WorldWideScience

Sample records for atom collisions

  1. Theoretical atomic collision physics

    Energy Technology Data Exchange (ETDEWEB)

    Lane, N.F. (Rice Univ., Houston, TX (USA) Rice Univ., Houston, TX (USA). Quantum Inst.)

    1990-01-01

    The theoretical atomic physics at Rice University focuses on obtaining a better understanding of the mechanisms that control inelastic collisions between excited atoms and atoms, molecules and ions. Particular attention is given to systems and processes that are of potential importance to advanced energy technologies. In the current year, significant progress has been made in quantitative studies of: quenching of low-Rydberg Na atoms in thermal energy collisions with He, Ne and Ar atoms; selective excitation resulting from charge transfer in collisions of highly stripped ions of He, Li, C, and with Li, Na and He atoms and H{sub 2} molecules at keV energies; differential elastic and single, and double electron transfer in He{sup ++} collisions with He at keV energies; inelastic electron-transfer in ultra-low-energy-energy (T=8 to 80K) collisions between {sup 3}He{sup +} and {sup 4}He and {sup 4}He{sup +} and {sup 3}He; a formalism for ionization by electron impact of ions in dense, high temperature plasmas.

  2. Atomic collisions, inelastic indeed

    Science.gov (United States)

    Bercegol, Herve; Ferrando, Gwenael; Lehoucq, Roland

    At the turn of the twentieth century, a hot controversy raged about the ability of Boltzmann's framework to take care of irreversibility. The so-called Loschmidt's paradox progressively faded with time during the last hundred years, due to the predictive efficiency of statistical mechanics. However, one detail at the origin of the controversy - the elasticity of atomic collisions - was not completely challenged. A semi-classical treatment of two atoms interacting with the vacuum zero-point field permits to predict a friction force acting against the rotation of the pair of atoms. By its form and its level, the calculated torque is a candidate as a physical cause for diffusion of energy and angular momentum, and consequently for entropy growth. It opens the way to a revision of the standard vision of irreversibility. This presentation will focus on two points. First we will discuss the recent result in a broader context of electromagnetic interactions during microscopic collisions. The predicted friction phenomenon can be compared to and distinguished from Collision-Induced Emission and other types of inelastic collisions. Second we will investigate the consequences of the friction torque on calculated trajectories of colliding atoms, quantifying the generation of dimers linked by dispersion forces.

  3. Electron-atom collisions

    International Nuclear Information System (INIS)

    This book is a comprehensive introduction to electron-atom collisions, covering both theory and experiment. The interaction of electrons with atoms is the field that most deeply probes both the structure and reaction dynamics of a many-body system. The book begins with a short account of experimental techniques of cross-section measurement. It then introduces the essential quantum mechanics background needed. The following chapters cover one-electron problems (from the classic particle in a box to a relativistic electron in a central potential), the theory of atomic bound states, formal scattering theory, calculation of scattering amplitudes, spin-independent and spin-dependent scattering observables, ionisation and electron momentum spectroscopy. The connections between experimental and theoretical developments are emphasised throughout. (author)

  4. Atomic collisions involving pulsed positrons

    DEFF Research Database (Denmark)

    Merrison, J. P.; Bluhme, H.; Field, D.;

    2000-01-01

    Conventional slow positron beams have been widely and profitably used to study atomic collisions and have been instrumental in understanding the dynamics of ionization. The next generation of positron atomic collision studies are possible with the use of charged particle traps. Not only can large...... instantaneous intensities be achieved with in-beam accumulation, but more importantly many orders of magnitude improvement in energy and spatial resolution can be achieved using positron cooling. Atomic collisions can be studied on a new energy scale with unprecedented precion and control. The use of...... accelerators for producing intense positron pulses will be discussed in the context of atomic physics experiments....

  5. Collision-produced atomic states

    International Nuclear Information System (INIS)

    The last 10-15 years have witnessed the development of a new, powerful class of experimental techniques for atomic collision studies, allowing partial or complete determination of the state of the atoms after a collision event, i.e. the full set of quantum-mechanical scattering amplitudes or - more generally - the density matrix describing the system. Evidently, such studies, involving determination of alignment and orientation parameters, provide much more severe tests of state-of-the-art scattering theories than do total or differential cross section measurements which depend on diagonal elements of the density matrix. The off-diagonal elements give us detailed information about the shape and dynamics of the atomic states. Therefore, close studies of collision-produced atomic states are currently leading to deeper insights into the fundamental physical mechanisms governing the dynamics of atomic collision events. The first part of the lectures deals with the language used to describe atomic states, while the second part presents a selection of recent results for model systems which display fundamental aspects of the collision physics in particularly instructive ways. I shall here restrict myself to atom-atom collisions. The discussion will be focused on states decaying by photon emission though most of the ideas can be easily modified to include electron emission as well. (orig./AH)

  6. Atomic collisions research with excited atomic species

    International Nuclear Information System (INIS)

    Measurements and calculations of fundamental atomic collision and spectroscopic properties such as collision cross sections, reaction rates, transition probabilities etc. underpin the understanding and operation of many plasma and gas-discharge-based devices and phenomena, for example plasma processing and deposition. In almost all cases the complex series of reactions which sustains the discharge or plasma, or produces the reactive species of interest, has a precursor electron impact excitation, attachment, dissociation or ionisation event. These processes have been extensively studied in a wide range of atomic and molecular species and an impressive data base of collision cross sections and reaction rates now exists. However, most of these measurements are for collisions with stable atomic or molecular species which are initially in their ground electronic state. Relatively little information is available for scattering from excited states or for scattering from unstable molecular radicals. Examples of such species would be metastable excited rare gases, which are often used as buffer gases, or CF2 radicals formed by electron impact dissociation in a CF4 plasma processing discharge. We are interested in developing experimental techniques which will enable the quantitative study of such exotic atomic and molecular species. In this talk I would like to outline one such facility which is being used for studies of collisions with metastable He(23S) atoms

  7. Theory of slow atomic collisions

    Science.gov (United States)

    Nikitin, E. E.; Umanskii, S. Ia.

    The theory presented in this book is self-contained. It can be applied to the interpretation of various processes occurring in atomic collisions over a relatively wide energy range, from thermal energies to hundreds of eV. The general formulation of the scattering problem under quasi-classical conditions is discussed, taking into account scattering amplitudes and cross sections, scattering equations, collisions of two many-electron atoms, and integral cross sections for isotropic collisions. Other topics explored are related to diatomic electronic states, approximate calculations of the electronic states of diatoms, elastic scattering, approximate calculations of a multichannel quasi-classical scattering matrix, the two-state scattering problem, the linear two-state Landau-Zener model, nonlinear two-state models of nonadiabatic coupling, multistate models of nonadiabatic coupling, and a case study involving intramultiplet mixing and depolarization of alkalis in collisions with noble gases.

  8. Photonic, Electronic and Atomic Collisions

    Science.gov (United States)

    Fainstein, Pablo D.; Lima, Marco Aurelio P.; Miraglia, Jorge E.; Montenegro, Eduardo C.; Rivarola, Roberto D.

    2006-11-01

    Plenary. Electron collisions - past, present and future / J. W. McConkey. Collisions of slow highly charged ions with surfaces / J. Burgdörfer ... [et al.]. Atomic collisions studied with "reaction-microscopes" / R. Moshammer ... [et al.]. Rydberg atoms: a microscale laboratory for studying electron-molecule tnteractions / F. B. Dunning -- Collisions involvintg photons. Quantum control of photochemical reaction dynamics and molecular functions / M. Yamaki ... [et al.]. Manipulating and viewing Rydberg wavepackets / R. R. Jones. Angle-resolved photoelectrons as a probe of strong-field interactions / M. Vrakking. Ultracold Rydberg atoms in a structured environment / I. C. H. Liu and J. M. Rost. Synchrotron-radiation-based recoil ion momentum spectroscopy of laser cooled and trapped cesium atoms / L. H. Coutinho. Reconstruction of attosecond pulse trains / Y. Mairesse ... [et al.]. Selective excitation of metastable atomic states by Femto- and attosecond laser pulses / A. D. Kondorskiy. Accurate calculations of triple differential cross sections for double photoionization of the hygrogen molecule / W. Vanroose ... [et al.]. Double and triple photoionization of Li and Be / J. Colgan, M. S. Pindzola and F. Robicheaux. Few/many body dynamics in strong laser fields / J. Zanghellini and T. Brabec. Rescattering-induced effects in electron-atom scattering in the presence of a circularly polarized laser field / A. V. Flegel ... [et al.]. Multidimensional photoelectron spectroscopy / P. Lablanquie ... [et al.]. Few photon and strongly driven transitions in the XUV and beyond / P. Lambropoulos, L. A. A. Nikolopoulos and S. I. Themelis. Ionization dynamics of atomic clusters in intense laser pulses / U. Saalmann and J. M. Rost. On the second order autocorrelation of an XUV attosecond pulse train / E. P. Benis ... [et al.]. Evidence for rescattering in molecular dissociation / I. D. Williams ... [et al.]. Photoionizing ions using synchrotron radiation / R. Phaneuf. Photo double

  9. Atomic and molecular collision processes

    International Nuclear Information System (INIS)

    530Accomplishments during the course of a 44-month program of code development and high precision calculations for electron collisions with atoms, atomic ions, and molecules are summarized. In electron-atom and -ion collisions, we were primarily concerned with the fundamental physics of the process that controls excitation in high temperature plasmas. In the molecular work, we pursued the development of techniques for accurate calculations of ro-vibrational excitation of polyatomic molecules, to the modeling of gas-phase laser systems. Highlights from the seven technical paper published as a result of this contract include: The resolution of a long history of unexplained anomalies and experimental/theoretical discrepancies by a demonstration that the Coulomb phase must be included in scattering amplitudes for electron-ion collisions. Definitive close-coupling calculations of cross sections for electron impact excitation of Be+, using a very elaborate expansion for the collision system and inclusion of both one- and two-body terms for the effect of core polarization. Detailed state-of-the-art calculations for electron-impact excitation of the sodium-like ion A ell 2+ that included core-polarization interactions, and which also produced new data on bound-state energy levels for the magnesium-like ion A ell + and oscillator strengths for A ell 2+. Partial cross sections for excitation of the 3p level of sodium at energies just above threshold calculated using a four-state close-coupling approach, including both total cross sections and those for excitation as a function of the change in the spin and orbital angular momentum projection quantum numbers of the target electron. Generalization of our electron-molecule scattering code to carry out full vibrational close-coupling calculations with an exact treatment of exchange and with a parameter-free representation of correlation and polarization interactions, and application to HF and H2

  10. Observation of atomic collisions in crystalline solids

    CERN Document Server

    Nelson, R S; Gevers, R

    2013-01-01

    The Observation of Atomic Collisions in Crystalline Solids presents a critical account of the more important experiments which have provided the basis for a better understanding of atomic collision phenomena in crystalline solids. Collisions have been divided into two artificial regimes; primary collisions which deal with the interaction of the incident particles with the solid, and secondary collisions which deal with those events which occur as a result of lattice atoms recoiling from primary encounters. Although the book is intended principally for the experimentalist some simple theoretica

  11. Sixteenth International Conference on the physics of electronic and atomic collisions

    International Nuclear Information System (INIS)

    This report contains abstracts of papers on the following topics: photons, electron-atom collisions; electron-molecule collisions; electron-ion collisions; collisions involving exotic species; ion- atom collisions, ion-molecule or atom-molecule collisions; atom-atom collisions; ion-ion collisions; collisions involving rydberg atoms; field assisted collisions; collisions involving clusters and collisions involving condensed matter

  12. Sixteenth International Conference on the physics of electronic and atomic collisions

    Energy Technology Data Exchange (ETDEWEB)

    Dalgarno, A.; Freund, R.S.; Lubell, M.S.; Lucatorto, T.B. (eds.)

    1989-01-01

    This report contains abstracts of papers on the following topics: photons, electron-atom collisions; electron-molecule collisions; electron-ion collisions; collisions involving exotic species; ion- atom collisions, ion-molecule or atom-molecule collisions; atom-atom collisions; ion-ion collisions; collisions involving rydberg atoms; field assisted collisions; collisions involving clusters and collisions involving condensed matter.

  13. Rydberg atom ionization by slow collisions with alkali element atoms

    International Nuclear Information System (INIS)

    A new mechanism for ionization of highexcited atoms due to the electron capture into the autoionization state of a negative ion is suggested. Calculations of cross-sections and the ionization rate for sodium and lithium atoms collisions are performed

  14. Atomic collision dynamics in optical lattices

    CERN Document Server

    Piilo, J; Berg-Sørensen, K

    2001-01-01

    We simulate collisions between two atoms, which move in an optical lattice under the dipole-dipole interaction. The model describes simultaneously the two basic dynamical processes, namely the Sisyphus cooling of single atoms, and the light-induced inelastic collisions between them. We consider the J=1/2 -> J=3/2 laser cooling transition for Cs, Rb and Na. We find that the hotter atoms in a thermal sample are selectively lost or heated by the collisions, which modifies the steady state distribution of atomic velocities, reminiscent of the evaporative cooling process.

  15. Electron detachment in ion-atom collisions

    International Nuclear Information System (INIS)

    The electron detachment process that occurs in negative ion-atom collisions is investigated. Differential cross sections were measured for the collisions of F-, Cl-, Br-, I- on He, Ne, Ar, Kr, Xe, Na and K. Electron energy distributions were obtained for some of the systems. (Auth.)

  16. Atomic collision experiments using pulsed synchrotron radiation

    International Nuclear Information System (INIS)

    High intensity and continuous nature of the synchrotron radiation are the properties that are fundamentally important for studies of some atomic collision experiments, and many processes have been investigated by using these characteristics. However, so far the property that the radiation is highly polarized and pulsed in time has not been exploited significantly in atomic physics. As an example of the atomic processes relevant to such polarized and pulsed features of the synchrotron radiation, collisions involving optically-allowed excited atoms and molecules will be presented. (author)

  17. Atomic Bremsstrahlung in ion-atom collisions (stripping)

    International Nuclear Information System (INIS)

    Atomic Bremsstrahlung produced in high energy (non relativistic) ion-atom collisions including retardation effects is studied. Mechanical states of the system are described by the symmetrical eikonal approximation and Hartree-Fock electronic wave functions for the calculation of the shape factor of each atom. Photon energy spectra are presented for collisions of protons against noble gases, Ne, Ar, Kr and Xe. The contribution of each atomic shell to these spectra is studied, where lowest shell (1s) corresponds to the hard X-ray region and the higher shells correspond to lower photon energies. (Author)

  18. Electron-Atom Collisions in Gases

    Science.gov (United States)

    Kraftmakher, Yaakov

    2013-01-01

    Electron-atom collisions in gases are an aspect of atomic physics. Three experiments in this field employing a thyratron are described: (i) the Ramsauer-Townsend effect, (ii) the excitation and ionization potentials of xenon and (iii) the ion-electron recombination after interrupting the electric discharge.

  19. Plasmas applied atomic collision physics, v.2

    CERN Document Server

    Barnett, C F

    1984-01-01

    Applied Atomic Collision Physics, Volume 2: Plasmas covers topics on magnetically confined plasmas. The book starts by providing the history of fusion research and describing the various approaches in both magnetically and inertially confined plasmas. The text then gives a general discussion of the basic concepts and properties in confinement and heating of a plasma. The theory of atomic collisions that result in excited quantum states, particularly highly ionized impurity atoms; and diverse diagnostic topics such as emission spectra, laser scattering, electron cyclotron emission, particle bea

  20. Applied atomic and collision physics special topics

    CERN Document Server

    Massey, H S W; Bederson, Benjamin

    1982-01-01

    Applied Atomic Collision Physics, Volume 5: Special Topics deals with topics on applications of atomic collisions that were not covered in the first four volumes of the treatise. The book opens with a chapter on ultrasensitive chemical detectors. This is followed by separate chapters on lighting, magnetohydrodynamic electrical power generation, gas breakdown and high voltage insulating gases, thermionic energy converters, and charged particle detectors. Subsequent chapters deal with the operation of multiwire drift and proportional chambers and streamer chambers and their use in high energy p

  1. Case studies in atomic collision physics

    CERN Document Server

    McDaniel, E W

    2013-01-01

    Case Studies in Atomic Collision Physics II focuses on studies on the role of atomic collision processes in astrophysical plasmas, including ionic recombination, electron transport, and position scattering. The book first discusses three-body recombination of positive and negative ions, as well as introduction to ionic recombination, calculation of the recombination coefficient, ions recombining in their parent gas, and three-body recombination at moderate and high gas-densities. The manuscript also takes a look at precision measurements of electron transport coefficients and differential cr

  2. Atomic collisions in fusion plasmas involving multiply charged ions

    International Nuclear Information System (INIS)

    A short survey is given on atomic collisions involving multiply charged ions. The basic features of charge transfer processes in ion-ion and ion-atom collisions relevant to fusion plasmas are discussed. (author)

  3. Positronium collisions with rare-gas atoms

    CERN Document Server

    Gribakin, G F; Wilde, R S; Fabrikant, I I

    2015-01-01

    We calculate elastic scattering of positronium (Ps) by the Xe atom using the recently developed pseudopotential method [Fabrikant I I and Gribakin G F 2014 Phys. Rev. A 90 052717] and review general features of Ps scattering from heavier rare-gas atoms: Ar, Kr and Xe. The total scattering cross section is dominated by two contributions: elastic scattering and Ps ionization (break-up). To calculate the Ps ionization cross sections we use the binary-encounter method for Ps collisions with an atomic target. Our results for the ionization cross section agree well with previous calculations carried out in the impulse approximation. Our total Ps-Xe cross section, when plotted as a function of the projectile velocity, exhibits similarity with the electron-Xe cross section for the collision velocities higher than 0.8 a.u., and agrees very well with the measurements at Ps velocities above 0.5 a.u.

  4. Atomic collisions under extreme conditions in space

    International Nuclear Information System (INIS)

    In space, atoms and molecules are often placed under the extreme conditions which are very difficult to be realized on Earth. For instance, extremely hot and dense plasmas are found in and around various stellar objects (e.g., neutron stars) on one hand and extremely cold and diffuse gases prevail in interstellar space on the other. There is so strong a magnetic field that electron clouds in atoms and molecules are distorted. The study of atomic collisions under the extreme conditions is not only helpful in understanding the astrophysical environment but also reveals new aspects of the physics of atoms and molecules. This paper is an invitation to the study. (References are not exhaustive but only provide a clue with which more details can be found.) (author)

  5. Atomic collision physics: A summary and some projections

    International Nuclear Information System (INIS)

    It seems that it is my task to represent the ''Collision Physics Community'' at this symposium. First, we consider the part of atomic collision physics covered at this conference, i.e., multiple electron transfer to highly charged ions, and second we consider some applications of atomic collision experiments to tests of QED

  6. Electron transfer, ionization, and excitation atomic collisions

    International Nuclear Information System (INIS)

    Basic atomic-collision processes at intermediate and high energies are being studied theoretically at Penn State by Alston and Winter. In the high velocity regime, single-electron capture is treated using a high order multiple-scattering approach; extensive comparison with experiment and analysis of mechanisms have been made. Fitting the calculated amplitude with a simple analytic form, the asymptotic velocity dependence of the cross section is obtained. The effect on the capture amplitude of altering the inner part of the internuclear potential has also been explored. In the intermediate velocity regime, earlier work on collisions between protons and hydrogenic-ion targets using a coupled-state approach is being extended to the two-electron helium target. 29 refs

  7. [Electron transfer, ionization and excitation in atomic collisions

    International Nuclear Information System (INIS)

    The research being carried out at Penn State by Winter and Alston addresses the fundamental atomic-collision processes of electron transfer, ionization, and excitation. Winter has focussed attention on intermediate and, more recently, higher collision energies -- proton energies of at least about 50 keV -- for which coupled-state approaches are appropriate. Alston has concentrated on perturbative approaches to symmetric ion-ion/atom collisions at high energies and to asymmetric collisions at intermediate to high energies

  8. Phase dynamics in a binary-collisions atom laser scheme

    OpenAIRE

    Zobay, O.; Meystre, P.

    1997-01-01

    Various aspects of the phase dynamics of an atom laser scheme based on binary collisions are investigated. Analytical estimates of the influence of elastic atom-atom collisions on the laser linewidth are given, and linewidths achievable in a recently proposed atom laser scheme [Phys. Rev. A 56, 2989 (1997)] are evaluated explicitly. The extent to which a relative phase can be established between two interfering atom lasers, as well as the properties of that phase, are also investigated.

  9. Correlation effects in electron-atom collisions

    International Nuclear Information System (INIS)

    This thesis deals with correlation effects occurring in the outer region of configuration space after an ionising collision. The motion of both escaping electrons in the external region is then fully determined by the long-range Coulomb forces. Firstly the threshold ionisation of hydrogen-like targets is studied. In that case two slow electrons attempt to escape from the Coulomb attraction of the residual ion. Secondly ionising collisions, with the formation of an autoionising state as an intermediate step, are considered. Such an autoionising state is in fact a quasi bound state of the neutral atom which lies imbedded in the ionisation continuum. The state decays after a certain lifetime by emission of an electron. Of all states to be formed in the reaction region only the autoionising state(s) under consideration is then relevant for this type of ionisation process. The energy positions of autoionising states usually are such that the electron to be ionised is ejected with a rather large velocity. The correlation in the outer region of configuration space then consists of the interaction of a fast ejected electron and, in case of threshold excitation of the autoionising state, a slow scattered electron. (Auth.)

  10. On the utility and ubiquity of atomic collision physics

    International Nuclear Information System (INIS)

    This paper is divided into three parts. In the introduction, we discuss the history and makeup of ICPEAC. In the second part, we discuss the extent of applicability of atomic collision physics. In the third part, we chose one subject (dielectronic excitation) to show the interrelationship of various sub-branches of atomic collision physics. 28 refs., 14 figs

  11. Mutual ionization in atomic collisions near the electronic threshold

    International Nuclear Information System (INIS)

    We study mutual ionization in collisions between atomic hydrogen and helium at impact velocities near the electronic threshold for this process. We show that this process is substantially influenced by the Coulomb repulsion between the emitted electrons and that the atomic nuclei are very strongly involved in the momentum balance along the collision velocity. (paper)

  12. Atomic Collision Processes for Astrophysical and Laboratory Plasmas

    International Nuclear Information System (INIS)

    An accurate knowledge of atomic collision processes is important for a better understanding of many astrophysical and laboratory plasmas. Collision databases which contain electron-impact excitation, ionization, and recombination cross sections and temperature dependent rate coefficients have been constructed using perturbative distorted-wave methods and non-perturbative R-matrix pseudo-states and time-dependent close-coupling methods. We present recent atomic collision results

  13. [Electron transfer, ionization, and excitation in atomic collisions]: Progress report

    International Nuclear Information System (INIS)

    The fundamental processes of electron transfer, ionization, and excitation in ion-atom collisions are being studied. These collision processes are treated in the context of simple one- or two-electron systems in order to provide unambiguous results and reveal more clearly the collisional mechanisms. As outlined in the original proposal, three coupled-state calculations are being carried out over the present three-year period: a Sturmian-pseudostate study of ionization in collisions between protons and the hydrogenic ions He+, Li2+, Be3+, ...; a triple-center, atomic-state study of ionization in collisions between α particles and H(ls) atoms and between protons and He+(ls) ions; and an atomic-state study of electron transfer and excitation in collisions between protons and neutral He atoms. 12 refs

  14. A metastable helium trap for atomic collision physics

    International Nuclear Information System (INIS)

    Full text: Metastable helium in the 23S state is an important species for atom optics and atomic collision physics. Because of its large internal energy (20eV), long lifetime (∼8000s) and large collision cross section for a range of processes, metastable helium plays an important role in atmospheric physics, plasma discharges and gas laser physics. We have embarked on a program of studies on atom-atom and electron-atom collision processes involving cold metastable helium. We confine metastable helium atoms in a magneto-optic trap (MOT), which is loaded by a transversely collimated, slowed and 2-D focussed atomic beam. We employ diode laser tuned to the 1083 nm (23S1 - 23P21) transition to generate laser cooling forces in both the loading beam and the trap. Approximately 10 million helium atoms are trapped at temperatures of ∼ 1mK. We use phase modulation spectroscopy to measure the trapped atomic density. The cold, trapped atoms can collide to produce either atomic He+ or molecular He2+ ions by Penning Ionisation (PI) or Associative Ionisation (AI). The rate of formation of these ions is dependant upon the detuning of the trapping laser from resonance. A further laser can be used to connect the 23S1 state to another higher lying excited state, and variation of the probe laser detuning used to measure interatomic collision potential. Electron-atom collision processes are studied using a monochromatic electron beam with a well defined spatial current distribution. The total trap loss due to electron collisions is measured as a function of electron energy. Results will be presented for these atomic collision physics measurements involving cold, trapped metastable helium atoms. Copyright (1999) Australian Optical Society

  15. Electron transfer, ionization, and excitation in atomic collisions: Progress report

    International Nuclear Information System (INIS)

    The fundamental processes of electron transfer, ionization, and excitation in ion-atom collisions are being studied at Penn State by Winter. (The related work of Alston, who recently came to Penn State, is not described here since he is not at present funded by DOE.) These collision processes are treated in the context of simple one- or two-electron systems in order to provide unambiguous results and reveal more clearly the collisional mechanisms. Three coupled-state calculations are being carried out over the present three-year period and are discussed here: a Sturmian-pseudostate study of electron transfer in collisions between protons and the hydrogenic ions He+, Li2+, Be3+, ...; a triple-center, atomic-state study of ionization in collisions between α particles and H(ls) atoms and between protons and He+(ls) ions; and a coupled-state study of electron transfer and excitation in collisions between protons and neutral He atoms

  16. On charge transfer in ion-atom collisions at intermediate collision velocities

    International Nuclear Information System (INIS)

    The authors study charge transfer at intermediate energies for multielectron ion-atom collisions within the coupled-state impact-parameter method. They point out the importance of assumptions about electronic relaxation by comparing various calculations of cross sections for KK charge transfer in F9+ + Si as a test case. In these calculations, either the unrelaxed Hamiltonian of the atomic model or a relaxed molecular Hamiltonian has been employed, and two-state atomic or molecular basis sets have been used. To correct for the inadequacy of atomic orbitals for close collisions at intermediate energies, the authors propose to add orbitals of the united atom at the two collision centers. With such an atomic basis set, quasimolecular behavior of the system is represented sufficiently well. The authors report on results for the collision system H+ + He+ for which calculations with large molecular and atomic basis sets exist

  17. Landau quantization effects in ultracold atom-ion collisions

    Science.gov (United States)

    Simoni, Andrea; Launay, Jean-Michel

    2011-12-01

    We study ultracold atom-ion collisions in the presence of an external magnetic field. At low collision energy the field can drastically modify the translational motion of the ion, which follows quantized cyclotron orbits. We present a rigorous theoretical approach for the calculation of quantum scattering amplitudes in these conditions. Collisions in different magnetic field regimes, identified by the size of the cyclotron radius with respect to the range of the interaction potential, are investigated. Our results are important in cases where use of a magnetic field to control the atom-ion collision dynamics is envisioned.

  18. Landau quantization effects in ultracold atom-ion collisions

    International Nuclear Information System (INIS)

    We study ultracold atom-ion collisions in the presence of an external magnetic field. At low collision energy the field can drastically modify the translational motion of the ion, which follows quantized cyclotron orbits. We present a rigorous theoretical approach for the calculation of quantum scattering amplitudes in these conditions. Collisions in different magnetic field regimes, identified by the size of the cyclotron radius with respect to the range of the interaction potential, are investigated. Our results are important in cases where use of a magnetic field to control the atom-ion collision dynamics is envisioned.

  19. Innershell ionisation at small impactparameters in proton-atom collisions

    International Nuclear Information System (INIS)

    This thesis concentrates on innershell ionisation in proton-atom collisions. An experiment on K-shell ionisation of argon is described, performed in a gasfilled collision chamber under single collision conditions. Further experiments with carbon and aluminium were performed, the K-shell vacancy production in the collision of protons with these atoms being detected through the measurement of Auger-electrons. A spectrometer with a large solid angle was specially constructed for this and its performance is described. K-shell ionisation accompanying nuclear (p,γ) reactions has also been measured using 26Mg and 27Al. (Auth./C.F.)

  20. Atom-molecule collisions in an optically trapped gas

    OpenAIRE

    Zahzam, Nassim; Vogt, Thibault; Mudrich, Marcel; Comparat, Daniel; Pillet, Pierre

    2005-01-01

    Cold inelastic collisions between confined cesium (Cs) atoms and Cs$\\_2$ molecules are investigated inside a CO$\\_2$ laser dipole trap. Inelastic atom-molecule collisions can be observed and measured with a rate coefficient of $\\sim 2.5 \\times 10^{-11} $cm$^3$ s$^{-1}$, mainly independent of the molecular ro-vibrational state populated. Lifetimes of purely atomic and molecular samples are essentially limited by rest gas collisions. The pure molecular trap lifetime ranges 0,3-1 s, four times s...

  1. Condensed matter applied atomic collision physics, v.4

    CERN Document Server

    Datz, Sheldon

    1983-01-01

    Applied Atomic Collision Physics, Volume 4: Condensed Matter deals with the fundamental knowledge of collision processes in condensed media.The book focuses on the range of applications of atomic collisions in condensed matter, extending from effects on biological systems to the characterization and modification of solids. This volume begins with the description of some aspects of the physics involved in the production of ion beams. The radiation effects in biological and chemical systems, ion scattering and atomic diffraction, x-ray fluorescence analysis, and photoelectron and Auger spectrosc

  2. Landau quantization effects in ultracold atom-ion collisions

    OpenAIRE

    Simoni, Andrea; Launay, Jean-Michel

    2011-01-01

    We study ultracold atom-ion collisions in the presence of an external magnetic field. At low collision energy the field can drastically modify the translational motion of the ion, which follows quantized cyclotron orbits. We present a rigorous theoretical approach for the calculation of quantum scattering amplitudes in these conditions. Collisions in different magnetic field regimes, identified by the size of the cyclotron radius with respect to the range of the interaction potential, are inv...

  3. Energetic ion-atom collisions: early beginnings and recent advances

    International Nuclear Information System (INIS)

    From the discovery of canal rays and radioactivity to the invention of accelerators and the first applications of the Born approximation, some developments which were seminal for the development of ion-atom collisions are described. Collision theory is shown to have played a key role in the evolution of the early quantum theory and of quantum mechanics and its probability interpretation

  4. R-Matrix Theory of Atomic Collisions Application to Atomic, Molecular and Optical Processes

    CERN Document Server

    Burke, Philip George

    2011-01-01

    Commencing with a self-contained overview of atomic collision theory, this monograph presents recent developments of R-matrix theory and its applications to a wide-range of atomic molecular and optical processes. These developments include electron and photon collisions with atoms, ions and molecules required in the analysis of laboratory and astrophysical plasmas, multiphoton processes required in the analysis of superintense laser interactions with atoms and molecules and positron collisions with atoms and molecules required in antimatter studies of scientific and technologial importance. Basic mathematical results and general and widely used R-matrix computer programs are summarized in the appendices.

  5. Gas lasers applied atomic collision physics, v.3

    CERN Document Server

    McDaniel, E W

    1982-01-01

    Applied Atomic Collision Physics, Volume 3: Gas Lasers describes the applications of atomic collision physics in the development of many types of gas lasers. Topics covered range from negative ion formation in gas lasers to high-pressure ion kinetics and relaxation of molecules exchanging vibrational energy. Ion-ion recombination in high-pressure plasmas is also discussed, along with electron-ion recombination in gas lasers and collision processes in chemical lasers.Comprised of 14 chapters, this volume begins with a historical summary of gas laser developments and an overview of the basic ope

  6. Comparison of universal potentials for atomic collisions in solids

    International Nuclear Information System (INIS)

    Elastic collisions in solid of ions having kinetic energy greater than about ten eV are fairly well described by the binary collision approximation, where screened coulomb potentials are often used. The aim of the present work is to compare calculations based on the Moliere potential and on the more realistic Biersack-Ziegler potential for atomic collisions in solids having an atomic number between Z=6 and Z=79 with experimental data. A reasonable agreement with data can be obtained, in general, by means of both potentials provided that the screening lenght is suitably modified in the Moliere case, while no parameter adjustment is needed in the Biersack-Ziegler potential

  7. Vibronic excitation in atom molecule collisions

    International Nuclear Information System (INIS)

    The molecular beam machine used for the experiments is described. Three setups are discussed: one to measure total cross sections for negative ion formation in Na, K, Cs + O2 collisions (3-6000 eV); another to measure differential cross sections for neutral scattering and positive ion formation in K, Cs + O2 and K + Br2 collisions (20 - 150 eV); and a third to measure energy-loss spectra for neutral K scattered at a certain angle after a collision with O2 or Br2 (20 - 150 eV). (Auth.)

  8. Newly appreciated roles for electrons in ion-atom collisions

    International Nuclear Information System (INIS)

    Since the previous Debrecen workshop on High-Energy Ion-Atom Collisions there have been numerous experiments and substantial theoretical developments in the fields of fast ion-atom and ion- solid collisions concerned with explicating the previously largely underappreciated role of electrons as ionizing and exciting agents in such collisions. Examples to be discussed include the double electron ionization problem in He; transfer ionization by protons in He; double excitation in He; backward scattering of electrons in He; the role of electron-electron interaction in determining beta parameters for ELC; projectile K ionization by target electrons; electron spin exchange in transfer excitation; electron impact ionization in crystal channels; resonant coherent excitation in crystal channels; excitation and dielectronic recombination in crystal channels; resonant transfer and excitation; the similarity of recoil ion spectra observed in coincidence with electron capture vs. electron loss; and new research on ion-atom collisions at relativistic energies

  9. MULTIPLY CHARGED IONS COLLISIONS WITH ATOMS INTO EXCITED STATES

    Institute of Scientific and Technical Information of China (English)

    PanGuangyan

    1990-01-01

    The emission spectra in collisions between Ions and Atoms have been measured by an Optical Multichannel Analysis System (OMA).The experimental results demonstrate that there are two channels of excitation in collision between single charged ions and atoms and three channels of excitation in collision between double charged ions and atoms.Emission cross cestions and excitation cross sections have been obtained.K.Kadota et al and R.Shingal et al suggested that,under the appropriate conditions,the H42+-Li and He2++Na collision systems can be used efficiently to produce a laser of Lyman-α(30,4nm) and Lyman-β(25.6nm)lines via cascade to He+(2P)state.

  10. Measurements of Scattering Processes in Negative Ion- Atom Collisions

    Energy Technology Data Exchange (ETDEWEB)

    Kvale, T. J.

    2000-12-22

    The main research activity is to study various scattering processes which occur in H{sup -} 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.

  11. Multichannel eikonal treatment of electron--atom collisions

    International Nuclear Information System (INIS)

    A multichannel treatment of atomic collisions is presented and applied to the excitation of atomic hydrogen and helium by electrons with incident energy above the ionization threshold. The calculated cross sections compare very favorably with other refined theoretical procedures and with various experiments

  12. Time-dependent, lattice approach to atomic collisions

    Energy Technology Data Exchange (ETDEWEB)

    Schultz, D.R. [Oak Ridge National Lab., TN (United States). Physics Div.

    1995-12-31

    Recent progress in developing and applying methods of direct numerical solution of atomic collision problems is described. Various forms of the three-body problem are used to illustrate these techniques. Specifically, the process of ionization in proton-, antiproton-, and electron-impact of atomic hydrogen is considered in applications ranging in computational intensity from collisions simulated in two spatial dimensions to treatment of the three-dimensional, fully correlated two-electron Schroedinger equation. These examples demonstrate the utility and feasibility of treating strongly interacting atomic systems through time-dependent, lattice approaches.

  13. Time-dependent, lattice approach to atomic collisions

    International Nuclear Information System (INIS)

    Recent progress in developing and applying methods of direct numerical solution of atomic collision problems is described. Various forms of the three-body problem are used to illustrate these techniques. Specifically, the process of ionization in proton-, antiproton-, and electron-impact of atomic hydrogen is considered in applications ranging in computational intensity from collisions simulated in two spatial dimensions to treatment of the three-dimensional, fully correlated two-electron Schroedinger equation. These examples demonstrate the utility and feasibility of treating strongly interacting atomic systems through time-dependent, lattice approaches

  14. Role of atomic collisions in fusion

    International Nuclear Information System (INIS)

    Atomic physics issues have played a large role in controlled fusion research. A general discussion of the present role of atomic processes in both magnetic and inertial controlled fusion work is presented

  15. [Electron transfer, ionization, and excitation in atomic collisions

    International Nuclear Information System (INIS)

    Fundamental processes of electron transfer, ionization, and excitation in ion-atom and ion-ion collisions are studied. Attention is focussed on one- and two-electron systems and, more recently, quasi-one-electron systems whose electron-target-ion core can be accurately modeled by one-electron potentials. The basic computational approaches can then be taken with few, if any, approximations, and the underlying collisional mechanisms can be more clearly revealed. At intermediate collision energies (e.g., proton energies for p-He+ collisions on the order of 100 kilo-electron volts), many electronic states are strongly coupled during the collision, a coupled-state approach, such as a coupled-Sturmian-pseudostate approach, is appropriate. At higher collision energies (million electron-volt energies) the coupling is weaker with, however, many more states being coupled together, so that high-order perturbation theory is essential

  16. PAMOP: Petascale Atomic, Molecular and Optical Collision Calculations

    OpenAIRE

    McLaughlin, Brendan M.; Ballance, Connor P.; Pindzola, Michael S.; Müller, Alfred

    2015-01-01

    Petaflop architectures are currently being utilized efficiently to perform large scale computations in Atomic, Molecular and Optical Collisions. We solve the Schr\\"odinger or Dirac equation for the appropriate collision problem using the R-matrix or R-matrix with pseudo-states approach. We briefly outline the parallel methodology used and implemented for the current suite of Breit-Pauli and DARC codes. In this report, various examples are shown from our theoretical results compared with exper...

  17. Petascale computations for Large-scale Atomic and Molecular collisions

    OpenAIRE

    McLaughlin, Brendan M.; Ballance, Connor P.

    2014-01-01

    Petaflop architectures are currently being utilized efficiently to perform large scale computations in Atomic, Molecular and Optical Collisions. We solve the Schroedinger or Dirac equation for the appropriate collision problem using the R-matrix or R-matrix with pseudo-states approach. We briefly outline the parallel methodology used and implemented for the current suite of Breit-Pauli and DARC codes. Various examples are shown of our theoretical results compared with those obtained from Sync...

  18. Hydrogen negative ions and collisions of atomic particles

    International Nuclear Information System (INIS)

    This paper will be an overview presenting some of the basic atomic collisions processes (gas phase) which are fundamental to production and destruction of H-(D-). More detailed discussions of the most important processes will be left to other papers at this Symposium, and primarily new results since the 1977 Symposium will be discussed. Recent results provide insight into mechanisms responsible for the high H-(D-) ion fractions in hydrogen gas discharges, and the ion-atom collision processes important for double capture negative ion sources are better understood than in 1977

  19. Spin Effects in Collisions of Electrons with Atoms and Molecules

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Some recent experimental and theoretical work on spin-dependent electron-atom and electron-molecule collisions is reviewed. The spin is involved in such collisions by explicit spin-dependent interactions such as the spin-orbit interaction of the continuum electron (Mott scattering) but also by exchange, which, in conjunction with the Pauli principle, gives rise to observable spin exchange effects. We present results for Mn and Na atoms and experiments in which electron dichroism with chiral molecules has been studied.

  20. Activities of the JILA Atomic Collisions Cross Sections Data Center

    International Nuclear Information System (INIS)

    The JILA Atomic Collisions Cross Sections Data Center compiles, critically evaluates, and reviews cross sections and rates for low energy (<100 keV) collisions of electrons, photons, and heavy particles with atoms, ions, and simple molecules. Reports are prepared which provide easily accessible recommended data with error limits, list the fundamental literature related to specific topics, identify regions where data are missing, and point out inconsistencies in existing data. The general methodology used in producing evaluated compilations is described. Recently completed projects and work in progress are reported

  1. Electron correlation dynamics in atomic collisions

    International Nuclear Information System (INIS)

    This graduate/research level text introduces the theory of multi-electron transitions in atomic, molecular and optical physics, emphasizing the emerging topic of dynamic electron correlation. The book begins with an overview of simple binomial probabilities, classical scattering theory, quantum scattering and correlation, followed by the theory of single electron transition probabilities. Multiple electron transition probabilities are then treated in detail. Various approaches to multiple electron transitions are covered including the independent electron approximation, useful statistical methods and perturbation expansions treating correlation in both weak and strong limits. The important topic of the dynamics of electron correlation is a central theme in this book. The text contains a comprehensive summary of data for few and many electron transitions in atoms and molecules, including transitions on different atomic centers, fast ion-atom and electron-atom interactions, and recent observations using synchrotron radiation. Emphasis is given to methods that may be used by non-specialists. This text provides a pedagogic introduction to graduate students and researchers new to this developing field, but will also serve as a valuable reference for atomic, chemical and optical scientists interested in correlation and multi-electron transitions. (author)

  2. Non vertical vibronic transitions in atom molecule collisions

    International Nuclear Information System (INIS)

    This thesis is mainly devoted to an experimental and theoretical study on vibronic transitions which occur in collisions between an alkali atom and several diatomic molecules. An experimental study on electron and ion production in repulsive Cs-CO and Cs-N2 collisions, and in Cs-NO and Cs-O2 non-repulsive collisions is presented. The experimental data are discussed in terms of some existing models. It is clear that a new consistent theory on vibronic transitions is needed to explain the experimental data. Such a theory is presented, and it is shown that some existing models are limiting cases of this theory. An experimental study on the relative probabilities for ion and electron production in collisions between a Na, K or Cs atom and an O2 or NO molecule is also described. These experiments suggest that the incident velocity of the alkali atoms has a predominant influence on the relative probabilities for ion and electron production in these collisions. (Auth.)

  3. Atom capture and loss in ion molecule collisions

    International Nuclear Information System (INIS)

    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+ beams collide with a CH4 target and ArH+ 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

  4. Multiple Electron Capture Processes in Slow Collisions of Ar9+ Ions with Na Atoms

    Institute of Scientific and Technical Information of China (English)

    ZhuXiaolong; ShaShan; LiuHuiping; WeiBaoren; MaXinwen; WangZhengling; CaoShiping; QianDongbing; YangZhihu

    2003-01-01

    Slow collisions of highly charged ions with neutral atoms and molecules are of great importance in basic atomic collision physics, Recently, we built a new research facility for atomic physics at the Institute of Modern Physics. We report here the multiple electron transfer processes in collisions of Ar9+ with Na gas target at energy of 180 keV.

  5. PAMOP: Petascale Atomic, Molecular and Optical Collision Calculations

    CERN Document Server

    McLaughlin, Brendan M; Pindzola, Michael S; Müller, Alfred

    2015-01-01

    Petaflop architectures are currently being utilized efficiently to perform large scale computations in Atomic, Molecular and Optical Collisions. We solve the Schr\\"odinger or Dirac equation for the appropriate collision problem using the R-matrix or R-matrix with pseudo-states approach. We briefly outline the parallel methodology used and implemented for the current suite of Breit-Pauli and DARC codes. In this report, various examples are shown from our theoretical results compared with experimental results obtained from Synchrotron Radiation facilities where the Cray architecture at HLRS is playing an integral part in our computational projects.

  6. Petascale computations for Large-scale Atomic and Molecular collisions

    CERN Document Server

    McLaughlin, Brendan M

    2014-01-01

    Petaflop architectures are currently being utilized efficiently to perform large scale computations in Atomic, Molecular and Optical Collisions. We solve the Schroedinger or Dirac equation for the appropriate collision problem using the R-matrix or R-matrix with pseudo-states approach. We briefly outline the parallel methodology used and implemented for the current suite of Breit-Pauli and DARC codes. Various examples are shown of our theoretical results compared with those obtained from Synchrotron Radiation facilities and from Satellite observations. We also indicate future directions and implementation of the R-matrix codes on emerging GPU architectures.

  7. TRIDYN - binary collision simulation of atomic collisions dynamic composition changes in solids

    International Nuclear Information System (INIS)

    The report deals with the computerized simulation of the following problem: a beam of fast ions entering a solid substance is slowed down and scattered due to electronic interaction and nuclear collisions. Together with created recoil atoms local compositional changes are produced. For large fluences collisional mixing is caused in layered substances. (BHO)

  8. Ion-atom collisions for materials study

    International Nuclear Information System (INIS)

    The diffusion process of silver in aluminium was studied in thin films as a function of temperature, the most important characteristics of dispersor atoms that technique permits us to study are the atomic mass and depth into the solid. This is possible because when a sample is bombarded with ions of a given energy, the ions are dispersed with different energies for different masses and depths, hence this technique is a useful instrument for research into the physical processes which ocurr in thin films up to depths of several microns, one of the results obtained after the bombardment of the target with protons having an energy of 650 KeV was that when the target reached a temperature of approximately 400C, 800C, 1100C and 1600C during 15 minutes and the spectra of heated and unheated targets were compared it was found that the aluminium peak, the valley, the silver peak and the peak over the silver peak change with the increase of temperature and tend to get mixed, that is to say that silver and the aluminium are diffusing themselves. The analysis is essentially qualitative with this technique we ca also measure the thickness of thin films, the silver thickness was measured (3320A). (author)

  9. Coherent coupling of alkali atoms by random collisions

    CERN Document Server

    Katz, Or; Firstenberg, Ofer

    2015-01-01

    Random spin-exchange collisions in warm alkali vapor cause rapid decoherence and act to equilibriate the spin state of the atoms. In contrast, here we demonstrate experimentally and theoretically a coherent coupling of one alkali specie to another specie, mediated by these random collisions. We show that, the minor specie (potassium) inherits the magnetic properties of the dominant specie (rubidium), including its lifetime (T1), coherence time (T2), gyromagnetic ratio, and SERF magnetic-field threshold. We further show that this coupling can be completely controlled by varying the strength of the magnetic field. Finally, we explain these phenomena analytically by modes-mixing of the two species via spin-exchange collisions.

  10. Learning from numerical calculations of ion-atom collisions

    International Nuclear Information System (INIS)

    Violent collision of two independent many-particle systems, victims, are discussed in the atomic sphere. The asymmetric region where the charge of the projectile Z/sub p/ is less than the target nuclear charge Z/sub n/ is now well understood though interesting details still need to be worked out. Negatively charged projectiles offer a new illustration of Fadeev re-arrangement collisions. Multi-electron coherence effects illustrate the richness of the field but a symmetric (Z/sub p/ approx. Z/sub n/) collision treatment is needed. A new one and a half center expansion method promises a solution to this problem. Future areas of interest are discussed

  11. Spin-dependent electron-atom scattering - a detailed test of atomic collision theory

    International Nuclear Information System (INIS)

    In recent years, much progress has been made in the experimental and theoretical studies of atomic collision processes. The use of polarized collision partners has enabled experimentalists to perform very detailed tests of theoretical models, particularly with regard to the description of spin-dependent effects such as electron exchange or the spin-orbit interactions. Besides the development of the general theoretical formulation of spin-dependent electron-atom collisions - predominantly in terms of the density matrix formalism - much progress has also been made in the numerical treatment of such processes. In particular, the non-perturbative R-matrix (close-coupling) method and the open-quotes Distorted Wave Born Approximationclose quotes (DWBA), based on the Born series expansion of the T-operator have been applied very successfully. The presentation will begin with an outline of the density matrix formalism and its use to describe several, apparently different, atomic collision processes in a common framework. Next, the origin of spin-dependence in these collisions will be investigated, with particular emphasis on the so-called open-quotes fine-structure effectclose quotes where explicitly spin-dependent terms in the projectile-target interaction (such as the spin-orbit interaction) are assumed to be negligible during the collision process. Selected results for elastic and inelastic (including ionization) electron scattering from various targets will be presented and compared with recent experimental data

  12. Atomic collision databases and data services -- A survey

    International Nuclear Information System (INIS)

    Atomic collision databases and data services constitute an important resource for scientific and engineering applications such as astrophysics, lighting, materials processing, and fusion energy, as well as an important knowledge base for current developments in atomic collision physics. Data centers and research groups provide these resources through a chain of efforts that include producing and collecting primary data, performing evaluation of the existing data, deducing scaling laws and semiempirical formulas to compactly describe and extend the data, producing the recommended sets of data, and providing convenient means of maintaining, updating, and disseminating the results of this process. The latest efforts have utilized modern database, storage, and distribution technologies including the Internet and World Wide Web. Given here is an informal survey of how these resources have developed, how they are currently characterized, and what their likely evolution will lead them to become in the future

  13. Energy distributions for ionization in ion-atom collisions

    CERN Document Server

    Amaya-Tapia, A

    2016-01-01

    In this paper we discuss how through the process of applying the Fourier transform to solutions of the Schr\\"odinger equation in the Close Coupling approach, good results for the ionization differential cross section in energy for electrons ejected in ion-atom collisions are obtained. The differential distributions are time dependent and through their time average, the comparison with experimental and theoretical data reported in the literature can be made. The procedure is illustrated with reasonable success in two systems, $p+H$ and $p+He$, and is expected to be extended without inherent difficulties to more complex systems. This allows advancing in the understanding of the calculation of ionization processes in ion-atom collisions.

  14. Formulating analytic expressions for atomic collision cross sections

    International Nuclear Information System (INIS)

    Methods to formulate analytic expression for atomic collision cross sections as a function of projectile energy are described on the basis of the experiences of the data compilation work for more than 20 years. Topics considered are the choice of appropriate functional forms for the expressions and optimization of adjustable parameters. To make extrapolation possible, functions to be used should have the form with reasonable asymptotic behavior. In this respect, modified Green-McNeal formulas have been found useful for various atomic collision cross sections. For ionization processes, a modified Lotz formula has often given a good fit. The ALESQ code for least-squares fits has been convenient to optimize adjustable parameters in analytic expressions. (author)

  15. 24. International Conference on Atomic Collisions in Solids ICACS-24

    International Nuclear Information System (INIS)

    This Book contains the abstracts of invited and contributed talks submitted for presentation at the 24th International Conference on Atomic Collisions in Solids - ICACS-24. Out of nearly 200 submitted abstracts the International Programme Committee selected 46 oral and 89 poster contributions. Furthermore, 15 plenary invited lectures and the honorary Lindhard lecture are included in the scientific program. An additional tutorial day with 4 tutorial lectures is organised on Sunday prior to the Conference.

  16. Low-energy collisions of antiprotons with atoms and molecules

    International Nuclear Information System (INIS)

    Time-dependent close-coupling calculations were performed using the impact parameter method for antiproton and proton collisions with alkali-metal atoms and hydrogen molecules. The targets are described as effective one-electron systems using appropriate model potentials. The proton data verify the employed method while the results for antiprotons improve the literature on these systems considerably. Cross sections for ionization and excitation as well as electron-energy spectra and stopping power will be presented.

