron-muon ranger: performance in the MICE muon beam

NASA Astrophysics Data System (ADS)

Adams, D.; Alekou, A.; Apollonio, M.; Asfandiyarov, R.; Barber, G.; Barclay, P.; de Bari, A.; Bayes, R.; Bayliss, V.; Bene, P.; Bertoni, R.; Blackmore, V. J.; Blondel, A.; Blot, S.; Bogomilov, M.; Bonesini, M.; Booth, C. N.; Bowring, D.; Boyd, S.; Bradshaw, T. W.; Bravar, U.; Bross, A. D.; Cadoux, F.; Capponi, M.; Carlisle, T.; Cecchet, G.; Charnley, C.; Chignoli, F.; Cline, D.; Cobb, J. H.; Colling, G.; Collomb, N.; Coney, L.; Cooke, P.; Courthold, M.; Cremaldi, L. M.; Debieux, S.; DeMello, A.; Dick, A.; Dobbs, A.; Dornan, P.; Drielsma, F.; Filthaut, F.; Fitzpatrick, T.; Franchini, P.; Francis, V.; Fry, L.; Gallagher, A.; Gamet, R.; Gardener, R.; Gourlay, S.; Grant, A.; Graulich, J. S.; Greis, J.; Griffiths, S.; Hanlet, P.; Hansen, O. M.; Hanson, G. G.; Hart, T. L.; Hartnett, T.; Hayler, T.; Heidt, C.; Hills, M.; Hodgson, P.; Hunt, C.; Husi, C.; Iaciofano, A.; Ishimoto, S.; Kafka, G.; Kaplan, D. M.; Karadzhov, Y.; Kim, Y. K.; Kuno, Y.; Kyberd, P.; Lagrange, J.-B.; Langlands, J.; Lau, W.; Leonova, M.; Li, D.; Lintern, A.; Littlefield, M.; Long, K.; Luo, T.; Macwaters, C.; Martlew, B.; Martyniak, J.; Masciocchi, F.; Mazza, R.; Middleton, S.; Moretti, A.; Moss, A.; Muir, A.; Mullacrane, I.; Nebrensky, J. J.; Neuffer, D.; Nichols, A.; Nicholson, R.; Nicola, L.; Noah Messomo, E.; Nugent, J. C.; Oates, A.; Onel, Y.; Orestano, D.; Overton, E.; Owens, P.; Palladino, V.; Pasternak, J.; Pastore, F.; Pidcott, C.; Popovic, M.; Preece, R.; Prestemon, S.; Rajaram, D.; Ramberger, S.; Rayner, M. A.; Ricciardi, S.; Roberts, T. J.; Robinson, M.; Rogers, C.; Ronald, K.; Rothenfusser, K.; Rubinov, P.; Rucinski, P.; Sakamato, H.; Sanders, D. A.; Sandström, R.; Santos, E.; Savidge, T.; Smith, P. J.; Snopok, P.; Soler, F. J. P.; Speirs, D.; Stanley, T.; Stokes, G.; Summers, D. J.; Tarrant, J.; Taylor, I.; Tortora, L.; Torun, Y.; Tsenov, R.; Tunnell, C. D.; Uchida, M. A.; Vankova-Kirilova, G.; Virostek, S.; Vretenar, M.; Warburton, P.; Watson, S.; White, C.; Whyte, C. G.; Wilson, A.; Wisting, H.; Yang, X.; Young, A.; Zisman, M.

2015-12-01

The Muon Ionization Cooling Experiment (MICE) will perform a detailed study of ionization cooling to evaluate the feasibility of the technique. To carry out this program, MICE requires an efficient particle-identification (PID) system to identify muons. The Electron-Muon Ranger (EMR) is a fully-active tracking-calorimeter that forms part of the PID system and tags muons that traverse the cooling channel without decaying. The detector is capable of identifying electrons with an efficiency of 98.6%, providing a purity for the MICE beam that exceeds 99.8%. The EMR also proved to be a powerful tool for the reconstruction of muon momenta in the range 100-280 MeV/c.

Peas in a Pod: Environment and Ionization in Green Pea Galaxies

NASA Astrophysics Data System (ADS)

Kurtz, Heather; Jaskot, Anne; Drew, Patrick; Pare, Dylan; Griffin, Jon; Petersen, Michael

2016-01-01

The Green Peas are extreme, highly ionized, starburst galaxies with strong [OIII] 5007 emission. Using the Sloan Digital Sky Survey, we present statistics on the environment of Green Peas and investigate its effects on their ionized gas properties. Although most dwarf starburst galaxies are in low-density environments, we identify a sample of Green Peas in dense environments. Emission line observations with the WIYN 0.9-meter telescope at Kitt Peak reveal that one cluster Green Pea is more highly ionized in the direction of the cluster center. Ram pressure stripping likely generates this ionization gradient. We explore the role of the environment in enhancing star formation rates and ionization, and we compare the nebular properties of Green Peas in high-density environments to those in low-density environments.

Analyzing non-LTE Kr plasmas produced in high energy density experiments: from the Z machine to the National Ignition Facility

NASA Astrophysics Data System (ADS)

Dasgupta, Arati

2015-11-01

Designing high fluence photon sources above 10 keV are a challenge for High Energy Density plasmas. This has motivated radiation source development investigations of Kr with K-shell energies around 13 keV. Recent pulsed power driven gas-puff experiments on the refurbished Z machine at Sandia have produced intense X-rays in the multi-keV photon energy range. K-shell radiative yields and efficiencies are very high for Ar, but rapidly decrease for higher atomic number (ZA) elements such as Kr. It has been suggested that an optimum exists corresponding to a trade-off between the increase of photon energy for higher ZA elements and the corresponding fall off in radiative power. However the conversion efficiency on NIF, where the drive, energy deposition process, and target dynamics are different, does not fall off with higher ZA as rapidly as on Z. We have developed detailed atomic structure and collisional data for the full K-, L- and partial M-shell of Kr using the Flexible Atomic Code (FAC). Our non-LTE atomic model includes all collisional and recombination processes, including state-specific dielectronic recombination (DR), that significantly affect ionization balance and spectra of Kr plasmas at the temperatures and densities of concern. The model couples ionization physics, radiation production and transport, and magnetohydrodynamics. In this talk, I will give a detailed description of the model and discuss 1D Kr simulations employing a multifrequency radiation transport scheme. Synthetic K- and L-shell spectra will be compared with available experimental data. This talk will analyze experimental data indicative of the differences between Z and NIF experimental data and discuss how they affect the K-shell radiative output of Kr plasma. Work supported by DOE/NNSA.

Atmospheric Ionizing Radiation (AIR): Analysis, Results, and Lessons Learned From the June 1997 ER-2 Campaign

NASA Technical Reports Server (NTRS)

Wilson, J. W. (Editor); Jones, I. W. (Editor); Maiden, D. L. (Editor); Goldhagen, P. (Editor)

2003-01-01

The United States initiated a program to assess the technology required for an environmentally safe and operationally efficient High Speed Civil Transport (HSCT) for entrance on the world market after the turn of the century. Due to the changing regulations on radiation exposures and the growing concerns over uncertainty in our knowledge of atmospheric radiations, the NASA High Speed Research Project Office (HSRPO) commissioned a review of "Radiation Exposure and High-Altitude Flight" by the National Council on Radiation Protection and Measurements (NCRP). On the basis of the NCRP recommendations, the HSRPO funded a flight experiment to resolve the environmental uncertainty in the atmospheric ionizing radiation levels as a step in developing an approach to minimize the radiation impact on HSCT operations. To minimize costs in this project, an international investigator approach was taken to assure coverage with instrument sensitivity across the range of particle types and energies to allow unique characterization of the diverse radiation components. The present workshop is a result of the flight measurements made at the maximum intensity of the solar cycle modulated background radiation levels during the month of June 1997.

Ionization processes in combined high-voltage nanosecond - laser discharges in inert gas

NASA Astrophysics Data System (ADS)

Starikovskiy, Andrey; Shneider, Mikhail; PU Team

2016-09-01

Remote control of plasmas induced by laser radiation in the atmosphere is one of the challenging issues of free space communication, long-distance energy transmission, remote sensing of the atmosphere, and standoff detection of trace gases and bio-threat species. Sequences of laser pulses, as demonstrated by an extensive earlier work, offer an advantageous tool providing access to the control of air-plasma dynamics and optical interactions. The avalanche ionization induced in a pre-ionized region by infrared laser pulses where investigated. Pre-ionization was created by an ionization wave, initiated by high-voltage nanosecond pulse. Then, behind the front of ionization wave extra avalanche ionization was initiated by the focused infrared laser pulse. The experiment was carried out in argon. It is shown that the gas pre-ionization inhibits the laser spark generation under low pressure conditions.

Impact desolvation of electrosprayed microdroplets--a new ionization method for mass spectrometry of large biomolecules.

PubMed

Aksyonov, S A; Williams, P

2001-01-01

Impact desolvation of electrosprayed microdroplets (IDEM) is a new method for producing gas-phase ions of large biomolecules. Analytes are dissolved in an electrolyte solution which is electrosprayed in vacuum, producing highly charged micron and sub-micron sized droplets (microdroplets). These microdroplets are accelerated through potential differences approximately 5 - 10 kV to velocities of several km/s and allowed to impact a target surface. The energetic impacts vaporize the droplets and release desolvated gas-phase ions of the analyte molecules. Oligonucleotides (2- to 12-mer) and peptides (bradykinin, neurotensin) yield singly and doubly charged molecular ions with no detectable fragmentation. Because the extent of multiple charging is significantly less than in atmospheric pressure electrospray ionization, and the method produces ions largely free of adducts from solutions of high ionic strength, IDEM has some promise as a method for coupling to liquid chromatographic techniques and for mixture analysis. Ions are produced in vacuum at a flat equipotential surface, potentially allowing efficient ion extraction. Copyright 2001 John Wiley & Sons, Ltd.

Femtosecond response of polyatomic molecules to ultra-intense hard X-rays.

PubMed

Rudenko, A; Inhester, L; Hanasaki, K; Li, X; Robatjazi, S J; Erk, B; Boll, R; Toyota, K; Hao, Y; Vendrell, O; Bomme, C; Savelyev, E; Rudek, B; Foucar, L; Southworth, S H; Lehmann, C S; Kraessig, B; Marchenko, T; Simon, M; Ueda, K; Ferguson, K R; Bucher, M; Gorkhover, T; Carron, S; Alonso-Mori, R; Koglin, J E; Correa, J; Williams, G J; Boutet, S; Young, L; Bostedt, C; Son, S-K; Santra, R; Rolles, D

2017-06-01

X-ray free-electron lasers enable the investigation of the structure and dynamics of diverse systems, including atoms, molecules, nanocrystals and single bioparticles, under extreme conditions. Many imaging applications that target biological systems and complex materials use hard X-ray pulses with extremely high peak intensities (exceeding 10 20 watts per square centimetre). However, fundamental investigations have focused mainly on the individual response of atoms and small molecules using soft X-rays with much lower intensities. Studies with intense X-ray pulses have shown that irradiated atoms reach a very high degree of ionization, owing to multiphoton absorption, which in a heteronuclear molecular system occurs predominantly locally on a heavy atom (provided that the absorption cross-section of the heavy atom is considerably larger than those of its neighbours) and is followed by efficient redistribution of the induced charge. In serial femtosecond crystallography of biological objects-an application of X-ray free-electron lasers that greatly enhances our ability to determine protein structure-the ionization of heavy atoms increases the local radiation damage that is seen in the diffraction patterns of these objects and has been suggested as a way of phasing the diffraction data. On the basis of experiments using either soft or less-intense hard X-rays, it is thought that the induced charge and associated radiation damage of atoms in polyatomic molecules can be inferred from the charge that is induced in an isolated atom under otherwise comparable irradiation conditions. Here we show that the femtosecond response of small polyatomic molecules that contain one heavy atom to ultra-intense (with intensities approaching 10 20 watts per square centimetre), hard (with photon energies of 8.3 kiloelectronvolts) X-ray pulses is qualitatively different: our experimental and modelling results establish that, under these conditions, the ionization of a molecule is considerably enhanced compared to that of an individual heavy atom with the same absorption cross-section. This enhancement is driven by ultrafast charge transfer within the molecule, which refills the core holes that are created in the heavy atom, providing further targets for inner-shell ionization and resulting in the emission of more than 50 electrons during the X-ray pulse. Our results demonstrate that efficient modelling of X-ray-driven processes in complex systems at ultrahigh intensities is feasible.

Femtosecond response of polyatomic molecules to ultra-intense hard X-rays

DOE PAGES

Rudenko, A.; Inhester, L.; Hanasaki, K.; ...

2017-05-31

We report x-ray free-electron lasers enable the investigation of the structure and dynamics of diverse systems, including atoms, molecules, nanocrystals and single bioparticles, under extreme conditions. Many imaging applications that target biological systems and complex materials use hard X-ray pulses with extremely high peak intensities (exceeding 10 20 watts per square centimetre). However, fundamental investigations have focused mainly on the individual response of atoms and small molecules using soft X-rays with much lower intensities. Studies with intense X-ray pulses have shown that irradiated atoms reach a very high degree of ionization, owing to multiphoton absorption, which in a heteronuclear molecularmore » system occurs predominantly locally on a heavy atom (provided that the absorption cross-section of the heavy atom is considerably larger than those of its neighbours) and is followed by efficient redistribution of the induced charge. In serial femtosecond crystallography of biological objects—an application of X-ray free-electron lasers that greatly enhances our ability to determine protein structure—the ionization of heavy atoms increases the local radiation damage that is seen in the diffraction patterns of these objects and has been suggested as a way of phasing the diffraction data. On the basis of experiments using either soft or less-intense hard X-rays, it is thought that the induced charge and associated radiation damage of atoms in polyatomic molecules can be inferred from the charge that is induced in an isolated atom under otherwise comparable irradiation conditions. Here we show that the femtosecond response of small polyatomic molecules that contain one heavy atom to ultra-intense (with intensities approaching 10 20 watts per square centimetre), hard (with photon energies of 8.3 kiloelectronvolts) X-ray pulses is qualitatively different: our experimental and modelling results establish that, under these conditions, the ionization of a molecule is considerably enhanced compared to that of an individual heavy atom with the same absorption cross-section. This enhancement is driven by ultrafast charge transfer within the molecule, which refills the core holes that are created in the heavy atom, providing further targets for inner-shell ionization and resulting in the emission of more than 50 electrons during the X-ray pulse. Fnally, our results demonstrate that efficient modelling of X-ray-driven processes in complex systems at ultrahigh intensities is feasible.« less

Femtosecond response of polyatomic molecules to ultra-intense hard X-rays

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

Rudenko, A.; Inhester, L.; Hanasaki, K.

We report x-ray free-electron lasers enable the investigation of the structure and dynamics of diverse systems, including atoms, molecules, nanocrystals and single bioparticles, under extreme conditions. Many imaging applications that target biological systems and complex materials use hard X-ray pulses with extremely high peak intensities (exceeding 10 20 watts per square centimetre). However, fundamental investigations have focused mainly on the individual response of atoms and small molecules using soft X-rays with much lower intensities. Studies with intense X-ray pulses have shown that irradiated atoms reach a very high degree of ionization, owing to multiphoton absorption, which in a heteronuclear molecularmore » system occurs predominantly locally on a heavy atom (provided that the absorption cross-section of the heavy atom is considerably larger than those of its neighbours) and is followed by efficient redistribution of the induced charge. In serial femtosecond crystallography of biological objects—an application of X-ray free-electron lasers that greatly enhances our ability to determine protein structure—the ionization of heavy atoms increases the local radiation damage that is seen in the diffraction patterns of these objects and has been suggested as a way of phasing the diffraction data. On the basis of experiments using either soft or less-intense hard X-rays, it is thought that the induced charge and associated radiation damage of atoms in polyatomic molecules can be inferred from the charge that is induced in an isolated atom under otherwise comparable irradiation conditions. Here we show that the femtosecond response of small polyatomic molecules that contain one heavy atom to ultra-intense (with intensities approaching 10 20 watts per square centimetre), hard (with photon energies of 8.3 kiloelectronvolts) X-ray pulses is qualitatively different: our experimental and modelling results establish that, under these conditions, the ionization of a molecule is considerably enhanced compared to that of an individual heavy atom with the same absorption cross-section. This enhancement is driven by ultrafast charge transfer within the molecule, which refills the core holes that are created in the heavy atom, providing further targets for inner-shell ionization and resulting in the emission of more than 50 electrons during the X-ray pulse. Fnally, our results demonstrate that efficient modelling of X-ray-driven processes in complex systems at ultrahigh intensities is feasible.« less

Interaction of intense ultrashort pulse lasers with clusters.

