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Sample records for ion clusters

  1. Recombination of cluster ions

    NASA Technical Reports Server (NTRS)

    Johnsen, Rainer

    1993-01-01

    Some of our recent work on molecular band emissions from recombination of molecular dimer ions (N4(+) and CO(+) CO) is discussed. Much of the experimental work was done by Y. S. Cao; the results on N4(+) recombination have been published. A brief progress report is given on our ongoing measurements of neutral products of recombination using the flowing-afterglow Langmuir-probe technique in conjunction with laser-induced fluorescence.

  2. Cluster Ions and Atmospheric Processes

    NASA Astrophysics Data System (ADS)

    D'Auria, R.; Turco, R. P.

    We investigate the properties and possible roles of naturally occurring ions under at- mospheric conditions. Among other things, the formation of stable charged molecular clusters represents the initial stages of aerosol nucleation [e.g., Keesee and Castle- man, 1982], while the conversion of vapor to aggregates is the first step in certain atmospheric phase transitions [e.g. Hamill and Turco, 2000]. We analyze the stability and size distributions of common ionic clusters by solving the differential equations describing their growth and loss. The necessary reaction rate coefficients are deter- mined using kinetic and thermodynamic data. The latter are derived from direct labo- ratory measurements of equilibrium constants, from the classical charged liquid drop model applied to large aggregates (i.e., the Thomson model [Thomson, 1906]), and from quantum mechanical calculations of the thermodynamic potentials associated with the cluster structures. This approach allows us to characterize molecular clusters across the entire size range from true molecular species to larger aggregates exhibiting macroscopic behavior [D'Auria, 2001]. Cluster systems discussed in this talk include the proton hydrates (PHs) and nitrate-water and nitrate-nitric acid series [D'Auria and Turco, 2001]. These ions have frequently been detected in the stratosphere and tropo- sphere [e.g., Arnold et al., 1977; Viggiano and Arnold, 1981]. We show how the pro- posed hybrid cluster model can be extended to a wide range of ion systems, including non-proton hydrates (NPHs), mixed-ligand clusters such as nitrate-water-nitric acid and sulfate-sulfuric acid-water, as well as more exotic species containing ammonia, pyridine and other organic compounds found on ions [e.g., Eisele, 1988; Tanner and Eisele, 1991]. References: Arnold, F., D. Krankowsky and K. H. Marien, First mass spectrometric measurements of posi- tive ions in the stratosphere, Nature, 267, 30-32, 1977. D'Auria, R., A study of ionic

  3. Hydrated Ions: From Individual Ions to Ion Pairs to Ion Clusters.

    PubMed

    Chen, Houyang; Ruckenstein, Eli

    2015-10-01

    The structure of hydrated ions plays a central role in chemical and biological sciences. In the present paper, five ions, namely, Na(+), K(+), Mg(2+), Ca(2+) and Cl(-), are examined using molecular dynamics simulations. In addition to hydrated individual ions and ion pairs identified previously, hydrated ion clusters containing 3, 4, 5, or more ions are identified in the present paper. The dependence of hydration numbers and mole fractions of individual ions, ion pairs, and larger ion clusters on the electrolyte concentration is determined. As the electrolyte concentration increases, the mole fraction of hydrated individual ions decreases, and the mole fraction of hydrated larger ion clusters increases. The results also reveal that the hydrogen bonding numbers of the H2O molecules of the first hydration shells of individual ions, ion pairs, and larger ion clusters are insensitive to the electrolyte concentration, but sensitive to the nature and conformation of ions.

  4. Clustered Ion Channels and Action Potentials

    NASA Astrophysics Data System (ADS)

    Zeng, Shangyou; Shuai, Jianwei; Jung, Peter

    2002-03-01

    It is known that even in unmyelinated neurons the ion channels relevant for action potential generation are in many cases spatially clustered. We study the consequences of spatial clustering of the ion channels for the generation and propagation of action potentials. In particular we report on the frequency and temporal coherence of spontaneous spikes generated by clusters of various sizes and on cluster-cluster synchronization along an axon. For the channel dynamics, we are using a stochastic Hodgkin-Huxley model supplemented by synaptic noise. The axon is modeled by an one dimensional cable equation.

  5. Surface processing using water cluster ion beams

    NASA Astrophysics Data System (ADS)

    Takaoka, Gikan H.; Ryuto, Hiromichi; Takeuchi, Mitsuaki; Ichihashi, Gaku

    2013-07-01

    Vaporized water clusters were produced by an adiabatic expansion phenomenon, and various substrates such as Si(1 0 0), SiO2, polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), and polycarbonate (PC) were irradiated by water cluster ion beams. The sputtered depth increased with increasing acceleration voltage, and the sputtering rate was much larger than that obtained using Ar monomer ion irradiation. The sputtering yield for PMMA was approximately 200 molecules per ion, at an acceleration voltage of 9 kV. X-ray photoelectron spectroscopy (XPS) measurements showed that high-rate sputtering for the PMMA surface can be ascribed to the surface erosion by the water cluster ion irradiation. Furthermore, the micropatterning was demonstrated on the PMMA substrate. Thus, the surface irradiation by water cluster ion beams exhibited a chemical reaction based on OH radicals, as well as excited hydrogen atoms, which resulted in a high sputtering rate and low irradiation damage of the substrate surfaces.

  6. Nitrogen ion clusters in Triton's atmosphere

    NASA Technical Reports Server (NTRS)

    Delitsky, Mona L.; Turco, Richard P.; Jacobson, Mark Z.

    1990-01-01

    The nitrogen ion chemistry that controls Triton's ionospheric composition and may be responsible for the hazes detected by the Voyager spacecraft are discussed. In particular, it is shown that nitrogen cluster ion formation should readily occur in Triton's thin cold atmosphere. The very low temperatures of Triton's atmosphere imply that these clustered ions can nucleate into solid nitrogen particles, creating the extended visible hazes. A model based on the chemical kinetics of nitrogen ions predicts a dense ionosphere at 200-400 km, as detected by Voyager radio occultation measurements.

  7. Photodissociation of semiconductor positive cluster ions

    SciTech Connect

    Zhang, Q.; Liu, Y.; Curl, R.F.; Tittel, F.K.; Smalley, R.E.

    1988-02-01

    Laser photofragmentation of Si, Ge, and GaAs positive cluster ions prepared by laser vaporization and supersonic beam expansion has been investigated using tandem time-of-flight mass spectrometry. Si clusters up to size 80, Ge clusters to size 40, and GaAs clusters up to a total of 31 atoms were studied. Si/sup +//sub n/ and Ge/sup +//sub n/ for n = 12--26 give daughter ions of about half their original size. For both Si and Ge, this apparent positive ion fissioning appears to go over with increasing n to neutral loss of seven and ten, but for Si/sup +//sub n/ the range of n values where this is observed is rather small. At low fluences, the larger Ge/sup +//sub n/ clusters up to the maximum size observed (50) sequentially lose Ge/sub 10/ (and in some cases with lower intensity Ge/sub 7/). Larger Si/sup +//sub n/ clusters (n>30) always fragment primarily to produce positive ion clusters in the 6--11 size range with a subsidiary channel of loss of a single Si atom. At high laser fluences, Ge/sup +//sub n/ also fragments to produce primarily positive ion clusters in the 6--11 size range with an intensity pattern essentially identical to Si/sup +//sub n/ at similar fluences. Ga/sub x/As/sup +//sub y/ clusters lose one or more atoms in what is probably a sequential process with positive ion clusters in which the total number of atoms, x+y, is odd being more prominent.

  8. Atmospheric Ion Clusters: Properties and Size Distributions

    NASA Astrophysics Data System (ADS)

    D'Auria, R.; Turco, R. P.

    2002-12-01

    Ions are continuously generated in the atmosphere by the action of galactic cosmic radiation. Measured charge concentrations are of the order of 103 ~ {cm-3} throughout the troposphere, increasing to about 5 x 103 ~ {cm-3} in the lower stratosphere [Cole and Pierce, 1965; Paltridge, 1965, 1966]. The lifetimes of these ions are sufficient to allow substantial clustering with common trace constituents in air, including water, nitric and sulfuric acids, ammonia, and a variety of organic compounds [e.g., D'Auria and Turco, 2001 and references cited therein]. The populations of the resulting charged molecular clusters represent a pre-nucleation phase of particle formation, and in this regard comprise a key segment of the over-all nucleation size spectrum [e.g., Castleman and Tang, 1972]. It has been suggested that these clusters may catalyze certain heterogeneous reactions, and given their characteristic crystal-like structures may act as freezing nuclei for supercooled droplets. To investigate these possibilities, basic information on cluster thermodynamic properties and chemical kinetics is needed. Here, we present new results for several relevant atmospheric ion cluster families. In particular, predictions based on quantum mechanical simulations of cluster structure, and related thermodynamic parameters, are compared against laboratory data. We also describe a hybrid approach for modeling cluster sequences that combines laboratory measurements and quantum predictions with the classical liquid droplet (Thomson) model to treat a wider range of cluster sizes. Calculations of cluster mass distributions based on this hybrid model are illustrated, and the advantages and limitations of such an analysis are summarized. References: Castelman, A. W., Jr., and I. N. Tang, Role of small clusters in nucleation about ions, J. Chem. Phys., 57, 3629-3638, 1972. Cole, R. K., and E. T. Pierce, Electrification in the Earth's atmosphere for altitudes between 0 and 100 kilometers, J

  9. Spectrometer for cluster ion beam induced luminescence

    SciTech Connect

    Ryuto, H. Sakata, A.; Takeuchi, M.; Takaoka, G. H.; Musumeci, F.

    2015-02-15

    A spectrometer to detect the ultra-weak luminescence originated by the collision of cluster ions on the surfaces of solid materials was constructed. This spectrometer consists of 11 photomultipliers with band-pass interference filters that can detect the luminescence within the wavelength ranging from 300 to 700 nm and of a photomultiplier without filter. The calibration of the detection system was performed using the photons emitted from a strontium aluminate fluorescent tape and from a high temperature tungsten filament. Preliminary measurements show the ability of this spectrometer to detect the cluster ion beam induced luminescence.

  10. Cluster Ion Stopping and Fragmentation for ICF

    NASA Astrophysics Data System (ADS)

    Deutsch, C.; Tahir, N. A.

    Cluster ion beam with energy in the several tens of keV/a.m.u. range are considered as a novel direct driver for a simple fusion pellet made of Deuterium + Tritium fuel surrounded by a Lithium pusher. The driver-pellet interaction is calculated through the hypothesis of maximum multifragmentation followed by highly correlated ion debris motion. One thus gets enhanced stopping and ablation pressure in the hundreds Mbar range. An implosion is then completed in 5 nsec. Indirect drive is also considered.

  11. Spiking synchronization of ion channel clusters on an axon

    NASA Astrophysics Data System (ADS)

    Zeng, Shangyou; Tang, Yi; Jung, Peter

    2007-07-01

    Ion channels are distributed in clusters in squid giant axons, rat retinal nerve fiber layers, pyramidal cell dendrites of Apteronotus, etc. Ion channel clusters along the unmyelinated axon generate spontaneous spiking due to ion channel noise. Ion channel clusters are coupled by the axonal cable, and spontaneous spiking of each ion channel cluster can be synchronized. This paper considers the spiking synchronization of two ion channel clusters coupled by an axon. It is shown that axonal parameters affect the spiking synchronization exponentially and ion channel clusters have maximal spiking synchronization when they have the same size. It is further shown that there is an optimal length of the ion channel clusters with maximal spiking synchronization and the optimal length accords with the length of the node of Ranvier in the myelinated axon.

  12. Comparison of Se and Te clusters produced by ion bombardment

    NASA Astrophysics Data System (ADS)

    Trzyna, Małgorzata

    2016-12-01

    Nanostructures based on tellurium and selenium are materials used as components for the manufacturing topological insulators. Therefore it is crucial to precisely characterize these materials. In this work the emission of selenium and tellurium cluster ions, sputtered by Bi+ primary ion guns, was investigated by using Time-of-Flight Secondary Ion Mass Spectrometry (TOF SIMS). It has been found that BixTex and BixSex clusters appear in addition to Sex and Tex clusters in the mass range up to 1300 m/z. Local maxima or minima (magic numbers) are observed in the ion intensity versus a number of atoms per cluster for both positive and negative ions spectra for all types of clusters and primary ions used. These extrema can be attributed to different yield and stability of certain clusters but also to fragmentation of high-mass clusters.

  13. Desorption of cluster ions from solid Ne by low-energy ion impact.

    PubMed

    Tachibana, T; Fukai, K; Koizumi, T; Hirayama, T

    2010-12-01

    We investigated Ne(+) ions and Ne(n)(+) (n = 2-20) cluster ions desorbed from the surface of solid Ne by 1.0 keV Ar(+) ion impact. Kinetic energy analysis shows a considerably narrower energy distribution for Ne(n)(+) (n ≥ 3) ions than for Ne(n)(+) (n = 1, 2) ions. The dependence of ion yields on Ne film thickness indicates that cluster ions (n ≥ 3) are desorbed only from relatively thick films. We conclude that desorbed ions grow into large cluster ions during the outflow of deep bulk atoms to the vacuum.

  14. Interaction between water cluster ions and mica surface

    SciTech Connect

    Ryuto, Hiromichi Ohmura, Yuki; Nakagawa, Minoru; Takeuchi, Mitsuaki; Takaoka, Gikan H.

    2014-03-15

    Water cluster ion beams were irradiated on mica surfaces to investigate the interaction between molecular cluster ions and a mica surface. The contact angle of the mica surface increased with increasing dose of the water cluster ion beam, but the increase in the contact angle was smaller than that induced by an ethanol cluster ion beam. The surface roughness also increased with increasing dose of the water cluster ion beam, whereas the intensity of K 2p x-ray photoelectron spectroscopy peaks decreased with increasing dose of the water cluster ion beam. The decrease in the number of potassium atoms together with the increase in the surface roughness may be the causes of the increase in the contact angle.

  15. Historical milestones and future prospects of cluster ion beam technology

    NASA Astrophysics Data System (ADS)

    Yamada, Isao

    2014-08-01

    Development of technology for processing of surfaces by means of gas cluster ion beams began only about a quarter century ago even though fundamental research related to generation of gas clusters began much earlier. Industrial applications of cluster ion beams did not start to be explored until commercial equipment was first introduced to the ion beam community in around 2000. The technology is now evolving rapidly with industrial equipment being engineered for many diverse surface processing applications which are made possible by the unique characteristics of cluster-ion/solid-surface interactions. In this paper, important historical milestones in cluster ion beam development are described. Present activities related to a wide range of industrial applications in semiconductors, magnetic and optical devices, and bio-medical devices are reviewed. Several emerging new advances in cluster beam applications for the future are also discussed.

  16. Consideration of rotational tunneling in rare gas cluster ions

    NASA Astrophysics Data System (ADS)

    Albertoni, C. R.; Ferguson, A. W. Castleman E. E., Jr.

    1989-04-01

    Tunneling transmission coefficients through rotational barriers are investigated as a function of argon cluster ion size using the WKB approximation. The results indicate that tunneling coefficients corresponding to transmissions of a few percent, extend over time windows of ten orders of magnitude. Hence, a very broad distribution of metastable lifetimes is expected for decay of cluster ions by tunneling through rotational barriers.

  17. Formation of high-mass cluster ions from compound semiconductors using time-of-flight secondary ion mass spectrometry with cluster primary ions.

    PubMed

    Goacher, Robyn E; Luo, Hong; Gardella, Joseph A

    2008-05-01

    The detection of high-mass, nonstoichiometric, GaxAsy and InxPy secondary ion clusters using time-of-flight secondary ion mass spectrometry is reported for the first time. The GaxAsy and InxPy clusters are detected in both positive and negative ion spectra and extend to masses of at least 6000 dalton (Da). Consecutive clusters differ by the addition of one gallium (indium) atom. This leads to nonstoichiometric clusters at high mass (i.e., Ga15As3 at 1270 Da) which are metastable above a critical mass. The relative secondary ion yields of high-mass GaxAsy clusters detected using several primary ion sources (Cs+, Bi+, Bi3+, Bi32+, Bi52+, C60+, and C602+) are compared. The relative secondary ion yield of high-mass GaxAsy clusters is significantly enhanced by the use of cluster primary ions and the best relative secondary ion yield is obtained using Bi3+ primary ions. An application of the high-mass GaxAsy clusters is presented, in which these clusters are utilized to distinguish between contaminant levels of Ga and bulk GaAs structure in a depth profile of a MnAs/GaAs heterojunction. These results illustrate improved analysis of inorganic materials using cluster primary ions and break the paradigm of stoichiometric secondary cluster ion formation for SIMS of inorganic compounds.

  18. Ion clustering in aqueous solutions probed with vibrational energy transfer

    PubMed Central

    Bian, Hongtao; Wen, Xiewen; Li, Jiebo; Chen, Hailong; Han, Suzee; Sun, Xiuquan; Song, Jian; Zhuang, Wei; Zheng, Junrong

    2011-01-01

    Despite prolonged scientific efforts to unravel the hydration structures of ions in water, many open questions remain, in particular concerning the existences and structures of ion clusters in 1∶1 strong electrolyte aqueous solutions. A combined ultrafast 2D IR and pump/probe study through vibrational energy transfers directly observes ion clustering in aqueous solutions of LiSCN, NaSCN, KSCN and CsSCN. In a near saturated KSCN aqueous solution (water/KSCN molar ratio = 2.4/1), 95% of the anions form ion clusters. Diluting the solution results in fewer, smaller, and tighter clusters. Cations have significant effects on cluster formation. A small cation results in smaller and fewer clusters. The vibrational energy transfer method holds promise for studying a wide variety of other fast short-range molecular interactions.

  19. Polishing superhard material surfaces with gas-cluster ion beams

    NASA Astrophysics Data System (ADS)

    Ieshkin, A. E.; Kushkina, K. D.; Kireev, D. S.; Ermakov, Yu. A.; Chernysh, V. S.

    2017-01-01

    We have studied the influence of bombardment with accelerated gas-cluster ions on the surface topography of silicon carbide and diamond. Atomic-force microscopy shows that exposure to 10-keV gas-cluster ions at a total dose above 1016 cm-2 leads to smoothing of the surface relief. The ion-etching rate and efficiency of the surface relief smoothing as dependent on the thickness of removed layer have been estimated. Raman-spectroscopy data show that surface irradiation with gas-cluster ions does not introduce defects into the crystalline structure of irradiated material.

  20. Ion aggregation in high salt solutions: ion network versus ion cluster.

    PubMed

    Kim, Seongheun; Kim, Heejae; Choi, Jun-Ho; Cho, Minhaeng

    2014-09-28

    The critical aggregation phenomena are ubiquitous in many self-assembling systems. Ions in high salt solutions could also spontaneously form larger ion aggregates, but their effects on hydrogen-bond structures in water have long been controversial. Here, carrying out molecular dynamics (MD) simulation studies of high salt solutions and comparing the MD simulation results with infrared absorption and pump-probe spectroscopy of O-D stretch mode of HDO in highly concentrated salt solutions and (13)C-NMR chemical shift of S(13)CN(-) in KSCN solutions, we find evidence on the onset of ion aggregate and large-scale ion-ion network formation that concomitantly breaks water hydrogen-bond structure in certain salt solutions. Despite that these experimental results cannot provide direct evidence on the three-dimensional morphological structures of ion aggregates, they serve as reference data for verifying MD simulation methods. The MD results suggest that disrupted water hydrogen-bond network is intricately intertwined with ion-ion network. This further shows morphological variation of ion aggregate structures from ion cluster to ion network in high salt solutions that are interrelated to the onset of macroscopic aggregate formation and the water hydrogen-bond structure making and breaking processes induced by Hofmeister ions.

  1. Ion aggregation in high salt solutions: Ion network versus ion cluster

    SciTech Connect

    Kim, Seongheun; Kim, Heejae; Choi, Jun-Ho; Cho, Minhaeng

    2014-09-28

    The critical aggregation phenomena are ubiquitous in many self-assembling systems. Ions in high salt solutions could also spontaneously form larger ion aggregates, but their effects on hydrogen-bond structures in water have long been controversial. Here, carrying out molecular dynamics (MD) simulation studies of high salt solutions and comparing the MD simulation results with infrared absorption and pump-probe spectroscopy of O–D stretch mode of HDO in highly concentrated salt solutions and {sup 13}C-NMR chemical shift of S{sup 13}CN{sup −} in KSCN solutions, we find evidence on the onset of ion aggregate and large-scale ion-ion network formation that concomitantly breaks water hydrogen-bond structure in certain salt solutions. Despite that these experimental results cannot provide direct evidence on the three-dimensional morphological structures of ion aggregates, they serve as reference data for verifying MD simulation methods. The MD results suggest that disrupted water hydrogen-bond network is intricately intertwined with ion-ion network. This further shows morphological variation of ion aggregate structures from ion cluster to ion network in high salt solutions that are interrelated to the onset of macroscopic aggregate formation and the water hydrogen-bond structure making and breaking processes induced by Hofmeister ions.

  2. Positive and negative cluster ions from liquid ethanol by fast ion bombardment.

    PubMed

    Kaneda, M; Shimizu, M; Hayakawa, T; Iriki, Y; Tsuchida, H; Itoh, A

    2010-04-14

    Secondary ion mass spectra have been measured for the first time for a liquid ethanol target bombarded by 2.0 MeV He(+) ions. Positive and negative ion spectra exhibit evidently a series of cluster ions of the forms [(EtOH)(n)H](+) and [(EtOH)(n)-H](-), respectively, in addition to light fragment ions from intact parent molecules. It was found that these cluster ions are produced only from liquid phase ethanol. Both positive and negative secondary ion spectra show similar cluster size distributions with almost the same decay slope. We also present for the first time the cluster ion distribution emitted from the liquid at different liquid temperatures.

  3. Cluster Ion Bombardment-Induced Surface Damage of Si

    NASA Astrophysics Data System (ADS)

    Ascheron, C. E.; Akizuki, M.; Matsuo, J.; Insepov, Z.; Takaoka, G. H.; Yamada, I.

    Surface damage of single-crystalline Si caused by irradiation with Ar-ion cluster beams of different energies has been studied in comparison with that caused by Ar-monomer ion beams. The defected layers have been characterized by RBS channeling, XTEM, and ellipsometry. The experimental results are interpreted on the basis of TRIM and molecular dynamics simulations of the interaction processes with the target. It is found that cluster irradiation damages only a very thin near-surface layer which has a smooth interface to the undamaged substrate. Cluster-ion bombardment forms an oxide layer on the surface by the activation of adsorbed O atoms and substrate atoms.

  4. Active spacecraft potential control: An ion emitter experiment. [Cluster mission

    NASA Technical Reports Server (NTRS)

    Riedler, W.; Goldstein, R.; Hamelin, M.; Maehlum, B. N.; Troim, J.; Olsen, R. C.; Pedersen, A.; Grard, R. J. L.; Schmidt, R.; Rudenauer, F.

    1988-01-01

    The cluster spacecraft are instrumented with ion emitters for charge neutralization. The emitters produce indium ions at 6 keV. The ion current is adjusted in a feedback loop with instruments measuring the spacecraft potential. The system is based on the evaporation of indium in the apex field of a needle. The design of the active spacecraft potential control instruments, and the ion emitters is presented.

  5. The Importance of Ion-Dipole Interaction in Ion-Clustering Thermodynamics and Ion-Mediated Nucleation

    NASA Astrophysics Data System (ADS)

    Nadykto, A.; Yu, F.

    2005-12-01

    Ions generated by cosmic rays and radioactive materials are ubiquitous in the atmosphere. The possible involvement of ions in the formation of new particles in the atmosphere has received increased attention in recent years. The classical Kelvin-Thomson (CKT) equation, which was derived by Thomson about a century ago, has been the fundamental of classical ion-induced nucleation theory. In the CKT equation, the effect of charge on Gibbs free energy change for the formation of the cluster (or equilibrium vapor pressure over an ion cluster) is taken into account by considering the electrostatic potential energy of the cluster. Recently, we find that the interaction of dipole molecules with small ion clusters, which is neglected in CKT equation, is important in ion-clustering thermodynamics. A modified Kelvin-Thomson (MKT) equation containing a dipole-ion interaction term (in addition to the Thomson term) is derived. The predictions based on MKT equation are in much better agreement with experimental ion clustering thermodynamic data and experimental ion cluster mobility-equivalent diameters. On top of Thomson effect, the dipole-charge interaction effect further stabilizes the small charged clusters. All major molecules known to be involved in nucleation in the atmospheric (H2SO4, H2O, NH3, HNO3, acetone, etc.) have high dipole moment, and the dipole-ion interaction effect increases the importance of ions in mediating the formation of new particles in the atmosphere.

  6. Shallow junction formation by polyatomic cluster ion implantation

    SciTech Connect

    Takeuchi, Daisuke; Shimada, Norihiro; Matsuo, Jiro; Yamada, Isao

    1996-12-31

    Recent integrated circuits require shallow junctions which are less than 0.1 {mu}m depth. This creates a strong demand for low energy ion beam techniques. Equivalent low-energy and high-current ion beams can be realized quite easily with clusters, because the kinetic energy of the cluster is shared between the constituent atoms. Additionally, cluster-ion beams avoid damage due to excessive charge. We have used polyatomic clusters, decaborane (B{sub 10}H{sub 14}), as a kind of B cluster, in order to form a very shallow p{sup +} junction. A B SIMS profile of B{sub 10}H{sub 14} implanted into Si (100) at 20keV was quite similar to that of B implanted at 2keV. These SIMS measurements revealed that the cluster ion beam can realize equivalent low-energy implantation quite easily. The implantation efficiency achieved was about 90%. The damage induced by B{sub 10}H{sub 14} implantation was completely removed by a 600{degrees}C furnace anneal for 30 min, and implanted B atoms were electrically activated. After rapid thermal annealing (RTA) at 900{degrees}C of a sample prepared with a close of 5{times}10{sup 13} ion/cm{sup 2}, the sheet resistance decreased to about 600W/sq. and the activation efficiency was about 50%. These results show that a polyatomic cluster ion beam is useful for shallow junction formation.

  7. Review of Cluster Ion Beam Facilities and Technology

    NASA Astrophysics Data System (ADS)

    Yamada, Isao; Toyoda, Noriaki

    2009-03-01

    The paper reviews the development of cluster ion beam technology, including historical background, fundamental characteristics of cluster ion to solid surface interactions, emerging industrial applications, and identification of some of the significant events which occurred as the technology has evolved into what it is today. Processes employing ions of clusters comprised of a few hundred to many thousand atoms are now being developed into a new field of ion beam technology. Cluster-surface collisions produce important non-linear effects which are being applied to shallow junction formation, to etching and smoothing of semiconductors, metals, and dielectrics, to assisted formation of thin films with nano-scale accuracy, and to other surface modification applications.

  8. Method and apparatus for the production of cluster ions

    DOEpatents

    Friedman, Lewis; Beuhler, Robert J.

    1988-01-01

    A method and apparatus for the production of cluster ions, and preferably isotopic hydrogen cluster ions is disclosed. A gas, preferably comprising a carrier gas and a substrate gas, is cooled to about its boiling point and expanded through a supersonic nozzle into a region maintained at a low pressure. Means are provided for the generation of a plasma in the gas before or just as it enters the nozzle.

  9. Method and apparatus for the production of cluster ions

    DOEpatents

    Friedman, L.; Beuhler, R.J.

    A method and apparatus for the production of cluster ions, and preferably isotopic hydrogen cluster ions is disclosed. A gas, preferably comprising a carrier gas and a substrate gas, is cooled to about its boiling point and expanded through a supersonic nozzle into a region maintained at a low pressure. Means are provided for the generation of a plasma in the gas before or just as it enters the nozzle.

  10. Peptide fragmentation caused by Ar cluster ions depending on primary ion energy.

    PubMed

    Aoyagi, Satoka; Kawashima, Tomoko; Yokoyama, Yuta

    2015-09-30

    Time-of-flight secondary ion mass spectrometry (TOF-SIMS) with an Ar cluster ion beam as a primary ion source provides useful information in terms of peptide analysis. It is, however, difficult to interpret the spectra. The ToF-SIMS peptide spectra obtained with Ar clusters having different energies have been investigated in order to classify the secondary ions into the peptide fragment ions and those related to contaminants or the substrate. Three peptides having different molecular weights from 600 to 1300 u were measured with Ar cluster beams having different energies per atom from 4 to 40 eV/atom. In the spectra normalized to a geometric average of all the spectra, the amino acid fragment ions are distinguished from other secondary ions. In the mass range above 600 u, the peptide fragment ions increase with mass while those not related to the peptide decrease with mass. Energy-dependence fragmentation helps in understanding the peptide spectra. Specific peptide fragment ions of the larger peptides are likely to be detected under lower energy than energy higher than 10 eV/atom. Although it is difficult to interpret the TOF-SIMS spectra of a peptide obtained with an Ar cluster ion beam, the secondary ions can be classified by comparing those obtained with different energy Ar cluster ion beams. Copyright © 2015 John Wiley & Sons, Ltd.

  11. Precise Fabrication of Silicon Wafers Using Gas Cluster Ion Beams

    SciTech Connect

    Isogai, Hiromichi; Toyoda, Eiji; Izunome, Koji; Kashima, Kazuhiko; Mashita, Takafumi; Toyoda, Noriaki; Yamada, Isao

    2009-03-10

    Precise surface processing of a silicon wafer was studied by using a gas cluster ion beam (GCIB). The damage caused to the silicon surface was strongly dependent on irradiation parameters. The extent of damage varied with the species of source gas and the acceleration voltage (Va) of cluster ions. It also varied with the cluster size and residual gas pressure. The influence of electron acceleration voltage (Ve) used for ionization of a neutral cluster was also investigated. The irradiation damage, such as an amorphous silicon (a-Si) layer, a mixed layer of a-Si and c-Si (transition layer), and surface roughness, was increased with Ve. It is suggested that the increase in the amount of energy per atom was induced by high Ve, because of variation of the cluster size and/or cluster charge. An undamaged smooth surface can be produced by Ar-GCIB irradiation at low Ve and Va.

  12. Generation of cluster states in ion-trap systems

    SciTech Connect

    Zheng Shibiao

    2006-06-15

    We propose two schemes for the generation of four-qubit cluster states in ion-trap systems. The first scheme is based on resonant sideband excitation, while the second scheme does not use the vibrational mode as the memory. The schemes can be realized with presently available ion-trap techniques.

  13. Ion clusters and the Venus ultraviolet haze layer

    NASA Technical Reports Server (NTRS)

    Aikin, A. C.

    1972-01-01

    The daytime ionosphere of Venus is observed between 100 and 500 km altitude. Below 200 km, CO2(+) is thought to be the principal ion unless oxygen is present. It was suggested that at altitudes less than 130 km the ion CO2(+)-CO2 is an important ionic constituent of the Venus ionosphere. Below 100 km, ion clustering processes combine with the low temperature at the mesopause to form coagulates giving rise to the ultraviolet haze layer which is frequently observed.

  14. Target current density effects in al-cluster ion emission

    NASA Astrophysics Data System (ADS)

    Ray, N.; Rajasekar, P.; Chakraborty, P.; Dey, S. D.

    1994-04-01

    Target current density effects in secondary emission of positively-charged sputtered clusters from an ion-bombarded polycrystalline aluminium surface have been investigated for various primary Cd+ ion energies. For each cluster type, at medium target current densities (Jp : 0?350 ?A/cm2), apart from the presence of the expected linear term in the I+ s α Jp curves, there is a square law term, depicting that some fraction of the pre-emitted neutral clusters gets ionized in vacuum above the target surface. Thus, a sum of these two terms constitutes the total cluster ion current which shows a non-linear dependence on the target current density. At higher target current densities (350 ?A cm?2?1.05 mA cm?2), in addition to the parabolic effect, a higher order non-linearity comes into play and the net cluster ion current I + s , measured as a function of target current density within the Ip range concerned, can be expressed in terms of our previously proposed semi-empirical formula I+ s = C.Ip + D.I2 p + F.In p , which was earlier found to be applicable in case of single and double charged secondary monomers. A higher power (n > 2) dependence has been observed here for the first time in case of cluster ion emission, suggesting chemical enhancement of secondary clusters. Our present observations seem to support ?direct emission model? even for small metal clusters?a proposition which is in apparent contradiction to the current notion in this field, i.e. vacuum recombination of individual atoms in small cluster formation.

  15. Ion-pair evaporation from ionic liquid clusters.

    PubMed

    Hogan, Christopher J; Fernandez de la Mora, Juan

    2010-08-01

    A differential mobility analyzer (DMA) is used in atmospheric pressure N(2) to select a narrow range of electrical mobilities from a complex mix of cluster ions of composition (CA)(n)(C(+))(z). The clusters are introduced into the N(2) gas by electrospraying concentrated (approximately 20 mM) acetonitrile solutions of ionic liquids (molten salts) of composition CA (C(+) = cation, A(-) = anion). Mass analysis of these mobility-selected ions reveals the occurrence of individual neutral ion-pair evaporation events from the smallest singly charged clusters: (CA)(n)C(+)-->(CA)(n-1)C(+)+CA. Although bulk ionic liquids are effectively involatile at room temperature, up to six sequential evaporation events are observed. Because this requires far more internal energy than available in the original clusters, substantial heating (approximately 10 eV) must take place in the ion guides leading to the mass analyzer. The observed increase in IL evaporation rate with decreasing size is drastic, in qualitative agreement with the exponential vapor pressure dependence predicted by Kelvin's formula. A single evaporation event is barely detectable at n = 13, while two or more are prominent for n < or = 9. Magic number clusters (CA)(4)C(+) with singularly low volatilities are found in three of the four ionic liquids studied. Like their recently reported liquid phase prenucleation cluster analogs, these magic number clusters could play a key role as gas-phase nucleation seeds. All the singularly involatile clusters seen are cations, which may help understand commonly observed sign effects in ion-induced nucleation. No other charge-sign asymmetry is seen on cluster evaporation. Copyright 2010 American Society for Mass Spectrometry. Published by Elsevier Inc. All rights reserved.

  16. Multiphoton ionization of ions, neutrals, and clusters. Progress report

    SciTech Connect

    Wessel, J.

    1991-06-28

    Scientific results are summarized from a three year research program on multiphoton ionization in aromatic molecules, clusters, and their ions. As originally proposed, the studies elucidated a new cluster ionization mechanism, characterized properties of long range intermolecular interactions, and investigated electronic transitions of aromatic cations cooled in a supersonic beam. The studies indicate that the new cluster ionization mechanism is highly efficient and dominates conventional 1 + 1 resonant ionization. In the case of the dimer of the large aromatic molecule fluorene, the results suggest that excimer formation competes with a direct ionization process. Highly selective excitonic spectra have been identified for several cluster species.

  17. Ion clusters in the lower stratosphere and upper troposphere

    NASA Astrophysics Data System (ADS)

    D'Auria, R.; Turco, R. P.

    2003-04-01

    Ions are continuously generated in the atmosphere under the action of galactic cosmic rays. Strong electrostatic interactions between the ions and surrounding neutral molecules lead to the formation of large ionic clusters. Recent measurements by Arnold and coworkers [ Eichkorn et al., 2002] by means of airborne ion mass spectrometry reveal the existence of positive ion cluster families reaching masses of up to 2500 amu in the upper troposphere. Ion clusters have also been detected in the stratosphere and throughout the troposphere [ e.g., Arnold et al., 1982; Eisele, 1988]. In all cases, positive ion families containing hydronium ions clustered with water and other trace gases such as acetone, acetonitrile and ammonia are detected. Negative ion cluster families are found consisting mainly of nitrate anions clustered with water and nitric acid, and sulfate anions associated with sulfuric acid and nitric acid ligands, with various degrees of hydration [e.g., Arnold et al., 1977]. Evidence also exists for very massive ions [Eichkorn et al., 2002; Hõrrak et al., 1998]. Ion clustering could play a role in aerosol formation through ion mediated nucleation [Turco and al., 1998; Yu and Turco, 2000; 2001], and could affect the microphysics of freezing in clouds. We have developed a ``hybrid'' model that characterizes the distributions of ionic clusters based on their structure and thermodynamics [D'Auria and Turco, 2001; 2002]. Here, we present results that describe the interaction of nitric acid vapor with hydronium/water clusters. We show, consistent with previous laboratory analyses [Zhang et al., 1994; Gilligan and Castleman, 2001], that the uptake of nitric acid on such clusters is a selective phenomenon, depending on the degree of cluster hydration. The clusters appear to take up nitric acid preferentially in ratios of nitric acid to water similar to those of solid nitric acid hydrates (particularly the trihydrate). It has been speculated that such stable nitric

  18. Clustering of ions at atomic dimensions in quantum plasmas

    NASA Astrophysics Data System (ADS)

    Shukla, Padma K.; Eliasson, Bengt; Eliasson

    2013-08-01

    By means of particle simulations of the equations of motion for ions interacting among themselves under the influence of newly discovered Shukla-Eliasson attractive force (SEAF) in a dense quantum plasma, we demonstrate that the SEAF can bring ions closer at atomic dimensions. We present simulation results of the dynamics of an ensemble of ions in the presence of the SEAF without and with confining external potentials and collisions between ions and degenerate electrons. Our particle simulations reveal that under the SEAF, ions attract each other, come closer, and form ionic clusters in the bath of degenerate electrons that shield ions. Furthermore, an external confining potential produces robust ion clusters that can have cigar- and ball-like shapes, which remain stable when the confining potential is removed. The stability of ion clusters is discussed. Our results may have applications to solid density plasmas (density exceeding 1023 per cm3), where the electrons will be degenerate and quantum forces due to the electron recoil effect caused by the overlapping of electron wave functions and electron tunneling through the Bohm potential, electron-exchange and electron-exchange and electron correlations associated with electron-1/2 spin effect, and the quantum statistical pressure of the degenerate electrons play a decisive role.

  19. Lithium formate ion clusters formation during electrospray ionization: Evidence of magic number clusters by mass spectrometry and ab initio calculations

    SciTech Connect

    Shukla, Anil; Bogdanov, Bogdan

    2015-02-14

    Small cationic and anionic clusters of lithium formate were generated by electrospray ionization and their fragmentations were studied by tandem mass spectrometry. Singly as well as multiply charged clusters were formed with the general formulae, (HCOOLi)nLi+, (HCOOLi)nLimm+, (HCOOLi)nHCOO- and (HCOOLi)n(HCOO)mm-. Several magic number cluster ions were observed in both the positive and negative ion modes although more predominant in the positive ion mode with (HCOOLi)3Li+ being the most abundant and stable cluster ions. Fragmentations of singly charged clusters proceed first by the loss of a dimer unit ((HCOOLi)2) followed by sequential loss of monomer units (HCOOLi). In the case of positive cluster ions, all fragmentations lead to the magic cluster (HCOOLi)3Li+ at higher collision energies which later fragments to dimer and monomer ions in lower abundance. Quantum mechanical calculations performed for smaller cluster ions showed that the trimer ion has a closed ring structure similar to the phenalenylium structure with three closed rings connected to the lithium ion. Further additions of monomer units result in similar symmetric structures for hexamer and nonamer cluster ions. Thermochemical calculations show that trimer cluster ion is relatively more stable than neighboring cluster ions, supporting the experimental observation of a magic number cluster with enhanced stability.

  20. Ion Mobility Mass Spectrometry Analysis of Isomeric Disaccharide Precursor, Product and Cluster Ions

    PubMed Central

    Li, Hongli; Bendiak, Brad; Siems, William F.; Gang, David R.; Hill, Herbert H.

    2015-01-01

    RATIONALE Carbohydrates are highly variable in structure owing to differences in their anomeric configurations, monomer stereochemistry, inter-residue linkage positions and general branching features. The separation of carbohydrate isomers poses a great challenge for current analytical techniques. METHODS The isomeric heterogeneity of disaccharide ions and monosaccharideglycolaldehyde product ions evaluated using electrospray traveling wave ion mobility mass spectrometry (Synapt G2 high definition mass spectrometer) in both positive and negative ion modes investigation. RESULTS The separation of isomeric disaccharide ions was observed but not fully achieved based on their mobility profiles. The mobilities of isomeric product ions, the monosaccharide-glycolaldehydes, derived from different disaccharide isomers were measured. Multiple mobility peaks were observed for both monosaccharide-glycolaldehyde cations and anions, indicating that there was more than one structural configuration in the gas phase as verified by NMR in solution. More importantly, the mobility patterns for isomeric monosaccharide-glycolaldehyde product ions were different, which enabled partial characterization of their respective disaccharide ions. Abundant disaccharide cluster ions were also observed. The Results showed that a majority of isomeric cluster ions had different drift times and, moreover, more than one mobility peak was detected for a number of specific cluster ions. CONCLUSIONS It is demonstrated that ion mobility mass spectrometry is an advantageous method to assess the isomeric heterogeneity of carbohydrate compounds. It is capable of differentiating different types of carbohydrate ions having identical m/z values as well as multiple structural configurations of single compounds. PMID:24591031

  1. Dynamic Reactive Ionization with Cluster Secondary Ion Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Tian, Hua; Wucher, Andreas; Winograd, Nicholas

    2016-02-01

    Gas cluster ion beams (GCIB) have been tuned to enhance secondary ion yields by doping small gas molecules such as CH4, CO2, and O2 into an Ar cluster projectile, Arn + ( n = 1000-10,000) to form a mixed cluster. The `tailored beam' has the potential to expand the application of secondary ion mass spectrometry for two- and three-dimensional molecular specific imaging. Here, we examine the possibility of further enhancing the ionization by doping HCl into the Ar cluster. Water deposited on the target surface facilitates the dissociation of HCl. This concerted effect, occurring only at the impact site of the cluster, arises since the HCl is chemically induced to ionize to H+ and Cl- , allowing improved protonation of neutral molecular species. This hypothesis is confirmed by depth profiling through a trehalose thin film exposed to D2O vapor, resulting in ~20-fold increase in protonated molecules. The results show that it is possible to dynamically maintain optimum ionization conditions during depth profiling by proper adjustment of the water vapor pressure. H-D exchange in the trehalose molecule M was monitored upon deposition of D2O on the target surface, leading to the observation of [Mn* + H]+ or [Mn* + D]+ ions, where n = 1-8 hydrogen atoms in the trehalose molecule M have been replaced by deuterium. In general, we discuss the role of surface chemistry and dynamic reactive ionization of organic molecules in increasing the secondary ion yield.

  2. Dynamic Reactive Ionization with Cluster Secondary Ion Mass Spectrometry

    PubMed Central

    Wucher, Andreas; Winograd, Nicholas

    2015-01-01

    Gas cluster ion beams (GCIB) have been tuned to enhance secondary ion yields by doping small gas molecules such as CH4, CO2, and O2 into an Ar cluster projectile, Arn+ (n = 1000–10,000) to form a mixed cluster. The ‘tailored beam’ has the potential to expand the application of secondary ion mass spectrometry for two- and three-dimensional molecular specific imaging. Here, we examine the possibility of further enhancing the ionization by doping HCl into the Ar cluster. Water deposited on the target surface facilitates the dissociation of HCl. This concerted effect, occurring only at the impact site of the cluster, arises since the HCl is chemically induced to ionize to H+ and Cl−, allowing improved protonation of neutral molecular species. This hypothesis is confirmed by depth profiling through a trehalose thin film exposed to D2O vapor, resulting in ~20-fold increase in protonated molecules. The results show that it is possible to dynamically maintain optimum ionization conditions during depth profiling by proper adjustment of the water vapor pressure. Protonation and H–D exchange in the trehalose molecule M was monitored upon deposition of D2O on the target surface, leading to the observation of [Mn* + H]+ or [Mn* + D]+ ions, where n = 1–8 hydrogen atoms in the trehalose molecule M have been replaced by deuterium. In general, we discuss the role of surface chemistry and dynamic reactive ionization of organic molecules in increasing the secondary ion yield. PMID:26463238

  3. Stability of Phosphine-Ligated Gold Cluster Ions toward Dissociation: Effect of Ligand and Cluster Size

    NASA Astrophysics Data System (ADS)

    Laskin, Julia

    2015-03-01

    Precise control of the composition of phosphine-ligated gold clusters is of interest to their applications in catalysis, sensing, and drug delivery. Reduction synthesis in solution typically generates a distribution of ligated clusters containing different number of gold atoms and capping ligands. Ligand binding energy is an important factor determining the kinetics of cluster nucleation and growth in solution and hence the resulting cluster distribution. Phosphines are popular capping ligands with tunable electronic and steric properties that affect their binding to the gold core. We examined the effect of the number of gold atoms in the cluster and the properties of the phosphine ligand on the ligand binding energy to the gold core using surface-induced dissociation (SID) of mass selected cluster cations produced through electrospray ionization. SID of vibrationally excited ions is ideally suited for studying gas-phase fragmentation of complex ions such as ligated gold clusters. The energetics, dynamics, and mechanisms of cluster ion fragmentation in the absence of solvent are determined through RRKM modeling of time and kinetic energy dependent SID spectra. This approach provides quantitative information on the ligand binding energies in phosphine-ligated gold clusters important for understanding their formation in solution. Furthermore, ligand binding energies derived from SID data provide the first benchmark values for comparison with electronic structure calculations. This work was supported by the US Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences.

  4. Lithium formate ion clusters formation during electrospray ionization: Evidence of magic number clusters by mass spectrometry and ab initio calculations.

    PubMed

    Shukla, Anil; Bogdanov, Bogdan

    2015-02-14

    Small cationic and anionic clusters of lithium formate were generated by electrospray ionization and their fragmentations were studied by tandem mass spectrometry (collision-induced dissociation with N2). Singly as well as multiply charged clusters were formed in both positive and negative ion modes with the general formulae, (HCOOLi)nLi(+), (HCOOLi)nLim (m+), (HCOOLi)nHCOO(-), and (HCOOLi)n(HCOO)m (m-). Several magic number cluster (MNC) ions were observed in both the positive and negative ion modes although more predominant in the positive ion mode with (HCOOLi)3Li(+) being the most abundant and stable cluster ion. Fragmentations of singly charged positive clusters proceed first by the loss of a dimer unit ((HCOOLi)2) followed by the loss of monomer units (HCOOLi) although the former remains the dominant dissociation process. In the case of positive cluster ions, all fragmentations lead to the magic cluster (HCOOLi)3Li(+) as the most abundant fragment ion at higher collision energies which then fragments further to dimer and monomer ions at lower abundances. In the negative ion mode, however, singly charged clusters dissociated via sequential loss of monomer units. Multiply charged clusters in both positive and negative ion modes dissociated mainly via Coulomb repulsion. Quantum chemical calculations performed for smaller cluster ions showed that the trimer ion has a closed ring structure similar to the phenalenylium structure with three closed rings connected to the central lithium ion. Further additions of monomer units result in similar symmetric structures for hexamer and nonamer cluster ions. Thermochemical calculations show that trimer cluster ion is relatively more stable than neighboring cluster ions, supporting the experimental observation of a magic number cluster with enhanced stability.

  5. Lithium formate ion clusters formation during electrospray ionization: Evidence of magic number clusters by mass spectrometry and ab initio calculations

    SciTech Connect

    Shukla, Anil; Bogdanov, Bogdan

    2015-02-14

    Small cationic and anionic clusters of lithium formate were generated by electrospray ionization and their fragmentations were studied by tandem mass spectrometry (collision-induced dissociation with N{sub 2}). Singly as well as multiply charged clusters were formed in both positive and negative ion modes with the general formulae, (HCOOLi){sub n}Li{sup +}, (HCOOLi){sub n}Li{sub m}{sup m+}, (HCOOLi){sub n}HCOO{sup −}, and (HCOOLi){sub n}(HCOO){sub m}{sup m−}. Several magic number cluster (MNC) ions were observed in both the positive and negative ion modes although more predominant in the positive ion mode with (HCOOLi){sub 3}Li{sup +} being the most abundant and stable cluster ion. Fragmentations of singly charged positive clusters proceed first by the loss of a dimer unit ((HCOOLi){sub 2}) followed by the loss of monomer units (HCOOLi) although the former remains the dominant dissociation process. In the case of positive cluster ions, all fragmentations lead to the magic cluster (HCOOLi){sub 3}Li{sup +} as the most abundant fragment ion at higher collision energies which then fragments further to dimer and monomer ions at lower abundances. In the negative ion mode, however, singly charged clusters dissociated via sequential loss of monomer units. Multiply charged clusters in both positive and negative ion modes dissociated mainly via Coulomb repulsion. Quantum chemical calculations performed for smaller cluster ions showed that the trimer ion has a closed ring structure similar to the phenalenylium structure with three closed rings connected to the central lithium ion. Further additions of monomer units result in similar symmetric structures for hexamer and nonamer cluster ions. Thermochemical calculations show that trimer cluster ion is relatively more stable than neighboring cluster ions, supporting the experimental observation of a magic number cluster with enhanced stability.

  6. Design and experimental testing of a gas cluster ion accelerator

    NASA Astrophysics Data System (ADS)

    Zeng, Xiao-Mei; Pelenovich, Vasiliy; Liu, Chuan-Sheng; Fu, De-Jun

    2017-08-01

    A gas cluster ion beam (GCIB) system with cluster energy up to 12 keV has been designed. To facilitate pumping of the nozzle chamber and increased pressure of the gas source up to 10 atm, pulse mode was used for the gas feeding. Argon was employed as the working gas. To separate monomers from clusters, both electromagnet and retarding electrode were utilized. A maximal pulsed cluster current of 90 nA has been achieved. The shape of pulsed ion beam currents has been analyzed in detail at different applied magnetic and retarding electric fields. Supported by International Cooperation Program of the Ministry of Science and Technology of China (2015DFR00720), Wuhan Municipal Science and Technology Bureau (2016030409020219), Suzhou Scientific Development Project (ZXG201448) and Hubei Province Technological Innovation Project (2016AHB004)

  7. Multiphoton ionization of ammonia clusters and the dissociation dynamics of protonated cluster ions

    SciTech Connect

    Echt, O.; Dao, P.D.; Morgan, S.; Castleman A.W. Jr.

    1985-05-01

    Ammonia clusters, produced via supersonic expansion, are subjected to multiphoton ionization using a tunable pulsed laser. The products of ionization and subsequent dissociation processes are investigated using a time-of-flight mass spectrometer equipped with a reflectron (reflecting electric field). Cluster ions containing more than 65 ammonia molecules were formed via internal ion molecule reactions taking place within the initially ionized aggregate. The proton transfer reaction which ensues leads to substantial excess internal energy and subsequent cluster decomposition. Dissociation due to both collisional and unimolecular processes was identified in the field-free region. Studies of the dynamics of dissociation were made for species up to the protonated 16-mer; the loss of up to at least five monomer units following cluster ion formation was observed. Results of an investigation of the influence of laser fluence and the energy of the ionizing photons are also presented.

  8. Proton-bound cluster ions in ion mobility spectrometry

    NASA Technical Reports Server (NTRS)

    Ewing, R. G.; Eiceman, G. A.; Stone, J. A.

    1999-01-01

    Gaseous oxygen and nitrogen bases, both singly and as binary mixtures, have been introduced into ion mobility spectrometers to study the appearance of protonated molecules, and proton-bound dimers and trimers. At ambient temperature it was possible to simultaneously observe, following the introduction of molecule A, comparable intensities of peaks ascribable to the reactant ion (H2O)nH+, the protonated molecule AH+ and AH+ H2O, and the symmetrical proton bound dimer A2H+. Mass spectral identification confirmed the identifications and also showed that the majority of the protonated molecules were hydrated and that the proton-bound dimers were hydrated to a much lesser extent. No significant peaks ascribable to proton-bound trimers were obtained no matter how high the sample concentration. Binary mixtures containing molecules A and B, in some cases gave not only the peaks unique to the individual compounds but also peaks due to asymmetrical proton bound dimers AHB+. Such ions were always present in the spectra of mixtures of oxygen bases but were not observed for several mixtures of oxygen and nitrogen bases. The dimers, which were not observable, notable for their low hydrogen bond strengths, must have decomposed in their passage from the ion source to the detector, i.e. in a time less than approximately 5 ms. When the temperature was lowered to -20 degrees C, trimers, both homogeneous and mixed, were observed with mixtures of alcohols. The importance of hydrogen bond energy, and hence operating temperature, in determining the degree of solvation of the ions that will be observed in an ion mobility spectrometer is stressed. The possibility is discussed that a displacement reaction involving ambient water plays a role in the dissociation.

  9. A meteor ablation-cluster ion atmospheric sodium theory

    NASA Technical Reports Server (NTRS)

    Richter, E. S.; Sechrist, C. F., Jr.

    1979-01-01

    Neutral and ionic forms of sodium form narrow, well-defined layers which peak in the 90-95 km altitude region at midlatitudes. A new theory for the sodium layer is presented, which is found to be in good agreement with existing atmospheric observations as well as available laboratory measurements of rate constants. The layer is believed to result naturally from a meteor ablation source over a chemical sink with vertical transport of Na(+) playing an important role in the layer shape and variation. While the neutral chemistry is believed to consist of chemical equilibrium between Na and NaO, the ion chemistry departs from earlier studies and considers a cluster ion scheme. It is possible that higher-order cluster ions of sodium play a role in the formation of aerosols, through attachment or ion-induced nucleation processes.

  10. Cluster Ion Spectrometry (CIS) Data Archiving in the CAA

    NASA Astrophysics Data System (ADS)

    Dandouras, I. S.; Barthe, A.; Penou, E.; Brunato, S.; Reme, H.; Kistler, L. M.; Blagau, A.; Facsko, G.; Kronberg, E.; Laakso, H. E.

    2009-12-01

    The Cluster Active Archive (CAA) aims at preserving the four Cluster spacecraft data, so that they are usable in the long-term by the scientific community as well as by the instrument team PIs and Co-Is. This implies that the data are filed together with the descriptive and documentary elements making it possible to select and interpret them. The CIS (Cluster Ion Spectrometry) experiment is a comprehensive ionic plasma spectrometry package onboard the four Cluster spacecraft, capable of obtaining full three-dimensional ion distributions (about 0 to 40 keV/e) with a time resolution of one spacecraft spin (4 sec) and with mass-per-charge composition determination. The CIS package consists of two different instruments, a Hot Ion Analyser (HIA) and a time-of-flight ion Composition Distribution Function (CODIF) analyser. For the archival of the CIS data a multi-level approach has been adopted. The CAA archival includes processed raw data (Level 1 data), moments of the ion distribution functions (Level 2 data), and calibrated high-resolution data in a variety of physical units (Level 3 data). The latter are 3-D ion distribution functions and 2-D pitch-angle distributions. In addition, a software package has been developed to allow the CAA user to interactively calculate partial or total moments of the ion distributions. Instrument cross-calibration has been an important activity in preparing the data for archival. The CIS data archive includes also experiment documentation, graphical products for browsing through the data, and data caveats. In addition, data quality indexes are under preparation, to help the user. Given the complexity of an ion spectrometer, and the variety of its operational modes, each one being optimised for a different magnetospheric region or measurement objective, consultation of the data caveats by the end user will always be a necessary step in the data analysis.

  11. Condensation and Storage of Hydrogen Cluster Ions

    DTIC Science & Technology

    1988-11-01

    Application to Hydrogen Mol- ecular Ion (H+) Ground State", J. Chem. Phys. 70(8), 3881-3 (1979). 58. Strand, Michael P .; Reinhardt, William P ...R radius of curvature L length of S.C. magnet (axial) Q cross section, throughput of pumping section r radius of annular plasma p integer A thickness...of plasma (annular) w plasma frequency p vo azimuthal velocity E° 0radial electric fieldr u mass to change ratio viii INTRODUCTION The future

  12. Formation, structures, and reactivities of niobium oxide cluster ions

    SciTech Connect

    Deng, H.T.; Kerns, K.P.; Castleman, A.W. Jr.

    1996-08-01

    Niobium oxide cluster ions are produced by a laser-induced plasma source. The cluster distribution, collision-induced dissociation (CID), and cluster reactivities are studied using a triple-quadrupole mass spectrometer. CID experiments on the cluster ions Nb{sub 3}O{sub 7-9}{sup +}, Nb{sub 4}O{sub 9-11}{sup +}, and Nb{sub 5}O{sub 12}{sup +} reveal that their building blocks are Nb{sub 2}O{sub 5}, NbO{sub 2}{sup +}, NbO{sub 3}, Nb{sub 3}O{sub 7}{sup +}, O, and O{sub 2}, whereby the cluster stoichiometry is assigned to have the general form (NbO{sub 3}){sub m}(NbO{sub 2}){sub n}(O){sub 0-4}{sup +}. The trends in the ionization potentials of these species are estimated in terms of the CID fragments produced. Nb{sub 3}O{sub 8-9}{sup +} and Nb{sub 4}O{sub 11}{sup +} cluster ions evidently form via the adsorption of one oxygen atom or molecule onto the cluster surface. Nb{sub 3}O{sub 7}{sup +}, Nb{sub 4}O{sub 9}{sup +}, and Nb{sub 5}O{sub 12}{sup +} have strong reactivities to abstract an oxygen atom from oxygen-containing molecules and adsorb small hydrocarbons at near thermal energies. In particular, the reactivity of the oxygen atom or molecule in the oxide clusters Nb{sub 3}O{sub 8-9}{sup +} and Nb{sub 4}O{sub 11}{sup +} is consistent with our suggestions that it has a radical oxygen character. 37 refs., 8 figs., 1 tab.

  13. Ionization reactions of ion complexes in mesoscopic water clusters

    NASA Astrophysics Data System (ADS)

    Consta, Styliani; Kapral, Raymond

    1999-12-01

    The free energy and dynamics of the dissociation reactions of the [Na+(Cl-)2] ion complex in mesoscopic water clusters are examined. The free energy surface shows the existence of stable single and double solvent-separated complex species formed from ionization of the stable double-contact ion complex. The reaction occurs on the cluster surface for mesoscale clusters composed of tens of water molecules. Passage between stable species is an activated process but barrier crossing has a large diffusive component so that dynamical corrections to transition state theory are large. The structure of the decay of the time-dependent rate constant reflects the diffusive character of the recrossing dynamics so that a plateau is not established on a 10 ps time scale in contrast to ionization dynamics in bulk fluids.

  14. Correspondence between ion-cluster and bulk thermodynamics: on the validity of the cluster pair approximation

    SciTech Connect

    Vlcek, Lukas; Chialvo, Ariel; Simonson, J Michael {Mike}

    2013-01-01

    Molecular models and experimental estimates based on the cluster pair approximation (CPA) provide inconsistent predictions of absolute single-ion hydration properties. To understand the origin of this discrepancy we used molecular simulations to study the transition between hydration of alkali metal and halide ions in small aqueous clusters and bulk water. The results demonstrate that the assumptions underlying the CPA are not generally valid as a result of a significant shift in the ion hydration free energies (~15 kJ/mol) and enthalpies (~47 kJ/mol) in the intermediate range of cluster sizes. When this effect is accounted for, the systematic differences between models and experimental predictions disappear, and the value of absolute proton hydration enthalpy based on the CPA gets in closer agreement with other estimates.

  15. Generation and reactivity of yttrium-carbon cluster ions

    SciTech Connect

    Kan, S.Z.; Lee, S.A.; Freiser, B.S.

    1995-12-31

    In 1992, Castleman and coworkers reported the production of the ionic transition metal-carbon clusters, M{sub 8}C{sub 12}{sup +} (M=Ti,V, Zr and Hf). Like the observations of pure carbon clusters such as C{sub 60} and C{sub 70}, these metal-carbon clusters were observed as {open_quotes}magic{close_quotes} peaks in the mass spectra obtained from a supersonic expansion ion source. These intense peaks are indicative of the high stability of these clusters which are proposed to have symmetrical, cagelike structures with the geometry of a pentagonal dodecahedron. M{sub 8}C{sub 12}{sup +} species are thus termed metallo-carbohedrenes, or met-cars for short. Like fullerenes, met-cars are of both fundamental interest and hold promise as a new class of important materials and, hence, have become the focus of both theoretical and experimental investigations. Along with these species, metal-carbon clusters of other stoichiometries such as Ti{sub 8}C{sub 11}{sup +}, Ti{sub 8}C{sub 13}{sup +}, Ti{sub 7}C{sub 12}, V{sub 14}C{sub 13}{sup +}, V{sub 14}C{sub 12}{sup +}, and Nb{sub 4}C{sub 4}{sup +} have also been examined. Here, the authors report on the yttrium-carb system in which a broad range of metal-carbon cluster ions are observed.

  16. Ion pinhole imaging diagnostics on fast ion source in femtosecond laser plasma of cluster targets.

    PubMed

    Makarov, Sergey; Pikuz, Sergey; Faenov, Anatoly; Pikuz, Tatiana; Fukuda, Yuji; Skobelev, Igor; Zhvaniya, Irina; Varzar, Sergey; Kando, Masaki; Kodama, Ryousuke

    2017-07-10

    The spatial configuration of the ion source generated under femtosecond laser interaction with clusters is investigated. While intense laser pulses (36 fs, 60 mJ, intensity of 4 × 10(17) W/cm(2)) propagated in CO2 cluster (~0.22 μm in diameter) media, the shape of the obtained plasma ion source was registered for the first time by means of pinhole imaging method. The remarkable decrease in fast ion yield in the vicinity of the assumed best laser focus near the gas cluster jet axis is observed. Such observed anisotropy of the ion source is suggested to originate from the influence of the laser prepulse destroying clusters in advance to the arrival of the main pulse. The assumption is confirmed by optical shadowgraphy images of the plasma channel and is important for further development of an efficient laser-plasma-based fast ion source. Following the observed geometry of the ion source, the laser intensity limit allowing to accelerate ions to ~100 keV energy range was estimated.

  17. CO2 Cluster Ion Beam, an Alternative Projectile for Secondary Ion Mass Spectrometry.

    PubMed

    Tian, Hua; Maciążek, Dawid; Postawa, Zbigniew; Garrison, Barbara J; Winograd, Nicholas

    2016-09-01

    The emergence of argon-based gas cluster ion beams for SIMS experiments opens new possibilities for molecular depth profiling and 3D chemical imaging. These beams generally leave less surface chemical damage and yield mass spectra with reduced fragmentation compared with smaller cluster projectiles. For nanoscale bioimaging applications, however, limited sensitivity due to low ionization probability and technical challenges of beam focusing remain problematic. The use of gas cluster ion beams based upon systems other than argon offer an opportunity to resolve these difficulties. Here we report on the prospects of employing CO2 as a simple alternative to argon. Ionization efficiency, chemical damage, sputter rate, and beam focus are investigated on model compounds using a series of CO2 and Ar cluster projectiles (cluster size 1000-5000) with the same mass. The results show that the two projectiles are very similar in each of these aspects. Computer simulations comparing the impact of Ar2000 and (CO2)2000 on an organic target also confirm that the CO2 molecules in the cluster projectile remain intact, acting as a single particle of m/z 44. The imaging resolution employing CO2 cluster projectiles is improved by more than a factor of two. The advantage of CO2 versus Ar is also related to the increased stability which, in addition, facilitates the operation of the gas cluster ion beams (GCIB) system at lower backing pressure. Graphical Abstract ᅟ.

  18. CO2 Cluster Ion Beam, an Alternative Projectile for Secondary Ion Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Tian, Hua; Maciążek, Dawid; Postawa, Zbigniew; Garrison, Barbara J.; Winograd, Nicholas

    2016-09-01

    The emergence of argon-based gas cluster ion beams for SIMS experiments opens new possibilities for molecular depth profiling and 3D chemical imaging. These beams generally leave less surface chemical damage and yield mass spectra with reduced fragmentation compared with smaller cluster projectiles. For nanoscale bioimaging applications, however, limited sensitivity due to low ionization probability and technical challenges of beam focusing remain problematic. The use of gas cluster ion beams based upon systems other than argon offer an opportunity to resolve these difficulties. Here we report on the prospects of employing CO2 as a simple alternative to argon. Ionization efficiency, chemical damage, sputter rate, and beam focus are investigated on model compounds using a series of CO2 and Ar cluster projectiles (cluster size 1000-5000) with the same mass. The results show that the two projectiles are very similar in each of these aspects. Computer simulations comparing the impact of Ar2000 and (CO2)2000 on an organic target also confirm that the CO2 molecules in the cluster projectile remain intact, acting as a single particle of m/z 44. The imaging resolution employing CO2 cluster projectiles is improved by more than a factor of two. The advantage of CO2 versus Ar is also related to the increased stability which, in addition, facilitates the operation of the gas cluster ion beams (GCIB) system at lower backing pressure.

  19. Cluster Ion Spectrometry (CIS) Data in the Cluster Active Archive (CAA)

    NASA Astrophysics Data System (ADS)

    Dandouras, I.; Barthe, A.; Penou, E.; Brunato, S.; Rème, H.; Kistler, L. M.; Bavassano-Cattaneo, M. B.; Blagau, A.

    The Cluster Active Archive (CAA) aims at preserving the four Cluster spacecraft data, so that they are usable in the long-term by the scientific community as well as by the instrument team PIs and Co-Is. This implies that the data are filed together with the descriptive and documentary elements making it possible to select and interpret them. The CIS (Cluster Ion Spectrometry) experiment is a comprehensive ionic plasma spectrometry package onboard the four Cluster spacecraft, capable of obtaining full three-dimensional ion distributions (about 0-40 keV/e) with a time resolution of one spacecraft spin (4 s) and with mass-per-charge composition determination. The CIS package consists of two different instruments, a Hot Ion Analyser (HIA) and a time-of-flight ion Composition Distribution Function (CODIF) analyser, plus a sophisticated dual-processor based instrument control and data processing system (DPS). For the archival of the CIS data a multi-level approach has been adopted. The CAA archival includes processed raw data (Level 1 data), moments of the ion distribution functions (Level 2 data), and calibrated high-resolution data in a variety of physical units (Level 3 data). The latter are 3-D ion distribution functions. In addition, a software package has been developed to allow the CAA user to interactively calculate partial or total moments of the ion distributions. The CIS data archive includes also experiment documentation, graphical products for browsing through the data, and data caveats. Given the complexity of an ion spectrometer, and the variety of its operational modes, each one being optimised for a different magnetospheric region or measurement objective, consultation of the data caveats by the end user will always be a necessary step in the data analysis.

  20. Application of Ion Mobility-Mass Spectrometry to the Study of Ionic Clusters: Investigation of Cluster Ions with Stable Sizes and Compositions

    PubMed Central

    Ohshimo, Keijiro; Komukai, Tatsuya; Takahashi, Tohru; Norimasa, Naoya; Wu, Jenna Wen Ju; Moriyama, Ryoichi; Koyasu, Kiichirou; Misaizu, Fuminori

    2014-01-01

    Stable cluster sizes and compositions have been investigated for cations and anions of ionic bond clusters such as alkali halides and transition metal oxides by ion mobility-mass spectrometry (IM-MS). Usually structural information of ions can be obtained from collision cross sections determined in IM-MS. In addition, we have found that stable ion sizes or compositions were predominantly produced in a total ion mass spectrum, which was constructed from the IM-MS measurement. These stable species were produced as a result of collision induced dissociations of the ions in a drift cell. We have confirmed this result in the sodium fluoride cluster ions, in which cuboid magic number cluster ions were predominantly observed. Next the stable compositions, which were obtained for the oxide systems of the first row transition metals, Ti, Fe, and Co, are characteristic for each of the metal oxide cluster ions. PMID:26819887

  1. Molecular dynamics simulation of fluorine cluster ion impact

    NASA Astrophysics Data System (ADS)

    Aoki, Takaaki; Matsuo, Jiro; Yamada, Isao

    2000-04-01

    Molecular dynamics (MD) simulations of fluorine atoms, molecules and clusters impacting a silicon substrate were performed in order to investigate the impact process of a reactive cluster ion. This result shows that when the incident energy of the impacting fluorine atom or molecule is less than 10 eV/atom, the species are only adsorbed on the surface and sputtering of substrate atoms does not occur. On the other hand, a fluorine cluster consisting of 30 molecules produces sputtering even at a low incident energy of 1 eV/atom. At these conditions, the surface atoms are desorbed as fluorine-containing species, such as SiF or SiF 2, indicating that chemical desorption is enhanced by irradiation with fluorine clusters. As the incident energy of the cluster increases to values as high as 100 eV/atom, almost all the fluorine atoms penetrate the surface and a crater-shaped damage is formed. The incident F atoms reside at the bottom region of the crater. In this case, silicon atoms leave the surface as monomers, dimers or clusters without F atoms, i.e., in this regime physical sputtering through atomic collisions has a higher probability than chemical reactions, like in the case of Ne or Ar cluster impact.

  2. Li-rich antiperovskite superionic conductors based on cluster ions.

    PubMed

    Fang, Hong; Jena, Puru

    2017-10-02

    Enjoying great safety, high power, and high energy densities, all-solid-state batteries play a key role in the next generation energy storage devices. However, their development is limited by the lack of solid electrolyte materials that can reach the practically useful conductivities of 10(-2) S/cm at room temperature (RT). Here, by exploring a set of lithium-rich antiperovskites composed of cluster ions, we report a lithium superionic conductor, Li3SBF4, that has an estimated 3D RT conductivity of 10(-2) S/cm, a low activation energy of 0.210 eV, a giant band gap of 8.5 eV, a small formation energy, a high melting point, and desired mechanical properties. A mixed phase of the material, Li3S(BF4)0.5Cl0.5, with the same simple crystal structure exhibits an RT conductivity as high as 10(-1) S/cm and a low activation energy of 0.176 eV. The high ionic conductivity of the crystals is enabled by the thermal-excited vibrational modes of the cluster ions and the large channel size created by mixing the large cluster ion with the small elementary ion.

  3. Ionization of large homogeneous and heterogeneous clusters generated in acetylene-Ar expansions: Cluster ion polymerization

    NASA Astrophysics Data System (ADS)

    Kočišek, J.; Lengyel, J.; Fárník, M.

    2013-03-01

    Pure acetylene and mixed Ar-acetylene clusters are formed in supersonic expansions of acetylene/argon mixtures and analysed using reflectron time-of-flight mass spectrometer with variable electron energy ionization source. Acetylene clusters composed of more than a hundred acetylene molecules are generated at the acetylene concentration of ≈8%, while mixed species are produced at low concentrations (≈0.7%). The electron energy dependence of the mass spectra revealed the ionization process mechanisms in clusters. The ionization above the threshold for acetylene molecule of 11.5 eV results in the main ionic fragment progression (C_2H_2)_n^+. At the electron energies ⩾21.5 eV above the CH+CH+ dissociative ionization limit of acetylene the fragment ions nominally labelled as (C2H2)nCH+, n ⩾ 2, are observed. For n ⩽ 7 these fragments correspond to covalently bound ionic structures as suggested by the observed strong dehydrogenation [(C2H2)n - k × H]+ and [(C2H2)nCH - k × H]+. The dehydrogenation is significantly reduced in the mixed clusters where evaporation of Ar instead of hydrogen can stabilize the nascent molecular ion. The C3 H_3^+ ion was previously assigned to originate from the benzene molecular ion; however, the low appearance energy of ≈13.7 eV indicates that a less rigid covalently bound structure of C6 H_6^+ ion must also be formed upon the acetylene cluster electron ionization. The appearance energy of Arn(C2H2)+ fragments above ≈15.1 eV indicates that the argon ionization is the first step in the fragment ion production, and the appearance energy of Ar_{n ≥ 2}(C2 H2)_{m≥ 2}^+ at ≈13.7 eV is discussed in terms of an exciton transfer mechanism.

  4. Ionization of large homogeneous and heterogeneous clusters generated in acetylene-Ar expansions: cluster ion polymerization.

    PubMed

    Kočišek, J; Lengyel, J; Fárník, M

    2013-03-28

    Pure acetylene and mixed Ar-acetylene clusters are formed in supersonic expansions of acetylene/argon mixtures and analysed using reflectron time-of-flight mass spectrometer with variable electron energy ionization source. Acetylene clusters composed of more than a hundred acetylene molecules are generated at the acetylene concentration of ≈8%, while mixed species are produced at low concentrations (≈0.7%). The electron energy dependence of the mass spectra revealed the ionization process mechanisms in clusters. The ionization above the threshold for acetylene molecule of 11.5 eV results in the main ionic fragment progression (C2H2)n(+). At the electron energies ≥21.5 eV above the CH+CH(+) dissociative ionization limit of acetylene the fragment ions nominally labelled as (C2H2)nCH(+), n ≥ 2, are observed. For n ≤ 7 these fragments correspond to covalently bound ionic structures as suggested by the observed strong dehydrogenation [(C2H2)n - k × H](+) and [(C2H2)nCH - k × H](+). The dehydrogenation is significantly reduced in the mixed clusters where evaporation of Ar instead of hydrogen can stabilize the nascent molecular ion. The C3H3(+) ion was previously assigned to originate from the benzene molecular ion; however, the low appearance energy of ≈13.7 eV indicates that a less rigid covalently bound structure of C6H6(+) ion must also be formed upon the acetylene cluster electron ionization. The appearance energy of Arn(C2H2)(+) fragments above ≈15.1 eV indicates that the argon ionization is the first step in the fragment ion production, and the appearance energy of Arn≥2(C2H2)m≥2(+) at ≈13.7 eV is discussed in terms of an exciton transfer mechanism.

  5. Evidence that Clouds of keV Hydrogen Ion Clusters Bounce Elastically from a Solid Surface

    NASA Technical Reports Server (NTRS)

    Lewis, R. A.; Martin, James J.; Chakrabarti, Suman; Rodgers, Stephen L. (Technical Monitor)

    2002-01-01

    The behavior of hydrogen ion clusters is tested by an inject/hold/extract technique in a Penning-Malmberg trap. The timing pattern of the extraction signals is consistent with the clusters bouncing elastically from a detector several times. The ion clusters behave more like an elastic fluid than a beam of ions.

  6. Determination of ion track radii in amorphous matrices via formation of nano-clusters by ion-beam irradiation

    SciTech Connect

    Buljan, M.; Karlusic, M.; Bogdanovic-Radovic, I.; Jaksic, M.; Radic, N.; Salamon, K.; Bernstorff, S.

    2012-09-03

    We report on a method for the determination of ion track radii, formed in amorphous materials by ion-beam irradiation. The method is based on the addition to an amorphous matrix of a small amount of foreign atoms, which easily diffuse and form clusters when the temperature is sufficiently increased. The irradiation causes clustering of these atoms, and the final separations of the formed clusters are dependent on the parameters of the ion-beam. Comparison of the separations between the clusters that are formed by ions with different properties in the same type of material enables the determination of ion-track radii.

  7. Determination of ion track radii in amorphous matrices via formation of nano-clusters by ion-beam irradiation

    NASA Astrophysics Data System (ADS)

    Buljan, M.; Karlušić, M.; Bogdanović-Radović, I.; Jakšić, M.; Salamon, K.; Bernstorff, S.; Radić, N.

    2012-09-01

    We report on a method for the determination of ion track radii, formed in amorphous materials by ion-beam irradiation. The method is based on the addition to an amorphous matrix of a small amount of foreign atoms, which easily diffuse and form clusters when the temperature is sufficiently increased. The irradiation causes clustering of these atoms, and the final separations of the formed clusters are dependent on the parameters of the ion-beam. Comparison of the separations between the clusters that are formed by ions with different properties in the same type of material enables the determination of ion-track radii.