  17. Seventh international seminar on ion-atom collisions (ISIAC VII): summary

    International Nuclear Information System (INIS)

    The scientific program was structured into eight symposia representing seven important research areas. The subject matter was expanded to include ion-molecule collisions as one of the eight symposia. The symposia were: (1) collisions involving strong binding phenomena and nuclear effects; (2) low-energy, high charge state collisions; (3) Rydberg states; (4) an Open Session; (5) ion-molecule collisions; (6) laser applications to atomic and molecular collisions; (7) collision spectroscopy; and (8) polarization, alignment and correlation

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

    OpenAIRE

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

    2010-01-01

    At impact energies $ \\stackrel{>}{\\sim}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. In order 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...

  19. Correlated charge-changing ion-atom collisions

    International Nuclear Information System (INIS)

    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

  20. Atomic collisions with 33-TeV lead ions

    International Nuclear Information System (INIS)

    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 Pb82+ ions from the CERN SPS accelerator in Geneva. Results of these studies are presented, along with comparisons with relevant theory

  1. The screening length of interatomic potential in atomic collisions

    International Nuclear Information System (INIS)

    In computer studies on the interaction of charged particle with solids, many authors treat the nuclear collision by the Thomas-Fermi screened Coulomb potential. For better agreement with experiment, the screening length is modified sometimes. We investigate the theoretical background for the correction factor of the screening length in the interatomic potential which can be deduced from two steps. The first step is to select the correction factor of an isolated atom so as to match the average radius of the Thomas-Fermi electron distribution with that of the Hartree-Fock electron distribution, where we use the Clementi and Roetti's table. The second step is to determine the correction factor of the screening length of the interatomic potential by using a combination rule. The correction factors obtained for the screening length are in good agreement with those determined by the computer analysis of the Impact Collision Ion Scattering Spectroscopy (ICISS) data. (author)

  2. Electron transfer, ionization, and excitation in atomic collisions

    International Nuclear Information System (INIS)

    The research being carried out at Penn State by Winter and Alston addresses the fundamental processes of electron transfer, ionization, and excitation in ion-atom (and ion-ion) collisions. The focus is on intermediate- and higher-energy collisions, corresponding to proton energies of about 25 kilo-electron-volts (keV) or larger. At intermediate energies, where the transition probabilities are not small, many states must be coupled in a large calculation, while at higher energies, perturbative approaches may be used. Several studies have been carried out in the current three-year period; most of these treat systems with only one or two electrons, so that fewer approximations need be made and the basic collisional mechanisms can be more clearly described

  3. Vacuum polarization effects in low-energy muonic atom collisions

    International Nuclear Information System (INIS)

    We estimate the vacuum polarization (VP) correction to the Coulomb interaction in collisions of muonic atoms. It is shown that the VP effect, amplified by the low-lying virtual state var-epsilon var-theta∼10 eV, is of the order of ∼1--2 % in the S-wave cross sections for pμ+p collisions as var-epsilon ≤ var-epsilon var-theta. The VP amplitude becomes comparable to the anomalously small pure Coulomb amplitude for the singlet tμ+t scattering as var-epsilon →0 and near the Ramsauer-Townsend minima in the dμ+p and tμ+p scattering

  4. Computer simulation of electronic excitation in atomic collision cascades

    International Nuclear Information System (INIS)

    The impact of an keV atomic particle onto a solid surface initiates a complex sequence of collisions among target atoms in a near-surface region. The temporal and spatial evolution of this atomic collision cascade leads to the emission of particles from the surface - a process usually called sputtering. In modern surface analysis the so called SIMS technology uses the flux of sputtered particles as a source of information on the microscopical stoichiometric structure in the proximity of the bombarded surface spots. By laterally varying the bombarding spot on the surface, the entire target can be scanned and chemically analyzed. However, the particle detection, which bases upon deflection in electric fields, is limited to those species that leave the surface in an ionized state. Due to the fact that the ionized fraction of the total flux of sputtered atoms often only amounts to a few percent or even less, the detection is often hampered by rather low signals. Moreover, it is well known, that the ionization probability of emitted particles does not only depend on the elementary species, but also on the local environment from which a particle leaves the surface. Therefore, the measured signals for different sputtered species do not necessarily represent the stoichiometric composition of the sample. In the literature, this phenomenon is known as the Matrix Effect in SIMS. In order to circumvent this principal shortcoming of SIMS, the present thesis develops an alternative computer simulation concept, which treats the electronic energy losses of all moving atoms as excitation sources feeding energy into the electronic sub-system of the solid. The particle kinetics determining the excitation sources are delivered by classical molecular dynamics. The excitation energy calculations are combined with a diffusive transport model to describe the spread of excitation energy from the initial point of generation. Calculation results yield a space- and time-resolved excitation

  5. Computer simulation of electronic excitation in atomic collision cascades

    Energy Technology Data Exchange (ETDEWEB)

    Duvenbeck, A.

    2007-04-05

    The impact of an keV atomic particle onto a solid surface initiates a complex sequence of collisions among target atoms in a near-surface region. The temporal and spatial evolution of this atomic collision cascade leads to the emission of particles from the surface - a process usually called sputtering. In modern surface analysis the so called SIMS technology uses the flux of sputtered particles as a source of information on the microscopical stoichiometric structure in the proximity of the bombarded surface spots. By laterally varying the bombarding spot on the surface, the entire target can be scanned and chemically analyzed. However, the particle detection, which bases upon deflection in electric fields, is limited to those species that leave the surface in an ionized state. Due to the fact that the ionized fraction of the total flux of sputtered atoms often only amounts to a few percent or even less, the detection is often hampered by rather low signals. Moreover, it is well known, that the ionization probability of emitted particles does not only depend on the elementary species, but also on the local environment from which a particle leaves the surface. Therefore, the measured signals for different sputtered species do not necessarily represent the stoichiometric composition of the sample. In the literature, this phenomenon is known as the Matrix Effect in SIMS. In order to circumvent this principal shortcoming of SIMS, the present thesis develops an alternative computer simulation concept, which treats the electronic energy losses of all moving atoms as excitation sources feeding energy into the electronic sub-system of the solid. The particle kinetics determining the excitation sources are delivered by classical molecular dynamics. The excitation energy calculations are combined with a diffusive transport model to describe the spread of excitation energy from the initial point of generation. Calculation results yield a space- and time-resolved excitation

  6. Atomic excitations in heavy ion collisions with nuclear contact

    International Nuclear Information System (INIS)

    The dynamical semiclassical theory of atomic excitations, especially of positron creation, in heavy ion scattering is presented and extended to collisions with nuclear contact. The characteristic dependence of inner shell vacancy formation on nuclear reaction times as well as the emergence of interference patterns in the energy spectra of emitted delta-electrons and positrons in delayed collisions is discussed in terms of a simplified, schematic model for the nuclear reaction dynamics. In addition, the spontaneous decay mechanism is giant nuclear systems with Z>=173 leads, for sufficiently long reaction times, to a characteristic line in the positron spectra at the position of th 1ssigma-resonance. The position and width of the positron line is calculated in dependence on the nuclear configuration taking into account the influence of the electron-electron interaction. Furthermore, a quantum mechanical extension of our semiclassical treatment of the atomic scattering process and its effect on atomic positron spectra are discussed. In addition, the influence of EO-transitions in the giant nuclear system on positron emission is treated qualitatively in a semiclassical approximation, indicating that nuclear collective modes can be revealed by the measurement of Stokes and anti-Stokes lines in the positron spectra. (orig./HSI)

  7. Atomic excitations in heavy ion collisions with nuclear contact

    International Nuclear Information System (INIS)

    The dynamical semiclassical theory of atomic excitations, especially of positron creation, in heavy ion scattering is presented and extended to collisions with nuclear contact. The characteristic dependence of inner shell vacancy formation on nuclear reaction times as well as the emergence of interference patterns in the energy spectra of emitted delta-electrons and positrons in delayed collisions is discussed in terms of a simplified, schematic model for the nuclear reaction dynamics. In addition, the spontaneous decay mechanism in giant nuclear systems with Z> or approx.173 leads, for sufficiently long reaction times, to a characteristic line in the positron spectra at the position of the 1ssigma-resonance. The position and width of the positron line is calculated in dependence on the nuclear configuration taking into account the influence of the electron-electron interaction. Furthermore, a quantum mechanical extension of our semiclassical treatment of the atomic scattering process and its effect on atomic positron spectra are discussed. In addition, the influence of E0-transitions in the giant nuclear system on positron emission is treated qualitatively in a semiclassical approximation, indicating that nuclear collective modes can be revealed by the measurement of Stokes and anti-Stokes lines in the positron spectra. (orig./HSI)

  8. Measurements of scattering processes in negative ion-atom collisions

    Energy Technology Data Exchange (ETDEWEB)

    Kvale, T.J.

    1992-01-01

    This Technical Progress Report describes the progress made on the research objectives during the past twelve months. This research project is designed to provide measurements of various scattering processes which occur in H{sup {minus}} collisions with atomic (specifically, noble gas and atomic hydrogen) targets at intermediate energies. 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 in progress will provide either experimentally-determined cross sections or set upper limits to those cross sections. In either case, these measurements will be stringent tests of our understanding in energetic negative ion-atom collisions. This series of experiments required the construction of a new facility and the initial ion beam was accelerated through the apparatus in April 1991.

  9. A reaction microscope for studies positron-atom collisions

    International Nuclear Information System (INIS)

    Complete text of publication follows. Differential investigations, especially in positron physics, are very time consuming. The data collection takes weeks if not months. In order to reduce the data collection time or increase the accuracy of the measured data, new methods are necessary. A recently developed system combines the advantages of the above mentioned methods i.e. simultaneous energy and angular detection, by measuring the energy and angular distribution of the recoil ion. A further benefit is the 4? collection of the recoil ions comparing with the traditional methods where only a small part of the collision events can be detected. This method, called Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS), has been successfully applied for investigating ion, electron and photon collisions (see [1] and reference therein). When the residual ions are recorded in coincidence with the outgoing fragments, a kinematically complete picture can be determined about the correlated motion of the fragments of atomic and molecular breakup processes. Up till now the COLTRIMS have not been used in positron collision physics due to the serious requirement for the quality of the projectile and the target beam. For good time and position resolution timed projectile beam of about 1mm or less diameter is necessary. For the target beam the requirements are similar: the diameter must be small (around 1 mm) and very dense (1011 - 1013atom/cm3) due to the low projectile beam intensity. A further requirement is the small initial momentum distribution of the target atoms due to the small momentum transfer (0.3-4 a.u.) during collision. (The momentum distribution of He is 5.8 a.u. at room temperature.) The solution is using a supersonic gas target which has small diameter, high density and small momentum distribution. It is about 0.05 - 0.2 a.u. in the jet direction. Application of the COLTRIMS method in positron physics has several advantages in spite of the technical difficulties

  10. Two-potential eikonal approximation for electron-atom collisions

    International Nuclear Information System (INIS)

    The Glauber approximation is known to be in appreciable error at all angles when applied to the elastic electron-atom scattering at medium and lower energies. It is shown that this is not due to the frozen-target approximation but mainly a result of the inadequate semiclassical treatment of close-encounter collisions in the Glauber approximation. A simple method is proposed to correct this inadequacy and is applied to e-H elastic scattering at energies from 20 to 100 eV. A remarkable improvement over the Glauber approximation is obtained, and the results agree with experiments very well at all angles where measurements are available

  11. Coherence and correlations in fast ion-atom collisions

    International Nuclear Information System (INIS)

    This paper focusses on the description, classification and interpretation of coherent excitation of atomic or ionic systems with Coulombic two-body final state interactions. A group-theoretical approach is used to classify and interpret coherent excitation. The most significant result is that the state of excitation represented by a density operator can be mapped one to one onto expectation values of a set of operators. Examples are used to illustrate what can be learned about the collision process from investigations of coherent excitation

  12. Ion-atom cold collision: Formation of cold molecular ion by radiative processes

    OpenAIRE

    Rakshit, Arpita; Deb, Bimalendu

    2010-01-01

    We discuss theoretically ion-atom collisions at low energy and predict the possibility of formation of cold molecular ion by photoassociation. We present results on radiative homo- and hetero-nuclear atom-ion cold collisions that reveal threshold behaviour of atom-ion systems.

  13. Formation of positron-atom bound states in collisions between Rydberg Ps and neutral atoms

    CERN Document Server

    Swann, A R; Deller, A; Gribakin, G F

    2016-01-01

    Predicted twenty years ago, positron binding to neutral atoms has not yet been observed experimentally. A new scheme is proposed to detect positron-atom bound states by colliding Rydberg positronium (Ps) with neutral atoms. Estimates of the charge-transfer-reaction cross section are obtained using the first Born approximation for a selection of neutral atom targets and a wide range of incident Ps energies and principal quantum numbers. We also estimate the corresponding Ps ionization cross section. The accuracy of the calculations is tested by comparison with earlier predictions for Ps charge transfer in collisions with hydrogen and antihydrogen. We describe an existing Rydberg Ps beam suitable for producing positron-atom bound states and estimate signal rates based on the calculated cross sections and realistic experimental parameters. We conclude that the proposed methodology is capable of producing such states and of testing theoretical predictions of their binding energies.

  14. Theory of ion-atom collisions at high energy, I

    International Nuclear Information System (INIS)

    Electron capture process by an ion from a neutral atom is one of the fundamental problems in the theory of atomic collision physics. Here a brief review is given mainly on the processes of non-radiative and radiative electron capture (charge transfer and REC). The main mechanism which govern the charge transfer process is introduced and the characteristic feature which is predicted by the theory is explained. As for the radiative electron capture process, after introducting the present theories, the full-quantum mechanical theoretical treatment is introduced. The theory leads a result which includes some inconsistency with formulae obtained by guage transformation. The relativistic quantum mechanical treatment is being tried in order to remove this inconsistency. The some results including mass and velocity dependence are reported and discussed. (author)

  15. Electron capture in collisions of S4+ with atomic hydrogen

    International Nuclear Information System (INIS)

    Charge transfer processes due to collisions of ground state S4+(3s21S) ions with atomic hydrogen are investigated for energies between 1 meV u-1 and 10 MeV u-1 using the quantum mechanical molecular-orbital close-coupling (MOCC), atomic-orbital close-coupling, classical trajectory Monte Carlo (CTMC) and continuum distorted wave methods. The MOCC calculations utilize ab initio adiabatic potentials and nonadiabatic radial coupling matrix elements obtained with the spin-coupled valence-bond approach. A number of variants of the CTMC approach were explored, including different momentum and radial distributions for the initial state, as well as effective charge and quantum-defect models to determine the corresponding quantum state after capture into final partially stripped S3+ excited classical states. Hydrogen target isotope effects are explored and rate coefficients for temperatures between 100 and 106 K are also presented. (author)

  16. Production of ultra slow antiprotons, its application to atomic collisions and atomic spectroscopy - ASACUSA project

    International Nuclear Information System (INIS)

    The Atomic Spectroscopy And Collisions Using Slow Antiprotons (ASACUSA) project aims at studying collision dynamics with slow antiprotons and high precision spectroscopy of antiprotonic atoms. To realize these purposes, the production of high quality ultra slow antiproton beams is essential, which is achieved by the combination of antiproton decelerator (AD) from 3 GeV to 5 MeV, a radio frequency quadrupole (RFQ) decelerator from 5 MeV to 50 keV, and finally an electromagnetic trap from 50 keV to 10 eV. From the atomic physics point of view, an antiproton is an extremely heavy electron and/or a negatively charged proton, i.e., the antiproton is a unique tool to shed light on collision dynamics from the other side of the world. In addition to this fundamentally important feature, the antiproton has also a big practical advantage, i.e., it annihilates with the target nuclei emitting several energetic pions, which provides high detection efficiency with very good time resolution. Many-body effects which are of great importance to several branches of science will be studied through ionization and antiprotonic atom formation processes under single collision conditions. Various antiprotonic atoms including protonium (p anti-p) are expected to be meta-stable in vacuum, which is never true for those in dense media except for antiprotonic helium. High precision spectroscopy of protonium will for the first time become feasible benefited by this meta-stability. The present review reports briefly the production scheme of ultra slow antiproton beams and several topics proposed in the ASACUSA project

  17. Classical theory of atomic collisions - The first hundred years

    Science.gov (United States)

    Grujić, Petar V.

    2012-05-01

    Classical calculations of the atomic processes started in 1911 with famous Rutherford's evaluation of the differential cross section for α particles scattered on foil atoms [1]. The success of these calculations was soon overshadowed by the rise of Quantum Mechanics in 1925 and its triumphal success in describing processes at the atomic and subatomic levels. It was generally recognized that the classical approach should be inadequate and it was neglected until 1953, when the famous paper by Gregory Wannier appeared, in which the threshold law for the single ionization cross section behaviour by electron impact was derived. All later calculations and experimental studies confirmed the law derived by purely classical theory. The next step was taken by Ian Percival and collaborators in 60s, who developed a general classical three-body computer code, which was used by many researchers in evaluating various atomic processes like ionization, excitation, detachment, dissociation, etc. Another approach was pursued by Michal Gryzinski from Warsaw, who started a far reaching programme for treating atomic particles and processes as purely classical objects [2]. Though often criticized for overestimating the domain of the classical theory, results of his group were able to match many experimental data. Belgrade group was pursuing the classical approach using both analytical and numerical calculations, studying a number of atomic collisions, in particular near-threshold processes. Riga group, lead by Modris Gailitis [3], contributed considerably to the field, as it was done by Valentin Ostrovsky and coworkers from Sanct Petersbourg, who developed powerful analytical methods within purely classical mechanics [4]. We shall make an overview of these approaches and show some of the remarkable results, which were subsequently confirmed by semiclassical and quantum mechanical calculations, as well as by the experimental evidence. Finally we discuss the theoretical and

  18. Charge Exchange Collisions between Ultracold Fermionic Lithium Atoms and Calcium Ions

    CERN Document Server

    Haze, Shinsuke; Saito, Ryoichi; Mukaiyama, Takashi

    2014-01-01

    An observation of charge exchange collisions between ultracold fermionic 6Li atoms and 40Ca+ ions is reported. The reaction product of the charge exchange collision is dentified via mass spectrometry where the motion of the ions is excited parametrically. We measure the cross section of the charge exchange collisions between the 6Li atoms in the ground state and the 40Ca+ ions in the ground and metastable excited states. Investigation of the inelastic collision characteristics in the atom-ion mixture is an important step toward ultracold chemistry based on ultracold atoms and ions.

  19. Collisions near threshold in atomic and molecular physics

    International Nuclear Information System (INIS)

    We review topics of current interest in the physics of electronic, atomic and molecular scattering in the vicinity of thresholds. Starting from phase space arguments, we discuss the modifications of the Wigner law that are required to deal with scattering by Coulomb, dipolar and dispersion potentials, as well as aspects of threshold behaviour observed in ultracold atomic collisions. We employ the tools of quantum defect and semiclassical theories to bring out the rich variety of threshold behaviours. The discussion is then turned to recent progress in understanding threshold behaviour of many-body break-ups into both charged and neutral species, including both Wannier double ionization and three-body recombination in ultracold gases. We emphasize the dominant role that hyperspherical coordinate methods have played in understanding these problems. We assess the effects of external fields on scattering, and the corresponding modification of phase space that alters the Wigner law. Threshold laws in low dimensions and examples of their applications to specific collision processes are discussed. (author)

  20. Convergent Close-Coupling Approach to Electron-Atom Collisions

    Science.gov (United States)

    Bray, Igor; Stelbovics, Andris

    2007-01-01

    It was with great pleasure and honour to accept the invitation to make a presentation at the symposium celebrating the life-long work of Aaron Temkin and Richard Drachman. The work of Aaron Temkin was particularly influential on our own during the development of the CCC method for electron-atom collisions. There are a number of key problems that need to be dealt with when developing a general computational approach to such collisions. Traditionally, the electron energy range was subdivided into the low, intermediate, and high energies. At the low energies only a finite number of channels are open and variational or close-coupling techniques could be used to obtain accurate results. At high energies an infinite number of discrete channels and the target continuum are open, but perturbative techniques are able to yield accurate results. However, at the intermediate energies perturbative techniques fail and computational approaches need to be found for treating the infinite number of open channels. In addition, there are also problems associated with the identical nature of electrons and the difficulty of implementing the boundary conditions for ionization processes. The beauty of the Temkin-Poet model of electron-hydrogen scattering is that it simplifies the full computational problem by neglecting any non-zero orbital angular momenta in the partial-wave expansion, without loosing the complexity associated with the above-mentioned problems. The unique nature of the problem allowed for accurate solution leading to benchmark results which could then be used to test the much more general approaches to electron-atom collision problems. The immense value of the Temkin-Poet model is readily summarised by the fact that the initial papers of Temkin and Poet have been collectively cited around 250 times to date and are still being cited in present times. Many of the citations came from our own work during the course of the development of the CCC method, which we now describe.

  1. Collision lifetimes of polyatomic molecules at low temperatures: Benzene–benzene vs benzene–rare gas atom collisions

    International Nuclear Information System (INIS)

    We use classical trajectory calculations to study the effects of the interaction strength and the geometry of rigid polyatomic molecules on the formation of long-lived collision complexes at low collision energies. We first compare the results of the calculations for collisions of benzene molecules with rare gas atoms He, Ne, Ar, Kr, and Xe. The comparison illustrates that the mean lifetimes of the collision complexes increase monotonically with the strength of the atom–molecule interaction. We then compare the results of the atom–benzene calculations with those for benzene–benzene collisions. The comparison illustrates that the mean lifetimes of the benzene–benzene collision complexes are significantly reduced due to non-ergodic effects prohibiting the molecules from sampling the entire configuration space. We find that the thermally averaged lifetimes of the benzene–benzene collisions are much shorter than those for Xe with benzene and similar to those for Ne with benzene

  2. Correlated charge-changing ion-atom collisions

    International Nuclear Information System (INIS)

    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

  3. Cold atomic and molecular collisions: approaching the universal loss regime

    CERN Document Server

    Frye, Matthew D; Hutson, Jeremy M

    2014-01-01

    We investigate the behaviour of single-channel theoretical models of cold and ultracold collisions that take account of inelastic and reactive processes using a single parameter to represent short-range loss. We present plots of the resulting energy-dependence of elastic and inelastic cross sections over the full parameter space of loss parameters and short-range phase shifts. We then test the single-channel model by comparing it with the results of coupled-channel calculations of rotationally inelastic collisions between LiH molecules and Li atoms. We find that the single-channel model becomes increasingly accurate as the initial LiH rotational quantum number increases, with a corresponding increase in the number of open loss channels. The results suggest that coupled-channel calculations at very low energy (in the s-wave regime) could in some cases be used to estimate a loss parameter and then to predict the range of possible loss rates at higher energy, without the need for an explicit partial-wave sum.

  4. Fast ion-atom and ion-molecule collisions

    CERN Document Server

    2013-01-01

    The principal goal of this book is to provide state-of-the art coverage of the non-relativistic three- and four-body theories at intermediate and high energy ion-atom and ion-molecule collisions. The focus is on the most frequently studied processes: electron capture, ionization, transfer excitation and transfer ionization. The content is suitable both for graduate students and experienced researchers. For these collisions, the literature has seen enormous renewal of activity in the development and applications of quantum-mechanical theories. This subject is of relevance in several branches of science and technology, like accelerator-based physics, the search for new sources of energy and high temperature fusion of light ions. Other important applications are in life sciences via medicine, where high-energy ion beams are used in radiotherapy for which a number of storage ring accelerators are in full operation, under construction or planned to be built worldwide. Therefore, it is necessary to review this fiel...

  5. Progress in numerical calculations of ion-atom collisions

    Energy Technology Data Exchange (ETDEWEB)

    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.

  6. Progress in numerical calculations of ion-atom collisions

    International Nuclear Information System (INIS)

    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

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

    Science.gov (United States)

    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. Cross sections for K- and L-shell excitation in energetic ion-atom collisions

    International Nuclear Information System (INIS)

    Absolute K- and L-shell vacancy production cross sections have been determined from Auger-electron measurements in various heavy-ion-atom collisions. Collision systems with atomic numbers Z between 5 and 18 and with projectile energies varied between 6 and 600 keV were investigated. From cross section plots for some exemplary collision systems general trends are indicated and discussed in terms of the molecular-orbital (MO) model. Cross section ratios are deduced and compared to theoretical predictions

  9. Atoms-for-Peace: A Galactic Collision in Action

    Science.gov (United States)

    2010-11-01

    European Southern Observatory astronomers have produced a spectacular new image of the famous Atoms-for-Peace galaxy (NGC 7252). This galactic pile-up, formed by the collision of two galaxies, provides an excellent opportunity for astronomers to study how mergers affect the evolution of the Universe. Atoms-for-Peace is the curious name given to a pair of interacting and merging galaxies that lie around 220 million light-years away in the constellation of Aquarius. It is also known as NGC 7252 and Arp 226 and is just bright enough to be seen by amateur astronomers as a very faint small fuzzy blob. This very deep image was produced by ESO's Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO's La Silla Observatory in Chile. A galaxy collision is one of the most important processes influencing how our Universe evolves, and studying them reveals important clues about galactic ancestry. Luckily, such collisions are long drawn-out events that last hundreds of millions of years, giving astronomers plenty of time to observe them. This picture of Atoms-for-Peace represents a snapshot of its collision, with the chaos in full flow, set against a rich backdrop of distant galaxies. The results of the intricate interplay of gravitational interactions can be seen in the shapes of the tails made from streams of stars, gas and dust. The image also shows the incredible shells that formed as gas and stars were ripped out of the colliding galaxies and wrapped around their joint core. While much material was ejected into space, other regions were compressed, sparking bursts of star formation. The result was the formation of hundreds of very young star clusters, around 50 to 500 million years old, which are speculated to be the progenitors of globular clusters. Atoms-for-Peace may be a harbinger of our own galaxy's fate. Astronomers predict that in three or four billion years the Milky Way and the Andromeda Galaxy will collide, much as has happened with Atoms-for-Peace. But don

  10. A high density target of ultracold atoms and momentum resolved measurements of ion-atom collisions

    International Nuclear Information System (INIS)

    In this thesis an ultracold high density target with high loading flux in combination with a recoil ion momentum spectrometer (RIMS) is presented. Trapped rubidium atoms serve as a high density target (up to 1011 atoms/cm3) at a temperature of only 200 μK. The target is loaded from a two-dimensional magnetooptical trap (2D MOT), which delivers an atom beam with a brilliance of 8 x 1012 atoms/(s.rad) and a longitudinal momentum spread of 0.25 a.u. The great advantage of this source is that the cold atom beam can be used as a target itself. The experimental setup, including the RIMS and the targets, are characterized using one-color two-photon ionization experiments. After the successful commissioning presented in this thesis the experiment is ready to be connected to the HITRAP beamline at the GSI Helmholtzzentrum fur Schwerionenforschung, where multiple charge transfer between ultracold atoms and highly charged ions up to bare uranium can be investigated. In a different experimental setup, in collaboration with the KVI in Groningen, the Netherlands, first experiments on the energy dependence of double charge transfer in alkali-ion collisions are preformed. Using RIMS, two distinct double capture mechanisms, sequential transfer and correlated transfer, are identified and the respective differential cross sections are determined. The effective interaction time of the collision is varied by changing the projectile's velocity. At short interaction times the sequential transfer is dominant, while at longer interaction times the correlated transfer becomes more important.

  11. Atomic jet with ionization detection for laser spectroscopy of Rydberg atoms under collisions and fields

    Science.gov (United States)

    Philip, G.

    2008-03-01

    An efficient atomic jet setup offering many unprecedented advantages over a conventional heat pipe setup used in multi-photon spectroscopy, mainly of alkaline-earth metals, has been constructed by a scheme in which the sample material is encapsulated in a disposable cartridge oven located inside a thermally stabilised heat-pipe and is made to effuse in to a row of atomic beams merging to form a jet target. This novel scheme combines the advantages of both high density atomic beam with convenient geometry for orthogonal excitation and high sensitive ionisation detection capabilities of thermionic diodes, besides eliminating several problems inherent in the usual heat-pipe operation. Out of various designs, typical results are presented for a linear heat-pipe with vertical atomic jet used in two-photon spectroscopy of highly excited states of Sr I. Controlled excitations of both Rydberg and non-Rydberg states, which cannot otherwise be accessed from the ground state due to parity and spectroscopic selection rules, have been achieved by employing a weak electric field complimented by collisions. The atomic jet setup is also found very useful for the study of collisional broadening and shift of excited states and time evolution of Rydberg atoms.

  12. Bibliography on electron transfer processes in ion-ion/atom/molecule collisions (updated 1993)

    International Nuclear Information System (INIS)

    Following our previous compilations [IPPJ-AM-45 (1986), NIFS-DATA-7 (1990)], bibliographic information on experimental and theoretical studies on electron transfer processes in ion-ion/atom/molecule collisions is up-dated. The references published through 1980-1992 are included. For easy finding references for particular combination of collision partners, a simple list is also provided. (author) 1542 refs

  13. Spectroscopic diagnostics of electron-atom collisions: Progress report, 1 January 1988--31 December 1988

    International Nuclear Information System (INIS)

    The fully-differential sodium electron excitation experiment has been completed during this contract year. This is a major milestone in our research program, as well as for electron-atom collision physics

  14. Heavy particle atomic collisions in astrophysics: Beyond H and He targets

    Energy Technology Data Exchange (ETDEWEB)

    Stancil, P.C.; Krstic, P.S.; Schultz, D.R.

    1998-06-01

    The physical conditions relating to the emission of x-rays from Jovian and cometary atmospheres and to supernova ejecta are briefly described. Emphasis is placed on elucidating the relevance and importance of atomic collision processes, the availability of data, and the outstanding data needs for modeling these environments. Some preliminary theoretical studies of electron capture for important collisions systems, involving molecular and atomic metal targets, are presented.

  15. Learning about three particle continuum states from fast ion-atom collisions

    International Nuclear Information System (INIS)

    Preliminary results for two fast ion-atom collision experiments were presented. The double detachment of H- leads to some low energy three-particle states which offer interesting possibilities for further investigations into the three-particle Coulomb problem. Secondary electrons from fast ion-atom collisions moving in the region between the two resulting ions appear to express some special features that merit further experimental and theoretical work. 8 refs.; 2 figs

  16. X-ray emission from heavy atomic collisions : couplings of inner shells in superheavy quasimolecules

    OpenAIRE

    Verma, Punita

    2010-01-01

    Overcritical electromagnetic fields with a coupling strength of ZUA greater than or equal to 1/alpha (=137, with alpha being the fine structure constant) can be experienced in superheavy quasimolecules (atomic number ZUA = Z1+Z2) formed transiently in close collisions of two very heavy atomic partners (Z1, Z2) at velocities (vion) smaller compared to the orbital velocity of the innermost electrons of concern (ve-). The inner shell processes in these collisions are governed approximately by th...

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

    International Nuclear Information System (INIS)

    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

  18. Positronium formation and ionization in slow positron-hydrogen atom collisions

    International Nuclear Information System (INIS)

    The electron capture and ionization processes in slow collisions of positrons with hydrogen atoms are considered within the advanced adiabatic approach to atomic collisions. The mass asymmetry of the (p,e-,e+) collision system is properly taken into account. The calculated positronium formation and ionization cross sections compare favourably with the available experimental data in the adiabatic energy region. It is shown that the potential energy curve of the 2p σ molecular state supports a quasi-bound level of the three-particle (p,e+,e-) system with an energy of -0.3 eV and decay width of 0.15 eV, approximately. (author)

  19. General model of depolarization and transfer of polarization of singly ionized atoms by collisions with hydrogen atoms

    CERN Document Server

    Derouich, Moncef

    2016-01-01

    Simulations of the generation of the atomic polarization is necessary for interpreting the second solar spectrum. For this purpose, it is important to rigorously determine the effects of the isotropic collisions with neutral hydrogen on the atomic polarization of the neutral atoms, ionized atoms and molecules. Our aim is to treat in generality the problem of depolarizing isotropic collisions between singly ionized atoms and neutral hydrogen in its ground state. Using our numerical code, we computed the collisional depolarization rates of the $p$-levels of ions for large number of values of the effective principal quantum number $n^{*}$ and the Uns\\"old energy $E_p$. Then, genetic programming has been utilized to fit the available depolarization rates. As a result, strongly non-linear relationships between the collisional depolarization rates, $n^{*}$ and $E_p$ are obtained, and are shown to reproduce the original data with accuracy clearly better than 10\\%. These relationships allow quick calculations of the ...

  20. A theoretical model for electron transfer in ion-atom collisions: Calculations for the collision of a proton with an argon atom

    International Nuclear Information System (INIS)

    We have developed a theoretical model of ion-atom collisions based on the time-dependent density-functional theory. We solve the time-dependent Kohn-Sham equation for electrons employing the real-space and real-time method, while the ion dynamics are described in classical mechanics by the Ehrenfest method. Taking advantage of the real-space grid method, we introduce the 'coordinate space translation' technique to allow one to focus on a certain space of interest. Benchmark calculations are given for collisions between proton and argon over a wide range of impact energy. Electron transfer total cross sections showed a fairly good agreement with available experimental data. -- Highlights: → We have developed a theoretical model of ion-atom collisions based on TDDFT. → The coordinate space translation technique was introduced into present calculation. → Charge transfer cross sections showed a good agreement with available experimental data.

  1. Mass and orientation effects in dissociative collisions between rare gas atoms and alkali halide molecules

    International Nuclear Information System (INIS)

    The collision induced dissociation of alkali halide molecules to ion pairs upon impact with hyperthermal rare gas atoms has been investigated using the crossed molecular beam method. Relative total cross sections for the dissociation of CsI, CsBr, RbI, and KI to ion pairs upon collision with xenon and krypton have been measured over a relative collision energy range from threshold to 10 and 8 eV, respectively. In addition, complete angular and energy distributions of both dissociated ions from Xe+CsI, CsBr, and RbI collisions and from Kr+CsI and CsBr collisions have been obtained at several collision energies within the above energy range. Mass, collision orientation, and energy dependence effects observed throughout this work define two limiting case dissociation mechanisms for the Xe(Kr)+MX→Xe(Kr)+M++X- processes. The dominant dissociation configuration consists of the rare gas atom incident on the light atom end of the alkali halide molecule in a near collinear collision. The less preferred dissociation mechanism results when the rare gas atom is incident in a near collinear configuration on the heavy atom end of the alkali halide molecule. Experimental measurements of the percentage of energy transfer from the relative kinetic energy between Xe(Kr) and MX to the relative motion of M+--X- range as high as 95%; these percentage energy transfers correlate well with the predictions of an impulsive collision model. Three-dimensional classical trajectory calculations using realistic interaction potentials have been performed and they verify the dynamical interpretation suggested by the experiments

  2. Multiple electron capture in close ion-atom collisions

    International Nuclear Information System (INIS)

    Multiple electron capture is reported for Ca17+ in Ar. Close collisions are defined by the observation of a coincident Ca K or Ar K x-ray. A large number of electrons is transferred to the projectile in a single close collision when the Ca ion projectile is of the order of the Ar L-shell electron velocity. The cross section for electron capture is reported

  3. Proceedings of the 2. Latin American Meeting on Atomic, Molecular and Electronic Collisions

    International Nuclear Information System (INIS)

    Annals of the II Latin American Meeting on Atomic, Molecular and Electronic Collisions. Over than 50 people from Latin America participated on this meeting giving talks on different subjects (theoretical and experimental), related to atomic and molecular physics, as well as, nuclear physics. (A.C.A.S.)

  4. Suppression of Zeeman Relaxation in Cold Collisions of \\(^2P_{1/2}\\) Atoms

    OpenAIRE

    Tscherbul, T.V.; Buchachenko, A. A.; Dalgarno, Alexander; Lu, M.-J.; Weinstein, J. D.

    2009-01-01

    We present a combined experimental and theoretical study of angular momentum depolarization in cold collisions of \\(^2P\\) atoms in the presence of an external magnetic field. We show that collision-induced Zeeman relaxation of Ga\\(^2P_{1/2}\\) and In \\(^2P_{1/2}\\) atoms in cold \\(^4\\)He gas is dramatically suppressed compared to atoms in \\(^2P_{3/2}\\) states. Using rigorous quantum-scattering calculations based on ab initio interaction potentials, we demonstrate that Zeeman transitions in coll...

  5. Time-evolution of many active electrons in slow ion-atom collisions

    Energy Technology Data Exchange (ETDEWEB)

    Runge, K.; Micha, D.A.

    1996-05-01

    The previously developed Eikonal/Time-dependent Hartree-Fock method is applied to slow ionic and atomic collisions involving many active electrons. The electronic density matrix is written in a basis of traveling atomic orbitals including s, p, and d-type atomic basis functions. One- and two-electron integrals are calculated in a static basis and transformed to the traveling basis. Electronic orbital polarization parameters are calculated during the collision to determine the degree of electonic orientation and alignment as a function of time. This method is currently being applied to slow collisions of hydrogen, alkali, alkali earth and rare gas atoms and ions, to calculate the time evolution of electronic energy and charge transfer, as well as orbital polarization.

  6. Unified treatment of hadronic annihilation and protonium formation in slow collisions of antiprotons with hydrogen atoms

    Science.gov (United States)

    Sakimoto, Kazuhiro

    2013-07-01

    Antiproton (p¯) collisions with hydrogen atoms, resulting in the hadronic process of particle-antiparticle annihilation and the atomic process of protonium (p¯p) formation (or p¯ capture), are investigated theoretically. As the collision energy decreases, the collision time required for the p¯ capture becomes necessarily longer. Then, there is the possibility that the p¯-p annihilation occurs significantly before the p¯ capture process completes. In such a case, one can no longer consider the annihilation decay separately from the p¯ capture process. The present study develops a rigorous unified quantum-mechanical treatment of the annihilation and p¯ capture processes. For this purpose, an R-matrix approach for atomic collisions is extended to have complex-valued R-matrix elements allowing for the hadronic annihilation. Detailed calculations are carried out at low collision energies ranging from 10-8 to 10-1 eV, and the annihilation and the p¯ capture (total and product-state selected) cross sections are reported. Consideration is given to the difference between the direct annihilation occurring during the collision and the annihilation of p¯p occurring after the p¯ capture. The present annihilation process is also compared with the annihilation in two-body p¯+p collisions.

  7. Collisions of metastable Ne*, He* atoms with ground-state He, Ne atoms studied by atomic beam and laser techniques

    International Nuclear Information System (INIS)

    A crossed nozzle-beam experiment is used to investigate thermal energy collisions: Ne* (2p53s, 3P0,2) + He(1s2, 1S0), almost purely elastic, and He*(1s2s, 1,3S + Ne(2p6, 1S0), in which inelastic excitation transfers occur. State and velocity selection of the scattered Ne* atoms is performed using a tunable cw dye laser frequency locked on a definite Zeeman component of the transition 1s5 → 2p6 (λ = 614.3 nm) of 20Ne or 22Ne. In the purely elastic case, this technique allows the selection of one of the two final velocities, and then an unambiguous transformation of the differential cross section at 62 meV tallies on accords with a calculation using a single effective potential. In He* on Ne collisions, the main inelastic processes are endothermic excitation transfers from He*(21S). Experimental results obtained at different energies (62, 95, 109, 124 meV) show that the transfers essentially result in levels 3s and 4d of Ne. (orig.)

  8. Excitation and charge transfer in low-energy hydrogen atom collisions with neutral atoms: Theory, comparisons, and application to Ca

    CERN Document Server

    Barklem, Paul S

    2016-01-01

    A theoretical method for the estimation of cross sections and rates for excitation and charge transfer processes in low-energy hydrogen atom collisions with neutral atoms, based on an asymptotic two-electron model of ionic-covalent interactions in the neutral atom-hydrogen atom system, is presented. The calculation of potentials and non-adiabatic radial couplings using the method is demonstrated. The potentials are used together with the multi-channel Landau-Zener model to calculate cross sections and rate coefficients. The main feature of the method is that it employs asymptotically exact atomic wavefunctions, which can be determined from known atomic parameters. The method is applied to Li+H, Na+H, and Mg+H collisions, and the results compare well with existing detailed full-quantum calculations. The method is applied to the astrophysically important problem of Ca+H collisions, and rate coefficients are calculated for temperatures in the range 1000-20000 K.

  9. Dissociative excitation of cesium atom upon e-CsOH collisions

    International Nuclear Information System (INIS)

    The process of dissociative excitation of cesium atom in collisions with mono-kinetic molecules of cesium hydroxide is studied. It is established that behaviour of dissociative excitations the cesium atom in spectral series corresponds of to the grade dependence of cross sections on the main quantum number of the upper level. The values of constants, characterizing the behaviour of cross sections in the eight spectral series of the cesium atom are determined

  10. Excitation of atoms and molecules in collisions with fast, highly charged ions

    International Nuclear Information System (INIS)

    This paper discusses the following topics: charge distributions for Ar recoil-ions produced in one- and two-electron capture collisions by Oq+ projectiles; charge distributions of He, Ne, and Ar recoil-ions produced in collisions with 10 to 30 MeV/u N7+ ions; studies of recoil ions produced in collisions of 40 MeV Ar13+ with atomic and molecular targets; two-fragment coincidence studies of molecular dissociation induced by heavy ion collisions; resonant electron transfer to double K-vacancy states in oxygen compounds; quenching of metastable states in fast Mg projectiles; and design and construction of an atomic physics beamline for the ECR ion source

  11. Investigation of the intermediate LK molecular orbital radiation in heavy ion-atom collisions

    International Nuclear Information System (INIS)

    The continuum consisting of an intensive low-energy and a high-energy components in heavy-ion atom collision systems with atomic numbers Z1, Z2 > 28 is studied. The aim of the study is to prove that the C1 continuum cannot be caused by ridiative electron capture (REC) being molecular orbital (MO) radiation to the 2ptau level. It is shown that the comparison of the C1 yields obtained in Kr+Nb asymmetric collisions in gas and solid targets is associated with the formation of vacancies in the lower-Z collision partner and can be interpreted as quasimolecular radiation to the 2ptau orbital level. The strong suppression of the C2 component in the gas target experimets indicates that the MO radiation to the 1stau orbit is emitted preferentially in the two-collision process in symmetric and near-symmetric systems with Z1, Z2 <= 41

  12. Analysis and manipulation of atomic and molecular collisions using laser light

    International Nuclear Information System (INIS)

    Optical collisions in a crossed beam experiment are examined for the atomic collision pairs LiHe, LiNe, NaNe. Differential cross sections are measured in order to probe the quality of quantum chemical calculated and spectroscopical determined molecular potentials. The linear polarization of the excitation laser is used to manipulate the contrast of the differential cross sections for NaNe. Using elliptical polarized light total control over the angular position and the contrast of the interference pattern is demonstrated. Differential cross sections for the collision pairs LiH2 and LiD2 show a pronounced oscillatory structure, which for the first time is observed for atom-molecule optical collisions. (orig.)

  13. Collective processes in heavy-ion collisions with atomic nuclei. Dissipation of energy and angular momentum

    International Nuclear Information System (INIS)

    The collective processes in collision of heavy-ions with atomic nuclei are discussed. Measured data on the S+Ti collision at Esub(LAB)=105, 130 and 144 MeV have been analysed in terms of a ''fission-like'' processes which seem to be a special case of deep inelastic collisions whose total available kinetic energy is completely dissipated. Applying transport theory it was possible to introduce a ''clock'' for measuring the time scale of nuclear processes in collision of heavy-ions by measuring the FWHM of mass distribution of emitted reaction products. Experimental data on continuum gamma spectra from Cu+Au collision at Esub(LAB)=400 MeV are presented and the angular momentum dissipation in this reaction is discussed. (author)

  14. Collision processes of Li3+ with atomic hydrogen: cross section database

    International Nuclear Information System (INIS)

    Using the available experimental and theoretical data, as well as established cross section scaling relationships, a cross section database for excitation, ionization and charge exchange in collisions of Li3+ ion with ground state and excited hydrogen atoms has been generated. The critically assessed cross sections are represented by analytic fit functions that have correct asymptotic behavior both at low and high collision energies. The derived cross sections are also presented in graphical form. (author)

  15. Bibliography on electron transfer processes in ion-ion/atom/molecule collisions. Updated 1997

    Energy Technology Data Exchange (ETDEWEB)

    Tawara, H.

    1997-04-01

    Following our previous compilations (IPPJ-AM-45 (1986), NIFS-DATA-7 (1990), NIFS-DATA-20 (1993)), bibliographic information on experimental and theoretical studies on electron transfer processes in ion-ion/atom/molecule collisions is up-dated. The references published through 1954-1996 are listed in the order of the publication year. For easy finding of the references for a combination of collision partners, a simple list is provided. (author)

  16. Bibliography on electron transfer processes in ion-ion/atom/molecule collisions. Updated 1997

    International Nuclear Information System (INIS)

    Following our previous compilations (IPPJ-AM-45 (1986), NIFS-DATA-7 (1990), NIFS-DATA-20 (1993)), bibliographic information on experimental and theoretical studies on electron transfer processes in ion-ion/atom/molecule collisions is up-dated. The references published through 1954-1996 are listed in the order of the publication year. For easy finding of the references for a combination of collision partners, a simple list is provided. (author)

  17. Large Effects of Electric Fields on Atom-Molecule Collisions at Millikelvin Temperatures

    OpenAIRE

    Parazzoli, L. P.; Fitch, N J; Zuchowski, P.S.; Hutson, J. M.; Lewandowsk, H.J.

    2011-01-01

    Controlling interactions between cold molecules using external fields can elucidate the role of quantum mechanics in molecular collisions. We create a new experimental platform in which ultracold rubidium atoms and cold ammonia molecules are separately trapped by magnetic and electric fields and then combined to study collisions. We observe inelastic processes that are faster than expected from earlier field-free calculations. We use quantum scattering calculations to show that electric field...

  18. Bibliography on electron transfer processes in ion-ion/atom/molecule collisions, updated 1990

    International Nuclear Information System (INIS)

    Following a previous compilation, new bibliographic information on experimental and theoretical studies on electron transfer processes in ion-ion/atom/molecule collisions is up-dated. The references published through 1989 are surveyed. For easy finding references for particular combination of collision partners, a simple list is also provided. Furthermore, for convenience, a copy of the previous compilation (IPPJ-AM-45 (1986)) is included. (author) 1363 refs

  19. Nonadiabatic nuclear dynamics of atomic collisions based on branching classical trajectories

    International Nuclear Information System (INIS)

    The branching classical trajectory method for inelastic atomic collision processes is proposed. The approach is based on two features: (i) branching of a classical trajectory in a nonadiabatic region and (ii) the nonadiabatic transition probability formulas particularly adapted for a classical trajectory treatment. In addition to transition probabilities and inelastic cross sections, the proposed approach allows one to calculate incoming and outgoing currents. The method is applied to inelastic Na + H collisions providing the results in reasonable agreement with full quantum calculations.

  20. K-Vacancy Production in the Collision of Highly Charged Relativistic Ions With Heavy Atoms

    OpenAIRE

    Khabibullaev, P. K.

    2000-01-01

    A general expression for the cross section of the inelastic collision of relativistic highly charged ion with heavy (relativistic) atoms is obtained using the generalized eikonal approximation. In the ultrarelativistic limit, the obtained formula coincides with a known exact one. As an application of the obtained result, probability and cross section of the K-vacany production in the U92+ - U91+ collision are calculated.

  1. Dynamical resonant electron capture in atom surface collisions: H- formation in H-Al(111) collisions

    Science.gov (United States)

    Borisov, A. G.; Teillet-Billy, D.; Gauyacq, J. P.

    1992-05-01

    The formation of H- ion by grazing-angle collisions of hydrogen on an Al(111) surface is investigated with the newly developed coupled angular mode method. The capture process involves a dynamical resonant process induced by the collision velocity. All the resonance properties of the H- level in front of an Al(111) surface are determined: position, width, and angular distribution of ejected electrons. The results are shown to account for the recent observations on H- formation by Wyputta, Zimny, and Winter.

  2. Electron emission in collisions of intermediate energy ions with atoms

    International Nuclear Information System (INIS)

    The aim of this work, is the analysis of the processes of electronic emission produced in the collisions of small ions (H+, He++) of intermediate energy (50 a 200 KeV/amu) with light gaseous targets. (A.C.A.G.)

  3. Dynamical approach to the statistical average of atom-diatom collision

    International Nuclear Information System (INIS)

    The dynamical Lie algebraic method is used for the description of statistical mechanics of the atom-diatom collision. The expression of the statistical average values is derived in terms of the density operator formalism in statistical mechanics. Also we use the time evolution operator calculate the transition probability. The method is applied to the collision of H2 with He. Comparing the results with the experimental results, the authors can see that the dynamical Lie algebraic method is useful for describing the collision problem. (authors)

  4. Some electron detachment data for H- ions in collisions with electrons, ions, atoms and molecules

    International Nuclear Information System (INIS)

    In order to provide information on the effectiveness of the conversion of negative hydrogen ions in collision with multiply charged ions into neutrals for plasma heating, the present situation is reviewed on the cross sections involving negative hydrogen ions in collisions with electrons, ions, atoms and molecules. It is pointed out that, though electron detachment from negative hydrogen ions is estimated to be effectively achievable under collisions with multiply charged ions, reliable data for such processes are still scanty in particular at the MeV/amu energy range and measurements of the cross sections are deserved to be performed urgently. (author)

  5. An empirical formula evaluation of the collision strength for the electrons with atoms and ions

    International Nuclear Information System (INIS)

    The experimental data and theoretical calculations have been researched for the collision excitation cross section Q, collision strength Ω and rate coefficient R on the electrons with atoms and ions. The empirical formulae of the different types have been compared, analysed and evaluated. These empirical formulae have been given by the strict theoretical model, formulae derivation and programme calculation. A set of values of the Q, Ω and R have been given by means of the calculating results and measuring values, particularly, on the calculating formula parametrization of the collision strength Ω. On the basis of evaluating data, a set of the reasonable and convenient empirical formulae have been recommended

  6. Theoretical study of electronic processes occurring in atom and molecule collisions: the non-perturbative approach

    International Nuclear Information System (INIS)

    This work is composed of 2 parts. The first part is dedicated to the study of ion collisions with atoms or molecules and the second part deals with electron-atom collisions in intense laser radiation. The 2 issues are not so independent as it seems since both involve diffusion processes or the dynamic of electronic structures of atoms and molecules in a non-perturbative framework. The first chapter describes the main collisional processes that happen in ion collisions with atoms and molecules. The eikonal method that is used to compute integral and differential cross-sections is presented in the second chapter. The third chapter reports the various concepts and methods used for studying the dynamics of quantum systems. The fourth chapter deals with the electronic capture in a mono-electronic molecular system and with the interference phenomena that may take place in the differential cross-sections. The fifth chapter studies the ionizing ion-molecule collisions with high impact energy, in such collisions very low amplitude interference structures have been observed experimentally. These structures can be explained by the multiple scattering of the wave packet representing the ejected electron by the 2 centers of the molecular target. The sixth chapter deals with ion-atom collisions in which 2 electrons are active for simple and double electronic capture. The second part of this work begins with chapter 7. The study of electron-atom collisions in intense laser radiation field implies to take into account 3 different interactions: first the interaction between the free electron and the atom, secondly the interaction between the laser field and the incident electron and thirdly, the interaction between the atom and the laser field. The seventh chapter presents a mathematical formalism able to describe the interaction of the atom with the laser field. This formalism is a non-perturbative approach based on the Floquet theorem. In chapter 8 we present an application to

  7. Ultracold atomic collisions in tight harmonic traps: Perturbation theory, ionization losses and application to metastable helium atoms

    CERN Document Server

    Beams, T J; Whittingham, I B

    2004-01-01

    Collisions between tightly confined atoms can lead to ionization and hence to loss of atoms from the trap. We develop second-order perturbation theory for a tensorial perturbation of a spherically symmetric system and the theory is then applied to processes mediated by the spin-dipole interaction. Redistribution and loss mechanisms are studied for the case of spin-polarized metastable helium atoms and results obtained for the five lowest s states in the trap and trapping frequencies ranging from 1 kHz to 10 MHz.