NASA Astrophysics Data System (ADS)

Petrov, George

2007-11-01

The last ten years have witnessed an explosion of activity involving the interaction of clusters with intense ultrashort pulse lasers. Atomic or molecular clusters are targets with unique properties, as they are halfway between solid and gases. The intense laser radiation creates hot dense plasma, which can provide a compact source of x-rays and energetic particles. The focus of this investigation is to understand the salient features of energy absorption and Coulomb explosion by clusters. The evolution of clusters is modeled with a relativistic time-dependent 3D Molecular Dynamics (MD) model [1]. The Coulomb interaction between particles is handled by a fast tree algorithm, which allows large number of particles to be used in simulations [2]. The time histories of all particles in a cluster are followed in time and space. The model accounts for ionization-ignition effects (enhancement of the laser field in the vicinity of ions) and a variety of elementary processes for free electrons and charged ions, such as optical field and collisional ionization, outer ionization and electron recapture. The MD model was applied to study small clusters (1-20 nm) irradiated by a high-intensity (10^16-10^20 W/cm^2) sub-picosecond laser pulse. We studied fundamental cluster features such as energy absorption, x-ray emission, particle distribution, average charge per atom, and cluster explosion as a function of initial cluster radius, laser peak intensity and wavelength. Simulations of novel applications, such as table-top nuclear fusion from exploding deuterium clusters [3] and high power synchrotron radiation for biological applications and imaging [4] have been performed. The application for nuclear fusion was motivated by the efficient absorption of laser energy (˜100%) and its high conversion efficiency into ion kinetic energy (˜50%), resulting in neutron yield of 10^6 neutrons/Joule laser energy. Contributors: J. Davis and A. L. Velikovich. [1] G. M. Petrov, et al Phys. Plasmas 12 063103 (2005); 13 033106 (2006) [2] G. M. Petrov, J. Davis, European Phys. J. D 41 629 (2007) [3] G. M. Petrov, J. Davis, A. L. Velikovich, Plasma Phys. Contr. Fusion 48 1721 (2006) [4] G. M. Petrov, J. Davis, A. L. Velikovich, J. Phys. B 39 4617 (2006)

Novel methods for matter interferometry with nanosized objects

NASA Astrophysics Data System (ADS)

Arndt, Markus

2005-05-01

We discuss the current status and prospects for novel experimental methods for coherence^1,2 and decoherence^3 experiments with large molecules. Quantum interferometry with nanosized objects is interesting for the exploration of the quantum-classical transition. The same experimental setup is also promising for metrology applications and molecular nanolithography. Our coherence experiments with macromolecules employ a Talbot-Lau interferometer. We discuss some modifications to this scheme, which are required to extend it to particles with masses in excess of several thousand mass units. In particular, the detection in all previous interference experiments with large clusters and molecules, was based on either laser ionization^1 (e.g. Fullerenes) or electron impact ionization^2 (e.g. Porphyrins etc.). However, most ionization schemes run into efficiency limits when the mass and complexity of the target particle increases. Here we present experimental results for an interference detector which is truly scalable, i.e. one which will even improve with increasing particle size and complexity. ``Mechanically magnified fluorescence imaging'' (MMFI), combines the high spatial resolution, which is intrinsic to Talbot Lau interferometry with the high detection efficiency of fluorophores adsorbed onto a substrate. In the Talbot Lau setup a molecular interference pattern is revealed by scanning the 3^rd grating across the molecular beam^1. The number of transmitted molecules is a function of the relative position between the mask and the molecular density pattern. Both the particle interference pattern and the mechanical mask structure may be far smaller than any optical resolution limit. After mechanical magnification by an arbitrary factor, in our case a factor 5000, the interference pattern can still be inspected in fluorescence microscopy. The fluorescent molecules are collected on a surface which is scanned collinearly and synchronously behind the 3rd grating. The resulting image of the interference pattern is by far large enough to be easily seen by the unaided eye. High contrast interference fringes could be recorded with dyes molecules. ^1B. Brezger et al. , Phys. Rev. Lett. 88, 100404 (2002). ^2L. Hackermüller et al. Phys. Rev. Lett 91, 90408 (2003). ^3L. Hackermüller et al. Nature 427, 711 (2004).

A large high-efficiency multi-layered Micromegas thermal neutron detector

NASA Astrophysics Data System (ADS)

Tsiledakis, G.; Delbart, A.; Desforge, D.; Giomataris, I.; Menelle, A.; Papaevangelou, T.

2017-09-01

Due to the so-called 3He shortage crisis, many detection techniques used nowadays for thermal neutrons are based on alternative converters. Thin films of 10B or 10B4C are used to convert neutrons into ionizing particles which are subsequently detected in gas proportional counters, but only for small or medium sensitive areas so far. The micro-pattern gaseous detector Micromegas has been developed for several years in Saclay and is used in a wide variety of neutron experiments combining high accuracy, high rate capability, excellent timing properties and robustness. We propose here a large high-efficiency Micromegas-based neutron detector with several 10B4C thin layers mounted inside the gas volume for thermal neutron detection. The principle and the fabrication of a single detector unit prototype with overall dimension of ~ 15 × 15 cm2 and a flexibility of modifying the number of layers of 10B4C neutron converters are described and simulated results are reported, demonstrating that typically five 10B4C layers of 1-2 μm thickness can lead to a detection efficiency of 20-40% for thermal neutrons and a spatial resolution of sub-mm. The design is well adapted to large sizes making possible the construction of a mosaic of several such detector units with a large area coverage and a high detection efficiency, showing the good potential of this novel technique.

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.

An Ultra-Trace Analysis Technique for SF6 Using Gas Chromatography with Negative Ion Chemical Ionization Mass Spectrometry.

PubMed

Jong, Edmund C; Macek, Paul V; Perera, Inoka E; Luxbacher, Kray D; McNair, Harold M

2015-07-01

Sulfur hexafluoride (SF6) is widely used as a tracer gas because of its detectability at low concentrations. This attribute of SF6 allows the quantification of both small-scale flows, such as leakage, and large-scale flows, such as atmospheric currents. SF6's high detection sensitivity also facilitates greater usage efficiency and lower operating cost for tracer deployments by reducing quantity requirements. The detectability of SF6 is produced by its high molecular electronegativity. This property provides a high potential for negative ion formation through electron capture thus naturally translating to selective detection using negative ion chemical ionization mass spectrometry (NCI-MS). This paper investigates the potential of using gas chromatography (GC) with NCI-MS for the detection of SF6. The experimental parameters for an ultra-trace SF6 detection method utilizing minimal customizations of the analytical instrument are detailed. A method for the detection of parts per trillion (ppt) level concentrations of SF6 for the purpose of underground ventilation tracer gas analysis was successfully developed in this study. The method utilized a Shimadzu gas chromatography with negative ion chemical ionization mass spectrometry system equipped with an Agilent J&W HP-porous layer open tubular column coated with an alumina oxide (Al2O3) S column. The method detection limit (MDL) analysis as defined by the Environmental Protection Agency of the tracer data showed the method MDL to be 5.2 ppt. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Establishment of a Charge Reversal Derivatization Strategy to Improve the Ionization Efficiency of Limaprost and Investigation of the Fragmentation Patterns of Limaprost Derivatives Via Exclusive Neutral Loss and Survival Yield Method

NASA Astrophysics Data System (ADS)

Sun, Dong; Meng, Xiangjun; Ren, Tianming; Fawcett, John Paul; Wang, Hualu; Gu, Jingkai

2018-04-01

Sensitivity is generally an issue in bioassays of prostaglandins and their synthetic analogs due to their extremely low concentration in vivo. To improve the ionization efficiency of limaprost, an oral prostaglandin E1 (PGE1) synthetic analog, we investigated a charge reversal derivatization strategy in electrospray ionization mass spectrometry (ESI-MS). We established that the cholamine derivative exhibits much greater signal intensity in the positive-ion mode compared with limaprost in the negative ion mode. Collision-induced dissociation (CID) involved exclusive neutral mass loss and positive charge migration to form stable cationic product ions with the positive charge on the limaprost residue rather than on the modifying group. This has the effect of maintaining the efficiency and specificity of multiple reaction monitoring (MRM) and avoiding cross talk. CID fragmentation patterns of other limaprost derivatives allowed us to relate the dissociation tendency of different neutral leaving groups to an internal energy distribution scale based on the survival yield method. Knowledge of the energy involved in the production of stabilized positive ions will potentially assist the selection of suitable derivatization reagents for the analysis of a wide variety of lipid acids. [Figure not available: see fulltext.

The study of lead vapor ionization in discharge with a hot cathode and efficiency of its deposition on the substrates applied for plasma separation method

NASA Astrophysics Data System (ADS)

Antonov, N. N.; Samokhin, A. A.; Zhabin, S. N.; Gavrikov, A. V.; Smirnov, V. P.

2016-11-01

Spent nuclear fuel plasma separation method approbation implies the use of model substances. Thus it is necessary to solve the problem of material conversion into a cold plasma flow, as well as the problem of deposition on collectors. For this purpose, we carried out a kinetic and hydrodynamic simulation of the discharge with hot cathode in the lead vapor (lead vapor was injected into the interelectrode gap). Dependencies of the ionization efficiency, electrostatic potential distribution, density distribution of ions and electrons in the discharge gap on the discharge current density and the model substance vapor concentration were obtained. The simulation results show that at discharge current density of about 3.5 A/cm2 and the lead vapor concentration of 2 × 1012 cm-3, the ionization efficiency is close to 60%. Experimental research of the discharge with a hot cathode in the lead vapor was carried out. We also carried out the research of the Pb condensation coefficients on various substrates. For experimental data analysis the numerical model based on Monte Carlo method was used. The research results show that deposition coefficients at medium temperatures of substrates near 70 °C do not drop lower than 75%.

Hydrazide and hydrazine reagents as reactive matrices for MALDI-MS to detect gaseous aldehydes.

PubMed

Shigeri, Yasushi; Ikeda, Shinya; Yasuda, Akikazu; Ando, Masanori; Sato, Hiroaki; Kinumi, Tomoya

2014-08-01

The reagents 19 hydrazide and 14 hydrazine were examined to function as reactive matrices for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) to detect gaseous aldehydes. Among them, two hydrazide (2-hydroxybenzohydrazide and 3-hydroxy-2-naphthoic acid hydrazide) and two hydrazine reagents [2-hydrazinoquinoline and 2,4-dinitrophenylhydrazine (DNPH)] were found to react efficiently with carbonyl groups of gaseous aldehydes (formaldehyde, acetaldehyde and propionaldehyde); these are the main factors for sick building syndrome and operate as reactive matrices for MALDI-MS. Results from accurate mass measurements by JMS-S3000 Spiral-TOF suggested that protonated ion peaks corresponding to [M + H](+) from the resulting derivatives were observed in all cases with the gaseous aldehydes in an incubation, time-dependent manner. The two hydrazide and two hydrazine reagents all possessed absorbances at 337 nm (wavelength of MALDI nitrogen laser), with, significant electrical conductivity of the matrix crystal and functional groups, such as hydroxy group and amino group, being important for desorption/ionization efficiency in MALDI-MS. To our knowledge, this is the first report that gaseous molecules could be derivatized and detected directly in a single step by MALDI-MS using novel reactive matrices that were derivatizing agents with the ability to enhance desorption/ionization efficiency. Copyright © 2014 John Wiley & Sons, Ltd.

Atmospheric Pressure Ionization Using a High Voltage Target Compared to Electrospray Ionization.

PubMed

Lubin, Arnaud; Bajic, Steve; Cabooter, Deirdre; Augustijns, Patrick; Cuyckens, Filip

2017-02-01

A new atmospheric pressure ionization (API) source, viz. UniSpray, was evaluated for mass spectrometry (MS) analysis of pharmaceutical compounds by head-to-head comparison with electrospray ionization (ESI) on the same high-resolution MS system. The atmospheric pressure ionization source is composed of a grounded nebulizer spraying onto a high voltage, cylindrical stainless steel target. Molecules are ionized in a similar fashion to electrospray ionization, predominantly producing protonated or deprotonated species. Adduct formation (e.g., proton and sodium adducts) and in-source fragmentation is shown to be almost identical between the two sources. The performance of the new API source was compared with electrospray by infusion of a mix of 22 pharmaceutical compounds with a wide variety of functional groups and physico-chemical properties (molecular weight, logP, and pKa) in more than 100 different conditions (mobile phase strength, solvents, pH, and flow rate). The new API source shows an intensity gain of a factor 2.2 compared with ESI considering all conditions on all compounds tested. Finally, some hypotheses on the ionization mechanism, similarities, and differences with ESI, are discussed. Graphical Abstract ᅟ.

Atmospheric Pressure Ionization Using a High Voltage Target Compared to Electrospray Ionization

NASA Astrophysics Data System (ADS)

Lubin, Arnaud; Bajic, Steve; Cabooter, Deirdre; Augustijns, Patrick; Cuyckens, Filip

2017-02-01

A new atmospheric pressure ionization (API) source, viz. UniSpray, was evaluated for mass spectrometry (MS) analysis of pharmaceutical compounds by head-to-head comparison with electrospray ionization (ESI) on the same high-resolution MS system. The atmospheric pressure ionization source is composed of a grounded nebulizer spraying onto a high voltage, cylindrical stainless steel target. Molecules are ionized in a similar fashion to electrospray ionization, predominantly producing protonated or deprotonated species. Adduct formation (e.g., proton and sodium adducts) and in-source fragmentation is shown to be almost identical between the two sources. The performance of the new API source was compared with electrospray by infusion of a mix of 22 pharmaceutical compounds with a wide variety of functional groups and physico-chemical properties (molecular weight, logP, and pKa) in more than 100 different conditions (mobile phase strength, solvents, pH, and flow rate). The new API source shows an intensity gain of a factor 2.2 compared with ESI considering all conditions on all compounds tested. Finally, some hypotheses on the ionization mechanism, similarities, and differences with ESI, are discussed.

High pressure xenon ionization detector

DOEpatents

Markey, J.K.

1989-11-14

A method is provided for detecting ionization comprising allowing particles that cause ionization to contact high pressure xenon maintained at or near its critical point and measuring the amount of ionization. An apparatus is provided for detecting ionization, the apparatus comprising a vessel containing a ionizable medium, the vessel having an inlet to allow high pressure ionizable medium to enter the vessel, a means to permit particles that cause ionization of the medium to enter the vessel, an anode, a cathode, a grid and a plurality of annular field shaping rings, the field shaping rings being electrically isolated from one another, the anode, cathode, grid and field shaping rings being electrically isolated from one another in order to form an electric field between the cathode and the anode, the electric field originating at the anode and terminating at the cathode, the grid being disposed between the cathode and the anode, the field shaping rings being disposed between the cathode and the grid, the improvement comprising the medium being xenon and the vessel being maintained at a pressure of 50 to 70 atmospheres and a temperature of 0 to 30 C. 2 figs.

High pressure xenon ionization detector

DOEpatents

Markey, John K.

1989-01-01

A method is provided for detecting ionization comprising allowing particles that cause ionization to contact high pressure xenon maintained at or near its critical point and measuring the amount of ionization. An apparatus is provided for detecting ionization, the apparatus comprising a vessel containing a ionizable medium, the vessel having an inlet to allow high pressure ionizable medium to enter the vessel, a means to permit particles that cause ionization of the medium to enter the vessel, an anode, a cathode, a grid and a plurality of annular field shaping rings, the field shaping rings being electrically isolated from one another, the anode, cathode, grid and field shaping rings being electrically isolated from one another in order to form an electric field between the cathode and the anode, the electric field originating at the anode and terminating at the cathode, the grid being disposed between the cathode and the anode, the field shaping rings being disposed between the cathode and the grid, the improvement comprising the medium being xenon and the vessel being maintained at a pressure of 50 to 70 atmospheres and a temperature of 0.degree. to 30.degree. C.

Ionization Processes in the Atmosphere of Titan (Research Note). III. Ionization by High-Z Nuclei Cosmic Rays

NASA Technical Reports Server (NTRS)

Gronoff, G.; Mertens, C.; Lilensten, J.; Desorgher, L.; Fluckiger, E.; Velinov, P.

