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Sample records for multi-charged ion atom

  1. Beam Extraction from Laser Driven Multi-Charged Ion Source

    SciTech Connect

    Anderson, O A; Logan, B G

    2001-03-19

    A newly proposed type of multicharged ion source offers the possibility of an economically advantageous high-charge-state fusion driver. Multiphoton absorption in an intense uniform laser focus can give multiple charge states of high purity, simplifying or eliminating the need for charge-state separation downstream. Very large currents (hundreds of amperes) can be extracted from this type of source. Several arrangements are possible. For example, the laser plasma could be tailored for storage in a magnetic bucket, with beam extracted from the bucket. A different approach, described in this report, is direct beam extraction from the expanding laser plasma. They discuss extraction and focusing for the particular case of a 4.1-MV beam of Xe{sup 16+} ions. The maximum duration of the beam pulse is limited by the total charge in the plasma, while the practical pulse length is determined by the range of plasma radii over which good beam optics can be achieved. The extraction electrode contains a solenoid for beam focusing. The design studies were carried out first with an envelope code and then with a self-consistent particle code. Results from the initial model showed that hundreds of amperes could be extracted, but that most of this current missed the solenoid entrance or was intercepted by the wall and that only a few amperes were able to pass through. They conclude with an improved design which increases the surviving beam to more than 70 amperes.

  2. An analytic expression for the sheath criterion in magnetized plasmas with multi-charged ion species

    SciTech Connect

    Hatami, M. M.

    2015-04-15

    The generalized Bohm criterion in magnetized multi-component plasmas consisting of multi-charged positive and negative ion species and electrons is analytically investigated by using the hydrodynamic model. It is assumed that the electrons and negative ion density distributions are the Boltzmann distribution with different temperatures and the positive ions enter into the sheath region obliquely. Our results show that the positive and negative ion temperatures, the orientation of the applied magnetic field and the charge number of positive and negative ions strongly affect the Bohm criterion in these multi-component plasmas. To determine the validity of our derived generalized Bohm criterion, it reduced to some familiar physical condition and it is shown that monotonically reduction of the positive ion density distribution leading to the sheath formation occurs only when entrance velocity of ion into the sheath satisfies the obtained Bohm criterion. Also, as a practical application of the obtained Bohm criterion, effects of the ionic temperature and concentration as well as magnetic field on the behavior of the charged particle density distributions and so the sheath thickness of a magnetized plasma consisting of electrons and singly charged positive and negative ion species are studied numerically.

  3. Theoretical investigations of the IO,q+ (q = 2, 3, 4) multi-charged ions: Metastability, characterization and spectroscopy

    NASA Astrophysics Data System (ADS)

    Hammami, H.; Yazidi, O.; Ben El Hadj Rhouma, M.; Al Mogren, M. M.; Hochlaf, M.

    2014-07-01

    Using ab initio methodology, we studied the IOq+ (q = 2, 3, 4) multi-charged ions. Benchmark computations on the IO(X2Π) neutral species allow validate the current procedure. For IO2+, several potential wells were found on the ground and the electronic excited states potentials with potential barriers with respect to dissociation, where this dication can exist in the gas phase as long-lived metastable molecules. We confirm hence the recent observation of the dication by mass spectrometry. Moreover, we predict the existence of the metastable IO3+ trication, where a shallow potential well along the IO internuclear distance is computed. This potential well supports more than 10 vibrational levels. The IO3+ excited states are repulsive in nature, as well as the computed potentials for the IO4+ tetracation. For the bound states, we give a set of spectroscopic parameters including excitation transition energies, equilibrium distances, harmonic and anharmonic vibrational terms, and rotational constants. At the MRCI + Q/aug-cc-pV5Z(-PP) level, the adiabatic double and triple ionization energies of IO are computed to be ˜28.1 eV and ˜55.0 eV, respectively.

  4. Theoretical investigations of the IO,{sup q+} (q = 2, 3, 4) multi-charged ions: Metastability, characterization and spectroscopy

    SciTech Connect

    Hammami, H.; Yazidi, O.; Ben El Hadj Rhouma, M.; Al Mogren, M. M.; Hochlaf, M.

    2014-07-07

    Using ab initio methodology, we studied the IO{sup q+} (q = 2, 3, 4) multi-charged ions. Benchmark computations on the IO(X{sup 2}Π) neutral species allow validate the current procedure. For IO{sup 2+}, several potential wells were found on the ground and the electronic excited states potentials with potential barriers with respect to dissociation, where this dication can exist in the gas phase as long-lived metastable molecules. We confirm hence the recent observation of the dication by mass spectrometry. Moreover, we predict the existence of the metastable IO{sup 3+} trication, where a shallow potential well along the IO internuclear distance is computed. This potential well supports more than 10 vibrational levels. The IO{sup 3+} excited states are repulsive in nature, as well as the computed potentials for the IO{sup 4+} tetracation. For the bound states, we give a set of spectroscopic parameters including excitation transition energies, equilibrium distances, harmonic and anharmonic vibrational terms, and rotational constants. At the MRCI + Q/aug-cc-pV5Z(-PP) level, the adiabatic double and triple ionization energies of IO are computed to be ∼28.1 eV and ∼55.0 eV, respectively.

  5. Theoretical investigations of the IO,q+ (q = 2, 3, 4) multi-charged ions: metastability, characterization and spectroscopy.

    PubMed

    Hammami, H; Yazidi, O; Ben El Hadj Rhouma, M; Al Mogren, M M; Hochlaf, M

    2014-07-01

    Using ab initio methodology, we studied the IO(q+) (q = 2, 3, 4) multi-charged ions. Benchmark computations on the IO(X(2)Π) neutral species allow validate the current procedure. For IO(2+), several potential wells were found on the ground and the electronic excited states potentials with potential barriers with respect to dissociation, where this dication can exist in the gas phase as long-lived metastable molecules. We confirm hence the recent observation of the dication by mass spectrometry. Moreover, we predict the existence of the metastable IO(3+) trication, where a shallow potential well along the IO internuclear distance is computed. This potential well supports more than 10 vibrational levels. The IO(3+) excited states are repulsive in nature, as well as the computed potentials for the IO(4+) tetracation. For the bound states, we give a set of spectroscopic parameters including excitation transition energies, equilibrium distances, harmonic and anharmonic vibrational terms, and rotational constants. At the MRCI + Q/aug-cc-pV5Z(-PP) level, the adiabatic double and triple ionization energies of IO are computed to be ~28.1 eV and ~55.0 eV, respectively.

  6. Generation of multi-charged high current ion beams using the SMIS 37 gas-dynamic electron cyclotron resonance (ECR) ion source

    SciTech Connect

    Dorf, M. A.; Zorin, V. G.; Sidorov, A. V.; Bokhanov, A. F.; Izotov, I. V.; Razin, S. V.; Skalyga, V. A.

    2013-06-02

    A gas-dynamic ECR ion source (GaDIS) is distinguished by its ability to produce high current and high brightness beams of moderately charged ions. Contrary to a classical ECR ion source where the plasma confinement is determined by the slow electron scattering into an empty loss-cone, the higher density and lower electron temperature in a GaDIS plasma lead to an isotropic electron distribution with the confinement time determined by the prompt gas-dynamic flow losses. As a result, much higher ion fluxes are available, however a decrease in the confinement time of the GaDIS plasma lowers the ion charge state. The gas-dynamic ECR ion source concept has been successfully realized in the SMIS 37 experimental facility operated at the Institute of Applied Physics, Russia. The use of high-power (~100 kW) microwave (37.5 GHz) radiation provides a dense plasma (~1013 cm-3) with a relatively low electron temperature (~50- 100 eV) and allows for the generation of high current (~1 A/cm2) beams of multi-charged ions. In this work we report on the present status of the SMIS 37 ion source and discuss the advanced numerical modeling of ion beam extraction using the particle-in-cell code WARP

  7. Formation of multi-charged ion beams by focusing effect of mid-electrode on electron cyclotron resonance ion source

    SciTech Connect

    Imai, Youta Kimura, Daiju; Kurisu, Yosuke; Nozaki, Dai; Yano, Keisuke; Kumakura, Sho; Sato, Fuminobu; Kato, Yushi; Iida, Toshiyuki

    2014-02-15

    We are constructing a tandem type electron cyclotron resonance ion source (ECRIS) and a beam line for extracting ion beams. The ion beam is extracted from the second stage by an accel-decel extraction system with a single-hole and the ion beam current on each electrode is measured. The total ion beam current is measured by a faraday cup downstream the extraction electrodes. We measure these currents as a function of the mid-electrode potential. We also change the gap length between electrodes and perform similar measurement. The behaviors of these currents obtained experimentally against the mid-electrode potential show qualitatively good agreement with a simple theoretical consideration including sheath potential effects. The effect of mid-electrode potential is very useful for decreasing the beam loss for enhancing ion beam current extracted from ECRIS.

  8. Atom-ion quantum gate

    SciTech Connect

    Doerk, Hauke; Idziaszek, Zbigniew; Calarco, Tommaso

    2010-01-15

    Ultracold collisions of ions with neutral atoms in traps are studied. Recently, ultracold atom-ion systems have become available in experimental setups, where their quantum states can be coherently controlled. This control allows for an implementation of quantum information processing, combining the advantages of charged and neutral particles. The state-dependent dynamics that is a necessary ingredient for quantum computation schemes is provided in this case by the short-range interaction forces that depend on the hyperfine states of both particles. In this work, a theoretical description of spin-state-dependent trapped atom-ion collisions is developed in the framework of a multichannel quantum-defect theory and an effective single-channel model is formulated that reduces the complexity of the problem. Based on this description, a two-qubit phase gate between a {sup 135}Ba{sup +} ion and a {sup 87}Rb atom is simulated using a realistic combination of the singlet and triplet scattering lengths. The gate process is optimized and accelerated with the help of optimal control techniques. The result is a gate fidelity of 1-10{sup -3} within 350 mus.

  9. Laser-cooled atomic ions as probes of molecular ions

    SciTech Connect

    Brown, Kenneth R.; Viteri, C. Ricardo; Clark, Craig R.; Goeders, James E.; Khanyile, Ncamiso B.; Vittorini, Grahame D.

    2015-01-22

    Trapped laser-cooled atomic ions are a new tool for understanding cold molecular ions. The atomic ions not only sympathetically cool the molecular ions to millikelvin temperatures, but the bright atomic ion fluorescence can also serve as a detector of both molecular reactions and molecular spectra. We are working towards the detection of single molecular ion spectra by sympathetic heating spectroscopy. Sympathetic heating spectroscopy uses the coupled motion of two trapped ions to measure the spectra of one ion by observing changes in the fluorescence of the other ion. Sympathetic heating spectroscopy is a generalization of quantum logic spectroscopy, but does not require ions in the motional ground state or coherent control of the ion internal states. We have recently demonstrated this technique using two isotopes of Ca{sup +} [Phys. Rev. A, 81, 043428 (2010)]. Limits of the method and potential applications for molecular spectroscopy are discussed.

  10. Ion-Atom Cold Collisions and Atomic Clocks

    NASA Technical Reports Server (NTRS)

    Prestage, John D.; Maleki, Lute; Tjoelker, Robert L.

    1997-01-01

    Collisions between ultracold neutral atoms have for some time been the subject of investigation, initially with hydrogen and more recently with laser cooled alkali atoms. Advances in laser cooling and trapping of neutral atoms in a Magneto-Optic Trap (MOT) have made cold atoms available as the starting point for many laser cooled atomic physics investigations. The most spectacularly successful of these, the observation of Bose-Einstein Condensation (BEC) in a dilute ultra-cold spin polarized atomic vapor, has accelerated the study of cold collisions. Experimental and theoretical studies of BEC and the long range interaction between cold alkali atoms is at the boundary of atomic and low temperature physics. Such studies have been difficult and would not have been possible without the development and advancement of laser cooling and trapping of neutral atoms. By contrast, ion-atom interactions at low temperature, also very difficult to study prior to modern day laser cooling, have remained largely unexplored. But now, many laboratories worldwide have almost routine access to cold neutral atoms. The combined technologies of ion trapping, together with laser cooling of neutrals has made these studies experimentally feasible and several very important, novel applications might come out of such investigations . This paper is an investigation of ion-atom interactions in the cold and ultra-cold temperature regime. Some of the collisional ion-atom interactions present at room temperature are very much reduced in the low temperature regime. Reaction rates for charge transfer between unlike atoms, A + B(+) approaches A(+) + B, are expected to fall rapidly with temperature, approximately as T(sup 5/2). Thus, cold mixtures of atoms and ions are expected to coexist for very long times, unlike room temperature mixtures of the same ion-atom combination. Thus, it seems feasible to cool ions via collisions with laser cooled atoms. Many of the conventional collisional interactions

  11. Atomic Clock Based On Linear Ion Trap

    NASA Technical Reports Server (NTRS)

    Prestage, John D.; Dick, G. John

    1992-01-01

    Highly stable atomic clock based on excitation and measurement of hyperfine transition in 199Hg+ ions confined in linear quadrupole trap by radio-frequency and static electric fields. Configuration increases stability of clock by enabling use of enough ions to obtain adequate signal while reducing non-thermal component of motion of ions in trapping field, reducing second-order Doppler shift of hyperfine transition. Features described in NPO-17758 "Linear Ion Trap for Atomic Clock." Frequency standard based on hyperfine transition described in NPO-17456, "Trapped-Mercury-Ion Frequency Standard."

  12. Atomic physics with highly charged ions

    SciTech Connect

    Richard, P.

    1991-08-01

    This report discusses: One electron outer shell processes in fast ion-atom collisions; role of electron-electron interaction in two-electron processes; multi-electron processes at low energy; multi-electron processes at high energy; inner shell processes; molecular fragmentation studies; theory; and, JRM laboratory operations.

  13. Quantum-classical electron distributions in atoms and atomic ions

    NASA Technical Reports Server (NTRS)

    Kunc, Joseph A.

    1988-01-01

    A quantum-classical approach is used to obtain the velocity distributions in atoms and positive and negative ions in both ground and excited states. In the analysis, Hartree-Fock electronic wavefunctions are used to determine the radial electron distributions, and the central-field approximation is used to study the the dynamic properties of the localized electrons. The distributions for the outer and inner shells are found to agree well with exact results obtained by numerical calculations.

  14. Experimental atomic physics in heavy-ion storage rings

    SciTech Connect

    Datz, S.; Andersen, L.H.; Briand, J.P.; Liesen, D.

    1987-01-01

    This paper outlines the discussion which took place at the ''round table'' on experimental atomic physics in heavy-ion storage rings. Areas of discussion are: electron-ion interactions, ion-ion collisions, precision spectroscopy of highly charged ions, beta decay into bound final states, and atomic binding energies from spectroscopy of conversion elections. 18 refs., 1 tab. (LSP)

  15. Atomic ion clock with two ion traps, and method to transfer ions

    NASA Technical Reports Server (NTRS)

    Prestage, John D. (Inventor); Chung, Sang K. (Inventor)

    2011-01-01

    An atomic ion clock with a first ion trap and a second ion trap, where the second ion trap is of higher order than the first ion trap. In one embodiment, ions may be shuttled back and forth from one ion trap to the other by application of voltage ramps to the electrodes in the ion traps, where microwave interrogation takes place when the ions are in the second ion trap, and fluorescence is induced and measured when the ions are in the first ion trap. In one embodiment, the RF voltages applied to the second ion trap to contain the ions are at a higher frequency than that applied to the first ion trap. Other embodiments are described and claimed.

  16. Linear ion trap based atomic frequency standard

    NASA Technical Reports Server (NTRS)

    Prestage, John D.; Dick, G. J.; Maleki, Lute

    1991-01-01

    In order to develop a trapped ion-based fieldable frequency standard with stability 1 x 10 to the -13th/sq rt tau for averaging times tau greater than 10,000 s, a hybrid RF/DC linear ion trap was developed which permits storage of large numbers of ions with reduced susceptibility to the second-order Doppler effect caused by the RF confining fields. The authors have confined Hg-199(+) ions in this trap and have measured very high Q transitions with good SNRs. In preliminary measurements they obtained stabilities of 1.6 x 10 to the -13th/sq rt tau (tau between 50 and 800 s) with a 160-mHz wide atomic resonance linewidth and a signal-to-noise ratio of 40 for each measurement cycle. Atomic resonance lines as narrow as 30 mHz on the 40.5-GHz clock transition have been measured with no appreciable reduction in the ion signal. A stability of 7 x 10 to the -14th/sq rt tau is made possible by the signal-to-noise and line Q of this measured transition. Analysis of fundamental sources of frequency instability indicates that a long-term stability of 2 x 10 to the -16th is feasible for this device with existing technology for tau = 10 to the 6th s or more.

  17. Cold atomic beam ion source for focused ion beam applications

    SciTech Connect

    Knuffman, B.; Steele, A. V.; McClelland, J. J.

    2013-07-28

    We report measurements and modeling of an ion source that is based on ionization of a laser-cooled atomic beam. We show a high brightness and a low energy spread, suitable for use in next-generation, high-resolution focused ion beam systems. Our measurements of total ion current as a function of ionization conditions support an analytical model that also predicts the cross-sectional current density and spatial distribution of ions created in the source. The model predicts a peak brightness of 2 × 10{sup 7} A m{sup −2} sr{sup −1} eV{sup −1} and an energy spread less than 0.34 eV. The model is also combined with Monte-Carlo simulations of the inter-ion Coulomb forces to show that the source can be operated at several picoamperes with a brightness above 1 × 10{sup 7} A m{sup −2} sr{sup −1} eV{sup −1}. We estimate that when combined with a conventional ion focusing column, an ion source with these properties could focus a 1 pA beam into a spot smaller than 1 nm. A total current greater than 5 nA was measured in a lower-brightness configuration of the ion source, demonstrating the possibility of a high current mode of operation.

  18. JPL Ultrastable Trapped Ion Atomic Frequency Standards.

    PubMed

    Burt, Eric A; Yi, Lin; Tucker, Blake; Hamell, Robert; Tjoelker, Robert L

    2016-07-01

    Recently, room temperature trapped ion atomic clock development at the Jet Propulsion Laboratory (JPL) has focused on three directions: 1) ultrastable atomic clocks, usually for terrestrial applications emphasizing ultimate stability performance and autonomous timekeeping; 2) new atomic clock technology for space flight applications that require strict adherence to size, weight, and power requirements; and 3) miniature clocks. In this paper, we concentrate on the first direction and present a design and the initial results from a new ultrastable clock referred to as L10 that achieves a short-term stability of 4.5 ×10(-14)/τ(1/2) and an initial measurement of no significant drift with an uncertainty of 2.4 ×10(-16) /day over a two-week period.

  19. JPL Ultrastable Trapped Ion Atomic Frequency Standards.

    PubMed

    Burt, Eric A; Yi, Lin; Tucker, Blake; Hamell, Robert; Tjoelker, Robert L

    2016-07-01

    Recently, room temperature trapped ion atomic clock development at the Jet Propulsion Laboratory (JPL) has focused on three directions: 1) ultrastable atomic clocks, usually for terrestrial applications emphasizing ultimate stability performance and autonomous timekeeping; 2) new atomic clock technology for space flight applications that require strict adherence to size, weight, and power requirements; and 3) miniature clocks. In this paper, we concentrate on the first direction and present a design and the initial results from a new ultrastable clock referred to as L10 that achieves a short-term stability of 4.5 ×10(-14)/τ(1/2) and an initial measurement of no significant drift with an uncertainty of 2.4 ×10(-16) /day over a two-week period. PMID:27249827

  20. Atomic forces between noble gas atoms, alkali ions, and halogen ions for surface interactions

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; Outlaw, R. A.; Heinbockel, J. H.

    1988-01-01

    The components of the physical forces between noble gas atoms, alkali ions, and halogen ions are analyzed and a data base developed from analysis of the two-body potential data, the alkali-halide molecular data, and the noble gas crystal and salt crystal data. A satisfactory global fit to this molecular and crystal data is then reproduced by the model to within several percent. Surface potentials are evaluated for noble gas atoms on noble gas surfaces and salt crystal surfaces with surface tension neglected. Within this context, the noble gas surface potentials on noble gas and salt crystals are considered to be accurate to within several percent.

  1. Continuum Absorption Coefficient of Atoms and Ions

    NASA Technical Reports Server (NTRS)

    Armaly, B. F.

    1979-01-01

    The rate of heat transfer to the heat shield of a Jupiter probe has been estimated to be one order of magnitude higher than any previously experienced in an outer space exploration program. More than one-third of this heat load is due to an emission of continuum radiation from atoms and ions. The existing computer code for calculating the continuum contribution to the total load utilizes a modified version of Biberman's approximate method. The continuum radiation absorption cross sections of a C - H - O - N ablation system were examined in detail. The present computer code was evaluated and updated by being compared with available exact and approximate calculations and correlations of experimental data. A detailed calculation procedure, which can be applied to other atomic species, is presented. The approximate correlations can be made to agree with the available exact and experimental data.

  2. Compact, Highly Stable Ion Atomic Clock

    NASA Technical Reports Server (NTRS)

    Prestage, John

    2008-01-01

    A mercury-ion clock now at the breadboard stage of development (see figure) has a stability comparable to that of a hydrogen-maser clock: In tests, the clock exhibited an Allan deviation of between 2 x 10(exp -13) and 3 x 10(exp -13) at a measurement time of 1 second, averaging to about 10(exp -15) at 1 day. However, the clock occupies a volume of only about 2 liters . about a hundredth of the volume of a hydrogen-maser clock. The ion-handling parts of the apparatus are housed in a sealed vacuum tube, wherein only a getter pump is used to maintain the vacuum. Hence, this apparatus is a prototype of a generation of small, potentially portable high-precision clocks for diverse ground- and space-based navigation and radio science applications. Furthermore, this new ion-clock technology is about 100 times more stable and precise than the rubidium atomic clocks currently in use in the NAV STAR GPS Earth-orbiting satellites. In this clock, mercury ions are shuttled between a quadrupole and a 16-pole linear radio-frequency trap. In the quadrupole trap, the ions are tightly confined and optical state selection from a Hg-202 radio-frequency-discharge ultraviolet lamp is carried out. In the 16-pole trap, the ions are more loosely confined and atomic transitions resonant at frequency of about 40.507 GHz are interrogated by use of a microwave beam at that frequency. The trapping of ions effectively eliminates the frequency pulling caused by wall collisions inherent to gas-cell clocks. The shuttling of the ions between the two traps enables separation of the state-selection process from the clock microwave- resonance process, so that each of these processes can be optimized independently of the other. The basic ion-shuttling, two-trap scheme as described thus far is not new: it has been the basis of designs of prior larger clocks. The novelty of the present development lies in major redesigns of its physics package (the ion traps and the vacuum and optical subsystems) to effect

  3. Trapped Atomic Ions and Quantum Information Processing

    SciTech Connect

    Wineland, D. J.; Leibfried, D.; Bergquist, J. C.; Blakestad, R. B.; Bollinger, J. J.; Britton, J.; Chiaverini, J.; Epstein, R. J.; Hume, D. B.; Itano, W. M.; Jost, J. D.; Koelemeij, J. C. J.; Langer, C.; Ozeri, R.; Reichle, R.; Rosenband, T.; Schaetz, T.; Schmidt, P. O.; Seidelin, S.; Shiga, N.

    2006-11-07

    The basic requirements for quantum computing and quantum simulation (single- and multi-qubit gates, long memory times, etc.) have been demonstrated in separate experiments on trapped ions. Construction of a large-scale information processor will require synthesis of these elements and implementation of high-fidelity operations on a very large number of qubits. This is still well in the future. NIST and other groups are addressing part of the scaling issue by trying to fabricate multi-zone arrays of traps that would allow highly-parallel and scalable processing. In the near term, some simple quantum processing protocols are being used to aid in quantum metrology, such as in atomic clocks. As the number of qubits increases, Schroedinger's cat paradox and the measurement problem in quantum mechanics become more apparent; with luck, trapped ion systems might be able to shed light on these fundamental issues.

  4. Reactions of atomic oxygen with the chlorate ion and the perchlorate ion

    NASA Astrophysics Data System (ADS)

    Anan'ev, Vladimir; Miklin, Mikhail; Kriger, Ludmila

    2014-06-01

    The reactions of the chlorate ion with atomic oxygen formed under photolysis of the nitrate ion introduced to potassium chlorate crystal by co-crystallization were studied by optical and infrared absorption spectroscopy. The perchlorate ion was found to form in solids as product of addition reaction of singlet atomic oxygen, formed under dissociation of the peroxynitrite ion - the product of isomerization of the excited nitrate ion. Triplet atomic oxygen does not react with the chlorate ion. The atomic oxygen formed under photolysis of the nitrate ion introduced to potassium perchlorate crystal by co-crystallization does not react with the perchlorate ion.

  5. Ionization Phenomena in Ion-Atom Collisions

    NASA Astrophysics Data System (ADS)

    Deveney, Edward Francis

    Two many-electron ion-atom collision systems are used to investigate atomic and molecular structure and collisional interactions. Electrons emitted from MeV/u C^{3+} projectile target -atom collisions were measured with a high-resolution position -sensitive electron spectrometer at Oak Ridge National Laboratory. The electrons are predominantly ionized by direct projectile -target interactions or autoionizing (AI) from doubly excited AI levels of the ion which were excited in the collision. The energy dependence of directly scattered target electrons, binary-encounter electrons (BEE), is investigated and compared with theory. AI levels of the projectile 1s to nl single electron excited series, (1s2snl) n = 2,3,4,....infty, including the series limit are identified uniquely using energy level calculations. Original Auger yield calculations using a code by Cowan were used to discover a 1/{n^3} scaling in intensities of Auger peaks in the aforementioned series. This is explained using scattering theory. A nonstatistical population of the terms in the (1s2s2l) configuration was identified and investigated as a function of the beam energy and for four different target atoms. Two electron excited configurations are identified and investigated. The angular distribution of a correlated transfer and excitation AI state is measured and compared to theory. The final scattered charge state distributions of Kr^ {n+}, n = 1, 2, 3, 4, 5, projectiles are measured following collisions with Kr targets in the Van de Graaff Laboratory here at The University of Connecticut. Average scattered charge states as high as 12 are observed. It appears that these electrons are ionized during the lifetime of the quasimolecular state but a complete picture of the ionization mechanism(s) is not known. Calculations using a statistical model of ionization, modified in several ways, are compared with the experimental results to see if it is possible to isolate whether or not the electrons originate

  6. HISTRAP proposal: heavy ion storage ring for atomic physics

    SciTech Connect

    Olsen, D.K.; Alton, G.D.; Datz, S.; Dittner, P.F.; Dowling, D.T.; Haynes, D.L.; Hudson, E.D.; Johnson, J.W.; Lee, I.Y.; Lord, R.S.

    1986-11-01

    HISTRAP, Heavy Ion Storage Ring for Atomic Physics, is a proposed 46.8-m-circumference synchrotron-cooling-storage ring optimized to accelerate, decelerate, and store beams of highly charged very-heavy ions at energies appropriate for advanced atomic physics research. The ring is designed to allow studies of electron-ion, photon-ion, ion-atom, and ion-ion interactions. An electron cooling system will provide ion beams with small angular divergence and energy spread for precision spectroscopic studies and also is necessary to allow the deceleration of heavy ions to low energies. HISTRAP will have a maximum bending power of 2.0 Tm and will be injected with ions from either the existing Holifield Heavy Ion Research Facility 25-MV tandem accelerator or from a dedicated ECR source and 250 keV/nucleon RFQ linac.

  7. Ultracold collisions between Rb atoms and a Sr+ ion

    NASA Astrophysics Data System (ADS)

    Meir, Ziv; Sikorsky, Tomas; Ben-Shlomi, Ruti; Dallal, Yehonatan; Ozeri, Roee

    2015-05-01

    In last decade, a novel field emerged, in which ultracold atoms and ions in overlapping traps are brought into interaction. In contrast to the short ranged atom-atom interaction which scales as r-6, atom-ion potential persists for hundreds of μm's due to its lower power-law scaling - r-4. Inelastic collisions between the consistuents lead to spin and charge transfer and also to molecule formation. Elastic collisions control the energy transfer between the ion and the atoms. The study of collisions at the μK range has thus far been impeded by the effect of the ion's micromotion which limited collision energy to mK scale. Unraveling this limit will allow to investigate few partial wave and even S-wave collisions. Our system is capable of trapping Sr+ ions and Rb and Sr atoms and cooling them to their quantum ground state. Atoms and ions are trapped and cooled in separate chambers. Then, the atoms are transported using an optical conveyer belt to overlap the ions. In contrast to other experiments in this field where the atoms are used to sympathetic cool the ion, our system is also capable of ground state cooling the ion before immersing it into the atom cloud. By this method, we would be able to explore heating and cooling dynamics in the ultracold regime.

  8. Problems with Accurate Atomic Lfetime Measurements of Multiply Charged Ions

    SciTech Connect

    Trabert, E

    2009-02-19

    A number of recent atomic lifetime measurements on multiply charged ions have reported uncertainties lower than 1%. Such a level of accuracy challenges theory, which is a good thing. However, a few lessons learned from earlier precision lifetime measurements on atoms and singly charged ions suggest to remain cautious about the systematic errors of experimental techniques.

  9. HISTRAP proposal: heavy ion storage ring for atomic physics

    SciTech Connect

    Olsen, D.K.; Alton, G.D.; Datz, S.; Dittner, P.F.; Dowling, D.T.; Haynes, D.L.; Hudson, E.D.; Johnson, J.W.; Lee, I.Y.; Lord, R.S.

    1986-01-01

    HISTRAP is a proposed synchrotron-cooling-storage ring optimized to accelerate, decelerate, and store beams of highly charged very-heavy ions at energies appropriate for advanced atomic physics research. The ring is designed to allow studies of electron-ion, photon-ion, ion-atom, and ion-ion interactions. An electron cooling system will provide ion beams with small angular divergence and energy spread for precision spectroscopic studies and also is necessary to allow the deceleration of heavy ions to low energies. HISTRAP will be injected with ions from either the existing Holifield Heavy Ion Research Facility 25-MV tandem accelerator or from a dedicated ECR source and 250 keV/nucleon RFQ linac. The ring will have a maximum bending power of 2.0 T.m and have a circumference of 46.8 m.

  10. Quantum Electrodynamics Effects in Heavy Ions and Atoms

    SciTech Connect

    Shabaev, V. M.; Andreev, O. V.; Bondarev, A. I.; Glazov, D. A.; Kozhedub, Y. S.; Maiorova, A. V.; Tupitsyn, I. I.; Plunien, G.; Volotka, A. V.

    2011-05-11

    Quantum electrodynamics theory of heavy ions and atoms is considered. The current status of calculations of the binding energies, the hyperfine splitting and g factor values in heavy few-electron ions is reviewed. The theoretical predictions are compared with available experimental data. A special attention is focused on tests of quantum electrodynamics in strong electromagnetic fields and on determination of the fundamental constants. Recent progress in calculations of the parity nonconservation effects with heavy atoms and ions is also reported.

  11. Controlled long-range interactions between Rydberg atoms and ions

    NASA Astrophysics Data System (ADS)

    Secker, T.; Gerritsma, R.; Glaetzle, A. W.; Negretti, A.

    2016-07-01

    We theoretically investigate trapped ions interacting with atoms that are coupled to Rydberg states. The strong polarizabilities of the Rydberg levels increase the interaction strength between atoms and ions by many orders of magnitude, as compared to the case of ground-state atoms, and may be mediated over micrometers. We calculate that such interactions can be used to generate entanglement between an atom and the motion or internal state of an ion. Furthermore, the ion could be used as a bus for mediating spin-spin interactions between atomic spins in analogy to much employed techniques in ion-trap quantum simulation. The proposed scheme comes with attractive features as it maps the benefits of the trapped-ion quantum system onto the atomic one without obviously impeding its intrinsic scalability. No ground-state cooling of the ion or atom is required and the setup allows for full dynamical control. Moreover, the scheme is to a large extent immune to the micromotion of the ion. Our findings are of interest for developing hybrid quantum information platforms and for implementing quantum simulations of solid-state physics.

  12. Entropy lowering in ion-atom collisions

    SciTech Connect

    Nguyen, H.; Bredy, R.; Camp, H.A.; DePaola, B.D.; Lee, T.G.; Awata, T.

    2005-06-15

    In ion-atom collisions, the charge transfer cross section is typically a strong function of the energy defect or Q value, typically with smaller energy defects giving rise to higher capture probabilities. In some theoretical treatments, for example those based on the Demkov model, the cross section is a strong function of the magnitude of the Q value, but is independent of its sign. In order to test this predicted sign independence, one must compare capture cross sections from energetically symmetric collision channels. In this work, relative capture cross sections, differential in scattering angle, are measured and compared for the energetically symmetric channels: Rb{sup +}+Rb(5s){yields}Rb(5p)+Rb{sup +} and Rb{sup +}+Rb(5p){yields}Rb(5s)+Rb{sup +}. It is found that not only are the two cross sections not equal, but that in this case the endoergic channel was 3 times more likely. That is, the entropy reducing channel was preferred. An intuitive model, based on molecular potential curves, is suggested. The endoergic propensity is found to be consistent with this model.

  13. Positron Interactions with Atoms and Ions

    NASA Technical Reports Server (NTRS)

    Bhatia, Anand K.

    2012-01-01

    Dirac, in 1928, combining the ideas of quantum mechanics and the ideas of relativity invented the well-known relativistic wave equation. In his formulation, he predicted an antiparticle of the electron of spin n-bar/2. He thought that this particle must be a proton. Dirac published his interpretation in a paper 'A theory of electrons and protons.' It was shown later by the mathematician Hermann Weyl that the Dirac theory was completely symmetric between negative and positive particles and the positive particle must have the same mass as that of the electron. In his J. Robert Oppenheimer Memorial Prize Acceptance Speech, Dirac notes that 'Blackett was really the first person to obtain hard evidence for the existence of a positron but he was afraid to publish it. He wanted confirmation, he was really over cautious.' Positron, produced by the collision of cosmic rays in a cloud chamber, was detected experimentally by Anderson in 1932. His paper was published in Physical Review in 1933. The concept of the positron and its detection were the important discoveries of the 20th century. I have tried to discuss various processes involving interactions of positrons with atoms and ions. This includes scattering, bound states and resonances. It has not been possible to include the enormous work which has been carried out during the last 40 or 50 years in theory and measurements.

  14. Confinement-induced resonances in ultracold atom-ion systems

    NASA Astrophysics Data System (ADS)

    Melezhik, V. S.; Negretti, A.

    2016-08-01

    We investigate confinement-induced resonances in a system composed of a tightly trapped ion and a moving atom in a waveguide. We determine the conditions for the appearance of such resonances in a broad region—from the "long-wavelength" limit to the opposite case when the typical length scale of the atom-ion polarization potential essentially exceeds the transverse waveguide width. We find considerable dependence of the resonance position on the atomic mass which, however, disappears in the "long-wavelength and zero-energy" limit, where the known result for the confined atom-atom scattering is reproduced. We also derive an analytic and a semianalytic formula for the resonance position in the long-wavelength and zero-energy limit and we investigate numerically the dependence of the resonance condition on the finite atomic colliding energy. Our results, which can be investigated experimentally in the near future, could be used to determine the atom-ion scattering length, to determine the temperature of the atomic ensemble in the presence of an ion impurity, and to control the atom-phonon coupling in a linear ion crystal in interaction with a quasi-one-dimensional atomic quantum gas.

  15. Analysis of the physical atomic forces between noble gas atoms, alkali ions and halogen ions

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; Heinbockel, J. H.; Outlaw, R. A.

    1986-01-01

    The physical forces between atoms and molecules are important in a number of processes of practical importance, including line broadening in radiative processes, gas and crystal properties, adhesion, and thin films. The components of the physical forces between noble gas atoms, alkali ions, and halogen ions are analyzed and a data base for the dispersion forces is developed from the literature based on evaluations with the harmonic oscillator dispersion model for higher order coefficients. The Zener model of the repulsive core is used in the context of the recent asymptotic wave functions of Handler and Smith; and an effective ionization potential within the Handler and Smith wave functions is defined to analyze the two body potential data of Waldman and Gordon, the alkali-halide molecular data, and the noble gas crystal and salt crystal data. A satisfactory global fit to this molecular and crystal data is then reproduced by the model to within several percent. Surface potentials are evaluated for noble gas atoms on noble gas and salt crystal surfaces with surface tension neglected. Within this context, the noble gas surface potentials on noble gas and salt crystals are considered to be accurate to within several percent.

  16. Atomic structure of highly-charged ions. Final report

    SciTech Connect

    Livingston, A. Eugene

    2002-05-23

    Atomic properties of multiply charged ions have been investigated using excitation of energetic heavy ion beams. Spectroscopy of excited atomic transitions has been applied from the visible to the extreme ultraviolet wavelength regions to provide accurate atomic structure and transition rate data in selected highly ionized atoms. High-resolution position-sensitive photon detection has been introduced for measurements in the ultraviolet region. The detailed structures of Rydberg states in highly charged beryllium-like ions have been measured as a test of long-range electron-ion interactions. The measurements are supported by multiconfiguration Dirac-Fock calculations and by many-body perturbation theory. The high-angular-momentum Rydberg transitions may be used to establish reference wavelengths and improve the accuracy of ionization energies in highly charged systems. Precision wavelength measurements in highly charged few-electron ions have been performed to test the most accurate relativistic atomic structure calculations for prominent low-lying excited states. Lifetime measurements for allowed and forbidden transitions in highly charged few-electron ions have been made to test theoretical transition matrix elements for simple atomic systems. Precision lifetime measurements in laser-excited alkali atoms have been initiated to establish the accuracy of relativistic atomic many-body theory in many-electron systems.

  17. Ion-Atom and Ion-Molecule Hybrid Systems: Ion-Neutral Chemistry at Ultralow Energies

    NASA Astrophysics Data System (ADS)

    Eberle, Pascal; Dörfler, Alexander D.; von Planta, Claudio; Ravi, Krishnamurthy; Haas, Dominik; Zhang, Dong; van de Meerakker, Sebastiaan Y. T.; Willitsch, Stefan

    2015-09-01

    The study of chemical reactions between ions and neutral species at very low energies reveals precise informations about the dynamics of collisions and fine details of intermolecular interactions. Here, we report progress towards the development of next- generation experiments for the investigation of cold ion-neutral reactions. First, we present a new ’’dynamic” hybrid ion-atom trap which enables the study of collisions with a superior energy resolution accessing a regime in which quantum scattering resonances may become observable. Second, we discuss and numerically characterize the concept and properties of a hybrid trap for cold neutral molecules and molecular ions which paves the way for the study of ion-molecule reactions in the millikelvin regime.

  18. Atomic physics with highly charged ions. Progress report

    SciTech Connect

    Richard, P.

    1994-08-01

    The study of inelastic collision phenomena with highly charged projectile ions and the interpretation of spectral features resulting from these collisions remain as the major focal points in the atomic physics research at the J.R. Macdonald Laboratory, Kansas State University, Manhattan, Kansas. The title of the research project, ``Atomic Physics with Highly Charged Ions,`` speaks to these points. The experimental work in the past few years has divided into collisions at high velocity using the primary beams from the tandem and LINAC accelerators and collisions at low velocity using the CRYEBIS facility. Theoretical calculations have been performed to accurately describe inelastic scattering processes of the one-electron and many-electron type, and to accurately predict atomic transition energies and intensities for x rays and Auger electrons. Brief research summaries are given for the following: (1) electron production in ion-atom collisions; (2) role of electron-electron interactions in two-electron processes; (3) multi-electron processes; (4) collisions with excited, aligned, Rydberg targets; (5) ion-ion collisions; (6) ion-molecule collisions; (7) ion-atom collision theory; and (8) ion-surface interactions.

  19. Study of Cold Potassium Atom - Calcium Ion Reactions

    NASA Astrophysics Data System (ADS)

    Egodapitiya, Kisra; Gang, Shu; Clark, Robert; Brown, Kenneth

    2016-05-01

    We report on our progress towards constructing a hybrid system for studying reactions between cold Potassium (K) atoms and cold Calcium (Ca+) ions. Ca+ ions will be trapped and Doppler-cooled inside a linear quadrupole ion trap. Cold K atoms will be created inside a magneto optical trap, such that the ion and the atoms are in an overlapping volume. Trapping and re-pumping beams for the Potassium MOT are derived from the same laser with wavelength 766 nm using two acousto optic modulators. The reaction products will be detected using a time-of- flight mass spectrometer that is designed to detect radially ejected ions. The main objective of this experiment is to study the rate coefficients, and identification of reaction channels between cold K atoms and Ca+ ions. Subsequently this setup will be used to study reactions between cold K atoms and sympathetically cooled molecular ions such as CaO+, and to study internal state quenching of molecular ions.

  20. Next Generation JPL Ultra-Stable Trapped Ion Atomic Clocks

    NASA Technical Reports Server (NTRS)

    Burt, Eric; Tucker, Blake; Larsen, Kameron; Hamell, Robert; Tjoelker, Robert

    2013-01-01

    Over the past decade, trapped ion atomic clock development at the Jet Propulsion Laboratory (JPL) has focused on two directions: 1) new atomic clock technology for space flight applications that require strict adherence to size, weight, and power requirements, and 2) ultra-stable atomic clocks, usually for terrestrial applications emphasizing ultimate performance. In this paper we present a new ultra-stable trapped ion clock designed, built, and tested in the second category. The first new standard, L10, will be delivered to the Naval Research Laboratory for use in characterizing DoD space clocks.

  1. An Atomic Abacus: Trapped ion quantum computing experiments at NIST

    NASA Astrophysics Data System (ADS)

    Demarco, Brian

    2003-03-01

    Trapped atomic ions are an ideal system for exploring quantum information science because deterministic state preparation and efficient state detection are possible and coherent manipulation of atomic systems is relatively advanced. In our experiment, a few singly charged Be ions are confined by static and radio-frequency electric fields in a micro-machined linear Paul trap. The internal and motional states of the ions are coherently manipulated using applied laser light. Our current work focuses on demonstrating the necessary ingredients to produce a scalable quantum computing scheme and on simplifying and improving quantum logic gates. I will speak about a new set of experiments that was made possible by recent improvements in trap technology. A novel trap with multiple trapping regions was used to demonstrate the first steps towards a fully scalable quantum computing scheme. Single ions were ``shuttled" between trapping regions without disturbing the ion's motional and internal state, and two ions were separated from a single to two different trapping zones. Improvements in the trap manufacturing process has led to a reduction of nearly two orders of magnitude in the ion's motional heating rate, making possible two new improved logic gates. The first gate utilizes the wave-packet nature of the ions to tune the laser-atom interaction and achieve a controlled-NOT gate between a single ion's spin and motional states. The second, a two-ion phase gate, uses phase-space dynamics to produce a state-sensitive geometric phase. I will end with a quick look at experiments using a Mg ion to sympathetically cool a simultaneously trapped Be ion and a glimpse of the next generation of ions traps currently under construction.

  2. New Atomic Ion SIMS Facility at the Naval Research Laboratory

    NASA Astrophysics Data System (ADS)

    Grabowski, K. S.; Fazel, K. C.; Fahey, A. J.

    2014-12-01

    Mass spectrometry of particulates and few micrometer regions of samples by Secondary Ion Mass Spectrometry (SIMS) is a very useful analytical tool. However, there are limitations caused by interferences from molecular species, such as hydrides, oxides, and carbides. Above mass 90 u, these interferences (> 104 M/ΔM) can exceed the resolving power of SIMS. Accelerator Mass Spectrometry (AMS) is capable of eliminating such molecular ion interferences, but lacks spatial information and generally requires use of negative ions. This requirement limits its sensitivity, since actinide and lanthanide elements preferentially generate positive atomic ions (~104 : 1). The Naval Research Laboratory (NRL) has installed a hybrid SIMS-AMS system, using a Single Stage AMS as a replacement for the normal Cameca IMS 4f SIMS electron multiplier detector. The NRL design enables analysis of either positive or negative ions. Thus, this system offers the potential to provide SIMS-like particle and micro-scale analysis without a forest of signals from molecular species, and is capable of measuring important positive atomic ions. This should improve measurement sensitivity and precision to determine isotopic distributions of actinides, lanthanides, and transition metals; and elemental abundances of trace species in particles or small features. Initial measurements show that molecule intensities can be reduced by seven orders of magnitude while atomic ion intensities are only diminished ~50%. We have chosen to call this instrument an atomic ion SIMS, or ai-SIMS, for short. The effect of basic operational parameters such as ion energy, charge state, molecule destruction gas and its pressure will be described, and examples of the benefits and capabilities of ai-SIMS will be presented.

  3. Bremsstrahlung spectra from atoms and ions at low relativistic energies

    NASA Astrophysics Data System (ADS)

    Avdonina, N. B.; Pratt, R. H.

    1999-09-01

    Analytic expressions for bremsstrahlung spectra from neutral atoms and ions, including the polarizational bremsstrahlung contribution in a stripped atom approximation, are developed for electron scattering at energies of 10-2000 keV. A modified Elwert factor and a simple higher Born correction are used for the Coulomb spectrum, with ordinary bremsstrahlung screening effects in ions and atoms adequately characterized in the non-relativistic Born approximation. In parallel with the development of this analytic description, new numerical results are obtained for ordinary bremsstrahlung from ions and from bare nuclei, appreciably extending the available data set which can be used to study dependences on element, ionicity, energy and the fraction of incident energy radiated. The accuracy of predictions with the analytic expressions is then determined by comparison with the full numerical relativistic partial-wave results for ordinary bremsstrahlung and with non-relativistic numerical results in the Born approximation or in partial waves for the polarizational amplitude.

  4. Scaling in the correlation energies of atomic ions

    NASA Astrophysics Data System (ADS)

    Odriazola, A.; González, A.; Räsänen, E.

    2014-11-01

    We show through numerical investigations that the ground-state correlation energies of atomic ions follow an unexpectedly simple scaling relation, Ec≈Z4 /3fc(Z /N ) , where N is the number of electrons, Z is the atomic number, and fc is a universal function, for which an analytic expression with a one-parameter fit can be provided. The relation agrees well with several sets of correlation energies obtained from different methods for atomic ions with N =2 ,...,18 and Z =2 ,...,28 . Moreover, our relation gives a good agreement with neutral atoms up to N ≈90 . Our main result is readily applicable to estimating correlation energies of heavy elements, for which there are no available data in the literature. The simplicity of the relation may also have implications in the development of correlation functionals within density-functional theory.

  5. Characterization of internal interfaces by atom probe field ion microscopy

    SciTech Connect

    Miller, M.K.; Jayaram, R.

    1992-12-31

    The near atomic spatial resolution of the atom probe field ion microscope permits the elemental characterization of internal interfaces, grain boundaries and surfaces to be performed in a wide variety of materials. Information such as the orientation relationship between grains, topology of the interface, and the coherency of small precipitates with the surrounding matrix may be obtained from field ion microscopy. Details of the solute segregation may be obtained at the plane of the interface and as a function of distance from the interface for all elements simultaneously from atom probe compositional analysis. Capabilities and limitations of the atom probe technique in characterization of internal interfaces is illustrated with examples of grain boundaries and interphase interfaces in a wide range of materials including intermetallics, model alloys, and commercial steels.

  6. Characterization of internal interfaces by atom probe field ion microscopy

    SciTech Connect

    Miller, M.K.; Jayaram, R.

    1992-01-01

    The near atomic spatial resolution of the atom probe field ion microscope permits the elemental characterization of internal interfaces, grain boundaries and surfaces to be performed in a wide variety of materials. Information such as the orientation relationship between grains, topology of the interface, and the coherency of small precipitates with the surrounding matrix may be obtained from field ion microscopy. Details of the solute segregation may be obtained at the plane of the interface and as a function of distance from the interface for all elements simultaneously from atom probe compositional analysis. Capabilities and limitations of the atom probe technique in characterization of internal interfaces is illustrated with examples of grain boundaries and interphase interfaces in a wide range of materials including intermetallics, model alloys, and commercial steels.

  7. A Modular Quantum System of Trapped Atomic Ions

    NASA Astrophysics Data System (ADS)

    Hucul, David Alexander

    Scaling up controlled quantum systems to involve large numbers of qubits remains one of the outstanding challenges of quantum information science. One path toward scalability is the use of a modular architecture where adjacent qubits may be entangled with applied electromagnetic fields, and remote qubits may be entangled using photon interference. Trapped atomic ion qubits are one of the most promising platforms for scaling up quantum systems by combining long coherence times with high fidelity entangling operations between proximate and remote qubits. In this thesis, I present experimental progress on combining entanglement between remote atomic ions separated by 1 meter with near-field entanglement between atomic ions in the same ion trap. I describe the experimental improvements to increase the remote entanglement rate by orders of magnitude to nearly 5 per second. This is the first experimental demonstration where the remote entanglement rate exceeds the decoherence rate of the entangled qubits. The flexibility of creating remote entanglement through photon interference is demonstrated by using the interference of distinguishable photons without sacrificing remote entanglement rate or fidelity. Next I describe the use of master clock in combination with a frequency comb to lock the phases of all laser-induced interactions between remote ion traps while removing optical phase stability requirements. The combination of both types of entanglement gates to create a small quantum network are described. Finally, I present ways to mitigate cross talk between photonic and memory qubits by using different trapped ion species. I show preliminary work on performing state detection of nuclear spin 0 ions by using entanglement between atomic ion spin and photon polarization. These control techniques may be important for building a large-scale modular quantum system.

  8. Radii of atomic ions determined from diatomic ion-He bond lengths.

    PubMed

    Wright, Timothy G; Breckenridge, W H

    2010-03-11

    We propose a new definition of the effective radius of an atomic ion: the bond distance (R(e)) of the ion/He diatomic complex minus the van der Waals radius of the helium atom. Our rationale is that He is the most chemically inert and least polarizable atom, so that its interaction with the outer portions of the electron cloud causes the smallest perturbation of it. We show that such radii, which we denote R(XHe), make good qualitative sense. We also compare our R(XHe) values to more traditional ionic radii from solid crystal X-ray measurements, as well as estimates of such radii from "ionic" gas-phase MF, MOM, MF(+), and MO molecules, where M is a metal atom. Such comparisons lead to interesting conclusions about bonding in ionic crystals and in simple gas-phase oxide and fluoride molecules. The definition is shown to be reasonable for -1, +1, and even for many of the larger +2 atomic ions. Another advantage of the R(XHe) definition is that it is also consistently valid for ground states and excited states of both neutral atoms and atomic ions, even for open-shell np and nd cases where the electron clouds of the ions are not spherically symmetric and R(XHe) thus depends on the "approach" direction of the He atom. Finally, we note that when there is a contribution from covalent bonding with the He atom, and/or in cases where the ion is small and has a very high charge, so that there is distortion even of the He 1s electrons, R(XHe) is not expected to be representative of the size of the ion. We then suggest that in these cases small, and sometimes unphysical, values of R(XHe) are diagnostic of the fact that simple "physical" interactions have been supplemented by a "chemical" component. PMID:20055395

  9. Radii of atomic ions determined from diatomic ion-He bond lengths.

    PubMed

    Wright, Timothy G; Breckenridge, W H

    2010-03-11

    We propose a new definition of the effective radius of an atomic ion: the bond distance (R(e)) of the ion/He diatomic complex minus the van der Waals radius of the helium atom. Our rationale is that He is the most chemically inert and least polarizable atom, so that its interaction with the outer portions of the electron cloud causes the smallest perturbation of it. We show that such radii, which we denote R(XHe), make good qualitative sense. We also compare our R(XHe) values to more traditional ionic radii from solid crystal X-ray measurements, as well as estimates of such radii from "ionic" gas-phase MF, MOM, MF(+), and MO molecules, where M is a metal atom. Such comparisons lead to interesting conclusions about bonding in ionic crystals and in simple gas-phase oxide and fluoride molecules. The definition is shown to be reasonable for -1, +1, and even for many of the larger +2 atomic ions. Another advantage of the R(XHe) definition is that it is also consistently valid for ground states and excited states of both neutral atoms and atomic ions, even for open-shell np and nd cases where the electron clouds of the ions are not spherically symmetric and R(XHe) thus depends on the "approach" direction of the He atom. Finally, we note that when there is a contribution from covalent bonding with the He atom, and/or in cases where the ion is small and has a very high charge, so that there is distortion even of the He 1s electrons, R(XHe) is not expected to be representative of the size of the ion. We then suggest that in these cases small, and sometimes unphysical, values of R(XHe) are diagnostic of the fact that simple "physical" interactions have been supplemented by a "chemical" component.

  10. The Helium Atom and Isoelectronic Ions in Two Dimensions

    ERIC Educational Resources Information Center

    Patil, S. H.

    2008-01-01

    The energy levels of the helium atom and isoelectronic ions in two dimensions are considered. The difficulties encountered in the analytical evaluation of the perturbative and variational expressions for the ground state, promote an interesting factorization of the inter-electronic interaction, leading to simple expressions for the energy. This…

  11. Total Born approximation cross sections for single electron loss by atoms and ions colliding with atoms

    NASA Technical Reports Server (NTRS)

    Rule, D. W.

    1977-01-01

    The first born approximation (FBA) is applied to the calculation of single electron loss cross sections for various ions and atoms containing from one to seven electrons. Screened hydrogenic wave functions were used for the states of the electron ejected from the projectile, and Hartree-Fock elastic and incoherent scattering factors were used to describe the target. The effect of the target atom on the scaling of projectile ionization cross sections with respect to the projectile nuclear charge was explored in the case of hydrogen-like ions. Scaling of the cross section with respect to the target nuclear charge for electron loss by Fe (+25) in collision with neutral atoms ranging from H to Fe is also examined. These results were compared to those of the binary encounter approximation and to the FBA for the case of ionization by completely stripped target ions.

  12. Correlated charge-changing ion-atom collisions

    SciTech Connect

    Tanis, J.A.

    1992-04-01

    This report summarizes the progress and accomplishments in accelerator atomic physics research supported by DOE grant DE-FG02-87ER13778 from March 16, 1991 through March 15, 1992. This work involves the experimental investigation of fundamental atomic processes in collisions of charged projectiles with neutral targets or electrons, with particular emphasis on two-electron interactions and electron correlation effects. Processes involving combinations of excitation, ionization, and charge transfer are investigated utilizing coincidence techniques in which projectiles charge-changing events are associated with x-ray emission, target recoil ions, or electron emission. New results have been obtained for studies involving (1) resonant recombination of atomic ions, (2) double ionization of helium, and (3) continuum electron emission. Experiments were conducted using accelerators at the Lawrence Berkeley Laboratory, Argonne National Laboratory, Michigan State University, Western Michigan University, and the Institute of Nuclear Research, Debrecen, Hungary. Brief summaries of work completed and work in progress are given in this report.

  13. A new ion sensing deep atomic force microscope

    NASA Astrophysics Data System (ADS)

    Drake, Barney; Randall, Connor; Bridges, Daniel; Hansma, Paul K.

    2014-08-01

    Here we describe a new deep atomic force microscope (AFM) capable of ion sensing. A novel probe assembly incorporates a micropipette that can be used both for sensing ion currents and as the tip for AFM imaging. The key advance of this instrument over previous ion sensing AFMs is that it uses conventional micropipettes in a novel suspension system. This paper focuses on sensing the ion current passively while using force feedback for the operation of the AFM in contact mode. Two images are obtained simultaneously: (1) an AFM topography image and (2) an ion current image. As an example, two images of a MEMS device with a microchannel show peaks in the ion current as the pipette tip goes over the edges of the channel. This ion sensing AFM can also be used in other modes including tapping mode with force feedback as well as in non-contact mode by utilizing the ion current for feedback, as in scanning ion conductance microscopy. The instrument is gentle enough to be used on some biological samples such as plant leaves.

  14. A new ion sensing deep atomic force microscope

    SciTech Connect

    Drake, Barney; Randall, Connor; Bridges, Daniel; Hansma, Paul K.

    2014-08-15

    Here we describe a new deep atomic force microscope (AFM) capable of ion sensing. A novel probe assembly incorporates a micropipette that can be used both for sensing ion currents and as the tip for AFM imaging. The key advance of this instrument over previous ion sensing AFMs is that it uses conventional micropipettes in a novel suspension system. This paper focuses on sensing the ion current passively while using force feedback for the operation of the AFM in contact mode. Two images are obtained simultaneously: (1) an AFM topography image and (2) an ion current image. As an example, two images of a MEMS device with a microchannel show peaks in the ion current as the pipette tip goes over the edges of the channel. This ion sensing AFM can also be used in other modes including tapping mode with force feedback as well as in non-contact mode by utilizing the ion current for feedback, as in scanning ion conductance microscopy. The instrument is gentle enough to be used on some biological samples such as plant leaves.

  15. A new ion sensing deep atomic force microscope

    PubMed Central

    Drake, Barney; Randall, Connor; Bridges, Daniel; Hansma, Paul K.

    2014-01-01

    Here we describe a new deep atomic force microscope (AFM) capable of ion sensing. A novel probe assembly incorporates a micropipette that can be used both for sensing ion currents and as the tip for AFM imaging. The key advance of this instrument over previous ion sensing AFMs is that it uses conventional micropipettes in a novel suspension system. This paper focuses on sensing the ion current passively while using force feedback for the operation of the AFM in contact mode. Two images are obtained simultaneously: (1) an AFM topography image and (2) an ion current image. As an example, two images of a MEMS device with a microchannel show peaks in the ion current as the pipette tip goes over the edges of the channel. This ion sensing AFM can also be used in other modes including tapping mode with force feedback as well as in non-contact mode by utilizing the ion current for feedback, as in scanning ion conductance microscopy. The instrument is gentle enough to be used on some biological samples such as plant leaves. PMID:25173275

  16. Estimates of Collisional Cooling and Quenching Rates for Atomic and Molecular Ion Collisions with Ultracold Atoms.

    NASA Astrophysics Data System (ADS)

    Smith, Winthrop; Wells, James

    2009-05-01

    Translational cross sections and rate coefficients for cold ion-neutral elastic and charge-exchange collisions (either atomic or molecular) are >> larger (˜10^6 a.u.) than neutral-neutral collisions at the same CM energy. This is due to the long range polarization potential V(R) = -C4/R^4, where C4 is proportional to the polarizability of the neutral partner. Thus collisions between ultracold alkali atoms (trapped in a magneto-optic trap or MOT) and low-energy ions can be used for sympathetic cooling experiments. We are building a prototype hybrid-trap apparatus [1] that applies these principles to collisions of Ca^+ ions (which can be laser pre-cooled) with MOT-trapped ultracold Na atoms. Some calculations on this system and other related ion-neutral systems have been published [2] and some initial experiments on other ion-neutral species have begun [3]. Estimates of cooling and quenching rates in the low K-mK CM energy range for Ca+ on Na and other cases will be presented and possible experiments described. [1] Winthrop W. Smith, Oleg P. Makarov and Jian Lin, J. Modern Optics 52, 2253 (2005). [2] R. Côt'e and A. Dalgarno, Phys. Rev. A 62, 012709 (2000); R. Côt'e, Phys. Rev. Lett. 85, 5316 (2000). [3] A. Grier, M. Cetina, F.Orucevic, and V. Vuletic, ArXiv atom-ph/0808.3620.

  17. Suppressing Loss of Ions in an Atomic Clock

    NASA Technical Reports Server (NTRS)

    Prestage, John; Chung, Sang

    2010-01-01

    An improvement has been made in the design of a compact, highly stable mercury- ion clock to suppress a loss of ions as they are transferred between the quadrupole and higher multipole ion traps. Such clocks are being developed for use aboard spacecraft for navigation and planetary radio science. The modification is also applicable to ion clocks operating on Earth: indeed, the success of the modification has been demonstrated in construction and operation of a terrestrial breadboard prototype of the compact, highly stable mercury-ion clock. Selected aspects of the breadboard prototype at different stages of development were described in previous NASA Tech Briefs articles. The following background information is reviewed from previous articles: In this clock as in some prior ion clocks, mercury ions are shuttled between two ion traps, one a 16- pole linear radio-frequency trap, while the other is a quadrupole radio-frequency trap. In the quadrupole trap, ions are tightly confined and optical state selection from a 202Hg lamp is carried out. In the 16-pole trap, the ions are more loosely confined and atomic transitions are interrogated by use of a microwave beam at approximately 40.507 GHz. The trapping of ions effectively eliminates the frequency pulling that would otherwise be caused by collisions between clock atoms and the wall of a gas cell. The shuttling of the ions between the two traps enables separation of the state-selection process from the clock microwave-resonance process, so that each of these processes can be optimized independently of the other. This is similar to the operation of an atomic beam clock, except that with ions the beam can be halted and reversed as ions are shuttled back and forth between the two traps. When the two traps are driven at the same radio frequency, the strength of confinement can be reduced near the junction between the two traps, depending upon the relative phase of the RF voltage used to operate each of the two traps, and

  18. Manipulating ion-atom collisions with coherent electromagnetic radiation.

    PubMed

    Kirchner, Tom

    2002-08-26

    Laser-assisted ion-atom collisions are considered in terms of a nonperturbative quantum mechanical description of the electronic motion. It is shown for the system He(2+) - H at 2 keV/amu that the collision dynamics depend strongly on the initial phase of the laser field and the applied wavelength. Whereas electronic transitions are caused by the concurrent action of the field and the projectile ion at relatively low frequencies, they can be separated into modified collisional capture and field ionization events in the region above the one-photon ionization threshold.

  19. Atomic Simulation of Ion-Solid Interaction in Ceramics

    SciTech Connect

    Gao, Fei; Weber, William J.

    2003-05-16

    Understanding dynamic processes during ion irradiation, as well as irradiation-induced microstructural changes, requires fundamental knowledge on defect properties, defect generation in atomic collision processes, multiple ion-solid interactions and defect migration. The multiple scale simulation methods are presented in this paper, and in particular, an application on SiC is discussed in detail. Density functional theory (DFT) has been employed to determine defect energetics and the most favorable interstitial configurations in SiC. Based on DFT calculations, a new empirical potential has been developed in order to carry out large-scale simulations of microstructural evolution. Multimillion atom systems (up to 6 million) have been used to study defect production, defect clustering, multiple ion-solid interactions and structural evolution in SiC. The defect-stimulated growth and coalescence of clusters represents an important mechanism for irradiation-induced crystalline-to-amorphous ( c-a) transformation. The relative disordering and swelling behavior, as well as HRTEM image simulations, based on molecular dynamics results provide atomic-level interpretations of experimentally observed features in SiC.

  20. Highly charged ions in exotic atoms research at PSI

    NASA Astrophysics Data System (ADS)

    Anagnostopoulos, D. F.; Biri, S.; Boisbourdain, V.; Demeter, M.; Borchert, G.; Egger, J. P.; Fuhrmann, H.; Gotta, D.; Gruber, A.; Hennebach, M.; Indelicato, P.; Liu, Y. W.; Manil, B.; Markushin, V. E.; Marton, H.; Nelms, N.; Rusi El Hassani, A. J.; Simons, L. M.; Stingelin, L.; Wasser, A.; Wells, A.; Zmeskal, J.

    2003-05-01

    During their de-excitation, exotic atoms formed in low pressure gases reach a state of high or even complete ionization. X-rays emitted from higher n-states of electron-free atoms have well defined energies with the error originating only from the error in the mass values of the constituent particles. They served as a basis for a new determination of the pion mass as well as for a high precision measurement of the pionic hydrogen ground state shift. The response function of the Bragg spectrometer has been determined with X-rays from completely ionized pionic carbon and with a dedicated electron cyclotron resonance ion trap (ECRIT). A further extension of the ECRIT method implemented in the experiment allows a direct calibration of exotic atom transitions as well as a precise determination of the energy of fluorescence lines.

  1. Hyperfine-mediated static polarizabilities of monovalent atoms and ions

    SciTech Connect

    Dzuba, V. A.; Flambaum, V. V.; Beloy, K.; Derevianko, A.

    2010-12-15

    We apply relativistic many-body methods to compute static differential polarizabilities for transitions inside the ground-state hyperfine manifolds of monovalent atoms and ions. Knowledge of this transition polarizability is required in a number of high-precision experiments, such as microwave atomic clocks and searches for CP-violating permanent electric dipole moments. While the traditional polarizability arises in the second order of interaction with the externally applied electric field, the differential polarizability involves an additional contribution from the hyperfine interaction of atomic electrons with nuclear moments. We derive formulas for the scalar and tensor polarizabilities including contributions from magnetic dipole and electric quadrupole hyperfine interactions. Numerical results are presented for Al, Rb, Cs, Yb{sup +}, Hg{sup +}, and Fr.

  2. Correlated electron processes in ion-atom collisions

    SciTech Connect

    McColm, D.W. . Dept. of Physics)

    1990-02-01

    This final report covers the work carried out under the LLNL Contract P.O. Number B055762, Subcontractor Regents University of California at Davis. The research carried out under this contract investigated electron processes occurring in collisions between heavy ions and atoms. The doubly-differential secondary electron yield following the impact of 3.5 to 8 MeV/uU{sup q+}(q = 38,68) ion impact on thin carbon foil targets has been investigated experimentally. The absolute electron emission yields were determined for ejection angles varied between 22.5{degree} and 157{degree} and electron energies ranging from 10 eV to 8 keV. The electron spectra are compared to previous investigations and new experimental data using lighter ion impact at MeV projectile energies. 14 refs., 5 figs.

  3. Atomic collisions with 33-TeV lead ions

    SciTech Connect

    Vane, C.R.; Datz, S.; Krause, H.F.

    1996-10-01

    Recent availability of relativistic and ultrarelativistic beams of heavy ions has permitted the first controlled studies of atomic collisions at energies sufficient to measure effects of several new basic phenomena. These include measurements substantiating recently predicted finite nuclear size effects resulting in a reduction in the total electronic energy loss of heavy ions in matter, and measurements of Coulomb collisions in which electrons are excited from the Dirac negative energy continuum. Measurements of total energy loss, free electron-positron pair production, and electron capture from pair production have been recently performed using 33-TeV Pb{sup 82+} ions from the CERN SPS accelerator in Geneva. Results of these studies are presented, along with comparisons with relevant theory.

  4. Structure of the alkali-metal-atom + strontium molecular ions: Towards photoassociation and formation of cold molecular ions

    SciTech Connect

    Aymar, M.; Dulieu, O.; Guerout, R.

    2011-08-14

    The potential energy curves, permanent and transition dipole moments, and the static dipolar polarizability, of molecular ions composed of one alkali-metal atom and a strontium ion are determined with a quantum chemistry approach. The molecular ions are treated as effective two-electron systems and are treated using effective core potentials including core polarization, large gaussian basis sets, and full configuration interaction. In the perspective of upcoming experiments aiming at merging cold atom and cold ion traps, possible paths for radiative charge exchange, photoassociation of a cold lithium or rubidium atom and a strontium ion are discussed, as well as the formation of stable molecular ions.