  8. Nonlinear phenomenon in nanostructures creation by fast cluster ions

    NASA Astrophysics Data System (ADS)

    Moslem, W. M.; El-Said, A. S.; Sabry, R.; Shalouf, A.; El-Labany, S. K.; Bahlouli, H.

    2017-01-01

    The development of accelerators technology offers a new window for the creation of surface nanostructures in an efficient and accurate way. The use of 30 MeV C60 cluster ions enables the creation of nano-hillocks of size larger than the ones produced by GeV monoatomic ions. The physical mechanism underlying the realization of such nanostructures is elucidated using a plasma expansion approach. Numerical analysis showed that increasing the ionic temperature (number density) ratios would lead to decrease (increase) the nano-hillocks height.

  9. Effect of silver ions and clusters on the luminescence properties of Eu-doped borate glasses

    SciTech Connect

    Jiao, Qing; Wang, Xi; Qiu, Jianbei; Zhou, Dacheng

    2015-12-15

    Highlights: • Ag{sup +} and Ag clusters are investigated in the borate glasses via ion exchange method. • The aggregation of silver ions to the clusters was controlled by the ion exchange concentration. • Eu{sup 3+}/Eu{sup 2+} ions emission was enhanced with the sensitization of the silver species. • Energy transfer process from Ag ions and Ag clusters to Eu ions is identified by the lifetime measurements. - Abstract: Silver ions and clusters were applied to Eu{sup 3+}-doped borate glasses via the Ag{sup +}–Na{sup +} ion exchange method. Eu{sup 3+}/Eu{sup 2+} ion luminescence enhancement was achieved after silver ion exchange. Absorption spectra showed no band at 420 nm, which indicates that silver nanoparticles can be excluded as a silver state in the glass. Silver ion aggregation into clusters during the ion exchange process may be inferred. The effect of silver ions and clusters on rare earth emissions was investigated using spectral information and lifetime measurements. Significant luminescence enhancements were observed from the energy transfer of Ag{sup +} ions and clusters to Eu{sup 3+}/Eu{sup 2+} ions, companied with the silver ions aggregated into the clusters state. The results of this research may extend the current understanding of interactions between rare-earth ions and Ag species.

  10. Buffer Gas Modifiers Effect Resolution in Ion Mobility Spectrometry through Selective Ion-Molecule Clustering Reactions

    PubMed Central

    Fernández-Maestre, Roberto; Wu, Ching; Hill, Herbert H.

    2013-01-01

    RATIONALE When polar molecules (modifiers) are introduced into the buffer gas of an ion mobility spectrometer, most ion mobilities decrease due to the formation of ion-modifier clusters. METHODS We used ethyl lactate, nitrobenzene, 2-butanol, and tetrahydrofuran-2-carbonitrile as buffer gas modifiers and electrospray ionization ion mobility spectrometry (IMS) coupled to quadrupole mass spectrometry. Ethyl lactate, nitrobenzene, and tetrahydrofuran-2-carbonitrile had not been tested as buffer gas modifiers and 2-butanol had not been used with basic amino acids. RESULTS The ion mobilities of several diamines (arginine, histidine, lysine, and atenolol) were not affected or only slightly reduced when these modifiers were introduced into the buffer gas (3.4% average reduction in an analyte's mobility for the three modifiers). Intramolecular bridges caused limited change in the ion mobilities of diamines when modifiers were added to the buffer gas; these bridges hindered the attachment of modifier molecules to the positive charge of ions and delocalized the charge, which deterred clustering. There was also a tendency towards large changes in ion mobility when the mass of the analyte decreased; ethanolamine, the smallest compound tested, had the largest reduction in ion mobility with the introduction of modifiers into the buffer gas (61%). These differences in mobilities, together with the lack of shift in bridge-forming ions, were used to separate ions that overlapped in IMS, such as isoleucine and lysine, and arginine and phenylalanine, and made possible the prediction of separation or not of overlapping ions. CONCLUSIONS The introduction of modifiers into the buffer gas in IMS can selectively alter the mobilities of analytes to aid in compound identification and/or enable the separation of overlapping analyte peaks. PMID:22956312

  11. Low-energy collisions of helium clusters with size-selected cobalt cluster ions

    NASA Astrophysics Data System (ADS)

    Odaka, Hideho; Ichihashi, Masahiko

    2017-04-01

    Collisions of helium clusters with size-selected cobalt cluster ions, Com+ (m ≤ 5), were studied experimentally by using a merging beam technique. The product ions, Com+Hen (cluster complexes), were mass-analyzed, and this result indicates that more than 20 helium atoms can be attached onto Com+ at the relative velocities of 103 m/s. The measured size distributions of the cluster complexes indicate that there are relatively stable complexes: Co2+Hen (n = 2, 4, 6, and 12), Co3+Hen (n = 3, 6), Co4+He4, and Co5+Hen (n = 3, 6, 8, and 10). These stabilities are explained in terms of their geometric structures. The yields of the cluster complexes were also measured as a function of the relative velocity (1 × 102-4 × 103 m/s), and this result demonstrates that the main interaction in the collision process changes with the increase of the collision energy from the electrostatic interaction, which includes the induced deformation of HeN, to the hard-sphere interaction. Supplementary material in the form of one pdf file available from the Journal web page at http://https://doi.org/10.1140/epjd/e2017-80015-0

  12. How unequivocally do ion chromatography experiments determine carbon cluster geometries?

    SciTech Connect

    Strout, D.L.; Book, L.D.; Millam, J.M.; Xu, C.; Scuseria, G.E.

    1994-09-01

    Ion chromatography experiments on carbon clusters have provided a powerful tool for characterizing the products of the laser ablation of graphite. Using this technique, several families of carbon clusters have been observed, and their role in a plausible fullerene formation process has been hypothesized. In this work, we have examined the experimental mobility results from a theoretical perspective. Our most interesting finding is the existence of a family of three-dimensional 2 + 4 cycloaddition products whose members match the experimental mobilities of the so-called `ring III` family over a range of cluster sizes, whereas previous studies have asserted that the `ring III` clusters are planar. In agreement with previous research, we find that the `ring I` and `ring II` families consist of monocyclic and bicycle rings, respectively. However, these families should be broadly defined so as to include ring structures with carbon branches, because short carbon branches have only a negligible effect on cluster mobility. 28 refs., 6 figs., 6 tabs.

  13. Negative ion photoelectron spectroscopic studies of transition metal cluster

    NASA Astrophysics Data System (ADS)

    Marcy, Timothy Paul

    The studies reported in this thesis were performed using a negative ion photoelectron spectrometer consisting of a cold cathode DC discharge ion source, a flowing afterglow ion-molecule reactor, a magnetic sector mass analyzer, an argon ion laser for photodetachment and a hemispherical electron kinetic energy analyzer and microchannel plate detector for photoelectron spectrum generation. The 476.5 nm (2.601 eV), 488.0 nm (2.540 eV) and 514.5 nm (2.410 eV) negative ion photoelectron spectra of VMn are reported and compared to the previously studied spectra of isoelectronic Cr2.1 The photoelectron spectra are remarkably similar to those of Cr2 in electron affinity and vibrational frequencies. The 488.0 nm photoelectron spectra and electron affinities of Nb n- (n = 1 - 9) are reported with discussion of observed vibrational structure. There are transitions to several electronic states of Nb2 in the reported spectra with overlapping vibrational progressions. The spectra of Nb3, Nb4 and Nb6 show partially resolved vibrational structure in the transitions to the lowest observed electronic state of each cluster. There is a single distinct active vibrational mode in the transition to the ground state of Nb8. Spin-orbit energies of Nb- are also reported. The 488.0 nm negative ion photoelectron spectra of Nb3H(D) are reported and compared to those of Nb3. There is a single vibrational mode active in the spectra of Nb3H(D) which is very similar to the most distinct mode active in the spectrum of Nb3. The 488.0 nm photoelectron spectra of the NbxCyH(D) y- (x = 1, 2, 3, y = 2, 4, 6) dehydrogenated products of the reactions of ethylene with niobium cluster anions are reported. Temperature studies of some of these species give evidence for the presence of multiple isomers of each molecule in the ion beam. The spectra of NbC6H(D) 6 are identical to those obtained from the reactions of benzene with niobium clusters and indicate that benzene is being formed from ethylene in the flow

  14. Electrospray Ionization Mass Spectrometry: From Cluster Ions to Toxic metal Ions in Biology

    SciTech Connect

    Lentz, Nicholas B.

    2007-01-01

    This dissertation focused on using electrospray ionization mass spectrometry to study cluster ions and toxic metal ions in biology. In Chapter 2, it was shown that primary, secondary and quarternary amines exhibit different clustering characteristics under identical instrument conditions. Carbon chain length also played a role in cluster ion formation. In Chapters 3 and 4, the effects of solvent types/ratios and various instrumental parameters on cluster ion formation were examined. It was found that instrument interface design also plays a critical role in the cluster ion distribution seen in the mass spectrum. In Chapter 5, ESI-MS was used to investigate toxic metal binding to the [Gln11]-amyloid β-protein fragment (1-16). Pb and Cd bound stronger than Zn, even in the presence of excess Zn. Hg bound weaker than Zn. There are endless options for future work on cluster ions. Any molecule that is poorly ionized in positive ion mode can potentially show an increase in ionization efficiency if an appropriate anion is used to produce a net negative charge. It is possible that drug protein or drug/DNA complexes can also be stabilized by adding counter-ions. This would preserve the solution characteristics of the complex in the gas phase. Once in the gas phase, CID could determine the drug binding location on the biomolecule. There are many research projects regarding toxic metals in biology that have yet to be investigated or even discovered. This is an area of research with an almost endless future because of the changing dynamics of biological systems. What is deemed safe today may show toxic effects in the future. Evolutionary changes in protein structures may render them more susceptible to toxic metal binding. As the understanding of toxicity evolves, so does the demand for new toxic metal research. New instrumentation designs and software make it possible to perform research that could not be done in the past. What was undetectable yesterday will

  15. Ionization of large homogeneous and heterogeneous clusters generated in acetylene-Ar expansions: Cluster ion polymerization

    SciTech Connect

    Kocisek, J.; Lengyel, J.; Farnik, M.

    2013-03-28

    Pure acetylene and mixed Ar-acetylene clusters are formed in supersonic expansions of acetylene/argon mixtures and analysed using reflectron time-of-flight mass spectrometer with variable electron energy ionization source. Acetylene clusters composed of more than a hundred acetylene molecules are generated at the acetylene concentration of Almost-Equal-To 8%, while mixed species are produced at low concentrations ( Almost-Equal-To 0.7%). The electron energy dependence of the mass spectra revealed the ionization process mechanisms in clusters. The ionization above the threshold for acetylene molecule of 11.5 eV results in the main ionic fragment progression (C{sub 2}H{sub 2}){sub n}{sup +}. At the electron energies Greater-Than-Or-Slanted-Equal-To 21.5 eV above the CH+CH{sup +} dissociative ionization limit of acetylene the fragment ions nominally labelled as (C{sub 2}H{sub 2}){sub n}CH{sup +}, n Greater-Than-Or-Slanted-Equal-To 2, are observed. For n Less-Than-Or-Slanted-Equal-To 7 these fragments correspond to covalently bound ionic structures as suggested by the observed strong dehydrogenation [(C{sub 2}H{sub 2}){sub n}-k Multiplication-Sign H]{sup +} and [(C{sub 2}H{sub 2}){sub n}CH -k Multiplication-Sign H]{sup +}. The dehydrogenation is significantly reduced in the mixed clusters where evaporation of Ar instead of hydrogen can stabilize the nascent molecular ion. The C{sub 3}H{sub 3}{sup +} ion was previously assigned to originate from the benzene molecular ion; however, the low appearance energy of Almost-Equal-To 13.7 eV indicates that a less rigid covalently bound structure of C{sub 6}H{sub 6}{sup +} ion must also be formed upon the acetylene cluster electron ionization. The appearance energy of Ar{sub n}(C{sub 2}H{sub 2}){sup +} fragments above Almost-Equal-To 15.1 eV indicates that the argon ionization is the first step in the fragment ion production, and the appearance energy of Ar{sub n{>=}2}(C{sub 2}H{sub 2}){sub m{>=}2}{sup +} at Almost-Equal-To 13

  16. Clustering Analysis of Fast-ion Driven Instabilities

    NASA Astrophysics Data System (ADS)

    Gresl, J.; Heidbrink, W. W.; Haskey, S.; Blackwell, B. D.

    2016-10-01

    Beam ions often drive Alfvén eigenmodes and other instabilities unstable in DIII-D. Many of these modes have been unambigously identified but some frequently occurring features have been neglected. In this work, datamining analysis techniques that successfully analyzed magnetics data from the H-1NF heliac are applied to arrays of magnetic and electron cyclotron emission (ECE) data from DIII-D. The techniques group instabilities with similar magnetic or ECE features into clusters. Once the clusters are found, a database of plasma parameters will facilitate mode identification. Work supported by the US Department of Energy under DE-FC02-04ER54698, DE-FG03-94ER54271, DE-AC02-09CH11466.

  17. Imaging Mass Spectrometry on the Nanoscale with Cluster Ion Beams

    DOE PAGES

    Winograd, Nicholas

    2014-12-02

    Imaging with cluster secondary ion mass spectrometry (SIMS) is reaching a mature level of development. When, using a variety of molecular ion projectiles to stimulate desorption, 3-dimensional imaging with the selectivity of mass spectrometry can now be achieved with submicrometer spatial resolution and <10 nm depth resolution. In this Perspective, stock is taken regarding what it will require to routinely achieve these remarkable properties. Some issues include the chemical nature of the projectile, topography formation, differential erosion rates, and perhaps most importantly, ionization efficiency. Shortcomings of existing instrumentation are also noted. One key part of this discussion involves speculation onmore » how best to resolve these issues.« less

  18. Cluster Observation Of Ion And Electron Cyclotron Waves Near Magnetopause

    NASA Astrophysics Data System (ADS)

    Silin, I.; Panov, E. V.

    2012-12-01

    We examine observations of electromagnetic ion cyclotron (EMIC) and electron cyclotron waves by Cluster spacecraft during a magnetopause transition near polar cusp region. The waves appear to be generated locally, on the magnetospheric side of the magnetopause current layer, due to large particle temperature anisotropy (T⊥}/T{∥ >3 for all ions and T⊥}/T{∥ ˜ 1.3 for electrons) and large plasma beta (0.5 < β < 10). The compact configuration of Cluster spacecraft and high-resolution electromagnetic field data allowed us to measure the wave vectors k by two independent methods: the wave-telescope and the polarization methods. Such measurements are essential for estimation of minimum energies of particles scattered by EMIC waves via cyclotron resonance. The results show good agreement with linear dispersion theory. The EMIC waves propagate along the magnetic field with frequencies near 1 Hz, wavelength of 260 km at speeds of ˜ 500 km/s. We discuss the implications of these results for the particle diffusion coefficients and minimum resonant scattering energies.

  19. O2 cluster ion assisted deposition for tin doped indium oxide (ITO) films

    NASA Astrophysics Data System (ADS)

    Matsuo, Jiro; Takaoka, Gikan; Yamada, Isao

    2001-07-01

    B S TO2 Gas Cluster Ion Beam assisted deposition technique has been developed to form ultra high quality tin doped indium-oxide (UHQ-ITO) films. This deposition process uses large cluster ions which can transport thousands of atoms in a ion with very low energy per constituent atom. Interactions between cluster ions and substrate atoms occur in the near-surface region and cluster ions can deposit their energy with a high density in a very localized surface region. The energetic oxygen clusters collapsed at the surface and reacted with the metal atoms and about 10% of them were incorporated, when the kinetic energy of the cluster ion was above 5 keV. Oxidation reaction can be enhanced by energetic cluster ion bombardment which offers a new technique for ion assisted thin film formation. Very smooth, highly transparent (>80 %) and low resistivity films, were obtained by using a 7 keV oxygen cluster ion beam. In order to realize high throughput for industrial application, a Multi-beam Gas Cluster Ion Beam equipment has been newly developed.

  20. Peptide structural analysis using continuous Ar cluster and C60 ion beams.

    PubMed

    Aoyagi, Satoka; Fletcher, John S; Sheraz Rabbani, Sadia; Kawashima, Tomoko; Berrueta Razo, Irma; Henderson, Alex; Lockyer, Nicholas P; Vickerman, John C

    2013-08-01

    A novel application of time-of-flight secondary ion mass spectrometry (ToF-SIMS) with continuous Ar cluster beams to peptide analysis was investigated. In order to evaluate peptide structures, it is necessary to detect fragment ions related to multiple neighbouring amino acid residues. It is, however, difficult to detect these using conventional ToF-SIMS primary ion beams such as Bi cluster beams. Recently, C60 and Ar cluster ion beams have been introduced to ToF-SIMS as primary ion beams and are expected to generate larger secondary ions than conventional ones. In this study, two sets of model peptides have been studied: (des-Tyr)-Leu-enkephalin and (des-Tyr)-Met-enkephalin (molecular weights are approximately 400 Da), and [Asn(1) Val(5)]-angiotensin II and [Val(5)]-angiotensin I (molecular weights are approximately 1,000 Da) in order to evaluate the usefulness of the large cluster ion beams for peptide structural analysis. As a result, by using the Ar cluster beams, peptide molecular ions and large fragment ions, which are not easily detected using conventional ToF-SIMS primary ion beams such as Bi3 (+), are clearly detected. Since the large fragment ions indicating amino acid sequences of the peptides are detected by the large cluster beams, it is suggested that the Ar cluster and C60 ion beams are useful for peptide structural analysis.

  1. The use of ion-milling to control clustering of nanostructured, columnar thin films

    NASA Astrophysics Data System (ADS)

    Kwan, Jonathan K.; Sit, Jeremy C.

    2010-07-01

    We present the use of ion-milling to reduce the capillary-induced clustering of vertical post nanostructures grown by glancing angle deposition. Nanostructures of several heights were grown and ion-milled for various times to investigate effects on post clustering. No clustering was observed given sufficient ion-mill exposure time, with the characteristic time being lower for shorter posts. The results demonstrate that these strengthened nanostructures are suitable for use in liquid environments.

  2. Upstream gyrating ion events: Cluster observations and simulations

    SciTech Connect

    Sauer, K.; Fraenz, M.; Dubinin, E.; Korth, A.; Mazelle, C.; Reme, H.; Dandouras, I.

    2005-08-01

    Localized events of low-frequency quasi-monochromatic waves in the 30s range observed by Cluster in the upstream region of Earth are analyzed. They are associated with a gyro-motion of the two ion populations consisting of the incoming solar wind protons and the back-streaming ions from the shock. A coordinate system is chosen in which one axis is parallel to the ambient magnetic field B0 and the other one is in the vswxB0 direction. The variation of the plasma parameters is compared with the result of two-fluid Hall-MHD simulations using different beam densities and velocities. Keeping a fixed (relative) beam density (e.g. {alpha}=0.005), non-stationary 'shock-like' structures are generated if the beam velocity exceeds a certain threshold of about ten times the Alfven velocity. Below the threshold, the localized events represent stationary, nonlinear waves (oscillitons) in a beam-plasma system in which the Reynold's stresses of the plasma and beam ions are balanced by the magnetic field stress.

  3. Time-of-flight secondary ion mass spectrometry with transmission of energetic primary cluster ions through foil targets

    SciTech Connect

    Hirata, K.; Saitoh, Y.; Chiba, A.; Yamada, K.; Matoba, S.; Narumi, K.

    2014-03-15

    We developed time-of-flight (TOF) secondary ion (SI) mass spectrometry that provides informative SI ion mass spectra without needing a sophisticated ion beam pulsing system. In the newly developed spectrometry, energetic large cluster ions with energies of the order of sub MeV or greater are used as primary ions. Because their impacts on the target surface produce high yields of SIs, the resulting SI mass spectra are informative. In addition, the start signals necessary for timing information on primary ion incidence are provided by the detection signals of particles emitted from the rear surface of foil targets upon transmission of the primary ions. This configuration allows us to obtain positive and negative TOF SI mass spectra without pulsing system, which requires precise control of the primary ions to give the spectra with good mass resolution. We also successfully applied the TOF SI mass spectrometry with energetic cluster ion impacts to the chemical structure characterization of organic thin film targets.

  4. Method of precisely modifying predetermined surface layers of a workpiece by cluster ion impact therewith

    DOEpatents

    Friedman, L.; Beuhler, R.J.; Matthew, M.W.; Ledbetter, M.

    1984-06-25

    A method of precisely modifying a selected area of a workpiece by producing a beam of charged cluster ions that is narrowly mass selected to a predetermined mean size of cluster ions within a range of 25 to 10/sup 6/ atoms per cluster ion, and accelerated in a beam to a critical velocity. The accelerated beam is used to impact a selected area of an outer surface of the workpiece at a preselected rate of impacts of cluster ions/cm/sup 2//sec in order to effect a precise modification in that selected area of the workpiece.

  5. Method of precisely modifying predetermined surface layers of a workpiece by cluster ion impact therewith

    DOEpatents

    Friedman, Lewis; Buehler, Robert J.; Matthew, Michael W.; Ledbetter, Myron

    1985-01-01

    A method of precisely modifying a selected area of a workpiece by producing a beam of charged cluster ions that is narrowly mass selected to a predetermined mean size of cluster ions within a range of 25 to 10.sup.6 atoms per cluster ion, and accelerated in a beam to a critical velocity. The accelerated beam is used to impact a selected area of an outer surface of the workpiece at a preselected rate of impacts of cluster ions/cm.sup.2 /sec. in order to effect a precise modification in that selected area of the workpiece.

  6. Nonlinear damage effect in graphene synthesis by C-cluster ion implantation

    SciTech Connect

    Zhang Rui; Zhang Zaodi; Wang Zesong; Wang Shixu; Wang Wei; Fu Dejun; Liu Jiarui

    2012-07-02

    We present few-layer graphene synthesis by negative carbon cluster ion implantation with C{sub 1}, C{sub 2}, and C{sub 4} at energies below 20 keV. The small C-clusters were produced by a source of negative ion by cesium sputtering with medium beam current. We show that the nonlinear effect in cluster-induced damage is favorable for graphene precipitation compared with monomer carbon ions. The nonlinear damage effect in cluster ion implantation shows positive impact on disorder reduction, film uniformity, and the surface smoothness in graphene synthesis.

  7. Evaluation of surface damage on organic materials irradiated with Ar cluster ion beam

    SciTech Connect

    Yamamoto, Y.; Ichiki, K.; Ninomiya, S.; Matsuo, J.; Seki, T.; Aoki, T.

    2011-01-07

    The sputtering yields of organic materials under large cluster ion bombardment are much higher than those under conventional monomer ion bombardment. The sputtering rate of arginine remains constant with fluence for an Ar cluster ion beam, but decreases with fluence for Ar monomer. Additionally, because Ar cluster etching induces little damage, Ar cluster ion can be used to achieve molecular depth profiling of organic materials. In this study, we evaluated the damage to poly methyl methacrylate (PMMA) and arginine samples irradiated with Ar atomic and Ar cluster ion beams. Arginine samples were analyzed by secondary ion mass spectrometry (SIMS) and PMMA samples were analyzed by X-ray photoelectron spectroscopy (XPS). The chemical structure of organic materials remained unchanged after Ar cluster irradiation, but was seriously damaged. These results indicated that bombardment with Ar cluster ions induced less surface damage than bombardment with Ar atomic ion. The damage layer thickness with 5 keV Ar cluster ion bombardment was less than 1 nm.

  8. Evaluation of surface damage on organic materials irradiated with Ar cluster ion beam

    NASA Astrophysics Data System (ADS)

    Yamamoto, Y.; Ichiki, K.; Ninomiya, S.; Seki, T.; Aoki, T.; Matsuo, J.

    2011-01-01

    The sputtering yields of organic materials under large cluster ion bombardment are much higher than those under conventional monomer ion bombardment. The sputtering rate of arginine remains constant with fluence for an Ar cluster ion beam, but decreases with fluence for Ar monomer. Additionally, because Ar cluster etching induces little damage, Ar cluster ion can be used to achieve molecular depth profiling of organic materials. In this study, we evaluated the damage to poly methyl methacrylate (PMMA) and arginine samples irradiated with Ar atomic and Ar cluster ion beams. Arginine samples were analyzed by secondary ion mass spectrometry (SIMS) and PMMA samples were analyzed by X-ray photoelectron spectroscopy (XPS). The chemical structure of organic materials remained unchanged after Ar cluster irradiation, but was seriously damaged. These results indicated that bombardment with Ar cluster ions induced less surface damage than bombardment with Ar atomic ion. The damage layer thickness with 5 keV Ar cluster ion bombardment was less than 1 nm.

  9. Computer simulations of cesium-water clusters: Do ion-water clusters form gas-phase clathrates?

    NASA Astrophysics Data System (ADS)

    Smith, David E.; Dang, Liem X.

    1994-11-01

    The structure and energetics of cesium ion-water clusters have been investigated using classical molecular dynamics computer simulations and a polarizable interaction model. Recent experiments by Selinger and Castleman [J. Phys. Chem. 95, 8442 (1991)] indicate that the mass-spectral distributions for these clusters exhibit ``magic number'' oscillations at temperatures below approximately 160 K. The observed behavior of this and related charged clusters is commonly attributed to the formation of clathratelike cage structures around a central ionic species. The relationship between the structural and energetic properties of cesium ion-water clusters is reported here as a function of temperature for clusters with between 18 and 22 water molecules. The clusters exhibit solidlike dynamical behavior at kinetic temperatures below about 170 K, and liquidlike behavior at higher temperatures. A thorough analysis of energy minimized (0 K) structures indicates that the most stable clusters consist of water cages surrounding the cesium ion. These cages are related to the proposed clathratelike structures but contain additional 4- and 6-membered water rings and fewer 5-membered rings. The calculated global energy minima exhibit an energetic alternation with cluster size that is consistent with the experimentally observed mass-spectral distributions. In contrast, in the liquidlike regime there are only minor variations in calculated structural and dynamical properties as a function of cluster size. In addition, there is no statistically significant size dependence for the cluster binding energies in the liquidlike regime that might be correlated with experimental data. These results suggest that magic number stability in ion-water clusters may occur only at ``low'' energies in the solidlike cluster regime.

  10. Analysis of cardiac tissue by gold cluster ion bombardment

    NASA Astrophysics Data System (ADS)

    Aranyosiova, M.; Chorvatova, A.; Chorvat, D.; Biro, Cs.; Velic, D.

    2006-07-01

    Specific molecules in cardiac tissue of spontaneously hypertensive rats are studied by using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The investigation determines phospholipids, cholesterol, fatty acids and their fragments in the cardiac tissue, with special focus on cardiolipin. Cardiolipin is a unique phospholipid typical for cardiomyocyte mitochondrial membrane and its decrease is involved in pathologic conditions. In the positive polarity, the fragments of phosphatydilcholine are observed in the mass region of 700-850 u. Peaks over mass 1400 u correspond to intact and cationized molecules of cardiolipin. In animal tissue, cardiolipin contains of almost exclusively 18 carbon fatty acids, mostly linoleic acid. Linoleic acid at 279 u, other fatty acids, and phosphatidylglycerol fragments, as precursors of cardiolipin synthesis, are identified in the negative polarity. These data demonstrate that SIMS technique along with Au 3+ cluster primary ion beam is a good tool for detection of higher mass biomolecules providing approximately 10 times higher yield in comparison with Au +.

  11. Ion dip spectroscopy of van der Waals clusters

    SciTech Connect

    Stanley, R.J.; Castleman, A.W. Jr. )

    1990-05-15

    We report the implementation of ion dip spectroscopy in a supersonic molecular beam time-of-flight mass spectrometer as a powerful mass-selective method for observing ground-state vibrational levels in van der Waals clusters. Ion dip spectra of phenylacetylene and phenylacetylene-NH{sub 3} are demonstrated in the range of 900--1100 cm{sup {minus}1}, showing prominent dips at 978.0, 1002.8, and 1028.0 cm{sup {minus}1}. These dips have been tentatively assigned as 13{sup 0}{sub 1} 35{sup 1}{sub 1}, 11{sup 0}{sub 1} 35{sup 1}{sub 0}, and 35{sup 1}{sub 2}, respectively, in phenylacetylene. Shifts in the 35{sup 1}{sub 2} and 11{sup 0}{sub 1}35{sup 1}{sub 0} vibrational bands of the complex are observed while the 13{sup 0}{sub 1}35{sup 1}{sub 1} band of the complex is either shifted or attenuated.

  12. Charged particles and cluster ions produced during cooking activities.

    PubMed

    Stabile, L; Jayaratne, E R; Buonanno, G; Morawska, L

    2014-11-01

    Previous studies showed that a significant number of the particles present in indoor air are generated by cooking activities, and measured particle concentrations and exposures have been used to estimate the related human dose. The dose evaluation can be affected by the particle charge level which is usually not considered in particle deposition models. To this purpose, in this paper we show, for the very first time, the electric charge of particles generated during cooking activities and thus extending the interest on particle charging characterization to indoor micro-environments, so far essentially focused on outdoors. Particle number, together with positive and negative cluster ion concentrations, was monitored using a condensation particle counter and two air ion counters, respectively, during different cooking events. Positively-charged particle distribution fractions during gas combustion, bacon grilling, and eggplant grilling events were measured by two Scanning Mobility Particle Sizer spectrometers, used with and without a neutralizer. Finally, a Tandem Differential Mobility Analyzer was used to measure the charge specific particle distributions of bacon and eggplant grilling experiments, selecting particles of 30, 50, 80 and 100 nm in mobility diameter. The total fraction of positively-charged particles was 4.0%, 7.9%, and 5.6% for gas combustion, bacon grilling, and eggplant grilling events, respectively, then lower than other typical outdoor combustion-generated particles.

  13. Formation of cold ion-neutral clusters using superfluid helium nanodroplets

    NASA Astrophysics Data System (ADS)

    Falconer, Travis M.; Lewis, William K.; Bemish, Raymond J.; Miller, Roger E.; Glish, Gary L.

    2010-05-01

    A strategy for forming and detecting cold ion-neutral clusters using superfluid helium nanodroplets is described. Sodium cations generated via thermionic emission are directed toward a beam of helium droplets that can also pick up neutral molecules and form a cluster with the captured Na+. The composition of the clusters is determined by mass spectrometric analysis following a desolvation step. It is shown that the polar molecules H2O and HCN are picked up and form ion-neutral clusters with sizes and relative abundances that are in good agreement with those predicted by the statistics used to describe neutral cluster formation in helium droplets. [Na(H2O)n]+ clusters containing six to 43 water molecules were observed, a size range of sodiated water clusters difficult to access in the gas phase. Clusters containing N2 were in lower abundance than expected, suggesting that the desolvation process heats the clusters sufficiently to dissociate those containing nonpolar molecules.

  14. A dual cryogenic ion trap spectrometer for the formation and characterization of solvated ionic clusters

    NASA Astrophysics Data System (ADS)

    Marsh, Brett M.; Voss, Jonathan M.; Garand, Etienne

    2015-11-01

    A new experimental approach is presented in which two separate cryogenic ion traps are used to reproducibly form weakly bound solvent clusters around electrosprayed ions and messenger-tag them for single-photon infrared photodissociation spectroscopy. This approach thus enables the vibrational characterization of ionic clusters comprised of a solvent network around large and non-volatile ions. We demonstrate the capabilities of the instrument by clustering water, methanol, and acetone around a protonated glycylglycine peptide. For water, cluster sizes with greater than twenty solvent molecules around a single ion are readily formed. We further demonstrate that similar water clusters can be formed around ions having a shielded charge center or those that do not readily form hydrogen bonds. Finally, infrared photodissociation spectra of D2-tagged GlyGlyH+ ṡ (H2O)1-4 are presented. They display well-resolved spectral features and comparisons with calculations reveal detailed information on the solvation structures of this prototypical peptide.

  15. Modeling the formation of ion clusters by applying classical nucleation theory

    NASA Astrophysics Data System (ADS)

    Yue, G. K.

    Experiments have been conducted to study the clustering of atmospheric trace gases around ion cores (Castleman and Tang, 1972; Searcy and Fenn, 1974; Castleman, 1978). The classical liquid-drop model is used to investigate this ion-induced formation mechanism. Results obtained from models of the distribution of Pb(+)-(H2O)n and H(+)-(H2O)n type clusters under various conditions are compared with experimental results. The distribution of water-ion clusters in the atmosphere as a function of altitude is calculated. In situ measurements of the water-ion cluster distributions in the upper atmosphere are then compared with present predictions. It is concluded that the classical nucleation theory can be used to predict rough estimates for ion cluster sizes under many conditions.

  16. Modeling the formation of ion clusters by applying classical nucleation theory. [aerosol mechanisms

    NASA Technical Reports Server (NTRS)

    Yue, G. K.

    1981-01-01

    Experiments have been conducted to study the clustering of atmospheric trace gases around ion cores (Castleman and Tang, 1972; Searcy and Fenn, 1974; Castleman, 1978). The classical liquid-drop model is used to investigate this ion-induced formation mechanism. Results obtained from models of the distribution of Pb(+)-(H2O)n and H(+)-(H2O)n type clusters under various conditions are compared with experimental results. The distribution of water-ion clusters in the atmosphere as a function of altitude is calculated. In situ measurements of the water-ion cluster distributions in the upper atmosphere are then compared with present predictions. It is concluded that the classical nucleation theory can be used to predict rough estimates for ion cluster sizes under many conditions.

  17. Range of plasma ions in cold cluster gases near the critical point

    NASA Astrophysics Data System (ADS)

    Zhang, G.; Quevedo, H. J.; Bonasera, A.; Donovan, M.; Dyer, G.; Gaul, E.; Guardo, G. L.; Gulino, M.; La Cognata, M.; Lattuada, D.; Palmerini, S.; Pizzone, R. G.; Romano, S.; Smith, H.; Trippella, O.; Anzalone, A.; Spitaleri, C.; Ditmire, T.

    2017-05-01

    We measure the range of plasma ions in cold cluster gases by using the Petawatt laser at the University of Texas-Austin. The produced plasma propagated in all directions some hitting the cold cluster gas not illuminated by the laser. From the ratio of the measured ion distributions at different angles we can estimate the range of the ions in the cold cluster gas. It is much smaller than estimated using popular models, which take only into account the slowing down of charged particles in uniform matter. We discuss the ion range in systems prepared near a liquid-gas phase transition.

  18. Cluster ion beam process technology 20 years of R&D history

    NASA Astrophysics Data System (ADS)

    Yamada, Isao

    2007-04-01

    More than 20 years have passed since the author first began to explore the feasibility of processing by gas cluster ion beams at the Ion Beam Engineering Experimental Laboratory of Kyoto University. Processes employing ions of gaseous material clusters comprised of a few hundred to many thousand atoms are now being developed into a new field of ion beam technology. Cluster-surface collisions produce important non-linear effects which are being applied to shallow junction formation, to etching and smoothing of semiconductors, metals and dielectrics, to assisted formation of thin films with nano-scale accuracy and to other surface modification applications.

  19. Ligand induced structural isomerism in phosphine coordinated gold clusters revealed by ion mobility mass spectrometry

    SciTech Connect

    Ligare, Marshall R.; Baker, Erin S.; Laskin, Julia; Johnson, Grant E.

    2017-01-01

    Structural isomerism in ligated gold clusters is revealed using electrospray ionization ion mobility spectrometry mass spectrometry. Phosphine ligated Au8 clusters are shown to adopt more “extended” type structures with increasing exchange of methyldiphenylphosphine (MePPh2) for triphenylphosphine (PPh3). These ligand-dependant structure-property relationships are critical to applications of clusters in catalysis.

  20. New gas phase inorganic ion cluster species and their atmospheric implications

    NASA Technical Reports Server (NTRS)

    Maerk, T. D.; Peterson, K. I.; Castleman, A. W., Jr.

    1980-01-01

    Recent experimental laboratory observations, with high-pressure mass spectroscopy, have revealed the existence of previously unreported species involving water clustered to sodium dimer ions, and alkali metal hydroxides clustered to alkali metal ions. The important implications of these results concerning the existence of such species are here discussed, as well as how from a practical aspect they confirm the stability of certain cluster species proposed by Ferguson (1978) to explain masses recently detected at upper altitudes using mass spectrometric techniques.

  1. Traveling Wave Ion Mobility Mass Spectrometry and Ab Initio Calculations of Phosphoric Acid Clusters

    NASA Astrophysics Data System (ADS)

    Lavanant, Hélène; Tognetti, Vincent; Afonso, Carlos

    2014-04-01

    Positive and negative ion electrospray mass spectra obtained from 50 mM phosphoric acid solutions presented a large number of phosphoric acid clusters: [(H3PO4)n + zH] z+ or [(H3PO4)n - zH] z- , with n up to 200 and z up to 4 for positively charged clusters, and n up to 270 and z up to 7 for negatively charged cluster ions. Ion mobility experiments allowed very explicit separation of the different charge states. Because of the increased pressures involved in ion mobility experiments, dissociation to smaller clusters was observed both in the trap and transfer areas. Voltages along the ion path could be optimized so as to minimize this effect, which can be directly associated with the cleavage of hydrogen bonds. Having excluded the ion mobility times that resulted from dissociated ions, each cluster ion appeared at a single drift time. These drift times showed a linear progression with the number of phosphoric atoms for cluster ions of the same charge state. Cross section calculations were carried out with MOBCAL on DFT optimized geometries with different hydrogen locations and with three types of atomic charges. DFT geometry optimizations yielded roughly spherical structures. Our results for nitrogen gas interaction cross sections showed that values were dependent on the atomic charges definition used in the MOBCAL calculation. This pinpointed the necessity to define a clear theoretical framework before any comparative interpretations can be attempted with uncharacterized compounds.

  2. Enhancing secondary ion yields in time of flight-secondary ion mass spectrometry using water cluster primary beams.

    PubMed

    Sheraz née Rabbani, Sadia; Barber, Andrew; Fletcher, John S; Lockyer, Nicholas P; Vickerman, John C

    2013-06-18

    Low secondary ion yields from organic and biological molecules are the principal limitation on the future exploitation of time of flight-secondary ion mass spectrometry (TOF-SIMS) as a surface and materials analysis technique. On the basis of the hypothesis that increasing the density of water related fragments in the ion impact zone would enhance proton mediated reactions, a prototype water cluster ion beam has been developed using supersonic jet expansion methodologies that enable ion yields using a 10 keV (H2O)1000(+) beam to be compared with those obtained using a 10 keV Ar1000(+) beam. The ion yields from four standard compounds, arginine, haloperidol, DPPC, and angiotensin II, have been measured under static+ and high ion dose conditions. Ion yield enhancements relative to the argon beam on the order of 10 or more have been observed for all the compounds such that the molecular ion yield per a 1 μm pixel can be as high as 20, relative to 0.05 under an argon beam. The water beam has also been shown to partially lift the matrix effect in a 1:10 mixture of haloperidol and dipalmitoylphosphatidylcholine (DPPC) that suppresses the haloperidol signal. These results provide encouragement that further developments of the water cluster beam to higher energies and larger cluster sizes will provide the ion yield enhancements necessary for the future development of TOF-SIMS.

  3. Modified Kelvin-Thomson equation considering ion-dipole interaction: Comparison with observed ion-clustering enthalpies and entropies

    NASA Astrophysics Data System (ADS)

    Yu, Fangqun

    2005-02-01

    The classical Kelvin-Thomson (CKT) equation does not consider the interaction of condensing molecules with the ions and hence is not able to treat polar and nonpolar molecules differently. The ion-clustering enthalpy and entropy changes predicted by CKT equation for small ions are known to be significantly less negative than those observed. In this paper, we derive a modified Kelvin-Thomson (MKT) equation, which considers the effect of dipole-ion interaction, by taking into account the kinetic energy change of condensing polar ligands as they approach the ions or the extra energy needed for dipole molecules to escape from the ion cluster. The clustering enthalpies and entropies for protonated clusters (H+Ln, with L =H2O, NH3, CH3OH, and C5H5N) are calculated based on MKT equation and compared with experimental data. Our calculations indicate that enthalpy values given by MKT equation are in very good agreement with experimental results for small ions (n ⩽5) of all four species investigated. MKT predictions appear to be consistent with observed enthalpies for CH3OH at n ⩾6 and for H2O at n =14-25, however, MKT equation cannot reproduce the observed discontinuous transition in enthalpy changes at n =6 for NH3 and at n =7-13 for H2O which is probably associated with the formation of inner shell. The stepwise entropy changes for small ions are 5-15cal mol-1K-1 more negative when the effect of dipole-ion interaction is considered, which suggests that the ordered structure of the cluster ions can somewhat be accounted for by the dipole-ion interaction term.

  4. Modified Kelvin-Thomson equation considering ion-dipole interaction: comparison with observed ion-clustering enthalpies and entropies.

    PubMed

    Yu, Fangqun

    2005-02-22

    The classical Kelvin-Thomson (CKT) equation does not consider the interaction of condensing molecules with the ions and hence is not able to treat polar and nonpolar molecules differently. The ion-clustering enthalpy and entropy changes predicted by CKT equation for small ions are known to be significantly less negative than those observed. In this paper, we derive a modified Kelvin-Thomson (MKT) equation, which considers the effect of dipole-ion interaction, by taking into account the kinetic energy change of condensing polar ligands as they approach the ions or the extra energy needed for dipole molecules to escape from the ion cluster. The clustering enthalpies and entropies for protonated clusters (H(+)L(n), with L=H(2)O, NH(3), CH(3)OH, and C(5)H(5)N) are calculated based on MKT equation and compared with experimental data. Our calculations indicate that enthalpy values given by MKT equation are in very good agreement with experimental results for small ions (n< or =5) of all four species investigated. MKT predictions appear to be consistent with observed enthalpies for CH(3)OH at n> or =6 and for H(2)O at n=14-25, however, MKT equation cannot reproduce the observed discontinuous transition in enthalpy changes at n=6 for NH(3) and at n=7-13 for H(2)O which is probably associated with the formation of inner shell. The stepwise entropy changes for small ions are 5-15 cal mol(-1) K(-1) more negative when the effect of dipole-ion interaction is considered, which suggests that the ordered structure of the cluster ions can somewhat be accounted for by the dipole-ion interaction term.

  5. Mixed clusters from the coexpansion of C2F6 and n2 in a pulsed, supersonic expansion cluster ion source and beam deflection time-of-flight mass spectrometer: A first application

    NASA Astrophysics Data System (ADS)

    Thompson, Steven D.

    The following topics are discussed: (1) cluster ion genesis; (2) cluster ion detection; (3) Ion source; (4) pulse valve; (5) e-gun; (6) Ion optics; (7) a first order model; and (8) a modified Bakker's model.

  6. Incorporation of sulfide ions into the cadmium(II) thiolate cluster of Cicer arietinum metallothionein2.

    PubMed

    Wan, Xiaoqiong; Freisinger, Eva

    2013-01-18

    The plant metallothionein2 from Cicer arietinum (chickpea), cic-MT2, is known to coordinate five divalent metal ions such as Zn(II) or Cd(II), which are arranged in a single metal thiolate cluster. When the Zn(II) form of the protein is titrated with Cd(II) ions in the presence of sulfide ions, an increased Cd(II) binding capacity and concomitant incorporation of sulfide ions into the cluster are observed. The exact stoichiometry of this novel cluster, its spectroscopic properties, and the significantly increased pH stability are analyzed with different techniques, including UV and circular dichroism spectroscopy and colorimetric assays. Limited proteolytic digestion provides information about the spacial arrangement of the cluster within the protein. Increasing the Cd(II) scavenging properties of a metallothionein by additionally recruiting sulfide ions might be an economic and very efficient detoxification strategy for plants.

  7. Ionization and fragmentation of cold clusters of PAH molecules - collisions with keV ions

    NASA Astrophysics Data System (ADS)

    Holm, A. I. S.; Zettergren, H.; Gatchell, M.; Johansson, H. A. B.; Seitz, F.; Schmidt, H. T.; Rousseau, P.; Ławicki, A.; Capron, M.; Domaracka, A.; Lattouf, E.; Maclot, S.; Maisonny, R.; Chesnel, J.-Y.; Manil, B.; Adoui, L.; Huber, B. A.; Cederquist, H.

    2012-11-01

    We discuss the ionization and fragmentation of isolated monomers and cold clusters of polycyclic aromatic hydrocarbon (PAH) molecules in collisions with keV ions in low or high charge states. With low charge state projectile ions, PAH cluster or monomer targets are thermally excited through electronic stopping processes directly in close peripheral or penetrating collisions while only single or few electrons are removed. With high charge state projectiles, electrons are very effectively removed from both the cluster and the monomer target already at very large distances with very little direct target heating. Singly charged and internally very hot PAH monomers are dominant fragmentation products following collisions between Xe20+ ions and PAH clusters. We suggest that this due to an unusually strong dominance of multiple-ionization over single ionization for PAH clusters interacting with highly charged ions. Here, charge and excitation energy is very rapidly redistributed within the clusters before they Coulomb explode and we suggest that these Coulomb explosions induce strong internal heating in the individual PAH molecules. We thus conclude that PAH cluster fragmentation always dominates strongly for all ionization processes regardless if these are due to interactions with ions in high or low charge states. These findings are discussed in view of simple models for cluster evaporation or single and multiple ionizations of PAH clusters.

  8. Highly charged ions from laser-cluster interactions: local-field-enhanced impact ionization and frustrated electron-ion recombination.

    PubMed

    Fennel, Thomas; Ramunno, Lora; Brabec, Thomas

    2007-12-07

    Our molecular dynamics analysis of Xe_{147-5083} clusters identifies two mechanisms that contribute to the yet unexplained observation of extremely highly charged ions in intense laser cluster experiments. First, electron impact ionization is enhanced by the local cluster electric field, increasing the highest charge states by up to 40%; a corresponding theoretical method is developed. Second, electron-ion recombination after the laser pulse is frustrated by acceleration electric fields typically used in ion detectors. This increases the highest charge states by up to 90%, as compared to the usual assumption of total recombination of all cluster-bound electrons. Both effects together augment the highest charge states by up to 120%, in reasonable agreement with experiments.

  9. Highly Charged Ions from Laser-Cluster Interactions: Local-Field-Enhanced Impact Ionization and Frustrated Electron-Ion Recombination

    SciTech Connect

    Fennel, Thomas; Ramunno, Lora; Brabec, Thomas

    2007-12-07

    Our molecular dynamics analysis of Xe{sub 147-5083} clusters identifies two mechanisms that contribute to the yet unexplained observation of extremely highly charged ions in intense laser cluster experiments. First, electron impact ionization is enhanced by the local cluster electric field, increasing the highest charge states by up to 40%; a corresponding theoretical method is developed. Second, electron-ion recombination after the laser pulse is frustrated by acceleration electric fields typically used in ion detectors. This increases the highest charge states by up to 90%, as compared to the usual assumption of total recombination of all cluster-bound electrons. Both effects together augment the highest charge states by up to 120%, in reasonable agreement with experiments.

  10. Doping of Cn (N = 1, 3, 5, 8) cluster ion tracks in polyimide

    NASA Astrophysics Data System (ADS)

    Fink, D.; Klett, R.; Chung, W. H.; Grünwald, R.; Döbeli, M.; Ames, F.; Chadderton, L. T.; Vacik, J.; Hnatowicz, V.

    Cn+ cluster ions (n = 1, 3, 5, and 8) are implanted at 1 MeV/carbon atom and at fluences of 1010 to 1014 cluster ions/cm2 into thin polyimide foils. The ion-induced radiochemical changes are examined by infrared spectroscopy. The samples are then doped with either aqueous LiCl, or methylene blue dye solutions. The dopant uptake is determined by UV-Vis spectrometry in the first, and by NDP (neutron depth profiling) in the latter case. NDP examinations additionally give information about the depth distributions of the incorporated Li+ ions. Remarkable changes in the infrared signals and in the dopant uptake are found only at fluences when ion track overlapping sets in. For the same fluence, clusters with larger size show more efficient destruction than smaller ones. Also the dopant uptake capability is higher in cluster-irradiated polymers than in single-atomic C+ ion irradiated samples. The depth distribution of the incorporated dopant usually consists of both a pronounced surface-near, and a bulk dopant-enriched region. The surface-near dopant profile increases in height and width with increasing cluster size and fluence. The depth profile shape of the bulk component follows the one of the ion's energy transfer to the target via nuclear collisions. A rule of thumb to describe the action of such a cluster ion onto polymers is given.

  11. Ion-Molecule Clustering in Differential Mobility Spectrometry: Lessons Learned from Tetraalkylammonium Cations and their Isomers

    NASA Astrophysics Data System (ADS)

    Campbell, J. Larry; Zhu, Mabel; Hopkins, W. Scott

    2014-09-01

    Differential mobility spectrometry (DMS) can distinguish ions based upon the differences in their high- and low-field ion mobilities as they experience the asymmetric waveform applied to the DMS cell. These mobilities are known to be influenced by the ions' structure, m/z, and charge distribution (i.e., resonance structures) within the ions themselves, as well as by the gas-phase environment of the DMS cell. While these associations have been developed over time through empirical observations, the exact role of ion structures or their interactions with clustering molecules remains generally unknown. In this study, that relationship is explored by observing the DMS behaviors of a series of tetraalkylammonium ions as a function of their structures and the gas-phase environment of the DMS cell. To support the DMS experiments, the basin-hopping search strategy was employed to identify candidate cluster structures for density functional theory treatment. More than a million cluster structures distributed across 72 different ion-molecule cluster systems were sampled to determine global minimum structures and cluster binding energies. This joint computational and experimental approach suggests that cluster geometry, in particular ion-molecule intermolecular separation, plays a critical role in DMS.

  12. X-ray photoelectron spectroscopy study of polyimide thin films with Ar cluster ion depth profiling

    SciTech Connect

    Miyayama, T.; Sanada, N.; Suzuki, M.; Hammond, J. S.; Si, S.-Q. D.; Takahara, A.

    2010-03-15

    X-ray photoelectron spectroscopy depth profiling of polyimide thin films on silicon substrates using an Ar cluster ion beam results in an extremely low degradation of the polyimide chemistry. In the range from 2.5 to 20 kV, a lower cluster ion energy produces a lower sputter induced damage to the polymer and results in an improved polyimide to silicon interface width. The sputtering rates of the polyimide are found to increase exponentially with an increase in the Ar cluster ion energy.

  13. Ion acceleration in the interaction of short pulse laser radiation with the cluster-gas target

    SciTech Connect

    Fukuda, Y.; Tampo, M.; Nakamura, T.; Kando, M.; Hayashi, Y.; Yogo, A.; Sakaki, H.; Kameshima, T.; Pirozhkov, A. S.; Ogura, K.; Mori, M.; Esirkepov, T. Zh.; Bolton, P. R.; Daido, H.; Faenov, A. Ya.; Pikuz, T. A.; Boldarev, A. S.; Gasilov, V. A.; Magunov, A. I.; Kodama, R.

    2009-07-25

    We demonstrate generation of 10-20 MeV/u ions with a compact 4 TW laser using a gas target mixed with submicron clusters, corresponding to tenfold increase in the ion energies compared to previous experiments with solid targets. It is inferred that the high energy ions are generated due to formation of a strong dipole vortex structure. The demonstrated method has a potential to construct compact and high repetition rate ion sources for hadron therapy and other applications.

  14. Electron exchange between an H - ion and a spherical cluster of aluminum atoms

    NASA Astrophysics Data System (ADS)

    Shestakov, D. K.; Polivnikova, T. Yu.; Gainullin, I. K.; Urazgildin, I. F.

    2009-08-01

    The resonant charge transfer (RCT) between a hydrogen anion and a cluster of aluminum atoms is investigated by means of the wave-packet propagation method that does not exploit the perturbation theory. The RCT on a spherical cluster is found to exhibit quantum size effects due to the finite size of the cluster. The survival amplitude of an ion state has been calculated as a function of the distance to the ion-surface in a normal collision. It is shown that depending on the velocity of the impinging particle, the cluster can behave either as a bulk metal or as a quantum structure with discrete energy states existing over two coordinates.

  15. Multiphoton ionization of acetone clusters: Metastable unimolecular decomposition of acetone cluster ions and the influence of solvation on intracluster ion-molecule reactions

    SciTech Connect

    Tzeng, W.B.; Wei, S.; Castleman, A.W. Jr. )

    1989-08-02

    A comprehensive investigation of the reactions of acetone ions in clusters was made to investigate and compare the similarities and differences in the ion reactions due to solvation effects. Neutral acetone clusters, prepared in a pulsed nozzle supersonic expansion, are ionized using multiphoton ionization and investigated using a time-of-flight reflectron technique. The observed major cluster ions resulting from prompt fragmentation following ionization are ((CH{sub 3}){sub 2}CO){sub m} {times} H{sup +} (m = 1-15), ((CH{sub 3}){sub 2}CO){sub m} {times} C{sub 2}H{sub 3}O{sup +} (m = 1-17), and ((CH{sub 3}){sub 2}CO){sub m} {times} CH{sub 3}{sup +} (m = 1-10). In a time window of a few tens of microseconds, all three classes of cluster ions unimolecularly decompose, losing only one acetone monomer. Interestingly, a reaction corresponding to the dehydration of ((CH{sub 3}){sub 2}CO){sub m} {times} H{sup +} and leading to the production of ((CH{sub 3}){sub 2}CO){sub m-2} {times} C{sub 6}H{sub 11}O{sup +} is observed for m = 2-6. The most striking finding of the present study is that the presence of water molecules in a cluster suppresses the dehydration reaction. This finding clarifies the discrepancy between earlier studies reported in the literature and, most importantly, provides further evidence for the influence of a solvent on ion reactions in clusters, and ion-molecule reactions in general.

  16. Surface collisions of small cluster ions at incident energies 10-102 eV

    NASA Astrophysics Data System (ADS)

    Herman, Zdenek

    2004-04-01

    A short review of the field of collisions of slow cluster ions with surfaces is presented. The main subject of the paper is a survey of results of a series of studies on slow cluster ion collisions with surfaces carried out in Innsbruck. In these studies the incident ions were fullerene multiply-charged ions and small cluster ions of polyatomic molecules (acetone and acetonitrile radical cations, protonated ethanol, clustered by 2-4 monomer molecules). For collisions of multiply-charged fullerene cations C60z+ (z from 1 to 5, incident energies 100-500 eV) only singly-charged product ions were observed which were formed by sequential loss of C2 units. The effect of multiple-charge of the projectile on its fragmentation was less pronounced than expected from a full conversion of electronic energy gained in the surface neutralization process. Fragmentation upon surface collision excitation of acetone, acetonitrile and protonated ethanol cluster ions (incident energies 10-80 eV) was found to follow the unimolecular dissociation kinetics. Formation of protonated monomers in collisions of acetone and acetonitrile stoechiometric clusters resulted both from an intra-cluster reaction and from a reaction of the monomer product ion with the surface hydrogen; it could be rationalized using the double-well potential model. Incident energy dependence of relative abundance of dissociation products from surface collisions of protonated ethanol trimers, dimers and monomers could be mutually rationalized, if the fraction of energy transformed in the surface collision into internal energy was related to one internal degree of freedom. A diagram resembling a break-down pattern of the projectile ion was obtained in this way. All internal degrees of freedom of the projectile ion seemed to be involved in the unimolecular dissociation kinetics.

  17. How to reliably detect molecular clusters and nucleation mode particles with Neutral cluster and Air Ion Spectrometer (NAIS)

    NASA Astrophysics Data System (ADS)

    Manninen, Hanna E.; Mirme, Sander; Mirme, Aadu; Petäjä, Tuukka; Kulmala, Markku

    2016-08-01

    To understand the very first steps of atmospheric particle formation and growth processes, information on the size where the atmospheric nucleation and cluster activation occurs, is crucially needed. The current understanding of the concentrations and dynamics of charged and neutral clusters and particles is based on theoretical predictions and experimental observations. This paper gives a standard operation procedure (SOP) for Neutral cluster and Air Ion Spectrometer (NAIS) measurements and data processing. With the NAIS data, we have improved the scientific understanding by (1) direct detection of freshly formed atmospheric clusters and particles, (2) linking experimental observations and theoretical framework to understand the formation and growth mechanisms of aerosol particles, and (3) parameterizing formation and growth mechanisms for atmospheric models. The SOP provides tools to harmonize the world-wide measurements of small clusters and nucleation mode particles and to verify consistent results measured by the NAIS users. The work is based on discussions and interactions between the NAIS users and the NAIS manufacturer.

  18. Compact non-rock-salt structures in sodium fluoride cluster ions at specific sizes revealed by ion mobility mass spectrometry.

    PubMed

    Ohshimo, Keijiro; Takahashi, Tohru; Moriyama, Ryoichi; Misaizu, Fuminori

    2014-10-30

    Structures of small sodium fluoride cluster cations, Na(n)F(n-1)(+), have been determined for n = 5-23 by ion mobility mass spectrometry. In the mass spectrum of Na(n)F(n-1)(+) cluster ions measured after collisions in the ion-drift cell, cuboid ions with near-regular hexahedron such as n = 14 (3 × 3 × 3), 23 (3 × 3 × 5), 38 (3 × 5 × 5), 63 (5 × 5 × 5), and 88 (5 × 5 × 7) were predominantly observed as magic numbers. By comparison of the collision cross sections obtained from the ion mobility measurements with theoretical ones, we have experimentally shown that the ions of n = 7 and 10 have stable non-rock-salt type structures in which one sodium atom is encapsulated into the sodium fluoride cuboid lattice. The collision cross sections of n = 12 and 13 are almost equal to that of the n = 14 cuboid. A similar feature was also observed in collision cross sections of n = 21 and 22, which are equal to that of the n = 23 cuboid. These features indicate that the cluster ions of n = 12, 13, 21, and 22 have near-cuboid structures with some surface defects.

  19. Probing thin over layers with variable energy/cluster ion beams

    NASA Astrophysics Data System (ADS)

    Spool, A.; White, R.

    2006-07-01

    A series of carbon-coated magnetic recording disks proved ideal for exploring sampling depth and ion formation trends as a function of variations in energy and cluster size (Au x) of the primary ion beam, and variations in over coat thickness and type. Ion yield from the underlying metal layer increased with increasing energy and decreasing cluster size of the primary ions. The yields varied nearly linearly with over layer thickness. In contrast, M xCs y depth profiles were unaffected by changes in the primary ion. The samples were fortuitously dosed with dinonyl phthalate, allowing a study similar to prior GSIMS work [I.S. Gilmore, M.P. Seah, J.E. Johnstone, in: A. Benninghoven, P. Bertrand, H.-N. Migeon, H.W. Werner (Eds.), Proceedings of the 12th International Conference on SIMS, Elsevier, Brussels, 2000, p. 801]. Ions prominent in the EI mass spectrum, including even electron ions, were more consistently enhanced at lower energies and higher cluster sizes than the primary ( M + H) + ion. The total secondary ion count was inversely proportional to the film thickness. Secondary electrons, largely originating in the buried metal layer, may be inducing organic ion formation [A.M. Spool, Surf. Interface Anal. 36 (2004) 264].

  20. Monte Carlo Simulation of Ion Trajectories of Reacting Chemical Systems: Mobility of Small Water Clusters in Ion Mobility Spectrometry

    NASA Astrophysics Data System (ADS)

    Wissdorf, Walter; Seifert, Luzia; Derpmann, Valerie; Klee, Sonja; Vautz, Wolfgang; Benter, Thorsten

    2013-04-01

    For the comprehensive simulation of ion trajectories including reactive collisions at elevated pressure conditions, a chemical reaction simulation (RS) extension to the popular SIMION software package was developed, which is based on the Monte Carlo statistical approach. The RS extension is of particular interest to SIMION users who wish to simulate ion trajectories in collision dominated environments such as atmospheric pressure ion sources, ion guides (e.g., funnels, transfer multi poles), chemical reaction chambers (e.g., proton transfer tubes), and/or ion mobility analyzers. It is well known that ion molecule reaction rate constants frequently reach or exceed the collision limit obtained from kinetic gas theory. Thus with a typical dwell time of ions within the above mentioned devices in the ms range, chemical transformation reactions are likely to occur. In other words, individual ions change critical parameters such as mass, mobility, and chemical reactivity en passage to the analyzer, which naturally strongly affects their trajectories. The RS method simulates elementary reaction events of individual ions reflecting the behavior of a large ensemble by a representative set of simulated reacting particles. The simulation of the proton bound water cluster reactant ion peak (RIP) in ion mobility spectrometry (IMS) was chosen as a benchmark problem. For this purpose, the RIP was experimentally determined as a function of the background water concentration present in the IMS drift tube. It is shown that simulation and experimental data are in very good agreement, demonstrating the validity of the method.

  1. Monte Carlo simulation of ion trajectories of reacting chemical systems: mobility of small water clusters in ion mobility spectrometry.

    PubMed

    Wissdorf, Walter; Seifert, Luzia; Derpmann, Valerie; Klee, Sonja; Vautz, Wolfgang; Benter, Thorsten

    2013-04-01

    For the comprehensive simulation of ion trajectories including reactive collisions at elevated pressure conditions, a chemical reaction simulation (RS) extension to the popular SIMION software package was developed, which is based on the Monte Carlo statistical approach. The RS extension is of particular interest to SIMION users who wish to simulate ion trajectories in collision dominated environments such as atmospheric pressure ion sources, ion guides (e.g., funnels, transfer multi poles), chemical reaction chambers (e.g., proton transfer tubes), and/or ion mobility analyzers. It is well known that ion molecule reaction rate constants frequently reach or exceed the collision limit obtained from kinetic gas theory. Thus with a typical dwell time of ions within the above mentioned devices in the ms range, chemical transformation reactions are likely to occur. In other words, individual ions change critical parameters such as mass, mobility, and chemical reactivity en passage to the analyzer, which naturally strongly affects their trajectories. The RS method simulates elementary reaction events of individual ions reflecting the behavior of a large ensemble by a representative set of simulated reacting particles. The simulation of the proton bound water cluster reactant ion peak (RIP) in ion mobility spectrometry (IMS) was chosen as a benchmark problem. For this purpose, the RIP was experimentally determined as a function of the background water concentration present in the IMS drift tube. It is shown that simulation and experimental data are in very good agreement, demonstrating the validity of the method.

  2. Uranyl peroxide oxalate cage and core-shell clusters containing 50 and 120 uranyl ions.

    PubMed

    Ling, Jie; Qiu, Jie; Burns, Peter C

    2012-02-20

    Cage clusters built from uranyl hexagonal bipyramids and oxalate ligands crystallize from slightly acidic aqueous solution under ambient conditions, facilitating structure analysis. Each cluster contains uranyl ions coordinated by peroxo ligands in a bidentate configuration. Uranyl ions are bridged by shared peroxo ligands, oxalate ligands, or through hydroxyl groups. U(50)Ox(20) contains 50 uranyl ions and 20 oxalate groups and is a topological derivative of the U(50) cage cluster that has a fullerene topology. U(120)Ox(90) contains 120 uranyl ions and 90 oxalate groups and is the largest and highest mass cluster containing uranyl ions that has been reported. It has a core-shell structure, in which the inner shell (core) consists of a cluster of 60 uranyl ions and 30 oxalate groups, identical to U(60)Ox(30), with a fullerene topology. The outer shell contains 12 identical units that each consist of five uranyl hexagonal bipyramids that are linked to form a ring (topological pentagon), with each uranyl ion also coordinated by a side-on nonbridging oxalate group. The five-membered rings of the inner and outer shells (the topological pentagons) are in correspondence and are linked through K cations. The inner shell topology has therefore templated the location of the outer shell rings, and the K counterions assume a structure-directing role. Small-angle X-ray scattering data demonstrated U(50)Ox(20) remains intact in aqueous solution upon dissolution. In the case of clusters of U(120)Ox(90), the scattering data for dissolved crystals indicates the U(60)Ox(30) core persists in solution, although the outer rings of uranyl bipyramids contained in the U(120)Ox(90) core-shell cluster appear to detach from the cluster when crystals are dissolved in water.

  3. XPS investigation of monatomic and cluster argon ion sputtering of tantalum pentoxide

    NASA Astrophysics Data System (ADS)

    Simpson, Robin; White, Richard G.; Watts, John F.; Baker, Mark A.

    2017-05-01

    In recent years, gas cluster ion beams (GCIB) have become the cutting edge of ion beam technology to sputter etch organic materials in surface analysis. However, little is currently known on the ability of argon cluster ions (Arn+) to etch metal oxides and other technologically important inorganic compounds and no depth profiles have previously been reported. In this work, XPS depth profiles through a certified (European standard BCR-261T) 30 nm thick Ta2O5 layer grown on Ta foil using monatomic Ar+ and Ar1000+ cluster ions have been performed at different incident energies. The preferential sputtering of oxygen induced using 6 keV Ar1000+ ions is lower relative to 3 keV and 500 eV Ar+ ions. Ar+ ions exhibit a steady state O/Ta ratio through the bulk oxide but Ar1000+ ions show a gradual decrease in the O/Ta ratio as a function of depth. The depth resolution and etch rate is substantially better for the monatomic beam compared to the cluster beam. Higher O concentrations are observed when the underlying Ta bulk metal is sputtered for the Ar1000+ profiles compared to the Ar+ profiles.

  4. A carbon-cluster laser ion source for TRIGA-TRAP

    NASA Astrophysics Data System (ADS)

    Smorra, C.; Blaum, K.; Eberhardt, K.; Eibach, M.; Ketelaer, J.; Ketter, J.; Knuth, K.; Nagy, Sz

    2009-08-01

    A new laser ablation ion source was developed and tested for the Penning trap mass spectrometer TRIGA-TRAP in order to provide carbon-cluster ions for absolute mass calibration. Ions of different cluster sizes up to C+24 were successfully produced, covering the mass range up to the heavy actinide elements. The ions were captured in a Penning trap, and their time-of-flight cyclotron resonances recorded in order to determine their cyclotron frequency. Furthermore, the same ion source was used to produce GdO+ ions from a gadolinium target in sufficient amount for mass spectrometry purposes. The design of the source and its characteristics are presented. This paper comprises partly the PhD theses of J Ketelaer and C Smorra.

  5. Ammonia-acetone mixed clusters: Internal ion-molecule reactions, structure, and bonding

    SciTech Connect

    Tzeng, W.B.; Wei, S.; Neyer, D.W.; Keesee, R.G.; Castleman, A.W. Jr. )

    1990-05-23

    Internal ion-molecule reactions in mixed ammonia-acetone clusters are studied by use of multiphoton ionization. Some differences in the branching ratios that arise in the clusters produced by using three clustering methods serve to elucidate reaction mechanisms. In experiments involving the coexpansion of the vapors, the ion intensity ratio ((C{sub 3}H{sub 6}O){sub m+1}{sup +})/(C{sub 3}H{sub 6}O){sub m}{center dot}H{sup +} increases as the ammonia/acetone mixing ratio increases. The result indicates that the unprotonated cluster ions (C{sub 3}H{sub 6}O){sub m+1}{sup +} result from the ionization of the mixed clusters (NH{sub 3}){sub p}{center dot}(C{sub 3}H{sub 6}O){sub q} and, most importantly, suggests that the keto form of the ion is responsible for photon transfer in this system. In the second method, involving the attachment of acetone to preformed ammonia clusters, the acetone molecules strongly interact with the preformed neat ammonia clusters to form long-lived mixed neutral acetone-molecule clusters (NH{sub 3}){sub p}{center dot}(C{sub 3}H{sub 6}O){sub q}. When mixed neutral clusters are formed by the addition of ammonia to preexisting acetone clusters, only small signals of ((NH{sub 3}){sub n}{center dot}(C{sub 3}H{sub 6}O){sub m})H{sup +} ion peaks for n = 1 and m = 1-4 are observed, even at high ammonia flow rates.

  6. Cluster secondary ion mass spectrometry microscope mode mass spectrometry imaging.

    PubMed

    Kiss, András; Smith, Donald F; Jungmann, Julia H; Heeren, Ron M A

    2013-12-30

    Microscope mode imaging for secondary ion mass spectrometry is a technique with the promise of simultaneous high spatial resolution and high-speed imaging of biomolecules from complex surfaces. Technological developments such as new position-sensitive detectors, in combination with polyatomic primary ion sources, are required to exploit the full potential of microscope mode mass spectrometry imaging, i.e. to efficiently push the limits of ultra-high spatial resolution, sample throughput and sensitivity. In this work, a C60 primary source was combined with a commercial mass microscope for microscope mode secondary ion mass spectrometry imaging. The detector setup is a pixelated detector from the Medipix/Timepix family with high-voltage post-acceleration capabilities. The system's mass spectral and imaging performance is tested with various benchmark samples and thin tissue sections. The high secondary ion yield (with respect to 'traditional' monatomic primary ion sources) of the C60 primary ion source and the increased sensitivity of the high voltage detector setup improve microscope mode secondary ion mass spectrometry imaging. The analysis time and the signal-to-noise ratio are improved compared with other microscope mode imaging systems, all at high spatial resolution. We have demonstrated the unique capabilities of a C60 ion microscope with a Timepix detector for high spatial resolution microscope mode secondary ion mass spectrometry imaging. Copyright © 2013 John Wiley & Sons, Ltd.

  7. Trap-based Cluster Research and Cluster-based Investigations of Ion Storage at ClusterTrap

    SciTech Connect

    Schweikhard, Lutz; Breitenfeldt, Martin; Herlert, Alexander; Martinez, Franklin; Marx, Gerrit; Walsh, Noelle

    2006-10-18

    ClusterTrap is a setup devoted to the investigation of atomic clusters. The Penning trap allows various studies after preceding preparation steps. In particular, the clusters may be size selected and their charge state may be varied by electron impact ionization or electron attachment during storage. On the other hand the clusters can be used for extended studies of the properties of the Penning trap. Both aspects are described with recent examples.

  8. X-ray photoelectron spectroscopy analysis of organic materials irradiated with gas cluster ion beam

    SciTech Connect

    Nakagiri, Motohiro; Toyoda, Noriaki; Yamada, Isao

    2011-01-07

    Irradiation effect of gas cluster ion beams (GCIB) on organic materials were studied with X-ray photoelectron spectroscopy by comparison to that with Ar-monomer ions. In the case of polyimide, the intensity of both N-C = O and -C-O- bond decreased with 500 eV Ar monomer ion irradiation. On the other hand, there was no significant change in the XPS spectra after Ar-GCIB irradiation. From the size-selected GCIB irradiation study, the damages in polyimide decreased with increasing the cluster size owing to the reduction of energy per atoms.

  9. Thermochemical Data on Gas-Phase Ion-Molecule Association and Clustering Reactions

    SciTech Connect

    Keesee, R.G.; Castleman, A.W. Jr.

    1986-07-01

    A comprehensive tabulation of the standard enthalpy change, ..delta..H/sup 0/, entropy change, ..delta..S/sup 0/, and free energy change, ..delta..G/sup 0/, for the formation of ion clusters from ion-molecule association reactions is given. The experimental methods which are used to derive the data are briefly discussed. For some experiments, dissociation energies of ion clusters are reported and listed under the category of ..delta..H/sup 0/. The relationship between ..delta..H/sup 0/ and dissociation energy is discussed in the text.

  10. Analysis of Molecular Clusters in Simulations of Lithium-Ion Battery Electrolytes

    SciTech Connect

    Tenney, Craig M.; Cygan, Randall T.

    2013-11-27

    Graph theoretic tools were used to identify and classify clusters of ions and solvent molecules in molecular dynamics simulations of lithium-ion battery electrolytes. Electrolytes composed of various concentrations of LiPF6 dissolved in ethylene carbonate (EC), dimethylene carbonate (DMC), or a 1:1 EC/DMC mixture were simulated at multiple temperatures using classical molecular dynamics. Contrary to Nernst–Einstein theory but consistent with experiment, pure DMC systems had the greatest diffusivity but the lowest conductivity. This disagreement with Nernst–Einstein theory is explained by the observed clustering behavior, which found that systems with pure EC as a solvent formed ion clusters with nonzero charge, whereas systems with pure DMC as a solvent formed primarily neutral clusters.

  11. Charge Retention by Monodisperse Gold Clusters on Surfaces Prepared Using Soft Landing of Mass Selected Ions

    NASA Astrophysics Data System (ADS)

    Johnson, Grant; Priest, Thomas; Laskin, Julia

    2012-02-01

    Monodisperse gold clusters have been prepared on surfaces in different charge states through soft landing of mass-selected ions. Gold clusters were synthesized in methanol solution by reduction of a gold precursor with a weak reducing agent in the presence of a diphosphine capping ligand. Electrospray ionization was used to introduce the clusters into the gas-phase and mass-selection was employed to isolate a single ionic cluster species which was delivered to surfaces at well controlled kinetic energies. Using in-situ time of flight secondary ion mass spectrometry (SIMS) it is demonstrated that the cluster retains its 3+ charge state when soft landed onto the surface of a fluorinated self assembled monolayer on gold. In contrast, when deposited onto carboxylic acid terminated and conventional alkyl thiol surfaces on gold the clusters exhibit larger relative abundances of the 2+ and 1+ charge states, respectively. The kinetics of charge reduction on the surface have been investigated using in-situ Fourier Transform Ion Cyclotron Resonance SIMS. It is shown that an extremely slow interfacial charge reduction occurs on the fluorinated monolayer surface while an almost instantaneous neutralization takes place on the surface of the alkyl thiol monolayer. Our results demonstrate that the size and charge state of small gold clusters on surfaces, both of which exert a dramatic influence on their chemical and physical properties, may be tuned through soft landing of mass-selected ions onto selected substrates.

  12. On the stability of ion water clusters at atmospheric conditions: Open system Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Zidi, Zouhaier S.

    2012-09-01

    The formation of water clusters on Li+, Na+, K+, Cl-, and I- ions from water vapor at atmospheric conditions have been studied using Monte Carlo simulations. The extended simple point charge model has been employed for water molecules. The polarization of ions in the field of molecules and the polarization of molecules in the field of ions have been considered explicitly in the total Hamiltonian of the molecular system. The cluster formation work and the Gibbs free energy and enthalpy of attachment reactions of one water molecule to the cluster have been calculated via the bicanonical ensemble method. Our results reveal the formation of stable clusters in equilibrium with the moist atmosphere in a wide range of vapor pressure values, with largest clusters are formed around cations. Decreasing the temperature, from 293 K to 253 K, leads to the formation of larger equilibrium clusters, and enhances the stability of systems as whole. According to clusters' molecular structures, negative ions are expected to be more active in atmospheric processes, including chemical reactions and cloud formation, than positive ones.