2011-01-01

Context. The Cassini-Huygens mission has revealed the importance of particle precipitation in the atmosphere of Titan thanks to in-situ measurements. These ionizing particles (electrons, protons, and cosmic rays) have a strong impact on the chemistry, hence must be modeled. Aims. We revisit our computation of ionization in the atmosphere of Titan by cosmic rays. The high-energy high-mass ions are taken into account to improve the precision of the calculation of the ion production profile. Methods. The Badhwahr and O Neill model for cosmic ray spectrum was adapted for the Titan model. We used the TransTitan model coupled with the Planetocosmics model to compute the ion production by cosmic rays. We compared the results with the NAIRAS/HZETRN ionization model used for the first time for a body that differs from the Earth. Results. The cosmic ray ionization is computed for five groups of cosmic rays, depending on their charge and mass: protons, alpha, Z = 8 (oxygen), Z = 14 (silicon), and Z = 26 (iron) nucleus. Protons and alpha particles ionize mainly at 65 km altitude, while the higher mass nucleons ionize at higher altitudes. Nevertheless, the ionization at higher altitude is insufficient to obscure the impact of Saturn s magnetosphere protons at a 500 km altitude. The ionization rate at the peak (altitude: 65 km, for all the different conditions) lies between 30 and 40/cu cm/s. Conclusions. These new computations show for the first time the importance of high Z cosmic rays on the ionization of the Titan atmosphere. The updated full ionization profile shape does not differ significantly from that found in our previous calculations (Paper I: Gronoff et al. 2009, 506, 955) but undergoes a strong increase in intensity below an altitude of 400 km, especially between 200 and 400 km altitude where alpha and heavier particles (in the cosmic ray spectrum) are responsible for 40% of the ionization. The comparison of several models of ionization and cosmic ray spectra (in intensity and composition) reassures us about the stability of the altitude of the ionization peak (65 km altitude) with respect to the solar activity.

A role for bioelectric effects in the induction of bystander signals by ionizing radiation?

PubMed

Mothersill, C; Moran, G; McNeill, F; Gow, M D; Denbeigh, J; Prestwich, W; Seymour, C B

2007-04-03

The induction of "bystander effects" i.e. effects in cells which have not received an ionizing radiation track, is now accepted but the mechanisms are not completely clear. Bystander effects following high and low LET radiation exposure are accepted but mechanisms are still not understood. There is some evidence for a physical component to the signal. This paper tests the hypothesis that bioelectric or biomagnetic phenomena are involved. Human immortalized skin keratinocytes and primary explants of mouse bladder and fish skin, were exposed directly to ionizing radiation or treated in a variety of bystander protocols. Exposure of cells was conducted by shielding one group of flasks using lead, to reduce the dose below the threshold of 2mGy (60)Cobalt gamma rays established for the bystander effect. The endpoint for the bystander effect in the reporter system used was reduction in cloning efficiency (RCE). The magnitude of the RCE was similar in shielded and unshielded flasks. When cells were placed in a Faraday cage the magnitude of the RCE was less but not eliminated. The results suggest that liquid media or cell-cell contact transmission of bystander factors may be only part of the bystander mechanism. Bioelectric or bio magnetic fields may have a role to play. To test this further, cells were placed in a Magnetic Resonance Imaging (MRI) machine for 10 min using a typical head scan protocol. This treatment also induced a bystander response. Apart from the obvious clinical relevance, the MRI results further suggest that bystander effects may be produced by non-ionizing exposures. It is concluded that bioelectric or magnetic effects may be involved in producing bystander signaling cascades commonly seen following ionizing radiation exposure.

A Role for Bioelectric Effects in the Induction of Bystander Signals by Ionizing Radiation?

PubMed Central

Mothersill, C.; Moran, G.; McNeill, F.; Gow, M.D.; Denbeigh, J.; Prestwich, W.; Seymour, C.B.

2007-01-01

The induction of “bystander effects” i.e. effects in cells which have not received an ionizing radiation track, is now accepted but the mechanisms are not completely clear. Bystander effects following high and low LET radiation exposure are accepted but mechanisms are still not understood. There is some evidence for a physical component to the signal. This paper tests the hypothesis that bioelectric or biomagnetic phenomena are involved. Human immortalized skin keratinocytes and primary explants of mouse bladder and fish skin, were exposed directly to ionizing radiation or treated in a variety of bystander protocols. Exposure of cells was conducted by shielding one group of flasks using lead, to reduce the dose below the threshold of 2mGy 60Cobalt gamma rays established for the bystander effect. The endpoint for the bystander effect in the reporter system used was reduction in cloning efficiency (RCE). The magnitude of the RCE was similar in shielded and unshielded flasks. When cells were placed in a Faraday cage the magnitude of the RCE was less but not eliminated. The results suggest that liquid media or cell-cell contact transmission of bystander factors may be only part of the bystander mechanism. Bioelectric or bio magnetic fields may have a role to play. To test this further, cells were placed in a Magnetic Resonance Imaging (MRI) machine for 10min using a typical head scan protocol. This treatment also induced a bystander response. Apart from the obvious clinical relevance, the MRI results further suggest that bystander effects may be produced by non-ionizing exposures. It is concluded that bioelectric or magnetic effects may be involved in producing bystander signaling cascades commonly seen following ionizing radiation exposure. PMID:18648606

Reduced atomic shadowing in HiPIMS: Role of the thermalized metal ions

NASA Astrophysics Data System (ADS)

Oliveira, João Carlos; Ferreira, Fábio; Anders, André; Cavaleiro, Albano

2018-03-01

In magnetron sputtering, the ability to tailor film properties depends primarily on the control of the flux of particles impinging on the growing film. Among deposition mechanisms, the shadowing effect leads to the formation of a rough surface and a porous, columnar microstructure. Re-sputtered species may be re-deposited in the valleys of the films surface and thereby contribute to a reduction of roughness and to fill the underdense regions. Both effects are non-local and they directly compete to shape the final properties of the deposited films. Additional control of the bombarding flux can be obtained by ionizing the sputtered flux, because ions can be controlled with respect to their energy and impinging direction, such as in High-Power Impulse Magnetron Sputtering (HiPIMS). In this work, the relation between ionization of the sputtered species and thin film properties is investigated in order to identify the mechanisms which effectively influence the shadowing effect in Deep Oscillation Magnetron Sputtering (DOMS), a variant of HiPIMS. The properties of two Cr films deposited using the same averaged target power by d.c. magnetron sputtering and DOMS have been compared. Additionally, the angle distribution of the Cr species impinging on the substrate was simulated using Monte Carlo-based programs while the energy distribution of the energetic particles bombarding the substrate was evaluated by energy-resolved mass analysis. It was found that the acceleration of the thermalized chromium ions at the substrate sheath in DOMS significantly reduces the high angle component of their impinging angle distribution and, thus, efficiently reduces atomic shadowing. Therefore, a high degree of ionization in HiPIMS results in almost shadowing effect-free film deposition and allows us to deposit dense and compact films without the need of high energy particle bombardment during growth.

LLE review

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

Bradley, D.K.

1989-01-01

This volume of the LLE Review, covering the period October--December 1989, contains an article discussing saturation effects and power-balance considerations in the design of high-power lasers and an article describing numerical modeling of the effects of power imbalances on target behavior. The advanced technology section reports on the development of a liquid crystal laser-beam apodizer and an experiment to study the high-intensity ionization of noble gases. Finally, the activities of the National Laser Users Facility and the GDL and OMEGA laser facilities are summarized. The highlights of this issue are: The problem of achieving power balance in high-efficiency, multibeam lasersmore » has been studied in terms of gain-saturation effects and the nonlinear nature of harmonic frequency conversion. It is shown that power imbalance can be minimized by balancing the gains and losses in equivalent amplification stages in each beamline. The effects of target implosion behavior of various power-imbalance sources in the OMEGA laser system have been studied using the two-dimensional hydrodynamics code ORCHID. The simulations show good agreement with an experiment in which a deliberate power imbalance was applied to the target drive. Laser-beam apodizers with large clear apertures have been fabricated using cholesteric liquid crystals. A soft-edge profile has been achieved by filling a cell with two separate liquid crystals with different selective-reflection bands, and allowing them to partially mix at the interface. A study of the ionization of noble gases in the tunneling regime using high- intensity, 1-ps pulses from the tabletop terawatt laser (T{sup 3}) has been carried out. The measured ion production is well predicted by a Coulomb barrier suppression ionization theory.« less

Large scale nanoparticle screening for small molecule analysis in laser desorption ionization mass spectrometry

DOE PAGES

Yagnik, Gargey B.; Hansen, Rebecca L.; Korte, Andrew R.; ...

2016-08-30

Nanoparticles (NPs) have been suggested as efficient matrixes for small molecule profiling and imaging by laser-desorption ionization mass spectrometry (LDI-MS), but so far there has been no systematic study comparing different NPs in the analysis of various classes of small molecules. Here, we present a large scale screening of 13 NPs for the analysis of two dozen small metabolite molecules. Many NPs showed much higher LDI efficiency than organic matrixes in positive mode and some NPs showed comparable efficiencies for selected analytes in negative mode. Our results suggest that a thermally driven desorption process is a key factor for metalmore » oxide NPs, but chemical interactions are also very important, especially for other NPs. Furthermore, the screening results provide a useful guideline for the selection of NPs in the LDI-MS analysis of small molecules.« less

Large scale nanoparticle screening for small molecule analysis in laser desorption ionization mass spectrometry

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

Yagnik, Gargey B.; Hansen, Rebecca L.; Korte, Andrew R.

Nanoparticles (NPs) have been suggested as efficient matrixes for small molecule profiling and imaging by laser-desorption ionization mass spectrometry (LDI-MS), but so far there has been no systematic study comparing different NPs in the analysis of various classes of small molecules. Here, we present a large scale screening of 13 NPs for the analysis of two dozen small metabolite molecules. Many NPs showed much higher LDI efficiency than organic matrixes in positive mode and some NPs showed comparable efficiencies for selected analytes in negative mode. Our results suggest that a thermally driven desorption process is a key factor for metalmore » oxide NPs, but chemical interactions are also very important, especially for other NPs. Furthermore, the screening results provide a useful guideline for the selection of NPs in the LDI-MS analysis of small molecules.« less

Electrospray-assisted laser desorption/ionization and tandem mass spectrometry of peptides and proteins.

PubMed

Peng, Ivory X; Shiea, Jentaie; Ogorzalek Loo, Rachel R; Loo, Joseph A

2007-01-01

We have constructed an electrospray-assisted laser desorption/ionization (ELDI) source which utilizes a nitrogen laser pulse to desorb intact molecules from matrix-containing sample solution droplets, followed by electrospray ionization (ESI) post-ionization. The ELDI source is coupled to a quadrupole ion trap mass spectrometer and allows sampling under ambient conditions. Preliminary data showed that ELDI produces ESI-like multiply charged peptides and proteins up to 29 kDa carbonic anhydrase and 66 kDa bovine albumin from single-protein solutions, as well as from complex digest mixtures. The generated multiply charged polypeptides enable efficient tandem mass spectrometric (MS/MS)-based peptide sequencing. ELDI-MS/MS of protein digests and small intact proteins was performed both by collisionally activated dissociation (CAD) and by nozzle-skimmer dissociation (NSD). ELDI-MS/MS may be a useful tool for protein sequencing analysis and top-down proteomics study, and may complement matrix-assisted laser desorption/ionization (MALDI)-based measurements. Copyright (c) 2007 John Wiley & Sons, Ltd.

Low pressure spark gap triggered by an ion diode

DOEpatents

Prono, Daniel S.

1985-01-01

Spark gap apparatus for use as an electric switch operating at high voltage, high current and high repetition rate. Mounted inside a housing are an anode, cathode and ion plate. An ionizable fluid is pumped through the chamber of the housing. A pulse of current to the ion plate causes ions to be emitted by the ion plate, which ions move into and ionize the fluid. Electric current supplied to the anode discharges through the ionized fluid and flows to the cathode. Current stops flowing when the current source has been drained. The ionized fluid recombines into its initial dielectric ionizable state. The switch is now open and ready for another cycle.

Low-pressure spark gap triggered by an ion diode

DOEpatents

Prono, D.S.

1982-08-31

Spark gap apparatus for use as an electric switch operating at high voltage, high current and high repetition rate. Mounted inside a housing are an anode, cathode and ion plate. An ionizable fluid is pumped through the chamber of the housing. A pulse of current to the ion plate causes ions to be emitted by the ion plate, which ions move into and ionize the fluid. Electric current supplied to the anode discharges through the ionized fluid and flows to the cathode. Current stops flowing when the current source has been drained. The ionized fluid recombines into its initial dielectric ionizable state. The switch is now open and ready for another cycle.

Design and application of a data-independent precursor and product ion repository.

PubMed

Thalassinos, Konstantinos; Vissers, Johannes P C; Tenzer, Stefan; Levin, Yishai; Thompson, J Will; Daniel, David; Mann, Darrin; DeLong, Mark R; Moseley, M Arthur; America, Antoine H; Ottens, Andrew K; Cavey, Greg S; Efstathiou, Georgios; Scrivens, James H; Langridge, James I; Geromanos, Scott J

2012-10-01

The functional design and application of a data-independent LC-MS precursor and product ion repository for protein identification, quantification, and validation is conceptually described. The ion repository was constructed from the sequence search results of a broad range of discovery experiments investigating various tissue types of two closely related mammalian species. The relative high degree of similarity in protein complement, ion detection, and peptide and protein identification allows for the analysis of normalized precursor and product ion intensity values, as well as standardized retention times, creating a multidimensional/orthogonal queryable, qualitative, and quantitative space. Peptide ion map selection for identification and quantification is primarily based on replication and limited variation. The information is stored in a relational database and is used to create peptide- and protein-specific fragment ion maps that can be queried in a targeted fashion against the raw or time aligned ion detections. These queries can be conducted either individually or as groups, where the latter affords pathway and molecular machinery analysis of the protein complement. The presented results also suggest that peptide ionization and fragmentation efficiencies are highly conserved between experiments and practically independent of the analyzed biological sample when using similar instrumentation. Moreover, the data illustrate only minor variation in ionization efficiency with amino acid sequence substitutions occurring between species. Finally, the data and the presented results illustrate how LC-MS performance metrics can be extracted and utilized to ensure optimal performance of the employed analytical workflows.

Ionization behavior of amino lipids for siRNA delivery: determination of ionization constants, SAR, and the impact of lipid pKa on cationic lipid-biomembrane interactions.

PubMed

Zhang, Jingtao; Fan, Haihong; Levorse, Dorothy A; Crocker, Louis S

2011-03-01

Ionizable amino lipids are being pursued as an important class of materials for delivering small interfering RNA (siRNA) therapeutics, and research is being conducted to elucidate the structure-activity relationships (SAR) of these lipids. The pK(a) of cationic lipid headgroups is one of the critical physiochemical properties of interest due to the strong impact of lipid ionization on the assembly and performance of these lipids. This research focused on developing approaches that permit the rapid determination of the relevant pK(a) of the ionizable amino lipids. Two distinct approaches were investigated: (1) potentiometric titration of amino lipids dissolved in neutral surfactant micelles; and (2) pH-dependent partitioning of a fluorescent dye to cationic liposomes formulated from amino lipids. Using the approaches developed here, the pK(a) values of cationic lipids with distinct headgroups were measured and found to be significantly lower than calculated values. It was also found that lipid-lipid interaction has a strong impact on the pK(a) values of lipids. Lysis of model biomembranes by cationic lipids was used to evaluate the impact of lipid pK(a) on the interaction between cationic lipids and cell membranes. It was found that cationic lipid-biomembrane interaction depends strongly on lipid pK(a) and solution pH, and this interaction is much stronger when amino lipids are highly charged. The presence of an optimal pK(a) range of ionizable amino lipids for siRNA delivery was suggested based on these results. The pK(a) methods reported here can be used to support the SAR screen of cationic lipids for siRNA delivery, and the information revealed through studying the impact of pK(a) on the interaction between cationic lipids and cell membranes will contribute significantly to the design of more efficient siRNA delivery vehicles.

Ionization asymmetry effects on the properties modulation of atmospheric pressure dielectric barrier discharge sustained by tailored voltage waveforms

NASA Astrophysics Data System (ADS)

Zhang, Z. L.; Nie, Q. Y.; Zhang, X. N.; Wang, Z. B.; Kong, F. R.; Jiang, B. H.; Lim, J. W. M.

2018-04-01

The dielectric barrier discharge (DBD) is a promising technology to generate high density and uniform cold plasmas in atmospheric pressure gases. The effective independent tuning of key plasma parameters is quite important for both application-focused and fundamental studies. In this paper, based on a one-dimensional fluid model with semi-kinetics treatment, numerical studies of ionization asymmetry effects on the properties modulation of atmospheric DBD sustained by tailored voltage waveforms are reported. The driving voltage waveform is characterized by an asymmetric-slope fundamental sinusoidal radio frequency signal superimposing one or more harmonics, and the effects of the number of harmonics, phase shift, as well as the fluctuation of harmonics on the sheath dynamics, impact ionization of electrons and key plasma parameters are investigated. The results have shown that the electron density can exhibit a substantial increase due to the effective electron heating by a spatially asymmetric sheath structure. The strategic modulation of harmonics number and phase shift is capable of raising the electron density significantly (e.g., nearly three times in this case), but without a significant increase in the gas temperature. Moreover, by tailoring the fluctuation of harmonics with a steeper slope, a more profound efficiency in electron impact ionization can be achieved, and thus enhancing the electron density effectively. This method then enables a novel alternative approach to realize the independent control of the key plasma parameters under atmospheric pressure.