  8. US-Japan Workshop on atomic-collision data for fusion

    International Nuclear Information System (INIS)

    This report, containing abstracts of each of the presentations and discussions, includes: brief talks on the applications of atomic data in tokamaks and in inertial confinement; reviews of the specific atomic collisions projects for fusion in Japan and the United States; discussions of how the data centers operate and manner of exchanging data; brief reviews of the status of electron-ion scattering and ion-atom scattering; discussions of criteria to be used in evaluating and selecting both experimental and theoretical data in these two areas; comparisons of data selected for each of six specific collision reactions which were evaluated by both groups prior to the workshop; brief reviews of activities in the related areas of atomic structure and plasma wall interactions; and a decision to pursue a joint or collaborative compilation of recommended cross sections for oxygen ions for electron impact excitation and electron capture from atomic hydrogen

  9. Lectures on ion-atom collisions from nonrelativistic to relativistic velocities

    CERN Document Server

    Eichler, Jörg

    2005-01-01

    Atomic collisions offer some unique opportunities to study atomic structure and reaction mechanisms in experiment and theory, especially for projectiles of high atomic number provided by modern accelerators. The book is meant as an introduction into the field and provides some basic theoretical understanding of the atomic processes occurring when a projectile hits another atom. It also furnishes the tools for a mathematical description, however, without going deeper into the technical details, which can be found in the literature given. With this aim, the focus is on reactions, in which only a single active electron participates. Collisional excitation, ionization and charge transfer are discussed for collision velocities ranging from slow to comparable to thespeed of light. For the highest projectile velocities, energy can be converted into mass, so that electron-positron pairs are created. In addition to the systematic treatment, a theoretical section specializes on electron-electroncorrelations and three...

  10. Single-collision studies of hot atom energy transfer and chemical reaction

    International Nuclear Information System (INIS)

    This report discusses research in the collision dynamics of translationally hot atoms, with funding with DOE for the project ''Single-Collision Studies of Hot Atom Energy Transfer and Chemical Reaction,'' Grant Number DE-FG03-85ER13453. The work reported here was done during the period September 9, 1988 through October 31, 1991. During this period this DOE-funded work has been focused on several different efforts: (1) experimental studies of the state-to-state dynamics of the H + RH → H2 R reactions where RH is CH4, C2H6, or C3H8, (2) theoretical (quasiclassical trajectory) studies of hot hydrogen atom collision dynamics, (3) the development of photochemical sources of translationally hot molecular free radicals and characterization of the high resolution CARS spectroscopy of molecular free radicals, (4) the implementation of stimulated Raman excitation (SRE) techniques for the preparation of vibrationally state-selected molecular reactants

  11. Dissociative Excitation of Even States of Tin Atoms in e-SnCl2 Collisions

    Science.gov (United States)

    Smirnov, Yu. M.

    2001-12-01

    Dissociative excitation of even levels of tin atoms in collisions of slow electrons with tin dichloride molecules is studied experimentally. The levels studied belong to the configurations 5 s 25 pnp 1, 3 L ( n=6, 7; L= S, P, D) and 5 s 25 p 4 f. Absolute values of cross sections for dissociative excitation at the electron energy of 100 eV are 1.05-2.56 times greater than cross sections for excitation in electron-atom collisions at the energy of 50 eV.

  12. Collision of Bare Ion Si14+ with the Same Z Slow-atom Si

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    We present the collision of bare ion Si14+ with the same Z slow-atom Si. It is shown that the cold-atom collisions are sensitive to the potential. In this paper, we present the cross sectiond for the most important transition from the 3p13d1 and 3p14d1 excited states. It is seen that there are large cross sections when the angle is larger than 80 degrees. With increasing energy, the cross section becomes decresasingly flat.PACS numbers:34.70.+e, 32.80. Fb

  13. Investigation of ion-atom collision dynamics through imaging techniques

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The principle and technique details of recoil ion momentum imaging are discussed and summarized. The recoil ion momentum spectroscopy built at the Institute of Modern Physics (Lanzhou) is presented. The first results obtained at the setup are analyzed. For 30 keV He2+ on He collision, it is found that the capture of single electron occurs dominantly into the first excited states, and the related scattering angle results show that the ground state capture occurs at large impact parameters, while the capture into excited states occurs at small impact parameters. The results manifest the collision dynamics for the sub-femto-second process can be studied through the techniques uniquely. Finally, the future possibilities of applications of the recoil ion momentum spectroscopy in other fields are outlined.

  14. Topics relating to atomic collisions in dilute Bose-Einstein condensates

    International Nuclear Information System (INIS)

    In this thesis, we investigate various aspects of applications and limitations arising from atomic collisions in dilute Bose-Einstein condensates. First, we investigate the relative particle number squeezing produced in the excited states of a dilute condensate at zero temperature using stimulated light scattering. We show that a modest number of relative number squeezed particles can be achieved when atoms, produced in pairs through collisions in the condensate, are scattered out by their interaction with the lasers. This squeezing is optimal when the momentum is larger than the inverse healing length. This modest number of relative number squeezed particles has the potential to be amplified in four-wave-mixing experiments. We study the limitations on the relative number squeezing between photons and atoms coupled out from a homogeneous Bose-Einstein condensate. We consider the coupling between the translational atomic states by two photon Bragg processes, one of the photon modes involved in the Bragg process being in a coherent state, and the other initially unpopulated. We start with an interacting condensate at zero temperature and compute the time evolution for the system. We discuss how collisions between the atoms and photon rescattering affect the degree of squeezing which may be reached in such experiments. We investigate the limitations arising from atomic collisions on the storage and delay times of probe pulses in EIT experiments. We find that the atomic collisions can be described by an effective decay rate that limits storage and delay times. We calculate the momentum and temperature dependence of the decay rate and find that it is necessary to excite atoms to a particular momentum depending on temperature and spacing of the energy levels involved in order to minimize the decoherence effects of atomic collisions. Finally, we propose a method to probe states in the Mott insulator regime produced from a condensate in an optical lattice. We consider a

  15. DC Stark effect on cold Rydberg atom nD + nD pair collisions

    International Nuclear Information System (INIS)

    We have observed a significant yield of (n + 2)P atoms after the excitation of nD Rydberg atoms in a Rb MOT, where 27 < n < 41, which can be attributed to binary collisions between Rydberg atoms. We have measured its dependence on principle quantum number as well as DC electric field. These results are compared to a model which uses the Landau-Zener method to calculate transition probabilities at avoided crossings in the two-atom potential energy curves, taking into account the effects of the DC Stark effect due to the background electric field.

  16. Atom trapping: application to electron collision studies of metastable helium

    International Nuclear Information System (INIS)

    Full text: We report on the first measurements of electron scattering from metastable helium atoms (He) confined in a magneto-optic trap (MOT). Using conventional crossed beam techniques, measurement of electron scattering cross sections for He is experimentally very difficult, due the intrinsically low atomic densities produced by nozzle discharge sources, and the need to locate the interaction region well away from stray electric and magnetic fields. Electron interactions with excited state atoms are fundamentally important to many naturally processes in atmospheric and astrophysical chemistry, gas lasers and plasma processing. Until these experiments, no data for He existed in the intermediate (10-100 eV) range to verify theoretical predictions. Our MOT contains up to 108 atoms at temperatures of ∼1mK that act as a high (∼109 cm-3) density target for a pulsed electron beam. We employ optical molasses to reduce the atomic velocity, and hence the trap decay time when released from the optical and magnetic fields. The total cross section is determined using phase modulation spectroscopy to measure the fractional loss rate of the trapped atoms with the electron gun on, and the electron current density is measured using scanning wire techniques to yield the absolute total cross section

  17. Non-thermal Dupree diffusivity and shielding effects on atomic collisions in Lorentzian turbulent plasmas

    Science.gov (United States)

    Lee, Myoung-Jae; Jung, Young-Dae

    2016-05-01

    The influence of non-thermal Dupree turbulence and the plasma shielding on the electron-ion collision is investigated in Lorentzian turbulent plasmas. The second-order eikonal analysis and the effective interaction potential including the Lorentzian far-field term are employed to obtain the eikonal scattering phase shift and the eikonal collision cross section as functions of the diffusion coefficient, impact parameter, collision energy, Debye length and spectral index of the astrophysical Lorentzian plasma. It is shown that the non-thermal effect suppresses the eikonal scattering phase shift. However, it enhances the eikonal collision cross section in astrophysical non-thermal turbulent plasmas. The effect of non-thermal turbulence on the eikonal atomic collision cross section is weakened with increasing collision energy. The variation of the atomic cross section due to the non-thermal Dupree turbulence is also discussed. This research was supported by Nuclear Fusion Research Program through NRF funded by the Ministry of Science, ICT & Future Planning (Grant No. 2015M1A7A1A01002786).

  18. 16. International Conference on Atomic Collisions in Solids. Book of abstracts

    International Nuclear Information System (INIS)

    In this conference book of abstracts the following topics are treated: The interaction of atomic, molecular or ion beams with surfaces of solid metals and crystals, scattering and collisions, ion bombardment, ion channeling, energy losses and charge exchange, thin films, secondary emission, the Auger effect, sputtering of particles and atomic and molecular clusters. Thereby not only experimental results are presented but also computerized simulation methods are applied. (Suda)

  19. Influence of the atomic-wall collision elasticity on the coherent population trapping resonance shape

    OpenAIRE

    Kazakov, G A; Litvinov, A. N.; Matisov, B. G.; Romanenko, V. I.; Yatsenko, L. P.; Romanenko, A. V.

    2011-01-01

    We studied theoretically a coherent population trapping resonance formation in cylindrical cell without buffer gas irradiated by a narrow laser beam. We take into account non-zero probabilities of elastic ("specular") and inelastic ("sticking") collision between the atom and the cell wall. We have developed a theoretical model based on averaging over the random Ramsey pulse sequences of times that atom spent in and out of the beam. It is shown that the shape of coherent population trapping re...

  20. Formation of heavy-Rydberg ion-pair states in Rydberg atom collisions with attaching targets

    Science.gov (United States)

    Wang, Changhao; Kelley, Michael; Buathong, Sitti; Dunning, F. Barry

    2014-05-01

    Electron transfer in collisions between K(np)Rydberg atoms and electron attaching molecules can lead to formation of heavy-Rydberg ion-pair states comprising a weakly-bound positive-negative ion pair orbiting at large internuclear separations. In the present work ion-pair states are created in a small collision cell and allowed to exit into an analysis region where their binding energy and velocity distributions are determined with the aid of electric-field-induced dissociation and a position sensitive detector. Ion pair production is analyzed using a Monte Carlo collision code that models both the initial Rydberg electron capture and the subsequent behavior of the product ion pair. The data demonstrate that collisions with SF6 and CCl4 lead to formation of long-lived ion pair states with a broad distribution of binding energies whose velocity distribution is strongly peaked in the forward direction. Research supported by the Robert A. Welch Foundation.

  1. Total angular momentum representation for atom-molecule collisions in electric fields

    CERN Document Server

    Tscherbul, T V

    2012-01-01

    It is shown that the atom-molecule collision problem in the presence of an external electric field can be solved using the total angular momentum representation in the body-fixed coordinated frame, leading to a computationally efficient method for ab initio modeling of low-temperature scattering phenomena. Our calculations demonstrate rapid convergence of the cross sections for vibrational and Stark relaxation in He-CaD collisions with the number of total angular momentum states in the basis set, leading to a 5-100 fold increase in computational efficiency over the previously used methods based on the fully uncoupled space-fixed representation. These results open up the possibility of carrying out numerically converged quantum scattering calculations on a wide array of atom-molecule collisions and chemical reactions in the presence of electric fields.

  2. Experimental investigation of atomic collisions in time scales varying from nanosecond to microseconds

    International Nuclear Information System (INIS)

    We present the results from two experiments investigating collisions that differ in time scale by three orders of magnitude. The first experiment enables the determination of absolute total collision cross sections using a technique that measures a change in the loss rate of trapped atoms from a magneto optical trap (MOT). We also investigate light assisted collision processes between cold metastable neon atoms in the 3P2 metastable state within the MOT. A catalysis laser is scanned in frequency across the 3P2 - 3D3 cooling transition and the ionization rate was observed. Ionization spectra are obtained which demonstrate a dependence on the magnetic sublevels of the transition that the catalysis laser is exciting.

  3. Positronium formation and ionization in slow positron-hydrogen atom collisions

    Energy Technology Data Exchange (ETDEWEB)

    Janev, R.K. [International Atomic Energy Agency, PO Box 100, A-1400 Vienna (Austria); Solov' ev, E.A. [Research Centre for Energy and Informatics, Macedonian Academy of Sciences and Arts, PO Box 428, 9100 Skopje (Macedonia, The Former Yugoslav Republic of)

    1999-07-14

    The electron capture and ionization processes in slow collisions of positrons with hydrogen atoms are considered within the advanced adiabatic approach to atomic collisions. The mass asymmetry of the (p,e{sup -},e{sup +}) collision system is properly taken into account. The calculated positronium formation and ionization cross sections compare favourably with the available experimental data in the adiabatic energy region. It is shown that the potential energy curve of the 2p {sigma} molecular state supports a quasi-bound level of the three-particle (p,e{sup +},e{sup -}) system with an energy of -0.3 eV and decay width of 0.15 eV, approximately. (author)

  4. Projectile energy loss in multiply ionizing ion-atom collisions

    International Nuclear Information System (INIS)

    The projectile energy loss for 7.5--25-MeV C6+,5+ and F6+ ions was measured for single collisions with He, Ne, Ar, and Kr as a function of the recoil-ion charge state and the projectile scattering. This energy loss was measured for collisions in which the projectile captured an electron and for those involving just direct ionization. We investigated and found a large average energy transfer (100--250 eV/electron) to the continuum electrons. A strong increase of the scattering angle with recoil-ion charge state was observed for both capture and direct ionization. The results imply that, for smaller impact parameters, higher recoil-ion charge states are produced and that higher energy losses are obtained. We observed a weak target-Z dependence of the energy loss. The results are compared with n-body classical-trajectory Monte Carlo calculations by Olson, semiclassical-approximation calculations by Schuch et al. [Nucl. Instrum. Methods Phys. Res. Sect. B 42, 566 (1989)], and the energy-deposition model

  5. Orientational invariance of the rotational transition probability in the sudden approximation. [atom-molecule collisions

    Science.gov (United States)

    Stallcop, J. R.

    1974-01-01

    Semiclassical collisions of an atom with a rigid-rotor molecule are examined in the sudden approximation. The rotational transition probability is shown to be invariant with respect to the choice of orientation for the molecular coordinate system; this fact contradicts recently reported results of a computer analysis. The present analysis may lead to an improved interpretation of recent molecular beam measurements.

  6. Relativistic effects in non-radiative electron capture in ion-atom collisions

    International Nuclear Information System (INIS)

    In this paper, a modified eikonal method (Blankenbecler-Goldberger) has been extended to perform calculations for the electron capture processes in relativistic ion-atom collisions. The results are compared with the first order Born approximation and the ordinary eikonal approximation. The relativistic effects are discussed. Some conclusions are drawn. (author)

  7. ELECTRON-CAPTURE IN HIGHLY-CHARGED ION-ATOM COLLISIONS

    NARCIS (Netherlands)

    MORGENSTERN, R

    1993-01-01

    An attempt is made to identify the most important mechanisms responsible for the rearrangement of electrons during collisions between multiply charged ions and atoms at keV energies. It is discussed to which extent the influence of binding energy, angular momentum of heavy particles and electrons, a

  8. Electron and X-ray emission in collisions of multiply charged ions and atoms

    International Nuclear Information System (INIS)

    The author presents experimental results of electron and X-ray emission following slow collisions of multiply charged ions and atoms. The aim of the investigation was to study the mechanisms which are responsible for the emission. (G.T.H.)

  9. Experimental study of inelastic collisions of slow electrons with terbium atoms

    International Nuclear Information System (INIS)

    The aim of the paper is experimental study of inelastic collisions of slow electrons with terbium atoms (TA) by the intersecting beam method. Data in the cross sections and optical excitation functions of TA in dependence on the electron energy in the range of 0-200 eV are presented. The TA state diagram with investigated transitions is presented too

  10. On cross sections of intercombination transitions between high-excited levels in electron-atom collisions

    International Nuclear Information System (INIS)

    The cross sections of intercombination transitions (ICT) between high-excited levels of atoms during the collisions of the latter with electrons are considered. A method is proposed for calculating ICT cross sections which are orbital quantum number totals. A comparison with the cross section calculated within the scope of quasiclassic approach is performed. Both methods yield close results

  11. Isotopic and Symmetry Effects in the Collision of Atomic Helium

    Science.gov (United States)

    Bouledroua, Moncef; Bouchelaghem, Fouzia; Tahar Bouazza, M.; Reggami, Lamia

    2006-11-01

    The thermophysical properties of a helium dilute gas at low and high temperatures are revisited with new and recent potential data points. The second virial coefficients are computed in order to assess the accuracy of the constructed He-He potentials. The results, mainly at high temperatures, are in a good agreement with the published values. The isotopic effects due to the presence of ^4He and ^3He atoms are also examined and the calculations of various transport parameters, namely diffusion, viscosity, and thermal conductivity, are extended to include the nuclear spins and the symmetry effects, which arise from the identity and indistinguishability of the colliding atoms.

  12. Ionization and electron emission of heavy ion-atom collisions: The argon-krypton collision system

    International Nuclear Information System (INIS)

    The Ar-Kr collision system has been studied by examining the charge states of the scattered ions together with the energies of the emitted electrons. The charge state data show that there are increases in the average scattered charge state at distances of closest approach that correspond well with internuclear distances for which the molecular orbital model1 predicts electron promotions of krypton and argon electrons to occur. The electron data show a well resolved Auger peak between 150-200 eV superimposed on an exponentially decreasing background of continuum electrons. Doppler shifts identify the Auger peak as originating from the argon collision partner. Ion-electron coincidence experiments exhibit the same peak and link it to a specific distance of closest approach. The threshold for this L-Auger electron production falls between 0.2 and 0.3 a.u., agreeing well with molecular orbital predictions

  13. Properties of the scattering amplitude for electron-atom collisions

    International Nuclear Information System (INIS)

    For the scattering of an electron by an atom finiteness of the amplitude at non threshold energies is proved in the framework of the N-body Schroedinger equation. It is also shown that both the direct and exchange amplitudes have analytic continuations for complex values of incident momentum, with pole or cut singularities on the imaginary axis

  14. Atomic Spectroscopy and Collisions Using Slow Antiprotons \\\\ ASACUSA Collaboration

    CERN Multimedia

    Matsuda, Y; Lodi-rizzini, E; Kuroda, N; Schettino, G; Hori, M; Soter, A; Pirkl, W; Mascagna, V; Malbrunot, C L S; Yamazaki, Y; Eades, J; Simon, M; Massiczek, O; Sauerzopf, C; Breuker, H; Nagata, Y; Uggerhoj, U I; Mc cullough, R W; Toekesi, K M; Venturelli, L; Widmann, E; Zmeskal, J; Kanai, Y; Hayano, R; Knudsen, H; Kristiansen, H; Todoroki, K; Bartel, M A; Moller, S P; Charlton, M; Leali, M; Diermaier, M; Kolbinger, B

    2002-01-01

    ASACUSA (\\underline{A}tomic \\underline{S}pectroscopy \\underline{A}nd \\underline{C}ollisions \\underline{U}sing \\underline{S}low \\underline{A}ntiprotons) is a collaboration between a number of Japanese and European research institutions, with the goal of studying bound and continuum states of antiprotons with simple atoms.\\\\ Three phases of experimentation are planned for ASACUSA. In the first phase, we use the direct $\\overline{p}$ beam from AD at 5.3 MeV and concentrate on the laser and microwave spectroscopy of the metastable antiprotonic helium atom, $\\overline{p}$He$^+$, consisting of an electron and antiproton bound by the Coulomb force to the helium nucleus. Samples of these are readily created by bringing AD antiproton beam bunches to rest in helium gas. With the help of techniques developed at LEAR for resonating high precision laser beams with antiproton transitions in these atoms, ASACUSA achieved several of these first-phase objectives during a few short months of AD operation in 2000. Six atomic tr...

  15. Relativistic ab initio calculations for ion-atom collisions

    International Nuclear Information System (INIS)

    Within the independent particle model we solve the time---dependent single-particle equation using ab initio SCF-DIRAC-FOCK-SLATER wavefunctions as a basis. To reinstate the many-particle aspect of the collision system we use the inclusive probability formalism to answer experimental questions. As an example we show an application to the case of S15+ on Ar where experimental data on the K-K charge transfer are available for a wide range of impact energies from 4.7 to 90 MeV. Our molecular adiabatic calculations and the evaluation using the inclusive probability formalism show good results in the low energy range from 4.7 to 16 MeV impact energy

  16. Photon emission spectroscopy of ion-atom collisions

    Energy Technology Data Exchange (ETDEWEB)

    Nystroem, B.

    1995-10-01

    Emission cross sections for the 1snp{sup 1}P{sub 1}-levels have been measured by photon emission spectroscopy for the collision systems He{sup +} + He at 10 keV and He{sup 2+} + He at 10-35 keV. Photon spectra of Krypton (Kr VIII) and Xenon (Xe V - IX) have also been obtained using 10q keV beams of Kr{sup q+} (q=7-9) and Xe{sup q+} (q=5-9) colliding with Helium and Argon. The Lifetimes of 3p{sup 2}P-levels in Na-like Nb are reported together with lifetime for the 3s3p{sup 3}P{sub 1}-level in Mg-like Ni, Kr, Y, Zr and Nb where this level has an intercombination transition to the ground state. 45 refs, 20 figs.

  17. Formation of protonium and positronium in atomic collisions

    CERN Document Server

    Whitehead, R J

    2001-01-01

    method. Statistically accurate cross sections for protonium and antihydrogen formation have been obtained and the energy dependence of the process established. Antihydrogen formation from antiproton collisions with positronium in the presence of a laser has also been simulated with the CTMC method and the effects of laser polarisation, frequency and intensity studied. Enhancements of the antihydrogen formation cross section were observed and it is suggested that more sophisticated calculations should be undertaken. A minimum-norm method has been developed for solving the coupled integro-differential equations describing the scattering of positrons by one-electron targets in which the rearrangement channels for positronium formation have been explicitly included. The minimum-norm method, applied to this application for the first time in this thesis, is an enhancement of a previously reported least-squares method which has enabled the extension to a significantly larger basis consisting of up to 26 states on th...

  18. Photon emission spectroscopy of ion-atom collisions

    International Nuclear Information System (INIS)

    Emission cross sections for the 1snp1P1-levels have been measured by photon emission spectroscopy for the collision systems He+ + He at 10 keV and He2+ + He at 10-35 keV. Photon spectra of Krypton (Kr VIII) and Xenon (Xe V - IX) have also been obtained using 10q keV beams of Krq+ (q=7-9) and Xeq+ (q=5-9) colliding with Helium and Argon. The Lifetimes of 3p2P-levels in Na-like Nb are reported together with lifetime for the 3s3p3P1-level in Mg-like Ni, Kr, Y, Zr and Nb where this level has an intercombination transition to the ground state. 45 refs, 20 figs

  19. Protonium formation in slow collisions of antiprotons with hydrogen atoms

    Energy Technology Data Exchange (ETDEWEB)

    Sakimoto, Kazuhiro [Institute of Space and Astronautical Science, Yoshinodai, Sagamihara (Japan)]. E-mail: sakimoto@pub.isas.ac.jp

    2001-05-14

    Protonium formation p-bar+H{yields}p-barp+e is investigated theoretically at centre-of-mass collision energies less than E=10 eV. In previous studies on the break-up ionization p-bar+H{yields}p-bar+p+e, the present author introduced the direct numerical method using a discrete-variable-representation technique to solve the time-dependent (semiclassical) Schroedinger equation. The same method is applied to protonium formation. The reliability of the adiabatic molecular picture is examined for the calculation of the formation cross section. At very low energies, the centrifugal barrier plays an important role in the protonium formation as found in a variety of ion-molecule chemical reactions. (author)

  20. Protonium formation in slow collisions of antiprotons with hydrogen atoms

    International Nuclear Information System (INIS)

    Protonium formation p-bar+H→p-barp+e is investigated theoretically at centre-of-mass collision energies less than E=10 eV. In previous studies on the break-up ionization p-bar+H→p-bar+p+e, the present author introduced the direct numerical method using a discrete-variable-representation technique to solve the time-dependent (semiclassical) Schroedinger equation. The same method is applied to protonium formation. The reliability of the adiabatic molecular picture is examined for the calculation of the formation cross section. At very low energies, the centrifugal barrier plays an important role in the protonium formation as found in a variety of ion-molecule chemical reactions. (author)

  1. Double-atom excitation in heavy-particle collisions induced by the electron-electron interaction

    International Nuclear Information System (INIS)

    We present an analytical method for rapid calculation of matrix elements for double-atom excitation induced by the electron-electron interaction. The method is applied to calculation of probabilities and cross sections for double-atom n = 2 excitation in H(1s)-H(1s) and various A(Zp-1)+(1s)-H(1s) collisions at intermediate and high projectile energies. Based on first-order perturbation theory an empirical scaling rule for the double-atom excitation cross sections is derived. The calculated cross sections are shown to be in good agreement with this scaling relation. (author)

  2. Energy losses of fast heavy multiply charged structural ions in collisions with complex atoms

    Science.gov (United States)

    Matveev, V. I.; Sidorov, D. B.

    2007-07-01

    A nonperturbatve theory of energy losses of fast heavy multiply charged structural ions in collisions with neutral complex atoms is elaborated with allowance for simultaneous excitations of ionic and atomic electron shells. Formulas for the effective deceleration that are similar to the well-known Bethe-Bloch formulas are derived. By way of example, the energy lost by partially stripped U q+ ions (10 ≤ q ≤ 70) colliding with argon atoms and also the energy lost by Au, Pb, and Bi ions colliding with various targets are calculated. The results of calculation are compared with experimental data.

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

    Science.gov (United States)

    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.

  4. Electron capture by fluorinated fullerene anions in collisions with Xe atoms

    DEFF Research Database (Denmark)

    Boltalina, OV; Hvelplund, P; Jørgensen, Thomas J. D.;

    2000-01-01

    Electron capture by 50-keV fluorinated fullerene anions (C60Fn- 18collisions with Xe atoms, The relative importance of nondissociative vs dissociative electron capture was found to depend strongly on the ion pro...... production method and on the number of attached F atoms. The absolute size of the cross section similar to 10(-16) cm(2) has been modeled within the over-the-barrier model......Electron capture by 50-keV fluorinated fullerene anions (C60Fn- 18collisions with Xe atoms, The relative importance of nondissociative vs dissociative electron capture was found to depend strongly on the ion...

  5. Quantum theory of ultracold atom-ion collisions

    CERN Document Server

    Idziaszek, Zbigniew; Julienne, Paul S; Simoni, Andrea

    2008-01-01

    We study atom-ion scattering in the ultracold regime. To this aim, an analytical model based on the multichannel quantum defect formalism is developed and compared to close-coupled numerical calculations. We investigate the occurrence of magnetic Feshbach resonances focusing on the specific 40Ca+ - Na system. The presence of several resonances at experimentally accessible magnetic fields should allow the atom-ion interaction to be precisely tuned. A fully quantum-mechanical study of charge exchange processes shows that charge-exchange rates should remain small even in the presence of resonance effects. Most of our results can be cast in a system-independent form and are important for the realization of the charge-neutral ultracold systems.

  6. Laser Assisted Free-Free Transition in Electron - Atom Collision

    Science.gov (United States)

    Sinha, C.; Bhatia, A. K.

    2011-01-01

    Free-free transition is studied for electron-Hydrogen atom system in ground state at very low incident energies in presence of an external homogeneous, monochromatic and linearly polarized laser field. The incident electron is considered to be dressed by the laser in a non perturbative manner by choosing the Volkov solutions in both the channels. The space part of the scattering wave function for the electron is solved numerically by taking into account the effect of electron exchange, short range as well as of the long range interactions. Laser assisted differential as well as elastic total cross sections are calculated for single photon absorption/emission in the soft photon limit, the laser intensity being much less than the atomic field intensity. A strong suppression is noted in the laser assisted cross sections as compared to the field free situations. Significant difference is noted in the singlet and the triplet cross sections.

  7. Parameters for Cold Collisions of Lithium and Caesium Atoms

    CERN Document Server

    Ouerdane, H

    2015-01-01

    We calculate the s-wave scattering length and effective range and the p-wave scattering volume for $^7$Li atoms interacting with $^{133}$Cs atoms via the X$^1\\Sigma^+_g$ molecular potential. The length and volume are found by fitting the log-derivative of the zero energy wave function evaluated at short range to a long range expression that accounts for the leading van der Waals dispersion potential and then incorporating the remaining long range dispersion contributions to first order. The effective range is evaluated from a quadrature formula. The calculated parameters are checked from the zero energy limits of the scattering phase shifts. We comment on ill-conditioning in the calculated s-wave scattering length.

  8. Coherence effects in heavy ion-atom collisions

    International Nuclear Information System (INIS)

    A new approach to charge capture and ionization by highly stripped projectiles is described and shown to explain cross section systematics through the periodic table. Oscillations in cross section with respect to charge state observed around atomic number 70 are explained as an f-wave resonance in the target electron-projectile scattering. The ratio of H2 to H cross sections for both light and heavy projectiles is shown to fit a two center coherent scattering model; independent scattering by the two centers is not a good assumption for velocities below 4 a.u. Similar coherence effects are predicted in stripping by molecular gases even in multi-electron processes where the independent atom model might be thought valid. Recent experiments on the forward peak of electrons ejected from the projectile show interesting structure which can be partly explained without invoking interference effects. 7 references

  9. Coherence and correlation in electron-atom collisions

    Energy Technology Data Exchange (ETDEWEB)

    Slevin, J.A. (Saint Patrick' s Coll., Maynooth (Ireland)); Chwirot, S. (Uniwersytet Mikolaja Kopernika, Torun (Poland). Inst. Fizyki)

    1990-01-28

    Recent developments in the field of alignment and orientation studies of electron impact excitation of atoms are discussed. This article reviews experiments which have a well defined planar symmetry, i.e. in which the initial and final momenta of electrons are determined. The experimental results obtained by different groups during the last four years are presented after a brief theoretical introduction followed by a description of typical experimental arrangements. (author).

  10. Coherence and correlation in electron-atom collisions

    International Nuclear Information System (INIS)

    Recent developments in the field of alignment and orientation studies of electron impact excitation of atoms are discussed. This article reviews experiments which have a well defined planar symmetry, i.e. in which the initial and final momenta of electrons are determined. The experimental results obtained by different groups during the last four years are presented after a brief theoretical introduction followed by a description of typical experimental arrangements. (author)

  11. Electron capture by impact of highly partially stripped ions on hydrogen atom in low collision energies

    International Nuclear Information System (INIS)

    Based on the reaction windows of electron capture obtained by using the two-state Landau-Zener model, the electron capture processes in collision of bare ions and highly partially stripped ions with hydrogen atoms are analysed. The capture cross sections predicted by multichannel Landau-Zener method are reliable if the cross points between the initial and final diabatic potential energy curves are located in the corresponding reaction windows. The calculations by the multichannel Landau-Zener method show that the present theoretical results are in accord with the analyses for slow C3+ + H and 5+ + H collisions

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

    Science.gov (United States)

    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

  13. Penning collisions of laser-cooled metastable helium atoms

    Science.gov (United States)

    Pereira Dos Santos, F.; Perales, F.; Léonard, J.; Sinatra, A.; Wang, Junmin; Saverio Pavone, F.; Rasel, E.; Unnikrishnan, C. S.; Leduc, M.

    2001-04-01

    We present experimental results on the two-body loss rates in a magneto-optical trap of metastable helium atoms. Absolute rates are measured in a systematic way for several laser detunings ranging from -5 to -30 MHz and at different intensities, by monitoring the decay of the trap fluorescence. The dependence of the two-body loss rate coefficient β on the excited state ( 23P2) and metastable state ( 23S1) populations is also investigated. From these results we infer a rather uniform rate constant Ksp = (1+/-0.4)×10-7 cm3/s.

  14. Associative ionization of neon and helium atoms by collisions of excited helium (31p) atoms of thermal energies

    International Nuclear Information System (INIS)

    The relative cross-sections of ionizing collisions between He + He and He + Ne atoms, have been studied, the helium being excited in a state (31p) by a laser beam. The results obtained made it possible (a) to reveal in a direct manner the production of molecular ions He2+ and He Ne+ and (b) to determine the relative change in the associative ionizing cross-section in the area (0.035 - 0.17 eV) in the He (31P) + Ne collision, despite the very short life of the He (31P) excited state (1.7 ns). The production of He2+ ions from an He (3 1P) + He collision sets an upper limit to the appearance potential of these ions. The experimental study of the associative ionization in the He (31P) + Ne system made it possible to extend the utilization of the GAMMA(R) self ionization model, already tested for the metastable states, to the radiative states. The GAMMA(R) model seems well suited for the description of collisions of the A excited + B type, where the excitation energy of A is greater than the ionization potential of B

  15. Direct probe of anisotropy in atom-molecule collisions via quantum scattering resonances

    CERN Document Server

    Klein, Ayelet; Skomorowski, Wojciech; Żuchowski, Piotr S; Pawlak, Mariusz; Janssen, Liesbeth M C; Moiseyev, Nimrod; van de Meerakker, Sebastiaan Y T; van der Avoird, Ad; Koch, Christiane P; Narevicius, Edvardas

    2016-01-01

    Anisotropy is a fundamental property of particle interactions. It occupies a central role in cold and ultra-cold molecular processes, where long range forces have been found to significantly depend on orientation in ultra-cold polar molecule collisions. Recent experiments have demonstrated the emergence of quantum phenomena such as scattering resonances in the cold collisions regime due to quantization of the intermolecular degrees of freedom. Although these states have been shown to be sensitive to interaction details, the effect of anisotropy on quantum resonances has eluded experimental observation so far. Here, we directly measure the anisotropy in atom-molecule interactions via quantum resonances by changing the quantum state of the internal molecular rotor. We observe that a quantum scattering resonance at a collision energy of $k_B$ x 270 mK appears in the Penning ionization of molecular hydrogen with metastable helium only if the molecule is rotationally excited. We use state of the art ab initio and ...

  16. One-electron capture and target ionization in He+-neutral-atom collisions

    International Nuclear Information System (INIS)

    One-electron capture and target-ionization cross sections in collisions of He+ ions with neutral atoms: He+ + A → He + A+ and He+ + A → He+ + A+ + e, A = H, He(1s2, 1s2s), Ne, Ar, Kr, Xe, are calculated and compared with available experimental data over the broad energy range E = 0.1 keV/u - 10 MeV/u of He+ ions. The role of the metastable states of neutral helium atoms in such collisions, which are of importance in plasma physics applications, is briefly discussed. The recommended cross section data for these processes are presented in a closed analytical form (nine-order polynomials) which can be used for a plasma modeling and diagnostics. (author)

  17. A high density target of ultracold atoms and momentum resolved measurements of ion-atom collisions

    OpenAIRE

    Götz, Simone Andrea

    2012-01-01

    In this thesis an ultracold high density target with high loading flux in combination with a recoil ion momentum spectrometer (RIMS) is presented. Trapped rubidium atoms serve as a high density target (up to 10¹¹ atoms/cm³) at a temperature of only 200 µK. The target is loaded from a two-dimensional magneto-optical trap (2D MOT), which delivers an atom beam with a brilliance of 8 x 10¹² atoms/(s*rad) and a longitudinal momentum spread of 0.25 a.u.. The great advantage of this source is that t...

  18. Effects of ion-atom collisions on the propagation and damping of ion-acoustic waves

    DEFF Research Database (Denmark)

    Andersen, H.K.; D'Angelo, N.; Jensen, Vagn Orla;

    1968-01-01

    Experiments are described on ion-acoustic wave propagation and damping in alkali plasmas of various degrees of ionization. An increase of the ratio Te/Ti from 1 to approximately 3-4, caused by ion-atom collisions, results in a decrease of the (Landau) damping of the waves. At high gas pressure and....../or low wave frequency a "fluid" picture adequately describes the experimental results....

  19. Bremsstrahlung radiation from electron-atom collisions in high pressure mercury lamps

    International Nuclear Information System (INIS)

    Bremsstrahlung coefficients for electron-mercury-atom collisions were computed using the corrected phase-shift approximation. These corrected bremsstrahlung coefficients are a weighted average of coefficients from the phase-shift and momentum transfer approximations. Phase-shifts determined from solutions of the Dirac-Fock scattering equations including both static and dynamic polarization potentials and exchange effects were used. The corrected coefficients approach the same limit at longer wavelengths as coefficients from the simpler momentum transfer approximation, but are generally larger

  20. Bremsstrahlung radiation from electron-atom collisions in high pressure mercury lamps

    Energy Technology Data Exchange (ETDEWEB)

    Lawler, J E [Department of Physics, University of Wisconsin, 1150 University Avenue, Madison, WI 53706 (United States)

    2004-06-07

    Bremsstrahlung coefficients for electron-mercury-atom collisions were computed using the corrected phase-shift approximation. These corrected bremsstrahlung coefficients are a weighted average of coefficients from the phase-shift and momentum transfer approximations. Phase-shifts determined from solutions of the Dirac-Fock scattering equations including both static and dynamic polarization potentials and exchange effects were used. The corrected coefficients approach the same limit at longer wavelengths as coefficients from the simpler momentum transfer approximation, but are generally larger.

  1. Bibliography of atomic and molecular excitation in heavy particle collisions, 1950--1975

    Energy Technology Data Exchange (ETDEWEB)

    Hawthorne, S.W.; Thomas, E.W.; Barnett, C.F.; Crandall, D.H.; Gilbody, H.B.; Kirkpatrick, M.I.; McDaniel, E.W.; Phaneuf, R.A. (eds.)

    1979-02-01

    This annotated bibliography lists published work on atomic and molecular excitation in heavy particle collisions for the period 1950 to 1975. Sources include scientific journals, abstract compilations, conference proceedings, books, and reports. The bibliography is arranged alphabetically by author. Each entry indicates whether the work was experimental or theoretical, what energy range was covered, and what reactants were investigated. Following the bibliographical listing are indexes of reactions and authors.

  2. Bibliography of atomic and molecular excitation in heavy particle collisions, 1950--1975

    International Nuclear Information System (INIS)

    This annotated bibliography lists published work on atomic and molecular excitation in heavy particle collisions for the period 1950 to 1975. Sources include scientific journals, abstract compilations, conference proceedings, books, and reports. The bibliography is arranged alphabetically by author. Each entry indicates whether the work was experimental or theoretical, what energy range was covered, and what reactants were investigated. Following the bibliographical listing are indexes of reactions and authors

  3. Quantum-mechanical theory including angular momenta analysis of atom-atom collisions in a laser field

    Science.gov (United States)

    Devries, P. L.; George, T. F.

    1978-01-01

    The problem of two atoms colliding in the presence of an intense radiation field, such as that of a laser, is investigated. The radiation field, which couples states of different electronic symmetry, is described by the number state representation while the electronic degrees of freedom (plus spin-orbit interaction) are discussed in terms of a diabatic representation. The total angular momentum of the field-free system and the angular momentum transferred by absorption (or emission) of a photon are explicitly considered in the derivation of the coupled scattering equations. A model calculation is discussed for the Xe + F collision system.

  4. Collisions of low-energy antiprotons and protons with atoms and molecules

    Energy Technology Data Exchange (ETDEWEB)

    Luehr, Armin

    2010-02-18

    Antiproton (anti p) collisions have evolved to a powerful tool for the testing of dynamic electron correlations in atoms and molecules. While advances in the understanding of anti p collisions with the simplest one- and two-electron atoms, H and He, have been achieved experiment and theory did not agree for low-energy anti p+He collisions (<40 keV), stimulating a vivid theoretical activity. On the other hand, only very few theoretical anti p studies can be found considering molecular as well as other atomic targets, in contrast to proton (p) collisions. This is in particular true for anti p impacts on H{sub 2} despite its fundamental role in representing the simplest two-electron molecule. The obtained results may be useful for the anti p experiments at CERN (e.g., antihydrogen production) and in particular for the facility design of low-energy anti p storage rings (e.g., at FLAIR) where a precise knowledge of the anti p interaction with the dominant residual-gas molecule H{sub 2} is needed. In this work a nonperturbative, time-dependent numerical approach is developed which describes ionization and excitation of atoms or molecules by either anti p or p impact based on the impact-parameter method. A spectral close-coupling method is employed for solving the time-dependent Schroedinger equation in which the scattering wave function is expanded in (effective) one- or two-electron eigenstates of the target. This includes for the first time a full two-electron, two-center description of the H{sub 2} molecule in anti p collisions. The radial part of the one-electron eigenstates is expanded in B splines while the two-electron basis is obtained with a configurationinteraction approach. Calculations are performed for anti p collisions with H, H{sub 2}{sup +}, and H{sub 2} as well as with He and alkali-metal atoms Li, Na, K, and Rb. Additionally, data are obtained for p collisions with H{sub 2}, Li, Na, and K. The developed method is tested and validated by detailed

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

    International Nuclear Information System (INIS)

    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.

  6. Application of the refined Born approximation to atom-rigid rotor collision

    International Nuclear Information System (INIS)

    Coupled equations obtained by Arthurs and Dalgarno for the collision of an atom with a rigid rotor have been solved with the help of the refined Born approximation in the case of a helium-atom-hydrogen-molecule scattering problem. An appriopriate choice of the trial function allowed us to find the solution with high accuracy. For several values of energy and several values of total angular-momentum quantum numbers we give the elements of the reactance matrix and partial cross sections. For comparison we also solved the problem by Gordon's numerical procedure. (author)

  7. Chemical reactivity of the compressed noble gas atoms and their reactivity dynamics during collisions with protons

    Indian Academy of Sciences (India)

    P K Chattaraj; B Maiti; U Sarkar

    2003-06-01

    Attempts are made to gain insights into the effect of confinement of noble gas atoms on their various reactivity indices. Systems become harder, less polarizable and difficult to excite as the compression increases. Ionization also causes similar effects. A quantum fluid density functional technique is adopted in order to study the dynamics of reactivity parameters during a collision between protons and He atoms in different electronic states for various projectile velocities and impact parameters. Dynamical variants of the principles of maximum hardness, minimum polarizability and maximum entropy are found to be operative.

  8. Sub-Poissonian atom number fluctuations using light-assisted collisions

    CERN Document Server

    Sortais, Y R P; Bourgain, R; Browaeys, A

    2011-01-01

    We investigate experimentally the number statistics of a mesoscopic ensemble of cold atoms in a microscopic dipole trap, and find that the atom number fluctuations are reduced with respect to a Poisson distribution due to light-assisted two-body collisions. For numbers of atoms larger than 2, we measure a reduction factor (Fano factor) close to 0.75. We analyze this fact by a general stochastic model describing the competition between the loading of the trap from a reservoir of cold atoms and multi-body losses, which leads to a master equation. The model indicates that we have reached the ultimate level of reduction in number fluctuations achievable in our experimental regime.

  9. Van der Waals universality in homonuclear atom-dimer elastic collisions

    CERN Document Server

    Giannakeas, P

    2016-01-01

    The universal aspects of atom-dimer elastic collisions are investigated within the framework of Faddeev equations. The two-body interactions between the neutral atoms are approximated by the separable potential approach. Our analysis considers a pure van der Waals potential tail as well as soft-core van der Waals interactions permitting us in this manner to address the universally general features of atom-dimer resonant spectra. In particular, we show that the atom-dimer resonances are solely associated with the {\\it excited} Efimov states. Furthermore, the positions of the corresponding resonances for a soft-core potentials with more than 5 bound states are in good agreement with the corresponding results from an infinitely deep pure van der Waals tail potential.

  10. On the relativistic and nonrelativistic electron descriptions in high-energy atomic collisions

    Energy Technology Data Exchange (ETDEWEB)

    Voitkiv, A.B [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany)

    2007-07-28

    We consider the relativistic and nonrelativistic descriptions of an atomic electron in collisions with point-like charged projectiles moving at relativistic velocities. We discuss three different forms of the fully relativistic first-order transition amplitude. Using the Schroedinger-Pauli equation to describe the atomic electron we establish the correct form of the nonrelativistic first-order transition amplitude. We also show that the so-called semi-relativistic treatment, in which the Darwin states are used to describe the atomic electron, is in fact fully equivalent to the nonrelativistic consideration. The comparison of results obtained with the relativistic and nonrelativistic electron descriptions shows that the latter is accurate within 20-30% up to Z{sub a}{approx}< 50-60, where Z{sub a} is the atomic nuclear charge.

  11. On the relativistic and nonrelativistic electron descriptions in high-energy atomic collisions

    Science.gov (United States)

    Voitkiv, A. B.

    2007-07-01

    We consider the relativistic and nonrelativistic descriptions of an atomic electron in collisions with point-like charged projectiles moving at relativistic velocities. We discuss three different forms of the fully relativistic first-order transition amplitude. Using the Schrödinger-Pauli equation to describe the atomic electron we establish the correct form of the nonrelativistic first-order transition amplitude. We also show that the so-called semi-relativistic treatment, in which the Darwin states are used to describe the atomic electron, is in fact fully equivalent to the nonrelativistic consideration. The comparison of results obtained with the relativistic and nonrelativistic electron descriptions shows that the latter is accurate within 20-30% up to Za<~ 50-60, where Za is the atomic nuclear charge.

  12. Program of ion-atom collision experiments planned in the frame of the JINR (Dubna) -ATOMKI (Debrecen)

    International Nuclear Information System (INIS)

    The results of earlier ion-atom collision experiments of ATOMKI are described. K and L vacancy production during the collisions are investigated. The program of future experiments at the JINR heavy ion cyclotron is presented. The ion-atom pairs to be collided are given. The construction and parameters of the new family of electrostatic electron spectrometers developed recently for these experiments are described. (D.Gy.)

  13. Fragmentation of neutral carbon clusters formed by high velocity atomic collision

    International Nuclear Information System (INIS)

    The aim of this work is to understand the fragmentation of small neutral carbon clusters formed by high velocity atomic collision on atomic gas. In this experiment, the main way of deexcitation of neutral clusters formed by electron capture with ionic species is the fragmentation. To measure the channels of fragmentation, a new detection tool based on shape analysis of current pulse delivered by semiconductor detectors has been developed. For the first time, all branching ratios of neutral carbon clusters are measured in an unambiguous way for clusters size up to 10 atoms. The measurements have been compared to a statistical model in microcanonical ensemble (Microcanonical Metropolis Monte Carlo). In this model, various structural properties of carbon clusters are required. These data have been calculated with Density Functional Theory (DFT-B3LYP) to find the geometries of the clusters and then with Coupled Clusters (CCSD(T)) formalism to obtain dissociation energies and other quantities needed to compute fragmentation calculations. The experimental branching ratios have been compared to the fragmentation model which has allowed to find an energy distribution deposited in the collision. Finally, specific cluster effect has been found namely a large population of excited states. This behaviour is completely different of the atomic carbon case for which the electron capture in the ground states predominates. (author)

  14. Measurement of the electronic excitation of atoms in atom-molecule collisions near threshold

    International Nuclear Information System (INIS)

    In first part of the paper the measurement of scattering cross sections is described and the energy transfer in molecule-alkali systems is investigated. The influence of translational and vibrational energy could be separated near the excitation threshold. In the second part of the work measurements are reported on the electronic excitation of the work measurements are reported on the electronic excitation of Xe in Xe-Xe-collisions. The experimental data are compared with theoretical calculations. (KBE) 891 KBE/KBE 892 HIS

  15. Will Allis Prize for the Study of Ionized Gases Lecture: Electron and Photon Collisions with Atoms and Molecules

    Science.gov (United States)

    Burke, Philip G.

    2012-06-01

    After a brief historical introduction this talk will review the broad range of collision processes involving electron and photon collisions with atoms and molecules that are now being considered. Their application in the analysis of astronomical spectra, atmospheric observations and laboratory plasmas will be considered. The talk will review the R-matrix computational method which has been widely used by international collaborations and by other scientists in the field to obtain accurate scattering amplitudes and cross sections of importance in these applications. Results of some recent calculations of electron and photon collisions with atoms and molecules will be presented. In conclusion some challenges for future research will be briefly discussed.