  13. Preparation of graphene on Cu foils by ion implantation with negative carbon clusters

    NASA Astrophysics Data System (ADS)

    Li, Hui; Shang, Yan-Xia; Zhang, Zao-Di; Wang, Ze-Song; Zhang, Rui; Fu, De-Jun

    2015-01-01

    We report on few-layer graphene synthesized on Cu foils by ion implantation using negative carbon cluster ions, followed by annealing at 950 °C in vacuum. Raman spectroscopy reveals IG/I2D values varying from 1.55 to 2.38 depending on energy and dose of the cluster ions, indicating formation of multilayer graphene. The measurements show that the samples with more graphene layers have fewer defects. This is interpreted by graphene growth seeded by the first layers formed via outward diffusion of C from the Cu foil, though nonlinear damage and smoothing effects also play a role. Cluster ion implantation overcomes the solubility limit of carbon in Cu, providing a technique for multilayer graphene synthesis. Project supported by the National Natural Science Foundation of China (Grant Nos. 11105100, 11205116, and 11375135) and the State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, China (Grant No. AWJ-M13-03).

  14. An infrared investigation of the (CO2)n- clusters: core ion switching from both the ion and solvent perspectives.

    PubMed

    Shin, J-W; Hammer, N I; Johnson, M A; Schneider, H; Glöss, A; Weber, J M

    2005-04-14

    The (CO2)n- clusters are thought to accommodate the excess electron by forming a localized molecular anion, or "core ion", solvated by the remaining, largely neutral CO2 molecules. Earlier studies interpreted discontinuities in the (CO2)n- photoelectron spectra to indicate that both the CO2- and C2O4- species were present in a size-dependent fashion. Here we use vibrational predissociation spectroscopy to unambiguously establish the molecular structures of the core ions in the 2 < or = n < or = 17 size range. Spectra are reported in the 2300-3800 cm(-1) region, which allows us to independently monitor the contribution of each ion through its characteristic overtone and combination bands. These signature bands are observed to be essentially intact in the larger clusters, establishing that the CO2- and C2O4- molecular ions are indeed the only electron accommodation modes at play. The size dependence of the core ion suggested in earlier analyses of the photoelectron spectra is largely confirmed, although both species are present over a range of clusters near the expected critical cluster sizes, as opposed to the prompt changes inferred earlier. Perturbations in the bands associated with the nominally neutral CO2 "solvent" molecules are correlated with the changes in the molecular structure of the core ion. These observations are discussed in the context of a diabatic model for electron delocalization over the CO2 dimer. In this picture, the driving force leading to the transient formation of the monomer ion is traced to the solvent asymmetry inherent in an incomplete coordination shell.

  15. Quantitative analysis of isolated and clustered DNA damage induced by gamma-rays, carbon ion beams, and iron ion beams.

    PubMed

    Terato, Hiroaki; Tanaka, Ruri; Nakaarai, Yusuke; Nohara, Tomonori; Doi, Yusuke; Iwai, Shigenori; Hirayama, Ryoichi; Furusawa, Yoshiya; Ide, Hiroshi

    2008-03-01

    Ionizing radiation induces multiple damaged sites (clustered damage) together with isolated lesions in DNA. Clustered damage consists of closely spaced lesions within a few helical turns of DNA and is considered to be crucial for understanding the biological consequences of ionizing radiation. In the present study, two types of DNA, supercoiled plasmid DNA and linear lambda DNA, were irradiated with gamma-rays, carbon ion beams, and iron ion beams, and the spectra and yield of isolated DNA damage and bistranded clustered DNA damage were fully analyzed. Despite using different methods for damage analysis, the experiments with plasmid and lambda DNA gave largely consistent results. The spectra of both isolated and clustered damage were essentially independent of the quality of the ionizing radiation used for irradiation. The yields of clustered damage as well as of isolated damage decreased with the different radiation beams in the order gamma> C > Fe, thus exhibiting an inverse correlation with LET [gamma (0.2 keV/microm) < C (13 keV/microm) < Fe (200 keV/microm)]. Consistent with in vitro data, the yield of chromosomal DNA DSBs decreased with increasing LET in Chinese hamster cells irradiated with carbon ion beams with different LETs, suggesting that the decrease in the yield of clustered damage with increasing LET is not peculiar to in vitro irradiation of DNA, but is common for both in vitro and in vivo irradiation. These results suggest that the adverse biological effect of the ionizing radiation is not simply accounted for by the yield of clustered DNA damage, and that the complexity of the clustered damage needs to be considered to understand the biological consequences of ionizing radiation.

  16. Charge Retention by Gold Clusters on Surfaces Prepared Using Soft Landing of Mass Selected Ions

    SciTech Connect

    Johnson, Grant E.; Priest, Thomas A.; Laskin, Julia

    2012-01-24

    Monodisperse gold clusters have been prepared on surfaces in different charge states through soft landing of mass-selected ions. Ligand-stabilized gold clusters were prepared in methanol solution by reduction of chloro(triphenylphosphine)gold(I) with borane tert-butylamine complex in the presence of 1,3-bis(diphenylphosphino)propane. Electrospray ionization was used to introduce the clusters into the gas-phase and mass-selection was employed to isolate a single ionic cluster species (Au11L53+, L = 1,3-bis(diphenylphosphino)propane) which was delivered to surfaces at well controlled kinetic energies. Using in-situ time of flight secondary ion mass spectrometry (TOF-SIMS) it is demonstrated that the Au11L53+ cluster retains its 3+ charge state when soft landed onto the surface of a 1H,1H,2H,2H-

  17. Progress Toward Innovations in Cryogenic Ion Cluster Spectrometers

    NASA Astrophysics Data System (ADS)

    Howdieshell, Casey J.; Garand, Etienne

    2017-06-01

    Cryogenic Ion Vibrational Spectroscopy (CIVS) is a useful technique that yields rich information about non-covalent interactions in various systems including catalytic complexes, small biologically relevant molecules, and solvent networks. Current instrumentation demands high production costs and large laboratory facilities. We have designed an affordable and compact instrument that is capable of current CIVS experiments. This setup utilizes an ion funnel and a Linear Trap Quadrupole (LTQ) which improves the ion density and allows for spectroscopic interrogation directly in the trap. Preliminary results and future innovations will be discussed.

  18. Ionization and fragmentation of polycyclic aromatic hydrocarbon clusters in collisions with keV ions

    SciTech Connect

    Johansson, H. A. B.; Zettergren, H.; Holm, A. I. S.; Seitz, F.; Schmidt, H. T.; Cederquist, H.; Rousseau, P.; Lawicki, A.; Capron, M.; Domaracka, A.; Lattouf, E.; Maclot, S.; Maisonny, R.; Chesnel, J.-Y.; Adoui, L.; Huber, B. A.

    2011-10-15

    We report on an experimental study of the ionization and fragmentation of clusters of k polycyclic aromatic hydrocarbon (PAH) molecules using anthracene, C{sub 14}H{sub 10}, or coronene, C{sub 24}H{sub 12}. These PAH clusters are moderately charged and strongly heated in small impact parameter collisions with 22.5-keV He{sup 2+} ions, after which they mostly decay in long monomer evaporation sequences with singly charged and comparatively cold monomers as dominating end products. We describe a simple cluster evaporation model and estimate the number of PAH molecules in the clusters that have to be hit by He{sup 2+} projectiles for such complete cluster evaporations to occur. Highly charged and initially cold clusters are efficiently formed in collisions with 360-keV Xe{sup 20+} ions, leading to cluster Coulomb explosions and several hot charged fragments, which again predominantly yield singly charged, but much hotter, monomer ions than the He{sup 2+} collisions. We present a simple formula, based on density-functional-theory calculations, for the ionization energy sequences as functions of coronene cluster size, rationalized in terms of the classic electrostatic expression for the ionization of a charged conducting object. Our analysis indicates that multiple electron removal by highly charged ions from a cluster of PAH molecules rapidly may become more important than single ionization as the cluster size k increases and that this is the main reason for the unexpectedly strong heating in these types of collisions.

  19. A dual cryogenic ion trap spectrometer for the formation and characterization of solvated ionic clusters

    SciTech Connect

    Marsh, Brett M.; Voss, Jonathan M.; Garand, Etienne

    2015-11-28

    A new experimental approach is presented in which two separate cryogenic ion traps are used to reproducibly form weakly bound solvent clusters around electrosprayed ions and messenger-tag them for single-photon infrared photodissociation spectroscopy. This approach thus enables the vibrational characterization of ionic clusters comprised of a solvent network around large and non-volatile ions. We demonstrate the capabilities of the instrument by clustering water, methanol, and acetone around a protonated glycylglycine peptide. For water, cluster sizes with greater than twenty solvent molecules around a single ion are readily formed. We further demonstrate that similar water clusters can be formed around ions having a shielded charge center or those that do not readily form hydrogen bonds. Finally, infrared photodissociation spectra of D{sub 2}-tagged GlyGlyH{sup +} ⋅ (H{sub 2}O){sub 1−4} are presented. They display well-resolved spectral features and comparisons with calculations reveal detailed information on the solvation structures of this prototypical peptide.

  20. A dual cryogenic ion trap spectrometer for the formation and characterization of solvated ionic clusters

    SciTech Connect

    Marsh, Brett M.; Voss, Jonathan M.; Garand, Etienne

    2015-11-24

    A new experimental approach is presented in which two separate cryogenic ion traps are used to reproducibly form weakly bound solvent clusters around electrosprayed ions and messenger-tag them for single-photon infrared photodissociation spectroscopy. This approach thus enables the vibrational characterization of ionic clusters comprised of a solvent network around large and non-volatile ions. We demonstrate the capabilities of the instrument by clustering water, methanol, and acetone around a protonated glycylglycine peptide. For water, cluster sizes with greater than twenty solvent molecules around a single ion are readily formed. We further demonstrate that similar water clusters can be formed around ions having a shielded charge center or those that do not readily form hydrogen bonds. Finally, infrared photodissociation spectra of D2-tagged GlyGlyH+·(H2O)1–4 are presented. As a result, they display well-resolved spectral features and comparisons with calculations reveal detailed information on the solvation structures of this prototypical peptide.

  1. Investigation of accelerated neutral atom beams created from gas cluster ion beams

    NASA Astrophysics Data System (ADS)

    Kirkpatrick, A.; Kirkpatrick, S.; Walsh, M.; Chau, S.; Mack, M.; Harrison, S.; Svrluga, R.; Khoury, J.

    2013-07-01

    A new concept for ultra-shallow processing of surfaces known as accelerated neutral atom beam (ANAB) technique employs conversion of energetic gas cluster ions produced by the gas cluster ion beam (GCIB) method into intense collimated beams of coincident neutral gas atoms having controllable average energies from less than 10 eV per atom to beyond 100 eV per atom. A beam of accelerated gas cluster ions is first produced as is usual in GCIB, but conditions within the source ionizer and extraction regions are adjusted such that immediately after ionization and acceleration the clusters undergo collisions with non-ionized gas atoms. Energy transfer during these collisions causes the energetic cluster ions to release many of their constituent atoms. An electrostatic deflector is then used to eliminate charged species, leaving the released neutral atoms to still travel collectively at the same velocities they had as bonded components of their parent clusters. Upon target impact, the accelerated neutral atom beams produce effects similar to those normally associated with GCIB, but to shallower depths, with less surface damage and with superior subsurface interfaces. The paper discusses generation and characterization of the accelerated neutral atom beams, describes interactions of the beams with target surfaces, and presents examples of ongoing work on applications for biomedical devices.

  2. Energetic ion dynamics of the inner magnetosphere revealed in coordinated Cluster-Double Star observations

    NASA Astrophysics Data System (ADS)

    Dandouras, Iannis; Cao, Jinbin; Vallat, Claire

    2009-01-01

    Since early 2004 the Chinese spacecraft Tan Ce 1 (TC-1), first component of the Double Star (DSP) mission, has been on an equatorial elliptical orbit (13.4 R E apogee), allowing the study of the dynamics of the Earth's magnetosphere in conjunction with the four European Cluster spacecraft (19.6 R E apogee). The Cluster and Double Star spacecraft orbits are such that the spacecraft are almost in the same meridian, allowing conjugate studies. The four Cluster spacecraft highly eccentric polar orbit at 4 R E perigee permits them to sample the ring current, the radiation belts, and the outer plasmasphere from south to north, almost following the same magnetic flux tube (latitudinal profile), whereas TC-1, with its very low-perigee equatorial orbit, gives the plasma profile across L shells. Coordinated ion measurements provided by the Cluster Ion Spectrometry and Hot Ion Analyzer instruments onboard Cluster and TC-1, respectively, obtained during quiet conditions, disturbed geomagnetic conditions, and an intense storm, are used to analyze crossings of the plasmasphere and the ring current region. Multiple narrow ion energy bands (``nose-like'' structures) are simultaneously observed by both Cluster and TC-1. These observations reveal the large-scale character of these structures and pose a challenge for the simulation and modeling of the inner magnetosphere populations.

  3. UV laser induced desorption of CsI and RbI ion clusters

    NASA Astrophysics Data System (ADS)

    Fernández-Lima, F. A.; Ponciano, C. R.; Filho, H. D. Fonseca; Pedrero, E.; Chaer Nascimento, M. A.; da Silveira, E. F.

    2006-09-01

    Experimental results of laser sputtering of cesium and rubidium iodide secondary ions are presented. A TOF mass spectrometer, operating in linear mode, continuous extraction for positive or negative ions, was used for the analysis of (CsI) nCs +, (CsI) nI -, (RbI) nRb + and (RbI) nI - ion emission as a function of the laser irradiance. Experimental data show that the cluster ion emission yields decrease exponentially with n, for all the laser irradiances applied. Theoretical analysis of the clusters structure was performed using density functional theory at the B3LYP/LACV3P level, for the positive and negative cluster series. A quasi-equilibrium evolution of the clusters is proposed to extract a parameter characteristic of the cluster recombination process: the effective temperature. The hypothesis of the atomic species' recombination (during the expansion of a high density highly ionized cloud) leading to cluster formation is confirmed to some extent in a second set of experiments: the UV laser ablation of a mixed and non-mixed cesium iodide and potassium bromide targets. These experiments show that the emission yields contain contributions from both the recombination process and from the sample stoichiometry, even for high laser irradiances.

  4. 20 Years History of Fundamental Research on Gas Cluster Ion Beams, and Current Status of the Applications to Industry

    NASA Astrophysics Data System (ADS)

    Yamada, Isao

    2006-11-01

    This paper reviews the development of gas cluster ion beam (GCIB) technology, including the generation of cluster beams, fundamental characteristics of cluster ion to solid surface interactions, emerging industrial applications, and identification of some of the significant events which occurred as the technology has evolved into what it is today. More than 20 years have passed since the author first began to explore feasibility of processing by gas cluster ion beams at the Ion Beam Engineering Experimental Laboratory of Kyoto University. Processes employing ions of gaseous material clusters comprised of a few hundred to many thousand atoms are now being developed into a new field of ion beam technology. Cluster-surface collisions produce important non-linear effects which are being applied to shallow junction formation, to etching and smoothing of semiconductors, metals, and dielectrics, to assisted formation of thin films with nano-scale accuracy, and to other surface modification applications.

  5. Systems and methods for producing metal clusters; functionalized surfaces; and droplets including solvated metal ions

    DOEpatents

    Cooks, Robert Graham; Li, Anyin; Luo, Qingjie

    2017-08-01

    The invention generally relates to systems and methods for producing metal clusters; functionalized surfaces; and droplets including solvated metal ions. In certain aspects, the invention provides methods that involve providing a metal and a solvent. The methods additionally involve applying voltage to the solvated metal to thereby produce solvent droplets including ions of the metal containing compound, and directing the solvent droplets including the metal ions to a target. In certain embodiments, once at the target, the metal ions can react directly or catalyze reactions.

  6. Structure of alcohol cluster ions in the gas phase, according to spectrometry and ab initio calculations

    NASA Astrophysics Data System (ADS)

    Krisilov, A. V.; Lantsuzskaya, E. V.; Levina, A. M.

    2017-01-01

    Reduced ion mobility and scattering cross sections are calculated from experimentally obtained spectra of the ion mobility of linear aliphatic alcohols with carbon atom numbers from 2 to 9. A linear increase in the scattering cross sections as the molecular weight grows is found. According to the results from experiments and quantum chemical calculations, alcohol cluster ions do not form a compact structure. Neither are dipole moments compensated for during dimerization, in contrast to the aldehydes and ketones described earlier. It was concluded from ab initio calculations that charge delocalization in monomeric and dimeric ions of alcohols increases the dipole moment many times over.

  7. Systems and methods for producing metal clusters; functionalized surfaces; and droplets including solvated metal ions

    DOEpatents

    Cooks, Robert Graham; Li, Anyin; Luo, Qingjie

    2017-01-24

    The invention generally relates to systems and methods for producing metal clusters; functionalized surfaces; and droplets including solvated metal ions. In certain aspects, the invention provides methods that involve providing a metal and a solvent. The methods additionally involve applying voltage to the solvated metal to thereby produce solvent droplets including ions of the metal containing compound, and directing the solvent droplets including the metal ions to a target. In certain embodiments, once at the target, the metal ions can react directly or catalyze reactions.

  8. Low-damage milling of an amino acid thin film with cluster ion beam

    SciTech Connect

    Hada, Masaki; Ibuki, Sachi; Ninomiya, Satoshi; Matsuo, Jiro; Hontani, Yusaku; Yamamoto, Yasuyuki; Ichiki, Kazuya; Seki, Toshio; Aoki, Takaaki

    2011-11-01

    In this work, we characterized the surface damage layer and sputtering yield of polycrystalline L-leucine films before and after irradiation with Ar cluster or monomer ion beams with x ray photoelectron spectroscopy and ellipsometry. Irradiation with Ar monomer ion beams induced heavy damage on the surface of L-leucine films, such as bond breaking and carbonization. In contrast, no significant surface damage was observed in the films irradiated with Ar cluster ion beams. The sputtering yield of L-leucine decreased dramatically with increasing fluence of monomer Ar ions and approached the value of the sputtering yield of graphite; but under irradiation with Ar cluster ion beams, the sputtering yield remained constant with fluence. The differences in sputtering yield behavior were explained in relation with the surface damage layer on organic materials. Thus, cluster ion beams could potentially be used to mill down biological materials without significant damage on the surface and could contribute to various applications in the analysis and processing of life matter.

  9. Clustered DNA damages induced by high and low LET radiation, including heavy ions

    NASA Technical Reports Server (NTRS)

    Sutherland, B. M.; Bennett, P. V.; Schenk, H.; Sidorkina, O.; Laval, J.; Trunk, J.; Monteleone, D.; Sutherland, J.; Lowenstein, D. I. (Principal Investigator)

    2001-01-01

    Clustered DNA damages--here defined as two or more lesions (strand breaks, oxidized purines, oxidized pyrimidines or abasic sites) within a few helical turns--have been postulated as difficult to repair accurately, and thus highly significant biological lesions. Further, attempted repair of clusters may produce double strand breaks (DSBs). However, until recently, there was no way to measure ionizing radiation-induced clustered damages, except DSB. We recently described an approach for measuring classes of clustered damages (oxidized purine clusters, oxidized pyrimidine clusters, abasic clusters, along with DSB). We showed that ionizing radiation (gamma rays and Fe ions, 1 GeV/amu) does induce such clusters in genomic DNA in solution and in human cells. These studies also showed that each damage cluster results from one radiation hit (and its track), thus indicating that they can be induced by very low doses of radiation, i.e. two independent hits are not required for cluster induction. Further, among all complex damages, double strand breaks comprise--at most-- 20%, with the other clustered damages being at least 80%.

  10. Clustered DNA damages induced by high and low LET radiation, including heavy ions

    NASA Technical Reports Server (NTRS)

    Sutherland, B. M.; Bennett, P. V.; Schenk, H.; Sidorkina, O.; Laval, J.; Trunk, J.; Monteleone, D.; Sutherland, J.; Lowenstein, D. I. (Principal Investigator)

    2001-01-01

    Clustered DNA damages--here defined as two or more lesions (strand breaks, oxidized purines, oxidized pyrimidines or abasic sites) within a few helical turns--have been postulated as difficult to repair accurately, and thus highly significant biological lesions. Further, attempted repair of clusters may produce double strand breaks (DSBs). However, until recently, there was no way to measure ionizing radiation-induced clustered damages, except DSB. We recently described an approach for measuring classes of clustered damages (oxidized purine clusters, oxidized pyrimidine clusters, abasic clusters, along with DSB). We showed that ionizing radiation (gamma rays and Fe ions, 1 GeV/amu) does induce such clusters in genomic DNA in solution and in human cells. These studies also showed that each damage cluster results from one radiation hit (and its track), thus indicating that they can be induced by very low doses of radiation, i.e. two independent hits are not required for cluster induction. Further, among all complex damages, double strand breaks comprise--at most-- 20%, with the other clustered damages being at least 80%.

  11. Size-restricted proton transfer within toluene-methanol cluster ions.

    PubMed

    Chiang, Chi-Tung; Shores, Kevin S; Freindorf, Marek; Furlani, Thomas; DeLeon, Robert L; Garvey, James F

    2008-11-20

    To understand the interaction between toluene and methanol, the chemical reactivity of [(C6H5CH3)(CH3OH) n=1-7](+) cluster ions has been investigated via tandem quadrupole mass spectrometry and through calculations. Collision Induced Dissociation (CID) experiments show that the dissociated intracluster proton transfer reaction from the toluene cation to methanol clusters, forming protonated methanol clusters, only occurs for n = 2-4. For n = 5-7, CID spectra reveal that these larger clusters have to sequentially lose methanol monomers until they reach n = 4 to initiate the deprotonation of the toluene cation. Metastable decay data indicate that for n = 3 and n = 4 (CH3OH)3H(+) is the preferred fragment ion. The calculational results reveal that both the gross proton affinity of the methanol subcluster and the structure of the cluster itself play an important role in driving this proton transfer reaction. When n = 3, the cooperative effect of the methanols in the subcluster provides the most important contribution to allow the intracluster proton transfer reaction to occur with little or no energy barrier. As n >or= 4, the methanol subcluster is able to form ring structures to stabilize the cluster structures so that direct proton transfer is not a favored process. The preferred reaction product, the (CH3OH)3H(+) cluster ion, indicates that this size-restricted reaction is driven by both the proton affinity and the enhanced stability of the resulting product.

  12. Sulfide ions as modulators of metal-thiolate cluster size in a plant metallothionein.

    PubMed

    Huber, Tamara; Freisinger, Eva

    2013-06-28

    Metallothioneins are small cysteine-rich proteins coordinating various transition metal ions preferably with the electron configuration d(10). They are ubiquitously present in all phyla, and next to phytochelatins they represent a successful molecular concept for high-capacity metal ion binding. Recent studies showed the incorporation of sulfide ions into the metal-thiolate cluster of metallothionein 2 from the plant Cicer arietinum (cicMT2) increasing the cadmium binding capacity and stability of the cluster. In the present work, the sulfide-induced structural changes accompanying the cluster formation and the sulfide-modulated increase in cluster size are analyzed in detail with a variety of analytical and spectroscopic techniques. Evaluation of the mechanism of sulfide containing Cd(II)-thiolate cluster formation in cicMT2 reveals a strong dependence on the sequence of metal and sulfide additions for successful sulfide incorporation. To probe the general ability of metallothioneins to form sulfide containing larger metal-thiolate clusters, analogous experiments were performed with a mammalian metallothionein. The observation that the cadmium binding ability of rabbit liver MT2A was only slightly increased led to the development of a hypothesis in which the long cysteine-free linker regions present in certain plant metallothioneins may contribute to the accommodation of the respective larger cluster assemblies.

  13. Induction and processing of oxidative clustered DNA lesions in 56Fe-ion-irradiated human monocytes.

    PubMed

    Tsao, Doug; Kalogerinis, Peter; Tabrizi, Isla; Dingfelder, Michael; Stewart, Robert D; Georgakilas, Alexandros G

    2007-07-01

    Space and cosmic radiation is characterized by energetic heavy ions of high linear energy transfer (LET). Although both low- and high-LET radiations can create oxidative clustered DNA lesions and double-strand breaks (DSBs), the local complexity of oxidative clustered DNA lesions tends to increase with increasing LET. We irradiated 28SC human monocytes with doses from 0-10 Gy of (56)Fe ions (1.046 GeV/ nucleon, LET = 148 keV/microm) and determined the induction and processing of prompt DSBs and oxidative clustered DNA lesions using pulsed-field gel electrophoresis (PFGE) and Number Average Length Analysis (NALA). The (56)Fe ions produced decreased yields of DSBs (10.9 DSB Gy(-1) Gbp(-1)) and clusters (1 DSB: approximately 0.8 Fpg clusters: approximately 0.7 Endo III clusters: approximately 0.5 Endo IV clusters) compared to previous results with (137)Cs gamma rays. The difference in the relative biological effectiveness (RBE) of the measured and predicted DSB yields may be due to the formation of spatially correlated DSBs (regionally multiply damaged sites) which result in small DNA fragments that are difficult to detect with the PFGE assay. The processing data suggest enhanced difficulty compared with gamma rays in the processing of DSBs but not clusters. At the same time, apoptosis is increased compared to that seen with gamma rays. The enhanced levels of apoptosis observed after exposure to (56)Fe ions may be due to the elimination of cells carrying high levels of persistent DNA clusters that are removed only by cell death and/or "splitting" during DNA replication.

  14. Depth resolution at organic interfaces sputtered by argon gas cluster ions: the effect of energy, angle and cluster size.

    PubMed

    Seah, M P; Spencer, S J; Havelund, R; Gilmore, I S; Shard, A G

    2015-10-07

    An analysis is presented of the effect of experimental parameters such as energy, angle and cluster size on the depth resolution in depth profiling organic materials using Ar gas cluster ions. The first results are presented of the incident ion angle dependence of the depth resolution, obtained at the Irganox 1010 to silicon interface, from profiles by X-ray photoelectron spectrometry (XPS). By analysis of all relevant published depth profile data, it is shown that such data, from delta layers in secondary ion mass spectrometry (SIMS), correlate with the XPS data from interfaces if it is assumed that the monolayers of the Irganox 1010 adjacent to the wafer substrate surface have an enhanced sputtering rate. SIMS data confirm this enhancement. These results show that the traditional relation for the depth resolution, FWHM = 2.1Y(1/3) or slightly better, FWHM = P(X)Y(1/3)/n(0.2), where n is the argon gas cluster size, and P(X) is a parameter for each material are valid both at the 45° incidence angle of the argon gas cluster sputtering ions used in most studies and at all angles from 0° to 80°. This implies that, for optimal depth profile resolution, 0° or >75° incidence may be significantly better than the 45° traditionally used, especially for the low energy per atom settings required for the best resolved profiles in organic materials. A detailed analysis, however, shows that the FWHM requires a constant contribution added in quadrature to the above such that there are minimal improvements at 0° or greater than 75°. A critical test at 75° confirms the presence of this constant contribution.

  15. Production of Protonated Methanol Ions Via Intermolecular Reactions within Van der Waals Clusters of Dime Dimethyl Ether. Revision

    DTIC Science & Technology

    1990-02-02

    preparation (17) This result also suggests that the protonated methanol ion is not produced via a reaction between the DME cluster and a water impurity. In...include Security Classification) Production ol Protonated Methanol Ions via "Intermolecular" Reactions within van der Waals Clusters of Dimethyl Ether...2/90 Production of Protonated Methanol Ions via "Intermolecular" Reactions within van der Waals Clusters of Dimethyl Ether M. Todd Coolbaugh, William

  16. Observation of ions and particles near busy roads using a neutral cluster and air ion spectrometer (NAIS)

    NASA Astrophysics Data System (ADS)

    Jayaratne, E. R.; Ling, X.; Morawska, L.

    2014-02-01

    Motor vehicles emit large quantities of ions in the form of both charged particles and molecular cluster ions. While, the health effects of inhalation of charged particles is largely unexplored, the concentrations near busy roads and the distance to which these particles and ions are carried have important implications for the exposure of the large percentage of the population that lives close to such roadways. We measured ion concentrations using a neutral cluster and air ion spectrometer (NAIS) near seven busy roads carrying on the average approximately 7000 vehicles h-1 including about 15% heavy duty diesel vehicles. In this study, charged particle concentrations were measured as a function of downwind distance from the road for the first time. We show that, at a moderate wind speed of 2.0 m s-1, mean charged particle concentrations at the kerb were of the order of 2 × 104 cm-3 and, more importantly, decreased as d-0.6 where d is the distance from the road. While cluster ions were rapidly depleted by attachment to particles and were not carried to more than about 20 m from the road, elevated concentrations of charged particle were detected up to at least 400 m from the road. Most of the charge on the downwind side was carried on the larger particles, with no excess charge on particles smaller than about 10 nm. At 30 nm, particles carried more than double the charge they would normally carry in equilibrium. There are very few measurements of ions near road traffic and this is the first study of the spatial dispersion of charged particles from a road.

  17. Reactivity of niobium-carbon cluster ions with hydrogen molecules in relation to formation mechanism of Met-Car cluster ions.

    PubMed

    Miyajima, Ken; Fukushima, Naoya; Mafuné, Fumitaka

    2008-07-03

    It is known that a niobium-carbon Met-Car cluster ion (Nb 8C 12 (+)) and its intermediates (Nb 4C 4 (+), Nb 6C 7 (+), etc.) are selectively formed by the aggregation of the Nb atoms in the presence of hydrocarbons. To elucidate the formation mechanism, we prepared Nb n C m (+) with every combination of n and m in the gas phase by the laser vaporization technique. The reactivity of Nb n C m (+) with H 2 was examined under the multiple collision condition, finding that Nb n C m (+) between Nb 2C 3 (+) and Nb 8C 12 (+) are not reactive with H 2. On the basis of the H 2 affinity of Nb n C m (+) experimentally obtained, we propose a dehydrogenation-controlled formation mechanism of niobium-carbon Met-Car cluster ions.

  18. Dissociation dynamics: Measurements of decay fractions of metastable ammonia cluster ions

    SciTech Connect

    Wei, S.; Tzeng, W.B.; Castleman, A.W. Jr. )

    1990-08-15

    The decay fractions of metastable ammonia cluster ions which undergo unimolecular (evaporative) dissociation in a time window of 1--40 {mu}s were measured by using a reflection time-of-flight mass spectrometer. Corrections concerning instrumental artifacts and ion trajectory of parents and daughters are made to imporve the precision of the measurements. The data are used to derive the Gspann parameter and heat capacity of clusters as described in evaporative ensemble model of metastable dissociation. Using the dissociation fractions measured in the present studies, in conjunction with kinetic energy release values previously measured in our laboratory, we apply Klots' evaporative ensemble model to obtain binding energies of ammonia cluster ions (NH{sub 3}){sub {ital n}}H{sup +}, 4{le}{ital n}{le}17. The deduced binding energy values are found to be in very good agreement with both thermochemical data and Engelking's modified statistical theory.

  19. Generation of CsI cluster ions for mass calibration in matrix-assisted laser desorption/ionization mass spectrometry.

    PubMed

    Lou, Xianwen; van Dongen, Joost L J; Meijer, E W

    2010-07-01

    A simple method was developed for the generation of cesium iodide (CsI) cluster ions up to m/z over 20,000 in matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). Calibration ions in both positive and negative ion modes can readily be generated from a single MALDI spot of CsI(3) with 2-[(2E)-3-(4-tert-butylphenyl)-2-methylprop-2-enylidene] malononitrile (DCTB) matrix. The major cluster ion series observed in the positive ion mode is [(CsI)(n)Cs](+), and in the negative ion mode is [(CsI)(n)I](-). In both cluster series, ions spread evenly every 259.81 units. The easy method described here for the production of CsI cluster ions should be useful for MALDI MS calibrations. Copyright 2010 American Society for Mass Spectrometry. Published by Elsevier Inc. All rights reserved.

  20. Mechanism for neuronal spike generation by small and large ion channel clusters

    NASA Astrophysics Data System (ADS)

    Zeng, Shangyou; Jung, Peter

    2004-07-01

    Neuronal action potentials are generated by clusters of ion channels between the Hillock and the first segment. If the clusters comprise a large number of sodium and potassium channels, action potentials are generated if the membrane potential exceeds a threshold of about -55mV . Such behavior is well described by an excitable model such as, for example, the Hodgkin-Huxley equations. In this paper we show through stochastic modeling that if the size of the generating ion channel cluster is small, action potentials are generated regardless of whether the membrane potential is below or above the excitation threshold. Action potential generation is then determined by single-channel kinetics. We further show that this switch in generation mechanism manifests itself in peculiar statistical properties of the generated spike trains at small cluster sizes.

  1. Mechanism for neuronal spike generation by small and large ion channel clusters.

    PubMed

    Zeng, Shangyou; Jung, Peter

    2004-07-01

    Neuronal action potentials are generated by clusters of ion channels between the Hillock and the first segment. If the clusters comprise a large number of sodium and potassium channels, action potentials are generated if the membrane potential exceeds a threshold of about -55 mV. Such behavior is well described by an excitable model such as, for example, the Hodgkin-Huxley equations. In this paper we show through stochastic modeling that if the size of the generating ion channel cluster is small, action potentials are generated regardless of whether the membrane potential is below or above the excitation threshold. Action potential generation is then determined by single-channel kinetics. We further show that this switch in generation mechanism manifests itself in peculiar statistical properties of the generated spike trains at small cluster sizes.

  2. Raman spectroscopy of few-layer graphene prepared by C2-C6 cluster ion implantation

    NASA Astrophysics Data System (ADS)

    Wang, Z. S.; Zhang, R.; Zhang, Z. D.; Huang, Z. H.; Liu, C. S.; Fu, D. J.; Liu, J. R.

    2013-07-01

    Few-layer graphene has been prepared on 300 nm-thick Ni films by C2-C6 cluster ion implantation at 20 keV/cluster. Raman spectroscopy reveals significant influence of the number of atoms in the cluster, the implantation dose, and thermal treatment on the structure of the graphene layers. In particular, the graphene samples exhibit a sharp G peak at 1584 cm-1 and 2D peaks at 2711-2717 cm-1. The IG/I2D ratios higher than 1.70 and IG/ID ratio as high as 1.95 confirm that graphene sheets with low density of defects have been synthesized with much improved quality by ion implantation with larger clusters of C4-C6.

  3. Geometric isotope effects on small chloride ion water clusters with path integral molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Suzuki, Kimichi; Nagashima, Umpei; Tachikawa, Masanori; Yan, Shiwei

    2013-11-01

    The geometric isotope effects on the structures of hydrated chloride ionic hydrogen bonded clusters are explored by carrying out path integral molecular dynamics simulations. First, an outer shell coordinate is selected to display the rearrangement of single and multi hydration shell cluster structures. Next, to show the competition of intramolecular and intermolecular nuclear quantum effects, the intramolecular OH∗ stretching and intermolecular ion-water wagging motions are studied for single and multi shell structures, respectively. The results indicate that the intermolecular nuclear quantum effects stabilize the ionic hydrogen bonds in single shell structures, while they are destabilized through the competition with intramolecular nuclear quantum effects in multi shell structures. In addition, the correlations between ion-water stretching motion and other cluster vibrational coordinates are discussed. The results indicate that the intermolecular nuclear quantum effects on the cluster structures are strongly related to the cooperation of the water-water hydrogen bond interactions.

  4. Size and Charge Distributions of Stable Clusters Formed in Ion Sputtering of Metals

    NASA Astrophysics Data System (ADS)

    Matveev, V. I.; Kapustin, S. N.

    2016-10-01

    A theory of ion sputtering of metals in the form of neutral and charged clusters with their subsequent fragmentation into the stable state is developed. The theory is based on simple physical assumptions and is in good agreement with experiment. Results are presented in the form of formulas convenient for practical application. As an example, calculations of the total yield of stable neutral and charged clusters of silver, indium, and niobium are carried out.

  5. Dissociative recombination of water cluster ions with free electrons: cross sections and branching ratios.

    PubMed

    Ojekull, J; Andersson, P U; Pettersson, J B C; Marković, N; Thomas, R D; Al Khalili, A; Ehlerding, A; Osterdahl, F; af Ugglas, M; Larsson, M; Danared, H; Källberg, A

    2008-01-28

    Dissociative recombination (DR) of water cluster ions H(+)(H(2)O)(n) (n=4-6) with free electrons has been studied at the heavy-ion storage ring CRYRING (Manne Siegbahn Laboratory, Stockholm University). For the first time, branching ratios have been determined for the dominating product channels and absolute DR cross sections have been measured in the energy range from 0.001 to 0.7 eV. Dissociative recombination is concluded to result in extensive fragmentation for all three cluster ions, and a maximum number of heavy oxygen-containing fragments is produced with a probability close to unity. The branching ratio results agree with earlier DR studies of smaller water cluster ions where the channel nH(2)O+H has been observed to dominate and where energy transfer to internal degrees of freedom has been concluded to be highly efficient. The absolute DR cross sections for H(+)(H(2)O)(n) (n=4-6) decrease monotonically with increasing energy with an energy dependence close to E(-1) in the lower part of the energy range and a faster falloff at higher energies, in agreement with the behavior of other studied heavy ions. The cross section data have been used to calculate DR rate coefficients in the temperature range of 10-2000 K. The results from storage ring experiments with water cluster ions are concluded to partly confirm the earlier results from afterglow experiments. The DR rate coefficients for H(+)(H(2)O)(n) (n=1-6) are in general somewhat lower than reported from afterglow experiments. The rate coefficient tends to increase with increasing cluster size, but not in the monotonic way that has been reported from afterglow experiments. The needs for further experimental studies and for theoretical models that can be used to predict the DR rate of polyatomic ions are discussed.

  6. Dissociative recombination of water cluster ions with free electrons: Cross sections and branching ratios

    NASA Astrophysics Data System (ADS)

    Öjekull, J.; Andersson, P. U.; Pettersson, J. B. C.; Marković, N.; Thomas, R. D.; Al Khalili, A.; Ehlerding, A.; Österdahl, F.; af Ugglas, M.; Larsson, M.; Danared, H.; Källberg, A.

    2008-01-01

    Dissociative recombination (DR) of water cluster ions H+(H2O)n (n=4-6) with free electrons has been studied at the heavy-ion storage ring CRYRING (Manne Siegbahn Laboratory, Stockholm University). For the first time, branching ratios have been determined for the dominating product channels and absolute DR cross sections have been measured in the energy range from 0.001to0.7eV. Dissociative recombination is concluded to result in extensive fragmentation for all three cluster ions, and a maximum number of heavy oxygen-containing fragments is produced with a probability close to unity. The branching ratio results agree with earlier DR studies of smaller water cluster ions where the channel nH2O +H has been observed to dominate and where energy transfer to internal degrees of freedom has been concluded to be highly efficient. The absolute DR cross sections for H+(H2O)n (n=4-6) decrease monotonically with increasing energy with an energy dependence close to E-1 in the lower part of the energy range and a faster falloff at higher energies, in agreement with the behavior of other studied heavy ions. The cross section data have been used to calculate DR rate coefficients in the temperature range of 10-2000K. The results from storage ring experiments with water cluster ions are concluded to partly confirm the earlier results from afterglow experiments. The DR rate coefficients for H+(H2O)n (n=1-6) are in general somewhat lower than reported from afterglow experiments. The rate coefficient tends to increase with increasing cluster size, but not in the monotonic way that has been reported from afterglow experiments. The needs for further experimental studies and for theoretical models that can be used to predict the DR rate of polyatomic ions are discussed.

  7. Evaporative dissociation of ammonia cluster ions: Quantification of decay fractions and isotope effects

    SciTech Connect

    Wei, S.; Kilgore, K.; Tzeng, W.B.; Castleman, A.W. Jr. )

    1991-10-17

    A modified version of the evaporative ensemble model is employed to deduce relative binding energies for protonated cluster ions using previously measured metastable dissociation fractions of ammonia cluster ions, (NH{sub 3}){sub n}H{sup +}, n = 4-22, obtained by using a laser-based time-of-flight mass spectrometer equipped with a reflection. The newly derived values are found to be in good agreement with those reported earlier based on high-pressure mass spectrometry (HPMS) and several other methods employing data on dissociation dynamics. The various methods are found to be complementary. New measurements are reported for the metastable decay of deuterated cluster ions to investigate the influence of mass effects on the dissociation rate. The decay fractions of the cluster ions (ND{sub 3}){sub n}D{sup +} are found to be consistently higher than those of the corresponding (NH{sub 3}){sub n}H{sup +} by 15%. The isotope effect can be well accounted for by considering the differences of their bulk heat capacities, and such studies are found to be a promising method for measuring the heat capacities of small, unsupported cluster systems.

  8. A dual cryogenic ion trap spectrometer for the formation and characterization of solvated ionic clusters

    DOE PAGES

    Marsh, Brett M.; Voss, Jonathan M.; Garand, Etienne

    2015-11-24

    A new experimental approach is presented in which two separate cryogenic ion traps are used to reproducibly form weakly bound solvent clusters around electrosprayed ions and messenger-tag them for single-photon infrared photodissociation spectroscopy. This approach thus enables the vibrational characterization of ionic clusters comprised of a solvent network around large and non-volatile ions. We demonstrate the capabilities of the instrument by clustering water, methanol, and acetone around a protonated glycylglycine peptide. For water, cluster sizes with greater than twenty solvent molecules around a single ion are readily formed. We further demonstrate that similar water clusters can be formed around ionsmore » having a shielded charge center or those that do not readily form hydrogen bonds. Finally, infrared photodissociation spectra of D2-tagged GlyGlyH+·(H2O)1–4 are presented. As a result, they display well-resolved spectral features and comparisons with calculations reveal detailed information on the solvation structures of this prototypical peptide.« less

  9. Study of clusters using negative ion photodetachment spectroscopy

    SciTech Connect

    Zhao, Yuexing

    1995-12-01

    The weak van der Waals interaction between an open-shell halogen atom and a closed-shell atom or molecule has been investigated using zero electron kinetic energy (ZEKE) spectroscopy. This technique is also applied to study the low-lying electronic states in GaAs and GaAs-. In addition, the spectroscopy and electron detachment dynamics of several small carbon cluster anions are studied using resonant multiphoton detachment spectroscopy.

  10. Dependence of multiply charged ions on the polarization state in nanosecond laser-benzene cluster interaction

    NASA Astrophysics Data System (ADS)

    Wang, Weiguo; Zhao, Wuduo; Hua, Lei; Hou, Keyong; Li, Haiyang

    2016-05-01

    This paper investigated the dependence of multiply charged ions on the laser polarization state when benzene cluster was irradiated with 532 and 1064 nm nanosecond laser. A circle, square and flower distribution for C2+, C3+ and C4+ were observed with 532 nm laser respectively, while flower petals for C2+, C3+ and C4+ were observed at 1064 nm as the laser polarization varied. A theoretical calculation was performed to interpret the polarization state and wavelength dependence of the multiply charged ions. The simulated results agreed well with the experimental observation with considering the contribution from the cluster disintegration.

  11. Unusual under-threshold ionization of neon clusters studied by ion spectroscopy

    NASA Astrophysics Data System (ADS)

    Nagaya, K.; Sugishima, A.; Iwayama, H.; Murakami, H.; Yao, M.; Fukuzawa, H.; Liu, X.-J.; Motomura, K.; Ueda, K.; Saito, N.; Foucar, L.; Rudenko, A.; Kurka, M.; Kühnel, K.-U.; Ullrich, J.; Czasch, A.; Dörner, R.; Feifel, R.; Nagasono, M.; Higashiya, A.; Yabashi, M.; Ishikawa, T.; Togashi, T.; Kimura, H.; Ohashi, H.

    2013-08-01

    We carried out time-of-flight mass spectrometry for neon clusters that were exposed to intense free electron laser pulses with the wavelength of 62 nm, which induce optical transition from the ground state (2s2 2p6) to an excited state (2s2 2p5 nl ) in the Ne atoms. In contrast to Ne+ ions produced by two-photon absorption from isolated Ne atoms, the Ne+ ion yield from Ne clusters shows a linear dependence on the laser intensity (I). We discuss the ionization mechanisms which give the linear behaviour with respect to I and expected features in the electron emission spectrum.

  12. Non-Contact Wafer Fabrication Process Using Gas Cluster Ion Beams

    SciTech Connect

    Toyoda, Noriaki; Yamada, Iaso; Isogai, Hiromichi

    2008-11-03

    Gas cluster ion beam (GCIB) was used for precise wafer fabrication process. GCIB realizes a quite low-energy ion beam and shows very precise and good repeatability. To obtain thickness uniformity of Si over the whole wafer, small beam diameter ({approx}4 mm) of GCIB was used. Thickness variations on the wafer can be reduced by location specific irradiation of collimated GCIB. By controlling the scan speed of GCIB irradiation based on the removal thickness at each irradiation position, thickness and height uniformity of Si can be improved to several tens of nm. In addition, etching enhancement by using Ar/SF{sub 6} mixed cluster was studied.

  13. Gas cluster ion beam assisted NiPt germano-silicide formation on SiGe

    SciTech Connect

    Ozcan, Ahmet S.; Lavoie, Christian; Jordan-Sweet, Jean; Alptekin, Emre; Zhu, Frank; Leith, Allen; Pfeifer, Brian D.; LaRose, J. D.; Russell, N. M.

    2016-04-21

    We report the formation of very uniform and smooth Ni(Pt)Si on epitaxially grown SiGe using Si gas cluster ion beam treatment after metal-rich silicide formation. The gas cluster ion implantation process was optimized to infuse Si into the metal-rich silicide layer and lowered the NiSi nucleation temperature significantly according to in situ X-ray diffraction measurements. This novel method which leads to more uniform films can also be used to control silicide depth in ultra-shallow junctions, especially for high Ge containing devices, where silicidation is problematic as it leads to much rougher interfaces.

  14. Controlled Formation and Vibrational Characterization of Large Solvated Ionic Clusters in Cryogenic Ion Traps

    NASA Astrophysics Data System (ADS)

    Garand, Etienne; Marsh, Brett; Voss, Jonathan; Duffy, Erin M.

    2016-06-01

    An experimental approach for the formation of solvated ionic clusters and their vibrational spectroscopy will be presented. This recently developed apparatus combines an electrospray ionization source, two temperature controlled cryogenic ion traps and a time-of-flight infrared photofragmentation spectrometer, to allow for a universal and controlled formation and characterization of solvent clusters around ionic core as well as product of ion-molecule reaction. Recent results on the spectroscopy of such solvated ions, will be presented and discussed. In particular, this talk will present the structural evolution of glycylglycine as a function of stepwise solvation, and show how the presence of just a few water can modify the geometry of this model peptide. I will also present results solvation of ion that do not form hydrogen bond or strongly interactions with the solvent.

  15. Electron and Ion Emission from Clusters exposed to Strong Laser Fields

    NASA Astrophysics Data System (ADS)

    Tiggesbämker, Josef

    2006-03-01

    When clusters interact with intense optical laser pulses energetic and highly charged atomic fragment ions e.g. are generated^1. In contrast to atoms the efficiency of the process could be enhanced by choosing a pair of optical delayed pulses instead of a single but more intense femtosecond pulse^2. In metals the stronger charging of the clusters can qualitatively be explained by a plasmon enhanced ionization process. We extended our studies and have made a compared analysis of the emission of highly charged ions and energetic electrons the interaction dynamics of intense femtosecond laser fields with nanometer-sized silver clusters. Using a pair of laser pulses with variable optical delay the time-dependent cluster response is resolved. A dramatic increase both in the atomic charge state of the ions and the maximum electron kinetic energy is observed for a certain delay of the pulses. Corresponding Vlasov calculations on a metal cluster model system indicate that enhanced cluster ionization as well as the generation of fast electrons coincide with resonant plasmon excitation.^3 *L. Köller, M. Schumacher, J. Köhn, S. Teuber, J. Tiggesbäumker, and K.-H. Meiwes-Broer, Phys. Rev. Lett. 82, 3783 (1999). *T. Döppner, Th. Fennel, Th. Diederich, J. Tiggesb äumker, and K.-H. Meiwes-Broer, Phys. Rev. Lett. 94, 013401 (2005). *Th. Fennel, G.F. Bertsch, and K.-H. Meiwes-Broer, Eur. Phys. J. D 29, 367 (2004).

  16. Photodissociation spectroscopy and dynamics of free radicals, clusters, and ions

    SciTech Connect

    Choi, Hyeon

    1999-12-01

    The photodissociation spectroscopy and dynamics of free radicals and ions is studied to characterize the dissociative electronic states in these species. To accomplish this, a special method of radical production, based on the photodetachment of the corresponding negative ion, has been combined with the technique of fast beam photofragment translational spectroscopy. The photofragment yield as a function of photon energy is obtained, mapping out the dissociative and predissociative electronic states. Branching ratios to various product channels, the translational energy distributions of the fragments, and bond dissociation energies are then determined at selected photon energies. The detailed picture of photodissociation dynamics is provided with the aid of ab initio calculations and a statistical model to interpret the observed data. Important reaction intermediates in combustion reactions have been studied: CCO, C2H5O, and linear Cn (n = 4--6).

  17. Energies, charges, and sizes of clusters under ion sputtering of a metal

    SciTech Connect

    Matveev, V. I. Kochkin, S. A.

    2010-04-15

    A theory of ion sputtering of a metal in the form of neutral and singly charged clusters with a number of atoms of N {>=} 5 has been developed. This theory is based on simple physical assumptions and agrees well with experiment. The results are presented in the form of expressions convenient for practical use. The energy spectra of clusters, charge distributions, ionization coefficients, and total yields of neutral and singly charged clusters at different target temperatures are calculated in terms of the proposed theory as an example.

  18. Metal etching with reactive gas cluster ion beams using pickup cell

    SciTech Connect

    Toyoda, Noriaki; Yamada, Isao

    2012-11-06

    Mixed gas cluster ion beams were formed using pickup cell for metal etching. O{sub 2} neutral clusters pick up acetic acid and formed mixed cluster beam. By using O{sub 2}-GCIB with acetic acid, enhancement of Cu etching was observed. Because of dense energy deposition by GCIB, etching of Cu proceeds by CuO formation, enhancement of chemical reaction with acetic acid and desorption of etching products. Surface roughening was not observed on poly crystalline Cu because of the small dependence of etching rate on crystal orientation. Halogen free and low-temperature metal etching with GCIB using pickup cell is possible.

  19. Global minima for rare gas clusters containing one alkali metal ion

    NASA Astrophysics Data System (ADS)

    Hernández-Rojas, Javier; Wales, David J.

    2003-10-01

    We present candidate structures for the global minima of N-atom rare gas clusters containing one additional alkali metal ion, LJNM. Lennard-Jones and Mason-Schamp potentials are used to represent the rare gas-rare gas and rare gas-alkali metal ion interactions, respectively. Results are presented for parameters appropriate to both Ar-K+ and Xe-Cs+ systems. When the ion is closer in size to the rare gas atoms (for XeNCs+) the global minima tend to be based on icosahedral packing. However, when the ion is relatively small (for ArNK+) the global minima below a certain size threshold are based on structures where the ion has lower coordination numbers. For larger clusters the global minima are again based on icosahedral packing. The latter structures can be found with minimal computational effort using the known global minima for clusters bound by Lennard-Jones or Morse potentials, substituting one atom at a time by the ion and minimizing.

  20. Hierarchical cluster analysis of ignitable liquids based on the total ion spectrum.

    PubMed

    Waddell, Erin E; Frisch-Daiello, Jessica L; Williams, Mary R; Sigman, Michael E

    2014-09-01

    Gas chromatography-mass spectrometry (GC-MS) data of ignitable liquids in the Ignitable Liquids Reference Collection (ILRC) database were processed to obtain 445 total ion spectra (TIS), that is, average mass spectra across the chromatographic profile. Hierarchical cluster analysis, an unsupervised learning technique, was applied to find features useful for classification of ignitable liquids. A combination of the correlation distance and average linkage was utilized for grouping ignitable liquids with similar chemical composition. This study evaluated whether hierarchical cluster analysis of the TIS would cluster together ignitable liquids of the same ASTM class assignment, as designated in the ILRC database. The ignitable liquids clustered based on their chemical composition, and the ignitable liquids within each cluster were predominantly from one ASTM E1618-11 class. These results reinforce use of the TIS as a tool to aid in forensic fire debris analysis. © 2014 American Academy of Forensic Sciences.

  1. Multiphoton ionization of ions, neutrals, and clusters. Final report

    SciTech Connect

    Wessel, J.

    1995-12-28

    A multiyear research program investigating molecular detection methods based on multiphoton spectroscopy has been completed under DOE sponsorship. A number of new laser-based spectroscopic methods were developed and applied to a variety of aromatic hydrocarbons, including monomer and cluster species. The objectives of sensitivities approaching single molecule detection combined with high selectivity were achieved. This report references the status of the field at the beginning of this work and summarizes the significant progress during the period from 1987 onward. Detailed scientific findings from the studies are presented in the published literature referenced throughout this report.

  2. TOF-SIMS with argon gas cluster ion beams: a comparison with C60+.

    PubMed

    Rabbani, Sadia; Barber, Andrew M; Fletcher, John S; Lockyer, Nicholas P; Vickerman, John C

    2011-05-15

    Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is an established technique for the characterization of solid sample surfaces. The introduction of polyatomic ion beams, such as C(60), has provided the associated ability to perform molecular depth-profiling and 3D molecular imaging. However, not all samples perform equally under C(60) bombardment, and it is probably naïve to think that there will be an ion beam that will be applicable in all situations. It is therefore important to explore the potential of other candidates. A systematic study of the suitability of argon gas cluster ion beams (Ar-GCIBs) of general composition Ar(n)(+), where n = 60-3000, as primary particles in TOF-SIMS analysis has been performed. We have assessed the potential of the Ar-GCIBs for molecular depth-profiling in terms of damage accumulation and sputter rate and also as analysis beams where spectral quality and secondary ion yields are considered. We present results with direct comparison with C(60) ions on the same sample in the same instrument on polymer, polymer additive, and biomolecular samples, including lipids and small peptides. Large argon clusters show reduced damage accumulation compared with C(60) with an approximately constant sputter rate as a function of Ar cluster size. Further, on some samples, large argon clusters produce changes in the mass spectra indicative of a more gentle ejection mechanism. However, there also appears to be a reduction in the ionization of secondary species as the size of the Ar cluster increases.

  3. Orientational dependence of electronic stopping of molecule and cluster ions

    NASA Astrophysics Data System (ADS)

    Jensen, J.; Mikkelsen, H. H.; Sigmund, P.

    1994-04-01

    The electronic energy deposited by a fast molecule or cluster penetrating through matter is estimated on the basis of a multipole expansion of the Coulomb interaction between the projectile and the target electrons. The treatment is directed at distant collisions, and the primary purpose has been to gain an impression of the dependence of the electronic energy loss on the orientation of the projectile relative to the beam direction. With this qualitative goal in mind, and considering that the total charge of a moving cluster can be quite high, we chose Bohr's classical-oscillator model of the target atom as the theoretical basis. The energy loss versus impact parameter consists of the familiar monopole term which applies to a point charge, plus a number of multipole terms, the leading one of which is found to be a monopole-quadrupole term. In the energy loss averaged over all orientations, that term vanishes, and the leading nonvanishing term then becomes the quadrupole-quadrupole term which reflects the properties of expressions in the literature based on Bethe theory. It is concluded that for anisotropic molecules, the directional dependence of electronic energy loss is more pronounced than what could be expected from published proximity factors. Explicit examples refer to a diatomic molecule.

  4. Formation of Nanometallic Clusters in Silica by Ion Implantation

    SciTech Connect

    Ila, D., Sarkisov, S., Williams, E.K. , Smith, C.C. , Poker, D.B., Hensley, D.K.

    1997-10-01

    We have changed both linear and nonlinear optical properties of suprasil-1 by implanting 2.0 MeV copper, 350 keV tin, 1.5 MeV silver and 3.0 MeV gold.These changes were induced both by over implantation above the threshold fluence for spontaneous cluster formation and by subsequent thermal annealing,and are due to an increase in resonance optical absorption as well as an enhancement of the nonlinear optical properties. Using optical absorption spectrophotometry and Rutherford Backscattering spectrometry, we have measured the cluster size for each heat treatment temperature. Using Z-scan technique we have determined the third order electric susceptibility for each implanted species to be 1.5 x 10(exp -6) esu for Sn nanoclusters, 2.7 x 10(exp -6) esu for Cu nanoclusters, 5 x 10(exp -7) esu for Ag nanoclusters, to 6.5 x 10(exp-7) esu for Au nanoclusters in suprasil- 1.

  5. Evaluation of different implementations of the Thomson liquid drop model: comparison to monovalent and divalent cluster ion experimental data.

    PubMed

    Donald, William A; Williams, Evan R

    2008-04-24

    The Thomson model, used for calculating thermodynamic properties of cluster ions from macroscopic properties, and variations of this model were compared to each other and to experimental data for both hydrated mono- and divalent ions. Previous models that used the Thomson equation to calculate sequential binding thermodynamic values of hydrated ions, either continuously or discretely including an ion-dipole interaction term, were compared to a discrete model that includes the excluded volume of an impurity ion. All models, given their limitations, provided reasonable agreement to data for monovalent ions. For divalent cluster ions, the continuous model, and a discrete model that includes the ion-exclusion volume provide significantly better agreement to both the binding enthalpy and the binding entropy data as compared to the model that includes an ion-dipole term. A systematic deviation in the continuous model resulted in significantly lower binding enthalpies than the discrete model for clusters with fewer than about nine and 19 water molecules for mono- and divalent ions, respectively, but this difference became negligible for larger clusters. Previous investigations of the various Thomson model implementations used parameters for bulk water at 313 K. Using parameters at 298 K has a negligible effect at small cluster sizes, but at larger sizes, the binding enthalpies are 0.2 kcal/mol higher than with the 313 K parameters. Although small, the effect is significant for ion nanocalorimetry experiments in which thermochemical information is obtained from the number of water molecules lost upon activating large clusters.

  6. ION INJECTION AT QUASI-PARALLEL SHOCKS SEEN BY THE CLUSTER SPACECRAFT

    SciTech Connect

    Johlander, A.; Vaivads, A.; Khotyaintsev, Yu. V.; Retinò, A.

    2016-01-20

    Collisionless shocks in space plasma are known to be capable of accelerating ions to very high energies through diffusive shock acceleration (DSA). This process requires an injection of suprathermal ions, but the mechanisms producing such a suprathermal ion seed population are still not fully understood. We study acceleration of solar wind ions resulting from reflection off short large-amplitude magnetic structures (SLAMSs) in the quasi-parallel bow shock of Earth using in situ data from the four Cluster spacecraft. Nearly specularly reflected solar wind ions are observed just upstream of a SLAMS. The reflected ions are undergoing shock drift acceleration (SDA) and obtain energies higher than the solar wind energy upstream of the SLAMS. Our test particle simulations show that solar wind ions with lower energy are more likely to be reflected off the SLAMS, while high-energy ions pass through the SLAMS, which is consistent with the observations. The process of SDA at SLAMSs can provide an effective way of accelerating solar wind ions to suprathermal energies. Therefore, this could be a mechanism of ion injection into DSA in astrophysical plasmas.

  7. Ion injection at Quasi-parallel Shocks Seen by the Cluster Spacecraft

    NASA Astrophysics Data System (ADS)

    Johlander, A.; Vaivads, A.; Khotyaintsev, Yu. V.; Retinò, A.; Dandouras, I.

    2016-01-01

    Collisionless shocks in space plasma are known to be capable of accelerating ions to very high energies through diffusive shock acceleration (DSA). This process requires an injection of suprathermal ions, but the mechanisms producing such a suprathermal ion seed population are still not fully understood. We study acceleration of solar wind ions resulting from reflection off short large-amplitude magnetic structures (SLAMSs) in the quasi-parallel bow shock of Earth using in situ data from the four Cluster spacecraft. Nearly specularly reflected solar wind ions are observed just upstream of a SLAMS. The reflected ions are undergoing shock drift acceleration (SDA) and obtain energies higher than the solar wind energy upstream of the SLAMS. Our test particle simulations show that solar wind ions with lower energy are more likely to be reflected off the SLAMS, while high-energy ions pass through the SLAMS, which is consistent with the observations. The process of SDA at SLAMSs can provide an effective way of accelerating solar wind ions to suprathermal energies. Therefore, this could be a mechanism of ion injection into DSA in astrophysical plasmas.

  8. Model of large volumetric capacitance in graphene supercapacitors based on ion clustering

    NASA Astrophysics Data System (ADS)

    Skinner, Brian; Fogler, M. M.; Shklovskii, B. I.

    2011-12-01

    Electric double-layer supercapacitors (SCs) are promising devices for high-power energy storage based on the reversible absorption of ions into porous conducting electrodes. Graphene is a particularly good candidate for the electrode material in SCs due to its high conductivity and large surface area. In this paper, we consider SC electrodes made from a stack of graphene sheets with randomly inserted spacer molecules. We show that the large volumetric capacitances C≳100F/cm3 observed experimentally can be understood as a result of collective intercalation of ions into the graphene stack and the accompanying nonlinear screening by graphene electrons that renormalizes the charge of the ion clusters.

  9. A model of large volumetric capacitance in graphene supercapacitors based on ion clustering

    NASA Astrophysics Data System (ADS)

    Skinner, Brian; Fogler, Michael; Shklovskii, Boris

    2012-02-01

    Electric double layer supercapacitors are promising devices for high-power energy storage based on the reversible absorption of ions into porous, conducting electrodes. Graphene is a particularly good candidate for the electrode material in supercapacitors due to its high conductivity and large surface area. In this paper we consider supercapacitor electrodes made from a stack of graphene sheets with randomly-inserted ``spacer" molecules. We show that the large volumetric capacitances C > 100 F/cm^3 observed experimentally can be understood as a result of collective intercalation of ions into the graphene stack and the accompanying nonlinear screening by graphene electrons that renormalizes the charge of the ion clusters.

  10. Ion-channeling analysis of boron clusters in silicon

    NASA Astrophysics Data System (ADS)

    Selen, L. J. M.; Janssen, F. J. J.; van IJzendoorn, L. J.; de Voigt, M. J. A.; Theunissen, M. J. J.; Smulders, P. J. M.; Eijkemans, T. J.

    2001-11-01

    We have measured axially channeled Rutherford backscattering spectra of Si1-xGex nanofilms in silicon(001). A step in the yield of the host crystal was found for off-normal axes at the depth of the nanofilm. The step was measured as a function of the angle between the incoming beam and the [011] axis and shows two maxima. It is found that Monte Carlo simulations assuming tetragonal distortion reproduce the experimental results. A universal curve was derived which enables determination of the tetragonal distortion from ion-channeling experiments, for a given film thickness. The results are compared with XRD measurements.

  11. Core Ion Structures and Solvation Effects in Gas Phase [Sn(CO_{2})_{n}]^{-} Clusters

    NASA Astrophysics Data System (ADS)

    Thompson, Michael C.; Weber, J. Mathias

    2017-06-01

    We report infrared photodissociation spectra of [Sn(CO_{2})_{n}] (n=2-6) clusters. We explore core ion geometries through quantum chemical calculations and assign our experimental spectra through comparison with calculated vibrational frequencies. We discuss our results in the context of heterogeneous catalytic reduction of CO_{2}, and compare our results with previous work on other post-transition metal species.

  12. Photoluminescence study of self-interstitial clusters and extended defects in ion-implanted silicon

    NASA Astrophysics Data System (ADS)

    Giri, P. K.

    2003-12-01

    We report on the photoluminescence (PL) studies of self-interstitial (I) clustering in ion-implanted Si at various stages of post-implantation annealing. Low-temperature PL measurements on as-implanted and low-temperature annealed (up to 450°C) samples show sharp X and W bands at 1200 and 1218 nm which are attributed to I4 and I3 clusters, respectively. Annealing at 600°C shows a drastic change in the PL spectra. In case of high-energy self-ion-implanted samples, 600°C annealing produces several peaks in the range 1250-1400 nm. For longer duration annealing, two broad bands form at 1322 and 1392 nm irrespective of the ion fluence. These PL signatures are attributed to I8 clusters and/or (1 0 0) I-chains, and they are believed to be the precursor of {3 1 1} rod-like defects. For annealing above 600°C and for fluence ⩾1×1013 cm-2, a sharp PL band is observed at 1376 nm and it is attributed to {3 1 1} rod-like defects. At higher fluences, an additional broad band appears in the PL spectrum at ∼1576 nm which is related to residual ion-damage or extended defect formation. These results illustrate the potential of silicon I-clusters as a possible source of light emission from Si.

  13. Summary of Industry-Academia Collaboration Projects on Cluster Ion Beam Process Technology

    NASA Astrophysics Data System (ADS)

    Yamada, Isao; Matsuo, Jiro; Toyoda, Noriaki

    2008-11-01

    Processes employing clusters of ions comprised of a few hundred to many thousand atoms are now being developed into a new field of ion beam technology. Cluster-surface collisions produce important non-linear effects which are being applied to shallow junction formation, to etching and smoothing of semiconductors, metals, and dielectrics, to assisted formation of thin films with nano-scale accuracy, and to other surface modification applications. In 2000, a four year R&D project for development of industrial technology began in Japan under funding from the New Energy and Industrial Technology Development Organization (NEDO). Subjects of the projects are in areas of equipment development, semiconductor surface processing, high accuracy surface processing and high-quality film formation. In 2002, another major cluster ion beam project which emphasized nano-technology applications has started under a contract from the Ministry of Economy and Technology for Industry (METI). This METI project involved development related to size-selected cluster ion beam equipment and processes, and development of GCIB processes for very high rate etching and for zero damage etching of magnetic materials and compound semiconductor materials. This paper describes summery of the results.

  14. Conical octopole ion guide: Design, focusing, and its application to the deposition of low energetic clusters

    SciTech Connect

    Roettgen, Martin A.; Judai, Ken; Antonietti, Jean-Marie; Heiz, Ueli; Rauschenbach, Stephan; Kern, Klaus

    2006-01-15

    A design of a radio-frequency (rf) octopole ion guide with truncated conical rods arranged in a conical geometry is presented. The performance is tested in a cluster deposition apparatus used for the soft-landing of size-selected clusters on well-characterized substrates used as a model system in heterogeneous catalysis in ultrahigh vacuum. This device allows us to focus 500 pA of a mass-selected Ni{sub 20}{sup +} cluster ion beam from 9 mm down to a spot size of 2 mm in diameter. The transmittance is 70%{+-}5% at a rf voltage of 420 V{sub pp} applied over an amateur radio transceiver with an interposed homemade amplifier-transformer circuit. An increase of the cluster density by a factor of 15 has been achieved. Three ion trajectories are simulated by using SIMION6, which are relevant for this focusing device: transmitted, reflected, and absorbed. The observed effects in the simulations can be successfully explained by the adiabatic approximation. The focusing behavior of the conical octopole lens is demonstrated by experiment and simulations to be a very useful technique for increasing molecule or cluster densities on a substrate and thus reducing deposition time.

  15. The structures and stabilities of helium cluster ions

    NASA Astrophysics Data System (ADS)

    Knowles, Peter J.; Murrell, John N.

    Previously published 2-body and 3-body terms for an n-valued representation of the potential functions of Hen+ have been used to examine the structures of larger clusters. For n = 3-8 the most stable structure has a linear He3+ core surrounded by weakly bound, nearly neutral atoms, with up to four lying in an equatorial plane. Such structures persist as metastable species up to n = 12. For n > 8 the most stable structure consists of a He2+ core with up to nine atoms closely attached. The first excited state is predicted to have a vertical excitation energy of between 5·5 eV and 5·9 eV, changing little with n. This is in broad agreement with experimental observations.

  16. Anionic Hydrogen Cluster Ions as a New Form of Condensed Hydrogen

    NASA Astrophysics Data System (ADS)

    Renzler, Michael; Kuhn, Martin; Mauracher, Andreas; Lindinger, Albrecht; Scheier, Paul; Ellis, Andrew M.

    2016-12-01

    We report the first experimental observation of negatively charged hydrogen and deuterium cluster ions, Hn- and Dn- , where n ≥5 . These anions are formed by an electron addition to liquid helium nanodroplets doped with molecular hydrogen or deuterium. The ions are stable for at least the lifetime of the experiment, which is several tens of microseconds. Only anions with odd values of n are detected, and some specific ions show anomalously high abundances. The sizes of these "magic number" ions suggest an icosahedral framework of H2 (D2 ) molecules in solvent shells around a central H- (D- ) ion. The first three shells, which contain a total of 44 H2 or D2 molecules, appear to be solidlike, but thereafter a more liquidlike arrangement of the H2 (D2 ) molecules is adopted.

  17. Measurements of Laser Absorption and Ion Energy in Femtosecond Laser-Cluster Interaction

    NASA Astrophysics Data System (ADS)

    Lin, Jing-Quan; Zhang, Jie; Li, Ying-Jun; Chen, Li-Ming; Lü, Tie-Zheng; Teng, Hao; Man, Bao-Yuan; Zhao, Li-Zeng

    2001-02-01

    Laser absorption is measured in Xe, Ar and He clusters irradiated by 5 mJ laser pulses in 150 fs. The measurements show that the absorption efficiency strongly depends on the backing pressure of the gas jets, the laser pulse duration and the atomic number Z of the working gas. The laser absorption for Xe clusters is found to be as high as 45% at a backing pressure of 20 atm and a laser intensity of 1×1015 W/cm2. Significant numbers of ions with energies up to 100 keV are detected from Xe cluster explosion. The variation trend of the average ion energy at different backing pressures is consistent with that of the laser energy absorption.

  18. Titanium-dioxide film formation using gas cluster ion beam assisted deposition technique

    NASA Astrophysics Data System (ADS)

    Nakatsu, O.; Matsuo, J.; Omoto, K.; Seki, T.; Takaoka, G.; Yamada, I.

    2003-05-01

    Gas cluster ion beam (GCIB) assisted deposition technique has been applied to form titanium-dioxide films. When oxygen cluster ions collide on solid surfaces, oxygen molecules in the clusters enhance oxidation due to high density energy deposition. Metal titanium pellets were used as source material for EB evaporation, because evaporation with metal pellets is much stable than that of oxide pellets. Films were deposited on sapphire (0 0 0 1) substrates with various conditions. Characteristics of the films were examined by use of XRD, RBS and AFM. When film was deposited with the acceleration voltage of 7 kV at 473 K, the well c-oriented rutile TiO 2 film was formed with average roughness of 0.4 nm. Without assistance of GCIB rough amorphous film was formed in an atmosphere of oxygen. Very smooth surface films with good crystallinity were formed by GCIB assisted deposition technique.

  19. Thermally and chemically stable mixed valence copper oxide cluster ions revealed by post heating.

    PubMed

    Morita, Keisuke; Sakuma, Kazuko; Miyajima, Ken; Mafuné, Fumitaka

    2013-10-10

    Copper oxide clusters, Cu(n)O(m)(+) (n = 5-12), were prepared in the gas phase by laser ablation of a copper metal rod in the presence of oxygen diluted in He as the carrier gas. The stoichiometry of the cluster ions was investigated using mass spectrometry. The number ratio of copper atoms and oxygen atoms in Cu(n)O(m)(+) was distributed from n:m = 1:1-3:2, which was not affected significantly by the concentration of oxygen in the carrier gas as long as it exceeded 2%. When the cluster ions were heated up to 573 K downstream of the cluster source (post heating), Cu(n)O(m)(+) (n:m ≈ 3:2) clusters were selectively and dominantly formed as a result of thermal dissociation. No further changes in the ratio were observed when the clusters were heated up to 623 K. From the stoichiometry, Cu(n)O(m)(+) is considered to comprise both Cu(I) and Cu(II). Hence, the mixed valence states are found to be thermally stable for the small clusters in the gas phase, but they are not stable in the bulk phase. In addition to the thermal stability, we observed reactivity of Cu(n)O(m)(+) with CO molecules. It was found that Cu12O8(+) hardly binds to CO and that Cu9O6(+) and Cu6O4(+) along with other clusters with n:m ≈ 3:2 bind to CO very weakly, whereas CO attaches strongly to oxygen-rich clusters with release of an oxygen molecule.

  20. Enhancing ion yields in time-of-flight-secondary ion mass spectrometry: a comparative study of argon and water cluster primary beams.

    PubMed

    Sheraz née Rabbani, Sadia; Razo, Irma Berrueta; Kohn, Taylor; Lockyer, Nicholas P; Vickerman, John C

    2015-02-17

    Following from our previous Letter on this topic, this Article reports a detailed study of time-of-flight-secondary ion mass spectrometry (TOF-SIMS) positive ion spectra generated from a set of model biocompounds (arginine, trehalose, DPPC, and angiotensin II) by water cluster primary ion beams in comparison to argon cluster beams over a range of cluster sizes and energies. Sputter yield studies using argon and water beams on arginine and Irganox 1010 have confirmed that the sputter yields using water cluster beams lie on the same universal sputtering curve derived by Seah for argon cluster beams. Thus, increased ion yield using water cluster beams must arise from increased ionization. The spectra and positive ion signals observed using cluster beams in the size range from 1,000 to 10,000 and the energy range 5-20 keV are reported. It is confirmed that water cluster beams enhance proton related ionization over against argon beams to a significant degree such that enhanced detection sensitivities from 1 μm(2) in the region of 100 to 1,000 times relative to static SIMS analysis with Ar2000 cluster beams appear to be accessible. These new studies show that there is an unexpected complexity in the ionization enhancement phenomenon. Whereas optimum ion yields under argon cluster bombardment occur in the region of E/n ≥ 10 eV (where E is the beam energy and n the number of argon atoms in the cluster) and fall rapidly when E/n < 10 eV; for water cluster beams, ion yields increase significantly in this E/n regime (where n is the number of water molecules in the cluster) and peak for 20 keV beams at a cluster size of 7,000 or E/n ∼3 eV. This important result is explored further using D2O cluster beams that confirm that in this low E/n regime protonation does originate to a large extent from the water molecules. The results, encouraging in themselves, suggest that for both argon and water cluster beams, higher energy beams, e.g., 40 and 80 keV, would enable larger

  1. Secondary ion counting for surface-sensitive chemical analysis of organic compounds using time-of-flight secondary ion mass spectroscopy with cluster ion impact ionization

    SciTech Connect

    Hirata, K.; Saitoh, Y.; Chiba, A.; Yamada, K.; Takahashi, Y.; Narumi, K.

    2011-03-15

    We report suitable secondary ion (SI) counting for surface-sensitive chemical analysis of organic compounds using time-of-flight (TOF) SI mass spectroscopy, based on considerably higher emission yields of SIs induced by cluster ion impact ionization. A SI counting system for a TOF SI mass spectrometer was developed using a fast digital storage oscilloscope, which allows us to perform various types of analysis as all the signal pulses constituting TOF SI mass spectra can be recorded digitally in the system. Effects of the SI counting strategy on SI mass spectra were investigated for C{sub 8} and C{sub 60} cluster ion impacts on an organically contaminated silicon wafer and on polytetrafluoroethylene targets by comparing TOF SI mass spectra obtained from the same recorded signals with different SI counting procedures. Our results show that the use of a counting system, which can cope with high SI yields, is necessary for quantitative analysis of SI mass spectra obtained under high SI yield per impact conditions, including the case of cluster ion impacts on organic compounds.

  2. Synthesis of iron and copper nano-clusters in SiO 2 by ion implantation and the magnetic properties

    NASA Astrophysics Data System (ADS)

    Hayashia, N.; Sakamoto, I.; Moriwaki, T.; Wakabayashi, H.; Toriyama, T.