  5. Gas field ion source current stability for trimer and single atom terminated W(111) tips

    SciTech Connect

    Urban, Radovan; Wolkow, Robert A.; Pitters, Jason L.

    2012-06-25

    Tungsten W(111) oriented trimer-terminated tips as well as single atom tips, fabricated by a gas and field assisted etching and evaporation process, were investigated with a view to scanning ion microscopy and ion beam writing applications. In particular, ion current stability was studied for helium and neon imaging gases. Large ion current fluctuations from individual atomic sites were observed when a trimer-terminated tip was used for the creation of neon ion beam. However, neon ion current was stable when a single atom tip was employed. No such current oscillations were observed for either a trimer or a single atom tip when imaged with helium.

  6. Use of predissociation to enhance the atomic hydrogen ion fraction in ion sources

    DOEpatents

    Kim, Jinchoon

    1979-01-01

    A duopigatron ion source is modified by replacing the normal oxide-coated wire filament cathode of the ion source with a hot tungsten oven through which hydrogen gas is fed into the arc chamber. The hydrogen gas is predissociated in the hot oven prior to the arc discharge, and the recombination rate is minimized by hot walls inside of the arc chamber. With the use of the above modifications, the atomic H.sub.1.sup.+ ion fraction output can be increased from the normal 50% to greater than 70% with a corresponding decrease in the H.sub.2.sup.+ and H.sub.3.sup.+ molecular ion fraction outputs from the ion source.

  7. Formation of molecular ions by radiative association of cold trapped atoms and ions

    NASA Astrophysics Data System (ADS)

    Dulieu, Olivier; da Silva, Humberto, Jr.; Aymar, Mireille; Raoult, Maurice

    2015-05-01

    Radiative emission during cold collisions between trapped laser-cooled Rb atoms and alkaline-earth ions (Ca+ , Sr+ , Ba+) and Yb+ are studied theoretically, using accurate effective-core-potential based quantum chemistry calculations of potential energy curves and transition dipole moments of the related molecular ions. Radiative association of molecular ions is predicted to occur for all systems with a cross section two to ten times larger than the radiative charge transfer one. Partial and total rate constants are also calculated and compared to available experiments. Narrow shape resonances are expected, which could be detectable at low temperature with an experimental resolution at the limit of the present standards. Vibrational distributions show that the final molecular ions are not created in their ground state level. Supported by the Marie-Curie ITN ``COMIQ: Cold Molecular Ions at the Quantum limit'' of the EU (#607491).

  8. Observation of a power-law energy distribution in atom-ion hybrid system

    NASA Astrophysics Data System (ADS)

    Meir, Ziv; Akerman, Nitzan; Sikorsky, Tomas; Ben-Shlomi, Ruti; Dallal, Yehonatan; Ozeri, Roee

    2016-05-01

    Understanding atom-ion collision dynamics is at the heart of the growing field of ultra-cold atom-ion physics. The naive picture of a hot ion sympathetically-cooled by a cold atomic bath doesn't hold due to the time dependent potentials generated by the ion Paul trap. The energy scale of the atom-ion system is determined by a combination of the atomic bath temperature, the ion's excess micromotion (EMM) and the back action of the atom-ion attraction on the ion's position in the trap. However, it is the position dependent ion's inherent micromotion which acts as an amplifier for the ion's energy during random consecutive collisions. Due to this reason, the ion's energy distribution deviates from Maxwell-Boltzmann (MB) characterized by an exponential tail to one with power-law tail described by Tsallis q-exponential function. Here we report on the observation of a strong deviation from MB to Tsallis energy distribution of a trapped ion. In our experiment, a ground-state cooled 88 Sr+ ion is immersed in an ultra-cold cloud of 87 Rb atoms. The energy scale is determined by either EMM or solely due to the back action on the ion position during a collision with an atom in the trap. Energy distributions are obtained using narrow optical clock spectroscopy.

  9. Charge exchange and ionization in hydrogen atom-fully stripped ion collisions in Debye plasmas

    SciTech Connect

    Zhang, H.; Wang, J. G.; He, B.; Qiu, Y. B.; Janev, R. K.

    2007-05-15

    The processes of charge exchange and ionization in collisions of ground state hydrogen atom with fully stripped ions in a weakly coupled plasma are studied by the classical trajectory Monte Carlo method in the collision energy range 10-900 keV/amu. The interparticle interactions are described by the Debye-Hueckel model with inclusion of dynamical effects associated with the projectile velocity. The microcanonical distribution of initial state electronic coordinates and momenta has been determined by inclusion of plasma screening effects. The cross section dependencies on plasma parameters and ion charge and velocity are investigated. It is shown that plasma effects on charge exchange and ionization cross sections are significant and particularly pronounced at low collision velocities. The results of systematic cross section calculations for different values of Debye screening length (in the range 1-50a{sub 0}) and ion charges (in the range 1-14) are presented.

  10. Transferable pseudoclassical electrons for aufbau of atomic ions.

    PubMed

    Ekesan, Solen; Kale, Seyit; Herzfeld, Judith

    2014-06-01

    Generalizing the LEWIS reactive force field from electron pairs to single electrons, we present LEWIS• in which explicit valence electrons interact with each other and with nuclear cores via pairwise interactions. The valence electrons are independently mobile particles, following classical equations of motion according to potentials modified from Coulombic as required to capture quantum characteristics. As proof of principle, the aufbau of atomic ions is described for diverse main group elements from the first three rows of the periodic table, using a single potential for interactions between electrons of like spin and another for electrons of unlike spin. The electrons of each spin are found to distribute themselves in a fashion akin to the major lobes of the hybrid atomic orbitals, suggesting a pointillist description of the electron density. The broader validity of the LEWIS• force field is illustrated by predicting the vibrational frequencies of diatomic and triatomic hydrogen species.

  11. Transferable pseudoclassical electrons for aufbau of atomic ions.

    PubMed

    Ekesan, Solen; Kale, Seyit; Herzfeld, Judith

    2014-06-01

    Generalizing the LEWIS reactive force field from electron pairs to single electrons, we present LEWIS• in which explicit valence electrons interact with each other and with nuclear cores via pairwise interactions. The valence electrons are independently mobile particles, following classical equations of motion according to potentials modified from Coulombic as required to capture quantum characteristics. As proof of principle, the aufbau of atomic ions is described for diverse main group elements from the first three rows of the periodic table, using a single potential for interactions between electrons of like spin and another for electrons of unlike spin. The electrons of each spin are found to distribute themselves in a fashion akin to the major lobes of the hybrid atomic orbitals, suggesting a pointillist description of the electron density. The broader validity of the LEWIS• force field is illustrated by predicting the vibrational frequencies of diatomic and triatomic hydrogen species. PMID:24752384

  12. A contemporary theoretical view of ion-atom, -molecule interactions

    NASA Astrophysics Data System (ADS)

    Schultz, David

    2009-05-01

    Energetic interactions among electrons, ions, atoms, and molecules within gaseous, plasma, and even material environments are fundamental to such diverse phenomena as low temperature plasma processing of semiconductors, collapsing giant molecular clouds forming stars, fluorescent lighting, cold atom condensates, radiation treatment of disease, and the chemistry of earth's atmosphere. Consequently, they have been studied using the contemporary theoretical and computational methods of the time for many years, yet progress continues as we are confronted with challenges presented by new, often more complex systems and by the drive to understand these foundational interactions at an ever more subtle and predictive level. I will illustrate some of this progress using examples from recent work treating very simple systems, for which our knowledge has been both subtly refined and significantly changed, and more complex systems, where complementary methods based on either elaborate treatments or broadly applicable simple models can be used to advance our knowledge.

  13. Creation and recovery of a W(111) single atom gas field ion source.

    PubMed

    Pitters, Jason L; Urban, Radovan; Wolkow, Robert A

    2012-04-21

    Tungsten single atom tips have been prepared from a single crystal W(111) oriented wire using the chemical assisted field evaporation and etching method. Etching to a single atom tip occurs through a symmetric structure and leads to a predictable last atom unlike etching with polycrystalline tips. The single atom tip formation procedure is shown in an atom by atom removal process. Rebuilds of single atom tips occur on the same crystalline axis as the original tip such that ion emission emanates along a fixed direction for all tip rebuilds. This preparation method could be utilized and developed to prepare single atom tips for ion source development.

  14. Theoretical Aspects of Ionization in Ion-Atom Collisions

    NASA Astrophysics Data System (ADS)

    Wang, Jianyi

    Mechanisms for ionization resulting from collisions between an ion (or atom) and an atom are discussed and analyzed for slow and fast collisions and for two different collision systems. The first collision system consists of an exactly solvable three-body model in which an electron moves in the field of two centers of zero range potentials travelling at constant speeds. The exact electron emission spectrum shows two important features: (a) Evidence is found for the existence of the so-called "v/2" (or ridge) electrons at intermediate collision speed. These electrons are emitted with about half the speed of the incident ion. It is shown that they are due to promotion to the continuum of the molecular orbitals. v/2 electron emission is strongly influenced by the relative interaction strengths of the electron with the two centers. (b) For fast collisions multiple scattering peaks can be seen to be a dominant feature in the ionization spectrum. Three-body effects are found to be responsible for generation of the peaks. In the second collision system the ionization spectrum resulting from electron loss by the incident ions (atoms) are studied with emphasis on large ejection angles. The ionization spectrum is shown to be composed of two parts: one is caused by the interaction of projectile electron with the mean field of the target core and the other by explicit electron-electron interaction. It is shown that for mean field ionization proper treatment of the off-energy -shell scattering matrix element is required to describe experimental data. The correlated ionization is treated via a double scattering represented by a second Born approximation. It is shown that this two-step mechanism is essential in describing the electron angular and energy distribution, especially on the low energy side of the spectrum for electron loss from atomic hydrogen. For other incident ions (like He ^+) it is found that in addition to double scattering, three-body effects are also very

  15. Generation of hyperentangled states between remote noninteracting atomic ions

    SciTech Connect

    Hu Baolin; Zhan Youbang

    2010-11-15

    We propose a scheme of generating four-qubit hyperentangled states between a pair of remote noninteracting atomic ions with a {Lambda} configuration that are confined in Paul traps. These hyperentangled states, different from the normal entangled states that are entangled in a single degree of freedom, are entangled in both spin and motion degrees of freedom. In our proposal, the entanglement is first generated in spin degrees of freedom using linear optics and then transferred to the motion degree of freedom using a sequence of laser pluses, including the stimulated Raman carrier transitions and sideband transitions. The proposal is completed with regenerating entanglement in spin degrees of freedom using linear optics.

  16. Metallic atoms and ions in comets: Comet Halley 1986 3

    NASA Technical Reports Server (NTRS)

    Ibadov, S.

    1992-01-01

    The origin of metallic atoms and ions in the cometary comae is investigated theoretically. Two effects are revealed in the comas of bright comets: (1) the Na anomalous type effect is possible within the gas-dust jets of comet P/Halley 1986 3 due to cooling cometary dust by cryogenic gas flow from the nucleus; and (2) the production of ions of refractory elements (Fe(+), Si(+), etc.) at large heliocentric distances is possible in the comas of the Halley type dusty comets due to high-velocity impacts between cometary and zodiacal dust particles. Spectral observations of comets with high sensitivity and spatial resolution are important for studying both comets and interplanetary dust.

  17. Semiempirical Theories of the Affinities of Negative Atomic Ions

    NASA Technical Reports Server (NTRS)

    Edie, John W.

    1961-01-01

    The determination of the electron affinities of negative atomic ions by means of direct experimental investigation is limited. To supplement the meager experimental results, several semiempirical theories have been advanced. One commonly used technique involves extrapolating the electron affinities along the isoelectronic sequences, The most recent of these extrapolations Is studied by extending the method to Include one more member of the isoelectronic sequence, When the results show that this extension does not increase the accuracy of the calculations, several possible explanations for this situation are explored. A different approach to the problem is suggested by the regularities appearing in the electron affinities. Noting that the regular linear pattern that exists for the ionization potentials of the p electrons as a function of Z, repeats itself for different degrees of ionization q, the slopes and intercepts of these curves are extrapolated to the case of the negative Ion. The method is placed on a theoretical basis by calculating the Slater parameters as functions of q and n, the number of equivalent p-electrons. These functions are no more than quadratic in q and n. The electron affinities are calculated by extending the linear relations that exist for the neutral atoms and positive ions to the negative ions. The extrapolated. slopes are apparently correct, but the intercepts must be slightly altered to agree with experiment. For this purpose one or two experimental affinities (depending on the extrapolation method) are used in each of the two short periods. The two extrapolation methods used are: (A) an isoelectronic sequence extrapolation of the linear pattern as such; (B) the same extrapolation of a linearization of this pattern (configuration centers) combined with an extrapolation of the other terms of the ground configurations. The latter method Is preferable, since it requires only experimental point for each period. The results agree within

  18. Influence of the ion/neutral atom mass ratio on the damping of electrostatic ion-cyclotron waves

    NASA Technical Reports Server (NTRS)

    Suszcynsky, D. M.; Cartier, S. L.; D'Angelo, N.; Merlino, R. L.

    1987-01-01

    The damping of electrostatic ion-cyclotron waves by ion-neutral collisions was studied in a single-ended Q machine. The amplitudes of K(+) and Cs(+) electrostatic ion-cyclotron waves were measured as a function of neutral pressure in helium, neon, argon, krypton, and xenon. For each ion/neutral atom combination, the electrostatic ion-cyclotron wave amplitude maximizes at a neutral pressure that scales monotonically with the m(+)/m(n) mass ratio. This result is interpreted by considering the dynamics of elastic collisions between the ions and the neutral atoms.

  19. Cycle Time Reduction in Trapped Mercury Ion Atomic Frequency Standards

    NASA Technical Reports Server (NTRS)

    Burt, Eric A.; Tjoelker, Robert L.; Taghavi, Shervin

    2011-01-01

    The use of the mercury ion isotope (201)Hg(+) was examined for an atomic clock. Taking advantage of the faster optical pumping time in (201)Hg(+) reduces both the state preparation and the state readout times, thereby decreasing the overall cycle time of the clock and reducing the impact of medium-term LO noise on the performance of the frequency standard. The spectral overlap between the plasma discharge lamp used for (201)Hg(+) state preparation and readout is much larger than that of the lamp used for the more conventional (199)Hg(+). There has been little study of (201)Hg(+) for clock applications (in fact, all trapped ion clock work in mercury has been with (199)Hg(+); however, recently the optical pumping time in (201)Hg(+) has been measured and found to be 0.45 second, or about three times faster than in (199)Hg(+) due largely to the better spectral overlap. This can be used to reduce the overall clock cycle time by over 2 seconds, or up to a factor of 2 improvement. The use of the (201)Hg(+) for an atomic clock is totally new. Most attempts to reduce the impact of LO noise have focused on reducing the interrogation time. In the trapped ion frequency standards built so far at JPL, the optical pumping time is already at its minimum so that no enhancement can be had by shortening it. However, by using (201)Hg(+), this is no longer the case. Furthermore, integrity monitoring, the mechanism that determines whether the clock is functioning normally, cannot happen faster than the clock cycle time. Therefore, a shorter cycle time will enable quicker detection of failure modes and recovery from them.

  20. Method for the production of atomic ion species from plasma ion sources

    DOEpatents

    Spence, D.; Lykke, K.

    1998-08-04

    A technique to enhance the yield of atomic ion species (H{sup +}, D{sup +}, O{sup +}, N{sup +}, etc.) from plasma ion sources. The technique involves the addition of catalyzing agents to the ion discharge. Effective catalysts include H{sub 2}O, D{sub 2}O, O{sub 2}, and SF{sub 6}, among others, with the most effective being water (H{sub 2}O) and deuterated water (D{sub 2}O). This technique has been developed at Argonne National Laboratory, where microwave generated plasmas have produced ion beams comprised of close to 100% purity protons (H{sup +}) and close to 100% purity deuterons (D{sup +}). The technique also increases the total yield of protons and deuterons by converting unwanted ion species, namely, H{sub 2}{sup +}, H{sub 3}{sup +} and D{sub 2}{sup +}, D{sub 3}{sup +}, into the desired ion species, H{sup +} and D{sup +}, respectively. 4 figs.

  1. Method for the production of atomic ion species from plasma ion sources

    DOEpatents

    Spence, David; Lykke, Keith

    1998-01-01

    A technique to enhance the yield of atomic ion species (H.sup.+, D.sup.+, O.sup.+, N.sup.+, etc.) from plasma ion sources. The technique involves the addition of catalyzing agents to the ion discharge. Effective catalysts include H.sub.2 O, D.sub.2 O, O.sub.2, and SF.sub.6, among others, with the most effective being water (H.sub.2 O) and deuterated water (D.sub.2 O). This technique has been developed at Argonne National Laboratory, where microwave generated plasmas have produced ion beams comprised of close to 100% purity protons (H.sup.+) and close to 100% purity deuterons (D.sup.+). The technique also increases the total yield of protons and deuterons by converting unwanted ion species, namely, H.sub.2.sup.+,H.sub.3.sup.+ and D.sub.2.sup.+, D.sub.3.sup.+, into the desired ion species, H.sup.+ and D.sup.+, respectively.

  2. Ion-neutral chemistry at ultralow energies: dynamics of reactive collisions between laser-cooled Ca+ ions and Rb atoms in an ion-atom hybrid trap†

    NASA Astrophysics Data System (ADS)

    Hall, Felix H. J.; Eberle, Pascal; Hegi, Gregor; Raoult, Maurice; Aymar, Mireille; Dulieu, Olivier; Willitsch, Stefan

    2013-08-01

    Cold chemical reactions between laser-cooled Ca+ ions and Rb atoms were studied in an ion-atom hybrid trap. Reaction rate constants were determined in the range of collision energies ⟨E coll⟩/k B=20 mK-20 K. The lowest energies were achieved in experiments using single localised Ca+ ions. Product branching ratios were studied using resonant-excitation mass spectrometry. The dynamics of the reactive processes in this system (non-radiative and radiative charge transfer as well as radiative association leading to the formation of CaRb+ molecular ions) have been analysed using high-level quantum-chemical calculations of the potential energy curves of CaRb+ and quantum-scattering calculations for the radiative channels. For the present low-energy scattering experiments, it is shown that the energy dependence of the reaction rate constants is governed by long-range interactions in line with the classical Langevin model, but their magnitude is determined by short-range non-adiabatic and radiative couplings which only weakly depend on the asymptotic energy. The quantum character of the collisions is predicted to manifest itself in the occurrence of narrow shape resonances at well-defined collision energies. The present results highlight both universal and system-specific phenomena in cold ion-neutral reactive collisions.

  3. Hydrodynamic flow of ions and atoms in partially ionized plasmas

    NASA Astrophysics Data System (ADS)

    Nemirovsky, R. A.; Fredkin, D. R.; Ron, A.

    2002-12-01

    We have derived the hydrodynamic equations of motion for a partially ionized plasma, when the ionized component and the neutral components have different flow velocities and kinetic temperatures. Starting from the kinetic equations for a gas of ions and a gas of atoms we have considered various processes of encounters between the two species: self-collisions, interspecies collisions, ionization, recombination, and charge exchange. Our results were obtained by developing a general approach for the hydrodynamics of a gas in a binary mixture, in particular when the components drift with respect to each other. This was applied to a partially ionized plasma, when the neutral-species gas and the charged-species gas have separate velocities. We have further suggested a generalized version of the relaxation time approximation and obtained the contributions of the interspecies encounters to the transport equations.

  4. Hydrodynamic flow of ions and atoms in partially ionized plasmas.

    PubMed

    Nemirovsky, R A; Fredkin, D R; Ron, A

    2002-12-01

    We have derived the hydrodynamic equations of motion for a partially ionized plasma, when the ionized component and the neutral components have different flow velocities and kinetic temperatures. Starting from the kinetic equations for a gas of ions and a gas of atoms we have considered various processes of encounters between the two species: self-collisions, interspecies collisions, ionization, recombination, and charge exchange. Our results were obtained by developing a general approach for the hydrodynamics of a gas in a binary mixture, in particular when the components drift with respect to each other. This was applied to a partially ionized plasma, when the neutral-species gas and the charged-species gas have separate velocities. We have further suggested a generalized version of the relaxation time approximation and obtained the contributions of the interspecies encounters to the transport equations.

  5. Characteristics of flows of energetic atoms reflected from metal targets during ion bombardment

    NASA Astrophysics Data System (ADS)

    Kuzmichev, A.; Perevertaylo, V.; Tsybulsky, L.; Volpian, O.

    2016-07-01

    Particle number and energy reflection coefficients for energetic neutralized gas ions (Ar and O atoms) backscattered from metal targets during ion bombardment have been calculated using TRIM code. The energy distributions of reflected atoms are computed, too, and their dependence on the primary ion energy and the angle of ion incidence is determined. The obtained data confirm the possibility of employing energetic atoms reflection for generation of high energy neutral beams and point out to take this phenomenon into account under analysis of the ion technology for coating deposition.

  6. Independent-particle models for light negative atomic ions

    NASA Technical Reports Server (NTRS)

    Ganas, P. S.; Talman, J. D.; Green, A. E. S.

    1980-01-01

    For the purposes of astrophysical, aeronomical, and laboratory application, a precise independent-particle model for electrons in negative atomic ions of the second and third period is discussed. The optimum-potential model (OPM) of Talman et al. (1979) is first used to generate numerical potentials for eight of these ions. Results for total energies and electron affinities are found to be very close to Hartree-Fock solutions. However, the OPM and HF electron affinities both depart significantly from experimental affinities. For this reason, two analytic potentials are developed whose inner energy levels are very close to the OPM and HF levels but whose last electron eigenvalues are adjusted precisely with the magnitudes of experimental affinities. These models are: (1) a four-parameter analytic characterization of the OPM potential and (2) a two-parameter potential model of the Green, Sellin, Zachor type. The system O(-) or e-O, which is important in upper atmospheric physics is examined in some detail.

  7. Treatment of Ion-Atom Collisions Using a Partial-Wave Expansion of the Projectile Wavefunction

    ERIC Educational Resources Information Center

    Wong, T. G.; Foster, M.; Colgan, J.; Madison, D. H.

    2009-01-01

    We present calculations of ion-atom collisions using a partial-wave expansion of the projectile wavefunction. Most calculations of ion-atom collisions have typically used classical or plane-wave approximations for the projectile wavefunction, since partial-wave expansions are expected to require prohibitively large numbers of terms to converge…

  8. Highly charged ions as a basis of optical atomic clockwork of exceptional accuracy.

    PubMed

    Derevianko, Andrei; Dzuba, V A; Flambaum, V V

    2012-11-01

    We propose a novel class of atomic clocks based on highly charged ions. We consider highly forbidden laser-accessible transitions within the 4f(12) ground-state configurations of highly charged ions. Our evaluation of systematic effects demonstrates that these transitions may be used for building exceptionally accurate atomic clocks which may compete in accuracy with recently proposed nuclear clocks.

  9. Highly charged ions as a basis of optical atomic clockwork of exceptional accuracy.

    PubMed

    Derevianko, Andrei; Dzuba, V A; Flambaum, V V

    2012-11-01

    We propose a novel class of atomic clocks based on highly charged ions. We consider highly forbidden laser-accessible transitions within the 4f(12) ground-state configurations of highly charged ions. Our evaluation of systematic effects demonstrates that these transitions may be used for building exceptionally accurate atomic clocks which may compete in accuracy with recently proposed nuclear clocks. PMID:23215265

  10. Highly Charged Ions as a Basis of Optical Atomic Clockwork of Exceptional Accuracy

    NASA Astrophysics Data System (ADS)

    Derevianko, Andrei; Dzuba, V. A.; Flambaum, V. V.

    2012-11-01

    We propose a novel class of atomic clocks based on highly charged ions. We consider highly forbidden laser-accessible transitions within the 4f12 ground-state configurations of highly charged ions. Our evaluation of systematic effects demonstrates that these transitions may be used for building exceptionally accurate atomic clocks which may compete in accuracy with recently proposed nuclear clocks.

  11. Screening-Antiscreening Effect in Ion-Atom Collisions.

    NASA Astrophysics Data System (ADS)

    Hulskotter, Hans-Peter G.

    1990-01-01

    In a collision between an atomic projectile carrying one or more electrons and a target atom, one of the events that may occur is the ionization of a projectile electron. Projectile ionization, usually called electron loss, is normally attributed to the Coulomb interaction between the target nucleus and projectile electron. The effect of the target electrons can be accounted for partially by introducing a screened Coulomb interaction between the target and the projectile electron. However, the target electrons can not only act coherently as screening agents, but may also act incoherently as ionizing (antiscreening) agents. We have measured the cross sections for projectile K-shell ionization for 0.75 - 3.5 MeV/Nucleon Li^{2+ }, C^{5+}, and O^{7+} projectiles, for projectile electron loss of 100 and 380 MeV/Nucleon Au^{52+} projectiles in collisions with H_2, He, and N _2, and for 380 MeV/N Au^ {75+} projectiles in collisions with H _2 and N_2 targets. We unambiguously demonstrate that for energies where the target electrons have sufficient kinetic energy in the projectile frame to ionize the projectile electron, the electron-electron interaction can lead to a significant increase in the total ionization cross section. The largest relative increase we have been able to observe is 76%. The experimental results generally agree with plane-wave Born approximation calculations by Bates and Griffing and modified by Anholt which take into account the interaction between projectile and target electrons. We also describe the properties of a new target gas cell which has been designed and built for the use at the relativistic heavy-ion accelerator at Lawrence Berkeley Laboratory.

  12. Progress in numerical calculations of ion-atom collisions

    SciTech Connect

    Reading, J.F.; Ford, A.L.; Becker, R.L.

    1983-01-01

    An ion-atom collision produces a time dependent perturbation of a many fermion system. In this collision, excitation, ionization and charge transfer can occur. The driving mechanism for these processes may be thought of as the potentials seen by individual electrons at any given separation of the projectile and target nuclei. If we think of these potentials as belonging to the target (a nucleus and electrons) and the projectile (another nucleus and electrons) then as detected by an electron the potentials change because: (a) the target and projectile change position, and (b) electrons on the target and projectile change states. Most work in the past fifty years has concentrated on solving the independent particle model (IPM). Cracks are beginning to appear in this model which only allows for type (a) changes in the potential. But in a short review we shall have quite enough to do in understanding the progress made in the last decade on the IPM. This paper is divided into three parts. The first deals with how to reduce the IPM to the single electron model (SEM). The second is on a new method where charge transfer is important. The third confronts some standard models with modern calculations.

  13. Atomic-layer-deposition oxide nanoglue for sodium ion batteries.

    PubMed

    Han, Xiaogang; Liu, Yang; Jia, Zheng; Chen, Yu-Chen; Wan, Jiayu; Weadock, Nicholas; Gaskell, Karen J; Li, Teng; Hu, Liangbing

    2014-01-01

    Atomic-layer-deposition (ALD) coatings have been increasingly used to improve battery performance. However, the electrochemical and mechanistic roles remain largely unclear, especially for ALD coatings on electrodes that undergo significant volume changes (up to 100%) during charging/discharging. Here we investigate an anode consisting of tin nanoparticles (SnNPs) with an ALD-Al2O3 coating. For the first time, in situ transmission electron microscopy unveiled the dynamic mechanical protection of the ALD-Al2O3 coating by coherently deforming with the SnNPs under the huge volume changes during charging/discharging. Battery tests in coin-cells further showed the ALD-Al2O3 coating remarkably boosts the cycling performance of the Sn anodes, comparing with those made of bare SnNPs. Chemomechanical simulations clearly revealed that a bare SnNP debonds and falls off the underlying substrate upon charging, and by contrast the ALD-Al2O3 coating, like ion-conductive nanoglue, robustly anchors the SnNP anode to the substrate during charging/discharging, a key to improving battery cycle performance.

  14. Atomic force microscope cantilever calibration using a focused ion beam.

    PubMed

    Slattery, Ashley D; Quinton, Jamie S; Gibson, Christopher T

    2012-07-20

    A calibration method is presented for determining the spring constant of atomic force microscope (AFM) cantilevers, which is a modification of the established Cleveland added mass technique. A focused ion beam (FIB) is used to remove a well-defined volume from a cantilever with known density, substantially reducing the uncertainty usually present in the added mass method. The technique can be applied to any type of AFM cantilever; but for the lowest uncertainty it is best applied to silicon cantilevers with spring constants above 0.7 N m(-1), where uncertainty is demonstrated to be typically between 7 and 10%. Despite the removal of mass from the cantilever, the calibration method presented does not impair the probes' ability to acquire data. The technique has been extensively tested in order to verify the underlying assumptions in the method. This method was compared to a number of other calibration methods and practical improvements to some of these techniques were developed, as well as important insights into the behavior of FIB modified cantilevers. These results will prove useful to research groups concerned with the application of microcantilevers to nanoscience, in particular for cases where maintaining pristine AFM tip condition is critical.

  15. Electron excitation collision strengths for positive atomic ions: a collection of theoretical data

    SciTech Connect

    Merts, A.L.; Mann, J.B.; Robb, W.D.; Magee, N.H. Jr.

    1980-03-01

    This report contains data on theoretical and experimental cross sections for electron impact excitation of positive atomic ions. It is an updated and corrected version of a preliminary manuscript which was used during an Atomic Data Workshop on Electron Excitation of Ions held at Los Alamos in November 1978. The current status of quantitative knowledge of collisional excitation collision strengths is shown for highly stripped ions where configuration mixing, relativistic and resonance effects may be important. The results show a reasonably satisfactory state for first-row isoelectronic ions and indicate that a considerable amount of work remains to be done for second-row and heavier ions.

  16. Emulating Solid-State Physics with a Hybrid System of Ultracold Ions and Atoms

    NASA Astrophysics Data System (ADS)

    Bissbort, U.; Cocks, D.; Negretti, A.; Idziaszek, Z.; Calarco, T.; Schmidt-Kaler, F.; Hofstetter, W.; Gerritsma, R.

    2013-08-01

    We propose and theoretically investigate a hybrid system composed of a crystal of trapped ions coupled to a cloud of ultracold fermions. The ions form a periodic lattice and induce a band structure in the atoms. This system combines the advantages of high fidelity operations and detection offered by trapped ion systems with ultracold atomic systems. It also features close analogies to natural solid-state systems, as the atomic degrees of freedom couple to phonons of the ion lattice, thereby emulating a solid-state system. Starting from the microscopic many-body Hamiltonian, we derive the low energy Hamiltonian, including the atomic band structure, and give an expression for the atom-phonon coupling. We discuss possible experimental implementations such as a Peierls-like transition into a period-doubled dimerized state.

  17. Emulating Solid-State Physics with a Hybrid System of Ultracold Ions and Atoms

    NASA Astrophysics Data System (ADS)

    Hofstetter, Walter; Ulf, Bissbort; Cocks, Daniel; Negretti, Antonio; Idziaszek, Zbigniew; Calarco, Tommaso; Schmidt-Kaler, Ferdinand; Gerritsma, Rene

    2014-05-01

    We propose and theoretically investigate a hybrid system composed of a crystal of trapped ions coupled to a cloud of ultracold fermions. The ions form a periodic lattice and induce a band structure in the atoms. This system combines the advantages of high fidelity operations and detection offered by trapped ion systems with ultracold atomic systems. It also features close analogies to natural solid-state systems, as the atomic degrees of freedom couple to phonons of the ion lattice, thereby emulating a solid-state system. Starting from the microscopic many-body Hamiltonian, we derive the low energy Hamiltonian, including the atomic band structure, and give an expression for the atom-phonon coupling. We discuss possible experimental implementations such as a Peierls-like transition into a period-doubled dimerized state.

  18. Emulating solid-state physics with a hybrid system of ultracold ions and atoms.

    PubMed

    Bissbort, U; Cocks, D; Negretti, A; Idziaszek, Z; Calarco, T; Schmidt-Kaler, F; Hofstetter, W; Gerritsma, R

    2013-08-23

    We propose and theoretically investigate a hybrid system composed of a crystal of trapped ions coupled to a cloud of ultracold fermions. The ions form a periodic lattice and induce a band structure in the atoms. This system combines the advantages of high fidelity operations and detection offered by trapped ion systems with ultracold atomic systems. It also features close analogies to natural solid-state systems, as the atomic degrees of freedom couple to phonons of the ion lattice, thereby emulating a solid-state system. Starting from the microscopic many-body Hamiltonian, we derive the low energy Hamiltonian, including the atomic band structure, and give an expression for the atom-phonon coupling. We discuss possible experimental implementations such as a Peierls-like transition into a period-doubled dimerized state.

  19. Emulating solid-state physics with a hybrid system of ultracold ions and atoms.

    PubMed

    Bissbort, U; Cocks, D; Negretti, A; Idziaszek, Z; Calarco, T; Schmidt-Kaler, F; Hofstetter, W; Gerritsma, R

    2013-08-23

    We propose and theoretically investigate a hybrid system composed of a crystal of trapped ions coupled to a cloud of ultracold fermions. The ions form a periodic lattice and induce a band structure in the atoms. This system combines the advantages of high fidelity operations and detection offered by trapped ion systems with ultracold atomic systems. It also features close analogies to natural solid-state systems, as the atomic degrees of freedom couple to phonons of the ion lattice, thereby emulating a solid-state system. Starting from the microscopic many-body Hamiltonian, we derive the low energy Hamiltonian, including the atomic band structure, and give an expression for the atom-phonon coupling. We discuss possible experimental implementations such as a Peierls-like transition into a period-doubled dimerized state. PMID:24010420

  20. An apparatus for immersing trapped ions into an ultracold gas of neutral atoms.

    PubMed

    Schmid, Stefan; Härter, Arne; Frisch, Albert; Hoinka, Sascha; Denschlag, Johannes Hecker

    2012-05-01

    We describe a hybrid vacuum system in which a single ion or a well-defined small number of trapped ions (in our case Ba(+) or Rb(+)) can be immersed into a cloud of ultracold neutral atoms (in our case Rb). This apparatus allows for the study of collisions and interactions between atoms and ions in the ultracold regime. Our setup is a combination of a Bose-Einstein condensation apparatus and a linear Paul trap. The main design feature of the apparatus is to first separate the production locations for the ion and the ultracold atoms and then to bring the two species together. This scheme has advantages in terms of stability and available access to the region where the atom-ion collision experiments are carried out. The ion and the atoms are brought together using a moving one-dimensional optical lattice transport which vertically lifts the atomic sample over a distance of 30 cm from its production chamber into the center of the Paul trap in another chamber. We present techniques to detect and control the relative position between the ion and the atom cloud.

  1. An apparatus for immersing trapped ions into an ultracold gas of neutral atoms.

    PubMed

    Schmid, Stefan; Härter, Arne; Frisch, Albert; Hoinka, Sascha; Denschlag, Johannes Hecker

    2012-05-01

    We describe a hybrid vacuum system in which a single ion or a well-defined small number of trapped ions (in our case Ba(+) or Rb(+)) can be immersed into a cloud of ultracold neutral atoms (in our case Rb). This apparatus allows for the study of collisions and interactions between atoms and ions in the ultracold regime. Our setup is a combination of a Bose-Einstein condensation apparatus and a linear Paul trap. The main design feature of the apparatus is to first separate the production locations for the ion and the ultracold atoms and then to bring the two species together. This scheme has advantages in terms of stability and available access to the region where the atom-ion collision experiments are carried out. The ion and the atoms are brought together using a moving one-dimensional optical lattice transport which vertically lifts the atomic sample over a distance of 30 cm from its production chamber into the center of the Paul trap in another chamber. We present techniques to detect and control the relative position between the ion and the atom cloud. PMID:22667603

  2. Atom-by-atom engineering of voltage-gated ion channels: magnified insights into function and pharmacology.

    PubMed

    Pless, Stephan A; Kim, Robin Y; Ahern, Christopher A; Kurata, Harley T

    2015-06-15

    Unnatural amino acid incorporation into ion channels has proven to be a valuable approach to interrogate detailed hypotheses arising from atomic resolution structures. In this short review, we provide a brief overview of some of the basic principles and methods for incorporation of unnatural amino acids into proteins. We also review insights into the function and pharmacology of voltage-gated ion channels that have emerged from unnatural amino acid mutagenesis approaches.

  3. Atom-by-atom engineering of voltage-gated ion channels: Magnified insights into function and pharmacology

    PubMed Central

    Pless, Stephan A; Kim, Robin Y; Ahern, Christopher A; Kurata, Harley T

    2015-01-01

    Unnatural amino acid incorporation into ion channels has proven to be a valuable approach to interrogate detailed hypotheses arising from atomic resolution structures. In this short review, we provide a brief overview of some of the basic principles and methods for incorporation of unnatural amino acids into proteins. We also review insights into the function and pharmacology of voltage-gated ion channels that have emerged from unnatural amino acid mutagenesis approaches. PMID:25640301

  4. Level-energy-dependent mean velocities of excited tungsten atoms sputtered by krypton-ion bombardment

    SciTech Connect

    Nogami, Keisuke; Sakai, Yasuhiro; Mineta, Shota; Kato, Daiji; Murakami, Izumi; Sakaue, Hiroyuki A.; Kenmotsu, Takahiro; Furuya, Kenji; Motohashi, Kenji

    2015-11-15

    Visible emission spectra were acquired from neutral atoms sputtered by 35–60 keV Kr{sup +} ions from a polycrystalline tungsten surface. Mean velocities of excited tungsten atoms in seven different 6p states were also obtained via the dependence of photon intensities on the distance from the surface. The average velocities parallel to the surface normal varied by factors of 2–4 for atoms in the different 6p energy levels. However, they were almost independent of the incident ion kinetic energy. The 6p-level energy dependence indicated that the velocities of the excited atoms were determined by inelastic processes that involve resonant charge exchange.

  5. 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.

  6. Low-Energy Ions from Laser-Cooled Atoms

    NASA Astrophysics Data System (ADS)

    Shayeganrad, G.; Fioretti, A.; Guerri, I.; Tantussi, F.; Ciampini, D.; Allegrini, M.; Viteau, M.; Fuso, F.

    2016-05-01

    We report the features of an ion source based on two-color photoionization of a laser-cooled cesium beam outsourced from a pyramidal magneto-optical trap. The ion source operates in continuous or pulsed mode. At acceleration voltages below 300 V, it delivers some ten ions per bunch with a relative energy spread Δ Urms/U ≃0.032 , as measured through the retarding field-energy-analyzer approach. Space-charge effects are negligible thanks to the low ion density attained in the interaction volume. The performances of the ion beam in a configuration using focused laser beams are extrapolated on the basis of the experimental results. Calculations demonstrate that our low-energy and low-current ion beam can be attractive for the development of emerging technologies requiring the delivery of a small amount of charge, down to the single-ion level and its eventual focusing in the 10-nm range.

  7. Matrix isolation spectra of metal atoms and ions: Ti, Zr, and Mo in Ar and Kr

    NASA Astrophysics Data System (ADS)

    Steinbrüchel, Christoph; Gruen, Dieter M.

    1981-01-01

    UV-absorption spectra are reported of neutral atoms and ions of Ti, Zr, and Mo in Ar and Kr matrices. The matrix-isolated species are produced by ion bombardment of a bulk metal target. Thermal and photoannealing experiments indicate that sputtered neutral atoms may occupy one or two distinct matrix sites, depending on the system. Sputtered ions, after being neutralized in the matrix, either go preferentially into the higher energy site, i.e., the site whose absorption bands are shifted farther to the blue, when atoms already populate two sites, or they create a new site at higher energy when there is only one site for atoms. Deconvolution of matrix isolation spectra into contributions from individual sites shows that spectra due to atoms in a particular site correspond much better to gas phase spectra than do total matrix isolation spectra. Matrix shifts of atomic absorption bands for both sites can be rationalized using a model by McCarty and Robinson if allowance is made for matrix distortion around solute atoms. The blue, or close-packed, site is found to correspond to a solute atom replacing a single matrix atom without inducing appreciable matrix distortion, whereas the red, or expanded, site requires the cage around a solute atom to be enlarged by a few percent.

  8. Highly charged ions for atomic clocks and search for variation of the fine structure constant

    NASA Astrophysics Data System (ADS)

    Dzuba, V. A.; Flambaum, V. V.

    2015-11-01

    We review a number of highly charged ions which have optical transitions suitable for building extremely accurate atomic clocks. This includes ions from Hf 12+ to U 34+, which have the 4 f 12 configuration of valence electrons, the Ir 17+ ion, which has a hole in almost filled 4 f subshell, the Ho 14+, Cf 15+, Es 17+ and Es 16+ ions. Clock transitions in most of these ions are sensitive to variation of the fine structure constant, α (α = e2/hbar c). E.g., californium and einsteinium ions have largest known sensitivity to α-variation while holmium ion looks as the most suitable ion for experimental study. We study the spectra of the ions and their features relevant to the use as frequency standards.

  9. Proceedings of the workshop on opportunities for atomic physics using slow, highly-charged ions

    SciTech Connect

    Not Available

    1987-01-01

    The study of atomic physics with highly-charged ions is an area of intense activity at the present time because of a convergence of theoretical interest and advances in experimental techniques. The purpose of the Argonne ''Workshop on Opportunities for Atomic Physics Using Slow, Highly-Charged Ions'' was to bring together atomic, nuclear, and accelerator physicists in order to identify what new facilities would be most useful for the atomic physics community. The program included discussion of existing once-through machines, advanced ion sources, recoil ion techniques, ion traps, and cooler rings. One of the topics of the Workshop was to discuss possible improvement to the ANL Tandem-Linac facility (ATLAS) to enhance the capability for slowing down ions after they are stripped to a high-charge state (the Accel/Decel technique). Another topic was the opportunity for atomic physics provided by the ECR ion source which is being built for the Uranium Upgrade of ATLAS. 18 analytics were prepared for the individual papers in this volume.

  10. Atomic physics measurements in an electron Beam Ion Trap

    SciTech Connect

    Marrs, R.E.; Beiersdorfer, P.; Bennett, C.; Chen, M.H.; Cowan, T.; Dietrich, D.; Henderson, J.R.; Knapp, D.A.; Osterheld, A.; Schneider, M.B.

    1989-03-01

    An electron Beam Ion Trap at Lawrence Livermore National Laboratory is being used to produce and trap very-highly-charged ions (q less than or equal to 70/+/) for x-ray spectroscopy measurements. Recent measurements of transition energies and electron excitation cross sections for x-ray line emission are summarized. 13 refs., 10 figs.

  11. Atom probe field ion microscopy and related topics: A bibliography 1992

    SciTech Connect

    Russell, K.F.; Godfrey, R.D.; Miller, M.K.

    1993-12-01

    This bibliography contains citations of books, conference proceedings, journals, and patents published in 1992 on the following types of microscopy: atom probe field ion microscopy (108 items); field emission microscopy (101 items); and field ion microscopy (48 items). An addendum of 34 items missed in previous bibliographies is included.

  12. Complex decay patterns in atomic core photoionization disentangled by ion-recoil measurements

    SciTech Connect

    Guillemin, Renaud; Bomme, Cedric; Marin, Thierry; Journel, Loic; Marchenko, Tatiana; Kushawaha, Rajesh K.; Piancastelli, Maria Novella; Simon, Marc; Trcera, Nicolas

    2011-12-15

    Following core 1s ionization and resonant excitation of argon atoms, we measure the recoil energy of the ions due to momentum conservation during the emission of Auger electrons. We show that such ion momentum spectroscopy can be used to disentangle to some degree complex decay patterns, involving both radiative and nonradiative decays.

  13. Calculation Of Change-Changing Cross Sections Of IONS Or Atoms Colliding With Fast IONS Using The Classical Trajectory Method

    SciTech Connect

    Kaganovich, I. D., Shnidman, Ariel, Mebane, Harrison, Davidson, R.C.

    2008-10-10

    Evaluation of ion-atom charge-changing cross sections is needed for many accelerator applications. A classical trajectory Monte Carlo (CTMC) simulation has been used to calculate ionization and charge exchange cross sections. For benchmarking purposes, an extensive study has been performed for the simple case of hydrogen and helium targets in collisions with various ions. Despite the fact that the simulation only accounts for classical mechanics, the calculations are comparable to experimental results for projectile velocities in the region corresponding to the vicinity of the maximum cross section. Shortcomings of the CTMC method for multielectron target atoms are discussed.

  14. Atom capture and loss in ion molecule collisions

    SciTech Connect

    Breinig, M.; Lasley, S.E.; Gaither, C.C. III

    1985-01-01

    Progress is reported in measuring the energy and angular distribution of protons emerging with velocity close to the beam velocity from the target region when Ar/sup +/ beams collide with a CH/sub 4/ target and ArH/sup +/ beams collide with a He target at asymptotically high speeds. The protons result from the transfer of a target constituent to the projectile (atom capture) or from the dissociation of the projectile molecule in the collision (atom loss). For atom capture processes the Thomas peak is clearly observed. 10 refs., 3 figs.

  15. First atomic physics experiments with cooled stored ion beams at the Heidelberg heavy-ion ring TSR

    SciTech Connect

    Wolf, A.; Balykin, V.; Baumann, W.; Berger, J.; Bisoffi, G.; Blatt, P.; Blum, M.; Faulstich, A.; Friedrich, A.; Gerhard, M.; Geyer, C.; Grieser, M.; Grieser, R.; Habs, D.; Heyng, H.W.; Hochadel, B.; Holzer, B.; Huber, G.; Jaeschke, E.; Jung, M.; Karafillidis, A.; Kilgus, G.; Klein, R.; Kraemer, D.; Krause, P.; Krieg, M.; Kuehl, T.; Matl, K.; Mueller, A.; Music, M.; Neumann, R.; Neureither, G.; Ott, W.; Petrich, W.; Povh, B.; Repnow, R.; Schroeder, S.; Schuch, R.; Schwalm, D.; Sigray, P.; Steck, M.; Stokstad, R.; Szmola, E.; Wagner, M.; Wanner, B.; Welti, K.; Zwickler, S. Max-Planck-Institut fuer Kernphysik, Heidelberg Manne Siegbahn Institute , Stockholm Institut fuer Kernphysik, Universitaet Giessen, Institut fuer Physik, Universitaet Mainz Gesellschaft fuer Schwerionenforschung , Darmstadt (Fed

    1990-06-01

    An overview of atomic physics experiments at the heavy ion Test Storage Ring (TSR) is given. Highly charged ions up to fully stripped silicon have been stored at energies between 4 and 12 MeV/u. The enhancement of the beam intensity by stacking, the beam lifetime, and electron cooling of these ion beams are discussed. Radiative and state-selective dielectronic recombination rates of hydrogen-like oxygen ions with free electrons from the electron cooler were measured. Beam noise spectra are being investigated with regard to collective effects caused by the Coulomb interaction in the cold ion beams. Resonance fluorescence from stored single-charged ions was observed using tunable narrow-band lasers. First indications of laser cooling in a storage ring were seen.

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

    DOEpatents

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

    1985-01-16

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

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

    DOEpatents

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

    1986-01-01

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

  18. PREFACE: Heavy-Ion Spectroscopy and QED Effects in Atomic Systems

    NASA Astrophysics Data System (ADS)

    Lindgren, Ingvar; Martinson, Indrek; Schuch, Reinhold

    1993-01-01

    Experimental studies of heavy and highly charged ions have made remarkable progress in recent years. Today it is possible to produce virtually any ion up to hydrogen-like uranium; to study collisions of those ions with atoms, electrons, and solid surfaces; to excite such an ion and accurately measure the radiation emitted. This progress is largely due to the development of new experimental methods, for instance, the high-energy ion accelerators, laser-produced plasmas, advanced ion sources and ion traps (such as EBIS, EBIT, ECR, etc.), high temperature magnetically confined plasmas and heavy-ion storage rings. The motivations for studies of collisions with highly charged ions and for the understanding of the structure of heavy atomic systems are multi-faceted. Besides of the basic scientific aspects which are mainly the subject of this symposium, much incentive is experienced by applications, e.g., the interpretation of spectra from space (solar corona, solar flares and hot stars), the modelling of stellar atmospheres, the diagnostics of fusion plasma impurities, and the development of X-ray lasers. Since quite some time highly charged ions play a key role for high-precision metrology of atomic structure. These studies have been benchmarks for tests of advanced theories, including many-body theories of interelectronic correlations, relativistic and quantum-electrodynamic (QED) effects, effects due to the finite size of the nucleus and to parity non-conservation (PNC). The interest in QED effects in heavy ions has increased drastically in the last few years. The remarkable experiment on Li-like uranium, recently reported from Berkeley, has stimulated several groups to perform very accurate Lamb-shift calculations on such systems, and reports from three groups were given about such work. The agreement between the calculations as well as with experiment was generally very good, which implies that the problem of evaluating the first-order Lamb shift for any element is

  19. An estimating formula for ion-atom association rates in gases

    NASA Technical Reports Server (NTRS)

    Chatterjee, B. K.; Johnsen, R.

    1990-01-01

    A simple estimating formula is derived for rate coefficients of three-body ion atom association in gases and compare its predictions to experimental data on ion association and three-body radiative charge transfer reactions of singly- and doubly-charged rare-gas ions. The formula appears to reproduce most experimental data quite well. It may be useful for estimating the rates of reactions that have not been studied in the laboratory.

  20. Atom probe field ion microscopy and related topics: A bibliography 1989

    SciTech Connect

    Miller, M.K.; Hawkins, A.R.; Russell, K.F.

    1990-12-01

    This bibliography includes references related to the following topics: atom probe field ion microscopy (APFIM), field ion spectroscopy (FIM), field emission microscopy (FEM), liquid metal ion sources (LMIS), scanning tunneling microscopy (STM), and theory. Technique-orientated studies and applications are included. This bibliography covers the period 1989. The references contained in this document were compiled from a variety of sources including computer searches and personal lists of publications.

  1. Atom probe field-ion microscopy and related topics: A bibliography, 1988

    SciTech Connect

    Miller, M.K.; Hawkins, A.R.

    1989-10-01

    This bibliography includes references related to the following topics: field-ion microscopy (FIM), field emission microscopy (FEM), atom probe field-ion microscopy (APFIM), and liquid metal ion sources (LMIS). Technique-orientated studies and applications are included. The references contained in this document were compiled from a variety of sources including computer searches and personal lists of publications. To reduce the length of this document, the references have been reduced to the minimum necessary to locate the articles.

  2. Kinetics and continuum emission of negative atomic ions in partially ionized plasmas

    NASA Technical Reports Server (NTRS)

    Soon, W. H.; Kunc, J. A.

    1991-01-01

    Kinetics and continuum emission of negative ions are studied in stationary atomic hydrogen, nitrogen, and oxygen plasmas. The intensity of the negative-ion emission was found to be neglibible when compared to those of bound-bound and free-bound emission at low and medium particle densities. However, the negative-ion continuum emission can contribute significantly in certain parts of the emission spectrum at high particle densities.

  3. Total Born-approximation cross sections for single-electron loss by atoms and ions colliding with atoms

    NASA Technical Reports Server (NTRS)

    Rule, D. W.

    1977-01-01

    The first Born approximation (FBA) is applied to the calculation of single-electron-loss cross sections for various ions and atoms containing from one to seven electrons. Screened hydrogenic wave functions are used for the states of the electron ejected from the projectile, and Hartree-Fock elastic and incoherent scattering factors are used to describe the target. The effect of the target atom on the scaling of projectile ionization cross sections with respect to the projectile nuclear charge is explored in the case of hydrogenlike ions. Also examined is the scaling of the cross section with respect to the target nuclear charge for electron loss by Fe(25+) in collision with neutral atoms ranging from H to Fe. These results are compared with those of the binary-encounter approximation (BEA) and with the FBA for the case of ionization by completely stripped target ions. Electron-loss cross sections are also calculated for the ions O(i+) (i = 3-7) and N(i+) (i = 0-6) in collision with He targets in the energy range of approximately 0.1 to 100 MeV/nucleon. These results are found to be in excellent agreement with the available data near the peak of the ionization cross section.

  4. Recrystallization and reactivation of dopant atoms in ion-implanted silicon nanowires.

    PubMed

    Fukata, Naoki; Takiguchi, Ryo; Ishida, Shinya; Yokono, Shigeki; Hishita, Shunichi; Murakami, Kouichi

    2012-04-24

    Recrystallization of silicon nanowires (SiNWs) after ion implantation strongly depends on the ion doses and species. Full amorphization by high-dose implantation induces polycrystal structures in SiNWs even after high-temperature annealing, with this tendency more pronounced for heavy ions. Hot-implantation techniques dramatically suppress polycrystallization in SiNWs, resulting in reversion to the original single-crystal structures and consequently high reactivation rate of dopant atoms. In this study, the chemical bonding states and electrical activities of implanted boron and phosphorus atoms were evaluated by Raman scattering and electron spin resonance, demonstrating the formation of p- and n-type SiNWs.

  5. New ion trap for atomic frequency standard applications

    NASA Technical Reports Server (NTRS)

    Prestage, J. D.; Dick, G. J.; Maleki, L.

    1989-01-01

    A novel linear ion trap that permits storage of a large number of ions with reduced susceptibility to the second-order Doppler effect caused by the radio frequency (RF) confining fields has been designed and built. This new trap should store about 20 times the number of ions a conventional RF trap stores with no corresponding increase in second-order Doppler shift from the confining field. In addition, the sensitivity of this shift to trapping parameters, i.e., RF voltage, RF frequency, and trap size, is greatly reduced.

  6. Autoionization of He atoms by partially stripped ion impact

    SciTech Connect

    Otranto, S.; Olson, R.E.

    2005-08-15

    A study of the autoionization process induced by partially stripped ion impact is performed. Electron spectra in momentum space are predicted within a classical model for partially stripped ions. The results are compared with those obtained for pure Coulomb-like projectiles. A quantum-mechanical extension of the Barrachina-Macek model is proposed for partially stripped projectiles. Structure on the electron angular distribution arising in quantum and classical treatments is identified and compared. The presence of rainbow scattering interference is observed in the binary ring profile of the outgoing autoionized electrons for positive-ion impact.

  7. Treatment of ion-atom collisions using a partial-wave expansion of the projectile wavefunction

    SciTech Connect

    Foster, M; Colgan, J; Wong, T G; Madison, D H

    2008-01-01

    We present calculations of ion-atom collisions using a partial-wave expansion of the projectile wavefunction. Most calculations of ion-atom collisions have typically used classical or plane-wave approximations for the projectile wavefunction, since partial-wave expansions are expected to require prohibitively large numbers of terms to converge scattering quantities. Here we show that such calculations are possible using modern high-performance computing. We demonstrate the utility of our method by examining elastic scattering of protons by hydrogen and helium atoms, problems familiar to undergraduate students of atomic scattering. Application to ionization of helium using partial-wave expansions of the projectile wavefunction, which has long been desirable in heavy-ion collision physics, is thus quite feasible.

  8. New source of MeV negative ion and neutral atom beams

    NASA Astrophysics Data System (ADS)

    Ter-Avetisyan, S.; Braenzel, J.; Schnürer, M.; Prasad, R.; Borghesi, M.; Jequier, S.; Tikhonchuk, V.

    2016-02-01

    The scenario of "electron-capture and -loss" was recently proposed for the formation of negative ion and neutral atom beams with MeV kinetic energies. However, it does not explain why the formation of negative ions in a liquid spray is much more efficient than with an isolated atom. The role of atomic excited states in the charge-exchange processes is considered, and it is shown that it cannot account for the observed phenomena. The processes are more complex than the single electron-capture and -loss approach. It is suggested that the shell effects in the electronic structure of the projectile ion and/or target atoms may influence the capture/loss probabilities.

  9. Generation of a fast atomic-oxygen beam from O - ions by resonant cavity radiation

    NASA Astrophysics Data System (ADS)

    Stephen, T. M.; Van Zyl, B.; Amme, R. C.

    1996-04-01

    An apparatus has been developed for producing a beam of ground-electronic-state oxygen atoms with energies variable from 4 to 1000 eV with a 1.5 eV FWHM energy distribution. The technique involves extraction of negative ions from a low-voltage gas-discharge source, mass selection of the extracted O- with a Wien-type velocity filter, O- acceleration or deceleration and focusing by electrostatic ion optics, and electron detachment from O- by intracavity laser radiation. A 25 W argon-ion-laser cavity has been extended to include the ion-beam vacuum chamber so that the intracavity radiation intersects the O- ion trajectories normally. Depending on the laser configuration in use, ion-neutralization efficiencies between 5% and 25% have been achieved at 5 eV O- energy. Thus, 5 eV O-atom fluxes of ˜1011 atoms/s (˜1012 atoms/cm2 s) have been achieved for O- currents of ˜10-7 A. The advantages and limitations of the technique are discussed, and preliminary measurements of the secondary-negative-charge production from low-energy O-atom impact on copper and stainless-steel surfaces are presented.

  10. Atomic Physics Effects on Convergent, Child-Langmuir Ion Flow between Nearly Transparent Electrodes

    SciTech Connect

    Santarius, John F.; Emmert, Gilbert A.

    2013-11-07

    Research during this project at the University of Wisconsin Fusion Technology Institute (UW FTI) on ion and neutral flow through an arbitrary, monotonic potential difference created by nearly transparent electrodes accomplished the following: (1) developed and implemented an integral equation approach for atomic physics effects in helium plasmas; (2) extended the analysis to coupled integral equations that treat atomic and molecular deuterium ions and neutrals; (3) implemented the key deuterium and helium atomic and molecular cross sections; (4) added negative ion production and related cross sections; and (5) benchmarked the code against experimental results. The analysis and codes treat the species D0, D20, D+, D2+, D3+, D and, separately at present, He0 and He+. Extensions enhanced the analysis and related computer codes to include He++ ions plus planar and cylindrical geometries.

  11. Measurement of the force on microparticles in a beam of energetic ions and neutral atoms

    SciTech Connect

    Trottenberg, Thomas; Schneider, Viktor; Kersten, Holger

    2010-10-15

    The force on microparticles in an energetic ion beam is investigated experimentally. Hollow glass microspheres are injected into the vertically upward directed beam and their trajectories are recorded with a charge-coupled device camera. The net force on the particles is determined by means of the measured vertical acceleration. The resulting beam pressures are compared with Faraday cup measurements of the ion current density and calorimetric measurements of the beam power density. Due to the neutral gas background, the beam consists, besides the ions, of energetic neutral atoms produced by charge-exchange collisions. It is found that the measured composition of the drag force by an ion and a neutral atom component agrees with a beam model that takes charge-exchange collisions into account. Special attention is paid to the momentum contribution from sputtered atoms, which is shown to be negligible in this experiment, but should become measurable in case of materials with high sputtering yields.

  12. Neutral atomic oxygen beam produced by ion charge exchange for Low Earth Orbital (LEO) simulation

    NASA Technical Reports Server (NTRS)

    Banks, Bruce; Rutledge, Sharon; Brdar, Marko; Olen, Carl; Stidham, Curt

    1987-01-01

    A low energy neutral atomic oxygen beam system was designed and is currently being assembled at the Lewis Research Center. The system utilizes a 15 cm diameter Kaufman ion source to produce positive oxygen ions which are charge exchange neutralized to produce low energy (variable from 5 to 150 eV) oxygen atoms at a flux simulating real time low Earth orbital conditions. An electromagnet is used to direct only the singly charged oxygen ions from the ion source into the charge exchange cell. A retarding potential grid is used to slow down the oxygen ions to desired energies prior to their charge exchange. Cryogenically cooled diatomic oxygen gas in the charge exchange cell is then used to transfer charge to the oxygen ions to produce a neutral atomic oxygen beam. Remaining non-charge exchanged oxygen ions are then swept from the beam by electromagnetic or electrostatic deflection depending upon the desired experiment configuration. The resulting neutral oxygen beam of 5 to 10 cm in diameter impinges upon target materials within a sample holder fixture that can also provide for simultaneous heating and UV exposure during the atomic oxygen bombardment.

  13. Symmetric eikonal model for projectile-electron excitation and loss in relativistic ion-atom collisions

    SciTech Connect

    Voitkiv, A. B.; Najjari, B.; Shevelko, V. P.

    2010-08-15

    At impact energies > or approx. 1 GeV/u the projectile-electron excitation and loss occurring in collisions between highly charged ions and neutral atoms is already strongly influenced by the presence of atomic electrons. To treat these processes in collisions with heavy atoms we generalize the symmetric eikonal model, used earlier for considerations of electron transitions in ion-atom collisions within the scope of a three-body Coulomb problem. We show that at asymptotically high collision energies this model leads to an exact transition amplitude and is very well suited to describe the projectile-electron excitation and loss at energies above a few GeV/u. In particular, by considering a number of examples we demonstrate advantages of this model over the first Born approximation at impact energies of {approx}1-30 GeV/u, which are of special interest for atomic physics experiments at the future GSI facilities.

  14. Determination of Optimum Conditions for Distinguishing the Pulse Height Distributions of Atomic and Polyatomic Ions

    SciTech Connect

    Kristo, M J

    2006-12-12

    This work explored the use of pulse height distributions (PHD) from multiplier-type detectors as a means of detecting and eliminating the effects of polyatomic interferences in secondary ion mass spectrometry (SIMS). We explored the behavior of PHD for {sup 235}U{sup +}, {sup 208}Pb{sup 27}Al{sup +} and {sup 207}Pb{sup 28}Si{sup +}, all with a nominal mass-to-charge ratio of 235. In every case, the distribution for the atomic ion ({sup 235}U{sup +}) was clearly shifted relative to the distributions for {sup 208}Pb{sup 27}Al{sup +} and {sup 207}Pb{sup 28}Si{sup +}. When the first surface of the detector is metallic in character, the polyatomic ions are shifted to larger pulse heights relative to the atomic ion. When the first surface of the detector is oxide in character, the atomic ion is shifted to larger pulse heights relative to the polyatomic ions. The relative positioning appear to be stable for a given detector over time at the same secondary ion impact energy. Consequently, it appears to be feasible to use PHD data to detect interfering polyatomic ions and eliminate their deleterious effects using peak deconvolution techniques. Consequently, the updated Ultrafast RAE detector will be designed to make the pulse height information available to the data acquisition system.

  15. Atomic-scale thermocapillary flow in focused ion beam milling

    SciTech Connect

    Das, K.; Johnson, H. T.; Freund, J. B.

    2015-05-15

    Focused ion beams provide a means of nanometer-scale manufacturing and material processing, which is used for applications such as forming nanometer-scale pores in thin films for DNA sequencing. We investigate such a configuration with Ga{sup +} bombardment of a Si thin-film target using molecular dynamics simulation. For a range of ion intensities in a realistic configuration, a recirculating melt region develops, which is seen to flow with a symmetrical pattern, counter to how it would flow were it driven by the ion momentum flux. Such flow is potentially important for the shape and composition of the formed structures. Relevant stress scales and estimated physical properties of silicon under these extreme conditions support the importance thermocapillary effects. A flow model with Marangoni forcing, based upon the temperature gradient and geometry from the atomistic simulation, indeed reproduces the flow and thus could be used to anticipate such flows and their influence in applications.

  16. Controlled collisions of a single atom and an ion guided by movable trapping potentials

    SciTech Connect

    Idziaszek, Zbigniew; Calarco, Tommaso; Zoller, Peter

    2007-09-15

    We consider a system composed of a trapped atom and a trapped ion. The ion charge induces in the atom an electric dipole moment, which attracts it with an r{sup -4} dependence at large distances. In the regime considered here, the characteristic range of the atom-ion interaction is comparable or larger than the characteristic size of the trapping potential, which excludes the application of the contact pseudopotential. The short-range part of the interaction is described in the framework of quantum-defect theory, by introducing some short-range parameters, which can be related to the s-wave scattering length. When the separation between traps is changed we observe trap-induced shape resonances between molecular bound states and vibrational states of the external trapping potential. Our analysis is extended to quasi-one-dimensional geometries, when the scattering exhibit confinement-induced resonances, similar to the ones studied before for short-range interactions. For quasi-one-dimensional systems we investigate the effects of coupling between the center of mass and relative motion, which occurs for different trapping frequencies of atom and ion traps. Finally, we show how the two types of resonances can be employed for quantum state control and spectroscopy of atom-ion molecules.

  17. Description of ion motion in a Paul trap immersed in a cold atomic gas

    NASA Astrophysics Data System (ADS)

    Krych, Michał; Idziaszek, Zbigniew

    2015-02-01

    We investigate the problem of a single ion in a radio-frequency trap immersed in an ultracold Bose gas in either a condensed or a noncondensed phase. We develop a master-equation formalism describing the sympathetic cooling, and we determine the cooling rates of ions. We show that the cold atomic reservoir modifies the stability diagram of the ion in the Paul trap, creating regions where the ion is either cooled or heated due to the energy quanta exchanged with the time-dependent potential.

  18. A new approach to the interpretation of atom probe field-ion microscopy images.

    PubMed

    Vurpillot, F; Bostel, A; Blavette, D

    2001-10-01

    The field distribution and the ion trajectories close to the tip surface are known to mainly control the contrast of field-ion microscopy and the resolution of the three-dimensional atom probe. The proper interpretation of images provided by these techniques requires the electric field and the ion trajectories to be determined accurately. A model has been developed in order to compute the ion trajectories close to a curved emitting surface modelled at the atomic scale. In this model, both the gradual change of the tip surface and the chemical nature of atoms were taken into account. Predictions and results given by this approach are shown to be in excellent agreement with experiments. The calculated electric field at the tip surface is consistent with field-ion microscopy contrasts. The preferential retention of surface atoms and the order of evaporation were correctly simulated. The ion trajectories were successfully described. In this way, the crucial problem of trajectory overlap and local magnification could be investigated. These simulations not only lead to a new understanding of the physical basis of image formation, but also have a predictive value.

  19. Energetic neutral atoms emitted from ice by ion bombardment under Ganymede surface conditions

    NASA Astrophysics Data System (ADS)

    Wieser, Martin; Barabash, Stas; Futaana, Yoshifumi; Wurz, Peter

    2013-04-01

    Magnetospheric or solar wind ions directly interacting with a planetary surface result in backscattering or sputtering of energetic neutral atoms. One example is the solar wind interaction with the surface of the Moon, where the produced energetic neutral atoms were observed by the Sub-keV Atom Reflecting Analyzer instrument (SARA) on Chandrayaan-1. At Jupiter, magnetospheric plasma interacts in a similar way with the surface of the Galilean moons. However, the emission of energetic neutral atoms from "dirty" ices as found e.g. on Ganymede's surface is poorly understood. We set up an experiment to study the ion to surface interaction under Ganymede surface environment conditions using the unique capabilities of the MEFISTO test facility at University of Bern. Ions of various species and energies up to 33 keV/q were impacted on a block of ice made from a mixture of water, NaCl and dry ice. The energetic neutral atoms produced by the interaction were detected with the prototype of the Jovian Neutrals Analyzer instrument (JNA.) JNA is proposed as part of the Particle Environment Package (PEP) for ESA's JUICE mission to Jupiter and instrument is based on the Energetic Energetic Neutral Atom instrument (ENA) built for the BepiColombo Magnetospheric Orbiter. We present energy spectra for different ion beam species and energetic neutral atom species combinations. The data show high yields for energetic neutral atoms up to the upper end of the instrument energy range of 3.3 keV. The energy spectra of the neutral atom flux emitted from the ice could only partially be fitted by the Sigmund-Thompson formula. In some cases, but not all, a Maxwellian distribution provides a reasonable description of the data.