Density Bounded H II Regions: Ionization of the Diffuse Interstellar and Intergalactic Media

NASA Astrophysics Data System (ADS)

Zurita, A.; Rozas, M.; Beckman, J. E.

2000-05-01

We present a study of the diffuse ionized gas (DIG) for a sample of nearby spiral galaxies using Hα images, after constructing their H II region catalogues. The integrated Hα emission of the DIG accounts for between 25% to 60% of the total Hα of the galaxy and a high ionizing photon flux is necessary to keep this gas ionized. We suggest that Lyman photons leaking from the most luminous H II regions are the prime source of the ionization of the DIG; they are more than enough to ionize the measured DIG in the model in which H II regions with luminosity in Hα greater than LStr=1038.6 erg sme are density bounded. We go on to show that this model can quantify the ionization observed in the skins of the high velocity clouds well above the plane of our Galaxy and predicts the ionization of the intergalactic medium.

Development of a center for light ion therapy and accurate tumor diagnostics at karolinska institutet and hospital

NASA Astrophysics Data System (ADS)

Brahme, Anders; Lind, Bengt K.

2002-04-01

Radiation therapy is today in a state of very rapid development with new intensity modulated treatment techniques continuously being developed. This has made intensity modulated electron and photon beams almost as powerful as conventional uniform beam proton therapy. To be able to cure also the most advanced hypoxic and radiation resistant tumors of complex local spread, intensity modulated light ion beams are really the ultimate tool and only slightly more expensive than proton therapy. The aim of the new center for ion therapy and tumor diagnostics in Stockholm is to develop radiobiologically optimized 3-dimensional pencil beam scanning techniques. Beside the "classical" approaches using low ionization density hydrogen ions (protons, but also deuterons and tritium nuclei) and high ionization density carbon ions, two new approaches will be developed. In the first one lithium or beryllium ions, that induce the least detrimental biological effect to normal tissues for a given biological effect in a small volume of the tumor, will be key particles. In the second approach, referred patients will be given a high-dose high-precision "boost" treatment with carbon or oxygen ions during one week preceding the final treatment with conventional radiations in the referring hospital. The rationale behind these approaches is to reduce the high ionization density dose to the normal tissue stroma inside the tumor and to ensure a microscopically uniform dose delivery. The principal idea of the center is to closely integrate ion therapy into the clinical routine and research of a large radiotherapy department. The light ion therapy center will therefore be combined with advanced tumor diagnostics including MR and PET-CT imaging to facilitate efficient high-precision high-dose boost treatment of remitted patients. The possibility to do 3D tumor diagnostics and 3D dose delivery verification with the same PET camera will be the ultimate step in high quality adaptive radiation therapy where alterations in the delivered dose can be corrected by subsequent treatments

Sheathless interface to match flow rate of capillary electrophoresis with electrospray mass spectrometry using regular-sized capillary.

PubMed

Yin, Yue; Li, Gongyu; Guan, Yafeng; Huang, Guangming

2016-08-01

The flow rate match has been a great challenge when coupling capillary electrophoresis (CE) with electrospray ionization mass spectrometry (ESI-MS). Conventional CE-ESI-MS interfaces used liquid sheath flow, narrowed capillary or additional pressure to meet this requirement; sacrifice of either capillary inner diameter (i.d.) or separation efficiency is often inevitable. Thus, a regular-sized capillary-based sheathless interface would be attractive for flow rate match in CE-MS. The regular-sized capillary-based CE-MS interface was achieved by coupling CE with induced electrospray ionization (iESI) which was stimulated by the fact that the iESI could both achieve flow rate down to 0.2 μL/min and retain ionization efficiency. The CE-iESI-MS interface was completed with an intact separation capillary, outside the outlet end of which a metal electrode was attached for the application of alternating current (ac) high voltage (HV). The feasibility of this CE-iESI-MS interface was demonstrated through the stable total ion chromatograms obtained by continuous CE infusion of tripropylamine with regular-sized capillaries. Tripropylamine and atenolol were separated and detected successfully in phosphate buffer solution (PBS) by CE-iESI-MS using a 50 or 75 μm i.d. capillary. Furthermore, this new interface showed a better signal-to-noise (S/N) of 3 to 7 times enhancement compared with another sheathless CE-ESI-MS interface that using one high voltage for both separation and electrospray when analyzing the mixture of tripropylamine and proline in NH4 OAc buffer. In addition, the reproducibility of this interface gave satisfactory results with relative standard deviation (RSD) in retention time in the range between 1% and 3%. The novel sheathless CE-MS interface introduced here could match conventional electroosmotic flow (EOF) with electrospray which could also preserve the separation efficiency and sensitivity of CE-MS. This newly developed CE-iESI-MS interface was also demonstrated to be effective for different buffers, PBS and NH4 OAc, without any additives such as methanol and acetic acid. Hence, we believe that this sheathless CE-MS interface could be operated with other nonvolatile and volatile buffers. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Colloidal aspects and packing behaviour of charged microparticulates in high efficiency ion chromatography.

PubMed

Wahab, M Farooq; Pohl, Christopher A; Lucy, Charles A

2012-12-28

The development of small particles in ion chromatography (IC) is a recent phenomenon. Very few studies are available on packing polymeric particles bearing ionizable functional groups. This study explores the colloidal and rheological properties that govern slurry packing to form high efficiency IC columns. The polymeric substrate used was non-porous 4.4 μm sulfonated ethylvinylbenzene–divinylbenzene (1.4 mequiv. SO(3)H/g resin) with 55% crosslink. We developed simple tests optical microscopy and sedimentation tests for predicting the quality of packed columns. The negatively charged particles (zeta potential: −52 mV in water) behave like colloids. The influence of counter-ion charge (Al(3+), Mg(2+), Na(+)) and ionic strength on column efficiency followed the Schulze–Hardy rule. Highly flocculating slurries give poorly packed columns with N ~ 900 whereas under non-agglomerating slurry conditions efficiencies up to N > 10,000 can be achieved. A non-agglomerating slurry also shows non-Newtonian behaviour, specifically shear thickening. Packing at lower flow rate (<1 mL/min) or higher temperature (>50 °C) reduces the shear thickening and produces higher efficiency columns. The packed sulfonated resin column is coated with 72 nm quaternary ammonium bearing latex (AS4A) and used in the separation of F(−), Cl(−), NO(2)(−), Br(−), and NO(3)(−) yielding a reduced plate height of 1.9 under optimum conditions.

Efficiency Analysis of a High-Specific Impulse Hall Thruster

NASA Technical Reports Server (NTRS)

Jacobson, David (Technical Monitor); Hofer, Richard R.; Gallimore, Alec D.

2004-01-01

Performance and plasma measurements of the high-specific impulse NASA-173Mv2 Hall thruster were analyzed using a phenomenological performance model that accounts for a partially-ionized plasma containing multiply-charged ions. Between discharge voltages of 300 to 900 V, the results showed that although the net decrease of efficiency due to multiply-charged ions was only 1.5 to 3.0 percent, the effects of multiply-charged ions on the ion and electron currents could not be neglected. Between 300 to 900 V, the increase of the discharge current was attributed to the increasing fraction of multiply-charged ions, while the maximum deviation of the electron current from its average value was only +5/-14 percent. These findings revealed how efficient operation at high-specific impulse was enabled through the regulation of the electron current with the applied magnetic field. Between 300 to 900 V, the voltage utilization ranged from 89 to 97 percent, the mass utilization from 86 to 90 percent, and the current utilization from 77 to 81 percent. Therefore, the anode efficiency was largely determined by the current utilization. The electron Hall parameter was nearly constant with voltage, decreasing from an average of 210 at 300 V to an average of 160 between 400 to 900 V. These results confirmed our claim that efficient operation can be achieved only over a limited range of Hall parameters.

Fundamental Studies of Molecular Secondary Ion Mass Spectrometry Ionization Probability Measured With Femtosecond, Infrared Laser Post-Ionization

NASA Astrophysics Data System (ADS)

Popczun, Nicholas James

The work presented in this dissertation is focused on increasing the fundamental understanding of molecular secondary ion mass spectrometry (SIMS) ionization probability by measuring neutral molecule behavior with femtosecond, mid-infrared laser post-ionization (LPI). To accomplish this, a model system was designed with a homogeneous organic film comprised of coronene, a polycyclic hydrocarbon which provides substantial LPI signal. Careful consideration was given to signal lost to photofragmentation and undersampling of the sputtered plume that is contained within the extraction volume of the mass spectrometer. This study provided the first ionization probability for an organic compound measured directly by the relative secondary ions and sputtered neutral molecules using a strong-field ionization (SFI) ionization method. The measured value of ˜10-3 is near the upper limit of previous estimations of ionization probability for organic molecules. The measurement method was refined, and then applied to a homogeneous guanine film, which produces protonated secondary ions. This measurement found the probability of protonation to occur to be on the order of 10-3, although with less uncertainty than that of the coronene. Finally, molecular depth profiles were obtained for SIMS and LPI signals as a function of primary ion fluence to determine the effect of ionization probability on the depth resolution of chemical interfaces. The interfaces chosen were organic/inorganic interfaces to limit chemical mixing. It is shown that approaching the inorganic chemical interface can enhance or suppress the ionization probability for the organic molecule, which can lead to artificially sharpened or broadened depths, respectively. Overall, the research described in this dissertation provides new methods for measuring ionization efficiency in SIMS in both absolute and relative terms, and will inform both innovation in the technique, as well as increase understanding of depth-dependent experiments.

The characteristic of evaporative cooling magnet for ECRIS

NASA Astrophysics Data System (ADS)

Xiong, B.; Ruan, L.; Gu, G. B.; Lu, W.; Zhang, X. Z.; Zhan, W. L.

2016-02-01

Compared with traditional de-ionized pressurized-water cooled magnet of ECRIS, evaporative cooling magnet has some special characteristics, such as high cooling efficiency, simple maintenance, and operation. The analysis is carried out according to the design and operation of LECR4 (Lanzhou Electron Cyclotron Resonance ion source No. 4, since July 2013), whose magnet is cooled by evaporative cooling technology. The insulation coolant replaces the de-ionized pressurized-water to absorb the heat of coils, and the physical and chemical properties of coolant remain stable for a long time with no need for purification or filtration. The coils of magnet are immersed in the liquid coolant. For the higher cooling efficiency of coolant, the current density of coils can be greatly improved. The heat transfer process executes under atmospheric pressure, and the temperature of coils is lower than 70 °C when the current density of coils is 12 A/mm2. On the other hand, the heat transfer temperature of coolant is about 50 °C, and the heat can be transferred to fresh air which can save cost of water cooling system. Two years of LECR4 stable operation show that evaporative cooling technology can be used on magnet of ECRIS, and the application advantages are very obvious.

The characteristic of evaporative cooling magnet for ECRIS

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

Xiong, B., E-mail: xiongbin@mail.iee.ac.cn; University of Chinese Academy of Sciences, Beijing 100049; Ruan, L.

2016-02-15

Compared with traditional de-ionized pressurized-water cooled magnet of ECRIS, evaporative cooling magnet has some special characteristics, such as high cooling efficiency, simple maintenance, and operation. The analysis is carried out according to the design and operation of LECR4 (Lanzhou Electron Cyclotron Resonance ion source No. 4, since July 2013), whose magnet is cooled by evaporative cooling technology. The insulation coolant replaces the de-ionized pressurized-water to absorb the heat of coils, and the physical and chemical properties of coolant remain stable for a long time with no need for purification or filtration. The coils of magnet are immersed in the liquidmore » coolant. For the higher cooling efficiency of coolant, the current density of coils can be greatly improved. The heat transfer process executes under atmospheric pressure, and the temperature of coils is lower than 70 °C when the current density of coils is 12 A/mm{sup 2}. On the other hand, the heat transfer temperature of coolant is about 50 °C, and the heat can be transferred to fresh air which can save cost of water cooling system. Two years of LECR4 stable operation show that evaporative cooling technology can be used on magnet of ECRIS, and the application advantages are very obvious.« less

Millimeter Astronomy at High Redshift

NASA Astrophysics Data System (ADS)

Decarli, Roberto

2017-11-01

Our understanding of galaxy formation and evolution critically depends on our ability of exposing the properties of the gaseous content of galaxies throughout cosmic history: how much gas is there, in which phase (ionized, atomic, molecular?), in which physical conditions (temperature, density), how efficiently does it turn into stars? We are now entering an exciting era where these questions can be addressed via observations of various gas tracers, especially at mm and sub-mm wavelengths. I will review how to observe various gas phases at high redshift, and discuss lessons we have learned so far from campaigns aimed at characterizing the gas content in galaxies in various cosmic epochs.

Apollo-Soyuz light-flash observations. [ionizing radiation effects measurement

NASA Technical Reports Server (NTRS)

Budinger, T. F.; Tobias, C. A.; Huesman, R. H.; Upham, F. T.; Wieskamp, T. F.; Hoffman, R. A.

1977-01-01

While dark adapted, two Apollo-Soyuz astronauts saw eighty-two light flash events during a complete 51 deg orbit which passed near the north magnetic pole and through the South Atlantic Anomaly. The frequency of events at the polar parts of the orbit is 25 times that noted in equatorial latitudes and no increased frequency was noted in the South Atlantic Anomaly at the 225-km altitude. The expected flux of heavy particles at the northern and southern points is 1-2/min per eye, and the efficiency for seeing high Z-high energy (HZE) particles which were below the Cerenkov threshold is 50%.

Ambient diode laser desorption dielectric barrier discharge ionization mass spectrometry of nonvolatile chemicals.

PubMed

Gilbert-López, Bienvenida; Schilling, Michael; Ahlmann, Norman; Michels, Antje; Hayen, Heiko; Molina-Díaz, Antonio; García-Reyes, Juan F; Franzke, Joachim

2013-03-19

In this work, the combined use of desorption by a continuous wave near-infrared diode laser and ionization by a dielectric barrier discharge-based probe (laser desorption dielectric barrier discharge ionization mass spectrometry (LD-DBDI-MS)) is presented as an ambient ionization method for the mass spectrometric detection of nonvolatile chemicals on surfaces. A separation of desorption and ionization processes could be verified. The use of the diode laser is motivated by its low cost, ease of use, and small size. To achieve an efficient desorption, the glass substrates are coated at the back side with a black point (target point, where the sample is deposited) in order to absorb the energy offered by the diode laser radiation. Subsequent ionization is accomplished by a helium plasmajet generated in the dielectric barrier discharge source. Examples on the application of this approach are shown in both positive and negative ionization modes. A wide variety of multiclass species with low vapor pressure were tested including pesticides, pharmaceuticals and explosives (reserpine, roxithromycin, propazine, prochloraz, spinosad, ampicillin, dicloxacillin, enrofloxacin, tetracycline, oxytetracycline, erythromycin, spinosad, cyclo-1,3,5,7-tetramethylene tetranitrate (HMX), and cyclo-1,3,5-trimethylene trinitramine (RDX)). A comparative evaluation revealed that the use of the laser is advantageous, compared to just heating the substrate surface.

Electron ionization and dissociation of aliphatic amino acids

NASA Astrophysics Data System (ADS)

Papp, P.; Shchukin, P.; Kočíšek, J.; Matejčík, Š.

2012-09-01

We present experimental and theoretical study of electron ionization and dissociative ionization to the gas phase amino acids valine, leucine, and isoleucine. A crossed electron/molecular beams technique equipped with quadrupole mass analyzer has been applied to measure mass spectra and ion efficiency curves for formation of particular ions. From experimental data the ionization energies of the molecules and the appearance energies of the fragment ions were determined. Ab initio calculations (Density Functional Theory and G3MP2 methods) were performed in order to calculate the fragmentation paths and interpret the experimental data. The experimental ionization energies of parent molecules [P]+ 8.91 ± 0.05, 8.85 ± 0.05, and 8.79 ± 0.05 eV and G3MP2 ionization energies (adiabatic) of 8.89, 8.88, and 8.81 eV were determined for valine, leucine, and isoleucine, respectively, as well as the experimental and theoretical threshold energies for dissociative ionization channels. The comparison of experimental data with calculations resulted in identification of the ions as well as the neutral fragments formed in the dissociative reactions. Around 15 mass/charge ratio fragments were identified from the mass spectra by comparison of experimental appearance energies with calculated reaction enthalpies for particular dissociative reactions.