    2005-04-01

    The formation of iron and copper nano-clusters in crystalline SiO2 by sequential implantations of Fe and Cu ions was studied. The implantation was performed at room temperature to a total dose of 1.9×1019 ions/cm2. The addition of Cu ions was done by a dose of 0.7×1017 Cu ions/cm2. It is shown by the measurements of conversion electron Mössbauer spectroscopy and X-ray diffraction that the addition of Cu ions promotes the transitions from superparamagnetic to ferromagnetic states in the iron nano-clusters aggregated beforehand.

  3. Ion Spectral Structures Observed by the Van Allen Probes and Cluster

    NASA Astrophysics Data System (ADS)

    Ferradas, C.; Zhang, J.; Luo, H.; Kistler, L. M.; Spence, H. E.; Larsen, B.; Skoug, R. M.; Funsten, H. O.; Reeves, G. D.

    2014-12-01

    During the last decades several missions have recorded the presence of dynamic spectral features of energetic ions in the inner magnetosphere. Previous studies have revealed single "nose-like" structures occurring alone and simultaneous nose-like structures (up to three). In this study we also include signatures of new types of ion structure, namely "trunk-like" and "tusk-like" structures. All the ion structures are named after the characteristic shapes of energy bands or gaps in the energy-time spectrograms of in situ measured ion fluxes. They constitute the observational signatures of ion acceleration, transport, and loss in the global magnetosphere. Multi-spacecraft analysis of these structures is important to understand their spatial distribution and temporal evolution. Mass spectrometers onboard Cluster (in a polar orbit) and the Van Allen Probes (in an equatorial orbit) measure energetic hydrogen, helium, and oxygen ions near the inner edge of the plasma sheet, where these ion structures are observed. We present a statistical study of the ion structures, using >1-year measurements from the two missions during the Van Allen Probes era. The results provide important details about the spatial distribution (dependence on geocentric distance and magnetic local time), spectral features of the structures (e.g., characteristic energy and differences among species), and geomagnetic and solar wind conditions under which these structures occur.

  4. Generation of argon-ion mixed silicon plasmas forming argon encapsulated silicon clusters

    NASA Astrophysics Data System (ADS)

    Kaneko, T.; Takaya, H.; Hatakeyama, R.

    2006-12-01

    An inductively coupled argon (Ar) plasma is superimposed on a silicon (Si) plasma generated by an electron beam gun in order to realize the formation of gas-atom encapsulated Si cage clusters. The Si clusters, which are formed and deposited on a substrate, are analyzed by laser-desorption time-of-flight mass spectrometry and are found to have the mass spectra of not only pure Si cluster (Sin; n =1-17) but also Si cluster doped with Ar atom (ArSin; n =10-20) in the case that the large amount of Ar ions is generated in addition to the Si plasma. Together with the analysis of x-ray photoelectron spectroscopy, it is revealed that the Ar atom is included in the Si cluster, forming the structure of endohedral Ar@Sin complexes. Furthermore, the mass spectrum of Ar@Sin indicates the existence of the magic numbered cluster size n =15, 16 similar to the metal encapsulated Si clusters.

  5. Ion probe detection of clusters in a remotely expanding thermal plasma

    NASA Astrophysics Data System (ADS)

    Petcu, M. C.; Sarkar, A.; Bronneberg, A. C.; Creatore, M.; van de Sanden, M. C. M.

    2010-12-01

    The investigation of a remote depositing Ar/NH3/SiH4-fed expanding thermal plasma by means of an ion probe, under high SiH4 flow rate ( \\Phi_{SiH_4} >1\\,sccs ) conditions, is reported here. Given the expanding nature of the plasma in the downstream region, a Gaussian-like ion flux radial profile is observed. A peculiar local off-axis ion peak for high \\Phi_{SiH_4} is also observed nearby. A hypothesis for this phenomenon is proposed, on the basis of the plasma chemistry occurring in the downstream region. The local depletion of electrons, being withdrawn by silicon-containing clusters formed at the boundaries between the plasma beam and the background gas, is responsible for the local enhancement of the ion flux. This hypothesis is corroborated by further studies aiming to evaluate the effects of thermophoretic and electrostatic forces on the above-mentioned clusters. The presented work suggests the application of the capacitive probe technique for cluster detection in specific plasma chemistries.

  6. Kinetic energy distribution of multiply charged ions in Coulomb explosion of Xe clusters.

    PubMed

    Heidenreich, Andreas; Jortner, Joshua

    2011-02-21

    We report on the calculations of kinetic energy distribution (KED) functions of multiply charged, high-energy ions in Coulomb explosion (CE) of an assembly of elemental Xe(n) clusters (average size (n) = 200-2171) driven by ultra-intense, near-infrared, Gaussian laser fields (peak intensities 10(15) - 4 × 10(16) W cm(-2), pulse lengths 65-230 fs). In this cluster size and pulse parameter domain, outer ionization is incomplete∕vertical, incomplete∕nonvertical, or complete∕nonvertical, with CE occurring in the presence of nanoplasma electrons. The KEDs were obtained from double averaging of single-trajectory molecular dynamics simulation ion kinetic energies. The KEDs were doubly averaged over a log-normal cluster size distribution and over the laser intensity distribution of a spatial Gaussian beam, which constitutes either a two-dimensional (2D) or a three-dimensional (3D) profile, with the 3D profile (when the cluster beam radius is larger than the Rayleigh length) usually being experimentally realized. The general features of the doubly averaged KEDs manifest the smearing out of the structure corresponding to the distribution of ion charges, a marked increase of the KEDs at very low energies due to the contribution from the persistent nanoplasma, a distortion of the KEDs and of the average energies toward lower energy values, and the appearance of long low-intensity high-energy tails caused by the admixture of contributions from large clusters by size averaging. The doubly averaged simulation results account reasonably well (within 30%) for the experimental data for the cluster-size dependence of the CE energetics and for its dependence on the laser pulse parameters, as well as for the anisotropy in the angular distribution of the energies of the Xe(q+) ions. Possible applications of this computational study include a control of the ion kinetic energies by the choice of the laser intensity profile (2D∕3D) in the laser-cluster interaction volume.

  7. Spatial distribution of particles sputtered from single crystals by gas cluster ions

    NASA Astrophysics Data System (ADS)

    Nazarov, A. V.; Chernysh, V. S.; Nordlund, K.; Djurabekova, F.; Zhao, J.

    2017-09-01

    The results of molecular dynamics simulations of the bombardment of the Cu (100) and Mo (100) single-crystals by 10 keV Ar cluster ions of different sizes are presented in this paper. Spatial distributions of sputtered material were calculated. The anisotropy of the angular distributions of sputtered atoms was revealed. It was found that the character of the anisotropy is different for Cu and Mo targets. The reasons leading to this anisotropy are discussed according to the dependences of the angular distributions on the cluster size and on the target material.

  8. Dissociative recombination of water cluster ions with free electrons: Cross sections and branching ratios

    SciTech Connect

    Oejekull, J.; Andersson, P. U.; Pettersson, J. B. C.; Markovic, N.; Thomas, R. D.; Al Khalili, A.; Ehlerding, A.; Oesterdahl, F.; Ugglas, M. af; Larsson, M.; Danared, H.; Kaellberg, A.

    2008-01-28

    Dissociative recombination (DR) of water cluster ions H{sup +}(H{sub 2}O){sub n} (n=4-6) with free electrons has been studied at the heavy-ion storage ring CRYRING (Manne Siegbahn Laboratory, Stockholm University). For the first time, branching ratios have been determined for the dominating product channels and absolute DR cross sections have been measured in the energy range from 0.001 to 0.7 eV. Dissociative recombination is concluded to result in extensive fragmentation for all three cluster ions, and a maximum number of heavy oxygen-containing fragments is produced with a probability close to unity. The branching ratio results agree with earlier DR studies of smaller water cluster ions where the channel nH{sub 2}O+H has been observed to dominate and where energy transfer to internal degrees of freedom has been concluded to be highly efficient. The absolute DR cross sections for H{sup +}(H{sub 2}O){sub n} (n=4-6) decrease monotonically with increasing energy with an energy dependence close to E{sup -1} in the lower part of the energy range and a faster falloff at higher energies, in agreement with the behavior of other studied heavy ions. The cross section data have been used to calculate DR rate coefficients in the temperature range of 10-2000 K. The results from storage ring experiments with water cluster ions are concluded to partly confirm the earlier results from afterglow experiments. The DR rate coefficients for H{sup +}(H{sub 2}O){sub n} (n=1-6) are in general somewhat lower than reported from afterglow experiments. The rate coefficient tends to increase with increasing cluster size, but not in the monotonic way that has been reported from afterglow experiments. The needs for further experimental studies and for theoretical models that can be used to predict the DR rate of polyatomic ions are discussed.

  9. Negative Ion Photoelectron Spectroscopy Reveals Thermodynamic Advantage of Organic Acids in Facilitating Formation of Bisulfate Ion Clusters: Atmospheric Implications

    SciTech Connect

    Hou, Gao-Lei; Lin, Wei; Deng, Shihu; Zhang, Jian; Zheng, Weijun; Paesani, Francesco; Wang, Xue B.

    2013-03-07

    Recent lab and field measurements have indicated critical roles of organic acids in enhancing new atmospheric aerosol formation. Such findings have stimulated theoretical studies with the aim of understanding interaction of organic acids with common aerosol nucleation precursors like bisulfate (HSO4-). In this Letter, we report a combined negative ion photoelectron spectroscopic and theoretical investigation of molecular clusters formed by HSO4- with succinic acid (SUA, HO2C(CH2)2CO2H), HSO4-(SUA)n (n = 0-2), along with HSO4-(H2O)n and HSO4-(H2SO4)n. It is found that one SUA molecule can stabilize HSO4- by ca. 39 kcal/mol, triple the corresponding value that one water molecule is capable of (ca. 13 kcal/mol). Molecular dynamics simulations and quantum chemical calculations reveal the most plausible structures of these clusters and attribute the stability of these clusters due to formation of strong hydrogen bonds. This work provides direct experimental evidence showing significant thermodynamic advantage by involving organic acid molecules to promote formation and growth in bisulfate clusters and aerosols.

  10. Spectroscopic Evidence for Clusters of Like-Charged Ions in Ionic Liquids Stabilized by Cooperative Hydrogen Bonding.

    PubMed

    Knorr, Anne; Stange, Peter; Fumino, Koichi; Weinhold, Frank; Ludwig, Ralf

    2016-02-16

    Direct spectroscopic evidence for hydrogen-bonded clusters of like-charged ions is reported for ionic liquids. The measured infrared O-H vibrational bands of the hydroxyethyl groups in the cations can be assigned to the dispersion-corrected DFT calculated frequencies of linear and cyclic clusters. Compensating the like-charge Coulomb repulsion, these cationic clusters can range up to cyclic tetramers resembling molecular clusters of water and alcohols. These ionic clusters are mainly present at low temperature and show strong cooperative effects in hydrogen bonding. DFT-D3 calculations of the pure multiply charged clusters suggest that the attractive hydrogen bonds can compete with repulsive Coulomb forces.

  11. Enhanced performance of anion exchange membranes via crosslinking of ion cluster regions for fuel cells

    NASA Astrophysics Data System (ADS)

    Lai, Ao Nan; Guo, Dong; Lin, Chen Xiao; Zhang, Qiu Gen; Zhu, Ai Mei; Ye, Mei Ling; Liu, Qing Lin

    2016-09-01

    Development of anion exchange membranes (AEMs) with high hydroxide conductivity, good dimensional and alkaline stabilities is still a challenge for the practical application of AEM fuel cells. In this study, we report a new strategy to prepare high-performance AEMs with crosslinked ionic regions. A series of phenolphthalein-containing poly(arylene ether sulfone)s crosslinked AEMs was synthesized by grafting ion groups selectively and densely on the phenolphthalein units to form ion clusters that are further crosslinked to generate the hydrophilic ionic regions. The crosslinking reaction not only improved the dimensional stability of the AEMs, but also increased the aggregation of the ion clusters leading to the formation of hydrophilic/hydrophobic phase-separated morphology and ion-conducting channels. As a result, enhancements in both ion conductivity and dimensional stability can be achieved. The crosslinked AEMs showed high hydroxide conductivities in the range of 52.2-143.4 mS cm-1 from 30 to 80 °C and a superb ratio of relative conductivity to relative swelling at 80 °C. Furthermore, the crosslinked AEMs also exhibited good mechanical properties, thermal and alkaline stabilities and desirable single cell performance. This work presents a promising strategy for the synthesis of high-performance AEMs for fuel cells.

  12. 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.

  13. Instability range of microsolvated multiply charged negative ions: prediction from detachment energy of stable hydrated clusters.

    PubMed

    Pathak, A K; Samanta, A K; Maity, D K; Mukherjee, T; Ghosh, S K

    2011-02-01

    We have presented a first-principle theory-based derivation of an exact expression for the solvent number-dependent electron-detachment energy of a solvated species in the thermodynamic limit. We also propose a generalized equation bridging the electron detachment energies for small and infinitely large clusters, thus providing a new route to calculate the ionization potential of a negatively charged ion from the electron-detachment energies of its stable hydrated clusters. Most importantly, it has the ability to predict the instability range of microhydrated anions. The calculated results for the ionization potential for a number of ions are found to be in good agreement with the available experimental results, and the predicted instability range for the doubly charged anions SO₄²⁻ and C₂O₄²⁻ is also consistent with experimental and ab initio results.

  14. Positively and Negatively Charged Cesium and (C60) m Cs n Cluster Ions.

    PubMed

    Renzler, Michael; Kranabetter, Lorenz; Goulart, Marcelo; Scheier, Paul; Echt, Olof

    2017-05-25

    We report on the formation and ionization of cesium and C60Cs clusters in superfluid helium nanodroplets. Size distributions of positively and negatively charged (C60) m Cs n(±) ions have been measured for m ≤ 7, n ≤ 12. Reproducible intensity anomalies are observed in high-resolution mass spectra. For both charge states, (C60) m Cs3(±) and (C60) m Cs5(±) are particularly abundant, with little dependence on the value of m. Distributions of bare cesium cluster ions also indicate enhanced stability of Cs3(±) and Cs5(±), in agreement with theoretical predictions. These findings contrast with earlier reports on highly Cs-doped cationic fullerene aggregates which showed enhanced stability of C60Cs6 building blocks attributed to charge transfer. The dependence of the (C60) m Cs3(-) anion yield on electron energy shows a resonance that, surprisingly, oscillates in strength as m increases from 1 to 6.

  15. Nuclear cluster structure effect on elliptic and triangular flows in heavy-ion collisions

    NASA Astrophysics Data System (ADS)

    Zhang, S.; Ma, Y. G.; Chen, J. H.; He, W. B.; Zhong, C.

    2017-06-01

    The initial geometry effect on collective flows, which are inherited from initial projectile structure, is studied in relativistic heavy-ion collisions of 12C+197Au by using a multiphase transport model (AMPT). Elliptic flow (v2) and triangular flow (v3) which are significantly resulted from the chain and triangle structure of 12C with three-α clusters, respectively, in central 12C+197Au collisions are compared with the flow from the Woods-Saxon distribution of nucleons in 12C. v3/v2 is proposed as a probe to distinguish the pattern of α -clustered 12C. This study demonstrates that the initial geometry of the collision zone inherited from nuclear structure can be explored by collective flow at the final stage in heavy-ion collisions.

  16. Silicon decorated cone shaped carbon nanotube clusters for lithium ion battery anodes.

    PubMed

    Wang, Wei; Ruiz, Isaac; Ahmed, Kazi; Bay, Hamed Hosseini; George, Aaron S; Wang, Johnny; Butler, John; Ozkan, Mihrimah; Ozkan, Cengiz S

    2014-08-27

    In this work, we report the synthesis of an three-dimensional (3D) cone-shape CNT clusters (CCC) via chemical vapor deposition (CVD) with subsequent inductively coupled plasma (ICP) treatment. An innovative silicon decorated cone-shape CNT clusters (SCCC) is prepared by simply depositing amorphous silicon onto CCC via magnetron sputtering. The seamless connection between silicon decorated CNT cones and graphene facilitates the charge transfer in the system and suggests a binder-free technique of preparing lithium ion battery (LIB) anodes. Lithium ion batteries based on this novel 3D SCCC architecture demonstrates high reversible capacity of 1954 mAh g(-1) and excellent cycling stability (>1200 mAh g(-1) capacity with ≈ 100% coulombic efficiency after 230 cycles). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Cluster ion dip spectroscopy of hydrogen bonded phenol(H sub 2 O) sub n clusters, n =0--4

    SciTech Connect

    Stanley, R.J.; Castleman, A.W. Jr. )

    1991-06-15

    Employing a laser based time-of-flight mass spectrometer system, ion dip spectra for phenol (Ph), Ph(H{sub 2}O){sub 1}, Ph(H{sub 2}O){sub 3}, and Ph(H{sub 2}O){sub 4} were obtained in the range of 500--1300 cm{sup {minus}1} from a variety of initially pumped states. Dramatic enhancement of the signal-to-noise ratio of the cluster ion dip spectra relative to that of the bare phenol is attributable to the increase in the excited state singlet lifetime of the hydrated phenol chromophore. Several dips in the Ph(H{sub 2}O){sub 1} spectrum exceed the saturation'' limit of 50%, indicating that significant relaxation of the downpumped ground state is occurring via low frequency vibrational modes of the H{sub 2}O solvent bath.'' Excitation of the hydrogen bond stretch ({sigma} {sup 1}{sub 0}=156 cm{sup {minus}1} ) in the {ital S}{sub 1} state of the Ph(H{sub 2}O){sub 1} cluster reveals that the ground state ({ital S}{sub 0}) hydrogen bond stretch, {sigma} {sup 0}{sub 1}, is 151({plus minus}1) cm{sup {minus}1}, a mode which appears to be built off of phenol fundamental and combination bands. A second intermolecular band is also evident at 141({plus minus}2) cm{sup {minus}1}. There is no evidence of an analogous wag mode when pumping the {ital S}{sub 1} bend ({beta}{sup 1}{sub 0}), suggesting that the intermolecular modes in {ital S}{sub 1} are highly coupled. Attempts to obtain ion dip spectra for Ph(H{sub 2}O){sub 2} went unrewarded, presumably due to the anomalously short {ital S}{sub 1} lifetime of the Ph(H{sub 2}O){sub 2} cluster. Spectra for Ph(H{sub 2}O){sub 3} and Ph(H{sub 2}O){sub 4} were obtained which show prominent phenol bands, with low frequency ({similar to}10 cm{sup {minus}1} ) progressions built off of these bands.

  18. Drift tube measurements on Na+ ions and clusters using the 24mNa+ tracer

    NASA Astrophysics Data System (ADS)

    Kasuya, A.; Abmayr, B.; Ohtsuki, T.; Masumoto, K.; Kotajima, H.; Huenges, E.; Morinaga, H.

    1997-06-01

    Mobilities of sodium ions and their clusters in different gases have been measured by gamma-ray spectrometry using the 20 ms isomeric state of 24Na as tracer. This isomer is obtained through the β-decay of 24Ne, which was produced by bombarding 22Ne with the 7 MeV triton beam of a cyclotron. This new technique of measurement allows us to determine the mobility of sodium ions in non-reacting gases of a pressure above 1 mbar. Measurements have been carried out in gases of pressures ranging from 6 mbar to 1000 mbar under an electric field up to 250 V/cm at room temperature. The measured mobility of 24Na+ in pure neon gas at 1000 mbar was determined to be 3.2 cm2/Vs. This value is lower than the zero field mobility of about 8.5 cm2/Vs measured by Tyndall and Akridge. A small amount of polar molecules such as water or ethanol introduced into the drift tube causes their clustering with the sodium ions through monopole-dipole interaction, resulting in a strong decrease in the mobility. This clustering effect has been studied for various combinations of polar molecules and inert gases. The usable pressure range from 1 mbar to high pressures in the range of some hundred bars is interesting because most other methods for cluster studies cannot be done at such high pressures. With this method it is possible to measure the mobility change of sodium ions towards the condensation point and eventually even towards the critical point.

  19. Cluster Ion Spectrometry (CIS) data quality indexes as a support for analysing magnetospheric measurements

    NASA Astrophysics Data System (ADS)

    Dandouras, Iannis; Barthe, Alain; Brunato, Sylvain; Rème, Henri; Laakso, Harri

    2016-04-01

    The Cluster Science Archive (CSA) aims at preserving the complete set of the measurements collected by the four Cluster spacecraft, so that they are usable in the long-term by the world-wide scientific community as well as by the instrument teams. This implies that the instrument data, properly calibrated, are filed together with the descriptive and documentary elements making it possible to select and interpret them. The CIS (Cluster Ion Spectrometry) experiment is a comprehensive ionic plasma spectrometry package onboard the Cluster spacecraft, capable of obtaining full three-dimensional ion distributions (about 0 to 40 keV/e) with a time resolution of one spacecraft spin (4 sec) and with mass-per-charge composition determination. For the archival of the CIS data a multi-level approach has been adopted. The CSA archival includes processed raw data, moments of the ion distribution functions, and calibrated high-resolution data in a variety of physical units. The latter are 3-D ion distribution functions, 2-D pitch-angle distributions and 1-D omni-directional fluxes. The CIS data archive includes also experiment documentation, graphical products for browsing through the data, data caveats and data quality indexes. The later constitute a novel product, which has been prepared in order to help the user asses the quality of the data acquired in different magnetospheric regions and during various operational modes. It provides information on which are in each case the issues that can affect the data quality, which are the data products affected, and gives a simple quantitative measurement of the severity of these issues. The principle of the CIS data quality indexes will be described and the various issues, that can under some conditions affect the data quality and are thus taken into account in generating the data quality indexes, will be discussed.

  20. Cluster linker approach: preparation of a luminescent porous framework with NbO topology by linking silver ions with gold(I) clusters.

    PubMed

    Lei, Zhen; Pei, Xiao-Li; Jiang, Zhan-Guo; Wang, Quan-Ming

    2014-11-17

    A cluster-based luminescent porous metal-organic framework has been constructed through a "cluster linker" approach. The luminescent gold(I) cluster, prefunctionalized with pyrazinyl groups, was used as a cluster linker, similar to an organic linker, to connect silver ions in order to form a 3D framework. 1D channels with 1.1 nm diameter were observed in the framework. The cluster with its intrinsic luminescence was incorporated into a porous framework to give a luminescent bifunctional NbO net. This MOF shows solvatochromic behavior, and the interactions between solvent molecules and silver ions inside the channels account for the changes in absorption and emission spectra. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Luminescent sub-nanometer clusters for metal ion sensing: a new direction in nanosensors.

    PubMed

    Chakraborty, Indranath; Udayabhaskararao, T; Pradeep, T

    2012-04-15

    We describe the application of a recently discovered family of materials called quantum clusters, which are sub-nanometer particles composed of a few atoms with well-defined molecular formulae, exhibiting intense absorption and emission in the visible region in metal ion sensing, taking Ag(25) as an example. The changes in the optical properties of the cluster, in both absorption and emission upon exposure to various metal ions in aqueous medium are explored. The cluster can detect Hg(2+) down to ppb levels. It can also detect 5d block ions (Pt(2+), Au(3+) and Hg(2+)) down to ppm limits. Hg(2+) interacts with the metal core as well as the functional groups of the capping agents and the interaction is concentration-dependent. To understand the mechanism behind this type of specific interaction, we have used spectroscopic and microscopic techniques such as UV-vis spectroscopy, luminescence spectroscopy, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD). Specific reasons responsible for the interaction of Hg(2+) have been proposed. Copyright © 2011 Elsevier B.V. All rights reserved.

  2. Structures, Hydration, and Electrical Mobilities of Bisulfate Ion-Sulfuric Acid-Ammonia/Dimethylamine Clusters: A Computational Study.

    PubMed

    Tsona, Narcisse T; Henschel, Henning; Bork, Nicolai; Loukonen, Ville; Vehkamäki, Hanna

    2015-09-17

    Despite the well-established role of small molecular clusters in the very first steps of atmospheric particle formation, their thermochemical data are still not completely available due to limitation of the experimental techniques to treat such small clusters. We have investigated the structures and the thermochemistry of stepwise hydration of clusters containing one bisulfate ion, sulfuric acid, base (ammonia or dimethylamine), and water molecules using quantum chemical methods. We found that water facilitates proton transfer from sulfuric acid or the bisulfate ion to the base or water molecules, and depending on the hydration level, the sulfate ion was formed in most of the base-containing clusters. The calculated hydration energies indicate that water binds more strongly to ammonia-containing clusters than to dimethylamine-containing and base-free clusters, which results in a wider hydrate distribution for ammonia-containing clusters. The electrical mobilities of all clusters were calculated using a particle dynamics model. The results indicate that the effect of humidity is negligible on the electrical mobilities of molecular clusters formed in the very first steps of atmospheric particle formation. The combination of the results of this study with those previously published on the hydration of neutral clusters by our group provides a comprehensive set of thermochemical data on neutral and negatively charged clusters containing sulfuric acid, ammonia, or dimethylamine.

  3. Encasing of Na+ ion in dimer-formed acetic acid clusters.

    PubMed

    Di Palma, Tonia M; Bende, Attila

    2015-10-01

    Peaks with anomalous abundance found in the mass spectra are associated with ions with enhanced stability. Among the scientific community focused on mass spectrometry, these peaks are called 'magic peaks' and their stability is often because of suggestive symmetric structures. Here, we report findings on ionised Na-acetic acid clusters [Na(+) -(AcA)n ] produced by Na-doping of (AcA)n and UV laser ionisation. Peaks labelled n = 2, 4, 8 are clearly distinguishable in the mass spectra from their anomalous intensity. Ab initio calculations helped elucidate cluster structures and energetic. A plausible interpretation of the magic peaks is given in terms of (AcA)n formed by dimer aggregation. The encasing of Na(+) by twisted dimers is proposed to be the origin of the enhanced cluster stability. A conceivable dimer-formed tube-like closed structure is found for the Na(+) -(AcA)8 . Copyright © 2015 John Wiley & Sons, Ltd.

  4. Bi-Directional Ion Emission from Massive Gold Cluster Impacts on Nanometric Carbon Foils

    PubMed Central

    DeBord, J. Daniel; Della-Negra, Serge; Fernandez-Lima, Francisco A.; Verkhoturov, Stanislav V.; Schweikert, Emile A.

    2012-01-01

    Carbon cluster emission from thin carbon foils (5–40 nm) impacted by individual Aun+q cluster projectiles (95–125 qkeV, n/q = 3–200) reveals features regarding the energy deposition, projectile range, and projectile fate in matter as a function of the projectile characteristics. For the first time, the secondary ion emission from thin foils has been monitored simultaneously in both forward and backward emission directions. The projectile range and depth of emission were examined as a function of projectile size, energy, and target thickness. A key finding is that the massive cluster impact develops very differently from that of a small polyatomic projectile. The range of the 125 qkeV Au100q+q (q ≈ 4) projectile is estimated to be 20 nm (well beyond the range of an equal velocity Au+) and projectile disintegration occurs at the exit of even a 5 nm thick foil. PMID:22888385

  5. Specific modification of polysulfone with cluster bombardment with assistance of Ar ion irradiation

    NASA Astrophysics Data System (ADS)

    Xu, Guochun; Hibino, Y.; Awazu, K.; Tanihara, M.; Imanishi, Y.

    2000-02-01

    Objective: To develop a rapid method for the modification of polysulfone with ammonium sulfamate with the assistance of Ar ion irradiation with a multi-source cluster deposition apparatus. These surfaces mimicking the structure of heparin, a bioactive molecule, have a high anti-thrombosis property. Experimental Design: Polysulfone film, setting on a turning holder, was irradiated by Ar ions during bombardment with ammonium sulfamate clusters. The Ar ion source serves for the activation of a polymer surface and a cluster ion source supplies ammonium sulfamate molecules to react with the activated surface. After thorough washing with de-ionized sterile water, the modified surfaces were evaluated in terms of the contact angle of water, elemental composition, and binding state on electron spectroscopy for chemical analysis and platelet adhesion with platelet rich plasma. Results: The modification of polysulfone decreased the contact angle of water on surfaces from 82.6 ° down to 34.5 °. Ammonium, amine, sulfate, and thiophene combinations were formed on the modified surfaces. The adhesion numbers of the platelet were decreased to one tenth compared to the original surface. The same process was also applied to other polymers such as polyethylene, polypropylene, and polystyrene and similar outcomes were also observed. Conclusion: The primary studies showed successful modification of polysulfone with ammonium sulfamate with the assistance of Ar ion irradiation. Since the same concept can also be applied to other materials with various substrates, combined with the features of no solvent and no topographic changes, this method might be developed into a promising way for modification of polymeric materials.

  6. Mass spectrometry of refractory black carbon particles from six sources: carbon-cluster and oxygenated ions

    NASA Astrophysics Data System (ADS)

    Corbin, J. C.; Sierau, B.; Gysel, M.; Laborde, M.; Keller, A.; Kim, J.; Petzold, A.; Onasch, T. B.; Lohmann, U.; Mensah, A. A.

    2013-10-01

    We discuss the major mass spectral features of different types of refractory carbonaceous particles, ionized after laser vapourization with an Aerodyne High-Resolution Soot-Particle Aerosol Mass Spectrometer (SP-AMS). The SP-AMS was operated with a switchable 1064 nm laser and a 600 °C thermal vapourizer, yielding respective measurements of the refractory and non-refractory particle components. Six samples were investigated, all of which were composed primarily of refractory material: fuel-rich and fuel-lean propane/air diffusion-flame combustion particles; graphite-spark-generated particles; a commercial Fullerene-enriched Soot; Regal Black, a commercial carbon black; and nascent aircraft-turbine combustion particles. All samples exhibited a spectrum of carbon-cluster ions Cxn+ in their refractory mass spectrum. Smaller clusters (x<6) were found to dominate the Cxn+ distribution. For Fullerene Soot, fuel-rich-flame particles and spark-generated particles, significant Cxn+ clusters at x≫6 were present, with significant contributions from multiply-charged ions (n>1). In all six cases, the ions C1+ and C3+ contributed over 60% to the total C1ions C1+/C3+ could be used to predict whether significant Cxn+ signals with x>5 were present. When such signals were present, C1+/C3+ was close to 1. When absent, C1+/C3+ was <0.8. This ratio may therefore serve as a proxy to distinguish between the two types of spectra in atmospheric SP-AMS measurements. Significant refractory oxygenated ions such as CO+ and CO2+ were also observed for all samples. We discuss these signals in detail for Regal Black, and describe their formation via decomposition of oxygenated moieties incorporated into the refractory carbon structure. These species may be of importance in atmospheric processes such as water uptake, aging and heterogeneous chemistry.

  7. Ions colliding with clusters of fullerenes--decay pathways and covalent bond formations.

    PubMed

    Seitz, F; Zettergren, H; Rousseau, P; Wang, Y; Chen, T; Gatchell, M; Alexander, J D; Stockett, M H; Rangama, J; Chesnel, J Y; Capron, M; Poully, J C; Domaracka, A; Méry, A; Maclot, S; Vizcaino, V; Schmidt, H T; Adoui, L; Alcamí, M; Tielens, A G G M; Martín, F; Huber, B A; Cederquist, H

    2013-07-21

    We report experimental results for the ionization and fragmentation of weakly bound van der Waals clusters of n C60 molecules following collisions with Ar(2+), He(2+), and Xe(20+) at laboratory kinetic energies of 13 keV, 22.5 keV, and 300 keV, respectively. Intact singly charged C60 monomers are the dominant reaction products in all three cases and this is accounted for by means of Monte Carlo calculations of energy transfer processes and a simple Arrhenius-type [C60]n(+) → C60(+)+(n-1)C60 evaporation model. Excitation energies in the range of only ~0.7 eV per C60 molecule in a [C60]13(+) cluster are sufficient for complete evaporation and such low energies correspond to ion trajectories far outside the clusters. Still we observe singly and even doubly charged intact cluster ions which stem from even more distant collisions. For penetrating collisions the clusters become multiply charged and some of the individual molecules may be promptly fragmented in direct knock-out processes leading to efficient formations of new covalent systems. For Ar(2+) and He(2+) collisions, we observe very efficient C119(+) and C118(+) formation and molecular dynamics simulations suggest that they are covalent dumb-bell systems due to bonding between C59(+) or C58(+) and C60 during cluster fragmentation. In the Ar(2+) case, it is possible to form even smaller C120-2m(+) molecules (m = 2-7), while no molecular fusion reactions are observed for the present Xe(20+) collisions.

  8. Ions colliding with clusters of fullerenes—Decay pathways and covalent bond formations

    NASA Astrophysics Data System (ADS)

    Seitz, F.; Zettergren, H.; Rousseau, P.; Wang, Y.; Chen, T.; Gatchell, M.; Alexander, J. D.; Stockett, M. H.; Rangama, J.; Chesnel, J. Y.; Capron, M.; Poully, J. C.; Domaracka, A.; Méry, A.; Maclot, S.; Vizcaino, V.; Schmidt, H. T.; Adoui, L.; Alcamí, M.; Tielens, A. G. G. M.; Martín, F.; Huber, B. A.; Cederquist, H.

    2013-07-01

    We report experimental results for the ionization and fragmentation of weakly bound van der Waals clusters of n C60 molecules following collisions with Ar2 +, He2 +, and Xe20 + at laboratory kinetic energies of 13 keV, 22.5 keV, and 300 keV, respectively. Intact singly charged C60 monomers are the dominant reaction products in all three cases and this is accounted for by means of Monte Carlo calculations of energy transfer processes and a simple Arrhenius-type [C_{60}]_n^+ → C_{60}+ + (n-1)C_{60} evaporation model. Excitation energies in the range of only ˜0.7 eV per C60 molecule in a [C_{60}]_{13}^+ cluster are sufficient for complete evaporation and such low energies correspond to ion trajectories far outside the clusters. Still we observe singly and even doubly charged intact cluster ions which stem from even more distant collisions. For penetrating collisions the clusters become multiply charged and some of the individual molecules may be promptly fragmented in direct knock-out processes leading to efficient formations of new covalent systems. For Ar2 + and He2 + collisions, we observe very efficient C_{119}+ and C_{118}+ formation and molecular dynamics simulations suggest that they are covalent dumb-bell systems due to bonding between C_{59}+ or C_{58}+ and C60 during cluster fragmentation. In the Ar2 + case, it is possible to form even smaller C_{120-2m}+ molecules (m = 2-7), while no molecular fusion reactions are observed for the present Xe20 + collisions.

  9. Ions colliding with clusters of fullerenes-Decay pathways and covalent bond formations

    SciTech Connect

    Seitz, F.; Zettergren, H.; Chen, T.; Gatchell, M.; Alexander, J. D.; Stockett, M. H.; Schmidt, H. T.; Cederquist, H.; Rousseau, P.; Chesnel, J. Y.; Capron, M.; Poully, J. C.; Mery, A.; Maclot, S.; Adoui, L.; Wang, Y.; Martin, F.; Rangama, J.; Domaracka, A.; Vizcaino, V. [CIMAP, UMR 6252, CEA and others

    2013-07-21

    We report experimental results for the ionization and fragmentation of weakly bound van der Waals clusters of n C{sub 60} molecules following collisions with Ar{sup 2+}, He{sup 2+}, and Xe{sup 20+} at laboratory kinetic energies of 13 keV, 22.5 keV, and 300 keV, respectively. Intact singly charged C{sub 60} monomers are the dominant reaction products in all three cases and this is accounted for by means of Monte Carlo calculations of energy transfer processes and a simple Arrhenius-type [C{sub 60}]{sub n}{sup +}{yields}C{sub 60}{sup +}+(n-1)C{sub 60} evaporation model. Excitation energies in the range of only {approx}0.7 eV per C{sub 60} molecule in a [C{sub 60}]{sub 13}{sup +} cluster are sufficient for complete evaporation and such low energies correspond to ion trajectories far outside the clusters. Still we observe singly and even doubly charged intact cluster ions which stem from even more distant collisions. For penetrating collisions the clusters become multiply charged and some of the individual molecules may be promptly fragmented in direct knock-out processes leading to efficient formations of new covalent systems. For Ar{sup 2+} and He{sup 2+} collisions, we observe very efficient C{sub 119}{sup +} and C{sub 118}{sup +} formation and molecular dynamics simulations suggest that they are covalent dumb-bell systems due to bonding between C{sub 59}{sup +} or C{sub 58}{sup +} and C{sub 60} during cluster fragmentation. In the Ar{sup 2+} case, it is possible to form even smaller C{sub 120-2m}{sup +} molecules (m= 2-7), while no molecular fusion reactions are observed for the present Xe{sup 20+} collisions.

  10. Study on the detection limits of a new argon gas cluster ion beam secondary ion mass spectrometry apparatus using lipid compound samples.

    PubMed

    Fujii, Makiko; Nakagawa, Shunichirou; Matsuda, Kazuhiro; Man, Naoki; Seki, Toshio; Aoki, Takaaki; Matsuo, Jiro

    2014-04-30

    Ar gas cluster ion beam secondary ion mass spectrometry (Ar-GCIB SIMS) has been developed as one of the most powerful tools used for analyzing complex biological materials because of its distinctively high secondary ion yield of large organic molecules. However, for the practical analysis of minor components in complex biological materials, the sensitivity of the technique is still insufficient. The detection limits of our original Ar-GCIB SIMS apparatus were investigated by measuring lipid compound samples in positive ion mode. The samples were mixtures of 1,2-distearoyl-sn-glycero-3-phosphocholine (C44 H88 NO8 P, DSPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (C40 H80 NO8 P, DPPC). The primary ions were accelerated with 10 keV and the mean cluster size was 1500. The secondary [M+H](+) ions emitted from the sample were analyzed using an orthogonal acceleration time-of-flight mass spectrometer (oa-TOF-MS). In addition, the isotope abundance ratio and the ratio of the [M+H](+) ion signal to the fragment ion signal acquired with Ar-GCIB SIMS were compared with those obtained with conventional Bi cluster SIMS. Secondary [M+H](+) ions and some characteristic fragment ions were clearly observed with high quantitative accuracy in the mass spectra acquired with Ar-GCIB SIMS. The results were clearly better than those obtained with conventional Bi cluster SIMS. The detection limit of Ar-GCIB SIMS was found to be below 0.1% and was much lower than that of conventional Bi cluster SIMS because of the high [M+H](+) ion yield and the low background. The results suggested that the new Ar-GCIB SIMS apparatus has the capability to acquire valuable information on complex biological materials. Copyright © 2014 John Wiley & Sons, Ltd.

  11. Engineer Examines Cluster of Ion Engines in the Electric Propulsion Laboratory

    NASA Image and Video Library

    1963-01-21

    New staff member Paul Margosian inspects a cluster of ion engines in the Electric Propulsion Laboratory’s 25-foot diameter vacuum tank at the National Aeronautics and Space Administration (NASA) Lewis Research Center. Lewis researchers had been studying different methods of electric rocket propulsion since the mid-1950s. Harold Kaufman created the first successful engine, the electron bombardment ion engine, in the early 1960s. These engines used electric power to create and accelerate small particles of propellant material to high exhaust velocities. Electric engines have a very small thrust, and but can operate for long periods of time. The ion engines are often clustered together to provide higher levels of thrust. The Electric Propulsion Laboratory contained two large vacuum tanks capable of simulating the space environment. The tanks were designed especially for testing ion and plasma thrusters and spacecraft. The larger 25-foot diameter tank was intended for testing electric thrusters with condensable propellants. The tank’s test compartment, seen here, was 10 feet in diameter. Margosian joined Lewis in late 1962 during a major NASA hiring phase. The Agency reorganized in 1961 and began expanding its ranks through a massive recruiting effort. Lewis personnel increased from approximately 2,700 in 1961 to over 4,800 in 1966. Margosian, who worked with Bill Kerslake in the Electromagnetic Propulsion Division’s Propulsion Systems Section, wrote eight technical reports on mercury and electron bombardment thrusters, thermoelectrostatic generators, and a high voltage insulator.

  12. Properties of clusters in the gas phase: V. Complexes of neutral molecules onto negative ions

    SciTech Connect

    Keesee, R.G.; Lee, N.; Castleman, A.W. Jr.

    1980-09-01

    Ion--molecules association reactions of the form A/sup -/(B)/sub n1/-+B=A/sup -/(B)/sub n/ were studied over a range of temperatures in the gas phase using high pressure mass spectrometry. Enthalpy and entropy changes were determined for the stepwise clustering reactions of (1) sulfur dioxide onto Cl/sup -/, I/sup -/, and NO/sub 2//sup -/ with n ranging from one to three or four, and onto SO/sub 2//sup -/ and SO/sub 3//sup -/ with n equal to one; and (2) carbon dioxide onto Cl/sup -/, I/sup -/, NO/sub 2//sup -/, CO/sub 3//sup -/, and SO/sub 3//sup -/ with n equal to one. From these data and earlier hydration results, the order of the magnitude of the enthalpy changes on the association of the first neutral for a series of negative ions was found to parallel the gas-phase basicity of those anions. For any given ion, the relative order of the addition enthalpies among the neutrals was found to be dependent on the polarizabilities of the neutrals and on the covalency in the ion-neutral bond. Dispersion of charge via covalent bonding was found to affect significantly the succeeding clustering steps.

  13. Field Observation of the Green Ocean Amazon. Neutral Cluster Air Ion Spectrometer (NAIS) Final Campaign Summary

    SciTech Connect

    Petaja, T.; Backman, J.; Manninen, H. E.; Wimmer, D.

    2016-03-01

    The neutral cluster and air ion spectrometer (NAIS) was deployed to the T3 site for Intensive Operations Periods 1 and 2 (IOP1 and IOP2). The NAIS is an instrument that measures aerosol particle and ion number size distributions in the mobility diameter range of 0.8 to 42 nm, corresponding to electrical mobility range between 3.2 and 0.0013 cm2 V-1 s-1. New particle formation (NPF) events were detected using the NAIS at the T3 field site during IOP1 and IOP2. Secondary NPF is a globally important source of aerosol number. To fully explain atmospheric NPF and subsequent growth, we need to directly measure the initial steps of the formation processes in different environments, including rain forest. Particle formation characteristics, such as formation and growth rates, were used as indicators of the relevant processes and participating compounds in the initial formation. In a case of parallel ion and neutral cluster measurements, we estimated the relative contribution of ion-induced and neutral nucleation to the total particle formation.

  14. Gas-phase catalysis by atomic and cluster metal ions: the ultimate single-site catalysts.

    PubMed

    Böhme, Diethard K; Schwarz, Helmut

    2005-04-15

    Gas-phase experiments with state-of-the-art techniques of mass spectrometry provide detailed insights into numerous elementary processes. The focus of this Review is on elementary reactions of ions that achieve complete catalytic cycles under thermal conditions. The examples chosen cover aspects of catalysis pertinent to areas as diverse as atmospheric chemistry and surface chemistry. We describe how transfer of oxygen atoms, bond activation, and coupling of fragments can be mediated by atomic or cluster metal ions. In some cases truly unexpected analogies of the idealized gas-phase ion catalysis can be drawn with related chemical transformations in solution or the solid state, and so improve our understanding of the intrinsic operation of a practical catalyst at a strictly molecular level.

  15. Optimum laser intensity for the production of energetic deuterium ions from laser-cluster interaction

    SciTech Connect

    Bang, W.; Dyer, G.; Quevedo, H. J.; Bernstein, A. C.; Gaul, E.; Rougk, J.; Aymond, F.; Donovan, M. E.; Ditmire, T.

    2013-09-15

    We measured, using Petawatt-level pulses, the average ion energy and neutron yield in high-intensity laser interactions with molecular clusters as a function of laser intensity. The interaction volume over which fusion occurred (1–10 mm{sup 3}) was larger than previous investigations, owing to the high laser power. Possible effects of prepulses were examined by implementing a pair of plasma mirrors. Our results show an optimum laser intensity for the production of energetic deuterium ions both with and without the use of the plasma mirrors. We measured deuterium plasmas with 14 keV average ion energies, which produced 7.2 × 10{sup 6} and 1.6 × 10{sup 7} neutrons in a single shot with and without plasma mirrors, respectively. The measured neutron yields qualitatively matched the expected yields calculated using a cylindrical plasma model.

  16. Formation of high mass carbon cluster ions from laser ablation of polymers and thin carbon films

    NASA Astrophysics Data System (ADS)

    Creasy, William R.; Brenna, J. T.

    1990-02-01

    Three materials were studied by laser ablation/Fourier transform mass spectrometry, using 266 nm laser radiation: a copolymer of ethylene and tetrafluoroethylene (ETFE), polyphenylene sulfide (PPS), and a diamond-like carbon film (DLC). In each case, positive ion mass spectra exhibit primarily even-numbered, high mass carbon clusters (``fullerenes'') of the type previously reported for graphite ablation. In the case of ETFE, a large C+60 peak (``buckminsterfullerene'') was observed. The polymer spectra showed a strong dependence on the number of laser pulses on one spot and the laser power density. For ETFE, the fullerene ion relative intensity first increases and then decreases as a function of the number of laser pulses. For the DLC film, fullerenes are observed with a single laser pulse on a fresh spot of the sample. The results are interpreted in terms of a gas phase growth model for the fullerene ion formation.

  17. Mass spectrometry of ion-induced water clusters: an explanation of the infrared continuum absorption.

    PubMed

    Carlon, H R; Harden, C S

    1980-06-01

    Mass spectrometry was used to study ion-induced water clusters [H(+)(H(2)O)(c)], where c = the cluster size, i.e.,the number of monomers per cluster. It is shown that the numbers of hydrogen bonds in populations of these clusters in water vapor vary as the square of partial pressure and inversely with temperature, with functional dependencies that are almost identical to those observed for the infrared continuum absorption and for anomalous absorption in other wavelength regions. Experimental mass spectra taken at constant temperature vs partial pressure and data obtained at constant water vapor partial pressure vs temperature are presented and discussed. These results are combined with the evidence of cloud physicists including C. T. R. Wilson to show rather conclusively that naturally occurring ionic processes in water vapor generate large populations of hydrogen-bonded neutral water clusters that are responsible for the infrared continuum absorption. These processes can be enhanced by various kinds of ionizing energy, thus increasing anomalous absorption in water vapor or in moist air. If electrical properties of the atmosphere influence the infrared continuum absorption, which is an important mechanism in determining climate at the earth's surface, it will be necessary to reexamine extensively existing models of atmospheric radiative transfer.

  18. Chemistry of (and on) transition metal clusters: a Fourier transform ion cyclotron resonance study of the reaction of niobium cluster cations with nitric oxide.

    PubMed

    Harding, Daniel J; Oliver, Thomas A A; Walsh, Tiffany R; Drewello, Thomas; Woodruff, D Phil; Derrick, Peter J; Mackenzie, Stuart R

    2009-01-01

    The reactions of niobium cluster cations, Nb(+)(n) (n = 2-19), with nitric oxide have been investigated using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR). The overall reaction rate constants are found to be in reasonable agreement with collision rates calculated using the surface charge capture model. The dominant reaction for small clusters (n <9) involves reaction-induced fragmentation resulting in the loss of either NbO or NbN. By contrast, the main reaction observed for the larger clusters (n> 11) is sequential NO chemisorption. Clusters n = 9, 10 exhibit both extremes of behaviour and are the only clusters upon which there is evidence of NO decomposition with N(2) loss observed whenever multiple NO molecules are co-adsorbed. The rate constants for each process have been determined as a function of cluster size.

  19. Probing ion-molecule structure and dynamics in isolated molecular clusters and proteins

    NASA Astrophysics Data System (ADS)

    Abate, Yohannes

    Ion-molecule interactions in isolated molecular clusters and proteins are studied in this work using experimental and theoretical methods. Photodissociation spectroscopy and chemical dynamics of several metal ion-molecule clusters are studied. The experimental tool used for these studies is an Angular Reflectron Time Of Flight Mass Spectrometer (ARTOFMS). The experimental work is supported by ab initio electronic structure calculations on the Gaussian and GAMESS platforms. This work also describes a computational study of the interaction of protonated histidine with other aromatic residues in proteins. We have studied the photodissociation spectroscopy of weakly bound Zn +(H2O) and Zn+(D2O) bimolecular complexes. We assign two molecular absorption bands in the near UV correlating to Zn+ (4s-4p)-metal centered transitions, and identify vibrational progressions associated with both intermolecular and intramolecular vibrational modes of the cluster. Partially resolved rotational structure is consistent with a C2 V equilibrium complex geometry. The photodissociation spectroscopy and chemical dynamics of Zn +-formaldehyde and Zn+-acetaldehyde clusters are investigated in the near UV spectral range. The work is also supported by ab initio electronic structure calculations to study the ground-state bonding and interactions in the low-lying doublet excited states. We identify absorption bands corresponding to photoinduced charge transfer, Zn+(4s-4p)-based transitions, and aldehyde-based excitations. We propose a reaction mechanism for the reactive dissociation that proceeds via H-atom abstraction on the charge-transfer surface. This work shows important differences with results from earlier experiments on Mg+- and Ca+-aldehyde complexes despite the similar valence character for these metal ions. In the study of Mg+-acetic acid we observe three distinct absorption bands, two red-shifted and one blue-shifted from the Mg +(3s ← 3p) resonance at 280 nm (35714 cm-1). We

  20. Structural characterization of (C2H2)1-6+ cluster ions by vibrational predissociation spectroscopy

    NASA Astrophysics Data System (ADS)

    Relph, Rachael A.; Bopp, Joseph C.; Roscioli, Joseph R.; Johnson, Mark A.

    2009-09-01

    Vibrational predissociation spectra are reported for the cationic acetylene clusters, (C2H2)n+, n =1-6, in the region of the C-H stretching fundamentals. For n =1 and 2, predissociation could only be observed for the Ar-tagged clusters. These were prepared by charge-transfer collisions of Ark+ with C2H2 to create C2H2+ṡArm clusters, which were then converted into larger members of the (C2H2)n+ṡAr series by sequential addition of acetylene molecules. The (C2H2)2+ṡAr spectrum indicates that this species is predominantly present as the cyclobutadiene cation. Although mobility measurements on the electron-impact-generated (C2H2)3+ ion indicated that it primarily occurs as the benzene cation, [P. O. Momoh, J. Am. Chem. Soc. 128, 12408 (2006)] photofragmentation of (C2H2)3+ṡAr in the C-H stretching region is dominated by the loss of C2H2 in addition to the weakly bound Ar atom. This suggests that the dominant n =3 species formed by sequential addition of C2H2 is based on a covalently bound C4H4+ core ion. Interestingly, the spectrum of this core C4H4+ species is different from that found for the cyclobutadiene cation, displaying instead a new band pattern that is retained in the higher (C2H2)3-6+ clusters. Multiple isomers are clearly involved, as yet another pattern of bands is recovered when the (C2H2)3+ṡAr action spectrum is recorded in the (minor) Ar loss fragmentation channel. One of these features does appear in the location of the single band characteristic of the Ar-tagged benzene cation reported earlier [Phys. Chem. Chem. Phys. 4, 24 (2002)], supporting a scenario where the benzene cation is one of the isomers present. We then compare the Ar predissociation results with (C2H2)n+ spectra obtained when the ions are prepared by electron impact ionization of neutral acetylene clusters. The photofragmentation behavior and vibrational spectra indicate that the dominant species formed in this way also occur with a covalently bound C4H4+ core. There are

  1. Determination of the sputtering yield of cholesterol using Arn(+) and C60(+(+)) cluster ions.

    PubMed

    Rakowska, P D; Seah, M P; Vorng, J-L; Havelund, R; Gilmore, I S

    2016-08-02

    The sputtering yield of cholesterol films on silicon wafers is measured using Arn(+) and C60(+(+)) ions in popular energy (E) and cluster size (n) ranges. It is shown that the C60(+(+)) ions form a surface layer that stabilizes the film so that a well-behaved profile is obtained. On the other hand, the Arn(+) gas clusters leave the material very clean but, at room temperature, the layer readily restructures into molecular bilayers, so that, although a useful measure may be made of the sputtering yield, the profiles become much more complex. This restructuring does not occur at room temperature normally but results from the actions of the beams in the sputtering process for profiling in secondary ion mass spectrometry. Better profiles may be made by reducing the sample temperature to -100 °C. This is likely to be necessary for many lower molecular weight materials (below 1000 Da) to avoid the movement of molecules. Measurements for cholesterol films on 37 nm of amiodarone on silicon are even better behaved and show the same sputtering yields at room temperature as those films directly on silicon at -100 °C. The yields for both C60(+(+)) and Arn(+) fit the Universal Equation to a standard deviation of 11%.

  2. Equilibrium properties of transition-metal ion-argon clusters via simulated annealing

    NASA Technical Reports Server (NTRS)

    Asher, Robert L.; Micha, David A.; Brucat, Philip J.

    1992-01-01

    The geometrical structures of M(+) (Ar)n ions, with n = 1-14, have been studied by the minimization of a many-body potential surface with a simulated annealing procedure. The minimization method is justified for finite systems through the use of an information theory approach. It is carried out for eight potential-energy surfaces constructed with two- and three-body terms parametrized from experimental data and ab initio results. The potentials should be representative of clusters of argon atoms with first-row transition-metal monocations of varying size. The calculated geometries for M(+) = Co(+) and V(+) possess radial shells with small (ca. 4-8) first-shell coordination number. The inclusion of an ion-induced-dipole-ion-induced-dipole interaction between argon atoms raises the energy and generally lowers the symmetry of the cluster by promoting incomplete shell closure. Rotational constants as well as electric dipole and quadrupole moments are quoted for the Co(+) (Ar)n and V(+) (Ar)n predicted structures.

  3. Equilibrium properties of transition-metal ion-argon clusters via simulated annealing

    NASA Technical Reports Server (NTRS)

    Asher, Robert L.; Micha, David A.; Brucat, Philip J.

    1992-01-01

    The geometrical structures of M(+) (Ar)n ions, with n = 1-14, have been studied by the minimization of a many-body potential surface with a simulated annealing procedure. The minimization method is justified for finite systems through the use of an information theory approach. It is carried out for eight potential-energy surfaces constructed with two- and three-body terms parametrized from experimental data and ab initio results. The potentials should be representative of clusters of argon atoms with first-row transition-metal monocations of varying size. The calculated geometries for M(+) = Co(+) and V(+) possess radial shells with small (ca. 4-8) first-shell coordination number. The inclusion of an ion-induced-dipole-ion-induced-dipole interaction between argon atoms raises the energy and generally lowers the symmetry of the cluster by promoting incomplete shell closure. Rotational constants as well as electric dipole and quadrupole moments are quoted for the Co(+) (Ar)n and V(+) (Ar)n predicted structures.

  4. ToF-SIMS cluster ion imaging of hippocampal CA1 pyramidal rat neurons

    NASA Astrophysics Data System (ADS)

    Francis, J. T.; Nie, H.-Y.; Taylor, A. R.; Walzak, M. J.; Chang, W. H.; MacFabe, D. F.; Lau, W. M.

    2008-12-01

    Recent studies have demonstrated the power of time-of-flight secondary ion mass spectrometry (ToF-SIMS) cluster ion imaging to characterize biological structures, such as that of the rat central nervous system. A large number of the studies to date have been carried out on the "structural scale" imaging several mm 2 using mounted thin sections. In this work, we present our ToF-SIMS cluster ion imaging results on hippocampal rat brain neurons, at the cellular and sub-cellular levels. As a part of an ongoing investigation to examine gut linked metabolic factors in autism spectrum disorders using a novel rat model, we have observed a possible variation in hippocampal Cornu ammonis 1 (CA1) pyramidal neuron geometry in thin, paraformaldehyde fixed brain sections. However, the fixation process alters the tissue matrix such that much biochemical information appears to be lost. In an effort to preserve as much as possible this original information, we have established a protocol using unfixed thin brain sections, along with low dose, 500 eV Cs + pre-sputtering that allows imaging down to the sub-cellular scale with minimal sample preparation.

  5. Shell Structure, Melting and Dynamics of Ion Clusters Confined in an Octupolar Trap

    NASA Astrophysics Data System (ADS)

    Calvo, F.; Yurtsever, E.

    2009-12-01

    The stable structures of clusters of identical ions trapped in an isotropic octupolar trap are investigated using global optimization methods. These clusters form well defined shells of ions that are approximately solutions of the Thomson problem. In particular, magic numbers are found to correlate with highly symmetric configurations. Using Monte Carlo simulations, finite temperature properties are also investigated. Melting proceeds from the core, and takes place through a very progressive loss of the shell structure. The hollow shape is eventually lost at very high temperatures, where the ions essentially feel the confinement but not the Coulomb repulsion. The vibrational density of states shows marked differences with the harmonic case, but also with bulk Wigner crystals. The variations of the maximal Lyapunov exponent obtained from additional molecular dynamics trajectories reveals that the dynamics becomes increasingly chaotic as the temperature increases. With the decreasing influence of the Coulomb interaction, a more regular behavior is found at very high temperatures but, contrary to the quadrupolar case, still highly chaotic.

  6. Ionospheric oxygen ions dominant bursty bulk flows: Cluster and Double Star observations

    NASA Astrophysics Data System (ADS)

    Zong, Q.-G.; Zhang, H.; Fu, S. Y.; Wang, Y. F.; Pu, Z. Y.; Korth, A.; Daly, P. W.; Fritz, T. A.

    2008-07-01

    Two extreme oxygen-rich bursty bulk flows (BBFs) with predominant ionospheric O+ ions have been observed on 8 November 2004 by the Cluster and Double Star spacecraft during a strong magnetic storm time period with Dst = -373 nT. The oxygen densities in two BBFs are found to be 3-5 times larger than the hydrogen densities and the oxygen thermal pressures in the BBFs are 8 times higher than the hydrogen thermal pressure. These BBFs are associated with nested magnetic structures and are observed simultaneously by the CLUSTER and the DSP TC-1 spacecraft. Thus, the flow braking region should be greatly pushed inside the usual pressure balance region (even inside the inner magnetosphere) since the BBF is dominated by oxygen ions. Results in this paper indicate that oxygen dominated BBFs can be formed during a strong magnetic storm time period. The observations made in this paper suggest that singly charged oxygen ions embedded in the BBFs could be carried into the ring current region by bursty flows during very intense magnetic storms.

  7. Cluster-assisted multiple-ionization of methyl iodide by a nanosecond laser: Wavelength dependence of multiple-charge ions

    NASA Astrophysics Data System (ADS)

    Wang, Weiguo; Li, Haiyang; Niu, Dongmei; Wen, Lihua; Zhang, Nazhen

    2008-09-01

    As efforts continue to elucidate laser-cluster interactions, we investigated the influence of laser wavelength on ion products. In this study, a pulsed methyl iodide cluster was irradiated with a Nd-YAG nanosecond laser, and the ion products were analyzed using time-of-flight mass spectrometry. Multiple-charge atomic ions of C q+ and I q+ ( q ⩾ 2) were observed using 532 and 1064 nm laser wavelengths; however, only single-charge atomic and molecular ions appeared at 266 and 355 nm. We show that the charge-state distribution for multiple-charge ions is almost independent of laser intensity. A three-stage model was developed to further understand these experimental results: the inverse electron bremsstrahlung heating rate is proportional to the square of laser wavelength, which seems to explain the dependence of multiple-charge ions on the wavelength.

  8. Concomitant formation of different nature clusters and hardening in reactor pressure vessel steels irradiated by heavy ions

    NASA Astrophysics Data System (ADS)

    Fujii, K.; Fukuya, K.; Hojo, T.

    2013-11-01

    Specimens of A533B steels containing 0.04, 0.09 and 0.21 wt%Cu were irradiated at 290 °C to 3 dpa with 3 MeV Fe ions and subjected to atom probe analyses, transmission electron microscopy observations and hardness measurements. The atom probe analysis results showed that two types of solute clusters were formed: Cu-enriched clusters containing Mn, Ni and Si atoms as irradiation-enhanced solute atom clusters and Mn/Ni/Si-enriched clusters as irradiation-induced solute atom clusters. Both cluster types occurred in the highest Cu-content steel and the ratio of Mn/Ni/Si-enriched clusters to Cu-enriched clusters increased with irradiation doses. It was confirmed that the cluster formation was a key factor in the microstructure evolution until the high dose irradiation was reached even in the low Cu content steels though the dislocation loops with much lower density than that of the clusters were observed as matrix damage. The difference in the hardening efficiency due to the difference in the nature of the clusters was small. The irradiation-induced clustering of undersized Si atoms suggested that a clustering driving force other than vacancy-driven diffusion, probably an interstitial mechanism, may become important at higher dose rates.

  9. New strategy to construct single-ion magnets: a unique Dy@Zn₆ cluster exhibiting slow magnetic relaxation.

    PubMed

    Xiong, Gang; Qin, Xiang-Yang; Shi, Peng-Fei; Hou, Yin-Ling; Cui, Jian-Zhong; Zhao, Bin

    2014-04-25

    Two unique heptanuclear clusters Ln@Zn6 (Ln = Dy (1), Er (2)) were structurally and magnetically characterized. Each Dy(3+)/Er(3+) is located in a nona-coordinate D(3h) coordination environment, and is encapsulated in a diamagnetic Zn6 cage. Compound 1 exhibits single-ion magnetic behavior, and is the first example of a single-ion magnet (SIM) constructed through embedding one magnetic anisotropic metal ion into a diamagnetic cage.

  10. Cation-pi-anion interaction in alkali ion-benzene-halogen ion clusters.

    PubMed

    Albertí, Margarita; Aguilar, Antonio; Pirani, Fernando

    2009-12-31

    The present investigation on some ternary M(+)-benzene-X(-) aggregates follows previous studies concerning the binary, M(+)-benzene (M = Li, Na, K, Rb, Cs) and X(-)-benzene (X = F, Cl, Br, I), systems. A semimepirical model describing the intermolecular potential energy, formulated as a combination of few leading effective components, is here extended and applied to investigate more complex systems. The balancing of size repulsion with induction and dispersion attraction is described as a combination of ion-bond interactions and an electrostatic component, rationalized on the basis of the benzene quadrupole moment, is also included. For M(+)-benzene-X(-) aggregates, the simultaneous presence of a cation and an anion close to the pi system originates a strong Coulombic attraction and nonadditivity effects of the induction energy, which are carefully considered and explicitly included to obtain a proper analytical functional representation of the ternary compound. The proposed semiempirical methodology, providing the whole potential energy surface in a convenient analytical form, is useful to predict the main features of stable and unstable configurations, saddle points, and energy barriers, allowing for investigation of their influence on molecular dynamics simulations.

  11. Observation of the influence of isomeric structures of cluster ions on the dynamics of dissociation: Ammonia-triethylamine system

    SciTech Connect

    Wei, S.; Tzeng, W.B.; Castleman, A.W. Jr. )

    1990-09-06

    The authors report what they believe to be the first experimental proof of the influence of isomeric cluster ions on their dynamics of dissociation, namely, for the cluster ion NH{sub 3}((C{sub 2}H{sub 5}){sub 3}N){sub 3}H{sup +} in the present case. The isomeric structures lead to important consequences in the dynamics of dissociation. No other comparable parallel dissociation processes for cluster ions NH{sub 3}-((C{sub 2}H{sub 5}){sub 3}N){sub m}H{sup +} are observed, establishing that there are no other isomers present for the cluster size range investigated in this work.

  12. Inertial confinement fusion using hohlraum radiation generated by heavy-ion clusters

    SciTech Connect

    Tahir, N.A.; Lutz, K.; Geb, O.; Maruhn, J.A.; Deutsch, C.; Hoffmann, D.H.

    1997-03-01

    This paper discusses the feasibility of employing heavy-ion cluster beams to generate thermal radiation that can be used to drive inertial fusion capsules. The low charge-to-mass ratio of a cluster may allow the driver beam to be focused to a very small spot size with a radius of the order of 100 {mu}m, while the low energy per nucleon (of the order of 10 keV) may lead to a very short range of the driver particles in the converter material. This would result in high specific power deposition that may lead to a very high conversion efficiency. The problem of cluster stopping in cold matter, as well as in hot dense plasmas has been thoroughly investigated. The conversion efficiency of cluster ions using a low-density gold converter has also been calculated over a wide range of parameters including converter density, converter geometry, and specific power deposition. These calculations have been carried out using a one-dimensional hydrodynamic computer code that includes a multigroup radiation transport scheme [Ramis {ital et al.}, Comput. Phys. Commun. {bold 49}, 475 (1988)]. The problem of symmetrization of this radiation field in a hohlraum with solid gold walls has also been thoroughly investigated using a three-dimensional view factor code. The characteristics of the radiation field obtained by this study are used as input to capsule implosion calculations that are done with a three-temperature radiation-hydrodynamic computer code MEDUSA-KAT [Tahir {ital et al.}, J. Appl. Phys. {bold 60}, 898 (1986)]. A reactor-size capsule which contains 5 mg deuterium{endash}tritium (DT) fuel is used in these calculations. The problem of using a fuel mixture with a substantially reduced tritium content has also been discussed. {copyright} {ital 1997 American Institute of Physics.}

  13. Negative ion productions in high velocity collision between small carbon clusters and Helium atom target

    NASA Astrophysics Data System (ADS)

    M, Chabot; K, Béroff; T, Pino; G, Féraud; N, Dothi; Padellec A, Le; G, Martinet; S, Bouneau; Y, Carpentier

    2012-11-01

    We measured absolute double capture cross section of Cn+ ions (n=1,5) colliding, at 2.3 and 2.6 a.u velocities, with an Helium target atom and the branching ratios of fragmentation of the so formed electronically excited anions Cn-*. We also measured absolute cross section for the electronic attachment on neutral Cn clusters colliding at same velocities with He atom. This is to our knowledge the first measurement of neutral-neutral charge exchange in high velocity collision.

  14. Structural origin for electron affinity of phenanthrene and ion cores of phenanthrene anion clusters

    NASA Astrophysics Data System (ADS)

    Lee, Sang Hak; Song, Jae Kyu; Kim, Seong Keun

    2015-04-01

    We studied anion clusters of phenanthrene using photoelectron spectra and theoretical calculations. The electron affinity of phenanthrene, which lies between those of naphthalene and anthracene, was explained by the orbital interaction model that reflected the structural differences among these molecules. The spectral feature of the photoelectron spectra indicated strong electron-vibration coupling along two symmetric vibrational modes. Since the spectral features of each ion core structure were uniquely characteristic, we could identify that the pentamer anion had coexisting monomeric and trimeric cores on the basis of the shape of the photoelectron spectra and the size-dependent evolution of the electron affinity.

  15. Direct fission versus sequential evaporation mechanism of sputtered caesium iodide cluster ions

    NASA Astrophysics Data System (ADS)

    Drewello, Thomas; Herzschuh, Rainer; Stach, Joachim

    1993-12-01

    A triple stage hybrid mass spectrometer was scanned for the trapping of the reaction intermediates of the over-all loss of two CsI-moieties from size-selected caesium iodide cluster ions of the general formula Cs (CsI)+ n . In addition to appropriate MS/MS/MS-methods an electrically floated collision cell has been applied to trap intermediates of unimolecular and collision-induced evaporations. In comparison with other experimental findings the features of the evaporation mechanism are discussed.

  16. Rapidly convergent cluster expansion and application to lithium ion battery materials

    NASA Astrophysics Data System (ADS)

    Lee, Eunseok; Iddir, Hakim; Benedek, Roy

    2017-02-01

    The convergence of a cluster expansion for lithium transition-metal (TM) oxides is improved by explicit treatment of TM magnetic moments. The approach is applied to layered LiC oyN i1 -yO2 (NC). The ground state and low-lying excited state structures are identified, and the distribution of TM ions and magnetic moment in those structures is investigated to explain the origin of Ni-antisite ions and Jahn-Teller distortion. The developed model also reveals the mechanisms governing the atomic arrangement of NC, including in-plane Co-Co vs Co-Ni competition, magnetic frustration vs disproportionation competition, and cationic interactions spanning adjacent layers.

  17. Planarization of amorphous carbon films on patterned substrates using gas cluster ion beams

    SciTech Connect

    Toyoda, Noriaki; Yamada, Isao; Nagato, Keisuke; Nakao, Masayuki; Hamaguchi, Tetsuya; Tani, Hiroshi; Sakane, Yasuo

    2009-04-01

    Surface planarization and modification of a patterned surface were demonstrated using gas cluster ion beam (GCIB). Grooves with 100-400 nm intervals were formed on amorphous carbon films using focused ion beams to study the special frequency dependence of the planarization. Also, line and space patterns were fabricated on Si substrates, and amorphous carbons were deposited as a model structure of discrete track media. Subsequently, surface planarization using Ar-GCIB was carried out. After GCIB irradiations, all of the grooves were completely removed, and a flat surface was realized. And it showed that GCIB irradiation planarized grooves without huge thickness loss. From the power spectrum density of an atomic force microscope, GCIB preferentially removed grooves with small intervals. It was found from energy dispersive x-ray spectroscopy that surface planarization without severe damage in the amorphous carbon and magnetic layers was carried out with GCIB.

  18. Properties of clusters in the gas phase. V - Complexes of neutral molecules onto negative ions

    NASA Technical Reports Server (NTRS)

    Keesee, R. G.; Lee, N.; Castleman, A. W., Jr.

    1980-01-01

    Ion-molecules association reactions of the form A(-)(B)n-1 + B = A(-)(B)n were studied over a range of temperatures in the gas phase using high pressure mass spectrometry. Enthalpy and entropy changes were determined for the stepwise clustering reactions of (1) sulfur dioxide onto Cl(-), I(-), and NO2(-) with n ranging from one to three or four, and onto SO2(-) and SO3(-) with n equal to one; and (2) carbon dioxide onto Cl(-), I(-), NO2(-), CO3(-), and SO3(-) with n equal to one. From these data and earlier hydration results, the order of the magnitude of the enthalpy changes on the association of the first neutral for a series of negative ions was found to parallel the gas-phase basicity of those anions.

  19. Mass spectrometry of refractory black carbon particles from six sources: carbon-cluster and oxygenated ions

    NASA Astrophysics Data System (ADS)

    Corbin, J. C.; Sierau, B.; Gysel, M.; Laborde, M.; Keller, A.; Kim, J.; Petzold, A.; Onasch, T. B.; Lohmann, U.; Mensah, A. A.

    2014-03-01

    We discuss the major mass spectral features of different types of refractory carbonaceous particles, ionized after laser vaporization with an Aerodyne high-resolution soot-particle aerosol mass spectrometer (SP-AMS). The SP-AMS was operated with a switchable 1064 nm laser and a 600 °C thermal vaporizer, yielding respective measurements of the refractory and non-refractory particle components. Six samples were investigated, all of which were composed primarily of refractory material: fuel-rich and fuel-lean propane/air diffusion-flame combustion particles; graphite-spark-generated particles; a commercial fullerene-enriched soot; Regal Black, a commercial carbon black; and nascent aircraft-turbine combustion particles. All samples exhibited a spectrum of carbon-cluster ions Cxn+ in their refractory mass spectrum. Smaller clusters (x < 6) were found to dominate the Cxn+ distribution. For fullerene soot, fuel-rich-flame particles and spark-generated particles, significant Cxn+ clusters at x ≫ 6 were present, with significant contributions from multiply charged ions (n > 1). In all six cases, the ions C1+ and C3+ contributed over 60% to the total C1ions C1+ / C3+ could be used to predict whether significant Cxn+ signals with x > 5 were present. When such signals were present, C1+ / C3+ was close to 1. When absent, C1+ / C3+ was < 0.8. This ratio may therefore serve as a proxy to distinguish between the two types of spectra in atmospheric SP-AMS measurements. Significant refractory oxygenated ions such as CO+ and CO2+ were also observed for all samples. We discuss these signals in detail for Regal Black, and describe their formation via decomposition of oxygenated moieties incorporated into the refractory carbon structure. These species may be of importance in atmospheric processes such as water uptake and heterogeneous chemistry. If atmospherically stable, these oxidized species may be useful for distinguishing

  20. Size-dependent stability toward dissociation and ligand binding energies of phosphine-ligated gold cluster ions

    SciTech Connect

    Johnson, Grant E.; Priest, Thomas A.; Laskin, Julia

    2014-01-01

    The stability of sub-nanometer size gold clusters ligated with organic molecules is of paramount importance to the scalable synthesis of monodisperse size-selected metal clusters with highly tunable chemical and physical properties. For the first time, a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR-MS) equipped with surface induced dissociation (SID) has been employed to investigate the time and collision energy resolved fragmentation behavior of cationic doubly charged gold clusters containing 7-9 gold atoms and 6-7 triphenylphosphine (TPP) ligands prepared by reduction synthesis in solution. The TPP ligated gold clusters are demonstrated to fragment through three primary dissociation pathways: (1) Loss of a neutral TPP ligand from the precursor gold cluster, (2) asymmetric fission and (3) symmetric fission and charge separation of the gold core resulting in formation of complementary pairs of singly charged fragment ions. Threshold energies and activation entropies of these fragmentation pathways have been determined employing Rice-Ramsperger-Kassel-Marcus (RRKM) modeling of the experimental SID data. It is demonstrated that the doubly charged cluster ion containing eight gold atoms and six TPP ligands, (8,6)2+, exhibits exceptional stability compared to the other cationic gold clusters examined in this study due to its large ligand binding energy of 1.76 eV. Our findings demonstrate the dramatic effect of the size and extent of ligation on the gas-phase stability and preferred fragmentation pathways of small TPP-ligated gold clusters.

  1. The structures of small gold cluster anions as determined by a combination of ion mobility measurements and density functional calculations

    NASA Astrophysics Data System (ADS)

    Furche, Filipp; Ahlrichs, Reinhart; Weis, Patrick; Jacob, Christoph; Gilb, Stefan; Bierweiler, Thomas; Kappes, Manfred M.

    2002-10-01

    A combined experimental and theoretical study of small gold cluster anions is performed. The experimental effort consists of ion mobility measurements that lead to the assignment of the collision cross sections for the different cluster sizes at room temperature. The theoretical study is based on ab initio molecular dynamics calculations with the goal to find energetically favorable candidate structures. By comparison of the theoretical results with the measured collision cross sections as well as vertical detachment energies (VDEs) from the literature, we assign structures for the small Aun- ions (n<13) and locate the transition from planar to three-dimensional structures. While a unique assignment based on the observed VDEs alone is generally not possible, the collision cross sections provide a direct and rather sensitive measure of the cluster structure. In contrast to what was expected from other metal clusters and previous theoretical studies, the structural transition occurs at an unusually large cluster size of twelve atoms.

  2. Formation of surface nanostructures on rutile (TiO2): comparative study of low-energy cluster ion and high-energy monoatomic ion impact

    NASA Astrophysics Data System (ADS)

    Popok, V. N.; Jensen, J.; Vučković, S.; Mackova, A.; Trautmann, C.