  16. A method for the calculation of collision strengths for complex atomic structures based on Slater parameter optimisation

    International Nuclear Information System (INIS)

    This report presents details of a new method to enable the computation of collision strengths for complex ions which is adapted from long established optimisation techniques previously applied to the calculation of atomic structures and oscillator strengths. The procedure involves the adjustment of Slater parameters so that they determine improved energy levels and eigenvectors. They provide a basis for collision strength calculations in ions where ab initio computations break down or result in reducible errors. This application is demonstrated through modifications of the DISTORTED WAVE collision code and SUPERSTRUCTURE atomic-structure code which interface via a transformation code JAJOM which processes their output. (author)

  17. Collisions of low-energy antiprotons and protons with atoms and molecules

    International Nuclear Information System (INIS)

    Antiproton (anti p) collisions have evolved to a powerful tool for the testing of dynamic electron correlations in atoms and molecules. While advances in the understanding of anti p collisions with the simplest one- and two-electron atoms, H and He, have been achieved experiment and theory did not agree for low-energy anti p+He collisions (2 despite its fundamental role in representing the simplest two-electron molecule. The obtained results may be useful for the anti p experiments at CERN (e.g., antihydrogen production) and in particular for the facility design of low-energy anti p storage rings (e.g., at FLAIR) where a precise knowledge of the anti p interaction with the dominant residual-gas molecule H2 is needed. In this work a nonperturbative, time-dependent numerical approach is developed which describes ionization and excitation of atoms or molecules by either anti p or p impact based on the impact-parameter method. A spectral close-coupling method is employed for solving the time-dependent Schroedinger equation in which the scattering wave function is expanded in (effective) one- or two-electron eigenstates of the target. This includes for the first time a full two-electron, two-center description of the H2 molecule in anti p collisions. The radial part of the one-electron eigenstates is expanded in B splines while the two-electron basis is obtained with a configurationinteraction approach. Calculations are performed for anti p collisions with H, H2+, and H2 as well as with He and alkali-metal atoms Li, Na, K, and Rb. Additionally, data are obtained for p collisions with H2, Li, Na, and K. The developed method is tested and validated by detailed comparison of the present findings for p impacts and for anti p+He collisions with literature data. On the other hand, total and differential cross sections for ionization and excitation of the targets by anti p impact complement the sparse literature data of this kind. Results gained from different targets as well

  18. Characteristic X-ray emission in close collisions between heavy ions and atoms

    International Nuclear Information System (INIS)

    In this paper an attempt is given to answer the question of how far the inner-shell vacancy production in very heavy ion-atom collisions is influenced by the electronic configuration of the projectile prepared prior to the collision producing the observed vacancy. The variation of this configuration has been induced by changing the primary charge state of the projectile, the target density and thickness or by inverting the collision system. It turns out from the performed analysis of the experimental data that the excitation of even most strongly bound MO's can be easily dependent on these factors which have been ignored until now, especially in discussions of the 1sσ or 2pσ vacancy production at ZUA > 130. Experiments performed for the first time with gaseous targets for such heavy systems show very convincingly the influence of the outer-shell configuration on the vacancy production in inner shells. The analysis of the data has been performed in terms of electronic transitions among MO's transiently formed during the collision. In many cases a satisfactory agreement between theoretical predictions and experiment has been achieved. (orig./HSI)

  19. Characterization of charge-exchange collisions between ultracold $\\rm{^6Li}$ atoms and $\\rm{^{40}Ca^+}$ ions

    CERN Document Server

    Saito, R; Sasakawa, M; Nakai, R; Raoult, M; Silva, H Da; Dulieu, O; Mukaiyama, T

    2016-01-01

    We investigate the energy dependence and the internal-state dependence of the charge-exchange collision cross sections in a mixture of $^6$Li atoms and $^{40}$Ca$^+$ ions in the collision energy range from 0.2 mK to 1 K. Deliberately excited ion micromotion is used to control the collision energy of atoms and ions. The energy dependence of the charge-exchange collision cross section obeys the Langevin model in the temperature range of the current experiment, and the measured magnitude of the cross section is correlated to the internal state of the $^{40}$Ca$^+$ ions. Revealing the relationship between the charge-exchange collision cross sections and the interaction potentials is an important step toward the realization of the full quantum control of the chemical reactions at an ultralow temperature regime.

  20. Making More-Complex Molecules Using Superthermal Atom/Molecule Collisions

    Science.gov (United States)

    Shortt, Brian; Chutjian, Ara; Orient, Otto

    2008-01-01

    A method of making more-complex molecules from simpler ones has emerged as a by-product of an experimental study in outer-space atom/surface collision physics. The subject of the study was the formation of CO2 molecules as a result of impingement of O atoms at controlled kinetic energies upon cold surfaces onto which CO molecules had been adsorbed. In this study, the O/CO system served as a laboratory model, not only for the formation of CO2 but also for the formation of other compounds through impingement of rapidly moving atoms upon molecules adsorbed on such cold interstellar surfaces as those of dust grains or comets. By contributing to the formation of increasingly complex molecules, including organic ones, this study and related other studies may eventually contribute to understanding of the origins of life.

  1. Technique for measuring the frequency of slow electron collisions with atoms and molecules

    International Nuclear Information System (INIS)

    The described technique was applied for registering the frequency of slow electrons collisions with molecules and atoms of substances. The registering is carried out through superpositioning of crossing high-frequency electrical and adjustable constant magnetic fields over the investigated media, through inserting in this media electrons with the necessary energy and by registering the forms of the curve that characterizes the electron-cyclotron resonance, by which a judgement can be made about the collision frequency. To lower the electrical field frequency, to simplify the apparatus and widen the nomenclature of the investigated substances a stationary flux of electrons is inserted in the investigated media with the help of thermoionic cathode, for example, hence the resonance curve of the electron power reaching the collector is registered. The described technique can be applied for investigating the plasma parameters. (author)

  2. Ion-metal and ion-atom collisions instant replays and mean-field theories

    International Nuclear Information System (INIS)

    In this paper, we describe the results of our general long-term programmatic goal of investigating the strengths and weaknesses of time-dependent mean-field theories for collisions. We have made some progress in: (a) obtaining a better formulation of the theory, which has the exact full Schroedinger equation as one limit and permits appropriate classical treatment of heavy particles correctly coupled to the quantally treated electrons; (b) restructuring our numerical treatment to make it fully three-dimensional, improve accuracy and decrease cycle time, so that larger problems more in keeping with the mean-field concept can be treated; and (c) incorporating the electrons in the conduction band of a metal into our quantal treatment, making possible the description of collisions of atoms and ions with solids. Numerical results for protons tranversing a thin metallic foil, among other examples, are presented and discussed

  3. Computer simulations of atomic collisions in solids with special emphasis on sputtering

    International Nuclear Information System (INIS)

    Computer simulations of atomic collisions in solids are traditionally divided into fully interacting or molecular dynamics (MD) simulations on the one side and simulations based on the binary collision approximation (BCA) on the other. The historical development of both branches is followed and other dichotomies viz. between static and dynamic target models and between models using crystalline and amorphous targets are introduced. The influence of the main input parameters, viz. interatomic potentials, surface- and bulk-binding energies and inelasticity is discussed before selected results are treated. Here, results for non-linear effects, clusters, fluctuations and for angular distributions are presented. The review is concluded with a discussion of the influence of computer developments on future simulations. With 392 refs

  4. Grazing incidence collisions of ions and atoms with surfaces: from charge exchange to atomic diffraction

    International Nuclear Information System (INIS)

    This thesis reports two studies about the interaction with insulating surfaces of keV ions or atoms under grazing incidence. The first part presents a study of charge exchange processes occurring during the interaction of singly charged ions with the surface of NaCl. In particular, by measuring the scattered charge fraction and the energy loss in coincidence with electron emission, the neutralization mechanism is determined for S+, C+, Xe+, H+, O+, Kr+, N+, Ar+, F+, Ne+ and He+. These results show the importance of the double electron capture as neutralization process for ions having too much potential energy for resonant capture and not enough for Auger neutralization. We have also studied the ionisation of the projectile and of the surface, and the different Auger-like neutralization processes resulting in electron emission, population of conduction band or excited state. For oxygen scattering, we have measured an higher electron yield in coincidence with scattered negative ion than with scattered atom suggesting the transient formation above the surface of the oxygen doubly negative ion. The second study deals with the fast atom diffraction, a new phenomenon observed for the first time during this work. Due to the large parallel velocity, the surface appears as a corrugated wall where rows interfere. Similarly to the Thermal Atom Scattering the diffraction pattern corresponds to the surface potential and is sensitive to vibrations. We have study the H-NaCl and He-LiF atom-surface potentials in the 20 meV - 1 eV range. This new method offers interesting perspectives for surface characterisation. (author)

  5. Multichannel quantum-defect theory for ultracold atom-ion collisions

    Science.gov (United States)

    Idziaszek, Zbigniew; Simoni, Andrea; Calarco, Tommaso; Julienne, Paul S.

    2011-08-01

    We develop an analytical model for ultracold atom-ion collisions using the multichannel quantum-defect formalism. The model is based on analytical solutions of the r-4 long-range potential and on the application of a frame transformation between asymptotic and molecular bases. This approach allows the description of atom-ion interaction in the ultracold domain in terms of only three parameters: the singlet and triplet scattering lengths, assumed to be independent of the relative motion angular momentum, and the lead dispersion coefficient of the asymptotic potential. We also introduce corrections to the scattering lengths that improve the accuracy of our quantum-defect model for higher-order partial waves, a particularly important result for an accurate description of shape and Feshbach resonances at finite temperature. The theory is applied to the system composed of a 40Ca+ ion and a Na atom, and compared with numerical coupled-channel calculations carried out using ab initio potentials. For this particular system, we investigate the spectrum of bound states, the rate of charge-transfer processes and the collision rates in the presence of magnetic Feshbach resonances at zero and finite temperature.

  6. Multichannel quantum-defect theory for ultracold atom-ion collisions

    Energy Technology Data Exchange (ETDEWEB)

    Idziaszek, Zbigniew [Faculty of Physics, University of Warsaw, 00-681 Warsaw (Poland); Simoni, Andrea [Institut de Physique de Rennes, UMR 6251 du CNRS and Universite de Rennes 1, 35042 Rennes Cedex (France); Calarco, Tommaso [Institute of Quantum Information Processing, University of Ulm, D-89069 Ulm (Germany); Julienne, Paul S, E-mail: idziaszek@fuw.edu.pl [Joint Quantum Institute, NIST and the University of Maryland, Gaithersburg, MD 20899-8423 (United States)

    2011-08-15

    We develop an analytical model for ultracold atom-ion collisions using the multichannel quantum-defect formalism. The model is based on analytical solutions of the r{sup -4} long-range potential and on the application of a frame transformation between asymptotic and molecular bases. This approach allows the description of atom-ion interaction in the ultracold domain in terms of only three parameters: the singlet and triplet scattering lengths, assumed to be independent of the relative motion angular momentum, and the lead dispersion coefficient of the asymptotic potential. We also introduce corrections to the scattering lengths that improve the accuracy of our quantum-defect model for higher-order partial waves, a particularly important result for an accurate description of shape and Feshbach resonances at finite temperature. The theory is applied to the system composed of a {sup 40}Ca{sup +} ion and a Na atom, and compared with numerical coupled-channel calculations carried out using ab initio potentials. For this particular system, we investigate the spectrum of bound states, the rate of charge-transfer processes and the collision rates in the presence of magnetic Feshbach resonances at zero and finite temperature.

  7. Collisions at thermal energy between metastable hydrogen atoms and hydrogen molecules: total and differential cross sections

    Science.gov (United States)

    Vassilev, G.; Perales, F.; Miniatura, Ch.; Robert, J.; Reinhardt, J.; Vecchiocattivi, F.; Baudon, J.

    1990-06-01

    A metastable hydrogen (deuterium) atom source in which groundstate atoms produced by a RF discharge dissociator are bombarded by electrons, provides a relatively large amount of slow metastable atoms (velocity 3 5 km/s). Total integral cross sections for H*(D*)(2 s) + H2( X 1Σ{g/+}, v=0) collisions have been measured in a wide range of relative velocity (2,5 30 km/s), by using the attenuation method. A significant improvement of accuracy is obtained, with respect to previous measurements, at low relative velocities. Total cross sections for H* and D*, as functions of the relative velocity, are different, especially in the low velocity range. H* + H2 total differential cross sections have also been measured, with an angular spread of 3.6°, for two different collision energy distributions, centered respectively at 100 meV and 390 meV. A first attempt of theoretical analysis of the cross sections, by means of an optical potential, is presented.

  8. Cold collisions of an open-shell S-state atom with a (2)Pi molecule : N(S-4) colliding with OH in a magnetic field.

    OpenAIRE

    Skomorowski, Wojciech; Gonzalez-Martinez, Maykel L.; Moszynski, Robert; Hutson, Jeremy M.

    2011-01-01

    We present quantum-theoretical studies of collisions between an open-shell S-state atom and a ^2Pi-state molecule in the presence of a magnetic field. We analyze the collisional Hamiltonian and discuss possible mechanisms for inelastic collisions in such systems. The theory is applied to the collisions of the nitrogen atom (^4S) with the OH molecule, with both collision partners initially in fully spin-stretched (magnetically trappable) states, assuming that the interaction takes place exclus...

  9. Scattering of NH3 and ND3 with rare gas atoms at low collision energy

    Science.gov (United States)

    Loreau, J.; van der Avoird, A.

    2015-11-01

    We present a theoretical study of elastic and rotationally inelastic collisions of NH3 and ND3 with rare gas atoms (He, Ne, Ar, Kr, Xe) at low energy. Quantum close-coupling calculations have been performed for energies between 0.001 and 300 cm-1. We focus on collisions in which NH3 is initially in the upper state of the inversion doublet with j = 1, k = 1, which is the most relevant in an experimental context as it can be trapped electrostatically and Stark-decelerated. We discuss the presence of resonances in the elastic and inelastic cross sections, as well as the trends in the inelastic cross sections along the rare gas series and the differences between NH3 and ND3 as a colliding partner. We also demonstrate the importance of explicitly taking into account the umbrella (inversion) motion of NH3 in order to obtain accurate scattering cross sections at low collision energy. Finally, we investigate the possibility of sympathetic cooling of ammonia using cold or ultracold rare gas atoms. We show that some systems exhibit a large ratio of elastic to inelastic cross sections in the cold regime, which is promising for sympathetic cooling experiments. The close-coupling calculations are based on previously reported ab initio potential energy surfaces for NH3-He and NH3-Ar, as well as on new, four-dimensional, potential energy surfaces for the interaction of ammonia with Ne, Kr, and Xe, which were computed using the coupled-cluster method and large basis sets. We compare the properties of the potential energy surfaces corresponding to the interaction of ammonia with the various rare gas atoms.

  10. δ-electron spectroscopy and the atomic clock effect in heavy-ion collisions

    International Nuclear Information System (INIS)

    The properties of strongly bound electrons in superheavy quasimolecular systems with combined nuclear charge numbers Z = ZP + ZT ≥ 110 are investigated. The emission of δ-electrons may serve as an atomic clock for nuclear reactions which is associated with the large overlap of the electron probability density with the nuclear interior. Excitation and emission rates of inner-shell electrons in collisions of very heavy ions with beam energies at or above the nuclear Coulomb barrier depend explicitly on details of the nuclear dynamics. Theoretical and experimental results are reviewed. (orig.)

  11. Spin-Exchange Collisions of the Ground State of Cs Atoms in a High Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    FU Li-Ping; LUO Jun; ZENG Xi-Zhi

    2000-01-01

    Cs atoms were optically pumped with a Ti:sapphire laser in a magnetic field of 1.516 T. Steady absorption spectra and populations of Zeeman sublevels of the ground state of Cs in N2 gas at various pressures (5, 40, and 80 Torr)were obtained. The results show that in a high magnetic field, the combined electron-nuclear spin transition(flip-flop transition), which is mainly induced by the collision modification δa( J.I)of hyperfine interaction, is an important relaxation mechanism at high buffer-gas pressures.

  12. Charge transfer in keV proton collision with atomic oxygen: Differential and total cross sections

    International Nuclear Information System (INIS)

    Classical Trajectory Monte Carlo method (CTMC) with the modal interaction potential has been used to simulate the differential, total and partial capture cross sections in proton-oxygen atom collisions in the energy range of 0.5 - 200 keV. An interesting feature of the calculated differential cross sections (DCS) curve below the scattering angle 0.1 degree is the presence of oscillations showing asymmetry in angular positions. The oscillations in the partial cross sections are explained in terms of swapping effect. The DCS and total cross sections are found to be in good agreement with the experimental as well as other theoretical results. (authors)

  13. Projectile X-ray emission in relativistic ion-atom collisions

    OpenAIRE

    Salem, Shadi

    2010-01-01

    This work reports on the study of the projectile x-ray emission in relativistic ion-atom collisions. Excitation of K-shell in He-like uranium ions, electron capture into H-like uranium ions and Simultaneous ionization and excitation of initially He-like uranium ions have been studied using the experimental storage ring at GSI. Information about the population of the excited states for the H- and He-like uranium ions, can be obtained by measuring the angular distribution of the decay radiation...

  14. Polarization effects in metastable neon atom (Ne* ( 3P 2)) on ground state neon atom collision at thermal energy

    Science.gov (United States)

    Baudon, J.; Perales, F.; Miniatura, Ch.; Robert, J.; Vassilev, G.; Reinhardt, J.; Haberland, H.

    1990-08-01

    The difference Δ between the differential cross section for Ne*( 3P 2 atoms polarized either in state | j=2, m=+2 > or | j=2, m=-2 >, colliding at thermal energy with a groundstate target (Ne,O 2), is measured. In the symmetric case Ne*-Ne, direct and exchange contribution are observed. General properties of Δ, derived from symmetry considerations, are established; in particular: (i) the interference character of Δ, (ii) the role played by the azimuthal dependence of the scattering amplitudes, (iii) the property Δ(0) = Δ(180°)=0. The relationship between the Fourier harmonics introduced in this discussion and the scattering amplitudes used in standard collision treatments are given.

  15. Theory of phonon inelastic atom--surface scattering. I. Quantum mechanical treatment of collision dynamics

    International Nuclear Information System (INIS)

    We present a systematic formulation of the atom--surface scattering dynamics which includes the vibrational states of the atoms in the solid (phonons). The properties of the total scattering wave function of the system, a representation of the interaction potential matrix, and the characteristics of the independent physical solutions are all derived from the translational invariance of the full Hamiltonian. The scattering equations in the integral forms as well as the related Green functions were also obtained. The configurational representations of the Green functions, in particular, are quite different from those of the conventional scattering theory where the collision partners are spatially localized. Various versions of the integral expression of scattering, transition, and reactance matrices were also obtained. They are useful for introducing approximation schemes. From the present formulation, some specific theoretical schemes which are more realistic compared to those that have been employed so far and at the same time capable of yielding effective ab initio computation are derived in the following paper. The time reversal invariance and the microscopic reversibility of the atom--surface scattering were discussed. The relations between the in and outgoing scattering wave functions which are satisfied in the atom--surface system and important in the transition matrix methods were presented. The phonon annihilation and creation, and the adsorption and desorption of the atom are related through the time reversal invariance, and thus the microscopic reversibility can be tested by the experiment

  16. A unified numerical model of collisional depolarization and broadening rates due to hydrogen atom collisions

    CERN Document Server

    Derouich, M; Barklem, P S

    2015-01-01

    Interpretation of solar polarization spectra accounting for partial or complete frequency redistribution requires data on various collisional processes. Data for depolarization and polarization transfer are needed but often missing, while data for collisional broadening are usually more readily available. Recent work by Sahal-Br\\'echot and Bommier concluded that despite underlying similarities in the physics of collisional broadening and depolarization processes, relationships between them are not possible to derive purely analytically. We aim to derive accurate numerical relationships between the collisional broadening rates and the collisional depolarization and polarization transfer rates due to hydrogen atom collisions. Such relationships would enable accurate and efficient estimation of collisional data for solar applications. Using earlier results for broadening and depolarization processes based on general (i.e. not specific to a given atom), semi-classical calculations employing interaction potentials...

  17. Model study of collision induced dissociation of a diatomic molecule by an atom

    International Nuclear Information System (INIS)

    The time-dependent Schroedinger equation for the collinear collision of an atom with a diatomic molecule is solved numerically after the manner of McCullough and Wyatt. The binding potential is taken to be a truncated square well and the interaction is impulsive (hard sphere). For the case in which all three masses are equal final relative momentum distributions and dissociation probabilities are obtained as a function of both the initial relative kinetic energy and the initial vibrational level. For purposes of comparison quasiclassical trajectory analyses of the same cases were performed. Quantum effects on collision-induced dissociation (CID) are seen to be important for this model. A very notable characteristic of the model, observed in both the quantum and classical results, yet not in most experimental results, is that CID is severely vibrationally inhibited, i.e., the probability of CID decreases as the initial vibrational quantum number increases at a fixed total collision energy. Probable causes of this strong vibrational inhibition are examined classically by a detailed trajectory analysis. It is concluded that the collinearity of the model is most likely responsible

  18. Orbital-angular-momentum change in sodium Rydbery atoms induced by collisions with slow ions

    Energy Technology Data Exchange (ETDEWEB)

    Smith, D.B.

    1987-01-01

    This dissertation describes the experimental measurement of angular-momentum change in sodium Rydberg-state atoms induced by collisions with slow Na/sup +/ ions. For these measurements an existing crossed-beam apparatus was modified by the addition of two ion sources, one a thermionic emitter, the other a duoplasmatron. In the experiments, Na atoms were laser-excited to Rydberg nd-levels (principal quantum numbers n = 21 to 29) and were exposed to a Na/sup +/ ion beam (energies 29 to 590 eV from the thermionic emitter) in a crossed-beam experiment. A method was devised for a direct measurement of the ion-beam current density in the interaction region. During an interaction time of approximately 3 ..mu..sec, collisions occurred in which the initial orbital-angular-momentum l was increased by an amount ..delta..l greater than or equal to 1. The distribution of final nl states was analyzed by selective field ionization (SFI). The cross section was measured as a function of velocity in the region v = 0.2 to 0.7, where the reduced velocity v is the ratio of incident-ion and orbital-electron velocities.

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

    Science.gov (United States)

    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.

  20. Anisotropy and linear polarization of radiative processes in energetic ion-atom collisions

    International Nuclear Information System (INIS)

    In the present thesis the linear polarization of radiation emitted in energetic ion-atom collisions at the ESR storage ring was measured by applying a novel type of position, timing and energy sensitive X-ray detector as a Compton polarimeter. In contrast to previous measurements, that mainly concentrate on studies of the spectral and angular distribution, the new detectors allowed the first polarization study of the Ly-α1 radiation (2p3/2→1s1/2) in U91+. Owing to the high precision of the polarimeters applied here, the experimental results indicate a significant depolarization of the Ly-α1 radiation caused by the interference of the E1 and M2 transition branches. Moreover, the current investigation shows that measurements of the linear polarization in combination with angular distribution studies provide a model-independent probe for the ratio of the E1 and M2 transition amplitudes and, consequently, of the corresponding transition probabilities. In addition, a first measurement of the linear polarization as well as an angular distribution study of the electron-nucleus Bremsstrahlung arising from ion-atom collisions was performed. The experimental results obtained were compared to exact relativistic calculations and, in case of the Bremsstrahlung, to a semirelativistic treatment. In general, good agreement was found between theoretical predictions and experimental findings. (orig.)

  1. Sign of the state-to-state steric asymmetry of rotationally inelastic atom-molecule collisions

    International Nuclear Information System (INIS)

    The sign of the theoretically predicted steric asymmetry S in rotational inelastic state resolved molecule-atom collisions is questioned. It is shown that the sign of the T-matrix obtained on a basis of non-oriented rotational states of the molecule depends on the choice of the Jacobi coordinates in which the collision problem is solved. Explicit expressions for the state-to-state dependence of the integral and differential cross-sections for oriented and non-oriented molecules are presented. The effect of the choice of Jacobi angles and the inertial frame of reference on the sign of S are discussed in detail. The sign of the earliest obtained expression for the steric asymmetry of the integral cross-section (as reported by van Leuken et al.) is found to be correct, whereas that of the orientational-dependent contribution of the differential cross-section (as reported by Alexander and Stolte) requires a negative multiplication factor. Quantum mechanical calculations on collisions of OH with Ar are performed. These calculations do not agree with the experimental sign of S and cannot be interpreted in terms of a simple ball and stick model. Inspection of the HIBRIDON source code shows that the prepared wavefunction carries an orientation that is opposite to the one assumed. This could offer an explanation for the disagreement for S. For collisions of NO with Ar, the signs of the quantum mechanically calculated and the experimental values of S appear to disagree with the simple ball and stick model. The experimental sign of S has been reinvestigated. Previous experimental results are confirmed

  2. Multicharged ions and experimental tests of multiple scattering effects in atomic collision at middle and high impact velocity

    International Nuclear Information System (INIS)

    The bare heavy ions or one electron ions Fesup(26+,25+), Krsup(36+,35+), Usup(92+,91+) given by the new accelerators of nuclear physics constitute a privilegiated tool in atom collision study because they allow for the first time to realize pure three-body problems. For many years, development of experiments using multicharged heavy ions and multiple scattering have greatly improved our high velocity collision phenomena understanding and our ability to realize quantitative predictions

  3. An investigation of a possible molecular effect in ion atom collision using a gaseous argon target

    International Nuclear Information System (INIS)

    The present work deals with an investigation of the molecular effect, which is defined as the difference in experimental results using isotachic atomic ion and molecular ion beams in ion atom collisions. Previous studies have dealt almost exclusively with total cross section measurements. This thesis explores the idea that the molecular effect may be more pronounced in the differential ionization probability of the target atoms. Also, a gaseous argon target of sufficiently low density was used in order to ensure that the two correlated protons in the H+2 beam did not interact with two adjacent target atoms simultaneously. The author reports that, contrary to the expectations noted above, the molecular effect in the K shell differential ionization probability of argon for scattering angles up to 90 degrees appears to be no more than the molecular effect in the total ionization probability. The uncertainty in the results is statistical in nature and can be improved upon by running the experiment for a longer duration of time

  4. Atomic collision studies at moderate projectile velocities using highly charged, decelerated heavy ions from the GSI-UNILAC

    International Nuclear Information System (INIS)

    Beams of highly ionized, very heavy atoms at moderate velocities have been produced at the UNILAC using the acceleration-stripping-deceleration method. The available ion species range from Kr33+ to U66+ in the energy region between 2 and 5 MeV/u. A survey on first experiments at GSI using these moderate velocity, few electron, heavy ion beams is given. The effectiveness of the method is demonstrated for Xesup(q+)-Xe collision experiments with 41 <= q <= 45. Results on vacancy transfer between inner quasimolecular levels for close collisions, and on distant collision electron capture are reported. (orig.)

  5. Application of an electro-optical modulator in inelastic collision studies with laser-excited Na*(3p) atoms

    International Nuclear Information System (INIS)

    In atomic collision experiments with laser-excited target atoms it is often desirable to maximize the fraction f* of excited atoms. In the case of Na atoms pumped by a single mode CW dye laser radiation several effects including hyperfine pumping limit f* to about 10%. Using two side-bands of laser radiation, produced by means of an electro-optical modulator (phase modulation of laser radiation by a LiTaO3 crystal in a microwave field) transitions from both hyperfine ground states of Na can be pumped simultaneously. In this way a significant increase of the fraction of excited Na atoms in the 32P states to typically 30% could be achieved. The advantage of using an electro-optical modulator is demonstrated for the case of state-selective single electron capture studies of the He2+-Na*(3p) collision system. (author)

  6. On the calculation of cross-sections for electron neutral atom collisions in the Born approximation to the reactance matrix

    International Nuclear Information System (INIS)

    Born partial wave integrals are considered for electron-neutral atom collisions. It is shown that for relatively general atomic wave functions these may be evaluated analytically. These form the Born reactance matrix Rsub(B) and can be used to calculate the collision strengths in the approximations Ωsup(I), Ωsup(II). It is shown how to modify Ωsup(I) to take some account of exchange using the simple Ochkur approximation. A result is presented for the coupling coefficients that occur in Seaton's multiplication theorem for spherical Bessel functions. (author)

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

    Science.gov (United States)

    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

  8. Excitation and charge transfer in low-energy hydrogen-atom collisions with neutral atoms: Theory, comparisons, and application to Ca

    Science.gov (United States)

    Barklem, Paul S.

    2016-04-01

    A theoretical method is presented for the estimation of cross sections and rates for excitation and charge-transfer processes in low-energy hydrogen-atom collisions with neutral atoms, based on an asymptotic two-electron model of ionic-covalent interactions in the neutral atom-hydrogen-atom system. The calculation of potentials and nonadiabatic radial couplings using the method is demonstrated. The potentials are used together with the multichannel Landau-Zener model to calculate cross sections and rate coefficients. The main feature of the method is that it employs asymptotically exact atomic wave functions, which can be determined from known atomic parameters. The method is applied to Li+H , Na+H , and Mg+H collisions, and the results compare well with existing detailed full-quantum calculations. The method is applied to the astrophysically important problem of Ca+H collisions, and rate coefficients are calculated for temperatures in the range 1000-20 000 K.

  9. The Kansas State atomic collision physics facility dedicated to the studies of atomic interactions of highly charged, low and medium energy ions

    International Nuclear Information System (INIS)

    We discuss our facility at Kansas State University, which is perfectly suited for studies of atomic collisions involving highly charged, low and medium energy ions. It should be fully operational by next year and will be operated as a user facility. We encourage collaborations with in-house researchers, because it facilitates communications and experiments. 13 refs., 3 figs

  10. Multichannel quantum-defect theory for ultracold atom-ion collisions

    CERN Document Server

    Idziaszek, Zbigniew; Calarco, Tommaso; Julienne, Paul S

    2011-01-01

    We develop an analytical model for ultracold atom-ion collisions using the multichannel quantum-defect formalism. The model is based on the analytical solutions of the r^-4 long-range potential and on the application of a frame transformation between asymptotic and molecular bases. This approach allows the description of the atom-ion interaction in the ultracold domain in terms of three parameters only: the singlet and triplet scattering lengths, assumed to be independent of the relative motion angular momentum, and the lead dispersion coefficient of the asymptotic potential. We also introduce corrections to the scattering lengths that improve the accuracy of our quantum-defect model for higher order partial waves, a particularly important result for an accurate description of shape and Feshbach resonances at finite temperature. The theory is applied to the system composed of a 40Ca+ ion and a Na atom, and compared to numerical coupled-channel calculations carried out using ab initio potentials. For this part...

  11. NATO Advanced Study Institute on Topics in Atomic and Nuclear Collisions

    CERN Document Server

    Rémaud, B; Zoran, V

    1994-01-01

    The ASI 'Topics in Atomic and Nuclear Collisions' was organized in Predeal from August 31 to September 11. It brought together people with a broad interest in Atomic and Nuclear Physics from several research institutes and universities in Ro­ mania and 16 other countries. The school continues a tradition that started on a small scale back in 1968, fo­ cussing mainly on current problems in nuclear physics. Though the organizing of this edition started very late and in very uncertain economic and financial conditions, it turned out to be the largest meeting of this type ever organized in Romania, both in topics and participation. There were many applicants for participation and grants, considerably more than could be handled. The selection made by the local organizing committee was based on the following criteria: a proper balance of atomic and nuclear physicists, a broad representation of people from Research Institutes and Universities, a balanced par­ ticipat!on with respect to age, sex, nationali...

  12. 2nd International Symposium "Atomic Cluster Collisions : Structure and Dynamics from the Nuclear to the Biological Scale"

    CERN Document Server

    Solov'yov, Andrey; ISACC 2007; Latest advances in atomic cluster collisions

    2008-01-01

    This book presents a 'snapshot' of the most recent and significant advances in the field of cluster physics. It is a comprehensive review based on contributions by the participants of the 2nd International Symposium on Atomic Cluster Collisions (ISACC 2007) held in July 19-23, 2007 at GSI, Darmstadt, Germany. The purpose of the Symposium is to promote the growth and exchange of scientific information on the structure and properties of nuclear, atomic, molecular, biological and complex cluster systems studied by means of photonic, electronic, heavy particle and atomic collisions. Particular attention is devoted to dynamic phenomena, many-body effects taking place in cluster systems of a different nature - these include problems of fusion and fission, fragmentation, collective electron excitations, phase transitions, etc.Both the experimental and theoretical aspects of cluster physics, uniquely placed between nuclear physics on the one hand and atomic, molecular and solid state physics on the other, are discuss...

  13. Rovibrationally Inelastic Atom-Molecule Collision Cross Sections from a Hard Sphere Model

    Science.gov (United States)

    Lashner, Jacob; Stewart, Brian

    2016-05-01

    Hard-shell models have long been used to elucidate the principal features of molecular energy transfer and exchange reaction in the A + BC system. Nevertheless, no three-dimensional hard-shell calculation of inelastic collision cross sections has been reported. This work aims to fill that void. A particular motivation comes from our experimental results, which show the importance of equatorial impacts in the vibrational excitation process. Working with the simple hard-sphere model, we incorporated secondary impacts, defined as those in which A strikes C after striking B. Such collisions are important in systems such as Li2 - X, in which vibrational energy transfer occurs principally through side impacts. We discuss the complexity this adds to the model and present fully three-dimensional cross sections for rovibrational excitation of an initially stationary molecule in the homonuclear A + B2 system, examining the cross section as a function of the masses and radii of the atoms. We show how the features in the cross section evolve as these parameters are varied and calculate the contribution of secondary (near-equatorial) impacts to the dynamics. We compare with recent measurements in our laboratory and with the results of quasiclassical trajectories.

  14. Atoms, molecules and optical physics 2. Molecules and photons - Spectroscopy and collisions

    Energy Technology Data Exchange (ETDEWEB)

    Hertel, Ingolf V.; Schulz, Claus-Peter [Max-Born-Institut fuer Nichtlineare Optik und Kurzzeitspektroskopie im Forschungsverbund Berlin e.V. (Germany)

    2015-09-01

    This is the second volume of textbooks on atomic, molecular and optical physics, aiming at a comprehensive presentation of this highly productive branch of modern physics as an indispensable basis for many areas in physics and chemistry as well as in state of the art bio- and material-sciences. It primarily addresses advanced students (including PhD students), but in a number of selected subject areas the reader is lead up to the frontiers of present research. Thus even the active scientist is addressed. This volume 2 introduces lasers and quantum optics, while the main focus is on the structure of molecules and their spectroscopy, as well as on collision physics as the continuum counterpart to bound molecular states. The emphasis is always on the experiment and its interpretation, while the necessary theory is introduced from this perspective in a compact and occasionally somewhat heuristic manner, easy to follow even for beginners.

  15. Recent theoretical studies of slow collisions between plasma impurity ions and H or He atoms

    Energy Technology Data Exchange (ETDEWEB)

    Fritsch, W. [Hahn-Meitner-Institut Berlin GmbH (Germany). Bereich Theoretische Physik; Tawara, H.

    1997-01-01

    We review recent progress in theoretical studies of slow collisions between light plasma impurity ions and atomic hydrogen or helium. We start with a brief overview of theory work that has been done by various groups in the past. We then proceed to discuss work that is published in the last two years. For the systems of Be{sup 2+}-He, Be{sup 4+}-He and C{sup 5+}-He we present yet unpublished work of our own. All of this work broadens our knowledge about systems that are of interest for the fusion community. Some of the new information is found to be at variance with what is known from other sources and hence needs further analysis. (author)

  16. Proceedings of the 2nd joint seminar on atomic collisions and heavy ion induced nuclear reactions

    International Nuclear Information System (INIS)

    The meeting of the 2nd joint seminar on atomic collisions and heavy ion induced nuclear reactions was held at the University of Tokyo, May 13 and 14, 1982. The aim of this seminar has been not only to recognize the common problems lying between above two research fields, but also to obtain an overview of the theoretical and experimental approaches to clear the current problems. In the seminar, more than 50 participants gathered and presented 16 papers. These are two general reviews and fourteen comprehensive surveys on topical subjects which have been developed very intensively in recent years. The editors would like to thank all participants for their assistance and cooperation in making possible a publication of these proceedings. (author)

  17. Fast low-rank approximations of multidimensional integrals in ion-atomic collisions modelling

    CERN Document Server

    Litsarev, M S

    2015-01-01

    An efficient technique based on low-rank separated approximations is proposed for computation of three-dimensional integrals arising in the energy deposition model that describes ion-atomic collisions. Direct tensor-product quadrature requires grids of size $4000^3$ which is unacceptable. Moreover, several of such integrals have to be computed simultaneously for different values of parameters. To reduce the complexity, we use the structure of the integrand and apply numerical linear algebra techniques for the construction of low-rank approximation. The resulting algorithm is $10^3$ faster than spectral quadratures in spherical coordinates used in the original DEPOSIT code. The approach can be generalized to other multidimensional problems in physics.

  18. Charge transfer and ionization in proton-alkali atoms collisions with and without electric field

    International Nuclear Information System (INIS)

    The classical trajectory Monte Carlo simulation has been used to investigate the collisions of protons with alkali metal atoms in their ground state. Model interaction potential has been used to describe the electron-ionic core interaction. The cross sections for the capture and ionization in the energy range 1-100 keV/amu have been calculated and compared with the available experimental and theoretical results. The effects of the presence of a strong static electric field in different geometrical features on the capture and ionization cross sections have also been investigated. It has been found that the electric field causes the cross section for the capture to decrease while for the ionization enhance dramatically. Many of the null field features are retained. The analyses of the final state n, l-distribution in the electron capture process reveals H(2p) to be the most populated level in both the cases, with and without electric field. (author)

  19. Many-electron stripping in collisions between atoms and heavy ions

    International Nuclear Information System (INIS)

    Recent experiments suggest that a highly stripped ion can remove up to 10 electrons in a single collision with a neutral atom or molecule. It is shown that this process can take place through the coherent superposition of the heavy ion's electric field at different times, in a way analogous to multiphoton ionisation by intense radiation fields. For relatively fast ions, a simple theory is developed and results are presented for a variety of cases. The theory is in reasonable agreement with measured cross sections for 1s-vacancy production in Ne by Clsup(z+) ions at 50 MeV (2 02 for effective charges 10 7+ (1s2s2p 4P) may be as large as 0.1 πa02. The dependence of these cross sections on energy is complicated but their variation with Z at a fixed energy is usually rather gentle. (author)

  20. Atoms, molecules and optical physics 2. Molecules and photons - Spectroscopy and collisions

    International Nuclear Information System (INIS)

    This is the second volume of textbooks on atomic, molecular and optical physics, aiming at a comprehensive presentation of this highly productive branch of modern physics as an indispensable basis for many areas in physics and chemistry as well as in state of the art bio- and material-sciences. It primarily addresses advanced students (including PhD students), but in a number of selected subject areas the reader is lead up to the frontiers of present research. Thus even the active scientist is addressed. This volume 2 introduces lasers and quantum optics, while the main focus is on the structure of molecules and their spectroscopy, as well as on collision physics as the continuum counterpart to bound molecular states. The emphasis is always on the experiment and its interpretation, while the necessary theory is introduced from this perspective in a compact and occasionally somewhat heuristic manner, easy to follow even for beginners.

  1. Cold collisions of polyatomic molecular radicals with S-state atoms in a magnetic field: An ab initio study of He + CH2(X) collisions

    OpenAIRE

    Tscherbul, T.V.; Grinev, T. A.; Yu, H.-G.; Dalgarno, A.; Klos, Jacek; Ma, Lifang; Alexander, Millard H.

    2012-01-01

    We develop a rigorous quantum mechanical theory for collisions of polyatomic molecular radicals with S-state atoms in the presence of an external magnetic field. The theory is based on a fully uncoupled space-fixed basis set representation of the multichannel scattering wavefunction. Explicit expressions are presented for the matrix elements of the scattering Hamiltonian for spin-1/2 and spin-1 polyatomic molecular radicals interacting with structureless targets. The theory is applied to calc...

  2. Magneto optical trap recoil ion momentum spectroscopy: application to ion-atom collisions

    International Nuclear Information System (INIS)

    87Rb atoms have been cooled, trapped and prepared as targets for collision studies with 2 and 5 keV Na+ projectiles. The physics studied deals with charge exchange processes. The active electron, which is generally the most peripheral electron of the atomic target, is transferred from the target onto the ionic projectile. The ionized target is called recoil ion. The technique used to study this physics is the MOTRIMS (Magneto Optical Trap Recoil Ion Momentum Spectroscopy) technique, which combines a magneto optical trap and a recoil ion momentum spectrometer. The spectrometer is used for the measurement of the recoil ions momentum, which gives access to all the information of the collision: the Q-value (which is the potential energy difference of the active electron on each particle) and the scattering angle of the projectile. The trap provides extremely cold targets to optimize the measurement of the momentum, and to release the latter from thermal motion. Through cinematically complete experiments, the MOTRIMS technique gives access to better resolutions on momentum measurements. Measurements of differential cross sections in initial and final capture states and in scattering angle have been done. Results obtained for differential cross sections in initial and final states show globally a good agreement with theory and an other experiment. Nevertheless, discrepancies with theory and this other experiment are shown for the measurements of doubly differential cross sections. These discrepancies are not understood yet. The particularity of the experimental setup designed and tested in this work, namely a low background noise, allows a great sensitivity to weak capture channels, and brings a technical and scientific gain compared with previous works. (author)

  3. Cold collisions of polyatomic molecular radicals with S-state atoms in a magnetic field: An ab initio study of He + CH2(X) collisions

    CERN Document Server

    Tscherbul, T V; Yu, H -G; Dalgarno, A; Klos, Jacek; Ma, Lifang; Alexander, Millard H; 10.1063/1.4748258

    2012-01-01

    We develop a rigorous quantum mechanical theory for collisions of polyatomic molecular radicals with S-state atoms in the presence of an external magnetic field. The theory is based on a fully uncoupled space-fixed basis set representation of the multichannel scattering wavefunction. Explicit expressions are presented for the matrix elements of the scattering Hamiltonian for spin-1/2 and spin-1 polyatomic molecular radicals interacting with structureless targets. The theory is applied to calculate the cross sections and thermal rate constants for spin relaxation in low-temperature collisions of the prototypical organic molecule methylene [CH2(X)] with He atoms. To this end, two highly accurate three-dimensional potential energy surfaces (PESs) of the He-CH2(X) complex are developed using the state-of-the-art CCSD(T) method and large basis sets. Both PESs exhibit shallow minima and are weakly anisotropic. Our calculations show that spin relaxation in collisions of CH2, CHD, and CD2 molecules with He atoms occu...

  4. The anisotropy of molecular X-rays produced in heavy-ion-atom collisions

    International Nuclear Information System (INIS)

    A photon energy dependent anisotropy of the molecular X-rays produced in quasiadiabatic heavy-ion-atom-collisions was predicted and observed by several authors. These and some additional new results can prove the molecular origin of this effect. The experimental data for six symmetric systems (Al-Al, Ca-Ca, Fe-Fe, Ni-Ni, Ag-Ag, I-I) and five asymmetric cases (Cl-Ni, Fe-Ni, Ni-Fe, Ag-I, I-Ag) at different beam energies in the range of 20 to 62.5 MeV give a check of the Z2-scaling not only for KX-rays but also for L- and M anisotropy peaks. The positions of the bumps are all as expected clearly above the united atom limit. They are independent of the beam energy. Some models to describe the anisotropy phenomena are discussed. A new striking feature was found with the fine structure of the X-ray anisotropies. These periodic intensity fluctuations appear if the evaluation is performed with sufficiently good energy resolution. There is an evidence, that the anisotropy effect can be used to perform spectroscopy of arbitrary two-centre levels. However caution is required if one is to apply these ideas to the spectroscopy of superheavy systems. (MKO)

  5. Cross section database for collision processes of helium atom with charged particles. 1. Electron impact processes

    International Nuclear Information System (INIS)

    A comprehensive and critically assessed cross section database for the inelastic collision processes of ground state and excited helium atoms colliding with electrons, protons and multiply-charged ions has been prepared at the Data and Planning Center at NIFS. The present report describes the first part of the database containing the recommended data for electron impact excitation and ionization of neutral helium. An states (atomic terms) with n ≤ 4 are treated individually while the states with n > 4 are considered degenerate. For the processes involving transitions to and from n > 4 levels, suitable cross section scaling relations are presented. For a large number of electron impact transitions, both from the ground and excited states, new convergent close coupling (CCC) calculations were performed to achieve a high accuracy of the data. The evaluated/recommended cross section data are presented by analytic fit functions which preserve the correct asymptotic behavior of the cross sections. The cross sections are also displayed in a graphical form. (author)

  6. The effect of van der Waals forces in two-atomic elastic collision

    CERN Document Server

    Ray, Hasi

    2013-01-01

    The effect of van der Waals interaction on two-atomic collision is studied for elastic scattering at colder energies. A modified static exchange model (MSEM) is used to determine the s-wave elastic phase shift and the corresponding amplitude square. The model includes the effect of dipole-dipole long-range van der Waals interaction in addition to the short-range electron-exchange force. Both are stronger at colder energies. The effective range theory is used to determine the scattering lengths and effective ranges. A system containing one positronium and one hydrogen e.g. the Ps-H system is chosen for the present study since both Ps and H are ideal atoms having only one electron; at the same time Ps is light so that the convergence in partial wave analysis is easier and it has a very high polarizability to make the van der Waals interaction stronger. In addition, the studies are made in search of Feshbach resonances using a very large number of mesh points. The observed interesting behavior with the variation...

  7. Cold collisions of polyatomic molecular radicals with S-state atoms in a magnetic field: An ab initio study of He + CH2(X~) collisions

    Science.gov (United States)

    Tscherbul, T. V.; Grinev, T. A.; Yu, H.-G.; Dalgarno, A.; Kłos, Jacek; Ma, Lifang; Alexander, Millard H.

    2012-09-01

    We develop a rigorous quantum mechanical theory for collisions of polyatomic molecular radicals with S-state atoms in the presence of an external magnetic field. The theory is based on a fully uncoupled space-fixed basis set representation of the multichannel scattering wave function. Explicit expressions are presented for the matrix elements of the scattering Hamiltonian for spin-1/2 and spin-1 polyatomic molecular radicals interacting with structureless targets. The theory is applied to calculate the cross sections and thermal rate constants for spin relaxation in low-temperature collisions of the prototypical organic molecule methylene [CH_2(tilde{X}^3B_1)] with He atoms. To this end, two accurate three-dimensional potential energy surfaces (PESs) of the He-CH_2(tilde{X}^3B_1) complex are developed using the state-of-the-art coupled-cluster method including single and double excitations along with a perturbative correction for triple excitations and large basis sets. Both PESs exhibit shallow minima and are weakly anisotropic. Our calculations show that spin relaxation in collisions of CH2, CHD, and CD2 molecules with He atoms occurs at a much slower rate than elastic scattering over a large range of temperatures (1 μK-1 K) and magnetic fields (0.01-1 T), suggesting excellent prospects for cryogenic helium buffer-gas cooling of ground-state ortho-CH_2(tilde{X}^3B_1) molecules in a magnetic trap. Furthermore, we find that ortho-CH2 undergoes collision-induced spin relaxation much more slowly than para-CH2, which indicates that magnetic trapping can be used to separate nuclear spin isomers of open-shell polyatomic molecules.

  8. Cold collisions of polyatomic molecular radicals with S-state atoms in a magnetic field: an ab initio study of He + CH2(X) collisions.

    Science.gov (United States)

    Tscherbul, T V; Grinev, T A; Yu, H-G; Dalgarno, A; Kłos, Jacek; Ma, Lifang; Alexander, Millard H

    2012-09-14

    We develop a rigorous quantum mechanical theory for collisions of polyatomic molecular radicals with S-state atoms in the presence of an external magnetic field. The theory is based on a fully uncoupled space-fixed basis set representation of the multichannel scattering wave function. Explicit expressions are presented for the matrix elements of the scattering Hamiltonian for spin-1/2 and spin-1 polyatomic molecular radicals interacting with structureless targets. The theory is applied to calculate the cross sections and thermal rate constants for spin relaxation in low-temperature collisions of the prototypical organic molecule methylene [CH(2)(X(3)B(1))] with He atoms. To this end, two accurate three-dimensional potential energy surfaces (PESs) of the He-CH(2)(X(3)B(1)) complex are developed using the state-of-the-art coupled-cluster method including single and double excitations along with a perturbative correction for triple excitations and large basis sets. Both PESs exhibit shallow minima and are weakly anisotropic. Our calculations show that spin relaxation in collisions of CH(2), CHD, and CD(2) molecules with He atoms occurs at a much slower rate than elastic scattering over a large range of temperatures (1 μK-1 K) and magnetic fields (0.01-1 T), suggesting excellent prospects for cryogenic helium buffer-gas cooling of ground-state ortho-CH(2)(X(3)B(1)) molecules in a magnetic trap. Furthermore, we find that ortho-CH(2) undergoes collision-induced spin relaxation much more slowly than para-CH(2), which indicates that magnetic trapping can be used to separate nuclear spin isomers of open-shell polyatomic molecules. PMID:22979854

  9. Processes involving electron capture and multiple ionization in collisions of fast H+ and He2+ ions with lead atoms

    Science.gov (United States)

    McCartney, P. C. E.; Shah, M. B.; Geddes, J.; Gilbody, H. B.

    1999-12-01

    A crossed-beam technique incorporating time-of-flight analysis and coincidence counting of the collision products has been used to study Pbq+ formation with q up to 8 in collisions between ground-state Pb atoms and H+ and He2+ ions within the range 50-600 keV amu-1. The separate cross sections for simple charge transfer, transfer ionization, and pure ionization leading to the formation of Pbq+ ions have been obtained and the relative importance of these processes has been established. Accurate measurements and rigorous theoretical descriptions of these multielectron processes in such heavy atoms are difficult and data are still very limited. The present measurements have been designed to extend our previous studies of multiple ionization of a few selected heavy metal atoms and to provide a further check on the extent to which the main collision processes can be described quantitatively in terms of simple models based on an independent electron description. In our previous work with Fe, Cu, and Ga atoms using the same experimental approach, we were able to describe the formation of multiply charged ions through both transfer ionization and pure ionization with a high degree of success using an independent electron model. However, the present results for Pb show that the success of this simple approach is much more limited for these much heavier atoms.

  10. Fragmentation of neutral carbon clusters formed by high velocity atomic collision; Fragmentation d'agregats de carbone neutres formes par collision atomique a haute vitesse

    Energy Technology Data Exchange (ETDEWEB)

    Martinet, G

    2004-05-01

    The aim of this work is to understand the fragmentation of small neutral carbon clusters formed by high velocity atomic collision on atomic gas. In this experiment, the main way of deexcitation of neutral clusters formed by electron capture with ionic species is the fragmentation. To measure the channels of fragmentation, a new detection tool based on shape analysis of current pulse delivered by semiconductor detectors has been developed. For the first time, all branching ratios of neutral carbon clusters are measured in an unambiguous way for clusters size up to 10 atoms. The measurements have been compared to a statistical model in microcanonical ensemble (Microcanonical Metropolis Monte Carlo). In this model, various structural properties of carbon clusters are required. These data have been calculated with Density Functional Theory (DFT-B3LYP) to find the geometries of the clusters and then with Coupled Clusters (CCSD(T)) formalism to obtain dissociation energies and other quantities needed to compute fragmentation calculations. The experimental branching ratios have been compared to the fragmentation model which has allowed to find an energy distribution deposited in the collision. Finally, specific cluster effect has been found namely a large population of excited states. This behaviour is completely different of the atomic carbon case for which the electron capture in the ground states predominates. (author)

  11. Coupled-Channel Investigation of the Collision of Protons and Antiprotons with Hydrogen- Like Atoms in the 2s States

    Institute of Scientific and Technical Information of China (English)

    Reda S. Tantawi

    2003-01-01

    The influence of the electric charge of both the projectile and the target nucleus on the cross section of the inelastic collision of protons and antiprotons with atoms is investigated at energies ranging from i to 2500 KeV. The impact parameter method is used to analyse the cross sections of the excitation of the n = 3 states of H atom and He+, Li2+ ions being initially in the excited 2s states. The calculated cross sections for hydrogen atoms are compared with the other theoretical results based on coupled-channels methods.

  12. Monte Carlo calculation of the collision density of superthermal produced H atoms in thermal H2 gas

    CERN Document Server

    Panarese, A

    2011-01-01

    We propose a simple and reliable method to study the collision density of H atoms following their production by chemical mechanisms. The problem is relevant to PDR's, shocks, photospheres, atmospheric entry problems. We show that the thermalization of H atoms can be conveniently studied by a simple method and set the basis for further investigations. Besides our aims are also to review the theoretical basis, the limitation of simpler approaches and address the analogue problems in neutronics. The method adopted is Monte Carlo method including the thermal distri- bution of background molecules. The transport cross section is determined by the inversion of transport data. Plots of the collisions density of H atoms in H2 gas are calculated and discussed also in the context of simple theories. The application of the results to astrophysical problems is outlined.