  20. Electron quantum dynamics in atom-ion interaction.

    PubMed

    Sabzyan, H; Jenabi, M J

    2016-04-01

    Electron transfer (ET) process and its dependence on the system parameters are investigated by solving two-dimensional time-dependent Schrödinger equation numerically using split operator technique. Evolution of the electron wavepacket occurs from the one-electron species hydrogen atom to another bare nucleus of charge Z > 1. This evolution is quantified by partitioning the simulation box and defining regional densities belonging to the two nuclei of the system. It is found that the functional form of the time-variations of these regional densities and the extent of ET process depend strongly on the inter-nuclear distance and relative values of the nuclear charges, which define the potential energy surface governing the electron wavepacket evolution. Also, the initial electronic state of the single-electron atom has critical effect on this evolution and its consequent (partial) electron transfer depending on its spreading extent and orientation with respect to the inter-nuclear axis. PMID:27059569

  1. Electron quantum dynamics in atom-ion interaction.

    PubMed

    Sabzyan, H; Jenabi, M J

    2016-04-01

    Electron transfer (ET) process and its dependence on the system parameters are investigated by solving two-dimensional time-dependent Schrödinger equation numerically using split operator technique. Evolution of the electron wavepacket occurs from the one-electron species hydrogen atom to another bare nucleus of charge Z > 1. This evolution is quantified by partitioning the simulation box and defining regional densities belonging to the two nuclei of the system. It is found that the functional form of the time-variations of these regional densities and the extent of ET process depend strongly on the inter-nuclear distance and relative values of the nuclear charges, which define the potential energy surface governing the electron wavepacket evolution. Also, the initial electronic state of the single-electron atom has critical effect on this evolution and its consequent (partial) electron transfer depending on its spreading extent and orientation with respect to the inter-nuclear axis.

  2. Electron quantum dynamics in atom-ion interaction

    NASA Astrophysics Data System (ADS)

    Sabzyan, H.; Jenabi, M. J.

    2016-04-01

    Electron transfer (ET) process and its dependence on the system parameters are investigated by solving two-dimensional time-dependent Schrödinger equation numerically using split operator technique. Evolution of the electron wavepacket occurs from the one-electron species hydrogen atom to another bare nucleus of charge Z > 1. This evolution is quantified by partitioning the simulation box and defining regional densities belonging to the two nuclei of the system. It is found that the functional form of the time-variations of these regional densities and the extent of ET process depend strongly on the inter-nuclear distance and relative values of the nuclear charges, which define the potential energy surface governing the electron wavepacket evolution. Also, the initial electronic state of the single-electron atom has critical effect on this evolution and its consequent (partial) electron transfer depending on its spreading extent and orientation with respect to the inter-nuclear axis.

  3. Inversion problem for ion-atom differential elastic scattering.

    NASA Technical Reports Server (NTRS)

    Rich, W. G.; Bobbio, S. M.; Champion, R. L.; Doverspike, L. D.

    1971-01-01

    The paper describes a practical application of Remler's (1971) method by which one constructs a set of phase shifts from high resolution measurements of the differential elastic scattering of protons by rare-gas atoms. These JWKB phase shifts are then formally inverted to determine the corresponding intermolecular potentials. The validity of the method is demonstrated by comparing an intermolecular potential obtained by direct inversion of experimental data with a fairly accurate calculation by Wolniewicz (1965).

  4. Retrieval of metal atom and ion number densities in the mesosphere and lower thermosphere

    NASA Astrophysics Data System (ADS)

    Langowski, Martin; Von Savigny, Christian; Burrows, John

    2016-07-01

    When meteoroids enter the Earth's atmosphere with velocities of several 10 km/s, they heat up due to frictional heating and meteoric material is ablated in the upper atmosphere at around 100 km. A certain part of this ablated material are metal atoms and ions, which form layers of about 10 km width at altitudes between 80 to 110 km. The metal atoms and ions are strong emitters of dayglow coming from resonance fluorescence. From satellite observations of these emission signature, densities of the metal atom and ion layers can be retrieved. From the densities of the metal layers in combination with model simulations the input rate of meteoric material can be estimated, which still shows a large uncertainty range between 1 to 300 tons per day. We will present results of the number density retrievals from the SCIAMACHY limb mesosphere and lower thermosphere measurements from 2008 to 2012 for Mg, Mg^{+} and Na.

  5. Probing dissociative electron attachment through heavy-Rydberg ion-pair production in Rydberg atom collisions

    NASA Astrophysics Data System (ADS)

    Buathong, S.; Kelley, M.; Dunning, F. B.

    2016-10-01

    Electron transfer in collisions between low-n, n = 12, Rydberg atoms and targets that attach low-energy electrons can lead to the formation of heavy-Rydberg ion-pair states comprising a weakly-bound positive-negative ion pair that orbit each other at large separations. Measurements of the velocity and angular distribution of ion-pair states produced in collisions with 1,1,1-C2Cl3F3, CBrCl3, BrCN, and Fe(CO)5 are used to show that electron transfer reactions furnish a new technique with which to examine the lifetime and decay energetics of the excited intermediates formed during dissociative electron capture. The results are analyzed with the aid of Monte Carlo simulations based on the free electron model of Rydberg atom collisions. The data further highlight the capabilities of Rydberg atoms as a microscale laboratory in which to probe the dynamics of electron attachment reactions.

  6. Preparation and Analysis of Atom Probe Tips by Xenon Focused Ion Beam Milling.

    PubMed

    Estivill, Robert; Audoit, Guillaume; Barnes, Jean-Paul; Grenier, Adeline; Blavette, Didier

    2016-06-01

    The damage and ion distribution induced in Si by an inductively coupled plasma Xe focused ion beam was investigated by atom probe tomography. By using predefined patterns it was possible to prepare the atom probe tips with a sub 50 nm end radius in the ion beam microscope. The atom probe reconstruction shows good agreement with simulated implantation profiles and interplanar distances extracted from spatial distribution maps. The elemental profiles of O and C indicate co-implantation during the milling process. The presence of small disc-shaped Xe clusters are also found in the three-dimensional reconstruction. These are attributed to the presence of Xe nanocrystals or bubbles that open during the evaporation process. The expected accumulated dose points to a loss of >95% of the Xe during analysis, which escapes undetected. PMID:27056544

  7. Preparation and Analysis of Atom Probe Tips by Xenon Focused Ion Beam Milling.

    PubMed

    Estivill, Robert; Audoit, Guillaume; Barnes, Jean-Paul; Grenier, Adeline; Blavette, Didier

    2016-06-01

    The damage and ion distribution induced in Si by an inductively coupled plasma Xe focused ion beam was investigated by atom probe tomography. By using predefined patterns it was possible to prepare the atom probe tips with a sub 50 nm end radius in the ion beam microscope. The atom probe reconstruction shows good agreement with simulated implantation profiles and interplanar distances extracted from spatial distribution maps. The elemental profiles of O and C indicate co-implantation during the milling process. The presence of small disc-shaped Xe clusters are also found in the three-dimensional reconstruction. These are attributed to the presence of Xe nanocrystals or bubbles that open during the evaporation process. The expected accumulated dose points to a loss of >95% of the Xe during analysis, which escapes undetected.

  8. A new trapped ion atomic clock based on 201Hg+.

    PubMed

    Burt, Eric A; Taghavi-Larigani, Shervin; Tjoelker, Robert L

    2010-03-01

    High-resolution spectroscopy has been performed on the ground-state hyperfine transitions in trapped (201)Hg+ ions as part of a program to investigate the viability of (201)Hg+ for clock applications. Part of the spectroscopy work was directed at magnetic-field-sensitive hyperfine lines with delta m(F) = 0, which allow accurate Doppler-free measurement of the magnetic field experienced by the trapped ions. Although it is possible to measure Doppler-free magnetic-field-sensitive transitions in the commonly used clock isotope, (199)Hg+, it is more difficult. In this paper, we discuss how this (199)Hg+ feature may be exploited to produce a more stable clock or one requiring less magnetic shielding in environments with magnetic field fluctuations far in excess of what is normally found in the laboratory. We have also determined that in discharge-lamp-based trapped mercury ion clocks, the optical pumping time for (201)Hg+ is about 3 times shorter than that of (199)Hg+ This can be used to reduce dead time in the interrogation cycle for these types of clocks, thereby reducing the impact of local oscillator noise aliasing effects.

  9. The use of 133 Ba+ as a new candidate for trapped atomic ion qubits

    NASA Astrophysics Data System (ADS)

    Hucul, David; Christiansen, Justin; Campbell, Wesley; Hudson, Eric

    2016-05-01

    Trapped atomic ions are qubit standards in quantum information science because of their long coherence times and high fidelity entangling gates. Many different atomic ions have been used as qubits, each with strengths and weaknesses dictated by its atomic structure. We propose to use 133 Ba+ as an atomic qubit. 133 Ba+ is a nearly ideal, all-purpose candidate by combining many of the strengths of different workhorse atomic ions. 133 Ba+, like 171 Yb+, has a nuclear spin 1/2, allowing for a robust hyperfine qubit with simple state preparation and readout via differential fluorescence. The lack of a low-lying F-state, like in Ca+, simplifies high-fidelity qubit state detection that relies on shelving a qubit level to a meta-stable excited state. In addition, 133 Ba+ can be used for background-free qubit state detection where the wavelength of the qubit detection light differs from all excitation light by at least 50 THz. Unlike all other ions in use, the optical transitions of barium are in the visible spectrum, enabling the use of high power lasers, low-loss fibers, high quantum efficiency detectors, and other technologies developed for visible wavelengths of light to ease some requirements toward scaling a quantum system.

  10. HISTRAP (Heavy Ion Storage Ring for Atomic Physics) prototype hardware studies

    SciTech Connect

    Olsen, D.K.; Atkins, W.H.; Dowling, D.T.; Johnson, J.W.; Lord, R.S.; McConnell, J.W.; Milner, W.T.; Mosko, S.W.; Tatum, B.A.

    1989-01-01

    HISTRAP, Heavy Ion Storage Ring for Atomic Physics, is a proposed 2.67-Tm synchrotron/cooler/storage ring optimized for advanced atomic physics research which will be injected with ions from either the HHIRF 25-MV tandem accelerator or a dedicated ECR source and RFQ linac. Over the last two years, hardware prototypes have been developed for difficult and long lead-time components. A vacuum test stand, the rf cavity, and a prototype dipole magnet have been designed, constructed, and tested. 7 refs., 8 figs., 2 tabs.

  11. Overview on collision processes of highly charged ions with atoms present status and problems

    SciTech Connect

    Janev, R.K.

    1983-05-01

    This paper provides a brief discussion on the present status of the collision physics of highly charged ions with atoms. The emphasis is on the main achievements in understanding and describing the most important collision processes, and as charge transfer, ionization and Auger-type processes, and even more on those open problems which, due either to their scientific or practical importance, represent challenges to current research in this field. The paper concentrates on general ideas and problems whose development and solutions have advanced or will advance our basic understanding of the collision dynamics of multiply charged ions with atoms.

  12. Pairing preferences of the model mono-valence mono-atomic ions investigated by molecular simulation

    SciTech Connect

    Zhang, Qiang; Zhang, Ruiting; Zhao, Ying; Li, HuanHuan; Zhuang, Wei E-mail: gaoyq@pku.edu.cn; Gao, Yi Qin E-mail: gaoyq@pku.edu.cn

    2014-05-14

    We carried out a series of potential of mean force calculations to study the pairing preferences of a series of model mono-atomic 1:1 ions with evenly varied sizes. The probabilities of forming the contact ion pair (CIP) and the single water separate ion pair (SIP) were presented in the two-dimensional plots with respect to the ion sizes. The pairing preferences reflected in these plots largely agree with the empirical rule of matching ion sizes in the small and big size regions. In the region that the ion sizes are close to the size of the water molecule; however, a significant deviation from this conventional rule is observed. Our further analysis indicated that this deviation originates from the competition between CIP and the water bridging SIP state. The competition is mainly an enthalpy modulated phenomenon in which the existing of the water bridging plays a significant role.

  13. Pairing preferences of the model mono-valence mono-atomic ions investigated by molecular simulation.

    PubMed

    Zhang, Qiang; Zhang, Ruiting; Zhao, Ying; Li, HuanHuan; Gao, Yi Qin; Zhuang, Wei

    2014-05-14

    We carried out a series of potential of mean force calculations to study the pairing preferences of a series of model mono-atomic 1:1 ions with evenly varied sizes. The probabilities of forming the contact ion pair (CIP) and the single water separate ion pair (SIP) were presented in the two-dimensional plots with respect to the ion sizes. The pairing preferences reflected in these plots largely agree with the empirical rule of matching ion sizes in the small and big size regions. In the region that the ion sizes are close to the size of the water molecule; however, a significant deviation from this conventional rule is observed. Our further analysis indicated that this deviation originates from the competition between CIP and the water bridging SIP state. The competition is mainly an enthalpy modulated phenomenon in which the existing of the water bridging plays a significant role.

  14. Observation of the continuous stern-gerlach effect on an electron bound in an atomic Ion

    PubMed

    Hermanspahn; Haffner; Kluge; Quint; Stahl; Verdu; Werth

    2000-01-17

    We report on the first observation of the continuous Stern-Gerlach effect on an electron bound in an atomic ion. The measurement was performed on a single hydrogenlike ion ( 12C5+) in a Penning trap. The measured g factor of the bound electron, g = 2.001 042(2), is in excellent agreement with the theoretical value, confirming the relativistic correction at a level of 0.1%. This proves the possibility of g-factor determinations on atomic ions to high precision by using the continuous Stern-Gerlach effect. The result demonstrates the feasibility of conducting experiments on single heavy highly charged ions to test quantum electrodynamics in the strong electric field of the nucleus.

  15. Chapter 11 Experiments on Highly Charged Heavy Ions in Conjunction with Exotic Atoms

    NASA Astrophysics Data System (ADS)

    Indelicato, P.; Trassinelli, M.; Anagnostopoulos, D. F.; Boucard, S.; Covita, D. S.; Borchert, G.; Dax, A.; Egger, J. P.; Gotta, D.; Gruber, A.; Hirtl, A.; Hennebach, M.; Fuhrmann, H.; Le Bigot, E.-O.; Liu, Y.-W.; Manil, B.; Nelms, N.; Schlesser, S.; Dos Santos, J. M. F.; Simons, L. M.; Stingelin, L.; Veloso, J.; Wasser, A.; Wells, A.; Zmeskal, J.

    We demonstrate how combining highly-charged ions and exotic atoms measurements can provide high-accuracy information on particle properties, like the pion mass, on interactions, like the pion-proton strong interaction at low energy, and bound-state QED in strong fields. The use of highly-charged ion X-rays emitted by the plasma inside a super-conducting ion source provides a very detailed characterization of the response function of the X-ray spectrometer used to study exotic atoms, allowing for very accurate measurements. Conversely the use of the same high-resolution and high transmission spectrometer provides very accurate measurements of X-ray lines of few-electron ions.

  16. Observation of the continuous stern-gerlach effect on an electron bound in an atomic Ion

    PubMed

    Hermanspahn; Haffner; Kluge; Quint; Stahl; Verdu; Werth

    2000-01-17

    We report on the first observation of the continuous Stern-Gerlach effect on an electron bound in an atomic ion. The measurement was performed on a single hydrogenlike ion ( 12C5+) in a Penning trap. The measured g factor of the bound electron, g = 2.001 042(2), is in excellent agreement with the theoretical value, confirming the relativistic correction at a level of 0.1%. This proves the possibility of g-factor determinations on atomic ions to high precision by using the continuous Stern-Gerlach effect. The result demonstrates the feasibility of conducting experiments on single heavy highly charged ions to test quantum electrodynamics in the strong electric field of the nucleus. PMID:11015930

  17. The Spectr-W3 database on the spectroscopic properties of atoms and ions

    NASA Astrophysics Data System (ADS)

    Skobelev, I. Yu.; Loboda, P. A.; Gagarin, S. V.; Ivliev, S. V.; Kozlov, A. I.; Morozov, S. V.; Pikuz, S. A.; Pikuz, T. A.; Popova, V. V.; Faenov, A. Ya.

    2016-04-01

    The Spectr-W3 database was developed in 2001-2013 and is available online (http://spectrw3. snz.ru). The database contains information on various spectroscopic constants of atoms and ions such as the wavelengths and probabilities of radiative transitions, energy levels of atoms and ions, ionization potentials, autoionization rates, and the parameters of analytical approximation of cross sections and rates of collisional transitions in atoms and ions. Spectr-W3 presently contains around 450 thousand records and is the world's largest factual database on spectral properties of multicharged ions. A new stage of development of Spectr-W3, which involves adding a new section titled "Emission Spectrograms" to the database, commenced in 2014. In contrast to the already existing sections that contain tabulated data, this new section provides graphical data (with necessary explanatory notes) on the spectrograms of emission of atoms and ions excited in various plasma sources. The structure of sections of the Spectr-W3 database is characterized, and examples of queries and the corresponding search results are given.

  18. Depth distribution of deuterium atoms and molecules in beryllium oxide implanted with deuterium ions

    NASA Astrophysics Data System (ADS)

    Alimov, V. Kh; Chernikov, V. N.

    1999-08-01

    In-depth concentration profiles of deuterium (D) in beryllium oxide (BeO) films implanted with 3 keV D ions at 300 and 700 K have been determined using SIMS and RGA (residual gas analysis) measurements in the course of surface sputtering. The microstructure of implanted specimens was studied by TEM. Implanted D is found to be retained in the BeO matrix in the form of D atoms and D 2 molecules. At 300 and 700 K, the maximum concentration of deuterium in both states reaches values of 0.2 and 0.07 D/BeO, respectively. Irradiation with D ions at 300 and 700 K leads to the formation of tiny D 2 bubbles of 0.6-0.7 nm radius and of high volume density ≈(4-5) × 10 24 m -3. These bubbles together with the intercrystalline gaps are responsible for the accumulation of D 2 molecules. At both irradiation temperatures, D 2 concentration reaches in the ion stopping zone its maximum of 0.01 molecules/BeO. At 300 and 700 K, the major part of deuterium implanted in BeO films is present in the form of D atoms, probably chemically bound to O atoms. Maximum D atom concentration is 0.18 D atoms/BeO for 300 K and 0.05 D atoms/BeO for 700 K.

  19. Effects of Ion Atomic Number on Single-Event Gate Rupture (SEGR) Susceptibility of Power MOSFETs

    NASA Technical Reports Server (NTRS)

    Lauenstein, Jean-Marie; Goldsman, Neil; Liu, Sandra; Titus, Jeffrey L.; Ladbury, Raymond L.; Kim, Hak S.; Phan, Anthony M.; LaBel, Kenneth A.; Zafrani, Max; Sherman, Phillip

    2012-01-01

    The relative importance of heavy-ion interaction with the oxide, charge ionized in the epilayer, and charge ionized in the drain substrate, on the bias for SEGR failure in vertical power MOSFETs is experimentally investigated. The results indicate that both the charge ionized in the epilayer and the ion atomic number are important parameters of SEGR failure. Implications on SEGR hardness assurance are discussed.

  20. Distortion effects in electron excitation of hydrogen atoms by impact of heavy ions

    SciTech Connect

    Ramirez, C.A.; Rivarola, R.D.

    1995-12-01

    Electron excitation from the fundamental state of hydrogen atoms by impact of bare ions is studied at intermediate and high collision velocities. Total cross sections for final {ital np} states by impact of protons, alpha particles, and He{sup +} ions are calculated using the symmetric eikonal approximation and compared with experimental data. This comparison supports the existence of distortion effects recently predicted by Bugacov and co-workers [Phys. Rev. A {bold 47}, 1052 (1993)]. The validity of scaling laws is analyzed.

  1. Ion heating during geomagnetic storms measured using energetic neutral atom imaging

    NASA Astrophysics Data System (ADS)

    Keesee, Amy; Elfritz, Justin; Katus, Roxanne; Scime, Earl

    2015-11-01

    Energy from the solar wind is deposited into the magnetosphere during geomagnetic storms. Much of this energy is deposited into the plasma sheet, driving phenomena that leads to heating. The plasma sheet ions are then injected to the inner magnetosphere, driving the ring current. While ions can undergo adiabatic heating during typical drift motion, collisional and wave-particle interactions can also lead to ion heating. A technique to measure ion temperatures using energetic neutral atom (ENA) data has been developed using ENA data from the Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) mission global maps of ion temperature during the evolution of geomagnetic storms are made. These maps exhibit the location and characteristics of regions of ion heating and during which storm phase they occur. Superposed epoch analyses of such maps have demonstrated typical characteristics of ion heating during storms driven by coronal mass ejections as compared to those driven by high speed solar wind streams. The temperatures have been used to establish boundary conditions for modeling of the inner magnetosphere. We will give an overview of recent studies using TWINS ion temperature maps. Work supported by NNX10AN08A and AGS-1113478.

  2. High-precision atomic clocks with highly charged ions: Nuclear-spin-zero f12-shell ions

    NASA Astrophysics Data System (ADS)

    Dzuba, V. A.; Derevianko, A.; Flambaum, V. V.

    2012-11-01

    Optical atomic clocks using highly charged ions hold an intriguing promise of metrology at the 19th significant figure. Here we study transitions within the 4f12 ground-state electronic configuration of highly charged ions. We consider isotopes lacking hyperfine structure and show that the detrimental effects of coupling of electronic quadrupole moments to the gradients of a trapping electric field can be effectively reduced by using specially chosen virtual clock transitions. The estimated systematic fractional clock accuracy is shown to be below 10-19.

  3. Formation of antihydrogen atoms and ions in a strongly magnetized plasma: A molecular dynamics simulation

    SciTech Connect

    Vrinceanu, D.; Hu, S.X.; Mazevet, S.; Collins, L.A.

    2005-10-15

    Formation of antihydrogen atoms in a magnetized plasma of positrons and antiprotons is explicitly demonstrated in a molecular dynamics simulation. The parameters chosen are compatible with the experimental setup. We employ a special, adaptive time step symplectic integrator to perform full dynamics simulation, without using the guiding center approximation, for very long times (of the order of {mu}s). The large number of antihydrogen atoms formed allows detailed statistical analysis and distributions for the binding energy, pseudomomentum, sizes, and other quantities that characterize these atoms. We also find that a significantly smaller number of antihydrogen positive ions form during the free expansion of the plasma.

  4. Hyperfine structure measurement of 87Rb atoms injected into superfluid helium as highly energetic ion beam

    NASA Astrophysics Data System (ADS)

    Imamura, Kei; Furukawa, Takeshi; Yang, Xiaofei; Fujita, Tomomi; Wakui, Takashi; Mitsuya, Yousuke; Hayasaka, Miki; Ichikawa, Yuichi; Hatakeyama, Atsushi; Kobayashi, Tohru; Odashima, Hitoshi; Ueno, Hideki; Matsuo, Yukari; Orochi Collaboration

    2014-09-01

    We have developed a new nuclear laser spectroscopy technique that is called OROCHI (Optical RI-atoms Observation in Condensed Helium as Ioncatcher). In OROCHI, highly energetic ion beam is injected into superfluid helium (He II) and is trapped as atoms. Hyperfine structure (HFS) and Zeeman splitting of trapped atoms is measured using laser-microwave (MW)/radiofrequency (RF) double resonance method. We deduce nuclear moments and spin values from the measured splittings, respectively So far, we measured Zeeman splitting of 84-87Rb atoms To evaluate the validity of the OROCHI method, it is necessary to investigate the following two points not only for Zeeman but also for HFS splitings. (i) What is the accuracy in frequency in our measurement? (ii) How high beam intensity is necessary to observe resonance spectra? For this purpose we conducted online experiment using 87Rb beam and measured the HFS splitting of injected 87Rb atoms in He II.

  5. Role of plasma enhanced atomic layer deposition reactor wall conditions on radical and ion substrate fluxes

    SciTech Connect

    Sowa, Mark J.

    2014-01-15

    Chamber wall conditions, such as wall temperature and film deposits, have long been known to influence plasma source performance on thin film processing equipment. Plasma physical characteristics depend on conductive/insulating properties of chamber walls. Radical fluxes depend on plasma characteristics as well as wall recombination rates, which can be wall material and temperature dependent. Variations in substrate delivery of plasma generated species (radicals, ions, etc.) impact the resulting etch or deposition process resulting in process drift. Plasma enhanced atomic layer deposition is known to depend strongly on substrate radical flux, but film properties can be influenced by other plasma generated phenomena, such as ion bombardment. In this paper, the chamber wall conditions on a plasma enhanced atomic layer deposition process are investigated. The downstream oxygen radical and ion fluxes from an inductively coupled plasma source are indirectly monitored in temperature controlled (25–190 °C) stainless steel and quartz reactors over a range of oxygen flow rates. Etch rates of a photoresist coated quartz crystal microbalance are used to study the oxygen radical flux dependence on reactor characteristics. Plasma density estimates from Langmuir probe ion saturation current measurements are used to study the ion flux dependence on reactor characteristics. Reactor temperature was not found to impact radical and ion fluxes substantially. Radical and ion fluxes were higher for quartz walls compared to stainless steel walls over all oxygen flow rates considered. The radical flux to ion flux ratio is likely to be a critical parameter for the deposition of consistent film properties. Reactor wall material, gas flow rate/pressure, and distance from the plasma source all impact the radical to ion flux ratio. These results indicate maintaining chamber wall conditions will be important for delivering consistent results from plasma enhanced atomic layer deposition

  6. In-situ observation and atomic resolution imaging of the ion irradiation induced amorphisation of graphene

    PubMed Central

    Pan, C.-T.; Hinks, J. A.; Ramasse, Q. M.; Greaves, G.; Bangert, U.; Donnelly, S. E.; Haigh, S. J.

    2014-01-01

    Ion irradiation has been observed to induce a macroscopic flattening and in-plane shrinkage of graphene sheets without a complete loss of crystallinity. Electron diffraction studies performed during simultaneous in-situ ion irradiation have allowed identification of the fluence at which the graphene sheet loses long-range order. This approach has facilitated complementary ex-situ investigations, allowing the first atomic resolution scanning transmission electron microscopy images of ion-irradiation induced graphene defect structures together with quantitative analysis of defect densities using Raman spectroscopy. PMID:25284688

  7. In-situ observation and atomic resolution imaging of the ion irradiation induced amorphisation of graphene.

    PubMed

    Pan, C-T; Hinks, J A; Ramasse, Q M; Greaves, G; Bangert, U; Donnelly, S E; Haigh, S J

    2014-01-01

    Ion irradiation has been observed to induce a macroscopic flattening and in-plane shrinkage of graphene sheets without a complete loss of crystallinity. Electron diffraction studies performed during simultaneous in-situ ion irradiation have allowed identification of the fluence at which the graphene sheet loses long-range order. This approach has facilitated complementary ex-situ investigations, allowing the first atomic resolution scanning transmission electron microscopy images of ion-irradiation induced graphene defect structures together with quantitative analysis of defect densities using Raman spectroscopy. PMID:25284688

  8. Reaction of O/sup +/, CO/sup +/, and CH/sup +/ ions with atomic hydrogen

    SciTech Connect

    Federer, W.; Villinger, H.; Howorka, F.; Lindinger, W.; Tosis, P.; Bassi, D.; Ferguson, E.

    1984-06-04

    Rate coefficients for reactions of the ions O/sup +/, CO/sup +/, and CH/sup +/ with atomic hydrogen have been measured for the first time at 300 K. This provides basic data for the ion chemistry of planetary atmospheres, cometary atmospheres, and interstellar molecular clouds. The O/sup +/+H measurement supports quantal calculations of this reaction. The CO/sup +/+H reaction provides an example of partial spin nonconservation in a charge-transfer reaction occurring in a deep potential well. Reactions of the same ions with H/sub 2/ that have been measured elsewhere are also reported.

  9. Charge transfer reactions in multiply charged ion-atom collisions. [in interstellar clouds

    NASA Technical Reports Server (NTRS)

    Steigman, G.

    1975-01-01

    Charge-transfer reactions in collisions between highly charged ions and neutral atoms of hydrogen and/or helium may be rapid at thermal energies. If these reactions are rapid, they will suppress highly charged ions in H I regions and guarantee that the observed absorption features from such ions cannot originate in the interstellar gas. A discussion of such charge-transfer reactions is presented and compared with the available experimental data. The possible implications of these reactions for observations of the interstellar medium, H II regions, and planetary nebulae are outlined.

  10. Tracing the atomic mass unit to the kilogram by ion accumulation

    NASA Astrophysics Data System (ADS)

    Gläser, Michael

    2003-12-01

    An experimental approach for linking the atomic mass unit to the kilogram with an uncertainty sufficiently small for a future re-definition of the kilogram is described. The concept consists of accumulation of ions from an ion beam up to a weighable mass and measurable total charge. The main problems and influencing factors connected with ion beam technology, weighing and current measurement together with the corresponding experimental solutions are discussed in detail. The first experiments with consistent results, but still large uncertainty, are described.

  11. Atom probe field ion microscopy and related topics: A bibliography 1990

    SciTech Connect

    Russell, K.F.; Miller, M.K.

    1991-12-01

    This bibliography includes references related to the following topics: atom probe field ion microscopy (APFIM), field ion microscopy (FIM), field emission (FE), ion sources, and field desorption mass microscopy (FDMM). Technique-orientated studies and applications are included. The bibliography covers the period 1990. The references contained in this document were compiled from a variety of sources including computer searches and personal lists of publications. To reduce the length of this document, the references have been reduced to the minimum necessary to locate the articles. The references, listed alphabetically by authors, are subdivided into the categories listed in paragraph one above. An Addendum of references missed in previous bibliographies is included.

  12. An ion cyclotron resonance study of reactions of some atomic and simple polyatomic ions with water

    NASA Technical Reports Server (NTRS)

    Karpas, Z.; Anicich, V. G.; Huntress, W. T., Jr.

    1978-01-01

    Reactions of various positive ions with water vapor were studied by ion cyclotron resonance mass spectrometric techniques. Rate constants and product distributions were determined for reactions of the ions: Ar(+), Co(+), N2(+), and CO2(+), CH2(+), and CH4(+), CH2Cl(+), HCO(+), H2CO(+), H2COH(+), H2S(+) and HS(+). The results obtained in this work are compared with earlier reported data where available.

  13. New recycling model for light ions and atoms

    SciTech Connect

    Singer, C.E.; Mann, K.; Rauh, K.; Heifetz, D.

    1985-01-01

    Recent theoretical studies and experimental results suggest a revision of light-ion reflection models used in simulation codes. Surface impenetrability leads to large reflection coefficients for hydrogen isotopes incident below 5 to 20 eV. Adsorption below 5 to 10 eV also depends on saturation of the surfaces. An effective surface roughness is included for all energy regimes. The fraction of nonreflected particles reemitted as molecules depends on the previous exposure of the surface and the incident flux. Simple models of these processes are collected in a form usable in neutral transport codes. The relevance of such models to tokamak design and of interpreting divertor tokamak data is discussed and illustrated by numerical computation.

  14. Solar Wind Charge Exchange Studies Of Highly Charged Ions On Atomic Hydrogen

    SciTech Connect

    Draganic, I. N.; Havener, C. C.; Seely, D. G.; McCammon, D.

    2011-06-01

    Accurate studies of low-energy charge exchange (CX) are critical to understanding underlying soft X-ray radiation processes in the interaction of highly charged ions from the solar wind with the neutral atoms and molecules in the heliosphere, cometary comas, planetary atmospheres, interstellar winds, etc.. Particularly important are the CX cross sections for bare, H-like, and He-like ions of C, N, O and Ne, which are the dominant charge states for these heavier elements in the solar wind. Absolute total cross sections for single electron capture by H-like ions of C, N, O and fully-stripped O ions from atomic hydrogen have been measured in an expanded range of relative collision energies (5 eV/u-20 keV/u) and compared to previous H-oven measurements. The present measurements are performed using a merged-beams technique with intense highly charged ion beams extracted from a 14.5 GHz ECR ion source installed on a high voltage platform at the Oak Ridge National Laboratory. For the collision energy range of 0.3 keV/u-3.3 keV/u, which corresponds to typical ion velocities in the solar wind, the new measurements are in good agreement with previous H-oven measurements. The experimental results are discussed in detail and compared with theoretical calculations where available.

  15. Solar Wind Charge Exchange Studies of Highly Charged Ions on Atomic Hydrogen

    SciTech Connect

    Draganic, Ilija N; Seely, D. G.; McCammon, D; Havener, Charles C

    2011-01-01

    Accurate studies of low energy charge exchange (CX) are critical to understanding underlying soft X ray radiation processes in the interaction of highly charged ions from the solar wind with the neutral atoms and molecules in the heliosphere, cometary comas, planetary atmospheres, interstellar winds, etc.. Particularly important are the CX cross sections for bare, H like, and He like ions of C, N, O and Ne, which are the dominant charge states for these heavier elements in the solar wind. Absolute total cross sections for single electron capture by H like ions of C, N, O and fully stripped O ions from atomic hydrogen have been measured in an expanded range of relative collision energies (5 eV u 20 keV u) and compared to previous H oven measurements. The present measurements are performed using a merged beams technique with intense highly charged ion beams extracted from a 14.5 GHz ECR ion source installed on a high voltage platform at the Oak Ridge National Laboratory. For the collision energy range of 0.3 keV u 3.3 keV u, which corresponds to typical ion velocities in the solar wind, the new measurements are in good agreement with previous H oven measurements. The experimental results are discussed in detail and compared with theoretical calculations where available.

  16. Atomic physics with highly charged ions. Progress report, FY 1989--91

    SciTech Connect

    Richard, P.

    1991-08-01

    This report discusses: One electron outer shell processes in fast ion-atom collisions; role of electron-electron interaction in two-electron processes; multi-electron processes at low energy; multi-electron processes at high energy; inner shell processes; molecular fragmentation studies; theory; and, JRM laboratory operations.

  17. Preface: Photon and fast Ion induced Processes in Atoms, MOlecules and Nanostructures (PIPAMON)

    NASA Astrophysics Data System (ADS)

    Kövér, László

    2016-02-01

    This Special Issue contains selected papers of contributions presented in the International Workshop on Photon and fast Ion induced Processes in Atoms, MOlecules and Nanostructures (PIPAMON), held between March 24 and 26, 2015 in Debrecen, Hungary. The venue, the Aquaticum Thermal and Wellness Hotel provided a pleasant "all-under-one-roof" environment for the event.

  18. Relativistic Quantum Chemistry of Heavy Ions and Hadronic Atomic Systems: Spectra and Energy Shifts

    SciTech Connect

    Glushkov, A. V.; Khetselius, O.; Gurnitskaya, E.; Loboda, A.; Sukharev, D.

    2009-03-09

    The levels energies and energy shifts are calculated for superheavy Li-like ions and some kaonic atoms on the basis of the gauge-invariant QED perturbation theory (PT) with an account of nuclear, exchange-correlation and radiative effects.

  19. Field Ion Microscopy and Atom Probe Tomography of Metamorphic Magnetite Crystals

    NASA Technical Reports Server (NTRS)

    Kuhlman, K.; Martens, R. L.; Kelly, T. F.; Evans, N. D.; Miller, M. K.

    2001-01-01

    Magnetite has been analysed using Field Ion Microscopy (FIM) and Atom Probe Tomography (APT), highly attractive techniques for the nanoanalysis of geological materials despite the difficulties inherent in analyzing semiconducting and insulating materials. Additional information is contained in the original extended abstract.

  20. Interaction of 3d transition metal atoms with charged ion projectiles from Electron Nuclear Dynamics computation

    NASA Astrophysics Data System (ADS)

    Hagelberg, Frank

    2003-03-01

    Computational results on atomic scattering between charged projectiles and transition metal target atoms are presented. This work aims at obtaining detailed information about charge, spin and energy transfer processes that occur between the interacting particles. An in-depth understanding of these phenomena is expected to provide a theoretical basis for the interpretation of various types of ion beam experiments, ranging from gas phase chromatography to spectroscopic observations of fast ions in ferromagnetic media. This contribution focuses on the scattering of light projectiles ranging from He to O, that are prepared in various initial charge states, by 3d transition metal atoms. The presented computations are performed in the framework of Electron Nuclear Dynamics (END)^1 theory which incorporates the coupling between electronic and nuclear degrees of freedom without reliance on the computationally cumbersome and frequently intractable determination of potential energy surfaces. In the present application of END theory to ion - transition metal atom scattering, a supermolecule approach is utilized in conjunction with a spin-unrestricted single determinantal wave function describing the electronic system. Integral scattering, charge and spin exchange cross sections are discussed as functions of the elementary parameters of the problem, such as projectile and target atomic numbers as well as projectile charge and initial kinetic energy. ^1 E.Deumens, A.Diz, R.Longo, Y.Oehrn, Rev.Mod.Phys. 66, 917 (1994)

  1. In-Situ atomic force microscopic observation of ion beam bombarded plant cell envelopes

    NASA Astrophysics Data System (ADS)

    Sangyuenyongpipat, S.; Yu, L. D.; Brown, I. G.; Seprom, C.; Vilaithong, T.

    2007-04-01

    A program in ion beam bioengineering has been established at Chiang Mai University (CMU), Thailand, and ion beam induced transfer of plasmid DNA molecules into bacterial cells (Escherichia coli) has been demonstrated. However, a good understanding of the fundamental physical processes involved is lacking. In parallel work, onion skin cells have been bombarded with Ar+ ions at energy 25 keV and fluence1-2 × 1015 ions/cm2, revealing the formation of microcrater-like structures on the cell wall that could serve as channels for the transfer of large macromolecules into the cell interior. An in-situ atomic force microscope (AFM) system has been designed and installed in the CMU bio-implantation facility as a tool for the observation of these microcraters during ion beam bombardment. Here we describe some of the features of the in-situ AFM and outline some of the related work.

  2. Quantum analysis of atom-ion sympathetic cooling in the presence of micromotion

    NASA Astrophysics Data System (ADS)

    Krych, Michal; Idziaszek, Zbigniew

    2014-05-01

    We investigate the problem of a single ion in a radio-frequency trap and immersed in an ultracold Bose gas either in condensed or non-condensed phase. We develop master equation formalism describing the sympathetic cooling and we determine the cooling rates and final energies of ions. We show that cold atomic reservoir modifies the stability diagram of the ion in the Paul trap creating the regions where the ion is either cooled or heated due to the energy quanta exchanged with the time-dependent potential. Our calculation indicates that micromotion constitutes an important source of heating limiting the final temperature of ions to values higher than 100 μK for parameters of present experiments.

  3. Single electron capture in fast ion-atom collisions

    NASA Astrophysics Data System (ADS)

    Milojević, Nenad

    2014-12-01

    Single-electron capture cross sections in collisions between fast bare projectiles and heliumlike atomic systems are investigated by means of the four-body boundary-corrected first Born (CB1-4B) approximation. The prior and post transition amplitudes for single charge exchange encompassing symmetric and asymmetric collisions are derived in terms of twodimensional real integrals in the case of the prior form and five-dimensional quadratures for the post form. The dielectronic interaction V12 = 1/r12 = 1/|r1 - r2| explicitly appears in the complete perturbation potential Vf of the post transition probability amplitude T+if. An illustrative computation is performed involving state-selective and total single capture cross sections for the p - He (prior and post form) and He2+, Li3+Be4+B5+C6+ - He (prior form) collisions at intermediate and high impact energies. We have also studied differential cross sections in prior and post form for single electron transfer from helium by protons. The role of dynamic correlations is examined as a function of increased projectile energy. Detailed comparisons with the measurements are carried out and the obtained theoretical cross sections are in reasonable agreement with the available experimental data.

  4. Application of Ion and Electron Momentum Imaging to Atomic Collisions

    NASA Astrophysics Data System (ADS)

    Cocke, C. L.

    2000-06-01

    COLTRIMS (COLd Target Recoil Ion Momentum Spectroscopy) combines fast imaging detectors with a supersonically cooled gas target to allow the charged particles from any ionizing collision, including both recoil ions and electrons, to be collected with extremely high efficiency and with fully measured vector momenta. Since all particles are measured in event mode, the full multi-dimensional momentum space is mapped. We will review several examples of the use of this technique to study two- , three- and four-body final states created in ionizing interactions of photons and charged particles with He and D2 . The momentum spectra of electrons ejected from these targets by slow projectiles reveal the stucture of the molecular orbitals which are promoted into the continuum. Double photoionization of the same targets reveals patterns which can be interpreted in terms of collective coordinates. Two-electron removal from D2 by Xe ^26+ reveals the influence of the projectile field on the dissociation process. A recent application of the technique to ionization by high intensity laser fields will be discussed. Work performed in collaboration with M.A.Abdallah^1, I.Ali^1, Matthias Achler^2, H.Braeuning^2,3, Angela Braeuning-Deminian^2, Achim Czasch^2,3, R.Doerner^2,3, R.DuBois^6, A. Landers^1,5, V.Mergel^2, R.E.Olson^6, T.Osipov^1, M.Prior^3, H.Schmidt-Boecking^2, M.Singh^1, A.Staudte^2,3, T.Weber^2, W.Wolff^4, and H.E.Wolf^4 ^1J.R.Macdonald Laboratory, Physics Department, Kansas State University, Manhattan, KS 66506; ^2 Institut fuer Kernphysik, Univ. Frankfurt, August-Euler-Str.6,D-60486 Frankfurt, Germany ; ^3Lawrence Berkeley National Laboratory, Berkeley, CA 94720; ^4Instituto de Fisica, Universidade Federal do Rio de Janeiro Caixa Postal 68.528, 21945-970, Rio de Janeiro, Brazil; ^5Physics Dept., Western Michigan University, Kalamazoo, MI 49008; ^6Physics Dept., Univ. Missouri Rolla, Rolla, MO 65409 Work supported by the Division of Chemical Sciences, Office of Basic

  5. Effects of anisotropic electron-ion interactions in atomic photoelectron angular distributions

    NASA Technical Reports Server (NTRS)

    Dill, D.; Starace, A. F.; Manson, S. T.

    1974-01-01

    The photoelectron asymmetry parameter beta in LS-coupling is obtained as an expansion into contributions from alternative angular momentum transfers j sub t. The physical significance of this expansion of beta is shown to be that: (1) the electric dipole interaction transfers to the atom a charcteristic single angular momentum j sub t = sub o, where sub o is the photoelectron's initial orbital momentum; and (2) angular momentum transfers indicate the presence of anisotropic interaction of the outgoing photoelectron with the residual ion. For open shell atoms the photoelectron-ion interaction is generally anisotropic; photoelectron phase shifts and electric dipole matrix elements depend on both the multiplet term of the residual ion and the total orbital momentum of the ion-photoelectron final state channel. Consequently beta depends on the term levels of the residual ion and contains contributions from all allowed values of j sub t. Numerical calculations of the asymmetry parameters and partial cross sections for photoionization of atomic sulfur are presented.

  6. Correlated charge-changing ion-atom collisions. Progress report, March 16, 1991--March 15, 1992

    SciTech Connect

    Tanis, J.A.

    1992-04-01

    This report summarizes the progress and accomplishments in accelerator atomic physics research supported by DOE grant DE-FG02-87ER13778 from March 16, 1991 through March 15, 1992. This work involves the experimental investigation of fundamental atomic processes in collisions of charged projectiles with neutral targets or electrons, with particular emphasis on two-electron interactions and electron correlation effects. Processes involving combinations of excitation, ionization, and charge transfer are investigated utilizing coincidence techniques in which projectiles charge-changing events are associated with x-ray emission, target recoil ions, or electron emission. New results have been obtained for studies involving (1) resonant recombination of atomic ions, (2) double ionization of helium, and (3) continuum electron emission. Experiments were conducted using accelerators at the Lawrence Berkeley Laboratory, Argonne National Laboratory, Michigan State University, Western Michigan University, and the Institute of Nuclear Research, Debrecen, Hungary. Brief summaries of work completed and work in progress are given in this report.

  7. An investigation of polarized atomic photofragments using the ion imaging technique

    SciTech Connect

    Bracker, A.S.

    1997-12-01

    This thesis describes measurement and analysis of the recoil angle dependence of atomic photofragment polarization (atomic v-J correlation). This property provides information on the electronic rearrangement which occurs during molecular photodissociation. Chapter 1 introduces concepts of photofragment vector correlations and reviews experimental and theoretical progress in this area. Chapter 2 described the photofragment ion imaging technique, which the author has used to study the atomic v-J correlation in chlorine and ozone dissociation. Chapter 3 outlines a method for isolating and describing the contribution to the image signal which is due exclusively to angular momentum alignment. Ion imaging results are presented and discussed in Chapter 4. Chapter 5 discusses a different set of experiments on the three-fragment dissociation of azomethane. 122 refs.

  8. An independent-atom-model description of ion-molecule collisions including geometric screening corrections

    NASA Astrophysics Data System (ADS)

    Lüdde, Hans Jürgen; Achenbach, Alexander; Kalkbrenner, Thilo; Jankowiak, Hans-Christian; Kirchner, Tom

    2016-04-01

    A new model to account for geometric screening corrections in an independent-atom-model description of ion-molecule collisions is introduced. The ion-molecule cross sections for net capture and net ionization are represented as weighted sums of atomic cross sections with weight factors that are determined from a geometric model of overlapping cross section areas. Results are presented for proton collisions with targets ranging from diatomic to complex polyatomic molecules. Significant improvement compared to simple additivity rule results and in general good agreement with experimental data are found. The flexibility of the approach opens up the possibility to study more detailed observables such as orientation-dependent and charge-state-correlated cross sections for a large class of complex targets ranging from biomolecules to atomic clusters.

  9. Surpassing the mass restriction of buffer gas cooling: Cooling of low mass ions by localized heavier atoms

    NASA Astrophysics Data System (ADS)

    Dutta, Sourav; Sawant, Rahul; Rangwala, S. A.

    2016-05-01

    Cooling of trapped ions has resulted in fascinating science including the realization of some of the most accurate atomic clocks. It has also found widespread application, for example, in mass spectrometry and cold chemistry. Among the different methods for cooling ions, cooling by elastic collisions with ultracold neutral atoms is arguably the most generic. However, in spite of its widespread application, there is confusion with regards the collisional heating/cooling of light ions by heavier neutral atoms. We address the question experimentally and demonstrate, for the first time, cooling of light ions by co-trapped heavy atoms. We show that trapped 39 K+ ions are cooled by localized ultracold neutral 85 Rb atoms. The atom-ion mass ratio (= 2.18) is well beyond any theoretical predictions so far. We further argue that cooling of ions by localized cold atoms is possible for any mass ratio. The result opens up the possibility of reaching the elusive s-wave collision regime in atom-ion collisions. S.D. is supported by DST-INSPIRE Faculty Fellowship, India.

  10. Test particle comparison of heavy atomic and molecular ion distributions at Mars

    NASA Astrophysics Data System (ADS)

    Curry, S. M.; Liemohn, M.; Fang, X.; Ma, Y.; Slavin, J.; Espley, J.; Bougher, S.; Dong, C. F.

    2014-03-01

    This study uses the Mars Test Particle simulation to create virtual detections of O+, O2+, and CO2+ in an orbital configuration in the Mars space environment. These atomic and molecular planetary pickup ions are formed when the solar wind directly interacts with the neutral atmosphere, causing the ions to be accelerated by the background convective electric field. The subsequent ion escape is the subject of great interest, specifically with respect to which species dominates ion loss from Mars. O+ is found to be the dominant escaping ion because of the large sources of transported ions in the low-energy (<10 eV) and high-energy (>1 keV) range. O2+ and CO2+ are observed at these energy ranges but with much lower fluxes and are generally only found in the tail between 10 eV and 1 keV. Using individual particle traces, we reveal the origin and trajectories of the low-energy downtail O+ populations and high-energy polar O+ populations that contribute to the total escape. Comparing them against O2+ and CO2+ reveals that the extended hot oxygen corona contributes to source regions of high- and low-energy escaping ions. Additionally, we present results for solar minimum and maximum conditions with respect to ion fluxes and energies in order to robustly describe the physical processes controlling planetary ion distributions and atmospheric escape.

  11. Formation of nanostructures on HOPG surface in presence of surfactant atom during low energy ion irradiation

    NASA Astrophysics Data System (ADS)

    Ranjan, M.; Joshi, P.; Mukherjee, S.

    2016-07-01

    Low energy ions beam often develop periodic patterns on surfaces under normal or off-normal incidence. Formation of such periodic patterns depends on the substrate material, the ion beam parameters, and the processing conditions. Processing conditions introduce unwanted contaminant atoms, which also play strong role in pattern formation by changing the effective sputtering yield of the material. In this work we have analysed the effect of Cu, Fe and Al impurities introduced during low energy Ar+ ion irradiation on HOPG substrate. It is observed that by changing the species of foreign atoms the surface topography changes drastically. The observed surface topography is co-related with the modified sputtering yield of HOPG. Presence of Cu and Fe amplify the effective sputtering yield of HOPG, so that the required threshold for the pattern formation is achieved with the given fluence, whereas Al does not lead to any significant change in the effective yield and hence no pattern formation occurs.

  12. Coupling all-atom molecular dynamics simulations of ions in water with Brownian dynamics

    PubMed Central

    2016-01-01

    Molecular dynamics (MD) simulations of ions (K+, Na+, Ca2+ and Cl−) in aqueous solutions are investigated. Water is described using the SPC/E model. A stochastic coarse-grained description for ion behaviour is presented and parametrized using MD simulations. It is given as a system of coupled stochastic and ordinary differential equations, describing the ion position, velocity and acceleration. The stochastic coarse-grained model provides an intermediate description between all-atom MD simulations and Brownian dynamics (BD) models. It is used to develop a multiscale method which uses all-atom MD simulations in parts of the computational domain and (less detailed) BD simulations in the remainder of the domain. PMID:27118886

  13. Kinetic theory and atomic physics corrections for determination of ion velocities from charge-exchange spectroscopy

    NASA Astrophysics Data System (ADS)

    Muñoz Burgos, J. M.; Burrell, K. H.; Solomon, W. M.; Grierson, B. A.; Loch, S. D.; Ballance, C. P.; Chrystal, C.

    2013-09-01

    Charge-exchange spectroscopy is a powerful diagnostic tool for determining ion temperatures, densities and rotational velocities in tokamak plasmas. This technique depends on detailed understanding of the atomic physics processes that affect the measured apparent velocities with respect to the true ion rotational velocities. These atomic effects are mainly due to energy dependence of the charge-exchange cross-sections, and in the case of poloidal velocities, due to gyro-motion of the ion during the finite lifetime of the excited states. Accurate lifetimes are necessary for correct interpretation of measured poloidal velocities, specially for high density plasma regimes on machines such as ITER, where l-mixing effects must be taken into account. In this work, a full nl-resolved atomic collisional radiative model coupled with a full kinetic calculation that includes the effects of electric and magnetic fields on the ion gyro-motion is presented for the first time. The model directly calculates from atomic physics first principles the excited state lifetimes that are necessary to evaluate the gyro-orbit effects. It is shown that even for low density plasmas where l-mixing effects are unimportant and coronal conditions can be assumed, the nl-resolved model is necessary for an accurate description of the gyro-motion effects to determine poloidal velocities. This solution shows good agreement when compared to three QH-mode shots on DIII-D, which contain a wide range of toroidal velocities and high ion temperatures where greater atomic corrections are needed. The velocities obtained from the model are compared to experimental velocities determined from co- and counter-injection of neutral beams on DIII-D.

  14. Visualization of steps and surface reconstructions in Helium Ion Microscopy with atomic precision.

    PubMed

    Hlawacek, Gregor; Jankowski, Maciej; Wormeester, Herbert; van Gastel, Raoul; Zandvliet, Harold J W; Poelsema, Bene

    2016-03-01

    Helium Ion Microscopy is known for its surface sensitivity and high lateral resolution. Here, we present results of a Helium Ion Microscopy based investigation of a surface confined alloy of Ag on Pt(111). Based on a change of the work function of 25meV across the atomically flat terraces we can distinguish Pt rich from Pt poor areas and visualize the single atomic layer high steps between the terraces. Furthermore, dechanneling contrast has been utilized to measure the periodicity of the hcp/fcc pattern formed in the 2-3 layers thick Ag/Pt alloy film. A periodicity of 6.65nm along the ⟨112⟩ surface direction has been measured. In terms of crystallography a hcp domain is obtained through a lateral displacement of a part of the outermost layer by 1/√3 of a nearest neighbor spacing along ⟨112⟩. This periodicity is measured with atomic precision: coincidence between the Ag and the Pt lattices is observed for 23 Ag atoms on 24 Pt atoms. The findings are perfectly in line with results obtained with Low Energy Electron Microscopy and Phase Contrast Atomic Force Microscopy. PMID:26720438

  15. Spectr-W3 online database on atomic properties of multicharged ions

    NASA Astrophysics Data System (ADS)

    Skobelev, I. Yu; Loboda, P. A.; Faenov, A. Ya; Gagarin, S. V.; Kozlov, A. I.; Morozov, S. V.; Pikuz, S. A.; Pikuz, T. A.; Popova, V. V.

    2015-11-01

    The Spectr-W3 information-reference system was developed in 2001-2013 and realized as an online Web resource based on the factual atomic database Spectr-W3. The information accumulated in the Spectr-W3 atomic database contains about 450,000 records and includes the experimental and theoretical data on ionization potentials, energy levels, wavelengths, radiation transition probabilities, and oscillator strengths, and the parameters of analytical approximations of electron-collisional cross-sections and rates for atoms and ions. Those data were extracted from publications in physical journals, proceedings of the related conferences, special-purpose publications on atomic data, provided directly by authors. The information is supplied with references to the original sources and comments, elucidating the details of experimental measurements or calculations. To date, the Spectr-W3 atomic database is still the largest factual database in the world, containing the information on spectral properties of multicharged ions. In 2014, the new stage in the development of the Spectr-W3 atomic database started. The purpose of this stage is the creation of a new information section of the Spectr-W3 database. This section would contain the information on the x-ray emission spectrograms registered from various plasma sources.

  16. Charge steering of laser plasma accelerated fast ions in a liquid spray — creation of MeV negative ion and neutral atom beams

    SciTech Connect

    Schnürer, M.; Abicht, F.; Priebe, G.; Braenzel, J.; Prasad, R.; Borghesi, M.; Andreev, A.; Nickles, P. V.; Jequier, S.; Tikhonchuk, V.; Ter-Avetisyan, S.

    2013-11-15

    The scenario of “electron capture and loss” has been recently proposed for the formation of negative ion and neutral atom beams with up to MeV kinetic energy [S. Ter-Avetisyan, et al., Appl. Phys. Lett. 99, 051501 (2011)]. Validation of these processes and of their generic nature is here provided in experiments where the ion source and the interaction medium have been spatially separated. Fast positive ions accelerated from a laser plasma source are sent through a cold spray where their charge is changed. Such formed neutral atom or negative ion has nearly the same momentum as the original positive ion. Experiments are released for protons, carbon, and oxygen ions and corresponding beams of negative ions and neutral atoms have been obtained. The electron capture and loss phenomenon is confirmed to be the origin of the negative ion and neutral atom beams. The equilibrium ratios of different charge components and cross sections have been measured. Our method is general and allows the creation of beams of neutral atoms and negative ions for different species which inherit the characteristics of the positive ion source.

  17. Ion Flux Measurements in Electron Beam Produced Plasmas in Atomic and Molecular Gases

    NASA Astrophysics Data System (ADS)

    Walton, S. G.; Leonhardt, D.; Blackwell, D. D.; Murphy, D. P.; Fernsler, R. F.; Meger, R. A.

    2001-10-01

    In this presentation, mass- and time-resolved measurements of ion fluxes sampled from pulsed, electron beam-generated plasmas will be discussed. Previous works have shown that energetic electron beams are efficient at producing high-density plasmas (10^10-10^12 cm-3) with low electron temperatures (Te < 1.0 eV) over the volume of the beam. Outside the beam, the plasma density and electron temperature vary due, in part, to ion-neutral and electron-ion interactions. In molecular gases, electron-ion recombination plays a significant role while in atomic gases, ion-neutral interactions are important. These interactions also determine the temporal variations in the electron temperature and plasma density when the electron beam is pulsed. Temporally resolved ion flux and energy distributions at a grounded electrode surface located adjacent to pulsed plasmas in pure Ar, N_2, O_2, and their mixtures are discussed. Measurements are presented as a function of operating pressure, mixture ratio, and electron beam-electrode separation. The differences in the results for atomic and molecular gases will also be discussed and related to their respective gas-phase kinetics.

  18. Atomic physics and synchrotron radiation: The production and accumulation of highly charged ions

    NASA Astrophysics Data System (ADS)

    Johnson, B. M.; Meron, M.; Agagu, A.; Jones, K. W.

    1987-04-01

    Synchrotron radiation can be used to produce highly-charged ions, and to study photoexcitation and photoionization for ions of virtually any element in the periodic table. To date, with few exceptions, atomic physics studies have been limited to rare gases and a few metal vapors, and to photoexcitation energies in the VUV region of the electromagnetic spectrum. These limitations can now be overcome using photons produced by high-brightness synchrotron storage rings, such as the X-ray ring at the National Synchrotron Light Source (NSLS) at Brookhaven. Furthermore, calculations indicate that irradiation of an ion trap with an intense energetic photon beam will result in a viable source of highly-charged ions that can be given the name PHOBIS: the photon beam ion source. Promising results, which encourage the wider systematic use of synchrotron radiation in atomic physics research, have been obtained in recent experiments on VUV photoemission and the production and storage of multiply-charged ions. An overview of the field, current plans, and future possibilities will be presented.

  19. Bright focused ion beam sources based on laser-cooled atoms

    PubMed Central

    McClelland, J. J.; Steele, A. V.; Knuffman, B.; Twedt, K. A.; Schwarzkopf, A.; Wilson, T. M.

    2016-01-01

    Nanoscale focused ion beams (FIBs) represent one of the most useful tools in nanotechnology, enabling nanofabrication via milling and gas-assisted deposition, microscopy and microanalysis, and selective, spatially resolved doping of materials. Recently, a new type of FIB source has emerged, which uses ionization of laser cooled neutral atoms to produce the ion beam. The extremely cold temperatures attainable with laser cooling (in the range of 100 μK or below) result in a beam of ions with a very small transverse velocity distribution. This corresponds to a source with extremely high brightness that rivals or may even exceed the brightness of the industry standard Ga+ liquid metal ion source. In this review we discuss the context of ion beam technology in which these new ion sources can play a role, their principles of operation, and some examples of recent demonstrations. The field is relatively new, so only a few applications have been demonstrated, most notably low energy ion microscopy with Li ions. Nevertheless, a number of promising new approaches have been proposed and/or demonstrated, suggesting that a rapid evolution of this type of source is likely in the near future. PMID:27239245

  20. Bright focused ion beam sources based on laser-cooled atoms

    NASA Astrophysics Data System (ADS)

    McClelland, J. J.; Steele, A. V.; Knuffman, B.; Twedt, K. A.; Schwarzkopf, A.; Wilson, T. M.

    2016-03-01

    Nanoscale focused ion beams (FIBs) represent one of the most useful tools in nanotechnology, enabling nanofabrication via milling and gas-assisted deposition, microscopy and microanalysis, and selective, spatially resolved doping of materials. Recently, a new type of FIB source has emerged, which uses ionization of laser cooled neutral atoms to produce the ion beam. The extremely cold temperatures attainable with laser cooling (in the range of 100 μK or below) result in a beam of ions with a very small transverse velocity distribution. This corresponds to a source with extremely high brightness that rivals or may even exceed the brightness of the industry standard Ga+ liquid metal ion source. In this review, we discuss the context of ion beam technology in which these new ion sources can play a role, their principles of operation, and some examples of recent demonstrations. The field is relatively new, so only a few applications have been demonstrated, most notably low energy ion microscopy with Li ions. Nevertheless, a number of promising new approaches have been proposed and/or demonstrated, suggesting that a rapid evolution of this type of source is likely in the near future.

  1. Correlated charge-changing ion-atom collisions. Progress report, February 16, 1990--February 15, 1993

    SciTech Connect

    Tanis, J.A.

    1993-02-01

    This report summarizes the progress and accomplishments in accelerator atomic physics research supported by DOE grant DE-FG02-87ER13778 from February 16, 1990 through February 15, 1993. This work involves the experimental investigation of atomic interactions in collisions of charged projectiles with neutral targets or electrons, with particular emphasis on two-electron interactions and electron-correlation effects. The processes studied are of interest both from fundamental and applied points of view. In the latter case, results are obtained which are relevant to the understanding of laboratory and astrophysical plasmas, highly-excited (Rydberg) and continuum states of atoms and ions, atomic structure effects, the interaction of ions with surfaces, and the development of heavy-ion storage-rings. The results obtained have provided the basis for several M.A. thesis projects at Western Michigan and several Ph.D. dissertation projects are currently underway. Summaries of work completed and work in progress are given below in Section II. This research has resulted in 26 papers (in print and in press), 12 invited presentations at national and international meetings, and 28 contributed presentations as detailed in Section III.

  2. High-coherence electron and ion bunches from laser-cooled atoms.

    PubMed

    Sparkes, Ben M; Thompson, Daniel J; McCulloch, Andrew J; Murphy, Dene; Speirs, Rory W; Torrance, Joshua S J; Scholten, Robert E

    2014-08-01

    Cold atom electron and ion sources produce electron bunches and ion beams by photoionization of laser-cooled atoms. They offer high coherence and the potential for high brightness, with applications including ultra-fast electron-diffractive imaging of dynamic processes at the nanoscale. The effective brightness of electron sources has been limited by nonlinear divergence caused by repulsive interactions between the electrons, known as the Coulomb explosion. It has been shown that electron bunches with ellipsoidal shape and uniform density distribution have linear internal Coulomb fields, such that the Coulomb explosion can be reversed using conventional optics. Our source can create bunches shaped in three dimensions and hence in principle achieve the transverse spatial coherence and brightness needed for picosecond-diffractive imaging with nanometer resolution. Here we present results showing how the shaping capability can be used to measure the spatial coherence properties of the cold electron source. We also investigate space-charge effects with ions and generate electron bunches with durations of a few hundred picoseconds. Future development of the cold atom electron and ion source will increase the bunch charge and charge density, demonstrate reversal of Coulomb explosion, and ultimately, ultra-fast coherent electron-diffractive imaging.

  3. A (201)Hg+ Comagnetometer for (199)Hg+ Trapped Ion Space Atomic Clocks

    NASA Technical Reports Server (NTRS)

    Burt, Eric A.; Taghavi, Shervin; Tjoelker, Robert L.

    2011-01-01

    A method has been developed for unambiguously measuring the exact magnetic field experienced by trapped mercury ions contained within an atomic clock intended for space applications. In general, atomic clocks are insensitive to external perturbations that would change the frequency at which the clocks operate. On a space platform, these perturbative effects can be much larger than they would be on the ground, especially in dealing with the magnetic field environment. The solution is to use a different isotope of mercury held within the same trap as the clock isotope. The magnetic field can be very accurately measured with a magnetic-field-sensitive atomic transition in the added isotope. Further, this measurement can be made simultaneously with normal clock operation, thereby not degrading clock performance. Instead of using a conventional magnetometer to measure ambient fields, which would necessarily be placed some distance away from the clock atoms, first order field-sensitive atomic transition frequency changes in the atoms themselves determine the variations in the magnetic field. As a result, all ambiguity over the exact field value experienced by the atoms is removed. Atoms used in atomic clocks always have an atomic transition (often referred to as the clock transition) that is sensitive to magnetic fields only in second order, and usually have one or more transitions that are first-order field sensitive. For operating parameters used in the (199)Hg(+) clock, the latter can be five orders of magnitude or more sensitive to field fluctuations than the clock transition, thereby providing an unambiguous probe of the magnetic field strength.

  4. Atomic layer deposition of HfO2 on graphene through controlled ion beam treatment

    NASA Astrophysics Data System (ADS)

    Kim, Ki Seok; Oh, Il-Kwon; Jung, Hanearl; Kim, Hyungjun; Yeom, Geun Young; Kim, Kyong Nam

    2016-05-01

    The polymer residue generated during the graphene transfer process to the substrate tends to cause problems (e.g., a decrease in electron mobility, unwanted doping, and non-uniform deposition of the dielectric material). In this study, by using a controllable low-energy Ar+ ion beam, we cleaned the polymer residue without damaging the graphene network. HfO2 grown by atomic layer deposition on graphene cleaned using an Ar+ ion beam showed a dense uniform structure, whereas that grown on the transferred graphene (before Ar+ ion cleaning) showed a non-uniform structure. A graphene-HfO2-metal capacitor fabricated by growing 20-nm thick HfO2 on graphene exhibited a very low leakage current (<10-11 A/cm2) for Ar+ ion-cleaned graphene, whereas a similar capacitor grown using the transferred graphene showed high leakage current.

  5. Loss of wave-packet coherence in ion-atom collisions

    NASA Astrophysics Data System (ADS)

    Sarkadi, L.; Fabre, I.; Navarrete, F.; Barrachina, R. O.

    2016-03-01

    The projectile beam coherence effects occurring in ion-atom collisions are analyzed on the basis of the recent theory of Karlovets et al. [Phys. Rev. A 92, 052703 (2015), 10.1103/PhysRevA.92.052703] developed for the elastic scattering of wave packets of particles off a potential field. This theory is generalized to estimate the loss of coherence for inelastically scattered projectiles in ionizing collisions. The results obtained by the suggested model are compared with experimental data for the ionization of hydrogen atoms and molecules by 75-keV proton impact. Significantly improved agreement is observed between the theory and experiment.

  6. 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.

  7. Atomic physics at the future facility for antiproton and ion research: status report 2014

    NASA Astrophysics Data System (ADS)

    Gumberidze, A.; Stöhlker, Th; Litvinov, Yu A.; SPARC Collaboration

    2015-11-01

    In this contribution, a brief overview of the Stored Particle Atomic physics Research Collaboration scientific program at the upcoming Facility for Antiproton and Ion Research (FAIR) is given. The program comprises a very broad range of research topics addressing atomic structure and dynamics in hitherto unexplored regimes, light-matter interactions, lepton pair production phenomena, precision tests of quantum electrodynamics and standard model in the regime of extreme fields and many more. We also present the current strategy for the realization of the envisioned physics program within the modularized start version (MSV) of FAIR.

  8. Trapping of hydrogen atoms inside small beryllium clusters and their ions

    NASA Astrophysics Data System (ADS)

    Naumkin, F. Y.; Wales, D. J.