    2009-10-01

    The formation of nanostructures on rutile (TiO2) surfaces formed after the implantation of kiloelectronvolt-energy Ar_n^+ cluster ions and megaelectronvolt- to gigaelectronvolt-energy multiply charged heavy ions (Iq+, Taq+ and Uq+) is studied. Despite the differences in stopping and energy transfer mechanisms between the kiloelectronvolt-energy cluster ions and megaelectronvolt-energy monoatomic ions, their impacts lead to a similar type of surface damage, namely craters. For the cluster ion implantation the craters are caused by the multiple-collision effect (dominated by nuclear stopping) and the high density of energy and momentum transferred to the target, while for the case of megaelectronvolt multiply charged ions the craters are probably formed due to the Coulomb explosion and fast energy transfer caused by the electronic stopping. At ion energies in the gigaelectronvolt range, nanosize protrusions, so-called hillocks, are observed on the surface. It is suggested that electronic stopping leads to the formation of continuous tracks and the transferred energy is high enough to melt the material along the whole projectile path. Elastic rebound of the tension between the molten and solid state phases leads to liquid flow, expansion and quenching of the melt, thus forming the hillocks. Atomic force microscopy measurements carried out under different environmental conditions (temperature and atmosphere) suggest that the damaged material at the nanosize impact spots has very different water affinity properties (higher hydrophilicity or water adsorption) compared with the non-irradiated rutile surface.

  3. The plasma focus as a source of collimated beams of negative ion clusters and of neutral deuterium atoms

    NASA Astrophysics Data System (ADS)

    Nardi, V.; Powell, C.

    1984-03-01

    We report the space anisotropy and brightness B4 (i.e., the momentum normalized density in four dimensional transverse phase space) of a high-intensity pulsed source of neutral-atom and negative-ion-cluster beams with energy/atom E≳0.2 Mev, ion clusters with m/Z (a.u.) ≳200. The source is formed in an 0.5 MA plasma focus-PF-discharge. The energy spectrum of different particle species is obtained from a 12.2 kG magnetic analyzer, energy filters and time resolved detectors. Collimated particle beams are ejected within a <6° cone along the discharge axis inside a ≳3 mm diameter plasma channel (neutral atoms, ion clusters, impurity heavy ions at 0°, electron beams, clusters and negatively-charged ion clumps at 180°). Pulsed kA currents of ions (and neutral fluence of comparable intensity at 180°) are detected in the 6° cone at 0° with B4˜107 (mA/cm2rad2) for particle energies E≳200 KeV. In the 180° direction the soruce ejects multiple pulses of electron and ion beams in alternating sequency (typical pulse duration ˜10 ns) with a net negative charge which provide charge neutralization for ion and ion cluster beams. The source which can operate—in principle—at a high repetition rate has a scaling law in which the particle-intensity increases without a detectable increase of the angular dispersion.

  4. Atomic layer etching of Cu film using gas cluster ion beam

    NASA Astrophysics Data System (ADS)

    Toyoda, Noriaki; Ogawa, Akihiro

    2017-05-01

    In this work, atomic layer etching (ALE) with a gas cluster ion beam (GCIB) was investigated for the first time. Since gas cluster ions produce dense energy deposition without severe damage, effective, low-damage, and low-temperature removal of chemically altered surface layers is expected. In this study, ALE of Cu films upon oxygen GCIB (O2-GCIB) irradiation in the presence of acetic acid vapor was investigated. Cu atoms were removed from the surface layer, owing to chemical reactions between adsorbed acetic acid molecules and Cu atoms upon O2-GCIB irradiation at room temperature. Since there was no physical sputtering upon 5 kV O2-GCIB irradiation, a self-limiting etch stop was observed after removal of the top layer. Conversely, upon 20 kV O2-GCIB irradiation, Cu atoms were physically sputtered after removal of the chemically altered surface layer. By applying low-energy (5 kV) GCIB irradiation, ALE with GCIB was achieved at room temperature.

  5. Copper quantum clusters in protein matrix: potential sensor of Pb2+ ion.

    PubMed

    Goswami, Nirmal; Giri, Anupam; Bootharaju, M S; Xavier, Paulrajpillai Lourdu; Pradeep, Thalappil; Pal, Samir Kumar

    2011-12-15

    A one-pot synthesis of extremely stable, water-soluble Cu quantum clusters (QCs) capped with a model protein, bovine serum albumin (BSA), is reported. From matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, we assign the clusters to be composed of Cu(5) and Cu(13) cores. The QCs also show luminescence properties having excitation and emission maxima at 325 and 410 nm, respectively, with a quantum yield of 0.15, which are found to be different from that of protein alone in similar experimental conditions. The quenching of luminescence of the protein-capped Cu QCs in the presence of very low hydrogen peroxide concentration (approximately nanomolar, or less than part-per-billion) reflects the efficacy of the QCs as a potential sensing material in biological environments. Moreover, as-prepared Cu QCs can detect highly toxic Pb(2+) ions in water, even at the part-per-million level, without suffering any interference from other metal ions.

  6. Study of Flux Ratio of C60 to Ar Cluster Ion for Hard DLC Film deposition

    NASA Astrophysics Data System (ADS)

    Miyauchi, K.; Kitagawa, T.; Toyoda, N.; Kanda, K.; Matsui, S.; Yamada, I.

    2003-08-01

    To study the influence of the flux ratio of C60 molecule to Ar cluster ion on DLC film characteristics, DLC films deposited under various flux ratios were characterized with Raman spectrometry and Near Edge X-ray Absorption Fine Structure (NEXAFS). From results of these measurements, hard DLC films were deposited when the flux ratio of C60 to Ar cluster ion was between 0.7 and 4. Furthermore the DLC film with constant sp2 content was obtained in the range of the ratio from 0.7 to 4, which contents are lower values than that of conventional films such as RF plasma. DLC films deposited under the ratio from 1 to 4 had hardness from 40 to 45GPa. It was shown that DLC films with stable properties of low sp2 content and high hardness were formed even when the fluxes were varied from 1 to 4 during deposition. It was indicated that this process was useful in the view of industrial application.

  7. Investigation into the reactivity of unsupported and supported Ag7 and Ag8 clusters with toxic metal ions.

    PubMed

    Bootharaju, M S; Pradeep, T

    2011-07-05

    We report the chemical interactions of unsupported and alumina-supported Ag(7) and Ag(8) clusters protected with MSA (mercaptosuccinic acid) with heavy metal ions Hg(II), Cd(II), and Pb(II) in water at different concentrations. The investigation was carried out to determine the feasibility of this interesting new class of materials called quantum clusters for water purification. These systems were studied using various spectroscopic and microscopic techniques such as ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, dynamic light scattering, zeta potential measurements, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and photoluminescence spectroscopy and in detail by X-ray photoelectron spectroscopy. We observed that the metal ions interact with both the silver atoms of the clusters and the functional groups of the capping agent (MSA). The mercuric ions were reduced to metallic mercury by both supported and unsupported clusters, due to the feasibility of the redox reaction, whereas no reduction was observed for Cd(II) and Pb(II). As a result of the interaction, the luminescence of the cluster is lost which can be used to sense Hg(II). At lower concentrations, the metal ions were chemically bonded to the carboxylate groups of MSA. Absence of reduction of Hg(II) at lower concentration is due to the chemical affinity of the ligands and the lower silver content per cluster compared to the number of carboxylate groups. © 2011 American Chemical Society

  8. Analysis of heterogeneous water vapor uptake by metal iodide cluster ions via differential mobility analysis-mass spectrometry

    SciTech Connect

    Oberreit, Derek; Rawat, Vivek K.; Larriba-Andaluz, Carlos; Ouyang, Hui; McMurry, Peter H.; Hogan, Christopher J.

    2015-09-14

    The sorption of vapor molecules onto pre-existing nanometer sized clusters is of importance in understanding particle formation and growth in gas phase environments and devising gas phase separation schemes. Here, we apply a differential mobility analyzer-mass spectrometer based approach to observe directly the sorption of vapor molecules onto iodide cluster ions of the form (MI){sub x}M{sup +} (x = 1-13, M = Na, K, Rb, or Cs) in air at 300 K and with water saturation ratios in the 0.01-0.64 range. The extent of vapor sorption is quantified in measurements by the shift in collision cross section (CCS) for each ion. We find that CCS measurements are sensitive enough to detect the transient binding of several vapor molecules to clusters, which shift CCSs by only several percent. At the same time, for the highest saturation ratios examined, we observed CCS shifts of up to 45%. For x < 4, cesium, rubidium, and potassium iodide cluster ions are found to uptake water to a similar extent, while sodium iodide clusters uptake less water. For x ≥ 4, sodium iodide cluster ions uptake proportionally more water vapor than rubidium and potassium iodide cluster ions, while cesium iodide ions exhibit less uptake. Measured CCS shifts are compared to predictions based upon a Kelvin-Thomson-Raoult (KTR) model as well as a Langmuir adsorption model. We find that the Langmuir adsorption model can be fit well to measurements. Meanwhile, KTR predictions deviate from measurements, which suggests that the earliest stages of vapor uptake by nanometer scale species are not well described by the KTR model.

  9. Analysis of heterogeneous water vapor uptake by metal iodide cluster ions via differential mobility analysis-mass spectrometry

    NASA Astrophysics Data System (ADS)

    Oberreit, Derek; Rawat, Vivek K.; Larriba-Andaluz, Carlos; Ouyang, Hui; McMurry, Peter H.; Hogan, Christopher J.

    2015-09-01

    The sorption of vapor molecules onto pre-existing nanometer sized clusters is of importance in understanding particle formation and growth in gas phase environments and devising gas phase separation schemes. Here, we apply a differential mobility analyzer-mass spectrometer based approach to observe directly the sorption of vapor molecules onto iodide cluster ions of the form (MI)xM+ (x = 1-13, M = Na, K, Rb, or Cs) in air at 300 K and with water saturation ratios in the 0.01-0.64 range. The extent of vapor sorption is quantified in measurements by the shift in collision cross section (CCS) for each ion. We find that CCS measurements are sensitive enough to detect the transient binding of several vapor molecules to clusters, which shift CCSs by only several percent. At the same time, for the highest saturation ratios examined, we observed CCS shifts of up to 45%. For x < 4, cesium, rubidium, and potassium iodide cluster ions are found to uptake water to a similar extent, while sodium iodide clusters uptake less water. For x ≥ 4, sodium iodide cluster ions uptake proportionally more water vapor than rubidium and potassium iodide cluster ions, while cesium iodide ions exhibit less uptake. Measured CCS shifts are compared to predictions based upon a Kelvin-Thomson-Raoult (KTR) model as well as a Langmuir adsorption model. We find that the Langmuir adsorption model can be fit well to measurements. Meanwhile, KTR predictions deviate from measurements, which suggests that the earliest stages of vapor uptake by nanometer scale species are not well described by the KTR model.

  10. Analysis of heterogeneous water vapor uptake by metal iodide cluster ions via differential mobility analysis-mass spectrometry.

    PubMed

    Oberreit, Derek; Rawat, Vivek K; Larriba-Andaluz, Carlos; Ouyang, Hui; McMurry, Peter H; Hogan, Christopher J

    2015-09-14

    The sorption of vapor molecules onto pre-existing nanometer sized clusters is of importance in understanding particle formation and growth in gas phase environments and devising gas phase separation schemes. Here, we apply a differential mobility analyzer-mass spectrometer based approach to observe directly the sorption of vapor molecules onto iodide cluster ions of the form (MI)xM(+) (x = 1-13, M = Na, K, Rb, or Cs) in air at 300 K and with water saturation ratios in the 0.01-0.64 range. The extent of vapor sorption is quantified in measurements by the shift in collision cross section (CCS) for each ion. We find that CCS measurements are sensitive enough to detect the transient binding of several vapor molecules to clusters, which shift CCSs by only several percent. At the same time, for the highest saturation ratios examined, we observed CCS shifts of up to 45%. For x < 4, cesium, rubidium, and potassium iodide cluster ions are found to uptake water to a similar extent, while sodium iodide clusters uptake less water. For x ≥ 4, sodium iodide cluster ions uptake proportionally more water vapor than rubidium and potassium iodide cluster ions, while cesium iodide ions exhibit less uptake. Measured CCS shifts are compared to predictions based upon a Kelvin-Thomson-Raoult (KTR) model as well as a Langmuir adsorption model. We find that the Langmuir adsorption model can be fit well to measurements. Meanwhile, KTR predictions deviate from measurements, which suggests that the earliest stages of vapor uptake by nanometer scale species are not well described by the KTR model.

  11. Cluster ions of diquat and paraquat in electrospray ionization mass spectra and their collision-induced dissociation spectra.

    PubMed

    Milman, Boris L

    2003-01-01

    Cluster ions such as [Cat+X+nM](+) (n = 0-4); [Cat-H+nM](+) (n = 1-3); and [2(Cat-H)+X+nM](+) (n = 0-2), where Cat, X, and M are the dication, anion, and neutral salt (CatX(2)), respectively, are observed in electrospray ionization (ESI) mass spectrometry of relatively concentrated solutions of diquat and paraquat. Collision-induced dissociation (CID) reactions of the clusters were observed by tandem mass spectrometry (MS/MS), including deprotonation to form [Cat-H](+), one-electron reduction of the dication to form Cat(+.), demethylation of the paraquat cation to form [Cat-CH(3)](+), and loss of neutral salt to produce smaller clusters. The difference in acidity and reduction power between diquat and paraquat, evaluated by thermodynamical estimates, can rationalize the different fractional yields of even-electron ([Cat-H](+) and its clusters) and odd-electron (mostly Cat(+)) ions in ESI mass spectra of these pesticides. The [Cat+n. Solv](2+) doubly charged cluster ions, where n ion CID spectra of the Cat(2+) salt cation at low collision energy. The presence of an anion and a solvent molecule in a cluster is assumed to be related to existence of tight and loose ion pairs, respectively, in multiply charged droplets/ions formed by ESI. The results emphasize again the role of solution chemistry concepts such as acidity/basicity, redox power, and ion-pair formation, for ESI. Copyright 2003 John Wiley & Sons, Ltd.

  12. Engineering Redox Potential of Lithium Clusters for Electrode Material in Lithium-Ion Batteries

    DOE PAGES

    Kushwaha, Anoop Kumar; Sahoo, Mihir Ranjan; Nanda, Jagjit; ...

    2017-07-01

    Low negative electrode potential and high reactivity makes lithium (Li) ideal candidate for obtaining highest possible energy density among other materials. Here, we show a novel route with which the overall electrode potential could significantly be enhanced through selection of cluster size. In using first principles density functional theory and continuum dielectric model, we studied free energy and redox potential as well as investigated relative stability of Lin (n ≤ 8) clusters in both gas phase and solution. We found that Li3 has the lowest negative redox potential (thereby highest overall electrode potential) suggesting that cluster based approach could providemore » a novel way of engineering the next generation battery technology. The microscopic origin of Li3 cluster’s superior performance is related to two major factors: gas phase ionization and difference between solvation free energy for neutral and positive ion. Taken together, our study provides insight into the engineering of redox potential in battery and could stimulate further work in this direction.« less

  13. A New Feature of Field-Aligned Auroral Ion Beams Observed by Cluster

    NASA Astrophysics Data System (ADS)

    Parks, George; lee, Ensang; Suiyan, Fu; Fillingim, Matt; Cui, Yanbon; Hong, Jinhy; Dandouras, Iaonnis; reme, henri; Canu, Patrick; Lin, Naiguo

    2015-04-01

    Cluster measures 3D distributions in one spin of the spacecraft (4s). Field-aligned ion beams (H+, He+ and O+) are often observed accelerated out of the ionosphere. The escaping beams can be narrow in velocity space or more extended with a continuous range of velocities. Narrow velocity beams indicate the particles have been accelerated by a potential structure localized in space and beams with a wider velocity range indicate the potential structure is extended and distributed along the magnetic field. The Cluster ion composition experiment has now revealed a new feature showing some H+, He+ and O+ field-aligned beams are broken into many discrete beams each with its own velocity covering a wide velocity range. To interpret the discrete beams, the potential model requires existence of many narrow isolated potential structures along a magnetic field but there are currently no U-shaped theories or models that can explain how the discrete potential structures are formed or maintained. Our interpretation is that Cluster SC have actually crossed an auroral arc structure at a height of 3.5 RE and the discrete beams represent particles accelerated on different equi-potential contours of an aurora. While similar beams are observed in three of the four SC, the detailed features are not identical, indicating the beams have limited spatial scales and/or the dynamics include temporal variations. The distance between two discrete beams is estimated to be as small as ~145-290 meters at the SC position. This dimension mapped to the ionosphere is ~72-145 meters, which is a typical thickness of an auroral arc (Maggs and Davis, PSS 16, 205, 1968). The velocity of the beam increases as the SC moves toward the equator indicating that the auroral potential is higher at lower latitudes. This talk will discuss the new discrete beams and their interesting properties.

  14. Critical Role of Energy Transfer Between Terbium Ions for Suppression of Back Energy Transfer in Nonanuclear Terbium Clusters

    PubMed Central

    Omagari, Shun; Nakanishi, Takayuki; Kitagawa, Yuichi; Seki, Tomohiro; Fushimi, Koji; Ito, Hajime; Meijerink, Andries; Hasegawa, Yasuchika

    2016-01-01

    Lanthanide (Ln(III)) complexes form an important class of highly efficient luminescent materials showing characteristic line emission after efficient light absorption by the surrounding ligands. The efficiency is however lowered by back energy transfer from Ln(III) ion to the ligands, especially at higher temperatures. Here we report a new strategy to reduce back energy transfer losses. Nonanuclear lanthanide clusters containing terbium and gadolinium ions, TbnGd9−n clusters ([TbnGd9−n(μ-OH)10(butylsalicylate)16]+NO3−, n = 0, 1, 2, 5, 8, 9), were synthesized to investigate the effect of energy transfer between Tb(III) ions on back energy transfer. The photophysical properties of TbnGd9−n clusters were studied by steady-state and time-resolved spectroscopic techniques and revealed a longer emission lifetime with increasing number of Tb(III) ions in TbnGd9−n clusters. A kinetic analysis of temperature dependence of the emission lifetime show that the energy transfer between Tb(III) ions competes with back energy transfer. The experimental results are in agreement with a theoretical rate equation model that confirms the role of energy transfer between Tb(III) ions in reducing back energy transfer losses. The results provide a new strategy in molecular design for improving the luminescence efficiency in lanthanide complexes which is important for potential applications as luminescent materials. PMID:27845407

  15. Critical Role of Energy Transfer Between Terbium Ions for Suppression of Back Energy Transfer in Nonanuclear Terbium Clusters.

    PubMed

    Omagari, Shun; Nakanishi, Takayuki; Kitagawa, Yuichi; Seki, Tomohiro; Fushimi, Koji; Ito, Hajime; Meijerink, Andries; Hasegawa, Yasuchika

    2016-11-15

    Lanthanide (Ln(III)) complexes form an important class of highly efficient luminescent materials showing characteristic line emission after efficient light absorption by the surrounding ligands. The efficiency is however lowered by back energy transfer from Ln(III) ion to the ligands, especially at higher temperatures. Here we report a new strategy to reduce back energy transfer losses. Nonanuclear lanthanide clusters containing terbium and gadolinium ions, TbnGd9-n clusters ([TbnGd9-n(μ-OH)10(butylsalicylate)16](+)NO3(-), n = 0, 1, 2, 5, 8, 9), were synthesized to investigate the effect of energy transfer between Tb(III) ions on back energy transfer. The photophysical properties of TbnGd9-n clusters were studied by steady-state and time-resolved spectroscopic techniques and revealed a longer emission lifetime with increasing number of Tb(III) ions in TbnGd9-n clusters. A kinetic analysis of temperature dependence of the emission lifetime show that the energy transfer between Tb(III) ions competes with back energy transfer. The experimental results are in agreement with a theoretical rate equation model that confirms the role of energy transfer between Tb(III) ions in reducing back energy transfer losses. The results provide a new strategy in molecular design for improving the luminescence efficiency in lanthanide complexes which is important for potential applications as luminescent materials.

  16. Critical Role of Energy Transfer Between Terbium Ions for Suppression of Back Energy Transfer in Nonanuclear Terbium Clusters

    NASA Astrophysics Data System (ADS)

    Omagari, Shun; Nakanishi, Takayuki; Kitagawa, Yuichi; Seki, Tomohiro; Fushimi, Koji; Ito, Hajime; Meijerink, Andries; Hasegawa, Yasuchika

    2016-11-01

    Lanthanide (Ln(III)) complexes form an important class of highly efficient luminescent materials showing characteristic line emission after efficient light absorption by the surrounding ligands. The efficiency is however lowered by back energy transfer from Ln(III) ion to the ligands, especially at higher temperatures. Here we report a new strategy to reduce back energy transfer losses. Nonanuclear lanthanide clusters containing terbium and gadolinium ions, TbnGd9‑n clusters ([TbnGd9‑n(μ-OH)10(butylsalicylate)16]+NO3‑, n = 0, 1, 2, 5, 8, 9), were synthesized to investigate the effect of energy transfer between Tb(III) ions on back energy transfer. The photophysical properties of TbnGd9‑n clusters were studied by steady-state and time-resolved spectroscopic techniques and revealed a longer emission lifetime with increasing number of Tb(III) ions in TbnGd9‑n clusters. A kinetic analysis of temperature dependence of the emission lifetime show that the energy transfer between Tb(III) ions competes with back energy transfer. The experimental results are in agreement with a theoretical rate equation model that confirms the role of energy transfer between Tb(III) ions in reducing back energy transfer losses. The results provide a new strategy in molecular design for improving the luminescence efficiency in lanthanide complexes which is important for potential applications as luminescent materials.

  17. Formation of ion clusters in the phase separated structures of neutral-charged polymer blends

    NASA Astrophysics Data System (ADS)

    Kwon, Ha-Kyung; Olvera de La Cruz, Monica

    2015-03-01

    Polyelectrolyte blends, consisting of at least one charged species, are promising candidate materials for fuel cell membranes, for their mechanical stability and high selectivity for proton conduction. The phase behavior of the blends is important to understand, as this can significantly affect the performance of the device. The phase behavior is controlled by χN, the Flory-Huggins parameter multiplied by the number of mers, as well as the electrostatic interactions between the charged backbone and the counterions. It has recently been shown that local ionic correlations, incorporated via liquid state (LS) theory, enhance phase separation of the blend, even in the absence of polymer interactions. In this study, we show phase diagrams of neutral-charged polymer blends including ionic correlations via LS theory. In addition to enhanced phase separation at low χN, the blends show liquid-liquid phase separation at high electrostatic interaction strengths. Above the critical strength, the charged polymer phase separates into ion-rich and ion-poor regions, resulting in the formation of ion clusters within the charged polymer phase. This can be shown by the appearance of multiple spinodal and critical points, indicating the coexistence of several charge separated phases. This work was performed under the following financial assistance award 70NANB14H012 from U.S. Department of Commerce, National Institute of Standards and Technology as part of the Center for Hierarchical Materials Design (CHiMaD).

  18. Peptide Fragmentation and Surface Structural Analysis by Means of ToF-SIMS Using Large Cluster Ion Sources.

    PubMed

    Yokoyama, Yuta; Aoyagi, Satoka; Fujii, Makiko; Matsuo, Jiro; Fletcher, John S; Lockyer, Nicholas P; Vickerman, John C; Passarelli, Melissa K; Havelund, Rasmus; Seah, Martin P

    2016-04-05

    Peptide or protein structural analysis is crucial for the evaluation of biochips and biodevices, therefore an analytical technique with the ability to detect and identify protein and peptide species directly from surfaces with high lateral resolution is required. In this report, the efficacy of ToF-SIMS to analyze and identify proteins directly from surfaces is evaluated. Although the physics governing the SIMS bombardment process precludes the ability for researchers to detect intact protein or larger peptides of greater than a few thousand mass unit directly, it is possible to obtain information on the partial structures of peptides or proteins using low energy per atom argon cluster ion beams. Large cluster ion beams, such as Ar clusters and C60 ion beams, produce spectra similar to those generated by tandem MS. The SIMS bombardment process also produces peptide fragment ions not detected by conventional MS/MS techniques. In order to clarify appropriate measurement conditions for peptide structural analysis, peptide fragmentation dependency on the energy of a primary ion beam and ToF-SIMS specific fragment ions are evaluated. It was found that the energy range approximately 6 ≤ E/n ≤ 10 eV/atom is most effective for peptide analysis based on peptide fragments and [M + H] ions. We also observed the cleaving of side chain moieties at extremely low-energy E/n ≤ 4 eV/atom.

  19. Isolated crater formation by gas cluster ion impact and their use as templates for carbon nanotube growth

    NASA Astrophysics Data System (ADS)

    Toyoda, Noriaki; Kimura, Asahi; Yamada, Isao

    2016-03-01

    Crater-like defects formations with gas cluster ion beams (GCIB) were used as templates for carbon nanotube (CNT) growth. Upon a gas cluster ion impact, dense energy is deposited on a target surface while energy/atom of gas cluster ion is low, which creates crater-like defects. Si and SiO2 were irradiated with Ar-GCIB, subsequently CNTs were grown with an alcohol catalytic CVD using Co and ethanol as catalyst and precursor, respectively. From SEM, AFM and Raman spectroscopy, it was shown that growth of CNT with small diameter was observed on SiO2 with Ar-GCIB irradiation. On Si targets, formation of craters with bottom oxide prevented Co diffusion during CNT growth, as a result, CNT growth was observed only on Si irradiated with high-energy Ar-GCIB. These results showed that isolated defects created by GCIB can be used as templates for nanotube growth.

  20. Measurement of cluster ions and residue nanoparticles from water samples with an electrospray/differential mobility analyzer.

    PubMed

    Han, Bangwoo; Lenggoro, I Wuled; Choi, Mansoo; Okuyama, Kikuo

    2003-06-01

    Cluster ions and residue nanoparticles with sizes below 30 nm were generated by electrospraying (ES) and drying droplets of pure water, tap water, and aqueous solutions of salts. The mobility spectra of the cluster ions between 9.1 and 9.3 x 10(-5) m2/(V s) were measured using a differential mobility analyzer (DMA) operated at room temperature and atmospheric pressure. A modified Faraday cup and a condensation nucleus counter were used for detection. The concentrations of total residue/contaminants in the water were determined as a function of sizes of measured aerosol particles and of the initial droplets. Method detection limits were at sub-ppb level for pure water and sub-ppm level for tap water. ES/DMA is capable of simultaneously measuring the mobility distribution of cluster ions and concentration of total residue present in water samples.

  1. Study of small carbon and semiconductor clusters using negative ion threshold photodetachment spectroscopy

    SciTech Connect

    Arnold, Caroline Chick

    1994-08-01

    The bonding and electronics of several small carbon and semiconductor clusters containing less than ten atoms are probed using negative ion threshold photodetachment (zero electron kinetic energy, or ZEKE) spectroscopy. ZEKE spectroscopy is a particularly advantageous technique for small cluster study, as it combines mass selection with good spectroscopic resolution. The ground and low-lying electronic states of small clusters in general can be accessed by detaching an electron from the ground anion state. The clusters studied using this technique and described in this work are C6-/C6, Sin-/Sin (n = 2, 3, 4), Ge2-/Ge2, In2P-/In2P,InP2-/InP2, and Ga2As-. The total photodetachment cross sections of several other small carbon clusters and the ZEKE spectrum of the I-•CH3I SN2 reaction complex are also presented to illustrate the versatility of the experimental apparatus. Clusters with so few atoms do not exhibit bulk properties. However, each specie exhibits bonding properties that relate to the type of bonding found in the bulk. C6, as has been predicted, exhibits a linear cumulenic structure, where double bonds connect all six carbon atoms. This double bonding reflects how important π bonding is in certain phases of pure carbon (graphite and fullerenes). The symmetric stretch frequencies observed in the C6- spectra, however, are in poor agreement with the calculated values. Also observed as sharp structure in total photodetachment cross section scans was an excited anion state bound by only ~40 cm-1 relative to the detachment continuum. This excited anion state appears to be a valence bound state, possible because of the high electron affinity of C6, and the open shell of the anion.

  2. Generation of “bastard” molecular ions from van der Waals clusters: Arn(C2Cl4)m+ ions, suspected interlopers in collection of solar neutrinos

    PubMed Central

    Buelow, S. J.; Worsnop, D. R.; Herschbach, D. R.

    1981-01-01

    Gaseous molecular ions containing argon and perchlorethylene, Arn(C2Cl4)m+ in which n ≥ 1-29 and m ≥ 1-4, are produced by electron bombardment of van der Waals clusters formed by expanding an Ar/C2Cl4 mixture through a supersonic nozzle. Previous attempts to observe such ions in a high-pressure mass spectrometer were not successful, as with many other (“bastard”) ions that similarly lack a stable chemically bound neutral parent molecule. This is probably due to dissociation induced by the large exoergicity from charge transfer between species that differ greatly in ionization potential. Use of van der Waals clusters as parent species avoids entirely the exoergicity problem and thus offers a general method to generate bastard ions. The Ar(C2Cl4)m+ ions have been suspected of interfering with collection of 37Ar+ ions produced by the 37Cl(v,e-)37Ar+ reaction in the solar neutrino observatory. Although, as shown by our results, these ions are stable, they are unlikely to inhibit collection on the long time scale of the solar neutrino experiment. PMID:16593130

  3. Calculation of composition distribution of ultrafine ion-H2O-H2SO4 clusters using a modified binary ion nucleation theory

    NASA Technical Reports Server (NTRS)

    Singh, J. J.; Smith, A. S.; Chan, L. Y.; Yue, G. K.

    1982-01-01

    Thomson's ion nucleation theory was modified to include the effects of curvature dependence of the microscopic surface tension of field dependent, nonlinear, dielectric properties of the liquid; and of sulfuric acid hydrate formation in binary mixtures of water and sulfuric acid vapors. The modified theory leads to a broadening of the ion cluster spectrum, and shifts it towards larger numbers of H2O and H2SO4 molecules. Whether there is more shifting towards larger numbers of H2O or H2SO4 molecules depends on the relative humidity and relative acidity of the mixture. Usually, a broadening of the spectrum is accompanied by a lowering of the mean cluster intensity. For fixed values of relative humidity and relative acidity, a similar broadening pattern is observed when the temperature is lowered. These features of the modified theory illustrate that a trace of sulfuric acid can facilitate the formation of ultrafine, stable, prenucleation ion clusters as well as the growth of the prenucleation ion clusters towards the critical saddle point conditions, even with low values of relative humidity and relative acidity.

  4. Use of ion-mobility mass spectrometry (IMS-MS) to map polyoxometalate Keplerate clusters and their supramolecular assemblies.

    PubMed

    Robbins, Philip J; Surman, Andrew J; Thiel, Johannes; Long, De-Liang; Cronin, Leroy

    2013-03-07

    We present the high-resolution (HRES-MS) and ion-mobility (IMS-MS) mass spectrometry studies of icosahedral nanoscale polyoxometalate-based {L(30)}{(Mo)Mo(5)} Keplerate clusters, and demonstrate the use of IMS-MS to resolve and map intact nanoclusters, and its potential for the discovery of new structures, in this case the first gas phase observation of 'proto-clustering' of higher order Keplerate supramolecular aggregates.

  5. Soft Landing of Mass-Selected Gold Clusters: Influence of Ion and Ligand on Charge Retention and Reactivity

    SciTech Connect

    Johnson, Grant E.; Laskin, Julia

    2015-02-01

    Herein, we employ a combination of reduction synthesis in solution, soft landing of mass-selected precursor and product ions, and in situ time-of-flight secondary ion mass spectrometry (TOF-SIMS) to examine the influence of ion and the length of diphosphine ligands on the charge retention and reactivity of ligated gold clusters deposited onto self-assembled monolayer surfaces (SAMs). Product ions (Au10L42+, (10,4)2+, L = 1,3-bis(diphenyl-phosphino)propane, DPPP) were prepared through in-source collision induced dissociation (CID) and precursor ions [(8,4)2+, L = 1,6-bis(diphenylphosphino)hexane, DPPH] were synthesized in solution for comparison to (11,5)3+ precursor ions ligated with DPPP investigated previously (ACS Nano 2012, 6, 573 and J. Phys. Chem. C. 2012, 116, 24977). Similar to (11,5)3+ precursor ions, the (10,4)2+ product ions are shown to retain charge on 1H,1H,2H,2H-perfluorodecanethiol monolayers (FSAMs). Additional abundant peaks at higher m/z indicative of reactivity are observed in the TOF-SIMS spectrum of (10,4)2+ product ions that are not seen for (11,5)3+ precursor ions. The abundance of (10,4)2+ on 16-mercaptohexadecanoic acid (COOH-SAMs) is demonstrated to be lower than on FSAMs, consistent with partial reduction of charge. The (10,4)2+ product ion on 1-dodecanethiol (HSAMs) exhibits peaks similar to those seen on the COOH-SAM. On the HSAM, higher m/z peaks indicative of reactivity are observed similar to those on the FSAM. The (8,4)2+ DPPH precursor ions are shown to retain charge on FSAMs similar to (11,5)3+ precursor ions prepared with DPPP. An additional peak corresponding to attachment of one gold atom to (8,4)2+ is observed at higher m/z for DPPH-ligated clusters. On the COOH-SAM, (8,4)2+ is less abundant than on the FSAM consistent with partial neutralization. The results indicate that although retention of charge by product ions generated by CID is similar to precursor ions their reactivity during analysis with SIMS is different

  6. Compositions and Structures of Vanadium Oxide Cluster Ions VmOn(±) (m = 2-20) Investigated by Ion Mobility Mass Spectrometry.

    PubMed

    Wu, Jenna W J; Moriyama, Ryoichi; Tahara, Hiroshi; Ohshimo, Keijiro; Misaizu, Fuminori

    2016-06-02

    Stable compositions and geometrical structures of vanadium oxide cluster ions, VmOn(±), were investigated by ion mobility mass spectrometry (IM-MS). The most stable compositions of vanadium oxide cluster cations were (V2O4)(V2O5)(m-2)/2(+) and (VO2)(V2O5)(m-1)/2(+), depending on the clusters with even and odd numbers of vanadium atoms. Compositions one-oxygen richer than the cations, such as (V2O5)m/2(-) and (VO3)(V2O5)(m-1)/2(-), were predominantly observed for cluster anions. Assignments of these stable cluster ion compositions, which were determined as a result of collision-induced dissociations in IM-MS, can partly be explained with consideration of spin density distribution. By comparing the experimental collision cross sections (CCSs) obtained from ion mobility measurement with CCSs of the theoretically calculated structures, we confirmed the patterned growth of geometrical structures partially discussed in previous theoretical and spectroscopic studies. We showed that even sized (V2O5)m/2(±) where m = 6-12 had right polygonal prism structures except for the anionic V12O30(-), and for the clusters of odd numbers of vanadium m, cations and anions can either have bridged or pyramid structures. Both of the odd sized structures proposed were derivatives from the even sized right polygonal prism structures. The exception, V12O30(-), which had a CCS almost equal to that of the neighboring smaller V11O28(-), should have a structure of higher density than the right hexagonal prism, in which it was proposed to be a captured pyramid structure, derived from V11O28(-).

  7. Preferential refilling and planarization of grooves with amorphous carbon by using gas cluster ion beam irradiations

    SciTech Connect

    Naito, K.; Toyoda, N.; Yamada, I.

    2011-01-07

    Surface planarization is important for fabrication of patterned media. One of the methods is smoothing of the patterned surface after deposition of refilling materials. However it requires two process steps. In this study, we studied planarization of patterned media by formation of refilling films with gas cluster ion beam (GCIB) assisted deposition to reduce the process step. Hard amorphous carbon films were deposited on line-and-space pattern (100 nm pitch, 20 nm in depth) by using Ar-GCIB assisted deposition. From the atomic force microscope and the cross-sectional transmission electron microscope observations, the line-and-space patterns were refilled with amorphous carbon films with Ar-GCIB assisted deposition and smooth surface was obtained. The thickness of the amorphous carbon film required for surface planarization was 32 nm, which was very small compared to the initial peak to valley (20 nm). By using this method, sputtering process for planarization can be omitted.

  8. Measurement of sodium-argon cluster ion recombination by coherent microwave scattering

    SciTech Connect

    Wu Yue; Sawyer, Jordan; Zhang Zhili; Shneider, Mikhail N.; Viggiano, Albert A.

    2012-03-12

    This present work demonstrates a non-intrusive measurement of the rate constant for sodium-argon cluster ions (Na{sup +}{center_dot}Ar) recombining with electrons. The measurements begin with resonance enhanced multi-photon ionization of the Na followed by coherent microwave scattering (radar) to monitor the plasma density. The Na{sup +}{center_dot}Ar adduct was formed in a three-body reaction. The plasma decay due to recombination reactions was monitored as a function of time and modeled to determine the rate constant. At 473 K, the rate constant is 1.8{sub -0.5}{sup +0.7}x10{sup -6}cm{sup 3}/s in an argon buffer at 100 Torr and initial Na number density of 5.5 x 10{sup 10} cm{sup -3}.

  9. Measurement of sodium-argon cluster ion recombination by coherent microwave scattering

    NASA Astrophysics Data System (ADS)

    Wu, Yue; Sawyer, Jordan; Zhang, Zhili; Shneider, Mikhail N.; Viggiano, Albert A.

    2012-03-01

    This present work demonstrates a non-intrusive measurement of the rate constant for sodium-argon cluster ions (Na+.Ar) recombining with electrons. The measurements begin with resonance enhanced multi-photon ionization of the Na followed by coherent microwave scattering (radar) to monitor the plasma density. The Na+.Ar adduct was formed in a three-body reaction. The plasma decay due to recombination reactions was monitored as a function of time and modeled to determine the rate constant. At 473 K, the rate constant is 1.8-0.5+0.7×10-6cm3/s in an argon buffer at 100 Torr and initial Na number density of 5.5 × 1010 cm-3.

  10. Improvement of the gas cluster ion beam-(GCIB)-based molecular secondary ion mass spectroscopy (SIMS) depth profile with O2(+) cosputtering.

    PubMed

    Chu, Yi-Hsuan; Liao, Hua-Yang; Lin, Kang-Yi; Chang, Hsun-Yun; Kao, Wei-Lun; Kuo, Ding-Yuan; You, Yun-Wen; Chu, Kuo-Jui; Wu, Chen-Yi; Shyue, Jing-Jong

    2016-04-21

    Over the last decade, cluster ion beams have displayed their capability to analyze organic materials and biological specimens. Compared with atomic ion beams, cluster ion beams non-linearly enhance the sputter yield, suppress damage accumulation and generate high mass fragments during sputtering. These properties allow successful Secondary Ion Mass Spectroscopy (SIMS) analysis of soft materials beyond the static limit. Because the intensity of high mass molecular ions is intrinsically low, enhancing the intensity of these secondary ions while preserving the sample in its original state is the key to highly sensitive molecular depth profiles. In this work, bulk poly(ethylene terephthalate) (PET) was used as a model material and analyzed using Time-of-Flight SIMS (ToF-SIMS) with a pulsed Bi3(2+) primary ion. The optimized hardware of a 10 kV Ar2500(+) Gas Cluster Ion Beam (GCIB) with a low kinetic energy (200-500 V) oxygen ion (O2(+)) as a cosputter beam was employed for generating depth profiles and for examining the effect of beam parameters. The results were then quantitatively analyzed using an established erosion model. It was found that the ion intensity of the PET monomer ([M + H](+)) and its large molecular fragment ([M - C2H4O + H](+)) steadily declined during single GCIB sputtering, with distortion of the distribution information. However, under an optimized GCIB-O2(+) cosputter, the secondary ion intensity quickly reached a steady state and retained >95% intensity with respect to the pristine surface, although the damage cross-section was larger than that of single GCIB sputtering. This improvement was due to the oxidation of molecules and the formation of -OH groups that serve as proton donors to particles emitted from the surface. As a result, the ionization yield was enhanced and damage to the chemical structure was masked. Although O2(+) is known to alter the chemical structure and cause damage accumulation, the concurrently used GCIB could

  11. Study of compressible coherent structures, close to ion scales, in solar wind turbulence using Cluster data

    NASA Astrophysics Data System (ADS)

    Perrone, Denise; Alexandrova, Olga; Mangeney, André; Maksimovic, Milan; Rocoto, Virgile; Pantellini, Filippo; Zaslavsky, Arnaud; Issautier, Karine

    2015-04-01

    The interplanetary medium, a weakly collisional and fully turbulent medium, can be considered the best natural laboratory to study the dynamical behavior of turbulent plasmas. A fundamental question in solar wind plasma physics is whether, space plasma turbulence can be considered as a mixture of quasi-linear waves or if the turbulence is strong with formation of coherent structures responsible for the dissipation. Here we present an automatic method to identify compressible coherent structures using Morlet wavelet decomposition of magnetic signal from Cluster spacecraft and reconstruction of magnetic fluctuations in a selected scale range (0.033-0.2 Hz). Different kind of coherent structures have been detected: from soliton-like compressible structures to current sheet- or vortex-like alfvenic structures. A multi-satellite analysis, in order to characterize 3D geometry and propagation in plasma rest frame, reveals that these structures propagate quasi-perpendicular to the mean magnetic field, with finite velocity. Moreover, the spatial scales of coherent structures have been estimated: for the selected frequency range, the distribution of spatial scales is picked around ~30 ion Larmor radius or ion inertial length (~1200 km). Our observations in the solar wind can provide constraints on theoretical modeling of small-scale turbulence and dissipation in collisionless magnetized plasmas.

  12. The Collision Cross Sections of Iodide Salt Cluster Ions in Air via Differential Mobility Analysis-Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Ouyang, Hui; Larriba-Andaluz, Carlos; Oberreit, Derek R.; Hogan, Christopher J.

    2013-12-01

    To date, most collision cross section (CCS) predictions have invoked gas molecule impingement-reemission rules in which specular and elastic scattering of spherical gas molecules from rigid polyatomic surfaces are assumed. Although such predictions have been shown to agree well with CCSs measured in helium bath gas, a number of studies reveal that these predictions do not agree with CCSs for ions in diatomic gases, namely, air and molecular nitrogen. To further examine the validity of specular-elastic versus diffuse-inelastic scattering models, we measured the CCSs of positively charged metal iodide cluster ions of the form [MI]n[M+]z, where M = Na, K, Rb, or Cs, n = 1 - 25, and z = 1 - 2. Measurements were made in air via differential mobility analysis mass spectrometry (DMA-MS). The CCSs measured are compared with specular-elastic as well as diffuse-inelastic scattering model predictions with candidate ion structures determined from density functional theory. It is found that predictions from diffuse-inelastic collision models agree well (within 5 %) with measurements from sodium iodide cluster ions, while specular-elastic collision model predictions are in better agreement with cesium iodide cluster ion measurements. The agreement with diffuse-inelastic and specular-elastic predictions decreases and increases, respectively, with increasing cation mass. However, even when diffuse-inelastic cluster ion predictions disagree with measurements, the disagreement is of a near-constant factor for all ions, indicating that a simple linear rescaling collapses predictions to measurements. Conversely, rescaling cannot be used to collapse specular-elastic predictions to measurements; hence, although the precise impingement reemission rules remain ambiguous, they are not specular-elastic.

  13. The collision cross sections of iodide salt cluster ions in air via differential mobility analysis-mass spectrometry.

    PubMed

    Ouyang, Hui; Larriba-Andaluz, Carlos; Oberreit, Derek R; Hogan, Christopher J

    2013-12-01

    To date, most collision cross section (CCS) predictions have invoked gas molecule impingement-reemission rules in which specular and elastic scattering of spherical gas molecules from rigid polyatomic surfaces are assumed. Although such predictions have been shown to agree well with CCSs measured in helium bath gas, a number of studies reveal that these predictions do not agree with CCSs for ions in diatomic gases, namely, air and molecular nitrogen. To further examine the validity of specular-elastic versus diffuse-inelastic scattering models, we measured the CCSs of positively charged metal iodide cluster ions of the form [MI]n[M(+)]z, where M = Na, K, Rb, or Cs, n = 1 - 25, and z = 1 - 2. Measurements were made in air via differential mobility analysis mass spectrometry (DMA-MS). The CCSs measured are compared with specular-elastic as well as diffuse-inelastic scattering model predictions with candidate ion structures determined from density functional theory. It is found that predictions from diffuse-inelastic collision models agree well (within 5%) with measurements from sodium iodide cluster ions, while specular-elastic collision model predictions are in better agreement with cesium iodide cluster ion measurements. The agreement with diffuse-inelastic and specular-elastic predictions decreases and increases, respectively, with increasing cation mass. However, even when diffuse-inelastic cluster ion predictions disagree with measurements, the disagreement is of a near-constant factor for all ions, indicating that a simple linear rescaling collapses predictions to measurements. Conversely, rescaling cannot be used to collapse specular-elastic predictions to measurements; hence, although the precise impingement reemission rules remain ambiguous, they are not specular-elastic.

  14. Relativistic coupled-cluster calculations of transition properties in highly charged inert-gas ions

    NASA Astrophysics Data System (ADS)

    Nandy, D. K.

    2016-11-01

    We have carried out an extensive investigation of various spectroscopic properties of highly charged inert-gas ions using a relativistic coupled-cluster method through a one-electron detachment procedure. In particular, we have calculated the atomic states 2 s22 p53/2 2P, 2 s22 p51/2 2P, and 2 s 2 p61/2 2S in F-like inert-gas ions; 3 s23 p53/2 2P, 3 s23 p51/2 2P, and 3 s 3 p61/2 2S states in Cl-like Kr, Xe, and Rn; and 4 s24 p53/2 2P, 4 s24 p51/2 2P, and 4 s 4 p61/2 2S states in Br-like Xe and Rn. Starting from a single-reference Dirac-Hartree-Fock wave function, we construct our exact atomic states by including the dynamic correlation effects in an all-order perturbative fashion. Employing this method, we estimate the ionization potential energies of three low-lying orbitals present in their respective closed-shell configurations. Since the considered highly charged inert-gas ions exhibit huge relativistic effects, we have taken into account the corrections due to Breit interaction as well as from the dominant quantum electrodynamic correction such as vacuum polarization and self-energy effects in these systems. Using our calculated relativistic atomic wave functions and energies, we accurately determine various transition properties such as wavelengths, line strengths, oscillator strengths, transition probabilities, and lifetimes of the excited states.

  15. Plasma cluster ions decrease the antigenicity of mite allergens and suppress atopic dermatitis in NC/Nga mice.

    PubMed

    Hiramoto, Keiichi; Orita, Kumi; Yamate, Yurika; Sato, Eisuke F; Okano, Hiroaki; Nishikawa, Kazuo; Inoue, Masayasu

    2011-07-01

    Mite antigens play important roles in the pathogenesis of atopic dermatitis (AD). We recently developed a novel air cleaner (KC-850U) using charged plasma cluster ions to eliminate a variety of allergens from house environments. The present work demonstrates the ability of KC-850U to decrease the symptoms of AD induced by mite allergens. Pooled sera from the conventional NC/Nga mice, and AD model animals, were incubated with varying concentrations of the control and KC-850U-pretreated allergens extracted from mite. The incubated mixtures were transferred to wells coated with intact allergens and subjected to ELISA to measure the amounts of immunoglobulin E (IgE) bound to the wells. Kinetic analysis revealed that exposure of mite extracts to plasma cluster ions destructed about 95% of the epitopes of the allergens. The specific pathogen-free and conventional mice were housed in rooms equipped with either KC-850U or a standard air cleaner and observed their dermal symptom for 2 weeks. Dermatological examination revealed the AD symptom of the conventional mice housed in a room equipped with an air cleaner. In contrast, the symptoms which became apparent during the experiments were suppressed remarkably exposing mice to plasma cluster ions. These observations suggested that plasma cluster ions generated by KC-850U destroyed the epitopes of mite allergens and suppressed the symptoms of AD in the mice.

  16. Tailoring Ion Charge State Distribution in Tetramethyltin Clusters under Influence of Moderate Intensity Picosecond Laser Pulse: Role of Laser Wavelength and Rate of Energy Deposition

    NASA Astrophysics Data System (ADS)

    Sharma, Pramod; Das, Soumitra; Vatsa, Rajesh K.

    2017-07-01

    Systematic manipulation of ionic-outcome in laser-cluster interaction process has been realized for studies carried out on tetramethyltin (TMT) clusters under picosecond laser conditions, determined by choice of laser wavelength and intensity. As a function of laser intensity, TMT clusters exhibit gradual enhancement in overall ionization of its cluster constituents, up to a saturation level of ionization, which was distinct for different wavelengths (266, 355, and 532 nm). Simultaneously, systematic appearance of higher multiply charged atomic ions and shift in relative abundance of multiply charged atomic ions towards higher charge state was observed, using time-of-flight mass spectrometer. At saturation level, multiply charged atomic ions up to (C2+, Sn2+) at 266 nm, (C4+, Sn4+) at 355 nm, and (C4+, Sn6+) at 532 nm were detected. In addition, at 355 nm intra-cluster ion chemistry within the ionized cluster leads to generation of molecular hydrogen ion (H2 +) and triatomic molecular hydrogen ion (H3 +). Generation of multiply charged atomic ions is ascribed to efficient coupling of laser pulse with the cluster media, facilitated by inner-ionized electrons produced within the cluster, at the leading edge of laser pulse. Role of inner-ionized electrons is authenticated by measuring kinetic energy distribution of electrons liberated upon disintegration of excessively ionized cluster, under the influence of picosecond laser pulse.

  17. Time-of-flight secondary ion mass spectrometry studies of cluster ion analysis for semiconductors and diffusion of manganese in gallium arsenide at low temperatures

    NASA Astrophysics Data System (ADS)

    Goacher, Robyn Elizabeth

    Secondary Ion Mass Spectrometry (SIMS) is an established method for the quantitative analysis of dopants in semiconductors. The quasi-parallel mass acquisition of Time-of-Flight SIMS, along with the development of polyatomic primary ions, have rapidly increased the use of SIMS for analysis of organic and biological specimens. However, the advantages and disadvantages of using cluster primary ions for quantitative analysis of inorganic materials are not clear. The research described in this dissertation investigates the consequences of using polyatomic primary ions for the analysis of inorganic compounds in ToF-SIMS. Furthermore, the diffusion of Mn in GaAs, which is important in Spintronic material applications such as spin injection, is also studied by quantitative ToF-SIMS depth profiling. In the first portion of this work, it was discovered that primary ion bombardment of pre-sputtered compound semiconductors GaAs and InP for the purpose of spectral analysis resulted in the formation of cluster secondary ions, as well as atomic secondary ions (Chapter 2). In particular, bombardment using a cluster primary ion such as Bi3q + or C60q+ resulted in higher yields of high-mass cluster secondary ions. These cluster secondary ions did not have bulk stoichiometry, "non-stoichiometric", in contrast to the paradigm of stoichiometric cluster ions generated from salts. This is attributed to the covalent bonding of the compound semiconductors, as well as to preferential sputtering. The utility of high-mass cluster secondary ions in depth profiling is also discussed. Relative sensitivity factors (RSFs) calculated for ion-implanted Fe and Mn samples in GaAs also exhibit differences based on whether monatomic or polyatomic primary ions are utilized (Chapter 3). These RSFs are important for the quantitative conversion of intensity to concentration. When Bi 32+ primary ions are used for analysis instead of Bi + primary ions, there is a significantly higher proportion of Mn and Fe

  18. High performance charge-state resolving ion energy analyzer optimized for intense laser studies on low-density cluster targets.

    PubMed

    Komar, D; Meiwes-Broer, K-H; Tiggesbäumker, J

    2016-10-01

    We report on a versatile ion analyzer which is capable to resolve ion charge states and energies with a resolution of E/ΔE = 100 at 75 keV/nucleon. Charge states are identified by their characteristic deflection in a magnetic field, whereas the ion energies are independently determined by a time-of-flight measurement. To monitor the signals a delay-line detector is used which records ion impact positions and times in each laser shot. Compared to conventional Thomson parabola spectrometers our instrument provides a low background measurement, hence a superior dynamic range. Further features are an improved energy resolution and a significantly increased transmission. We demonstrate the performance by showing charge-state resolved ion energy spectra from the Coulomb explosion of a low-density target, i.e., silver clusters exposed to intense femtosecond laser pulses.

  19. A new method for measuring ion clusters produced by charged particles in nanometre track sections of DNA size

    NASA Astrophysics Data System (ADS)

    Pszona, S.; Kula, J.; Marjanska, S.

    2000-06-01

    A new method is presented for measuring the frequency distribution of ion clusters, formed in nanometre sections of track, by charged particles. The simulated nanometer-size sites are produced in a device, called the Jet Counter. It consists of a pulse-operated valve which injects an expanding jet of nitrogen gas into an interaction chamber. The resulting distributions of ion clusters produced by alpha particle tracks (from 241Am) in sections ranging from 2 to around 10 nm at unit density in nitrogen gas have been measured. Analysis of the experimental results confirm that the primary ionisation distributions produced in the nanometer sections comply with the Poisson distribution. The ionisation cluster distributions produced in the 2-10 nm track-segments are the first ever to be determined experimentally.

  20. Ion mobility spectrometry-mass spectrometry examination of the structures, stabilities, and extents of hydration of dimethylamine-sulfuric acid clusters.

    PubMed

    Thomas, Jikku M; He, Siqin; Larriba-Andaluz, Carlos; DePalma, Joseph W; Johnston, Murray V; Hogan, Christopher J

    2016-08-17

    We applied an atmospheric pressure differential mobility analyzer (DMA) coupled to a time-of-flight mass spectrometer to examine the stability, mass-mobility relationship, and extent of hydration of dimethylamine-sulfuric acid cluster ions, which are of relevance to nucleation in ambient air. Cluster ions were generated by electrospray ionization and were of the form: [H((CH3)2NH)x(H2SO4)y](+) and [(HSO4)((CH3)2NH)x(H2SO4)y](-), where 4 ≤ x ≤ 8, and 5 ≤ y ≤ 12. Under dry conditions, we find that positively charged cluster ions dissociated via loss of both multiple dimethylamine and sulfuric acid molecules after mobility analysis but prior to mass analysis, and few parent ions were detected in the mass spectrometer. Dissociation also occurred for negative ions, but to a lesser extent than for positive ions for the same mass spectrometer inlet conditions. Under humidified conditions (relative humidities up to 30% in the DMA), positively charged cluster ion dissociation in the mass spectrometer inlet was mitigated and occurred primarily by H2SO4 loss from ions containing excess acid molecules. DMA measurements were used to infer collision cross sections (CCSs) for all identifiable cluster ions. Stokes-Millikan equation and diffuse/inelastic gas molecule scattering predicted CCSs overestimate measured CCSs by more than 15%, while elastic-specular collision model predictions are in good agreement with measurements. Finally, cluster ion hydration was examined by monitoring changes in CCSs with increasing relative humidity. All examined cluster ions showed a modest amount of water molecule adsorption, with percentage increases in CCS smaller than 10%. The extent of hydration correlates directly with cluster ion acidity for positive ions.

  1. Comment on {open_quotes}Stopping power of nonmonochromatic heavy-ion clusters with two-ion correlation effects{close_quotes}

    SciTech Connect

    Tkachenko, I.M.; Munoz-Cobo, J.L.; Munoz, A. |

    1997-11-01

    We reconsider the results of Lontano and Raimondi [Phys. Rev. E {bold 51}, R2755 (1995)] within the full random-phase approximation. We show that the correlation and also velocity dispersion of the cluster ions enhance and reduce the stopping power, respectively. Nevertheless, the enhancement of energy losses due to ionic correlation is much stronger than that obtained by Lontano and Raimondi, and furthermore, the projectile velocity dependence of the stopping power is strictly monotonic, presenting no oscillations. We also did not obtain negative values for the cluster stopping power, as did Lontano and Raimondi. {copyright} {ital 1997} {ital The American Physical Society}

  2. Changes in cluster magnetism and suppression of local superconductivity in amorphous FeCrB alloy irradiated by Ar+ ions

    NASA Astrophysics Data System (ADS)

    Okunev, V. D.; Samoilenko, Z. A.; Szymczak, H.; Szewczyk, A.; Szymczak, R.; Lewandowski, S. J.; Aleshkevych, P.; Malinowski, A.; Gierłowski, P.; Więckowski, J.; Wolny-Marszałek, M.; Jeżabek, M.; Varyukhin, V. N.; Antoshina, I. A.

    2016-02-01

    We show that сluster magnetism in ferromagnetic amorphous Fe67Cr18B15 alloy is related to the presence of large, D=150-250 Å, α-(Fe Cr) clusters responsible for basic changes in cluster magnetism, small, D=30-100 Å, α-(Fe, Cr) and Fe3B clusters and subcluster atomic α-(Fe, Cr, B) groupings, D=10-20 Å, in disordered intercluster medium. For initial sample and irradiated one (Φ=1.5×1018 ions/cm2) superconductivity exists in the cluster shells of metallic α-(Fe, Cr) phase where ferromagnetism of iron is counterbalanced by antiferromagnetism of chromium. At Φ=3×1018 ions/cm2, the internal stresses intensify and the process of iron and chromium phase separation, favorable for mesoscopic superconductivity, changes for inverse one promoting more homogeneous distribution of iron and chromium in the clusters as well as gigantic (twice as much) increase in density of the samples. As a result, in the cluster shells ferromagnetism is restored leading to the increase in magnetization of the sample and suppression of local superconductivity. For initial samples, the temperature dependence of resistivity ρ(T) T2 is determined by the electron scattering on quantum defects. In strongly inhomogeneous samples, after irradiation by fluence Φ=1.5×1018 ions/cm2, the transition to a dependence ρ(T) T1/2 is caused by the effects of weak localization. In more homogeneous samples, at Φ=3×1018 ions/cm2, a return to the dependence ρ(T) T2 is observed.

  3. Dual shell-like magnetic clusters containing Ni(II) and Ln(III) (Ln = La, Pr, and Nd) ions.

    PubMed

    Kong, Xiang-Jian; Ren, Yan-Ping; Long, La-Sheng; Zheng, Zhiping; Nichol, Gary; Huang, Rong-Bin; Zheng, Lan-Sun

    2008-04-07

    Dual shell-like nanoscopic magnetic clusters featuring a polynuclear nickel(II) framework encapsulating that of lanthanide ions (Ln = La, Pr, and Nd) were synthesized using Ni(NO3)(2).6H2O, Ln(NO3)(3).6H2O, and iminodiacetic acid (IDA) under hydrothermal conditions. Structurally established by crystallographic studies, these clusters are [La20Ni30(IDA)30(CO3)6(NO3)6(OH)30(H2O)12](CO3)(6).72H2O (1), [Ln20Ni21(C4H5NO4)21(OH)24(C2H2O3)6(C2O4)3(NO3)9(H2O)12](NO3)9.nH2O [C2H2O3 is the alkoxide form of glycolate; Ln = Pr (2), n = 42; Nd (3), n = 50], and {[La4Ni5Na(IDA)5(CO3)(NO3)4(OH)5(H2O)5][CO3].10H2O} infinity (4). Carbonate, oxalate, and glycolate are products of hydrothermal decomposition of IDA. Compositions of these compounds were confirmed by satisfactory elemental analyses. It has been found that the cluster structure is dependent on the identity of the lanthanide ion as well as the starting Ln/Ni/IDA ratio. The cationic cluster of 1 features a core of the Keplerate type with an outer icosidodecahedron of Ni(II) ions encaging a dodecahedral kernel of La(III). Clusters 2 and 3, distinctly different from 1, are isostructural, possessing a core of an outer shell of 21 Ni(II) ions encapsulating an inner shell of 20 Ln(III) ions. Complex 4 is a three-dimensional assembly of cluster building blocks connected by units of Na(NO3)/La(NO3)3; the structure of the building block resembles closely that of 1, with a hydrated La(III) ion internalized in the decanuclear cage being an extra feature. Magnetic studies indicated ferromagnetic interactions in 1, while overall antiferromagnetic interactions were revealed for 2 and 3. The polymeric, three-dimensional cluster network 4 displayed interesting ferrimagnetic interactions.

  4. Gas cluster ion beam for the characterization of organic materials in submarine basalts as Mars analogs

    SciTech Connect

    Sano, Naoko Barlow, Anders J.; Cumpson, Peter J.; Purvis, Graham W. H.; Abbott, Geoffrey D.; Gray, Neil N. D.

    2016-07-15

    The solar system contains large quantities of organic compounds that can form complex molecular structures. The processing of organic compounds by biological systems leads to molecules with distinctive structural characteristics; thus, the detection and characterization of organic materials could lead to a high degree of confidence in the existence of extra-terrestrial life. Given the nature of the surface of most planetary bodies in the solar system, evidence of life is more likely to be found in the subsurface where conditions are more hospitable. Basalt is a common rock throughout the solar system and the primary rock type on Mars and Earth. Basalt is therefore a rock type that subsurface life might exploit and as such a suitable material for the study of methods required to detect and analyze organic material in rock. Telluric basalts from Earth represent an analog for extra-terrestrial rocks where the indigenous organic matter could be analyzed for molecular biosignatures. This study focuses on organic matter in the basalt with the use of surface analysis techniques utilizing Ar gas cluster ion beams (GCIB); time of flight secondary ion mass spectrometry (ToF-SIMS), and x-ray photoelectron spectroscopy (XPS), to characterize organic molecules. Tetramethylammonium hydroxide (TMAH) thermochemolysis was also used to support the data obtained using the surface analysis techniques. The authors demonstrate that organic molecules were found to be heterogeneously distributed within rock textures. A positive correlation was observed to exist between the presence of microtubule textures in the basalt and the organic compounds detected. From the results herein, the authors propose that ToF-SIMS with an Ar GCIB is effective at detecting organic materials in such geological samples, and ToF-SIMS combined with XPS and TMAH thermochemolysis may be a useful approach in the study of extra-terrestrial organic material and life.

  5. Three-Dimensional Image of Cleavage Bodies in Nuclei Is Configured Using Gas Cluster Ion Beam with Time-of-Flight Secondary Ion Mass Spectrometry

    PubMed Central

    Masaki, Noritaka; Ishizaki, Itsuko; Hayasaka, Takahiro; Fisher, Gregory L.; Sanada, Noriaki; Yokota, Hideo; Setou, Mitsutoshi

    2015-01-01

    Structural variations of DNA in nuclei are deeply related with development, aging, and diseases through transcriptional regulation. In order to bare cross sections of samples maintaining sub-micron structures, an Ar2500+-gas cluster ion beam (GCIB) sputter was recently engineered. By introducing GCIB sputter to time-of-flight secondary ion mass spectrometry (TOF-SIMS), we analyzed the 3D configuration and chemical composition of subnuclear structures of pyramidal cells in the CA2 region in mouse brain hippocampus. Depth profiles of chemicals were analyzed as 3D distributions by combining topographic analyses. Signals corresponding to anions such as CN− and PO3− were distributed characteristically in the shape of cell organelles. CN− signals overlapped DAPI fluorescence signals corresponding to nuclei. The clusters shown by PO3− and those of adenine ions were colocalized inside nuclei revealed by the 3D reconstruction. Taking into account their size and their number in each nucleus, those clusters could be in the cleavage bodies, which are a kind of intranuclear structure. PMID:25961407

  6. Ion channel clustering at the axon initial segment and node of Ranvier evolved sequentially in early chordates.

    PubMed

    Hill, Alexis S; Nishino, Atsuo; Nakajo, Koichi; Zhang, Giuxin; Fineman, Jaime R; Selzer, Michael E; Okamura, Yasushi; Cooper, Edward C

    2008-12-01

    In many mammalian neurons, dense clusters of ion channels at the axonal initial segment and nodes of Ranvier underlie action potential generation and rapid conduction. Axonal clustering of mammalian voltage-gated sodium and KCNQ (Kv7) potassium channels is based on linkage to the actin-spectrin cytoskeleton, which is mediated by the adaptor protein ankyrin-G. We identified key steps in the evolution of this axonal channel clustering. The anchor motif for sodium channel clustering evolved early in the chordate lineage before the divergence of the wormlike cephalochordate, amphioxus. Axons of the lamprey, a very primitive vertebrate, exhibited some invertebrate features (lack of myelin, use of giant diameter to hasten conduction), but possessed narrow initial segments bearing sodium channel clusters like in more recently evolved vertebrates. The KCNQ potassium channel anchor motif evolved after the divergence of lampreys from other vertebrates, in a common ancestor of shark and humans. Thus, clustering of voltage-gated sodium channels was a pivotal early innovation of the chordates. Sodium channel clusters at the axon initial segment serving the generation of action potentials evolved long before the node of Ranvier. KCNQ channels acquired anchors allowing their integration into pre-existing sodium channel complexes at about the same time that ancient vertebrates acquired myelin, saltatory conduction, and hinged jaws. The early chordate refinements in action potential mechanisms we have elucidated appear essential to the complex neural signaling, active behavior, and evolutionary success of vertebrates.

  7. Effects of molecular weight and cationization agent on the sensitivity of Bi cluster secondary ion mass spectrometry.

    PubMed

    Fujii, Makiko; Shishido, Rie; Satoh, Takaya; Suzuki, Shigeru; Matsuo, Jiro

    2016-07-30

    Bi cluster secondary ion mass spectrometry (SIMS) is one of the most promising tools for precise analysis of synthetic polymers. However, the sensitivity in the high-mass region is still insufficient compared with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). Accordingly, the effects of metal assistance (cationization agents) were investigated in this study. To investigate the effects caused by varying the ionization agent, three different polyethylene glycol (PEG) samples were prepared, one with an Ag-deposited film, and two others mixed with Ag and Na, respectively. The measurements were performed by using a commercial Bi cluster SIMS and MALDI-TOFMS systems. The mass spectrum obtained with MALDI-TOFMS was used as a reference molecular weight distribution to evaluate the effects of molecular weight and primary ion species (Bi(+) , Bi3(+) , Bi3(2)(+) ) on the sensitivity of Bi cluster SIMS. The intensity of each secondary ion was the highest in Bi3(2)(+) irradiation, and the lowest in Bi(+) irradiation. Regarding the cationization agents, the secondary ion yield was the highest for the sample mixed with Ag, while the degree of decay of sensitivity along with the increase in molecular weight was the smallest for the sample mixed with Na. It was suggested that the cationization mechanism consists of pre-formed ionization and gas-phase ionization processes. The sensitivity of Bi cluster SIMS decreases to approximately one-fiftieth in every 1000 u. These results might help in understanding the mechanism of cationization and further enhancement of secondary ion yields of polymers. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  8. Molecular activation by surface coordination model: Insight into heterogeneous atmospheric chemistry through cluster-ion molecule reactions

    NASA Astrophysics Data System (ADS)

    Mactaylor, Ronald T. Stanford

    One specific discipline for which cluster work has particular relevance is atmospheric science. The original application of the fast flow reactor technique employed in this thesis was atmospheric science. Coincidentally, fast flow reactors are readily adaptable to cluster studies and in some cases the optimal methodology. Successive studies of a chemical reaction over a range of pressures using a fast flow reactor can allow the experimentalist to distinguish whether a reaction product is formed by a bimolecular or termolecular mechanism. This type of study applied to the HCl water cluster system revealed two distinct processes for HCl uptake. The bimolecular and termolecular HCl uptake processes, noted along with the specific ratios of water molecules to HCl molecules lead directly to the Molecular Activation by Surface Coordination model for heterogeneous processes involving HCl on water-ice polar stratospheric clouds. The efficiency of the termolecular uptake process indicated a strong interaction with the cluster. Since the association product is only observable on clusters where one HCl has already been incorporated by a bimolecular process, and this bimolecular process is interpreted as ionic dissolution, the logical conclusion is that the efficient association process must involve an ion-induced dipole interaction. The ramifications of this conclusion are that it is possible that the efficient heterogeneous chemical conversion processes which are required to explain polar stratospheric ozone loss, are in part due to the surface coordination of HCl (making it readily available to participate in reactions) and also a chemical activation aspect resulting from an ion-induced dipole. A noteworthy feature of this model is that it ties together the results of many studies of the HCl/ice system, which previously did not appear to be in accord with one another. Further exploration of the HCl protonated water cluster system reveal striking similarities to surface

  9. Cluster of differentiation antibody microarrays on plasma immersion ion implanted polycarbonate.

    PubMed

    Kosobrodova, E; Mohamed, A; Su, Y; Kondyurin, A; dos Remedios, C G; McKenzie, D R; Bilek, M M M

    2014-02-01

    Plasma immersion ion implantation (PIII) modifies the surface properties of polymers, enabling them to covalently immobilize proteins without using linker chemistry. We describe the use of PIII treated polycarbonate (PC) slides as a novel platform for producing microarrays of cluster of differentiation (CD) antibodies. We compare their performance to identical antibody microarrays printed on nitrocellulose-coated glass slides that are currently the industry standard. Populations of leukocytes are applied to the CD microarrays and unbound cells are removed revealing patterns of differentially immobilized cells that are detected in a simple label-free approach by scanning the slides with visible light. Intra-slide and inter-slide reproducibility, densities of bound cells, and limits of detection were determined. Compared to the nitrocellulose-coated glass slides, PIII treated PC slides have a lower background noise, better sensitivity, and comparable or better reproducibility. They require three-fold lower antibody concentrations to yield equivalent signal strength, resulting in significant reductions in production cost. The improved transparency of PIII treated PC in the near-UV and visible wavelengths combined with superior immobilization of biomolecules makes them an attractive platform for a wide range of microarray applications.

  10. Cross-sectional TEM Observations of Si Wafers Irradiated With Gas Cluster Ion Beams

    SciTech Connect

    Isogai, Hiromichi; Toyoda, Eiji; Senda, Takeshi; Izunome, Koji; Kashima, Kazuhiko; Toyoda, Noriaki; Yamada, Isao

    2006-11-13

    Irradiation by a Gas Cluster Ion Beam (GCIB) is a promising technique for precise surface etching and planarization of Si wafers. However, it is very important to understand the crystalline structure of Si wafers after GCIB irradiation. In this study, the near surface structure of a Si (100) wafer was analyzed after GCIB irradiation, using a cross-sectional transmission electron microscope (XTEM). Ar-GCIB, that physically sputters Si atoms, and SF6-GCIB, that chemically etches the Si surface, were both used. After GCIB irradiation, high temperature annealing was performed in a hydrogen atmosphere. From XTEM observations, the surface of a virgin Si wafer exhibited completely crystalline structures, but the existence of an amorphous Si and a transition layer was confirmed after GCIB irradiation. The thickness of amorphous layer was about 30 nm after Ar-GCIB irradiation at 30 keV. However, a very thin (< 5 nm) layer was observed when 30 keV SF6-GCIB was used. The thickness of the transition layer was the same both Ar and SF6-GCIB irradiation. After annealing, the amorphous Si and transition layers had disappeared, and a complete crystalline structure with an atomically smooth surface was observed.

  11. Ion-pair dissociation of highly excited carbon clusters: Size and charge effects

    NASA Astrophysics Data System (ADS)

    Launoy, Thibaut; Béroff, Karine; Chabot, Marin; Martinet, Guillaume; Le Padellec, Arnaud; Pino, Thomas; Bouneau, Sandra; Vaeck, Nathalie; Liévin, Jacques; Féraud, Géraldine; Loreau, Jérôme; Mahajan, Thejus

    2017-02-01

    We present measurements of ion-pair dissociation (IPD) of highly excited neutral and ionized carbon clusters Cn=2 -5 (q =0 -3 )+. The tool for producing these species was a high-velocity collision between Cn+ projectiles (v =2.25 a.u.) and helium atoms. The setup allowed us to detect in coincidence anionic and cationic fragments, event by event, leading to a direct and unambiguous identification of the IPD process. Compared with dissociation without anion emission, we found typical 10-4 IPD rates, not depending much on the size and charge of the (n ,q ) species. Exceptions were observed for C2+ and, to a lesser extent, C43 + whose IPDs were notably lower. We tentatively interpret IPDs of C2+ and C3+ by using a statistical approach based on the counting of final states allowed by energetic criteria. The model is able to furnish the right order of magnitude for the experimental IPD rates and to provide a qualitative explanation of the lower IPD rate observed in C2+.

  12. Adsorption and Formation of Small Na Clusters on Pristine and Double-Vacancy Graphene for Anodes of Na-Ion Batteries.

    PubMed

    Liang, Zhicong; Fan, Xiaofeng; Zheng, Weitao; Singh, David J

    2017-05-24

    Layered carbon is a likely anode material for Na-ion batteries (NIBs). Graphitic carbon has a low capacity of approximately 35 (mA h)/g due to the formation of NaC64. Using first-principles methods including van der Waals interactions, we analyze the adsorption of Na ions and clusters on graphene in the context of anodes. The interaction between Na ions and graphene is found to be weak. Small Na clusters are not stable on the surface of pristine graphene in the electrochemical environment of NIBs. However, we find that Na ions and clusters can be stored effectively on defected graphene that has double vacancies. In addition, the adsorption energy of small Na clusters near a double vacancy is found to decrease with increasing cluster size. With high concentrations of vacancies the capacity of Na on defective graphene is found to be as much as 10-30 times higher than that of graphitic carbon.

  13. Variation of index of refraction in the ion-exchanged glasses with the evolution of ionic and neutral silver nano-clusters

    NASA Astrophysics Data System (ADS)

    Nahal, A.; Jalehdoost, A.; Hassani, Kh.; Farokhniaee, A.

    2011-01-01

    Using spectroscopic and small angle X-ray scattering analyses, temporal evolution of ionic and neutral silver clusters inside and on the surface of a glass matrix has been studied during the ion-exchange process. It is found that in the beginning of the ion-exchange process the ionic clusters (AgN+; where N is the number of atoms of the ionic silver cluster) form and start to grow. But, with continuation of the process the generated ionic silver clusters begin fragmentation and resizing which, in turn, results in modification of the interaction with the glass matrix. Our results show that, longer ion-exchange processing time results in re-growing of the ionic silver clusters. Simultaneously, the index of refraction of the ion-exchanged glass first increases, then decreases and increases again. Our findings imply that, there is no simple linear relation between the index of refraction and the ion-exchange duration time. Some of the ionic clusters may transform to neutral ones by absorbing electrons available in the glass matrix. X-ray and AFM analyses confirm that, at the same time, some neutral silver nanoparticles form on the surface of the samples, and their evolution follows the evolution of the forming ionic clusters. Resizing, movement toward the surface and aggregation of the clusters, are the most important consequences of the interaction of the forming clusters with the glass matrix observed in this study.

  14. Doubly charged trimeric cluster ions: effective in mutual chiral recognition of tadalafil and three proton pump inhibitors.