Schinus terebinthifolius scale-up countercurrent chromatography (Part I): High performance countercurrent chromatography fractionation of triterpene acids with off-line detection using atmospheric pressure chemical ionization mass spectrometry.

PubMed

Vieira, Mariana Neves; Costa, Fernanda das Neves; Leitão, Gilda Guimarães; Garrard, Ian; Hewitson, Peter; Ignatova, Svetlana; Winterhalter, Peter; Jerz, Gerold

2015-04-10

'Countercurrent chromatography' (CCC) is an ideal technique for the recovery, purification and isolation of bioactive natural products, due to the liquid nature of the stationary phase, process predictability and the possibility of scale-up from analytical to preparative scale. In this work, a method developed for the fractionation of Schinus terebinthifolius Raddi berries dichloromethane extract was thoroughly optimized to achieve maximal throughput with minimal solvent and time consumption per gram of processed crude extract, using analytical, semi-preparative and preparative 'high performance countercurrent chromatography' (HPCCC) instruments. The method using the biphasic solvent system composed of n-heptane-ethyl acetate-methanol-water (6:1:6:1, v/v/v/v) was volumetrically scaled up to increase sample throughput up to 120 times, while maintaining separation efficiency and time. As a fast and specific detection alternative, the fractions collected from the CCC-separations were injected to an 'atmospheric pressure chemical ionization mass-spectrometer' (APCI-MS/MS) and reconstituted molecular weight MS-chromatograms of the APCI-ionizable compounds from S. terebinthifolius were obtained. This procedure led to the direct isolation of tirucallane type triterpenes such as masticadienonic and 3β-masticadienolic acids. Also oleanonic and moronic acids have been identified for the first time in the species. In summary, this approach can be used for other CCC scale-up processes, enabling MS-target-guided isolation procedures. Copyright © 2015 Elsevier B.V. All rights reserved.

Enhancing Sensitivity of Liquid Chromatography-Mass Spectrometry of Peptides and Proteins Using Supercharging Agents.

PubMed

Nshanian, Michael; Lakshmanan, Rajeswari; Chen, Hao; Ogorzalek Loo, Rachel R; Loo, Joseph A

2018-04-01

Trifluoroacetic acid (TFA) is often used as a mobile phase modifier to enhance reversed phase chromatographic performance. TFA adjusts solution pH and is an ion-pairing agent, but it is not typically suitable for electrospray ionization-mass spectrometry (ESI-MS) and liquid chromatography/MS (LC/MS) because of its significant signal suppression. Supercharging agents elevate peptide and protein charge states in ESI, increasing tandem MS (MS/MS) efficiency. Here, LC/MS protein supercharging was effected by adding agents to LC mobile phase solvents. Significantly, the ionization suppression generally observed with TFA was, for the most part, rescued by supercharging agents, with improved separation efficiency (higher number of theoretical plates) and lowered detection limits.

Electron-Muon Ranger: Performance in the MICE muon beam

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

Adams, D.

2015-12-16

The Muon Ionization Cooling Experiment (MICE) will perform a detailed study of ionization cooling to evaluate the feasibility of the technique. To carry out this program, MICE requires an efficient particle-identification (PID) system to identify muons. The Electron-Muon Ranger (EMR) is a fully-active tracking-calorimeter that forms part of the PID system and tags muons that traverse the cooling channel without decaying. The detector is capable of identifying electrons with an efficiency of 98.6%, providing a purity for the MICE beam that exceeds 99.8%. Lastly, the EMR also proved to be a powerful tool for the reconstruction of muon momenta inmore » the range 100–280 MeV/c.« less

Predicting ESI/MS Signal Change for Anions in Different Solvents.

PubMed

Kruve, Anneli; Kaupmees, Karl

2017-05-02

LC/ESI/MS is a technique widely used for qualitative and quantitative analysis in various fields. However, quantification is currently possible only for compounds for which the standard substances are available, as the ionization efficiency of different compounds in ESI source differs by orders of magnitude. In this paper we present an approach for quantitative LC/ESI/MS analysis without standard substances. This approach relies on accurately predicting the ionization efficiencies in ESI source based on a model, which uses physicochemical parameters of analytes. Furthermore, the model has been made transferable between different mobile phases and instrument setups by using a suitable set of calibration compounds. This approach has been validated both in flow injection and chromatographic mode with gradient elution.

Quantitative Method for Simultaneous Analysis of Acetaminophen and 6 Metabolites.

PubMed

Lammers, Laureen A; Achterbergh, Roos; Pistorius, Marcel C M; Romijn, Johannes A; Mathôt, Ron A A

2017-04-01

Hepatotoxicity after ingestion of high-dose acetaminophen [N-acetyl-para-aminophenol (APAP)] is caused by the metabolites of the drug. To gain more insight into factors influencing susceptibility to APAP hepatotoxicity, quantification of APAP and metabolites is important. A few methods have been developed to simultaneously quantify APAP and its most important metabolites. However, these methods require a comprehensive sample preparation and long run times. The aim of this study was to develop and validate a simplified, but sensitive method for the simultaneous quantification of acetaminophen, the main metabolites acetaminophen glucuronide and acetaminophen sulfate, and 4 Cytochrome P450-mediated metabolites by using liquid chromatography with mass spectrometric (LC-MS) detection. The method was developed and validated for the human plasma, and it entailed a single method for sample preparation, enabling quick processing of the samples followed by an LC-MS method with a chromatographic run time of 9 minutes. The method was validated for selectivity, linearity, accuracy, imprecision, dilution integrity, recovery, process efficiency, ionization efficiency, and carryover effect. The method showed good selectivity without matrix interferences. For all analytes, the mean process efficiency was >86%, and the mean ionization efficiency was >94%. Furthermore, the accuracy was between 90.3% and 112% for all analytes, and the within- and between-run imprecision were <20% for the lower limit of quantification and <14.3% for the middle level and upper limit of quantification. The method presented here enables the simultaneous quantification of APAP and 6 of its metabolites. It is less time consuming than previously reported methods because it requires only a single and simple method for the sample preparation followed by an LC-MS method with a short run time. Therefore, this analytical method provides a useful method for both clinical and research purposes.

Ultraviolet absorption by highly ionized atoms in the Orion Nebula

NASA Technical Reports Server (NTRS)

Franco, J.; Savage, B. D.

1982-01-01

The International Ultraviolet Explorer was used to obtain high-resolution, far-UV spectra of theta 1 A, theta 1 C, theta 1 D, and theta 2 A Orionis. The interstellar absorption lines in these spectra are discussed with an emphasis on the high-ionization lines of C IV and Si IV. Theta 2 A Ori has interstellar C IV and Si IV absorption of moderate strength at the velocity found for normal H II region ions. Theta 1 C Ori has very strong interstellar C IV and Si IV absorption at velocities blueshifted by about 25 km/s from that found for the normal H II region ions. The possible origin of the high-ionization lines by three processes is considered: X-ray ionization, collisional ionization, and UV photoionization. It is concluded that the C IV and Si IV ions toward theta 2 A and theta 1 C Ori are likely produced by UV photoionization of surrounding nebular gas. In the case of theta 1 C Ori, the velocity shift of the high-ionization lines may be produced through the acceleration of high-density globules in the core of the nebula by the stellar wind of theta 1 C Ori.

Removal of detergents from proteins and peptides in a spin-column format.

PubMed

Antharavally, Babu S

2012-08-01

To enable downstream analysis, it is critical to remove unbound detergents from protein and peptide samples. This unit describes the use of a high-performance resin that offers exceptional detergent removal for proteins and peptides. The easy-to-use spin format significantly improves results over the standard drip column and batch methodologies, with >95% removal of 1% to 5% detergents, including SDS, sodium deoxycholate, CHAPS, Triton X-100, Triton X-114, NP-40, Brij-35, octyl glucoside, octyl thioglucoside, and lauryl maltoside, with high recovery of proteins and peptides. Detergent removal efficiency is evaluated using colorimetric methods and mass spectrometry (MS). BSA tryptic peptides have been successfully analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and matrix-assisted laser desorption/ionization (MALDI)-MS for identification of protein, following detergent removal using the resin. Advantages of this method include speed (less than 15 min), efficient detergent removal, and high recovery of proteins and peptides. © 2012 by John Wiley & Sons, Inc.

Self-organization and self-limitation in high power impulse magnetron sputtering

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

Anders, Andre

The plasma over the racetrack in high power impulse magnetron sputtering develops in traveling ionization zones. Power densities can locally reach 10{sup 9} W/m{sup 2}, which is much higher than usually reported. Ionization zones move because ions are 'evacuated' by the electric field, exposing neutrals to magnetically confined, drifting electrons. Drifting secondary electrons amplify ionization of the same ionization zone where the primary ions came from, while sputtered and outgassing atoms are supplied to the following zone(s). Strong density gradients parallel to the target disrupt electron confinement: a negative feedback mechanism that stabilizes ionization runaway.

Inductively coupled plasma mass spectrometry (ICP MS): a versatile tool.

PubMed

Ammann, Adrian A

2007-04-01

Inductively coupled plasma (ICP) mass spectrometry (MS) is routinely used in many diverse research fields such as earth, environmental, life and forensic sciences and in food, material, chemical, semiconductor and nuclear industries. The high ion density and the high temperature in a plasma provide an ideal atomizer and element ionizer for all types of samples and matrices introduced by a variety of specialized devices. Outstanding properties such as high sensitivity (ppt-ppq), relative salt tolerance, compound-independent element response and highest quantitation accuracy lead to the unchallenged performance of ICP MS in efficiently detecting, identifying and reliably quantifying trace elements. The increasing availability of relevant reference compounds and high separation selectivity extend the molecular identification capability of ICP MS hyphenated to species-specific separation techniques. While molecular ion source MS is specialized in determining the structure of unknown molecules, ICP MS is an efficient and highly sensitive tool for target-element orientated discoveries of relevant and unknown compounds. This special-feature, tutorial article presents the principle and advantages of ICP MS, highlighting these using examples from recently published investigations. Copyright 2007 John Wiley & Sons, Ltd.

Atomic and Molecular Systems in Intense Ultrashort Laser Pulses

NASA Astrophysics Data System (ADS)

Saenz, A.

2008-07-01

The full quantum mechanical treatment of atomic and molecular systems exposed to intense laser pulses is a so far unsolved challenge, even for systems as small as molecular hydrogen. Therefore, a number of simplified qualitative and quantitative models have been introduced in order to provide at least some interpretational tools for experimental data. The assessment of these models describing the molecular response is complicated, since a comparison to experiment requires often a number of averages to be performed. This includes in many cases averaging of different orientations of the molecule with respect to the laser field, focal volume effects, etc. Furthermore, the pulse shape and even the peak intensity is experimentally not known with very high precision; considering, e.g., the exponential intensity dependence of the ionization signal. Finally, experiments usually provide only relative yields. As a consequence of all these averagings and uncertainties, it is possible that different models may successfully explain some experimental results or features, although these models disagree substantially, if their predictions are compared before averaging. Therefore, fully quantum-mechanical approaches at least for small atomic and molecular systems are highly desirable and have been developed in our group. This includes efficient codes for solving the time-dependent Schrodinger equation of atomic hydrogen, helium or other effective one- or two-electron atoms as well as for the electronic motion in linear (effective) one-and two-electron diatomic molecules like H_2.Very recently, a code for larger molecular systems that adopts the so-called single-active electron approximation was also successfully implemented and applied. In the first part of this talk popular models describing intense laser-field ionization of atoms and their extensions to molecules are described. Then their validity is discussed on the basis of quantum-mechanical calculations. Finally, some peculiar molecular strong-field effects and the possibility of strong-field control mechanisms will be demonstrated. This includes phenomena like enhanced ionization and bond softening as well as the creation of vibrational wavepacket in the non-ionized electronic ground state of H_2 by creating a Schrodinger-cat state between the ionized and the non-ionized molecules. The latter, theoretically predicted phenomenon was very recently experimentally observed and lead to the real-time observation of the so far fastest molecular motion.

Quasar Outflows and AGN Feedback in the Extreme UV: HST/COS Observations of QSO HE0238-1904

NASA Astrophysics Data System (ADS)

Arav, Nahum; Borguet, B.; Chamberlain, C.; Edmonds, D.; Danforth, C.

2014-01-01

Spectroscopic observations of quasar outflows at rest-frame 500-1000 Angstrom have immense diagnostic power. We present analyses of such data, where absorption troughs from three important ions are measured: first, O IV and O IV* that allow us to obtain the distance of high ionization outflows from the AGN; second, Ne VIII and Mg X that are sensitive to the very high ionization phase of the outflow. Their inferred column densities, combined with those of troughs from O VI, N IV, and H I, yield two important results: 1) The outflow shows two ionization phases, where the high ionization phase carries the bulk of the material. This is similar to the situation seen in x-ray warm absorber studies. Furthermore, the low ionization phase is inferred to have a volume filling factor of 10^(-5)-10^(-6). 2) From the O IV to O IV* column density ratio, and the knowledge of the ionization parameter, we determine a distance of 3000 pc. from the outflow to the central source. Since this is a typical high ionization outflow, we can determine robust values for the mass flux and kinetic luminosity of the outflow: 40 solar masses per year and 10^45 ergs/s, respectively, where the latter is roughly equal to 1% of the bolometric luminosity. Such a large kinetic luminosity and mass flow rate measured in a typical high ionization wind suggests that quasar outflows are a major contributor to AGN feedback mechanisms.

A Physical Model for the Evolving Ultraviolet Luminosity Function of High Redshift Galaxies and their Contribution to the Cosmic Reionization

NASA Astrophysics Data System (ADS)

Cai, Zhen-Yi; Lapi, Andrea; Bressan, Alessandro; De Zotti, Gianfranco; Negrello, Mattia; Danese, Luigi

2014-04-01

We present a physical model for the evolution of the ultraviolet (UV) luminosity function of high-redshift galaxies, taking into account in a self-consistent way their chemical evolution and the associated evolution of dust extinction. Dust extinction is found to increase fast with halo mass. A strong correlation between dust attenuation and halo/stellar mass for UV selected high-z galaxies is thus predicted. The model yields good fits of the UV and Lyman-α (Lyα) line luminosity functions at all redshifts at which they have been measured. The weak observed evolution of both luminosity functions between z = 2 and z = 6 is explained as the combined effect of the negative evolution of the halo mass function; of the increase with redshift of the star formation efficiency due to the faster gas cooling; and of dust extinction, differential with halo mass. The slope of the faint end of the UV luminosity function is found to steepen with increasing redshift, implying that low luminosity galaxies increasingly dominate the contribution to the UV background at higher and higher redshifts. The observed range of the UV luminosities at high z implies a minimum halo mass capable of hosting active star formation M crit <~ 109.8 M ⊙, which is consistent with the constraints from hydrodynamical simulations. From fits of Lyα line luminosity functions, plus data on the luminosity dependence of extinction, and from the measured ratios of non-ionizing UV to Lyman-continuum flux density for samples of z ~= 3 Lyman break galaxies and Lyα emitters, we derive a simple relationship between the escape fraction of ionizing photons and the star formation rate. It implies that the escape fraction is larger for low-mass galaxies, which are almost dust-free and have lower gas column densities. Galaxies already represented in the UV luminosity function (M UV <~ -18) can keep the universe fully ionized up to z ~= 6. This is consistent with (uncertain) data pointing to a rapid drop of the ionization degree above z ~= 6, such as indications of a decrease of the comoving emission rate of ionizing photons at z ~= 6, a decrease of sizes of quasar near zones, and a possible decline of the Lyα transmission through the intergalactic medium at z > 6. On the other hand, the electron scattering optical depth, τes, inferred from cosmic microwave background (CMB) experiments favor an ionization degree close to unity up to z ~= 9-10. Consistency with CMB data can be achieved if M crit ~= 108.5 M ⊙, implying that the UV luminosity functions extend to M UV ~= -13, although the corresponding τes is still on the low side of CMB-based estimates.

Direct analysis of triterpenes from high-salt fermented cucumbers using infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI)

USDA-ARS?s Scientific Manuscript database

High-salt samples present a challenge to mass spectrometry (MS) analysis, particularly when electrospray ionization (ESI) is used, requiring extensive sample preparation steps such as desalting, extraction, and purification. In this study, infrared matrix-assisted laser desorption electrospray ioniz...