    2016-08-01

    Structure, stability and electronic properties are evaluated computationally for small Ben (n = 5-9) cluster cages accommodating atomic H inside and forming core-shell species. These parameters are predicted to vary significantly upon insertion of H, for ionic derivatives, and with the system size. In particular, the energy barrier for H-atom exit from the cage changes significantly for ions compared to the neutral counterparts. The corresponding effects predicted for cage assemblies suggest the possibility of efficient charge-control of hydrogen release. This, together with a high capacity for storing hydrogen in extended such assemblies might indicate a possible way towards feasible hydrogen-storage solutions.

  9. Effects of anisotropic electron-ion interactions in atomic photoelectron angular distributions

    NASA Technical Reports Server (NTRS)

    Dill, D.; Starace, A. F.; Manson, S. T.

    1975-01-01

    A summary of the angular momentum transfer formulation of the differential photoionization cross section is presented and photoionization amplitudes in LS coupling are considered. The application of the theoretical concepts and relations developed is illustrated with the aid of an example involving the calculation of the angular distribution of photoelectrons ionized from atomic sulfur according to a certain reaction. The investigation shows that anisotropic electron-ion interactions in atomic sulfur lead to measurable differences between photoelectron angular distribution asymmetry parameters corresponding to alternative ionic term levels.

  10. Two-electron exchange interaction between polar molecules and atomic ions — Asymptotic approach

    NASA Astrophysics Data System (ADS)

    Karbovanets, Oleksandr M.; Karbovanets, Myroslav I.; Khoma, Mykhaylo V.; Lazur, Volodymyr Yu.

    2015-05-01

    We have described the asymptotic approach for calculation of the two-electron exchange interaction between atomic ion and polar molecule responsible for direct double electron transfer processes. The closed analytic expression for matrix element of exchange interaction has been obtained in the framework of the semiclassical version of the asymptotic theory and point-dipole approximation for description of the polar molecule. Contribution to the Topical Issue "Elementary Processes with Atoms and Molecules in Isolated and Aggregated States", edited by Friedrich Aumayr, Bratislav Marinkovic, Štefan Matejčik, John Tanis and Kurt H. Becker.

  11. Vibrationally resolved transitions in ion-molecule and atom-molecular ion slow collisions

    DOE Data Explorer

    The data tables and interactive graphs made available here contain theoretical integral cross sections for vibrational excitation and vibrationally resolved charge transfer from vibrationally excited states of H2 and H2+ with protons and hydrogen atoms, respectively. [From http://www-cfadc.phy.ornl.gov/h2mol/home.html] (Specialized Interface)

  12. Atom probe field ion microscopy and related topics: A bibliography 1993

    SciTech Connect

    Godfrey, R.D.; Miller, M.K.; Russell, K.F.

    1994-10-01

    This bibliography, covering the period 1993, includes references related to the following topics: atom probe field ion microscopy (APFIM), field emission (FE), and field ion microscopy (FIM). Technique-oriented studies and applications are included. The references contained in this document were compiled from a variety of sources including computer searches and personal lists of publications. To reduce the length of this document, the references have been reduced to the minimum necessary to locate the articles. The references are listed alphabetically by authors, an Addendum of references missed in previous bibliographies is included.

  13. Using Barium Ions for Heavy-Atom Derivatization and Phasing of Xylanse ll from Trichoderma longibrachiatum

    SciTech Connect

    Moiseeva,N.; Allaire, M.

    2007-01-01

    This paper describes the use of barium chloride to produce a heavy-atom derivative of xylanase II crystals from Trichoderma longibrachiatum, which was obtained either by cocrystallization or soaking. SAD phasing led to interpretable electron-density maps that allowed unambiguous chain tracing. In the best case, with a data set collected at 9.5 keV, 88% of the residues were built, with 83% of the side chains assigned. The barium ions are found to mainly interact with main-chain carbonyl groups and water molecules. It is suggested that barium ions could also be used as a potential anomalous scatterer in the quick cryosoaking procedure for phasing.

  14. Electron-impact ionization of the Se2+ and Se3+ atomic ions

    NASA Astrophysics Data System (ADS)

    Loch, S. D.; Pindzola, M. S.

    2016-05-01

    Semi-relativistic configuration-average distorted-wave (CADW) calculations are made for the electron-impact ionization of the Se2+ and Se3+ atomic ions. The CADW calculations are found to be in reasonable agreement with recent measurements made at the Multicharged Ion Research Facility at the University of Nevada in Reno. The CADW calculations for configurations near ionization thresholds are checked against level to level distorted-wave (LLDW) calculations. Work supported in part by Grants from NASA, NSF, and DOE.

  15. Stimulated Raman adiabatic passage for improved performance of a cold-atom electron and ion source

    NASA Astrophysics Data System (ADS)

    Sparkes, B. M.; Murphy, D.; Taylor, R. J.; Speirs, R. W.; McCulloch, A. J.; Scholten, R. E.

    2016-08-01

    We implement high-efficiency coherent excitation to a Rydberg state using stimulated Raman adiabatic passage in a cold-atom electron and ion source. We achieve an efficiency of 60% averaged over the laser excitation volume with a peak efficiency of 82%, a 1.6 times improvement relative to incoherent pulsed-laser excitation. Using pulsed electric field ionization of the Rydberg atoms we create electron bunches with durations of 250 ps. High-efficiency excitation will increase source brightness, crucial for ultrafast electron diffraction experiments, and coherent excitation to high-lying Rydberg states could allow for the reduction of internal bunch heating and the creation of a high-speed single-ion source.

  16. Atomic Data and Spectral Line Intensities for Be-like Ions

    NASA Technical Reports Server (NTRS)

    Bhatia, Anand; Landi, E.

    2008-01-01

    Atomic data and collision rates are needed to model the spectrum of optically thin astrophysical sources. Recent observations from solar instrumentation such as SOH0 and Hinode have revealed the presence of hosts of lines emitted by high-energy configurations from ions belonging to the Be-like to the 0-like isoelectronic sequences. Data for such configurations are often unavailable in the literature. We have started a program to calculate the atomic parameters and rates for the high-energy configurations of Be-like ions of the type ls2.21.nl' where n=3,4,5. We report on the results of this project and on the diagnostic application of the predicted spectral lines.

  17. Sympathetic cooling of the Ba{sup +} ion by collisions with ultracold Rb atoms: Theoretical prospects

    SciTech Connect

    Krych, Michal; Skomorowski, Wojciech; Pawlowski, Filip; Moszynski, Robert; Idziaszek, Zbigniew

    2011-03-15

    State-of-the-art ab initio techniques have been applied to compute the potential energy curves of the (BaRb){sup +} molecular ion in the Born-Oppenheimer approximation for the singlet and triplet states dissociating into the ground-state {sup 1}S Rb{sup +} ion and the Ba atom in the ground {sup 1}S state or the lowest singlet or triplet d excited states, and for the singlet and triplet states dissociating into the ground-state {sup 2}S Rb atom and the ground-state {sup 2}S Ba{sup +} ion. The ground-state potential energy was obtained with the coupled-cluster method restricted to single, double, and nonperturbative triple excitations. The first triplet states in the {Sigma}, {Pi}, and {Delta} symmetries were computed with the restricted open-shell coupled-cluster method restricted to single, double, and nonperturbative triple excitations. All other excited-state potential energy curves were computed using the equation of motion approach within the coupled-cluster singles, doubles, and linear triples framework. The long-range coefficients describing the electrostatic, induction, and dispersion interactions at large interatomic distances are also reported. The electric transition dipole moments governing the x {sup 1{Sigma}{yields}1{Sigma}},{sup 1{Pi}} transitions have been obtained as the first residue of the polarization propagator computed with the linear response coupled-cluster method restricted to single and double excitations. Nonadiabatic radial and angular coupling matrix elements as well as the spin-orbit coupling matrix elements have been evaluated using the multireference configuration-interaction method restricted to single and double excitations with a large active space. With these couplings, the spin-orbit-coupled (relativistic) potential energy curves for the 0{sup +} and 1 states relevant for the running experiments have been obtained. Finally, relativistic transition moments and nonadiabatic coupling matrix elements were obtained from the

  18. Sympathetic cooling of the Ba+ ion by collisions with ultracold Rb atoms: Theoretical prospects

    NASA Astrophysics Data System (ADS)

    Krych, Michał; Skomorowski, Wojciech; Pawłowski, Filip; Moszynski, Robert; Idziaszek, Zbigniew

    2011-03-01

    State-of-the-art ab initio techniques have been applied to compute the potential energy curves of the (BaRb)+ molecular ion in the Born-Oppenheimer approximation for the singlet and triplet states dissociating into the ground-state 1S Rb+ ion and the Ba atom in the ground 1S state or the lowest singlet or triplet d excited states, and for the singlet and triplet states dissociating into the ground-state 2S Rb atom and the ground-state 2S Ba+ ion. The ground-state potential energy was obtained with the coupled-cluster method restricted to single, double, and nonperturbative triple excitations. The first triplet states in the Σ, Π, and Δ symmetries were computed with the restricted open-shell coupled-cluster method restricted to single, double, and nonperturbative triple excitations. All other excited-state potential energy curves were computed using the equation of motion approach within the coupled-cluster singles, doubles, and linear triples framework. The long-range coefficients describing the electrostatic, induction, and dispersion interactions at large interatomic distances are also reported. The electric transition dipole moments governing the x 1Σ→1Σ,1Π transitions have been obtained as the first residue of the polarization propagator computed with the linear response coupled-cluster method restricted to single and double excitations. Nonadiabatic radial and angular coupling matrix elements as well as the spin-orbit coupling matrix elements have been evaluated using the multireference configuration-interaction method restricted to single and double excitations with a large active space. With these couplings, the spin-orbit-coupled (relativistic) potential energy curves for the 0+ and 1 states relevant for the running experiments have been obtained. Finally, relativistic transition moments and nonadiabatic coupling matrix elements were obtained from the nonrelativistic results and spin-orbit eigenvectors. The electronic structure input has been

  19. Highly charged ions for atomic clocks, quantum information, and search for α variation.

    PubMed

    Safronova, M S; Dzuba, V A; Flambaum, V V; Safronova, U I; Porsev, S G; Kozlov, M G

    2014-07-18

    We propose 10 highly charged ions as candidates for the development of next generation atomic clocks, quantum information, and search for α variation. They have long-lived metastable states with transition wavelengths to the ground state between 170-3000 nm, relatively simple electronic structure, stable isotopes, and high sensitivity to α variation (e.g., Sm(14+), Pr(10+), Sm(13+), Nd(10+)). We predict their properties crucial for the experimental exploration and highlight particularly attractive systems for these applications.

  20. High charge state, ion-atom collision experiments using accel-decel

    SciTech Connect

    Bernstein, E.M.; Clark, M.W.; Tanis, J.A.; Graham, W.G.

    1987-01-01

    Recent studies of /sub 16/S/sup 13 +/ + He collisions between 2.5 and 200 MeV, which were made using the accel-decel technique with the Brookhaven National Laboratory coupled MP tandem Van de Graaff accelerators, are discussed. Cross sections were measured for single electron-capture and -loss as well as K x rays correlated to electron-capture. Other planned ion-atom collision experiments requiring accel-decel are also presented. 18 refs., 3 figs.

  1. Indirect determination of cations by ion chromatography and anions by atomic emission spectroscopy

    SciTech Connect

    Ervin, A.M.; Panayappan, R.; Cooper, J.C.

    1988-11-01

    A method for the indirect determination of cations by Ion Chromatography (IC) and anions by Atomic Emission Spectroscopy (DCP) is described. The method allows for quantification of suspected impurities in aqueous systems where multiple analyses are desired. The described method is based on the selection of a precipitating agent for the desired analyte. In this study, silver(I) and barium(II) were analyzed indirectly by IC, and chloride and sulfate, by DCP.

  2. Nonlinear effects in defect production by atomic and molecular ion implantation

    SciTech Connect

    David, C. Dholakia, Manan; Chandra, Sharat; Nair, K. G. M.; Panigrahi, B. K.; Amirthapandian, S.; Amarendra, G.; Varghese Anto, C.; Santhana Raman, P.; Kennedy, John

    2015-01-07

    This report deals with studies concerning vacancy related defects created in silicon due to implantation of 200 keV per atom aluminium and its molecular ions up to a plurality of 4. The depth profiles of vacancy defects in samples in their as implanted condition are carried out by Doppler broadening spectroscopy using low energy positron beams. In contrast to studies in the literature reporting a progressive increase in damage with plurality, implantation of aluminium atomic and molecular ions up to Al{sub 3}, resulted in production of similar concentration of vacancy defects. However, a drastic increase in vacancy defects is observed due to Al{sub 4} implantation. The observed behavioural trend with respect to plurality has even translated to the number of vacancies locked in vacancy clusters, as determined through gold labelling experiments. The impact of aluminium atomic and molecular ions simulated using MD showed a monotonic increase in production of vacancy defects for cluster sizes up to 4. The trend in damage production with plurality has been explained on the basis of a defect evolution scheme in which for medium defect concentrations, there is a saturation of the as-implanted damage and an increase for higher defect concentrations.

  3. Spin-Orbit Interactions and Quantum Spin Dynamics in Cold Ion-Atom Collisions

    NASA Astrophysics Data System (ADS)

    Tscherbul, Timur V.; Brumer, Paul; Buchachenko, Alexei A.

    2016-09-01

    We present accurate ab initio and quantum scattering calculations on a prototypical hybrid ion-atom system Yb+ -Rb, recently suggested as a promising candidate for the experimental study of open quantum systems, quantum information processing, and quantum simulation. We identify the second-order spin-orbit (SO) interaction as the dominant source of hyperfine relaxation in cold Yb+ -Rb collisions. Our results are in good agreement with recent experimental observations [L. Ratschbacher et al., Phys. Rev. Lett. 110, 160402 (2013)] of hyperfine relaxation rates of trapped Yb+ immersed in an ultracold Rb gas. The calculated rates are 4 times smaller than is predicted by the Langevin capture theory and display a weak T-0.3 temperature dependence, indicating significant deviations from statistical behavior. Our analysis underscores the deleterious nature of the SO interaction and implies that light ion-atom combinations such as Yb+ -Li should be used to minimize hyperfine relaxation and decoherence of trapped ions in ultracold atomic gases.

  4. Atoms and Ions; Universality, Singularity and Particularity:. on Boltzmann's Vision a Century Later

    NASA Astrophysics Data System (ADS)

    Fisher, Michael

    2008-12-01

    Ludwig Boltzmann died by his own hand 101 years ago last September. He was a passionate believer in atoms: underlying thermodynamics, he felt, lay a statistical world governed by the mechanics of individual particles. His struggles against critics -- "Have you ever seen an atom?" taunted Ernst Mach -- left him pessimistic. Nevertheless, following Maxwell and clarified by Gibbs, he established the science of Statistical Mechanics. But today, especially granted our understanding of critical singularities and their universality, how much do atomic particles and their charged partners, ions, really matter? The answers we have also met opposition. But Boltzmann would have welcomed the insights gained and approved of applications of statistical dynamics to biology, sociology, and other enterprises. Note from Publisher: This article contains the abstract only.

  5. Influence of the plasma environment on atomic structure using an ion-sphere model

    DOE PAGESBeta

    Belkhiri, Madeny Jean; Fontes, Christopher John; Poirier, Michel

    2015-09-03

    Plasma environment effects on atomic structure are analyzed using various atomic structure codes. To monitor the effect of high free-electron density or low temperatures, Fermi-Dirac and Maxwell-Boltzmann statistics are compared. After a discussion of the implementation of the Fermi-Dirac approach within the ion-sphere model, several applications are considered. In order to check the consistency of the modifications brought here to extant codes, calculations have been performed using the Los Alamos Cowan Atomic Structure (cats) code in its Hartree-Fock or Hartree-Fock-Slater form and the parametric potential Flexible Atomic Code (fac). The ground-state energy shifts due to the plasma effects for themore » six most ionized aluminum ions have been calculated using the fac and cats codes and fairly agree. For the intercombination resonance line in Fe22+, the plasma effect within the uniform electron gas model results in a positive shift that agrees with the MCDF value of B. Saha et al.« less

  6. Influence of the plasma environment on atomic structure using an ion-sphere model

    SciTech Connect

    Belkhiri, Madeny Jean; Fontes, Christopher John; Poirier, Michel

    2015-09-03

    Plasma environment effects on atomic structure are analyzed using various atomic structure codes. To monitor the effect of high free-electron density or low temperatures, Fermi-Dirac and Maxwell-Boltzmann statistics are compared. After a discussion of the implementation of the Fermi-Dirac approach within the ion-sphere model, several applications are considered. In order to check the consistency of the modifications brought here to extant codes, calculations have been performed using the Los Alamos Cowan Atomic Structure (cats) code in its Hartree-Fock or Hartree-Fock-Slater form and the parametric potential Flexible Atomic Code (fac). The ground-state energy shifts due to the plasma effects for the six most ionized aluminum ions have been calculated using the fac and cats codes and fairly agree. For the intercombination resonance line in Fe22+, the plasma effect within the uniform electron gas model results in a positive shift that agrees with the MCDF value of B. Saha et al.

  7. A highly miniaturized vacuum package for a trapped ion atomic clock

    DOE PAGESBeta

    Schwindt, Peter D. D.; Jau, Yuan-Yu; Partner, Heather; Casias, Adrian; Wagner, Adrian R.; Moorman, Matthew; Manginell, Ronald P.; Kellogg, James R.; Prestage, John D.

    2016-05-12

    We report on the development of a highly miniaturized vacuum package for use in an atomic clock utilizing trapped ytterbium-171 ions. The vacuum package is approximately 1 cm3 in size and contains a linear quadrupole RF Paul ion trap, miniature neutral Yb sources, and a non-evaporable getter pump. We describe the fabrication process for making the Yb sources and assembling the vacuum package. To prepare the vacuum package for ion trapping, it was evacuated, baked at a high temperature, and then back filled with a helium buffer gas. Once appropriate vacuum conditions were achieved in the package, the package wasmore » sealed with a copper pinch-off and was then pumped only by the non-evaporable getter. We demonstrated ion trapping in this vacuum package and the operation of an atomic clock, stabilizing a local oscillator to the 12.6 GHz hyperfine transition of 171Yb+. The fractional frequency stability of the clock was measured to be 2 × 10-11 / τ1/2.« less

  8. A highly miniaturized vacuum package for a trapped ion atomic clock

    NASA Astrophysics Data System (ADS)

    Schwindt, Peter D. D.; Jau, Yuan-Yu; Partner, Heather; Casias, Adrian; Wagner, Adrian R.; Moorman, Matthew; Manginell, Ronald P.; Kellogg, James R.; Prestage, John D.

    2016-05-01

    We report on the development of a highly miniaturized vacuum package for use in an atomic clock utilizing trapped ytterbium-171 ions. The vacuum package is approximately 1 cm3 in size and contains a linear quadrupole RF Paul ion trap, miniature neutral Yb sources, and a non-evaporable getter pump. We describe the fabrication process for making the Yb sources and assembling the vacuum package. To prepare the vacuum package for ion trapping, it was evacuated, baked at a high temperature, and then back filled with a helium buffer gas. Once appropriate vacuum conditions were achieved in the package, it was sealed with a copper pinch-off and was subsequently pumped only by the non-evaporable getter. We demonstrated ion trapping in this vacuum package and the operation of an atomic clock, stabilizing a local oscillator to the 12.6 GHz hyperfine transition of 171Y b+. The fractional frequency stability of the clock was measured to be 2 × 10-11/τ1/2.

  9. A highly miniaturized vacuum package for a trapped ion atomic clock.

    PubMed

    Schwindt, Peter D D; Jau, Yuan-Yu; Partner, Heather; Casias, Adrian; Wagner, Adrian R; Moorman, Matthew; Manginell, Ronald P; Kellogg, James R; Prestage, John D

    2016-05-01

    We report on the development of a highly miniaturized vacuum package for use in an atomic clock utilizing trapped ytterbium-171 ions. The vacuum package is approximately 1 cm(3) in size and contains a linear quadrupole RF Paul ion trap, miniature neutral Yb sources, and a non-evaporable getter pump. We describe the fabrication process for making the Yb sources and assembling the vacuum package. To prepare the vacuum package for ion trapping, it was evacuated, baked at a high temperature, and then back filled with a helium buffer gas. Once appropriate vacuum conditions were achieved in the package, it was sealed with a copper pinch-off and was subsequently pumped only by the non-evaporable getter. We demonstrated ion trapping in this vacuum package and the operation of an atomic clock, stabilizing a local oscillator to the 12.6 GHz hyperfine transition of (171)Y b(+). The fractional frequency stability of the clock was measured to be 2 × 10(-11)/τ(1/2). PMID:27250397

  10. Atomic resolution study of displacement cascades in ion-irradiated platinum

    NASA Astrophysics Data System (ADS)

    Pramanik, Dipankar; Seidman, David N.

    1986-07-01

    The field-ion microscope technique has been employed to study, on an atomic scale, the vacancy structure of individual depleted zones (DZs) in platinum specimens which had been created by 20-keV Kr+ ions. DZs are the final quiescent state of collision cascades. The irradiations were performed in situ at 60 K and the specimens were examined at this temperature by the pulse field-evaporation technique. The following experimental quantities were determined for each DZ: (a) the absolute number of vacancies (ν); (b) the average diameter; (c) the average vacancy concentration based on ν and the actual volume filled by the vacancies; (d) the radial distribution function of the vacancies out to the ninth nearest-neighbor; (e) the fraction of first-nearest-neighbor vacancies in clusters of size n; (f) the average depth (L) from the irradiated surface, measured along a direction parallel to the incident ion beam, at which each DZ was detected and its direction of elongation; and (g) the sputtering yield based on the number of vacancies detected in the near-surface region (<5 Å thick). All of the measured quantities are compared with corresponding quantities extracted from either an analytical model or a Monte Carlo computer code (Transport of Ions in Matter—trim) of radiation damage. We demonstrate that it is possible to transform a microscopic spatial distribution of vacancies to a continuous radiation damage profile with atomic resolution.

  11. Fabrication of ion conductive tin oxide-phosphate amorphous thin films by atomic layer deposition

    SciTech Connect

    Park, Suk Won; Jang, Dong Young; Kim, Jun Woo; Shim, Joon Hyung

    2015-07-15

    This work reports the atomic layer deposition (ALD) of tin oxide-phosphate films using tetrakis(dimethylamino)tin and trimethyl phosphate as precursors. The growth rates were 1.23–1.84 Å/cycle depending upon the deposition temperature and precursor combination. The ionic conductivity of the ALD tin oxide-phosphate films was evaluated by cross-plane impedance measurements in the temperature range of 50–300 °C under atmospheric air, with the highest conductivity measured as 1.92 × 10{sup −5} S cm{sup −1} at 300 °C. Furthermore, high-resolution x-ray photoelectron spectroscopy exhibited two O1s peaks that were classified as two subpeaks of hydroxyl ions and oxygen ions, revealing that the quantity of hydroxyl ions in the ALD tin oxide-phosphate films influences their ionic conductivity.

  12. Atomic Scale Picture of the Ion Conduction Mechanism in Tetrahedral Network of Lanthanum Barium Gallate

    SciTech Connect

    Jalarvo, Niina H; Gourdon, Olivier; Bi, Zhonghe; Gout, Delphine J; Ohl, Michael E; Paranthaman, Mariappan Parans

    2013-01-01

    Combined experimental study of impedance spectroscopy, neutron powder diffraction and quasielastic neutron scattering was performed to shed light into the atomic scale ion migration processes in proton and oxide ion conductor; La0.8Ba1.2GaO3.9 . This material consist of tetrahedral GaO4 units, which are rather flexible and rocking motion of these units promotes the ionic migration process. The oxide ion (vacancy) conduction takes place on channels along c axis, involving a single elementary step, which occurs between adjacent tetrahedron (inter-tetrahedron jump). The proton conduction mechanism consists of intra-tetrahedron and inter-tetrahedron elementary processes. The intra-tetrahedron proton transport is the rate-limiting process, with activation energy of 0.44 eV. The rocking motion of the GaO4 tetrahedron aids the inter-tetrahedral proton transport, which has the activation energy of 0.068 eV.

  13. Correlated electron ion dynamics: the excitation of atomic motion by energetic electrons

    NASA Astrophysics Data System (ADS)

    Horsfield, Andrew P.; Bowler, D. R.; Fisher, A. J.; Todorov, Tchavdar N.; Sánchez, Cristián G.

    2005-08-01

    Correlated electron-ion dynamics (CEID) is an extension of molecular dynamics that allows us to introduce in a correct manner the exchange of energy between electrons and ions. The formalism is based on a systematic approximation: small amplitude moment expansion. This formalism is extended here to include the explicit quantum spread of the ions and a generalization of the Hartree-Fock approximation for incoherent sums of Slater determinants. We demonstrate that the resultant dynamical equations reproduce analytically the selection rules for inelastic electron-phonon scattering from perturbation theory, which control the mutually driven excitations of the two interacting subsystems. We then use CEID to make direct numerical simulations of inelastic current-voltage spectroscopy in atomic wires, and to exhibit the crossover from ionic cooling to heating as a function of the relative degree of excitation of the electronic and ionic subsystems.

  14. On accurate computations of slowly convergent atomic properties in few-electron ions and electron-electron correlations

    NASA Astrophysics Data System (ADS)

    Frolov, Alexei M.; Wardlaw, David M.

    2016-09-01

    We discuss an approach to accurate numerical computations of slowly convergent properties in two-electron atoms/ions which include the negatively charged Ps- ( e - e + e -) and H- ions, He atom and positively charged, helium-like ions from Li+ to Ni26+. All these ions are considered in their ground 11S-state(s). The slowly convergent properties selected in this study include the electron-nulceus ( r 2k eN) and electron-electron ( r 2k ee) expectation values for k = 2, 3, 4 and 5.

  15. Ionization, ion distribution, and ion focusing in laser plasmas from atomic and diatomic targets

    SciTech Connect

    Srivastava, S. N.; Rohr, K.; Sinha, B. K.

    2006-04-01

    Charge-resolved measurements of the total number of particles from plasmas produced from planar, monoatomic targets of copper and tungsten as well as the binary targets of copper and tungsten are reported, using a 125 mJ, 5 ns, Nd:YAG laser, at a laser intensity of about 10{sup 10} W/cm{sup 2}. The measurements show a severe quenching of the ionization states in the case of the diatomic targets. These measurements and their variations with ionization state support the theoretical investigations of plasma motion under the influence of the viscous force in case of plasmas consisting of light and heavy particles. Gaussian width measurements of the angular particle distribution showed a focusing effect towards the target normal, the width decreasing as the ion mass and ionization state increased. From the analysis of the theoretical results on self-similarity expansion it is concluded that the ion acceleration due to the built-in electrostatic potential is not significant.

  16. Ion-neutral chemistry at ultralow energies:Dynamics of reactive collisions between laser-cooled Ca+ or Ba+ ions and Rb atoms in an ion-atom hybrid trap

    NASA Astrophysics Data System (ADS)

    Dulieu, O.; Hall, F. H. J.; Eberle, P.; Hegi, G.; Raoult, M.; Aymar, M.; Willitsch, S.

    2013-05-01

    Cold chemical reactions between laser-cooled Ca+ or Ba+ ions and Rb atoms were studied in an ion-atom hybrid trap. Reaction rate constants were determined in the collision energy range Ecoll /kB = 20 mK-20 K. Product branching ratios were studied using resonant-excitation mass spectrometry. The dynamics of the reactive processes including the radiative formation of CaRb+ and BaRb+ molecular ions has been analyzed using accurate potential energy curves and quantum-scattering calculations for the radiative channels. It is shown that the energy dependence of the reaction rates is governed by long-range interactions, while its magnitude is determined by short-range non-adiabatic and radiative couplings. The quantum character of the collisions is predicted to manifest itself in the occurrence of narrow shape resonances at well-defined collision energies. The present results highlight both universal and system-specific phenomena in cold ion-neutral collisions. This work was supported by the Swiss National Science Foundation and the COST Action ''Ion Traps for Tomorrow's Applications''.

  17. Proposal for a novel method of precisely determining the atomic mass unit by the accumulation of ions

    NASA Astrophysics Data System (ADS)

    Gläser, Michael

    1991-10-01

    An experiment for direct measurement of the atomic mass unit is proposed. A mononuclidic ion flux is collected and accumulated to an amount that can be weighed with high accuracy. Simultaneously, the ion current is measured and integrated. By means of voltage and resistance references based on the Josephson and the quantum Hall effect, the mass is then related to atomic mass by frequency counting over a certain time interval. This experiment may enable a new, physical definition of the kilogram.

  18. Transition rates for lithium-like ions, sodium-like ions, and neutral alkali-metal atoms

    SciTech Connect

    Johnson, W.R.; Liu, Z.W.; Sapirstein, J.

    1996-11-01

    Third-order many-body perturbation theory is used to obtain E1 transition amplitudes for ions of the lithium and sodium isoelectronic sequences and for the neutral alkali-metal atoms potassium, rubidium, cesium, and francium. Complete angular reductions of the first, second, and third-order amplitudes are given. Tables of transition energies and rates are given for the 2p{sub {1/2}} {yields} 2s{sub {1/2}}, 2p{sub 3/2} {yields} 2s{sub {1/2}}, 3s{sub {1/2}} {yields} 2p{sub {1/2}}, and 3s{sub {1/2}} {yields} 2p{sub 3/2} transitions in the lithium isoelectronic sequence and for the corresponding 3p{sub 1/2} {yields} 3s{sub 1/2}, 3p{sub 3/2} {yields} 3s{sub {1/2}}, 4s{sub {1/2}} {yields} 3p{sub 1/2}, and 4s{sub {1/2}} {yields} 3p{sub 3/2} transitions in the sodium sequence. For neutral alkali atoms, amplitudes of np{sub {1/2}} {yields} ns{sub {1/2}}, np{sub 3/2} {yields} ns{sub {1/2}}, (n + 1)s{sub {1/2}} {yields} np{sub {1/2}}, and (n + 1)s{sub {1/2}} {yields} np{sub 3/2} transitions are evaluated, where n is the principal quantum number of the valence electron in the atomic ground state, Semi-empirical corrections for the omitted fourth- and higher-order terms in perturbation theory are given for the neutral alkali-metal atoms. Comparisons with previous high-precision calculations and with experiment are made. 42 refs., 1 fig., 12 tabs.

  19. Development of series H{sup −} multicusp ion source at China Institute of Atomic Energy

    SciTech Connect

    TianJue, Zhang; XianLu, Jia ZhenGuo, Li; Yinlong, Lu; JiuChang, Qin; Xia, Zheng; Hongjuan, Yao; JunQing, Zhong; GaoFeng, Pan; Tao, Ge; Fengping, Guan

    2014-02-15

    The development of H{sup −} multicusp ion sources has been carried out at China Institute of Atomic Energy (CIAE) for more than ten years. The first H{sup −} ion source with 5.2 mA was made in 2002. After improving the configured magnetic field, a H{sup −} ion source of 10 mA was made in 2004, and the beam intensity of 15 mA was obtained in 2008 after further improvements of the filter field. The beam intensity of 18 mA was achieved in 2010 following the in-depth study and optimization on some essential operation conditions. Now a series of H{sup −} cusp sources with different sizes and beam intensity ranging from 3 mA to 18 mA have been successfully developed at CIAE. All the ion sources can fast finish the test on the test stand now, since all the connections are modularized and can fit all kinds of H{sup −} mulitcusp source of CIAE. The development status of the various H{sup −} multicusp ion sources at CIAE are presented in the paper.

  20. Energetic atomic and molecular ions of ionospheric origin observed in distant magnetotail flow-reversal events

    SciTech Connect

    Christon, S.P.; Gloeckler, G.; Williams, D.J.; McEntire, R.W.; Jacquey, C.; Angelopoulos, V.; Lui, A.T.Y.; Mukai, T.; Kokubun, S.; Fairfield, D.H.

    1994-12-15

    Energetic atomic (O{sup +1} and N{sup +1}) and molecular (O{sub 2}{sup +1}, NO{sup +1}, and N{sub 2}{sup +1}) ions of ionospheric origin were observed in Earth`s magnetotail at X {approximately} {minus}146 R{sub E} during two plasma sheet sunward/tailward flow-reversal events measured by instruments on the GEOTAIL spacecraft. These events were associated with concurrent ground-measured geomagnetic disturbance intensification at auroral- and mid-latitudes (Kp = 7{sup {minus}}). Energetic ions in the sunward-component and tailward flows were from both the solar wind and ionosphere. Plasma and energetic ions participated in the flows. During tailward flow, ionospheric origin ion abundance ratios at {approximately} 200-900 km/s in the rest frame were N{sup +1}/O{sup +1} = {approximately} 25-30% and (O{sub 2}{sup +1}, NO{sup +1}, and N{sub 2}{sup +1})/O{sup +1} = {approximately} 1-2%. The authors argue that tailward flow most likely initiated {approximately} 80-100 R{sub E} tailward of Earth and molecular ions were in the plasma sheet prior to geomagnetic intensification onset. 13 refs., 4 figs.

  1. Solar radiation pressure as a mechanism of acceleration of atoms and first ions with low ionization potentials

    NASA Astrophysics Data System (ADS)

    Shestakova, L. I.

    2015-04-01

    Calculated results are presented for solar radiation pressure acting on atoms and first ions. For some of these particles, radiation pressure exceeds the gravitational attraction and can accelerate them to large velocities. A comparison of the results with ionization potentials shows that the maxima of radiation pressure on neutral atoms coincide with the minima of the first ionization potentials (FIPs). This relationship is even more apparent for first ions. The minima of the second ionization potentials (SIPs) coincide with the radiation pressure maxima for a number of ions such as Be II, Mg II, Ca II, and the neighboring elements. Thus, radiation pressure may serve as a possible mechanism of acceleration of pickup ions and energetic neutral atoms (ENA) coming from an inner source (zodiacal dust and sungrazing comets). These atoms and ions, which are not typical of the solar wind, are formed as a result of the disintegration of comets or meteor showers near the Sun and can accelerate and reach the Earth's orbit as part of the solar wind. Doubly ionized atoms have resonance lines in the UV range, where solar radiation pressure has no apparent impact on the particle dynamics; thus, the proposed acceleration mechanism can only be applied to neutral atoms and first ions with low potentials of the subsequent ionization.

  2. Arc plasma generator of atomic driver for steady-state negative ion source

    NASA Astrophysics Data System (ADS)

    Ivanov, A. A.; Belchenko, Yu. I.; Davydenko, V. I.; Ivanov, I. A.; Kolmogorov, V. V.; Listopad, A. A.; Mishagin, V. V.; Putvinsky, S. V.; Shulzhenko, G. I.; Smirnov, A.

    2014-02-01

    The paper reviews the results of development of steady-state arc-discharge plasma generator with directly heated LaB6 cathode. This arc-discharge plasma generator produces a plasma jet which is to be converted into an atomic one after recombination on a metallic plate. The plate is electrically biased relative to the plasma in order to control the atom energies. Such an intensive jet of hydrogen atoms can be used in negative ion sources for effective production of negative ions on a cesiated surface of plasma grid. All elements of the plasma generator have an augmented water cooling to operate in long pulse mode or in steady state. The thermo-mechanical stresses and deformations of the most critical elements of the plasma generator were determined by simulations. Magnetic field inside the discharge chamber was optimized to reduce the local power loads. The first tests of the steady-state arc plasma generator prototype have performed in long-pulse mode.

  3. Arc plasma generator of atomic driver for steady-state negative ion source

    SciTech Connect

    Ivanov, A. A.; Belchenko, Yu. I.; Davydenko, V. I.; Ivanov, I. A.; Kolmogorov, V. V.; Listopad, A. A. Mishagin, V. V.; Shulzhenko, G. I.; Putvinsky, S. V.; Smirnov, A.

    2014-02-15

    The paper reviews the results of development of steady-state arc-discharge plasma generator with directly heated LaB{sub 6} cathode. This arc-discharge plasma generator produces a plasma jet which is to be converted into an atomic one after recombination on a metallic plate. The plate is electrically biased relative to the plasma in order to control the atom energies. Such an intensive jet of hydrogen atoms can be used in negative ion sources for effective production of negative ions on a cesiated surface of plasma grid. All elements of the plasma generator have an augmented water cooling to operate in long pulse mode or in steady state. The thermo-mechanical stresses and deformations of the most critical elements of the plasma generator were determined by simulations. Magnetic field inside the discharge chamber was optimized to reduce the local power loads. The first tests of the steady-state arc plasma generator prototype have performed in long-pulse mode.

  4. Arc plasma generator of atomic driver for steady-state negative ion source.

    PubMed

    Ivanov, A A; Belchenko, Yu I; Davydenko, V I; Ivanov, I A; Kolmogorov, V V; Listopad, A A; Mishagin, V V; Putvinsky, S V; Shulzhenko, G I; Smirnov, A

    2014-02-01

    The paper reviews the results of development of steady-state arc-discharge plasma generator with directly heated LaB6 cathode. This arc-discharge plasma generator produces a plasma jet which is to be converted into an atomic one after recombination on a metallic plate. The plate is electrically biased relative to the plasma in order to control the atom energies. Such an intensive jet of hydrogen atoms can be used in negative ion sources for effective production of negative ions on a cesiated surface of plasma grid. All elements of the plasma generator have an augmented water cooling to operate in long pulse mode or in steady state. The thermo-mechanical stresses and deformations of the most critical elements of the plasma generator were determined by simulations. Magnetic field inside the discharge chamber was optimized to reduce the local power loads. The first tests of the steady-state arc plasma generator prototype have performed in long-pulse mode.

  5. Short-range ordering of ion-implanted nitrogen atoms in SiC-graphene

    SciTech Connect

    Willke, P.; Druga, T.; Wenderoth, M.; Amani, J. A.; Weikert, S.; Hofsäss, H.; Thakur, S.; Maiti, K.

    2014-09-15

    We perform a structural analysis of nitrogen-doped graphene on SiC(0001) prepared by ultra low-energy ion bombardment. Using scanning tunneling microscopy, we show that nitrogen atoms are incorporated almost exclusively as graphitic substitution in the graphene honeycomb lattice. With an irradiation energy of 25 eV and a fluence of approximately 5 × 10{sup 14 }cm{sup −2}, we achieve a nitrogen content of around 1%. By quantitatively comparing the position of the N-atoms in the topography measurements with simulated random distributions, we find statistically significant short-range correlations. Consequently, we are able to show that the dopants arrange preferably at lattice sites given by the 6 × 6-reconstruction of the underlying substrate. This selective incorporation is most likely triggered by adsorbate layers present during the ion bombardment. This study identifies low-energy ion irradiation as a promising method for controlled doping in epitaxial graphene.

  6. Metastable atom-activated dissociation mass spectrometry of phosphorylated and sulfonated peptides in negative ion mode.

    PubMed

    Cook, Shannon L; Jackson, Glen P

    2011-06-01

    The dissociation behavior of phosphorylated and sulfonated peptide anions was explored using metastable atom-activated dissociation mass spectrometry (MAD-MS) and collision-induced dissociation (CID). A beam of high kinetic energy helium (He) metastable atoms was exposed to isolated phosphorylated and sulfonated peptides in the 3- and 2- charge states. Unlike CID, where phosphate losses are dominant, the major dissociation channels observed using MAD were C(α) - C peptide backbone cleavages and neutral losses of CO(2), H(2)O, and [CO(2) + H(2)O] from the charge reduced (oxidized) product ion, consistent with an electron detachment dissociation (EDD) mechanism such as Penning ionization. Regardless of charge state or modification, MAD provides ample backbone cleavages with little modification loss, which allows for unambiguous PTM site determination. The relative abundance of certain fragment ions in MAD is also demonstrated to be somewhat sensitive to the number and location of deprotonation sites, with backbone cleavage somewhat favored adjacent to deprotonated sites like aspartic acid residues. MAD provides a complementary dissociation technique to CID, ECD, ETD, and EDD for peptide sequencing and modification identification. MAD offers the unique ability to analyze highly acidic peptides that contain few to no basic amino acids in either negative or positive ion mode.

  7. Performance predictions of a focused ion beam from a laser cooled and compressed atomic beam

    SciTech Connect

    Haaf, G. ten; Wouters, S. H. W.; Vredenbregt, E. J. D.; Mutsaers, P. H. A.; Geer, S. B. van der

    2014-12-28

    Focused ion beams are indispensable tools in the semiconductor industry because of their ability to image and modify structures at the nanometer length scale. Here, we report on performance predictions of a new type of focused ion beam based on photo-ionization of a laser cooled and compressed atomic beam. Particle tracing simulations are performed to investigate the effects of disorder-induced heating after ionization in a large electric field. They lead to a constraint on this electric field strength which is used as input for an analytical model which predicts the minimum attainable spot size as a function of, amongst others, the flux density of the atomic beam, the temperature of this beam, and the total current. At low currents (I < 10 pA), the spot size will be limited by a combination of spherical aberration and brightness, while at higher currents, this is a combination of chromatic aberration and brightness. It is expected that a nanometer size spot is possible at a current of 1 pA. The analytical model was verified with particle tracing simulations of a complete focused ion beam setup. A genetic algorithm was used to find the optimum acceleration electric field as a function of the current. At low currents, the result agrees well with the analytical model, while at higher currents, the spot sizes found are even lower due to effects that are not taken into account in the analytical model.

  8. Status of Charge Exchange Cross Section Measurements for Highly Charged Ions on Atomic Hydrogen

    NASA Astrophysics Data System (ADS)

    Draganic, I. N.; Havener, C. C.; Schultz, D. R.; Seely, D. G.; Schultz, P. C.

    2011-05-01

    Total cross sections of charge exchange (CX) for C5+, N6+, and O7+ ions on ground state atomic hydrogen are measured in an extended collision energy range of 1 - 20,000 eV/u. Absolute CX measurements are performed using an improved merged-beams technique with intense highly charged ion beams extracted from a 14.5 GHz ECR ion source mounted on a high voltage platform. In order to improve the problematic H+ signal collection for these exoergic CX collisions at low relative energies, a new double focusing electrostatic analyzer was installed. Experimental CX data are in good agreement with all previous H-oven relative measurements at higher collision energies. We compare our results with the most recent molecular orbital close-coupling (MOCC) and atomic orbital close-coupling (AOCC) theoretical calculations. Work supported by the NASA Solar & Heliospheric Physics Program NNH07ZDA001N, the Office of Fusion Energy Sciences and the Division of Chemical Sciences, Geosciences, and Biosciences, and the Office of Basic Energy Sciences of the U.S. DoE.

  9. The development of the high intensity electron cyclotron resonance ion source at China Institute of Atomic Energy

    NASA Astrophysics Data System (ADS)

    Tang, B.; Ma, R.; Ma, Y.; Chen, L.; Huang, Q.; Liang, H.; Cui, B.; Jiang, W.

    2014-02-01

    High-current microwave ion source has been under development over 15 years for accelerator driven sub-critical system research at China Institute of Atomic Energy, and the beam intensity higher than 140 mA proton beam is produced by this ion source with long lifetime and high reliability. The emittance of high intensity continue-wave and pulse beam is measured on a test-bench in the laboratory. Based on the good performance of this proton ion source, a new 120 mA deuterium ion source is proposed for a high intensity neutron generator. The ion source details and status will be presented.

  10. Radioactive ion beam transportation for the fundamental symmetry study with laser-trapped atoms.

    PubMed

    Arikawa, Hiroshi; Ando, S; Aoki, T; Ezure, S; Harada, K; Hayamizu, T; Inoue, T; Ishikawa, T; Itoh, M; Kawamura, H; Kato, K; Kato, T; Uchiyama, A; Aoki, T; Furukawa, T; Hatakeyama, A; Hatanaka, K; Imai, K; Murakami, T; Nataraj, H S; Sato, T; Shimizu, Y; Wakasa, T; Yoshida, H P; Sakemi, Y

    2014-02-01

    The search for the violation of the fundamental symmetry in a radioactive atom is the promising candidate for precision tests of the standard model and its possible extensions. The subtle signal arising from the symmetry violation is enhanced in heavy atoms, such as a francium (Fr). To realize high precision measurements, a large amount of radioactive isotopes is required. The Fr is produced via a nuclear fusion reaction using a melted gold target with a (18)O primary beam at Cyclotron and Radioisotope Center, Tohoku University. The maximum extraction efficiency of the Fr ion was achieved at approximately 35%. The beam line consists of an electrostatic deflector, three electrostatic quadrupole triplets to the measurement area at 10 m away from the reaction point, and several beam diagnosis systems. We optimized parameters of the beam line. PMID:24593466

  11. Radioactive ion beam transportation for the fundamental symmetry study with laser-trapped atoms

    NASA Astrophysics Data System (ADS)

    Arikawa, Hiroshi; Ando, S.; Aoki, T.; Ezure, S.; Harada, K.; Hayamizu, T.; Inoue, T.; Ishikawa, T.; Itoh, M.; Kawamura, H.; Kato, K.; Kato, T.; Uchiyama, A.; Aoki, T.; Furukawa, T.; Hatakeyama, A.; Hatanaka, K.; Imai, K.; Murakami, T.; Nataraj, H. S.; Sato, T.; Shimizu, Y.; Wakasa, T.; Yoshida, H. P.; Sakemi, Y.

    2014-02-01

    The search for the violation of the fundamental symmetry in a radioactive atom is the promising candidate for precision tests of the standard model and its possible extensions. The subtle signal arising from the symmetry violation is enhanced in heavy atoms, such as a francium (Fr). To realize high precision measurements, a large amount of radioactive isotopes is required. The Fr is produced via a nuclear fusion reaction using a melted gold target with a 18O primary beam at Cyclotron and Radioisotope Center, Tohoku University. The maximum extraction efficiency of the Fr ion was achieved at approximately 35%. The beam line consists of an electrostatic deflector, three electrostatic quadrupole triplets to the measurement area at 10 m away from the reaction point, and several beam diagnosis systems. We optimized parameters of the beam line.

  12. Radioactive ion beam transportation for the fundamental symmetry study with laser-trapped atoms.

    PubMed

    Arikawa, Hiroshi; Ando, S; Aoki, T; Ezure, S; Harada, K; Hayamizu, T; Inoue, T; Ishikawa, T; Itoh, M; Kawamura, H; Kato, K; Kato, T; Uchiyama, A; Aoki, T; Furukawa, T; Hatakeyama, A; Hatanaka, K; Imai, K; Murakami, T; Nataraj, H S; Sato, T; Shimizu, Y; Wakasa, T; Yoshida, H P; Sakemi, Y

    2014-02-01

    The search for the violation of the fundamental symmetry in a radioactive atom is the promising candidate for precision tests of the standard model and its possible extensions. The subtle signal arising from the symmetry violation is enhanced in heavy atoms, such as a francium (Fr). To realize high precision measurements, a large amount of radioactive isotopes is required. The Fr is produced via a nuclear fusion reaction using a melted gold target with a (18)O primary beam at Cyclotron and Radioisotope Center, Tohoku University. The maximum extraction efficiency of the Fr ion was achieved at approximately 35%. The beam line consists of an electrostatic deflector, three electrostatic quadrupole triplets to the measurement area at 10 m away from the reaction point, and several beam diagnosis systems. We optimized parameters of the beam line.

  13. Charge exchange transition probability for collisions between unlike ions and atoms within the adiabatic approximation

    NASA Technical Reports Server (NTRS)

    Xu, Y. J.; Khandelwal, G. S.; Wilson, John W.

    1989-01-01

    A simple formula for the transition probability for electron exchange between unlike ions and atoms is established within the adiabatic approximation by employing the Linear Combination of Atomic Orbitals (LCAO) method. The formula also involves an adiabatic parameter, introduced by Massey, and thus the difficulties arising from the internal energy defect and the adiabatic approximation are avoided. Specific reactions Li(+++) + H to Li(++) + H(+) and Be(4+) + H to Be(3+) + H(+) are considered as examples. The calculated capture cross section results of the present work are compared with the experimental data and with the calculation of other authors over the velocity range of 10(7) cm/sec to 10(8) cm/sec.

  14. Radioactive ion beam transportation for the fundamental symmetry study with laser-trapped atoms

    SciTech Connect

    Arikawa, Hiroshi Ando, S.; Aoki, T.; Ezure, S.; Harada, K.; Hayamizu, T.; Inoue, T.; Ishikawa, T.; Itoh, M.; Kawamura, H.; Kato, K.; Kato, T.; Uchiyama, A.; Sakemi, Y.; Aoki, T.; Furukawa, T.; Hatakeyama, A.; Hatanaka, K.; Yoshida, H. P.; Imai, K.; and others

    2014-02-15

    The search for the violation of the fundamental symmetry in a radioactive atom is the promising candidate for precision tests of the standard model and its possible extensions. The subtle signal arising from the symmetry violation is enhanced in heavy atoms, such as a francium (Fr). To realize high precision measurements, a large amount of radioactive isotopes is required. The Fr is produced via a nuclear fusion reaction using a melted gold target with a {sup 18}O primary beam at Cyclotron and Radioisotope Center, Tohoku University. The maximum extraction efficiency of the Fr ion was achieved at approximately 35%. The beam line consists of an electrostatic deflector, three electrostatic quadrupole triplets to the measurement area at 10 m away from the reaction point, and several beam diagnosis systems. We optimized parameters of the beam line.

  15. Ion-biomolecule collisions studied within the independent atom model including geometric screening corrections

    NASA Astrophysics Data System (ADS)

    Lüdde, H. J.; Achenbach, A.; Kalkbrenner, T.; Jankowiak, H. C.; Kirchner, T.

    2016-05-01

    A recently introduced model to account for geometric screening corrections in an independent-atom-model description of ion-molecule collisions is applied to proton collisions from amino acids and DNA and RNA nucleobases. The correction coefficients are obtained from using a pixel counting method (PCM) for the exact calculation of the effective cross sectional area that emerges when the molecular cross section is pictured as a structure of (overlapping) atomic cross sections. This structure varies with the relative orientation of the molecule with respect to the projectile beam direction and, accordingly, orientation-independent total cross sections are obtained from averaging the pixel count over many orientations. We present net capture and net ionization cross sections over wide ranges of impact energy and analyze the strength of the screening effect by comparing the PCM results with Bragg additivity rule cross sections and with experimental data where available. Work supported by NSERC, Canada.

  16. Charge transfer in cold collisions of rubidium atoms with calcium and ytterbium ions

    NASA Astrophysics Data System (ADS)

    Yakovleva, S. A.; Belyaev, A. K.; Buchachenko, A. A.

    2014-12-01

    Low-energy collisions of the Ca and Yb cations with Rb atoms are investigated theoretically using accurate ab initio potential energy curves and coupling matrix elements to elucidate the dominant charge transfer mechanisms. The cross sections calculated at collision energies above 10-5 cm-1 exhibit the features typical to Langevin ion-atom collision regime, including a rich structure associated with the centrifugal barrier tunnelling (orbiting) resonances. It is shown that the dominant process in Yb+ + Rb collisions is the radiative charge transfer, while in the case of Ca+ + Rb collisions nonadiabatic transitions due to spin-orbit coupling dominate. Theoretical results are in a good agreement with available experimental data.

  17. Hierarchical surface atomic structure of a manganese-based spinel cathode for lithium-ion batteries.

    PubMed

    Lee, Sanghan; Yoon, Gabin; Jeong, Minseul; Lee, Min-Joon; Kang, Kisuk; Cho, Jaephil

    2015-01-19

    The increasing use of lithium-ion batteries (LIBs) in high-power applications requires improvement of their high-temperature electrochemical performance, including their cyclability and rate capability. Spinel lithium manganese oxide (LiMn2O4) is a promising cathode material because of its high stability and abundance. However, it exhibits poor cycling performance at high temperatures owing to Mn dissolution. Herein we show that when stoichiometric lithium manganese oxide is coated with highly doped spinels, the resulting epitaxial coating has a hierarchical atomic structure consisting of cubic-spinel, tetragonal-spinel, and layered structures, and no interfacial phase is formed. In a practical application of the coating to doped spinel, the material retained 90% of its capacity after 800 cycles at 60 °C. Thus, the formation of an epitaxial coating with a hierarchical atomic structure could enhance the electrochemical performance of LIB cathode materials while preventing large losses in capacity.

  18. Microstructural characterization of irradiated PWR steels using the atom probe field-ion microscope

    SciTech Connect

    Miller, M.K.; Burke, M.G.

    1987-08-01

    Atom probe field-ion microscopy has been used to characterize the microstructure of a neutron-irradiated A533B pressure vessel steel weld. The atomic spatial resolution of this technique permits a complete structural and chemical description of the ultra-fine features that control the mechanical properties to be made. A variety of fine scale features including roughly spherical copper precipitates and clusters, spherical and rod-shaped molybdenum carbide and disc-shaped molybdenum nitride precipitates were observed to be inhomogeneously distributed in the ferrite. The copper content of the ferrite was substantially reduced from the nominal level. A thin film of molybdenum carbides and nitrides was observed on grain boundaries in addition to a coarse copper-manganese precipitate. Substantial enrichment of manganese and nickel were detected at the copper-manganese precipitate-ferrite interface and this enrichment extended into the ferrite. Enrichment of nickel, manganese and phosphorus were also measured at grain boundaries.

  19. Near resonance charge exchange in ion-atom collisions of lithium isotopes.

    PubMed

    Zhang, Peng; Bodo, Enrico; Dalgarno, Alexander

    2009-12-31

    Collisions of ions and atoms of (6)Li and (7)Li are explored theoretically over a wide range of energy from 10(-14) to 1 eV. Accurate ab initio calculations are carried out of the Born-Oppenheimer potentials and the nonadiabatic couplings that are responsible for the near resonance charge exchange. Scattering studies show that the calculated charge exchange cross section follows Wigner's law for inelastic processes for energies below 10(-10) eV and that the zero temperature rate constant for it is 2.1 x 10(-9) cm(3) s(-1). At collision energies much larger than the isotope shift of the ionization potentials of the atoms, we show that the near resonance charge exchange process is equivalent to the resonance charge exchange with cross sections having a logarithmic dependence on energy. A comparison with the Langevin model at intermediate energies is also presented.

  20. Dynamic dipole polarizabilities of the Li atom and the Be{sup +} ion

    SciTech Connect

    Tang Liyan; Yan Zongchao; Shi Tingyun; Mitroy, J.

    2010-04-15

    The dynamic dipole polarizabilities for Li atoms and Be{sup +} ions in the 2 {sup 2}S and 2 {sup 2}P states are calculated using the variational method with a Hylleraas basis. The present polarizabilities represent the definitive values in the nonrelativistic limit. Corrections due to relativistic effects are also estimated. Analytic representations of the polarizabilities for frequency ranges encompassing the n=3 excitations are presented. The recommended polarizabilities for {sup 7}Li and {sup 9}Be{sup +} are 164.11{+-}0.03 a{sub 0}{sup 3} and 24.489{+-}0.004 a{sub 0}{sup 3}, respectively.

  1. High-power Ti:sapphire lasers for spectroscopy of antiprotonic atoms and radioactive ions

    NASA Astrophysics Data System (ADS)

    Hori, M.; Dax, A.; Soter, A.

    The ASACUSA collaboration has developed injection-seeded Ti:sapphire lasers of linewidth Γpl ˜ 6 MHz, pulse energy 50-100 mJ, and output wavelength λ = 726-941 nm. They are being used in two-photon spectroscopy experiments of antiprotonic helium atoms at the Antiproton Decelerator (AD) of CERN. Ti:sapphire lasers of larger linewidth Γpl ˜ 100 MHz but more robust design will also be used in collinear resonance ionization spectroscopy (CRIS) experiments of neutron-deficient francium ions at the ISOLDE facility.

  2. High-power Ti:sapphire lasers for spectroscopy of antiprotonic atoms and radioactive ions

    NASA Astrophysics Data System (ADS)

    Hori, M.; Dax, A.; Soter, A.

    2012-12-01

    The ASACUSA collaboration has developed injection-seeded Ti:sapphire lasers of linewidth Γpl ˜ 6 MHz, pulse energy 50-100 mJ, and output wavelength λ = 726-941 nm. They are being used in two-photon spectroscopy experiments of antiprotonic helium atoms at the Antiproton Decelerator (AD) of CERN. Ti:sapphire lasers of larger linewidth Γpl ˜ 100 MHz but more robust design will also be used in collinear resonance ionization spectroscopy (CRIS) experiments of neutron-deficient francium ions at the ISOLDE facility.

  3. Electron collisions with atoms, ions, molecules, and surfaces: Fundamental science empowering advances in technology

    NASA Astrophysics Data System (ADS)

    Bartschat, Klaus; Kushner, Mark J.

    2016-06-01

    Electron collisions with atoms, ions, molecules, and surfaces are critically important to the understanding and modeling of low-temperature plasmas (LTPs), and so in the development of technologies based on LTPs. Recent progress in obtaining experimental benchmark data and the development of highly sophisticated computational methods is highlighted. With the cesium-based diode-pumped alkali laser and remote plasma etching of Si3N4 as examples, we demonstrate how accurate and comprehensive datasets for electron collisions enable complex modeling of plasma-using technologies that empower our high-technology–based society.

  4. Electron collisions with atoms, ions, molecules, and surfaces: Fundamental science empowering advances in technology

    NASA Astrophysics Data System (ADS)

    Bartschat, Klaus; Kushner, Mark J.

    2016-06-01

    Electron collisions with atoms, ions, molecules, and surfaces are critically important to the understanding and modeling of low-temperature plasmas (LTPs), and so in the development of technologies based on LTPs. Recent progress in obtaining experimental benchmark data and the development of highly sophisticated computational methods is highlighted. With the cesium-based diode-pumped alkali laser and remote plasma etching of Si3N4 as examples, we demonstrate how accurate and comprehensive datasets for electron collisions enable complex modeling of plasma-using technologies that empower our high-technology-based society.

  5. Electron collisions with atoms, ions, molecules, and surfaces: Fundamental science empowering advances in technology.

    PubMed

    Bartschat, Klaus; Kushner, Mark J

    2016-06-28

    Electron collisions with atoms, ions, molecules, and surfaces are critically important to the understanding and modeling of low-temperature plasmas (LTPs), and so in the development of technologies based on LTPs. Recent progress in obtaining experimental benchmark data and the development of highly sophisticated computational methods is highlighted. With the cesium-based diode-pumped alkali laser and remote plasma etching of Si3N4 as examples, we demonstrate how accurate and comprehensive datasets for electron collisions enable complex modeling of plasma-using technologies that empower our high-technology-based society. PMID:27317740

  6. Highly charged ions for atomic clocks, quantum information, and search for α variation.

    PubMed

    Safronova, M S; Dzuba, V A; Flambaum, V V; Safronova, U I; Porsev, S G; Kozlov, M G

    2014-07-18

    We propose 10 highly charged ions as candidates for the development of next generation atomic clocks, quantum information, and search for α variation. They have long-lived metastable states with transition wavelengths to the ground state between 170-3000 nm, relatively simple electronic structure, stable isotopes, and high sensitivity to α variation (e.g., Sm(14+), Pr(10+), Sm(13+), Nd(10+)). We predict their properties crucial for the experimental exploration and highlight particularly attractive systems for these applications. PMID:25083627

  7. Electron collisions with atoms, ions, molecules, and surfaces: Fundamental science empowering advances in technology.

    PubMed

    Bartschat, Klaus; Kushner, Mark J

    2016-06-28

    Electron collisions with atoms, ions, molecules, and surfaces are critically important to the understanding and modeling of low-temperature plasmas (LTPs), and so in the development of technologies based on LTPs. Recent progress in obtaining experimental benchmark data and the development of highly sophisticated computational methods is highlighted. With the cesium-based diode-pumped alkali laser and remote plasma etching of Si3N4 as examples, we demonstrate how accurate and comprehensive datasets for electron collisions enable complex modeling of plasma-using technologies that empower our high-technology-based society.

  8. Three-dimensional simulation of atom and ion dynamics in a stationary plasma thruster

    SciTech Connect

    Lazurenko, A.; Kim, V.; Bishaev, A.; Auweter-Kurtz, M.

    2005-08-15

    A three-dimensional model of atom and ion dynamics in the accelerating channel of a stationary plasma thruster (SPT) is based on the model kinetic equations. Electron dynamics is described based on available experimental data. The expression for the electric field was obtained from the equation of electron impulse conservation law with the use of 'thermalized potential' assumption. The simulation was performed for a particular SPT with a thrust vector deviation. A quantitative agreement with the experimental results was obtained on thrust and thrust vector deviation angles for two different SPT operation modes. Calculated distributions of macroparameters demonstrate azimuthally asymmetrical ionization and acceleration processes in this particular SPT.

  9. Wave packet dynamics of an atomic ion in a Paul trap

    NASA Astrophysics Data System (ADS)

    Hashemloo, A.; Dion, C. M.; Rahali, G.

    2016-07-01

    Using numerical simulations of the time-dependent Schrödinger equation, we study the full quantum dynamics of the motion of an atomic ion in a linear Paul trap. Such a trap is based on a time-varying, periodic electric field and hence corresponds to a time-dependent potential for the ion, which we model exactly. We compare the center-of-mass motion with that obtained from classical equations of motion, as well as to results based on a time-independent effective potential. We also study the oscillations of the width of the ion’s wave packet, including close to the border between stable (bounded) and unstable (unbounded) trajectories. Our results confirm that the center-of-mass motion always follows the classical trajectory, that the width of the wave packet is bounded for trapping within the stability region, and therefore that the classical trapping criterion is fully applicable to quantum motion.

  10. Coating and functionalization of high density ion track structures by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Mättö, Laura; Szilágyi, Imre M.; Laitinen, Mikko; Ritala, Mikko; Leskelä, Markku; Sajavaara, Timo

    2016-10-01

    In this study flexible TiO2 coated porous Kapton membranes are presented having electron multiplication properties. 800 nm crossing pores were fabricated into 50 μm thick Kapton membranes using ion track technology and chemical etching. Consecutively, 50 nm TiO2 films were deposited into the pores of the Kapton membranes by atomic layer deposition using Ti(iOPr)4 and water as precursors at 250 °C. The TiO2 films and coated membranes were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray reflectometry (XRR). Au metal electrode fabrication onto both sides of the coated foils was achieved by electron beam evaporation. The electron multipliers were obtained by joining two coated membranes separated by a conductive spacer. The results show that electron multiplication can be achieved using ALD-coated flexible ion track polymer foils.

  11. Hg-201 (+) CO-Magnetometer for HG-199(+) Trapped Ion Space Atomic Clocks

    NASA Technical Reports Server (NTRS)

    Burt, Eric A. (Inventor); Taghavi, Shervin (Inventor); Tjoelker, Robert L. (Inventor)

    2011-01-01

    Local magnetic field strength in a trapped ion atomic clock is measured in real time, with high accuracy and without degrading clock performance, and the measurement is used to compensate for ambient magnetic field perturbations. First and second isotopes of an element are co-located within the linear ion trap. The first isotope has a resonant microwave transition between two hyperfine energy states, and the second isotope has a resonant Zeeman transition. Optical sources emit ultraviolet light that optically pump both isotopes. A microwave radiation source simultaneously emits microwave fields resonant with the first isotope's clock transition and the second isotope's Zeeman transition, and an optical detector measures the fluorescence from optically pumping both isotopes. The second isotope's Zeeman transition provides the measure of magnetic field strength, and the measurement is used to compensate the first isotope's clock transition or to adjust the applied C-field to reduce the effects of ambient magnetic field perturbations.

  12. A fully relativistic approach for calculating atomic data for highly charged ions

    SciTech Connect

    Zhang, Hong Lin; Fontes, Christopher J; Sampson, Douglas H

    2009-01-01

    We present a review of our fully relativistic approach to calculating atomic data for highly charged ions, highlighting a research effort that spans twenty years. Detailed discussions of both theoretical and numerical techniques are provided. Our basic approach is expected to provide accurate results for ions that range from approximately half ionized to fully stripped. Options for improving the accuracy and range of validity of this approach are also discussed. In developing numerical methods for calculating data within this framework, considerable emphasis is placed on techniques that are robust and efficient. A variety of fundamental processes are considered including: photoexcitation, electron-impact excitation, electron-impact ionization, autoionization, electron capture, photoionization and photorecombination. Resonance contributions to a variety of these processes are also considered, including discussions of autoionization, electron capture and dielectronic recombination. Ample numerical examples are provided in order to illustrate the approach and to demonstrate its usefulness in providing data for large-scale plasma modeling.

  13. Depth distribution of deuterium atoms and molecules in beryllium implanted with D ions

    NASA Astrophysics Data System (ADS)

    Alimov, V. Kh.; Chernikov, V. N.; Zakharov, A. P.

    1997-02-01

    In-depth concentration profiles of deuterium atoms and molecules in beryllium implanted with 9 keV D ions to fluences, Φ, in the range from 6 × 10 19 to 9 × 10 22D/ m2 at temperatures, Tirr, of 300 and 700 K have been determined using SIMS and RGA (residual gas analysis) measurements in the course of surface sputtering. The microstructure of implanted specimens was studied by TEM. Implanted deuterium is retained in Be matrix in the form of both D atoms and D 2 molecules. The total amount of gas captured within the sub-surface layer of ˜ 700 nm in thickness as a result of implantation at 300 and 700 K reaches 4 × 10 21 and 1 × 10 21D/ m2, correspondingly. The ratio of deuterium quantities retained in the form of atoms and molecules, QD: QD2, varies from 1:3 for Tirr = 300 K to 1:4 for Tirr = 700 K. At Tirr = 300 K the concentration of D 2 molecules at the depth of the ion mean range reaches its maximum of 4 × 10 27molecules/ m3 at Φ ≈ 2 × 10 21D/ m2. The molecules are present in tiny bubbles which show a tendency toward interconnection at higher fluences. At Tirr = 700 K, along with relatively small facetted bubbles (near the very surface), large oblate gas-filled cavities and channels forming extended labyrinths appear and they accumulate most of the injected gas. The maximum D 2 concentration in the latter case is of 1 × 10 27molecules/ m3. The high concentration of D atoms in the ion stopping zone after implantation at Tirr = 300 and 700 K (about 2 × 10 27and 1 × 10 27atoms/ m3, respectively) is attributed to deuterium (i) trapped in radiation vacancies, (ii) adsorbed on the walls of bubbles and channels and (iii) bonded to/by BeO formed on the surface and present in the form of metallurgical inclusions in the bulk.