    PubMed

    Wang, Lu; Chai, Yunfeng; Zhu, Wenquan; Pan, Yuanjiang; Sun, Cuirong; Zeng, Su

    2017-02-27

    Mutual chiral recognition of four stereoisomers of tadalafil and three pairs of enantiomers of proton pump inhibitors (PPIs) including pantoprazole, lansoprazole, and omeprazole, as well as quantitative analysis of enantiomeric excess is achieved on the basis of the competitive fragmentation of doubly charged trimeric Ni(II) cluster ions. Compared with a singly charged trimeric cluster ion, a doubly charged trimeric cluster ion was proved efficient in the recognition of chiral drugs with one or multiple chiral centers, due to its rich fragmentation ions. Upon collision-induced dissociation (CID), the cluster ion [Ni(II)(PPIs)(tadalafil)2](2+) yielded two diagnostic ions [tadalafil + H](+) and [tadalafil - benzo[d][1,3]dixoloe](+) through electrospray ionization quadrupole time-of-flight mass spectrometry. The abundance ratio of the two fragment ions relied mainly on the configuration of PPIs and tadalafil, and therefore the chiral selectivity (Rchiral) of one enantiomer relative to the others is different. The chiral recognition of all four stereoisomers of tadalafil was achieved by using S configuration PPIs as references, and S-omeprazole showed the best selectivity. The Rchiral values for R,R/S,S, R,S/S,R, R,R/R,S and R,R/S,R-tadalafils were 1.47, 1.17, 2.37, and 2.10, respectively. In a reciprocal process, the Rchiral was 1.36 and 1.31 for R/S-pantoprazole and R/S-lansoprazole, respectively, by using R,R-tadalafil as a reference. Although omeprazole is a racemic drug, it can also be discriminated with S-omeprazole. Calibration curves were constructed with favorable correlation coefficients (r(2) > 0.991) by relating the ln(Rchiral) values to the isomeric composition in a mixture. The sensitivity of the methodology allows mixtures to be analyzed for the enantiomeric excess (ee) by recording the ratios of fragment ion abundances in a mass spectrum. The sensitivity of the methodology allowed the determination of enantiomeric impurities of 5% molar composition in

  15. The nature and evolution of excess electron binding in cluster anions studied via negative ion photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Hendricks, Jay H.

    1997-07-01

    The technique of negative ion photoelectron spectroscopy (NIPES) has been used to study a variety of cluster anion systems with the aim of elucidating the nature and evolution of excess electron binding in clusters. The systems studied include molecular and cluster dipole- bound anions, conventional valence molecular anions, ion- molecule cluster anions, solvated electron cluster anions, metal cluster anions, metal oxide anions, and metal hydride anions. The generation and characterization of nanophase Lunsford catalyst, and the study of gas- phase anionic polymerization reactions were also conducted. The studies of dipole-bound anions, (Uracil)/sp-, (Uracil...Xe)/sp-, (Thymine)/sp-, (1- Methylcytosine)/sp-, (HF)2-, (H2O)2-, (EG)2-, where EG = Ethylene Glycol, (CH3CN[/cdots]H2O)/sp-,/ (HCl[/cdots] H2O)/sp-,/ (HCN[/cdots]H2O)/sp-, and (H2S)4- provide some of the best experimental evidence to date confirming the long standing predictions of theory that an excess electron can be bound to a dipole field if the dipole moment of the neutral molecule or cluster exceeds a critical minimum value. The photodetachment of the conventional valence anions /[(2,4,6-tricyanobenzene)/sp-, (CAN3-3HCl)/sp-, where CAN = 2- choloracrylonitrile, (CH3NO2)/sp-/], metal cluster anions /[Lin=1-7-/], metal oxide anions /[NaO/sp-,/ KO/sp-,/ RbO/sp-, and CsO/sp-/] and metal hydride anions /[LiH/sp-,/ LiD/sp-/] enabled the first time determinations of vertical detachment energies, and adiabatic election affinities. The studies of ion-molecule cluster anions /[O/sp- (Ar)n=1-26,34,/ NO/sp-(Ar)n=1-14,/ O/sp- (Kr)n=1-4,/ O/sp-(Xe)n=1-4,/ O/sp-(N2),/ NO/sp-(Kr),/ NO/sp-(Xe)n=1-3,/ NO/sp- (N2O)n=1-5, and NO/sp-(EG),/ (Uracil[/cdots]H2O)/sp-,/ (Uracil[/cdots]Xe)/sp-/] permitted the energetics and structure of microscopic ion solvation to be examined as a function of cluster size and cluster solvent. The photodetachment of solvated the electron clusters anions /[(H2O)n-,/ [(H2O)x[/cdots](NH3)y

  16. Structure and hydration of the C4H4•+ ion formed by electron impact ionization of acetylene clusters

    NASA Astrophysics Data System (ADS)

    Momoh, Paul O.; Hamid, Ahmed M.; Abrash, Samuel A.; Samy El-Shall, M.

    2011-05-01

    Here we report ion mobility experiments and theoretical studies aimed at elucidating the identity of the acetylene dimer cation and its hydrated structures. The mobility measurement indicates the presence of more than one isomer for the C4H4•+ ion in the cluster beam. The measured average collision cross section of the C4H4•+ isomers in helium (38.9 ± 1 Å2) is consistent with the calculated cross sections of the four most stable covalent structures calculated for the C4H4•+ ion [methylenecyclopropene (39.9 Å2), 1,2,3-butatriene (41.1 Å2), cyclobutadiene (38.6 Å2), and vinyl acetylene (41.1 Å2)]. However, none of the single isomers is able to reproduce the experimental arrival time distribution of the C4H4•+ ion. Combinations of cyclobutadiene and vinyl acetylene isomers show excellent agreement with the experimental mobility profile and the measured collision cross section. The fragment ions obtained by the dissociation of the C4H4•+ ion are consistent with the cyclobutadiene structure in agreement with the vibrational predissociation spectrum of the acetylene dimer cation (C2H2)2•+ [R. A. Relph, J. C. Bopp, J. R. Roscioli, and M. A. Johnson, J. Chem. Phys. 131, 114305 (2009)], 10.1063/1.3212595. The stepwise hydration experiments show that dissociative proton transfer reactions occur within the C4H4•+(H2O)n clusters with n ≥ 3 resulting in the formation of protonated water clusters. The measured binding energy of the C4H4•+H2O cluster, 38.7 ± 4 kJ/mol, is in excellent agreement with the G3(MP2) calculated binding energy of cyclobutadiene•+.H2O cluster (41 kJ/mol). The binding energies of the C4H4•+(H2O)n clusters change little from n = 1 to 5 (39-48 kJ/mol) suggesting the presence of multiple binding sites with comparable energies for the water-C4H4•+ and water-water interactions. A significant entropy loss is measured for the addition of the fifth water molecule suggesting a structure with restrained water molecules, probably a

  17. Structure and hydration of the C4H4●+ ion formed by electron impact ionization of acetylene clusters.

    PubMed

    Momoh, Paul O; Hamid, Ahmed M; Abrash, Samuel A; El-Shall, M Samy

    2011-05-28

    Here we report ion mobility experiments and theoretical studies aimed at elucidating the identity of the acetylene dimer cation and its hydrated structures. The mobility measurement indicates the presence of more than one isomer for the C(4)H(4)(●+) ion in the cluster beam. The measured average collision cross section of the C(4)H(4)(●+) isomers in helium (38.9 ± 1 Å(2)) is consistent with the calculated cross sections of the four most stable covalent structures calculated for the C(4)H(4)(●+) ion [methylenecyclopropene (39.9 Å(2)), 1,2,3-butatriene (41.1 Å(2)), cyclobutadiene (38.6 Å(2)), and vinyl acetylene (41.1 Å(2))]. However, none of the single isomers is able to reproduce the experimental arrival time distribution of the C(4)H(4)(●+) ion. Combinations of cyclobutadiene and vinyl acetylene isomers show excellent agreement with the experimental mobility profile and the measured collision cross section. The fragment ions obtained by the dissociation of the C(4)H(4)(●+) ion are consistent with the cyclobutadiene structure in agreement with the vibrational predissociation spectrum of the acetylene dimer cation (C(2)H(2))(2)(●+) [R. A. Relph, J. C. Bopp, J. R. Roscioli, and M. A. Johnson, J. Chem. Phys. 131, 114305 (2009)]. The stepwise hydration experiments show that dissociative proton transfer reactions occur within the C(4)H(4)(●+)(H(2)O)(n) clusters with n ≥ 3 resulting in the formation of protonated water clusters. The measured binding energy of the C(4)H(4)(●+)H(2)O cluster, 38.7 ± 4 kJ/mol, is in excellent agreement with the G3(MP2) calculated binding energy of cyclobutadiene(●+)·H(2)O cluster (41 kJ/mol). The binding energies of the C(4)H(4)(●+)(H(2)O)(n) clusters change little from n = 1 to 5 (39-48 kJ/mol) suggesting the presence of multiple binding sites with comparable energies for the water-C(4)H(4)(●+) and water-water interactions. A significant entropy loss is measured for the addition of the fifth water

  18. Atomic-Level Design of Water-Resistant Hybrid Perovskites for Solar Cells by Using Cluster Ions.

    PubMed

    Fang, Hong; Jena, Puru

    2017-08-17

    Organic-inorganic hybrid perovskites have emerged as the most promising material in the development of next-generation solar cells. However, the stability of these materials exemplified by CH3NH3PbI3 is the most pressing challenge; it readily decomposes when exposed to moisture. Here, we show how one can use a particular type of cluster ions, known as pseudohalides, to enhance the water resistance of the hybrid perovskite, while maintaining its favorable electronic properties. Starting with a simple physical model, we propose a new class of water-resistant hybrid perovskites as solar-cell absorbers based on the cluster ions by using DFT calculations and ab initio molecular dynamics. Limitations of applying the currently known pseudohalides for our purpose are also discussed.

  19. NEXAFS study on the local structures of DLC thin films formed by Ar cluster ion beam assisted deposition

    NASA Astrophysics Data System (ADS)

    Kanda, Kazuhiro; Kitagawa, Teruyuki; Shimizugawa, Yutaka; Tsubakino, Harushige; Yamada, Isao; Matsui, Shinji

    2003-08-01

    Near-edge X-ray absorption fine structure (NEXAFS) spectra were measured for the optimization of synthesis conditions on the production of diamond-like carbon (DLC) thin films by the Ar gas cluster ion beam (GCIB) assisted deposition of fullerene. The sp2 contents of DLC films were estimated from the analysis of the peak corresponding to the transition of the excitation electron from a carbon 1s orbital to a π* orbital in the NEXAFS spectrum of the carbon K-edge over the excitation energy range 275-320 eV. Substrate temperature and Ar cluster ion acceleration voltage in the synthesis conditions of DLC films were optimized to make the sp2 content minimum.

  20. Long-term observations of positive cluster ion concentration, sources and sinks at the high altitude site of the Puy de Dôme

    NASA Astrophysics Data System (ADS)

    Rose, C.; Boulon, J.; Hervo, M.; Holmgren, H.; Asmi, E.; Ramonet, M.; Laj, P.; Sellegri, K.

    2013-06-01

    Cluster particles (0.8-1.9 nm) are key entities involved in nucleation and new particle formation processes in the atmosphere. Cluster ions were characterized in clear sky conditions at the Puy de Dôme station (1465 m a.s.l). The studied dataset spread over five years (February 2007-February 2012), which provided a unique chance to catch seasonal variations of cluster ion properties at high altitude. Statistical values of the cluster ion concentration and diameter are reported for both positive and negative polarities. Cluster ions were found to be ubiquitous at the Puy de Dôme and displayed an annual variation with lower concentrations in spring. Positive cluster ions were less numerous than negative ones but were larger in diameters. Negative cluster ion properties seemed insensitive to the occurrence of a new particle formation (NPF) event while positive cluster ions appeared to be significantly more numerous and larger on event days. The parameters of the balance equation for the positive cluster concentration are reported, separately for the different seasons and for the NPF event days and non-event days. The steady state assumption suggests that the ionization rate is balanced with two sinks which are the ion recombination and the attachment on aerosol particles, referred as "aerosol ion sink". The aerosol ion sink was found to be higher during the warm season and dominated the loss of ions. The positive ionization rates derived from the balance equation were well correlated with the ionization rates obtained from radon measurement, and they were on average higher in summer and fall compared to winter and spring. Neither the aerosol ion sink nor the ionization rate were found to be significantly different on event days compared to non-event days, and thus they were not able to explain the different positive cluster concentrations between event and non-event days. Hence, the excess of positive small ions on event days may derive from an additional source of

  1. The effect of acid-base clustering and ions on the growth of atmospheric nano-particles

    NASA Astrophysics Data System (ADS)

    Lehtipalo, Katrianne; Rondo, Linda; Kontkanen, Jenni; Schobesberger, Siegfried; Jokinen, Tuija; Sarnela, Nina; Kürten, Andreas; Ehrhart, Sebastian; Franchin, Alessandro; Nieminen, Tuomo; Riccobono, Francesco; Sipilä, Mikko; Yli-Juuti, Taina; Duplissy, Jonathan; Adamov, Alexey; Ahlm, Lars; Almeida, João; Amorim, Antonio; Bianchi, Federico; Breitenlechner, Martin; Dommen, Josef; Downard, Andrew J.; Dunne, Eimear M.; Flagan, Richard C.; Guida, Roberto; Hakala, Jani; Hansel, Armin; Jud, Werner; Kangasluoma, Juha; Kerminen, Veli-Matti; Keskinen, Helmi; Kim, Jaeseok; Kirkby, Jasper; Kupc, Agnieszka; Kupiainen-Määttä, Oona; Laaksonen, Ari; Lawler, Michael J.; Leiminger, Markus; Mathot, Serge; Olenius, Tinja; Ortega, Ismael K.; Onnela, Antti; Petäjä, Tuukka; Praplan, Arnaud; Rissanen, Matti P.; Ruuskanen, Taina; Santos, Filipe D.; Schallhart, Simon; Schnitzhofer, Ralf; Simon, Mario; Smith, James N.; Tröstl, Jasmin; Tsagkogeorgas, Georgios; Tomé, António; Vaattovaara, Petri; Vehkamäki, Hanna; Vrtala, Aron E.; Wagner, Paul E.; Williamson, Christina; Wimmer, Daniela; Winkler, Paul M.; Virtanen, Annele; Donahue, Neil M.; Carslaw, Kenneth S.; Baltensperger, Urs; Riipinen, Ilona; Curtius, Joachim; Worsnop, Douglas R.; Kulmala, Markku

    2016-05-01

    The growth of freshly formed aerosol particles can be the bottleneck in their survival to cloud condensation nuclei. It is therefore crucial to understand how particles grow in the atmosphere. Insufficient experimental data has impeded a profound understanding of nano-particle growth under atmospheric conditions. Here we study nano-particle growth in the CLOUD (Cosmics Leaving OUtdoors Droplets) chamber, starting from the formation of molecular clusters. We present measured growth rates at sub-3 nm sizes with different atmospherically relevant concentrations of sulphuric acid, water, ammonia and dimethylamine. We find that atmospheric ions and small acid-base clusters, which are not generally accounted for in the measurement of sulphuric acid vapour, can participate in the growth process, leading to enhanced growth rates. The availability of compounds capable of stabilizing sulphuric acid clusters governs the magnitude of these effects and thus the exact growth mechanism. We bring these observations into a coherent framework and discuss their significance in the atmosphere.

  2. Negative ion photoelectron spectroscopy of 2,2'-bithiophene cluster anions, (2T)n- (n = 1 100)

    NASA Astrophysics Data System (ADS)

    Mitsui, M.; Matsumoto, Y.; Ando, N.; Nakajima, A.

    2005-07-01

    Cluster anions of 2,2'-bithiophene, (2T){n}-, were produced up to n ˜ 500 in the gas-phase. The energetics of the excess electron in the (2T){n}- clusters with n =1{-}100 were explored by negative ion photoelectron spectroscopy. When the vertical detachment energies (VDEs) obtained from the photoelectron spectra were analyzed by a plot against n-1/3, it has been revealed that the excess electron trapping level thus extrapolated is located at ˜ 0.8 eV below the conduction band minimum (i.e. LUMO) of the 2T thin film. The large slope of the VDEs vs. n-1/3 plot suggests that the neutral 2T molecules surrounding the anion core take non-planar twisted conformations with permanent dipole moments, resulting in the exceedingly deep trapping of the excess electron in the 2T cluster anions.

  3. Monte Carlo simulation of energy-deposit clustering for ions of the same LET in liquid water.

    PubMed

    Francis, Z; Incerti, S; Ivanchenko, V; Champion, C; Karamitros, M; Bernal, M A; El Bitar, Z

    2012-01-07

    This work presents a Monte Carlo study of energy depositions due to protons, alpha particles and carbon ions of the same linear-energy-transfer (LET) in liquid water. The corresponding track structures were generated using the Geant4-DNA toolkit, and the energy deposition spatial distributions were analyzed using an adapted version of the DBSCAN clustering algorithm. Combining the Geant4 simulations and the clustering algorithm it was possible to compare the quality of the different radiation types. The ratios of clustered and single energy depositions are shown versus particle LET and frequency-mean lineal energies. The estimated effect of these types of radiation on biological tissues is then discussed by comparing the results obtained for different particles with the same LET.

  4. The influence of silver ion exchange on the formation and luminescent properties of lead sulfide molecular clusters and quantum dots

    NASA Astrophysics Data System (ADS)

    Abdrshin, A. N.; Lipatova, Zh. O.; Kolobkova, E. V.; Sgibnev, E. M.; Nikonorov, N. V.

    2016-12-01

    PbS molecular clusters and quantum dots are formed by heat treatment in fluorophosphate glasses of the Na2O3-P2O5-Ga2O3-AlF3-ZnO(S)-PbF2 system with different lead concentrations. PbS molecular clusters are characterized by optical absorption in the range of 300-800 nm and low quantum yields, which decrease from 8.9 to 2.7% with a semiconductor component concentration. It is shown that the parameters of formation of quantum dots luminescing in the wavelength range of 1000-1500 nm are considerably different at different semiconductor component concentrations. The influence of silver ion exchange on the formation of PbS nanoparticles is studied. Introduction of silver stimulates the growth of molecular clusters, which is seen in the absorption spectra. A possible mechanism of interaction of silver nanoparticles with PbS quantum dots is presented.

  5. The effect of acid–base clustering and ions on the growth of atmospheric nano-particles

    SciTech Connect

    Lehtipalo, Katrianne; Rondo, Linda; Kontkanen, Jenni; Schobesberger, Siegfried; Jokinen, Tuija; Sarnela, Nina; Kürten, Andreas; Ehrhart, Sebastian; Franchin, Alessandro; Nieminen, Tuomo; Riccobono, Francesco; Sipilä, Mikko; Yli-Juuti, Taina; Duplissy, Jonathan; Adamov, Alexey; Ahlm, Lars; Almeida, Joao; Amorim, Antonio; Bianchi, Federico; Breitenlechner, Martin; Dommen, Josef; Downard, Andrew J.; Dunne, Eimear M.; Flagan, Richard C.; Guida, Roberto; Hakala, Jani; Hansel, Armin; Jud, Werner; Kangasluoma, Juha; Kerminen, Veli-Matti; Keskinen, Helmi; Kim, Jaeseok; Kirkby, Jasper; Kupc, Agnieszka; Kupiainen-Maatta, Oona; Laaksonen, Ari; Lawler, Michael J.; Leiminger, Markus; Mathot, Serge; Olenius, Tinja; Ortega, Ismael K.; Onnela, Antti; Petaja, Tuukka; Praplan, Arnaud; Rissanen, Matti P.; Ruuskanen, Taina; Santos, Filipe D.; Schallhart, Simon; Schnitzhofer, Ralf; Simon, Mario; Smith, James N.; Trostl, Jasmin; Tsagkogeorgas, Georgios; Tomé, António; Vaattovaara, Petri; Vehkamaki, Hanna; Vrtala, Aron E.; Wagner, Paul E.; Williamson, Christina; Wimmer, Daniela; Winkler, Paul M.; Virtanen, Annele; Donahue, Neil M.; Carslaw, Kenneth S.; Baltensperger, Urs; Riipinen, Ilona; Curtius, Joachim; Worsnop, Douglas R.; Kulmala, Markku

    2016-05-20

    The growth of freshly formed aerosol particles can be the bottleneck in their survival to cloud condensation nuclei. It is therefore crucial to understand how particles grow in the atmosphere. Insufficient experimental data has impeded a profound understanding of nano-particle growth under atmospheric conditions. Here we study nano-particle growth in the CLOUD (Cosmics Leaving OUtdoors Droplets) chamber, starting from the formation of molecular clusters. We present measured growth rates at sub-3 nm sizes with different atmospherically relevant concentrations of sulphuric acid, water, ammonia and dimethylamine. We find that atmospheric ions and small acid-base clusters, which are not generally accounted for in the measurement of sulphuric acid vapour, can participate in the growth process, leading to enhanced growth rates. The availability of compounds capable of stabilizing sulphuric acid clusters governs the magnitude of these effects and thus the exact growth mechanism. Furthermore, we bring these observations into a coherent framework and discuss their significance in the atmosphere.

  6. Properties of microsolvated ions: from the microenvironment of chromophore and alkali metal ions in proteins to negative ions in water clusters.

    PubMed

    Nielsen, Steen Brøndsted; Andersen, Lars H

    2006-12-01

    Here we discuss the fascinating chemistry and physics of microsolvated ions that bridge the transition from bare ions in gas phase to ions in solution. Such ions occur in many situations in biochemistry and are crucial for several functions; metal ions, for example, must remove their water shell to pass through ion pumps in membranes. Furthermore, only a few water molecules are buried in the hydrophobic pockets of proteins where they are bound to charged amino acid residues or ionic chromophores. Another aspect is the reactivity of microsolvated ions and the importance in atmospheric, organic and inorganic chemistry. We close by a discussion of the stability of molecular dianions, and how hydration affects the electronic binding energy. There is a vast literature on microsolvated ions, and in this review we are far from being comprehensive, rather we mainly bring examples of our own work.

  7. Imaging with mass spectrometry: a secondary ion and VUV-photoionization study of ion-sputtered atoms and clusters from GaAs and Au.

    PubMed

    Takahashi, Lynelle K; Zhou, Jia; Wilson, Kevin R; Leone, Stephen R; Ahmed, Musahid

    2009-04-23

    A new mass spectrometry surface imaging method is presented in which ion-sputtered neutrals are postionized by wavelength-tunable vacuum ultraviolet (VUV) light from a synchrotron source. Mass spectra and signal counts of the photoionized neutrals from GaAs (100) and Au are compared to those of the secondary ions. While clusters larger than dimers are more efficiently detected as secondary ions, certain species, such as As(2), Au, and Au(2), are more efficiently detected through the neutral channel. Continuously tuning the photon wavelength allows photoionization efficiency (PIE) curves to be obtained for sputtered As(m) (m = 1,2) and Au(n) (n = 1-4). From the observed ionization thresholds, sputtered neutral As and Au show no clear evidence of electronic excitation, while neutral clusters have photoionization onsets shifted to lower energies by approximately 0.3 eV. These shifts are attributed to unresolved vibrational and rotational excitations. High-spatial resolution chemical imaging with synchrotron VUV postionization is demonstrated at two different photon energies using a copper TEM grid embedded in indium. The resulting images are used to illustrate the use of tunable VUV light for verifying mass peak assignments by exploiting the unique wavelength-dependent PIE of each sputtered neutral species. This capability is valuable for identifying compounds when imaging chemically complex systems with mass spectrometry-based techniques.

  8. Reactivity Control of Rhodium Cluster Ions by Alloying with Tantalum Atoms.

    PubMed

    Mafuné, Fumitaka; Tawaraya, Yuki; Kudoh, Satoshi

    2016-02-18

    Gas phase, bielement rhodium and tantalum clusters, RhnTam(+) (n + m = 6), were prepared by the double laser ablation of Rh and Ta rods in He carrier gas. The clusters were introduced into a reaction gas cell filled with nitric oxide (NO) diluted with He and were subjected to collisions with NO and He at room temperature. The product species were observed by mass spectrometry, demonstrating that the NO molecules were sequentially adsorbed on the RhnTam(+) clusters to form RhnTam(+)NxOx (x = 1, 2, 3, ...) species. In addition, oxide clusters, RhnTam(+)O2, were also observed, suggesting that the NO molecules were dissociatively adsorbed on the cluster, the N atoms migrated on the surface to form N2, and the N2 molecules were released from RhnTam(+)N2O2. The reactivity, leading to oxide formation, was composition dependent: oxide clusters were dominantly formed for the bielement clusters containing both Rh and Ta atoms, whereas such clusters were hardly formed for the single-element Rhn(+) and Tam(+) clusters. DFT calculations indicated that the Ta atoms induce dissociation of NO on the clusters by lowering the dissociation energy, whereas the Rh atoms enable release of N2 by lowering the binding energy of the N atoms on the clusters.

  9. Vibrational and unimolecular dissociation of mixed solvent cluster ions: Na +((CH 3) 2CO) n(CH 3OH) m

    NASA Astrophysics Data System (ADS)

    Weinheimer, Corey J.; Lisy, James M.

    1998-12-01

    The competitive solvation of the sodium ion by acetone and methanol has been investigated by vibrational spectroscopy of the C-O and O-H stretching modes of methanol and by unimolecular dissociation of mass-selected cluster ions using a tandem mass spectrometer. The onset of hydrogen bonding was detected by substantial shifts in the C-O (+12 to +16 cm -1) and O-H (-200 cm -1) stretches, as well as by significant increases in the intensity and width of the O-H bands. These onsets were observed when a total of five molecules were present about the ion. The unimolecular dissociation rates of metastable ion clusters of composition Na +((CH 3) 2CO) 1-9 and Na +((CH 3) 2CO) 1-8(CH 3OH) 1 were also measured using the same experimental apparatus. A significant increase in rate was observed when seven or more acetone molecules were present, suggesting a solvent shell size of six.

  10. Stable compositions and geometrical structures of titanium oxide cluster cations and anions studied by ion mobility mass spectrometry

    NASA Astrophysics Data System (ADS)

    Ohshimo, Keijiro; Norimasa, Naoya; Moriyama, Ryoichi; Misaizu, Fuminori

    2016-05-01

    Geometrical structures of titanium oxide cluster cations and anions have been investigated by ion mobility mass spectrometry and quantum chemical calculations based on density functional theory. Stable cluster compositions with respect to collision induced dissociation were also determined by changing ion injection energy to an ion drift cell for mobility measurements. The TinO2n-1+ cations and TinO2n- anions were predominantly observed at high injection energies, in addition to TinO2n+ for cations and TinO2n+1- for anions. Collision cross sections of TinO2n+ and TinO2n+1- for n = 1-7, determined by ion mobility mass spectrometry, were compared with those obtained theoretically as orientation-averaged cross sections for the optimized structures by quantum chemical calculations. All of the geometrical structures thus assigned have three-dimensional structures, which are in marked contrast with other oxides of late transition metals. One-oxygen atom dissociation processes from TinO2n+ and TinO2n+1- by collisions were also explained by analysis of spin density distributions.

  11. Stable compositions and geometrical structures of titanium oxide cluster cations and anions studied by ion mobility mass spectrometry.

    PubMed

    Ohshimo, Keijiro; Norimasa, Naoya; Moriyama, Ryoichi; Misaizu, Fuminori

    2016-05-21

    Geometrical structures of titanium oxide cluster cations and anions have been investigated by ion mobility mass spectrometry and quantum chemical calculations based on density functional theory. Stable cluster compositions with respect to collision induced dissociation were also determined by changing ion injection energy to an ion drift cell for mobility measurements. The TinO2n-1 (+) cations and TinO2n (-) anions were predominantly observed at high injection energies, in addition to TinO2n (+) for cations and TinO2n+1 (-) for anions. Collision cross sections of TinO2n (+) and TinO2n+1 (-) for n = 1-7, determined by ion mobility mass spectrometry, were compared with those obtained theoretically as orientation-averaged cross sections for the optimized structures by quantum chemical calculations. All of the geometrical structures thus assigned have three-dimensional structures, which are in marked contrast with other oxides of late transition metals. One-oxygen atom dissociation processes from TinO2n (+) and TinO2n+1 (-) by collisions were also explained by analysis of spin density distributions.

  12. Improved mass resolution and mass accuracy in TOF-SIMS spectra and images using argon gas cluster ion beams.

    PubMed

    Shon, Hyun Kyong; Yoon, Sohee; Moon, Jeong Hee; Lee, Tae Geol

    2016-06-09

    The popularity of argon gas cluster ion beams (Ar-GCIB) as primary ion beams in time-of-flight secondary ion mass spectrometry (TOF-SIMS) has increased because the molecular ions of large organic- and biomolecules can be detected with less damage to the sample surfaces. However, Ar-GCIB is limited by poor mass resolution as well as poor mass accuracy. The inferior quality of the mass resolution in a TOF-SIMS spectrum obtained by using Ar-GCIB compared to the one obtained by a bismuth liquid metal cluster ion beam and others makes it difficult to identify unknown peaks because of the mass interference from the neighboring peaks. However, in this study, the authors demonstrate improved mass resolution in TOF-SIMS using Ar-GCIB through the delayed extraction of secondary ions, a method typically used in TOF mass spectrometry to increase mass resolution. As for poor mass accuracy, although mass calibration using internal peaks with low mass such as hydrogen and carbon is a common approach in TOF-SIMS, it is unsuited to the present study because of the disappearance of the low-mass peaks in the delayed extraction mode. To resolve this issue, external mass calibration, another regularly used method in TOF-MS, was adapted to enhance mass accuracy in the spectrum and image generated by TOF-SIMS using Ar-GCIB in the delayed extraction mode. By producing spectra analyses of a peptide mixture and bovine serum albumin protein digested with trypsin, along with image analyses of rat brain samples, the authors demonstrate for the first time the enhancement of mass resolution and mass accuracy for the purpose of analyzing large biomolecules in TOF-SIMS using Ar-GCIB through the use of delayed extraction and external mass calibration.

  13. Hybrid global model of water cluster ions in atmospheric pressure Ar/ H2O RF capacitive discharges

    NASA Astrophysics Data System (ADS)

    Tavant, A.; Lieberman, M. A.

    2016-11-01

    Water is a trace gas of strong interest for plasma-based medical applications. We use a hybrid global model to simulate a chemically complex Ar/{{\\text{H}}2}\\text{O} atmospheric pressure, radio frequency capacitive discharge, including 47 species with positive ion clusters up to {{\\text{H}}21}\\text{O}10+ . For a discharge gap of 1.5 mm driven at 27.12 MHz, we determine the discharge properties over a range of rf currents (150-500 A m-2) and initial {{\\text{H}}2}\\text{O} concentrations (0.25-2%). An isothermal plug-flow model is used with a gas residence time of 0.2 s for most calculations, with the gas temperature calculated self-consistently from the input power. The cluster density distributions are determined, and we find that the higher mass cluster densities decrease rapidly with increasing gas temperature. A simplified cluster dynamics analytic model is developed and solved to determine the cluster density distributions, which is in good agreement with the hybrid simulation results.

  14. Examining the Critical Roles of Protons in Facilitating Oxidation of Chloride Ions by Permanganates: A Cluster Model Study

    SciTech Connect

    Zhang, Jian; Sun, Zhenrong; Wang, Xue B.

    2015-06-18

    The oxidation power of permanganates (MnO4–) is known to be strongly dependent on pH values, and is greatly enhanced in acidic solutions, in which, for example, MnO4– can even oxidize Cl– ions to produce Cl2 molecules. Although such dependence has been ascribed due to the different reduced states of Mn affordable in different pH media, a molecular level understanding and characterization of initial redox pair complexes available in different pH solutions is very limited. Herein, we report a comparative study of [MnO4]– and [MnO4•Sol]– (Sol = H2O, KCl, and HCl) anion clusters by negative ion photoelectron spectroscopy (NIPES) and theoretical computations to probe chemical bonding and electronic structures of [MnO4•Sol]– clusters, aimed to obtain a microscopic understanding of how MnO4– interacts with surrounding molecules. Our study shows that H2O behaves as a solvent molecule, KCl is a spectator bound by pure electrostatic interactions, both of which do not influence the MnO4– identity in their respective clusters. In contrast, in [MnO4•HCl]–, the proton is found to interact with both MnO4– and Cl– with appreciable covalent characters, and the frontier MOs of the cluster are comprised of contributions from both MnO4– and Cl– moieties. Therefore the proton serves as a chemical bridge, bringing two negatively charged redox species together to form an intimate redox pair. By adding more H+ to MnO4–, the oxygen atom can be taken away in the form of a water molecule, leaving MnO4– as an electron deficient MnO3+ species, which can subsequently oxidize Cl– ions.

  15. Mega-Amp Opening Switch with Nested Electrodes/Pulsed Generator of Ion and Ion Cluster Beams

    DTIC Science & Technology

    1987-07-30

    Advanced Plasma Focus as Neutron Source for Neutron Raigrpy conrb thEi i e-ar Resonance Radiogrphy~ or sop" une(Lynn edit., LANSCE, Los Alamos N. Lab). 8. V...C. Powell: Repetitive Mode of Operation of a Plasma Focus as MA-Openin Switch, prepalreTTor uIcat3Ion.-- 3 VI List of Completed Experiments and...of ejected ions ,f.b lam \\\\1-fom nutron t-o-f.Sl Fig. 2) via .. =4 -fillts & airsdayl Ct .ST.1121.3 lei’. ’ttt &FailtamacaSIT.,R4f.S Y,,. = nir a(E

  16. Sampling Depths, Depth Shifts, and Depth Resolutions for Bi(n)(+) Ion Analysis in Argon Gas Cluster Depth Profiles.

    PubMed

    Havelund, R; Seah, M P; Gilmore, I S

    2016-03-10

    Gas cluster sputter depth profiling is increasingly used for the spatially resolved chemical analysis and imaging of organic materials. Here, a study is reported of the sampling depth in secondary ion mass spectrometry depth profiling. It is shown that effects of the sampling depth leads to apparent shifts in depth profiles of Irganox 3114 delta layers in Irganox 1010 sputtered, in the dual beam mode, using 5 keV Ar₂₀₀₀⁺ ions and analyzed with Bi(q+), Bi₃(q+) and Bi₅(q+) ions (q = 1 or 2) with energies between 13 and 50 keV. The profiles show sharp delta layers, broadened from their intrinsic 1 nm thickness to full widths at half-maxima (fwhm's) of 8-12 nm. For different secondary ions, the centroids of the measured delta layers are shifted deeper or shallower by up to 3 nm from the position measured for the large, 564.36 Da (C₃₃H₄₆N₃O₅⁻) characteristic ion for Irganox 3114 used to define a reference position. The shifts are linear with the Bi(n)(q+) beam energy and are greatest for Bi₃(q+), slightly less for Bi₅(q+) with its wider or less deep craters, and significantly less for Bi(q+) where the sputtering yield is very low and the primary ion penetrates more deeply. The shifts increase the fwhm’s of the delta layers in a manner consistent with a linearly falling generation and escape depth distribution function (GEDDF) for the emitted secondary ions, relevant for a paraboloid shaped crater. The total depth of this GEDDF is 3.7 times the delta layer shifts. The greatest effect is for the peaks with the greatest shifts, i.e. Bi₃(q+) at the highest energy, and for the smaller fragments. It is recommended that low energies be used for the analysis beam and that carefully selected, large, secondary ion fragments are used for measuring depth distributions, or that the analysis be made in the single beam mode using the sputtering Ar cluster ions also for analysis.

  17. Recoiled ions from polyatomic cluster impacts on organic and inorganic targets

    NASA Astrophysics Data System (ADS)

    Diehnelt, C. W.; Van Stipdonk, M. J.; Schweikert, E. A.

    1998-08-01

    We report the observation of a polyatomic cluster constituent, fluorine in this case, recoiling from the projectile upon impact with a surface. The clusters (NaF) nNa + ( n=1, 2, and 4), PF 6-, BF 4-, and SiF 5-, with incident kinetic energies of 12-28 keV, were impacted on Au, SiO 2, and α-cyano-4-hydroxycinnamic acid targets. The Au surface gave the highest F - yield when compared to the "light" SiO 2 surface, for the same incident cluster. This supports previous MD predications of polyatomic cluster constituents "splashing" upon impact with a surface.

  18. Cluster-continuum quasichemical theory calculation of the lithium ion solvation in water, acetonitrile and dimethyl sulfoxide: an absolute single-ion solvation free energy scale.

    PubMed

    Carvalho, Nathalia F; Pliego, Josefredo R

    2015-10-28

    Absolute single-ion solvation free energy is a very useful property for understanding solution phase chemistry. The real solvation free energy of an ion depends on its interaction with the solvent molecules and on the net potential inside the solute cavity. The tetraphenyl arsonium-tetraphenyl borate (TATB) assumption as well as the cluster-continuum quasichemical theory (CC-QCT) approach for Li(+) solvation allows access to a solvation scale excluding the net potential. We have determined this free energy scale investigating the solvation of the lithium ion in water (H2O), acetonitrile (CH3CN) and dimethyl sulfoxide (DMSO) solvents via the CC-QCT approach. Our calculations at the MP2 and MP4 levels with basis sets up to the QZVPP+diff quality, and including solvation of the clusters and solvent molecules by the dielectric continuum SMD method, predict the solvation free energy of Li(+) as -116.1, -120.6 and -123.6 kcal mol(-1) in H2O, CH3CN and DMSO solvents, respectively (1 mol L(-1) standard state). These values are compatible with the solvation free energy of the proton of -253.4, -253.2 and -261.1 kcal mol(-1) in H2O, CH3CN and DMSO solvents, respectively. Deviations from the experimental TATB scale are only 1.3 kcal mol(-1) in H2O and 1.8 kcal mol(-1) in DMSO solvents. However, in the case of CH3CN, the deviation reaches a value of 9.2 kcal mol(-1). The present study suggests that the experimental TATB scale is inconsistent for CH3CN. A total of 125 values of the solvation free energy of ions in these three solvents were obtained. These new data should be useful for the development of theoretical solvation models.

  19. Ab initio dynamics and photoionization mass spectrometry reveal ion-molecule pathways from ionized acetylene clusters to benzene cation

    DOE PAGES

    Stein, Tamar; Bandyopadhyay, Biswajit; Troy, Tyler P.; ...

    2017-05-08

    The growth mechanism of hydrocarbons in ionizing environments, such as the interstellar medium (ISM), and some combustion conditions remains incompletely understood. Ab initio molecular dynamics (AIMD) simulations and molecular beam vacuum-UV (VUV) photoionization mass spectrometry experiments were performed to understand the ion-molecule growth mechanism of small acetylene clusters (up to hexamers). A dramatic dependence of product distribution on the ionization conditions is demonstrated experimentally and understood from simulations. The products change from reactive fragmentation products in a higher temperature, higher density gas regime toward a very cold collision-free cluster regime that is dominated by products whose empirical formula is (C2H2)n+,more » just like ionized acetylene clusters. The fragmentation products result from reactive ion- molecule collisions in a comparatively higher pressure and temperature regime followed by unimolecular decomposition. The isolated ionized clusters display rich dynamics that contain bonded C4H4+ and C6H6+ structures solvated with one or more neutral acetylene molecules. Such species contain large amounts ( > 2 eV) of excess internal energy. The role of the solvent acetylene molecules is to affect the barrier crossing dynamics in the potential energy surface (PES) between (C2H2)n+ isomers and provide evaporative cooling to dissipate the excess internal energy and stabilize products including the aromatic ring of the benzene cation. Formation of the benzene cation is demonstrated in AIMD simulations of acetylene clusters with n > 3, as well as other metastable C6H6+ isomers. Lastly, these results suggest a path for aromatic ring formation in cold acetylene-rich environments such as parts of the ISM.« less

  20. Coverage Dependent Charge Reduction of Cationic Gold Clusters on Surfaces Prepared Using Soft Landing of Mass-selected Ions

    SciTech Connect

    Johnson, Grant E.; Priest, Thomas A.; Laskin, Julia

    2012-11-29

    The ionic charge state of monodisperse cationic gold clusters on surfaces may be controlled by selecting the coverage of mass-selected ions soft landed onto a substrate. Polydisperse diphosphine-capped gold clusters were synthesized in solution by reduction of chloro(triphenylphosphine)gold(I) with borane tert-butylamine in the presence of 1,3-bis(diphenylphosphino)propane. The polydisperse gold clusters were introduced into the gas phase by electrospray ionization and mass selection was employed to select a multiply charged cationic cluster species (Au11L53+, m/z = 1409, L = 1,3-bis(diphenylphosphino)propane) which was delivered to the surfaces of four different self-assembled monolayers on gold (SAMs) at coverages of 1011 and 1012 clusters/mm2. Employing the spatial profiling capabilities of in-situ time-of-flight secondary ion mass spectrometry (TOF-SIMS) it is shown that, in addition to the chemical functionality of the monolayer (as demonstrated previously: ACS Nano, 2012, 6, 573) the coverage of cationic gold clusters on the surface may be used to control the distribution of ionic charge states of the soft-landed multiply charged clusters. In the case of a 1H,1H,2H,2H-perfluorodecanethiol SAM (FSAM) almost complete retention of charge by the deposited Au11L53+ clusters was observed at a lower coverage of 1011 clusters/mm2. In contrast, at a higher coverage of 1012 clusters/mm2, pronounced reduction of charge to Au11L52+ and Au11L5+ was observed on the FSAM. When soft landed onto 16- and 11-mercaptohexadecanoic acid surfaces on gold (16,11-COOH-SAMs), the mass-selected Au11L53+ clusters exhibited partial reduction of charge to Au11L52+ at lower coverage and additional reduction of charge to both Au11L52+ and Au11L5+ at higher coverage. The reduction of charge was found to be more pronounced on the surface of the shorter (thinner) C11 than the longer (thicker) C16-COOH-SAM. On the surface of the 1-dodecanethiol (HSAM) monolayer, the most abundant charge state

  1. Trapping and diffusion kinetic of hydrogen in carbon-cluster ion-implantation projected range in Czochralski silicon wafers

    NASA Astrophysics Data System (ADS)

    Okuyama, Ryosuke; Masada, Ayumi; Kadono, Takeshi; Hirose, Ryo; Koga, Yoshihiro; Okuda, Hidehiko; Kurita, Kazunari

    2017-02-01

    We investigated the diffusion behavior of hydrogen in a silicon wafer made by a carbon-cluster ion-implantation technique after heat treatment and silicon epitaxial growth. A hydrogen peak was observed after high-temperature heat treatment (>1000 °C) and silicon epitaxial growth by secondary ion mass spectrometry analysis. We also confirmed that the hydrogen peak concentration decreased after epitaxial growth upon additional heat treatment. Such a hydrogen diffusion behavior has not been reported. Thus, we derived the activation energy from the projected range of a carbon cluster, assuming only a dissociation reaction, and obtained an activation energy of 0.76 ± 0.04 eV. This value is extremely close to that for the diffusion of hydrogen molecules located at the tetrahedral interstitial site and hydrogen molecules dissociated from multivacancies. Therefore, we assume that the hydrogen in the carbon-cluster projected range diffuses in the molecular state, and hydrogen remaining in the projected range forms complexes of carbon, oxygen, and vacancies.

  2. IR photodissociation spectroscopy of (OCS){sub n}{sup +} and (OCS){sub n}{sup −} cluster ions: Similarity and dissimilarity in the structure of CO{sub 2}, OCS, and CS{sub 2} cluster ions

    SciTech Connect

    Inokuchi, Yoshiya Ebata, Takayuki

    2015-06-07

    Infrared photodissociation (IRPD) spectra of (OCS){sub n}{sup +} and (OCS){sub n}{sup −} (n = 2–6) cluster ions are measured in the 1000–2300 cm{sup −1} region; these clusters show strong CO stretching vibrations in this region. For (OCS){sub 2}{sup +} and (OCS){sub 2}{sup −}, we utilize the messenger technique by attaching an Ar atom to measure their IR spectra. The IRPD spectrum of (OCS){sub 2}{sup +}Ar shows two bands at 2095 and 2120 cm{sup −1}. On the basis of quantum chemical calculations, these bands are assigned to a C{sub 2} isomer of (OCS){sub 2}{sup +}, in which an intermolecular semi-covalent bond is formed between the sulfur ends of the two OCS components by the charge resonance interaction, and the positive charge is delocalized over the dimer. The (OCS){sub n}{sup +} (n = 3–6) cluster ions show a few bands assignable to “solvent” OCS molecules in the 2000–2080 cm{sup −1} region, in addition to the bands due to the (OCS){sub 2}{sup +} ion core at ∼2090 and ∼2120 cm{sup −1}, suggesting that the dimer ion core is kept in (OCS){sub 3–6}{sup +}. For the (OCS){sub n}{sup −} cluster anions, the IRPD spectra indicate the coexistence of a few isomers with an OCS{sup −} or (OCS){sub 2}{sup −} anion core over the cluster range of n = 2–6. The (OCS){sub 2}{sup −}Ar anion displays two strong bands at 1674 and 1994 cm{sup −1}. These bands can be assigned to a C{sub s} isomer with an OCS{sup −} anion core. For the n = 2–4 anions, this OCS{sup −} anion core form is dominant. In addition to the bands of the OCS{sup −} core isomer, we found another band at ∼1740 cm{sup −1}, which can be assigned to isomers having an (OCS){sub 2}{sup −} ion core; this dimer core has C{sub 2} symmetry and {sup 2}A electronic state. The IRPD spectra of the n = 3–6 anions show two IR bands at ∼1660 and ∼2020 cm{sup −1}. The intensity of the latter component relative to that of the former one becomes stronger and stronger with

  3. Thermodynamics of small alkali metal halide cluster ions: comparison of classical molecular simulations with experiment and quantum chemistry.

    PubMed

    Vlcek, Lukas; Uhlik, Filip; Moucka, Filip; Nezbeda, Ivo; Chialvo, Ariel A

    2015-01-22

    We evaluate the ability of selected classical molecular models to describe the thermodynamic and structural aspects of gas-phase hydration of alkali metal halide ions and the formation of small water clusters. To understand the effect of many-body interactions (polarization) and charge penetration effects on the accuracy of a force field, we perform Monte Carlo simulations with three rigid water models using different functional forms to account for these effects: (i) point charge nonpolarizable SPC/E, (ii) Drude point charge polarizable SWM4-DP, and (iii) Drude Gaussian charge polarizable BK3. Model predictions are compared with experimental Gibbs free energies and enthalpies of ion hydration, and with microscopic structural properties obtained from quantum DFT calculations. We find that all three models provide comparable predictions for pure water clusters and cation hydration but differ significantly in their description of anion hydration. None of the investigated classical force fields can consistently and quantitatively reproduce the experimental gas-phase hydration thermodynamics. The outcome of this study highlights the relation between the functional form that describes the effective intermolecular interactions and the accuracy of the resulting ion hydration properties.

  4. Mass and energy distribution of negatively and positively charged small cluster ions sputtered from GaAs(100) by 150 keV Ar+ bombardment

    NASA Astrophysics Data System (ADS)

    Angelin, E. J.; Hippler, R.

    2017-09-01

    Mass and energy distribution of positively and negatively charged small GaxAsy cluster ions consisting of up to six atoms sputtered from a GaAs(100) surface after 150 keV Ar+ ion bombardment are reported. Positively charged ions contain a larger fraction of Ga atoms while negatively charged ions are rich in As. Measured energy distributions display a maximum at low kinetic energies of a few eV followed by a steep decrease with increasing energy which is more pronounced for larger ions.

  5. Electron-ion plasma dynamics in the presence of highly charged dust-clusters

    SciTech Connect

    Djebli, Mourad Benkhelifa, El-Amine

    2015-05-15

    Electron-ion plasma expansion is studied in the presence of positively (negatively) highly charged uniformly distributed dust particles, considered as impurities. For that purpose, a multi-fluid model is used, where the charged impurities characteristics are included in Poisson's equation. We found that ion acceleration is enhanced by the presence of positively charged dust. The latter leads to spiky structures in the ion front which have a higher amplitude as the charge increases. The charged impurities have a significant effect when the combination of their charge and density is greater than a critical value which depends on ion to electron temperature ratio.

  6. On the composition of ammonia-sulfuric-acid ion clusters during aerosol particle formation

    NASA Astrophysics Data System (ADS)

    Schobesberger, S.; Franchin, A.; Bianchi, F.; Rondo, L.; Duplissy, J.; Kürten, A.; Ortega, I. K.; Metzger, A.; Schnitzhofer, R.; Almeida, J.; Amorim, A.; Dommen, J.; Dunne, E. M.; Ehn, M.; Gagné, S.; Ickes, L.; Junninen, H.; Hansel, A.; Kerminen, V.-M.; Kirkby, J.; Kupc, A.; Laaksonen, A.; Lehtipalo, K.; Mathot, S.; Onnela, A.; Petäjä, T.; Riccobono, F.; Santos, F. D.; Sipilä, M.; Tomé, A.; Tsagkogeorgas, G.; Viisanen, Y.; Wagner, P. E.; Wimmer, D.; Curtius, J.; Donahue, N. M.; Baltensperger, U.; Kulmala, M.; Worsnop, D. R.

    2015-01-01

    The formation of particles from precursor vapors is an important source of atmospheric aerosol. Research at the Cosmics Leaving OUtdoor Droplets (CLOUD) facility at CERN tries to elucidate which vapors are responsible for this new-particle formation, and how in detail it proceeds. Initial measurement campaigns at the CLOUD stainless-steel aerosol chamber focused on investigating particle formation from ammonia (NH3) and sulfuric acid (H2SO4). Experiments were conducted in the presence of water, ozone and sulfur dioxide. Contaminant trace gases were suppressed at the technological limit. For this study, we mapped out the compositions of small NH3-H2SO4 clusters over a wide range of atmospherically relevant environmental conditions. We covered [NH3] in the range from < 2 to 1400 pptv, [H2SO4] from 3.3 × 106 to 1.4 × 109 cm-3 (0.1 to 56 pptv), and a temperature range from -25 to +20 °C. Negatively and positively charged clusters were directly measured by an atmospheric pressure interface time-of-flight (APi-TOF) mass spectrometer, as they initially formed from gas-phase NH3 and H2SO4, and then grew to larger clusters containing more than 50 molecules of NH3 and H2SO4, corresponding to mobility-equivalent diameters greater than 2 nm. Water molecules evaporate from these clusters during sampling and are not observed. We found that the composition of the NH3-H2SO4 clusters is primarily determined by the ratio of gas-phase concentrations [NH3] / [H2SO4], as well as by temperature. Pure binary H2O-H2SO4 clusters (observed as clusters of only H2SO4) only form at [NH3] / [H2SO4] < 0.1 to 1. For larger values of [NH3] / [H2SO4], the composition of NH3-H2SO4 clusters was characterized by the number of NH3 molecules m added for each added H2SO4 molecule n (Δm/Δ n), where n is in the range 4-18 (negatively charged clusters) or 1-17 (positively charged clusters). For negatively charged clusters, Δ m/Δn saturated between 1 and 1.4 for [NH3] / [H2SO4] > 10. Positively

  7. Electrospray ionization tandem mass spectrometric study of salt cluster ions: part 2--salts of polyatomic acid groups and of multivalent metals.

    PubMed

    Hao, C; March, R E

    2001-05-01

    Salt cluster ions formed from 0.05 M solutions of CaCl(2), CuCl(2) and Na(A)B (where A = 1 or 2 and B = CO(3)(2-), HCO(3)(-), H(2)PO(4)(-) and HPO(4)(2-)) were studied by electrospray ionization tandem mass spectrometry. The effects on salt cluster ions of droplet pH and of redox reactions induced by electrospray provide information on the electrospray process. CaCl(2) solution yielded salt cluster ions of the form (CaCl(2))(n)(CaCl)(x)(x+) and (CaCl(2))(n)(Cl)(y)(y-), where x, y = 1-3, in positive- and negative-ion modes, respectively. Upon collision induced dissociation (CID), singly charged CaCl(2) cluster ions fragmented, doubly charged cluster ions generated either singly or both singly and doubly charged fragment ions, depending on the cluster mass, and triply charged clusters fragmented predominantly by the loss of charged species. CuCl(2) solution yielded nine series of cluster ions of the form (CuCl(2))(n)(CuCl)(m) plus Cu(+), CuCl(+), or Cl(-). CuCl, the reductive product of CuCl(2), was observed as a neutral component of positively and negatively charged cluster ions. Free electrons were formed in a visible discharge that bridged the gap between the electrospray capillary and the sampling cone brought about the reduction of Cu(2+) to Cu(+). Upon CID, these cluster ions fragmented to lose CuCl(2), CuCl, Cl, and Cl(2). Na(2)CO(3) and NaHCO(3) solutions yielded cluster ions of the form (Na(2)CO(3))(n) plus Na(+) or NaCO(3)(-). Small numbers of NaHCO(3) molecules were found in some cluster ions obtained with the NaHCO(3) solution. For both Na(2)HPO(4) and NaH(2)PO(4) solutions, ions of the form (Na(2)HPO(4))(h), (NaH(2)PO(4))(i), (Na(3)PO(4))(j), (NaPO(3))(k) plus Na(+), PO(3)(-) or H(2)PO(4)(-) were observed. In addition, ions having one or two phosphoric acid (H(3)PO(4)) molecules were observed from the NaH(2)PO(4) solution while ions containing one sodium hydroxide (NaOH) molecule were observed from the Na(2)HPO(4) solution. The cluster ions observed from

  8. Reactions of simple aromatic heterocycles with niobium cluster ions (n<=30)

    NASA Astrophysics Data System (ADS)

    Pfeffer, Britta; Jaberg, Stephanie; Niedner-Schatteburg, Gereon

    2009-11-01

    Prior work on benzene activation by size selected niobium cluster cations and anions of up to 30 atoms is extended systematically through studying aromatic poly- and heterocyclic molecules such as naphthalene, pyridine, thiophene, pyrrole, furan, and benzofuran. Naphthalene is found to act much like benzene when reacting under single collision conditions with individual clusters. The most likely process is carbidization through complete dehydrogenation. Some clusters of particular sizes (most notably n=19) fail to activate both homocyclic molecules. Instead seemingly intact adsorption is observed which proves that activation is kinetically hindered at some point. All of the five studied heterocyclic aromatic molecules react unconditionally and by complete dehydrogenation with cationic niobium clusters, while they only attach to or react with anionic clusters larger than a minimum size of n=19-21. These findings are taken as strong evidence for initial coordination to the metal clusters of the heterocycles through their lone pair orbitals. The paper comprehends the observations in terms of cluster surface structure and reactivity.

  9. Monodisperse Au11 Clusters Prepared by Soft Landing of Mass Selected Ions

    SciTech Connect

    Johnson, Grant E.; Wang, Chong M.; Priest, Thomas A.; Laskin, Julia

    2011-11-01

    Preparation of clean monodisperse samples of clusters and nanoparticles for characterization using cutting-edge analytical techniques is essential to understanding their size-dependent properties. Herein, we report a general method for the preparation of high surface coverage samples of monodisperse clusters containing an exact number of atoms. Polydisperse solutions of diphosphine-capped gold clusters were produced by reduction synthesis. Electrospray ionization was used to introduce the clusters into the gas phase where they were filtered by mass-tocharge ratio allowing clusters of a selected size to be deposited onto carbon coated copper grids at well controlled kinetic energies. Scanning transmission electron microscopy (STEM) analysis of the soft landed clusters confirms their monodispersity and high coverage on the substrate. The soft landing approach may be extended to other materials compatible with an array of available ionization techniques and, therefore, has widespread utility as a means for controlled preparation of monodisperse samples of nanoparticles and clusters for analysis by transmission electron microscopy (TEM)

  10. Monodisperse Au11 clusters prepared by soft landing of mass selected ions.

    PubMed

    Johnson, Grant E; Wang, Chongmin; Priest, Thomas; Laskin, Julia

    2011-11-01

    Preparation of clean monodisperse samples of clusters and nanoparticles for characterization using cutting-edge analytical techniques is essential to understanding their size-dependent properties. Herein, we report a general method for the preparation of high surface coverage samples of monodisperse clusters containing an exact number of atoms. Polydisperse solutions of diphosphine-capped gold clusters were produced by reduction synthesis. Electrospray ionization was used to introduce the clusters into the gas phase where they were filtered by mass-to-charge ratio allowing clusters of a selected size to be deposited onto carbon coated copper grids at well controlled kinetic energies. Scanning transmission electron microscopy (STEM) analysis of the soft landed clusters confirms their monodispersity and high coverage on the substrate. The soft landing approach may be extended to other materials compatible with an array of available ionization techniques and, therefore, has widespread utility as a means for controlled preparation of monodisperse samples of nanoparticles and clusters for analysis by transmission electron microscopy (TEM).

  11. Entropic clocks in the service of electrical signaling: 'Ball and chain' mechanisms for ion channel inactivation and clustering.

    PubMed

    Zandany, Nitzan; Lewin, Limor; Nirenberg, Valerie; Orr, Irit; Yifrach, Ofer

    2015-09-14

    Electrical signaling in the nervous system relies on action potential generation, propagation and transmission. Such processes are dynamic in nature and rely on precisely timed events associated with voltage-dependent ion channel conformational transitions between their primary open, closed and inactivated states and clustering at unique membrane sites. In voltage-dependent potassium (Kv) channels, fast inactivation and clustering processes rely on entropic clock chains as described by 'ball and chain' mechanisms, suggesting important roles for such chains in electrical signaling. Here, we consider evidence supporting the proposed 'ball and chain' mechanisms for Kv channel fast inactivation and clustering associated with intrinsically disordered N- and C-terminal regions of the protein, respectively. Based on this comparison, we delineate the requirements that argue for such a process and establish the thermodynamic signature of a 'ball and chain' mechanism. Finally, we demonstrate how 'chain'-level alternative splicing of the Kv channel gene modulates the entropic clock-based 'ball and chain' inactivation and clustering channel functions underlying changes in electrical signaling. As such, the Kv channel model system exemplifies how linkage between alternative splicing and intrinsic disorder enables functional diversity.

  12. Formation of ion clusters by low-energy electrons in nanometric targets: experiment and Monte Carlo simulation.

    PubMed

    Bantsar, A; Grosswendt, B; Pszona, S

    2006-01-01

    The first experimental data on the distribution of ionisation cluster size produced by low energy electrons in a target cylinder of nitrogen, 3.5 nm in diameter at unit density, which is equivalent to approximately 2 nm in liquid water are presented. In the experiment, nanometric targets were simulated in the so-called Jet Counter. It consists of a pulse-operated valve which injects an expanding jet of nitrogen into an interaction chamber where a cylindrical sensitive volume is created. This sensitive volume was irradiated by electrons at 300 eV, 500 eV and 1 keV, emitted by an electron gun. The distribution of ionisation cluster size was measured using the single-ion-counting method and compared with the results of Monte Carlo simulation.

  13. Nitriles as directionally tolerant hydrogen bond acceptors: IR-UV ion depletion spectroscopy of benzenepropanenitrile and its hydrate clusters

    NASA Astrophysics Data System (ADS)

    Robertson, Patrick A.; Lobo, Isabella A.; Wilson, David J. D.; Robertson, Evan G.

    2016-09-01

    Benzenepropanenitrile (BPN) and its hydrate clusters are studied by R2PI and IR-UV ion-depletion spectroscopy in the CH/OH stretch regions, aided by theoretical calculations. A single water molecule binds to the terminal nitrile 'lone-pair' of the anti-BPN host, but there is also evidence for a side-type structure with OH donating to the nitrile π-electrons. In the gauche-BPN cluster, water is located at an intermediate angle that facilitates O⋯HC(ortho) interaction. A wide range of attachment angles is possible, as the intrinsic preference for linear hydrogen bonding is mediated by additional CH⋯O interactions that depend on molecular geometry near the nitrile group.

  14. SIMS depth profiling analysis of halogens in CdTe/CdS/TSO solar cells using Cs 2M + cluster ions

    NASA Astrophysics Data System (ADS)

    Koudriavtseva, O.; Morales-Acevedo, A.; Kudriavtsev, Yu.; Gallardo, S.; Asomoza, R.; Mendoza-Perez, R.; Sastre-Hernandez, J.; Contreras-Puente, G.

    2008-12-01

    SIMS depth profiling analysis of Au(Cu)/CdTe/CdS/SnO 2 solar cell structures were done. We analyzed these structures in the so-called CsM + mode and found an extremely high yield of Cs 2Hn + cluster ions, where Hn is halogen, in comparison with CsHn + ion yield and in comparison with yields of other Cs 2M + clusters, where M is another metal or non-metal element. There was no any interference for Cs 2Hn + cluster ions (for F and Cl) with other clusters in the concentration range of interest. This makes it possible to perform analysis of all elements of interest in noticed solar cells (halogens, metals and non-metals) during only one SIMS analysis. Possible explanation of the found anomalous yield is discussed.

  15. In Situ Studies on Twin-Thickness-Dependent Distribution of Defect Clusters in Heavy Ion-Irradiated Nanotwinned Ag

    NASA Astrophysics Data System (ADS)

    Li, Jin; Chen, Y.; Wang, H.; Zhang, X.

    2017-03-01

    Recent studies have shown that twin boundaries are effective defect sinks in heavy ion irradiated nanotwinned (nt) metals. Prior in situ radiation studies on nt Ag at room temperature indicate that the accumulative defect concentration is higher in center areas in the 60-nm-thick twins, and twin boundaries are distorted and self-heal during the absorption of different types of defect clusters. In this follow-up study, we show that the spatial distribution of accumulative defect concentrations in nt metals has a clear dependence on twin thickness, and in certain cases, the trend of spatial distribution is reversed. Potential mechanisms for the counterintuitive findings are discussed.

  16. In Situ Studies on Twin-Thickness-Dependent Distribution of Defect Clusters in Heavy Ion-Irradiated Nanotwinned Ag

    NASA Astrophysics Data System (ADS)

    Li, Jin; Chen, Y.; Wang, H.; Zhang, X.

    2017-01-01

    Recent studies have shown that twin boundaries are effective defect sinks in heavy ion irradiated nanotwinned (nt) metals. Prior in situ radiation studies on nt Ag at room temperature indicate that the accumulative defect concentration is higher in center areas in the 60-nm-thick twins, and twin boundaries are distorted and self-heal during the absorption of different types of defect clusters. In this follow-up study, we show that the spatial distribution of accumulative defect concentrations in nt metals has a clear dependence on twin thickness, and in certain cases, the trend of spatial distribution is reversed. Potential mechanisms for the counterintuitive findings are discussed.

  17. Graphene synthesis on SiC: Reduced graphitization temperature by C-cluster and Ar-ion implantation

    NASA Astrophysics Data System (ADS)

    Zhang, R.; Li, H.; Zhang, Z. D.; Wang, Z. S.; Zhou, S. Y.; Wang, Z.; Li, T. C.; Liu, J. R.; Fu, D. J.

    2015-08-01

    Thermal decomposition of SiC is a promising method for high quality production of wafer-scale graphene layers, when the high decomposition temperature of SiC is substantially reduced. The high decomposition temperature of SiC around 1400 °C is a technical obstacle. In this work, we report on graphene synthesis on 6H-SiC with reduced graphitization temperature via ion implantation. When energetic Ar, C1 and C6-cluster ions implanted into 6H-SiC substrates, some of the Si-C bonds have been broken due to the electronic and nuclear collisions. Owing to the radiation damage induced bond breaking and the implanted C atoms as an additional C source the graphitization temperature was reduced by up to 200 °C.

  18. A preparation approach of exploring cluster ion implantation: from ultra-thin carbon film to graphene

    PubMed Central

    2014-01-01

    Based on the extensive application of 2 × 1.7MV Tandetron accelerator, a low-energy cluster chamber has been built to explore for synthesizing graphene. Raman spectrum and atomic force microscopy (AFM) show that an amorphous carbon film in nanometer was deposited on the silicon by C4 cluster implantation. And we replaced the substrate with Ni/SiO2/Si and measured the thickness of Ni film by Rutherford backscattering spectrometry (RBS). Combined with suitable anneal conditions, these samples implanted by various small carbon clusters were made to grow graphene. Results from Raman spectrum reveal that few-layer graphene were obtained and discuss whether IG/I2D can contribute to explain the relationship between the number of graphene layers and cluster implantation dosage. PMID:24910570

  19. Structure of aldehyde cluster ions in the gas phase, according to data from ion mobility spectrometry and ab initio calculations

    NASA Astrophysics Data System (ADS)

    Lantsuzskaya (Krisilova), E. V.; Krisilov, A. V.; Levina, A. M.

    2015-09-01

    Ion-mobility spectra of a set of aliphatic linear aldehydes with the number of carbon atoms from 3 to 7 are obtained. Values of the mobility corresponding to two most intense peaks, considered to be those of a monomer and dimer, are determined according the spectra. Based on mobility, collision cross sections are calculated using the Mason-Schamp equation. The linear increase in the collision cross sections upon an increase in molecular weight is determined. According to the experimental results, the contribution to the cross section that has no dependence on molecular weight diminishes with the formation of dimers. It is established using quantum chemical calculations that this is associated with a reduction in the dipole moment upon the formation of dimers.

  20. Studies of Transition States, Clusters, and Radicals by Negative Ion Photodetachment and Photodissociation

    DTIC Science & Technology

    2006-04-24

    developed a new method for high resolution photodetachment spectroscopy of negative ions based on photoelectron imaging ( SEVI , or Slow photoElectron...new method for high resolution photodetachment spectroscopy of negative ions based on photoelectron imaging ( SEVI , or Slow photoElectron Velocity-map...velocity map imaging and anion threshold photodetachment. This method, Slow Electron Velocity-map Imaging ( SEVI ), provides spectral line widths of better

  1. Charge state of C10 and C5 energetic cluster ions in amorphous carbon targets: simulations

    NASA Astrophysics Data System (ADS)

    Nardi, E.; Tombrello, T. A.

    2006-12-01

    We present here detailed simulations of the interaction of energetic C10 and C5 clusters at the energies of 1, 2, and 4 MeV per carbon atom with an amorphous carbon target. The spatial evolution of the cluster components is simulated accounting for both scattering and Coulomb explosion. The former is calculated by means of the Monte Carlo method while the latter is computed by means of molecular dynamics. The charge state of the individual cluster components is calculated as a function of penetration depth, and is determined by the competition between electron ionization and recombination. The results of calculations of the effect of the neighbouring cluster components on the suppression of the values of the charge state are presented and compared to the experimental values of Brunelle et al. Charge state suppression calculations for the 2 MeV/C clusters for both C10 and C5 agree well with the experimental results for penetration depths of less than about 500 and 250 Å respectively, assuming the intracluster Coulomb potential is screened by four target valence electrons. At 4 MeV/C the results are similar although less screening is required; a possible explanation is the inability of the plasma to completely screen the higher velocity projectiles. The 1 MeV/C calculated results however differ in their behaviour from the 2 and 4 MeV/C cases.

  2. The fragmentation dynamics of small Cs(CsI)n+ cluster ions under low-energy multiple collision conditions

    NASA Astrophysics Data System (ADS)

    Herzschuh, Rainer; Drewello, Thomas

    2004-04-01

    The collision-induced dissociations of small caesium iodide cluster ions of the type Cs(CsI)n+ where n=3-7, have been investigated under low-energy multiple collision conditions. The collisions were performed in the rf-only quadrupole of a BEqQ hybrid mass spectrometer. Breakdown graphs of selected parent ions were obtained by varying the laboratory collision energy in the range of 0-400 eV. The fragmentation dynamic established under these conditions provides a link between the well-known decay behaviour occurring unimolecularly and the dissociations following high energy (keV) collisional activation. Of particular interest is the observation that the energy-dependent dissociation pattern supplies support for the occurrence of one-step fission reactions, featuring the evaporation of presumably intact (CsI)n neutrals as opposed to a sequential decay via nCsI losses. The breakdown graphs thus provide a valuable tool to enhance insight into the fragmentation mechanism of these clusters.

  3. Ion channel clustering by membrane-associated guanylate kinases. Differential regulation by N-terminal lipid and metal binding motifs.

    PubMed

    El-Husseini, A E; Topinka, J R; Lehrer-Graiwer, J E; Firestein, B L; Craven, S E; Aoki, C; Bredt, D S

    2000-08-04

    The postsynaptic density protein PSD-95 and related membrane-associated guanylate kinase (MAGUK) proteins assemble signal transduction complexes at sites of cell-cell contact including synapses. Whereas PSD-95 and PSD-93 occur only at postsynaptic sites in hippocampal neurons, SAP-102 also occurs in axons. In heterologous cells, PSD-95 and PSD-93 mediate cell surface ion channel clustering, but SAP-102 and SAP-97 do not. This selective ion channel clustering activity by MAGUKs is explained by differential palmitoylation, as PSD-93 and PSD-95 are palmitoylated though SAP-97, and SAP-102 are not. Rather than being palmitoylated, we find that N-terminal cysteines from SAP-102 tightly bind to zinc. And, appending the N terminus of SAP-102 to PSD-95 results in localization of the chimera to both axons and dendrites. These data suggest that lipid modifications and heavy metal associations with the N termini of MAGUKs mediate differential functions and subcellular localizations of these synaptic scaffolds.

  4. Surface-induced reactions and dissociations of small acetone, acetonitrile and ethanol cluster ions: competitive chemical reactions, dissociation mechanisms and determination of dissociation energy

    NASA Astrophysics Data System (ADS)

    Mair, C.; Fedor, J.; Lezius, M.; Scheier, P.; Probst, M.; Herman, Z.; Märk, T. D.

    2003-01-01

    Using a recently commissioned tandem mass spectrometer system, BESTOF, we have carried out systematic investigations (using also deuterated molecules) on the interaction of various molecular cluster ions (including stoichiometric acetone and acetonitrile cluster ions and protonated ethanol cluster ions) with a hydrocarbon-covered stainless steel surface. Besides observing competitive chemical reactions for the stoichiometric cluster ions driven by the energy transfer in the surface collision (intra-cluster reactions versus surface H-atom pick-up reactions), we were able to see clear evidence that unimolecular dissociation kinetics determines the production of the observed decay patterns in collision energy-resolved mass spectra (CERMS). From characteristic shifts in these CERMS we can deduce corresponding binding energies, i.e., {D}((CD3CN)2+ - CD3CN) = 0.66 eV, {D}((C2H5OH)2H+ - C2H5OH) = 0.95 eV, and for the protonated dimer {D}((C2H5OH)H+ - C2H5OH) = 1.6 eV. The first value is in good agreement with values currently calculated using the B3LYP (Becke-Lee-Yang-Parr) density functional and the 6-311G(d, p) basis set, the latter values are in good agreement with values derived earlier from thermochemical data. Moreover, in the case of the protonated ethanol cluster ion, it is possible to arrive at a single (universal) breakdown graph for the trimer composed of data derived from monomer, dimer and trimer CERMS. This can be achieved by renormalizing the energy scale in the CERMS for the monomer, dimer and trimer ions (taking into account the conversion from translational to internal energy and assuming that the clusters behave like a statistical ensemble with the corresponding degrees of freedom).

  5. Photofragmentation and vibrational relaxation of size-selected clusters ions : Non-adiabatic molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Douady, J.; Gervais, B.; Jacquet, E.; Zanuttini, D.; Giglio, E.

    2009-11-01

    We present non-adiabatic molecular dynamics simulations of size-selected Na2+ Arn (n=6-11-17) cluster. Their electronic structure is obtained from an accurate 1-electron model using core polarization pseudopotentials. We follow the dynamics of two specific photoexcitation processes (X2 Σ+g → A2Σ+u) and (X2 Σ+g → B2 Πu) during the first 10 ps. We identify a variety of processes in these clusters, such as dissociation of the Na2+ chromophore, solvation of the Na+ fragment as Na+ Arp and the recombination to the ground state of the Na2+ Arp with an important solvent evaporation. These processes depend significantly on the transition and on the isomer. We discuss these processes as a function of the cluster size.

  6. Ion-ion interactions in β-NaGdF4:Yb3+,Er3+ nanocrystals - the effect of ion concentration and their clustering

    NASA Astrophysics Data System (ADS)

    Noculak, A.; Podhorodecki, A.; Pawlik, G.; Banski, M.; Misiewicz, J.

    2015-08-01

    In this work we report co-thermolysis as a suitable method for nanomaterial synthesis which allows the creation of hexagonal upconverting nanocrystals, NaGdF4:Yb3+,Er3+, in a wide range of sizes (20-120 nm). Only a very high Yb3+ concentration (above 70%) results in pure cubic-phase nanocrystals with irregular shape. Additionally, we showed that the impact of Yb3+, Er3+ and Gd3+ ions on the size and optical properties of nanocrystals is significant. We found that the main changes in optical properties do not depend on the nanocrystal size mostly, but are determined by the ion-ion interactions which include both Er3+-Er3+ and Er3+-Yb3+ cross relaxation.In this work we report co-thermolysis as a suitable method for nanomaterial synthesis which allows the creation of hexagonal upconverting nanocrystals, NaGdF4:Yb3+,Er3+, in a wide range of sizes (20-120 nm). Only a very high Yb3+ concentration (above 70%) results in pure cubic-phase nanocrystals with irregular shape. Additionally, we showed that the impact of Yb3+, Er3+ and Gd3+ ions on the size and optical properties of nanocrystals is significant. We found that the main changes in optical properties do not depend on the nanocrystal size mostly, but are determined by the ion-ion interactions which include both Er3+-Er3+ and Er3+-Yb3+ cross relaxation. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03385c

  7. Energy Increase in Multi-MeV Ion Acceleration in the Interaction of a Short Pulse Laser with a Cluster-Gas Target

    SciTech Connect

    Fukuda, Y.; Faenov, A. Ya.; Tampo, M.; Pikuz, T. A.; Nakamura, T.; Kando, M.; Hayashi, Y.; Yogo, A.; Sakaki, H.; Kameshima, T.; Pirozhkov, A. S.; Ogura, K.; Mori, M.; Esirkepov, T. Zh.; Koga, J.; Bolton, P. R.; Kato, Y.; Tajima, T.; Daido, H.; Boldarev, A. S.

    2009-10-16

    An approach for accelerating ions, with the use of a cluster-gas target and an ultrashort pulse laser of 150-mJ energy and 40-fs duration, is presented. Ions with energy 10-20 MeV per nucleon having a small divergence (full angle) of 3.4 deg. are generated in the forward direction, corresponding to approximately tenfold increase in the ion energies compared to previous experiments using solid targets. It is inferred from a particle-in-cell simulation that the high energy ions are generated at the rear side of the target due to the formation of a strong dipole vortex structure in subcritical density plasmas.