  13. mJ mixing and multipole relaxation in 6 2P rubidium atoms induced by He, Ne, and Ar collisions

    International Nuclear Information System (INIS)

    Rubidium vapor, contained together with a buffer gas in a quartz cell located in a 4.75-T magnetic field, was irradiated with light from a pulsed dye laser producing selective excitation of each 6 2P Zeeman substate in turn. Collisions of the excited and polarized atoms with the ground-state He, Ne, or Ar atoms and the resulting Zeeman mixing produced a population of the whole Zeeman manifold and resulted in the emission of a Zeeman fluorescence spectrum that was resolved with a scanning Fabry-Perot interferometer and recorded with a photomultiplier and a multichannel scaler. Measurements of the relative intensities of the fluorescence components in relation to the buffer-gas pressures yielded the absolute (thermally averaged) cross sections for Zeeman mixing and cross sections for relaxation of the atomic multipole moments for collisions with He, Ne, and Ar

  14. A high resolution X-ray crystal spectrometer to study electron and heavy-ion impact atomic collisions

    Indian Academy of Sciences (India)

    Ajay Kumar; D Misra; A H Kelkar; U R Kadhane; K V Thulasiram; Lokesh C Tribedi

    2007-06-01

    We have studied fast ion–atom and electron–atom collision processes using a reconditioned high resolution X-ray spectrometer. The X-rays, generated by the collisions, are dispersed by a curved ADP crystal (Johansson geometry) and detected by a gas proportional counter. A self-written LabVIEW based program has been used to give precise and controlled movement to the crystal and for data acquisition. The performance was tested by detecting the K diagram and satellite lines of several elements. The K satellite lines of Al have been studied in collision with 3–12 keV electrons and 40 MeV C4+ ions. In ion collisions as large as four L-vacancies are created simultaneously with the K-vacancy, compared to two satellites in case of the e-impact. In addition, we have measured the X-rays from H-, He- and Li-like Si ions which arise due to the electron loss/capture process in highly charged 80 MeV Si7+ ions in collision with thin carbon foil. Approximate charge state distribution has been obtained using this new technique.

  15. Impact-collision ion scattering spectroscopy applied to the determination of atomic surface structure

    International Nuclear Information System (INIS)

    The technique of impact collision ion scattering spectroscopy (ICISS) was used to investigate the atomic structure and low energy ion scattering dynamics from various surfaces. A new formalism for calculating the three-dimensional cross section for an ion to scatter sequentially and classically from two atoms has been developed. This method can be used to assist in the interpretation of ICISS data in terms of quantitative surface-structure models. In an ICISS investigation of the Ag(110) surface, a surface flux peak analysis demonstrated that the surface was not a complete monolayer, but rather contained 10-15% random vacancies. Subsurface Li+ scattering results confirmed the oscillatory relaxation of the first two atomic layers of the surface, with Δ12 = -7.5% and Δ23 = 4.0%. Modeling of the neutralization mechanism for the He+ scattering gave a best fit time-dependent Auger neutralization time constant of 0.84 ± 0.08 fs. A neutralization study of 5 keV He+ ions scattered from Au adatoms on the Si(111)-√3 x √3-Au surface showed the He+ ICISS data contained false shadowing features that were actually the result of local neutralization effects. A detailed examination of the Si(111)-√3 x √3-Ag surface was also made. The 5 keV Li+ ICISS data gave evidence for Ag island formation at single monolayer coverages of silver, while the LEED, AES and LEIS data showed that at relatively high coverages of Ag (35 ML) small areas of √3 x √3 character were still present

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

    Science.gov (United States)

    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.

  17. Four-body charge transfer processes in collisions of bare projectile ions with helium atoms

    Science.gov (United States)

    Jana, S.; Mandal, C. R.; Purkait, M.

    2015-02-01

    Single-electron capture by a bare ion from a helium atom at intermediate and high energies in the framework of four-body distorted wave (DW-4B) approximation in both prior and post form has been considered. In the entrance channel, the initial bound state wave function is distorted by the incoming projectile ion, and the corresponding distortion is related to the Coulomb continuum states of the active electron and the residual target ion in the field of the projectile ion respectively. Continuum states of the active electron and the projectile ion in the field of the residual target ion are also included in the exit channel. It may be mentioned that the effect of dynamic electron correlation is explicitly taken into account through the complete perturbation potential. The total single-electron capture cross sections are obtained by summing over all contributions up to n = 3 shells and sub-shells respectively. In addition, the differential cross sections for alpha particle-helium collision are calculated at impact energies of 60, 150, 300, 450, and 630 keV amu-1, respectively. The cross sections exhibit a monotonically decreasing angular dependence, with clear peak structures around 0.1 to 0.2 mrad being found at low impact energies. The current theoretical results, both in prior and post forms of the transition amplitude for symmetric and asymmetric collision, are compared with the available theoretical and experimental results. Current computed results have been found to be satisfactory in comparison with other theoretical and experimental findings.

  18. Models for inner-shell excitation in ion-atom collisions

    International Nuclear Information System (INIS)

    Models of inner-shell vacancy production which include translation factors are developed for the change transfer process in ion-atom collisions. Translation factors are included in the basis set in which the electronic wavefunction is expanded in order to correctly describe the motion of the electron during the collision. Though several numerical studies have been done which employ this concept, the present models for change exchange are based on stationary state expansions. First the problem is formulated in the adiabatic framework. Having chosen a case in which the form of the translation factors is simple and in which additional approximations may be made, i.e., the case of long-range coupling, all terms in the equations of motion can be evaluated in closed form. An analytic solution is derived with the adiabatic theory which shows explicitly the effects of translation factors on the sharing ratio (defined as the ratio of vacancy production cross-sections of the high Z to low Z partners). The result reduces to that of the Demkov model in the low velocity limit. As the velocity increases, a sharing ratio is predicted which drops below the Demkov curve and reaches a maximum at finite velocity. Numerical calculations using translation factors in a molecular orbital basis exhibit such a fall-off. It is shown that this effect is due solely to the inclusion of the momentum transfer of the electron. The assumptions of the adiabatic approach, however, limit its application to the low velocity region. A new formulation is developed of the problem which is not limited by the adiabatic assumptions. Solutions of the equations of motion in closed form are obtained. This new treatment gives not only the correct adiabatic limit but also the exact Born result directly from the analytic solution of the coupled equations

  19. Four-body charge transfer processes in collisions of bare projectile ions with helium atoms

    International Nuclear Information System (INIS)

    Single-electron capture by a bare ion from a helium atom at intermediate and high energies in the framework of four-body distorted wave (DW-4B) approximation in both prior and post form has been considered. In the entrance channel, the initial bound state wave function is distorted by the incoming projectile ion, and the corresponding distortion is related to the Coulomb continuum states of the active electron and the residual target ion in the field of the projectile ion respectively. Continuum states of the active electron and the projectile ion in the field of the residual target ion are also included in the exit channel. It may be mentioned that the effect of dynamic electron correlation is explicitly taken into account through the complete perturbation potential. The total single-electron capture cross sections are obtained by summing over all contributions up to n = 3 shells and sub-shells respectively. In addition, the differential cross sections for alpha particle–helium collision are calculated at impact energies of 60, 150, 300, 450, and 630 keV amu−1, respectively. The cross sections exhibit a monotonically decreasing angular dependence, with clear peak structures around 0.1 to 0.2 mrad being found at low impact energies. The current theoretical results, both in prior and post forms of the transition amplitude for symmetric and asymmetric collision, are compared with the available theoretical and experimental results. Current computed results have been found to be satisfactory in comparison with other theoretical and experimental findings. (paper)

  20. Measurement of Absolute Atomic Collision Cross Section with Helium Using 87Rb Atoms Confined in Magneto-Optic and Magnetic Traps

    Institute of Scientific and Technical Information of China (English)

    WANG Ji-Cheng; ZHOU Ke-Ya; WANG Yue-Yuan; LIAO Qing-Hong; LIU Shu-Tian

    2011-01-01

    We present the measurements and calculations of the absolute total collision cross sections for a room-temperature gas of helium using 87 Rb atoms confined in either a magneto-optic or a magnetic quadrupole trap. The loss rates from the magneto-optic trap and the pure magnetic trap are compared and show significant differences. The collision cross sections as a function of trap depth for helium gas are obtained. These findings are significant for extracting the information about the different cross sections when the trap depth is changed.%@@ We present the measurements and calculations of the absolute total collision cross sections for a room-temperature gas of helium using 87Rb atoms confined in either a magneto-optic or a magnetic quadrupole trap.The loss rates from the magneto-optic trap and the pure magnetic trap are compared and show significant differences.The collision cross sections as a function of trap depth for helium gas are obtained.These findings are significant for extracting the information about the different cross sections when the trap depth is changed.

  1. Ionization and excitation of Rydberg states in collisions of fast metastable helium atoms with He, Ne, and N2

    International Nuclear Information System (INIS)

    The experimental values of the cross sections of elementary collision processes involving neutral atoms and covering the energy range 01.-1,000 keV are of interest because they can be used to model some phenomena which occur under laboratory conditions and in outer space, and also to check the precision of various models and methods used in the theory of atomic collisions. The latter task is particularly important at moderate collision energies (usually below 100 keV) where the Born approximation for the cross sections of collisional processes gives results greatly at variance with the experimental data and the precision of the more complex theoretical methods being developed at present requires a careful experimental check. Here, the cross sections for ionization and excitation into Rydberg states (n = 21-27) were determined for fast (accelerated to 3.9 keV) metastable helium atoms colliding with He, Ne, and N2. An analysis of the collisionally excited helium atoms in terms of their principal quantum number was carried out using for the ionization by an electric field a system capable of separation in accordance with n and was calibrated using signals from Rydberg states excited selectively by laser radiation

  2. New methods for quantum mechanical calculations of inelastic atom-molecule collisions and electron scattering

    International Nuclear Information System (INIS)

    New methods for the accurate quantum mechanical treatment of inelastic atom-molecule collisions and electron scattering are considered. The advantages of expanding the system wave function in adiabatic basis functions are emphasized. For a model collinear He-H2 system, the advantages of using vibrationally adiabatic basis functions in close coupling calculations of vibrationally elastic and inelastic transition probabilities are shown. For this system the detailed dynamics of multiquantum transitions is also considered, and the significance of various reactance matrix elements is probed. The close coupling method with conventional, l-dominant, and rotationally and orbitally adiabatic basis functions is applied to rotationally inelastic electron-molecule scattering in the laboratory frame. Electron-N2 scattering is treated in the rigid rotator approximation at total energy E = 30 eV and total angular momentum J = 5. The l-dominant bases afford a useful approximation, but dramatically more accurate results can be obtained with even smaller adiabatic bases. The accuracy and efficiency of close coupling calculations using conventional, l-dominant, adiabatic, and adiabatic l-dominant bases in rotationally inelastic atom-molecule scattering are compared. He-HF is treated in the rigid-rotator approximation at E = 0.05 and 0.017 eV for J = 4, 12, and 20. The effect of various reactance matrix elements on the partial cross sections is shown. S-, p-, and d-wave inelastic e-H scattering is treated in the 1s-2s close coupling approximation. The effects of electron exchange can be successfully approximated by replacing the nonlocal exchange potentials with approximate energy-dependent local potentials

  3. Collision between two ortho-positronium (Ps) atoms: A four-body Coulomb problem

    Indian Academy of Sciences (India)

    RAY HASI

    2016-05-01

    The elastic collision between two ortho-positronium (e.g. $S = 1$) atoms is studied using an {\\it ab-initio} static exchange model (SEM) in the centre of mass (CM) frame by considering the system as a four-body Coulomb problem where all the Coulomb interaction terms in the direct and exchange channels are treated exactly. A coupled channel methodology in momentum space is used to solve Lippman–Schwinger equation following the integral approach. A new SEM code is developed in which the Born–Oppenheimer (BO) scattering amplitude acts as input to derive the SEM amplitude adapting the partial wave analysis. The $s$-, $p$- and $d$-wave elastic phase shifts and the corresponding partial cross-sections for the spin alignment $S = 0$, i.e., singlet (+) and $S = 2$, i.e., triplet (−) states are studied. An augmented Born approximation is used to includethe contribution of higher partial waves more accurately to determine the total/integrated elastic cross-section $(\\sigma)$, the quenching cross-section (σq) and ortho-to-para conversion ratio $(\\sigma/\\sigma q)$. The effective range theory is used to determine the scattering lengths and effective ranges in the s-wave elastic scattering. The theory includes the non-adiabatic short-range effects due to exchange.

  4. Pion correlations as a function of atomic mass in heavy ion collisions

    International Nuclear Information System (INIS)

    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 · A GeV 56Fe + Fe, 1.82 · A GeV 40Ar + KCl and 1.54 · A GeV 93Nb + Nb, allowing for a search for dependences on the atomic number. Two acceptances (centered, in the lab., at ∼ 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

  5. Single and double electron capture cross sections in keV-collisions between fully stripped ions with helium atom

    OpenAIRE

    Ibaaz, Aicha; Dubois, Alain

    2015-01-01

    International audience We present cross section calculations for single-, double-capture, and double capture to auto-ionizing states occurring in the course of collisions between fully stripped ions Aq+ (q≤10) and helium atom at impact energies ranging from 0.25 to 625 keV/u. These calculations were performed by applying a semiclassical nonperturbative close coupling approach, based on the expansion of the scattering wave function into asymptotic bielectronic states with proper translation...

  6. PREFACE: XXIX International Conference on Photonic, Electronic, and Atomic Collisions (ICPEAC2015)

    Science.gov (United States)

    Díaz, C.; Rabadán, I.; García, G.; Méndez, L.; Martín, F.

    2015-09-01

    The 29th International Conference on Photonic, Electronic and Atomic Collisions (XXIX ICPEAC) was held at the Palacio de Congresos ''El Greco'', Toledo, Spain, on 22-28 July, 2015, and was organized by the Universidad Autónoma de Madrid (UAM) and the Consejo Superior de Investigaciones Científicas (CSIC). ICPEAC is held biannually and is one of the most important international conferences on atomic and molecular physics. The topic of the conference covers the recent progresses in photonic, electronic, and atomic collisions with matter. With a history back to 1958, ICPEAC came to Spain in 2015 for the very first time. UAM and CSIC had been preparing the conference for six years, ever since the ICPEAC International General Committee made the decision to hold the XXIX ICPEAC in Toledo. The conference gathered 670 participants from 52 countries and attracted 854 contributed papers for presentation in poster sessions. Among the latter, 754 are presented in issues 2-12 of this volume of the Journal of Physics Conference Series. In addition, five plenary lectures, including the opening one by the Nobel laureate Prof. Ahmed H. Zewail and the lectures by Prof. Maciej Lewenstein, Prof. Paul Scheier, Prof. Philip H. Bucksbaum, and Prof. Stephen J. Buckman, 62 progress reports and 26 special reports were presented following the decision of the ICPEAC International General Committee. Detailed write-ups of most of the latter are presented in issue 1 of this volume, constituting a comprehensive tangible record of the meeting. On the occasion of the International Year of Light (IYL2015) and with the support of the Fundación Española para la Ciencia y la Tecnología (FECYT), the program was completed with two public lectures delivered by the Nobel laureate Prof. Serge Haroche and the Príncipe de Asturias laureate Prof. Pedro M. Echenique on, respectively, ''Fifty years of laser revolutions in physics'rquot; and ''The sublime usefulness of useless science''. Also a

  7. Molecular theory of K-vacancy production in heavy-ion-atom collisions at small impact parameters

    International Nuclear Information System (INIS)

    1 s sigma vacancy production is calculated by approximating the 1 s sigma molecular wave function with an atomic 1s wave function for a charge Z(R) centered at a distance h(R) from the heavier nucleus. h(R) and Z(R) are determined by minimizing the 1 s sigma electronic energy. Previous calculations with the atomic semi-classsical approximation (h = 0, Z(R) = Z2, the target atomic number) showed that the probability of making Cu K vacancies in 0.5- to 2-MeV/a.m.u. H+, D+, and He+ + Cu collisions can be written as P(theta) = A(1 + B cos theta), where theta is the scattering angle and A and B are constants for theta approx. > 100. Although the recoil and dipole excitation contributions to P(theta) (which interfere destructively in the atomic theory) are independently smaller in the molecular calculations, similar B values are obtained. (orig.)

  8. The two-electron attosecond streak camera for time-resolving intra-atomic collisions

    Energy Technology Data Exchange (ETDEWEB)

    Emmanouilidou, A [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Staudte, A; Corkum, P B, E-mail: a.emmanouilidou@ucl.ac.u [Joint Laboratory for Attosecond Science, University of Ottawa and National Research Council, 100 Sussex Drive, Ottawa, ON, K1A 0R6 (Canada)

    2010-10-15

    We generalize the one-electron attosecond streak camera to time-resolve the correlated two-electron escape dynamics during a collision process involving a deep core electron. The collision process is triggered by an extreme ultraviolet (XUV) attosecond pulse (single-photon absorption) and probed by a weak infrared field. The principle of our two-electron streak camera is that by placing the maximum of the vector potential of the probing field at the time of collision, we get the maximum splitting of the inter-electronic angle of escape. We thereby determine the time of collision.

  9. Velocity dependence of the absolute total ionization cross section for collisions of argon atoms with singlet and triplet metastable helium atoms

    International Nuclear Information System (INIS)

    Measurements of the velocity dependence of the absolute total ionization cross section of argon atoms upon impact with selected metastable states of helium atoms are reported. A low voltage dc discharge was used as the source of the excited atoms, and a rotating slotted disk selector was used for velocity selection of the excited atoms. Selection of the electronic spin state of the excited atoms was accomplished by irradiation of the excited atoms with radiation from a helium discharge lamp. Ionization of the argon target atoms by metastable helium atoms was studied by the gas cell technique in which all ionization products were collected. The ionization measurements were of sufficient precision to allow simultaneous determination of the cross section and the second electron ejection efficiency for each metastable state of helium. The secondary electron ejection efficiency of triplet metastable helium atoms on an electroplated gold surface was determined to be 0.440 +- 0.018 in the presence of argon gas. The secondary electron ejection efficiency of singlet metastable atoms was determined to be 0.582 +- 0.024 under similar conditions. The total ionization cross section for the He(23S)-Ar system was found to increase almost linearly from 8.8 to 21.95 A2 with an increase of relative velocity from 1162 to 2787 m/sec. After an initial increase of the cross section from 9.8 A2 to 26.2 A2 with an increase in relative velocity from 989 m/sec to 2058 m/sec, the velocity dependence of the cross section of the He(21S)-Ar system entered a saturation region in which the cross section changed very little with relative velocity. The collision energy dependence of the He(23S)-Ar system was also used to determine the values of adjustable parameters present in a current theory based on the potential curve model for Penning and associative Penning ionization

  10. Projectile X-ray emission in relativistic ion-atom collisions

    Energy Technology Data Exchange (ETDEWEB)

    Salem, Shadi Mohammad Ibrahim

    2010-03-16

    This work reports on the study of the projectile X-ray emission in relativistic ion-atom collisions. Excitation of K-shell in He-like uranium ions, electron capture into H-like uranium ions and Simultaneous ionization and excitation of initially He-like uranium ions have been studied using the experimental storage ring at GSI. For the K{sub {alpha}}{sub 1} and K{sub {alpha}}{sub 2} transitions originating from the excitation of the He-like uranium ions, no alignment was observed. In contrast, the Ly{sub {alpha}}{sub 1} radiation from the simultaneous ionization-excitation process of the He-like uranium ions shows a clear alignment. The experimental value leads to the inclusion of a magnetic term in the interaction potential. The capture process of target electrons into the highly-charged heavy ions was studied using H-like uranium ions at an incident energy of 220 MeV/u, impinging on N{sub 2} gas-target. It was shown that, the strongly aligned electrons captured in 2p{sub 3/2} level couple with the available 1s{sub 1/2} electron which shows no initial directional preference. The magnetic sub-state population of the 2p{sub 3/2} electron is redistributed according to the coupling rules to the magnetic sub-states of the relevant two-electron states. This leads to the large anisotropy in the corresponding individual ground state transitions contributing to the K{sub {alpha}}{sub 1} emission. From the K{sub {alpha}}{sub 1}/K{sub {alpha}}{sub 2} ratio, the current results show that the incoherent addition of the E1 and M2 transition components yield to an almost isotropic emission of the total K{sub {alpha}}{sub 1}. In contrast to the radiative electron capture, the experimental results for the K-shell single excitation of He-like uranium ions indicate that only the {sup 1}P{sub 1} level contributes to the K{sub {alpha}}{sub 1} transition. For this case, the anisotropy parameter {beta}{sub 20} was found to be -0.20{+-}0.03. This work also reports on the study of a two

  11. Rearrangement reactions in ion-ion and ion-atom collisions: results and problems

    Energy Technology Data Exchange (ETDEWEB)

    Presnyakov, L.P. [Lebedev Physical Institute, Moscow (Russian Federation); Tawara, H.

    1997-01-01

    Recent experimental and theoretical results are discussed for ionic collisions with large cross sections at intermediate and small energies of the relative motion. Single- and double-electron removal from H{sup -} ions in slow collisions with other ions is considered in more details. The theoretical methods are discussed from the viewpoint of general requirements of scattering theory. (author)

  12. Experimental investigation of the formation of negative hydrogen ions in collisions between positive ions and atomic or molecular targets

    International Nuclear Information System (INIS)

    The formation of the negative hydrogen ion (H-) in collisions between a positive ion and a neutral atomic or molecular target is studied experimentally at impact energies of a few keV. The doubly-differential cross sections for H- formation are measured as a function of the kinetic energy and emission angle for the collision systems OH+ + Ar and O+ + H2O at 412 eV/a.m.u. These H- ions can be emitted at high energies (keV) in hard quasi-elastic two-body collisions involving a large momentum transfer to the H center. However, H- anions are preferentially emitted at low energy (eV) due to soft many-body (≥ 2) collisions resulting in a low momentum transfer. The formation of H- ions by electron capture follows excitation or ionization of the molecule. The molecular fragmentation dynamics is modeled to simulate the emission of H- ions. The overall good agreement between the simulation and the experiment leads to the understanding of most of the experimental observations. (author)

  13. Charge transfer, excitation and evaporation in low energy collisions of simple metal clusters and fullerenes with atomic targets

    International Nuclear Information System (INIS)

    We present charge transfer, excitation and evaporation cross sections in low energy collisions of small and medium-size metal clusters (Nanq+, Linq+) and C60 with atomic targets (H+, He2+ and Cs) using a molecular close-coupling formalism and a post-collision rate equation model. The theoretical model benefits from different time scales associated with the collision and the internal motion of the cluster nuclei. The collision description includes the many-electron aspect of the problem and makes use of a realistic cluster potential obtained with density functional theory and a spherical jellium model. The evaporation model takes into account the non-harmonic effects of the ionic motion and describes sequential evaporation to any order within the framework of the microcanonical statistical model of Weisskopf. We show that the relative abundance of different fragments depends critically on the cluster temperature and the spectrometer time of flight window. We have found good agreement with recent experimental results [Eur. Phys. J. D 12 (2000) 185

  14. Modified oscillator approach to ultracold collisions in tight harmonic traps General model and application to metastable helium atoms

    CERN Document Server

    Peach, G; Beams, T J; Peach, Gillian; Whittingham, Ian B; Beams, Timothy J

    2002-01-01

    A novel modified oscillator method of calculating energy eigenvalues for colliding ultracold atoms tightly confined in harmonic potentials is presented and applied to trapped spin-polarized metastable helium atoms. The perturbed harmonic oscillator problem is characterized by a long asymptotic region beyond the effective range of the interatomic potential, and a very efficient method for integrating inwards through this outer region is developed. The calculated eigenvalues for states with $l=0$ agree closely with those computed directly from the radial Schr\\"{o}dinger equation for the trapped atoms using a discrete variable method, and with those computed self-consistently from an energy-dependent effective scattering length. Finally, the self-consistent method is generalized to collisions with $l \

  15. Investigating the effect of electric field on ionization cross sections in antiproton–hydrogen/deuterium atoms collisions

    International Nuclear Information System (INIS)

    The Classical Trajectory Monte Carlo (CTMC) method has been used to investigate the effects of aligned electric field on the ionization cross sections in antiproton and hydrogen atoms collisions. The cross sections for the ionization of hydrogen/deuterium collision with antiproton in the energy range 10–500 keV/amu have been calculated and compared with the available experiment and theoretical results. The ionization cross sections are in reasonable agreement with the recently reported experimental and theoretical results. Isotope effect in the ionization cross section is reported to be negligible. The effects of the external electric field are seen to be quite prominent. Differential cross sections for ionization at the scattering angle up to 0.1° are also reported in this paper.

  16. Direct probe of anisotropy in atom-molecule collisions via quantum scattering resonances

    OpenAIRE

    Klein, Ayelet; Shagam, Yuval; Skomorowski, Wojciech; Żuchowski, Piotr. S.; Pawlak, Mariusz; Janssen, Liesbeth M. C.; Moiseyev, Nimrod; van de Meerakker, Sebastiaan Y. T.; van der Avoird, Ad; Koch, Christiane P.; Narevicius, Edvardas

    2016-01-01

    Anisotropy is a fundamental property of particle interactions. It occupies a central role in cold and ultra-cold molecular processes, where long range forces have been found to significantly depend on orientation in ultra-cold polar molecule collisions. Recent experiments have demonstrated the emergence of quantum phenomena such as scattering resonances in the cold collisions regime due to quantization of the intermolecular degrees of freedom. Although these states have been shown to be sensi...

  17. Directional `superradiant' collisions: bosonic amplification of atom pairs emitted from an elongated Bose-Einstein condensate

    OpenAIRE

    Vardi, A.; Moore, M. G.

    2002-01-01

    We study spontaneous directionality in the bosonic amplification of atom pairs emitted from an elongated Bose-Einstein condensate (BEC), an effect analogous to `superradiant' emission of atom-photon pairs. Using a simplified model, we make analytic predictions regarding directional effects for both atom-atom and atom-photon emission. These are confirmed by numerical mean-field simulations, demonstrating the the feasibility of nearly perfect directional emission along the condensate axis. The ...

  18. Charge breeding investigation in EBIS/T and collision study of ions with cold atoms for HITRAP

    International Nuclear Information System (INIS)

    Highly charged ions (HCI) at low velocities or at rest are interesting systems for various atomic physics experiments. For investigations on HCI of heavy stable or radioactive nuclides the HITRAP (Highly charged Ion TRAP) decelerator facility has been set up at GSI to deliver cooled beams of HCI at an energy of 5 keV/q. The HCI are produced in a stripper foil at relativistic energies and are decelerated in several steps at ESR storage ring and HITRAP before they are delivered to experimental setups. One of the experiments is the investigation of multi-electron charge exchange in collisions of heavy HCI with cold atoms using novel MOTRIMS technique. Collision experiments on light ions from an ECR ion source colliding with cold atoms in a MOT have been performed and the results are described. An electron beam ion trap (EBIT) has been tested and optimized for commissioning of the HITRAP physics experiments. The process of charge breeding in the EBIT has been successfully studied with gaseous elements and with an alkaline element injected from an external ion source. (orig.)

  19. Measurements of scattering processes in negative ion-atom collisions. Technical progress report, 1 September 1991--31 August 1992

    Energy Technology Data Exchange (ETDEWEB)

    Kvale, T.J.

    1992-04-01

    This Technical Progress Report describes the progress made on the research objectives during the past twelve months. This research project is designed to provide measurements of various scattering processes which occur in H{sup {minus}} collisions with atomic (specifically, noble gas and atomic hydrogen) targets at intermediate energies. 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 in progress will provide either experimentally-determined cross sections or set upper limits to those cross sections. In either case, these measurements will be stringent tests of our understanding in energetic negative ion-atom collisions. This series of experiments required the construction of a new facility and the initial ion beam was accelerated through the apparatus in April 1991.

  20. Measurements of scattering processes in negative ion-atom collisions. Technical progress report, 1 September 1992--31 August 1993

    Energy Technology Data Exchange (ETDEWEB)

    Kvale, T.J.

    1993-05-01

    This Technical Progress Report describes the progress made on the research objectives during the past twelve months. This research project is designed to provide measurements of various scattering processes which occur in H{sup {minus}} collisions with atomic (specifically, noble gas and atomic hydrogen) targets at intermediate energies. 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 in progress will provide either experimentally determined cross sections or set upper limits to those cross sections. In either case, these measurements will be stringent tests of our understanding in energetic negative ion - atom collisions. In addition secondary negative particle emission yields for H{sup 0} on Cu in the 3 to 50 keV range are shown.

  1. Charge breeding investigation in EBIS/T and collision study of ions with cold atoms for HITRAP

    Energy Technology Data Exchange (ETDEWEB)

    Sokolov, Alexey

    2010-01-29

    Highly charged ions (HCI) at low velocities or at rest are interesting systems for various atomic physics experiments. For investigations on HCI of heavy stable or radioactive nuclides the HITRAP (Highly charged Ion TRAP) decelerator facility has been set up at GSI to deliver cooled beams of HCI at an energy of 5 keV/q. The HCI are produced in a stripper foil at relativistic energies and are decelerated in several steps at ESR storage ring and HITRAP before they are delivered to experimental setups. One of the experiments is the investigation of multi-electron charge exchange in collisions of heavy HCI with cold atoms using novel MOTRIMS technique. Collision experiments on light ions from an ECR ion source colliding with cold atoms in a MOT have been performed and the results are described. An electron beam ion trap (EBIT) has been tested and optimized for commissioning of the HITRAP physics experiments. The process of charge breeding in the EBIT has been successfully studied with gaseous elements and with an alkaline element injected from an external ion source. (orig.)

  2. Interatomic collisions

    International Nuclear Information System (INIS)

    The relevance of the study and understanding of atomic collision processes to nuclear power developments and the impact of the particular contributions made by members of the Theoretical Physics Division, Harwell to this work are considered. These contributions fall into two main parts; up to 1970 when interest concentrated on the lighter collision systems involving protons, α-particles and the helium and hydrogen atoms at collision energies in the range 1 keV - 1 MeV, and after 1970 when interest broadened to include the collisions of heavy atoms, such as the O+-Ne collision system which was used as a prototype for the development of scaling laws for inner-shell excitation in any heavy-ion collision. Particular aspects of the work discussed include the Born expansion and beyond, close-coupling expansions, and continuum x-ray emission. (UK)

  3. Scattering of NH{sub 3} and ND{sub 3} with rare gas atoms at low collision energy

    Energy Technology Data Exchange (ETDEWEB)

    Loreau, J., E-mail: jloreau@ulb.ac.be [Service de Chimie Quantique et Photophysique, Université Libre de Bruxelles (ULB) CP 160/09, 50 av. F.D. Roosevelt, 1050 Brussels (Belgium); Avoird, A. van der, E-mail: A.vanderAvoird@theochem.ru.nl [Theoretical Chemistry, Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen (Netherlands)

    2015-11-14

    We present a theoretical study of elastic and rotationally inelastic collisions of NH{sub 3} and ND{sub 3} with rare gas atoms (He, Ne, Ar, Kr, Xe) at low energy. Quantum close-coupling calculations have been performed for energies between 0.001 and 300 cm{sup −1}. We focus on collisions in which NH{sub 3} is initially in the upper state of the inversion doublet with j = 1, k = 1, which is the most relevant in an experimental context as it can be trapped electrostatically and Stark-decelerated. We discuss the presence of resonances in the elastic and inelastic cross sections, as well as the trends in the inelastic cross sections along the rare gas series and the differences between NH{sub 3} and ND{sub 3} as a colliding partner. We also demonstrate the importance of explicitly taking into account the umbrella (inversion) motion of NH{sub 3} in order to obtain accurate scattering cross sections at low collision energy. Finally, we investigate the possibility of sympathetic cooling of ammonia using cold or ultracold rare gas atoms. We show that some systems exhibit a large ratio of elastic to inelastic cross sections in the cold regime, which is promising for sympathetic cooling experiments. The close-coupling calculations are based on previously reported ab initio potential energy surfaces for NH{sub 3}–He and NH{sub 3}–Ar, as well as on new, four-dimensional, potential energy surfaces for the interaction of ammonia with Ne, Kr, and Xe, which were computed using the coupled-cluster method and large basis sets. We compare the properties of the potential energy surfaces corresponding to the interaction of ammonia with the various rare gas atoms.

  4. Anisotropy and linear polarization of radiative processes in energetic ion-atom collisions; Untersuchung zur Anisotropie und linearen Polarisation radiativer Prozesse in energiereichen Ion-Atom-Stoessen

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Guenter

    2010-06-16

    In the present thesis the linear polarization of radiation emitted in energetic ion-atom collisions at the ESR storage ring was measured by applying a novel type of position, timing and energy sensitive X-ray detector as a Compton polarimeter. In contrast to previous measurements, that mainly concentrate on studies of the spectral and angular distribution, the new detectors allowed the first polarization study of the Ly-{alpha}{sub 1} radiation (2p{sub 3/2}{yields}1s{sub 1/2}) in U{sup 91+}. Owing to the high precision of the polarimeters applied here, the experimental results indicate a significant depolarization of the Ly-{alpha}{sub 1} radiation caused by the interference of the E1 and M2 transition branches. Moreover, the current investigation shows that measurements of the linear polarization in combination with angular distribution studies provide a model-independent probe for the ratio of the E1 and M2 transition amplitudes and, consequently, of the corresponding transition probabilities. In addition, a first measurement of the linear polarization as well as an angular distribution study of the electron-nucleus Bremsstrahlung arising from ion-atom collisions was performed. The experimental results obtained were compared to exact relativistic calculations and, in case of the Bremsstrahlung, to a semirelativistic treatment. In general, good agreement was found between theoretical predictions and experimental findings. (orig.)

  5. Suppression of angular momentum transfer in cold collisions of transition metal atoms in ground States with nonzero orbital angular momentum.

    Science.gov (United States)

    Hancox, Cindy I; Doret, S Charles; Hummon, Matthew T; Krems, Roman V; Doyle, John M

    2005-01-14

    The Zeeman relaxation rate in cold collisions of Ti(3d(2)4s(2) 3F2) with He is measured. We find that collisional transfer of angular momentum is dramatically suppressed due to the presence of the filled 4s(2) shell. The degree of electronic interaction anisotropy, which is responsible for Zeeman relaxation, is estimated to be about 200 times smaller in the Ti-He complex than in He complexes with typical non-S-state atoms. PMID:15698077

  6. First research coordination meeting on atomic collision data for diagnostics of magnetic fusion plasmas, Vienna, 21-25 June 1982

    International Nuclear Information System (INIS)

    Proceedings of the first meeting of the participants in the IAEA Coordinated Research Programme on atomic collision data for diagnostics of magnetically confined fusion plasmas, convened by the IAEA Nuclear Data Section on 21 - 25 June 1982, at IAEA Headquarters in Vienna. The meeting participants reviewed the status of electron excitation, electron ionization and charge transfer data for selected fusion relevant elements, made specific recommendations on the use of these existing data, and identified those data which needed to be measured or calculated. (author)

  7. Precision measurements of cross sections of inelastic processes realized in collisions of alkali metal ions with atoms of rare gases

    CERN Document Server

    Lomsadze, R A; Mosulishvili, N O; Kezerashvili, R Ya

    2015-01-01

    This work presents a multifaceted experimental study of collisions of Na$^{+}$ and K$^{+}$ ions in the energy range 0.5 -- 10 keV with He and Ar atoms. Absolute cross sections for charge-exchange, ionization, stripping and excitation were measured using a refined version of the transfer electric field method, angle- and energy-dependent collection of product ions, energy loss, and optical spectroscopy. The experimental data and the schematic correlation diagrams have been employed to analyze and determine the mechanisms for these processes.

  8. Ionizing reaction cross sections in the collision of argon atoms in high Rydberg states with various molecules

    International Nuclear Information System (INIS)

    Measurements of absolute ionizing reaction cross sections in collisions between argon atoms in high Rydberg states (HR) and CCl4, CCl3F, CH3I, SF6, C6F6, CF4, and CO are reported together with their dependence on the HR argon velocity (570--2100 m/sec). The identity of the positively and negatively charged reaction products has been investigated with a coincidence TOF mass spectrometer. A comparison of the present data with results of other bound and free electron experiments and theoretical predictions is given

  9. Simultaneous K plus L shell ionized atoms during heavy-ion collision process

    Indian Academy of Sciences (India)

    G A V Ramana Murty; G J Naga Raju; V Vijayan; T Ranjan Rautray; B Seetharami Reddy; S Lakshminarayana; K L Narasimham; S Bhuloka Reddy

    2004-06-01

    The fraction of simultaneous K plus L shell ionized atoms is estimated in Fe, Co and Cu elements using carbon ions at different projectile energies. The present results indicate that the fraction of simultaneous K plus L shell ionization probability decreases with increase in projectile energy as well as with increase in the atomic number of the targets atoms.

  10. Renormalization shielding and eikonal analysis on the atomic collision in dense partially ionized hydrogen plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sung Soo [Department of Applied Mathematics, Hanyang University, Ansan, Kyunggi-Do 426-791 (Korea, Republic of); Jung, Young-Dae [Department of Applied Physics and Department of Bionanotechnology, Hanyang University, Ansan, Kyunggi-Do 426-791 (Korea, Republic of); Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, New York 12180-3590 (United States)

    2013-12-15

    The renormalization plasma screening effects on the electron-ion collision are investigated in dense partially ionized hydrogen plasmas. The Hamilton-Jacobi and eikonal methods with the effective interaction potential are employed to obtain the eikonal scattering phase shift and eikonal cross section for the electron-ion collision. It is found that the influence of renormalization screening strongly suppresses the eikonal scattering phase shift as well as the eikonal cross section, especially, for small impact parameter regions. In addition, the renormalization screening effect reduces the total eikonal cross section in all energy domains. The variation of the renormalization effects on the electron-ion collision in dense partially ionized hydrogen plasmas is also discussed.

  11. Multi-electronic processes in atomic and molecular collisions at intermediate impact energies

    International Nuclear Information System (INIS)

    We present a new approach to describe multi-electronic processes occurring in ionatom/molecule collisions at impact energies ranging from 0.1 to 500 keV.u-1. The treatment is based on the semiclassical approximation in which the time-dependent Schrödinger equation is solved non perturbatively, taking into account all the electrons of the collision system. To insure both the correct spin multiplicity and spatial symmetry we use the permutation group theory together with Young diagrams instead of combinations of Slater determinants. In the conference results for H+-Li collisions will be presented in order to illustrate the power of the approach on a known system, and to provide an interesting benchmark description of processes involving inner- and valence-shell electrons in a coupled way. (author)

  12. Measurements of scattering processes in negative ion: Atom collisions. Technical progress report, 1 September 1991--31 December 1994

    Energy Technology Data Exchange (ETDEWEB)

    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).

  13. Study of elementary transfer mechanisms during a collision between a swift multi-charged heavy ion and a neutral atom

    International Nuclear Information System (INIS)

    This work is dedicated to the study of the energy transfer mechanisms which occur during a collision between a swift multicharged heavy ion and a neutral atom. The elementary energy energy transfer mechanisms (scattering, excitation, ionization, capture) and their consequences on the target velocity after the collision (recoil velocity) are recalled in the first chapter. In the case of small projectile diffusion angles, we show that the recoil velocity component, transverse to the incident projectile direction, results principally from the diffusion mechanism, while the longitudinal component is due essentially to the mass transfer and the inelastic energy transfer mechanisms. Since the target recoil velocities are very small, we have built an experimental set-up which reduces the impreciseness on their measurement due to the target thermal spread using, as targets, cooled atoms of a supersonic jet (temperature 44+(6.7 MeV/A) + Ar => Xe44 + Arq++qe- (q ranging from 1 to 7); Xe44+ (6.7 MeV/A) + He => Xe44+ He1+,2++1e-,2e-. We show that it is possible to interpret the recoil velocity in terms of kinetic energy transferred to the target and to the electrons ejected from the target. (author)

  14. Collisions of electrons with hydrogen atoms I. Package outline and high energy code

    Science.gov (United States)

    Benda, Jakub; Houfek, Karel

    2014-11-01

    Being motivated by the applied researchers’ persisting need for accurate scattering data for the collisions of electrons with hydrogen atoms, we developed a computer package-Hex-that is designed to provide trustworthy results for all basic discrete and continuous processes within non-relativistic framework. The package consists of several computational modules that implement different methods, valid for specific energy regimes. Results of the modules are kept in a common database in the unified form of low-level scattering data (partial-wave T-matrices) and accessed by an interface program which is able to produce various derived quantities like e.g. differential and integral cross sections. This article is the first one of a series of articles that are concerned with the implementation and testing of the modules. Here we give an overview of their structure and present (a) the command-line interface program hex-db that can be also easily compiled into a derived code or used as a backend for a web-page form and (b) simple illustrative module specialized for high energies, hex-dwba, that implements distorted and plane wave Born approximation. Catalogue identifier: AETH_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AETH_v1_0.html Program obtainable from: CPC Program library, Queen’s University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data etc.: 30367 No. of bytes in distributed program, including test data etc.: 232032 Distribution format: tar.gz Programming language: C++11 Operating system: Any system with a C++11 compiler (e.g. GCC 4.8.1; tested on OpenSUSE 13.1 and Windows 8). RAM: Test run 3 MiB. CPC Library Classification: 2.4 Electron scattering External libraries:GSL [49], FFTW3[52], SQLite3 [46]. All of the libraries are open-source and maintained. Nature of problem: Extraction of derived (observable) quantities from partial

  15. A Slater parameter optimisation interface for the CIV3 atomic structure code and its possible use with the R-matrix close coupling collision code

    International Nuclear Information System (INIS)

    Details are here provided of amendments to the atomic structure code CIV3 which allow the optional adjustment of Slater parameters and average energies of configurations so that they result in improved energy levels and eigenvectors. It is also indicated how, in principle, the resultant improved eigenvectors can be utilised by the R-matrix collision code, thus providing an optimised target for close coupling collision strength calculations. An analogous computational method was recently reported for distorted wave collision strength calculations and applied to Fe XIII. The general method is suitable for the computation of collision strengths for complex ions and in some cases can then provide a basis for collision strength calculations in ions where ab initio computations break down or result in unnecessarily large errors. (author)

  16. Transmutations of atomic nuclei in hadron-nuclei nuclear collisions at GeV energies

    International Nuclear Information System (INIS)

    In hadron-nuclei nuclear collisions nuclei change their mass numbers A and the charge numbers Z. The mechanism of transmutation of a target nucleus was prompted experimentally and is described in this work. The information about the nuclei transmutation may be a basis for elaboration of the method of nuclei changes in beams of hadrons from accelerators

  17. Internal excitation of UF-6 and MoF-6 ions in collisions with argon atoms

    International Nuclear Information System (INIS)

    Beams of UF-6 and MoF-6 of controlled average internal energy from 0.7 to 2.4 eV have been collided with argon at 200 eV laboratory kinetic energy. Analysis of the outgoing kinetic energy distributions shows that increased internal excitation prior to collision enhances the conversion of kinetic to internal energy. (orig.)

  18. Coriolis coupling effects in time-dependent Hartree-Fock calculations of ion-atom collisions

    International Nuclear Information System (INIS)

    Effects on the collision dynamics due to the inclusion of the Coriolis term in the time-dependent Hartree-Fock Hamiltonian are investigated for the He2++He colliding system both at low and high incident energies. Whereas at low energies these effects are perturbative, Coriolis terms produce drastic reductions in charge-exchange cross sections at high energies

  19. l- and n-changing collisions during interaction of a pulsed beam of Li Rydberg atoms with CO2

    International Nuclear Information System (INIS)

    The pulsed Li atomic beam produced in our experiment is based on controlled transversely-excited-atmospheric CO2 laser-induced ablation of a Li metal target. The atomic beam is propagated in vacuum or in CO2 gas at low pressure. Atoms in the beam are probed by laser-induced fluorescence spectroscopy. This allows the determination of time-of-flight and velocity distributions. Li Rydberg states (n=5--13) are populated in the beam by two-step pulsed-laser excitation. The excited atoms interact with CO2 molecules. l- and n-changing cross sections are deduced from the time evolution of the resonant or collision-induced fluorescence following this selective excitation. l-changing cross sections of the order of 104 A2 are measured; they increase with n as opposed to the plateau observed for Li/sup */ colliding with a diatomic molecule. This behavior is qualitatively well explained in the framework of the free-electron model. n yields n' changing processes with large cross sections (10--100 A2) are also observed even in the case of large electronic energy change (ΔE/sub nn'/>103 cm/sup -1/). These results can be interpreted in terms of resonant-electronic to vibrational energy transfers between Li Rydberg states and CO2 vibrational modes

  20. l- and n-changing collisions during interaction of a pulsed beam of Li Rydberg atoms with CO2

    Science.gov (United States)

    Dubreuil, B.; Harnafi, M.

    1989-07-01

    The pulsed Li atomic beam produced in our experiment is based on controlled transversely-excited-atmospheric CO2 laser-induced ablation of a Li metal target. The atomic beam is propagated in vacuum or in CO2 gas at low pressure. Atoms in the beam are probed by laser-induced fluorescence spectroscopy. This allows the determination of time-of-flight and velocity distributions. Li Rydberg states (n=5-13) are populated in the beam by two-step pulsed-laser excitation. The excited atoms interact with CO2 molecules. l- and n-changing cross sections are deduced from the time evolution of the resonant or collision-induced fluorescence following this selective excitation. l-changing cross sections of the order of 104 AṦ are measured; they increase with n as opposed to the plateau observed for Li* colliding with a diatomic molecule. This behavior is qualitatively well explained in the framework of the free-electron model. n-->n' changing processes with large cross sections (10-100 AṦ) are also observed even in the case of large electronic energy change (ΔEnn'>103 cm-1). These results can be interpreted in terms of resonant-electronic to vibrational energy transfers between Li Rydberg states and CO2 vibrational modes.

  1. On the behavior of scattering phases in collisions of electrons with multi-atomic objects

    CERN Document Server

    Amusia, M Ya

    2015-01-01

    We have studied the energy dependence of several first scattering phases with multi-atomic object. As concrete examples representing the general trends endohedrals Neon inside C60 and Argon inside C60 are considered. It appeared that the presence of an inner atom, either Ne or Ar, qualitatively affects the scattering phases, in spite of the fact that the fullerene consists of 60 carbon atoms, while the atom staffed inside is only one. Calculations are performed in the one-electron Hartree-Fock (HF) and random phase approximation with exchange (RPAE) for the inner atom while the fullerenes shell is substituted by static potential without and with the polarization potential. It appeared that the total endohedral scattering phase is simply a sum of atomic, Ne or Ar, and fullerenes C60 phases, contrary to the intuitive assumption that the total phases on C60 and Neon inside C60 or Ar inside C60 has to be the same.

  2. Study of e-+ alkaline atom inelastic collisions with the Glauber approxmation

    International Nuclear Information System (INIS)

    Glauber's approximation is used to study discrete excitations in alkali atoms by electron impact. The interaction between the incident electron and the core electrons and (N-1) nuclear charges is described through an Yukawa-like potential. Analitical expressions for m2S and m2P excitations are obtained, as well as numerical results for several excitations processes in alkali atoms. (Author)

  3. Fluctuations in atomic collision cascades - variance and correlations in sputtering and defect distributions

    International Nuclear Information System (INIS)

    Fluctuation phenomena are investigated in various collision processes, i.e. ion bombardment induced sputtering and defect creation. The mean and variance of the sputter yield and the vacancies and interstitials are calculated as functions of the ion energy and the ion-target mass ratio. It is found that the relative variance of the defects in half-spaces and the relative variance of the sputter yield are not monotonous functions of the mass ratio. Two-point correlation functions in the depth variable, as well as sputtered energy, are also calculated. These functions help interpreting the behaviour of the relative variances of the integrated quantities, as well as understanding the cascade dynamics. All calculations are based on Lindhard power-law cross sections and use a binary collision Monte Carlo algorithm. 30 refs, 25 figs

  4. van der Waals-induced level coupling in metastable atom on surface collisions

    Science.gov (United States)

    Boustimi, M.; Viaris de Lesegno, B.; Perales, F.; Reinhardt, J.; Baudon, J.; Robert, J.; Ducloy, M.

    2001-01-01

    The symmetry of atomic wave functions is broken by the quadrupolar component of the van der Waals interaction between the atom and a planar surface. This results into a coupling able to mix levels of same parity such as 3P0 and 3P2 metastable levels of heavy rare gas atoms. The 3P0-3P2 transition in Ar and Kr has been evidenced in a time-of-flight experiment using as a surface the edge of a copper slit.

  5. A simple nonbinary scattering model applicable to atomic collisions is crystals at 1ow energies

    DEFF Research Database (Denmark)

    Andersen, Hans Henrik; Sigmund, Peter

    1966-01-01

    Presents the solution of a special scattering problem which may be important in the theory of slowing-down of atomic particles in crystals. A projectile moves along the centre axis of a regular ring of n equal atoms which are free and do not interact with each other. The interaction between the...... projectile and each ring atom is described by a Born-Mayer potential, and the scattering is assumed to be elastic and governed by the classical equations of motion. Because of symmetry, the problem can be reduced to plane motion of a particle in a potential of elliptic symmetry. The elliptic force field is...... asymptotic velocities of the ring atoms as well as the energy loss of the projectile. Furthermore, it can be decided whether the projectile is reflected by the ring. Both the feasibility of assumptions specifying the problem and the validity of different approximations made in the transformation from the...

  6. Theory of Neutrino-Atom Collisions: The History, Present Status, and BSM Physics

    International Nuclear Information System (INIS)

    An overview of the current theoretical studies on neutrino-atom scattering processes is presented. The ionization channel of these processes, which is studied in experiments searching for neutrino magnetic moments, is brought into focus. Recent developments in the theory of atomic ionization by impact of reactor antineutrinos are discussed. It is shown that the stepping approximation is well applicable for the data analysis practically down to the ionization threshold

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

    CERN Document Server

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

    2013-01-01

    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 /k_B = 20 mK-20 K. The lowest energies were achieved in experiments using single localized 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 analyzed 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 ...

  8. Relative level excitation in ion-atom collisions as a function of the orbital angular momentum quantum number

    International Nuclear Information System (INIS)

    In a previous study of projectile Rydberg state excitations in the collisions Be+, Mg+-He at 10-75 keV it was found, for a fixed value of the principal quantum number n, that the ratio of the s, p, and d level cross sections was close to 1:3:5, whereas the f and g level cross sections drop to approximately the same value as for s levels. Blaney and Berry (1976) found essentially the same increase in cross section for electron transfer into excited Li I states in the Li+-H2 collision. In contrast to this behavior, beam-foil excitations oscillate as a function of the orbital angular momentum quantum number with maxima at odd values of l (p, f,...) and minima at even l (s, d, g,...). Since no model is available to describe these features, the measurements have been extended to other systems to test their general validity. A large conjugated molecule (benzene) was chosen as target gas in one experiment to bridge the gap between ion-atom and ion-foil excitations. The data presented here have all been obtained by optical spectrometry. A quasi molecular approach is used to explain the results. (Auth.)