  14. Near-threshold photoionization of hydrogenlike uranium studied in ion-atom collisions via the time-reversed process.

    PubMed

    Stöhlker, T; Ma, X; Ludziejewski, T; Beyer, H F; Bosch, F; Brinzanescu, O; Dunford, R W; Eichler, J; Hagmann, S; Ichihara, A; Kozhuharov, C; Krämer, A; Liesen, D; Mokler, P H; Stachura, Z; Swiat, P; Warczak, A

    2001-02-01

    Radiative electron capture, the time-reversed photoionization process occurring in ion-atom collisions, provides presently the only access to photoionization studies for very highly charged ions. By applying the deceleration mode of the ESR storage ring, we studied this process in low-energy collisions of bare uranium ions with low- Z target atoms. This technique allows us to extend the current information about photoionization to much lower energies than those accessible for neutral heavy elements in the direct reaction channel. The results prove that for high- Z systems, higher-order multipole contributions and magnetic corrections persist even at energies close to the threshold.

  15. Atomic data and theoretical X-ray spectra of Ge-like through V-like W ions

    NASA Astrophysics Data System (ADS)

    Clementson, J.; Beiersdorfer, P.; Brage, T.; Gu, M. F.

    2014-03-01

    The atomic structure and spectra of ten tungsten ions have been calculated using the Flexible Atomic Code. The calculations yield energy levels, radiative lifetimes, spectral line positions, transition probability rates, and oscillator strengths for the tungsten ions isoelectronic to germanium, W42, through vanadium, W51. Collisional-radiative models for high-temperature, low-density plasmas have been implemented to produce line emissivities for X-ray transitions in the 1-4 keV (3-12 Å) spectral interval. The Ge-like through V-like W ions are important in nuclear fusion research where their spectra may provide diagnostic information on magnetically confined plasmas.

  16. Near-threshold photoionization of hydrogenlike uranium studied in ion-atom collisions via the time-reversed process.

    PubMed

    Stöhlker, T; Ma, X; Ludziejewski, T; Beyer, H F; Bosch, F; Brinzanescu, O; Dunford, R W; Eichler, J; Hagmann, S; Ichihara, A; Kozhuharov, C; Krämer, A; Liesen, D; Mokler, P H; Stachura, Z; Swiat, P; Warczak, A

    2001-02-01

    Radiative electron capture, the time-reversed photoionization process occurring in ion-atom collisions, provides presently the only access to photoionization studies for very highly charged ions. By applying the deceleration mode of the ESR storage ring, we studied this process in low-energy collisions of bare uranium ions with low- Z target atoms. This technique allows us to extend the current information about photoionization to much lower energies than those accessible for neutral heavy elements in the direct reaction channel. The results prove that for high- Z systems, higher-order multipole contributions and magnetic corrections persist even at energies close to the threshold. PMID:11177990

  17. Optical field ionization of atoms and ions using ultrashort laser pulses

    SciTech Connect

    Fittinghoff, D.N.

    1993-12-01

    This dissertation research is an investigation of the strong optical field ionization of atoms and ions by 120-fs, 614-run laser pulses and 130-fs, 800-nm laser pulses. The experiments have shown ionization that is enhanced above the predictions of sequential tunneling models for He{sup +2}, Ne{sup +2} and Ar{sup +2}. The ion yields for He{sup +l}, Ne{sup +l} and Ar{sup +l} agree well with the theoretical predictions of optical tunneling models. Investigation of the polarization dependence of the ionization indicates that the enhancements are consistent with a nonsequential ionization mechanism in which the linearly polarized field drives the electron wavefunction back toward the ion core and causes double ionization through inelastic e-2e scattering. These investigations have initiated a number of other studies by other groups and are of current scientific interest in the fields of high-irradiance laser-matter interactions and production of high-density plasmas. This work involved: (1) Understanding the characteristic nature of the ion yields produced by tunneling ionization through investigation of analytic solutions for tunneling at optical frequencies. (2) Extensive characterization of the pulses produced by 614-nm and 800-ran ultrashort pulse lasers. Absolute calibration of the irradiance scale produced shows the practicality of the inverse problem--measuring peak laser irradiance using ion yields. (3) Measuring the ion yields for three noble gases using linear, circular and elliptical polarizations of laser pulses at 614-nm and 800-nm. The measurements are some of the first measurements for pulse widths as low as 120-fs.

  18. Atomic Data for Nebular Abundance Determinations: Photoionization and Recombination Properties of Xenon Ions

    NASA Astrophysics Data System (ADS)

    Sterling, Nicholas C.; Kerlin, Austin B.

    2016-01-01

    We present preliminary results of a study of the photoionization (PI) and recombination properties of low-charge Xe ions. The abundances of neutron(n)-capture elements (atomic number Z > 30) are of interest in planetary nebulae (PNe) since they can be enriched by slow n-capture nucleosynthesis (the ``s-process'') in the progenitor asymptotic giant branch (AGB) stars. Xe is particularly valuable, because it is the most widely-observed ``heavy-s'' species (Z > 40) in PNe. Its abundance relative to lighter n-capture elements can be used to determine s-process neutron exposures, and constrain s-process enrichment patterns as a function of progenitor metallicity. Using the atomic structure code AUTOSTRUCTURE (Badnell 2011, Comp. Phys. Comm., 182, 1528), we have computed multi-configuration Breit-Pauli distorted-wave PI cross sections and radiative recombination (RR) and dielectronic recombination (DR) rate coefficients for neutral through six-times ionized Xe, data which are critically needed for accurate Xe abundance determinations in ionized nebulae. We find good agreement between our computed direct PI cross sections and experimental measurements. Internal uncertainties are estimated for our calculations by using three different configuration interaction expansions for each ion, and by testing the sensitivity of our results to the radial orbital scaling parameters. As found for other n-capture elements (Sterling & Witthoeft 2011, A&A, 529, A147; Sterling 2011, A&A, 533, A62), DR is the dominant recombination mechanism for Xe ions at nebular temperatures (~104 K). Following Sterling et al. (2015, ApJS, 218, 25), these data will be added to nebular modeling codes to compute ionization correction factors for unobserved Xe ions in PNe, which will enable elemental Xe abundances to be determined with much higher accuracy than is currently possible. This work is supported by NSF award AST-1412928.

  19. Two Azimuthally Separated Regions of Cusp Ion Injection Observed via Energetic Neutral Atoms

    NASA Technical Reports Server (NTRS)

    Abe, M.; Taguchi, S.; Collier, M. R.; Moore, T. E.

    2011-01-01

    The low-energy neutral atom (LENA) imager on the IMAGE spacecraft can detect energetic neutral atoms produced by ion injection into the cusp through a charge exchange with the Earth's hydrogen exosphere. We examined the occurrence of the LENA cusp signal during positive IMF B(sub z) in terms of the arrival direction and the IMF clock angle theta(sub CA). Results of statistical analyses show that the occurrence frequency is high on the postnoon side when theta(sub CA) is between approximately 20 degrees and approximately 50 degrees. This is ascribed to ion injection caused by cusp reconnection typical of positive IMF B(sub z). Our results also show that there is another situation of high occurrence frequency, which can be identified with theta(sub CA) of approximately 30 degrees to approximately 80 degrees. When theta(sub CA) is relatively large (60 degrees - 80 degrees), occurrence frequencies are high at relatively low latitudes over a wide extent spanning both prenoon and postnoon sectors. This feature suggests that the ion injection is caused by reconnection at the dayside magnetopause. Its postnoon side boundary shifts toward the prenoon as theta(sub CA) decreases. When theta(sub CA) is less than approximately 50 degrees, the high occurrence frequency exists well inside the prenoon sector, which is azimuthally separated from the postnoon region ascribed to cusp reconnection. The prenoon region, which is thought due to ion injection caused by dayside reconnection, may explain the recent report that proton aurora brightening occurs in the unanticipated prenoon sector of the northern high-latitude ionosphere for IMF B(sub y) greater than 0 and B(sub z) greater than 0.

  20. Atomic scale verification of oxide-ion vacancy distribution near a single grain boundary in YSZ.

    PubMed

    An, Jihwan; Park, Joong Sun; Koh, Ai Leen; Lee, Hark B; Jung, Hee Joon; Schoonman, Joop; Sinclair, Robert; Gür, Turgut M; Prinz, Fritz B

    2013-01-01

    This study presents atomic scale characterization of grain boundary defect structure in a functional oxide with implications for a wide range of electrochemical and electronic behavior. Indeed, grain boundary engineering can alter transport and kinetic properties by several orders of magnitude. Here we report experimental observation and determination of oxide-ion vacancy concentration near the Σ13 (510)/[001] symmetric tilt grain-boundary of YSZ bicrystal using aberration-corrected TEM operated under negative spherical aberration coefficient imaging condition. We show significant oxygen deficiency due to segregation of oxide-ion vacancies near the grain-boundary core with half-width < 0.6 nm. Electron energy loss spectroscopy measurements with scanning TEM indicated increased oxide-ion vacancy concentration at the grain boundary core. Oxide-ion density distribution near a grain boundary simulated by molecular dynamics corroborated well with experimental results. Such column-by-column quantification of defect concentration in functional materials can provide new insights that may lead to engineered grain boundaries designed for specific functionalities.

  1. Atomic Scale Verification of Oxide-Ion Vacancy Distribution near a Single Grain Boundary in YSZ

    PubMed Central

    An, Jihwan; Park, Joong Sun; Koh, Ai Leen; Lee, Hark B.; Jung, Hee Joon; Schoonman, Joop; Sinclair, Robert; Gür, Turgut M.; Prinz, Fritz B.

    2013-01-01

    This study presents atomic scale characterization of grain boundary defect structure in a functional oxide with implications for a wide range of electrochemical and electronic behavior. Indeed, grain boundary engineering can alter transport and kinetic properties by several orders of magnitude. Here we report experimental observation and determination of oxide-ion vacancy concentration near the Σ13 (510)/[001] symmetric tilt grain-boundary of YSZ bicrystal using aberration-corrected TEM operated under negative spherical aberration coefficient imaging condition. We show significant oxygen deficiency due to segregation of oxide-ion vacancies near the grain-boundary core with half-width < 0.6 nm. Electron energy loss spectroscopy measurements with scanning TEM indicated increased oxide-ion vacancy concentration at the grain boundary core. Oxide-ion density distribution near a grain boundary simulated by molecular dynamics corroborated well with experimental results. Such column-by-column quantification of defect concentration in functional materials can provide new insights that may lead to engineered grain boundaries designed for specific functionalities. PMID:24042150

  2. Hydrogen atom temperature measured with wavelength-modulated laser absorption spectroscopy in large scale filament arc negative hydrogen ion source

    SciTech Connect

    Nakano, H. Goto, M.; Tsumori, K.; Kisaki, M.; Ikeda, K.; Nagaoka, K.; Osakabe, M.; Takeiri, Y.; Kaneko, O.; Nishiyama, S.; Sasaki, K.

    2015-04-08

    The velocity distribution function of hydrogen atoms is one of the useful parameters to understand particle dynamics from negative hydrogen production to extraction in a negative hydrogen ion source. Hydrogen atom temperature is one of the indicators of the velocity distribution function. To find a feasibility of hydrogen atom temperature measurement in large scale filament arc negative hydrogen ion source for fusion, a model calculation of wavelength-modulated laser absorption spectroscopy of the hydrogen Balmer alpha line was performed. By utilizing a wide range tunable diode laser, we successfully obtained the hydrogen atom temperature of ∼3000 K in the vicinity of the plasma grid electrode. The hydrogen atom temperature increases as well as the arc power, and becomes constant after decreasing with the filling of hydrogen gas pressure.

  3. Rovibrational molecular populations, atoms, and negative ions in H2 and D2 magnetic multicusp discharges

    NASA Astrophysics Data System (ADS)

    Pealat, M.; Taran, J.-P. E.; Bacal, M.; Hillion, F.

    1985-06-01

    Coherent anti-Stokes Raman scattering is applied to the study of rovibrational populations in magnetic multicusp H2 and D2 discharges. This subject is of interest to negative hydrogen-ion formation by volume plasma processes. The populations of high-lying rotational states (J greater than 5) in the vibrational levels v = 0, 1, and 2 are found to be significantly higher than expected from the Boltzmann law. In H2 the net populations of the first four vibrational levels follow approximately the Boltzmann law, with the vibrational temperature of 2390 K (in a 90 V-10 A discharge at 55 micro bar). In similar discharge conditions, the population of the state v = 3 in D2 is higher than expected from the Boltzmann law. In the presence of the discharge a deficiency in H2 and D2 molecule density was observed and was attributed to the possible presence of H and D atoms. This was verified by an independent measurement of the atomic fraction and temperature. The density of negative ions, measured by the photodetachment technique, is also reported.

  4. Theoretical study of electron capture in ion-ion and ion-atom collisions. Progress report, September 1, 1980-April 30, 1981

    SciTech Connect

    Lieber, M.; Chan, F.T.

    1981-04-01

    The eikonal approximation has been recently shown to be of significant utility in the study of electron capture cross sections for energetic ion-atom collisions. The method generally gives much better agreement with available experimental data than does the simple OBK approximation without substantially increasing the difficulty of computation. In the present work, the total cross section is computed for electron capture into an arbitrary nl subshell of H/sup +/, C/sup +6/, O/sup +8/, and Fe/sup +24/ ions from ground state hydrogen atoms, at energies of 40 to 200 keV/nuclear (30 to 100 keV in the H/sup +/ case). These species were selected because of their importance in fusion studies. Interesting variations with l were obtained. Cross sections for capture into an arbitrary final n-shell, or into all final bound states were also obtained. An analytical closed form expression is derived for electron capture from an arbitrary initial nlm state to an arbitrary final n'l'm' state of a hydrogenic target. Numerical results are presented for all n' = 2,3 final states in hydrogen, which may be subjected to experimental test in the near future. Extension of the eikonal method to multielectron targets was studied. There are ambiguities in the method requiring further analysis. Agreement with experimental data is nevertheless satisfactory, but the high energy results are suspect.

  5. Quasidiatomic Approach to the Collisions of Low KEV Molecular Ions with Atoms

    NASA Astrophysics Data System (ADS)

    Yenen, Orhan

    The polarization of L(,(alpha)) radiation is measured in coincidence with a charged particle scattered at specific laboratory angles, resulting from the collision induced dissociation of low keV H(,2)('+) and H(,3)('+) incident on target gases. Coincidence measurements of the polarization pattern are made for a variety of scattering angles for 3.22 keV H(,2)('+) incident on He and Ne, and for 4.83 keV H(,3)('+) incident on He. The molecular states excited during the collision are determined from the alignment of the observed polarization patterns. A quasidiatomic collision model, which is an extension of the electron promotion model of ion-atom collisions at low keV energies to molecule-atom collisional systems, is developed to interpret the experimental results. The rules of building simple quasidiatomic correlation diagrams, to qualitatively estimate the dynamical behavior of molecular collisions, are presented. The general idea of treating the molecule as an atom under certain circumstances, is applied to a molecular two-state calculation of the differential charge-transfer probabilities in H('+)-H(,2) collisions. This calculation reproduces the essential features of previous experiments.

  6. Database for inelastic collisions of sodium atoms with electrons, protons, and multiply charged ions

    SciTech Connect

    Igenbergs, K.; Schweinzer, J.; Bray, I.; Bridi, D.; Aumayr, F.

    2008-11-15

    The available experimental and theoretical cross section data for inelastic collision processes of ground (3s) and excited (3p, 4s, 3d, 4p, 5s, 4d, and 4f) state Na atoms with electrons, protons, and multiply charged ions have been collected and critically assessed. In addition to existing data, electron-impact cross sections, for both excitation and ionization, have been calculated using the convergent close-coupling approach. In the case of proton-impact cross section, the database was enlarged by new atomic-orbital close-coupling calculations. Both electron-impact and proton-impact processes include excitation from the ground state and between excited states (n = 3-5). For electron-impact, ionization from all states is also considered. In the case of proton-impact electron loss, cross sections (the sum of ionization and single-electron charge transfer) are given. Well-established analytical formulae used to fit cross sections, published by Wutte et al. and Schweinzer et al. for collisions with lithium atoms, were adapted to sodium. The 'recommended cross sections' for the processes considered have been critically evaluated and fitted using the adapted analytical formulae. For each inelastic process the fit parameters determined are tabulated. We also present the assessed data in graphical form. The criteria for comprehensively evaluating the accuracy of the experimental data, theoretical calculations, and procedures used in determining the recommended cross sections are discussed.

  7. Temporal behavior of unresolved transition array emission in water window soft x-ray spectral region from multiply charged ions

    NASA Astrophysics Data System (ADS)

    Dinh, Thanh-Hung; Suzuki, Yuhei; Arai, Goki; Li, Bowen; Dunne, Padraig; O'Sullivan, Gerry; Fujioka, Shinsuke; Hasegawa, Noboru; Kawachi, Tetsuya; Nishikino, Masaharu; Higashiguchi, Takeshi

    2015-09-01

    We have characterized the spectral structure and the temporal history of the laser-produced high-Z multi-charged ion plasmas for the efficient water window soft x-ray sources. Strong unresolved transition array emission was observed due to 4d-4f and 4f-5g transitions from Au, Pb, and Bi plasmas in the 280-700 eV photon energy region. The temporal behavior of the emission was essentially similar of that of the laser pulse with a slight delay between different transitions. These results provide feedback for accurate modeling of the atomic processes with the radiative hydrodynamic simulations.

  8. Temporal behavior of unresolved transition array emission in water window soft x-ray spectral region from multiply charged ions

    SciTech Connect

    Dinh, Thanh-Hung Suzuki, Yuhei; Arai, Goki; Higashiguchi, Takeshi; Li, Bowen; Dunne, Padraig; O'Sullivan, Gerry; Fujioka, Shinsuke; Hasegawa, Noboru; Kawachi, Tetsuya; Nishikino, Masaharu

    2015-09-21

    We have characterized the spectral structure and the temporal history of the laser-produced high-Z multi-charged ion plasmas for the efficient water window soft x-ray sources. Strong unresolved transition array emission was observed due to 4d–4f and 4f–5g transitions from Au, Pb, and Bi plasmas in the 280–700 eV photon energy region. The temporal behavior of the emission was essentially similar of that of the laser pulse with a slight delay between different transitions. These results provide feedback for accurate modeling of the atomic processes with the radiative hydrodynamic simulations.

  9. Electron capture in collisions of Al2+ ions with He atoms at intermediate energies

    NASA Astrophysics Data System (ADS)

    Watanabe, A.; Sato, H.; Gu, J. P.; Hirsch, G.; Buenker, R. J.; Kimura, M.

    2001-09-01

    Electron capture resulting from collisions of Al2+ ions with He atoms from 0.15 to 1000 keV/u is investigated using a molecular-orbital representation within a semiclassical frame. Molecular electronic states and corresponding couplings are determined by the ALCHEMY program. Sixteen molecular states all connecting to single-electron-capture processes are included, and hence radial and rotational couplings among these channels are fully considered. The trajectory effect arising from the straight-line, Coulomb, and ground-state potential trajectories for electron-capture and excitation processes is carefully assessed. The electron-capture cross section by ground-state Al2+(2S) ions slowly increases before it reaches a maximum of 1.3×10-16 cm2 at 100 keV/u. Those for metastable Al2+(2P) ions sharply increase with increasing energy, and reach a peak at 1 keV/u with a value of 1.5×10-16 cm2. The earlier experimental data are found to be larger by an order of magnitude although their energy dependence is in good accord with the present result. Excitation cross sections for both the ground and metastable states are found to be much larger by a factor of 2-3 than corresponding capture cross sections above 1 keV/u although they become comparable below this energy.

  10. Effects of ions and atomic hydrogen in plasma-assisted growth of single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Denysenko, I.; Ostrikov, K.; Yu, M. Y.; Azarenkov, N. A.

    2007-10-01

    The growth of single-walled carbon nanotubes (SWCNTs) in plasma-enhanced chemical vapor deposition (PECVD) is studied using a surface diffusion model. It is shown that at low substrate temperatures (⩽1000K), the atomic hydrogen and ion fluxes from the plasma can strongly affect nanotube growth. The ion-induced hydrocarbon dissociation can be the main process that supplies carbon atoms for SWCNT growth and is responsible for the frequently reported higher (compared to thermal chemical vapor deposition) nanotube growth rates in plasma-based processes. On the other hand, excessive deposition of plasma ions and atomic hydrogen can reduce the diffusion length of the carbon-bearing species and their residence time on the nanotube lateral surfaces. This reduction can adversely affect the nanotube growth rates. The results here are in good agreement with the available experimental data and can be used for optimizing SWCNT growth in PECVD.

  11. Surface Modification and Chemical Sputtering of Graphite Induced by Low Energy Atomic and Molecular Deuterium Ions

    SciTech Connect

    Zhang, Hengda; Meyer, Fred W; Meyer III, Harry M; Lance, Michael J

    2008-01-01

    The surface morphology, and chemical/structural modifications induced during chemical sputtering of ATJ graphite by low-energy (<200 eV/D) deuterium atomic and molecular ions are explored by Scanning Electron Microscopy (SEM), Raman and Auger Electron Spectroscopy (AES) diagnostics. At the lowest impact energies, the ion range may become less than the probe depth of Raman and AES spectroscopy diagnostics. We show that such diagnostics are still useful probes at these energies. As demonstration, we used these surface diagnostics to confirm the characteristic changes of surface texture, increased amorphization, enhanced surface reactivity to impurity species, and increased sp{sup 3} content that low-energy deuterium ion bombardment to steady-state chemical sputtering conditions produces. To put these studies into proper context, we also present new chemical sputtering yields for methane production of ATJ graphite at room temperature by impact of D{sub 2}{sup +} in the energy range 10-250 eV/D, and by impact of D{sup +} and D{sub 3}{sup +} at 30 eV/D and 125 eV/D, obtained using a Quadrupole Mass Spectroscopy (QMS) approach. Below 100 eV/D, the methane production in ATJ graphite is larger than that in HOPG by a factor of {approx} 2. In the energy range 10-60 eV/D, the methane production yield is almost independent of energy and then decreases with increasing ion energies. The results are in good agreement with recent molecular dynamics simulations.

  12. Development of the negative ion beams relevant to ITER and JT-60SA at Japan Atomic Energy Agency.

    PubMed

    Hanada, M; Kojima, A; Tobari, H; Nishikiori, R; Hiratsuka, J; Kashiwagi, M; Umeda, N; Yoshida, M; Ichikawa, M; Watanabe, K; Yamano, Y; Grisham, L R

    2016-02-01

    In order to realize negative ion sources and accelerators to be applicable to International Thermonuclear Experimental Reactor and JT-60 Super Advanced, a large cesium (Cs)-seeded negative ion source and a multi-aperture and multi-stage electric acceleration have been developed at Japan Atomic Energy Agency (JAEA). Long pulse production and acceleration of the negative ion beams have been independently carried out. The long pulse production of the high current beams has achieved 100 s at the beam current of 15 A by modifying the JT-60 negative ion source. The pulse duration time is increased three times longer than that before the modification. As for the acceleration, a pulse duration time has been also extended two orders of magnitudes from 0.4 s to 60 s. The developments of the negative ion source and acceleration at JAEA are well in progress towards the realization of the negative ion sources and accelerators for fusion applications. PMID:26932050

  13. Development of the negative ion beams relevant to ITER and JT-60SA at Japan Atomic Energy Agency.

    PubMed

    Hanada, M; Kojima, A; Tobari, H; Nishikiori, R; Hiratsuka, J; Kashiwagi, M; Umeda, N; Yoshida, M; Ichikawa, M; Watanabe, K; Yamano, Y; Grisham, L R

    2016-02-01

    In order to realize negative ion sources and accelerators to be applicable to International Thermonuclear Experimental Reactor and JT-60 Super Advanced, a large cesium (Cs)-seeded negative ion source and a multi-aperture and multi-stage electric acceleration have been developed at Japan Atomic Energy Agency (JAEA). Long pulse production and acceleration of the negative ion beams have been independently carried out. The long pulse production of the high current beams has achieved 100 s at the beam current of 15 A by modifying the JT-60 negative ion source. The pulse duration time is increased three times longer than that before the modification. As for the acceleration, a pulse duration time has been also extended two orders of magnitudes from 0.4 s to 60 s. The developments of the negative ion source and acceleration at JAEA are well in progress towards the realization of the negative ion sources and accelerators for fusion applications.

  14. Ultracold magnetically tunable interactions without radiative-charge-transfer losses between Ca+, Sr+, Ba+, and Yb+ ions and Cr atoms

    NASA Astrophysics Data System (ADS)

    Tomza, Michał

    2015-12-01

    The Ca+, Sr+, Ba+, and Yb+ ions immersed in an ultracold gas of the Cr atoms are proposed as experimentally feasible heteronuclear systems in which ion-atom interactions at ultralow temperatures can be controlled with magnetically tunable Feshbach resonances without charge transfer and radiative losses. Ab initio techniques are applied to investigate electronic-ground-state properties of the (CaCr)+, (SrCr)+, (BaCr)+, and (YbCr)+ molecular ions. The potential energy curves, permanent electric dipole moments, and static electric dipole polarizabilities are computed. The spin-restricted open-shell coupled-cluster method restricted to single, double, and noniterative triple excitations and the multireference configuration-interaction method restricted to single and double excitations are employed. The scalar relativistic effects are included within the small-core energy-consistent pseudopotentials. The leading long-range induction and dispersion interaction coefficients are also reported. Finally, magnetic Feshbach resonances between the Ca+, Sr+, Ba+, and Yb+ ions interacting with the Cr atoms are analyzed. The present proposal opens the way towards robust quantum simulations and computations with ultracold ion-atom systems free of radiative charge-transfer losses.

  15. Atomic force microscopy studies on molybdenum disulfide flakes as sodium-ion anodes.

    PubMed

    Lacey, Steven D; Wan, Jiayu; von Wald Cresce, Arthur; Russell, Selena M; Dai, Jiaqi; Bao, Wenzhong; Xu, Kang; Hu, Liangbing

    2015-02-11

    A microscale battery comprised of mechanically exfoliated molybdenum disulfide (MoS2) flakes with copper connections and a sodium metal reference was created and investigated as an intercalation model using in situ atomic force microscopy in a dry room environment. While an ethylene carbonate-based electrolyte with a low vapor pressure allowed topographical observations in an open cell configuration, the planar microbattery was used to conduct in situ measurements to understand the structural changes and the concomitant solid electrolyte interphase (SEI) formation at the nanoscale. Topographical observations demonstrated permanent wrinkling behavior of MoS2 electrodes upon sodiation at 0.4 V. SEI formation occurred quickly on both flake edges and planes at voltages before sodium intercalation. Force spectroscopy measurements provided quantitative data on the SEI thickness for MoS2 electrodes in sodium-ion batteries for the first time. PMID:25549278

  16. Electron-impact ionization of moderately charged atomic ions in excited states

    SciTech Connect

    Pindzola, M. S.; Ballance, C. P.; Loch, S. D.

    2011-06-15

    Nonperturbative R-matrix and perturbative distorted-wave methods are used to calculate electron-impact ionization cross sections for C{sup 3+} in excited states. Convergence studies for the cross sections of the 1s{sup 2}5s excited configuration reveal that both the R-matrix and distorted-wave methods need fairly high ejected electron angular momenta. Reasonable agreement is found between the converged R-matrix and distorted-wave cross sections. Thus, the use of the computationally less demanding distorted-wave method as a tool for the n scaling of excited-state ionization cross sections appears to be reasonable for atomic ions with charge q{>=}3.

  17. Numerical analysis of atomic density distribution in arc driven negative ion sources

    SciTech Connect

    Yamamoto, T. Shibata, T.; Hatayama, A.; Kashiwagi, M.; Hanada, M.; Sawada, K.

    2014-02-15

    The purpose of this study is to calculate atomic (H{sup 0}) density distribution in JAEA 10 ampere negative ion source. A collisional radiative model is developed for the calculation of the H{sup 0} density distribution. The non-equilibrium feature of the electron energy distribution function (EEDF), which mainly determines the H{sup 0} production rate, is included by substituting the EEDF calculated from 3D electron transport analysis. In this paper, the H{sup 0} production rate, the ionization rate, and the density distribution in the source chamber are calculated. In the region where high energy electrons exist, the H{sup 0} production and the ionization are enhanced. The calculated H{sup 0} density distribution without the effect of the H{sup 0} transport is relatively small in the upper region. In the next step, the effect should be taken into account to obtain more realistic H{sup 0} distribution.

  18. Simultaneous Scanning Ion Conductance Microscopy and Atomic Force Microscopy with Microchanneled Cantilevers

    NASA Astrophysics Data System (ADS)

    Ossola, Dario; Dorwling-Carter, Livie; Dermutz, Harald; Behr, Pascal; Vörös, János; Zambelli, Tomaso

    2015-12-01

    We combined scanning ion conductance microscopy (SICM) and atomic force microscopy (AFM) into a single tool using AFM cantilevers with an embedded microchannel flowing into the nanosized aperture at the apex of the hollow pyramid. An electrode was positioned in the AFM fluidic circuit connected to a second electrode in the bath. We could thus simultaneously measure the ionic current and the cantilever bending (in optical beam deflection mode). First, we quantitatively compared the SICM and AFM contact points on the approach curves. Second, we estimated where the probe in SICM mode touches the sample during scanning on a calibration grid and applied the finding to image a network of neurites on a Petri dish. Finally, we assessed the feasibility of a double controller using both the ionic current and the deflection as input signals of the piezofeedback. The experimental data were rationalized in the framework of finite elements simulations.

  19. Analysis of atomic and ion debris features of laser-produced Sn and Li plasmas

    SciTech Connect

    Coons, R. W.; Harilal, S. S.; Campos, D.; Hassanein, A.

    2010-09-15

    Tin and lithium plasmas emit efficiently in the in-band region (13.5 nm with 2% bandwidth) necessary for extreme ultraviolet (EUV) lithography. We have made a detailed comparison of the atomic and ionic debris, as well as the emission features of Sn and Li plasmas under identical experimental conditions. Planar slabs of pure Sn and Li were irradiated with 1064 nm, 9 ns neodymium-doped yttrium aluminum garnet laser pulses for producing plasmas. A suite of diagnostics were used to analyze the emission and debris features, including optical emission spectroscopy (OES), a Faraday cup, an EUV pinhole camera, the absolute measurement of EUV conversion efficiency (CE), etc. Our results show that Sn plasmas provide a CE nearly twice that of Li. However, the kinetic energies of Sn ions are considerably higher, though with a lower flux. OES studies have showed that the kinetic energies of neutral species are substantially lower compared to that of the charged particle species.

  20. Experiments on continuum electron capture in atomic hydrogen and collisional interaction of trapped ions. Progress report

    SciTech Connect

    Sellin, I.A.; Elston, S.B.

    1981-01-01

    This section describes the background and scope of as well as progress made on experiments designed to test the present theory of charge exchange to continuum for the case of bare nuclei on atomic hydrogen. The charge transfer process is well known to be an essential ingredient of any attempt to understand the ionization of gaseous media traversed by highly-charged energetic ions. Surprisingly, a sometimes dominant contribution to such ionization remained undiscovered until the past decade. This process, known as charge transfer to the continuum, involves the ionization of electrons from the target species into unbound states closely matched in exit direction and speed to the charged particles which generate them. Subsequent measurements of the resultant forward electron production, performed by University of Tennessee searchers at Oak Ridge and Brookhaven National Laboratories, were unique in employing more highly charged projectiles than previously.

  1. Simultaneous Scanning Ion Conductance Microscopy and Atomic Force Microscopy with Microchanneled Cantilevers.

    PubMed

    Ossola, Dario; Dorwling-Carter, Livie; Dermutz, Harald; Behr, Pascal; Vörös, János; Zambelli, Tomaso

    2015-12-01

    We combined scanning ion conductance microscopy (SICM) and atomic force microscopy (AFM) into a single tool using AFM cantilevers with an embedded microchannel flowing into the nanosized aperture at the apex of the hollow pyramid. An electrode was positioned in the AFM fluidic circuit connected to a second electrode in the bath. We could thus simultaneously measure the ionic current and the cantilever bending (in optical beam deflection mode). First, we quantitatively compared the SICM and AFM contact points on the approach curves. Second, we estimated where the probe in SICM mode touches the sample during scanning on a calibration grid and applied the finding to image a network of neurites on a Petri dish. Finally, we assessed the feasibility of a double controller using both the ionic current and the deflection as input signals of the piezofeedback. The experimental data were rationalized in the framework of finite elements simulations. PMID:26684144

  2. Ion-reversibility studies in amorphous solids using the two-atom scattering model. [Rutherford backscattering from disordered solids

    SciTech Connect

    Oen, O.S.

    1981-06-01

    An analytical two-atom scattering model has been developed to treat the recent discovery of the enhancement near 180/sup 0/ of Rutherford backscattering yields from disordered solids. In contrast to conventional calculations of Rutherford backscattering that treat scattering from a single atom only (the backscattering atom), the present model includes the interaction of a second atom lying between the target surface and the backscattering plane. The projectile ion makes a glancing collision with this second atom both before and after it is backscattered. The model predicts an enhancement effect whose physical origin arises from the tolerance of path for those ions whose inward and outward trajectories lie in the vicinity of the critical impact parameter. Results using Moliere scattering show how the yield enhancement depends on ion energy, backscattering depth, exit angle, scattering potential, atomic numbers of the projectile and target, and target density. In the model the critical impact parameter and critical angle play important roles. It is shown that these quantities depend on a single dimensionless parameter and analytical expressions for them are given which are accurate to better than 1%.

  3. Wave-packet continuum-discretization approach to ion-atom collisions: Nonrearrangement scattering

    NASA Astrophysics Data System (ADS)

    Abdurakhmanov, I. B.; Kadyrov, A. S.; Bray, I.

    2016-08-01

    A general single-center close-coupling approach based on a continuum-discretization procedure is developed to calculate excitation and ionization processes in ion-atom collisions. The continuous spectrum of the target is discretized using stationary wave packets constructed from the Coulomb wave functions, the eigenstates of the target Hamiltonian. Such continuum discretization allows one to generate pseudostates with arbitrary energies and distribution. These features are ideal for detailed differential ionization studies. The approach starts from the semiclassical three-body Schrödinger equation for the scattering wave function and leads to a set of coupled differential equations for the transition probability amplitudes. To demonstrate its utility the method is applied to calculate collisions of antiprotons with atomic hydrogen. A comprehensive set of benchmark results from integrated to fully differential cross sections for antiproton-impact ionization of hydrogen in the energy range from 1 keV to 1 MeV is provided. Contrary to previous predictions, we find that at low incident energies the singly differential cross section has a maximum away from the zero emission energy. This feature could not be seen without a fine discretization of the low-energy part of the continuum.

  4. Atomic resolution study of reversible conversion reaction in metal oxide electrodes for lithium-ion battery.

    PubMed

    Luo, Langli; Wu, Jinsong; Xu, Junming; Dravid, Vinayak P

    2014-11-25

    Electrode materials based on conversion reactions with lithium ions have shown much higher energy density than those based on intercalation reactions. Here, nanocubes of a typical metal oxide (Co3O4) were grown on few-layer graphene, and their electrochemical lithiation and delithiation were investigated at atomic resolution by in situ transmission electron microscopy to reveal the mechanism of the reversible conversion reaction. During lithiation, a lithium-inserted Co3O4 phase and a phase consisting of nanosized Co-Li-O clusters are identified as the intermediate products prior to the subsequent formation of Li2O crystals. In delithiation, the reduced metal nanoparticles form a network and breakdown into even smaller clusters that act as catalysts to prompt reduction of Li2O, and CoO nanoparticles are identified as the product of the deconversion reaction. Such direct real-space, real-time atomic-scale observations shed light on the phenomena and mechanisms in reaction-based electrochemical energy conversion and provide impetus for further development in electrochemical charge storage devices.

  5. Atom ejection from a fast-ion track: A molecular-dynamics study

    SciTech Connect

    Urbassek, H.M. ); Kafemann, H. ); Johnson, R.E. )

    1994-01-01

    As a model for atom ejection from fast-ion tracks, molecular-dynamics simulations of a cylindrical track of energized particles are performed. An idealized situation is studied where every atom in a cylindrical track of radius [ital R][sub 0] is energized with energy [ital E][sub 0]. The emission yield [ital Y]([ital E][sub 0],[ital R][sub 0]) shows the existence of two ejection regimes. If the particle energy [ital E][sub 0] is below the sublimation energy [ital U] of the material, a threshold regime is seen in which [ital Y] rises roughly like the third power of [ital E][sub 0]; for high-energy densities [ital E][sub 0][approx gt][ital U], the yield rises much more slowly, roughly linearly. In both cases, ejected particles mostly originate from the track, rather than from its surroundings, and from the first or the first few monolayers. The behavior found is interpreted here in terms of emission due to a pressure-driven jet (linear regime) or due to a pressure pulse (threshold regime). These both behave differently from the often-used thermal-spike sputtering model.

  6. Electron emission in collisions of fast highly charged bare ions with helium atoms

    NASA Astrophysics Data System (ADS)

    Mondal, Abhoy; Mandal, Chittranjan; Purkait, Malay

    2016-01-01

    We have studied the electron emission from ground state helium atom in collision with fast bare heavy ions at intermediate and high incident energies. In the present study, we have applied the present three-body formalism of the three Coulomb wave (3C-3B) model and the previously adopted four-body formalism of the three Coulomb wave (3C-4B). To represent the active electron in the helium atom in the 3C-3B model, the initial bound state wavefunction is chosen to be hydrogenic with an effective nuclear charge. The wavefunction for the ejected electron in the exit channel has been approximated to be a Coulomb continuum wavefunction with same effective nuclear charge. Effectively the continuum-continuum correlation effect has been considered in the present investigation. Here we have calculated the energy and angular distribution of double differential cross sections (DDCS) at low and high energy electron emission from helium atom. The large forward-backward asymmetry is observed in the angular distribution which is explained in terms of the two-center effect (TCE). Our theoretical results are compared with available experimental results as well as other theoretical calculations based on the plain wave Born approximation (PWBA), continuum-distorted wave (CDW) approximation, continuum-distorted wave eikonal-initial state (CDW-EIS) approximation, and the corresponding values obtained from the 3C-4B model [S. Jana, R. Samanta, M. Purkait, Phys. Scr. 88, 055301 (2013)] respectively. It is observed that the four-body version of the present investigation produces results which are in better agreement with experimental observations for all cases.

  7. Conversion of an atomic to a molecular argon ion and low pressure argon relaxation

    NASA Astrophysics Data System (ADS)

    M, N. Stankov; A, P. Jovanović; V, Lj Marković; S, N. Stamenković

    2016-01-01

    The dominant process in relaxation of DC glow discharge between two plane parallel electrodes in argon at pressure 200 Pa is analyzed by measuring the breakdown time delay and by analytical and numerical models. By using the approximate analytical model it is found that the relaxation in a range from 20 to 60 ms in afterglow is dominated by ions, produced by atomic-to-molecular conversion of Ar+ ions in the first several milliseconds after the cessation of the discharge. This conversion is confirmed by the presence of double-Gaussian distribution for the formative time delay, as well as conversion maxima in a set of memory curves measured in different conditions. Finally, the numerical one-dimensional (1D) model for determining the number densities of dominant particles in stationary DC glow discharge and two-dimensional (2D) model for the relaxation are used to confirm the previous assumptions and to determine the corresponding collision and transport coefficients of dominant species and processes. Project supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia (Grant No. ON171025).

  8. Atomic layer deposited tungsten nitride thin films as a new lithium-ion battery anode.

    PubMed

    Nandi, Dip K; Sen, Uttam K; Sinha, Soumyadeep; Dhara, Arpan; Mitra, Sagar; Sarkar, Shaibal K

    2015-07-14

    This article demonstrates the atomic layer deposition (ALD) of tungsten nitride using tungsten hexacarbonyl [W(CO)6] and ammonia [NH3] and its use as a lithium-ion battery anode. In situ quartz crystal microbalance (QCM), ellipsometry and X-ray reflectivity (XRR) measurements are carried out to confirm the self-limiting behaviour of the deposition. A saturated growth rate of ca. 0.35 Å per ALD cycle is found within a narrow temperature window of 180-195 °C. In situ Fourier transform infrared (FTIR) vibrational spectroscopy is used to determine the reaction pathways of the surface bound species after each ALD half cycle. The elemental presence and chemical composition is determined by XPS. The as-deposited material is found to be amorphous and crystallized to h-W2N upon annealing at an elevated temperature under an ammonia atmosphere. The as-deposited materials are found to be n-type, conducting with an average carrier concentration of ca. 10(20) at room temperature. Electrochemical studies of the as-deposited films open up the possibility of this material to be used as an anode material in Li-ion batteries. The incorporation of MWCNTs as a scaffold layer further enhances the electrochemical storage capacity of the ALD grown tungsten nitride (WNx). Ex situ XRD analysis confirms the conversion based reaction mechanism of the as-grown material with Li under operation. PMID:26076771

  9. Inhibitive formation of nanocavities by introduction of Si atoms in Ge nanocrystals produced by ion implantation

    SciTech Connect

    Cai, R. S.; Shang, L.; Liu, X. H.; Zhang, Y. J.; Wang, Y. Q. E-mail: barba@emt.inrs.ca; Ross, G. G.; Barba, D. E-mail: barba@emt.inrs.ca

    2014-05-28

    Germanium nanocrystals (Ge-nc) were successfully synthesized by co-implantation of Si and Ge ions into a SiO{sub 2} film thermally grown on (100) Si substrate and fused silica (pure SiO{sub 2}), respectively, followed by subsequent annealing at 1150 °C for 1 h. Transmission electron microscopy (TEM) examinations show that nanocavities only exist in the fused silica sample but not in the SiO{sub 2} film on a Si substrate. From the analysis of the high-resolution TEM images and electron energy-loss spectroscopy spectra, it is revealed that the absence of nanocavities in the SiO{sub 2} film/Si substrate is attributed to the presence of Si atoms inside the formed Ge-nc. Because the energy of Si-Ge bonds (301 kJ·mol{sup −1}) are greater than that of Ge-Ge bonds (264 kJ·mol{sup −1}), the introduction of the Si-Ge bonds inside the Ge-nc can inhibit the diffusion of Ge from the Ge-nc during the annealing process. However, for the fused silica sample, no crystalline Si-Ge bonds are detected within the Ge-nc, where strong Ge outdiffusion effects produce a great number of nanocavities. Our results can shed light on the formation mechanism of nanocavities and provide a good way to avoid nanocavities during the process of ion implantation.

  10. Ion-exchange preconcentration and determination of vanadium in milk samples by electrothermal atomic absorption spectrometry.

    PubMed

    López-García, Ignacio; Viñas, Pilar; Romero-Romero, Rafael; Hernández-Córdoba, Manuel

    2009-06-15

    A new method for the electrothermal atomic absorption spectrometric determination of vanadium in milk and infant formulas using suspensions to avoid the need for previous dissolution of samples is described. Sensitivity is improved by a procedure based on preconcentration and removal of the matrix, using ion-exchange (Dowex 1X8-100). Suspensions of 15% (m/v) infant formula samples were prepared in a medium containing 0.05M sodium citrate (pH 7.2) and passed through the ion exchange column. Vanadium was eluted from the column using 1M hydrochloric acid and injected in the graphite furnace using a mixture of hydrofluoric acid plus magnesium nitrate as chemical modifiers. Calibration was carried out using multiple injection and aqueous standards prepared in the same medium. Detection limits were 0.2 ng g(-1) for infant formulas and 0.02 microg L(-1) for cow milk samples. The reliability of the procedure was checked by comparing the results obtained with those found using a previous mineralization stage and by analyzing five certified reference materials.

  11. Multiple ionization and coupling effects in L-subshell ionization of heavy atoms by oxygen ions

    SciTech Connect

    Pajek, M.; Banas, D.; Semaniak, J.; Braziewicz, J.; Majewska, U.; Chojnacki, S.; Czyzewski, T.; Fijal, I.; Jaskola, M.; Glombik, A.; Kretschmer, W.; Trautmann, D.; Lapicki, G.; Mukoyama, T.

    2003-08-01

    The multiple-ionization and coupling effects in L-shell ionization of atoms by heavy-ion impact have been studied by measuring the L x-ray production cross sections in solid targets of Au, Bi, Th, and U bombarded by oxygen ions in the energy range 6.4-70 MeV. The measured L x-ray spectra were analyzed using the recently proposed method accounting for the multiple-ionization effects, such as x-ray line shifting and broadening, which enables one to obtain the ionization probabilities for outer shells. The L-subshell ionization cross sections have been obtained from measured x-ray production cross sections for resolved L{alpha}{sub 1,2}, L{gamma}{sub 1}, and L{gamma}{sub 2,3} transitions using the L-shell fluorescence and Coster-Kronig yields being substantially modified by the multiple ionization in the M and N shells. In particular, the effect of closing of strong L{sub 1}-L{sub 3}M{sub 4,5} Coster-Kronig transitions in multiple-ionized atoms was evidenced and discussed. The experimental ionization cross sections for the L{sub 1}, L{sub 2}, and L{sub 3} subshells have been compared with the predictions of the semiclassical approximation (SCA) and the ECPSSR theory that includes the corrections for the binding-polarization effect within the perturbed stationary states approximation, the projecticle energy loss, and Coulomb deflection effects as well as the relativistic description of inner-shell electrons. These approaches were further modified to include the L-subshell couplings within the ''coupled-subshell model'' (CSM). Both approaches, when modified for the coupling effects, are in better agreement with the data. Particularly, the predictions of the SCA-CSM calculations reproduce the experimental L-subshell ionization cross section reasonably well. Remaining discrepancies are discussed qualitatively, in terms of further modifications of the L-shell decay rates caused by a change of electronic wave functions in multiple-ionized atoms.

  12. Metal-Organic Framework Thin Films as Platforms for Atomic Layer Deposition of Cobalt Ions To Enable Electrocatalytic Water Oxidation.

    PubMed

    Kung, Chung-Wei; Mondloch, Joseph E; Wang, Timothy C; Bury, Wojciech; Hoffeditz, William; Klahr, Benjamin M; Klet, Rachel C; Pellin, Michael J; Farha, Omar K; Hupp, Joseph T

    2015-12-30

    Thin films of the metal-organic framework (MOF) NU-1000 were grown on conducting glass substrates. The films uniformly cover the conducting glass substrates and are composed of free-standing sub-micrometer rods. Subsequently, atomic layer deposition (ALD) was utilized to deposit Co(2+) ions throughout the entire MOF film via self-limiting surface-mediated reaction chemistry. The Co ions bind at aqua and hydroxo sites lining the channels of NU-1000, resulting in three-dimensional arrays of separated Co ions in the MOF thin film. The Co-modified MOF thin films demonstrate promising electrocatalytic activity for water oxidation.

  13. Metal-Organic Framework Thin Films as Platforms for Atomic Layer Deposition of Cobalt Ions To Enable Electrocatalytic Water Oxidation.

    PubMed

    Kung, Chung-Wei; Mondloch, Joseph E; Wang, Timothy C; Bury, Wojciech; Hoffeditz, William; Klahr, Benjamin M; Klet, Rachel C; Pellin, Michael J; Farha, Omar K; Hupp, Joseph T

    2015-12-30

    Thin films of the metal-organic framework (MOF) NU-1000 were grown on conducting glass substrates. The films uniformly cover the conducting glass substrates and are composed of free-standing sub-micrometer rods. Subsequently, atomic layer deposition (ALD) was utilized to deposit Co(2+) ions throughout the entire MOF film via self-limiting surface-mediated reaction chemistry. The Co ions bind at aqua and hydroxo sites lining the channels of NU-1000, resulting in three-dimensional arrays of separated Co ions in the MOF thin film. The Co-modified MOF thin films demonstrate promising electrocatalytic activity for water oxidation. PMID:26636174

  14. A setup for transmission measurements of low energy multiply charged ions through free-standing few atomic layer films

    NASA Astrophysics Data System (ADS)

    Smejkal, V.; Gruber, E.; Wilhelm, R. A.; Brandl, L.; Heller, R.; Facsko, S.; Aumayr, F.

    2016-09-01

    We report the design and testing of a setup for transmission measurements of multiply charged ions through free-standing films with a thickness of a few atomic layers. The investigation thereof can yield deeper insight into charge equilibration and pre-equilibrium stopping phenomena which can ultimately be used to specifically tailor and modify these materials.

  15. Experimental measurement of the mobilities of atomic and dimer Ar, Kr, and Xe ions in their parent gases

    NASA Astrophysics Data System (ADS)

    Neves, P. N. B.; Conde, C. A. N.; Távora, L. M. N.

    2010-09-01

    A new experimental technique for measuring the mobilities of positive ions in their parent gases is presented. The technique was applied to the rare gases, Ar, Kr, and Xe, and, for pressures typically below 10 Torr, two different types of positive ions were observed. The reduced mobilities of these ions in their parent gases were measured as a function of E /N, the ratio of the electric field strength to the gas number density, at a temperature of 300±1 K. The results were compared with others available in the literature and the two ions were identified as being the atomic and the dimer rare gas ions. The results are in good agreement with those from other authors. Space charge and impurities effects are discussed.

  16. Characterization of ion-irradiation-induced nanodot structures on InP surfaces by atom probe tomography.

    PubMed

    Gnaser, Hubert; Radny, Tobias

    2015-12-01

    Surfaces of InP were bombarded by 1.9 keV Ar(+) ions under normal incidence. The total accumulated ion fluence the samples were exposed to was varied from 1 × 10(17) cm(-2) to 3 × 10(18)cm(-2) and ion flux densities f of (0.4-2) × 10(14) cm(-2) s(-1) were used. Nanodot structures were found to evolve on the surface from these ion irradiations, their dimensions however, depend on the specific bombardment conditions. The resulting surface morphology was examined by atomic force microscopy (AFM). As a function of ion fluence, the mean radius, height, and spacing of the dots can be fitted by power-law dependences. In order to determine possible local compositional changes in these nanostructures induced by ion impact, selected samples were prepared for atom probe tomography (APT). The results indicate that by APT the composition of individual InP nanodots evolving under ion bombardment could be examined with atomic spatial resolution. At the InP surface, the values of the In/P concentration ratio are distinctly higher over a distance of ~1 nm and amount to 1.3-1.8. However, several aspects critical for the analyses were identified: (i) because of the small dimensions of these nanostructures a successful tip preparation proved very challenging. (ii) The elemental compositions obtained from APT were found to be influenced pronouncedly by the laser pulse energy; typically, low energies result in the correct stoichiometry whereas high ones lead to an inhomogeneous evaporation from the tips and deviations from the nominal composition. (iii) Depending again on the laser energy, a prolific emission of Pn cluster ions was observed, with n ≤ 11. PMID:25980895

  17. Characterization of ion-irradiation-induced nanodot structures on InP surfaces by atom probe tomography.

    PubMed

    Gnaser, Hubert; Radny, Tobias

    2015-12-01

    Surfaces of InP were bombarded by 1.9 keV Ar(+) ions under normal incidence. The total accumulated ion fluence the samples were exposed to was varied from 1 × 10(17) cm(-2) to 3 × 10(18)cm(-2) and ion flux densities f of (0.4-2) × 10(14) cm(-2) s(-1) were used. Nanodot structures were found to evolve on the surface from these ion irradiations, their dimensions however, depend on the specific bombardment conditions. The resulting surface morphology was examined by atomic force microscopy (AFM). As a function of ion fluence, the mean radius, height, and spacing of the dots can be fitted by power-law dependences. In order to determine possible local compositional changes in these nanostructures induced by ion impact, selected samples were prepared for atom probe tomography (APT). The results indicate that by APT the composition of individual InP nanodots evolving under ion bombardment could be examined with atomic spatial resolution. At the InP surface, the values of the In/P concentration ratio are distinctly higher over a distance of ~1 nm and amount to 1.3-1.8. However, several aspects critical for the analyses were identified: (i) because of the small dimensions of these nanostructures a successful tip preparation proved very challenging. (ii) The elemental compositions obtained from APT were found to be influenced pronouncedly by the laser pulse energy; typically, low energies result in the correct stoichiometry whereas high ones lead to an inhomogeneous evaporation from the tips and deviations from the nominal composition. (iii) Depending again on the laser energy, a prolific emission of Pn cluster ions was observed, with n ≤ 11.

  18. Two-electron excitation in slow ion-atom collisions: Excitation mechanisms and interferences among autoionizing states

    SciTech Connect

    Kimura, M. Rice Univ., Houston, TX . Dept. of Physics)

    1990-01-01

    The two-electron capture or excitation process resulting from collisions of H{sup +} and O{sup 6+} ions with He atoms in the energy range from 0.5 keV/amu to 5 keV/amu is studied within a molecular representation. The collision dynamics for formation of doubly excited O{sup 4+} ions and He** atoms and their (n{ell}, n{prime}{ell}{prime}) populations are analyzed in conjunction with electron correlations. Autoionizing states thus formed decay through the Auger process. An experimental study of an ejected electron energy spectrum shows ample structures in addition to two characteristic peaks that are identified by atomic and molecular autoionizations. These structures are attributable to various interferences among electronic states and trajectories. We examine the dominant sources of the interferences. 12 refs., 5 figs.

  19. Effective atomic numbers of biological materials in the energy region 1 to 50 MeV for photons, electrons, and He ions.

    PubMed

    Parthasaradhi, K; Rao, B M; Prasad, S G

    1989-01-01

    A study of effective atomic numbers for biological materials such as bone, muscle, spleen, liver, mucin, and water has been carried out in the energy region 1 to 50 MeV for photons, electrons, and He ions. It is noticed that the effective atomic number for photons and electrons increases with energy, and remains, more or less the same, for He ions.

  20. Energetic ion, atom, and molecule reactions and excitation in low-current H2 discharges: H(alpha) Doppler profiles.

    PubMed

    Petrović, Z Lj; Phelps, A V

    2009-12-01

    Absolute spectral emissivities for Doppler broadened H(alpha) profiles are measured and compared with predictions of energetic hydrogen ion, atom, and molecule behavior in low-current electrical discharges in H2 at very high electric field E to gas density N ratios E/N and low values of Nd , where d is the parallel-plate electrode separation. These observations reflect the energy and angular distributions for the excited atoms and quantitatively test features of multiple-scattering kinetic models in weakly ionized hydrogen in the presence of an electric field that are not tested by the spatial distributions of H(alpha) emission. Absolute spectral intensities agree well with predictions. Asymmetries in Doppler profiles observed parallel to the electric field at 4atoms directed toward the cathode and diffusely reflected from the cathode. (1 Td=10(-21) V m(2)) The effects of reflection of hydrogen particles and of changes with cathode material are modeled accurately without adjustable parameters. Maximum measured wavelength shifts result from acceleration of H+ ions and charge transfer to fast H atoms. The Doppler profiles are consistent with models of reactions among H+, H2+, H3 , H, and H2 leading to fast H atoms and then fast excited H(n=3) atoms. PMID:20365280

  1. Formation and atomic configuration of binary metallic glasses studied by ion beam mixing and molecular dynamics simulation

    SciTech Connect

    Tai, K. P.; Gao, N.; Dai, X. D.; Li, J. H.; Liu, B. X.

    2007-06-15

    Metallic glasses are obtained in an immiscible Ag-Nb system with overall composition ranging from 25 to 90 at. % of Nb by ion beam mixing. Interestingly, the diffraction analysis shows that the formed Nb-rich metallic glass features are two distinct atomic configurations. In atomistic modeling, an n-body Ag-Nb potential is derived, under the assistance of ab initio calculation, and then applied in molecular dynamics simulations. An atomic configuration is discovered, i.e., an icositetrahedral ordering, and as well as an icosahedral ordering observed in the Ag-Nb metallic glasses and in some previously reported systems. Simulations confirm that the two dominate local atomic packing units are formed through a structural phase transition from the Nb-based bcc and fcc solid solutions, respectively, suggesting a concept of structural heredity that the crystalline structure of the constituent metals play a decisive role in determining the atomic structure of the resultant metallic glasses.

  2. Investigating Global Ion and Neutral Atom Populations with IBEX and Voyager

    NASA Technical Reports Server (NTRS)

    Florinski, Vladimir

    2016-01-01

    The main objective of this project was to investigate pickup ion (PUI) production in the solar wind and heliosheath (the region between the termination shock and the heliopause) and compute the distributed energetic neutral atom fluxes throughout the helioshpere. The simulations were constrained by comparing the model output against observations from Ulysses, New Horizons, Voyager 1 and 2, and IBEX space probes. As evidenced by the number of peer reviewed journal publications resulting from the project (13 plus three submitted) and their citation rate (156 citations over three years), the project has made a lasting contribution to the field. The outcome is a significant improvement of our understanding of the pickup ion production and distribution in the distant heliosphere. The team has accomplished the entire set of tasks A-H set forth in the proposal. Namely, the transport modeling framework has been augmented with two populations of pickup ions (PUIs), the boundary conditions for the plasma and interstellar neutral hydrogen were verified against Ulysses and New Horizons PUI and an optimal set of velocity diffusion parameters established. The multi-component fluxes of PUIs were computed and isotropic velocity distributions generated for each cell in the computer simulation that covered the heliosphere from 1.5 AU to the heliopause. The distributions were carefully compared with in situ measurements at 3 AU (Ulysses), 12 AU (New Horizons), and 80-90 AU (Voyager 1 and 2) as well as those inferred from ENA fluxes measured by Cassini and IBEX (Wu et al., 2016). Some examples of modeldata comparison are shown in Figure 1. We have used coupled MHD-plasma and kinetic-neutral code to investigate the likely range of plasma and magnetic field parameters in the local interstellar medium (LISM), based on the assumption that the shape of the IBEX ribbon could be used to determine the orientation of the interstellar magnetic field. While the magnetic field is believed to be

  3. Intense-field ionization of atoms and molecules: Spatially resolved ion detection and ultrashort optical vortices

    NASA Astrophysics Data System (ADS)

    Strohaber, James

    The interaction of light and matter has for many years provided a venue in which scientists have been able to increase their understanding of fundamental quantum mechanics and electromagnetism. The advent of the laser in the early sixties significantly changed the way in which experiments were performed. These coherent sources of radiation played a pivotal role in the investigations of new phenomenon such as multiphoton ionization. As time progressed many significant advances have been made in laser technology. For instance, the development of mode-locking techniques such as Q-switching and the nonlinear Kerr effect have made pulsed lasers possible (now down to ˜ 5 fs), the discovery of Chirped-Pulse-Amplification allowed for these ultrashort pulses to be amplified up to Joules in energy per pulse. As a result of these new advances in laser technology, new and exciting physics have been illuminated. When ultrashort intense laser fields interact with matter, one possible outcome is the ionization of the target into its constituents (atoms, molecules, electrons or photons). Because the constituents are usually ions which may have different masses and charges, time-of-flight (TOF) techniques are often employed in the analysis of the ionization yields. In these experiments, the usual quantity of physical interest is the ionization probability as a function of a well known intensity. However, in reality the impinging laser radiation possesses a distribution of intensities. To further add to this annoyance, it is difficult for a TOF spectrometer to distinguish between ions created at different intensities and the usual course of action is to integrate ions from over the entire focal volume. The inevitable result of this so-called spatial averaging is to limit information about the underlying physical process. Additionally, coherent sources of radiation have captured the attention of researchers whose main interests are in spatially modulating the phase and amplitude of

  4. Large-scale relativistic calculations of ionization energies and total binding energies of all atoms and positive atomic ions with nuclear charge Z = 1-110

    NASA Astrophysics Data System (ADS)

    Kramida, Alexander; Froese Fischer, Charlotte; Reader, Joseph; Indelicato, Paul

    2015-05-01

    The latest versions of advanced multiconfiguration Dirac-Fock atomic codes, MCDFGME and Grasp2K, are used to calculate ionization energies (IE) and total binding energies of all atomic systems. Comparison with experiment and other benchmark data shows an excellent accuracy achieved in these calculations for H-, He-, and Li-like ions. In particular, our results for H-like ions with Z >2, obtained with the MCDFGME code, are the most accurate available today. For multi-electron ions, we combine the accurate single-configuration MCDFGME calculations with the correlation-difference energy (difference between the multiconfiguration and single-configuration total energies) calculated with Grasp2K. This approach results in a dramatically improved agreement of calculated IEs with experiment (less than 0.7 eV on average) for all systems, excluding those involving open f-shells. The most probable ground states are found for most systems, leaving questionable only about 100 out of total 6105 considered systems.

  5. Reactions of State-Selected Atomic Oxygen Ions O(+)((4)S, (2)D, (2)P) with Methane.

    PubMed

    Cunha de Miranda, Barbara; Romanzin, Claire; Chefdeville, Simon; Vuitton, Véronique; Žabka, Jan; Polášek, Miroslav; Alcaraz, Christian

    2015-06-11

    An experimental study has been carried out on the reactions of state selected O(+)((4)S, (2)D, (2)P) ions with methane with the aims of characterizing the effects of both the parent ion internal energy and collision energy on the reaction dynamics and determining the fate of oxygen species in complex media, in particular the Titan ionosphere. Absolute cross sections and product velocity distributions have been determined for the reactions of (16)O(+) or (18)O(+) ions with CH4 or CD4 from thermal to 5 eV collision energies by using the guided ion beam (GIB) technique. Dissociative photoionization of O2 with vacuum ultraviolet (VUV) synchrotron radiation delivered by the DESIRS beamline at the SOLEIL storage ring and the threshold photoion photoelectron coincidence (TPEPICO) technique are used for the preparation of purely state-selected O(+)((4)S, (2)D, (2)P) ions. A complete inversion of the product branching ratio between CH4(+) and CH3(+) ions in favor of the latter is observed for excitation of O(+) ions from the (4)S ground state to either the (2)D or the (2)P metastable state. CH4(+) and CH3(+) ions, which are by far the major products for the reaction of ground state and excited states, are strongly backward scattered in the center of mass frame relative to O(+) parent ions. For the reaction of O(+)((4)S), CH3(+) production also rises with increasing collision energy but with much less efficiency than with O(+) excitation. We found that a mechanism of dissociative charge transfer, mediated by an initial charge transfer step, can account very well for all the observations, indicating that CH3(+) production is associated with the formation of H and O atoms (CH3(+) + H + O) rather than with OH formation by an hydride transfer process (CH3(+) + OH). Therefore, as the CH4(+) production by charge transfer is also associated with O atoms, the fate of oxygen species in these reactions is essentially the O production, except for the reaction of O(+)((4)S), which also

  6. Reactions of State-Selected Atomic Oxygen Ions O(+)((4)S, (2)D, (2)P) with Methane.

    PubMed

    Cunha de Miranda, Barbara; Romanzin, Claire; Chefdeville, Simon; Vuitton, Véronique; Žabka, Jan; Polášek, Miroslav; Alcaraz, Christian

    2015-06-11

    An experimental study has been carried out on the reactions of state selected O(+)((4)S, (2)D, (2)P) ions with methane with the aims of characterizing the effects of both the parent ion internal energy and collision energy on the reaction dynamics and determining the fate of oxygen species in complex media, in particular the Titan ionosphere. Absolute cross sections and product velocity distributions have been determined for the reactions of (16)O(+) or (18)O(+) ions with CH4 or CD4 from thermal to 5 eV collision energies by using the guided ion beam (GIB) technique. Dissociative photoionization of O2 with vacuum ultraviolet (VUV) synchrotron radiation delivered by the DESIRS beamline at the SOLEIL storage ring and the threshold photoion photoelectron coincidence (TPEPICO) technique are used for the preparation of purely state-selected O(+)((4)S, (2)D, (2)P) ions. A complete inversion of the product branching ratio between CH4(+) and CH3(+) ions in favor of the latter is observed for excitation of O(+) ions from the (4)S ground state to either the (2)D or the (2)P metastable state. CH4(+) and CH3(+) ions, which are by far the major products for the reaction of ground state and excited states, are strongly backward scattered in the center of mass frame relative to O(+) parent ions. For the reaction of O(+)((4)S), CH3(+) production also rises with increasing collision energy but with much less efficiency than with O(+) excitation. We found that a mechanism of dissociative charge transfer, mediated by an initial charge transfer step, can account very well for all the observations, indicating that CH3(+) production is associated with the formation of H and O atoms (CH3(+) + H + O) rather than with OH formation by an hydride transfer process (CH3(+) + OH). Therefore, as the CH4(+) production by charge transfer is also associated with O atoms, the fate of oxygen species in these reactions is essentially the O production, except for the reaction of O(+)((4)S), which also

  7. Customized atomic force microscopy probe by focused-ion-beam-assisted tip transfer.

    PubMed

    Wang, Andrew; Butte, Manish J

    2014-08-01

    We present a technique for transferring separately fabricated tips onto tipless atomic force microscopy (AFM) cantilevers, performed using focused ion beam-assisted nanomanipulation. This method addresses the need in scanning probe microscopy for certain tip geometries that cannot be achieved by conventional lithography. For example, in probing complex layered materials or tall biological cells using AFM, a tall tip with a high-aspect-ratio is required to avoid artifacts caused by collisions of the tip's sides with the material being probed. We show experimentally that tall (18 μm) cantilever tips fabricated by this approach reduce squeeze-film damping, which fits predictions from hydrodynamic theory, and results in an increased quality factor (Q) of the fundamental flexural mode. We demonstrate that a customized tip's well-defined geometry, tall tip height, and aspect ratio enable improved measurement of elastic moduli by allowing access to low-laying portions of tall cells (T lymphocytes). This technique can be generally used to attach tips to any micromechanical device when conventional lithography of tips cannot be accomplished. PMID:25161320

  8. Customized atomic force microscopy probe by focused-ion-beam-assisted tip transfer

    NASA Astrophysics Data System (ADS)

    Wang, Andrew; Butte, Manish J.

    2014-08-01

    We present a technique for transferring separately fabricated tips onto tipless atomic force microscopy (AFM) cantilevers, performed using focused ion beam-assisted nanomanipulation. This method addresses the need in scanning probe microscopy for certain tip geometries that cannot be achieved by conventional lithography. For example, in probing complex layered materials or tall biological cells using AFM, a tall tip with a high-aspect-ratio is required to avoid artifacts caused by collisions of the tip's sides with the material being probed. We show experimentally that tall (18 μm) cantilever tips fabricated by this approach reduce squeeze-film damping, which fits predictions from hydrodynamic theory, and results in an increased quality factor (Q) of the fundamental flexural mode. We demonstrate that a customized tip's well-defined geometry, tall tip height, and aspect ratio enable improved measurement of elastic moduli by allowing access to low-laying portions of tall cells (T lymphocytes). This technique can be generally used to attach tips to any micromechanical device when conventional lithography of tips cannot be accomplished.

  9. A recoil ion momentum spectrometer for molecular and atomic fragmentation studies.

    PubMed

    Khan, Arnab; Tribedi, Lokesh C; Misra, Deepankar

    2015-04-01

    We report the development and performance studies of a newly built recoil ion momentum spectrometer for the study of atomic and molecular fragmentation dynamics in gas phase upon the impact of charged particles and photons. The present design is a two-stage Wiley-McLaren type spectrometer which satisfies both time and velocity focusing conditions and is capable of measuring singly charged ionic fragments up-to 13 eV in all directions. An electrostatic lens has been introduced in order to achieve velocity imaging. Effects of the lens on time-of-flight as well as on the position have been investigated in detail, both, by simulation and in experiment. We have used 120 keV proton beam on molecular nitrogen gas target. Complete momentum distributions and kinetic energy release distributions have been derived from the measured position and time-of-flight spectra. Along with this, the kinetic energy release spectra of fragmentation of doubly ionized nitrogen molecule upon various projectile impacts are presented.