Epoch of Reionization : An Investigation of the Semi-Analytic 21CMMC Code

NASA Astrophysics Data System (ADS)

Miller, Michelle

2018-01-01

After the Big Bang the universe was filled with neutral hydrogen that began to cool and collapse into the first structures. These first stars and galaxies began to emit radiation that eventually ionized all of the neutral hydrogen in the universe. 21CMMC is a semi-numerical code that takes simulated boxes of this ionized universe from another code called 21cmFAST. Mock measurements are taken from the simulated boxes in 21cmFAST. Those measurements are thrown into 21CMMC and help us determine three major parameters of this simulated universe: virial temperature, mean free path, and ionization efficiency. My project tests the robustness of 21CMMC on universe simulations other than 21cmFAST to see whether 21CMMC can properly reconstruct early universe parameters given a mock “measurement” in the form of power spectra. We determine that while two of the three EoR parameters (Virial Temperature and Efficiency) have some reconstructability, the mean free path parameter in the code is the least robust. This requires development of the 21CMMC code.

Cellular Response to Ionizing Radiation: A MicroRNA Story

PubMed Central

Halimi, Mohammad; Asghari, S. Mohsen; Sariri, Reyhaneh; Moslemi, Dariush; Parsian, Hadi

2012-01-01

MicroRNAs (miRNAs) represent a class of small non-coding RNA molecules that regulate gene expression at the post-transcriptional level. They play a crucial role in diverse cellular pathways. Ionizing radiation (IR) is one of the most important treatment protocols for patients that suffer from cancer and affects directly or indirectly cellular integration. Recently it has been discovered that microRNA-mediated gene regulation interferes with radio-related pathways in ionizing radiation. Here, we review the recent discoveries about miRNAs in cellular response to IR. Thoroughly understanding the mechanism of miRNAs in radiation response, it will be possible to design new strategies for improving radiotherapy efficiency and ultimately cancer treatment. PMID:24551775

Resonance Ionization Mass Spectrometry System for Measurement of Environmental Samples

NASA Astrophysics Data System (ADS)

Pibida, L.; McMahon, C. A.; Nörtershäuser, W.; Bushaw, B. A.

2002-10-01

A resonance ionization mass spectrometry (RIMS) system has been developed at the National Institute of Standards and Technology (NIST) for sensitive and selective determination of radio-cesium in the environment. The overall efficiency was determined to be 4×10-7 with a combined (laser and mass spectrometer) selectivity of 108 for both 135Cs and 137Cs with respect to 133Cs. RIMS isotopic ratio measurements of 135Cs/ 137Cs were performed on a nuclear fuel burn-up sample and compared to measurements on a similar system at Pacific Northwest National Laboratory (PNNL) and to conventional thermal ionization mass spectrometry (TIMS). Results of preliminary RIMS investigations on a freshwater lake sediment sample are also discussed.

Evidence for impact ionization in vanadium dioxide

DOE PAGES

Holleman, Joshua; Bishop, Michael M.; Garcia, Carlos; ...

2016-10-17

Pump-probe optical spectroscopy was used to investigate charge carrier multiplication via impact ionization in the M 1 insulating phase of VO 2. By comparing the transient reflectivities of the film when pumped at less than and then more than twice the band-gap energy, we observed an enhancement of the ultrafast response with the higher energy pump color while the film was still transiently in the insulating phase. We additionally identified multiple timescales within the charge dynamics and analyzed how these changed when the pump and probe wavelengths were varied. This experiment provided evidence that impact ionization acts efficiently as amore » carrier multiplication process in this prototypical strongly-correlated insulator.« less

Binary and ternary gas mixtures for use in glow discharge closing switches

DOEpatents

Hunter, S.R.; Christophorou, L.G.

1988-04-27

Highly efficient binary and ternary gas mixtures for use in diffuse glow discharge closing switches are disclosed. The binary mixtures are combinations of helium or neon and selected perfluorides. The ternary mixtures are combinations of helium, neon, or argon, a selected perfluoride, and a small amount of gas that exhibits enhanced ionization characteristics. These mixtures are shown to be the optimum choices for use in diffuse glow discharge closing switches by virtue if the combines physio-electric properties of the mixture components. 9 figs.

First charge breeding results at CARIBU EBIS

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

Kondrashev, S., E-mail: kondrashev@anl.gov; Barcikowski, A., E-mail: kondrashev@anl.gov; Dickerson, C., E-mail: kondrashev@anl.gov

The Electron Beam Ion Source (EBIS) developed to breed CARIBU radioactive beams at ATLAS is currently in the off-line commissioning stage. The beam commissioning is being performed using a low emittance surface ionization source producing singly-charged cesium ions. The primary goal of the off-line commissioning is the demonstration of high-efficiency charge breeding in the pulsed injection mode. An overview of the final design of the CARIBU EBIS charge breeder, the off-line commissioning installation and the first results on charge breeding of stable cesium ions are presented and discussed.

Flagged uniform particle splitting for variance reduction in proton and carbon ion track-structure simulations

NASA Astrophysics Data System (ADS)

Ramos-Méndez, José; Schuemann, Jan; Incerti, Sebastien; Paganetti, Harald; Schulte, Reinhard; Faddegon, Bruce

2017-08-01

Flagged uniform particle splitting was implemented with two methods to improve the computational efficiency of Monte Carlo track structure simulations with TOPAS-nBio by enhancing the production of secondary electrons in ionization events. In method 1 the Geant4 kernel was modified. In method 2 Geant4 was not modified. In both methods a unique flag number assigned to each new split electron was inherited by its progeny, permitting reclassification of the split events as if produced by independent histories. Computational efficiency and accuracy were evaluated for simulations of 0.5-20 MeV protons and 1-20 MeV u-1 carbon ions for three endpoints: (1) mean of the ionization cluster size distribution, (2) mean number of DNA single-strand breaks (SSBs) and double-strand breaks (DSBs) classified with DBSCAN, and (3) mean number of SSBs and DSBs classified with a geometry-based algorithm. For endpoint (1), simulation efficiency was 3 times lower when splitting electrons generated by direct ionization events of primary particles than when splitting electrons generated by the first ionization events of secondary electrons. The latter technique was selected for further investigation. The following results are for method 2, with relative efficiencies about 4.5 times lower for method 1. For endpoint (1), relative efficiency at 128 split electrons approached maximum, increasing with energy from 47.2  ±  0.2 to 66.9  ±  0.2 for protons, decreasing with energy from 51.3  ±  0.4 to 41.7  ±  0.2 for carbon. For endpoint (2), relative efficiency increased with energy, from 20.7  ±  0.1 to 50.2  ±  0.3 for protons, 15.6  ±  0.1 to 20.2  ±  0.1 for carbon. For endpoint (3) relative efficiency increased with energy, from 31.0  ±  0.2 to 58.2  ±  0.4 for protons, 23.9  ±  0.1 to 26.2  ±  0.2 for carbon. Simulation results with and without splitting agreed within 1% (2 standard deviations) for endpoints (1) and (2), within 2% (1 standard deviation) for endpoint (3). In conclusion, standard particle splitting variance reduction techniques can be successfully implemented in Monte Carlo track structure codes.

Tunable Ionization Modes of a Flowing Atmospheric-Pressure Afterglow (FAPA) Ambient Ionization Source.

PubMed

Badal, Sunil P; Michalak, Shawn D; Chan, George C-Y; You, Yi; Shelley, Jacob T

2016-04-05

Plasma-based ambient desorption/ionization sources are versatile in that they enable direct ionization of gaseous samples as well as desorption/ionization of analytes from liquid and solid samples. However, ionization matrix effects, caused by competitive ionization processes, can worsen sensitivity or even inhibit detection all together. The present study is focused on expanding the analytical capabilities of the flowing atmospheric-pressure afterglow (FAPA) source by exploring additional types of ionization chemistry. Specifically, it was found that the abundance and type of reagent ions produced by the FAPA source and, thus, the corresponding ionization pathways of analytes, can be altered by changing the source working conditions. High abundance of proton-transfer reagent ions was observed with relatively high gas flow rates and low discharge currents. Conversely, charge-transfer reagent species were most abundant at low gas flows and high discharge currents. A rather nonpolar model analyte, biphenyl, was found to significantly change ionization pathway based on source operating parameters. Different analyte ions (e.g., MH(+) via proton-transfer and M(+.) via charge-transfer) were formed under unique operating parameters demonstrating two different operating regimes. These tunable ionization modes of the FAPA were used to enable or enhance detection of analytes which traditionally exhibit low-sensitivity in plasma-based ADI-MS analyses. In one example, 2,2'-dichloroquaterphenyl was detected under charge-transfer FAPA conditions, which were difficult or impossible to detect with proton-transfer FAPA or direct analysis in real-time (DART). Overall, this unique mode of operation increases the number and range of detectable analytes and has the potential to lessen ionization matrix effects in ADI-MS analyses.

Possible influence of the Kuramoto length in a photo-catalytic water splitting reaction revealed by Poisson-Nernst-Planck equations involving ionization in a weak electrolyte

NASA Astrophysics Data System (ADS)

Suzuki, Yohichi; Seki, Kazuhiko

2018-03-01

We studied ion concentration profiles and the charge density gradient caused by electrode reactions in weak electrolytes by using the Poisson-Nernst-Planck equations without assuming charge neutrality. In weak electrolytes, only a small fraction of molecules is ionized in bulk. Ion concentration profiles depend on not only ion transport but also the ionization of molecules. We considered the ionization of molecules and ion association in weak electrolytes and obtained analytical expressions for ion densities, electrostatic potential profiles, and ion currents. We found the case that the total ion density gradient was given by the Kuramoto length which characterized the distance over which an ion diffuses before association. The charge density gradient is characterized by the Debye length for 1:1 weak electrolytes. We discuss the role of these length scales for efficient water splitting reactions using photo-electrocatalytic electrodes.

Specific interaction between negative atmospheric ions and organic compounds in atmospheric pressure corona discharge ionization mass spectrometry.

PubMed

Sekimoto, Kanako; Sakai, Mami; Takayama, Mitsuo

2012-06-01

The interaction between negative atmospheric ions and various types of organic compounds were investigated using atmospheric pressure corona discharge ionization (APCDI) mass spectrometry. Atmospheric negative ions such as O(2)(-), HCO(3)(-), COO(-)(COOH), NO(2)(-), NO(3)(-), and NO(3)(-)(HNO(3)) having different proton affinities served as the reactant ions for analyte ionization in APCDI in negative-ion mode. The individual atmospheric ions specifically ionized aliphatic and aromatic compounds with various functional groups as atmospheric ion adducts and deprotonated analytes. The formation of the atmospheric ion adducts under certain discharge conditions is most likely attributable to the affinity between the analyte and atmospheric ion and the concentration of the atmospheric ion produced under these conditions. The deprotonated analytes, in contrast, were generated from the adducts of the atmospheric ions with higher proton affinity attributable to efficient proton abstraction from the analyte by the atmospheric ion.

Detection limits of organic compounds achievable with intense, short-pulse lasers.

PubMed

Miles, Jordan; De Camillis, Simone; Alexander, Grace; Hamilton, Kathryn; Kelly, Thomas J; Costello, John T; Zepf, Matthew; Williams, Ian D; Greenwood, Jason B

2015-06-21

Many organic molecules have strong absorption bands which can be accessed by ultraviolet short pulse lasers to produce efficient ionization. This resonant multiphoton ionization scheme has already been exploited as an ionization source in time-of-flight mass spectrometers used for environmental trace analysis. In the present work we quantify the ultimate potential of this technique by measuring absolute ion yields produced from the interaction of 267 nm femtosecond laser pulses with the organic molecules indole and toluene, and gases Xe, N2 and O2. Using multiphoton ionization cross sections extracted from these results, we show that the laser pulse parameters required for real-time detection of aromatic molecules at concentrations of one part per trillion in air and a limit of detection of a few attomoles are achievable with presently available commercial laser systems. The potential applications for the analysis of human breath, blood and tissue samples are discussed.

Single electron dynamics in a Hall thruster electromagnetic field profile

NASA Astrophysics Data System (ADS)

Marini, Samuel; Pakter, Renato

2017-05-01

In this work, the single electron dynamics in a simplified three dimensional Hall thruster model is studied. Using Hamiltonian formalism and the concept of limiting curves, one is able to determine confinement conditions for the electron in the acceleration channel. It is shown that as a given parameter of the electromagnetic field is changed, the particle trajectory may transit from regular to chaotic without affecting the confinement, which allows one to make a detailed analysis of the role played by the chaos. The ionization volume is also computed, which measures the probability of an electron to ionize background gas atoms. It is found that there is a great correlation between chaos and increased effective ionization volume. This indicates that a complex dynamical behavior may improve the device efficiency by augmenting the ionization capability of each electron, requiring an overall lower electron current.

Selected cis- and trans-3-fluorostyrene rotamers studied by two-color resonant two-photon mass-analyzed threshold ionization spectroscopy

NASA Astrophysics Data System (ADS)

Wu, Pei Ying; Tzeng, Wen Bih

2015-10-01

We applied two-color resonant two-photon ionization and mass-analyzed threshold ionization techniques to record the vibronic, photoionization efficiency, and cation spectra of the selected rotamers of 3-fluorostyrene. The adiabatic ionization energies of cis- and trans-3-fluorostyrene were determined to be 69 960 ± 5 and 69 856 ± 5 cm-1, respectively. Cation vibrations 10a, 15, 6b, and 12 of both rotamers have been found to have frequencies of 218, 404, 452, and 971 cm-1, respectively. This finding shows that the relative orientation of the vinyl group with respect to the F atom does not affect these vibrations of the 3-fluorostyrene cation. Our one-dimensional potential energy surface calculations support that the cis-trans isomerization of 3-fluorostyrene does not occur under the present experimental conditions.

Interstellar gas in the Gum Nebula

NASA Technical Reports Server (NTRS)

Wallerstein, G.; Jenkins, E. B.; Silk, J.

1980-01-01

A survey of the interstellar gas near the Gum Nebula by optical observation of 67 stars at Ca II, 42 stars at Na I, and 14 stars in the UV with the Copernicus satellite provided radial velocities and column densities for all resolved absorption components. Velocity dispersions for gas in the Gum Nebula are not significantly larger than in the general interstellar medium; the ionization structure is predominantly that of an H II region with moderately high ionization. Denser, more highly ionized clouds are concentrated toward the Gum Nebula; these clouds do not show the anomalously high ionization observed in the Vela remnant clouds.

High-intensity xenon plasma discharge lamp for bulk-sensitive high-resolution photoemission spectroscopy.

PubMed

Souma, S; Sato, T; Takahashi, T; Baltzer, P

2007-12-01

We have developed a highly brilliant xenon (Xe) discharge lamp operated by microwave-induced electron cyclotron resonance (ECR) for ultrahigh-resolution bulk-sensitive photoemission spectroscopy (PES). We observed at least eight strong radiation lines from neutral or singly ionized Xe atoms in the energy region of 8.4-10.7 eV. The photon flux of the strongest Xe I resonance line at 8.437 eV is comparable to that of the He Ialpha line (21.218 eV) from the He-ECR discharge lamp. Stable operation for more than 300 h is achieved by efficient air-cooling of a ceramic tube in the resonance cavity. The high bulk sensitivity and high-energy resolution of PES using the Xe lines are demonstrated for some typical materials.

Space-based laser-driven MHD generator: Feasibility study

NASA Technical Reports Server (NTRS)

Choi, S. H.

1986-01-01

The feasibility of a laser-driven MHD generator, as a candidate receiver for a space-based laser power transmission system, was investigated. On the basis of reasonable parameters obtained in the literature, a model of the laser-driven MHD generator was developed with the assumptions of a steady, turbulent, two-dimensional flow. These assumptions were based on the continuous and steady generation of plasmas by the exposure of the continuous wave laser beam thus inducing a steady back pressure that enables the medium to flow steadily. The model considered here took the turbulent nature of plasmas into account in the two-dimensional geometry of the generator. For these conditions with the plasma parameters defining the thermal conductivity, viscosity, electrical conductivity for the plasma flow, a generator efficiency of 53.3% was calculated. If turbulent effects and nonequilibrium ionization are taken into account, the efficiency is 43.2%. The study shows that the laser-driven MHD system has potential as a laser power receiver for space applications because of its high energy conversion efficiency, high energy density and relatively simple mechanism as compared to other energy conversion cycles.

Low temperature plasmas induced in SF6 by extreme ultraviolet (EUV) pulses

NASA Astrophysics Data System (ADS)

Bartnik, A.; Skrzeczanowski, W.; Czwartos, J.; Kostecki, J.; Fiedorowicz, H.; Wachulak, P.; Fok, T.