  8. The effect of acid–base clustering and ions on the growth of atmospheric nano-particles

    PubMed Central

    Lehtipalo, Katrianne; Rondo, Linda; Kontkanen, Jenni; Schobesberger, Siegfried; Jokinen, Tuija; Sarnela, Nina; Kürten, Andreas; Ehrhart, Sebastian; Franchin, Alessandro; Nieminen, Tuomo; Riccobono, Francesco; Sipilä, Mikko; Yli-Juuti, Taina; Duplissy, Jonathan; Adamov, Alexey; Ahlm, Lars; Almeida, João; Amorim, Antonio; Bianchi, Federico; Breitenlechner, Martin; Dommen, Josef; Downard, Andrew J.; Dunne, Eimear M.; Flagan, Richard C.; Guida, Roberto; Hakala, Jani; Hansel, Armin; Jud, Werner; Kangasluoma, Juha; Kerminen, Veli-Matti; Keskinen, Helmi; Kim, Jaeseok; Kirkby, Jasper; Kupc, Agnieszka; Kupiainen-Määttä, Oona; Laaksonen, Ari; Lawler, Michael J.; Leiminger, Markus; Mathot, Serge; Olenius, Tinja; Ortega, Ismael K.; Onnela, Antti; Petäjä, Tuukka; Praplan, Arnaud; Rissanen, Matti P.; Ruuskanen, Taina; Santos, Filipe D.; Schallhart, Simon; Schnitzhofer, Ralf; Simon, Mario; Smith, James N.; Tröstl, Jasmin; Tsagkogeorgas, Georgios; Tomé, António; Vaattovaara, Petri; Vehkamäki, Hanna; Vrtala, Aron E.; Wagner, Paul E.; Williamson, Christina; Wimmer, Daniela; Winkler, Paul M.; Virtanen, Annele; Donahue, Neil M.; Carslaw, Kenneth S.; Baltensperger, Urs; Riipinen, Ilona; Curtius, Joachim; Worsnop, Douglas R.; Kulmala, Markku

    2016-01-01

    The growth of freshly formed aerosol particles can be the bottleneck in their survival to cloud condensation nuclei. It is therefore crucial to understand how particles grow in the atmosphere. Insufficient experimental data has impeded a profound understanding of nano-particle growth under atmospheric conditions. Here we study nano-particle growth in the CLOUD (Cosmics Leaving OUtdoors Droplets) chamber, starting from the formation of molecular clusters. We present measured growth rates at sub-3 nm sizes with different atmospherically relevant concentrations of sulphuric acid, water, ammonia and dimethylamine. We find that atmospheric ions and small acid-base clusters, which are not generally accounted for in the measurement of sulphuric acid vapour, can participate in the growth process, leading to enhanced growth rates. The availability of compounds capable of stabilizing sulphuric acid clusters governs the magnitude of these effects and thus the exact growth mechanism. We bring these observations into a coherent framework and discuss their significance in the atmosphere. PMID:27197574

  9. The effect of acid–base clustering and ions on the growth of atmospheric nano-particles

    DOE PAGES

    Lehtipalo, Katrianne; Rondo, Linda; Kontkanen, Jenni; ...

    2016-05-20

    The growth of freshly formed aerosol particles can be the bottleneck in their survival to cloud condensation nuclei. It is therefore crucial to understand how particles grow in the atmosphere. Insufficient experimental data has impeded a profound understanding of nano-particle growth under atmospheric conditions. Here we study nano-particle growth in the CLOUD (Cosmics Leaving OUtdoors Droplets) chamber, starting from the formation of molecular clusters. We present measured growth rates at sub-3 nm sizes with different atmospherically relevant concentrations of sulphuric acid, water, ammonia and dimethylamine. We find that atmospheric ions and small acid-base clusters, which are not generally accounted formore » in the measurement of sulphuric acid vapour, can participate in the growth process, leading to enhanced growth rates. The availability of compounds capable of stabilizing sulphuric acid clusters governs the magnitude of these effects and thus the exact growth mechanism. Furthermore, we bring these observations into a coherent framework and discuss their significance in the atmosphere.« less

  10. The effect of acid-base clustering and ions on the growth of atmospheric nano-particles.

    PubMed

    Lehtipalo, Katrianne; Rondo, Linda; Kontkanen, Jenni; Schobesberger, Siegfried; Jokinen, Tuija; Sarnela, Nina; Kürten, Andreas; Ehrhart, Sebastian; Franchin, Alessandro; Nieminen, Tuomo; Riccobono, Francesco; Sipilä, Mikko; Yli-Juuti, Taina; Duplissy, Jonathan; Adamov, Alexey; Ahlm, Lars; Almeida, João; Amorim, Antonio; Bianchi, Federico; Breitenlechner, Martin; Dommen, Josef; Downard, Andrew J; Dunne, Eimear M; Flagan, Richard C; Guida, Roberto; Hakala, Jani; Hansel, Armin; Jud, Werner; Kangasluoma, Juha; Kerminen, Veli-Matti; Keskinen, Helmi; Kim, Jaeseok; Kirkby, Jasper; Kupc, Agnieszka; Kupiainen-Määttä, Oona; Laaksonen, Ari; Lawler, Michael J; Leiminger, Markus; Mathot, Serge; Olenius, Tinja; Ortega, Ismael K; Onnela, Antti; Petäjä, Tuukka; Praplan, Arnaud; Rissanen, Matti P; Ruuskanen, Taina; Santos, Filipe D; Schallhart, Simon; Schnitzhofer, Ralf; Simon, Mario; Smith, James N; Tröstl, Jasmin; Tsagkogeorgas, Georgios; Tomé, António; Vaattovaara, Petri; Vehkamäki, Hanna; Vrtala, Aron E; Wagner, Paul E; Williamson, Christina; Wimmer, Daniela; Winkler, Paul M; Virtanen, Annele; Donahue, Neil M; Carslaw, Kenneth S; Baltensperger, Urs; Riipinen, Ilona; Curtius, Joachim; Worsnop, Douglas R; Kulmala, Markku

    2016-05-20

    The growth of freshly formed aerosol particles can be the bottleneck in their survival to cloud condensation nuclei. It is therefore crucial to understand how particles grow in the atmosphere. Insufficient experimental data has impeded a profound understanding of nano-particle growth under atmospheric conditions. Here we study nano-particle growth in the CLOUD (Cosmics Leaving OUtdoors Droplets) chamber, starting from the formation of molecular clusters. We present measured growth rates at sub-3 nm sizes with different atmospherically relevant concentrations of sulphuric acid, water, ammonia and dimethylamine. We find that atmospheric ions and small acid-base clusters, which are not generally accounted for in the measurement of sulphuric acid vapour, can participate in the growth process, leading to enhanced growth rates. The availability of compounds capable of stabilizing sulphuric acid clusters governs the magnitude of these effects and thus the exact growth mechanism. We bring these observations into a coherent framework and discuss their significance in the atmosphere.

  11. Cluster secondary ion mass spectrometry imaging of interfacial reactions of TiO2 microspheres embedded in ionic liquids.

    PubMed

    Shen, Kan; Tarolli, Jay G; Winograd, Nicholas

    2016-02-15

    Our goal is to develop protocols for the elucidation of the identity and structure of reaction products embedded in a reaction medium. Results should find significance in a variety of disciplines ranging from the study of biological cells and tissues, to the steps associated with the functionalization of nanoparticles. We utilize cluster secondary ion mass spectrometry (cluster-SIMS) to acquire three-dimensional (3D) information about 5-30 µm TiO2 microspheres imbedded into an ionic liquid. The method allows molecular depth profiling with submicron spatial resolution and depth profiling with a resolution of several tens of nanometers. The ionic liquid matrix enshrouds the spheres, allowing them to be introduced into the vacuum environment of the mass spectrometer. The results provide 3D chemical information about these microspheres as they are synthesized by interfacial sol-gel reactions. We show that with 40 keV C60 (+) , it is possible to erode through the reaction medium and map the distribution of those embedded TiO2 microspheres. Moreover, we demonstrate that it is possible to monitor surface modification of the particles and, via ion beam drilling, elucidate their internal structure. Using cluster-SIMS imaging, we are able to elucidate the identity and structure of reaction products embedded in a reaction medium, a problem of long-standing interest for materials characterization. With this strategy, we have provided a new approach that may be especially useful for the characterization of biological tissue and cells within the vacuum confines of the mass spectrometer. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

  12. Glutathione depletion and carbon ion radiation potentiate clustered DNA lesions, cell death and prevent chromosomal changes in cancer cells progeny.

    PubMed

    Hanot, Maïté; Boivin, Anthony; Malésys, Céline; Beuve, Michaël; Colliaux, Anthony; Foray, Nicolas; Douki, Thierry; Ardail, Dominique; Rodriguez-Lafrasse, Claire

    2012-01-01

    Poor local control and tumor escape are of major concern in head-and-neck cancers treated by conventional radiotherapy or hadrontherapy. Reduced glutathione (GSH) is suspected of playing an important role in mechanisms leading to radioresistance, and its depletion should enable oxidative stress insult, thereby modifying the nature of DNA lesions and the subsequent chromosomal changes that potentially lead to tumor escape.This study aimed to highlight the impact of a GSH-depletion strategy (dimethylfumarate, and L-buthionine sulfoximine association) combined with carbon ion or X-ray irradiation on types of DNA lesions (sparse or clustered) and the subsequent transmission of chromosomal changes to the progeny in a radioresistant cell line (SQ20B) expressing a high endogenous GSH content. Results are compared with those of a radiosensitive cell line (SCC61) displaying a low endogenous GSH level. DNA damage measurements (γH2AX/comet assay) demonstrated that a transient GSH depletion in resistant SQ20B cells potentiated the effects of irradiation by initially increasing sparse DNA breaks and oxidative lesions after X-ray irradiation, while carbon ion irradiation enhanced the complexity of clustered oxidative damage. Moreover, residual DNA double-strand breaks were measured whatever the radiation qualities. The nature of the initial DNA lesions and amount of residual DNA damage were similar to those observed in sensitive SCC61 cells after both types of irradiation. Misrepaired or unrepaired lesions may lead to chromosomal changes, estimated in cell progeny by the cytome assay. Both types of irradiation induced aberrations in nondepleted resistant SQ20B and sensitive SCC61 cells. The GSH-depletion strategy prevented the transmission of aberrations (complex rearrangements and chromosome break or loss) in radioresistant SQ20B only when associated with carbon ion irradiation. A GSH-depleting strategy combined with hadrontherapy may thus have considerable advantage in the

  13. Glutathione Depletion and Carbon Ion Radiation Potentiate Clustered DNA Lesions, Cell Death and Prevent Chromosomal Changes in Cancer Cells Progeny

    PubMed Central

    Hanot, Maïté; Boivin, Anthony; Malésys, Céline; Beuve, Michaël; Colliaux, Anthony; Foray, Nicolas; Douki, Thierry; Ardail, Dominique; Rodriguez-Lafrasse, Claire

    2012-01-01

    Poor local control and tumor escape are of major concern in head-and-neck cancers treated by conventional radiotherapy or hadrontherapy. Reduced glutathione (GSH) is suspected of playing an important role in mechanisms leading to radioresistance, and its depletion should enable oxidative stress insult, thereby modifying the nature of DNA lesions and the subsequent chromosomal changes that potentially lead to tumor escape. This study aimed to highlight the impact of a GSH-depletion strategy (dimethylfumarate, and l-buthionine sulfoximine association) combined with carbon ion or X-ray irradiation on types of DNA lesions (sparse or clustered) and the subsequent transmission of chromosomal changes to the progeny in a radioresistant cell line (SQ20B) expressing a high endogenous GSH content. Results are compared with those of a radiosensitive cell line (SCC61) displaying a low endogenous GSH level. DNA damage measurements (γH2AX/comet assay) demonstrated that a transient GSH depletion in resistant SQ20B cells potentiated the effects of irradiation by initially increasing sparse DNA breaks and oxidative lesions after X-ray irradiation, while carbon ion irradiation enhanced the complexity of clustered oxidative damage. Moreover, residual DNA double-strand breaks were measured whatever the radiation qualities. The nature of the initial DNA lesions and amount of residual DNA damage were similar to those observed in sensitive SCC61 cells after both types of irradiation. Misrepaired or unrepaired lesions may lead to chromosomal changes, estimated in cell progeny by the cytome assay. Both types of irradiation induced aberrations in nondepleted resistant SQ20B and sensitive SCC61 cells. The GSH-depletion strategy prevented the transmission of aberrations (complex rearrangements and chromosome break or loss) in radioresistant SQ20B only when associated with carbon ion irradiation. A GSH-depleting strategy combined with hadrontherapy may thus have considerable advantage in the

  14. Dual beam organic depth profiling using large argon cluster ion beams.

    PubMed

    Holzweber, M; Shard, A G; Jungnickel, H; Luch, A; Unger, Wes

    2014-01-01

    Argon cluster sputtering of an organic multilayer reference material consisting of two organic components, 4,4'-bis[N-(1-naphthyl-1-)-N-phenyl- amino]-biphenyl (NPB) and aluminium tris-(8-hydroxyquinolate) (Alq3), materials commonly used in organic light-emitting diodes industry, was carried out using time-of-flight SIMS in dual beam mode. The sample used in this study consists of a ∽400-nm-thick NPB matrix with 3-nm marker layers of Alq3 at depth of ∽50, 100, 200 and 300 nm. Argon cluster sputtering provides a constant sputter yield throughout the depth profiles, and the sputter yield volumes and depth resolution are presented for Ar-cluster sizes of 630, 820, 1000, 1250 and 1660 atoms at a kinetic energy of 2.5 keV. The effect of cluster size in this material and over this range is shown to be negligible. © 2014 The Authors. Surface and Interface Analysis published by John Wiley & Sons Ltd.

  15. Annealing studies of cluster defects in ion-implanted silicon using high resolution DLTS

    NASA Astrophysics Data System (ADS)

    Gad, M. A.; Evans-Freeman, J. H.

    2006-12-01

    High resolution Laplace deep level transient spectroscopy (LDLTS) has been applied to investigate the annealing behaviour of small cluster defects in n-type Si. The Si was implanted with either Ge or Si, with energies 1500 keV and 850 keV respectively, and doses of 1 × 10 10 cm -2. The low dose ensured that there was a minimum of carrier removal due to deep defect states after implantation. Defect states in the as-implanted samples were attributed to VO pairs, divacancies and very small interstitial cluster defects, after detailed depth profiling. LDLTS of Ge + and Si + implanted silicon shows that there are three closely spaced deep levels associated with these clusters, with energies in the region of Ec-400 meV. Samples were then isochronally annealed in very small temperature intervals up to 560 K, in situ in our high temperature measurement cryostat, and the LDLTS re-examined as a function of annealing temperature. A new deeper energy level emerges as the cluster-related signal reduces, and it is suggested that this new trap is a major recombination centre, by comparison with current-voltage data.

  16. Frequency sweep rates of rising tone electromagnetic ion cyclotron waves: Comparison between nonlinear theory and Cluster observation

    SciTech Connect

    He, Zhaoguo; Zong, Qiugang Wang, Yongfu; Liu, Siqing; Lin, Ruilin; Shi, Liqin

    2014-12-15

    Resonant pitch angle scattering by electromagnetic ion cyclotron (EMIC) waves has been suggested to account for the rapid loss of ring current ions and radiation belt electrons. For the rising tone EMIC wave (classified as triggered EMIC emission), its frequency sweep rate strongly affects the efficiency of pitch-angle scattering. Based on the Cluster observations, we analyze three typical cases of rising tone EMIC waves. Two cases locate at the nightside (22.3 and 22.6 magnetic local time (MLT)) equatorial region and one case locates at the duskside (18MLT) higher magnetic latitude (λ = –9.3°) region. For the three cases, the time-dependent wave amplitude, cold electron density, and cold ion density ratio are derived from satellite data; while the ambient magnetic field, thermal proton perpendicular temperature, and the wave spectral can be directly provided by observation. These parameters are input into the nonlinear wave growth model to simulate the time-frequency evolutions of the rising tones. The simulated results show good agreements with the observations of the rising tones, providing further support for the previous finding that the rising tone EMIC wave is excited through the nonlinear wave growth process.

  17. Structural analysis of the outermost hair surface using TOF-SIMS with gas cluster ion beam sputtering.

    PubMed

    Lshikawa, Kazutaka; Okamoto, Masayuki; Aoyagi, Satoka

    2016-06-28

    A hair cuticle, which consists of flat overlapping scales that surround the hair fiber, protects inner tissues against external stimuli. The outermost surface of the cuticle is covered with a thin membrane containing proteins and lipids called the epicuticle. In a previous study, the authors conducted a depth profile analysis of a hair cuticle's amino acid composition to characterize its multilayer structure. Time-of-flight secondary ion mass spectrometry with a bismuth primary ion source was used in combination with the C60 sputtering technique for the analysis. It was confirmed that the lipids and cysteine-rich layer exist on the outermost cuticle surface, which is considered to be the epicuticle, though the detailed structure of the epicuticle has not been clarified. In this study, depth profile analysis of the cuticle surface was conducted using the argon gas cluster ion beam (Ar-GCIB) sputtering technique, in order to characterize the structure of the epicuticle. The shallow depth profile of the cuticle surface was investigated using an Ar-GCIB impact energy of 5 keV. Compared to the other amino acid peaks rich in the epicuticle, the decay of 18-methyleicosanic acid (18-MEA) thiolate peak was the fastest. This result suggests that the outermost surface of the hair is rich in 18-MEA. In conclusion, our results indicate that the outermost surfaces of cuticles have a multilayer (lipid and protein layers), which is consistent with the previously proposed structure.

  18. Structure and thermodynamic properties of positive and negative cluster ions in saturated vapour over barium dichloride

    NASA Astrophysics Data System (ADS)

    Pogrebnoi, Alexander M.; Pogrebnaya, Tatiana P.; Kudin, Lev S.; Tuyizere, Sarathiel

    2013-11-01

    Geometrical structure, vibration spectra, and enthalpies of dissociation have been investigated for the ions BaCl3-, Ba2Cl3+, Ba3Cl5+, and Ba4Cl7+ which were detected earlier in the saturated vapour over BaCl2. Quantum chemical methods of density functional theory, the second and the fourth order Møller-Plesset perturbation theory have been applied. The effective core potential with cc-pVTZ basis set for barium atom and two full-electron basis sets including the diffuse and polarised basis functions for chlorine atom were used. The effect of the basis set size and the computation method on the results was analysed. According to the results, all the ions possess the compact shaped structure. The equilibrium geometrical structures were found as follows: the planar D3h for BaCl3-, triple bridged bipyramidal D3h for Ba2Cl3+, hexabridged D3h for Ba3Cl5+, and septuple bridged C2v for Ba4Cl7+. For positive ions, the different isomeric structures were considered, but no isomers for these ions have been found. The geometrical parameters and vibration frequencies were utilised for computing of thermodynamic functions of the ions, and then the thermodynamic functions were used for the treatment of the experimental mass spectrometric data. The enthalpies of formation ΔfH°(0 K) of the ions were determined (in kJ/mol): -994 ± 6 (BaCl3-), -481 ± 10 (Ba2Cl3+), -1276 ± 14 (Ba3Cl5+), -2048 ± 35 (Ba4Cl7+).

  19. Experimental studies of the formation of cluster ions formed by corona discharge in an atmosphere containing SO2, NH3, and H2O

    NASA Astrophysics Data System (ADS)

    Pedersen, J. O.; Hvelplund, P.; Støchkel, K.; Enghoff, M. B.; Kurten, T.

    2013-12-01

    We report on studies of ion induced nucleation in a corona discharge taking place in an atmosphere containing SO2, NH3, and H2O at standard temperature and pressure. Positive ions such as H3O+(H2O)n, NH4+(H2O)n, and H+(H2SO4)(H2O)n and negative ions such as HSO5-(H2O)n, SO4-(H2O)n, HSO4-(H2O)n and NO3-(H2O)n have been recorded. Large values of n (> 100) were observed and the experiment indicates the existence of even larger water clusters. In contrast, only clusters with a maximum of 2 sulfuric acid molecules were observed. Fragmentation studies also revealed that the negative ion HSO5-, which has been observed in many studies, in our experiments is contaminated by O2-(HNO3)(H2O) ions, and this may also have been the case in other experiments. Finally an ion with m/z = 232 (where m is the cluster mass in amu and z the charge state), capable of attaching H2O-molecules was observed and studied by fragmentation. Positive ion m/z (mass/charge) spectrum

  20. A tray-shaped, Pd(II)-clipped Au₃ complex as a scaffold for the modular assembly of [3×n] Au ion clusters.

    PubMed

    Osuga, Takafumi; Murase, Takashi; Hoshino, Manabu; Fujita, Makoto

    2014-10-13

    A tray-shaped Pd(II)3Au(I)3 complex (1) is prepared from 3,5-bis(3-pyridyl)pyrazole by means of tricyclization with Au(I) followed by Pd(II) clipping. Tray 1 is an efficient scaffold for the modular assembly of [3×n] Au(I) clusters. Treatment of 1 with the Au(I)3 tricyclic guest 2 in H2O/CH3CN (7:3) or H2O results in the selective formation of a [3×2] cluster (1⋅2) or a [3×3] cluster (1⋅2⋅1), respectively. Upon subsequent addition of Ag(I) ions, these complexes are converted to an unprecedented Au3-Au3-Ag-Au3-Au3 metal ion cluster. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Formation and Fragmentation of Protonated Molecules after Ionization of Amino Acid and Lactic Acid Clusters by Collision with Ions in the Gas Phase.

    PubMed

    Poully, Jean-Christophe; Vizcaino, Violaine; Schwob, Lucas; Delaunay, Rudy; Kocisek, Jaroslav; Eden, Samuel; Chesnel, Jean-Yves; Méry, Alain; Rangama, Jimmy; Adoui, Lamri; Huber, Bernd

    2015-08-03

    Collisions between O(3+) ions and neutral clusters of amino acids (alanine, valine and glycine) as well as lactic acid are performed in the gas phase, in order to investigate the effect of ionizing radiation on these biologically relevant molecular systems. All monomers and dimers are found to be predominantly protonated, and ab initio quantum-chemical calculations on model systems indicate that for amino acids, this is due to proton transfer within the clusters after ionization. For lactic acid, which has a lower proton affinity than amino acids, a significant non-negligible amount of the radical cation monomer is observed. New fragment-ion channels observed from clusters, as opposed to isolated molecules, are assigned to the statistical dissociation of protonated molecules formed upon ionization of the clusters. These new dissociation channels exhibit strong delayed fragmentation on the microsecond time scale, especially after multiple ionization. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Mass accuracy improvement of reversed-phase liquid chromatography/electrospray ionization mass spectrometry based urinary metabolomic analysis by post-run calibration using sodium formate cluster ions.

    PubMed

    Juo, Chiun-Gung; Chen, Chien-Lun; Lin, Shiang-Ting; Fu, Shu-Hsuan; Chen, Yi-Ting; Chang, Yu-Sun; Yu, Jau-Song

    2014-08-30

    Typically, a batch metabolomics analysis using liquid chromatography/electrospray ionization time-of-flight mass spectrometry (LC/ESI-TOF MS) takes 2 to 3 days. However, the mass accuracy - which has an important influence on metabolite identification - can drift by as much as about 17 ppm in such a time period. In an untargeted urinary metabolomics analysis by reversed-phase liquid chromatography (RPLC)/ESI-MS, the signals of sodium formate cluster ions were detected at the column-washing step. The cluster ions were used to calibrate the mass spectrometer for more accurate detection. The spectra were calibrated post-run by the sodium formate cluster ions, which were used as the internal standard, in order to improve the mass accuracy. In the analysis of urine samples, we calibrated the spectra acquired by the micrOTOF with the sodium cluster ions. In positive mode ESI, the average errors of these cluster ions were improved to ±0.48 ppm and in negative mode ESI, to ±0.94 ppm after calibration. The mass accuracy remained within ±0.01 ppm over the duration of 6.25 days. An error window of 4 ppm appears to be suitable for metabolite identification when using post-calibration. The results showed that sodium formate cluster ions could be utilized for the calibration of LC/ESI-TOF MS and the average instrumental errors could be maintained at low levels for long-term analyses. This method could be applied not only to urine sample, but also to low sodium samples, such as saliva, by dissolving the sample in 1 μM sodium formate solution. This method provides a good solution for accurate mass detection of metabolomic analysis. Copyright © 2014 John Wiley & Sons, Ltd.

  3. Water mediated attraction between repulsive ions: A cluster-based simulation approach

    NASA Astrophysics Data System (ADS)

    Keasler, Samuel J.; Nellas, Ricky B.; Chen, Bin

    2006-10-01

    Could two like ions be attractive to each other in the presence of water? To address this question and to further interrogate the intriguing solvent effects at a molecular level on multiply charged species, a "bottom-up" simulation approach was formulated, from which the inter-ionic potential of mean force and other properties were monitored closely with the gradual addition of the water molecules. This approach was first tested on a commonly studied ion pair (namely, Na+ and Cl-), where excellent agreement with the published bulk-phase data was found. Further application of this approach to the like-ion pair indicated that an attractive interaction between two anions or two cations can be induced by the addition of an appropriate number of water molecules. This result corroborates a recent experimental report of an intriguing folding of a dianionic polymer into a more compact structure with the addition of water molecules in gas phase as well as previous theoretical findings of possible attraction between like-ion pairs in bulk aqueous phases.

  4. Sputtering Yields for Mixtures of Organic Materials Using Argon Gas Cluster Ions.

    PubMed

    Seah, M P; Havelund, R; Shard, A G; Gilmore, I S

    2015-10-22

    The sputtering yield volumes of binary mixtures of Irganox 1010 with either Irganox 1098 or Fmoc-pentafluoro-L-phenylalanine (FMOC) have been measured for 5 keV Ar2000(+) ions incident at 45° to the surface normal. The sputtering yields are determined from the doses to sputter through various compositions of 100 nm thick, intimately mixed, layers. Because of matrix effects, the profiles for secondary ions are distorted, and profile shifts in depth of 15 nm are observed leading to errors above 20% in the deduced sputtering yield. Secondary ions are selected to avoid this. The sputtering yield volumes for the mixtures are shown to be lower than those deduced from a linear interpolation from the pure materials. This is shown to be consistent with a simple model involving the changing energy absorbed for the sputtering of intimate mixtures. Evidence to support this comes from the secondary ion data for pairs of the different molecules. Both binary mixtures behave similarly, but matrix effects are stronger for the Irganox 1010/FMOC system.

  5. Metallo-carbohedrenes (M sub 8 C sub 12 sup + (M = V, Zr, Hf, and Ti)): A class of stable molecular cluster ions

    SciTech Connect

    Guo, B.C.; Wei, S.; Purnell, J.; Buzza, S.; Castleman, A.W. Jr. )

    1992-04-24

    Findings of magic peaks corresponding to M{sub 8}C{sub 12}{sup +} (M = V, Zr, and Hf) formed from reactions of the respective metals with various small hydrocarbons, in conjunction with recent findings for the titanium system, establish metallo-carbohedrenes as a stable general class of molecular cluster ions. A dodecahedral structure of T{sub h} point symmetry accounts for the stability of these ionic clusters.

  6. Cluster expansion of the solvation free energy difference: Systematic improvements in the solvation of single ions

    NASA Astrophysics Data System (ADS)

    Pliego, Josefredo R.

    2017-07-01

    The cluster expansion method has been used in the imperfect gas theory for several decades. This paper proposes a cluster expansion of the solvation free energy difference. This difference, which results from a change in the solute-solvent potential energy, can be written as the logarithm of a finite series. Similar to the Mayer function, the terms in the series are related to configurational integrals, which makes the integrand relevant only for configurations of the solvent molecules close to the solute. In addition, the terms involve interaction of solute with one, two, and so on solvent molecules. The approach could be used for hybrid quantum mechanical and molecular mechanics methods or mixed cluster-continuum approximation. A simple form of the theory was applied for prediction of pKa in methanol; the results indicated that three explicit methanol molecules and the dielectric continuum lead to a root of mean squared error (RMSE) of only 1.3 pKa units, whereas the pure continuum solvation model based on density method leads to a RMSE of 6.6 pKa units.

  7. Study of cluster anions generated by laser ablation of titanium oxides: a high resolution approach based on Fourier transform ion cyclotron resonance mass spectrometry.

    PubMed

    Barthen, Nicolas; Millon, Eric; Aubriet, Frédéric

    2011-03-01

    Laser ablation of titanium oxides at 355 nm and ion-molecule reactions between [(TiO(2))(x)](-•) cluster anions and H(2)O or O(2) were investigated by Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) with an external ion source. The detected anions correspond to [(TiO(2))(x)(H(2)O)(y)OH](-) and [(TiO(2))(x)(H(2)O)(y)O(2)](-•) oxy-hydroxide species with x=1 to 25 and y=1, 2, or 3 and were formed by a two step process: (1) laser ablation, which leads to the formation of [(TiO(2))(x)](-•) cluster anions as was previously reported, and (2) ion-molecule reactions during ion storage. Reactions of some [(TiO(2))(x)](-•) cluster anions with water and dioxygen conducted in the FTICR cell confirm this assessment. Tandem mass spectrometry experiments were also performed in sustained off-resonance irradiation collision-induced dissociation (SORI-CID) mode. Three fragmentation pathways were observed: (1) elimination of water molecules, (2) O(2) loss for radical anions, and (3) fission of the cluster. Density functional theory (DFT) calculations were performed to explain the experimental data.

  8. State density formalism of the Iwamoto-Harada model: A suitable tool to treat cluster emission from heavy-ion collisions with account for spin variables

    NASA Astrophysics Data System (ADS)

    Běták, Emil; Cseh, József

    2017-09-01

    We study the possibility to include the cluster emission into the statistical pre-equilibrium (exciton) model suitable also for heavy ion collisions. The direct motivation of this paper is a possibility of producing superdeformed nuclei, which are easier to be detected in heavy-ion reactions than in those induced by light projectiles (nucleons, deuterons, α-particles). Note to the reader: the pdf file has been changed on September 22, 2017.

  9. The University of Bern Ion Model: Modeling the Mixed H+(H2O)m(CH_3CN)_n Clusters in the Stratosphere

    NASA Astrophysics Data System (ADS)

    Kopp, E.; Kazil, J.; Arijs, E.; Livesey, N.

    2001-12-01

    Methyl cyanide (CH3CN) replaces water molecules in proton hydrates H+(H2O)n at high rates in the stratosphere. Our global 2D ion model uses the latest stratospheric UARS MLS CH3CN data together with neutral input from the NCAR SOCRATES model and computes mixed ion cluster H+(H2O)n(CH_3CN) densities. The results are compared with in situ measurements from different sources.

  10. Single-ion hydration thermodynamics from clusters to bulk solutions: Recent insights from molecular modeling

    DOE PAGES

    Vlcek, Lukas; Chialvo, Ariel A.

    2016-01-03

    The importance of single-ion hydration thermodynamic properties for understanding the driving forces of aqueous electrolyte processes, along with the impossibility of their direct experimental measurement, have prompted a large number of experimental, theoretical, and computational studies aimed at separating the cation and anion contributions. Here we provide an overview of historical approaches based on extrathermodynamic assumptions and more recent computational studies of single-ion hydration in order to evaluate the approximations involved in these methods, quantify their accuracy, reliability, and limitations in the light of the latest developments. Finally, we also offer new insights into the factors that influence the accuracymore » of ion–water interaction models and our views on possible ways to fill this substantial knowledge gap in aqueous physical chemistry.« less

  11. Single-ion hydration thermodynamics from clusters to bulk solutions: Recent insights from molecular modeling

    SciTech Connect

    Vlcek, Lukas; Chialvo, Ariel A.

    2016-01-03

    The importance of single-ion hydration thermodynamic properties for understanding the driving forces of aqueous electrolyte processes, along with the impossibility of their direct experimental measurement, have prompted a large number of experimental, theoretical, and computational studies aimed at separating the cation and anion contributions. Here we provide an overview of historical approaches based on extrathermodynamic assumptions and more recent computational studies of single-ion hydration in order to evaluate the approximations involved in these methods, quantify their accuracy, reliability, and limitations in the light of the latest developments. Finally, we also offer new insights into the factors that influence the accuracy of ion–water interaction models and our views on possible ways to fill this substantial knowledge gap in aqueous physical chemistry.

  12. Membrane tension influences the spike propagation between voltage-gated ion channel clusters of excitable membranes

    NASA Astrophysics Data System (ADS)

    Assmann, Marcus-Alexander; Lenz, Peter

    2014-08-01

    Ion channels of excitable membranes are known to be sensitive to various kinds of stimuli, but the case of simultaneous occurrence of different stimuli is poorly understood. Here, we theoretically analyze the influence of membrane tension on the dynamics of voltage-gated ion channels of excitable membranes. To do so, we develop a modification of the well-known Hodgkin-Huxley model to study numerically the spike generation and propagation in a single and two coupled excitable cells. We find that these cells can use membrane tension to trigger sub-threshold spike propagation, to suppress spike propagation and to alter the intensity of the signal transmission. These effects indicate that cells could use membrane tension to regulate cell-to-cell communication.

  13. Spectral-luminescent properties of silver molecular clusters and nanoparticles formed by ion exchange in antimony-doped photo-thermo-refractive glasses

    NASA Astrophysics Data System (ADS)

    Sgibnev, E. M.; Nikonorov, N. V.; Ignat'ev, A. I.

    2017-01-01

    The formation of silver molecular clusters and nanoparticles in photo-thermo-refractive (PTR) glasses with different antimony contents has been investigated using ion exchange with subsequent thermal treatment. The influence of the antimony oxide (Sb2O3) concentration and treatment temperature on the spectral-luminescent properties of silver molecular clusters and nanoparticles in glass has been investigated. It is shown that silver molecular clusters in PTR glasses are characterized by strong broadband luminescence in the visible and near-IR ranges and that the formation of silver nanoparticles leads to luminescence quenching.

  14. Voltage clustering in redox-active ligand complexes: mitigating electronic communication through choice of metal ion

    DOE PAGES

    Zarkesh, Ryan A.; Ichimura, Andrew S.; Monson, Todd C.; ...

    2016-02-01

    We used the redox-active bis(imino)acenapthene (BIAN) ligand to synthesize homoleptic aluminum, chromium, and gallium complexes of the general formula (BIAN)3M. The resulting compounds were characterized using X-ray crystallography, NMR, EPR, magnetic susceptibility and cyclic voltammetry measurements and modeled using both DFT and ab initio wavefunction calculations to compare the orbital contributions of main group elements and transition metals in ligand-based redox events. Ultimately, complexes of this type have the potential to improve the energy density and electrolyte stability of grid-scale energy storage technologies, such as redox flow batteries, through thermodynamically-clustered redox events.

  15. Voltage clustering in redox-active ligand complexes: mitigating electronic communication through choice of metal ion

    SciTech Connect

    Zarkesh, Ryan A.; Ichimura, Andrew S.; Monson, Todd C.; Tomson, Neil C.; Anstey, Mitchell R.

    2016-02-01

    We used the redox-active bis(imino)acenapthene (BIAN) ligand to synthesize homoleptic aluminum, chromium, and gallium complexes of the general formula (BIAN)3M. The resulting compounds were characterized using X-ray crystallography, NMR, EPR, magnetic susceptibility and cyclic voltammetry measurements and modeled using both DFT and ab initio wavefunction calculations to compare the orbital contributions of main group elements and transition metals in ligand-based redox events. Ultimately, complexes of this type have the potential to improve the energy density and electrolyte stability of grid-scale energy storage technologies, such as redox flow batteries, through thermodynamically-clustered redox events.

  16. Overlap model and ab initio cluster calculations of polarisabilities of ions in solids

    NASA Astrophysics Data System (ADS)

    Domene, C.; Fowler, P. W.; Madden, P. A.; Wilson, M.; Wheatley, R. J.

    1999-11-01

    A recently developed overlap model for exchange-induction is used to simulate in-crystal anion polarisabilities for alkali halides and chalcogenides (LiF, NaF, KF, LiCl, NaCl, KCl, LiBr, NaBr, KBr, MgO, CaO, SrO, MgS, CaS and SrS) in overall qualitative agreement with results of ab initio cluster calculations and experiment. Extension to AgF supports the proposal that crystal-field splitting causes significant enhancement of cation polarisability for d 10 systems, in contrast to the demonstrated insensitivity of s 2 and p 6 spherical cations.

  17. Effects of incident energy and angle on carbon cluster ions implantation on silicon substrate: a molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Wei, Ye; Sang, Shengbo; Zhou, Bing; Deng, Xiao; Chai, Jing; Ji, Jianlong; Ge, Yang; Huo, Yuanliang; Zhang, Wendong

    2017-09-01

    Carbon cluster ion implantation is an important technique in fabricating functional devices at micro/nanoscale. In this work, a numerical model is constructed for implantation and implemented with a cutting-edge molecular dynamics method. A series of simulations with varying incident energies and incident angles is performed for incidence on silicon substrate and correlated effects are compared in detail. Meanwhile, the behavior of the cluster during implantation is also examined under elevated temperatures. By mapping the nanoscopic morphology with variable parameters, numerical formalism is proposed to explain the different impacts on phrase transition and surface pattern formation. Particularly, implantation efficiency (IE) is computed and further used to evaluate the performance of the overall process. The calculated results could be properly adopted as the theoretical basis for designing nano-structures and adjusting devices’ properties. Project supported by the National Natural Science Foundation of China (Nos. 51622507, 61471255, 61474079, 61403273, 51502193, 51205273), the Natural Science Foundation of Shanxi (Nos. 201601D021057, 201603D421035), the Youth Foundation Project of Shanxi Province (Nos. 2015021097), the Doctoral Fund of MOE of China (No. 20131402110013), the National High Technology Research and Development Program of China (No. 2015AA042601), and the Specialized Project in Public Welfare from The Ministry of Water Resources of China (Nos. 1261530110110).

  18. In situ encapsulation of germanium clusters in carbon nanofibers: high-performance anodes for lithium-ion batteries.

    PubMed

    Wang, Wei; Xiao, Ying; Wang, Xia; Liu, Bing; Cao, Minhua

    2014-10-01

    Alloyed anode materials for lithium-ion batteries (LIBs) usually suffer from considerable capacity losses during charge-discharge process. Herein, in situ-grown germanium clusters are homogeneously encapsulated into porous nitrogen-doped carbon nanofibers (N-CNFs) to form Ge/N-CNFs hybrids, using a facile electrospinning method followed by thermal treatment. When used as anode in LIBs, the Ge/N-CNFs hybrids exhibit excellent lithium storage performance in terms of specific capacity, cycling stability, and rate capability. The excellent electrochemical properties can be attributed to the unique structural features: the distribution of the germanium clusters, porous carbon nanofibers, and GeN chemical bonds all contribute to alleviating the large volume changes of germanium during the discharge-charge process, while at same time the unique porous N-CNFs not only increase the contact area between the electrode and the electrolyte, but also the conductivity of the hybrid. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Development of gas cluster ion beam surface treatments for reducing field emission and breakdown in RF cavities

    SciTech Connect

    Swenson, D R; Degenkolb, E; Wu, A T; Insepov, Z

    2006-11-01

    Sub-micron-scale surface roughness and contamination cause field emission that can lead to high voltage breakdown of electrodes, and these are limiting factors in the development of high gradient RF technology. We are studying various Gas Cluster Ion Beam (GCIB) treatments to smooth, clean, etch and/or chemically alter electrode surfaces to allow higher fields and accelerating gradients, and to reduce the time and cost of conditioning high voltage electrodes. For this paper, we have processed Nb, Stainless Steel, and Ti electrode materials using beams of Ar, O2, or NF3 +O2 clusters with accelerating potentials up to 35 kV. Using a Scanning Field Emission Microscope (SFEM), we have repeatedly seen a dramatic reduction in the number of field emission sites on Nb coupons treated with GCIB. Smoothing effects on Stainless steel and Ti substrates have been evaluated using AFM imaging and show that 200-nm wide polishing scratch marks are greatly attenuated. A 150-mm diameter GCIB treated stainless steel electrode has now shown virtually no DC field emission current at gradients over 20 MV/m.

  20. Role of isolated and clustered DNA damage and the post-irradiating repair process in the effects of heavy ion beam irradiation.

    PubMed

    Tokuyama, Yuka; Furusawa, Yoshiya; Ide, Hiroshi; Yasui, Akira; Terato, Hiroaki

    2015-05-01

    Clustered DNA damage is a specific type of DNA damage induced by ionizing radiation. Any type of ionizing radiation traverses the target DNA molecule as a beam, inducing damage along its track. Our previous study showed that clustered DNA damage yields decreased with increased linear energy transfer (LET), leading us to investigate the importance of clustered DNA damage in the biological effects of heavy ion beam radiation. In this study, we analyzed the yield of clustered base damage (comprising multiple base lesions) in cultured cells irradiated with various heavy ion beams, and investigated isolated base damage and the repair process in post-irradiation cultured cells. Chinese hamster ovary (CHO) cells were irradiated by carbon, silicon, argon and iron ion beams with LETs of 13, 55, 90 and 200 keV µm(-1), respectively. Agarose gel electrophoresis of the cells with enzymatic treatments indicated that clustered base damage yields decreased as the LET increased. The aldehyde reactive probe procedure showed that isolated base damage yields in the irradiated cells followed the same pattern. To analyze the cellular base damage process, clustered DNA damage repair was investigated using DNA repair mutant cells. DNA double-strand breaks accumulated in CHO mutant cells lacking Xrcc1 after irradiation, and the cell viability decreased. On the other hand, mouse embryonic fibroblast (Mef) cells lacking both Nth1 and Ogg1 became more resistant than the wild type Mef. Thus, clustered base damage seems to be involved in the expression of heavy ion beam biological effects via the repair process. © The Author 2015. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

  1. Role of isolated and clustered DNA damage and the post-irradiating repair process in the effects of heavy ion beam irradiation

    PubMed Central

    Tokuyama, Yuka; Furusawa, Yoshiya; Ide, Hiroshi; Yasui, Akira; Terato, Hiroaki

    2015-01-01

    Clustered DNA damage is a specific type of DNA damage induced by ionizing radiation. Any type of ionizing radiation traverses the target DNA molecule as a beam, inducing damage along its track. Our previous study showed that clustered DNA damage yields decreased with increased linear energy transfer (LET), leading us to investigate the importance of clustered DNA damage in the biological effects of heavy ion beam radiation. In this study, we analyzed the yield of clustered base damage (comprising multiple base lesions) in cultured cells irradiated with various heavy ion beams, and investigated isolated base damage and the repair process in post-irradiation cultured cells. Chinese hamster ovary (CHO) cells were irradiated by carbon, silicon, argon and iron ion beams with LETs of 13, 55, 90 and 200 keV µm−1, respectively. Agarose gel electrophoresis of the cells with enzymatic treatments indicated that clustered base damage yields decreased as the LET increased. The aldehyde reactive probe procedure showed that isolated base damage yields in the irradiated cells followed the same pattern. To analyze the cellular base damage process, clustered DNA damage repair was investigated using DNA repair mutant cells. DNA double-strand breaks accumulated in CHO mutant cells lacking Xrcc1 after irradiation, and the cell viability decreased. On the other hand, mouse embryonic fibroblast (Mef) cells lacking both Nth1 and Ogg1 became more resistant than the wild type Mef. Thus, clustered base damage seems to be involved in the expression of heavy ion beam biological effects via the repair process. PMID:25717060

  2. Friction measurements of nanometer-thick lubricant films using ultra-smooth sliding pins treated with gas cluster ion beam

    NASA Astrophysics Data System (ADS)

    Lu, Renguo; Zhang, Hedong; Mitsuya, Yasunaga; Fukuzawa, Kenji; Itoh, Shintaro

    2013-09-01

    Friction properties of nanometer-thick lubricant films confined between two ultra-smooth solid surfaces are crucial to the practical performance of technologically advanced mechanical devices such as micro-electro-mechanical systems and hard disk drives. In this work, we applied argon gas cluster ion beam (Ar-GCIB) treatments to obtain ultra-smooth sliding pins for pin-on-disk tests of nanometer-thick perfluoropolyether (PFPE) lubricant films coated on magnetic disk surfaces. The GCIB treatments effectively smoothed the pin surfaces, and increases in the Ar dose decreased surface roughness. An ultra-smooth surface with a maximum peak height (Rp) less the monolayer lubricant film thickness was achieved when the Ar dose was increased to 8 × 1016 ions/cm2. We observed that both surface roughness and film thickness affected the friction coefficients of the PFPE films. To quantitatively describe the interplay of surface roughness and film thickness, we introduced two roughness characteristics: the ratio of film thickness to the surface’s root-mean-square roughness (h/σ), and a surface-pattern parameter (γ), defined as the ratio of correlation lengths in two orthogonal directions. We infer that a fixed γ and higher h/σlead to lower friction coefficients, while a fixed h/σand higher γ induce higher friction coefficients.

  3. Coupling between whistler waves and ion-scale solitary waves: cluster measurements in the magnetotail during a substorm.

    PubMed

    Tenerani, A; Le Contel, O; Califano, F; Pegoraro, F; Robert, P; Cornilleau-Wehrlin, N; Sauvaud, J A

    2012-10-12

    We present a new model of self-consistent coupling between low frequency, ion-scale coherent structures with high frequency whistler waves in order to interpret Cluster data. The idea relies on the possibility of trapping whistler waves by inhomogeneous external fields where they can be spatially confined and propagate for times much longer than their characteristic electronic time scale. Here we take the example of a slow magnetosonic soliton acting as a wave guide in analogy with the ducting properties of an inhomogeneous plasma. The soliton is characterized by a magnetic dip and density hump that traps and advects high frequency waves over many ion times. The model represents a new possible way of explaining space measurements often detecting the presence of whistler waves in correspondence to magnetic depressions and density humps. This approach, here given by means of slow solitons, but more general than that, is alternative to the standard approach of considering whistler wave packets as associated with nonpropagating magnetic holes resulting from a mirror-type instability.

  4. Equation-Of Coupled-Cluster Calculations of Photodetachment Cross Sections for Atomic Negative Ions across the Periodic Table

    NASA Astrophysics Data System (ADS)

    Ichino, Takatoshi; Cheng, Lan; Stanton, John F.

    2016-06-01

    The innovative application of the ion-trap technique by Wester and coworkers has yielded definitive experimental values of photodetachment cross sections for the atomic oxygen radical anion (Obullet -) [Hlavenka et al., J. Chem. Phys. 130, 061105 (2009)]. In the present study, equation-of-motion coupled-cluster (EOM-CC) calculations have been performed to derive theoretical values of photodetachment cross sections for the negative ions of atoms in the first two periods of the periodic table as well as of those which belong to the alkali metal and halogen groups. Two methods have been employed to derive the cross sections. One involves the Dyson orbitals obtained from EOM-CC calculations and plane wave functions for the detached electron in the transition dipole moment integrals. The other method utilizes the moment theory following EOM-CC calculations of transition dipole moments for a large number of pseudo-states. The cross sections so evaluated for Obullet - match the experimental values very well. Generally good agreement has been found between the theoretical and experimental values of the cross sections for the atoms in the first two periods, while the present calculations cast some doubt on reported experimental values for some atoms beyond the second period. Substantial relativistic effects on the cross section have been observed for heavy elements in the alkali metal and halogen groups.

  5. Carbon nanotube growth from catalytic nano-clusters formed by hot-ion-implantation into the SiO2/Si interface

    NASA Astrophysics Data System (ADS)

    Hoshino, Yasushi; Arima, Hiroki; Yokoyama, Ai; Saito, Yasunao; Nakata, Jyoji

    2012-07-01

    We have studied growth of chirality-controlled carbon nanotubes (CNTs) from hot-implantation-formed catalytic nano-clusters in a thermally grown SiO2/Si substrate. This procedure has the advantage of high controllability of the diameter and the number of clusters by optimizing the conditions of the ion implantation. In the present study, Co+ ions with ion dose of 8 × 1016 cm-2 are implanted in the vicinity of the SiO2/Si interface at 300 °C temperature. The implanted Co atoms located in the SiO2 layer has an amorphous-like structure with a cluster diameter of several nm. In contrast, implanted Co atoms in the Si substrate are found to take a cobalt silicide structure, confirmed by the high-resolution image of transmission electron microscope. CNTs are grown by microwave-plasma-enhanced chemical vapor deposition. We have confirmed a large amount of vertically-aligned multi-walled CNTs from the Co nano-clusters formed by the hot-ion-implantation near the SiO2/Si interface.

  6. Gas-Phase Reactions of Silver Cluster Ions Produced by Fast Atom Bombardment

    DTIC Science & Technology

    1992-03-20

    oxide , AgO, produces Ag.* clusters with x = 1 -9 and Ag.O , y = 1 and 2 (fig. 3). Similar spectra are obtained from FAB of Ag20 and from...Ag5 + Ethene AgL4+ NR a Ag31-6+ NR NR Propene AgL2’ AgL2+ Ag3L3 + NR NR 1 - Butene AgL2+ AgL2+ Ag3 1 -3 + Ag4L+ NR Cis-2- Butene AgL2+ AgL2+ Ag3 1 -3...C)4 0 S3 C 0 CC 0: o4:rC Figure 3 C CNC CNC I).6 ( x CN Cl + + N 000 1 ( N q N LON en C.C 0 CNC CYV) 0Y CC3 cv 0C) 0 C) C0 3 C

  7. Smoothing of Si{sub 0.7}Ge{sub 0.3} virtual substrates by gas-cluster-ion beam

    SciTech Connect

    Chen, H.; Chen, F.; Wang, X.M.; Yu, X.K.; Liu, J.R.; Ma, K.B.; Chu, W.K.; Cheng, H.H.; Yu, I.S.; Ho, Y.T.; Horng, K.Y.

    2005-09-05

    The planarization of the SiGe virtual substrate surface is crucial for the fabrication of high-performance strained-Si metal-oxide-semiconductor field-effect transistors. In this letter, we report on the smoothing of the inherently crosshatched rough surfaces of SiGe deposited by molecular beam epitaxy on Si substrates by gas cluster ion beams. Atomic force microscopy measurements show that the average surface roughness (R{sub a}) of the SiGe layer could be reduced considerably from 3.2 to 0.7 nm without any crosshatched pattern. Rutherford backscattering in combination with channeling was used to study the damage produced by cluster bombardment. No visible surface damage was observed for the normal-incidence smoothed SiGe with postsmoothing glancing angle cluster ion beam etching.

  8. RCCPAC: A parallel relativistic coupled-cluster program for closed-shell and one-valence atoms and ions in FORTRAN

    NASA Astrophysics Data System (ADS)

    Mani, B. K.; Chattopadhyay, S.; Angom, D.

    2017-04-01

    We report the development of a parallel FORTRAN code, RCCPAC, to solve the relativistic coupled-cluster equations for closed-shell and one-valence atoms and ions. The parallelization is implemented through the use of message passing interface, which is suitable for distributed memory computers. The coupled-cluster equations are defined in terms of the reduced matrix elements, and solved iteratively using Jacobi method. The ground and excited states of coupled-cluster wave functions obtained from the code could be used to compute different properties of closed-shell and one-valence atom or ion. As an example we compute the ground state correlation energy, attachment energies, E1 reduced matrix elements and hyperfine structure constants.

  9. ToF-SIMS and laser-SNMS analysis of Madin-Darby canine kidney II cells with silver nanoparticles using an argon cluster ion beam.

    PubMed

    Nees, Ricarda; Pelster, Andreas; Körsgen, Martin; Jungnickel, Harald; Luch, Andreas; Galla, Hans-Joachim; Arlinghaus, Heinrich F

    2015-06-15

    The use of nanoparticles is one of the fastest expanding fields in industrial as well as in medical applications, owing to their remarkable characteristics. Silver nanoparticles (AgNPs) are among the most-commercialized nanoparticles because of their antibacterial effects. Laser postionization secondary neutral mass spectrometry (laser-SNMS) and time-of-flight secondary ion mass spectrometry in combination with argon cluster ion sputtering was used for the first time to investigate the effects of AgNPs on Madin-Darby canine kidney (MDCK) II cells. Depth profiles and high-resolution three dimensional (3D) images of nanoparticles and organic compounds from cells were obtained using an Ar cluster ion beam for sputtering and Bi3 (+) primary ions for the analysis. The 3D distribution of AgNPs and other organic compounds in MDCK II cells could be readily detected with very high efficiency, sensitivity, and submicron lateral resolution. The argon cluster ion beam is well suited for the sputtering of biological samples. It enables a high sample removal rate along with low molecular degradation. The outer membrane, the cytoplasm, and the nuclei of the cells could be clearly visualized using the signals PO(+) and C3H8N(+) or CN(+) and C3H8N(+). The laser-SNMS images showed unambiguously that AgNPs are incorporated by MDCK II cells and often form silver aggregates with a diameter of a few micrometers, mainly close to the outside of the cell nuclei.

  10. Bistable regulation of integrin adhesiveness by a bipolar metal ion cluster.

    PubMed

    Chen, JianFeng; Salas, Azucena; Springer, Timothy A

    2003-12-01

    Integrin alpha(4)beta(7) mediates rolling adhesion in Ca(2+) and Ca(2+) + Mg(2+), and firm adhesion in Mg(2+) and Mn(2+), mimicking the two key steps in leukocyte accumulation in inflamed vasculature. We mutated an interlinked linear array of three divalent cation-binding sites present in integrin beta-subunit I-like domains. The middle, metal ion-dependent adhesion site (MIDAS) is required for both rolling and firm adhesion. One polar site, that adjacent to MIDAS (ADMIDAS), is required for rolling because its mutation results in firm adhesion. The other polar site, the ligand-induced metal binding site (LIMBS), is required for firm adhesion because its mutation results in rolling. The LIMBS mediates the positive regulatory effects of low Ca(2+) concentrations, whereas the ADMIDAS mediates the negative regulatory effects of higher Ca(2+) concentrations, which are competed by Mn(2+). The bipolar sites thus stabilize two alternative phases of adhesion.

  11. Rare-gas clusters in intense VUV, XUV and soft x-ray pulses: signatures of the transition from nanoplasma-driven cluster expansion to Coulomb explosion in ion and electron spectra

    NASA Astrophysics Data System (ADS)

    Arbeiter, Mathias; Fennel, Thomas

    2011-05-01

    We investigate the wavelength-dependent ionization, heating, and expansion dynamics of medium-sized rare-gas clusters (Ar923) under intense femtosecond short-wavelength free-electron laser pulses by quasi-classical molecular dynamics simulations. A comparison of the interaction dynamics for pulses with planckω=20, 38 and 90 eV photon energy at fixed total excitation energy indicates a smooth transition from plasma-driven cluster expansion, where predominantly surface ions are expelled by hydrodynamic forces, to quasi-electrostatic behavior with almost pure Coulomb explosion. Corresponding signatures in the time-dependent cluster dynamics, as well as in the final ion and electron spectra, corroborate that this transition is linked to a crossover in the electron emission processes. The resulting signatures in the electron spectra are shown to be even more reliable for identifying the cluster expansion mechanisms than ion energy spectra. It is shown that the prevailing ionization mechanism and the dominant expansion process can be roughly estimated by a simple frustration parameter.

  12. Structure and dynamics of Cl - (H2O)20 clusters: The effect of the polarizability and the charge of the ion

    NASA Astrophysics Data System (ADS)

    Perera, Lalith; Berkowitz, Max L.

    1992-06-01

    The effect of the polarizability and the sign of the ionic charge were studied in Cl-(H2O)20 clusters using molecular dynamics computer simulation technique. From our simulations we concluded that the reduction in the ionic polarizability did not significantly change the structure and dynamics of the Cl-(H2O)20 cluster, but the inversion of the sign of the ionic charge produced a large effect. The energetic considerations helped us to understand why Cl- is located on the surface of the cluster. By being on the surface the anion permits the creation of the hydrogen bonded network between water molecules and that lowers the total energy of the cluster. Simulations with the inverted sign of the ionic charge correspond to that with a hypothetical ``Cl+ '' ion which is similar in size and polarizability to a Cs+ ion. The dynamical structures and the quenched structures of Cl+(H2O)20 clusters are compared with the idealized structure of the Cs+(H2O)20 cluster proposed recently [A. Selinger and A. W. Castleman, Jr., J. Phys. Chem. 95, 8442 (1991)].

  13. Structure and dynamics of Cl(H2O)20 clusters. The effect of the polarizability and the charge ofthe ion

    NASA Astrophysics Data System (ADS)

    Perera, L.; Berkowitz, M.

    1992-05-01

    The effect of the polarizability and the sign of the ionic charge were studied in Cl(H2O)20 clusters using a molecular dynamics computer simulation technique. From our simulations, we concluded that the reduction in the ionic polarizability did not significantly change the structure and dynamics of Cl7(H2O)20 cluster, but the inversion of the sign of the ionic charge produced a large effect. The energetic considerations helped us to understand why Cl is located on the surface of the cluster. By being on the surface, the anion permits the creation of the hydrogen bonded network between water molecules and that lowers the total energy of the cluster. Simulations with the inverted sign of the ionic charge correspond to that with a hypothetical Cl ion which is similar in size and polarizability to a Cs+ ion. The dynamical structures and the quenched structures of Cl(H2O)20 clusters are compared with the idealized structure of Cs+(H2O)20 cluster proposed recently (A. Selinger and A. W. Castleman, Jr., J. Phys Chem. 95, 8442 (1991)).

  14. When Like Charged Ions Attract in Ionic Liquids: Controlling the Formation of Cationic Clusters by the Interaction Strength of the Counterions.

    PubMed

    Strate, Anne; Niemann, Thomas; Michalik, Dirk; Ludwig, Ralf

    2017-01-09

    The properties of ionic liquids are described by a subtle balance between Coulomb interaction, hydrogen bonding, and dispersion forces. We show that lowering the attractive Coulomb interaction by choosing weakly coordinating anions leads to the formation of cationic clusters. These clusters of like-charged ions are stabilized by cooperative hydrogen bonding and controlled by the interaction potential of the anion. IR and NMR spectroscopy combined with computational methods are used to detect and characterize these unusual, counter-intuitively formed clusters. They can be only observed for weakly coordinating anions. When cationic clusters are formed, cyclic tetramers are particularly stable. Therein, cooperative hydrogen-bond attraction can compete with like-charge repulsion. We present a simple but effective spectroscopic scale for the possibility of like-charge attraction in ionic liquids, based on IR and NMR signatures.

  15. Fluorohydrogenate Cluster Ions in the Gas Phase: Electrospray Ionization Mass Spectrometry of the [1-Ethyl-3-methylimidazolium+][F(HF)2.3–] Ionic Liquid

    SciTech Connect

    Gary S. Groenewold; James E. Delmore; Michael T. Benson; Tetsuya Tsuda; Rika Hagiwara

    2013-12-01

    Electrospray ionization of the fluorohydrogenate ionic liquid [1-ethyl-3-methylimidazolium][F(HF)2.3] ionic liquid was conducted to understand the nature of the anionic species as they exist in the gas phase. Abundant fluorohydrogenate clusters were produced; however, the dominant anion in the clusters was [FHF-], and not the fluoride-bound HF dimers or trimers that are seen in solution. Density functional theory (DFT) calculations suggest that HF molecules are bound to the clusters by about 30 kcal/mol. The DFT-calculated structures of the [FHF-]-bearing clusters show that the favored interactions of the anions are with the methynic and acetylenic hydrogen atoms on the imidazolium cation, forming planar structures similar to those observed in the solid state. A second series of abundant negative ions was also formed that contained [SiF5-] together with the imidazolium cation and the fluorohydrogenate anions that originate from reaction of the spray solution with silicate surfaces.

  16. Infrared Predissociation Spectra of Cl^-(CH_3OH)_nAr Cluster Ions, n=1-3

    NASA Astrophysics Data System (ADS)

    Beck, Jordan P.; Lisy, James M.

    2010-06-01

    Infrared predissociation spectra of Cl^-(CH_3OH)_nAr and Cl^-(CH_3OD)_nAr, n=1-3, will be presented and discussed in terms of isomer trapping and cooperative enhancement of hydrogen bonds. Due to the strong ionic hydrogen bonds between the chloride ion and methanol, spectra with d_1-methanol were obtained to distinguish between CH stretches and hydrogen-bonded OH features. For Cl^-(CH_3OH)_1Ar, the ionic hydrogen bond shifts the OH stretch -584 cm-1 from the gas-phase value of neutral methanol, which is slightly larger than the shift reported for the non-argonated, Cl^-(CH_3OH)_1 cluster. A methanol\\cdotsmethanol hydrogen bond was observed as the dominant feature in the n=2 spectrum. For n=3, we observe three isomers, including a methanol trimer chain which is calculated to be approximately 9 kJ/mol above the minimum-energy isomer. The cooperative effects of hydrogen bonding are pronounced in the n=2-3 spectra. The largest effect comes in the methanol trimer chain where the ionic hydrogen bond results in a shift of the OH stretch of -364 cm-1 compared to the n=1 structure, or in comparison to neutral methanol, a remarkable -948 cm-1 shift. These results indicate that high-energy isomers which exhibit very strong hydrogen bonds can be readily formed by introducing Cl^- into cold, argonated methanol clusters. O. M. Cabarcos, C. J. Weinheimer, T. J. Martinez and J. M. Lisy, J. Chem. Phys. 1999, 110, 9516-9526.

  17. Stabilities and structures in cluster ions of five-membered heterocyclic compounds containing O, N, and S atoms

    SciTech Connect

    Hiraoka, K.; Takimoto, H.; Yamabe, S.

    1987-11-25

    Clustering and hydration reactions of protonated and radical cations of heterocyclic compounds, e.g., furan, tetrahydrofuran, pyrrole, pyrrolidine, thiophene, and tetrahydrothiophene, have been studied using a pulsed electron beam mass spectrometer. The bond energies of proton-held dimer cations for furan, pyrrole, and thiophene are much smaller than those for tetrahydrofuran, pyrrolidine, and tetrahydrothiophene, respectively. This result suggests that not the heteroatoms but the ..cap alpha.. carbon atoms are protonated for furan, pyrrole, and thiophene. The hydrogen-bond site for the protonated furan and thiophene is calculated to be the unprotonated ..cap alpha.. hydrogen (C-H/sub ..cap alpha../ adjacent to the heteroatom) which is the most acidic one. On the other hand, the N-H hydrogen is the best hydrogen-bond site for the protonated pyrrole. It was found that the radical-cations dimers have greater bond energies than the proton-held dimer cations for furan and thiophene. This suggests that the bonds of the former have more covalent nature. Some unique reactions of C/sub 4/H/sub 4/O/sup .+/ and C/sub 4/H/sub 5/O/sup +/ with a furan molecule were observed. With an increase of temperature, the ions with m/z which are the same as those for (C/sub 4/H/sub 4/O)/sub 2//sup .+/ and H/sup +/(C/sub 4/H/sub 4/O)/sub 2/ are found to be formed at the expense of C/sup 4/H/sub 4/O/sup .+/ and C/sub 4/H/sub 5/O/sup +/ ions, respectively. It is suggested that the reactions observed are Diels-Alder type condensation reactions.

  18. A statistical study of magnetospheric ion composition along the geomagnetic field using the Cluster spacecraft for L values between 5.9 and 9.5

    NASA Astrophysics Data System (ADS)

    Sandhu, J. K.; Yeoman, T. K.; Fear, R. C.; Dandouras, I.

    2016-03-01

    Using ion density data obtained by the CODIF (ion Composition and Distribution Function analyser) instrument on board the Cluster spacecraft, for the interval spanning 2001-2005, an empirical model describing the average ion mass distribution along closed geomagnetic field lines is determined. The empirical model describes the region spanning 5.9≤L < 9.5, with dependences on L shell and magnetic local time included, and represents ions in the energy range of 0.025 to 40 keV/charge. The data reduction process involves the identification and rejection of CODIF data contaminated by penetrating energetic radiation belt particles, found to frequently occur for L < 5.9. Furthermore, a comparison of data with observations of the cold plasma population in the region provides evidence that the CODIF data set is representative of the full plasma population. The variations in average ion mass along the field lines were modeled using a power law form, which maximizes toward the magnetic equatorial plane, with observed power law index values ranging between approximately -2.0 and 0.0. The resulting model illustrates some key features of the average ion mass spatial distribution, such as an average ion mass enhancement at low L in the evening sector, indicating the transport of high-latitude heavy ion outflows to the closed inner magnetosphere.

  19. Generation of new Agm Ten clusters via laser ablation synthesis using Ag-Te nano-composite as precursor. Quadrupole ion trap time-of-flight mass spectrometry.

    PubMed

    Mawale, Ravi Madhukar; Amato, Filippo; Alberti, Milan; Havel, Josef

    2014-12-30

    Silver tellurides find applications in the development of infrared detection, imaging, magnetics, sensors, memory devices, and optic materials. However, only a limited number of silver tellurides have been described to date. Laser ablation synthesis (LAS) was selected to generate new Ag-Te clusters. Isothermal adsorption was used to study the formation of silver nano-particles-tellurium aggregates. Laser desorption ionization quadrupole ion trap time-of-flight mass spectrometry (LDI-QIT-TOFMS) was used for the generation and analysis of Agm Ten clusters. Scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to visualize the structure of materials. The stoichiometry of the generated clusters was determined by computer modeling of isotopic patterns. A simple, one-pot method for the preparation of Ag-Te nano-composite was developed and found suitable for LAS of silver tellurides. The LDI of Ag-Te nano-composite leads to the formation of 11 unary and 52 binary clusters. The stoichiometry of the 34 novel Agm Ten clusters is reported here for the first time. LAS with TOFMS detection was proven to be a powerful technique for the generation of silver telluride clusters. Knowledge of the stoichiometry of the generated clusters might facilitate the further development of novel high-tech silver tellurium nano-materials. Copyright © 2014 John Wiley & Sons, Ltd.

  20. Large O2 Cluster Ions as Sputter Beam for ToF-SIMS Depth Profiling of Alkali Metals in Thin SiO2 Films.

    PubMed

    Holzer, Sabine; Krivec, Stefan; Kayser, Sven; Zakel, Julia; Hutter, Herbert

    2017-02-21

    A sputter beam, consisting of large O2 clusters, was used to record depth profiles of alkali metal ions (Me(+)) within thin SiO2 layers. The O2 gas cluster ion beam (O2-GCIB) exhibits an erosion rate comparable to the frequently used O2(+) projectiles. However, because of its high sputter yield the necessary beam current is considerably lower (factor 50), resulting in a decreased amount of excess charges at the SiO2 surface. Hence, a reduced electric field is obtained within the remaining dielectric layer. This drastically mitigates the Me(+) migration artifact, commonly observed in depth profiles of various dielectric materials, if analyzed by time-of-flight secondary ion mass spectrometry (ToF-SIMS) in dual beam mode. It is shown, that the application of O2-GCIB results in a negligible residual ion migration for Na(+) and K(+). This enables artifact-free depth profiling with high sensitivity and low operational effort. Furthermore, insight into the migration behavior of Me(+) during O2(+) sputtering is given by switching the sputter beam from O2(+) to O2 clusters and vice versa. K(+) is found to be transported through the SiO2 layer only within the proceeding sputter front. For Na(+) a steadily increasing fraction is observed, which migrates through the unaffected SiO2 layer toward the adjacent Si/SiO2 interface.

  1. Melatonin protects human cells from clustered DNA damages, killing and acquisition of soft agar growth induced by X-rays or 970 MeV/n Fe ions.

    PubMed

    Das, Birajalaxmi; Bennett, Paula V; Cutter, Noelle C; Sutherland, John C; Sutherland, Betsy M

    2011-06-01

    We tested the ability of melatonin (N-acetyl-5 methoxytryptamine), a highly effective radical scavenger and human hormone, to protect DNA in solution and in human cells against induction of complex DNA clusters and biological damage induced by low or high linear energy transfer radiation (100 kVp X-rays, 970 MeV/nucleon Fe ions). Plasmid DNA in solution was treated with increasing concentrations of melatonin (0.0-3.5 mM) and were irradiated with X-rays. Human cells (28SC monocytes) were also irradiated with X-rays and Fe ions with and without 2 mM melatonin. Agarose plugs containing genomic DNA were subjected to Contour Clamped Homogeneous Electrophoretic Field (CHEF) followed by imaging and clustered DNA damages were measured by using Number Average length analysis. Transformation experiments on human primary fibroblast cells using soft agar colony assay were carried out which were irradiated with Fe ions with or without 2 mM melatonin. In plasmid DNA in solution, melatonin reduced the induction of single- and double-strand breaks. Pretreatment of human 28SC cells for 24 h before irradiation with 2 mM melatonin reduced the level of X-ray induced double-strand breaks by ∼50%, of abasic clustered damages about 40%, and of Fe ion-induced double-strand breaks (41% reduction) and abasic clusters (34% reduction). It decreased transformation to soft agar growth of human primary cells by a factor of 10, but reduced killing by Fe ions only by 20-40%. Melatonin's effective reduction of radiation-induced critical DNA damages, cell killing, and striking decrease of transformation suggest that it is an excellent candidate as a countermeasure against radiation exposure, including radiation exposure to astronaut crews in space travel.

  2. Melatonin Protects Human Cells from Clustered DNA Damages, Killing and Acquisition of Soft Agar Growth Induced by X-rays or 970 MeV/n Fe ions

    SciTech Connect

    Das, B.; Sutherland, B.; Bennett, P. V.; Cutter, N. C.; Sutherland, J. C.

    2011-06-01

    We tested the ability of melatonin (N-acetyl-5 methoxytryptamine), a highly effective radical scavenger and human hormone, to protect DNA in solution and in human cells against induction of complex DNA clusters and biological damage induced by low or high linear energy transfer radiation (100 kVp X-rays, 970 MeV/nucleon Fe ions). Plasmid DNA in solution was treated with increasing concentrations of melatonin (0.0-3.5 mM) and were irradiated with X-rays. Human cells (28SC monocytes) were also irradiated with X-rays and Fe ions with and without 2 mM melatonin. Agarose plugs containing genomic DNA were subjected to Contour Clamped Homogeneous Electrophoretic Field (CHEF) followed by imaging and clustered DNA damages were measured by using Number Average length analysis. Transformation experiments on human primary fibroblast cells using soft agar colony assay were carried out which were irradiated with Fe ions with or without 2 mM melatonin. In plasmid DNA in solution, melatonin reduced the induction of single- and double-strand breaks. Pretreatment of human 28SC cells for 24 h before irradiation with 2 mM melatonin reduced the level of X-ray induced double-strand breaks by {approx}50%, of abasic clustered damages about 40%, and of Fe ion-induced double-strand breaks (41% reduction) and abasic clusters (34% reduction). It decreased transformation to soft agar growth of human primary cells by a factor of 10, but reduced killing by Fe ions only by 20-40%. Melatonin's effective reduction of radiation-induced critical DNA damages, cell killing, and striking decrease of transformation suggest that it is an excellent candidate as a countermeasure against radiation exposure, including radiation exposure to astronaut crews in space travel.

  3. A Comparative High-Resolution Electron Microscope Study of Ag Clusters Produced by a Sputter-Gas Aggregation and Ion Cluster Beam Technique

    NASA Astrophysics Data System (ADS)

    Hohl, Georg-Friedrich; Hihara, Takehiko; Sakurai, Masaki; Oishi, Takashi; Wakoh, Kimio; Sumiyama, Kenji; Suzuki, Kenji

    1994-03-01

    Ag clusters were formed by a sputter-gas-aggregation process [H. Haberland et al..: J. Vac. Sci. Technol. A 10 (1992) 3266] and the ionized cluster beam (ICB) [T. Takagi: Ionized-Cluster Beam Deposition and Epitaxy (Noyes, Park Ridge, 1988)] technique. The Ag clusters deposited on collodion-coated microgrids were investigated by high-resolution transmission electron microscopy. The diameter of those clusters, d, ranges from 1 nm up to about 10 nm for specimens produced by the sputter-gas aggregation technique, depending on the sputter condition and the deposition time. Comparable times of the ICB deposition lead to a broader distribution up to d≈20 nm, suggesting the formation of islands with extremely flat shapes. High percentages of crystalline particles obtained by both techniques are either single crystals or multiple twins with clear lattice images.

  4. Hydrothermal synthesis and crystal structural characterization of two new modified polyoxometalates constructed of positive and negative metal oxo cluster ions

    NASA Astrophysics Data System (ADS)

    Sun, Ying-Hua; Xu, Ji-Qing; Ye, Ling; Cui, Xiao-Bing; Li, Yong; Yu, Hai-Hui; Li, Guang-Hua; Yang, Guang-Di; Chen, Yan

    2005-04-01

    Two new interesting polyoxometalate derivatives {[HO]2[Mo3VMo5VIV8IVO(PO)]}{[O]2[Mo3VMo5VIV8IVO(PO)]}·5HO1 and {[HO]4[Mo4VMo4VIV8IVO(PO)]}{[HO]2[Mo3VMo5VIV8IVO(PO)]}(HO)·4HO2 constructed of modified metal-oxo cluster ions carrying positive and negative changes, respectively, was hydrothermally prepared and structurally characterized by IR, ESR, XPS, elemental analysis and X-ray crystallography. The result of structure determination shows that compound 1 and 2 are isostructural and both contain polyoxocation and polyoxoanion, and both cation and anion are built on mixed Mo-V tetra-capped pseudo-Keggin units with P centre, [Mo 8V 8O 40(PO 4)] n- , bonded to four or two [Ni(2,2'-bipy) 2H 2O] 2+ complexes, respectively, via terminal oxygen of the capping V atoms. Magnetism measurement indicates that there exists antiferromagnetic interaction in complex 1 and 2.

  5. Molecular Beam Epitaxy on Gas Cluster Ion Beam Prepared GaSb Substrates: Towards Improved Surfaces and Interfaces

    SciTech Connect

    Krishnaswami, Kannan; Shivashankar, Vangala; Dauplaise, Helen; Allen, Lisa; Dallas, Gordon; Bakken, Daniel; Bliss, David; Goodhue, William

    2008-04-01

    A key problem in producing mid-infrared optoelectronic and low-power electronic devices in the GaSb material system is the lack of substrates with appropriate surfaces for epitaxial growth. Chemical mechanical polishing (CMP) of GaSb results in surface damage accompanied by tenacious oxides that do not easily desorb. To overcome this, we have developed a process using gas cluster ion beams (GCIB) to remove surface damage and produce engineered surface oxides. In this paper, we present surface modification results on GaSb substrates using O2-, CF4/O2-, and HBr-GCIB processes. X-ray photoelectron spectroscopy of GCIB produced surface layers showed the presence of mixed Ga- and Sb-oxides, with mostly Ga-oxides at the interface, desorbing at temperatures ranging 530°C to 560°C. Cross-sectional transmission electron microscopy of molecular beam epitaxy grown GaSb/AlGaSb layers showed that GCIB surfaces yielded smooth defect free substrate to epi transitions as compared to CMP surfaces. Furthermore, HBr-GCIB surfaces exhibited neither dislocation layers nor discernable interfaces, indicating complete oxide desorbtion prior to epigrowth on a clean single crystal template. Atomic force microscopy of GCIB epilayers exhibited smooth surfaces with characteristic step-terrace formations comprising monatomic steps and wide terraces. The HBr-GCIB process can be easily adapted to a large scale manufacturing process for epi-ready GaSb.

  6. Observational Study of Ion Diffusion Region tailward of the Cusp: Polar and Cluster Observations in 1998-2008

    NASA Astrophysics Data System (ADS)

    Muzamil, F. M.; Farrugia, C. J.; Torbert, R. B.; Argall, M. R.; Wang, S.

    2015-12-01

    Asymmetries in plasma density and the presence of a guide field significantly alter the structure of the ion diffusion region (IDR) in symmetric, collisionless reconnection. These features have been shown by numerical simulations under moderate density asymmetries (~10), and theoretical analyses. However, very few studies have addressed these issues with in-situ observations. We have compiled a collection of Cluster and Polar crossings of the high-latitude magnetopause poleward of the cusp under northward interplanetary magnetic field in the years 1998-2008 when signatures of reconnection inside the IDR are observed. They encompass a wide range of density asymmetries (~10 to 1000), magnetic field asymmetries (~0.2 to 0.9), and guide fields (~10 to ~60 %). In this dedicated observational study, we target the following topics: (1) The alteration of the structure of the IDR -- i.e., its width, the non-colocation of stagnation and X-lines, jet outflow speed, and biasing of the reconnection outflow jet toward the magnetosphere -- as a function of increasing density asymmetry, and (2) the diamagnetic drift of the X-line. Further, focusing on IDR crossings during plasma flow reversals and/or near-simultaneous crossings on either side of the X-line by two spacecraft under steady ambient conditions, we report on the contrast in the Hall fields and the plasma behavior on the sunward versus the tailward sides of the X-line in its dependence on the strength of the guide field.