  9. Improved adiabatic calculation of muonic-hydrogen-atom cross sections. II. Hyperfine transitions and elastic scattering in symmetric collisions

    International Nuclear Information System (INIS)

    The improved adiabatic representation is used in calculations of elastic and hyperfine-transition cross sections for symmetric collisions of pμ, dμ, and tμ with bare p, d, and t nuclei and with H, D, and T atoms, respectively. The cross sections for dμ+d and tμ+t are in excellent agreement with other recent determinations, while those for pμ+p are about 30% larger at low energies. The electronic screening is calculated nonperturbatively and found to be about 30% smaller in magnitude than the previously calculated value at large internuclear distances, and to deviate considerably from the asymptotic form in the molecular region. The resulting screened elastic cross sections are up to 60% smaller than those obtained using the old screening potential. The reactance matrices, needed for calculations of molecular-target effects, are given in tables

  10. Quantum-kinetic modeling of electron release in low-energy surface collisions of atoms and molecules

    International Nuclear Information System (INIS)

    In this work we present a theoretical description of electron release in the collision of atomic and molecular projectiles with metallic and especially dielectric surfaces. The associated electron yield, the secondary electron emission coefficient, is an important input parameter for numerical simulations of dielectric barrier discharges and other bounded low-temperature gas discharges. The available reference data for emission coefficients is, however, very sparse and often uncertain, especially for molecular projectiles. With the present work we aim to contribute to the filling of these gaps by providing a flexible and easy-to-use model that allows for a convenient calculation of the emission coefficient and related quantities for a wide range of projectile-surface systems and the most dominant reaction channels.

  11. Quantum-kinetic modeling of electron release in low-energy surface collisions of atoms and molecules

    Energy Technology Data Exchange (ETDEWEB)

    Marbach, Johannes

    2012-09-20

    In this work we present a theoretical description of electron release in the collision of atomic and molecular projectiles with metallic and especially dielectric surfaces. The associated electron yield, the secondary electron emission coefficient, is an important input parameter for numerical simulations of dielectric barrier discharges and other bounded low-temperature gas discharges. The available reference data for emission coefficients is, however, very sparse and often uncertain, especially for molecular projectiles. With the present work we aim to contribute to the filling of these gaps by providing a flexible and easy-to-use model that allows for a convenient calculation of the emission coefficient and related quantities for a wide range of projectile-surface systems and the most dominant reaction channels.

  12. Transport properties derived from ion-atom collisions: 6Li-6Li+ and 6Li-7Li+ Cases

    Science.gov (United States)

    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.

  13. Atomic data on inelastic processes in low-energy beryllium-hydrogen collisions

    Science.gov (United States)

    Yakovleva, Svetlana A.; Voronov, Yaroslav V.; Belyaev, Andrey K.

    2016-08-01

    Aims: Inelastic processes in low-energy Be + H and Be+ + H- collisions are treated for the states from the ground and up to the ionic state with the aim to provide rate coefficients needed for non-local thermodynamic equilibrium (non-LTE) modeling of beryllium spectra in cool stellar atmospheres. Methods: The electronic molecular structure is determined by using a recently proposed model quantum approach that is based on an asymptotic method. Nonadiabatic nuclear dynamics is treated by means of multichannel formulas, based on the Landau-Zener model for nonadiabatic transition probabilities. Results: The cross sections and the rate coefficients for inelastic processes in Be + H and Be+ + H- collisions are calculated for all transitions between 13 low-lying covalent states plus the ionic state. It is shown that the highest rate coefficient values correspond to the mutual neutralization processes with the final states Be(2s3s 1S), Be(2s3p 1,3P), Be(2s3d 3D). These processes, as well as some of the excitation, de-excitation and ion-pair formation processes, are likely to be important for non-LTE modeling. Tables A.1-A.10 are also available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/593/A27

  14. Quasi-free scattering in the ionization and destruction of hydrogen and helium Rydberg atoms in collision with neutral targets

    International Nuclear Information System (INIS)

    Hydrogen and helium Rydberg atoms (H** and He**), with principal quantum number n ranging from 10 to 20, have been used in collision experiments from 1 to 40 keV/amu. These were produced by electron capture in a charge-exchange cell and analyzed by ionization in a modulated electric field combined with phase-sensitive detection. Three experiments have been conducted. In the first, spectra of the band of H and He Rydberg states from electron capture were produced by the modulated field technique and compared. Considerable differences were found between the two. Both types of spectra were analyzed with calculations of Stark energies and field ionization rates. Attempts were made to simulate the spectra using this information and some assumptions about the state distribution produced in the electron capture. In the second experiment, destruction cross sections for H** incident on N2, Ar, and SF6 were measured. This was a further test of the independent-particle model for Rydberg atom scattering; in this model, the atom is destroyed by quasi-free scattering of either the ionic core or the outer electron. Already proven valid for n = 20-35, this has been extended to n as low as 10, as measurements with n = 10 showed full compliance with the model. In the third experiment, not only destruction cross sections but also ionization cross sections for H** and He** incident on Xe, AR, and N2 were measured. The ionization measurement is a more sensitive test of the quasi-free scattering of the Rydberg electron. This was especially important for the Xe and Ar targets, which exhibits a Ramsauer-Townsend minimum in their free-electron scattering cross sections. The quasi-free Rydberg electron should reproduce these data. Unmistakable deviations from the quasi-free prediction were seen in Xe and N2 but not in Ar. This represents the first measurement of a breakdown of the Independent Particle Model for fast Rydberg atom scattering

  15. Resonant coherent ionization in grazing ion/atom-surface collisions at high velocities

    International Nuclear Information System (INIS)

    The resonant coherent interaction of a fast ion/atom with an oriented crystal surface under grazing incidence conditions is shown to contribute significantly to ionize the probe for high enough velocities and motion along a random direction. The dependence of this process on both the distance to the surface and the velocity of the projectile is studied in detail. We focus on the case of hydrogen moving with a velocity above 2 a.u. Comparison with other mechanisms of charge transfer, such as capture from inner shells of the target atoms, permits us to draw some conclusions about the charge state of the outgoing projectiles. (orig.)

  16. Resonant coherent ionization in grazing ion/atom-surface collisions at high velocities

    Energy Technology Data Exchange (ETDEWEB)

    Garcia de Abajo, F.J. (Dept. de Ciencias de la Computacion e Inteligencia Artificial, Facultad de Informatica, Univ. del Pais Vasco, San Sebastian (Spain)); Pitarke, J.M. (Materia Kondentsatuaren Fisika Saila, Zientzi Fakultatea, Euskal Herriko Univ., Bilbo (Spain))

    1994-05-01

    The resonant coherent interaction of a fast ion/atom with an oriented crystal surface under grazing incidence conditions is shown to contribute significantly to ionize the probe for high enough velocities and motion along a random direction. The dependence of this process on both the distance to the surface and the velocity of the projectile is studied in detail. We focus on the case of hydrogen moving with a velocity above 2 a.u. Comparison with other mechanisms of charge transfer, such as capture from inner shells of the target atoms, permits us to draw some conclusions about the charge state of the outgoing projectiles. (orig.)

  17. Close-Coupling R-Matrix Approach to Simulating Ion-Atom Collisions for Accelerator Applications

    CERN Document Server

    Stoltz, Peter

    2005-01-01

    We have implemented an R-matrix close coupling approach to calculate capture, ionization, stripping and excitation cross-sections for 0.5 to 8.0 MeV K+ incident on Ar. This is relevant to the High Current Experiment at Lawrence Berkley National Laboratory. These cross sections are used to model accelerator particle dynamics where background gasses can interfere with beam quality. This code is a semi-classical approach that uses quantum mechanics to describe the particle interactions and uses classical mechanics to describe the nuclei trajectories. We compare a hydrogenic approximation for K+ with a pseudo-potential approach. Further we are developing a variational approach to quickly determine the best pseudo-potential parameters. Since many R-Matrix computationalists use this pseudo-potential approach, this approach will be useful for helping generate cross sections for any collision system.

  18. Relativistic effect in inelastic collision of electron with atom or ion

    International Nuclear Information System (INIS)

    Based on relativistic Born approximation theory, we have calculated the relativistic and non-relativistic generalized oscillator strengthens (GOS) of the Li-likes iso-electron sequence. The difference between the two calculations shows the relativistic effect of both the target and impact electron in the inelastic collision process. For low Z target (e.g. Li), the relativistic effect is negligible. For the 2s-3p transition of Au+'76, the relativistic GOS is 27.1% smaller than the non-relativistic one. At high impact energy, the contribution of transverse term of GOS to the differential cross section is important at certain angle. At extremely high impact energy (e.g. 106, 107 eV), the transverse term of GOS becomes dominant at forward small angle and such forward peak makes overwhelming contribution to the total inelastic cross section

  19. Radiative electron capture studied in relativistic heavy-ion atom collisions

    International Nuclear Information System (INIS)

    The process of Radiative Electron Capture (REC) in relativistic collisions of high-Z ions with low-Z gaseous and solid targets is studied experimentally and theoretically. The observed X-ray spectra are analysed with respect to photon angular distributions as well as to total K-REC cross sections. The experimental results for angle-differential cross sections are well-reproduced by exact relativistic calculations which yield significant deviations from standard sin2θ distributions. Total cross sections for K-REC are shown to follow a simple scaling rule obtained from exact relativistic calculations as well as from a non-relativistic dipole approximation. The agreement between these different theoretical approaches must be regarded as fortuitous, but it lends support to the use of the non-relativistic approach for practical purposes. (orig.)

  20. Correlated charge changing ion-atom collisions: Progress report for the period February 15, 1987-March 14, 1988

    International Nuclear Information System (INIS)

    This report summarizes the progress and accomplishments in accelerator atomic physics research supported by DOE grant DE-FG02-87ER13778 for a period of 13 months from February 15, 1987 through March 14, 1988. The general scope of this work involves the experimental investigation of fundamental atomic interactions in collisions of highly charged projectiles with neutral targets, with a particular emphasis on two-electron interactions. Inner-shell processes involving excitation, ionization, and charge transfer are investigated using coincidence techniques in which projectile charge-changing events are associated with x-ray emission, target recoil ions, or electron emission. New measurements were conducted using accelerators at the Lawrence Berkeley Laboratory, Argonne National Laboratory, Hahn-Meitner-Institut (Berlin), and Western Michigan University. The work at Hahn-Meitner resulted from a collaboration initiated while J. A. T. was on research leave from Western Michigan University during the 1986-1987 academic year. The principal new results obtained during the past year using each of the three coincidence techniques are summarized below. A major emphasis of all these investigations is to determine the role of electron correlation in two- (and multiple-) electron interactions

  1. Perfect/complete scattering experiments. Probing quantum mechanics on atomic and molecular collisions and coincidences

    Energy Technology Data Exchange (ETDEWEB)

    Lohmann, Bernd [Muenster Univ. (Germany). Inst. fuer Theoretische Physik 1; Grum-Grzhimailo, Alexei N. [Moscow State Univ. (Russian Federation). Skobeltsyn Inst. of Nuclear Physics; Kleinpoppen, Hans

    2013-07-01

    Derives parameters for electrons, photons, atoms, ions, molecules calculated from theory. Delivers the quantum mechanical knowledge of atomic and molecular physics. Presents state-of-the-art experiments in atomic and molecular physics and related theoretical approaches. The main goal of this book is to elucidate what kind of experiment must be performed in order to determine the full set of independent parameters which can be extracted and calculated from theory, where electrons, photons, atoms, ions, molecules, or molecular ions may serve as the interacting constituents of matter. The feasibility of such perfect' and-or 'complete' experiments, providing the complete quantum mechanical knowledge of the process, is associated with the enormous potential of modern research techniques, both, in experiment and theory. It is even difficult to overestimate the role of theory in setting of the complete experiment, starting with the fact that an experiment can be complete only within a certain theoretical framework, and ending with the direct prescription of what, and in what conditions should be measured to make the experiment 'complete'. The language of the related theory is the language of quantum mechanical amplitudes and their relative phases. This book captures the spirit of research in the direction of the complete experiment in atomic and molecular physics, considering some of the basic quantum processes: scattering, Auger decay and photo-ionization. It includes a description of the experimental methods used to realize, step by step, the complete experiment up to the level of the amplitudes and phases. The corresponding arsenal includes, beyond determining the total cross section, the observation of angle and spin resolved quantities, photon polarization and correlation parameters, measurements applying coincidence techniques, preparing initially polarized targets, and even more sophisticated methods. The 'complete' experiment is

  2. Perfect/complete scattering experiments. Probing quantum mechanics on atomic and molecular collisions and coincidences

    International Nuclear Information System (INIS)

    Derives parameters for electrons, photons, atoms, ions, molecules calculated from theory. Delivers the quantum mechanical knowledge of atomic and molecular physics. Presents state-of-the-art experiments in atomic and molecular physics and related theoretical approaches. The main goal of this book is to elucidate what kind of experiment must be performed in order to determine the full set of independent parameters which can be extracted and calculated from theory, where electrons, photons, atoms, ions, molecules, or molecular ions may serve as the interacting constituents of matter. The feasibility of such perfect' and-or 'complete' experiments, providing the complete quantum mechanical knowledge of the process, is associated with the enormous potential of modern research techniques, both, in experiment and theory. It is even difficult to overestimate the role of theory in setting of the complete experiment, starting with the fact that an experiment can be complete only within a certain theoretical framework, and ending with the direct prescription of what, and in what conditions should be measured to make the experiment 'complete'. The language of the related theory is the language of quantum mechanical amplitudes and their relative phases. This book captures the spirit of research in the direction of the complete experiment in atomic and molecular physics, considering some of the basic quantum processes: scattering, Auger decay and photo-ionization. It includes a description of the experimental methods used to realize, step by step, the complete experiment up to the level of the amplitudes and phases. The corresponding arsenal includes, beyond determining the total cross section, the observation of angle and spin resolved quantities, photon polarization and correlation parameters, measurements applying coincidence techniques, preparing initially polarized targets, and even more sophisticated methods. The 'complete' experiment is, until today, hardly to perform

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

    Science.gov (United States)

    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.

  4. Hydrogen Atom Collision Processes in Cool Stellar Atmospheres: Effects on Spectral Line Strengths and Measured Chemical Abundances in Old Stars

    International Nuclear Information System (INIS)

    The precise measurement of the chemical composition of stars is a fundamental problem relevant to many areas of astrophysics. State-of-the-art approaches attempt to unite accurate descriptions of microphysics, non-local thermodynamic equilibrium (non-LTE) line formation and 3D hydrodynamical model atmospheres. In this paper I review progress in understanding inelastic collisions of hydrogen atoms with other species and their influence on spectral line formation and derived abundances in stellar atmospheres. These collisions are a major source of uncertainty in non-LTE modelling of spectral lines and abundance determinations, especially for old, metal-poor stars, which are unique tracers of the early evolution of our galaxy. Full quantum scattering calculations of direct excitation processes X(nl) + H ↔ X(n'l') + H and charge transfer processes X(nl) + H ↔ X+ + H− have been done for Li, Na and Mg [1,2,3] based on detailed quantum chemical data, e.g. [4]. Rate coefficients have been calculated and applied to non-LTE modelling of spectral lines in stellar atmospheres [5,6,7,8,9]. In all cases we find that charge transfer processes from the first excited S-state are very important, and the processes affect measured abundances for Li, Na and Mg in some stars by as much as 60%. Effects vary with stellar parameters (e.g. temperature, luminosity, metal content) and so these processes are important not only for accurate absolute abundances, but also for relative abundances among dissimilar stars.

  5. Excitation of atoms and molecules in collisions with highly charged ions

    International Nuclear Information System (INIS)

    A study of the double ionization of He by high-energy N7+ ions was extended up in energy to 40 MeV/amu. Coincidence time-of-flight studies of multicharged N2, O2, and CO molecular ions produced in collisions with 97-MeV Ar14+ ions were completed. Analysis of the total kinetic energy distributions and comparison with the available data for CO2+ and CO3+ 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 CO1+ and CO2+ molecular ions, and the branching ratios for the most prominent charge division channels of CO2+ through CO7+ 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

  6. Several manifestations of Pauli correlations in energetic ion-atom collisions

    International Nuclear Information System (INIS)

    In our discussion of Pauli correlation effects in collisions, we shall limit consideration to a fixed basis of spin-orbitals of the target, given by the static Hartree-Fock (HF) approximation, together with hydrogenic orbitals for electrons captured by the projectile. Moreover, we shall restrict attention to closed shell cases or to the case with one half-occupied s-shell, so that the mean field has spherical symmetry. The case of more general open shells requires multiplet theory which, strictly speaking, goes beyond the independent particle model (IPM) by involving a linear combination of determinants. In the case discussed here we can use the m-scheme in which many-electron states are specified by the quantum numbers k = (n,l,m/sub l/,m/sub s/) of each occupied spin-orbital. The initial state of an F-electron system will be specified by the spin-orbital labels h1,...,h/sub F/. Reactions will be described in terms of occupancies and vacancies of spin-orbitals. 19 refs

  7. Atomic collision experiments utilizing low-velocity, highly-charged ion beams

    International Nuclear Information System (INIS)

    Intense beams of highly-stripped ions are now routinely produced at low velocities using the Brookhaven dual MP-tandems 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 S6-16+ on He and Ar at 6-20 MeV and P(b) measurements for MO x-rays produced in Cl16+ + 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

  8. Ionization and charge transfer in high-energy ion-atom collisions

    International Nuclear Information System (INIS)

    Electron capture and loss by fast highly charged ions in a gas target, and ionization of the target by passage of the fast projectile beam, are fundamental processes in atomic physics. These processes, along with excitation, can be experimentally studied separately (''singles'') or together (''coincidence''). This paper is a review of recent results on singles measurements for electron capture and loss and for target ionization, for velocities which are generally high relative to the active electron, including recent ionization measurements for a nearly relativistic projectile. 11 refs., 6 figs

  9. Quantum mechanical theory of a structured atom-diatom collision system - A + BC/1-Sigma/

    Science.gov (United States)

    Devries, P. L.; George, T. F.

    1977-01-01

    The problem of a 2-p state atom colliding with a singlet sigma state diatom, which involves multiple potential surfaces, is investigated. Within a diabatic representation for the electronic degrees of freedom (plus spin-orbit interaction), coupled scattering equations are derived in both space-fixed and body-fixed coordinate systems. Coefficients, analogous to Percival-Seaton coefficients, are obtained. Approximations to the exact equations, including angular momenta decoupling approximations, are discussed for both the space-fixed and body-fixed formalisms.

  10. Optical excitation cross-sections for electron collisions with atoms and molecules

    International Nuclear Information System (INIS)

    A brief review of the status of absolute electron-impact excitation cross-section measurements for atoms and molecules is presented. Some of the reasons for the wide discrepancies which exist in the published data are discussed. Tables are presented of recent publications in the field which are not included in the J.I.L.A. compilations. A tabular compilation of the existing data for e-impact on H2O is also given and discussed. Some recent experiments of particular interest to the development of the theory of electron-molecule excitation are mentioned. 112 references, 3 figures, 3 tables

  11. Electron capture and ionization for ion-Rydberg atom collisions in a magnetic field

    International Nuclear Information System (INIS)

    Within the classical trajectory Monte Carlo (CTMC) model, we calculate electron transfer and ionization cross sections for 1.3-130 eV amu-1 singly charged ions colliding with Rydberg atoms in the presence of a laboratory-strength magnetic field of 4 tesla. A new method for generating a stationary microcanonical ensemble for a quasi-integrable initial-state Hamiltonian is presented. The calculated cross sections show signatures of electron capture and ionization mechanisms for the field-free case, e.g. multiple swaps and saddle-point electrons; their structure as well as their magnitude, however, are strongly modified by the presence of the magnetic field. (Author)

  12. An empirical curve describing the ionization cross-sections in atomic collisions involving heavy ions

    International Nuclear Information System (INIS)

    In a recent paper, a fifth order polynomial curve was presented which fits very well to the existing experimental data on K-shell ionization cross-sections induced by protons. It is a universal curve, in the sense that it includes target atoms of any Z number at any projectile (proton) energy. In principle, it is possible to fit in the same curve the cross-sections obtained with any ion as a projectile, by means of a scaling law derived from the plane wave Born approximation (PWBA) and the binary encounter approximation (BEA) models. Experimental data with deuterons, alpha particles and 3He ions were fit into the same curve, with a good agreement. The agreement was poorer for experimental cross-sections obtained with heavier ions, like 12C, 14N and 40Ar. The discrepancies are attributable to several aspects of the ion-atom interaction, not considered in the derivation of such scaling law. The ECPSSR model has been more successful on predicting the cross-sections for heavy ions. Within the considerations in the ECPSSR and other models, arguments are given to explain the former discrepancies and suggestions are made to generalize the scaling law to fit the heavy ion data in a single curve

  13. Absolute Doubly Differential Cross Sections for Ejection of Electrons in - and Five-Body Collisions of 20 TO 114-KEV Protons on Atomic and Molecular Hydrogen.

    Science.gov (United States)

    Kerby, George W., III

    A crossed-beam experiment was performed to detect ejected electrons from ground-state atomic and molecular hydrogen after collisions with 20- to 114-keV protons. Because a pure atomic hydrogen target is not readily attainable, a method has been devised which yields atomic to molecular hydrogen doubly differential cross section (DDCS) ratios. Since the molecular hydrogen DDCS's were independently measured, the atomic cross sections could be directly calculated. Absolute cross sections differential in electron energy and angle were measured for electron energies ranging from 1.5 to 400 eV and scattering angles from 15^circ to 165^circ with respect to the fast beam. Electrons and ions were energy analyzed by an electrostatic hemispherical analyzer, which has an energy resolution of 5% and is rotatable in the scattering plane about the collision center. Atomic hydrogen is produced by a radio-frequency discharge of the type devised by J. Slevin. Hydrogen gas effuses from a 1 mm diameter nozzle in a nearly cos theta distribution. The projectile beam intersects the thermal gas targets 4 mm below the tip of the nozzle. Dissociation fractions of 74% and atomic hydrogen densities of 7 times 10 ^{11} cm^ {-3} were typical. The fraction of dissociated hydrogen was measured by detecting the reduced 9-eV ion signal from the molecular target when the RF is on. This characteristic ion signal originates from the coulomb breakup of the molecule and dissociative channels of excited H _sp{2}{+}. An auxiliary experiment was performed to determine the target densities with the aid of a low-resolution magnetic mass spectrometer after the slow recoil ions were extracted from the collision volume by a weak electric field. Comparisons of the atomic cross sections are made with theories such as the classical-trajectory Monte Carlo (CTMC) method, the plane-wave Born approximation (PWBA) and the continuum-distorted-wave eikonal-initial-state (CDW-EIS) approximation.

  14. Screening and antiscreening by projectile electrons in high-velocity atomic collisions

    International Nuclear Information System (INIS)

    The scattering amplitude for a projectile of nuclear charge Z1 carrying N electrons colliding with an atomic target with charge Z2, evaluated in the first Born approximation using hydrogenic wave functions, is compared with recent experimental results. In the present approximation where the minimum momentum transfer t/sub min/ is considered to be approximately independent of the final state of the projectile, the differential cross sections separate into a product of one term that depends only on the target times the square Z21(t) of an effective projectile charge. Here an analytic expression for Z21(t) is given for 2, 1, and 0 electrons. Some total ionization cross-section ratios are also given

  15. Penning and dissociative ionizations of methane molecules in collisions with metastable helium atoms

    International Nuclear Information System (INIS)

    Measurements of relative ion production yields in the Penning and dissociative ionizations of methane molecules on impact of metastable helium atoms have been carried out using a new crossed-beam apparatus, ''Perfectron''. Due to the perfect focusing property of the perfectron, the total ion yield as well as differential ion yield of each reaction channel can be measured. Though the measurement is at present only preliminary and no attempt is made to discriminate between 21S and 23S states in the primary helium beam, obtained spectra are in good agreement with those of Cermak et. al. and of Herce et. al. in the measurement of total ion yields. The CH3+ ions are most abundant in contrast with electron impact where the parent CH4+ ions predominate. On the other hand, in the measurement of differential ion yields at 00 with respect to the methane beam, the parent CH4+ ions slightly predominate over the fragment CH3+ ions. (author)

  16. Calculation of the elastic collision properties of Na and Li atoms at ultracold temperature

    Institute of Scientific and Technical Information of China (English)

    Zhang Ji-Cai; Zhang Ying; Du Bing-Ge; Sun Jin-Feng

    2009-01-01

    This paper firstly reports a theoretical study of elastic scattering properties in a mixture of 23Na and 7Li atoms at cold and ultracold temperatures in detail.Based on the new constructed accurate singlet X1∑+g and the triplet a3∑+u states interatomic potentials for 23Na7Li mixture,it calculates the scattering lengths and the effective ranges by three computational methods,and obtains good agreements.Using the mass scaling method,it also calculates 23Na6Li scattering lengths and s-wave and total elastic cross sections,whose rich resonance structures were found and interpreted in terms of quasibound diatomic levels trapped behind a centrifugal barrier.

  17. Atomic and plasma-material interaction data for fusion. V. 8. Elastic and related transport cross sections for collisions among isotopomers of H+ + H, H+ + H2, H+ + He, H + H, and H + H2

    International Nuclear Information System (INIS)

    The Volume 8 of the 'Atomic and Plasma-Material Interaction Data for Fusion' provides an exhaustive source of information on elastic scattering, momentum transfer and viscosity cross sections for collisions of hydrogenic ions, atoms and molecules, and their isotopes, in the energy range pertinent to fusion reactor divertor plasmas and extending (in its low-energy part) to collision conditions that are relevant for astrophysics. Hydrogen ion-helium atom collisions are also included. The reported cross sections are obtained from extensive quantum-mechanical calculations and can be regarded as having very high accuracy

  18. Grazing incidence collisions of ions and atoms with surfaces: from charge exchange to atomic diffraction; Collisions rasantes d'ions ou d'atomes sur les surfaces: de l'echange de charge a la diffraction atomique

    Energy Technology Data Exchange (ETDEWEB)

    Rousseau, P

    2006-09-15

    This thesis reports two studies about the interaction with insulating surfaces of keV ions or atoms under grazing incidence. The first part presents a study of charge exchange processes occurring during the interaction of singly charged ions with the surface of NaCl. In particular, by measuring the scattered charge fraction and the energy loss in coincidence with electron emission, the neutralization mechanism is determined for S{sup +}, C{sup +}, Xe{sup +}, H{sup +}, O{sup +}, Kr{sup +}, N{sup +}, Ar{sup +}, F{sup +}, Ne{sup +} and He{sup +}. These results show the importance of the double electron capture as neutralization process for ions having too much potential energy for resonant capture and not enough for Auger neutralization. We have also studied the ionisation of the projectile and of the surface, and the different Auger-like neutralization processes resulting in electron emission, population of conduction band or excited state. For oxygen scattering, we have measured an higher electron yield in coincidence with scattered negative ion than with scattered atom suggesting the transient formation above the surface of the oxygen doubly negative ion. The second study deals with the fast atom diffraction, a new phenomenon observed for the first time during this work. Due to the large parallel velocity, the surface appears as a corrugated wall where rows interfere. Similarly to the Thermal Atom Scattering the diffraction pattern corresponds to the surface potential and is sensitive to vibrations. We have study the H-NaCl and He-LiF atom-surface potentials in the 20 meV - 1 eV range. This new method offers interesting perspectives for surface characterisation. (author)

  19. Molecular-orbital treatment of electron capture in an external magnetic field: collisions of B4+ ions with H atoms

    International Nuclear Information System (INIS)

    A semiclassical close-coupling equation is formulated for the electron-capture process in ion-atom collisions under the influence of an external magnetic field. The direction of the magnetic field is chosen to be parallel to an initial velocity vector of a projectile. As we deal with the case for the magnetic field strength less than the critical field strength (2.35 x 105 T), the second- and higher-order terms for the magnetic field are neglected. Eigenfunctions in zero magnetic field are employed as a basis set for expansion. The equation obtained is the same in structure as that at zero magnetic field except that the relative velocity υ is replaced by the scaled velocity υB. Effects due to the magnetic field are: (i) dynamic couplings, similar to rotational couplings and (ii) the Zeeman splitting of energies. The phase factor due to the gauge transformation is similar in form to the electron-translation factor. We apply this close-coupling equation to a study of electron-capture processes in a singlet (B4+ + H) system at 0 ≤ B ≤ 2.35 x 104 T, for which the zero-field results have been reported earlier. (author)

  20. Rotationally inelastic collisions of LiH with He: Quasiclassical dynamics of atom-rigid rotor trajectories

    International Nuclear Information System (INIS)

    Rotationally inelastic cross sections for the LiH--He collision system are computed classically using a previously derived ab initio potential energy surface [D. M. Silver, J. Chem. Phys. 72, 6445 (1980)]. The LiH is in its ground vibronic state and is initially taken to be in its j = 1 rotational state. The He is in its ground electronic state. The system is treated as an atom-rigid rotor interaction. The results are compared with previously computed cross sections derived from the same ab initio potential energy surface using the coupled states approximation for quantum mechanical scattering [E. F. Jendrek and M. H. Alexander, J. Chem. Phys. 72, 6452 (1980)]. The theoretical total cross sections are averaged over a temperature distribution and are then compared with experimental measurements of corresponding cross sections for a rotationally resolved LiH beam ( j = 1) incident on a He gas target in thermal equilibrium at room temperature [P. J. Dagdigian and B. E. Wilcomb, J. Chem. Phys. 72, 6462 (1980)]. The agreement between classical, quantum and experimental results is discussed

  1. Atomic Collisions and Spectroscopy at the Heavy-Ion Storage Ring TSR

    International Nuclear Information System (INIS)

    The storage ring TSR is used to cool and accumulate a wide range of heavy-ion beams produced at the Max-Planck Institute for Nuclear Physics in Heidelberg, Germany. With ionization stages reaching up to 50 (bare nuclei up to Cl17) and beam energies of typically 5-8 MeV/u, storage lifetimes amount to minutes up to hours; repeated cycles of injection and electron cooling (reducing the ion beam diameter Tom centimeters to millimeters in about 2 sec) make it possible to accumulate beam currents up to 1 mA in the ring. With the circulating beam, in particular the interaction of multicharged atomic ions with electrons of variable, well defined energies (10 MeV to 3 keV) is studied, detecting recombination and electron impact ionization. High-resolution spectra of the dielectronic recombination cross section have been obtained, which provide a sensitive test for atomic-structure calculations describing the large number of doubly excited states contributing to the recombination rate. For lithiumlike ions (Si11+, Cl14+) all possible outer- and inner-shell excitations were investigated[1]. Low-energy di- electronic recombination measurements are presently being extended[2] also to more complex open-L-shell ions (F11+-F23+). Very recently the enhancement of dielectronic recombination by ambient electric fields was studied with Cl14=; at well-controlled fields of order 100 V /cm the enhancement of the cross section by up to a factor of 3 in certain energy regions could be followed in detail[3] . In addition to the information on doubly excited levels from dielectronic recombination experiments, spectroscopic results on multicharged ions were also obtained by laser-stimulated recombination[4] , allowing highly excited levels in multicharged ions to be reached by laser transitions from continuum states populated by surrounding free electrons. Moreover, for a number of metastable levels in multicharged ions the natural lifetimes in the millisecond to second range could be

  2. Perfect/complete scattering experiments probing quantum mechanics on atomic and molecular collisions and coincidences

    CERN Document Server

    Kleinpoppen, Hans; Grum-Grzhimailo, Alexei N

    2013-01-01

    The main goal of this book is to elucidate what kind of experiment must be performed in order to determine the full set of independent parameters which can be extracted and calculated from theory, where electrons, photons, atoms, ions, molecules, or molecular ions may serve as the interacting constituents of matter.  The feasibility of such perfect' and-or `complete' experiments, providing the complete quantum mechanical knowledge of the process, is associated with the enormous potential of modern research techniques, both, in experiment and theory.  It is even difficult to overestimate the role of theory in setting of the complete experiment, starting with the fact that an experiment can be complete only within a certain theoretical framework, and ending with the direct prescription of what, and in what conditions should be measured to make the experiment `complete'.  The language of the related theory is the language of quantum mechanical amplitudes and their relative phases.  This book captures the spi...

  3. Power-law temperature dependence of collision broadening and shift of atomic and molecular rovibronic lines

    International Nuclear Information System (INIS)

    The classical phase-shift theory of spectral line shapes is used to examine various aspects of the applicability of the power-law relations to the description of temperature variations of pressure broadening and shifting coefficients of the isolated atomic and rovibronic molecular lines in a wide temperature range. Model calculations performed for potentials of the Lennard-Jones type indicate that the temperature dependence exponents of the broadening and shifting can be related to the details of the intermolecular interactions. It is shown that they are sensitive to the range of temperatures assumed in the fit and therefore extreme care must be taken when the power-law temperature dependence is used as a scaling law. The problems of the failure of the power-law and of variations in the sign of pressure shift coefficients with increasing temperature are discussed. Very good fits of Frost's empirical formula for temperature dependence of pressure shift to the theoretical ones are obtained. -- Highlights: ► Classical theory of line shapes is used to examine the power-law relations. ► The broadening and shifting exponents depend on the range of temperatures in the fit. ► Extreme care must be taken when using the power-law dependence as a scaling law

  4. Penning and dissociative ionizations of methane molecules in collisions with metastable helium atoms

    Energy Technology Data Exchange (ETDEWEB)

    Arikawa, Tatsuo; Kanazawa, Ken-ichi; Tsurubuchi, Seiji (Tokyo Univ. of Agriculture and Technology, Koganei (Japan). Faculty of Technology)

    1983-06-01

    Measurements of relative ion production yields in the Penning and dissociative ionizations of methane molecules on impact of metastable helium atoms have been carried out using a new crossed-beam apparatus, ''Perfectron''. Due to the perfect focusing property of the perfectron, the total ion yield as well as differential ion yield of each reaction channel can be measured. Though the measurement is at present only preliminary and no attempt is made to discriminate between 2/sup 1/S and 2/sup 3/S states in the primary helium beam, obtained spectra are in good agreement with those of Cermak et. al. and of Herce et. al. in the measurement of total ion yields. The CH/sub 3//sup +/ ions are most abundant in contrast with electron impact where the parent CH/sub 4//sup +/ ions predominate. On the other hand, in the measurement of differential ion yields at 0/sup 0/ with respect to the methane beam, the parent CH/sub 4//sup +/ ions slightly predominate over the fragment CH/sub 3//sup +/ ions.

  5. Absolute fragmentation cross sections in atom-molecule collisions: Scaling laws for non-statistical fragmentation of polycyclic aromatic hydrocarbon molecules

    International Nuclear Information System (INIS)

    We present scaling laws for absolute cross sections for non-statistical fragmentation in collisions between Polycyclic Aromatic Hydrocarbons (PAH/PAH+) and hydrogen or helium atoms with kinetic energies ranging from 50 eV to 10 keV. Further, we calculate the total fragmentation cross sections (including statistical fragmentation) for 110 eV PAH/PAH+ + He collisions, and show that they compare well with experimental results. We demonstrate that non-statistical fragmentation becomes dominant for large PAHs and that it yields highly reactive fragments forming strong covalent bonds with atoms (H and N) and molecules (C6H5). Thus nonstatistical fragmentation may be an effective initial step in the formation of, e.g., Polycyclic Aromatic Nitrogen Heterocycles (PANHs). This relates to recent discussions on the evolution of PAHNs in space and the reactivities of defect graphene structures

  6. Absolute fragmentation cross sections in atom-molecule collisions: Scaling laws for non-statistical fragmentation of polycyclic aromatic hydrocarbon molecules

    Energy Technology Data Exchange (ETDEWEB)

    Chen, T.; Gatchell, M.; Stockett, M. H.; Alexander, J. D.; Schmidt, H. T.; Cederquist, H.; Zettergren, H., E-mail: henning@fysik.su.se [Department of Physics, Stockholm University, S-106 91 Stockholm (Sweden); Zhang, Y. [Department of Mathematics, Faculty of Physics, M. V. Lomonosov Moscow State University, Leninskie Gory, 119991 Moscow (Russian Federation); Rousseau, P.; Maclot, S.; Delaunay, R.; Adoui, L. [CIMAP, UMR 6252, CEA/CNRS/ENSICAEN/Université de Caen Basse-Normandie, bd Henri Becquerel, BP 5133, F-14070 Caen Cedex 05 (France); Université de Caen Basse-Normandie, Esplanade de la Paix, F-14032 Caen (France); Domaracka, A.; Huber, B. A. [CIMAP, UMR 6252, CEA/CNRS/ENSICAEN/Université de Caen Basse-Normandie, bd Henri Becquerel, BP 5133, F-14070 Caen Cedex 05 (France); Schlathölter, T. [Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747AG Groningen (Netherlands)

    2014-06-14

    We present scaling laws for absolute cross sections for non-statistical fragmentation in collisions between Polycyclic Aromatic Hydrocarbons (PAH/PAH{sup +}) and hydrogen or helium atoms with kinetic energies ranging from 50 eV to 10 keV. Further, we calculate the total fragmentation cross sections (including statistical fragmentation) for 110 eV PAH/PAH{sup +} + He collisions, and show that they compare well with experimental results. We demonstrate that non-statistical fragmentation becomes dominant for large PAHs and that it yields highly reactive fragments forming strong covalent bonds with atoms (H and N) and molecules (C{sub 6}H{sub 5}). Thus nonstatistical fragmentation may be an effective initial step in the formation of, e.g., Polycyclic Aromatic Nitrogen Heterocycles (PANHs). This relates to recent discussions on the evolution of PAHNs in space and the reactivities of defect graphene structures.

  7. Excitation of Lα- Hydrogen Atomic Line in the Collisions of H3+ and H2+ Molecules with He, Ar, O2 Targets

    International Nuclear Information System (INIS)

    We have presented results of experimental measurment of the excitation function of hydrogen atomic line Lα (I=121.6nm), which was emitted during dissociative excitation processes of hydrogen molecules at collisions H2+, H3+ - He, Ar, O2 in the energy interval 3-9 keV of ion. It was determined that the intensity of radiation depends on internal (vibrational) excitation of H3+ molecular ion in the initial ground electronic state. (author)

  8. Study of the anti-hydrogen atom and ion formation in the collisions antiproton-positronium

    International Nuclear Information System (INIS)

    The future CERN experiment called GBAR intends to measure the gravitational acceleration of antimatter on Earth using cold (neV) anti-hydrogen atoms undergoing a free fall. The experiment scheme first needs to cool anti-hydrogen positive ions, obtained thanks to two consecutive reactions occurring when an antiproton beam collides with a dense positronium cloud.The present thesis studies these two reactions in order to optimise the production of the anti-ions. The total cross sections of both reactions have been computed in the framework of a perturbation theory model (Continuum Distorted Wave - Final State), in the range 0 to 30 keV antiproton kinetic energy; several excited states of positronium have been investigated. These cross sections have then been integrated to a simulation of the interaction zone where antiprotons collide with positronium; the aim is to find the optimal experimental parameters for GBAR. The results suggest that the 2P, 3D or, to a lower extend, 1S states of positronium should be used, respectively with 2, less than 1 or 6 keV antiprotons. The importance of using short pulses of antiprotons has been underlined; the positronium will have to be confined in a tube of 20 mm length and 1 mm diameter. In the prospect of exciting the 1S-3D two-photon transition in positronium at 410 nm, a pulsed laser system had already been designed. It consists in the frequency doubling of an 820 nm pulsed titanium-sapphire laser. The last part of the thesis has been dedicated to the realisation of this laser system, which delivers short pulses (9 ns) of 4 mJ energy at 820 nm. (author)

  9. Atoms

    Institute of Scientific and Technical Information of China (English)

    刘洪毓

    2007-01-01

    Atoms(原子)are all around us.They are something like the bricks (砖块)of which everything is made. The size of an atom is very,very small.In just one grain of salt are held millions of atoms. Atoms are very important.The way one object acts depends on what

  10. Differential cross sections of muonic atoms scattering. Asymmetric collisions: pμ + (d,t), dμ + (p,t) and tμ + (p,d)

    International Nuclear Information System (INIS)

    We present the differential cross sections dσ(E,Ω)/dΩ for elastic and inelastic (isotopic exchange) scattering of muonic hydrogen, deuterium and tritium on hydrogen isotopes nuclei for the case of difference in masses of the projectile μ-atom and the target nucleus. Available partial phase shifts have been used in the calculations and the results are presented in tables and figures for different CMS collision energies. The cross sections are important for description of the slowing down and diffusion of μ-atoms in matter and particularly for description of kinetics of muon catalyzed nuclear fusion. 12 refs., 11 figs., 12 tabs

  11. Compendium of structure and collision data in the first 12 issues of the international bulletin on atomic and molecular data for fusion

    International Nuclear Information System (INIS)

    This document is a compendium of the structure, spectra and collision data in the first 12 issues of the International Bulletin on Atomic and Molecular Data for Fusion. The Bulletin is issued quarterly by the International Atomic Energy Agency to assist the development of fusion research and technology. Not included in this compendium are those parts of the Bulletin concerned with Surface Effects, Work in Progress, Contributed Numerical Data, and Data Requests. Where necessary, corrections have been made to the data previously published to make the compendium as accurate as possible. The editors would appreciate any information on errors, duplications or omissions which would make future compendia more accurate and useful. (author)

  12. I. Charge exchange collisions of highly stripped ions with atomic hydrogen. II. Development of a three-stage double tandem accelerator-decelerator system for low energy, highly stripped ions. Final report, March 1, 1977-May 30, 1981

    International Nuclear Information System (INIS)

    The first measurements of charge exchange (electron transfer) in kiloelectron-volt-energy highly stripped boron, carbon, nitrogen and oxygen ion collisions with atoms have been extended to additional collision energies and charge values for the ions. A first accelerator-decelerator source of very highly stripped ions has been developed, and its usefulness in charge exchange studies established

  13. Atoms

    International Nuclear Information System (INIS)

    Completed by recent contributions on various topics (atoms and the Brownian motion, the career of Jean Perrin, the evolution of atomic physics since Jean Perrin, relationship between scientific atomism and philosophical atomism), this book is a reprint of a book published at the beginning of the twentieth century in which the author addressed the relationship between atomic theory and chemistry (molecules, atoms, the Avogadro hypothesis, molecule structures, solutes, upper limits of molecular quantities), molecular agitation (molecule velocity, molecule rotation or vibration, molecular free range), the Brownian motion and emulsions (history and general features, statistical equilibrium of emulsions), the laws of the Brownian motion (Einstein's theory, experimental control), fluctuations (the theory of Smoluchowski), light and quanta (black body, extension of quantum theory), the electricity atom, the atom genesis and destruction (transmutations, atom counting)

  14. Observation of correlated atom pairs in spontaneous four wave mixing of two colliding Bose-Einstein condensates; Observation de paires d'atomes correles au travers de la collision de deux condensats de Bose-Einstein

    Energy Technology Data Exchange (ETDEWEB)

    Perrin, A

    2007-11-15

    In this thesis, we report on the observation of pairs of correlated atoms produced in the collision of two Bose-Einstein condensates of metastable helium. Three laser beams perform a Raman transfer which extracts the condensate from the magnetic trap and separates it into two parts with opposite mean momenta. While the condensates propagate, elastic scattering of pairs of atoms occurs, whose momenta satisfy energy and momentum conservation laws. Metastable helium atoms large internal energy allows the use of a position-sensitive, single-atom detector which permits a three-dimensional reconstruction of the scattered atoms'momenta. The statistics of these momenta show correlations for atoms with opposite momenta. The measured correlation volume can be understood from the uncertainty-limited momentum spread of the colliding condensates. This interpretation is confirmed by the observation of the momentum correlation function for two atoms scattered in the same direction. This latter effect is a manifestation of the Hanbury Brown-Twiss effect for indistinguishable bosons. Such a correlated-atom-pair source is a first step towards experiments in which one would like to confirm the pairs'entanglement. (author)

  15. The dependence of scattering length on van derWaals interaction and reduced mass of the system in two-atomic collision at cold energies

    Indian Academy of Sciences (India)

    RAY HASI

    2016-07-01

    The static exchange model (SEM) and the modified static exchange model (MSEM) recently introduced by Ray in {\\it Pramana – J. Phys.} 83, 907 (2014) are used to study the elastic collision between two hydrogen-like atoms when both are in ground states by considering the system as a four-body Coulomb system in the centre of mass frame, in which all the Coulomb interaction terms in direct and exchange channels are treated exactly. The SEM includes the non-adiabatic short-range effect due to electron exchange. The MSEM added init, the long-range effect due to induced dynamic dipole polarizabilities between the atoms e.g., the van der Waals interaction. Applying the SEM code in different H-like two-atomic systems, a reduced mass $(\\mu)$ dependence on the scattering length is observed. Again, applying the MSEM code on H(1s)–H(1s) elastic scattering and varying the minimum values of interatomic distance $R_0$, the dependence of scattering length on the effective interatomic potential consistent with the existing physics is observed. Both these basic findings in low and cold energy atomic collision physics are quite useful and are being reported for the first time.

  16. The dependence of scattering length on van der Waals interaction and reduced mass of the system in two-atomic collision at cold energies

    Science.gov (United States)

    RAY, HASI

    2016-06-01

    The static-exchange model (SEM) and the modified static-exchange model (MSEM) recently introduced by Ray [1] is applied to study the elastic collision between two hydrogen-like atoms when both are in ground states considering the system as a four-body Coulomb problem in the center of mass frame, in which all the Coulomb interaction terms in direct and exchange channels are treated exactly. The SEM includes the non-adiabatic short-range effect due to electron-exchange. The MSEM added in it, the long-range effect due to induced dynamic dipole polarizabilities between the atoms e.g. the Van der Waals interaction. Applying the SEM code in different H-like two-atomic systems, a reduced mass dependence on scattering length is observed. Again applying the MSEM code on H(1s)-H(1s) elastic scattering and varying the minimum values of interatomic distance, the dependence of scattering length on the effective interatomic potential consistent with the existing physics are observed. Both these basic findings in low and cold energy atomic collision physics are quite useful and are being reported for the first time.

  17. Low-Energy Charge Transfer in Multiply-Charged Ion-Atom Collisions Studied with the Combined SCVB-MOCC Approach

    Directory of Open Access Journals (Sweden)

    B. Zygelman

    2002-03-01

    Full Text Available A survey of theoretical studies of charge transfer involving collisions of multiply-charged ions with atomic neutrals (H and He is presented. The calculations utilized the quantum-mechanical molecular-orbital close-coupling (MOCC approach where the requisite potential curves and coupling matrix elements have been obtained with the spin-coupled valence bond (SCVB method. Comparison is made among various collision partners, for equicharged systems, where it is illustrated that even for total charge transfer cross sections, scaling-laws do not exist for low-energy collisions (i.e. < 1 keV/amu. While various empirical scaling-laws are well known in the intermediateand high-energy regimes, the multi-electron configurations of the projectile ions results in a rich and varied low-energy dependence, requiring an explicit calculation for each collision-partner pair. Future charge transfer problems to be addressed with the combined SCVB-MOCC approach are briefly discussed.

  18. Electron Capture in Collisions of Slow Highly Charged Ions with an Atom and a Molecule: Processes and Fragmentation Dynamics

    OpenAIRE

    Xavier Husson; Dominique Hennecart; Xavier Fléchard; Jean-Yves Chesnel; Amine Cassimi; Lamri Adoui; Medhi Tarisien; Przemyslaw Sobocinski; Jimmy Rangama; Guillaume Laurent; François Frémont

    2002-01-01

    Abstract : Processes involved in slow collisions between highly charged ions (HCI) and neutral targets are presented. First, the mechanisms responsible for double electron capture are discussed. We show that, while the electron-nucleus interaction is expected to be dominant at projectile velocities of about 0.5 a.u., the electron-electron interaction plays a decisive role during the collision and gains importance when the projectile velocity decreases. This interaction has also to be invoked ...

  19. Excitation of atoms and molecules in collisions with fast, highly charged ions: Progress report for the period January 1, 1988 to February 28, 1989

    International Nuclear Information System (INIS)

    This report summarizes progress in research supported by DOE Grant FG05-84ER13262 during the period January 1, 1988 to February 29, 1989. The research program continues to emphasize the investigation of multielectron ionization and capture processes in fast heavy-ion collisions. Several major projects were completed this year and a number of new ones begun. Among the completed projects were an investigation of resonant multielectron transfer to double K-vacancy states in solid oxygen compounds, and a study of collisional quenching of 23P and 24P states in 33 MeV two- and three-electron Mg ions. New projects include a systematic investigation of the projectile charge dependence of cross sections for Ar recoil-ion production in 1 MeV/amu oxygen ion collisions production, and a design study for an atomic physics beam line to be connected to an electron-cyclotron-resonance (ECR) ion source. Work on molecular fragmentation in heavy-ion collisions continued

  20. Quasi-Classical Trajectory Study of Atom-Diatomic Molecule Collisions in Symmetric Hyperspherical Coordinates: The F + HCl Reaction as a Test Case.

    Science.gov (United States)

    Freixas-Lemus, Victor Manuel; Martínez-Mesa, Aliezer; Uranga-Piña, Llinersy

    2016-04-01

    We investigate the reactive dynamics of the triatomic system F + HCl → HF + Cl for total angular momentum equal zero and for different low-lying rovibrational states of the diatomic molecule. For each of the initial vibrational quantum numbers, the time evolution of the atom-diatom collision process is investigated for a wide range of impact angles and collision energies. To this purpose, the Quasi-Classical Trajectories (QCT) method was implemented in a hyperspherical configuration space. The Hamilton equations of motion are solved numerically in an intermediate effective Cartesian space to exploit the relative simplicity of this intermediate representation. Interatomic interactions are described by a London-Eyring-Polanyi-Sato potential energy surface, specifically developed for the title reaction, and the results of the QCT simulations are discussed in terms of the time-evolution of the hyperangles. The analysis of the collision dynamics using symmetric hyperspherical coordinates provides, in addition to the description in terms of a natural reaction coordinate (the hyperradius), a more striking representation of the exchange dynamics, in terms of the time-dependent probability distribution along the kinematic rotation hyperangle, and a precise distinction between direct and indirect mechanisms of the reaction. PMID:27002240

  1. Influence of inelastic collisions with hydrogen atoms on the formation of AlI and SiI lines in stellar spectra

    Science.gov (United States)

    Mashonkina, L. I.; Belyaev, A. K.; Shi, J.-R.