2018-06-01

In this work, a comparative study of extreme ultraviolet (EUV) induced low temperature SF6-based plasmas, created using two different irradiation systems, was performed. Both systems utilized laser-produced plasma (LPP) EUV sources. The essential difference between the systems concerned the formation of the driving EUV beam. The first one contained an efficient ellipsoidal EUV collector allowing for focusing of the EUV radiation at a large distance from the LPP source. The spectrum of focused radiation was limited to the long-wavelength part of the total LPP emission, λ > 8 nm, due to the reflective properties of the collector. The second system did not contain any EUV collector. The gas to be ionized was injected in the vicinity of the LPP, at a distance of the order of 10 mm. In both systems, energies of the driving photons were high enough for dissociative ionization of the SF6 molecules and ionization of atoms or even singly charged ions. Plasmas, created due to these processes, were investigated by spectral measurements in the EUV, ultraviolet (UV), and visible (VIS) spectral ranges. These low temperature plasmas were employed for preliminary experiments concerning surface treatment. The formation of pronounced nanostructures on the silicon surface after plasma treatment was demonstrated.

Ultrafast Screening and Quantitation of Pesticides in Food and Environmental Matrices by Solid-Phase Microextraction-Transmission Mode (SPME-TM) and Direct Analysis in Real Time (DART).

PubMed

Gómez-Ríos, Germán Augusto; Gionfriddo, Emanuela; Poole, Justen; Pawliszyn, Janusz

2017-07-05

The direct interface of microextraction technologies to mass spectrometry (MS) has unquestionably revolutionized the speed and efficacy at which complex matrices are analyzed. Solid Phase Micro Extraction-Transmission Mode (SPME-TM) is a technology conceived as an effective synergy between sample preparation and ambient ionization. Succinctly, the device consists of a mesh coated with polymeric particles that extracts analytes of interest present in a given sample matrix. This coated mesh acts as a transmission-mode substrate for Direct Analysis in Real Time (DART), allowing for rapid and efficient thermal desorption/ionization of analytes previously concentrated on the coating, and dramatically lowering the limits of detection attained by sole DART analysis. In this study, we present SPME-TM as a novel tool for the ultrafast enrichment of pesticides present in food and environmental matrices and their quantitative determination by MS via DART ionization. Limits of quantitation in the subnanogram per milliliter range can be attained, while total analysis time does not exceed 2 min per sample. In addition to target information obtained via tandem MS, retrospective studies of the same sample via high-resolution mass spectrometry (HRMS) were accomplished by thermally desorbing a different segment of the microextraction device.

Fourier Transform Mass Spectrometry and Nuclear Magnetic Resonance Analysis for the Rapid and Accurate Characterization of Hexacosanoylceramide.

PubMed

Ross, Charles W; Simonsick, William J; Bogusky, Michael J; Celikay, Recep W; Guare, James P; Newton, Randall C

2016-06-28

Ceramides are a central unit of all sphingolipids which have been identified as sites of biological recognition on cellular membranes mediating cell growth and differentiation. Several glycosphingolipids have been isolated, displaying immunomodulatory and anti-tumor activities. These molecules have generated considerable interest as potential vaccine adjuvants in humans. Accurate analyses of these and related sphingosine analogues are important for the characterization of structure, biological function, and metabolism. We report the complementary use of direct laser desorption ionization (DLDI), sheath flow electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) and high-field nuclear magnetic resonance (NMR) analysis for the rapid, accurate identification of hexacosanoylceramide and starting materials. DLDI does not require stringent sample preparation and yields representative ions. Sheath-flow ESI yields ions of the product and byproducts and was significantly better than monospray ESI due to improved compound solubility. Negative ion sheath flow ESI provided data of starting materials and products all in one acquisition as hexacosanoic acid does not ionize efficiently when ceramides are present. NMR provided characterization of these lipid molecules complementing the results obtained from MS analyses. NMR data was able to differentiate straight chain versus branched chain alkyl groups not easily obtained from mass spectrometry.

Internuclear separation dependent ionization of the valence orbitals of I2 by strong laser fields.

PubMed

Chen, H; Tagliamonti, V; Gibson, G N

2012-11-09

Using a pump-dump-probe technique and Fourier-transform spectroscopy, we study the internuclear separation R dependence and relative strength of the ionization rates of the π and σ electrons of I2, whose valence orbitals are σ(g)(2)π(u)(4)π(g)(4)σ(u)(0). We find that ionization of the highest occupied molecular orbital (HOMO)-2 (σ(g)) has a strong dependence on R while the HOMO and HOMO-1 do not. Surprisingly, the ionization rate of the HOMO-2 exceeds the combined ionization rate of the less bound orbitals and this branching ratio increases with R. Since our technique produces target molecules that are highly aligned with the laser polarization, the σ orbitals will be preferentially ionized and undergo enhanced ionization at larger R compared to the π orbitals. Nevertheless, it is highly unusual that an inner orbital provides the dominant strong field ionization pathway in a small molecule.

Internuclear Separation Dependent Ionization of the Valence Orbitals of I2 by Strong Laser Fields

NASA Astrophysics Data System (ADS)

Chen, H.; Tagliamonti, V.; Gibson, G. N.

2012-11-01

Using a pump-dump-probe technique and Fourier-transform spectroscopy, we study the internuclear separation R dependence and relative strength of the ionization rates of the π and σ electrons of I2, whose valence orbitals are σg2πu4πg4σu0. We find that ionization of the highest occupied molecular orbital (HOMO)-2 (σg) has a strong dependence on R while the HOMO and HOMO-1 do not. Surprisingly, the ionization rate of the HOMO-2 exceeds the combined ionization rate of the less bound orbitals and this branching ratio increases with R. Since our technique produces target molecules that are highly aligned with the laser polarization, the σ orbitals will be preferentially ionized and undergo enhanced ionization at larger R compared to the π orbitals. Nevertheless, it is highly unusual that an inner orbital provides the dominant strong field ionization pathway in a small molecule.

Realizing Efficient Energy Harvesting from Organic Photovoltaic Cells

NASA Astrophysics Data System (ADS)

Zou, Yunlong

Organic photovoltaic cells (OPVs) are emerging field of research in renewable energy. The development of OPVs in recent years has made this technology viable for many niche applications. In order to realize widespread application however, the power conversion efficiency requires further improvement. The efficiency of an OPV depends on the short-circuit current density (JSC), open-circuit voltage (VOC) and fill factor (FF). For state-of-the-art devices, JSC is mostly optimized with the application of novel low-bandgap materials and a bulk heterojunction device architecture (internal quantum efficiency approaching 100%). The remaining limiting factors are the low VOC and FF. This work focuses on overcoming these bottlenecks for improved efficiency. Temperature dependent measurements of device performance are used to examine both charge transfer and exciton ionization process in OPVs. The results permit an improved understanding of the intrinsic limit for VOC in various device architectures and provide insight on device operation. Efforts have also been directed at engineering device architecture for optimized FF, realizing a very high efficiency of 8% for vapor deposited small molecule OPVs. With collaborators, new molecules with tailored desired energy levels are being designed for further improvements in efficiency. A new type of hybrid organic-inorganic perovskite material is also included in this study. By addressing processing issues and anomalous hysteresis effects, a very high efficiency of 19.1% is achieved. Moving forward, topics including engineering film crystallinity, exploring tandem architectures and understanding degradation mechanisms will further push OPVs toward broad commercialization.

Saturation current and collection efficiency for ionization chambers in pulsed beams.

PubMed

DeBlois, F; Zankowski, C; Podgorsak, E B

2000-05-01

Saturation currents and collection efficiencies in ionization chambers exposed to pulsed megavoltage photon and electron beams are determined assuming a linear relationship between 1/I and 1/V in the extreme near-saturation region, with I and V the chamber current and polarizing voltage, respectively. Careful measurements of chamber current against polarizing voltage in the extreme near-saturation region reveal a current rising faster than that predicted by the linear relationship. This excess current combined with conventional "two-voltage" technique for determination of collection efficiency may result in an up to 0.7% overestimate of the saturation current for standard radiation field sizes of 10X10 cm2. The measured excess current is attributed to charge multiplication in the chamber air volume and to radiation-induced conductivity in the stem of the chamber (stem effect). These effects may be accounted for by an exponential term used in conjunction with Boag's equation for collection efficiency in pulsed beams. The semiempirical model follows the experimental data well and accounts for both the charge recombination as well as for the charge multiplication effects and the chamber stem effect.

Channel electron multipliers - Detection efficiencies with opaque MgF2 photocathodes at XUV wavelengths

NASA Technical Reports Server (NTRS)

Lapson, L. B.; Timothy, J. G.

1976-01-01

Detection efficiencies of channel electron multipliers (CEM) with opaque MgF2 photocathodes obtained in the extreme ultraviolet (XUV), 44 A to 990 A, are reported. A stable highly efficient response is reported for that interval, with no adverse effects on CEM performance. Efficiencies twice those of uncoated CEMs are obtained for 50 A to 350 A. The Mullard B419BL and Galileo 4510WL single-stage cone-cathode CEMs were used in the experiments. A rare-gas double ionization chamber was employed as absolute standard detector for 406 A to 990 A, and a flow Geiger counter filled with 96% argon and 4% isobutane for 44 A to 256 A. Absolute detection efficiencies are 10% higher from 67 A to 990 A when photocathodes are illuminated at an angle of incidence 45 deg. The photocathodes suffered no loss of response in storage (in vacuum or air) after an initial aging period. Effects of scattered UV radiation are greatly reduced when MgF2-coated CEMs are used in the XUV.

An Efficient, Affordable Optically Stimulated Luminescent (OSL) Annealer.

PubMed

Abraham, Sara A; Frank, Samuel J; Kearfott, Kimberlee J

2017-07-01

Optically stimulated luminescent (OSL) dosimeters are devices used for measuring doses of ionizing radiation. Signal is stored within an OSL material so that when stimulated with light, light of a specific wavelength is emitted in proportion to the integrated ionizing radiation dose. Each interrogation of the material results in the loss of a small fraction of signal, thus allowing multiple interrogations leading to more accurate measurements of dose. In order to reuse a dosimeter, the residual signals from prior doses must be taken into account and subtracted from current readings, adding uncertainty to any future measurements. To reduce these errors when they become large, it is desirable to completely clear the stored signal or anneal the dosimeter. Traditionally, heating the material has accomplished this. In a commercially available dosimeter badge system, the OSL material Al2O3:C is incorporated into a plastic slide that would melt at the necessary high temperatures, which can reach 900 °C, required for annealing. Fortunately, due to the material's high sensitivity to light, OSLs can be optically annealed instead. In order to do this, an affordable OSL dosimeter annealer was designed with inexpensive, exchangeable blue, green, and white high intensity light-emitting diodes (LEDs). Several dosimeters were repeatedly annealed for recorded intervals and then read out. A single dosimeter was partially annealed through repeated interrogations with the LED array from a commercial reader. The signal loss due to the exposure to each light was analyzed to determine the practicality and efficiency of each color. The rate and extent of signal loss was dependent not only on the spectrum of annealing light but on the initial signal levels as well. These findings suggest that blue LEDs are the most promising for effective and rapid clearing of the OSL material Al2O3:C.

Atmospheric sampling glow discharge ionization source

DOEpatents

McLuckey, Scott A.; Glish, Gary L.

1989-01-01

An atmospheric sampling glow discharge ionization source that can be used in combination with an analytical instrument which operates at high vacuum, such as a mass spectrometer. The atmospheric sampling glow discharge ionization source comprises a chamber with at least one pair of electrodes disposed therein, an inlet for a gaseous sample to be analyzed and an outlet communicating with an analyzer which operates at subatmospheric pressure. The ionization chamber is maintained at a pressure below atmospheric pressure, and a voltage difference is applied across the electrodes to induce a glow discharge between the electrodes, so that molecules passing through the inlet are ionized by the glow discharge and directed into the analyzer. The ionization source accepts the sample under atmospheric pressure conditions and processes it directly into the high vacuum instrument, bridging the pressure gap and drawing off unwanted atmospheric gases. The invention also includes a method for analyzing a gaseous sample using the glow discharge ionization source described above.

Radiation sterilization of medical devices. Effects of ionizing radiation on ultra-high molecular-weight polyethylene

NASA Astrophysics Data System (ADS)

Buchalla, R.; Schüttler, C.; Bögl, K. W.

1995-02-01

Sterilization by ionizing radiation has become, next to ethylene oxide treament, the most important "cold" sterilization process for medical devices made from plastics. The effects of ionizing radiation on the most important polymer for medical devices, ultra-high molecular-weight polyethylene, are briefly described in this review.

Development and characterization of high-efficiency, high-specific impulse xenon Hall thrusters

NASA Astrophysics Data System (ADS)

Hofer, Richard Robert

This dissertation presents research aimed at extending the efficient operation of 1600 s specific impulse Hall thruster technology to the 2000--3000 s range. While recent studies of commercially developed Hall thrusters demonstrated greater than 4000 s specific impulse, maximum efficiency occurred at less than 3000 s. It was hypothesized that the efficiency maximum resulted as a consequence of modern magnetic field designs, optimized for 1600 s, which were unsuitable at high-specific impulse. Motivated by the industry efforts and mission studies, the aim of this research was to develop and characterize xenon Hall thrusters capable of both high-specific impulse and high-efficiency operation. The research divided into development and characterization phases. During the development phase, the laboratory-model NASA-173M Hall thrusters were designed with plasma lens magnetic field topographies and their performance and plasma characteristics were evaluated. Experiments with the NASA-173M version 1 (v1) validated the plasma lens design by showing how changing the magnetic field topography at high-specific impulse improved efficiency. Experiments with the NASA-173M version 2 (v2) showed there was a minimum current density and optimum magnetic field topography at which efficiency monotonically increased with voltage. Between 300--1000 V, total specific impulse and total efficiency of the NASA-173Mv2 operating at 10 mg/s ranged from 1600--3400 s and 51--61%, respectively. Comparison of the thrusters showed that efficiency can be optimized for specific impulse by varying the plasma lens design. During the characterization phase, additional plasma properties of the NASA-173Mv2 were measured and a performance model was derived accounting for a multiply-charged, partially-ionized plasma. Results from the model based on experimental data showed how efficient operation at high-specific impulse was enabled through regulation of the electron current with the magnetic field. The decrease of efficiency due to multiply-charged ions was minor. Efficiency was largely determined by the current utilization, which suggested maximum Hall thruster efficiency has yet to be reached. The electron Hall parameter was approximately constant with voltage, decreasing from an average of 210 at 300 V to an average of 160 between 400--900 V, which confirmed efficient operation can be realized only over a limited range of Hall parameters.

Pulse mode readout techniques for use with non-gridded industrial ionization chambers

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

Popov, Vladimir E.; Degtiarenko, Pavel V.

2011-10-01

Highly sensitive readout technique for precision long-term radiation measurements has been developed and tested in the Radiation Control Department at Jefferson Lab. The new electronics design is used to retrieve ionization data in a pulse mode. The dedicated data acquisition system works with M=Audio Audiophile 192 High-Definition 24-bit/192 kHz audio cards, taking data in continuous waveform recording mode. The on-line data processing algorithms extract signals of the ionization events from the data flow and measure the ionization value for each event. Two different ion chambers are evaluated. The first is a Reuter-Stokes Argon-filled (at 25 atm) High Pressure Ionization Chambermore » (HPIC), commonly used as a detector part in many GE Reuter-Stokes instruments of the RSS series. The second is a VacuTec Model 70181, 5 atm Xenon-filled ionization chamber. Results for both chambers indicate that the techniques allow using industrial ICs for high sensitivity and precision long-term radiation measurements, while at the same time providing information about spectral characteristics of the radiation fields.« less

Bipolar Mass Spectrometry of Labile Coordination Complexes, Redox Active Inorganic Compounds, and Proteins Using a Glass Nebulizer for Sonic-Spray Ionization

NASA Astrophysics Data System (ADS)

Antonakis, Manolis M.; Tsirigotaki, Alexandra; Kanaki, Katerina; Milios, Constantinos J.; Pergantis, Spiros A.

2013-08-01

In this study, we report on the development of a novel nebulizer configuration for sonic-spray ionization (SSI) mass spectrometry (MS), more specifically for a version of SSI that is referred to as Venturi easy ambient sonic-spray ionization (V-EASI) MS. The developed nebulizer configuration is based on a commercially available pneumatic glass nebulizer that has been used extensively for aerosol formation in atomic spectrometry. In the present study, the nebulizer was modified in order to achieve efficient V-EASI-MS operation. Upon evaluating this system, it has been demonstrated that V-EASI-MS offers some distinct advantages for the analysis of coordination compounds and redox active inorganic compounds over the predominantly used electrospray ionization (ESI) technique. Such advantages, for this type of compounds, are demonstrated here for the first time. More specifically, a series of labile heptanuclear heterometallic [CuII 6LnIII] clusters held together with artificial amino acid ligands, in addition to easily oxidized inorganic oxyanions of selenium and arsenic, were analyzed. The observed advantages pertain to V-EASI appearing to be a "milder" ionization source than ESI, not requiring electrical potentials for gas phase ion formation, thus eliminating the possibility of unwanted redox transformations, allowing for the "simultaneous" detection of negative and positive ions (bipolar analysis) without the need to change source ionization conditions, and also not requiring the use of syringes and delivery pumps. Because of such features, especially because of the absence of ionization potentials, EASI can be operated with minimal requirements for source parameter optimization. We observed that source temperature and accelerating voltage do not seem to affect labile compounds to the extent they do in ESI-MS. In addition, bipolar analysis of proteins was demonstrated here by acquiring both positive and negative ion mass spectra from the same protein solutions, without the need to independently adjust solution and source conditions in each mode. Finally, the simple and efficient operation of a dual-nebulizer configuration was demonstrated for V-EASI-MS for the first time.