  7. The dynamics on migrations of Li + ion and Li atom at 700 K around the circumference of graphite cluster model: A direct molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Shimizu, Akira; Tachikawa, Hiroto

    2001-05-01

    For the diffusion species of Li + ion and Li atom stabilized at the same site of the circumference of the graphite, migration processes are simulated using the direct molecular orbital (MO) dynamics calculation on the hydrogen terminated cluster model, C54H18, at AM1 level. Although Li + forms ionic bond with two carbon atoms in the circumference, Li bonds covalently with one atom through sp3 hybrid orbital at 0 K. At 700 K, Li+ dissociated goes across the bulk and escapes from the cluster model after 0.6 ps. On the other hand, Li circulates only around the carbon atom, keeping the covalent bond.

  8. Absolute solvation free energy of Li{sup +} and Na{sup +} ions in dimethyl sulfoxide solution: A theoretical ab initio and cluster-continuum model study

    SciTech Connect

    Westphal, Eduard; Pliego, Josefredo R. Jr.

    2005-08-15

    The solvation of the lithium and sodium ions in dimethyl sulfoxide solution was theoretically investigated using ab initio calculations coupled with the hybrid cluster-continuum model, a quasichemical theory of solvation. We have investigated clusters of ions with up to five dimethyl sulfoxide (DMSO) molecules, and the bulk solvent was described by a dielectric continuum model. Our results show that the lithium and sodium ions have four and five DMSO molecules into the first coordination shell, and the calculated solvation free energies are -135.5 and -108.6 kcal mol{sup -1}, respectively. These data suggest a solvation free energy value of -273.2 kcal mol{sup -1} for the proton in dimethyl sulfoxide solution, a value that is more negative than the present uncertain experimental value. This and previous studies on the solvation of ions in water solution indicate that the tetraphenylarsonium tetraphenylborate assumption is flawed and the absolute value of the free energy of transfer of ions from water to DMSO solution is higher than the present experimental values.

  9. Photoinduced ion-pair formation in the (HI){sub m}(H{sub 2}O){sub n} cluster system

    SciTech Connect

    Dermota, T.E.; Hydutsky, D.P.; Bianco, N.J.; Castleman, A.W. Jr.

    2005-12-01

    The temporal behavior of the photoinduced ion-pair formation process in the (HI){sub m}(H{sub 2}O){sub n} (n=1-6 for m=1 and n=1-4 for m=2) cluster system has been studied via the coupling between the g {sup 3}{sigma}{sup -} Rydberg and V {sup 1}{sigma}{sup +} valence states. Comparison of the time constants obtained to those measured in previous experiments for the analogous process in HBr-water clusters, along with a detailed analysis of the signal intensity as a function of laser-pulse power, provides new insight into and confirmation of the previously proposed ion-pair formation mechanism.

  10. Investigation of defect clusters in ion-irradiated Ni and NiCo using diffuse X-ray scattering and electron microscopy

    SciTech Connect

    Olsen, Raina J.; Jin, Ke; Lu, Chenyang; Beland, Laurent K.; Wang, Lumin M.; Bei, Hongbin; Specht, Eliot D.; Larson, Bennett C.

    2016-01-01

    The nature of defect clusters in Ni and Ni$_{50}$Co$_{50}$ (NiCo) irradiated at room temperature with 2–16 MeV Ni ions is studied using asymptotic diffuse X-ray scattering and transmission electron microscopy (TEM). Analysis of the scattering data provides separate size distributions for vacancy and interstitial type defect clusters, showing that both types of defect clusters have a smaller size and higher density in NiCo than in Ni. Diffuse scattering results show good quantitative agreement with TEM results for cluster sizes greater than 4 nm diameter, but find that the majority of vacancy clusters are under 2 nm in NiCo, which, if not detected, would lead to the conclusion that defect density was actually lower in the alloy. Interstitial dislocation loops and stacking fault tetrahedra are identified by TEM. Lastly comparison of diffuse scattering lineshapes to those calculated for dislocation loops and SFTs indicates that most of the vacancy clusters are SFTs.

  11. Investigation of defect clusters in ion-irradiated Ni and NiCo using diffuse X-ray scattering and electron microscopy

    DOE PAGES

    Olsen, Raina J.; Jin, Ke; Lu, Chenyang; ...

    2016-01-01

    The nature of defect clusters in Ni and Nimore » $$_{50}$$Co$$_{50}$$ (NiCo) irradiated at room temperature with 2–16 MeV Ni ions is studied using asymptotic diffuse X-ray scattering and transmission electron microscopy (TEM). Analysis of the scattering data provides separate size distributions for vacancy and interstitial type defect clusters, showing that both types of defect clusters have a smaller size and higher density in NiCo than in Ni. Diffuse scattering results show good quantitative agreement with TEM results for cluster sizes greater than 4 nm diameter, but find that the majority of vacancy clusters are under 2 nm in NiCo, which, if not detected, would lead to the conclusion that defect density was actually lower in the alloy. Interstitial dislocation loops and stacking fault tetrahedra are identified by TEM. Lastly comparison of diffuse scattering lineshapes to those calculated for dislocation loops and SFTs indicates that most of the vacancy clusters are SFTs.« less

  12. Ion induced dipole clusters H(n)- (3 ≤ n-odd ≤ 13): density functional theory calculations of structure and energy.

    PubMed

    Huang, Lulu; Matta, Chérif F; Massa, Lou

    2011-11-17

    We investigate anew the possible equilibrium geometries of ion induced dipole clusters of hydrogen molecular ions, of molecular formula H(n)(-) (3 ≤ n-odd ≤ 13). Our previous publications [Sapse, A. M.; et al. Nature 1979, 278, 332; Rayez, J. C.; et al., J. Chem. Phys. 1981, 75, 5393] indicated these molecules would have a shallow minimum and adopt symmetrical geometries that accord with the valence shell electron pair repulsion (VSEPR) rules for geometries defined by electron pairs surrounding a central point of attraction. These earlier calculations were all based upon Hartree-Fock (HF) calculations with a fairly small basis of atomic functions, except for the H3(-) ion for which configuration interaction (CI) calculations were carried out. A related paper [Hirao, K.; et al., Chem. Phys. 1983, 80, 237] carried out similar calculations on the same clusters, finding geometries similar to our earlier calculations. However, although that paper argued that the stabilization energy of negative ion clusters H(n)(-) is small, vibration frequencies for the whole set of clusters was not reported, and so a definitive assertion of a true equilibrium was not present. In this paper we recalculate the energetics of the ion induced dipole clusters using density function theory (DFT) B3LYP method calculations in a basis of functions (6-311++G(d,p)). By calculating the vibration frequencies of the VSEPR geometries, we prove that in general they are not true minima because not all the resulting frequencies correspond to real values. By searching the energy surface of the B3LYP calculations, we find the true minimum geometries, which are surprising configurations and are perhaps counterintuitive. We calculate the total energy and binding energy of the new geometries. We also calculate the bond paths associated with the quantum theory of atoms in molecules (QTAIM). The B3LYP/6-311++G(d,p) results, for each molecule, deliver bond paths that radiate between each polarized H2

  13. Evidence for the encagement of alkali metal ions through the formation of gas-phase clathrates: Cs sup + in water clusters

    SciTech Connect

    Selinger, A.; Castleman, A.W. Jr. )

    1991-10-31

    Reported herein is the first evidence for the encagement of an atomic ion in a cluster leading to the formation of a gas-phase clathrate, namely Cs{sup +} contained within a complex comprised of 20 water molecules. Evidence is also presented for the encagement of Cs{sup +} by other (distorted) clathrates involving 18, 22, 24, 27 and 29 water molecules. All of these species were reduced under thermal reaction conditions in a fast-flow reactor.

  14. Long-term observations of cluster ion concentration, sources and sinks in clear sky conditions at the high-altitude site of the Puy de Dôme, France

    NASA Astrophysics Data System (ADS)

    Rose, C.; Boulon, J.; Hervo, M.; Holmgren, H.; Asmi, E.; Ramonet, M.; Laj, P.; Sellegri, K.

    2013-11-01

    Cluster particles (0.8-1.9 nm) are key entities involved in nucleation and new particle formation processes in the atmosphere. Cluster ions were characterized in clear sky conditions at the Puy de Dôme station (1465 m a.s.l.). The studied data set spread over five years (February 2007-February 2012), which provided a unique chance to observe seasonal variations of cluster ion properties at high altitude. Statistical values of the cluster ion concentrations and diameters are reported for both positive and negative polarities. Cluster ions were found to be ubiquitous at the Puy de Dôme and displayed an annual variation with lower concentrations in spring. Positive cluster ions were less numerous than negative, but were larger in diameter. Negative cluster ion properties were not sensitive to the occurrence of a new particle formation (NPF) event, while positive cluster ions appeared to be significantly more numerous and larger on event days. The parameters of the balance equation for the positive cluster concentration are reported separately for the different seasons and for the NPF event days and non-event days. The steady-state assumption suggests that the ionization rate is balanced with two sinks: the ion recombination and the attachment onto background aerosol particles, referred to as "aerosol ion sink". The aerosol ion sink was predominant compared to the recombination sink. The positive ionization rates derived from the balance equation (Qcalc) were well correlated with the ionization rates obtained from radon measurement (Qmeas). When ignoring the gamma radiation contribution to the ion production, Qcalc is on average higher than Qmeas during the warm season. In contrast, when a seasonal gamma contribution is taken into account, Qmeas always exceeds Qcalc. We found that neither the aerosol ion sink nor the ionization rate (calculated or measured, with or without the gamma contribution) were significantly different on event days compared to non-event days

  15. Polynuclear Bismuth Oxido Sulfonato Clusters, Polymers, and Ion Pairs from Bi2O3 under Mild Conditions.

    PubMed

    Senevirathna, Dimuthu C; Blair, Victoria L; Werrett, Melissa V; Andrews, Philip C

    2016-11-07

    Eight novel bismuth(III) sulfonato compounds have been synthesized and characterized using the sonochemical reaction of Bi2O3 with a range of sulfonic acids, including 2,5-dimethylbenzenesulfonic acid (2,5-DMSH), 2,4-dinitrobenzenesulfonic acid (2,4-DNSH), 2,5-dichlorobenzenesulfonic acid (2,5-DCSH), 1,2-benzenedisulfonic acid (1,2-BDSH2), 1,3-benzenedisulfonic acid (1,3-BDSH2), 2-sulfobenzoic acid (2-SBH2), 3-sulfobenzoic acid (3-SBH2), and 2-naphthalenesulfonic acid (NPSH). Six of the complexes (1, 2, 4, and 6-8) were structurally characterized through single-crystal X-ray crystallography. In the presence of the monosulfonic acids 2,5-DMSH, 2,4-DNSH, and 2,5-DCSH, polynuclear bismuth(III) oxido clusters were isolated: namely, [Bi6O4(OH)4(2,5-DMS)6(H2O)6]·10H2O (1·10H2O), [Bi6O4(OH)4(2,4-DNS)6(H2O)6]·6H2O (2·6H2O), and [Bi6O4(OH)4(2,5-DCS)6(H2O)6] (3). The disulfonic acid 1,3-BDSH2 also produced an oxido cluster: [Bi6O4(OH)4(1,3-BDS)3]·8H2O (5·8H2O). The remaining diacid ligands (1,2-BDSH2, 2-SBH2, and 3-SBH2), upon reaction with Bi2O3, produced polymeric Bi(III) sulfonato complexes: namely [Bi(1,2-BDS)(OH)(H2O)2]∞ (4), [Bi(2-SB)(2-SBH)H2O]∞·2H2O (6·2H2O), and [NH2(Me)2]2[Bi2(3-SB)4]∞ (7). The larger NPSH ligand produced the monomeric contact ion pair [Bi(NPS)2(H2O)6][NPS]·3H2O (8·3H2O), upon sonication with Bi2O3.

  16. Control of metal-ion composition in the synthesis of ternary II-II'-VI nanoparticles by using a mixed-metal cluster precursor approach.

    PubMed

    DeGroot, Marty W; Rösner, Harald; Corrigan, John F

    2006-02-01

    The ternary molecular nanoclusters [Zn(x)Cd(10-x)Se4(SePh)12(PnPr3)4] (x = 1.8, 1 a; x = 2.6, 1 b) were employed as single-source precursors for the synthesis of high-quality hexagonal Zn(x)Cd(1-x)Se nanocrystals. The tellurium clusters [Zn(x)Cd(10-x)Te4(TePh)12(PnPr3)4] (x = 1.8, 2 a; x = 2.6, 2 b) are equally convenient precursors for the synthesis cubic Zn(x)Cd(1-x)E nanoparticles. The thermolysis of the cluster molecules in hexadecylamine provides an efficient system in which the inherent metal-ion stoichiometry of the clusters is retained in the nanocrystalline products, whilst also affording control of particle size within the 2-5 nm range. In all cases, the nanoparticles are monodisperse, and luminescence spectra exhibit emission energies close to the absorption edge. Analysis of the optical spectra and X-ray diffraction patterns of these materials indicates a metal-ion concentration gradient within the structures of the nanocrystals, with Zn(II) ions predominantly located near the surface of the particles.

  17. Guided ion beam studies of the reactions of Con+ (n=1-18) with N2: Cobalt cluster mononitride and dinitride bond energies

    NASA Astrophysics Data System (ADS)

    Liu, Fuyi; Li, Ming; Tan, Lin; Armentrout, P. B.

    2008-05-01

    The reactions of Con+ (n=1-18) with N2 are measured as a function of kinetic energy over a range of 0-15eV in a guided ion beam tandem mass spectrometer. A variety of Com+, ComN+, and ComN2+ (m⩽n) product ions are observed, all in endothermic processes, with collision-induced dissociation dominating the products for all clusters. Bond dissociation energies for both cobalt cluster nitrides and dinitrides are derived from threshold analysis of the energy dependence of the endothermic reactions using several different approaches. These values show only a mild dependence on cluster size over the range studied, although the Co13+-N bond energy is relatively weak. The bond energies of Con+-N for larger clusters suggest that a reasonable value for the desorption energy of atomic nitrogen from bulk phase cobalt is 6.3±0.2eV, which is somewhat lower than the only available value in the literature, an estimate based on the enthalpy of formation of bulk cobalt nitride. The trends in the cobalt nitride thermochemistry are also compared to previously determined metal-metal bond energies, D0(Con+-Co), and to D0(Fen+-N). Implications for catalytic ammonia production using cobalt versus iron are discussed.

  18. A broader view on ion heating in traveling-wave devices using fragmentation of CsI clusters and extent of H˙ migration as molecular thermometers.

    PubMed

    Lermyte, Frederik; Sobott, Frank

    2017-09-08

    Electron transfer dissociation (ETD) is becoming increasingly important in mass spectrometry-based analysis of peptides and proteins. Supplemental collisional activation of undissociated electron transfer products can significantly increase fragmentation yield and sequence coverage, but hydrogen rearrangements - specifically, transfer of a hydrogen radical from a c to a z fragment - lead to distorted isotope distributions and increased potential for signal overlap. Concomitant collisional activation during the ion/ion reaction significantly reduces these rearrangements, but, in ion traps, also leads to lower reaction rates and reduced overlap of anion and cation clouds. In traveling-wave ion mobility devices, it has been reported - although not under ETD conditions - that significant ion activation can occur depending on the T-wave height and velocity. Here, we investigate this phenomenon in more detail using a commercial instrument (Waters Synapt G2) and report that a similar effect can be induced within the traveling-wave Trap cell where the ETD reaction occurs, using fairly typical T-wave settings. This ion 'heating' is demonstrated by analyzing the observed isotope distributions (sensitive to the aforementioned hydrogen rearrangements) of ETD fragments of ubiquitin and substance P. A more detailed investigation of ion activation using cesium iodide clusters (without ETD reagent anions present) shows that the observed behavior is consistent with the known dynamics of ions within traveling-wave devices. The insights gained in this work are potentially relevant both for 'native ETD' studies (in which tuning needs to be optimized to avoid unintentional ion activation) as well as the design of future T-wave ETD devices (where this 'heating' effect might be exploited to promote fragment release).

  19. Accurate argon cluster-ion sputter yields: Measured yields and effect of the sputter threshold in practical depth-profiling by x-ray photoelectron spectroscopy and secondary ion mass spectrometry

    SciTech Connect

    Cumpson, Peter J.; Portoles, Jose F.; Barlow, Anders J.; Sano, Naoko

    2013-09-28

    Argon Gas Cluster-Ion Beam sources are likely to become widely used on x-ray photoelectron spectroscopy and secondary ion mass spectrometry instruments in the next few years. At typical energies used for sputter depth profiling the average argon atom in the cluster has a kinetic energy comparable with the sputter threshold, meaning that for the first time in practical surface analysis a quantitative model of sputter yields near threshold is needed. We develop a simple equation based on a very simple model. Though greatly simplified it is likely to have realistic limiting behaviour and can be made useful for estimating sputter yields by fitting its three parameters to experimental data. We measure argon cluster-ion sputter yield using a quartz crystal microbalance close to the sputter threshold, for silicon dioxide, poly(methyl methacrylate), and polystyrene and (along with data for gold from the existing literature) perform least-squares fits of our new sputter yield equation to this data. The equation performs well, with smaller residuals than for earlier empirical models, but more importantly it is very easy to use in the design and quantification of sputter depth-profiling experiments.

  20. Study of optical band gap, carbonaceous clusters and structuring in CR-39 and PET polymers irradiated by 100 MeV O 7+ ions

    NASA Astrophysics Data System (ADS)

    Ramola, R. C.; Chandra, Subhash; Negi, Ambika; Rana, J. M. S.; Annapoorni, S.; Sonkawade, R. G.; Kulriya, P. K.; Srivastava, A.

    2009-01-01

    Commercially purchased CR-39 and PET polymers were irradiated by 100 MeV O 7+ ions of varying fluences, ranging from 1×10 11 to 1×10 13 ions/cm 2. The effects of swift heavy ions (SHI) on the structural, optical and chemical properties of CR-39 and PET polymers were studied using X-ray diffraction (XRD), UV-visible spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The XRD patterns of CR-39 show that the intensity of the peak decreases with increasing ion fluence, which indicates that the semicrystalline structure of polymer changes to amorphous with increasing fluences. The XRD patterns of PET show a slight increase in the intensity of the peaks, indicating an increase in the crystallinity. The UV-visible spectra show the shift in the absorbance edge towards the higher wavelength, indicating the change in band gap. Band gap in PET and CR-39 found to be decrease from 3.87 to 2.91 and 5.3-3.5 eV, respectively. The cluster size also shows a variation in the carbon atoms per cluster that varies from 42 to 96 in CR-39 and from 78 to 139 in PET. The FTIR spectra show an overall reduction in intensity of the typical bands, indicating the degradation of polymers after irradiation.

  1. Effects of low concentrations of O2 and CO on the ion-clustering reactions in the lower ionosphere of Mars

    NASA Technical Reports Server (NTRS)

    Sieck, L. W.; Gorden, R., Jr.; Ausloos, P.

    1973-01-01

    It is demonstrated that under conditions which approximate those of the Martian ionosphere traces of CO and O2 can be effectively incorporated in ion clusters via ion-molecule reaction schemes initiated by the CO2(+) ion. For example, when 0.3% CO is added to CO2, (CO)2(+), and /(CO)2CO2/(+) appear as the major cations (584 A radiation, 300 K). In mixtures containing O2 in addition to CO, (CO2,O2+) and /(CO2)2O2/(+) are important species. A recently proposed mechanism to account for the low abundance of CO and O2 in the Martian atmosphere is discussed in the light of these observations.

  2. Rapid flame synthesis of internal Mo6+ doped TiO2 nanocrystals in situ decorated with highly dispersed MoO3 clusters for lithium ion storage

    NASA Astrophysics Data System (ADS)

    Li, Yunfeng; Hu, Yanjie; Shen, Jianhua; Jiang, Haibo; Min, Guoquan; Qiu, Shengjie; Song, Zhitang; Sun, Zhuo; Li, Chunzhong

    2015-11-01

    The rational design of nanoheterostructured materials has attracted much attention because of its importance for developing highly efficient LIBs. Herein, we have demonstrated that internal Mo6+ doped TiO2 nanocrystals in situ decorated with highly dispersed MoO3 clusters have been realized by a facile and rapid flame spray pyrolysis route for electrochemical energy storage. In such intriguing nanostructures, internal Mo6+ doping can improve the conductivity of electrode materials and facilitate rapid Li+ intercalation and ion transport and the heteroassembly of highly dispersed ultrafine MoO3 clusters with excellent electrochemical activity endows the TiO2 with extra Li+ ion storage ability as well as incorporates Mo6+. Thus, the as-prepared nanohybrid electrodes exhibit a high specific capacity and superior rate capability due to the maximum synergetic effect of TiO2, Mo6+ and ultrafine MoO3 clusters. Moreover, the aerosol flame process with a unique temperature gradient opens a new strategy to design novel hybrid materials by the simultaneous doping and heteroassembly engineering for next-generation LIBs.The rational design of nanoheterostructured materials has attracted much attention because of its importance for developing highly efficient LIBs. Herein, we have demonstrated that internal Mo6+ doped TiO2 nanocrystals in situ decorated with highly dispersed MoO3 clusters have been realized by a facile and rapid flame spray pyrolysis route for electrochemical energy storage. In such intriguing nanostructures, internal Mo6+ doping can improve the conductivity of electrode materials and facilitate rapid Li+ intercalation and ion transport and the heteroassembly of highly dispersed ultrafine MoO3 clusters with excellent electrochemical activity endows the TiO2 with extra Li+ ion storage ability as well as incorporates Mo6+. Thus, the as-prepared nanohybrid electrodes exhibit a high specific capacity and superior rate capability due to the maximum synergetic effect

  3. Studies on the Application of High Voltage Discharge Ionization and Ablation in Supersonic-Jets for the Generation of Intense Cluster Ion Beams.

    NASA Astrophysics Data System (ADS)

    Brock, Ansgar

    Glow discharge and pulsed capacitor discharge ionization in supersonic expansions were investigated for the production of intense beams of molecular cluster ions from seeded and ablated compounds. A low cost high voltage high current pulser based on a triggered spark gap switch is described as a mean for ionization and ablation. Besides, details of the molecular beam apparatus and modified pulsed valve are given. Cluster cations rm (Ar)_ {n}^+, rm (CO_2) _{n}^{+}, rm (C_6H_6)_{n}^+ and rm (H_2O)_{n }^+ were produced by pulsed capacitor discharge ionization in the expansion region of a seeded free-jet. The observed cluster mass spectra (CMS) for Ar, rm C_6H_6 and H _2O show the characteristic features (magic numbers) of electron beam and photo ionized clusters under molecular flow conditions. Indications for the presence of magic numbers in the CMS of {(CO _2)_{n}^+} cluster ions at n = 20, 26, 30 and 34 similar to those found for rare gas clusters have been found. Cationic metal ligand complexes Cu(Toluene) _{rm n}^+, Cu(Acetone) _{rm n}^+, Cu(Methanol)_{rm n}^+ , Cu(Ethylether)_{rm n }^+, Cu(Water)_{ rm n}^+, Al(Water)_ {rm n}^+ were synthesized by ablation of the metal from metallic discharge electrodes in a discharge gas mixture of helium seeded with the ligand of choice. The CMS of the expanded plasmas show little background ion signal besides the metal-ligand species. Charge exchange processes in the expansion guarantee high ionization yields of the desired species and account for low backgrounds. Changes in the successive binding energy of Cu(Water)_ {rm n}^+ clusters n = 1-4 are clearly observed in the CMS as step formation. A similar pattern found in the Cu(Acetone)_{ rm n}^+ CMS suggests the same trend in the successive binding energy as known for water. Ablation from a Cr(acac)_3 in a copper matrix was employed for the synthesis of Cr(Acetone) _{rm n}^+ and Cr(Benzene)^+ complexes demonstrating the ability to use nonconducting compounds as a metal source

  4. Determination of binding energy in molecular clusters by ion imaging methods: A test on the phenol-water 1:1 cluster

    NASA Astrophysics Data System (ADS)

    Mazzoni, F.; Pasquini, M.; Pietraperzia, G.; Becucci, M.

    2015-06-01

    In this paper we present a test on the velocity mapping imaging approach for the experimental direct determination of the binding energy in clusters formed by strongly interacting polyatomic molecules. The method is applied to the phenol-water cluster, a system for which the binding energies were already determined in different experiments. The binding energy values that we obtained, 1975 cm-1 in the S0 state, 2327 cm-1 in the S1 state and 6586 cm-1 in the ionic D0 state, are in very good agreement with the previous determinations. We report our results and we discuss advantages and limitations resulting from our experience.

  5. Clustering effects and decay analysis of the light-mass N =Z and N ≠Z composite systems formed in heavy ion collisions

    NASA Astrophysics Data System (ADS)

    Kaur, Manpreet; Singh, BirBikram; Patra, S. K.; Gupta, Raj K.

    2017-01-01

    We investigate the clustering effects in light mass N =Z and N ≠Z composite systems *20Ne, *28Si, *40Ca and Ne,22*21, *39K, respectively, formed in low-energy heavy ion reactions at different excitation energies, within the collective clusterization approach of the dynamical cluster-decay model (DCM) of Gupta and collaborators based on quantum-mechanical fragmentation theory (QMFT). Considering quadrupole deformed and compact orientated nuclei, a comparative decay analysis of these systems has been undertaken for the emission of different intermediate mass fragments (IMFs) or clusters, specifically the IMFs having Z =3 , 4, and 5 (or Z =7 , 6, and 5 complimentary fragments from the *20Ne and Ne,22*21 composite systems) which are having the experimental data available for their Z distribution. Quite interestingly, the QMFT supports clustering in N =Z (*20Ne and *28Si) and N ≠Z (*21Ne and *22Ne) nuclear systems at excitation energies corresponding to their respective decay threshold or resonant-state energies for the 4 α , 16O cluster and non-α cluster 14C (more so in *22NeN ≠Z composite system), supported by the Ikeda diagrams, taking into account the proper pairing strength in the temperature-dependent liquid drop energies. Within the DCM, we notice that at higher excitation energies in addition to x α -type (where x is an integer) clusters from N =Z composite systems and x n -x α -type clusters from N ≠Z composite systems, n p -x α -type clusters are relatively quite dominant, with larger preformation probability due to the decreased pairing strength at higher temperatures in the liquid drop energies. Also, the study reveals the presence of competing reaction mechanisms of compound nucleus (fusion-fission, FF) and of noncompound nucleus origin (deep inelastic orbiting, DIO) in the decay of very-light-mass composite systems *20,21,22Ne and *28Si at different excitation energies. The DIO contribution in the IMF cross section σIMF is extracted for these

  6. Solubility of Co clusters in Co-implanted ZnO thin films by 200 MeV Ag15+ ions irradiation

    NASA Astrophysics Data System (ADS)

    Wasi Khan, M.; Kumar, Ravi; Majeed Khan, M. A.; Angadi, Basavaraj; Jung, Y. S.; Choi, W. K.; Srivastava, J. P.

    2009-09-01

    We have investigated the structural, electrical resistivity, pink noise (1/f noise) and magnetic properties of 200 MeV Ag15+ ions (fluence ~1 × 1012 ions cm-2) irradiated Co-implanted ZnO thin films. The ZnO films were grown on Al2O3 substrate by the PA-MBE technique and 80 keV Co ion implantation with 1 × 1016 ions cm-2 dose value. The structural studies of an unirradiated film show the presence of Co clusters, which dissolve in the ZnO matrix on swift heavy ion (SHI) irradiation. The temperature-dependent electrical resistivity plots of pristine (unirradiated) and irradiated films demonstrated semiconducting nature. The resistivity data were fitted in the Mott's variable range hopping (VRH) model and the activation energies were estimated. The magnitude of normalized noise SV/V2 increases with decrease in temperature and estimated Hooge's parameters have higher values as compared to other semiconductors. We observe a clear magnetic hysteresis loop with coercivity ~65 Oe for both the films at room temperature, establishing the ferromagnetic nature. The correlation between the electrical transport and magnetic properties in the present system formulates it to be a potential aspirant for the spintronics-oriented devices.

  7. Mass Spectra and Yields of Intact Charged Biomolecules Ejected by Massive Cluster Impact for Bioimaging in a Time-of-Flight Secondary Ion Microscope.

    PubMed

    Zhang, Jitao; Franzreb, Klaus; Aksyonov, Sergei A; Williams, Peter

    2015-11-03

    Impacts of massive, highly charged glycerol clusters (≳10(6) Da, ≳ ± 100 charges) have been used to eject intact charged molecules of peptides, lipids, and small proteins from pure solid samples, enabling imaging using these ion species in a time-of-flight secondary ion microscope with few-micrometer spatial resolution. Here, we report mass spectra and useful ion yields (ratio of intact charged molecules detected to molecules sputtered) for several molecular species-two peptides, bradykinin and angiotensin II; two lipids, phosphatidylcholine and sphingomyelin; Irganox 1010 (a detergent); insulin; and rhodamine B-and show that useful ion yields are high enough to enable bioimaging of peptides and lipids in biological samples with few-micrometer resolution and acceptable signals. For example, several hundred molecular ion counts should be detectable from a 3 × 3 μm(2) area of a pure lipid bilayer given appropriate instrumentation or tens of counts from a minor constituent of such a layer.

  8. Classification of biodiesel and fuel blends using gas chromatography - differential mobility spectrometry with cluster analysis and isolation of C18:3 me by dual ion filtering.

    PubMed

    Pasupuleti, Dedeepya; Eiceman, Gary A; Pierce, Karisa M

    2016-08-01

    Fatty acid alkyl esters (FAAEs) were determined at 10-100mg/L in biodiesel and blends with petrodiesel without sample pre-treatment using gas chromatography with a tandem differential mobility detector. Selectivity was provided through chromatographic separations and atmospheric pressure chemical ionization reactions in the detector with mobility characterization of gas ions. Limits of detection were ~0.5ng with an average of 2.98% RSD for peak area precision, ≤1.3% RSD for retention time precision, and ≤9.2% RSD for compensation voltage precision. Biodiesel blends were classified using principal component analysis (PCA) and hierarchical cluster analysis (HCA). Unsupervised cluster analysis captured 52.72% of variance in a single PC while supervised analysis captured 71.64% of variance using Fisher ratio feature selection. Test set predictions showed successful clustering according to source or feedstock when regressed onto the training set model. Detection of the regulated substance methyl linolenate (C18:3 me) was achieved in 6-10s with a 1m long capillary column using dual ion filtering in the tandem differential mobility detector.

  9. Rapid flame synthesis of internal Mo(6+) doped TiO2 nanocrystals in situ decorated with highly dispersed MoO3 clusters for lithium ion storage.

    PubMed

    Li, Yunfeng; Hu, Yanjie; Shen, Jianhua; Jiang, Haibo; Min, Guoquan; Qiu, Shengjie; Song, Zhitang; Sun, Zhuo; Li, Chunzhong

    2015-11-28

    The rational design of nanoheterostructured materials has attracted much attention because of its importance for developing highly efficient LIBs. Herein, we have demonstrated that internal Mo(6+) doped TiO2 nanocrystals in situ decorated with highly dispersed MoO3 clusters have been realized by a facile and rapid flame spray pyrolysis route for electrochemical energy storage. In such intriguing nanostructures, internal Mo(6+) doping can improve the conductivity of electrode materials and facilitate rapid Li(+) intercalation and ion transport and the heteroassembly of highly dispersed ultrafine MoO3 clusters with excellent electrochemical activity endows the TiO2 with extra Li(+) ion storage ability as well as incorporates Mo(6+). Thus, the as-prepared nanohybrid electrodes exhibit a high specific capacity and superior rate capability due to the maximum synergetic effect of TiO2, Mo(6+) and ultrafine MoO3 clusters. Moreover, the aerosol flame process with a unique temperature gradient opens a new strategy to design novel hybrid materials by the simultaneous doping and heteroassembly engineering for next-generation LIBs.

  10. Convenient purification of gold clusters by co-precipitation for improved sensing of hydrogen peroxide, mercury ions and pesticides.

    PubMed

    Guan, Guijian; Zhang, Shuang-Yuan; Cai, Yongqing; Liu, Shuhua; Bharathi, M S; Low, Michelle; Yu, Yong; Xie, Jianping; Zheng, Yuangang; Zhang, Yong-Wei; Han, Ming-Yong

    2014-06-01

    An effective separation process is developed to remove free protein from the protein-protected gold clusters via co-precipitation with zinc hydroxide on their surface. After dialysis, the purified clusters exhibit an enhanced fluorescence for improved sensitive detection and selective visualization.

  11. Reaction of anionic and cationic silicon clusters with tungsten hexafluoride studied by fourier transform ion cyclotron resonance mass spectrometry

    NASA Astrophysics Data System (ADS)

    Reents, W. D., Jr.; Mandich, M. L.; Bondybey, V. E.

    1986-10-01

    Anionic and cationic silicon clusters react exothermically with WF 6 to give a variety of tungsten and silicon fluorides. All the silicon anionic clusters transfer their charge to WF 6. The electron affinities of Si 2-6 are estimated to be less than the electron affinity of WF 6 (350 kJ/mole (3.6 eV)).

  12. Imaging with Mass Spectrometry: A SIMS and VUV-Photoionization Study of Ion-Sputtered Atoms and Clusters from GaAs and Au

    SciTech Connect

    Takahashi, Lynelle; Zhou, Jia; Wilson, Kevin R.; Leone, Stephen R.; Ahmed, Musahid

    2008-12-05

    A new mass spectrometry surface imaging method is presented in which ion-sputtered neutrals are postionized by wavelength-tunable vacuum ultraviolet (VUV) light from a synchrotron source. Mass spectra and signal counts of the photoionized neutrals from GaAs (100) and Au are compared to those of the secondary ions. While clusters larger than dimers are more efficiently detected as secondary ions, certain species, such as As2, Au and Au2, are more efficiently detected through the neutral channel. Continuously tuning the photon wavelength allows photoionization efficiency (PIE) curves to be obtained for sputtered Asm (m=1,2) and Aun (n=1-4). From the observed ionization thresholds, sputtered neutral As and Au show no clear evidence of electronic excitation, while neutral clusters have photoionization onsets shifted to lower energies by ~;;0.3 eV. These shifts are attributed to unresolved vibrational and rotational excitations. High-spatial resolution chemical imaging with synchrotron VUV postionization is demonstrated at two different photon energies using a copper TEM grid embedded in indium. The resulting images are used to illustrate the use of tunable VUV light for verifying mass peak assignments by exploiting the unique wavelength-dependent PIE of each sputtered neutral species. This capability is valuable for identifying compounds when imaging chemically complex systems with mass spectrometry-based techniques.

  13. The closo-[Sn9M(CO)314- Zintl ion clusters where M = Cr, Mo, W: two structural isomers and their dynamic behavior.

    PubMed

    Kesanli, B; Fettinger, J; Eichhorn, B

    2001-12-17

    The closo-[Sn9M(CO)3]4-ions where M = Cr (1), Mo (2), W (3) were prepared from [LM(CO)3] precursors (L=mesitylene, cycloheptatriene), K4Sn9. and 2,2,2-cryptand in ethylenediamine/toluene solvent mixtures. The [K(2,2,2-cryptand)]+ salts are very air and moisture sensitive and have been characterized by IR, 119Sn, and 13C NMR spectroscopy and single-crystal X-ray diffraction studies. Complexes 1-3 form bicapped square-antiprismatic 10-vertex 22-electron closo structures in which the [M(CO)3] units occupy cluster vertices. For 1 and 2, the clusters have C4. symmetry in the solid state in which the [M(CO)A] fragments occupy capping positions with Sn9(4-) ions that are bound to the metal in an 4 fashion. For 3, the [M(CO)3] fragment occupies a position in the square plane with an eta/5-Sn9(4-) ion and C(s) point symmetry. For 1-3, a dynamic equilibrium exists between the eta4 and eta5 structures yielding three 119Sn NMR signals that reflect the three chemically distinct Sn environments of the higher symmetry C(4v) structure. The 119Sn NMR chemical shifts and coupling constants show solvent and temperature dependencies due to the equilibrium process. A triangular-face rotation mechanism is proposed to describe the dynamic behavior.

  14. Soft-landing ion mobility of silver clusters for small-molecule matrix-assisted laser desorption ionization mass spectrometry and imaging of latent fingerprints.

    PubMed

    Walton, Barbara L; Verbeck, Guido F

    2014-08-19

    Matrix-assisted laser desorption ionization (MALDI) imaging is gaining popularity, but matrix effects such as mass spectral interference and damage to the sample limit its applications. Replacing traditional matrices with silver particles capable of equivalent or increased photon energy absorption from the incoming laser has proven to be beneficial for low mass analysis. Not only can silver clusters be advantageous for low mass compound detection, but they can be used for imaging as well. Conventional matrix application methods can obstruct samples, such as fingerprints, rendering them useless after mass analysis. The ability to image latent fingerprints without causing damage to the ridge pattern is important as it allows for further characterization of the print. The application of silver clusters by soft-landing ion mobility allows for enhanced MALDI and preservation of fingerprint integrity.

  15. Observation of different core water cluster ions Y-(H2O)n (Y = O2, HCN, HOx, NOx, COx) and magic number in atmospheric pressure negative corona discharge mass spectrometry

    NASA Astrophysics Data System (ADS)

    Sekimoto, K.; Takayama, M.

    2010-12-01

    Atmospheric ion water clusters have been of long-standing interest in the field of atmospheric sciences, because of them playing a central role in the formation of tropospheric aerosols which affect the photochemistry, radiation budget of the atmosphere and climate. On the basis of a mechanism of aerosol formation in the troposphere proposed by Yu and Turco, termed “ion-mediated nucleation” (Geophys. Res. Lett. 2000, 27, 883), atmospheric ion water clusters are most likely to be produced via two processes; 1) direct attachment of polar solvent molecules H2O to atmospheric ions due to them having strong binding energy via ion-dipole interactions, and 2) growth of ion-induced hydrates into larger water clusters bound via hydrogen-bonding networks by condensation with H2O molecules. The stability and growth rates of water clusters are strongly dependent on the thermochemical properties of individual atmospheric core ions. A large number of thermochemical information of the positive atmospheric ion H3O+ and its hydrates H3O+(H2O)n have been reported so far, while there has been little information of the water clusters with the negative atmospheric core ions. Therefore, fundamental studies of the thermochemistry of various negative atmospheric ion water clusters will contribute towards furthering an understanding of their unique role in atmospheric sciences and climate change. We have recently established an atmospheric pressure DC corona discharge device containing a specific corona needle electrode that made it possible to reproducibly generate negative core ions Y- originating from ambient air (Int. J. Mass Spectrom. 2007, 261, 38; Eur. Phys. J. D 2008, 50, 297). The change in electric field strength on the needle tip resulted in the formation of negative atmospheric core ions Y- with various different lifetimes in air. The low field strength brought about the dominant formation of core ions with short lifetimes in air such as O2- and HOx-, while the longer

  16. Low energy (0-4 eV) electron impact to N{sub 2}O clusters: Dissociative electron attachment, ion-molecule reactions, and vibrational Feshbach resonances

    SciTech Connect

    Vizcaino, Violaine; Denifl, Stephan; Maerk, Tilmann D.; Scheier, Paul; Illenberger, Eugen

    2010-10-21

    Electron attachment to clusters of N{sub 2}O in the energy range of 0-4 eV yields the ionic complexes [(N{sub 2}O){sub n}O]{sup -}, [(N{sub 2}O){sub n}NO]{sup -}, and (N{sub 2}O){sub n}{sup -} . The shape of the ion yields of the three homologous series differs substantially reflecting the different formation mechanisms. While the generation of [(N{sub 2}O){sub n}O]{sup -} can be assigned to dissociative electron attachment (DEA) of an individual N{sub 2}O molecule in the target cluster, the formation of [(N{sub 2}O){sub n}NO]{sup -} is interpreted via a sequence of ion molecule reactions involving the formation of O{sup -} via DEA in the first step. The nondecomposed complexes (N{sub 2}O){sub n}{sup -} are preferentially formed at very low energies (below 0.5 eV) as a result of intramolecular stabilization of a diffuse molecular anion at low energy. The ion yields of [(N{sub 2}O){sub n}O]{sup -} and (N{sub 2}O){sub n}{sup -} versus electron energy show sharp peaks at the threshold region, which can be assigned to vibrational Feshbach resonances mediated by the diffuse anion state as already observed in an ultrahigh resolution electron attachment study of N{sub 2}O clusters [E. Leber, S. Barsotti, J. Boemmels, J. M. Weber, I. I. Fabrikant, M.-W. Ruf, and H. Hotop, Chem. Phys. Lett. 325, 345 (2000)].

  17. Trapping of Li(+) Ions by [ThFn](4-n) Clusters Leading to Oscillating Maxwell-Stefan Diffusivity in the Molten Salt LiF-ThF4.

    PubMed

    Chakraborty, Brahmananda; Kidwai, Sharif; Ramaniah, Lavanya M

    2016-08-18

    A molten salt mixture of lithium fluoride and thorium fluoride (LiF-ThF4) serves as a fuel as well as a coolant in the most sophisticated molten salt reactor (MSR). Here, we report for the first time dynamic correlations, Onsager coefficients, Maxwell-Stefan (MS) diffusivities, and the concentration dependence of density and enthalpy of the molten salt mixture LiF-ThF4 at 1200 K in the composition range of 2-45% ThF4 and also at eutectic composition in the temperature range of 1123-1600 K using Green-Kubo formalism and equilibrium molecular dynamics simulations. We have observed an interesting oscillating pattern for the MS diffusivity for the cation-cation pair, in which ĐLi-Th oscillates between positive and negative values with the amplitude of the oscillation reducing as the system becomes rich in ThF4. Through the velocity autocorrelation function, vibrational density of states, radial distribution function analysis, and structural snapshots, we establish an interplay between the local structure and multicomponent dynamics and predict that formation of negatively charged [ThFn](4-n) clusters at a higher ThF4 mole % makes positively charged Li(+) ions oscillate between different clusters, with their range of motion reducing as the number of [ThFn](4-n) clusters increases, and finally Li(+) ions almost get trapped at a higher ThF4% when the electrostatic force on Li(+) exerted by various surrounding clusters gets balanced. Although reports on variations of density and enthalpy with temperature exist in the literature, for the first time we report variations of the density and enthalpy of LiF-ThF4 with the concentration of ThF4 (mole %) and fit them with the square root function of ThF4 concentration, which will be very useful for experimentalists to obtain data over a range of concentrations from fitting the formula for design purposes. The formation of [ThFn](4-n) clusters and the reduction in the diffusivity of the ions at a higher ThF4% may limit the

  18. Ultrashallow (<10 nm) p{sup +}/n junction formed by B{sub 18}H{sub 22} cluster ion implantation and excimer laser annealing

    SciTech Connect

    Heo, Sungho; Hwang, Hyunsang; Cho, H. T.; Krull, W. A.

    2006-12-11

    In order to form an ultrashallow p{sup +}/n junction, incorporation of a top amorphous-silicon (a-Si) layer is necessary so as to avoid channeling and to fully activate the dopant. Conventional ultrashallow junction processes require two-step implantation such as preamorphization by Si{sup +} or Ge{sup +} implantation and ultralow (<0.5 keV) energy B{sup +} implantation. In this report, the authors investigate B{sub 18}H{sub 22}{sup +} implantation. Due to the heavy mass of cluster ions, one-step ion implantation at 5 keV readily forms a 5-nm-thick a-Si layer and an ultrashallow junction without B channeling. By employing excimer laser annealing, the authors have obtained a shallow junction depth ({approx}9 nm) and low R{sub s} ({approx}830 {omega}/{open_square})

  19. Adsorption of single Li and the formation of small Li clusters on graphene for the anode of lithium-ion batteries.

    PubMed

    Fan, Xiaofeng; Zheng, W T; Kuo, Jer-Lai; Singh, David J

    2013-08-28

    We analyzed the adsorption of Li on graphene in the context of anodes for lithium-ion batteries (LIBs) using first-principles methods including van der Waals interactions. We found that although Li can reside on the surface of defect-free graphene under favorable conditions, the binding is much weaker than to graphite and the concentration on a graphene surface is not higher than in graphite. At low concentration, Li ions spread out on graphene because of Coulomb repulsion. With increased Li content, we found that small Li clusters can be formed on graphene. Although this result suggests that graphene nanosheets can conceivably have a higher ultimate Li capacity than graphite, it should be noted that such nanoclusters can potentially nucleate Li dendrites, leading to failure. The implications for nanostructured carbon anodes in batteries are discussed.

  20. Towards reliable modelling of large clusters: on the overall accuracy of the diatomics-in-molecule method for rare gas cluster ions

    NASA Astrophysics Data System (ADS)

    Naumkin, Fedor Yu.; Knowles, Peter J.; Murrell, John N.

    1995-04-01

    The accuracy of the diatomics-in-molecules (DIM) method is examined for the case of rare gas ionic clusters through a series of careful calibration calculations. Ab initio potential energy functions for Rg 3+ and Rg 4+ (RgHe, Ne, Ar) are compared with the DIM model, taking diatomic potentials computed at exactly the same level of ab initio theory as input. For Ne n+, agreement is satisfactory (in most important regions within 0.05 eV), whereas for He n+, large deviations occur.

  1. Towards reliable modelling of large clusters: On the overall accuracy of the diatomics-in-molecule method for rare gas cluster ions

    NASA Astrophysics Data System (ADS)

    Naumkin, Fedor Yu.; Knowles, Peter J.; Murrell, John N.

    1995-04-01

    The accuracy of the diatomics-in-molecules (DIM) method is examined for the case of rare gas ionic clusters through a series of careful calibration calculations. Ab initio potential energy functions for Rg3(+) and Rg4(+) (Rg=He, Ne, Ar) are compared with the DIM model, taking diatomic potentials computed at exactly the same level of ab initio theory as input. For Ne(n)(+) and Ar(n)(+), agreement is satisfactory (in most important regions within 0.05 eV), whereas for He(n)(+), large deviations occur.

  2. Thermochemistry of the activation of N2 on iron cluster cations: Guided ion beam studies of the reactions of Fen+ (n=1-19) with N2

    NASA Astrophysics Data System (ADS)

    Tan, Lin; Liu, Fuyi; Armentrout, P. B.

    2006-02-01

    The kinetic energy dependences of the reactions of Fen+ (n=1-19) with N2 are studied in a guided ion beam tandem mass spectrometer over the energy range of 0-15eV. In addition to collision-induced dissociation forming Fem+ ions, which dominate the product spectra, a variety of FemN2+ and FemN+ product ions, where m ⩽n, is observed. All processes are observed to exhibit thresholds. Fem+-N and Fem+-2N bond energies as a function of cluster size are derived from the threshold analysis of the kinetic energy dependences of the endothermic reactions. The trends in this thermochemistry are compared to the isoelectronic D0(Fen+-CH), and to bulk phase values. A fairly uniform barrier of 0.48±0.03eV at 0K is observed for formation of the FenN2+ product ions (n =12, 15-19) and can be related to the rate-limiting step in the Haber process for catalytic ammonia production.

  3. Three novel Cu6S6 cluster-based coordination compounds: synthesis, framework modulation and the sensing of small molecules and Fe(3+) ions.

    PubMed

    Song, Jiang-Feng; Li, Si-Zhe; Zhou, Rui-Sha; Shao, Jia; Qiu, Xiao-Min; Jia, Ying-Ying; Wang, Jun; Zhang, Xiao

    2016-08-07

    Three novel Cu6S6 cluster-based coordination compounds formulated as [Cu(mpymt)3]2 (1), {(CuBr4)[Cu(mpymt)6]}n (2), and {(CuI6)[Cu(mpymt)6]}n (3) (Hmpymt = 4-methylpyrimidine-2-thione), have been synthesized under solvothermal conditions and characterized by elemental analysis, infrared (IR) spectroscopy, thermal gravimetric analysis, powder X-ray diffraction and single-crystal X-ray diffraction. Structural analysis reveals that compound 1 shows a distorted octahedral core of six copper atoms (Cu6S6) constructed from four α and two β type N[double bond, length as m-dash]C-SH parts from six mpymt(-) anions. Compound 2 displays an interesting 3D framework constructed from Cu6S6 and Cu4Br4 Cu(i) clusters simultaneously, interestingly, six mpymt(-) with α type N[double bond, length as m-dash]C-SH parts are involved in the formation of Cu6S6. Compound 3 displays an infinite 1D framework constructed from Cu6S6 and Cu6I6 Cu(i) clusters, notably, four α and two β type N[double bond, length as m-dash]C-SH parts are involved in the formation of the Cu6S6 cluster, however, only mpymt(-) ligands containing α type N[double bond, length as m-dash]C-SH parts form the bridged Cu6I6 cluster. The experimental results reveal that halogen ions finely modulate the structural features of compounds 1-3. The fluorescent properties of compounds 1-3 in the solid state and in various solvent emulsions were investigated in detail, the results of which indicate that compounds 1-3 are all highly sensitive naked eye colorimetric sensors for NB, 2-NT and Fe(3+) (NB = nitrobenzene and 2-NT = 2-nitrotoluene).

  4. Ion distribution in quaternary-ammonium-functionalized aromatic polymers: effects on the ionic clustering and conductivity of anion-exchange membranes.

    PubMed

    Weiber, E Annika; Jannasch, Patric

    2014-09-01

    A series of copoly(arylene ether sulfone)s that have precisely two, three, or four quaternary ammonium (QA) groups clustered directly on single phenylene rings along the backbone are studied as anion-exchange membranes. The copolymers are synthesized by condensation polymerizations that involve either di-, tri-, or tetramethylhydroquinone followed by virtually complete benzylic bromination using N-bromosuccinimide and quaternization with trimethylamine. This synthetic strategy allows excellent control and systematic variation of the local density and distribution of QA groups along the backbone. Small-angle X-ray scattering of these copolymers shows extensive ionic clustering, promoted by an increasing density of QA on the single phenylene rings. At an ion-exchange capacity (IEC) of 2.1 meq g(-1), the water uptake decreases with the increasing local density of QA groups. Moreover, at moderate IECs at 20 °C, the Br(-) conductivity of the densely functionalized copolymers is higher than a corresponding randomly functionalized polymer, despite the significantly higher water uptake of the latter. Thus, the location of multiple cations on single aromatic rings in the polymers facilitates the formation of a distinct percolating hydrophilic phase domain with a high ionic concentration to promote efficient anion transport, despite probable limitations by reduced ion dissociation. These findings imply a viable strategy to improve the performance of alkaline membrane fuel cells.

  5. Ultrathin mesoporous Co3O4 nanosheets-constructed hierarchical clusters as high rate capability and long life anode materials for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Wu, Shengming; Xia, Tian; Wang, Jingping; Lu, Feifei; Xu, Chunbo; Zhang, Xianfa; Huo, Lihua; Zhao, Hui

    2017-06-01

    Herein, Ultrathin mesoporous Co3O4 nanosheets-constructed hierarchical clusters (UMCN-HCs) have been successfully synthesized via a facile hydrothermal method followed by a subsequent thermolysis treatment at 600 °C in air. The products consist of cluster-like Co3O4 microarchitectures, which are assembled by numerous ultrathin mesoporous Co3O4 nanosheets. When tested as anode materials for lithium-ion batteries, UMCN-HCs deliver a high reversible capacity of 1067 mAh g-1 at a current density of 100 mA g-1 after 100 cycles. Even at 2 A g-1, a stable capacity as high as 507 mAh g-1 can be achieved after 500 cycles. The high reversible capacity, excellent cycling stability, and good rate capability of UMCN-HCs may be attributed to their mesoporous sheet-like nanostructure. The sheet-layered structure of UMCN-HCs may buffer the volume change during the lithiation-delithiation process, and the mesoporous characteristic make lithium-ion transfer more easily at the interface between the active electrode and the electrolyte.

  6. Formation of Cluster Complexes by Cluster-Cluster-Collisions

    NASA Astrophysics Data System (ADS)

    Ichihashi, Masahiko; Odaka, Hideho

    2015-03-01

    Multi-element clusters are interested in their chemical and physical properties, and it is expected that they are utilized as catalysts, for example. Their properties critically depend on the size, composition and atomic ordering, and it should be important to adjust the above parameters for their functionality. One of the ways to form a multi-element cluster is to employ a low-energy collision between clusters. Here, we show characteristic results obtained in the collision between a neutral Ar cluster and a size-selected Co cluster ion. Low-energy collision experiment was accomplished by using a newly developed merging-beam apparatus. Cobalt cluster ions were produced by laser ablation, and mass-selected. On the other hand, argon clusters were prepared by the supersonic expansion of Ar gas. Both cluster beams were merged together in an ion guide, and ionic cluster complexes were mass-analyzed. In the collision of Co2+ and ArN, Co2Arn+ (n = 1 - 30) were observed, and the total intensity of Co2Arn+ (n >= 1) is inversely proportional to the relative velocity between Co2+ and ArN. This suggests that the charge-induced dipole interaction between Co2+ and a neutral Ar cluster is dominant in the formation of the cluster complex, Co2+Arn.

  7. Confined SnO2 quantum-dot clusters in graphene sheets as high-performance anodes for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Zhu, Chengling; Zhu, Shenmin; Zhang, Kai; Hui, Zeyu; Pan, Hui; Chen, Zhixin; Li, Yao; Zhang, Di; Wang, Da-Wei

    2016-05-01

    Construction of metal oxide nanoparticles as anodes is of special interest for next-generation lithium-ion batteries. The main challenge lies in their rapid capacity fading caused by the structural degradation and instability of solid-electrolyte interphase (SEI) layer during charge/discharge process. Herein, we address these problems by constructing a novel-structured SnO2-based anode. The novel structure consists of mesoporous clusters of SnO2 quantum dots (SnO2 QDs), which are wrapped with reduced graphene oxide (RGO) sheets. The mesopores inside the clusters provide enough room for the expansion and contraction of SnO2 QDs during charge/discharge process while the integral structure of the clusters can be maintained. The wrapping RGO sheets act as electrolyte barrier and conductive reinforcement. When used as an anode, the resultant composite (MQDC-SnO2/RGO) shows an extremely high reversible capacity of 924 mAh g‑1 after 200 cycles at 100 mA g‑1, superior capacity retention (96%), and outstanding rate performance (505 mAh g‑1 after 1000 cycles at 1000 mA g‑1). Importantly, the materials can be easily scaled up under mild conditions. Our findings pave a new way for the development of metal oxide towards enhanced lithium storage performance.

  8. Measuring composition and growth of ion clusters of sulfuric acid, ammonia, amines and oxidized organics as first steps of nucleation in the CLOUD experiment

    NASA Astrophysics Data System (ADS)

    Schobesberger, Siegfried; Praplan, Arnaud; Junninen, Heikki; Bianchi, Federico; Lönn, Gustaf; Ehn, Mikael; Lehtipalo, Katrianne; Dommen, Josef; Ehrhart, Sebastian; Franchin, Alessandro; Ortega, Ismael K.; Riccobono, Francesco; Duplissy, Jonathan; Rissanen, Matti; Sipilä, Mikko; Petäjä, Tuukka; Kulmala, Markku; Donahue, Neil M.; Worsnop, Douglas R.; Cloud Collaboration

    2013-05-01

    The mechanisms behind the nucleation of vapors forming new particles in the atmosphere had been proven difficult to establish. One main aim of the CLOUD experiment was to explore in detail these first steps of atmospheric new particle formation by performing extremely well controlled laboratory experiments. We examined nucleation and growth in the presence of different mixtures of vapors, including sulfuric acid, ammonia, dimethylamine, and oxidation products of pinanediol or α-pinene. Among the employed state-of-the-art instrumentation, a high-resolution mass spectrometer that directly sampled negatively charged ions and clusters proved particularly useful. We were able to resolve most of the chemical compositions found for charged sub-2nm clusters and to observe their growth in time. These compositions reflected the mixture of condensable vapors in the chamber and the role of each individual vapor in forming sub-2nm clusters could be explored. By inter-comparing between individual experiments and ambient observations, we try to establish which vapors participate in nucleation in the actual atmosphere, and how.

  9. MOF-derived self-assembled ZnO/Co3O4 nanocomposite clusters as high-performance anodes for lithium-ion batteries.

    PubMed

    Zhu, Dequan; Zheng, Fangcai; Xu, Shihao; Zhang, Yuanguang; Chen, Qianwang

    2015-10-14

    Although different kinds of metal oxide nanoparticles are extensively investigated as anode materials for lithium-ion batteries (LIBs), their cycle life and energy/power density are still not suitable for commercial applications. Metal oxides have a large storage capacity, but they suffer from low electrical conductivity and severe volume change during the charge/discharge process. Herein, we present a facile route to prepare self-assembled ZnO/Co3O4 nanocomposite clusters through calcination of preformed Prussian Blue Analogue (PBA) Zn3[Co(CN)6]2 nanospheres. These self-assembled ZnO/Co3O4 nanocomposite clusters exhibit superior lithium storage capabilities with good cycling properties. A reversible capacity of 957 mA h g(-1) was retained at a current density of 100 mA g(-1) up to 100 cycles. The enhanced electrochemical performance of the ZnO/Co3O4 nanocomposite anode can be ascribed to the rational design of the self-assembled cluster structures and the synergetic effect of two-component functional nanoparticle systems.

  10. Confined SnO2 quantum-dot clusters in graphene sheets as high-performance anodes for lithium-ion batteries

    PubMed Central

    Zhu, Chengling; Zhu, Shenmin; Zhang, Kai; Hui, Zeyu; Pan, Hui; Chen, Zhixin; Li, Yao; Zhang, Di; Wang, Da-Wei

    2016-01-01

    Construction of metal oxide nanoparticles as anodes is of special interest for next-generation lithium-ion batteries. The main challenge lies in their rapid capacity fading caused by the structural degradation and instability of solid-electrolyte interphase (SEI) layer during charge/discharge process. Herein, we address these problems by constructing a novel-structured SnO2-based anode. The novel structure consists of mesoporous clusters of SnO2 quantum dots (SnO2 QDs), which are wrapped with reduced graphene oxide (RGO) sheets. The mesopores inside the clusters provide enough room for the expansion and contraction of SnO2 QDs during charge/discharge process while the integral structure of the clusters can be maintained. The wrapping RGO sheets act as electrolyte barrier and conductive reinforcement. When used as an anode, the resultant composite (MQDC-SnO2/RGO) shows an extremely high reversible capacity of 924 mAh g−1 after 200 cycles at 100 mA g−1, superior capacity retention (96%), and outstanding rate performance (505 mAh g−1 after 1000 cycles at 1000 mA g−1). Importantly, the materials can be easily scaled up under mild conditions. Our findings pave a new way for the development of metal oxide towards enhanced lithium storage performance. PMID:27181691

  11. Hydrogen transfer dynamics in a photoexcited phenol/ammonia (1:3) cluster studied by picosecond time-resolved UV-IR-UV ion dip spectroscopy.

    PubMed

    Ishiuchi, Shun-ichi; Sakai, Makoto; Daigoku, Kota; Hashimoto, Kenro; Fujii, Masaaki

    2007-12-21

    The picosecond time-resolved IR spectra of phenol/ammonia (1:3) cluster were measured by UV-IR-UV ion dip spectroscopy. The time-resolved IR spectra of the reaction products of the excited state hydrogen transfer were observed. From the different time evolution of two vibrational bands at 3180 and 3250 cm(-1), it was found that two isomers of hydrogenated ammonia radical cluster .NH(4)(NH(3))(2) coexist in the reaction products. The time evolution was also measured in the near-IR region, which corresponds to 3p-3s Rydberg transition of .NH(4)(NH(3))(2); a clear wavelength dependence was found. From the observed results, we concluded that (1) there is a memory effect of the parent cluster, which initially forms a metastable product, .NH(4)-NH(3)-NH(3), and (2) the metastable product isomerizes successively to the most stable product, NH(3)-.NH(4)-NH(3). The time constant for OH cleaving, the isomerization, and its back reaction were determined by rate-equation analysis to be 24, 6, and 9 ps, respectively.

  12. Clusters of α-LiFeO2 nanoparticles incorporated into multi-walled carbon nanotubes: a lithium-ion battery cathode with enhanced lithium storage properties.

    PubMed

    Rahman, Md Mokhlesur; Glushenkov, Alexey M; Chen, Zhiqiang; Dai, Xiujuan J; Ramireddy, Thrinathreddy; Chen, Ying

    2013-12-14

    We report the preparation of a novel nanocomposite architecture of α-LiFeO2-MWCNT based on clusters of α-LiFeO2 nanoparticles incorporated into multiwalled carbon nanotubes (MWCNTs). The composite represents a promising cathode material for lithium-ion batteries. The preparation of the nanocomposite is achieved by combining a molten salt precipitation process and a radio frequency oxygen plasma for the first time. We demonstrate that clusters of α-LiFeO2 nanoparticles incorporated into MWCNTs are capable of delivering a stable and high reversible capacity of 147 mA h g(-1) at 1 C after 100 cycles with the first cycle Coulombic efficiency of ~95%. The rate capability of the composite is significantly improved and its reversible capacity is measured to be 101 mA h g(-1) at a high current rate of 10 C. Both rate capability and cycling stability are not simply a result of introduction of functionalized MWCNTs but most likely originate from the unique composite structure of clusters of α-LiFeO2 nanoparticles integrated into a network of MWCNTs. The excellent electrochemical performance of this new nanocomposite opens up new opportunities in the development of high-performance electrode materials for energy storage application using the radio frequency oxygen plasma technique.

  13. Dissociative recombination of H+(H2O)3 and D+(D2O)3 water cluster ions with electrons: Cross sections and branching ratios

    NASA Astrophysics Data System (ADS)

    Öjekull, J.; Andersson, P. U.; Nâgârd, M. B.; Pettersson, J. B. C.; Marković, N.; Derkatch, A. M.; Neau, A.; Al Khalili, A.; Rosén, S.; Larsson, M.; Semaniak, J.; Danared, H.; Källberg, A.; Österdahl, F.; af Ugglas, M.

    2007-11-01

    Dissociative recombination (DR) of the water cluster ions H+(H2O)3 and D+(D2O)3 with electrons has been studied at the heavy-ion storage ring CRYRING (Manne Siegbahn Laboratory, Stockholm University). For the first time, absolute DR cross sections have been measured for H+(H2O)3 in the energy range of 0.001-0.8eV, and relative cross sections have been measured for D+(D2O)3 in the energy range of 0.001-1.0eV. The DR cross sections for H+(H2O)3 are larger than previously observed for H+(H2O)n (n=1,2), which is in agreement with the previously observed trend indicating that the DR rate coefficient increases with size of the water cluster ion. Branching ratios have been determined for the dominating product channels. Dissociative recombination of H+(H2O)3 mainly results in the formation of 3H2O+H (probability of 0.95±0.05) and with a possible minor channel resulting in 2H2O+OH+H2 (0.05±0.05). The dominating channels for DR of D+(D2O)3 are 3D2O+D (0.88±0.03) and 2D2O+OD+D2 (0.09±0.02). The branching ratios are comparable to earlier DR results for H+(H2O)2 and D+(D2O)2, which gave 2X2O+X (X=H,D) with a probability of over 0.9.

  14. Reduction of the copper ion to its metal and clusters in alcoholic media: A radiation chemical study

    NASA Astrophysics Data System (ADS)

    Dey, G. R.

    2005-10-01

    Reduction of Cu 2+ ions with and without I - as a ligand was studied in N 2-purged alcoholic solutions by pulse radiolysis. In the absence of iodide ion, the initial rate constant for e -sol reaction with Cu 2+ was determined following the decay of solvated electrons in different alcohols; kbimol values are in the range of 0.8-1.1×10 10 dm 3 mol -1 s -1. In the presence of 10 -3 mol dm -3 KI, the respective kbimol remained almost same. Generally, on reduction, Cu(II) ion changes to Cu(I) ion initially and later it produces metallic copper (Cu°), and the stability of these intermediates depends on the conditions of the matrix. In the presence of I -, Copper ions such as Cu(II) or Cu(I) ions get reduced to metallic copper (Cu°) having initial absorption around 740 and below 400 nm. Later, at 100 μs time after the electron pulse, it gets transformed into a nanoparticle with an absorption band at 580 nm. Such formation of copper nanoparticle was observed only in 2-propanolic medium in the presence of iodide ions. During γ-radiolysis of N 2-purged 1.5×10 -4 CuSO 4 solutions in 2-propanol, reddish pink colored copper nanoparticles were formed, which are quite similar to those reported earlier in aqueous solution. But, in the presence of I - (2-propanolic solutions), such phenomenon was not noticed on γ-radiolysis. Interestingly, the formation of copper nanoparticle was observed also in the reactions of copper (II) ions with alcohol radicals formed during γ-radiolysis in N 2O-purged system, where e -sol were scavenged by N 2O. The nanoparticles generated both in N 2 and N 2O-purged alcoholic systems, viz. methanol, ethanol and 2-propanol, were found to be oxygen sensitive. The contradictory results from pulse and γ-radiolysis studies in the presence and absence of iodide ions are explained to account for the nanoparticle generation.

  15. Mechanisms of formation of nonlinear optical light guide structures in metal cluster composites produced by ion beam implantation

    SciTech Connect

    Sarkisov, S.S.; Williams, E.K.; Curley, M.; Smith, C.C.; Ila, D.; Venkateswarlu, P.; Poker, D.B.; Hensley, D.K.

    1997-11-01

    Ion implantation has been shown to produce a high density of metal colloids in glasses and crystalline materials. The high-precipitate volume fraction and small size of metal nanoclusters formed leads to values for the third-order susceptibility much greater than those for metal doped solids. This has stimulated interest in use of ion implantation to make nonlinear optical materials. On the other side, LiNbO{sub 3} has proved to be a good material for optical waveguides produced by MeV ion implantation. Light confinement in these waveguides is produced by refractive index step difference between the implanted region and the bulk material. Implantation of LiNbO{sub 3} with MeV metal ions can therefore result into nonlinear optical waveguide structures with great potential in a variety of device applications. The authors describe linear and nonlinear optical properties of a waveguide structure in LiNbO{sub 3}-based composite material produced by silver ion implantation in connection with mechanisms of its formation.

  16. Magnetic properties of nano-clusters lanthanum chromite powders doped with samarium and strontium ions synthesized via a novel combustion method

    SciTech Connect

    Rashad, M.M.; El-Sheikh, S.M.

    2011-03-15

    Graphical abstract: Nanocrystalline Sm{sup 3+} and Sr{sup 2+} doped LaCrO{sub 3} powders have been synthesized through a novel gel combustion synthesis using triethanol amine (TEA). The saturation magnetization of the LaCrO{sub 3} increased with an increase Sm{sup 3+} ion and it decreased with an increase in the Sr{sup 3+} ion to 0.3 at temperature 1000 {sup o}C for 2 h due to the formation of a monodispersed uniform octahedral structure as shown in the Fig. Research highlights: {yields} Single-phase orthorhombic lanthanum chromite LaCrO{sub 3} nanoclusters have been successfully synthesized through a novel gel combustion synthesis using triethanol amine (TEA). {yields} Sr{sup 2+} ions doped LaCrO{sub 3} increased the unit cell volume and the crystallite size whereas Sm{sup 3+} ions doped LaCrO{sub 3} decreased the unit cell volume and the crystallite size. {yields} The saturation magnetization of the LaCrO{sub 3} powders increased continuously with an increase in the Sm concentration and it decreased with an increase in the Sr ion up to 0.3 at annealing temperature of 1000 {sup o}C for 2 h. -- Abstract: A novel approach to synthesize a single-phase orthorhombic perovskite lanthanum chromite LaCrO{sub 3} clusters doped with Sm{sup 3+} and Sr{sup 2+} ions via gel combustion route was reported. The producing materials were synthesized using metal nitrates as oxidizers and triethanol amine (TEA), N-butyl amine (NBA) or ethylene diamine (EDA) as a fuel. The effect of the annealing temperature, type of organic fuel and the variation of the samarium and/or strontium substitution and its impact on crystal structure, crystallite size, microstructure and magnetic properties of the LaCrO{sub 3} powders formed was systematically studied. The results revealed that a well crystalline single phase of pure LaCrO{sub 3} can be achieved at annealing temperature from 800 to 1000 {sup o}C for 2 h. Moreover, each organic carrier materials exhibited a different degree of effectiveness

  17. High-mass heterogeneous cluster formation by ion bombardment of the ternary alloy Au7Cu5Al4

    DOE PAGES

    Zinovev, Alexander V.; King, Bruce V.; Veryovkin, Igor V.; ...

    2016-02-04

    The ternary alloy Au7Cu5Al4 was irradiated with 0.1–10 keV Ar+ and the surface composition analyzed using laser sputter neutral mass spectrometry. Ejected clusters containing up to seven atoms, with masses up to 2000 amu, were observed. By monitoring the signals from sputtered clusters, the surface composition of the alloy was seen to change with 100 eV Ar+ dose, reaching equilibrium after 10 nm of the surface was eroded, in agreement with TRIDYN simulation and indicating that the changes were due to preferential sputtering of Al and Cu. Ejected gold containing clusters were found to increase markedly in intensity while aluminummore » containing clusters decreased in intensity as a result of Ar sputtering. Such an effect was most pronounced for low energy (<1 keV) Ar+ sputtering and was consistent with TRIDYN simulations of the depth profiling. As a result, the component sputter yields from the ternary alloy were consistent with previous binary alloy measurements but showed greater Cu surface concentrations than expected from TRIDYN simulations.« less

  18. Laser initiated reactions in N{sub 2}O clusters studied by time-sliced ion velocity imaging technique

    SciTech Connect

    Honma, Kenji

    2013-07-28

    Laser initiated reactions in N{sub 2}O clusters were studied by a time-sliced velocity imaging technique. The N{sub 2}O clusters, (N{sub 2}O){sub n}, generated by supersonic expansion were irradiated by an ultraviolet laser around 204 nm to convert reactant pairs, O({sup 1}D{sub 2})-(N{sub 2}O){sub n−1}. The NO molecules formed from these reactant pairs were ionized by the same laser pulse and their velocity distribution was determined by the time-sliced velocity imaging technique. At low nozzle pressure, lower than 1.5 atm, the speed distribution in the frame moving with the clusters consists of two components. These components were ascribed to the products appeared in the backward and forward directions in the center-of-mass frame, respectively. The former consists of the vibrational ground state and the latter consists of highly vibrational excited states. At higher nozzle pressure, a single broad speed distribution became dominant for the product NO. The pressure and laser power dependences suggested that this component is attributed to the product formed in the clusters larger than dimer, (N{sub 2}O){sub n} (n ≥ 3)

  19. Negative ions in liquid helium

    NASA Astrophysics Data System (ADS)

    Khrapak, A. G.; Schmidt, W. F.

    2011-05-01

    The structure of negative ions in liquid 4He is analyzed. The possibility of cluster or bubble formation around impurity ions of both signs is discussed. It is shown that in superfluid helium, bubbles form around negative alkaline earth metal ions and clusters form around halogen ions. The nature of "fast" and "exotic" negative ions is also discussed. It is assumed that "fast" ions are negative ions of helium excimer molecules localized inside bubbles. "Exotic" ions are stable negative impurity ions, which are always present in small amounts in gas discharge plasmas. Bubbles or clusters with radii smaller the radius of electron bubbles develop around these ions.

  20. A Statistical Study of the Solar Wind Turbulence at Ion Kinetic Scales Using the k-filtering Technique and Cluster Data

    NASA Astrophysics Data System (ADS)

    Roberts, O. W.; Li, X.; Jeska, L.

    2015-03-01

    Plasma turbulence at ion kinetic scales in the solar wind is investigated using the multi-point magnetometer data from the Cluster spacecraft. By applying the k-filtering method, we are able to estimate the full three-dimensional power spectral density P(ωsc, k) at a certain spacecraft frequency ωsc in wavevector (k) space. By using the wavevector at the maximum power in P(ωsc, k) at each sampling frequency ωsc and the Doppler shifted frequency ωpla in the solar wind frame, the dispersion plot ωpla = ωpla(k) is found. Previous studies have been limited to very few intervals and have been hampered by large errors, which motivates a statistical study of 52 intervals of solar wind. We find that the turbulence is predominantly highly oblique to the magnetic field k Gt k ∥, and propagates slowly in the plasma frame with most points having frequencies smaller than the proton gyrofrequency ωpla < Ω p . Weak agreement is found that turbulence at the ion kinetic scales consists of kinetic Alfvén waves and coherent structures advected with plasma bulk velocity plus some minor more compressible components. The results suggest that anti-sunward and sunward propagating magnetic fluctuations are of similar nature in both the fast and slow solar wind at ion kinetic scales. The fast wind has significantly more anti-sunward flux than sunward flux and the slow wind appears to be more balanced.

  1. Chemistry Within Molecular Clusters

    DTIC Science & Technology

    1990-01-01

    DME )nCH3OCH 2 +). We speculate that this is due to the fragments being consumed by an ion-molecule reaction within the cluster. One likely candidate is...the ion-molecule reaction of the fragment cations with a neutral DME , within the bulk cluster to form a trimethyloxonlum cation intermediate. This...the observed products. We therefore speculate that the DME cluster reactions leading to the same products, should involve the same mechanism found to

  2. Solar Wind Magnetic Field Turbulence at Ion Kinetic Scales Measured by Cluster Using k-filtering Technique

    NASA Astrophysics Data System (ADS)

    Li, X.; Roberts, O. W.; Jeska, L.; Li, B.; Lu, Q.

    2014-12-01

    The nature of turbulence at kinetic scales is important since turbulence energy is believed to dissipate as heat at these scales. Here we report our several work on the solar wind turbulence at ion kinetic scales using the k-filtering technique. We found evidence of ion cyclotron resonance in solar wind intervals. In the wave vector space, in addition to the commonly observed population of magnetic field fluctuations propagating at quasi-perpendicular angles to the global mean field B0, a population propagating at quasi-parallel angles are also observed with no local plasma instabilities identified. At low wavenumbers (kv_A/Omega_p <= 0.6 ) both components are present, and have similar powers, while at higher wavenumbers (kv_A/Omega_p> 0.6) only the perpendicular component can be identified. A statistical study of 52 intervals of solar wind finds that the turbulence is predominantly highly oblique to the magnetic field with perpendicular wavenumbers much greater than parallel wavenumbers, and propagates slowly in the plasma frame with most points having frequencies smaller than the proton gyrofrequency. Weak agreement is found that turbulence at the ion kinetic scales consists of kinetic Alfven waves and coherent structures advected with plasma bulk velocity plus some minor more compressible components. The results suggest that anti-sunward and sunward propagating magnetic fluctuations have similar nature in both the fast and slow solar wind. The fast wind was shown to have significantly more anti-sunward flux than sunward flux and the slow wind appears to be more balanced at ion kinetic scales. The fluctuated magnetic field and magnitude of the magnetic field are used to compute the power of incompressible and compressible turbulence for the fast solar wind.