  10. Increase in the power of lasing on atomic and ion transitions in chemical elements

    SciTech Connect

    Klimkin, V M; Sokovikov, V G

    2007-02-28

    A method for increasing the power of pulsed lasing on atomic and ion transitions in chemical elements obtained by the conversion of the UV radiation of excimer lasers in cells with metal vapours is studied. A part of UV radiation transmitted through a cell with metal vapour is used for pumping a dye solution in such a way that the cell converter with metal vapour represents a master oscillator, while the dye cell represents an amplifier. The study is performed by the example of amplification of weak spectral components of radiation from a XeCl* laser converted in mercury and barium vapours. In the amplifying stage the longitudinal pumping of the dye is used and a scheme for suppressing self-excitation is employed. It is found by selecting dyes that the alcohol solution of uranin is nearly optimal for amplification of the 546.1-nm laser line of mercury, while the best results in amplification of the 533-nm and 648.2-nm laser lines of barium were obtained by using alcohol solutions of rhodamine 6G and oxazine 17, respectively. The power of the 546.1-nm mercury line was increased by an order of magnitude, while the power of the 533-nm and 648.2-nm lines of barium - almost by a factor of twenty-five. (lasers)

  11. Dynamics of the fully stripped ion-hydrogen atom charge exchange process in dense quantum plasmas

    SciTech Connect

    Zhang, Ling-yu; Wan, Jiang-feng; Zhao, Xiao-ying; Xiao, Guo-qing; Duan, Wen-shan; Qi, Xin; Yang, Lei

    2014-09-15

    The plasma screening effects of dense quantum plasmas on charge exchange processes of a fully stripped ion colliding with a hydrogen atom are studied by the classical trajectory Monte Carlo method. The inter-particle interactions are described by the exponential cosine-screened Coulomb potentials. It is found that in weak screening conditions, cross sections increase with the increase of the ionic charge Z. However, in strong screening conditions, the dependence of cross sections on the ionic charge is related to the incident particle energy. At high energies, cross sections show a linear increase with the increase of Z, whereas at low energies, cross sections for Z≥4 become approximately the same. The He{sup 2+} and C{sup 6+} impacting charge exchange cross sections in dense quantum plasmas are also compared with those in weakly coupled plasmas. The interactions are described by the static screened Coulomb potential. It is found that for both He{sup 2+} and C{sup 6+}, the oscillatory screening effects of dense quantum plasmas are almost negligible in weak screening conditions. However, in strong screening conditions, the oscillatory screening effects enhance the screening effects of dense quantum plasmas, and the enhancement becomes more and more significant with the increase of the screening parameter and the ionic charge.

  12. Customized atomic force microscopy probe by focused-ion-beam-assisted tip transfer

    SciTech Connect

    Wang, Andrew; Butte, Manish J.

    2014-08-04

    We present a technique for transferring separately fabricated tips onto tipless atomic force microscopy (AFM) cantilevers, performed using focused ion beam-assisted nanomanipulation. This method addresses the need in scanning probe microscopy for certain tip geometries that cannot be achieved by conventional lithography. For example, in probing complex layered materials or tall biological cells using AFM, a tall tip with a high-aspect-ratio is required to avoid artifacts caused by collisions of the tip's sides with the material being probed. We show experimentally that tall (18 μm) cantilever tips fabricated by this approach reduce squeeze-film damping, which fits predictions from hydrodynamic theory, and results in an increased quality factor (Q) of the fundamental flexural mode. We demonstrate that a customized tip's well-defined geometry, tall tip height, and aspect ratio enable improved measurement of elastic moduli by allowing access to low-laying portions of tall cells (T lymphocytes). This technique can be generally used to attach tips to any micromechanical device when conventional lithography of tips cannot be accomplished.

  13. A recoil ion momentum spectrometer for molecular and atomic fragmentation studies

    SciTech Connect

    Khan, Arnab; Tribedi, Lokesh C.; Misra, Deepankar

    2015-04-15

    We report the development and performance studies of a newly built recoil ion momentum spectrometer for the study of atomic and molecular fragmentation dynamics in gas phase upon the impact of charged particles and photons. The present design is a two-stage Wiley-McLaren type spectrometer which satisfies both time and velocity focusing conditions and is capable of measuring singly charged ionic fragments up-to 13 eV in all directions. An electrostatic lens has been introduced in order to achieve velocity imaging. Effects of the lens on time-of-flight as well as on the position have been investigated in detail, both, by simulation and in experiment. We have used 120 keV proton beam on molecular nitrogen gas target. Complete momentum distributions and kinetic energy release distributions have been derived from the measured position and time-of-flight spectra. Along with this, the kinetic energy release spectra of fragmentation of doubly ionized nitrogen molecule upon various projectile impacts are presented.

  14. Pion correlations as a function of atomic mass in heavy ion collisions

    SciTech Connect

    Chacon, A.D.

    1989-11-26

    The method of two pion interferometry was used to obtain source-size and lifetime parameters for the pions produced in heavy ion collisions. The systems used were 1.70 {center dot} A GeV {sup 56}Fe + Fe, 1.82 {center dot} A GeV {sup 40}Ar + KCl and 1.54 {center dot} A GeV {sup 93}Nb + Nb, allowing for a search for dependences on the atomic number. Two acceptances (centered, in the lab., at {approximately} 0{degrees} and 45{degrees}) were used for each system, allowing a search for dependences on the viewing angle. The correlation functions were calculated by comparing the data samples to background (or reference) samples made using the method of event mixing, where pions from different events are combined to produce a data sample in which the Bose-Einstein correlation effect is absent. The effect of the correlation function on the background samples is calculated, and a method for weighting the events to remove the residual correlation effect is presented. The effect of the spectrometer design on the measured correlation functions is discussed, as are methods for correcting for these effects during the data analysis. 58 refs., 39 figs., 18 tabs.

  15. Effect of electron-nuclei interaction on internuclear motions in slow ion-atom collisions

    NASA Astrophysics Data System (ADS)

    Tolstikhina, Inga Yu.; Tolstikhin, Oleg I.

    2015-10-01

    The electron-nuclei interaction affects the internuclear motion in slow ion-atom collisions, which in turn affects theoretical results for the cross sections of various collision processes. The results are especially sensitive to the details of the internuclear dynamics in the presence of a strong isotope effect on the cross sections, as is the case, e.g., for the charge transfer in low-energy collisions of He2+ with H, D, and T. By considering this system as an example, we show that internuclear trajectories defined by the Born-Oppenheimer (BO) potential in the entrance collision channel, which effectively accounts for the electron-nuclei interaction, are in much better agreement with trajectories obtained in the ab initio electron-nuclear dynamics approach [R. Cabrera-Trujillo et al., Phys. Rev. A 83, 012715 (2011), 10.1103/PhysRevA.83.012715] than the corresponding Coulomb trajectories. We also show that the use of the BO trajectory instead of the Coulomb trajectory in the calculations of the charge-transfer cross sections within the adiabatic approach improves the agreement of the results with ab initio calculations.

  16. Icositetrahedral and icosahedral atomic configurations observed in the Nb-Ag metallic glasses synthesized by ion beam mixing

    SciTech Connect

    Tai, K. P.; Gao, N.; Dai, X. D.; Li, J. H.; Lai, W. S.; Liu, B. X.

    2006-08-28

    Metallic glasses are obtained in an immiscible Nb-Ag system by ion beam mixing and an atomic configuration in the amorphous structure is discovered, i.e., an icositetrahedral ordering, which, together with an icosahedral ordering also observed in the Nb-Ag metallic glasses and in some previously reported systems, helps in formulating a structural spectrum of the amorphous solids. The experimental characterization and atomistic modeling with an ab initio derived Nb-Ag potential demonstrate the significance of structural heredity, i.e., the crystalline structures of the constituent metals play a decisive role in determining the atomic structure of the metallic glasses in the system.

  17. Plasma desorption mass spectrometry in studies of formation and sputtering of fullerenes by MeV atomic ions

    NASA Astrophysics Data System (ADS)

    Bitensky, I.; Brinkmalm, G.; Demirev, P.; Eriksson, J.; H»Kansson, P.; Papaléo, R.; Sundqvist, B. U. R.; Zubarev, R.

    1994-10-01

    An account is presented on plasma desorption mass spectrometry (PDMS) studies of different carbon-containing organic solids utilizing megaelectronvolt (MeV) atomic ions from the Uppsvala EN-tandem accelerator. Positive ions of even-numbered carbon clusters (C+n, n = 40 to> 200) are ejected as a result of the interaction of the fast MeV ions with the target. The distribution of cluster sizes suggests that stable, closed carbon-cage structures -- fullerenes - are formed. Among the investigated materials that produce carbon clusters are poly(vinylidenefluoride) and fluorinated fullerenes -- C60F2m. For comparison purposes data from C60 targets have been also collected and analyzed. PDMS has been used for the in situ assessment of the damaging of C60 films by MeV heavy ions. Results on delayed electron emission from C-60 sputtered by MeV ions from C60 fullerene targets are also presented. A model of fullerene formation as a result of MeV ion interactions with the organic solid, including the yield dependence on primary ion charge state, is summarized. Both the data and the model suggest that fullerenes are formed as a result of a single primary ion impact and that they are ejected from an axially expanding infratrack plasma region. Results on different types of coalescence reactions in synthetic C60 fullerene targets and in blends of pure (synthetic) C60 with polystyrene leading to ejection of higher mass positive fullerene ions (C+k, k from 60 to more than 200) are also reported. The coalescence reactions are induced by the interaction of a single MeV ion with the solid. We argue that our data contribute to elucidating some general patterns of the fullerene formation mechanism.

  18. Synthesis of nine-atom deltahedral Zintl ions of germanium and their functionalization with organic groups.

    PubMed

    Gillett-Kunnath, Miriam M; Sevov, Slavi C

    2012-01-01

    Although the first studies of Zintl ions date between the late 1890's and early 1930's they were not structurally characterized until many years later. Their redox chemistry is even younger, just about ten years old, but despite this short history these deltahedral clusters ions E9(n-) (E = Si, Ge, Sn, Pb; n = 2, 3, 4) have already shown interesting and diverse reactivity and have been at the forefront of rapidly developing and exciting new chemistry. Notable milestones are the oxidative coupling of Ge9(4-) clusters to oligomers and infinite chains, their metallation, capping by transition-metal organometallic fragments, insertion of a transition-metal atom at the center of the cluster which is sometimes combined with capping and oligomerization, addition of main-group organometallic fragments as exo-bonded substituents, and functionalization with various organic residues by reactions with organic halides and alkynes. This latter development of attaching organic fragments directly to the clusters has opened up a new field, namely organo-Zintl chemistry, that is potentially fertile for further synthetic explorations, and it is the step-by-step procedure for the synthesis of germanium-divinyl clusters described herein. The initial steps outline the synthesis of an intermetallic precursor of K4Ge9 from which the Ge9(4-) clusters are extracted later in solution. This involves fused-silica glass blowing, arc-welding of niobium containers, and handling of highly air-sensitive materials in a glove box. The air-sensitive K4Ge9 is then dissolved in ethylenediamine in the box and then alkenylated by a reaction with Me3SiC≡CSiMe3. The reaction is followed by electrospray mass spectrometry while the resulting solution is used for obtaining single crystals containing the functionalized clusters [H2C=CH-Ge9-CH=CH2](2-). For this purpose the solution is centrifuged, filtered, and carefully layered with a toluene solution of 18-crown-6. Left undisturbed for a few days, the so

  19. Synthesis of Nine-atom Deltahedral Zintl Ions of Germanium and their Functionalization with Organic Groups

    PubMed Central

    Gillett-Kunnath, Miriam M.; Sevov, Slavi C.

    2012-01-01

    Although the first studies of Zintl ions date between the late 1890's and early 1930's they were not structurally characterized until many years later.1,2 Their redox chemistry is even younger, just about ten years old, but despite this short history these deltahedral clusters ions E9n- (E = Si, Ge, Sn, Pb; n = 2, 3, 4) have already shown interesting and diverse reactivity and have been at the forefront of rapidly developing and exciting new chemistry.3-6 Notable milestones are the oxidative coupling of Ge94- clusters to oligomers and infinite chains,7-19 their metallation,14-16,20-25 capping by transition-metal organometallic fragments,26-34 insertion of a transition-metal atom at the center of the cluster which is sometimes combined with capping and oligomerization,35-47 addition of main-group organometallic fragments as exo-bonded substituents,48-50 and functionalization with various organic residues by reactions with organic halides and alkynes.51-58 This latter development of attaching organic fragments directly to the clusters has opened up a new field, namely organo-Zintl chemistry, that is potentially fertile for further synthetic explorations, and it is the step-by-step procedure for the synthesis of germanium-divinyl clusters described herein. The initial steps outline the synthesis of an intermetallic precursor of K4Ge9 from which the Ge94- clusters are extracted later in solution. This involves fused-silica glass blowing, arc-welding of niobium containers, and handling of highly air-sensitive materials in a glove box. The air-sensitive K4Ge9 is then dissolved in ethylenediamine in the box and then alkenylated by a reaction with Me3SiC≡CSiMe3. The reaction is followed by electrospray mass spectrometry while the resulting solution is used for obtaining single crystals containing the functionalized clusters [H2C=CH-Ge9-CH=CH2]2-. For this purpose the solution is centrifuged, filtered, and carefully layered with a toluene solution of 18-crown-6. Left

  20. Thermodynamics of various F420 coenzyme models as sources of electrons, hydride ions, hydrogen atoms and protons in acetonitrile.

    PubMed

    Xia, Ke; Shen, Guang-Bin; Zhu, Xiao-Qing

    2015-06-14

    32 F420 coenzyme models with alkylation of the three different N atoms (N1, N3 and N10) in the core structure (XFH(-)) were designed and synthesized and the thermodynamic driving forces (defined in terms of the molar enthalpy changes or the standard redox potentials in this work) of the 32 XFH(-) releasing hydride ions, hydrogen atoms and electrons, the thermodynamic driving forces of the 32 XFH˙ releasing protons and hydrogen atoms and the thermodynamic driving forces of XF(-)˙ releasing electrons in acetonitrile were determined using titration calorimetry and electrochemical methods. The effects of the methyl group at N1, N3 and N10 and a negative charge on N1 and N10 atoms on the six thermodynamic driving forces of the F420 coenzyme models and their related reaction intermediates were examined; the results show that seating arrangements of the methyl group and the negative charge have remarkably different effects on the thermodynamic properties of the F420 coenzyme models and their related reaction intermediates. The effects of the substituents at C7 and C8 on the six thermodynamic driving forces of the F420 coenzyme models and their related reaction intermediates were also examined; the results show that the substituents at C7 and C8 have good Hammett linear free energy relationships with the six thermodynamic parameters. Meanwhile, a reasonable determination of possible reactions between members of the F420 family and NADH family in vivo was given according to a thermodynamic analysis platform constructed using the elementary step thermodynamic parameter of F420 coenzyme model 2FH(-) and NADH model MNAH releasing hydride ions in acetonitrile. The information disclosed in this work can not only fill a gap in the chemical thermodynamics of F420 coenzyme models as a class of very important organic sources of electrons, hydride ions, hydrogen atoms and protons, but also strongly promote the fast development of the chemistry and applications of F420 coenzyme.

  1. Thermodynamics of various F420 coenzyme models as sources of electrons, hydride ions, hydrogen atoms and protons in acetonitrile.

    PubMed

    Xia, Ke; Shen, Guang-Bin; Zhu, Xiao-Qing

    2015-06-14

    32 F420 coenzyme models with alkylation of the three different N atoms (N1, N3 and N10) in the core structure (XFH(-)) were designed and synthesized and the thermodynamic driving forces (defined in terms of the molar enthalpy changes or the standard redox potentials in this work) of the 32 XFH(-) releasing hydride ions, hydrogen atoms and electrons, the thermodynamic driving forces of the 32 XFH˙ releasing protons and hydrogen atoms and the thermodynamic driving forces of XF(-)˙ releasing electrons in acetonitrile were determined using titration calorimetry and electrochemical methods. The effects of the methyl group at N1, N3 and N10 and a negative charge on N1 and N10 atoms on the six thermodynamic driving forces of the F420 coenzyme models and their related reaction intermediates were examined; the results show that seating arrangements of the methyl group and the negative charge have remarkably different effects on the thermodynamic properties of the F420 coenzyme models and their related reaction intermediates. The effects of the substituents at C7 and C8 on the six thermodynamic driving forces of the F420 coenzyme models and their related reaction intermediates were also examined; the results show that the substituents at C7 and C8 have good Hammett linear free energy relationships with the six thermodynamic parameters. Meanwhile, a reasonable determination of possible reactions between members of the F420 family and NADH family in vivo was given according to a thermodynamic analysis platform constructed using the elementary step thermodynamic parameter of F420 coenzyme model 2FH(-) and NADH model MNAH releasing hydride ions in acetonitrile. The information disclosed in this work can not only fill a gap in the chemical thermodynamics of F420 coenzyme models as a class of very important organic sources of electrons, hydride ions, hydrogen atoms and protons, but also strongly promote the fast development of the chemistry and applications of F420 coenzyme

  2. Excitation and Ionization-Excitation of Helium in Fast Ion-Atom Collisions.

    NASA Astrophysics Data System (ADS)

    Fuelling, Stephan R. K.

    1991-02-01

    The purpose of this work is to investigate several aspects of many-body effects in fast ion-atom collisions using the target gas helium where the projectile velocities are above the Bohr velocity. The method of high resolution extreme ultraviolet (EUV) spectroscopy has been applied in order to measure absolute state selective cross sections of emitted light from excited HeI and HeII target states. We have performed a relative intensity calibration of our 1.5 m spectrometer by comparing 1MeV C^+ + Ne spectra with those examined from a wavelength-calibrated 2.2 m grazing incidence monochromator installed at the Dynamitron Tandem Laboratory at the University of Bochum, Germany. The absolute calibration of our instrument has been accomplished with a single measurement of the Ly_alpha transition of He^+ from 200 eV e-He collisions, where the absolute cross section is known. A comparison between the two-electron processes of ionization-excitation and the one-electron process of excitation of helium following e^-, H^+ and C^{6+ } impact is made for projectile Bohr velocities (v_0) ranging between 1.5 and 9.6. Therefore, the Lyman series of He^+(np) ^2P to (1s) ^2S for n = 2 to 5 and the Rydberg series of He (1snp) ^1P to (1s^2) ^1 S for n = 2 to 5 have been measured. We have been the first to report such extensive absolute state selective cross section measurements. The absolute EUV emission cross sections for ionization-excitation show a significant difference in magnitude for projectiles e^ -, H^+ and C^ {6+} when compared at equal velocities. These differences are possibly due to interference effects between different collision processes. These differences can also be considered as interference between first and second order Born expansions terms. The cross section for electron impact at projectile velocities between 1.5 and 8 v _0 exceeds that for protons by a factor of up to about 3. The H^+ and C ^{6+} cross sections scale approximately as Z_sp{p}{3}. Finally, cross

  3. 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.

  4. Excitation of atoms and molecules in collisions with highly charged ions

    SciTech Connect

    Watson, R.L.

    1992-03-01

    This report discusses research of multicharged nitrogen, oxygen and carbon monoxide molecular ions produced with collision with multicharged argon ions. Properties like ionization, dissociation, and excitation are investigated. (LSP)

  5. 'Programming' Electron Beam Ion Traps To Produce Atomic Data Relevant To Plasma Physics

    SciTech Connect

    Currell, Fred; O'Rourke, Brian; Kavanagh, Anthony; Li Yueming; Nakamura, Nobuyuki; Ohtani, Shunsuke; Watanabe, Hirofumi

    2009-09-10

    After a brief review of the processes taking place in electron beam ions traps (EBITs), the means by which EBITs are used to make measurements of electron impact ionization cross-sections and dielectronic recombination resonance strengths are discussed. In particular, results from a study involving holmium ions extracted from an electron beam ion trap are used to illustrate a technique for studying dielectronic recombination in open-shell target ions.

  6. Energetic Neutral Atom Imaging at Low Altitudes from the Swedish Microsatellite Astrid: Extraction of the Equatorial Ion Distribution. Paper 2

    NASA Technical Reports Server (NTRS)

    Brandt, Pontus C:son; Barabash, Stas; Roelof, Edmond C.; Chase, Christopher J.

    1999-01-01

    Energetic neutral atom (ENA) images obtained by the ENA imager on- board the Astrid satellite in the polar cap at 1000 km during a moderate magnetic storm (Dst greater than or equal to 80 nT) on 8 February 1995 are simulated using a parameterized model of the equatorial ion distribution and a six-component Chamberlain exo-sphere with parameters from the MSISE-90 model. By changing the ion parameters until a matching ENA image is obtained one can extract the equatorial ion distribution. Four consecutive images from different view points several of minutes apart are simulated assuming H(+) and O(+), respectively, as parent ions. The optimal set of parameters is extracted by minimizing the chi(exp 2) difference between simulated and observed ENA image using Powell's minimization algorithm. The optimal equatorial model ion distribution consists of O(+) peaked in around dusk. The lower intensity of fluxes obtained from vantage points closer to the pole is an effect of the loss cone of the parent ion distribution being empty.

  7. Heavy Ion Storage Ring for Atomic Physics (HISTRAP) vacuum test stand for pressures of 10/sup -12/ Torr

    SciTech Connect

    Johnson, J.W.; Atkins, W.H.; Dowling, D.T.; McConnell, J.W.; Milner, W.T.; Olsen, D.K.

    1989-05-01

    HISTRAP (Heavy Ion Storage Ring for Atomic Physics) is a proposed synchrotron/cooler/storage ring accelerator optimized for advanced atomic physics research. The ring has a circumference of 46.8 m, a bore diameter of /similar to/15 cm, and requires a vacuum of 10/sup -12/ Torr to decelerate highly charged, very heavy ions down to low energies. To be able to test components and procedures to achieve this pressure, a test stand approximately modeling 1/16 of the ring vacuum chamber has been built. The 3.5-m-long test stand has been fabricated from 10-cm-diam components, with 316LN stainless-steel flanges. Prior to assembly, these components were vacuum fired at 950 /sup 0/C at a pressure of 10/sup -4/ Torr. The test stand is bakable in situ at 300 /sup 0/C. Pumping is achieved with two 750 l/s titanium sublimator pumps and one 60 l/s ion pump. Pressure is measured with two extractor ion gauges and a 10/sup -4/ partial pressure residual gas analyser. The roughing for the test stand consists of cryosorption pumps followed by a cryopump. A pressure of 4 x 10/sup -12/ Torr has been achieved.

  8. HISTRAP (Heavy Ion Storage Ring for Atomic Physics) vacuum test stand for pressures of 10/sup -12/ Torr

    SciTech Connect

    Johnson, J.W.; Atkins, W.H.; Dowling, D.T.; McConnell, J.W.; Milner, W.T.; Olsen, D.K.

    1988-01-01

    HISTRAP, Heavy Ion Storage Ring for Atomic Physics, is a proposed synchrotron/cooler/storage ring accelerator optimized for advanced atomic physics research. The ring has a circumference of 46.8 m, a bore diameter of about 15 cm, and requires a vacuum of 10/sup -12/ Torr in order to decelerate highly-charged very-heavy ions down to low energies. To be able to test components and procedures to achieve this pressure, a test stand approximately modeling one-sixteenth of the ring vacuum chamber has been built. The 3.5-m-long test stand has been fabricated from 10-cm-diameter components, with 316LN stainless steel flanges. Prior to assembly, these components were vacuum fired at 950/degree/C at a pressure of 10/sup -4/ Torr. The test stand is bakeable in situ at 300/degree/C. Pumping is achieved with two 750-L/s titanium sublimator pumps and one 60-L/s ion pump. Pressure is measured with two extractor ion gauges and a 10/sup -14/ PP RGA. The roughing for the test stand consists of cryosorption pumps followed by a cryopump. A pressure of 4 x 10/sup -12/ Torr has been achieved. 7 refs., 5 figs.

  9. Alfvén ion-cyclotron instability in an axisymmetric trap with oblique injection of fast atoms

    SciTech Connect

    Tsidulko, Yu. A.; Chernoshtanov, I. S.

    2014-12-15

    Conditions for the onset of Alfvén ion-cyclotron instability and the spatial structure of unstable modes in an axisymmetric mirror trap with oblique injection of fast atoms are studied. It is shown that the main contribution to instability comes from the inverse population of ions in the velocity space domain into which atoms are injected. Using the distribution function of fast ions obtained by approximately solving the Fokker-Planck equation, the instability threshold in terms of β{sub ⊥} is determined in the Wentzel-Kramers-Brillouin approximation as a function of the geometric parameters and the parameters of injection and target plasma. It is demonstrated that the stability threshold increases substantially when the radius of the hot plasma decreases to a size comparable with the Larmor radius of fast ions. It is shown that the perturbed fields near the axis and at the plasma periphery can rotate in opposite directions, which is important for the interpretation of experimental data.

  10. Ion mobility studies of electronically excited States of atomic transition metal cations: development of an ion mobility source for guided ion beam experiments.

    PubMed

    Iceman, Christopher; Rue, Chad; Moision, Robert M; Chatterjee, Barun K; Armentrout, P B

    2007-07-01

    The design of an ion mobility source developed to couple to a guided ion beam tandem mass spectrometer is presented. In these exploratory studies, metal ions are created continuously by electron ionization of the volatile hexacarbonyls of the three group 6 transition metals. These ions are focused into a linear hexapole ion trap, which collects the ions and then creates high intensity pulses of ions, avoiding excessive ion losses resulting from the low duty cycle of pulsed operation. The ion pulses are injected into a six-ring drift cell filled with helium where ions having different electronic configurations can separate because they have different ion mobilities. Such separation is observed for chromium ions and compares favorably with the pioneering work of Kemper and Bowers (J. Phys. Chem.1991, 95, 5134). The results are then extended to Mo(+) and W(+), which also show efficient configuration separation. The source conditions needed for high intensities and good configuration separation are discussed in detail and suggestions for further improvements are also provided.

  11. Atom penetration from a thin film into the substrate during sputtering by polyenergetic Ar{sup +} ion beam with mean energy of 9.4 keV

    SciTech Connect

    Kalin, B.A.; Gladkov, V.P.; Volkov, N.V.; Sabo, S.E.

    1995-12-31

    Penetration of alien atoms (Be, Ni) into Be, Al, Zr, Si and diamond was investigated under Ar{sup +} ion bombardment of samples having thermally evaporated films of 30--50 nm. Sputtering was carried out using a wide energy spectrum beam of Ar{sup +} ions of 9.4 keV to dose D = 1 {times} 10{sup 16}--10{sup 19} ion/cm{sup 2}. Implanted atom distribution in the targets was measured by Rutherford backscattering spectrometry (RBS) of H{sup +} and He{sup +} ions with energy of 1.6 MeV as well as secondary ion mass-spectrometry (SIMS). During the bombardment, the penetration depth of Ar atoms increases with dose linearly. This depth is more than 3--20 times deeper than the projected range of bombarding ions and recoil atoms. This is a deep action effect. The analysis shows that the experimental data for foreign atoms penetration depth are similar to the data calculated for atom migration through the interstitial site in a field of internal (lateral) compressive stresses created in the near-surface layer of the substrate as a result of implantation. Under these experimental conditions atom ratio r{sub i}/r{sub m} (r{sub i} -- radius of dopant, r{sub m} -- radius target of substrate) can play a principal determining role.

  12. Thomson spectrometer-microchannel plate assembly calibration for MeV-range positive and negative ions, and neutral atoms

    NASA Astrophysics Data System (ADS)

    Prasad, R.; Abicht, F.; Borghesi, M.; Braenzel, J.; Nickles, P. V.; Priebe, G.; Schnürer, M.; Ter-Avetisyan, S.

    2013-05-01

    We report on the absolute calibration of a microchannel plate (MCP) detector, used in conjunction with a Thomson parabola spectrometer. The calibration delivers the relation between a registered count numbers in the CCD camera (on which the MCP phosphor screen is imaged) and the number of ions incident on MCP. The particle response of the MCP is evaluated for positive, negative, and neutral particles at energies below 1 MeV. As the response of MCP depends on the energy and the species of the ions, the calibration is fundamental for the correct interpretation of the experimental results. The calibration method and arrangement exploits the unique emission symmetry of a specific source of fast ions and atoms driven by a high power laser.

  13. Role of silver ions in destabilization of intermolecular adhesion forces measured by atomic force microscopy in Staphylococcus epidermidis biofilms.

    PubMed

    Chaw, K C; Manimaran, M; Tay, Francis E H

    2005-12-01

    In this paper, we report on the potential use of atomic force microscopy (AFM) as a tool to measure the intermolecular forces in biofilm structures and to study the effect of silver ions on sessile Staphylococcus epidermidis cell viability and stability. We propose a strategy of destabilizing the biofilm matrix by reducing the intermolecular forces within the extracellular polymeric substances (EPSs) using a low concentration (50 ppb) of silver ions. Our AFM studies on the intermolecular forces within the EPSs of S. epidermidis RP62A and S.epidermidis 1457 biofilms suggest that the silver ions can destabilize the biofilm matrix by binding to electron donor groups of the biological molecules. This leads to reductions in the number of binding sites for hydrogen bonds and electrostatic and hydrophobic interactions and, hence, the destabilization of the biofilm structure.

  14. Thomson spectrometer-microchannel plate assembly calibration for MeV-range positive and negative ions, and neutral atoms

    SciTech Connect

    Prasad, R.; Abicht, F.; Braenzel, J.; Priebe, G.; Schnuerer, M.; Borghesi, M.; Ter-Avetisyan, S.; Nickles, P. V.

    2013-05-15

    We report on the absolute calibration of a microchannel plate (MCP) detector, used in conjunction with a Thomson parabola spectrometer. The calibration delivers the relation between a registered count numbers in the CCD camera (on which the MCP phosphor screen is imaged) and the number of ions incident on MCP. The particle response of the MCP is evaluated for positive, negative, and neutral particles at energies below 1 MeV. As the response of MCP depends on the energy and the species of the ions, the calibration is fundamental for the correct interpretation of the experimental results. The calibration method and arrangement exploits the unique emission symmetry of a specific source of fast ions and atoms driven by a high power laser.

  15. Production of Highly Charged Ga Ions from Organic Metal Comppound Using the Liquid-He-Free Superconducting Electron Cyclotron Resonance Ion Source at RIKEN

    NASA Astrophysics Data System (ADS)

    Higurashi, Yoshihide; Nakagawa, Takahide; Kidera, Masanori; Kageyama, Tadashi; Kase, Masayuki; Yano, Yasushige

    2002-08-01

    We successfully produced the multi-charged Ga ions using metal ions from volatile compounds (MIVOC) method from liquid-He-free super conducting electron cyclotron resonance ion source at RIKEN (RAMSES). The beam intensities of Ga15+ and Ga16+ ions were 5 and 4 eμA at the injected microwave power of 200 W, respectively.

  16. Simulation of the low earth orbital atomic oxygen interaction with materials by means of an oxygen ion beam

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.; Rutledge, Sharon K.; Paulsen, Phillip E.; Steuber, Thomas J.

    1989-01-01

    Atomic oxygen is the predominant species in low-Earth orbit between the altitudes of 180 and 650 km. These highly reactive atoms are a result of photodissociation of diatomic oxygen molecules from solar photons having a wavelength less than or equal to 2430A. Spacecraft in low-Earth orbit collide with atomic oxygen in the 3P ground state at impact energies of approximately 4.2 to 4.5 eV. As a consequence, organic materials previously used for high altitude geosynchronous spacecraft are severely oxidized in the low-Earth orbital environment. The evaluation of materials durability to atomic oxygen requires ground simulation of this environment to cost effectively screen materials for durability. Directed broad beam oxygen sources are necessary to evaluate potential spacecraft materials performance before and after exposure to the simulated low-Earth orbital environment. This paper presents a description of a low energy, broad oxygen ion beam source used to simulate the low-Earth orbital atomic oxygen environment. The results of materials interaction with this beam and comparison with actual in-space tests of the same meterials will be discussed. Resulting surface morphologies appear to closely replicate those observed in space tests.

  17. Elucidating the mechanism behind the stabilization of multi-charged metal cations in water: A case study of the electronic states of microhydrated Mg2+, Ca2+ and Al3+”

    SciTech Connect

    Miliordos, Evangelos; Xantheas, Sotiris S.

    2014-04-21

    Metal atoms typically have second and higher ionization potentials (IPs) that are larger than the IP of water, resulting in the Coulombic explosion of the first few [M(H2O)n]+q (q ≥ 2) clusters as the M+ + (H2O)n + or MOH+ + H3O+(H2O)n energy levels are energetically more stable than the M2+ + (H2O)n ones for small n. We present a theoretical analysis of the various electronic states correlating with the above channels that are involved in the sequential hydration of the Ca2+, Mg2+ and Al3+ cations with up to six water molecules that, for the first time, quantifies their relative shift with the degree of solvation accounting for the observed stabilization of those multi-charged metal cations in an aqueous solution. *

  18. ATOMIC AND MOLECULAR PHYSICS: Guided transmission of oxygen ions through Al2O3 nanocapillaries

    NASA Astrophysics Data System (ADS)

    Chen, Yi-Feng; Chen, Xi-Meng; Lou, Feng-Jun; Xu, Jin-Zhang; Shao, Jian-Xiong; Sun, Guang-Zhi; Wang, Jun; Xi, Fa-Yuan; Yin, Young-Zhi; Wang, Xing-An; Xu, Jun-Kui; Cui, Ying; Ding, Bao-Wei

    2009-07-01

    The transmissions of oxygen ions through Al2O3 nanocapillaries each 50 nm in diameter and 10 μm in length at a series of different tilt angles are measured, where the ions with energies ranging from 10 to 60 keV and charge states from 1 up to 6 are involved. The angular distribution and the transmission yields of transported ions are investigated. Our results indicate both the existence of a guiding effect when ions pass through the capillary and a significant dependence of the ion transmission on the energy and the charge state of the ions. The guiding effects are observed to be enhanced at lower projectile energies and higher charge states. Meanwhile, the results also exhibit that the transmission yields increase as the tilt angle decreases at a given energy and charge state.

  19. Production of NaCa+ molecular ions in the ground state from cold atom-ion mixtures by photoassociation via an intermediate state

    NASA Astrophysics Data System (ADS)

    Gacesa, Marko; Montgomery, John A.; Michels, H. Harvey; Côté, Robin

    2016-07-01

    We present a theoretical analysis of optical pathways for formation of cold ground-state (NaCa) + molecular ions via an intermediate state. The formation schemes are based on ab initio potential energy curves and transition dipole moments calculated using effective-core-potential methods of quantum chemistry. In the proposed approach, starting from a mixture of cold trapped Ca+ ions immersed into an ultracold gas of Na atoms, (NaCa) + molecular ions are photoassociated in the excited E +1Σ electronic state and allowed to spontaneously decay either to the ground electronic state or an intermediate state from which the population is transferred to the ground state via an additional optical excitation. By analyzing all possible pathways, we find that the efficiency of a two-photon scheme, via either the B +1Σ or C +1Σ potential, is sufficient to produce significant quantities of ground-state (NaCa) + molecular ions. A single-step process results in lower formation rates that would require either a high-density sample or a very intense photoassociation laser to be viable.

  20. Transfer of a weakly bound electron in collisions of Rydberg atoms with neutral particles. II. Ion-pair formation and resonant quenching of the Rb(nl) and Ne(nl) States by Ca, Sr, and Ba atoms

    SciTech Connect

    Narits, A. A.; Mironchuk, E. S.; Lebedev, V. S.

    2013-10-15

    Electron-transfer processes are studied in thermal collisions of Rydberg atoms with alkaline-earth Ca(4s{sup 2}), Sr(5s{sup 2}), and Ba(6s{sup 2}) atoms capable of forming negative ions with a weakly bound outermost p-electron. We consider the ion-pair formation and resonant quenching of highly excited atomic states caused by transitions between Rydberg covalent and ionic terms of a quasi-molecule produced in collisions of particles. The contributions of these reaction channels to the total depopulation cross section of Rydberg states of Rb(nl) and Ne(nl) atoms as functions of the principal quantum number n are compared for selectively excited nl-levels with l Much-Less-Than n and for states with large orbital quantum numbers l = n - 1, n - 2. It is shown that the contribution from resonant quenching dominates at small values of n, and the ion-pair formation process begins to dominate with increasing n. The values and positions of the maxima of cross sections for both processes strongly depend on the electron affinity of an alkaline-earth atom and on the orbital angular momentum l of a highly excited atom. It is shown that in the case of Rydberg atoms in states with large l {approx} n - 1, the rate constants of ion-pair formation and collisional quenching are considerably lower than those for nl-levels with l Much-Less-Than n.

  1. Electron emission in slow collisions of inert gas and reactive ions with W(110) partially covered by alkali atoms

    NASA Astrophysics Data System (ADS)

    Müller, H.; Hausmann, R.; Brenten, H.; Kempter, V.

    1993-05-01

    Electron energy spectra from slow (50 to 1000 eV) collisions of inert gas (He +, He 2+ and Ar +) and reactive (H +, N +) ions colliding under grazing incidence with W(110) surfaces are reported. The surface work function is varied by the exposure of the W(110) surface to alkali atoms. For clean W(110) the sequence of electronic transitions during a slow (50 eV, typically) collision is similar as reported for other clean metals: Auger capture processes involving two electrons from the surface dominate for all projectiles. For sufficiently large coverages by alkali atoms resonant capture of one or two surface electrons by the projectiles leads to the formation of excited states of the projectiles with one or two electrons occupying valence orbitals. These states decay by Auger deexcitation (Penning ionization) and intra-atomic Auger processes (autoionization and autodetachment), respectively. For the case of Ar + ions colliding with W(110) partially covered by potassium it is demonstrated that core vacancies (Ar3p -1) are created during the collision provided the kinetic energy of the projectile surmounts about 300 eV. Contributions from both potential and kinetic emission can then be seen in the spectra of the emitted electrons.

  2. Colorimetric and atomic absorption spectrometric determination of mucolytic drug ambroxol through ion-pair formation with iron and thiocyanate.

    PubMed

    Levent, Abdulkadir; Sentürk, Zühre

    2010-09-01

    Colorimetric and atomic absorption spectrometric methods have been developed for the determination of mucolytic drug Ambroxol. These procedures depend upon the reaction of iron(III) metal ion with the drug in the presence of thiocyanate ion to form stable ion-pair complex which extractable chloroform. The red-coloured complex was determined either colorimetrically at 510 nm or by indirect atomic absorption spectrometry (AAS) via the determination of the iron content in the formed complex. The optimum experimental conditions for pH, concentrations of Fe(3+) and SCN(-), shaking time, phase ratio, and the number of extractions were determined. Under the proposed conditions, linearity was obeyed in the concentration ranges 4.1x10(-6) - 5.7x10(-5) M (1.7-23.6 µg mL(-1)) using both methods, with detection limits of 4.6x10(-7) M (0.19 µg mL(-1)) for colorimetry and 1.1x10(-6) M (0.46 µg mL(-1)) for AAS. The proposed methods were applied for the determination of Ambroxol in tablet dosage forms. The results obtained were statistically analyzed and compared with those obtained by applying the high-performance liquid chromatographic method with diode-array detection.

  3. Measurement of a Large Chemical Reaction Rate between Ultracold Closed-Shell {sup 40}Ca Atoms and Open-Shell {sup 174}Yb{sup +} Ions Held in a Hybrid Atom-Ion Trap

    SciTech Connect

    Rellergert, Wade G.; Sullivan, Scott T.; Chen Kuang; Schowalter, Steven J.; Hudson, Eric R.; Kotochigova, Svetlana; Petrov, Alexander

    2011-12-09

    Ultracold {sup 174}Yb{sup +} ions and {sup 40}Ca atoms are confined in a hybrid trap. The charge exchange chemical reaction rate constant between these two species is measured and found to be 4 orders of magnitude larger than recent measurements in other heteronuclear systems. The structure of the CaYb{sup +} molecule is determined and used in a calculation that explains the fast chemical reaction as a consequence of strong radiative charge transfer. A possible explanation is offered for the apparent contradiction between typical theoretical predictions and measurements of the radiative association process in this and other recent experiments.

  4. Beam dynamics of a double-gap acceleration cell for ion implantation with multiple atomic species

    SciTech Connect

    Wadlinger, E.A.; Lysenko, W.P.; Rusnak, B.; Saadatmand, K.

    1997-02-01

    As a result of our work on ion implantation, we derived equations for the beam dynamics of a two-gap-resonator cavity for accelerating and bunching various ion species of varying energies with the cavity designed for one particular ion species of a given energy (the design-reference particle). A two gap structure is useful at low resonant frequencies where lumped circuit elements (inductors) can be used and the structure kept small. A single gap structure has the advantage that each gap can be independently phased to produce the desired beam dynamics behavior for various ion species and ion energies. However at low frequencies, single gap resonant structures can be large. We find that the two-gap structure, where the phase difference between gaps, for the design reference particle, is fixed at {pi} radians can give acceptable performance provided that the individual two gap cells in the entire accelerator are optimized for the ion species having the largest mass to charge ratio and having the maximum required output energy. Our equations show how to adjust the cavity phases and electric fields to obtain equivalent first-order accelerator performance for various ion species and energies. These equations allow for the effective evaluation of various accelerator concepts and can facilitate the tuning of a linac when changing energies and ion species. Extensive simulations have confirmed the efficacy of our equations. {copyright} {ital 1997 American Institute of Physics.}

  5. X-ray spectroscopy of highly-ionized atoms in an electron beam ion trap (EBIT)

    SciTech Connect

    Marrs, R.E.; Bennett, C.; Chen, M.H.; Cowan, T.; Dietrich, D.; Henderson, J.R.; Knapp, D.A.; Levine, M.A.; Schneider, M.B.; Scofield, J.H.

    1988-01-01

    An Electron Beam Ion Trap at Lawrence Livermore National Laboratory is being used to produce and trap very-highly-charged-ions (q /le/ 70+) for x-ray spectroscopy measurements. Recent measurements of dielectronic recombination, electron impact excitation and transition energies are presented. 15 refs., 12 figs., 1 tab.

  6. Design study of low-energy beam transport for multi-charge beams at RAON

    NASA Astrophysics Data System (ADS)

    Bahng, Jungbae; Qiang, Ji; Kim, Eun-San

    2015-12-01

    The Rare isotope Accelerator Of Newness (RAON) at the Rare Isotope Science Project (RISP) is being designed to simultaneously accelerate beams with multiple charge states. It includes a driver superconducting (SC) linac for producing 200 MeV/u and 400 kW continuous wave (CW) heavy ion beams from protons to uranium. The RAON consists of a few electron cyclotron resonance ion sources, a low-energy beam transport (LEBT) system, a CW 81.25 MHz, 500 keV/u radio frequency quadrupole (RFQ) accelerator, a medium-energy beam transport system, the SC linac, and a charge-stripper system. The LEBT system for the RISP accelerator facility consists of a high-voltage platform, two 90° dipoles, a multi-harmonic buncher (MHB), solenoids, electrostatic quadrupoles, a velocity equalizer, and a diagnostic system. The ECR ion sources are located on a high-voltage platform to reach an initial beam energy of 10 keV/u. After extraction, the ion beam is transported through the LEBT system to the RFQ accelerator. The generated charge states are selected by an achromatic bending system and then bunched by the MHB in the LEBT system. The MHB is used to achieve a small longitudinal emittance in the RFQ by generating a sawtooth wave with three harmonics. In this paper, we present the results and issues of the beam dynamics of the LEBT system.

  7. Pickup Ion Production in the Global Heliosphere and Heliosheath and Their Diagnostics by Fluxes of Energetic Neutral Atoms

    NASA Astrophysics Data System (ADS)

    Wu, Y.

    2015-12-01

    An anisotropic particle transport model, based on an expansion of a focused transport equation in Legendre polynomials, is used here as a tool to analyze the distributions of pickup ions (PUIs) in the heliosphere and heliosheath. A three-dimensional, MHD-kinetic model for flows of a thermal plasma, neutral atoms and PUIs has been developed. The preliminary results from our model are in qualitative agreement with observations made by New Horizons, Ulysses, Voyager 1 and 2. All-sky maps of energetic neutral atoms (ENA) fluxes with energies of about 0.2-6 keV based on our current PUI model are qualitatively similar to IBEX-Hi distributed ENA maps. Also, simulated spectra of ENA fluxes nearly match IBEX-Hi spectra of distributed ENA fluxes. It is demonstrated that preserving some pitch-angle information of the PUI distribution is important for correctly interpreting the data.

  8. Measurements of scattering processes in negative ion: Atom collisions. Technical progress report, 1 September 1991--31 December 1994

    SciTech Connect

    Kvale, T.J.

    1994-09-27

    This report describes the progress made on the research objectives during the past three years of the grant. This research project is designed to study various scattering processes which occur in H{sup {minus}} collisions with atomic (specifically, noble gas and atomic hydrogen) targets in the intermediate energy region. These processes include: elastic scattering, single- and double-electron detachment, and target excitation/ionization. For the elastic and target inelastic processes where H{sup {minus}} is scattered intact, the experimental technique of Ion Energy-Loss Spectroscopy (IELS) will be employed to identify the final target state(s). In most of the above processes, cross sections are unknown both experimentally and theoretically. The measurements will provide total cross sections (TCS) initially, and once the angular positioning apparatus is installed, will provide angular differential cross sections (ADCS).

  9. Atomic data and spectral analysis of carbon, nitrogen, oxygen and silicon ions observed with the International Ultraviolet Explorer

    NASA Technical Reports Server (NTRS)

    Pradhan, Anil K.

    1992-01-01

    According to the plan presented in the original proposal we have now completed most of the atomic calculations involving collision strengths and rate coefficients for electron impact excitation of C II, N III, and O IV ions. These have been reported in the first two publications appended with this report. We have now moved into the applications phase of the project with the new data being used to analyze the International Ultraviolet Explorer (IUE) observations of a variety of objects, as described in the third publication recently submitted (also appended). The analysis and interpretation of archival data will continue well into the next year with several collaborators that the PI and Co-PI are involved with. In addition, the atomic calculations on Si II have been started.

  10. Nondestructive atomic compositional analysis of BeMgZnO quaternary alloys using ion beam analytical techniques

    NASA Astrophysics Data System (ADS)

    Zolnai, Z.; Toporkov, M.; Volk, J.; Demchenko, D. O.; Okur, S.; Szabó, Z.; Özgür, Ü.; Morkoç, H.; Avrutin, V.; Kótai, E.

    2015-02-01

    The atomic composition with less than 1-2 atom% uncertainty was measured in ternary BeZnO and quaternary BeMgZnO alloys using a combination of nondestructive Rutherford backscattering spectrometry with 1 MeV He+ analyzing ion beam and non-Rutherford elastic backscattering experiments with 2.53 MeV energy protons. An enhancement factor of 60 in the cross-section of Be for protons has been achieved to monitor Be atomic concentrations. Usually the quantitative analysis of BeZnO and BeMgZnO systems is challenging due to difficulties with appropriate experimental tools for the detection of the light Be element with satisfactory accuracy. As it is shown, our applied ion beam technique, supported with the detailed simulation of ion stopping, backscattering, and detection processes allows of quantitative depth profiling and compositional analysis of wurtzite BeZnO/ZnO/sapphire and BeMgZnO/ZnO/sapphire layer structures with low uncertainty for both Be and Mg. In addition, the excitonic bandgaps of the layers were deduced from optical transmittance measurements. To augment the measured compositions and bandgaps of BeO and MgO co-alloyed ZnO layers, hybrid density functional bandgap calculations were performed with varying the Be and Mg contents. The theoretical vs. experimental bandgaps show linear correlation in the entire bandgap range studied from 3.26 eV to 4.62 eV. The analytical method employed should help facilitate bandgap engineering for potential applications, such as solar blind UV photodetectors and heterostructures for UV emitters and intersubband devices.

  11. Many-electron relativistic calculation and interpretation of atomic processes in time dependent heavy-ion scattering

    NASA Astrophysics Data System (ADS)

    Thies, B.; Sepp, W.-D.; Fricke, B.

    1989-07-01

    The time dependence of a heavy-ion-atom collision system is solved via a set of coupled channel equations using energy eigen-values and matrix elements from a self-consistent field relativistic molecular many-electron Dirac-Fock-Slater calculation. Within this independent particle model we give a full many-particle interpretation by performing a small number of single-particle calculations. First results for the P( b) curves for the Ne K-hole excitation for the systems F 8+-Ne and F 6+-Ne as examples are discussed.

  12. A suggested periodic table up to Z≤ 172, based on Dirac-Fock calculations on atoms and ions.

    PubMed

    Pyykkö, Pekka

    2011-01-01

    Extended Average Level (EAL) Dirac-Fock calculations on atoms and ions agree with earlier work in that a rough shell-filling order for the elements 119-172 is 8s < 5g≤ 8p(1/2) < 6f < 7d < 9s < 9p(1/2) < 8p(3/2). The present Periodic Table develops further that of Fricke, Greiner and Waber [Theor. Chim. Acta 1971, 21, 235] by formally assigning the elements 121-164 to (nlj) slots on the basis of the electron configurations of their ions. Simple estimates are made for likely maximum oxidation states, i, of these elements M in their MX(i) compounds, such as i = 6 for UF(6). Particularly high i are predicted for the 6f elements.

  13. Ion exchange in the atomic energy industry with particular reference to actinide and fission product separation

    SciTech Connect

    Jenkins, I.L.

    1984-01-01

    Reviewed are some of the uses of ion exchange processes used by the nuclear industry for the period April, 1978 to April, 1983. The topics dealt with are: thorium, protactinium, uranium, neptunium, plutonium, americium, cesium and actinide-lanthanide separations; the higher actinides - Cm, Bk, Cf, Es and Fm; fission products; ion exchange in the geological disposal of radioactive waste. Consideration is given to safety in the use of ion exchangers and in safe methods of disposal of such materials. Full scale and pilot plant process descriptions are included as well as summaries of laboratory studies. 130 references.

  14. Kinetics of interlayer ion migration in non-swelling clays: An atomic-scale study

    NASA Astrophysics Data System (ADS)

    Lammers, L. N.; Kolluri, K.

    2015-12-01

    Clay-rich geologic repositories serve as hosts for fossil methane reserves and as traps for contaminant radionuclides and sequestered CO2. Despite the abundance of non-swelling clay minerals in sedimentary formations, the mechanisms of ion exchange and mass transport mediated by these minerals are not well understood. Ion exchange kinetics in collapsed clays are characterized by a long tail of slow exchange, which suggests that interlayer ions can exchange with the bulk solution. Recent High-Resolution TEM evidence suggests that Cs+ ion exchange K+ in collapsed interlayers leads to interstratified structures, where entire interlayers are completely exchanged while others remain pristine [Okamura T et al., (2005) Microscopy 6365-72]. This phenomenon could be explained by kinetic feedbacks arising when a larger ion substitutes for a smaller one, although the details of this exchange mechanism are currently unknown. We investigated the kinetics and mechanisms of interlayer cation migration in illite (K0.7Al2[Al0.7Si3.3O10](OH)2) using molecular simulations. A Monte Carlo scheme was used to distribute interlayer K ions, and these ions were found to prefer sites neighboring two or more Al3+ substitutions in the tetrahedral sheets. Interlayer K+ ion migration between stable ditrigonal cavity sites was observed directly in molecular dynamics simulations performed at temperatures ranging from 500 K to 900 K and at constant volume. The Climbing Image Nudged Elastic Band method was used to determine the activation energy barrier on 660 K+ ion migration paths. Interlayer ions were observed to migrate between stable lattice sites with migration barriers of 2.35 ± 1.06 eV. Only about 20% of this variation is statistically explained by the distribution of charge deficit sites in the layer caused by Al3+ substitution for Si4+. Remarkably, we find that migration barriers decrease as we increase interlayer spacing. These results suggest that frayed edge sites - local regions with

  15. Redox-inactive metal ions promoted the catalytic reactivity of non-heme manganese complexes towards oxygen atom transfer.

    PubMed

    Choe, Cholho; Yang, Ling; Lv, Zhanao; Mo, Wanling; Chen, Zhuqi; Li, Guangxin; Yin, Guochuan

    2015-05-21

    Redox-inactive metal ions can modulate the reactivity of redox-active metal ions in a variety of biological and chemical oxidations. Many synthetic models have been developed to help address the elusive roles of these redox-inactive metal ions. Using a non-heme manganese(II) complex as the model, the influence of redox-inactive metal ions as a Lewis acid on its catalytic efficiency in oxygen atom transfer was investigated. In the absence of redox-inactive metal ions, the manganese(II) catalyst is very sluggish, for example, in cyclooctene epoxidation, providing only 9.9% conversion with 4.1% yield of epoxide. However, addition of 2 equiv. of Al(3+) to the manganese(II) catalyst sharply improves the epoxidation, providing up to 97.8% conversion with 91.4% yield of epoxide. EPR studies of the manganese(II) catalyst in the presence of an oxidant reveal a 16-line hyperfine structure centered at g = 2.0, clearly indicating the formation of a mixed valent di-μ-oxo-bridged diamond core, Mn(III)-(μ-O)2-Mn(IV). The presence of a Lewis acid like Al(3+) causes the dissociation of this diamond Mn(III)-(μ-O)2-Mn(IV) core to form monomeric manganese(iv) species which is responsible for improved epoxidation efficiency. This promotional effect has also been observed in other manganese complexes bearing various non-heme ligands. The findings presented here have provided a promising strategy to explore the catalytic reactivity of some di-μ-oxo-bridged complexes by adding non-redox metal ions to in situ dissociate those dimeric cores and may also provide clues to understand the mechanism of methane monooxygenase which has a similar diiron diamond core as the intermediate.

  16. Microstructural evolution of Fesbnd 22%Cr model alloy under thermal ageing and ion irradiation conditions studied by atom probe tomography

    NASA Astrophysics Data System (ADS)

    Korchuganova, Olesya A.; Thuvander, Mattias; Aleev, Andrey A.; Rogozhkin, Sergey V.; Boll, Torben; Kulevoy, Timur V.

    2016-08-01

    Nanostructure evolution during ion irradiation of two thermally aged binary Fee22Cr alloys has been investigated using atom probe tomography. Specimens aged at 500 °C for 50 and 200 h were irradiated by 5.6 MeV Fe ions at room temperature up to fluences of 0.3 × 1015 ions/cm2 and 1 × 1015 ions/cm2. The effect of irradiation on the material nanostructure was examined at a depth of 1 μm from the irradiated surface. The analysis of Cr radial concentration functions reveals that dense α‧-phase precipitates in the 200 h aged alloy become diffuse and thereby larger when subjected to irradiation. On the other hand, less Cr-enriched precipitates in the alloy aged for 50 h are less affected. The CreCr pair correlation function analysis shows that matrix inhomogeneity decreases under irradiation. Irradiation leads to a decrease in the number density of diffuse clusters, whereas in the case of well-developed precipitates it remains unchanged.

  17. Electron structure of AgCl nanocrystal with silver ion adsorbed on atomic-rough surface and quantum transitions

    NASA Astrophysics Data System (ADS)

    Timoshenko, Yury K.; Shunina, Valentina A.

    2009-08-01

    Adsorption was considered as on the atomically-rough surface (near the step and step fracture) as on the smooth surface. The electron structure of AgCl nanocrystals with the adsorbed silver ion were calculated by semiempirical tight-binding method relying on a self-consistent approach for the effective charges and dipole moments of the ions and in frame of DFT method B3LYP/HW. The quantum transitions were investigated in semiempirical approach. Visualization of the wave functions was performed for the localized states. Basing on the obtained data a conclusion is specically made that one can expect an enhancement of photoelectron localization with a decrease of the anions number in the substrate nearest to the adsorbed ion. It means that the most ecient trapping of photoelectron should occur under adsorption on a smooth surface rather than near the steps and their fractures as it was assumed previously. Also probabilities of quantum transitions for AgCl : J nanocrystal with the adsorbed silver ion were been discussed. This work is a continuation of paper [1].

  18. Multiple ionization of neon atoms in collisions with bare and dressed ions: A mean-field description considering target response

    NASA Astrophysics Data System (ADS)

    Schenk, Gerald; Kirchner, Tom

    2015-05-01

    We investigate projectile-charge-state-differential electron removal from neon atoms by impact of He2+, Li3+, B2+, and C3+ ions at intermediate projectile energies (25 keV/u to 1 MeV/u ). The many-electron problem is described with an independent electron model in which active electrons at both collision centers are propagated in a common mean-field potential. Response to electron removal is taken into account in terms of a time-dependent screening potential, and a Slater-determinant-based method is used for the final-state analysis. Total cross sections for net recoil ion production, multiple ionization, and capture channels are mostly in good agreement with published experimental data. Results from equicharged bare and dressed ions are compared and the net recoil ion production cross section is broken down into contributions associated with different final projectile charge states in order to shed light on the role of the projectile electrons.

  19. Au Colloids Formed by Ion Implantation in Muscovite Mica Studied by Vibrational and Electronic Spectroscopes and Atomic Force Microscopy

    NASA Technical Reports Server (NTRS)

    Tung, Y. S.; Henderson, D. O.; Mu, R.; Ueda, A.; Collins, W. E.; White, C. W.; Zuhr, R. A.; Zhu, Jane G.

    1997-01-01

    Au was implanted into the (001) surface of Muscovite mica at an energy of 1.1 MeV and at doses of 1, 3, 6, and 10 x 10(exp 16) ions/cu cm. Optical spectra of the as-implanted samples revealed a peak at 2.28 eV (545 nm) which is attributed to the surface plasmon absorption of Au colloids. The infrared reflectance measurements show a decreasing reflectivity with increasing ion dose in the Si-O stretching region (900-1200 /cm). A new peak observed at 967 /cm increases with the ion dose and is assigned to an Si-O dangling bond. Atomic force microscopy images of freshly cleaved samples implanted with 6 and 10 x 10(exp 16) ions/sq cm indicated metal colloids with diameters between 0.9- 1.5 nm. AFM images of the annealed samples showed irregularly shaped structures with a topology that results from the fusion of smaller colloids.

  20. Effects of Ion Atomic Number on Single-Event Gate Rupture (SEGR) Susceptibility of Power MOSFETs

    NASA Technical Reports Server (NTRS)

    Lauenstein, J.-M.; Goldsman, N.; Liu, S.; Titus, J.; Ladbury, R. L.; Kim, H. S.; Phan, A. M.; Zafrani, M.; Sherman, P.

    2011-01-01

    The relative importance of heavy-ion interaction with the oxide, charge ionized in the epilayer, and charge ionized in the drain substrate, on the bias for SEGR failure is experimentally investigated.

  1. Atomic charges of Cl- ions confined in a model Escherichia coli ClC-Cl-/H+ ion exchanger: a density functional theory study

    NASA Astrophysics Data System (ADS)

    Nieto-Delgado, P. G.; Arreola, J.; Guirado-López, R. A.

    2013-11-01

    We present extensive semi-empirical and pseudo-potential density functional theory calculations dedicated to analyse the stability, charge density distribution and migration behaviour of Cl- ions confined in model Escherichia coli (ec) ClC-Cl-/H+ ion-exchangers. Following recent high-resolution crystal structure determination in these kinds of systems, we use a finite-cluster model approach and construct various chemically simplified pore structures made of a glutamate residue -CH2-CH2-COO- (E148) and its closets 15, 19, 23 and 26 amino acids into which the Cl- ions will be confined. We reveal the sequence of molecular rearrangements induced on the E148 chain, which blocks the middle of the conduction pathway, leading to the pore opening. The -CH2-CH2-COO- fragment shows notable variations in its average charge density for small changes in the intra-cellular environment varying from -0.4e to -0.3e to -0.1e in the presence of zero, one and two confined Cl- ions, respectively, a result that reveals an interesting functionality of the E148 chain during Cl- conduction. We also obtain complex fluctuations in the ionic charge of the confined Cl- ions varying from ∼-0.7e to -0.2e, which deviate significantly from the value (-1e) usually used in classical simulations. By attaching a single H species to one of the oxygens of the glutamate group, we obtain that the -CH2-CH2-COOH fragment has now a small effective charge of ∼+0.25e. The energy barriers opposing the exit of the Cl- ions from our considered ion-exchangers vary from 0.65 eV to 4.7 eV, the smallest values being obtained for model structures exhibiting a high degree of flexibility and having protonated E148 fragments. Our results reinforce previous findings and provide additional physical insight, at the atomic level, on the gating process. Finally, we underline the importance of using electronically polarisable force fields to describe the transport of anionic species through this kind of molecular

  2. Cascade Problems in Some Atomic Lifetime Measurements at a Heavy-Ion Storage Ring

    SciTech Connect

    Trabert, E; Hoffmann, J; Krantz, C; Wolf, A; Ishikawa, Y; Santana, J

    2008-10-09

    Lifetimes of 3s{sup 2}3p{sup k} ground configuration levels of Al-, Si-, P-, and S-like ions of Be, Co, and Ni have been measured at a heavy-ion storage ring. Some of the observed decay curves show strong evidence of cascade repopulation from specific 3d levels that feature lifetimes in the same multi-millisecond range as the levels of the ground configuration.

  3. 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.

  4. Energetic ion, atom, and molecule reactions and excitation in low-current H2 discharges: spatial distributions of emissions.

    PubMed

    Petrović, Z Lj; Phelps, A V

    2009-07-01

    Spatial distributions of H alpha , H beta , and the near-uv continuum emission from the H2 a ;{3}Sigma g;+ state are measured and compared with a model for low-current electrical discharges in H2 at high E/N and low Nd , where E is the spatially uniform electric field, N is the gas density, and d is the electrode separation. Data are analyzed for 300 Tdatoms and molecules with mean energies from 5 to 1500 eV. Electron-induced emission, dominant at low E/N and low pressures, is distinguished by its buildup toward the anode. Excitation of H alpha by fast H atoms dominates at high E/N and increases toward the cathode. The observed H alpha emission at low E/N is normalized to previous experiments to yield absolute experimental excitation coefficients for all E/N and Nd . Small adjustments of model parameters yield good agreement with H alpha data. Cross sections are derived for excitation of the H2 near-uv continuum by H atoms. Spatial and pressure dependencies of H alpha and H2 near-uv emissions agree well with a model in which reactions of H2+ , H3+ , and H+ ions with H2 lead to fast H atoms and H2 molecules, which then excite H atoms or H2 molecules. PMID:19658824

  5. Ultrafast emission of ions during laser ablation of metal for 3D atom probe

    NASA Astrophysics Data System (ADS)

    Vella, A.; Houard, J.; Vurpillot, F.; Deconihout, B.

    2009-03-01

    The 3D atom probe(3DAP) is an imaging instrument based on the controlled field evaporation of single atoms from a sample having a tip shape with an end radius of 50 nm. In the fs laser assisted 3DAP the evaporation is induced by the laser pulses so that the physical process involved in this 3DAP analysis might correspond to the very early stages of the ablation process. In this paper we present the principle of the 3DAP and we discuss the existing models of the fs assisted evaporation. At last, we test the relevance of these models with pump-probe experiments on tungsten tips in the tomographic atom probe.

  6. Rovibrational molecular populations, atoms, and negative ions in H/sub 2/ and D/sub 2/ magnetic multicusp discharges

    SciTech Connect

    Pealat, M.; Taran, J.E.; Bacal, M.; Hillion, F.

    1985-06-01

    Coherent anti-Stokes Raman scattering is applied to the study of rovibrational populations in magnetic multicusp H/sub 2/ and D/sub 2/ discharges. This subject is of interest to negative hydrogen ion formation by volume plasma processes. The populations of high-lying rotational states (J>5) in the vibrational levels v = 0, 1, and 2 are found to be significantly higher than expected from the Boltzmann law. In H/sub 2/ the net populations of the first four vibrational levels follow approximately the Boltzmann law, with the vibrational temperature of 2390 K (in a 90 V-10 A discharge at 55 ..mu..bar). In similar discharge conditions, the population of the state v = 3 in D/sub 2/ is higher than expected from the Boltzmann law. In the presence of the discharge a deficiency in H/sub 2/ and D/sub 2/ molecule density was observed and was attributed to the possible presence of H and D atoms. This was verified by an independent measurement of the atomic fraction and temperature. The density of negative ions, measured by the photodetachment technique, is also reported.

  7. The creation, destruction, and transfer of multipole moments in electron- and proton-impact ionization of atoms and ions

    NASA Astrophysics Data System (ADS)

    Csanak, G.; Inal, M. K.; Fontes, C. J.; Kilcrease, D. P.

    2013-12-01

    Expanding on previous works that involved elastic and inelastic scattering of electrons by atoms and ions, we use the wave-packet propagation scheme of Dollard to define multipole moment creation, destruction and transfer cross sections for electron- and proton-impact ionization of atoms and ions. The electron-impact cross sections can then be used by defining appropriate rate coefficients for use in Fujimoto’s population-alignment collisional-radiative model for cylindrically symmetric plasmas. Our result for the alignment creation cross section is in agreement with those formulae that were obtained earlier intuitively or by semi-classical collisional methods. The multipole cross sections obtained here can be used also for modelling the relaxation behaviour of laser-excited plasmas under cylindrical symmetry conditions. We have also derived the electron- and proton-impact ionization multipole cross sections in terms of Liouville-space quantities, which then enabled us by using group theoretical methods to obtain the azimuthal-angle dependence of the multipole cross sections and symmetry properties that are results of reflection across a plane over the collisional axis.

  8. Atomic/molecular depth profiling of nanometric-metallized polymer thin films by secondary ion mass spectrometry.

    PubMed

    Téllez, Helena; Vadillo, José Miguel; Laserna, José Javier

    2010-02-01

    The capability of secondary ion mass spectrometry (SIMS) to perform atomic and molecular in-depth analysis in complex nanometric-metallized thin polymer films used to manufacture capacitors is demonstrated through three different case studies related to failure analysis. The excellent repeatability and sensitivity of the technique allow us to study the degradation process of the nanometric-metallized layer in the capacitor films and the accurate location of the metal-polymer interface. The analysis of the sample is challenging due to the extreme difference in conductivity between layers, and the reduced thickness of the metallization grown on top of a rough polymeric base. However, SIMS has provided reliable and reproducible results with relative standard deviation (RSD) values better than 1.5% in the metallic layer thickness estimation. The detailed information of atomic and molecular ion in-depth distributions provided by SIMS depth profiling has allowed the identification of different factors (demetallization, generation of interstitial oxide regions, and diffusion processes or modification in the metallization thickness) that can be directly related to the origin of the lack of performance of the mounted devices.