Bipolar mass spectrometry of labile coordination complexes, redox active inorganic compounds, and proteins using a glass nebulizer for sonic-spray ionization.

PubMed

Antonakis, Manolis M; Tsirigotaki, Alexandra; Kanaki, Katerina; Milios, Constantinos J; Pergantis, Spiros A

2013-08-01

In this study, we report on the development of a novel nebulizer configuration for sonic-spray ionization (SSI) mass spectrometry (MS), more specifically for a version of SSI that is referred to as Venturi easy ambient sonic-spray ionization (V-EASI) MS. The developed nebulizer configuration is based on a commercially available pneumatic glass nebulizer that has been used extensively for aerosol formation in atomic spectrometry. In the present study, the nebulizer was modified in order to achieve efficient V-EASI-MS operation. Upon evaluating this system, it has been demonstrated that V-EASI-MS offers some distinct advantages for the analysis of coordination compounds and redox active inorganic compounds over the predominantly used electrospray ionization (ESI) technique. Such advantages, for this type of compounds, are demonstrated here for the first time. More specifically, a series of labile heptanuclear heterometallic [Cu(II) 6Ln(III)] clusters held together with artificial amino acid ligands, in addition to easily oxidized inorganic oxyanions of selenium and arsenic, were analyzed. The observed advantages pertain to V-EASI appearing to be a "milder" ionization source than ESI, not requiring electrical potentials for gas phase ion formation, thus eliminating the possibility of unwanted redox transformations, allowing for the "simultaneous" detection of negative and positive ions (bipolar analysis) without the need to change source ionization conditions, and also not requiring the use of syringes and delivery pumps. Because of such features, especially because of the absence of ionization potentials, EASI can be operated with minimal requirements for source parameter optimization. We observed that source temperature and accelerating voltage do not seem to affect labile compounds to the extent they do in ESI-MS. In addition, bipolar analysis of proteins was demonstrated here by acquiring both positive and negative ion mass spectra from the same protein solutions, without the need to independently adjust solution and source conditions in each mode. Finally, the simple and efficient operation of a dual-nebulizer configuration was demonstrated for V-EASI-MS for the first time.

Probing the Physical Properties and Origins of Ultra-fast Outflows in AGN

NASA Astrophysics Data System (ADS)

Kraemer, Steven B.; Tombesi, Francesco; Bottorff, Mark

2017-01-01

Approximately half of Type 1 AGN possess intrinsic absorption and high resolution UV and X-ray spectroscopy have revealed that the absorbing gas is radially outflowing, with velocities of 100s to 1000s km/sec. X-ray ("warm") absorbers, originally revealed by the presence of bound-free edges of O~VII and O~VIII, are more highly ionized than their UV counterparts, and photo-ionization modeling studies have determined that they have ionization parameters of logU ~ -1 to 1. Recently, muchmore highly ionized gas, with logU > 2, has been detected in XMM-Newton spectra, as evidenced by absorption lines from H- and He-like Fe. Some of these absorbers, ``Ultra Fast Outlows (UFOs)'', have radial velocities up to 0.2c. We have undertaken a detailed photo-ionization study of high-ionization Fe absorbers, both UFOs and non-UFOs, in a sample of AGN observed by XMM-Newton. We find that the UFOs are completely Compton-cooled, unlike the non-UFOS. Both types are too highly ionized to be radiatively accelerated, hence they are more likely driven via Magneto-Hydrodynamic processes. Their large column densities and velocity gradients are consistent with flows along magnetic streamlines emanating from accretion disks. Open questions include: the temporal stability of the UFOs, the apparent lack of non-UFOs in UFO sources, and their relationship to warm absorbers.

Efficient ECH-assisted plasma start-up using trapped particle configuration in the versatile experiment spherical torus

NASA Astrophysics Data System (ADS)

An, YoungHwa; Lee, Jeongwon; Jo, JongGab; Jung, Bong-Ki; Lee, HyunYeong; Chung, Kyoung-Jae; Na, Yong-Su; Hahm, T. S.; Hwang, Y. S.

2017-01-01

An efficient and robust ECH (electron cyclotron heating)-assisted plasma start-up scheme with a low loop voltage and low volt-second consumption utilizing the trapped particle configuration (TPC) has been developed in the versatile experiment spherical torus (VEST). The TPC is a mirror-like magnetic field configuration providing a vertical magnetic field in the same direction as the equilibrium field. It significantly enhances ECH pre-ionization with enhanced particle confinement due to its mirror effect, and intrinsically provides an equilibrium field with a stable decay index enabling prompt plasma current initiation. Consequently, the formation of TPC before the onset of the loop voltage allows the plasma to start up with a lower loop voltage and lower volt-second consumption as well as a wider operation range in terms of ECH pre-ionization power and H2 filling pressure. The TPC can improve the widely-used field null configuration significantly for more efficient start-up when ECH pre-ionization is used. This can then be utilized in superconducting tokamaks requiring a low loop voltage start-up, such as ITER, or in spherical tori with limited volt-seconds. The TPC can be particularly useful in superconducting tokamaks with a limited current slew-rate of superconducting PF coils, as it can save volt-second consumption before plasma current initiation by providing prompt initiation with an intrinsic stable equilibrium field.

Decomposition reaction of the veterinary antibiotic ciprofloxacin using electron ionizing energy.

PubMed

Cho, Jae Young; Chung, Byung Yeoup; Lee, Kyeong-Bo; Lee, Geon-Hwi; Hwang, Seon Ah

2014-12-01

The application of electron ionizing energy for degrading veterinary antibiotic ciprofloxacin (CFX) in aqueous solution was elucidated. The degradation efficiency of CFX after irradiation with electron ionizing energy was 38% at 1 kGy, 80% at 5kGy, and 97% at 10 kGy. Total organic carbon of CFX in aqueous solution after irradiation with electron ionizing energy decreased 2% at 1 kGy, 18% at 5 kGy, and 53% at 10 kGy. The CFX degradation products after irradiation with electron ionizing energy were CFX1 ([M+H] m/z 330), CFX2 ([M+H] m/z 314), and CFX3 ([M+H] m/z 263). CFX1 had an F atom substituted with OH and CFX2 was expected to originate from CFX via loss of F or H2O. CFX3 was expected to originate from CFX via loss of the piperazynilic ring. Among the several radicals, hydrate electron (eaq(-)) is expected to play an important role in degradation of veterinary antibiotic during irradiation with electron ionizing energy. The toxicity of the degraded products formed during irradiation with electron ionizing energy was evaluated using microbes such as Escherichia coli, Pseudomonas putida, and Bacillus subtilis, and the results revealed that the toxicity decreased with irradiation. These results demonstrate that irradiation technology using electron ionizing energy is an effective was to remove veterinary antibiotics from an aquatic ecosystem. Copyright © 2014 Elsevier Ltd. All rights reserved.

The role of exciton ionization processes in bulk heterojunction organic photovoltaic cells

NASA Astrophysics Data System (ADS)

Zou, Yunlong; Holmes, Russell

2015-03-01

Dissociating photogenerated excitons into their constituent charges is essential for efficient photoconversion in organic semiconductors. Organic photovoltaics cells (OPV) widely adopt a heterojunction architecture where dissociation is facilitated by charge transfer at a donor-acceptor (D-A) interface. Interestingly, recent work on MoOx/C60 Schottky OPVs has demonstrated that excitons in C60 may also undergo bulk-ionization to generate photocurrent, driven by the built-in field at the MoOx/C60 interface. Here, we show that bulk-ionization processes also contribute to the photocurrent in bulk heterojunction (BHJ) OPVs with fullerene-rich compositions. The short-circuit current density (JSC) in a MoOx/C60 Schottky OPVs shows almost no dependence on temperature down to 80 K. This characteristic of bulk-ionization allows the use of temperature-dependent measurements of JSC to distinguish dissociation by bulk-ionization from charge transfer at a D-A interface. For BHJ OPVs constructed using the D-A pairing of boron subphthalocyanine chloride (SubPc)-C60, bulk-ionization is found to contribute >10% of the total photocurrent and >30% of the photocurrent from C60. We further find that fullerene-rich SubPc-C60 BHJ OPVs show a larger open-circuit voltage (VOC) than evenly mixed BHJs due to the presence of bulk-ionization. This talk will examine the dependence of JSC and VOC on the relative fraction of dissociation by charge transfer and bulk-ionization processes.

The evolution of and challenges for industrial radiation processing—2012

NASA Astrophysics Data System (ADS)

Berejka, A. J.; Cleland, M. R.; Walo, M.

2014-01-01

The evolution of industrial radiation processing is traced from Roentgen's discovery of X-radiation in 1895 by following the development of high current, electron beam accelerators (EB) throughout the twentieth century. Although Becquerel soon followed Roentgen with his discovery of what became to be known as radioactivity, electrical sources for ionizing radiation dominate industrial processing with there being more than ten times as many industrial installations using high current EB equipment than the facilities relying upon large concentrations of radioactive isotopes. In the 1950s, the discovery that ionizing radiation would enhance the value of what has become the world's largest volume commodity plastic, polyethylene (PE), opened the way for full scale commercial use of high current EB equipment. While the crosslinking of the PE insulation on wire became one of the first major industrial applications, other uses of EB processing soon followed. In the 1970s, low-energy, self-shielded EB equipment made the surface curing of inks, coatings and adhesives more industrially viable. In the early part of the twenty-first century, new market applications involving the low-energy EB surface decontamination of packaging materials emerged. This new area poses challenges for the metrology needed to control industrial processes, in that there is limited EB penetration into what have been used as dosimeters by industry. Major industrial use of radiation process is now over 50 years old. Because of the diversity of end-uses and the fact that the use of ionizing radiation in industry is a process technique, it is hard to quantify the value-added to numerous commercial products that benefit from this energy efficient process. It may be in excess of a trillion Euros in value-added to articles of commerce. In this milieu, there are some broad-based opportunities for research which are noted.

Bacterial and archaeal resistance to ionizing radiation

NASA Astrophysics Data System (ADS)

Confalonieri, F.; Sommer, S.

2011-01-01

Organisms living in extreme environments must cope with large fluctuations of temperature, high levels of radiation and/or desiccation, conditions that can induce DNA damage ranging from base modifications to DNA double-strand breaks. The bacterium Deinococcus radiodurans is known for its resistance to extremely high doses of ionizing radiation and for its ability to reconstruct a functional genome from hundreds of radiation-induced chromosomal fragments. Recently, extreme ionizing radiation resistance was also generated by directed evolution of an apparently radiation-sensitive bacterial species, Escherichia coli. Radioresistant organisms are not only found among the Eubacteria but also among the Archaea that represent the third kingdom of life. They present a set of particular features that differentiate them from the Eubacteria and eukaryotes. Moreover, Archaea are often isolated from extreme environments where they live under severe conditions of temperature, pressure, pH, salts or toxic compounds that are lethal for the large majority of living organisms. Thus, Archaea offer the opportunity to understand how cells are able to cope with such harsh conditions. Among them, the halophilic archaeon Halobacterium sp and several Pyrococcus or Thermococcus species, such as Thermococcus gammatolerans, were also shown to display high level of radiation resistance. The dispersion, in the phylogenetic tree, of radioresistant prokaryotes suggests that they have independently acquired radioresistance. Different strategies were selected during evolution including several mechanisms of radiation byproduct detoxification and subtle cellular metabolism modifications to help cells recover from radiation-induced injuries, protection of proteins against oxidation, an efficient DNA repair tool box, an original pathway of DNA double-strand break repair, a condensed nucleoid that may prevent the dispersion of the DNA fragments and specific radiation-induced proteins involved in radioresistance. Here, we compare mechanisms and discuss hypotheses suggested to contribute to radioresistance in several Archaea and Eubacteria.

Ionizing radiation and autoimmunity: Induction of autoimmune disease in mice by high dose fractionated total lymphoid irradiation and its prevention by inoculating normal T cells

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

Sakaguchi, N.; Sakaguchi, S.; Miyai, K.

1992-11-01

Ionizing radiation can functionally alter the immune system and break self-tolerance. High dose (42.5 Gy), fractionated (2.5 Gy 17 times) total lymphoid irradiation (TLI) on mice caused various organ-specific autoimmune diseases, such as gastritis, thyroiditis, and orchitis, depending on the radiation dosages, the extent of lymphoid irradiation, and the genetic background of the mouse strains. Radiation-induced tissue damage is not the primary cause of the autoimmune disease because irradiation of the target organs alone failed to elicit the autoimmunity and shielding of the organs from irradiation was unable to prevent it. In contrast, irradiation of both the thymus and themore » peripheral lymphoid organs/tissues was required for efficient induction of autoimmune disease by TLI. TLI eliminated the majority of mature thymocytes and the peripheral T cells for 1 mo, and inoculation of spleen cell, thymocyte, or bone marrow cell suspensions (prepared from syngeneic nonirradiated mice) within 2 wk after TLI effectively prevented the autoimmune development. Depletion of T cells from the inocula abrogated the preventive activity. CD4[sup +] T cells mediated the autoimmune prevention but CD8[sup +] T cells did not. CD4[sup +] T cells also appeared to mediate the TLI-induced autoimmune disease because CD4[sup +] T cells from disease-bearing TLI mice adoptively transferred the autoimmune disease to syngeneic naive mice. Taken together, these results indicate that high dose, fractionated ionizing radiation on the lymphoid organs/tissues can cause autoimmune disease by affecting the T cell immune system, rather than the target self-Ags, presumably by altering T cell-dependent control of self-reactive T cells. 62 refs., 9 figs., 2 tabs.« less

The ionization parameter of star-forming galaxies evolves with the specific star formation rate

NASA Astrophysics Data System (ADS)

Kaasinen, Melanie; Kewley, Lisa; Bian, Fuyan; Groves, Brent; Kashino, Daichi; Silverman, John; Kartaltepe, Jeyhan

2018-07-01

We investigate the evolution of the ionization parameter of star-forming galaxies using a high-redshift (z˜ 1.5) sample from the FMOS-COSMOS (Fibre Multi-Object Spectrograph-COSMic evOlution Survey) and matched low-redshift samples from the Sloan Digital Sky Survey. By constructing samples of low-redshift galaxies for which the stellar mass (M*), star formation rate (SFR), and specific star formation rate (sSFR) are matched to the high-redshift sample, we remove the effects of an evolution in these properties. We also account for the effect of metallicity by jointly constraining the metallicity and ionization parameter of each sample. We find an evolution in the ionization parameter for main-sequence, star-forming galaxies and show that this evolution is driven by the evolution of sSFR. By analysing the matched samples as well as a larger sample of z< 0.3, star-forming galaxies we show that high ionization parameters are directly linked to high sSFRs and are not simply the by-product of an evolution in metallicity. Our results are physically consistent with the definition of the ionization parameter, a measure of the hydrogen ionizing photon flux relative to the number density of hydrogen atoms.

Highly sensitive screening method for nitroaromatic, nitramine and nitrate ester explosives by high performance liquid chromatography-atmospheric pressure ionization-mass spectrometry (HPLC-API-MS) in forensic applications.

PubMed

Xu, Xiaoma; van de Craats, Anick M; de Bruyn, Peter C A M

2004-11-01

A highly sensitive screening method based on high performance liquid chromatography atmospheric pressure ionization mass spectrometry (HPLC-API-MS) has been developed for the analysis of 21 nitroaromatic, nitramine and nitrate ester explosives, which include the explosives most commonly encountered in forensic science. Two atmospheric pressure ionization (API) methods, atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI), and various experimental conditions have been applied to allow for the detection of all 21 explosive compounds. The limit of detection (LOD) in the full-scan mode has been found to be 0.012-1.2 ng on column for the screening of most explosives investigated. For nitrobenzene, an LOD of 10 ng was found with the APCI method in the negative mode. Although the detection of nitrobenzene, 2-, 3-, and 4-nitrotoluene is hindered by the difficult ionization of these compounds, we have found that by forming an adduct with glycine, LOD values in the range of 3-16 ng on column can be achieved. Compared with previous screening methods with thermospray ionization, the API method has distinct advantages, including simplicity and stability of the method applied, an extended screening range and a low detection limit for the explosives studied.