    2016-06-01

    We have performed calculations by abandoning the assumption of local thermodynamic equilibrium (within the so-called non-LTE approach) for Al I and Si I with model atmospheres corresponding to stars of spectral types F-G-Kwith differentmetal abundances. To take into account inelastic collisions with hydrogen atoms, for the first time we have applied the cross sections calculated by Belyaev et al. using model approaches within the formalism of the Born-Oppenheimer quantum theory. We show that for Al I non-LTE leads to higher ionization (overionization) than in LTE in the spectral line formation region and to a weakening of spectral lines, which is consistent with earlier non-LTE studies. However, our results, especially for the subordinate lines, differ quantitatively from the results of predecessors. Owing to their large cross sections, the ion-pair production and mutual neutralization processes Al I( nl) + HI(1 s) ↔ Al II(3 s 2) + H- provide a close coupling of highly excited Al I levels with the Al II ground state, which causes the deviations from the equilibrium level population to decrease compared to the calculations where the collisions only with electrons are taken into account. For three moderately metal-deficient dwarf stars, the aluminum abundance has been determined from seven Al I lines in different models of their formation. Under the assumption of LTE and in non-LTE calculations including the collisions only with electrons, the Al I 3961 ˚A resonance line gives a systematically lower abundance than the mean abundance from the subordinate lines, by 0.25-0.45 dex. The difference for each star is removed by taking into account the collisions with hydrogen atoms, and the rms error of the abundance derived from all seven Al I lines decreases by a factor of 1.5-3 compared to the LTE analysis. We have calculated the non- LTE corrections to the abundance for six subordinate Al I lines as a function of the effective temperature (4500 K ≤ T eff ≤ 6500 K

  2. Electron Capture in Collisions of Slow Highly Charged Ions with an Atom and a Molecule: Processes and Fragmentation Dynamics

    Directory of Open Access Journals (Sweden)

    Xavier Husson

    2002-03-01

    Full Text Available Abstract : Processes involved in slow collisions between highly charged ions (HCI and neutral targets are presented. First, the mechanisms responsible for double electron capture are discussed. We show that, while the electron-nucleus interaction is expected to be dominant at projectile velocities of about 0.5 a.u., the electron-electron interaction plays a decisive role during the collision and gains importance when the projectile velocity decreases. This interaction has also to be invoked in the capture of core electrons by HCI. Finally, the molecular fragmentation of H2 following the impact of HCI is studied.

  3. Study of thermal energies of the excitation transfer of potassium atoms in the (4Psub(1/2)) state in collision with helium atoms

    International Nuclear Information System (INIS)

    The collision theory is established for fine structure changes in the first doublet of the alkali metal - rare gas couple: the adiabatic potential curves are calculated, the semi-classical and quantum treatments of collision are given and the influence of the interaction potential on the total cross-section is analyzed. The experimental device built to measure the total cross-sections of fine structure transition for the K*-He couple is described: rare gas jet system, alkali jet system, laser, optics, detection. The results obtained on the cross-section sigma(4Psub(1/2)→4Psub(3/2)) are given for the couple K*-He from 0.07 to 0.4 eV

  4. Initial distributions, cascade, and annihilation of p p atoms formed in p +H and p +H sup minus collisions in near vacuum

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, J.S.; Padial, N.T. (Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (USA))

    1990-04-01

    The initial-capture conditions and subsequent near-vacuum cascade are described for protonium ({ital {bar p}p}) formation in collisions of antiprotons ({ital {bar p}}) with the neutral H atom or with the negative ion H{sup {minus}}. The {ital {bar p}p} cascade is simulated by Monte Carlo with the initial states determined by previous classical-trajectory Monte Carlo calculations of the cross sections for {bar {ital p}} capture. The cascades of {ital {bar p}p} formed in corotating beams of {bar {ital p}} and H{sup {minus}} or in extremely low-density hydrogen gas are very similar, both yielding {approx}97% {ital {bar p}}-{ital p} annihilation in the 2{ital p} state of {ital {bar p}p} and {approx}1% each in the 1{ital s}, 3{ital d}, and higher-{ital p} states; the sensitivity to the strong-interaction parameters is examined. The time for the purely radiative cascade is quite long ({much gt}1 {mu}s) for {ital {bar p}p} atoms formed at the upper end of the 0.4{approx lt}{ital E}{sub lab}{approx lt}1.4 a.u. reaction window for {ital {bar p}}+H{sup {minus}} collisions. Possible experimental ramifications are discussed.

  5. Collisions of electrons with hydrogen atoms II. Low-energy program using the method of the exterior complex scaling

    Science.gov (United States)

    Benda, Jakub; Houfek, Karel

    2014-11-01

    While collisions of electrons with hydrogen atoms pose a well studied and in some sense closed problem, there is still no free computer code ready for “production use”, that would enable applied researchers to generate necessary data for arbitrary impact energies and scattering transitions directly if absent in on-line scattering databases. This is the second article on the Hex program package, which describes a new computer code that is, with a little setup, capable of solving the scattering equations for energies ranging from a fraction of the ionization threshold to approximately 100 eV or more, depending on the available computational resources. The program implements the exterior complex scaling method in the B-spline basis. Catalogue identifier: AETI_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AETI_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 44 440 No. of bytes in distributed program, including test data, etc.: 322 643 Distribution format: tar.gz Programming language: C++11. Computer: Any. Operating system: Any system with a C++11 compiler (e.g. GCC 4.8.1; tested on OpenSUSE 13.1 and Windows 8). Has the code been vectorized or parallelized?: Parallelized by OpenMP and MPI. RAM: Depending on input; 4.9 GiB for the test run. Classification: 2.4. External routines: GSL [1], HDF5 [2], UMFPACK [3], FFTW3 [4], optionally with OpenBLAS [5]. Nature of problem: Solution of the two-particle Schrödinger equation in central field. Solution method: The two-electron states are expanded into angular momentum eigenstates, which gives rise to the coupled bi-radial equations. The bi-radially dependent solution is then represented in a B-spline basis, which transforms the set of equations into a large matrix equation in this basis. The boundary condition

  6. Evidence for an additional coupling of the innermost shells in very heavy quasi-molecular ion-atom collisions

    International Nuclear Information System (INIS)

    Due to the tremendous spin-orbit splitting of quasi-molecular levels in super-heavy collision systems (Z=Z1+Z2>approximately137) bombarding energy 0.5-6 MeV N-1, unusual couplings may occur around Z approximately equal to 165. Experimental evidence for such a theoretically predicted coupling is discussed. (author)

  7. Effects of autoionization in electron loss from helium-like highly charged ions in collisions with photons and fast atomic particles

    CERN Document Server

    Lyashchenko, K N; Voitkiv, A B

    2016-01-01

    We study theoretically single electron loss from helium-like highly charged ions involving excitation and decay of autoionizing states of the ion. Electron loss is caused by either photo absorption or the interaction with a fast atomic particle (a bare nucleus, a neutral atom, an electron). The interactions with the photon field and the fast particles are taken into account in the first order of perturbation theory. Two initial states of the ion are considered: $1s^2$ and $(1s2s)_{J=0}$. We analyze in detail how the shape of the emission pattern depends on the atomic number $Z_{I}$ of the ion discussing, in particular, the inter-relation between electron loss via photo absorption and due to the impact of atomic particles in collisions at modest relativistic and extreme relativistic energies. According to our results, in electron loss from the $1s^2$ state autoionization may substantially influence the shape of the emission spectra only up to $Z_{I} \\approx 35-40$. A much more prominent role is played by autoi...

  8. Cross sections for electron capture and excitation in proton collisions with the metastable Be(2s2p3P) atom

    International Nuclear Information System (INIS)

    Previous studies have shown that it appears that the metastable Be(1s22s2p 3P) atoms can constitute a significant fraction of the atomic beryllium in the ITER plasma edge. The two-center atomic orbital close-coupling method is employed to study electron capture and excitation processes in proton collisions with the metastable Be(1s22s2p 3P) atom. The interaction of the active electron with the Be+ ion core is represented by a model potential reproducing accurately (to within 3.5%) the energies of triplet excited states Be(1s22snl 3L) (at least up to n = 7). The excitation and state-selective electron capture cross sections up to the n = 5 shells of both centers are calculated in the energy range 1-200 keV/u using an expansion basis involving all the states with n ≤ 7 on H and all triplet states with n ≤ 7 on Be, augmented with a number of pseudo-states. In the energy region below ∼ 10 keV/u, the cross sections of both processes exhibit oscillatory structures, resulting from the multi-state coupling accounted for in the dynamical model. It has been found that the magnitude of excitation cross sections above ∼ 10 keV/u is dominated by the multipole interactions, while below this energy the excitation process proceeds through intermediate electron capture states

  9. Withdrawal of Chinese Physics Letters 28 (2011) 043401 “Measurement of Absolute Atomic Collision Cross Section with Helium Using 87Rb Atoms Confined in Magneto-Optic and Magnetic Traps” by WANG Ji-Cheng et al.

    Institute of Scientific and Technical Information of China (English)

    WANG Ji-Cheng; ZHOU Ke-Ya; WANG Yue-Yuan; LIAO Qing-Hong; LIU Shu-Tian

    2011-01-01

    We announce the withdrawal of the article entitled “Measurement of Absolute Atomic Collision Cross Section with Helium Using 87Rb Atoms Confined in Magneto-Optic and Magnetic Traps”,which was published in Chinese Physics Letters [28(4)(2011)043401].The first author,Jicheng Wang,had participated in related research with Professor Kirk Madison's group at the Department of Physics & Astronomy at the University of British Columbia,Canada from September 2008 to February 2010.Even though consent had been granted for some of the experimental data to be used by Jicheng Wang in his own thesis,its publication had not been authorized.We apologize to Professor K.Madison for the misunderstanding,and to Chinese Physics Letters and the readers of Chinese Physics Letters for any inconvenience this mistake may have caused.%We announce the withdrawal of the article entitled "Measurement of Absolute Atomic Collision Cross Section with Helium Using 87Rb Atoms Confined in Magneto-Optic and Magnetic Traps", which was published in Chinese Physics Letters [28(4) (2011)043401]. The first author, Jicheng Wang, had participated in related research with Professor Kirk Madison's group at the Department of Physics & Astronomy at the University of British Columbia, Canada from September 2008 to February 2010. Even though consent had been granted for some of the experimental data to be used by Jicheng Wang in his own thesis, its publication had not been authorized. We apologize to Professor K. Madison for the misunderstanding, and to Chinese Physics Letters ad the readers of Chinese Physics Letters for any inconvenience this mistake may have caused.

  10. Temperature dependence of the formation rates of hydrogen-helium mesic molecules in collisions of slow hydrogen atoms with helium

    International Nuclear Information System (INIS)

    Muon transfer from the ground state of the muonic hydrogen to helium is of special interest, since it is connected with problem of muon-catalyzed fusion in the deuterium-tritium mixture. The muon transfer rates are calculated at low energy collisions of hydrogen isotopes with helium isotopes. The calculations are carried out in an improved adiabatic approximation. The particular attention is given to the construction of the effective potential. The level energies ε00 and ε10 of the hydrogen-helium muonic molecules are presented. For collision energies ε ≤ 0.1 eV rate of the direct muon transfer does not depend on energy and amounts to λ pHe ∼ 0.06 x 108 s-1. The theoretical results λ obtained by various temperatures are compared with the available experimental data

  11. Interacting He and Ar atoms: Revised theoretical interaction potential, dipole moment, and collision-induced absorption spectra

    International Nuclear Information System (INIS)

    Coupled cluster quantum chemical calculations of the potential energy surface and the induced dipole surface are reported for the He–Ar van der Waals collisional complex. Spectroscopic parameters are derived from global analytical fits while an accurate value for the long-range dipole coefficient D7 is obtained by perturbation methods. Collision-induced absorption spectra are computed quantum mechanically and compared with existing measurements

  12. The dependence of scattering length on van der Waals interaction and on the reduced-mass of the system in two-atomic collision at cold energies

    CERN Document Server

    Ray, Hasi

    2015-01-01

    The static-exchange model (SEM) and the modified static-exchange model (MSEM) recently introduced by Ray [1] is applied to study the elastic collision between two hydrogen-like atoms when both are in ground states considering the system as a four-body Coulomb problem in the center of mass frame, in which all the Coulomb interaction terms in direct and exchange channels are treated exactly. The SEM includes the non-adiabatic short-range effect due to electron-exchange. The MSEM added in it, the long-range effect due to induced dynamic dipole polarizabilities between the atoms e.g. the Van der Waals interaction. Applying the SEM code in different H-like two-atomic systems, a reduced mass dependence on scattering length is observed. Again applying the MSEM code on H(1s)-H(1s) elastic scattering and varying the minimum values of interatomic distance, the dependence of scattering length on the effective interatomic potential consistent with the existing physics are observed. Both these basic findings in low and co...

  13. Theoretical study of intramultiplet transitions in collisions of atoms in 3P electronic states with structureless targets: Ca(3P)+He

    International Nuclear Information System (INIS)

    The quantum close-coupling (CC) treatment of collisions of an atom in a 3P electronic state with a structureless target is developed, based on earlier work of Mies [Phys. Rev. A 7, 942 (1973)], and a j/sub z/-conserving [coupled-states (CS)] simplification presented. There is no direct coupling between the J = 0 and J = 1 levels; transitions between these levels will occur only as a result of Coriolis coupling involving the J = 2 state. Actual CC and CS calculations are reported for collisions of Ca 43P/sup o/ with He, based on the potential curves of Malvern [J. Phys. B 11, 831 (1978)]. In the CC results, of the three independent cross sections, J = 2→1 is predicted to be largest, and J = 2→0 smallest, over the entire range of collision energies sampled. By contrast, the CS approximation predicts the 1→0 transition to be forbidden, and yields only fair accuracy for the CC 2→1 and 2→0 transitions. The coupling between spin-orbit states is also interpreted within an adiabatic model. A comparison with the experimental results of Yuh and Dagdigian (preceding paper) is made by averaging the CC cross sections over the experimental translational energy distribution. The experimental cross sections for the 2→1 and 2→0 transitions are 3--4 times larger than the theoretical values, and the 2→0 cross section is found experimentally to be approx.3 times larger than the 1→0 cross section, in direct contrast with the theoretical prediction for this ratio

  14. Experimental study of the collision mechanisms involved in one-electron capture by slow N5+ ions in atomic and molecular hydrogen

    International Nuclear Information System (INIS)

    Translational energy spectroscopy (TES) in the range 214-857 eV amu-1 has been used to study the collision mechanisms involved in one-electron capture by slow helium-like N5+ in both atomic and molecular hydrogen. In the case of N5+-H2 collisions, our measurements show that non-dissociative electron capture leading to the N4+ (n=3) states is the main product channel at the higher impact energies with smaller contributions to the N4+ (n=4) states. While this has also been observed in previous studies based on photon emission spectroscopy (PES), there are substantial differences in both magnitude and energy dependence between the TES and PES results. Theoretical predictions for n=3 formation are also in poor accord with experiment. Unlike previous PES measurements, the present TES study has been able to identify the presence of dissociative one-electron capture channels and two-electron autoionizing capture channels, both leading to N4+ (n=2) formation. Two-electron autoionizing electron capture is found to be the main collision mechanism leading to N4+ ions at the lowest energies considered. Our measurements of one-electron capture in N5+ + H(1s) are in excellent accord with previous higher measurements based on PES and now provide a useful extension to energies below 1 keV amu-1. In this case, only the N4+ (n=4) and N4+ (n=3) product channels are observed, with contributions from the latter becoming insignificant at our lowest energies

  15. Independent-electron analysis of the x-ray spectra from single-electron capture in Ne10 + collisions with He, Ne, and Ar atoms

    Science.gov (United States)

    Leung, Anthony C. K.; Kirchner, Tom

    2015-09-01

    We present a theoretical study on the x-ray spectra from single-electron capture in 4.54 keV/amu Ne10 +-He, -Ne, and -Ar collisions. Single-particle capture probabilities were calculated using the two-center basis generator method within the independent electron model. In this framework we investigated the effects of a time-dependent screening potential that models target response on capture cross sections and x-ray spectra. Excellent agreement is shown with the previously measured relative cross sections and x-ray spectra and calculations based on the classical trajectory Monte Carlo method using the no-response single-particle electron capture probabilities in a multinomial single-electron capture analysis. Our results demonstrate the importance of using this consistent statistical analysis of single-electron capture within the independent electron model; a requirement that a previous calculation for the same collision problem using the two-center atomic-orbital close-coupling method may not have considered.

  16. Electron transfer processes in collisions of highly charged energetic (0. 1 to 1. 0 MeV/nucleon) ions with helium atoms

    Energy Technology Data Exchange (ETDEWEB)

    Datz, S.; Hippler, R.; Andersen, L.H.; Dittner, P.F.; Knudsen, H.; Krause, H.F.; Miller, P.D.; Pepmiller, P.L.; Rosseel, T.; Stolterfoht, N.

    1987-01-01

    We have investigated charge transfer in collisions of energetic (0.1 - 1 MeV/nucleon) highly charged ions with helium atoms with the principal aim clarifying the nature of two-electron processes. The sensitivity of partial charge-changing cross sections (i.e., single- and double-charge transfer, transfer ionization (TI), and single and double ionization) to core configuration and scaling rules for one- and two-electron processes were investigated with iodine ions (q = 5+ ..-->.. 26+) and uranium ions (q = 17+ ..-->.. 44+) using an ion-charge state, recoil-ion coincidence method. Using zero-degree electron spectroscopy in coincidence with charge transfer, we found that at the higher energies, as in the case of 0.1 MeV/nucleon ions previously reported, TI involves the transfer of two electrons to a higher correlated state followed by loss of one electron to the continuum. In addition, we observe very high Rydberg electrons in coincidence with TI, implying a possible up-down correlation in the pair transfer. In addition, we made measurements of VUV photons emitted at the collision in coincidence with He/sup +/ and He/sup 2 +/ recoils. The results show that TI leads to capture into lower n states than single-charge transfer. 15 refs., 10 figs.

  17. Interaction of an atom with the radiation field in the presence of collisions. Application to the problem of frequency redistribution of light

    International Nuclear Information System (INIS)

    The purpose of this work mainly consisted in (a) taking into account all the orders of the atom-radiation interaction (in a low intensity field) for strictly processing the natural enlargement over the entire spectral domain of the line and (b) simultaneously applying the unified theories of the collision enlargement to the radiation distribution problem. These redistribution formulae also drawn up by Nienhuis et al. were supposed to apply also outside the impact domain. However, it was soon realised that these results were not satisfactory since, in certain cases (observation in the wings and excitation in the centre or vice-versa), they could give rise to a negative fluorescence profile. This drawback was due to the approximation consisting in disregarding the effect of the radiative processes throughout the duration of a collision. An accurate treatment of the redistribution that no longer makes use of the incriminated approximation is presented in the appendix. In this way, new results are obtained which no longer exhibit the irregularities of those obtained in the preceding treatment and which apply from the centre of the line to the near-by quasi-static domain

  18. A time-dependent wave packet approach to atom-diatom reactive collision probabilities - Theory and application to the H + H2(J = 0) system

    Science.gov (United States)

    Neuhauser, Daniel; Baer, Michael; Judson, Richard S.; Kouri, Donald J.

    1990-01-01

    This paper describes a new approach to the study of atom-diatom reactive collisions in three dimensions employing wave packets and the time-dependent Schroedinger equation. The method uses a projection operator approach to couple the inelastic and reactive portions of the total wave function and optical potentials to circumvent the necessity of using product arrangement coordinates. Reactive transition probabilities are calculated from the state resolved flux of the wave packet as it leaves the interaction region in the direction of the reactive arrangement channel. The present approach is used to obtain such vibrationally resolved probabilities for the three-dimensional H + H2 (J = 0) hydrogen exchange reaction, using a body-fixed system of coordinates.

  19. Retraction notice to "Measurements of total absolute collision cross section of ultracold Rb atom using magneto-optic and pure magnetic traps" [Chinese Optics Letters 9, 060201 (2011)

    Institute of Scientific and Technical Information of China (English)

    Jicheng Wang; Yueyuan Wang; Yueke Wang; Guangyu Fang; Shutian Liu

    2011-01-01

    This article "Measurements of total absolute collision cross section of ultracold Rb atom using magneto-optic and pure magnetic traps",which was published on Chinese Optics Letters (9,060201 (2011)) has been retracted at the request of the authors.Reason:The first author,Jicheng Wang,participated in a related research in Professor Kirk Madison's group in the Department of Physics & Astronomy at the University of British Columbia,Canada from September 2008 to February 2010.Some of the experimental data have not been authorized for publication,even though they have been consented to be used by Jicheng Wang in his own research.The authors apologize to Professor K.Madison for misunderstanding,and to Chinese Optics Letters and the readers of Chinese Optics Letters for any inconvenience this mistake may have caused.

  20. Calculation of total excitation cross section in the collision of bare ions with atomic hydrogen for transition from ground to and states using Born-Faddeev approximation

    Directory of Open Access Journals (Sweden)

    R Fathi

    2013-09-01

    Full Text Available  In this work, total excitation cross section of atomic hydrogen in the collision of bare ion was calculated employing a three body Faddeev formalism. In the present calculation, initially the first order electronic amplitude was calculated using the interaction potential which led to inelastic form factor. Secondly, the first order nuclear amplitude was calculated and added to the first order electronic amplitude. This second term was calculated employing the near-the-shell two body transition operator. The interaction energy was assumed to be in the intermediate and high energy limits . Finally, the results were compared with the relevant cross sections calculated under monocentric close-coupling data in the literature.

  1. Trajectory dependent energy loss in grazing collisions of keV He atoms from a LiF(0 0 1) surface

    International Nuclear Information System (INIS)

    Angular distributions for scattering of 12 keV He atoms from a LiF(0 0 1) surface under a grazing angle of incidence were recorded in coincidence with the projectile energy loss and the number of electrons emitted from the target surface during the collision. For scattering along the low indexed 〈1 1 0〉 and 〈1 0 0〉 directions of the crystal surface collisional rainbow peaks were observed. For scattering along a 〈1 1 0〉 direction the resulting rainbow peaks can be attributed to scattering from strings of anions which form active sites for charge exchange and emission of electrons. The data can be interpreted by trajectory computer simulations where charge transfer takes place from F− sites

  2. K vacancy production in collisions of 63 MeV Cu ions with Ge and Ag atoms

    International Nuclear Information System (INIS)

    The mechanism of K-shell vacancy production is studied in t in an X-ray-scattered ion coincidence experiment with 1 MeV/a.m.u. 63Cu4+ ion incident onto natural Ge and Ag targets. The impact parameter dependent K-shell vacancy production probability measured in the experiment is interpreted in terms of the rotational coupling and the statistical models. The dependence of the vacancy sharing process in the Cu-Ge collision system on the impact parameter is obtained and compared with the predictions of the Briggs-Myerhof-Demkov model

  3. Atomic scattering in the diffraction limit: electron transfer in keV Li+-Na(3s, 3p) collisions

    DEFF Research Database (Denmark)

    Poel, Mike van der; Nielsen, C.V.; Rybaltover, M.;

    2002-01-01

    We measure angle differential cross sections (DCS) in Li+ + Na --> Li + Na+ electron transfer collisions in the 2.7-24 keV energy range. We do this with a newly constructed apparatus which combines the experimental technique of cold target recoil ion momentum spectroscopy with a laser-cooled target...... quantum scattering amplitudes are derived by the eikonal method. The resulting angle-differential electron transfer cross sections and their diffraction patterns agree with the experimental level-to-level results over most scattering angles in the energy range....

  4. Atomic phenomena in dense plasmas

    International Nuclear Information System (INIS)

    The following chapters are included: (1) the plasma environment, (2) perturbations of atomic structure, (3) perturbations of atomic collisions, (4) formation of spectral lines, and (5) dielectronic recombination

  5. Penning and associative ionisations of argon atoms by collisions with metastable helium atoms He(21S) and He(23S) of thermal energies 0.03-0.40eV

    International Nuclear Information System (INIS)

    This work, devoted to the 21S and 23S metastable states of the helium atom, is mainly experimental. It centres on observation of the non-bound states Ar+ and bound states HeAr+ created during collisions of these metastable atoms with argon atoms in the ground state. The Penning and associative ionisation cross-sections corresponding to these two processes were obtained as a function of the relative speed of approach of the He*+Ar particles in the thermal region 1200-4500m/s (0.3-0.40eV). The experimental time of flight method used in this experiment is original in its application to the measurement of reaction products such as Ar+ and HeAr+ ions. The results obtained testify to the efficiency of this method since the variations in the Penning ionisation cross-section sigmasub(IP)(v) and associative ionisation cross-section sigmasub(IA)(v) against speed have not been observed in other laboratories. They are given here for the couples He(23S)+Ar and He(21S) + Ar. The theoretical interpretation attempted for the cross-sections sigmasub(IP)(v) and sigmasub(IA)(v) is based on a very recent model due to the American school of Miller and the Japanese school of Nakamura. This model, common to all interpretations, can lead to different results according to whether quantum effects are taken into account

  6. Influence of Inelastic Collisions with Hydrogen Atoms on the Formation of Al I and Si I Lines in Stellar Spectra

    CERN Document Server

    Mashonkina, Lyudmila; Shi, Jianrong

    2016-01-01

    The non-LTE line formation for Al I and Si I was calculated with model atmospheres corresponding to F-G-K type stars of different metallicity. To account for inelastic collisions with H I, for the first time we applied the cross sections calculated by Belyaev et al. using model approaches within the formalism of the Born-Oppenheimer quantum theory. For Al I non-LTE leads to overionization in the line formation layers and to weakened spectral lines, in line with earlier non-LTE studies. However, in contrast to the previuos studies, our results predict smaller magnitude of the non-LTE effects for the subordinate lines. Owing to large cross sections, the ion-pair production and mutual neutralization processes Al I(nl) + H I(1s) $\\leftrightarrow$ Al~II(3s^2) + H^- provide a close coupling of high-excitation Al I levels to the Al II ground state, which causes smaller deviations from the TE populations compared to the case of pure electron collisions. For three metal-poor stars, the Al abundance was determined from...

  7. Differential and total excitation cross sections in the collision of protons with He atoms at intermediate and high energies under a three body formalism

    Directory of Open Access Journals (Sweden)

    R Fathi

    2011-09-01

    Full Text Available  A three-body model is devised to study differential and total cross sections for the excitation of helium atom under impact of energetic protons. The actual process is a four body one but in the present model the process is simplified into a three-body one. In this model, an electron of helium atom is assumed to be inactive and only one electron of the atom is active. Therefore, the active electron is assumed to be in an atomic state with a potential of the nucleus, T, being screened by the inactive electron, e, and, thus, an effective charge of Ze. As a result, the ground state, 11S, or the excited states, 21S and 21P, wave function of the active electron is deduced from similar hydrogenic wave functions assuming effective charge, Ze for the combined nucleus (T+e. In this three-body model, the Faddeev-Watson-Lovelace formalism for excitation channel is used to calculate the transition amplitude. In the first order approximation, electronic and nuclear interaction is assumed in the collision to be A(1e= and A(1n=, respectively. Here, A(1, Txy, |i> and |f> are the first order transition amplitude, the transition matrix for the interaction between particles x and y, the initial state and the final state, respectively. The transition matrix for the first order electronic interaction implemented into A(1e is approximated as the corresponding two-body interaction, Vxy. In order to calculate first order nuclear amplitude A(1n, the near-the-shell form of transition matrix TPT is used. Calculations are performed in the energy range of 50 keV up to 1MeV. The results are then compared with those of theoretical and experimental works in the literature.

  8. {2p_\\pi}-{2p_\\sigma} crossing in heavy symmetric ion-atom collisions: I. Level structure

    OpenAIRE

    Morovi´c, Tihomir; Sepp, Wolf-Dieter; Fricke, Burkhard

    1982-01-01

    Ab initio self-consistent DFS calculations are performed for five different symmetric atomic systems from Ar-Ar to Pb-Pb. The level structure for the {2p_\\pi}-{2p_\\sigma} crossing as function of the united atomic charge Z_u is studied and interpreted. Manybody effects, spin-orbit splitting, direct relativistic effects as well as indirect relativistic effects are differently important for different Z_u. For the I-I system a comparison with other calculations is given.

  9. The study of interaction potentials and differential cross sections for collisions between He atoms and hydrogen halide molecules

    Institute of Scientific and Technical Information of China (English)

    孙桂华; 杨向东; 朱俊; 王彩霞

    2002-01-01

    In this paper, we present the uniform interaction potentials for helium atoms and halogen hydride molecules (HF,HC1 and HBr). The differential cross sections are calculated using the above interaction potentials for the He-HF,HCl and HBr systems, respectively, and the results of the calculations are found to be in agreement with the existingtheoretical results and experimental data.

  10. Correlated charge changing ion-atom collisions: Progress report for the period August 15, 1984-February 14, 1987

    International Nuclear Information System (INIS)

    Correlations between x-ray emission and charge-changing interactions have been measured for high charged ions (16 ≤ Z ≤ 23) in the energy range of 0.1 to 10 MeV/u incident on gas targets under single collision conditions. These experiments combined with theoretical studies have established the existence of resonant transfer and excitation (RTE) and indicated a close relationship between RTE and dielectronic recombination. Detailed investigations of RTE include: (1) the projectile Z dependence; (2) the projectile charge-state dependence; (3) the effect of the target electron momentum distribution; and (4) observations of RTE involving L-shell excitation. These measurements are in reasonable agreement with theoretical calculations. Evidence for non-resonant transfer and excitation has been obtained from studies of 15 to 200 MeV S13+ + He collisions. Single-electron capture and loss were measured for 2.5 to 200 MeV S13+ + He thereby providing a comparison with theory over a very wide energy range. For single capture in Ca/sup 16,17,18,19+ + H2 a significant contribution due to RTE was observed for energies where RTE is important. Cross sections for double-electron capture for S13+ + He and Ne and Ar15+ + Ne were found to be 1 to 2 orders of magnitude smaller than the corresponding single-capture cross sections. Target ionization associated with projectile charge exchange has been measured for 0.5 to 1.5 MeV/u O/sup 5,6,7,8+ + He and H2. 26 refs., 13 figs

  11. Evaluation of interatomic potentials for noble gas atoms from rainbow scattering under axial channeling at Ag(1 1 1) surface by computer simulations based on binary collision approximation

    Science.gov (United States)

    Takeuchi, Wataru

    2016-01-01

    The rainbow angles corresponding to pronounced peaks in the angular distributions of scattered projectiles with small angle, attributed to rainbow scattering (RS), under axial surface channeling conditions are strongly dependent on the interatomic potentials between projectiles and target atoms. The dependence of rainbow angles on normal energy of projectile energy to the target surface that has been experimentally obtained by Schüller and Winter (SW) (2007) for RS of He, Ne and Ar atoms from a Ag(1 1 1) surface with projectile energies of 3-60 keV was evaluated by the three-dimensional computer simulations using the ACOCT code based on the binary collision approximation with interatomic pair potentials. Consequently, the ACOCT results employing the Moliere pair potential with screening length correction close to adjustable one of O'Connor and Biersack (OB) formula are almost in agreement with the experimental ones, being self-consistent with the SW's ones analyzed by computer simulations of classical trajectory calculations as RS from corrugated equipotential planes based on continuum potentials including the Moliere pair potential with screening length correction of the OB formula.

  12. On corrections to spectroscopically measured Franck-Condon energies arising from motion of the parent molecules and from ion collisions in fusion plasmas: relevant time scales for atomic velocity distributions

    International Nuclear Information System (INIS)

    We show that while corrections to spectroscopically measured Franck-Condon energies, arising from motion of the parent molecules at the edge of fusion plasmas, are insignificant in many practical cases, ion collisions play an important role in randomizing and redistributing the velocities of the atomic products of molecular dissociation. Formulae are obtained from which the time scales for randomization and equilibration of the atomic velocity distribution may be estimated, and hence compared with characteristic times for other important atomic processes. Examples of the latter are: spontaneous emission, production of atoms by electron impact-induced dissociation and ionization of molecules, electron collisions of the first and second kinds, charge-exchange recombination and electron impact ionization. We show that the time scales of randomization and equilibration can be comparable with those for some of the other processes listed above, but are much longer than typical times for spontaneous emission. The ion-atom collisional processes considered here therefore affect the atomic velocity distribution mainly after the atoms produced directly by molecular dissociation have arrived in their ground states. The formulae derived for these collisional time scales may well be useful in modelling hydrogen transport and recycling in fusion plasmas

  13. Atomic Number Dependence of Hadron Production at Large Transverse Momentum in 300 GeV Proton--Nucleus Collisions

    Science.gov (United States)

    Cronin, J. W.; Frisch, H. J.; Shochet, M. J.; Boymond, J. P.; Mermod, R.; Piroue, P. A.; Sumner, R. L.

    1974-07-15

    In an experiment at the Fermi National Accelerator Laboratory we have compared the production of large transverse momentum hadrons from targets of W, Ti, and Be bombarded by 300 GeV protons. The hadron yields were measured at 90 degrees in the proton-nucleon c.m. system with a magnetic spectrometer equipped with 2 Cerenkov counters and a hadron calorimeter. The production cross-sections have a dependence on the atomic number A that grows with P{sub 1}, eventually leveling off proportional to A{sup 1.1}.

  14. Charge breeding investigation in EBIS/T and collision study of ions with cold atoms for HITRAP

    OpenAIRE

    Sokolov, Alexey

    2010-01-01

    Highly charged ions (HCI) at low velocities or at rest are interesting systems for various atomic physics experiments. For investigations on HCI of heavy stable or radioactive nuclides the HITRAP (Highly charged Ion TRAP) decelerator facility has been set up at GSI to deliver cooled beams of HCI at an energy of 5 keV/q. The HCI are produced in a stripper foil at relativistic energies and are decelerated in several steps at ESR storage ring and HITRAP before they are delivered to experimental ...

  15. Relevant effects of localized atomic interactions and surface density of states on charge transfer in ion-surface collisions

    Energy Technology Data Exchange (ETDEWEB)

    Bonetto, F.; Romero, M.A.; Garcia, E.A.; Vidal, R.; Ferron, J.; Goldberg, E.C. [Instituto de Desarrollo Tecnologico para la Industria Quimica, Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Santa Fe (Argentina); Ferron, J.; Goldberg, E.C. [Universidad Nacional del Litoral, J., Dept. de Ingenieria de Materiales, Facultad de Ingenieria Quimica, Santa Fe (Argentina)

    2007-12-15

    Through a time-dependent quantum-mechanical calculation of the H{sup +} scattering by a highly oriented pyrolytic graphite (HOPG) surface, we are able to satisfactorily reproduce the interesting features we observed in ion scattering experiments in H{sup +}/HOPG system. We found that the combined effects of the semimetal character of HOPG together with the localized nature of the carbon atom states primarily determine the angular dependence and the magnitude of the ion fractions for large outgoing angles. The spin fluctuation effects (not considered in the present calculation) are discussed as one of the the main causes of the disagreement between the spinless theory results and the experiments for small exit angles. (authors)

  16. Fraunhofer-type diffraction patterns of matter-wave scattering of projectiles: Electron transfer in energetic ion-atom collisions

    Science.gov (United States)

    Agueny, Hicham

    2015-07-01

    We present results for single and double electron captures in intermediate energies H+ and 2H+ projectiles colliding with a helium target. The processes under investigations are treated using a nonperturbative semiclassical approach in combination with Eikonal approximation to calculate the scattering differential cross sections. The latter reveals pronounced minima and maxima in the scattering angles, in excellent agreement with the recent experimental data. It turns out that the present structure depends strongly on the projectile energy and shows only slight variations with different capture channels. The observed structure demonstrates the analogy of atomic de Broglie's matter-wave scattering with λd B=1.3 -3.2 ×10-3 a.u. and Fraunhofer-type diffraction of light waves.

  17. Absolute measurement of excitation cross sections for the 2P-states of atomic hydrogen in charge exchange collisions of protons in argon and nitrogen

    International Nuclear Information System (INIS)

    Cross sections for the excitation of the 2P-states of atomic hydrogen in charge exchange collisions of protons in argon and nitrogen were measured by observing the Lyman-α radiation emitted in transitions from this state. For the measurement of the target gas pressure, a modified ionization gauge was developed, which eliminated distortions of pressure measurements due to charging effects on the glass envelope. Because of the lack of light standards in the vacuum ultraviolet region of the spectrum, the major problem of the measurements was the absolute calibration of the L/sub alpha/-photometer. This calibration was obtained from coincidence measurements of H/sub alpha/- and L/sub alpha/-photons in the presence of an electric field. The measurements were corrected for the effect of Doppler shift on photometer sensitivity. For the evaluation of the coincidence measurements, the branching ratio of H/sub alpha/-transitions to the 2S-state and the polarization of Lyman-α radiation, emitted in cascade processes, were needed. These quantities were obtained from quantum mechanical calculations of a hydrogen atom in a weak electric field. Cross sections for the 2P-states were obtained in the energy range from 0.5 to 30 keV. The 2P-cross sections in argon had maxima of 2.23 x 10-17 and 2.68 x 10-17 cm2 at 3.35 and 11.86 keV, respectively, and in N2 maxima of 2.17 x 10-17 and 2.10 x 10-17 cm2 were observed at 3.39 and 11.3 keV, respectively. The energy dependence of the measured cross sections is in agreement with that of published measurements. Differences in the absolute values are discussed

  18. Quantum dynamics through a wave packet method to study electron-hydrogen and atom-dihydrogen collisions; Dynamique quantique par une methode de paquets d'ondes. Etude des collisions electron-hydrogene et atome-dihydrogene

    Energy Technology Data Exchange (ETDEWEB)

    Mouret, L

    2002-11-01

    The thesis concerns the development and implementation of numerical methods for solving the time-dependent Schroedinger equation. We first considered the case of electron-hydrogen scattering. The originality of our method is the use of a non-uniform radial grid defined by a Schwarz interpolation based on a Coulomb reference function. This grid allows many hydrogen bound states and associated matrix elements of various operators to be reproduced to machine accuracy. The wave function is propagated in time using a Split-Operator method. The efficiency of our method allows the wave function to be propagated out to large distances for all partial waves. We obtain excitation and ionization cross sections in excellent agreement with the best experimental and theoretical data. We subsequently adapted the method and the program package to study reactive atom-dihydrogen scattering. The wave packet is described using product Jacobi coordinates on a regular grid of radial coordinates combined with a basis of Legendre polynomials for the angular part (partial wave S). The wave function is analysed using a time-to-energy Fourier transform, which provides results over the energy range covered by the initial wave packet in one calculation. The method was first tested on the quasi-direct (F,H2) reaction and then applied to the indirect (C(1D),H2)reaction. The state-to-state reaction probabilities are in good agreement with those obtained by a time-independent approach. In particular, the strongly resonant structure of the (C(1D),H2) reaction probabilities is well reproduced. (author)

  19. PREFACE: International Symposium on (e,2e), Double Photoionization and Related Topics & 15th International Symposium on Polarization and Correlation in Electronic and Atomic Collisions

    Science.gov (United States)

    Martin, Nicholas L. S.; deHarak, Bruno A.

    2010-01-01

    From 30 July to 1 August 2009, over a hundred scientists from 18 countries attended the International Symposium on (e,2e), Double Photoionization and Related Topics and the 15th International Symposium on Polarization and Correlation in Electronic and Atomic Collisions which were held at the W T Young Library of the University of Kentucky, USA. Both conferences were satellite meetings of the XXVI International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC) held in Kalamazoo, Michigan, USA, 21-28 July 2009. These symposia covered a broad range of experimental and theoretical topics involving excitation, ionization (single and multiple), and molecular fragmentation, of a wide range of targets by photons and charged particles (polarized and unpolarized). Atomic targets ranged from hydrogen to the heavy elements and ions, while molecular targets ranged from H2 to large molecules of biological interest. On the experimental front, cold target recoil ion momentum spectroscopy (COLTRIMS), also known as the Reaction Microscope because of the complete information it gives about a wide variety of reactions, is becoming commonplace and has greatly expanded the ability of researchers to perform previously inaccessible coincidence experiments. Meanwhile, more conventional spectrometers are also advancing and have been used for increasingly sophisticated and exacting measurements. On the theoretical front great progress has been made in the description of target states, and in the scattering calculations used to describe both simple and complex reactions. The international nature of collaborations between theorists and experimentalists is exemplified by, for example, the paper by Ren et al which has a total of 13 authors of whom the experimental group of six is from Heidelberg, Germany, one theoretical group is from Australia, with the remainder of the theoreticians coming from several different institutions in the United States. A total of 52 invited talks and

  20. High-energy collision-induced dissociation of [M+Na]+ ions desorbed by fast atom bombardment of ceramides isolated from the starfish Distolasterias nipon.

    Science.gov (United States)

    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. PMID:23378088

  1. Investigations on molecular constants of the CD(X2Ⅱ) radical and elastic collisions between ground-state C and D atoms at low temperatures

    Institute of Scientific and Technical Information of China (English)

    Shi De-Heng; Zhang Jin-Ping; Sun Jin-Feng; Liu Yu-Fang; Zhu Zun-Lue

    2009-01-01

    The potential energy curve of the CD(X2Ⅱ) radical is obtained using the coupled-cluster singles-doublesapproximate-triples [CCSD(T)] theory in combination with the correlation-consistent quintuple basis set augmented with diffuse functions,aug-cc-pV5Z. The potential energy curve is fitted to the Murrell-Sorbie function,which is usedto determine the spectroscopic parameters. The obtained D0,De,Re,ωe,ωeXe,αe and Be values are 3.4971 eV,3.6261 eV,0.11197 nm,2097.661 cm-1,34.6963 cm-1,0.2083 cm-1 and 7.7962 cm-1,respectively,which conform almost perfectly to the available measurements. With the potential obtained at the UCCSD(T)/aug-cc-pV5Z level of theory,a total of 24 vibrational states have been predicted for the first time when J = 0 by solving the radial SchrSdinger equation of nuclear motion. The complete vibrational levels,the classical turning points,the inertial rotation constants and centrifugal distortion constants are reproduced from the CD(X2Ⅱ) potential when J = 0,and are in excellent agreement with the available measurements. The total and the various partial-wave cross sections are calculated for the elastic collisions between the ground-state C and D atoms at energies from 1.0× 10-11 to 1.0× 10-4 a.u. When the two atoms approach each other along the CD(X2Ⅱ) potential energy curve. Only one shape resonance is found in the total elastic cross sections,and the resonant energy is 8.36×10-6 a.u. The results show that the shape of the total elastic cross section is mainly dominated by the s partial wave at very low temperatures. Because of the weak shape resonances coming from higher partial waves,most of them are passed into oblivion by the strong total elastic cross sections.

  2. Elastic collisions between Si and D atoms at low temperatures and accurate analytic potential energy function and molecular constants of the SiD(X2∏) radical

    Institute of Scientific and Technical Information of China (English)

    Shi De-Heng; Zhang Jin-Ping; Sun Jin-Feng; Zhu Zun-Lue

    2009-01-01

    Interaction potential of the SiD(X2∏) radical is constructed by using the CCSD(T) theory in combination with the largest correlation-consistent quintuple basis set augmented with the diffuse functions in the valence range. Using the interaction potential, the spectroscopic parameters are accurately determined. The present D0, De, Re, ωe, αe and Be values are of 3.0956 eV, 3.1863 eV, 0.15223 nm, 1472.894 cm-1, 0.07799 cm-1 and 3.8717 cm-1, respectively,which are in excellent agreement with the measurements. A total of 26 vibrational states is predicted when J = 0 by solving the radial Schr(o)dinger equation of nuclear motion. The complete vibrational levels, classical turning points,initial rotation and centrifugal distortion constants when J = 0 are reported for the first time, which are in good accord with the available experiments. The total and various partial-wave cross sections are calculated for the elastic collisions between Si and D atoms in their ground states at 1.0×10-11-1.0×10-3 a.u. when the two atoms approach each other along the SiD(X2∏) potential energy curve. Four shape resonances are found in the total elastic cross sections, and their resonant energies are of 1.73×10-5, 4.0×10-5, 6.45×10-5 and 5.5×10-4 a.u., respectively. Each shape resonance in the total elastic cross sections is carefully investigated. The results show that the shape of the total elastic cross sections is mainly dominated by the s partial wave at very low temperatures. Because of the weakness of the shape resonances coming from the higher partial waves, most of them are passed into oblivion by the strong s partial-wave elastic cross sections.

  3. The problems of solar-terrestrial coupling and new processes introduced to the physics of the ionosphere from the physics of atomic collisions

    Science.gov (United States)

    Avakyan, Sergei

    2010-05-01

    Further progress in research of solar-terrestrial coupling requires better understanding of solar variability influence on the ionosphere. The most powerful manifestations of solar variability are solar flares and geomagnetic storms. During a flare EUV/X-ray irradiations are completely absorbed in the ionosphere producing SID. During geomagnetic storms precipitations of electrons with energy of several keV (and to a lesser extent protons precipitations) from radiation belts and geomagnetosphere produce additional ionization and low latitude auroras. Considering the physics of ionosphere during the last several decades we have been taking into account three novel processes well known in the physics of atomic collisions. These are Auger effect [S. V. Avakyan, The consideration of Auger processes in the upper atmosphere of Earth. In Abstracts of paper presented at the Tenth scien. and techn. Conf. of young specialists of S.I. Vavilov State Optical Institute, 1974, 29-31.], multiple photoionization of upper, valence shell [S.V. Avakyan, The source of O++ ions in the upper atmosphere, 1979, Cosmic Res, 17, 942 - 943] and Rydberg excitation of all the components of upper atmosphere [S.V. Avakyan, The new factor in the physics of solar - terrestrial relations - Rydberg atomic and molecules states. Conf. on Physics of solar-terrestrial relationships, 1994, Almaty, 3 - 5]. In the present paper the results of bringing these new processes in the ionospheric physics are discussed and also its possible role in the physics of solar-terrestrial coupling is considered. Involving these processes to the model estimations allowed us for the first time to come to the following important conclusions: - Auger electrons play the determinant role at the formation of energy spectrum of photoelectrons and secondary auroral electrons at the range above 150 eV; - double photoionization of the outer shell of the oxygen atom (by a single photon) plays a dominant role in the formation of

  4. Collisions between complex atomic nuclei

    International Nuclear Information System (INIS)

    The use of heavy ion accelerators in the study of nuclear structure and states is reviewed. The reactions discussed are the quasielastic reactions in which small amounts of energy and few particles are exchanged between the colliding nuclei. The development of heavy ion accelerators is also discussed, as well as detection equipment. Exotic phenomena, principally the possible existence of superheavy nuclei, are also treated. (JIW)

  5. Charge-transfer cross sections of ground state He+ ions in collisions with He atoms and simple molecules in the energy range below 4.0 keV

    International Nuclear Information System (INIS)

    Charge-transfer cross sections of the ground state He+ ions in collisions with He atoms and simple molecules (H2, D2, N2, CO and CO2) have been measured in the energy range of 0.20 to 4.0 keV with the initial growth rate method. Since previously published experimental data are scattered in the low energy region, the present observations would provide reasonably reliable cross section data below 4 keV. The charge transfer accompanied by dissociation of product molecular ion can be dominant at low energies for molecular targets. In He+ + D2 collisions, any isotope effect was not observed over the present energy range, compared to H2 molecule. (author)

  6. Cold collisions in dissipative optical lattices

    CERN Document Server

    Piilo, J

    2004-01-01

    In the past, light-assisted cold collisions between laser cooled atoms have been widely studied in magneto-optical atom traps (MOTs). We describe here theoretical studies of dynamical interactions, specifically cold collisions, between atoms trapped in near-resonant, dissipative optical lattices. The developed quantum-mechanical model is based on Monte Carlo wave-function simulations and combines atomic cooling and collision dynamics in a single framework. It turns out, that the radiative heating mechanism affects the dynamics of atomic cloud in a red-detuned lattice in a way that is not directly expected from the MOT studies. The optical lattice and position dependent light-matter coupling introduces selectivity of collision partners. Atoms, which are most mobile and energetic, are strongly favored to participate in collisions, and are more often ejected from the lattice, than the slow ones in the laser parameter region selected for study. For blue-detuned lattices, we study how optical shielding emerges as ...

  7. Rydberg atoms in astrophysics

    CERN Document Server

    Gnedin, Yu N; Ignjatovic, Lj M; Sakan, N M; Sreckovic, V A; Zakharov, M Yu; Bezuglov, N N; Klycharev, A N; 10.1016/j.newar.2009.07.003

    2012-01-01

    Elementary processes in astrophysical phenomena traditionally attract researchers attention. At first this can be attributed to a group of hemi-ionization processes in Rydberg atom collisions with ground state parent atoms. This processes might be studied as a prototype of the elementary process of the radiation energy transformation into electrical one. The studies of nonlinear mechanics have shown that so called regime of dynamic chaos should be considered as typical, rather than exceptional situation in Rydberg atoms collision. From comparison of theory with experimental results it follows that a such kind of stochastic dynamic processes, occurred during the single collision, may be observed.

  8. Theoretical atomic and molecular physics: Progress report

    International Nuclear Information System (INIS)

    The theoretical atomic and molecular physics program at Rice University addresses basic problems on the structure and collision dynamics of electrons, atoms, ions and molecules, emphasizing processes related to possible new energy technologies and other applications. The program focuses on collision processes under ''disturbed'' conditions, i.e., high levels of excitation, ionization, energy transfer, and external influences. Research projects include: collision processes in ICF plasmas; excitation and charge-transfer processes; Rydberg atom collisions; Penning ionization of atoms; excitation in electron-molecule collisions; and related topics. 48 refs

  9. Cross section measurements of the processes occurring in the fragmentation of Hn+ (3 ≤ n ≤ 35) hydrogen clusters induced by high speed (60 keV/u) collisions on helium atoms

    International Nuclear Information System (INIS)

    Different processes involved in the fragmentation of ionised hydrogen clusters H3 + (H2)(n-3)/2 (n = 5-35) have been studied in the same experiment: the fragmentation of the cluster is induced by the collision with an helium atom at high velocity (≅ c/100). The collision is realised in reversed kinematic - clusters are accelerated - which allows the detection of neutral and charged fragments. The different channels of fragmentation are identified by using coincidence techniques. For all the cluster sizes studied the capture cross sections of one electron of the target by the cluster is equal to the capture cross section of the H3+ ion. In the same way, the dissociation cross section of the H3+ core of the cluster does not depend on cluster size. These fragmentation processes are due to the interaction of H3+ core of the cluster and the helium atom without ionization of another component of the cluster. On the contrary, the cross sections of loss of one, two and three molecules by the cluster and the dissociation cross section of the cluster in all its molecular components depends strongly on the cluster size. This dependence is different from the one measured for the metastable decay of the cluster. Thus, the process of loss of molecules induced by a collision should correspond to a different dissociation mechanism. In regard of the singularities observed for the size dependence, the H9+, H15+, H19+ and H29+ clusters could be the 'core' of the biggest clusters. These observation are in agreement with the size effects of smaller magnitude observed for the dissociation cross section (all the processes). The values of the cross section for the process of at least one ionization of the cluster indicate that about 80% of the fragmentation events result from this process. (author)

  10. Antiprotonic Helium Atoms

    OpenAIRE

    Kartavtsev, O. I.