  9. Hydrogen atom scrambling in ion-molecule reactions of methane and ethylene.

    NASA Technical Reports Server (NTRS)

    Huntress, W. T., Jr.

    1972-01-01

    The extent of hydrogen atom exchange in the reaction, CH3(+) + CH4 yields C2H5(+) + H2, is determined by examining the product distribution for the reactions CH3(+) + CD4 and CD3(+) + CH4 as a function of relative kinetic energy from thermal energies to 10 eV. It is found that the reaction of CH4(+) with the parent neutral proceeds both via proton transfer and hydrogen abstraction accompanied by approximately 10% hydrogen atom exchange during the reaction.

  10. Ripple formation on atomically flat cleaved Si surface with roughness of 0.038 nm rms by low-energy Ar{sup 1+} ion bombardment

    SciTech Connect

    Pahlovy, Shahjada A.; Mahmud, S. F.; Yanagimoto, K.; Miyamoto, I.

    2011-03-15

    The authors have conducted research regarding ripple formation on an atomically flat cleaved Si surface by low-energy Ar{sup +} ion bombardment. The cleaved atomically flat and smooth plane of a Si wafer was obtained by cutting vertically against the orientation of a Si (100) wafer. Next, the cleaved surface was sputtered by a 1 keV Ar{sup +} ion beam at ion-incidence angles of 0 deg., 60 deg., 70 deg., and 80 deg. The results confirm the successful ripple formation at ion-incidence angles of 60 deg. - 80 deg. and that the wavelength of the ripples increases with the increase of the ion-incidence angle, as well as the inverse of ion doses. The direction of the ripple also changes from perpendicular to parallel to the projection of the ion-beam direction along the surface with the increasing ion-incidence angle. The authors have also observed the dose effects on surface roughness of cleaved Si surface at the ion-incidence angle of 60 deg., where the surface roughness increases with the increased ion dose. Finally, to understand the roughening mechanism, the authors studied the scaling behavior, measured the roughness exponent {alpha}, and compared the evolution of scaling regimes with Cuerno's one-dimensional simulation results.

  11. On the role of atomic metastability in the production of Balmer line radiation from ‘cold’ atomic hydrogen, deuterium and hydrogenic ion impurities in fusion edge plasmas

    NASA Astrophysics Data System (ADS)

    Hey, J. D.

    2012-03-01

    Published arguments, which assign an important role to atomic metastability in the production of ‘narrow’ Zeeman component radiation from the boundary region of fusion plasmas, are examined critically in relation to l-redistribution by proton and electron collisions, and mixing of unperturbed atomic states by the ion microfield and microfield gradient. It is concluded that these important processes indeed severely constrain the contribution from ‘metastable’ states to the generation of the hydrogen Balmer spectra, for electron concentrations above 1012 cm-3, as pointed out before by the present author (Hey et al 1999 J. Phys. B: At. Mol. Opt. Phys. 32 3555). The analysis of collision-induced l-redistribution represents an extension of that used previously (Hey et al 1996 Contrib. Plasma Phys. 36 583), applicable up to higher electron densities. For comparison purposes, we also consider the question of metastability of ionized helium in a low-temperature plasma, and that of some common hydrogenic impurities (C5+ and Ne9+) in a hydrogen (deuterium) fusion plasma. While for low nuclear charge Z the metastability of 2s1/2 levels is quenched by the plasma environment, it is much reduced in high-Z ions owing to the rapid increase with Z of the two-photon electric dipole (2E1) and magnetic dipole (M1) spontaneous transition rates to the ground state, whereas the role of the plasma in these cases is less important. The main new principle elaborated in this work is the sensitivity of atomic line strengths, and hence collision strengths, to perturbation by the plasma environment for transitions between fine-structure sublevels of the same principal quantum number. As the plasma microfield strength grows, ‘allowed’ transitions diminish in strength, while ‘forbidden’ transitions grow. However, owing to violation of the parity selection rule, there is an overall loss of collision strength available to transitions, resulting from the appearance of significant

  12. Prise en compte de l'anisotropie des collisions ion-atome sur le transport des ions par simulation de Monte-Carlo

    NASA Astrophysics Data System (ADS)

    Hennad, A.; Eichwald, O.; Yousfi, M.; Lamrous, O.

    1997-09-01

    This paper is devoted to the determination of the differential and integral collision cross sections needed for the calculation of the transport coefficient of ions in weakly ionized gases. In the case of Ar^+/Ar system and for energy interval varying up to 100 eV, the cross sections are obtained from the interaction potential of polarization for low energies and of Lennard-Jones for higher energies. The calculation method of the collision cross sections based on the classical mechanics has been first validated from comparisons of measured and calculated differential cross sections. Then, these cross sections have been used in a Monte-Carlo code for simulation of the transport of Ar^+ ions in Ar gas at room temperature (300 K). The obtained transport coefficients (ion mobility, drift velocity and diffusion coefficient) are in good agreement with the drift tube measurements given in the literature thus confirming the validity of the method of collision cross section calculation. Cet article est consacré à la détermination des sections efficaces différentielles et intégrales ion-atome nécessaires au calcul des coefficients de transport des ions dans les gaz faiblement ionisés. Dans le cas du système Ar^+/Ar et pour des intervalles d'énergie allant jusqu'à quelques dizaines d'eV, les sections efficaces sont obtenues à partir des potentiels d'interaction de polarisation pour les faibles énergies et de Lennard-Jones pour les énergies plus élevées. La méthode de calcul des sections efficaces basée sur la mécanique classique a d'abord été validée par comparaison des sections efficaces différentielles mesurées et calculées. Ensuite, ces sections efficaces ont été utilisées dans un code de simulation statistique de Monte-Carlo du transport des ions Ar^+ dans l'Argon à la température ambiante (300 K). Les coefficients de transport (vitesse de dérive, mobilité ionique et coefficient de diffusion) obtenus sont en bon accord avec les mesures de

  13. Ion-channeling study of anomalous atomic displacements at the superconducting transition in high-T sub c materials

    SciTech Connect

    Rehn, L.E.; Sharma, R.P.; Baldo, P.M.

    1990-06-01

    Ion channeling along the (001) direction in high-quality single crystals of (Y/Er)Ba{sub 2}Cu{sub 3}O{sub 7-x} revealed an abrupt change in displacements in the a-b plane of the Cu and O atoms at the superconducting transition, {Tc}; normal Debye-like'' vibrations were found for the Y/Er and Ba atoms. The anomalous change in Cu-O displacements was found to shift directly with stoichiometry-induced changes in {Tc}, implying a direct link between the observed phonon anomaly and the superconducting transition. Recent measurements of ion-channeling along the (001) axis in (Bi{sub 1.7}Pb{sub 0.3})Sr{sub 2}Ca{sub 1}Cu{sub 2}O{sub x} single-crystals revealed a similar change at {Tc}, suggesting that this phonon anomaly is a general feature of high-{Tc} superconductivity. In order to identify more specifically the crystallographic directions and displacement amplitudes associated with the anomalous phonon behavior, axial channeling scans using RBS, as well as characteristic x-ray production, were taken at several temperatures between 30 and 300K along the (301) and (331) directions of YBa{sub 2}Cu{sub 3}O{sub 7-x} single crystals. Twins present in the specimens, and the existing static atomic displacements present along these directions, caused the channeling to be poorer along these axes compared to the (001) direction. Also, a much stronger dependence of the minimum yield on depth was observed. However, since only one twin variant generally dominated over sufficiently wide areas of the specimens, reasonably good ({approximately}10%) minimum yields could be obtained along the appropriate (331) axis, and detwinned crystals produced good results along (301). 22 refs., 5 figs.

  14. X-ray emission from charge exchange of highly-charged ions in atoms and molecules

    NASA Technical Reports Server (NTRS)

    Greenwood, J. B.; Williams, I. D.; Smith, S. J.; Chutjian, A.

    2000-01-01

    Charge exchange followed by radiative stabilization are the main processes responsible for the recent observations of X-ray emission from comets in their approach to the Sun. A new apparatus was constructed to measure, in collisions of HCIs with atoms and molecules, (a) absolute cross sections for single and multiple charge exchange, and (b) normalized X-ray emission cross sections.

  15. Interaction of atomic and low-energy deuterium with tungsten pre-irradiated with self-ions

    NASA Astrophysics Data System (ADS)

    Ogorodnikova, O. V.; Markelj, S.; von Toussaint, U.

    2016-02-01

    Polycrystalline tungsten (W) specimens were pre-irradiated with self-ions to create identical samples with high density of defects up to ˜2.5 μm near the surface. Then, W specimens were exposed to either thermal atomic deuterium (D) beam with an incident energy of ˜0.2 eV or low energy D plasma with the incident energy varied between 5 and 200 eV at different sample temperatures. Each sample was exposed once at certain temperature and fluence. The D migration and accumulation in W were studied post-mortem by nuclear reaction method. It was shown that the rate of the D to occupy radiation-induced defects increases with increasing the incident energy, ion flux, and temperature. Experimental investigation was accompanied by modelling using the rate-equation model. Moreover, the analytical model was developed and benchmarked against numerical model. The calculations of the deuterium diffusion with trapping at radiation-induced defects in tungsten by analytical model are consistent with numerical calculations using rate-equation model. The data of reflection and penetration of atomic and low-energy D were taking from calculations using molecular dynamics (MD) with Juslin interatomic potentials and a binary collision code TRIM. MD calculations show an agreement with a binary collision code TRIM only in a very narrow range of deuterium energies between 1 and 20 eV. Incorporation of the data of reflection and penetration of deuterium in the macroscopic modelling has been done to verify the range of validity of calculations using MD and binary collision code TRIM by comparison of modelling results with experimental data. Modelling results are consistent with experiments using reflection and penetration data of D obtained from TRIM code for incident ion energy above 1 eV. Otherwise, the parameters obtained from MD should be incorporated in the rate-equation model to have a good agreement with the experiments.

  16. Atomically precise doping of monomanganese ion into coreless supertetrahedral chalcogenide nanocluster inducing unusual red shift in Mn(2+) emission.

    PubMed

    Lin, Jian; Zhang, Qian; Wang, Le; Liu, Xiaochun; Yan, Wenbo; Wu, Tao; Bu, Xianhui; Feng, Pingyun

    2014-03-26

    We report a simple and yet effective method to introduce Mn(2+) ions into semiconducting nanoclusters with atomically precise control. Our method utilizes one type of micrometer-sized crystals, composed of well-defined isolated supertetrahedral chalcogenide nanoclusters (∼2 nm, [Cd6In28S52(SH)4]) whose core metal site is unoccupied in as-synthesized pristine form. This unique model structure with vacant core site makes it possible to achieve ordered distribution of Mn(2+) dopants, and at the same time effectively preclude the formation of Mn(2+) clusters in the host matrix. A two-step synthesis strategy is applied to realize an atomically precise doping of Mn(2+) ion into the core site of the nanoclusters, and to achieve uniform distribution of Mn(2+) dopants in the crystal lattice. The PL, X-ray photoelectron (XPS), as well as the electron paramagnetic resonance (EPR) spectra reveal the successful incorporation of Mn(2+) ion into the core site of the nanocluster. Different from the pristine host material with weak green emission (∼490 nm), the Mn(2+)-doped material shows a strong red emission (630 nm at room temperature and 654 nm at 30 K), which is significantly red-shifted relative to the orange emission (∼585 nm) observed in traditional Mn(2+)-doped II-VI semiconductors. Various experiments including extensive synthetic variations and PL dynamics have been performed to probe the mechanistic aspects of synthesis process and resultant unusual structural and PL properties. The quaternary semiconductor material reported here extends the emission window of Mn(2+)-doped II-VI semiconductor from yellow-orange to red, opening up new opportunities in applications involving photonic devices and bioimaging.

  17. Multiple ionization and capture in relativistic heavy-ion atom collisions

    SciTech Connect

    Meyerhof, W.E.; Anholt, R.; Xu, Xiang-Yuan; Gould, H.; Feinberg, B.; McDonald, R.J.; Wegner, H.E.; Thieberger, P.

    1987-02-01

    We show that in relativistic heavy-ion collisions the independent electron model can be used to predict cross sections for multiple inner-shell ionization and capture in a single collision. Charge distributions of 82- to 200-MeV/amu Xe and 105- to 955-MeV/amu U ion beams emerging from thin solid targets were used to obtain single- and multiple-electron stripping and capture cross sections. The probabilities of stripping electrons from the K, L, or M shells were calculated using the semiclassical approximation and Dirac hydrogenic wavefunctions. For capture, a simplified model for electron capture was uded. The data generally agree with theory.

  18. Loss of Pickup Ions in the Heliosheath by Energetic Neutral Atoms - Implications for the Width of the Heliosheath (Invited)

    NASA Astrophysics Data System (ADS)

    Heerikhuisen, J.; Zirnstein, E. J.; Zank, G. P.; Pogorelov, N. V.; Desai, M. I.

    2013-12-01

    Pickup ions (PUIs) are formed when Hydrogen atoms charge-exchange with plasma protons to produce non-thermal protons. In the supersonic solar wind (SW), newly formed PUIs scatter, by wave-particle interactions, onto a shell in velocity space. At the termination shock, we know from Voyager 2 observations that most of the thermal energy of the SW is passed to the PUIs, while the core SW remains relatively cool in the downstream heliosheath. Charge-exchange in the heliosheath will remove these energetic PUIs and replace them with new ions which have a similar thermal speed as the core. Since the charge-exchange rate depends on the relative speed between individual ions and neutrals, suprathermal PUIs will be efficiently removed through the creation of ENAs, leading to a rapid reduction in heliosheath pressure and a corresponding decrease of the heliosheath thickness. We present some insights from modeling of the global heliosphere into the relative partitioning of PUIs downstream of the termination shock. We show the resulting ENA spectra and compare these to IBEX data, and quantify the extinction of PUIs as a function of distance from the termination shock. Finally we show how ENAs from the heliosheath can escape the heliosphere and form PUIs in the disturbed interstellar plasma just outside the heliopause.

  19. Electronic and atomic kinetics in solids irradiated with free-electron lasers or swift-heavy ions

    NASA Astrophysics Data System (ADS)

    Medvedev, N.; Volkov, A. E.; Ziaja, B.

    2015-12-01

    In this brief review we discuss the transient processes in solids under irradiation with femtosecond X-ray free-electron-laser (FEL) pulses and swift-heavy ions (SHI). Both kinds of irradiation produce highly excited electrons in a target on extremely short timescales. Transfer of the excess electronic energy into the lattice may lead to observable target modifications such as phase transitions and damage formation. Transient kinetics of material excitation and relaxation under FEL or SHI irradiation are comparatively discussed. The same origin for the electronic and atomic relaxation in both cases is demonstrated. Differences in these kinetics introduced by the geometrical effects (μm-size of a laser spot vs nm-size of an ion track) and initial irradiation (photoabsorption vs an ion impact) are analyzed. The basic mechanisms of electron transport and electron-lattice coupling are addressed. Appropriate models and their limitations are presented. Possibilities of thermal and nonthermal melting of materials under FEL and SHI irradiation are discussed.

  20. Hybrid compounds of Keggin polyoxotungstate with transition metal ion as the central atom. Synthesis, structure and properties

    NASA Astrophysics Data System (ADS)

    Li, Xiao-Min; Chen, Ya-Guang; Shi, Tian

    2016-02-01

    The compounds (Hbipy)2[Co(bipy)2(H2O)4]2(CoW12O40)·2bipy·7H2O (1) and [Ni2(Hbipy)2(bipy)(H2O)4(H2W12O40)]·5H2O (2) (bipy = 4,4-bipyridine) were synthesized hydrothermally and characterized by elemental analysis, IR spectroscopy, TG analyses, solid ultraviolet diffuse spectroscopy and single crystal X-ray diffraction method. In 1 the complex ions, [Co(bipy)2(H2O)4]2+, construct a supramolecular layer through π-π stacking interaction. The heteropolyanions with central Co atom and supramolecular layers are linked by hydrogen bonds. In 2 a 2D structure is formed from metatungstate anions and binuclear Ni-bipy complexes through the coordination of metatungstate anions and bipy to Ni ions. Between the layers and bipyridine molecules are the hydrogen bond interactions. The formation of 1 and 2 shows that the solution acidity and metal ions influence greatly the structure of the compounds. Solid ultraviolet diffusion results indicate that the compounds 1 and 2 are potential semiconductor materials. In 1 and 2 there exists a weak antiferromagnetic interaction.

  1. Absolute Transition Probabilities of Lines in the Spectra of Astrophysical Atoms, Molecules, and Ions

    NASA Technical Reports Server (NTRS)

    Parkinson, W. H.; Smith, P. L.; Yoshino, K.

    1984-01-01

    Progress in the investigation of absolute transition probabilities (A-values or F values) for ultraviolet lines is reported. A radio frequency ion trap was used for measurement of transition probabilities for intersystem lines seen in astronomical spectra. The intersystem line at 2670 A in Al II, which is seen in pre-main sequence stars and symbiotic stars, was studied.

  2. Algebraic tools for dealing with the atomic shell model. I. Wavefunctions and integrals for hydrogen-like ions

    NASA Astrophysics Data System (ADS)

    Surzhykov, Andrey; Koval, Peter; Fritzsche, Stephan

    2005-01-01

    Today, the 'hydrogen atom model' is known to play its role not only in teaching the basic elements of quantum mechanics but also for building up effective theories in atomic and molecular physics, quantum optics, plasma physics, or even in the design of semiconductor devices. Therefore, the analytical as well as numerical solutions of the hydrogen-like ions are frequently required both, for analyzing experimental data and for carrying out quite advanced theoretical studies. In order to support a fast and consistent access to these (Coulomb-field) solutions, here we present the DIRAC program which has been developed originally for studying the properties and dynamical behavior of the (hydrogen-like) ions. In the present version, a set of MAPLE procedures is provided for the Coulomb wave and Green's functions by applying the (wave) equations from both, the nonrelativistic and relativistic theory. Apart from the interactive access to these functions, moreover, a number of radial integrals are also implemented in the DIRAC program which may help the user to construct transition amplitudes and cross sections as they occur frequently in the theory of ion-atom and ion-photon collisions. Program summaryTitle of program:DIRAC Catalogue number: ADUQ Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADUQ Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Licensing provisions: None Computer for which the program is designed and has been tested: All computers with a license of the computer algebra package MAPLE [1] Program language used: Maple 8 and 9 No. of lines in distributed program, including test data, etc.:2186 No. of bytes in distributed program, including test data, etc.: 162 591 Distribution format: tar gzip file CPC Program Library subprograms required: None Nature of the physical problem: Analytical solutions of the hydrogen atom are widely used in very different fields of physics [2,3]. Despite of the rather simple structure

  3. Photoassociative ionization of cold Na atoms: repulsive levels effects on the ion production rate

    NASA Astrophysics Data System (ADS)

    Paiva, R. R.; Muhammad, R.; Shiozaki, R. F.; de Oliveira, A. L.; Magalhães, D. V.; Ramirez-Serrano, J.; Bagnato, V. S.; Magalhães, K. M. F.

    2009-02-01

    We have revisited photoassociative ionization (PAI) in a cold sample of Na atoms. A two-color experiment was performed in a magneto-optical trap through the addition of a probe laser. The observation of a marked change in the PAI rate for a definite frequency range can be attributed to the influence of repulsive levels and a possible avoided crossing between long-range molecular levels.

  4. Interaction of Sn atoms with defects introduced by ion implantation in Ge substrate

    SciTech Connect

    Taoka, Noriyuki Fukudome, Motoshi; Takeuchi, Wakana; Arahira, Takamitsu; Sakashita, Mitsuo; Nakatsuka, Osamu; Zaima, Shigeaki

    2014-05-07

    The interaction of Sn atoms with defects induced by Sn implantation of Ge substrates with antimony (Sb) as an n-type dopant and the impact of H{sub 2} annealing on these defects were investigated by comparison with defects induced by Ge self-implantation. In the Ge samples implanted with either Sn or Ge, and annealed at temperatures of less than 200 °C, divacancies, Sb-vacancy complexes with single or double acceptor-like states, and defects related to Sb and interstitial Ge atoms were present. On the other hand, after annealing at 500 °C in an N{sub 2} or H{sub 2} atmosphere, defects with different structures were observed in the Sn-implanted samples by deep level transition spectroscopy. The energy levels of the defects were 0.33 eV from the conduction band minimum and 0.55 eV from the valence band maximum. From the capacitance-voltage (C-V) characteristics, interaction between Sn atoms and defects after annealing at 500 °C was observed. The effect of H{sub 2} annealing at around 200 °C was observed in the C-V characteristics, which can be attributed to hydrogen passivation, and this effect was observed in both the Ge- and Sn-implanted samples. These results suggest the presence of defects that interact with Sn or hydrogen atoms. This indicates the possibility of defect control in Ge substrates by Sn or hydrogen incorporation. Such defect control could yield high-performance Ge-based devices.

  5. VizieR Online Data Catalog: N-like ions atomic data (Radziute+, 2015)

    NASA Astrophysics Data System (ADS)

    Radziute, L.; Ekman, J.; Jonsson, P.; Gaigalas, G.

    2015-08-01

    Table 5. Excitation energy in cm-1 for the active sets n=8 (E{cal,n=8}) and n=9 (E{cal,n=9}) in LSJ-coupling for FeXX compared with Gu (2005, Cat. J/ApJS/156/105) (E_{CI+MBPT} ) and observed energies Eobs from NIST Atomic Spectra Database (Kramida et al., 2013, NIST Atomic Spectra Database (version 5.1) (Gaithersburg, MD: US NIST)). Tables 6, 8, 10, 12. Excitation energy E (in cm-1), hyperfine magnetic dipole constants AJ(I/μI) (in MHz per units of μ_N), electric quadrupole constants BJ/Q (MHz/barn), Lande gJ-factors, normal mass shift {widetilde}K_{NMS} (GHzu) parameters, specific mass shift {widetilde}K_{SMS} (GHzu), field shift {widetilde}F (GHz/fm2) parameters for levels of FeXX, CrXVIII, NiXXII and ZnXXIV respectively. Tables 7, 9, 11 and 13. Excitation energy E (in cm-1) and composition of atomic state function in LSJ-coupling FeXX, CrXVIII, NiXXII and ZnXXIV respectively. Tables 18 - 21. Excitation energy E (in cm-1) and lifetimes in s for FeXX, CrXVIII, NiXXII and ZnXXIV respectively in length ({tau}_l) and velocity ({tau}_v) forms. (17 data files).

  6. Effects of ion beam treatment on atomic and macroscopic adhesion of copper to different polymer materials

    NASA Astrophysics Data System (ADS)

    Zaporojtchenko, V.; Zekonyte, J.; Faupel, F.

    2007-12-01

    Low-energy ion irradiation of polymer induces different phenomena in the near surface layer, which effect strongly the metal-polymer interface formation and promotes adhesion of polymers to metals. Low-energy argon and oxygen ion beams were used to alter the chemical and physical properties of different polymers (PS (polystyrene), PαMS (poly(α-methylstyrene), BPA-PC (bisphenol-A-polycarbonate) and PMMA (poly(methyl methacrylate)), in order to understand the adhesion phenomena between a deposited Cu layer and the polymers. The resulting changes were investigated by various techniques including X-ray photoelectron spectroscopy, measurements of the metal condensation coefficient and a new technique to measure cross-linking at the polymer surface. Two types of practical adhesion strengths of Cu-polymer systems, measured using 90° peel tests, were observed: (i) peel strength increased at low ion fluences, reached a maximum and then decreased after prolonged treatment and (ii) no improvement in the peel strength on treated polymer surfaces was recorded. The improvement in the metal-polymer adhesion in the ion fluence range of 10 13-10 15 cm -2 is attributed to the creation of a large density of new adsorption sites resulting in a larger contact area and incorporation of chemically active groups that lead to increased interaction between metal and polymer by metal-oxygen-polymer species formation. XPS analysis of peeled-off surfaces showed that in most cases the failure location changed from interfacial for untreated polymers to cohesive failure in the polymer for treated surfaces. These observations and measurements of the metal condensation coefficients suggest that bonding is improved at the metal-polymer interface for all metal-polymer systems. However, the decrease in the peel strength at high ion fluences is attributed to the formation of a weak boundary layer in polymers. The correlation between sputter rate of polymers and altering in the peel strength for

  7. Atomic Data for Neutron-capture Elements I. Photoionization and Recombination Properties of Low-charge Selenium Ions

    NASA Technical Reports Server (NTRS)

    Sterling, N. C.; Witthoeft, Michael

    2011-01-01

    We present multi-configuration Breit-Pauli AUTOSTRUCTURE calculations of distorted-wave photoionization (PI) cross sections. and total and partial final-state resolved radiative recombination (RR) and dielectronic recombination (DR) rate coefficients for the first six ions of the trans-iron element Se. These calculations were motivated by the recent detection of Se emission lines in a large number of planetary nebulae. Se is a potentially useful tracer of neutron-capture nucleosynthesis. but accurate determinations of its abundance in photoionized nebulae have been hindered by the lack of atomic data governing its ionization balance. Our calculations were carried out in intermediate coupling with semi re1ativistic radial wavefunctions. PI and recombination data were determined for levels within the ground configuration of each ion, and experimental PI cross-section measurements were used to benchmark our results. For DR, we allowed (Delta)n = 0 core excitations, which are important at photoionized plasma temperatures. We find that DR is the dominant recombination process for each of these Se ions at temperatures representative of photoionized nebulae (approx.10(exp 4) K). In order to estimate the uncertainties of these data, we compared results from three different configuration-interaction expansions for each ion, and also tested the sensitivity of the results to the radial scaling factors in the structure calculations. We find that the internal uncertainties are typically 30-50% for the direct PI cross sections and approx.10% for the computed RR rate coefficients, while those for low-temperature DR can be considerably larger (from 15-30% up to two orders of magnitude) due to the unknown energies of near-threshold autoionization resonances. These data are available at the CDS, and fitting coefficients to the total RR and DR rate coefficients are presented. The results are suitable for incorporation into photoionization codes used to numerically simulate

  8. Atomic-level observation of Ag-ion hopping motion in AgI

    NASA Astrophysics Data System (ADS)

    Sato, W.; Komatsuda, S.; Mizuuchi, R.; Irioka, N.; Kawata, S.; Ohkubo, Y.

    2015-04-01

    Applicability of the 111mCd(→111Cd) and 111In(→111Cd) probes to the study of dynamics in polycrystalline silver iodide (AgI) was examined by means of the time-differential perturbed angular correlation technique. It was found that the 111mCd(→111Cd) probe occupies a unique site in γ-AgI and exhibits nuclear relaxation caused by dynamic perturbation arising from Ag + hopping motion in α-AgI; while the residential sites of 111In(→111Cd) vary, suggesting that 111In ions can not settle themselves in a fixed site in the AgI crystal structure. We here demonstrate that 111mCd(→111Cd) can be a potential nucleus to probe the Ag +-ion dynamic motion in α-AgI.

  9. Mechanism of 'GSI oscillations' in electron capture by highly charged hydrogen-like atomic ions

    SciTech Connect

    Krainov, V. P.

    2012-07-15

    We suggest a qualitative explanation of oscillations in electron capture decays of hydrogen-like {sup 140}Pr and {sup 142}Pm ions observed recently in an ion experimental storage ring (ESR) of Gesellschaft fuer Schwerionenforschung (GSI) mbH, Darmstadt, Germany. This explanation is based on the electron multiphoton Rabi oscillations between two Zeeman states of the hyperfine ground level with the total angular momentum F = 1/2. The Zeeman splitting is produced by a constant magnetic field in the ESR. Transitions between these states are produced by the second, sufficiently strong alternating magnetic field that approximates realistic fields in the GSI ESR. The Zeeman splitting amounts to only about 10{sup -5} eV. This allows explaining the observed quantum beats with the period 7 s.

  10. Electron correlation and relativistic effects in atomic structure calculations of Th+, Th2+ ions

    NASA Astrophysics Data System (ADS)

    Roy, S. K.; Prasad, Rajendra; Datta, Sambhu N.; Chandra, P.

    2012-10-01

    Relativistic two-component ab initio calculations through second-order Douglas-Kroll-Hess (DKH2) transformation are performed on Th+ and Th2+ ions. Spin-orbit-free calculations are done at SA-CASSCF and MS-CASPT2 levels. Spin-orbit coupled states are studied using effective mean-field operator. Spin-orbit states of Th+, below 23 000 cm-1 are compared with experimental values. Relative separations between various energy levels depend on the amount of electron correlation included in the calculation. For Th2+, spin-orbit energy levels below 20 000 cm-1 agree well with the experimental levels. Transition properties of several spin-orbit states in case of Th2+ ion are predicted.

  11. Metal ions and flexibility in a viral RNA pseudoknot at atomic resolution

    SciTech Connect

    Egli, Martin; Minasov, George; Su, Li; Rich, Alexander

    2010-03-05

    Many pathogenic viruses use programmed -1 ribosomal frameshifting to regulate translation of their structural and enzymatic proteins from polycistronic mRNAs. Frameshifting is commonly stimulated by a pseudoknot located downstream from a slippery sequence, the latter positioned at the ribosomal A and P sites. We report here the structures of two crystal forms of the frameshifting RNA pseudoknot from beet western yellow virus at resolutions of 1.25 and 2.85 {angstrom}. Because of the very high resolution of 1.25 {angstrom}, ten mono- and divalent metal ions per asymmetric unit could be identified, giving insight into potential roles of metal ions in stabilizing the pseudoknot. A magnesium ion located at the junction of the two pseudoknot stems appears to play a crucial role in stabilizing the structure. Because the two crystal forms exhibit mostly unrelated packing interactions and local crystallographic disorder in the high-resolution form was resolvable, the two structures offer the most detailed view yet of the conformational preference and flexibility of an RNA pseudoknot.

  12. Atomic-orbital close-coupling calculations for collisions involving fusion relevant highly charged impurity ions using very large basis sets

    SciTech Connect

    Igenbergs, Katharina; Wallerberger, Markus; Schweinzer, Josef; Aumayr, Friedrich

    2012-05-25

    The atomic-orbital close-coupling formalism is a well-known method for the semiclassical treatment of ion-atom collisions. Cross sections for these kinds of collisions are mainly needed in the analysis of certain spectroscopic data from nuclear fusion experiments as well as astrophysical data. We shall outline how the computational implementation can be improved in such a way that collisions involving heavy, highly charged impurity ions, such as Ar{sup 18+} can be treated. Furthermore we show and discuss exemplary results.

  13. Damage effects of {ion}/{atom} beam milling on MNOS (Al/Si 3N 4/SiO 2/Si) capacitors

    NASA Astrophysics Data System (ADS)

    Bangert, U.; Belson, J.; Wilson, I. H.

    1984-02-01

    Low energy argon ion and atom beams produced by saddle field sources have been used to study changes in CVD Si 3N 4/SiO 2/Si structures after bombardment of the bare nitride at a particle energy of 2.9 keV. Interface state densities Nst and flatband voltages VFB were extracted from high frequency (1.3 MHz) and quasi-static C- V curves. Bombardment was found to induce an increase in Nst and positive and negative charge storage associated with the nitride (or the nitride/oxide interface). The effect was more pronounced under ion bombardment. On the supposition that displacement damage is similar for ion and atom bombardments the differences in charge storage are interpreted in terms of enhanced trapping under the field associated with ion bombardment.

  14. The emission of energetic electrons from atoms by fast ions considered as a charge-transfer process

    NASA Astrophysics Data System (ADS)

    Miraglia, J. E.; Ponce, V. H.

    1980-03-01

    The ejection of energetic electrons from atoms by fast ions is described using as final electron states the continuum orbitals in the field of the projectile. The electronic distribution in the first-order Born approximation is equal to the distribution for direct ionisation where the final electron state is described by a plane wave times the Coulomb factor centred on the projectile. In the second-order Born approximation the distribution of ejected electrons is significantly decreased, and it is shown that it is equivalent to the correct distribution for direct ionisation in first order times the Coulomb factor around the projectile. For the case of ejected electrons with negligible momentum in the frame of the projectile, it is shown that the electron distribution centered on the projectile is isotropic to order v to the -12th, while the double scattering term in v to the -11th depends on the direction of motion of the electron.

  15. Interplay between atomic disorder, lattice swelling and defect energy in ion-irradiation-induced amorphization of SiC

    DOE PAGESBeta

    Debelle, Aurelien; Boulle, Alexandre; Chartier, Alain; Gao, Fei; Weber, William J

    2014-11-25

    We present a combination of experimental and computational evaluations of disorder level and lattice swelling in ion-irradiated materials. Information obtained from X-ray diffraction experiments is compared to X-ray diffraction data generated using atomic-scale simulations. The proposed methodology, which can be applied to a wide range of crystalline materials, is used to study the amorphization process in irradiated SiC. Results show that this process can be divided into two steps. In the first step, point defects and small defect clusters are produced and generate both large lattice swelling and high elastic energy. In the second step, enhanced coalescence of defects andmore » defect clusters occurs to limit this increase in energy, which rapidly leads to complete amorphization.« less

  16. Atomic force microscopy imaging reveals the formation of ASIC/ENaC cross-clade ion channels.

    PubMed

    Jeggle, Pia; Smith, Ewan St J; Stewart, Andrew P; Haerteis, Silke; Korbmacher, Christoph; Edwardson, J Michael

    2015-08-14

    ASIC and ENaC are co-expressed in various cell types, and there is evidence for a close association between them. Here, we used atomic force microscopy (AFM) to determine whether ASIC1a and ENaC subunits are able to form cross-clade hybrid ion channels. ASIC1a and ENaC could be co-isolated from detergent extracts of tsA 201 cells co-expressing the two subunits. Isolated proteins were incubated with antibodies against ENaC and Fab fragments against ASIC1a. AFM imaging revealed proteins that were decorated by both an antibody and a Fab fragment with an angle of ∼120° between them, indicating the formation of ASIC1a/ENaC heterotrimers. PMID:26032502

  17. Transport properties derived from ion-atom collisions: 6Li-6Li+ and 6Li-7Li+ Cases

    NASA Astrophysics Data System (ADS)

    Bouledroua, Moncef; Bouchelaghem, Fouzia; LPR Team

    2014-10-01

    This investigation treats quantum-mechanically the ion- atom collisions and computes the transport coefficients, such as the coefficients of mobility and diffusion. For the case of lithium, the calculations start by determining the gerade and ungerade potential curves through which ionic lithium approaches ground lithium. Then, by considering the isotopic effects and nuclear spins, the elastic and charge-transfer cross sections are calculated for the case of 6Li+and7Li+ colliding with 6Li. Finally, the temperature-dependent diffusion and mobility coefficients are analyzed, and the results are contrasted with those obtained from literature. The main results of this work have been recently published in. This work has been realized within the frames of the CNEPRU Project D01120110036 of the Algerian Ministry of Higher Education.

  18. Stability of nanoclusters in 14YWT oxide dispersion strengthened steel under heavy ion-irradiation by atom probe tomography

    SciTech Connect

    Jianchao He; Farong Wan; Kumar Sridharan; Todd R. Allen; A. Certain; V. Shutthanandan; Y.Q. Wu

    2014-12-01

    14YWT oxide dispersion strengthened (ODS) ferritic steel was irradiated with of 5 MeV Ni2+ ions, at 300 C, 450 C, and 600 C to a damage level of 100 dpa. The stability of Ti–Y–O nanoclusters was investigated by applying atom probe tomography (APT) in voltage mode, of the samples before and after irradiations. The average size and number density of the nanoclusters was determined using the maximum separation method. These techniques allowed for the imaging of nanoclusters to sizes well below the resolution limit of conventional transmission electron microscopy techniques. The most significant changes were observed for samples irradiated at 300 C where the size (average Guinier radius) and number density of nanoclusters were observed to decrease from 1.1 nm to 0.8 nm and 12 1023 to 3.6 1023, respectively. In this study, the nanoclusters are more stable at higher temperature.

  19. Sum rules and other properties involving resonance projection operators. [for optical potential description of electron scattering from atoms and ions

    NASA Technical Reports Server (NTRS)

    Berk, A.; Temkin, A.

    1985-01-01

    A sum rule is derived for the auxiliary eigenvalues of an equation whose eigenspectrum pertains to projection operators which describe electron scattering from multielectron atoms and ions. The sum rule's right-hand side depends on an integral involving the target system eigenfunctions. The sum rule is checked for several approximations of the two-electron target. It is shown that target functions which have a unit eigenvalue in their auxiliary eigenspectrum do not give rise to well-defined projection operators except through a limiting process. For Hylleraas target approximations, the auxiliary equations are shown to contain an infinite spectrum. However, using a Rayleigh-Ritz variational principle, it is shown that a comparatively simple aproximation can exhaust the sum rule to better than five significant figures. The auxiliary Hylleraas equation is greatly simplified by conversion to a square root equation containing the same eigenfunction spectrum and from which the required eigenvalues are trivially recovered by squaring.

  20. Interplay between atomic disorder, lattice swelling and defect energy in ion-irradiation-induced amorphization of SiC

    SciTech Connect

    Debelle, Aurelien; Boulle, Alexandre; Chartier, Alain; Gao, Fei; Weber, William J

    2014-11-25

    We present a combination of experimental and computational evaluations of disorder level and lattice swelling in ion-irradiated materials. Information obtained from X-ray diffraction experiments is compared to X-ray diffraction data generated using atomic-scale simulations. The proposed methodology, which can be applied to a wide range of crystalline materials, is used to study the amorphization process in irradiated SiC. Results show that this process can be divided into two steps. In the first step, point defects and small defect clusters are produced and generate both large lattice swelling and high elastic energy. In the second step, enhanced coalescence of defects and defect clusters occurs to limit this increase in energy, which rapidly leads to complete amorphization.

  1. Classical-quantum correspondence for ionization in fast ion-atom collisions

    SciTech Connect

    Burgdoerfer, J. |; Reinhold, C.O.

    1994-10-01

    We analyze the interplay between classical and quantum dynamics in ionization of atoms by fast charged particles The convergence to the classical limit is studied as a function of the momentum transferred to the electron during the collision, the impact parameter. the energy and angle of the emitted electron, and the initial state of the target. One goal is to assess the validity of exact classical (CTMC) methods and approximate classical models such as the Thomson model. Applications to data for electron ejection at large angles are presented. The connection between collisional ionization by charged particles and ionization by half-cycle pulses is discussed.

  2. Atom trap for 221Fr from 225Ac ion beam implantation

    NASA Astrophysics Data System (ADS)

    Tandecki, M.; Behr, J. A.; Pearson, M. R.; Zhang, J.; Orozco, L.; Collister, R.; Gwinner, G.; Gomez, E.; Aubin, S.

    2012-10-01

    A neutral atom trap for francium parity violation experiments is being set up at TRIUMF. The half-lives of the longest isotopes are minutes, which mostly will be produced by the online mass separator of the ISAC facility. For systematic error studies for precision measurements, it can help to have a longer-lived source. ^221Fr is produced by t1/2=10 day ^225Ac α decay, and has been trapped at JILA [Z.-T. Lu PRL 79 994 (1997)]. Our approach would implant the mass-separated ^225Ac beam produced by ISAC at 1x10^7/s for a day after the production proton beam is turned off. The scheme to be tested: 30 keV ^225Ac beam is implanted in tantalum for a day; the sample is held in front of an yttrium foil (normally used to stop a mass-separated Fr beam) for 1 minute; 100 keV ^221Fr recoils escape and implant in the yttrium; tantalum is withdrawn, yttrium is moved to trap and heated; cycle repeats. First tests are planned for September, and one goal is precise measurements of atomic hyperfine splittings sensitive to the spatial distribution of nuclear magnetism.

  3. In situ atomic force microscopy nanoindentation of lithiated silicon nanopillars for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    McAllister, Quinn P.; Strawhecker, Kenneth E.; Becker, Collin R.; Lundgren, Cynthia A.

    2014-07-01

    In this study, atomic force microscopy based nanoindentation techniques are used to measure the in situ mechanical properties of thin film, nanometer sized amorphous-silicon nanopillars (pillar diameters of 1000 nm, 500 nm, and 200 nm) at various stages of lithiation. The pillar indentation modulus and hardness are measured ex situ as-fabricated, in situ during lithiation at two different potentials (or stages of lithiation, 50 mV and 10 mV), and in situ after delithiation at 2 V. The measured modulus of the pristine amorphous silicon nanopillars was 74.7 ± 12.1 GPa. The hardness of the pristine pillars depended on depth and the contact conditions. In general, the mechanical properties of the nanopillars decreased with increased degrees of lithiation and only partially recovered upon delithiation. The inability of the silicon to recover the as fabricated mechanical properties indicates overall degradation of the pillar during only one lithiation-delithiation cycle, which could only be directly measured in situ using the employed atomic force microscopy based technique.

  4. Total single electron capture cross sections for collisions of multicharged ions with He atoms

    NASA Astrophysics Data System (ADS)

    Rahmanian, M.; Shojaei, F.; Fathi, R.

    2016-09-01

    The three-body boundary corrected Born distorted wave method is utilized to compute the total cross sections for single electron capture in the collisions of the fast ions ({{{H}}}1+, He{}2+, Li{}3+, {{{B}}}5+ and {{{C}}}6+) with helium targets in their ground states. Both post and prior forms of the transition amplitude are obtained in terms of two-dimensional integrals and the total cross sections are computed via three-dimensional numerical integrations. The present results show reasonable agreement with the measurements and three- and four-body theoretical computations, especially at higher incident energies.

  5. Fabrication of sharp tungsten-coated tip for atomic force microscopy by ion-beam sputter deposition

    SciTech Connect

    Kinoshita, Yukinori; Naitoh, Yoshitaka; Li, Yan Jun; Sugawara, Yasuhiro

    2011-11-15

    Tungsten (W) is significantly suitable as a tip material for atomic force microscopy (AFM) because its high mechanical stiffness enables the stable detection of tip-sample interaction forces. We have developed W sputter-coating equipment to compensate the drawbacks of conventional Si cantilever tips used in AFM measurements. By employing an ion gun commonly used for sputter cleaning of a cantilever tip, the equipment is capable of depositing conductive W films in the preparation chamber of a general ultrahigh vacuum (UHV)-AFM system without the need for an additional chamber or transfer system. This enables W coating of a cantilever tip immediately after sputter cleaning of the tip apex and just before the use in AFM observations. The W film consists of grain structures, which prevent tip dulling and provide sharpness (<3 nm in radius of curvature at the apex) comparable to that of the original Si tip apex. We demonstrate that in non-contact (NC)-AFM measurement, a W-coated Si tip can clearly resolve the atomic structures of a Ge(001) surface without any artifacts, indicating that, as a force sensor, the fabricated W-coated Si tip is superior to a bare Si tip.

  6. The atomic structure and chemical composition of HfOx (x < 2) films prepared by ion-beam sputtering deposition

    NASA Astrophysics Data System (ADS)

    Aliev, V. S.; Gerasimova, A. K.; Kruchinin, V. N.; Gritsenko, V. A.; Prosvirin, I. P.; Badmaeva, I. A.

    2016-08-01

    Non-stoichiometric HfOx films of different chemical composition (x < 2) were fabricated by ion-beam sputtering deposition (IBSD) at room temperature. The ratio of O and Hf atoms in films x was varied by setting the O2 partial pressure in a chamber. An effect of chemical composition on the atomic structure of the films was studied by reflection high-energy electron diffraction, x-ray photoelectron spectroscopy and field emission scanning electron microscopy methods. The films were found to be amorphous, consisting only of three components: Hf-metal clusters, Hf4O7 suboxide and stoichiometric HfO2. The relative concentration of these components varies with changing x. The surface of the films contains the increased oxygen content compared to the bulk. It was found that the Hf4O7 suboxide concentration is maximal at x = 1.8. The concept of hafnium oxide film growth by the IBSD method is proposed to explain the lack of suboxides variety in the films and the instability of HfO2, when annealed at high temperature.

  7. Electron-ion dynamics in laser-assisted desorption of hydrogen atoms from H-Si(111) surface

    SciTech Connect

    Bubin, Sergiy; Varga, Kalman

    2011-09-15

    In the framework of real time real space time-dependent density functional theory we have studied the electron-ion dynamics of a hydrogen-terminated silicon surface H-Si(111) subjected to intense laser irradiation. Two surface fragments of different sizes have been used in the simulations. When the intensity and duration of the laser exceed certain levels (which depend on the wavelength) we observe the desorption of the hydrogen atoms, while the underlying silicon layer remains essentially undamaged. Upon further increase of the laser intensity, the chemical bonds between silicon atoms break as well. The results of the simulations suggest that with an appropriate choice of laser parameters it should be possible to remove the hydrogen layer from the H-Si(111) surface in a matter of a few tens of femtoseconds. We have also observed that at high laser field intensities (2-4 V/A in this work) the desorption occurs even when the laser frequency is smaller than the optical gap of the silicon surface fragments. Therefore, nonlinear phenomena must play an essential role in such desorption processes.

  8. Fabrication of sharp tungsten-coated tip for atomic force microscopy by ion-beam sputter deposition.

    PubMed

    Kinoshita, Yukinori; Naitoh, Yoshitaka; Li, Yan Jun; Sugawara, Yasuhiro

    2011-11-01

    Tungsten (W) is significantly suitable as a tip material for atomic force microscopy (AFM) because its high mechanical stiffness enables the stable detection of tip-sample interaction forces. We have developed W sputter-coating equipment to compensate the drawbacks of conventional Si cantilever tips used in AFM measurements. By employing an ion gun commonly used for sputter cleaning of a cantilever tip, the equipment is capable of depositing conductive W films in the preparation chamber of a general ultrahigh vacuum (UHV)-AFM system without the need for an additional chamber or transfer system. This enables W coating of a cantilever tip immediately after sputter cleaning of the tip apex and just before the use in AFM observations. The W film consists of grain structures, which prevent tip dulling and provide sharpness (<3 nm in radius of curvature at the apex) comparable to that of the original Si tip apex. We demonstrate that in non-contact (NC)-AFM measurement, a W-coated Si tip can clearly resolve the atomic structures of a Ge(001) surface without any artifacts, indicating that, as a force sensor, the fabricated W-coated Si tip is superior to a bare Si tip.

  9. Atomic collision experiments utilizing low-velocity, highly-charged ion beams

    SciTech Connect

    Johnson, B.M.; Jones, K.W.; Meron, M.

    1982-01-01

    Intense beams of highly-stripped ions are now routinely produced at low velocities using the Brookhaven dual MP-tandens in a unique four-stage accel/decel mode. This mode of operation combines three stages of acceleration, stripping at high energy, and one stage of deceleration to near-zero velocity. To date, experiments have used 10-100 nA beams of bare and few-electron heavy ions at energies as low as 0.2 MeV/amu, and upgrades of the facility should push the lower limit below 0.1 MeV/amu. Recent experiments, such as measurements of charge transfer and x-ray production for S/sup 6-16+/ on He and Ar at 6 to 20 MeV and P(b) measurements for MO x-rays produced in Cl/sup 16 +/ + Ar collisions at 20, 10, and 5 MeV have demonstrated the usefulness of highly-stripped, low-velocity projectiles. These experiments and a few possibilities for future experiments are discussed.

  10. HISTRAP: Proposal for a Heavy Ion Storage Ring for Atomic Physics

    SciTech Connect

    Not Available

    1988-11-01

    This paper presents an overview of the physics capabilities of HISTRAP together with a brief description of the facility and a sampling of the beams which will be available for experimentation, and surveys some of the lines of investigation in the physics of multicharged ions, molecular ion spectroscopy, condensed beams, and nuclear physics that will become possible with the advent of HISTRAP. Details of the accelerator design are discussed, including computer studies of beam tracking in the HISTRAP lattice, a discussion of the HHIRF tandem and ECR/RFQ injectors, and a description of the electron beam cooling system. In the past three years, HISTRAP has received substantial support from Oak Ridge National Laboratory management and staff. The project has used discretionary funds to develop hardware prototypes and carry out design studies. Construction has been completed on a vacuum test stand which models 1/16 of the storage ring and has attained a pressure of 4 x 10/sup -12/ Torr; a prototype rf cavity capable of accelerating beams up to 90 MeV/nucleon and decelerating to 20 keV/nucleon; and a prototype dipole magnet, one of the eight required for the HISTRAP lattice. This paper also contains a summary of the work on electron cooling carried out by one of our staff members at CERN. Building structures and services are described. Details of cost and schedule are also discussed. 77 refs.

  11. On the Chemistry of Hydrides of N Atoms and O+ Ions

    NASA Astrophysics Data System (ADS)

    Awad, Zainab; Viti, Serena; Williams, David A.

    2016-08-01

    Previous work by various authors has suggested that the detection by Herschel/HIFI of nitrogen hydrides along the low-density lines of sight toward G10.6-0.4 (W31C) cannot be accounted for by gas-phase chemical models. In this paper we investigate the role of surface reactions on dust grains in diffuse regions, and we find that formation of the hydrides by surface reactions on dust grains with efficiency comparable to that for H2 formation reconciles models with observations of nitrogen hydrides. However, similar surface reactions do not contribute significantly to the hydrides of O+ ions detected by Herschel/HIFI that are present along many sight lines in the Galaxy. The O+ hydrides can be accounted for by conventional gas-phase chemistry either in diffuse clouds of very low density with normal cosmic-ray fluxes or in somewhat denser diffuse clouds with high cosmic-ray fluxes. Hydride chemistry in dense dark clouds appears to be dominated by gas-phase ion-molecule reactions.

  12. Atomic-Scale Mechanisms for Electrolyte Decomposition in Li-ion Battery Cathodes

    NASA Astrophysics Data System (ADS)

    Fuhst, Mallory; Siegel, Donald

    Li-ion batteries using high energy density LiCoO2 (LCO) intercalation cathodes are known to generate gaseous species inside the cell, which can lead to venting flammable solvent vapor. It has been hypothesized that reactions at the cathode/electrolyte interface catalyze the production of these gaseous species. To elucidate the underlying reaction mechanism, first principles calculations were used to model interactions between LCO surfaces and Ethylene Carbonate (EC), a commonly used solvent in Li-ion batteries. A Metropolis Monte Carlo algorithm was used to identify likely low energy adsorption configurations for EC on the (10-14) surface of LCO. Several of these geometries were further analyzed with DFT. The thermodynamics and kinetics of EC decomposition were evaluated for plausible reaction pathways and associated various solvent decomposition mechanisms, such as hydrogen abstraction. Preliminary results indicate that hydrogen abstraction may lead to the spontaneous decomposition of EC into CO and other adsorbed species at the surface. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE 1256260.

  13. L-Auger Electron Production in Krypton Ion-Atom Collisions.

    NASA Astrophysics Data System (ADS)

    de Groot, Peter Jonathon

    1987-09-01

    Secondary electron production as a consequence of inner-shell vacancy decay for the Kr-Kr system has been studied. Electron-energy spectra differential in impact parameter have been obtained by detecting electrons in coincidence with projectile ions scattered through a known angle. The spectra exhibit structure attributable to Auger decay of L-shell vacancies. The collision-energy dependence of the L-Auger yields is consistent with the L-shell excitation being due to rotational coupling of the 4fsigma , 4fpi, 4fdelta and 4fvarphi orbitals of the Kr-Kr quasimolecule, as originally proposed by Shanker and coworkers.^1 The L-Auger electron energies and relative transition-group intensities suggest that L-shell vacancy decay occurs in Kr ions with initial charge states greater than +10, indicating that a surprisingly large number of electrons are emitted prior to the decay of the L-shell vacancy. These prior ionizations, most of which occur during the collision, are the source of the 100-600 eV continuum electrons which dominate the low -energy region of the electron spectrum. ftn^1 R. Shanker, U. Wille, R. Bilau, R. Hippler, W. R. McMurray, and H. O. Lutz, J. Phys. B: At. Mol. Phys., 17 (1984) 1353.

  14. Measurements of transition probabilities for spin-changing lines of atomic ions used in diagnostics of astrophysical plasmas

    NASA Technical Reports Server (NTRS)

    Smith, P. L.; Johnson, B. C.; Kwong, H. S.; Parkinson, W. H.; Knight, R. D.

    1984-01-01

    The intensities of ultraviolet, spin-changing, 'intersystem' lines of low-Z atomic ions are frequently used in determinations of electron densities and temperatures in astrophysical plasmas as well as in measurements of element abundances in the interstellar gas. The transition probabilities (A-values) of these lines, which are about five orders of magnitude weaker than allowed lines, have not been measured heretofore and various calculations produce A-values for these lines that differ by as much as 50 percent A radio-frequency ion trap has been used for the first measurements of transition probabilities for intersystem lines seen in astronomical spectra. The measurement procedure is discussed and results for Si III, O III, N II, and C III are reviewed and compared to calculated values. Discrepancies exist; these indicate that some of the calculated A-values may be less reliable than has been beleived and that revisions to the electron densities determined for some astrophysical plasmas may be required.

  15. High-performance atom-probe field ion microscope study of segregation and hydrogen cracking in Fe-0. 29 Ti

    SciTech Connect

    Kuk, Y.; Pickering, H.W.; Sakurai, T.

    1980-01-01

    With the greatly improved resolution now available in energy focused atom probes, hydrogen can be readily resolved even when combined with metals having several isotopes. In addition to finding that H, H/sub 2/, FeH and TiH/sub 2/ accumulate at segregated grain boundaries in Fe-0.29 wt % Ti, a striking observation was made - the formation and propagation of a microcrack when the (field ion microscope) tip was exposed to hydrogen gas at elevated temperature. A small crack (approx. 200 A in length) was first noticed at a grain-boundary intersection during field ion imaging. This was an open crack, formed by detachment of metal between the intersecting grain boundaries, which was observed to be much larger after the tip was reheated to 1300/sup 0/K for 10 min. in the presence of 10/sup 2/ Pa (1 torr) H/sub 2/. This crack could be easily reduced in size by gradually field evaporating the surface. Its propagation was repeated several times and reproducible results were obtained. Hydrogen was identified in quantity in the crack surface, though not elsewhere. The observation of H/sub 2/ is taken to mean that H/sub 2/ gas was trapped in the grain boundary. The grain boundary was also observed to be enriched in Ti, O, C and S, in agreement with earlier results for Fe-Ti.

  16. Atomic force microscopy imaging reveals the formation of ASIC/ENaC cross-clade ion channels

    SciTech Connect

    Jeggle, Pia; Smith, Ewan St. J.; Stewart, Andrew P.; Haerteis, Silke; Korbmacher, Christoph; Edwardson, J. Michael

    2015-08-14

    ASIC and ENaC are co-expressed in various cell types, and there is evidence for a close association between them. Here, we used atomic force microscopy (AFM) to determine whether ASIC1a and ENaC subunits are able to form cross-clade hybrid ion channels. ASIC1a and ENaC could be co-isolated from detergent extracts of tsA 201 cells co-expressing the two subunits. Isolated proteins were incubated with antibodies against ENaC and Fab fragments against ASIC1a. AFM imaging revealed proteins that were decorated by both an antibody and a Fab fragment with an angle of ∼120° between them, indicating the formation of ASIC1a/ENaC heterotrimers. - Highlights: • There is evidence for a close association between ASIC and ENaC. • We used AFM to test whether ASIC1a and ENaC subunits form cross-clade ion channels. • Isolated proteins were incubated with subunit-specific antibodies and Fab fragments. • Some proteins were doubly decorated at ∼120° by an antibody and a Fab fragment. • Our results indicate the formation of ASIC1a/ENaC heterotrimers.

  17. Quantum simulation of spin models and the discrete Truncated Wigner Approximation: from Rydberg atoms to trapped ions

    NASA Astrophysics Data System (ADS)

    Pineiro Orioli, Asier; Berges, Juergen; Signoles, Adrien; Schempp, Hanna; Whitlock, Shannon; Weidemueller, Matthias; Safavi-Naini, Arghavan; Wall, Michael; Schachenmayer, Johannes; Rey, Ana Maria

    2016-05-01

    Accurate description of the dynamics of quantum spin models is a theoretically challenging problem with widespread applications ranging from condensed matter to high-energy physics. Furthermore recent experimental progress in AMO experiments allows for the physical realization of these models in a variety of setups, such as Rydberg systems and trapped ion experiments, with an unprecedented degree of control and flexibility. Therefore, it is vital to develop efficient theoretical methods capable of simulating the many-body dynamics of such systems. In this work, we employ and extend the recently developed discrete Truncated Wigner Approximation (dTWA), an approximation based on the phase space description of quantum mechanics, to compute the dynamics of two types of spin models: the long-range XY model, which can be realized with Rydberg atoms, and a coupled spin-boson model, which is relevant to trapped ion experiments. Comparisons to experimental results and to available exact solutions to benchmark the method show that the dTWA is capable of capturing important features of the spin evolution and can also help uncovering some underlying non-equilibrium processes.

  18. Theory and calculation of resonances and autoionization of two-electron atoms and ions

    NASA Technical Reports Server (NTRS)

    Temkin, A.; Bhatia, A. K.

    1985-01-01

    Techniques for calculating the electron scattering from one-electron hydrogen-like targets on the basis of the Feshback formalism, are discussed. The principal similarities between resonance parameters in the Feshbach formalism and the corresponding Breit-Wigner quantities, are described in detail. Special attention is devoted to a description of the Fano line shape parameter q, and a technique for formulating it in terms of a projector operator is proposed. The theoretical methods are illustrated by numerical calculations for 1S, 3P, and 1D states of H(-) below the first excited threshold of the target atom. Calculations of 1,3S 1,3P, 1,3D states for He are also presented.

  19. Optical radiation from the interaction of energetic atoms, ions, electrons, and photons with surfaces

    NASA Technical Reports Server (NTRS)

    Tolk, N. H.; Albridge, R. G.; Haglund, R. F., Jr.; Mendenhall, M. H.

    1985-01-01

    Heavy particle, electron, and UV photon bombardment of solid surfaces has been recently observed to result in the emission of infrared, visible, and ultraviolet radiation. This effect occurs over a wide range of incident projectile energies. Line radiation arising from transitions between discrete atomic or molecular levels may be attributed to the decay of excited particles which have been sputtered or electronically/chemically desorbed from the surface. Broadband continuum radiation, which is also observed, is believed to arise either from fluorescence of the near surface bulk or from the radiative decay of desorbed excited clusters. Spacecraft, in the ambient near Earth environment, are subject to such bombardment. The dynamics of energetic particle and photon beam interactions with surfaces which lead to surface erosion and glow phenomena will be treated. In addition, projected experimental and theoretical studies of oxygen and nitrogen beam surface interactions on materials characteristic of spacecraft surfaces will be discussed.

  20. Measurement of Atomic Oxygen in Diffuse Aurora and Ion Density in the E-Region

    NASA Technical Reports Server (NTRS)

    Sharp, William E.

    1997-01-01

    An ion mass spectrometer (IMS) was refurbished, calibrated and supplied to the University of Colorado payload (Dr. Charles Barth, P.I.) which was launched from White Sands in September of 1993 as NASA 33.062. The nose cone failed to deploy and their were problems with the ACS so the mission was declared a failure. However, the door covering the IMS deployed and the instrument obtained data. The launch occurred shortly after a payload carrying solar x-ray detectors was launched. Thus a small portion of the Colorado payload science was salvaged; namely, the NO(+)/O2(+) ratio to compare with the measured x-ray flux. Figure I shows the NO(+) to O2(+) ratio vs. altitude. The behavior is typical of the E-region.

  1. Magnetic circular dichroism in the ion yield of polarized chromium atoms at the 2p edge

    SciTech Connect

    Pruemper, G.; Viefhaus, J.; Becker, U.; Kroeger, S.; Mueller, R.; Zimmermann, P.; Martins, M.

    2003-09-01

    The effect of magnetic dichroism in the partial and total ion yield of chromium, i.e., the absorption of polarized chromium vapor was observed in the gas phase. The measurements were performed at the 2p edge and at photon energies above the 2p edge. The structure of the dichroism at the 2p edge can be understood by including the coupling of the 2p hole with the 3d and 4s shells. Our experimental results for the dichroism at the 2p edge are similar to results of solid-state experiments. Implications for the sum rules used as a standard tool to calculate the spin and orbital momentum are discussed.

  2. Photodetachment Studies Of Atomic Negative Ions Through Velocity-Map Imaging Spectroscopy

    NASA Astrophysics Data System (ADS)

    Chartkunchand, Kiattichart

    The technique of velocity-map imaging (VMI) spectroscopy as been adapted to a keV-level negative ion beamline for studies of photon-negative ion collisions. The design and operation of the VMI spectrometer takes into consideration the use of continuous, fast-moving (5 keV to 10 keV) ion beams, as well as a continuous wave (CW) laser as the source of photons. The VMI spectrometer has been used in photodetachment studies of the Group 14 negative ions Ge--, Sn--, and Pb-- at a photon wavelength of 532 nm. Measurements of the photoelectron angular distributions and asymmetry parameters for Ge-- and Sn-- were benchmarked against those measured previously [W. W. Williams, D. L. Carpenter, A. M. Covington, and J. S. Thompson, Phys. Rev. A 59, 4368 (1999), V. T. Davis, J. Ashokkumar, and J. S. Thompson, Phys. Rev. A 65, 024702 (2002)], while fine-structure-resolved asymmetry parameters for Pb-- were measured for the first time. Definitive evidence of a "forbidden" 4S 3/2→1D2 transition was observed in both the Ge-- and Sn-- photoelectron kinetic energy spectra. This transition is explained in terms of the inadequacy of the single-configuration description for the 1D2 excited state in the corresponding neutral. Near-threshold photodetachment studies of S-- were carried out in order to measure the spectral dependence of the photoelectron angular distribution. The resulting asymmetry parameters were measured at several photon wavelengths in the range of 575 nm (2.156 eV photon energy) to 615 nm (2.016 eV photon energy). Comparison of the measurements to a qualitative model of p-electron photodetachment [D. Hanstorp, C. Bengtsson, and D. J. Larson, Phys. Rev. A 40, 670 (1989)] were made. Deviations of the measured asymmetry parameters from the Hanstorp model near photodetachment thresholds suggests a reduced degree of suppression of d partial-waves than predicted by models. Measurement of the electron affinity of terbium was performed along with a determination of the

  3. The Effects of the Pauli Exclusion Principle in Determining the Ionization Energies of the Helium Atom and Helium-Like Ions

    ERIC Educational Resources Information Center

    Deeney, F. A.; O'Leary, J. P.

    2012-01-01

    For helium and helium-like ions, we have examined the differences between the values of the ionization energies as calculated from the Bohr theory and those measured in experiments. We find that these differences vary linearly with the atomic number of the system. Using this result, we show how the Bohr model for single-electron systems may be…

  4. Speciation of arsenic(III)/arsenic(V) and selenium(IV)/ selenium(VI) using coupled ion chromatography - hydride generation atomic absorption spectrometry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Simple analytical methods have been developed to speciate inorganic arsenic and selenium in the ppb range using coupled ion chromatography-hydride generation atomic absorption spectrometry. Because of the differences in toxicity and adsorption behavior, determinations of the redox states arsenite A...

  5. Multi-photon two-color ionization of atoms and ions by femtosecond pulses

    NASA Astrophysics Data System (ADS)

    Douguet, Nicolas; Venzke, Joel; Bartschat, Klaus; Grum-Grzhimailo, Alexei N.; Gryzlova, Elena; Staroselskaya, Ekaterina

    2016-05-01

    We consider several processes related to two-color ionization induced by femtosecond pulses. Using the first and second harmonics of an XUV pulse, one can produce two-pathway interferences, which directly influence the photoelectron angular distribution. We discuss the process with linearly as well as circularly polarized light of various mutual orientations and helicities. Furthermore, combining the XUV light with an optical laser, one can generate sidebands around the main photoelectron line and study a variety of asymmetries in photoelectron emission and their dependencies on the absolute and relative intensities, time delay, and polarization of the light. Calculations for atomic hydrogen, He+(1s) generated by an initial XUV pulse, and Ne(2p) were performed by directly solving the time-dependent Schrödinger equation as well as employing second-order nonstationary perturbation theory. Our predictions serve as guidelines for experiments at various X-ray Free-Electron Laser facilities, such as LCLS, FERMI, FLASH, and the European XFEL. Supported by the NSF under PHY-1430245 and XSEDE PHY-090031.

  6. An atomic force microscopy study of the dissolution of calcite in the presence of phosphate ions

    NASA Astrophysics Data System (ADS)

    Klasa, J.; Ruiz-Agudo, E.; Wang, L. J.; Putnis, C. V.; Valsami-Jones, E.; Menneken, M.; Putnis, A.

    2013-09-01

    Dissolution of calcite in the presence of phosphate solutions was studied in situ by Atomic Force Microscopy. Results of experiments in slightly alkaline (NH4)2HPO4 solutions showed that dissolution, measured from etch pit spreading, is significantly reduced compared to that observed in pure deionized water, confirming an inhibitory effect of (NH4)2HPO4 on calcite dissolution. However, rates measured in the presence of Na-phosphate solutions at the same pH remained close to that in pure water. This would indicate that the inhibitory effect could be caused by the presence of the NH4+ group. Moreover, for phosphate solution concentrations >5 mM, the precipitation of a calcium phosphate phase occurred simultaneously while calcite was dissolving, despite the continuous flow of the reaction solution. Such reactions may play an important role in phosphorus recovery from P-bearing solutions. Importantly this study gives insights into the mechanism of interface-coupled dissolution-precipitation reactions occurring during the interaction of phosphate-bearing solutions with calcium carbonate minerals and emphasizes the importance of performing direct observations when determining the kinetics of dissolution reactions, as they can be significantly affected by the precipitation of secondary phases that could alter dissolution rates determined from measurements of bulk solution composition.

  7. Analytic basis set for high-Z atomic QED calculations: Heavy He-like ions

    SciTech Connect

    Hylton, D.J.; Snyderman, N.J.

    1997-04-01

    A relativistic Sturmian analytic basis set representation for the Coulomb-Dirac Green function, previously studied by Zapryagaev, Manakov, and Pal{close_quote}chikov [Opt. Spectrosc. {bold 52}, 248 (1982)], is investigated for application to high-Z atomic QED calculations. This pseudoeigenfunction representation follows from exact identities starting from the Whittaker function representation. It eliminates the radial ordering problem of that representation, and so is particularly useful for numerical calculation of the perturbation theory Feynman diagrams with more than one electron Green function. While the Green function represents discrete bound states, and both positive and negative energy continuum states, the Sturmian (bound-state-like) form for the pseudoeigenfunctions makes it possible to more analytically calculate matrix elements for full photon exchange, reducing numerical problems for high photon frequency. For He-like Fm (Z=100) we calculate the perturbation theory equivalent of the Dirac-Fock-Breit ground-state energy, agreeing well with the Grant code and with the numerical B-spline basis set approach results of Blundell, Mohr, Johnson, and Sapirstein [Phys. Rev. A {bold 48}, 2615 (1993)]. Preliminary results on the relativistic and QED correlation are also reported. {copyright} {ital 1997} {ital The American Physical Society}

  8. Atom probe field-ion microscopy investigation of nickel base superalloy welds

    SciTech Connect

    Babu, S.S.; David, S.A.; Vitek, J.M.; Miller, M.K.

    1998-11-01

    Microstructure development and elemental partitioning between {gamma} and {gamma}{prime} were measured in PWA-1480 electron beam welds and CMSX-4 pulsed-laser welds. In PWA-1480 EB welds, eutectic {gamma}{prime} phases were observed along the dendritic boundaries. The elemental partitioning between {gamma} and {gamma}{prime} was found to be similar to that in PWA-1480 base metal. In CMSX-4 pulsed laser welds, negligible eutectic {gamma}{prime} was observed. In addition, fine and irregularly shaped {gamma}{prime} precipitates were observed. The elemental partitioning between {gamma} and {gamma}{prime} was found to be different from that measured in the base metal. Large concentration gradients were observed in the {gamma} phase. The {gamma}{prime} precipitation kinetics in CM247DS alloy was measured using dilatometry and showed differences with different cooling rates. The microstructural investigations showed that at large undercoolings the number density of {gamma}{prime} precipitates increased and led to a finer size. This supports the microstructure development observations in PWA-1480 and CMSX-4 welds. Thermodynamic and kinetic calculations for the Ni-Al-Cr alloy system showed that as the cooling rate increases, the {gamma}{prime} growth leads to large concentration gradients in the {gamma} phase. The calculations agree with the atom probe results from PWA-1480 and CMSX-4 welds.

  9. Charge transfer in collisions of the effectively-one-electron isocharged ions Si3+, C3+, and O3+ with atomic hydrogen

    NASA Astrophysics Data System (ADS)

    Guevara, N. L.; Teixeira, E.; Hall, B.; Öhrn, Y.; Deumens, E.; Sabin, J. R.

    2011-05-01

    In a recent paper [Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.77.064702 77, 064702 (2008)], Bruhns reported on an experimental investigation of charge transfer in collisions of Si3+ ions with atomic hydrogen and compared the energy dependence of the transfer cross sections with published theoretical results and with earlier experimental results for other effectively-one-electron isocharged ions, including C3+ and O3+. These authors observe that these three ions all have the structure of a single electron outside a closed subshell and thus might be expected to behave similarly. However, their results show quite different behavior, and they conclude that the influence of quantum-mechanical effects from the ionic core is clearly seen. We have investigated theoretically three collision systems, Si3+, C3+, and O3+ with atomic hydrogen, at projectile energies up to 10 keV/amu using the method of electron nuclear dynamics (END). In this paper we want to clarify and describe in some detail these quantum-mechanical effects by showing the time-dependent dynamics of the electrons during the collision of these three ions with atomic hydrogen. Total charge transfer cross sections were calculated for all three ions and compared with other theoretical and experimental results, showing good overall agreement. With this validation of the END description of the processes, we analyze the details of the computed dynamics of the electrons in each of the processes and illustrate the different mechanisms underlying observed differences in reaction outcomes.

  10. Atomic data for neutron-capture elements. I. Photoionization and recombination properties of low-charge selenium ions

    NASA Astrophysics Data System (ADS)

    Sterling, N. C.; Witthoeft, M. C.

    2011-05-01

    We present multi-configuration Breit-Pauli AUTOSTRUCTURE calculations of distorted-wave photoionization (PI) cross sections, and total and partial final-state resolved radiative recombination (RR) and dielectronic recombination (DR) rate coefficients for the first six ions of the trans-iron element Se. These calculations were motivated by the recent detection of Se emission lines in a large number of planetary nebulae. Se is a potentially useful tracer of neutron-capture nucleosynthesis, but accurate determinations of its abundance in photoionized nebulae have been hindered by the lack of atomic data governing its ionization balance. Our calculations were carried out in intermediate coupling with semi-relativistic radial wavefunctions. PI and recombination data were determined for levels within the ground configuration of each ion, and experimental PI cross-section measurements were used to benchmark our results. For DR, we allowed Δn = 0 core excitations, which are important at photoionized plasma temperatures. We find that DR is the dominant recombination process for each of these Se ions at temperatures representative of photoionized nebulae (~104 K). In order to estimate the uncertainties of these data, we compared results from three different configuration-interaction expansions for each ion, and also tested the sensitivity of the results to the radial scaling factors in the structure calculations. We find that the internal uncertainties are typically 30-50% for the direct PI cross sections and ~10% for the computed RR rate coefficients, while those for low-temperature DR can be considerably larger (from 15-30% up to two orders of magnitude) due to the unknown energies of near-threshold autoionization resonances. These data are available at the CDS, and fitting coefficients to the total RR and DR rate coefficients are presented. The results are suitable for incorporation into photoionization codes used to numerically simulate astrophysical nebulae, and will

  11. On the Chemistry of Hydrides of N Atoms and O+ Ions

    NASA Astrophysics Data System (ADS)

    Awad, Zainab; Viti, Serena; Williams, David A.

    2016-08-01

    Previous work by various authors has suggested that the detection by Herschel/HIFI of nitrogen hydrides along the low-density lines of sight toward G10.6-0.4 (W31C) cannot be accounted for by gas-phase chemical models. In this paper we investigate the role of surface reactions on dust grains in diffuse regions, and we find that formation of the hydrides by surface reactions on dust grains with efficiency comparable to that for H2 formation reconciles models with observations of nitrogen hydrides. However, similar surface reactions do not contribute significantly to the hydrides of O+ ions detected by Herschel/HIFI that are present along many sight lines in the Galaxy. The O+ hydrides can be accounted for by conventional gas-phase chemistry either in diffuse clouds of very low density with normal cosmic-ray fluxes or in somewhat denser diffuse clouds with high cosmic-ray fluxes. Hydride chemistry in dense dark clouds appears to be dominated by gas-phase ion–molecule reactions.

  12. Methods of Calculating Ionization Energies of Multielectron (Five or More) Isoelectronic Atomic Ions

    PubMed Central

    Lang, Peter F.; Smith, Barry C.

    2013-01-01

    We have previously used simple empirical equations to reproduce the literature values of the ionization energies of isoelectronic sequences of up to four electrons which gave very good agreement. We reproduce here a kinetic energy expression with corrections for relativity and Lamb shift effects which give excellent agreement with the literature values. These equations become more complex as the number of electrons in the system increases. Alternative simple quadratic expressions for calculating ionization energies of multielectron ions are discussed. A set of coefficients when substituted into a simple expression produces very good agreement with the literature values. Our work shows that Slater's rules are not appropriate for predicting trends or screening constants. This work provides very strong evidence that ionization energies are not functions of complete squares, and when calculating ionization energies electron transition/relaxation has to be taken into account. We demonstrate clearly that for particular isoelectronic sequences, the ionizing electrons may occupy different orbitals and in such cases more than one set of constants are needed to calculate the ionization energies. PMID:23766674

  13. Interaction of ions, atoms, and small molecules with quantized vortex lines in superfluid 4He

    NASA Astrophysics Data System (ADS)

    Mateo, David; Eloranta, Jussi; Williams, Gary A.

    2015-02-01

    The interaction of a number of impurities (H2, Ag, Cu, Ag2, Cu2, Li, He3 + , He* (3S), He2∗ (3Σu), and e-) with quantized rectilinear vortex lines in superfluid 4He is calculated by using the Orsay-Trento density functional theory (DFT) method at 0 K. The Donnelly-Parks (DP) potential function binding ions to the vortex is combined with DFT data, yielding the impurity radius as well as the vortex line core parameter. The vortex core parameter at 0 K (0.74 Å) obtained either directly from the vortex line geometry or through the DP potential fitting is smaller than previously suggested but is compatible with the value obtained from re-analysis of the Rayfield-Reif experiment. All of the impurities have significantly higher binding energies to vortex lines below 1 K than the available thermal energy, where the thermally assisted escape process becomes exponentially negligible. Even at higher temperatures 1.5-2.0 K, the trapping times for larger metal clusters are sufficiently long that the previously observed metal nanowire assembly in superfluid helium can take place at vortex lines. The binding energy of the electron bubble is predicted to decrease as a function of both temperature and pressure, which allows adjusting the trap depth for either permanent trapping or to allow thermally assisted escape. Finally, a new scheme for determining the trapping of impurities on vortex lines by optical absorption spectroscopy is outlined and demonstrated for He*.

  14. Modeling of neutrals in the Linac4 H(-) ion source plasma: hydrogen atom production density profile and Hα intensity by collisional radiative model.

    PubMed

    Yamamoto, T; Shibata, T; Ohta, M; Yasumoto, M; Nishida, K; Hatayama, A; Mattei, S; Lettry, J; Sawada, K; Fantz, U

    2014-02-01

    To control the H(0) atom production profile in the H(-) ion sources is one of the important issues for the efficient and uniform surface H(-) production. The purpose of this study is to construct a collisional radiative (CR) model to calculate the effective production rate of H(0) atoms from H2 molecules in the model geometry of the radio-frequency (RF) H(-) ion source for Linac4 accelerator. In order to validate the CR model by comparison with the experimental results from the optical emission spectroscopy, it is also necessary for the model to calculate Balmer photon emission rate in the source. As a basic test of the model, the time evolutions of H(0) production and the Balmer Hα photon emission rate are calculated for given electron energy distribution functions in the Linac4 RF H(-) ion source. Reasonable test results are obtained and basis for the detailed comparisons with experimental results have been established. PMID:24593558

  15. Production, formation, and transport of high-brightness atomic hydrogen beam studies for the relativistic heavy ion collider polarized source upgrade

    SciTech Connect

    Kolmogorov, A. Stupishin, N.; Atoian, G.; Ritter, J.; Zelenski, A.; Davydenko, V.; Ivanov, A.

    2014-02-15

    The RHIC polarized H{sup −} ion source had been successfully upgraded to higher intensity and polarization by using a very high brightness fast atomic beam source developed at BINP, Novosibirsk. In this source the proton beam is extracted by a four-grid multi-aperture ion optical system and neutralized in the H{sub 2} gas cell downstream from the grids. The proton beam is extracted from plasma emitter with a low transverse ion temperature of ∼0.2 eV which is formed by plasma jet expansion from the arc plasma generator. The multi-hole grids are spherically shaped to produce “geometrical” beam focusing. Proton beam formation and transport of atomic beam were experimentally studied at test bench.

  16. Production, formation, and transport of high-brightness atomic hydrogen beam studies for the relativistic heavy ion collider polarized source upgrade.

    PubMed

    Kolmogorov, A; Atoian, G; Davydenko, V; Ivanov, A; Ritter, J; Stupishin, N; Zelenski, A

    2014-02-01

    The RHIC polarized H(-) ion source had been successfully upgraded to higher intensity and polarization by using a very high brightness fast atomic beam source developed at BINP, Novosibirsk. In this source the proton beam is extracted by a four-grid multi-aperture ion optical system and neutralized in the H2 gas cell downstream from the grids. The proton beam is extracted from plasma emitter with a low transverse ion temperature of ∼0.2 eV which is formed by plasma jet expansion from the arc plasma generator. The multi-hole grids are spherically shaped to produce "geometrical" beam focusing. Proton beam formation and transport of atomic beam were experimentally studied at test bench.

  17. Production, formation, and transport of high-brightness atomic hydrogen beam studies for the relativistic heavy ion collider polarized source upgrade

    NASA Astrophysics Data System (ADS)

    Kolmogorov, A.; Atoian, G.; Davydenko, V.; Ivanov, A.; Ritter, J.; Stupishin, N.; Zelenski, A.

    2014-02-01

    The RHIC polarized H- ion source had been successfully upgraded to higher intensity and polarization by using a very high brightness fast atomic beam source developed at BINP, Novosibirsk. In this source the proton beam is extracted by a four-grid multi-aperture ion optical system and neutralized in the H2 gas cell downstream from the grids. The proton beam is extracted from plasma emitter with a low transverse ion temperature of ˜0.2 eV which is formed by plasma jet expansion from the arc plasma generator. The multi-hole grids are spherically shaped to produce "geometrical" beam focusing. Proton beam formation and transport of atomic beam were experimentally studied at test bench.

  18. Atomic supersymmetry

    NASA Technical Reports Server (NTRS)

    Kostelecky, V. Alan

    1993-01-01

    Atomic supersymmetry is a quantum-mechanical supersymmetry connecting the properties of different atoms and ions. A short description of some established results in the subject are provided and a few recent developments are discussed including the extension to parabolic coordinates and the calculation of Stark maps using supersymmetry-based models.

  19. Microstructural development in PWA-1480 electron beam welds: An atom probe field ion microscopy study

    SciTech Connect

    David, S.A.; Miller, M.K.; Babu, S.S.

    1995-12-31

    The microstructure development in PWA-1480 superalloy electron beam weld (Ni-11.0 at. % Al-11.5% Cr-1.9% Ti-5.1% Co-4.0% Ta-1.3% W) was characterized. Optical microscopy revealed a branched dendritic structure in the weld metal. Transmission electron microscopy of these welds, in the as-welded condition, showed fine cuboidal (0.05--0.5 {mu}m) L1{sub 2}-ordered {gamma}{prime} precipitates within the y grains. The average volume percentage of {gamma}{prime} precipitates was found to be {approx}5%. Atom probe analyses revealed that the composition of {gamma} matrix was Ni-4.6 at. % Al-25.5% Cr-0.4% Ti-9.4% Co-0.8% Ta-2.9% W and that of {gamma}{prime} precipitates was Ni-17.3 at. % Al-2.6% Cr-2.4% Ti-3.0% Co-7.4% Ta-1.3% W. These compositions were compared with the previous APFIM analyses of commercial PWA-1480 single crystals that had received conventional heat treatments. Small differences were found in the chromium and aluminum levels and these may be due to the nonequilibrium nature of phase transformations that occur during weld cooling. No solute segregation was detected at the {gamma}-{gamma}{prime}interface. The APFIM results were also compared with the thermodynamic calculations of alloying element partitioning between {gamma} and {gamma}{prime} using the ThermoCalc{trademark} software.

  20. Determination of selected elements in whole coal and in coal ash from the eight argonne premium coal samples by atomic absorption spectrometry, atomic emission spectrometry, and ion-selective electrode

    USGS Publications Warehouse

    Doughten, M.W.; Gillison, J.R.

    1990-01-01

    Methods for the determination of 24 elements in whole coal and coal ash by inductively coupled argon plasma-atomic emission spectrometry, flame, graphite furnace, and cold vapor atomic absorption spectrometry, and by ion-selective electrode are described. Coal ashes were analyzed in triplicate to determine the precision of the methods. Results of the analyses of NBS Standard Reference Materials 1633, 1633a, 1632a, and 1635 are reported. Accuracy of the methods is determined by comparison of the analysis of standard reference materials to their certified values as well as other values in the literature.

  1. Interaction of ions, atoms, and small molecules with quantized vortex lines in superfluid {sup 4}He

    SciTech Connect

    Mateo, David; Eloranta, Jussi; Williams, Gary A.

    2015-02-14

    The interaction of a number of impurities (H{sub 2}, Ag, Cu, Ag{sub 2}, Cu{sub 2}, Li, He{sub 3}{sup +}, He{sup *} ({sup 3}S), He{sub 2}{sup ∗} ({sup 3}Σ{sub u}), and e{sup −}) with quantized rectilinear vortex lines in superfluid {sup 4}He is calculated by using the Orsay-Trento density functional theory (DFT) method at 0 K. The Donnelly-Parks (DP) potential function binding ions to the vortex is combined with DFT data, yielding the impurity radius as well as the vortex line core parameter. The vortex core parameter at 0 K (0.74 Å) obtained either directly from the vortex line geometry or through the DP potential fitting is smaller than previously suggested but is compatible with the value obtained from re-analysis of the Rayfield-Reif experiment. All of the impurities have significantly higher binding energies to vortex lines below 1 K than the available thermal energy, where the thermally assisted escape process becomes exponentially negligible. Even at higher temperatures 1.5-2.0 K, the trapping times for larger metal clusters are sufficiently long that the previously observed metal nanowire assembly in superfluid helium can take place at vortex lines. The binding energy of the electron bubble is predicted to decrease as a function of both temperature and pressure, which allows adjusting the trap depth for either permanent trapping or to allow thermally assisted escape. Finally, a new scheme for determining the trapping of impurities on vortex lines by optical absorption spectroscopy is outlined and demonstrated for He{sup *}.

  2. THE APPLICATION OF SOME HARTREE-FOCK MODEL CALCULATION TO THE ANALYSIS OF ATOMIC AND FREE-ION OPTICAL SPECTRA

    SciTech Connect

    Hayhurst, Thomas Laine

    1980-08-06

    Techniques for applying ab-initio calculations to the is of atomic spectra are investigated, along with the relationship between the semi-empirical and ab-initio forms of Slater-Condon theory. Slater-Condon theory is reviewed with a focus on the essential features that lead to the effective Hamiltonians associated with the semi-empirical form of the theory. Ab-initio spectroscopic parameters are calculated from wavefunctions obtained via self-consistent field methods, while multi-configuration Hamiltonian matrices are constructed and diagonalized with computer codes written by Robert Cowan of Los Alamos Scientific Laboratory. Group theoretical analysis demonstrates that wavefunctions more general than Slater determinants (i.e. wavefunctions with radial correlations between electrons) lead to essentially the same parameterization of effective Hamiltonians. In the spirit of this analysis, a strategy is developed for adjusting ab-initio values of the spectroscopic parameters, reproducing parameters obtained by fitting the corresponding effective Hamiltonian. Secondary parameters are used to "screen" the calculated (primary) spectroscopic parameters, their values determined by least squares. Extrapolations of the secondary parameters determined from analyzed spectra are attempted to correct calculations of atoms and ions without experimental levels. The adjustment strategy and extrapolations are tested on the K I sequence from K{sup 0+} through Fe{sup 7+}, fitting to experimental levels for V{sup 4+}, and Cr{sup 5+}; unobserved levels and spectra are predicted for several members of the sequence. A related problem is also discussed: Energy levels of the Uranium hexahalide complexes, (UX{sub 6}){sup 2-} for X= F, Cl, Br, and I, are fit to an effective Hamiltonian (the f{sup 2} configuration in O{sub h} symmetry) with corrections proposed by Brian Judd.

  3. Surface Passivation of MoO₃ Nanorods by Atomic Layer Deposition toward High Rate Durable Li Ion Battery Anodes.

    PubMed

    Ahmed, B; Shahid, Muhammad; Nagaraju, D H; Anjum, D H; Hedhili, Mohamed N; Alshareef, H N

    2015-06-24

    We demonstrate an effective strategy to overcome the degradation of MoO3 nanorod anodes in lithium (Li) ion batteries at high-rate cycling. This is achieved by conformal nanoscale surface passivation of the MoO3 nanorods by HfO2 using atomic layer deposition (ALD). At high current density such as 1500 mA/g, the specific capacity of HfO2-coated MoO3 electrodes is 68% higher than that of bare MoO3 electrodes after 50 charge/discharge cycles. After 50 charge/discharge cycles, HfO2-coated MoO3 electrodes exhibited specific capacity of 657 mAh/g; on the other hand, bare MoO3 showed only 460 mAh/g. Furthermore, we observed that HfO2-coated MoO3 electrodes tend to stabilize faster than bare MoO3 electrodes because nanoscale HfO2 layer prevents structural degradation of MoO3 nanorods. Additionally, the growth temperature of MoO3 nanorods and the effect of HfO2 layer thickness was studied and found to be important parameters for optimum battery performance. The growth temperature defines the microstructural features and HfO2 layer thickness defines the diffusion coefficient of Li-ions through the passivation layer to the active material. Furthermore, ex situ high resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray diffraction were carried out to explain the capacity retention mechanism after HfO2 coating.

  4. Imaging atomic-scale effects of high-energy ion irradiation on superconductivity and vortex pinning in Fe(Se,Te).

    PubMed

    Massee, Freek; Sprau, Peter Oliver; Wang, Yong-Lei; Davis, J C Séamus; Ghigo, Gianluca; Gu, Genda D; Kwok, Wai-Kwong

    2015-05-01

    Maximizing the sustainable supercurrent density, J C, is crucial to high-current applications of superconductivity. To achieve this, preventing dissipative motion of quantized vortices is key. Irradiation of superconductors with high-energy heavy ions can be used to create nanoscale defects that act as deep pinning potentials for vortices. This approach holds unique promise for high-current applications of iron-based superconductors because J C amplification persists to much higher radiation doses than in cuprate superconductors without significantly altering the superconducting critical temperature. However, for these compounds, virtually nothing is known about the atomic-scale interplay of the crystal damage from the high-energy ions, the superconducting order parameter, and the vortex pinning processes. We visualize the atomic-scale effects of irradiating FeSe x Te1-x with 249-MeV Au ions and find two distinct effects: compact nanometer-sized regions of crystal disruption or "columnar defects," plus a higher density of single atomic site "point" defects probably from secondary scattering. We directly show that the superconducting order is virtually annihilated within the former and suppressed by the latter. Simultaneous atomically resolved images of the columnar crystal defects, the superconductivity, and the vortex configurations then reveal how a mixed pinning landscape is created, with the strongest vortex pinning occurring at metallic core columnar defects and secondary pinning at clusters of point-like defects, followed by collective pinning at higher fields.

  5. Imaging atomic-scale effects of high-energy ion irradiation on superconductivity and vortex pinning in Fe(Se,Te).

    PubMed

    Massee, Freek; Sprau, Peter Oliver; Wang, Yong-Lei; Davis, J C Séamus; Ghigo, Gianluca; Gu, Genda D; Kwok, Wai-Kwong

    2015-05-01

    Maximizing the sustainable supercurrent density, J C, is crucial to high-current applications of superconductivity. To achieve this, preventing dissipative motion of quantized vortices is key. Irradiation of superconductors with high-energy heavy ions can be used to create nanoscale defects that act as deep pinning potentials for vortices. This approach holds unique promise for high-current applications of iron-based superconductors because J C amplification persists to much higher radiation doses than in cuprate superconductors without significantly altering the superconducting critical temperature. However, for these compounds, virtually nothing is known about the atomic-scale interplay of the crystal damage from the high-energy ions, the superconducting order parameter, and the vortex pinning processes. We visualize the atomic-scale effects of irradiating FeSe x Te1-x with 249-MeV Au ions and find two distinct effects: compact nanometer-sized regions of crystal disruption or "columnar defects," plus a higher density of single atomic site "point" defects probably from secondary scattering. We directly show that the superconducting order is virtually annihilated within the former and suppressed by the latter. Simultaneous atomically resolved images of the columnar crystal defects, the superconductivity, and the vortex configurations then reveal how a mixed pinning landscape is created, with the strongest vortex pinning occurring at metallic core columnar defects and secondary pinning at clusters of point-like defects, followed by collective pinning at higher fields. PMID:26601180

  6. Interaction of atoms, molecules, and ions with constant electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Johnson, Bruce R.; Hirschfelder, Joseph O.; Yang, Kuo-Ho

    1983-01-01

    "pseudoseparated" and the internal degrees of freedom are coupled to the center of mass motion only by the "motional Stark Effect," which involves the constant of motion K. For ionic systems, only one component of the center of mass is coupled to the internal motion. Quantitative estimates of the weak center-of-mass coupling are made for both neutral and ionic n=1 and n=2 quantum states of two-body systems by perturbation expansions in powers of the field strengths. In the usual nonrigorous treatments of systems in magnetic fields, no distinction is made between Π and K and both are approximated by MR˙, where M is the mass of the molecule and R is taken to be the classical orbital position of a single particle having the same mass and charge. This is an excellent approximation for ground-state molecules and ions in weak fields. However, the resulting errors can be much larger if the system is in either intense fields or high-lying states (e.g., Rydberg levels). These are the conditions under which the rigorous formalism should be most useful. The determination of the wave functions and energy levels for many-particle ionic systems is complicated due to the coupling with the center of mass. The suggestion is made that it might be useful to boost the reference frame so that it moves with the velocity R˙ of a single classical particle. The Schrödinger equation in this frame could serve as a more suitable basis for perturbative or variational treatments.

  7. Properties of alkali-metal atoms and alkaline-earth-metal ions for an accurate estimate of their long-range interactions

    NASA Astrophysics Data System (ADS)

    Kaur, Jasmeet; Nandy, D. K.; Arora, Bindiya; Sahoo, B. K.

    2015-01-01

    Accurate knowledge of interaction potentials among the alkali-metal atoms and alkaline-earth ions is very useful in the studies of cold atom physics. Here we carry out theoretical studies of the long-range interactions among the Li, Na, K, and Rb alkali-metal atoms with the Ca+, Ba+, Sr+, and Ra+ alkaline-earth ions systematically, which are largely motivated by their importance in a number of applications. These interactions are expressed as a power series in the inverse of the internuclear separation R . Both the dispersion and induction components of these interactions are determined accurately from the algebraic coefficients corresponding to each power combination in the series. Ultimately, these coefficients are expressed in terms of the electric multipole polarizabilities of the above-mentioned systems, which are calculated using the matrix elements obtained from a relativistic coupled-cluster method and core contributions to these quantities from the random-phase approximation. We also compare our estimated polarizabilities with the other available theoretical and experimental results to verify accuracies in our calculations. In addition, we also evaluate the lifetimes of the first two low-lying states of the ions using the above matrix elements. Graphical representations of the dispersion coefficients versus R are given among all the alkaline ions with Rb.

  8. Core-shell Si@TiO2 nanosphere anode by atomic layer deposition for Li-ion batteries

    DOE PAGESBeta

    Dai, Sheng

    2016-01-28

    Silicon (Si) is regarded as next-generation anode for high-energy lithium-ion batteries (LIBs) due to its high Li storage capacity (4200 mA h g-1). However, the mechanical degradation and resultant capacity fade critically hinder its practical application. In this regard, we demonstrate that nanocoating of Si spheres with a 3 nm titanium dioxide (TiO2) layer via atomic layer deposition (ALD) can utmostly balance the high conductivity and the good structural stability to improve the cycling stability of Si core material. The resultant sample, Si@TiO2-3 nm core–shell nanospheres, exhibits the best electrochemical performance of all with a highest initial Coulombic efficiency andmore » specific charge capacity retention after 50 cycles at 0.1C (82.39% and 1580.3 mA h g-1). In addition to making full advantage of the ALD technique, we believe that our strategy and comprehension in coating the electrode and the active material could provide a useful pathway towards enhancing Si anode material itself and community of LIBs.« less

  9. High-resolution X-ray study of the multiple ionization of Pd atoms by fast oxygen ions

    NASA Astrophysics Data System (ADS)

    Czarnota, M.; Banaś, D.; Berset, M.; Chmielewska, D.; Dousse, J.-Cl.; Hoszowska, J.; Maillard, Y.-P.; Mauron, O.; Pajek, M.; Polasik, M.; Raboud, P. A.; Rzadkiewicz, J.; Słabkowska, K.; Sujkowski, Z.

    2010-04-01

    The multiple ionization of the L- and M-shells of Pd by fast oxygen ions has been studied by measuring with high-resolution the satellite structures of the Lα1,2 X-ray transitions. Relativistic multi-configuration Dirac-Fock (MCDF) calculations were used to interpret the complex X-ray spectrum, allowing to derive the number of L- and M-shell spectator vacancies at the moment of the X-ray emission. After correcting these numbers for the atomic vacancy rearrangement processes that take place prior to the X-ray emission, the ionization probabilities corresponding to the collision time were obtained. The latter were compared to predictions of the semiclassical approximation (SCA) and the geometrical model. The SCA calculations were performed using relativistic hydrogenic and self-consistent Dirac-Hartree-Fock (DHF) electronic wave functions. It was found that the use of the more realistic DHF wave functions in the SCA calculations leads to a much better description of the measured ionization probabilities for both the L- and M-shells.

  10. Core-shell Si@TiO2 nanosphere anode by atomic layer deposition for Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Bai, Ying; Yan, Dong; Yu, Caiyan; Cao, Lina; Wang, Chunlei; Zhang, Jinshui; Zhu, Huiyuan; Hu, Yong-Sheng; Dai, Sheng; Lu, Junling; Zhang, Weifeng

    2016-03-01

    Silicon (Si) has been regarded as next-generation anode for high-energy lithium-ion batteries (LIBs) due to its high Li storage capacity (4200 mA h g-1). However, the mechanical degradation and resultant capacity fade critically hinder its practical application. In this regard, we demonstrate that nanocoating of Si spheres with a 3 nm titanium dioxide (TiO2) layer via atomic layer deposition (ALD) can utmostly balance the high conductivity and the good structural stability to improve the cycling stability of Si core material. The resultant sample, Si@TiO2-3 nm core-shell nanospheres, exhibits the best electrochemical performance of all with a highest initial Coulombic efficiency and specific charge capacity retention after 50 cycles at 0.1C (82.39% and 1580.3 mA h g-1). In addition to making full advantage of the ALD technique, we believe that our strategy and comprehension in coating the electrode and the active material could provide a useful pathway towards enhancing Si anode material itself and community of LIBs.

  11. Determination of arsenic speciation in sulfidic waters by Ion Chromatography Hydride-Generation Atomic Fluorescence Spectrometry (IC-HG-AFS).

    PubMed

    Keller, Nicole S; Stefánsson, Andri; Sigfússon, Bergur

    2014-10-01

    A method for the analysis of arsenic species in aqueous sulfide samples is presented. The method uses an ion chromatography system connected with a Hydride-Generation Atomic Fluorescence Spectrometer (IC-HG-AFS). With this method inorganic As(III) and As(V) species in water samples can be analyzed, including arsenite (HnAs(III)O3(n-3)), thioarsenite (HnAs(III)S3(n-3)), arsenate (HnAs(V)O4(n-3)), monothioarsenate (HnAs(V)SO3(n-3)), dithioarsenate (HnAs(V)S2O2(n-3)), trithioarsenate (HnAs(V)S3O(n-3)) and tetrathioarsenate (HnAs(V)S4(n-3)). The peak identification and retention times were determined based on standard analysis of the various arsenic compounds. The analytical detection limit was ~1-3 µg L(-1) (LOD), depending on the quality of the baseline. This low detection limit makes this method also applicable to discriminate between waters meeting the drinking water standard of max. 10 µg L(-1) As, and waters that do not meet this standard. The new method was successfully applied for on-site determination of arsenic species in natural sulfidic waters, in which seven species were unambiguously identified.

  12. Elegant design of electrode and electrode/electrolyte interface in lithium-ion batteries by atomic layer deposition.

    PubMed

    Liu, Jian; Sun, Xueliang

    2015-01-16

    Lithium-ion batteries (LIBs) are very promising power supply systems for a variety of applications, such as electric vehicles, plug-in hybrid electric vehicles, grid energy storage, and microelectronics. However, to realize these practical applications, many challenges need to be addressed in LIBs, such as power and energy density, cycling lifetime, safety, and cost. Atomic layer deposition (ALD) is emerging as a powerful technique for solving these problems due to its exclusive advantages over other film deposition counterparts. In this review, we summarize the state-of-the-art progresses of employing ALD to design novel nanostructured electrode materials and solid-state electrolytes and to tailor electrode/electrolyte interface by surface coatings in order to prevent unfavorable side reactions and achieve optimal performance of the electrode. Insights into the future research and development of the ALD technique for LIB applications are also discussed. We expect that this review article will provide resourceful information to researchers in both fields of LIBs and ALD and also will stimulate more insightful studies of using ALD for the development of next-generation LIBs.

  13. Atomic absorption spectroscopic, conductometric and colorimetric methods for determination of fluoroquinolone antibiotics using ammonium reineckate ion-pair complex formation

    NASA Astrophysics Data System (ADS)

    Ragab, Gamal H.; Amin, Alaa S.

    2004-03-01

    Three accurate, rapid and simple atomic absorption spectrometric, conductometric and colorimetric methods were developed for the determination of norfloxacin (NRF), ciprofloxacin (CIP), ofloxacin (OFL) and enrofloxacin (ENF). The proposed methods depend upon the reaction of ammonium reineckate with the studied drugs to form stable precipitate of ion-pair complexes, which was dissolved in acetone. The pink coloured complexes were determined either by AAS or colorimetrically at λmax 525 nm directly using the dissolved complex. Using conductometric titration, the studied drugs could be evaluated in 50% (v/v) acetone in the range 5.0-65, 4.0-48, 5.0-56 and 6.0-72 μg ml -1 of NRF, CPF, OFL and ENF, respectively. The optimizations of various experimental conditions were described. The results obtained showed good recoveries of 99.15±1.15, 99.30±1.40, 99.60±1.50, and 99.00±1.25% with relative standard deviations of 0.81, 1.06, 0.97, and 0.69% for NRF, CPF, OFL, and ENF, respectively. Applications of the proposed methods to representative pharmaceutical formulations are successfully presented.

  14. Stability Of Nanoclusters In 14YWT Oxide Dispersion Strengthened Steel Under Heavy Ion-irradiation By Atom Probe Tomography

    SciTech Connect

    He, Jianchao; Wan, F.; Sridharan, Kumar; Allen, Todd R.; Certain, Alicia G.; Shutthanandan, V.; Wu, Yaqiao

    2014-12-01

    14YWT oxide dispersion strengthened (ODS) ferritic steel was irradiated with of 5 MeV Ni2+ ions, at 300 °C, 450 °C, and 600 °C to a damage level of 100 dpa. The stability of Ti–Y–O nanoclusters was investigated by applying atom probe tomography (APT) in voltage mode, of the samples before and after irradiations. The average size and number density of the nanoclusters was determined using the maximum separation method. These techniques allowed for the imaging of nanoclusters to sizes well below the resolution limit of conventional transmission electron microscopy techniques. The most significant changes were observed for samples irradiated at 300 °C where the size (average Guinier radius) and number density of nanoclusters were observed to decrease from 1.1 nm to 0.8 nm and 12 × 1023 to 3.6 × 1023, respectively. In this study, the nanoclusters are more stable at higher temperature.

  15. Dimensional comparison between amplitude-modulation atomic force microscopy and scanning ion conductance microscopy of biological samples

    NASA Astrophysics Data System (ADS)

    Kim, Joonhui; Choi, MyungHoon; Jung, Goo-Eun; Rahim Ferhan, Abdul; Cho, Nam-Joon; Cho, Sang-Joon

    2016-08-01

    The range of scanning probe microscopy (SPM) applications for atomic force microscopy (AFM) is expanding in the biological sciences field, reflecting an increasing demand for tools that can improve our fundamental understanding of the physics behind biological systems. However, the complexity associated with applying SPM techniques in biomedical research hampers the full exploitation of its capabilities. Recently, the development of scanning ion conductance microscopy (SICM) has overcome these limitations and enabled contact-free, high resolution imaging of live biological specimens. In this work, we demonstrate the limitation of AFM for imaging biological samples in liquid due to artifacts arising from AFM tip-sample interaction, and how SICM imaging is able to overcome those limitations with contact-free scanning. We also demonstrate that SICM measurements, when compared to AFM, show better fit to the actual dimensions of the biological samples. Our results highlight the superiority of SICM imaging, enabling it to be widely adopted as a general and versatile research tool for biological studies in the nanoscale.

  16. Dimensional comparison between amplitude-modulation atomic force microscopy and scanning ion conductance microscopy of biological samples

    NASA Astrophysics Data System (ADS)

    Kim, Joonhui; Choi, MyungHoon; Jung, Goo-Eun; Rahim Ferhan, Abdul; Cho, Nam-Joon; Cho, Sang-Joon

    2016-08-01

    The range of scanning probe microscopy (SPM) applications for atomic force microscopy (AFM) is expanding in the biological sciences field, reflecting an increasing demand for tools that can improve our fundamental understanding of the physics behind biological systems. However, the complexity associated with applying SPM techniques in biomedical research hampers the full exploitation of its capabilities. Recently, the development of scanning ion conductance microscopy (SICM) has overcome these limitations and enabled contact-free, high resolution imaging of live biological specimens. In this work, we demonstrate the limitation of AFM for imaging biological samples in liquid due to artifacts arising from AFM tip–sample interaction, and how SICM imaging is able to overcome those limitations with contact-free scanning. We also demonstrate that SICM measurements, when compared to AFM, show better fit to the actual dimensions of the biological samples. Our results highlight the superiority of SICM imaging, enabling it to be widely adopted as a general and versatile research tool for biological studies in the nanoscale.

  17. Metal atom and ion layers observed by a frequency-tunable resonance scattering lidar in the midlatitude

    NASA Astrophysics Data System (ADS)

    Ejiri, Mitsumu K.; Nakamura, Takuji; Kawahara, Takuya D.; Tsuno, Katsuhiko; Abo, Makoto; Nishiyama, Takanori; Tsuda, Takuo; Wada, Satoshi; Ogawa, Takayo

    2016-07-01

    The National Institute of Polar Research (NIPR) is leading a six year prioritized project of the Antarctic research observations since 2010. One of the sub-project is entitled the global environmental change revealed through the Antarctic middle and upper atmosphere. Profiling dynamical parameters such as temperature and wind, as well as minor constituents is the key component of observations in this project, together with a long term observations using existent various instruments in Syowa, the Antarctica (69S). As a part of the sub-project, we are developing a new resonance lidar system with multiple wavelengths and plan to install and operate it at Syowa, Antarctica. The lidar will observe temperature profiles and variations of minor constituents such as Fe, K, Ca+, and aurorally excited N2+. The lidar system is being developed with trial and error in test observations of the metal atom and ion density and the MLT temperature profiles. The lidar will be installed at Syowa in Antarctica by the 58th Japan Antarctic Research Expedition (JARE 58). In this presentation, we will report current status of the system developments and discuss results of the test observations.

  18. Determination of arsenic speciation in sulfidic waters by Ion Chromatography Hydride-Generation Atomic Fluorescence Spectrometry (IC-HG-AFS).

    PubMed

    Keller, Nicole S; Stefánsson, Andri; Sigfússon, Bergur

    2014-10-01

    A method for the analysis of arsenic species in aqueous sulfide samples is presented. The method uses an ion chromatography system connected with a Hydride-Generation Atomic Fluorescence Spectrometer (IC-HG-AFS). With this method inorganic As(III) and As(V) species in water samples can be analyzed, including arsenite (HnAs(III)O3(n-3)), thioarsenite (HnAs(III)S3(n-3)), arsenate (HnAs(V)O4(n-3)), monothioarsenate (HnAs(V)SO3(n-3)), dithioarsenate (HnAs(V)S2O2(n-3)), trithioarsenate (HnAs(V)S3O(n-3)) and tetrathioarsenate (HnAs(V)S4(n-3)). The peak identification and retention times were determined based on standard analysis of the various arsenic compounds. The analytical detection limit was ~1-3 µg L(-1) (LOD), depending on the quality of the baseline. This low detection limit makes this method also applicable to discriminate between waters meeting the drinking water standard of max. 10 µg L(-1) As, and waters that do not meet this standard. The new method was successfully applied for on-site determination of arsenic species in natural sulfidic waters, in which seven species were unambiguously identified. PMID:25059187

  19. Atomic/Molecular Layer Deposition of Lithium Terephthalate Thin Films as High Rate Capability Li-Ion Battery Anodes.

    PubMed

    Nisula, Mikko; Karppinen, Maarit

    2016-02-10

    We demonstrate the fabrication of high-quality electrochemically active organic lithium electrode thin films by the currently strongly emerging combined atomic/molecular layer deposition (ALD/MLD) technique using lithium terephthalate, a recently found anode material for lithium-ion battery (LIB), as a proof-of-the-concept material. Our deposition process for Li-terephthalate is shown to well comply with the basic principles of ALD-type growth including the sequential self-saturated surface reactions, a necessity when aiming at micro-LIB devices with three-dimensional architectures. The as-deposited films are found crystalline across the deposition temperature range of 200-280 °C, which is a trait highly desired for an electrode material but rather unusual for hybrid inorganic-organic thin films. Excellent rate capability is ascertained for the Li-terephthalate films with no conductive additives required. The electrode performance can be further enhanced by depositing a thin protective LiPON solid-state electrolyte layer on top of Li-terephthalate; this yields highly stable structures with capacity retention of over 97% after 200 charge/discharge cycles at 3.2 C.

  20. A study of the population dynamics of the electron states of atoms and ions in a self-sustained discharge in an HCl-Xe-He mixture

    NASA Astrophysics Data System (ADS)

    Demianov, A. V.; Egorov, V. S.; Kochetov, I. V.; Napartovich, A. P.; Pastor, A. A.

    1986-06-01

    Rozdestvenskii's crochet method is used to investigate the concentration dynamics of excited xenon and helium atoms and excited xenon ions; the concentration of Cl(-) ions is studied by the absorption method. The experimentally determined concentrations are then compared with theoretical predictions. It is shown that an allowance for the cascade excitation of the vibrational levels of the HCl molecule by an electron impact as well as capture by the highly excited vibrational states of the HCl molecule results in a factor of 1.5 increase in the voltage across the discharge gap.

  1. Computation of Ion Charge State Distributions After Inner-Shell Ionization In Ne, Ar And Kr Atoms Using Monte Carlo Simulation

    SciTech Connect

    Mohammedein, Adel M.; Ghoneim, Adel A.; Al-Zanki, Jasem M.; El-Essawy, Ashraf H.

    2010-01-05

    Atomic reorganization starts by filling the initially inner-shell vacancy by a radiative transition (x-ray) or by a non-radiative transition (Auger and Coster-Kronig processes). New vacancies created during this atomic reorganization may in turn be filled by further radiative and non-radiative transitions until all vacancies reach the outermost occupied shells. The production of inner-shell vacancy in an atom and the de-excitation decays through radiative and non-radiative transitions may result in a change of the atomic potential; this change leads to the emission of an additional electron in the continuum (electron shake-off processes). In the present work, the ion charge state distributions (CSD) and mean atomic charge ions produced from inner-shell vacancy de-excitation decay are calculated for neutral Ne, Ar and Kr atoms. The calculations are carried out using Monte Carlo (MC) technique to simulate the cascade development after primary vacancy production. The radiative and non-radiative transitions for each vacancy are calculated in the simulation. In addition, the change of transition energies and transition rates due to multi vacancies produced in the atomic configurations through the cascade development are considered in the present work. It is found that considering the electron shake--off process and closing of non-allowed non-radiative channels improves the results of both charge state distributions (CSD) and average charge state. To check the validity of the present calculations, the results obtained are compared with available theoretical and experimental data. The present results are found to agree well with the available theoretical and experimental values.

  2. Multidimensional characterisation of biomechanical structures by combining Atomic Force Microscopy and Focused Ion Beam: A study of the rat whisker.

    PubMed

    Adineh, Vahid Reza; Liu, Boyin; Rajan, Ramesh; Yan, Wenyi; Fu, Jing

    2015-07-01

    Understanding the heterogeneity of biological structures, particularly at the micro/nano scale can offer insights valuable for multidisciplinary research in tissue engineering and biomimicry designs. Here we propose to combine nanocharacterisation tools, particularly Focused Ion Beam (FIB) and Atomic Force Microscopy (AFM) for three dimensional mapping of mechanical modulus and chemical signatures. The prototype platform is applied to image and investigate the fundamental mechanics of the rat face whiskers, a high-acuity sensor used to gain detailed information about the world. Grazing angle FIB milling was first applied to expose the interior cross section of the rat whisker sample, followed by a "lift-out" method to retrieve and position the target sample for further analyses. AFM force spectroscopy measurements revealed a non-uniform pattern of elastic modulus across the cross section, with a range from 0.8GPa to 13.5GPa. The highest elastic modulus was found at the outer cuticle region of the whisker, and values gradually decreased towards the interior cortex and medulla regions. Elemental mapping with EDS confirmed that the interior of the rat whisker is dominated by C, O, N, S, Cl and K, with a significant change of elemental distribution close to the exterior cuticle region. Based on these data, a novel comprehensive three dimensional (3D) elastic modulus model was constructed, and stress distributions under realistic conditions were investigated with Finite Element Analysis (FEA). The simulations could well account for the passive whisker deflections, with calculated resonant frequency as well as force-deflection for the whiskers being in good agreement with reported experimental data. Limitations and further applications are discussed for the proposed FIB/AFM approach, which holds good promise as a unique platform to gain insights on various heterogeneous biomaterials and biomechanical systems.

  3. The use of ion chromatography-dc plasma atomic emission spectrometry for the speciation of trace metals

    SciTech Connect

    Urasa, I.T.

    1991-09-20

    The original objects of this research program were: to interface d.c. plasma atomic emission spectrometer with an ion chromatograph; to characterize and optimize the combined systems for application in the speciation of metals in aqueous solutions; to use this system in the study of the solution chemistry of various metals; and to find ways in which the measurement sensitivity of the method can be enhanced, thereby allowing the detection of metal species at low ppb concentration levels. This approach has been used to study the chemistry of and speciate several elements in solution including: arsenic, chromium, iron, manganese, nickel phosphorus, platinum, selenium, and vanadium. During the course of this research, we have found that the solution chemistry of the elements studied and the speciation data obtained can vary considerably depending on the solution, and the chromatographic conditions employed. The speciation of chromium, iron, and vanadium was found to be highly influenced by the acidity of the sample. The element selective nature of the d.c. plasma detector allows these changes to be monitored, thereby providing quantitative information on the new moieties formed. New approaches are being developed including the use of chelating ligands as preconcentration agents for purposes of reducing further the detection limits of the elements of interest and to improve the overall element speciation scheme. New thrusts are being directed towards the employment of post-column derivatization method coupled with colorimetric measurements to detect and quantify metal species eluting from the chromatographic column. The influence of sample acidity on these investigations will be carefully evaluated. These new thrusts are described in the accompanying Project Renewal Proposal.

  4. Multidimensional characterisation of biomechanical structures by combining Atomic Force Microscopy and Focused Ion Beam: A study of the rat whisker.

    PubMed

    Adineh, Vahid Reza; Liu, Boyin; Rajan, Ramesh; Yan, Wenyi; Fu, Jing

    2015-07-01

    Understanding the heterogeneity of biological structures, particularly at the micro/nano scale can offer insights valuable for multidisciplinary research in tissue engineering and biomimicry designs. Here we propose to combine nanocharacterisation tools, particularly Focused Ion Beam (FIB) and Atomic Force Microscopy (AFM) for three dimensional mapping of mechanical modulus and chemical signatures. The prototype platform is applied to image and investigate the fundamental mechanics of the rat face whiskers, a high-acuity sensor used to gain detailed information about the world. Grazing angle FIB milling was first applied to expose the interior cross section of the rat whisker sample, followed by a "lift-out" method to retrieve and position the target sample for further analyses. AFM force spectroscopy measurements revealed a non-uniform pattern of elastic modulus across the cross section, with a range from 0.8GPa to 13.5GPa. The highest elastic modulus was found at the outer cuticle region of the whisker, and values gradually decreased towards the interior cortex and medulla regions. Elemental mapping with EDS confirmed that the interior of the rat whisker is dominated by C, O, N, S, Cl and K, with a significant change of elemental distribution close to the exterior cuticle region. Based on these data, a novel comprehensive three dimensional (3D) elastic modulus model was constructed, and stress distributions under realistic conditions were investigated with Finite Element Analysis (FEA). The simulations could well account for the passive whisker deflections, with calculated resonant frequency as well as force-deflection for the whiskers being in good agreement with reported experimental data. Limitations and further applications are discussed for the proposed FIB/AFM approach, which holds good promise as a unique platform to gain insights on various heterogeneous biomaterials and biomechanical systems. PMID:25839121

  5. Spectroscopic Investigation of H Atom Transfer in a Gas-phase Dissociation Reaction: McLafferty Rearrangement of Model Gas-phase Peptide Ions

    SciTech Connect

    Michael J. Van Stipdonk; Dale R. Kersetter; Christopher M. Leavitt; Gary S. Groenewold; Jeffrey Steill; Jos Oomens

    2008-07-01

    Wavelength-selective infrared multiple-photon photodissociation (WS-IRMPD) was used to study isotopically-labeled ions generated by McLafferty rearrangement of nicotinyl-glycine-tert-butyl ester and betaine-glycine-tert-butyl ester. The tert-butyl esters were incubated in a mixture of D2O and CH3OD to induce solution-phase hydrogen-deuterium exchange and then converted to gas-phase ions using electrospray ionization. McLafferty rearrangement was used to generate the free-acid forms of the respective model peptides through transfer of an H atom and elimination of butene. The specific aim was to use vibrational spectra generated by WS-IRMPD technique to determine whether the H atom remains at the acid group, or migrates to one or more of the other exchangeable sites. Comparison of the IRMPD results in the region from 1200-1900 cm-1 to theoretical spectra for different isotopically-labeled isomers clearly shows that the H atom is situated at the C-terminal acid group and migration to amide positions is negligible on the time scale of the experiment. The results of this study suggest that use of the McLafferty rearrangement for peptide esters could be an effective approach for generation of H-atom isotope tracers, in-situ, for subsequent investigation of intra-molecular proton migration during peptide fragmentation studies.

  6. Excitation of atoms and molecules in collisions with highly charged ions. Progress report, January 1, 1991--March 1, 1992

    SciTech Connect

    Watson, R.L.

    1992-03-01

    This report discusses research of multicharged nitrogen, oxygen and carbon monoxide molecular ions produced with collision with multicharged argon ions. Properties like ionization, dissociation, and excitation are investigated. (LSP)

  7. Scanning-force-microscopy study of MeV-atomic-ion-induced surface tracks in organic crystals

    SciTech Connect

    Kopniczky, J.; Reimann, C.T.; Hallen, A.; Sundqvist, B.U.R. ); Tengvall, P.; Erlandsson, R. )

    1994-01-01

    We present scanning force microscope images of craterlike defects induced by individual 78.2-MeV [sup 127]I ions incident on organic single-crystal [ital L]-valine surfaces. For grazing incidence ions, the craters are elongated along the ion azimuth of incidence and display a raised tail in the surface above the ion track. This permanent plastic deformation of the surface indicates that a hydrodynamic pressure-pulse phenomenon occurs in response to the electronically deposited energy.

  8. Search for heavy long-lived multi-charged particles in pp collisions at √s = 8  TeV using the ATLAS detector

    DOE PAGESBeta

    None

    2015-08-08

    A search for heavy long-lived multi-charged particles is performed using the ATLAS detector at the LHC. Data collected in 2012 at √s = 8 TeV from pp collisions corresponding to an integrated luminosity of 20.3 fb-1 are examined. Particles producing anomalously high ionisation, consistent with long-lived massive particles with electric charges from |q| = 2e to |q| = 6e are searched for. No signal candidate events are observed, and 95 % confidence level cross-section upper limits are interpreted as lower mass limits for a Drell–Yan production model. The mass limits range between 660 and 785 GeV.

  9. Cross section for stripping of argon ions in atomic collisions with argon gas at energies from 2 to 15 keV per incident charge

    NASA Astrophysics Data System (ADS)

    Bliman, S.; Chan-Tung, N.; Dousson, S.; Jacquot, B.; van Houtte, D.

    1980-06-01

    Cross sections for the stripping of one electron from Ar+, Ar2+, and Ar3+ ions in single collisions on argon atoms have been measured. The measurements were made at energies from 2 to 15 keV per incident-ion charge. The growth-rate method has been used to check that the single-collision condition is realized. Cross sections are then deduced. During the collision, incident ions are scattered out of the acceptance angle of the analyzing device: An estimate of losses is made, and corrected cross sections are proposed. Comparisons to previously published data are attempted: For σ1,2 one value at 6 keV exists which is in fair agreement with our value; for σ2,3 our value at 30 keV coincides with the single σ2,3 value existing.

  10. Atomic Oxygen (ATOX) simulation of Teflon FEP and Kapton H surfaces using a high intensity, low energy, mass selected, ion beam facility

    NASA Technical Reports Server (NTRS)

    Vered, R.; Grossman, E.; Lempert, G. D.; Lifshitz, Y.

    1994-01-01

    A high intensity (greater than 10(exp 15) ions/sq cm) low energy (down to 5 eV) mass selected ion beam (MSIB) facility was used to study the effects of ATOX on two polymers commonly used for space applications (Kapton H and Teflon FEP). The polymers were exposed to O(+) and Ne(+) fluences on 10(exp 15) - 10(exp 19) ions/sq cm, using 30eV ions. A variety of analytical methods were used to analyze the eroded surfaces including: (1) atomic force microscopy (AFM) for morphology measurements; (2) total mass loss measurements using a microbalance; (3) surface chemical composition using x-ray photoelectron spectroscopy (XPS), and (4) residual gas analysis (RGA) of the released gases during bombardment. The relative significance of the collisional and chemical degradation processes was evaluated by comparing the effects of Ne(+) and O(+) bombardment. For 30 eV ions it was found that the Kapton is eroded via chemical mechanisms while Teflon FEP is eroded via collisional mechanisms. AFM analysis was found very powerful in revealing the evolution of the damage from its initial atomic scale (roughness of approx. 1 nm) to its final microscopic scale (roughness greater than 1 micron). Both the surface morphology and the average roughness of the bombarded surfaces (averaged over 1 micron x 1 micron images by the system's computer) were determined for each sample. For 30 eV a non linear increase of the Kapton roughness with the O(+) fluence was discovered (a slow increase rate for fluences phi less than 5 x 10(exp 17) O(+)/sq cm, and a rapid increase rate for phi greater than 5 x 10(exp 17) O(+)/sq cm). Comparative studies on the same materials exposed to RF and DC oxygen plasmas indicate that the specific details of the erosion depend on the simulation facility emphasizing the advantages of the ion beam facility.

  11. Trends in Atomic Parameters for Crystals and Free Ions across the Lanthanide Series: The Case of LaCl3:Ln(3+).

    PubMed

    Yeung, Y Y; Tanner, P A

    2015-06-18

    Analyses of the crystal field energy levels of the series LaCl3:Ln(3+) using a semiempirical Hamiltonian shows that only five ions (Pr, Nd, Pm, Dy, Ho) meet the criteria to avoid overfitting of the atomic part. A new parameter (SNES) has been introduced to represent the strength of the normalized electrostatic repulsion for these ions. This parameter varies linearly (R(2)adj = 0.9994, N = 5) with the reciprocal of the radius of the tripositive lanthanide ion, as expected from the form of repulsive Coulomb interaction. The Slater parameters from the crystal field analyses, F(k)(corr) (i.e., corrected for the effects of the two-particle component of the three-body operator associated with the T(2) parameter), exhibit an exponential variation with the number of electrons, n, in 4f(n). This is explained by reference to the radial part of a hydrogen-like wave function. The ratio of F(k)(corr) with the ab initio free ion Slater parameter F(k)(ab initio) varies linearly with n. Fitted parameters F(k)(corr: free ion) from the free ion data for Pr(3+) and Nd(3+) show that the corresponding ab initio values are between 14 and 27% too high. The spin-orbit coupling constant from crystal field analyses (ζ4f) exhibits a quartic variation with atomic number, and the ratio ζ4f/ζ4f(ab initio) follows an exponential growth model with n. The results serve to confirm the hypothesis that smooth trends can be observed across the Ln(3+) series for the fitted parameters despite the fact that the majority of experimental data is lacking. PMID:25985076

  12. Trends in Atomic Parameters for Crystals and Free Ions across the Lanthanide Series: The Case of LaCl3:Ln(3+).

    PubMed

    Yeung, Y Y; Tanner, P A

    2015-06-18

    Analyses of the crystal field energy levels of the series LaCl3:Ln(3+) using a semiempirical Hamiltonian shows that only five ions (Pr, Nd, Pm, Dy, Ho) meet the criteria to avoid overfitting of the atomic part. A new parameter (SNES) has been introduced to represent the strength of the normalized electrostatic repulsion for these ions. This parameter varies linearly (R(2)adj = 0.9994, N = 5) with the reciprocal of the radius of the tripositive lanthanide ion, as expected from the form of repulsive Coulomb interaction. The Slater parameters from the crystal field analyses, F(k)(corr) (i.e., corrected for the effects of the two-particle component of the three-body operator associated with the T(2) parameter), exhibit an exponential variation with the number of electrons, n, in 4f(n). This is explained by reference to the radial part of a hydrogen-like wave function. The ratio of F(k)(corr) with the ab initio free ion Slater parameter F(k)(ab initio) varies linearly with n. Fitted parameters F(k)(corr: free ion) from the free ion data for Pr(3+) and Nd(3+) show that the corresponding ab initio values are between 14 and 27% too high. The spin-orbit coupling constant from crystal field analyses (ζ4f) exhibits a quartic variation with atomic number, and the ratio ζ4f/ζ4f(ab initio) follows an exponential growth model with n. The results serve to confirm the hypothesis that smooth trends can be observed across the Ln(3+) series for the fitted parameters despite the fact that the majority of experimental data is lacking.

  13. Atomic Oxygen (ATOX) simulation of Teflon FEP and Kapton H surfaces using a high intensity, low energy, mass selected, ion beam facility

    NASA Astrophysics Data System (ADS)

    Vered, R.; Grossman, E.; Lempert, G. D.; Lifshitz, Y.

    1994-11-01

    A high intensity (greater than 10(exp 15) ions/sq cm) low energy (down to 5 eV) mass selected ion beam (MSIB) facility was used to study the effects of ATOX on two polymers commonly used for space applications (Kapton H and Teflon FEP). The polymers were exposed to O(+) and Ne(+) fluences on 10(exp 15) - 10(exp 19) ions/sq cm, using 30eV ions. A variety of analytical methods were used to analyze the eroded surfaces including: (1) atomic force microscopy (AFM) for morphology measurements; (2) total mass loss measurements using a microbalance; (3) surface chemical composition using x-ray photoelectron spectroscopy (XPS), and (4) residual gas analysis (RGA) of the released gases during bombardment. The relative significance of the collisional and chemical degradation processes was evaluated by comparing the effects of Ne(+) and O(+) bombardment. For 30 eV ions it was found that the Kapton is eroded via chemical mechanisms while Teflon FEP is eroded via collisional mechanisms. AFM analysis was found very powerful in revealing the evolution of the damage from its initial atomic scale (roughness of approx. 1 nm) to its final microscopic scale (roughness greater than 1 micron). Both the surface morphology and the average roughness of the bombarded surfaces (averaged over 1 micron x 1 micron images by the system's computer) were determined for each sample. For 30 eV a non linear increase of the Kapton roughness with the O(+) fluence was discovered (a slow increase rate for fluences phi less than 5 x 10(exp 17) O(+)/sq cm, and a rapid increase rate for phi greater than 5 x 10(exp 17) O(+)/sq cm). Comparative studies on the same materials exposed to RF and DC oxygen plasmas indicate that the specific details of the erosion depend on the simulation facility emphasizing the advantages of the ion beam facility.

  14. QED Theory of Radiation Emission and Absorption Lines for Atoms and Ions in a Strong Laser Field

    SciTech Connect

    Glushkov, A. V.

    2008-10-22

    The results of numerical calculating the multi-photon resonance shift and width for transition 6S-6F in the atom of Cs (wavelength 1059nm) in a laser pulse of the Gaussian and soliton-like shapes are presented. QED theory of radiation atomic lines is used.

  15. Imidazole-Modified Nanoporous Silica for Lead Ion Solid Phase Extraction Prior to Determination from Industrial Wastewaters by Flame Atomic Absorption Spectrometry.

    PubMed

    Behbahani, Ali; Ardjmand, Mehdi

    2015-01-01

    A new method was applied to produce modified nanoporous silica as a novel sorbent for Pb(II) ion SPE from industrial wastewater samples. In this modified method, the produced nanoporous silica has a higher functional group loading, which leads to a higher preconcentration factor as well as a lower LOD. This modified nanoporous silica was used for preconcentration prior to subsequent determination of Pb(II) ions by flame atomic absorption spectrometry. Various parameters such as the eluent, pH of the sample solution, and flow rate were optimized during this work. Also, the effect of a variety of ions on preconcentration and recovery of Pb(II) ions was investigated. The LOD, defined as five times the SD of the blank, was determined to be lower than 0.1 mg/L with an RSD of <2%. The accuracy of the method was established by analyzing standard reference materials with certified Pb concentrations. Finally, the established method was successfully applied for determination of the Pb(II) ion concentration in industrial wastewater samples.

  16. Preparation of modified magnetic nanoparticles as a sorbent for the preconcentration and determination of cadmium ions in food and environmental water samples prior to flame atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Mirabi, Ali; Dalirandeh, Zeinab; Rad, Ali Shokuhi

    2015-05-01

    A new method has been developed for the separation/preconcentration of trace level cadmium ions using diphenyl carbazone/sodium dodecyl sulfate immobilized on magnetic nanoparticle Fe3O4 as a new sorbent SPE and their determination by flame atomic absorption spectrometry (FAAS). Synthesized nanoparticle was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). Various influencing parameters on the separation and preconcentration of trace level cadmium ions such as, pH value, amount of nanoparticles, amount of diphenyl carbazone, condition of eluting solution, the effects of matrix ions were examined. The cadmium ions can be eluted from the modified magnetic nanoparticle using 1 mol L-1 HCl as a desorption reagent. The detection limit of this method for cadmium was 3.71 ng ml-1 and the R.S.D. was 0.503% (n=6). The advantages of this new method include rapidity, easy preparation of sorbents and a high concentration factor. The proposed method has been applied to the determination of Cd ions at trace levels in real samples such as, green tea, rice, tobacco, carrot, lettuce, ginseng, spice, tap water, river water, sea water with satisfactory results.

  17. Imidazole-Modified Nanoporous Silica for Lead Ion Solid Phase Extraction Prior to Determination from Industrial Wastewaters by Flame Atomic Absorption Spectrometry.

    PubMed

    Behbahani, Ali; Ardjmand, Mehdi

    2015-01-01

    A new method was applied to produce modified nanoporous silica as a novel sorbent for Pb(II) ion SPE from industrial wastewater samples. In this modified method, the produced nanoporous silica has a higher functional group loading, which leads to a higher preconcentration factor as well as a lower LOD. This modified nanoporous silica was used for preconcentration prior to subsequent determination of Pb(II) ions by flame atomic absorption spectrometry. Various parameters such as the eluent, pH of the sample solution, and flow rate were optimized during this work. Also, the effect of a variety of ions on preconcentration and recovery of Pb(II) ions was investigated. The LOD, defined as five times the SD of the blank, was determined to be lower than 0.1 mg/L with an RSD of <2%. The accuracy of the method was established by analyzing standard reference materials with certified Pb concentrations. Finally, the established method was successfully applied for determination of the Pb(II) ion concentration in industrial wastewater samples. PMID:26525261

  18. High-energy collision-induced dissociation of [M+Na]+ ions desorbed by fast atom bombardment of ceramides isolated from the starfish Distolasterias nipon.

    PubMed

    Yoo, Ji Sun; Park, Taeseong; Bang, Geul; Lee, Chulhyun; Rho, Jung-Rae; Kim, Young Hwan

    2013-02-01

    Ten ceramides and four cerebrosides were extracted from the starfish Distolasterias nipon by solvent extraction, silica gel column chromatography and reversed-phase high-performance liquid chromatography. Structural identification was conducted using tandem mass spectrometry of monosodiated ions desorbed by fast atom bombardment. The complete structures of four cerebrosides were determined by a previously reported method. The high-energy collision-induced dissociation (CID) spectral characteristics of ceramides with various structures depend on the number and positions of double bonds on both the N-acyl and sphingoid chains, the presence of a hydroxyl group or a double bond at the C-4 position of the sphingoid chain and the presence of an α-hydroxy group on the N-acyl chain. The high-energy CID of the monosodiated ion, [M+Na](+), of each ceramide molecular species generated abundant ions, providing information on the composition of the fatty acyl chains and sphingoid long-chain bases. Each homologous ion series along the fatty acyl group and aliphatic chain of the sphingoid base was used for locating the double-bond positions of both chains and hydroxyl groups on the sphingoid base chain. The double-bond positions were also confirmed by the m/z values of abundant allylic even- and odd-electron ions, and the intensity ratio of the T ion peak relative to the O ion peak. This technique could determine the complete structures of ceramides and cerebrosides in an extract mixture and has great potential for determining other sphingolipids isolated from various biological sources.

  19. Excitation of atoms and molecules in collisions with highly charged ions. [Cyclotron Inst. , Texas A M Univ. , College Station, Texas

    SciTech Connect

    Watson, R.L.

    1993-01-01

    A study of the double ionization of He by high-energy N[sup 7+] ions was extended up in energy to 40 MeV/amu. Coincidence time-of-flight studies of multicharged N[sub 2], O[sub 2], and CO molecular ions produced in collisions with 97-MeV Ar[sup 14+] ions were completed. Analysis of the total kinetic energy distributions and comparison with the available data for CO[sup 2+] and CO[sup 3+] from synchrotron radiation experiments led to the conclusion that ionization by Ar-ion impact populates states having considerably higher excitation energies than those accessed by photoionization. The dissociation fractions for CO[sup 1+] and CO[sup 2+] molecular ions, and the branching ratios for the most prominent charge division channels of CO[sup 2+] through CO[sup 7+] were determined from time-of-flight singles and coincidence data. An experiment designed to investigate the orientation dependence of dissociative multielectron ionization of molecules by heavy ion impact was completed. Measurements of the cross sections for K-shell ionization of intermediate-Z elements by 30-MeV/amu H, N, Ne, and Ar ions were completed. The cross sections were determined for solid targets of Z = 13, 22, 26, 29, 32, 40, 42, 46, and 50 by recording the spectra of K x rays with a Si(Li) spectrometer.

  20. Excitation of atoms and molecules in collisions with highly charged ions. Progress report, January 1, 1990--December 1, 1992

    SciTech Connect

    Watson, R.L.

    1993-01-01

    A study of the double ionization of He by high-energy N{sup 7+} ions was extended up in energy to 40 MeV/amu. Coincidence time-of-flight studies of multicharged N{sub 2}, O{sub 2}, and CO molecular ions produced in collisions with 97-MeV Ar{sup 14+} ions were completed. Analysis of the total kinetic energy distributions and comparison with the available data for CO{sup 2+} and CO{sup 3+} from synchrotron radiation experiments led to the conclusion that ionization by Ar-ion impact populates states having considerably higher excitation energies than those accessed by photoionization. The dissociation fractions for CO{sup 1+} and CO{sup 2+} molecular ions, and the branching ratios for the most prominent charge division channels of CO{sup 2+} through CO{sup 7+} were determined from time-of-flight singles and coincidence data. An experiment designed to investigate the orientation dependence of dissociative multielectron ionization of molecules by heavy ion impact was completed. Measurements of the cross sections for K-shell ionization of intermediate-Z elements by 30-MeV/amu H, N, Ne, and Ar ions were completed. The cross sections were determined for solid targets of Z = 13, 22, 26, 29, 32, 40, 42, 46, and 50 by recording the spectra of K x rays with a Si(Li) spectrometer.