    1995-01-01

    Metastable antiprotonic helium atoms $^{3,4}\\! H\\! e\\bar pe$ have been discovered recently in experiments of the delayed annihilation of antiprotons in helium media. These exotic atoms survive for an enormous time (about tens of microseconds) and carry the extremely large total angular momentum $L\\sim 30-40$. The theoretical treatment of the intrinsic properties of antiprotonic helium atoms, their formation and collisions with atoms and molecules is discussed.

  11. Atomic Physics 16: Sixteenth International Conference on Atomic Physics. Proceedings

    International Nuclear Information System (INIS)

    These proceedings represent papers presented at the 16th International Conference on Atomic Physics held in Windsor, Ontario, Canada, in August, 1998. The topics discussed included a wide array of subjects in atomic physics such as atom holography, alignment in atomic collisions, coulomb-interacting particles, muon experiments, x-rays from comets, atomic electron collisions in intense laser fields, spectroscopy of trapped ions, and Bose-Einstein condensates. This conference represents the single most important meeting world wide on fundamental advances in atomic physics. There were 30 papers presented at the conference,out of which 4 have been abstracted for the Energy, Science and Technology database

  12. Spectral anomalies of the effect of light-induced drift of caesium atoms caused by the velocity dependence of transport collision frequencies

    International Nuclear Information System (INIS)

    The spectral features of the light-induced drift (LID) velocity of caesium atoms in inert buffer gases are studied theoretically. A strong temperature dependence of the spectral LID line shape of Cs atoms in Ar or Kr atmosphere in the vicinity of T ∼ 1000 K is predicted. It is shown that the anomalous LID of Cs atoms in binary buffer mixtures of two different inert gases can be observed at virtually any (including ambient) temperature, depending on the content of the components in these mixtures. The results obtained make it possible to precisely test the interatomic interaction potentials in the experiments on the anomalous LID. (quantum optics)

  13. Atom Skimmers and Atom Lasers Utilizing Them

    Science.gov (United States)

    Hulet, Randall; Tollett, Jeff; Franke, Kurt; Moss, Steve; Sackett, Charles; Gerton, Jordan; Ghaffari, Bita; McAlexander, W.; Strecker, K.; Homan, D.

    2005-01-01

    Atom skimmers are devices that act as low-pass velocity filters for atoms in thermal atomic beams. An atom skimmer operating in conjunction with a suitable thermal atomic-beam source (e.g., an oven in which cesium is heated) can serve as a source of slow atoms for a magneto-optical trap or other apparatus in an atomic-physics experiment. Phenomena that are studied in such apparatuses include Bose-Einstein condensation of atomic gases, spectra of trapped atoms, and collisions of slowly moving atoms. An atom skimmer includes a curved, low-thermal-conduction tube that leads from the outlet of a thermal atomic-beam source to the inlet of a magneto-optical trap or other device in which the selected low-velocity atoms are to be used. Permanent rare-earth magnets are placed around the tube in a yoke of high-magnetic-permeability material to establish a quadrupole or octupole magnetic field leading from the source to the trap. The atoms are attracted to the locus of minimum magnetic-field intensity in the middle of the tube, and the gradient of the magnetic field provides centripetal force that guides the atoms around the curve along the axis of the tube. The threshold velocity for guiding is dictated by the gradient of the magnetic field and the radius of curvature of the tube. Atoms moving at lesser velocities are successfully guided; faster atoms strike the tube wall and are lost from the beam.

  14. Collision rates in near-resonant optical lattices

    CERN Document Server

    Piilo, J

    2002-01-01

    We present a simple method to calculate the binary collision rate between atoms in near-resonant optical lattices. The method is based on the Monte Carlo wave function simulations and the collision rate is obtained by monitoring the quantum flux beyond the average distance between the atoms. To illustrate the usefulness of the method, we calculate the collision rates for a wide range of occupation densities and various modulation depths of the lattice. The method presented here combined with the semiclassical calculations accounting for intra-well collisions can simplify the study of the effects of binary collisions on the dynamics of atomic clouds trapped in near-resonant optical lattices.

  15. Excited atoms. Vozbuzhdennye atomy

    Energy Technology Data Exchange (ETDEWEB)

    Smirnov, B.M.

    1982-01-01

    An examination is made of the properties of excited atoms and molecules, the processes of their formation in a gas and plasma, and the diffusion of excited atoms in a gas. A presentation is made of the processes in which excited and metastable atoms and molecules in a gas are destroyed upon collision with electrons, atoms, and molecules. A study is made of the relaxation of excited states during collisions - excitation transfer, depolarization, transitions between fine structure states, etc. Information is given on ionization that includes the participation of excited atoms - the Penning process, associative ionization. An examination is made of highly excited states of atoms and the processes that take place during their participation. The book is intended for personnel in the area of physics and chemistry of plasma, atomic and molecular physics, chemical physics as well as in allied areas of physics. 1280 references, 52 figures, 76 tables.

  16. 质子与Be原子的碰撞电离过程研究%Research on collision ionization process of Be atom by proton

    Institute of Scientific and Technical Information of China (English)

    胡亚华; 叶丹丹; 祁月盈; 刘晓菊; 刘玲

    2012-01-01

    The impact ionization process of Be by H+ is investigated using the continuum-distorted-wave and the eikonal-initial-state (CDW- EIS) approximation in this paper. The single and double differential cross sections are calculated for the projectile energies ranging from 50keV/u to 10000 keV/u. The total cross sections are consistant well with the previous results. The ionization mechanism of soft- collision, electron captured to continuum states and binary-encounter collisions are discussed. The soft-collision ionization mechanism is the mostimportant contributor to the total cross section. Auger process for Be(1s2s2) is under study by adopting the FAC code.%本文采用初态程函近似一连续扭曲波方法研究了质子和Be原子的碰撞电离过程:计算了入射离子能量从50keV/u到10000keV/u时一阶和二阶微分散射截面随电离电子能量和角度的变化规律,并对各种碰撞电离机理进行了详细讨论;计算所得总截面随入射离子能量的变化规律也与已有数据一致;另外采用FAC代码研究了Be原子的内壳层电子(1s)被电离后的俄歇过程.

  17. Distributions over the 4s, 4p and 4d sublevels and their emission cross sections of the excited hydrogen atom produced in e-CH4 and H2O collisions

    International Nuclear Information System (INIS)

    Dissociation of CH4 and H2O induced in collisions with electrons was investigated by measuring decay curves of the intensity of the Balmer emission of the excited hydrogen atom H*(n = 4). The azimuthal quantum number (s, p, d) distributions of H*(n = 4) were obtained by a time-resolved single-photon counting method. The distribution (%) for methane is H*(4s):H*(4p):H*(4d)=42±4:4±11:51±11 at the electron energy of 25-300 eV, and that for water is H*(4s):H*(4p):H*(4d)=27±5:15±11:55±11 at 23-300 eV. The emission cross sections of each sublevel were obtained at 35, 50, 100 and 300 eV. (author)

  18. Application of the Landau-Zener model and the classical trajectory Monte Carlo method for capture processes in collisions of highly charged ions with light atoms

    International Nuclear Information System (INIS)

    In describing the collision dynamics of processes SEC and DEC (single and double electron capture, respectively) in case of the He target the one active electron approximation was used with a single-centre effective potential for calculations of the dominant (n,l)-level state selective and total charge exchange cross sections. For He target part of the diexcited states of the projectile ions produced by DEC decay by Auger emission of one electron. This autoionizing double capture channel (ADEC) is not taken into account in the present work. (R.P.)

  19. Theoretical Penning electron-energy distributions for alkali-metal atoms: He(2 /sup 1,3/S) collisions with sodium and potassium

    Energy Technology Data Exchange (ETDEWEB)

    Padial, N. T.; Cohen, J. S.; Martin, R. L.; Lane, N. F.

    1989-07-01

    Penning electron-energy distributions are calculated for collisions ofHe(2 /sup 1/S) and He(2 /sup 3/S) with sodium and potassiumatoms. The formulation is in terms of quantum-mechanical wave functions, whichare determined using previously published complex potentials for the initialstates and available experimental or presently calculated Hartree-Fockpotential curves for the final state. Sensitivities to these potentials aretested. The mechanisms for the observed energy structure are analyzed, and theeffects of experimental finite energy resolution and collisional velocityspread on the structure are shown.

  20. Collision Mechanics

    DEFF Research Database (Denmark)

    Pedersen, Preben Terndrup; Servis, D.P.; Zhang, Shengming;

    1999-01-01

    The first section of the present report describes the procedures that are being programmed at DTU for evaluation of the external collision dynamics. Then follows a detailed description of a comprehensive finite element analysis of one collision scenario for MS Dextra carried out at NTUA. The last...

  1. Improved atomic data for electron-transport predictions by the codes TIGER and TIGERP. I. Inner-shell ionization by electron collision

    International Nuclear Information System (INIS)

    The inner-shell ionization data for electron-target collisions now in use in the TIGER and TIGERP electron-transport codes are extracted and compared with other data for these processes. The TIGER cross sections for K-shell ionization by electron collisions are found to be seriously in error for large-Z targets and incident electron energies greater than 1 MeV. A series of TIGER and TIGERP runs were carried out with and without improved K-shell electron ionization cross section data replacing that now in use. The relative importance of electron-impact and photon ionization of the various subshells was also extracted from these runs. In general, photon ionization dominated in the examples studied so the sensitivity of many predicted properties to errors in the electron-impact subshell ionization data was not large. However, some differences were found and, as all possible applications were not covered in this study, it is recommended that these electron-impact data now in TIGER and TIGERP be replaced. Cross section data for the processes under study are reviewed and those that are most suitable for this application are identified. 19 references, 9 figures, 2 tables

  2. Proceedings of the workshop on 'spin-charge transfer reaction in atomic collision process' for planning of next period of cascade project

    International Nuclear Information System (INIS)

    This workshop was held on February 29, 1992, and was planned to investigate from the theoretical side the spin-charge transfer reaction which is used for a polarized heavy ion source, the development of which has been advanced in the Research Center for Nuclear Physics. In fiscal year 1992, the plan of installing an ECR ion source, Neomafios-10 GHz, as the AVF cyclotron external incident ion source is in progress. This external incidence system can be used also for the research on various atomic physics, in addition to the research on atomic nucleus physics. In this workshop, heated discussion was carried out on what research on atomic physics can be advanced in the Research Center for Nuclear Physics hereafter, through the investigation of the various problems that the atomic physics from low to high energy holds and new technical development. Particularly, the atomic physics using polarized ions seems to become a very unique study in the world. It seems proper to name this polarized heavy ion incidence system Spin factory. This report was edited based on the copies of the transparencies. (K.I.)

  3. The direct ionization processes in the collisions of partially stripped carbon and oxygen ions with helium atoms at low-to-intermediate energies

    International Nuclear Information System (INIS)

    The values of direct double-to-single ionization ratio R of helium atoms induced by Cq+, Oq++ (q = 1–4) ions at incident energies from 0.2 to 8.5MeV are measured. Based on the existing model (Shao J X, Chen X M and Ding B W 2007 Phys. Rev. A 75 012701) the effective charge of the projectile is introduced to theoretically estimate the value of R for the partially stripped ions impacting on helium atoms. The results calculated from our 'effective charge' model are in good agreement with the experimental data, and the dependence of the effective charge on the ionization energy of the projectile is also discussed qualitatively. (atomic and molecular physics)

  4. Energy pooling to the Ba 6s6p 1P01 level arising from collisions between pairs of metastable Ba 6s5d 3DJ atoms

    International Nuclear Information System (INIS)

    The energy-pooling rate coefficient for the Ba(6s5d3DJ)+Ba(6s5d3DJ)→Ba(6s21S0)+Ba(6s6p1P01) process has been measured. The barium atoms were excited by a cw diode laser tuned to the frequency of the 791.3 nm intercombination line and the metastable atoms in the 6s5d 3DJ state were produced due to radiative and collisional depopulation of the laser-excited 6s6p 3P01 state. The measurements were performed at 138 Ba number densities of about 4 x 1010 cm-3 and at 30 mbar argon as the buffer gas. Most of the barium ground state atoms in the excitation zone were transferred to the trip let metastable state at the laser pump power applied. The energy pooling rate coefficient was determined by comparing the fluorescence intensity of the barium 553.6 nm resonance line and the fluorescence intensity of the intercombination line 791.3 nm. In addition, the populations of the metastable atoms were probed with low intensity laser radiation from a single mode ring dye laser. The rate coefficient was found to be k = 1 x 10-10 cm3s-1 at T = 730 K. (orig.)

  5. Collision-induced Raman scattering by rare-gas atoms: The isotropic spectrum of Ne–Ne and its mean polarizability

    Energy Technology Data Exchange (ETDEWEB)

    Rachet, Florent; Chrysos, Michael, E-mail: michel.chrysos@univ-angers.fr [LUNAM Université, Université d’Angers, CNRS UMR 6200, Laboratoire MOLTECH-Anjou, 2 Bd Lavoisier, 49045 Angers (France); Dixneuf, Sophie [Forschungszentrum Jülich GmbH IEK-8, Troposphere, 52425 Jülich (Germany)

    2015-05-07

    We report the room-temperature isotropic collision-induced light scattering spectrum of Ne–Ne over a wide interval of Raman shifts, and we compare it with the only available experimental spectrum for that system as well as with spectra calculated quantum-mechanically with the employ of advanced ab initio-computed data for the incremental mean polarizability. The spectral range previously limited to 170 cm{sup −1} is now extended to 485 cm{sup −1} allowing us to successfully solve the inverse-scattering problem toward an analytic model for the mean polarizability that perfectly matches our measurements. We also report the depolarization ratio of the scattering process, lingering over the usefulness of this property for more stringent checks between the various polarizability models.

  6. Cross section measurements of the processes occurring in the fragmentation of H{sub n}{sup +} (3 {<=} n {<=} 35) hydrogen clusters induced by high speed (60 keV/u) collisions on helium atoms; Mesure des sections efficaces des differents processus intervenant dans la fragmentation d`agregats d`hydrogene H{sub n}{sup +} (3 {<=} n {<=} 35) induite par collision a haute vitesse (60 keV/u) sur un atome d`helium

    Energy Technology Data Exchange (ETDEWEB)

    Louc, Sandrine [Inst. de Physique Nucleaire, Lyon-1 Univ., 69 - Villeurbanne (France)

    1997-09-15

    Different processes involved in the fragmentation of ionised hydrogen clusters H{sub 3} + (H{sub 2}){sub (n-3)/2} (n = 5-35) have been studied in the same experiment: the fragmentation of the cluster is induced by the collision with an helium atom at high velocity ({approx_equal} c/100). The collision is realised in reversed kinematic - clusters are accelerated - which allows the detection of neutral and charged fragments. The different channels of fragmentation are identified by using coincidence techniques. For all the cluster sizes studied the capture cross sections of one electron of the target by the cluster is equal to the capture cross section of the H{sub 3}{sup +} ion. In the same way, the dissociation cross section of the H{sub 3}{sup +} core of the cluster does not depend on cluster size. These fragmentation processes are due to the interaction of H{sub 3}{sup +} core of the cluster and the helium atom without ionization of another component of the cluster. On the contrary, the cross sections of loss of one, two and three molecules by the cluster and the dissociation cross section of the cluster in all its molecular components depends strongly on the cluster size. This dependence is different from the one measured for the metastable decay of the cluster. Thus, the process of loss of molecules induced by a collision should correspond to a different dissociation mechanism. In regard of the singularities observed for the size dependence, the H{sub 9}{sup +}, H{sub 15}{sup +}, H{sub 19}{sup +} and H{sub 29}{sup +} clusters could be the `core` of the biggest clusters. These observation are in agreement with the size effects of smaller magnitude observed for the dissociation cross section (all the processes). The values of the cross section for the process of at least one ionization of the cluster indicate that about 80% of the fragmentation events result from this process. (author) 114 refs., 74 figs., 9 tabs.

  7. Universal bosonic tetramers of dimer-atom-atom structure

    OpenAIRE

    Deltuva, A.

    2012-01-01

    Unstable four-boson states having an approximate dimer-atom-atom structure are studied using momentum-space integral equations for the four-particle transition operators. For a given Efimov trimer the universal properties of the lowest associated tetramer are determined. The impact of this tetramer on the atom-trimer and dimer-dimer collisions is analyzed. The reliability of the three-body dimer-atom-atom model is studied.

  8. Electromagnetic processes in relativistic heavy ion collisions

    International Nuclear Information System (INIS)

    A study of the processes generated by the electromagnetic interaction in relativistic nuclear, and atomic collisions is presented. Very strong electromagnetic fields for a very short time are present in distant collisions with no nuclear contact. Such fields can also lead to interesting effects, which are discussed here. (orig.)

  9. Control of the 133 cesium cold collisions, search for a variation of the fine structure constant using a dual rubidium-cesium atomic fountain; Controle des collisions froides du cesium {sup 133}Cs: tests de la variation de la constante de structure fine a l'aide d'une fontaine atomique double rubidium-cesium

    Energy Technology Data Exchange (ETDEWEB)

    Marion, H

    2005-03-15

    We developed a method of measurement of the frequency shift due to the collisions between cold atoms. This is the main systematic limitation for the accuracy of the Cs{sup 133} based fountains ({approx} 10{sup -15} in relative frequency). Consequently, we can measure this effect near 0.5% This opens prospects for improvements of the fountains performances in term of accuracy until 10{sup -16}. The fountain has also obtained a stability about 10{sup -14} at 1 s. We discovered for the first time, at very low magnetic field (5 {+-} 1 mG), Feshbach resonances. We also took a new absolute measurement of the hyperfine transition of the Rb{sup 87}, which is the most precise ever carried out and is used now as definition for the secondary standard. By comparing this value with those measured the previous years, we could carry out a test of the stability of the fine structure constant on the level of 10{sup -15} /yr. We led local comparisons between atomic fountains and the other fountains of the laboratory. Most stable it is unrolled with a combined stability of 5.10{sup -14} at 1 s. The behavior of the difference of the two clocks goes like white frequency noise up to 3.10{sup -16}. The assessment of the dual fountain accuracy budget has been evaluated at 7.10{sup -16} for the cesium part and 8.10{sup -16} for the rubidium part. We contributed to the realization of the scale of International Atomic Time, by series of calibrations of hydrogen masers. An atomic comparison of fountain by satellite links was tested between our laboratory and our German counterpart. This measurement has determined the good agreement between the two clocks. (author)

  10. Shape and dynamics of states excited in electron-atom collisions: A comment on orientation and alignment parameters by consideration of attractive and repulsive forces

    International Nuclear Information System (INIS)

    Several ways of parametrising results of coherence and correlation analysis of atomic excitation in planar scattering experiments have been suggested over the years. Recently, Beyer and Kleinpoppen introduced new scattering amplitudes related to contributions from predominantly the attractive and the repulsive parts of the electron-atom potential. We clarify their relation to the so-called natural amplitudes of Hermann and Hertel and pursue the ideas further for the example of 80 eV electron excitation of the He(21p)-state. We demonstrate that this way of parametrising the data is directly related to the experimental observables, enables easy visualisation of the shape and dynamics of the charge cloud of the excited electron, and clarifies comparison between theory and experiment. (orig.)

  11. The direct ionization processes in the collisions of partially stripped carbon and oxygen ions with helium atoms at low-to-intermediate energies

    Institute of Scientific and Technical Information of China (English)

    Zhou Chun-Lin; Shao Jian-Xiong; Chen Xi-Meng; Sun Guang-Zhi; Zou Xian-Rong

    2008-01-01

    The values of direct double- to-single ionization ratio R of helium atoms induced by Cq+,Oq+ (q=1-4) ions at incident energies from 0.2 to 8.5MeV are measured.Based on the existing model (Shao J X,Chen X M and Ding B W 2007 Phys.Rev.A 75 012701) the effective charge of the projectile is introduced to theoretically estimate the value of R for the partially stripped ions impacting on helium atoms.The results calculated from our "effective charge" model are in good agreement with the experimental data,and the dependence of the effective charge on the ionization energy of the projectile is also discussed qualitatively.

  12. Atomic-orbital close-coupling calculations of charge exchange and ionisation in collisions of H(1s) and highly charged neon and argon ions

    International Nuclear Information System (INIS)

    Atomic-orbital close-coupling calculations of neon and argon ions colliding with H(1s) will be presented. The high principal quantum numbers n that need to be included in the expansion of the wavefunction of the active electron in the ion center make very large basis sets necessary. The resulting state resolved charge exchange and ionisation cross sections are of special interest for nuclear fusion research.

  13. Electromagnetic pair production in relativistic heavy-ion collisions

    International Nuclear Information System (INIS)

    We survey the phenomenon of pair production by the transient electromagnetic fields produced in relativistic heavy-ion collisions, as it impinges upon atomic, nuclear, and particle physics, and the design of accelerators and detectors. The subject is naturally divided between coherent production in peripheral collisions, and incoherent production in central collisions. We discuss examples illustrating both regimes

  14. Atomic and molecular theory

    Energy Technology Data Exchange (ETDEWEB)

    Inokuti, Mitio.

    1990-01-01

    The multifaceted role of theoretical physics in understanding the earliest stages of radiation action is discussed. Scientific topics chosen for the present discourse include photoabsorption, electron collisions, and ionic collisions, and electron transport theory, Connections of atomic and molecular physics with condensed-matter physics are also discussed. The present article includes some historical perspective and an outlook for the future. 114 refs., 3 figs.

  15. Atomic and molecular theory

    International Nuclear Information System (INIS)

    The multifaceted role of theoretical physics in understanding the earliest stages of radiation action is discussed. Scientific topics chosen for the present discourse include photoabsorption, electron collisions, and ionic collisions, and electron transport theory, Connections of atomic and molecular physics with condensed-matter physics are also discussed. The present article includes some historical perspective and an outlook for the future. 114 refs., 3 figs

  16. collision zone of an ISR

    CERN Multimedia

    This is a collision region from the world’s first proton collider, the Intersecting Storage Rings. The ISR was used at CERN from 1971-84 to study proton-proton collisions at the highest energy then available (60GeV). When operational, ISR collision regions were surrounded by detectors as shown in the photo. In 1972, the surprising discovery of fragments flying out sideways from head-on proton-proton collisions was the first evidence of quark-quark scattering inside the colliding protons . This was similar to Rutherford’s observation in 1911 of alpha particles scattering off the tiny nucleus inside atoms of gold. The ISR beamtubes had to be as empty as outer space, a vacuum 100 000 times better than other CERN machines at the time.

  17. collision region of the ISR

    CERN Multimedia

    1970-01-01

    This is a collision region from the world’s first proton collider, the Intersecting Storage Rings. The ISR was used at CERN from 1971-84 to study proton-proton collisions at the highest energy then available (60GeV). When operational, ISR collision regions were surrounded by detectors as shown in the photo. In 1972, the surprising discovery of fragments flying out sideways from head-on proton-proton collisions was the first evidence of quark-quark scattering inside the colliding protons . This was similar to Rutherford’s observation in 1911 of alpha particles scattering off the tiny nucleus inside atoms of gold. The ISR beamtubes had to be as empty as outer space, a vacuum 100 000 times better than other CERN machines at the time.

  18. Extensions to the two atom blocking model

    International Nuclear Information System (INIS)

    This paper contains viewgraphs on the use of the blocking model to describe atom-atom collisions in solids. Experimental results on two particle emissions for attractive and repulsive coulomb potentials are given

  19. Collision physics with highly stripped slow ions

    International Nuclear Information System (INIS)

    A review about recent studies with highly stripped heavy ions is given. Its scope is limited to mainly inner shell processes and slow collisions compared to the Bohr velocity of electrons in these shells. The processes discussed are: population of excited states by electron capture in asymmetric collision systems; electron capture and excitation in symmetric collisions with an emphasis on the impact parameter dependence of K- to L-shell and K- to K-shell vacancy transfer; the interference structure in the quasimolecular X-rays from slow hydrogen-like ion-atom collisions which is used for direct spectroscopy of quasimolecular energies. (Auth.)

  20. Penning ionization : In benzene · Ar and fluorobenzene · Ar van der waals molecules and in collisions of benzene with metastable Ar atoms

    Science.gov (United States)

    Rühl, E.; Bisling, P.; Brutschy, B.; Beckmann, K.; Leisen, O.; Morgner, H.

    1986-08-01

    The photoion efficiency curves of the van der Waals complexes benzene ·Ar (Bz·Ar) and fluorobenzene·Ar (Fb·Ar) exhibit sharp resonances, which correspond to excitation to the Ar 2P 3/24s and 2P 1/24s resonance states. The peaks are redshifted relative to their asymptotic values (Bz·Ar, Δ E = -70 ± 10 meV; Fb·Ar, Δ E = -40 ± 10 meV). These findings are supported by electron spectroscopy studies of the Penning ionization of benzene by state-selected metastable Ar ( 3p 2, 3p 0) atoms. Strong evidence is presented that Penning ionization is the process observed in both cases.

  1. Collisional destruction of fast H(2p), H(3s) and H(3d) hydrogen atoms in collision with He, Ar, H2, N2 and O2

    International Nuclear Information System (INIS)

    In the energy range 5-100 keV the collisional destruction of H(3s), H(3d) and H(2p) atoms in He, Ar, H2, N2 and O2 has been investigated. In the case of 3s and 3d states the measured cross sections which are subject to errors in the range 20-30% are in general agreement with the cross sections predicted by a simple model in which the orbital electron and the proton nuclear core are assumed to act independently on the target. Collisional destruction cross sections for n = 2 and 3 were found to be independent of the l value within the experimental error, typically 20-30%. (author)

  2. Collisions involving positronium

    International Nuclear Information System (INIS)

    Recent progress on the scattering of an ortho-positronium beam is reviewed. Similarities are noted amongst the total cross-sections for positronium scattering from various targets. The integrated Ps fragmentation cross-sections, determined by detecting each of the ejected particles, are presented for collisions with He and Xe atoms. In the case of He, a good agreement is found with theory, whilst preliminary results for Xe suggests that significant target ionisation occurs for this target at 30 eV Ps impact energy

  3. Collision cascade temperature

    International Nuclear Information System (INIS)

    Interaction of a projectile with a solid has been considered in detail. It has been found that any collision cascade generated by a projectile can be characterized by the average kinetic energy of cascade atoms that represents an 'instantaneous temperature' of the cascade during its very short lifetime (10-12 s). We refer to this value as the 'dynamic temperature' in order to emphasize the fact that cascade atoms are in a dynamic equilibrium and have a definite energy distribution. The dynamic temperature defines the electron distribution in the cascade area and, hence, the ionization probability of sputtered atoms. The energy distribution of cascade atoms and, as a consequence, the dynamic temperature can be found experimentally by measuring the energy distribution of sputtered atoms. The calculated dynamic temperature has been found to be in good agreement with the experimental data on ion formation in the case of cesium and oxygen ion sputtering of silicon. Based on the developed model we suggest an experimental technique for a radical improvement of the existing cascade sputtering models

  4. Theory of collisions between an atom and a diatomic molecule in the body-fixed coordinate system.)/sup a/ I. Coupled differential equation and asymptotic boundary conditions

    International Nuclear Information System (INIS)

    The body-fixed (BF) formulation for atom--diatom scatterings is developed to the extent that one can use it to perform accurate close-coupling calculation, without introducing further approximation except truncating a finite basis set of the target molecular wave function, on the same ground as one use the space-fixed (SF) formulation. In this formulation, the coupled differential equations are solved an the boundary conditions matched entirely in the BF coordinate system. A unitary transformation is used to obtain both the coupled differential equation and the boundary condition in BF system system from SF system. All properties of the solution with respect to parity are derived entirely from the transformation, without using the parity eignfunctions of the BF frame. Boundary conditions that yield the scattering (S) matrix and the reactance (R) matrix are presented for each parity in both the far asymptotic region (where the interaction and the centrifugal potentials are both negligible) and the near asymptotic region (where the interaction potential is negligible but the centrifugal potential is not). While our differential equations are the same as those derived by others with different methods, our asymptotic boundary conditions disagree with some existing ones. With a given form of the BF coupled differential equations, the acceptable boundary conditions are discussed

  5. Manipulating Higher Partial-Wave Atom-Atom Interaction by Strong Photoassoiative Coupling

    OpenAIRE

    Deb, Bimalendu; Hazra, Jisha

    2009-01-01

    We show that it is possible to change not only s-wave but also higher partial wave atom-atom interactions in cold collision in the presence of relatively intense laser fields tuned near a photoassociative transition.

  6. Scattering of electronically excited metastable rare gas atoms

    International Nuclear Information System (INIS)

    Low energy collisions of metastable rare gas atoms (mostly He) are reviewed. Principles of the experiment are presented as well as data analysis, excimer systems, excitation transfer collisions and Penning systems

  7. Dissipative heavy-ion collisions

    International Nuclear Information System (INIS)

    This report is a compilation of lecture notes of a series of lectures held at Argonne National Laboratory in October and November 1984. The lectures are a discussion of dissipative phenomena as observed in collisions of atomic nuclei. The model is based on a system which has initially zero temperature and the initial energy is kinetic and binding energy. Collisions excite the nuclei, and outgoing fragments or the compound system deexcite before they are detected. Brownian motion is used to introduce the concept of dissipation. The master equation and the Fokker-Planck equation are derived. 73 refs., 59 figs

  8. Experimental atomic physics

    International Nuclear Information System (INIS)

    The atomic structure and collision phenomena of highly stripped ions in the range Z = 6 to 35 were studied. Charge-transfer and multiple-electron-loss cross sections were determined. Absolute x-ray-production cross sections for incident heavy ions were measured. 10 figures, 1 table

  9. Determination of polarization relaxation times of atomic levels

    International Nuclear Information System (INIS)

    Probe signal polarization plane rotation in the field of an advanced in time intensive pulse is investigated taking into account optical pumping of atoms in a resonant medium. It is shown that the polarization plane modification is due to two processes: atoms radiation relaxation and collisions induced by atom magnetic sublevels redistribution. This method enables to measure large times of atoms collisions on the background of short times of the atom radiation decay

  10. Grazing Ion-Surface Collisions

    Science.gov (United States)

    Gravielle, M. S.

    Electron emission after grazing ion-surface collisions is studied for high impact velocities. We have focused on glancing angles of electron emission where the dominant mechanism is the ionization from atomic bound states. To describe this process, we introduce a quantum model called field distorted-wave (FDW) approximation, which takes into account the effect of the surface interaction on the electronic transition. The FDW model is applied to analyze electron distributions produced by impact of protons on Al and LiF surfaces, which are metal and insulator materials respectively. In the case of metals, we also evaluate the contibution coming from the valence band by employing the binary collisional formalism. Calculated electron emission yields are in reasonable agreement with the available experimental data. We find that the maximum of the convoy electron distribution is accelerated for Al and decelerated for LiF, with respect to its position in ion-atom collisions, in quantitative accordance with experiments.

  11. Molecular vibrational states during a collision

    Science.gov (United States)

    Recamier, Jose A.; Jauregui, Rocio

    1995-01-01

    Alternative algebraic techniques to approximate a given Hamiltonian by a harmonic oscillator are described both for time-independent and time-dependent systems. We apply them to the description of a one dimensional atom-diatom collision. From the resulting evolution operator, we evaluate vibrational transition probabilities as well as other time-dependent properties. As expected, the ground vibrational state becomes a squeezed state during the collision.

  12. Molecular vibrational states during a collision

    Energy Technology Data Exchange (ETDEWEB)

    Recamier, J.A.; Jauregui, R. [Universidad Nacional Autonoma de Mexico, Mexico City (Mexico)

    1995-01-01

    Alternative algebraic techniques to approximate a given Hamiltonian by a harmonic oscillator are described both for time-independent and time-dependent systems. The authors apply them to the description of a one dimensional atom-diatom collision. From the resulting evolution operator, they evaluate vibrational transition probabilities as well as other time-dependent properties. As expected, the ground vibrational state becomes a squeezed state during the collision.

  13. Electron collision cross sections and radiation chemistry

    International Nuclear Information System (INIS)

    A survey is given of the cross section data needs in radiation chemistry, and of the recent progress in electron impact studies on dissociative excitation of molecules. In the former some of the important target species, processes, and collision energies are presented, while in the latter it is demonstrated that radiation chemistry is a source of new ideas and information in atomic collision research. 37 references, 4 figures

  14. Atomic data for fusion

    International Nuclear Information System (INIS)

    This report provides a handbook of recommended cross-section and rate-coefficient data for inelastic collisions between hydrogen, helium and lithium atoms, molecules and ions, and encompasses more than 400 different reactions of primary interest in fusion research. Published experimental and theoretical data have been collected and evaluated, and the recommended data are presented in tabular, graphical and parametrized form. Processes include excitation and spectral line emission, charge exchange, ionization, stripping, dissociation and particle interchange reactions. The range of collision energies is appropriate to applications in fusion-energy research

  15. Atomic data for fusion

    Energy Technology Data Exchange (ETDEWEB)

    Hunter, H.T.; Kirkpatrick, M.I.; Alvarez, I.; Cisneros, C.; Phaneuf, R.A. (eds.); Barnett, C.F.

    1990-07-01

    This report provides a handbook of recommended cross-section and rate-coefficient data for inelastic collisions between hydrogen, helium and lithium atoms, molecules and ions, and encompasses more than 400 different reactions of primary interest in fusion research. Published experimental and theoretical data have been collected and evaluated, and the recommended data are presented in tabular, graphical and parametrized form. Processes include excitation and spectral line emission, charge exchange, ionization, stripping, dissociation and particle interchange reactions. The range of collision energies is appropriate to applications in fusion-energy research.

  16. Anisotropy in electron-atom collisions

    International Nuclear Information System (INIS)

    Most of the work described in this thesis deals with studies using coincidence experiments, particularly for investigating the electron impact excitation of the 21P and 31D states in helium. A peculiarity is that in the 31D studies the directly emitted 31D → 21P photons are not observed but the 21P → 11S photons resulting from the 31D → 21P → 11S cascade instead. Another interesting point is the choice of the quantisation axis. The author demonstrates that it is of great advantage to take the quantisation axis perpendicular to the scattering plane rather than in the direction of the incident beam, as was done (on historical grounds) in previously reported electron-photon coincidence experiments. Contrary to the incident beam direction the axis perpendicular to the scattering plane really represents an axis of symmetry in the coincidence experiment. In Chapter II the so-called 'parity unfavoured' excitation of the (2p2)3P state of helium by electrons is studied. In chapter III the anisotropy parameters for the electron impact excitation of the 21P state of helium in the energy range from 26.6 to 40 eV and in the angular range from 300 to 1100 are determined. Chapter IV contains a description of a scattered electron cascaded-photon coincidence experiment on the electron impact excitation of helium's 31D state. The measurement of complex scattering amplitudes for electron impact excitation of the 31D and 31P states of helium is discussed in Chapter V. (Auth./C.F.)

  17. Spectroscopic diagnostics of electron-atom collisions

    International Nuclear Information System (INIS)

    Progress from May 1, 1987 to April 30, 1991 is summarized in two Progress Reports that are reproduced in Appendix A, and in attached publications. Since then, we have completed manuscript preparations and publications of earlier observations, while carrying out a high energy-resolution measurement of electron collisional excitations in sodium. The results of the latter experiment have not been prepared for publication, and the manuscript is included as Appendix B. An additional manuscript, describing the unique high-current electron monochromator developed for this experiment, is in preparation and not enclosed. All additional results and conclusions of our work under the contract are now available in four publications that are attached at the back of this report. Consequently, we will elaborate on those only to note that we have achieved our proposed goals, with the full detail proposed but at a slightly slower pace than we had hoped

  18. Fragments detection of the Ar+ collision in air

    International Nuclear Information System (INIS)

    The different components of a lineal accelerator of particles to low energy that will be used in experiments of atomic and molecular collisions are described. By means of the technique of flight time the fragments of the collision of positive ions were identified in gases. In this work values of some parameters are presented guided to optimize the operation of the accelerator, as well as preliminary data of the collision of argon ions in air. (Author)

  19. Atomic-process cross section data, 1

    International Nuclear Information System (INIS)

    Compiled by the Data Study Group, the data are intended for fusion plasma physics research. Cross sections of the latest experimental and theoretic studies cover the processes involving H,D,T as principal plasma materials as well as photons and electrons: emission and absorption of electromagnetic wave, electron collision, ion collision, recombination, neutral atom mutual collision, etc. Edition is so made to enable the future renewal by users. (J.P.N.)

  20. R-Matrix Calculations of Electron Molecule Collision Data

    International Nuclear Information System (INIS)

    Results for R-matrix calculations performed during the Coordinated Research Project (CRP) on Atomic and Molecular Data for Plasma Modelling are discussed. Electron collision problems studied include collisions with various carbon containing molecules including C2, HCCH, CH4, C2H6 and C3H8. (author)

  1. Inelastic Collisions and Chemical Reactions of Molecules at Ultracold Temperatures

    OpenAIRE

    Quéméner, Goulven; Balakrishnan, Naduvalath; Dalgarno, Alexander

    2010-01-01

    This paper summarizes the recent theoretical works on inelastic collisions and chemical reactions at cold and ultracold temperatures involving neutral or ionic systems of atoms and molecules. Tables of zero-temperature rate constants of various molecules are provided.

  2. An interface between the nuclear physics and the atomic physics; how to measure nuclear times observing atomic transitions

    International Nuclear Information System (INIS)

    Recent observations are related in which processes resulting from the ionization in ion-atom collisions are observed in coincidence with nuclear processes (where the incidence ion nucleus hits the target atom nucleus). The delay introduced by the nuclear reaction contaminates the results of the atomic collision and manifest itself either in the X rays (positrons) emitted in the joined atom system or in the X rays (Auger electrons) emitted by separeted atoms, after the collision. Both effects serve to obtain information on the reaction times (in general much less then 10-16 sec). Following this line, other experimental possibilities are discussed. (L.C.)

  3. Modeling of L-vacancy formation in ion-gas and ion-solid collisions

    Energy Technology Data Exchange (ETDEWEB)

    Babenko, P.Yu., E-mail: babenko@npd.ioffe.ru; Zinoviev, A.N., E-mail: zinoviev@inprof.ioffe.rssi.ru; Shergin, A.P.

    2015-07-01

    The paper suggests a scaling for calculating cross-sections of L-vacancy formation due to atomic collisions in the keV range of collision energies. A technique for estimating the probability of inelastic transition by differentiating its cross-section dependence on the collision energy is also proposed.

  4. Atomic effects of electrons and protons at low energies

    International Nuclear Information System (INIS)

    Some aspects of electronic and atomic collisions are discussed. Impact ionization by electrons and protons, and electron bremsstrahlung processes are considered in some detail. Emphasis is also given to (uncorrelated and correlated) many-electron processes, which are of particular importance in collisions of highly-charged ions with atoms. 84 refs., 15 figs

  5. Theoretical atomic and molecular physics: Progress report, July 1, 1988 through June 30, 1989

    International Nuclear Information System (INIS)

    The theoretical atomic and molecular physics program at Rice University emphasizes fundamental questions regarding the structure and collision dynamics of various atomic and molecular systems with some attention given to atomic processes at surfaces. Our activities have been centered on continuing the projects initiated last year as well as beginning some new studies. These include: differential elastic and charge-transfer scattering and alignment and orientation of the excited electron cloud in ion-atom, atom-atom and ion-molecule collisions, using a molecular-orbital representation and both semiclassical and quantal methods; quenching of low-lying Rydberg states of a sodium atom in a collision with a rare-gas atom, using a semiclassical representation; so far, target atoms He, Ne and Ar have been studied; chemiionization and ion-pair formation in a collision of a Li atom with a metastable He atom at intermediate collision energies, using a combination of quantal and semi-classical methods; Penning ionization of alkali atoms Na and K, using advanced Cl and Stieltjes imaging methods; radiative and nonradiative charge-transfer in He+ + H collisions at ultra-low collision energies, using quantal methods; elastic and inelastic processes in electron-molecule collisions, using the continuum-multiple-scattering method; and inelastic collision processes in dense, high-temperature plasmas. Selected highlights of our research progress are briefly summarized in this paper

  6. Muonium/muonic hydrogen formation in atomic hydrogen

    Indian Academy of Sciences (India)

    V S Kulhar

    2004-09-01

    The muonium/muonic hydrogen atom formation in ± –H collisions is investigated, using a two-state approximation in a time dependent formalism. It is found that muonium cross-section results are similar to the cross-section results obtained for positronium formation in + –H collision. Muonic hydrogen atom formation cross-sections in - –H collision are found to be significant in a narrow range of energy (5 eV–25 eV).

  7. Positron spectroscopy after heavy ion collisions

    International Nuclear Information System (INIS)

    The author reviews the theoretical and experimental results on positron production in heavy ion collisions. After a discussion of the quasi-atomic picture, the possible observation of the axion, and the inverse Bhabha scattering, the positron spectrometer EPOS of the GSI Darmstadt is described. Thereafter the experimental results are presented. (HSI)

  8. Collision Risk and Damage after Collision

    DEFF Research Database (Denmark)

    Pedersen, Preben Terndrup; Hansen, Peter Friis; Nielsen, Lars Peter

    1996-01-01

    The paper presents a new and complete procedure for calculation of ship-ship collision rates on specific routes and the hull damage caused by such collisions.The procedure is applied to analysis of collision risks for Ro-Ro pasenger vessels. Given a collision the spatial probability distribution of...... are presented for threee different Ro-Ro passenger vessels of length 98 m 150 m and 180 m, respectively operating at three different routes. These routes are the Danish Great Belt route, a Finland-Sweden route and the Dover-Calais route....

  9. Rydberg atoms in ultracold plasmas

    Science.gov (United States)

    Rolston, Steven

    2009-05-01

    Ultracold plasmas are formed through the photoionization of laser-cooled atoms, or spontaneous ionization of a dense cloud of Rydberg atoms or now molecules[1]. Ultracold plasmas are inherently metastable, as the ions and electrons would be in a lower energy state bound together as atoms. The dominant process of atom formation in these plasmas is three-body recombination, a collision between two electrons and an ion that leads to the formation of a Rydberg atom. This collisional process is not only important in determining the lifetime and density of the plasma, but is also critical in determining the time evolution of the temperature. The formation of the Rydberg atoms is accompanied by an increase in electron energy for the extra electron in the collision, and is a source of heating in these plasmas. Classical three-body recombination theory scales as T-9/2, and thus as a plasma cools due to a process such as adiabatic expansion, recombination-induced heating turns on, limiting the temperature [2]. The Rydberg atoms formed live in the plasma and contribute to the temperature dynamics, as collisions with plasma electrons can change the principal quantum number of the Rydberg atom, driving it to more tightly bound states (a source of plasma heating) or to higher states (a source of plasma cooling). If the plasma is cold and dense enough to be strongly coupled, classical three-body recombination theory breaks down. Recent theoretical work [3] suggests that the rate limits as the plasma gets strongly coupled. I will review the role of Rydberg atoms in ultracold plasmas and prospects for probing Rydberg collisions in the strongly coupled environment. [4pt] [1] J. P. Morrison, et al., Phys. Rev. Lett. 101, 205005 (2008 [0pt] [2] R. S. Fletcher, X. Zhang, and S. L. Rolston, Phys. Rev. Lett. 99, 145001 (2007 [0pt] [3] T. Pohl, private communication.

  10. Division XII / Commission 14 / Working Group Collision Processes

    CERN Document Server

    Peach, Gillian

    2012-01-01

    Research in atomic and molecular collision processes and spectral line broadening has been very active since our last report, Peach, Dimitrijevic & Stancil 2009. Given the large volume of the published literature and the limited space available, we have attempted to identify work most relevant to astrophysics. Since our report can not be comprehensive, additional publications can be found in the databases at the web addresses listed in the final section. Elastic and inelastic collisions among electrons, atoms, ions, and molecules are included and charge transfer can be very important in collisions between heavy particles.

  11. Division B Commission 14 Working Group: Collision Processes

    Science.gov (United States)

    Peach, Gillian; Dimitrijevic, Milan S.; Barklem, Paul S.

    2016-04-01

    Since our last report (Peach & Dimitrijević 2012), a large number of new publications on the results of research in atomic and molecular collision processes and spectral line broadening have been published. Due to the limited space available, we have only included work of importance for astrophysics. Additional relevant papers, not included in this report, can be found in the databases at the web addresses provided in Section 6. Elastic and inelastic collisions between electrons, atoms, ions, and molecules are included, as well as charge transfer in collisions between heavy particles which can be very important.

  12. Collisional process involving atomic cluster ions

    International Nuclear Information System (INIS)

    Collision of Ar cluster ions, Ar+n (n = 3-16), with He and Ne atoms was investigated by use of mass spectroscopic techniques. The cross sections for the production of Ar+n' (n' < n) were measured as functions of the size of the parent cluster ion and the collision energy (0.1-10 eV in the center-of-mass frame). These results were analyzed in the scheme of hard-sphere spectator collision with RRK theory. It was concluded that the reaction proceeds via collisional excitation of the parent cluster ion and following sequential loss of the constituent Ar atoms. (orig.)

  13. Sympathetic cooling of fluorine atoms with ultracold atomic hydrogen

    CERN Document Server

    González-Martínez, Maykel L

    2013-01-01

    We consider the prospect of using ultracold hydrogen atoms for sympathetic cooling of fluorine atoms to microkelvin temperatures. We carry out quantum-mechanical calculations on collisions between cold F and H atoms in magnetically trappable states and show that the ratio of elastic to inelastic cross sections remains high across a wide range of temperatures and magnetic fields. For F atoms initially in the spin-stretched state ($^2$P$_{3/2}$, $f=m_f=+2$), sympathetic cooling appears likely to succeed from starting temperatures around 1 K or even higher. This occurs because inelastic collisions are suppressed by p-wave and d-wave barriers that are 600 mK and 3.2 K high, respectively. In combination with recent results on H + NH and H + OH collisions [M. L. Gonz\\'alez-Mart\\'{\\i}nez and J. M. Hutson, arXiv:1305.6282 (2013)], this establishes ultracold H atoms as a very promising and versatile coolant for atoms and molecules that cannot be laser-cooled.

  14. Theory of Electron-Ion Collisions

    Energy Technology Data Exchange (ETDEWEB)

    Griffin, Donald C

    2009-10-02

    Collisions of electrons with atoms and ions play a crucial role in the modeling and diagnostics of fusion plasmas. In the edge and divertor regions of magnetically confined plasmas, data for the collisions of electrons with neutral atoms and low charge-state ions are of particular importance, while in the inner region, data on highly ionized species are needed. Since experimental measurements for these collisional processes remain very limited, data for such processes depend primarily on the results of theoretical calculations. Over the period of the present grant (January 2006 - August 2009), we have made additional improvements in our parallel scattering programs, generated data of direct fusion interest and made these data available on The Controlled Fusion Atomic Data Center Web site at Oak Ridge National Laboratory. In addition, we have employed these data to do collsional-radiative modeling studies in support of a variety of experiments with magnetically confined fusion plasmas.

  15. Atomic Rydberg Reservoirs for Polar Molecules

    CERN Document Server

    Zhao, Bo; Pupillo, Guido; Zoller, Peter

    2011-01-01

    We discuss laser dressed dipolar and Van der Waals interactions between atoms and polar molecules, so that a cold atomic gas with laser admixed Rydberg levels acts as a designed reservoir for both elastic and inelastic collisional processes. The elastic scattering channel is characterized by large elastic scattering cross sections and repulsive shields to protect from close encounter collisions. In addition, we discuss a dissipative (inelastic) collision where a spontaneously emitted photon carries away (kinetic) energy of the collision partners, thus providing a significant energy loss in a single collision. This leads to the scenario of rapid thermalization and cooling of a molecule in the mK down to the \\mu K regime by cold atoms.

  16. Ionization of atomic hydrogen by 30 1000 keV antiprotons

    Energy Technology Data Exchange (ETDEWEB)

    Knudsen, H.; Mikkelsen, U.; Paludan, K. [Institute of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark); Kirsebom, K.; Moller, S.P.; Uggerhoj, E. [Institute for Synchrotron Radiation, University of Aarhus, DK-8000 Aarhus C (Denmark); Slevin, J. [Department of Experimental Physics, St. Patrick`s College, Maynooth (Ireland); Charlton, M. [Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom); Morenzoni, E. [Paul Scherrer Institut, Villigen, CH-4234 (Switzerland)

    1995-06-05

    Ionization in collisions between antiprotons and atomic hydrogen is perhaps the least complicated and most fundamental process that can be treated by atomic-collision theory. We present measurements of the ionization cross section for 30--1000 keV antiprotons colliding with atomic hydrogen.

  17. Atomic processes relevant to polarization plasma spectroscopy

    International Nuclear Information System (INIS)

    When atoms (ions) are excited anisotropically, polarized excited atoms are produced and the radiation emitted by these atoms is polarized. From the standpoint of plasma spectroscopy research, we review the existing data for various atomic processes that are related to the polarization phenomena. These processes are: electron impact excitation, excitation by atomic and ionic collisions, photoexcitation, radiative recombination and bremsstrahlung. Collisional and radiative relaxation processes of atomic polarization follow. Other topics included are: electric-field measurement, self alignment, Lyman doublet intensity ratio, and magnetic-field measurement of the solar prominence. (author)

  18. Non-LTE Balmer line formation in late-type spectra: Effects of atomic processes involving hydrogen atoms

    CERN Document Server

    Barklem, P S

    2007-01-01

    (*** abridged ***) Context: The wings of Balmer lines are often used as effective temperature diagnostics for late-type stars under the assumption they form in local thermodynamic equilibrium. Aims: Our goal is to investigate the non-LTE formation of Balmer lines in late-type stellar atmospheres, to establish if the assumption of LTE is justified. Furthermore, we aim to determine which collision processes are important for the problem; in particular, the role of collision processes with hydrogen atoms is investigated. Method: A model hydrogen atom for non-LTE calculations has been constructed accounting for various collision processes using the best available data from the literature. The processes included are inelastic collisions with electrons and hydrogen atoms, mutual neutralisation and Penning ionisation. Non-LTE calculations are performed, and the relative importance of the collision processes is investigated. Results: Our calculations show electron collisions alone are not sufficient to establish LTE ...

  19. Investigations in atomic physics by heavy ion projectiles

    International Nuclear Information System (INIS)

    Investigations in atomic physics by high-energy heavy ions are discussed. The main attention is paid to collision mechanisms (direct Coulomb interaction, quasi-molecular collision mechanism and other models) and the structure of highly ionized and excited atoms. Some problems of fundamental issues (Lamb shift of H-like heavy ions, the superheavy quasi-atoms and the position production in supercritical fields) are conside-- red in detail

  20. 5. International workshop on autoionization phenomena in atoms. Abstracts

    International Nuclear Information System (INIS)

    Summaries of the reports presented at the 5 International Workshop on Autoionization Phenomena in Atoms (Dubna, 12-14 December 1995). The main topics of these 53 reports are the following ones: photoexcitation of autoionizing states in atoms and ions, autoionization in electron-atom collisions, autoionization in heavy particle collisions, coincidence experiments in autoionization studies, investigations of autoionizing states with lasers and wave functions and decay characteristics of autoionizing states