WorldWideScience

Sample records for atomic collision cascades

  1. Atom-atom collision cascades localization

    International Nuclear Information System (INIS)

    Kirsanov, V.V.

    1980-01-01

    The presence of an impurity and thermal vibration influence on the atom-atom collision cascade development is analysed by the computer simulation method (the modificated dynamic model). It is discovered that the relatively low energetic cascades are localized with the temperature increase of an irradiated crystal. On the basis of the given effect the mechanism of splitting of the high energetic cascades into subcascades is proposed. It accounts for two factors: the primary knocked atom energy and the irradiated crystal temperature. Introduction of an impurity also localizes the cascades independently from the impurity atom mass. The cascades localization leads to intensification of the process of annealing in the cascades and reduction of the post-cascade vacancy cluster sizes. (author)

  2. Particle fluxes in atomic collision cascades

    International Nuclear Information System (INIS)

    Sckerl, B.W.; Sigmund, P.; Vicanek, M.

    1996-01-01

    The flux of recoil atoms in atomic collision cascades induced by an ion beam or another source of energetic particles in a material is known to approach isotropy at kinetic energies far below the beam energy. A variety of irradiation effects can be explained satisfactorily on the basis of an isotropic particle flux, but significant deviations from this simple behavior are known to exist. While numerous examples have been studied by numerical simulation of cascade processes, the systematics is, by and large, unknown. The present study aims at general scaling properties and estimates of the magnitude of moderate deviations from isotropy and their spatial dependence for a wide range of beam and material parameters. Anisotropies introduced by crystal structure are ignored. Although it is well established that cascade anisotropy is related to the momentum of beam particles, previous attempts to quantify this relation have failed. We have found that there are two leading correction terms to the isotropic particle flux, a well-known term centered around the beam direction as a symmetry axis and a new term proportional to the gradient of the deposited-energy density. As a general rule the two contributions are either both significant or both negligible. Specific situations in which the gradient term dominates are, however, of considerable interest in applications. The parameters which characterize the anisotropy of collision cascades also determine the deposition of momentum, but the connection is less straightforward than asserted hitherto. General principles are first illustrated on the specific case of elastic-collision cascades under self-bombardment which contains the essentials. Thereafter several generalizations are made, including atomic binding forces and inelasticity as well as allowance for multicomponent materials. Application areas in mixing and sputtering are outlined. (au) 58 refs

  3. Computer simulation of electronic excitation in atomic collision cascades

    International Nuclear Information System (INIS)

    Duvenbeck, A.

    2007-01-01

    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

  4. 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

  5. Effect of inelastic energy losses on development of atom-atom collision cascades

    International Nuclear Information System (INIS)

    Marinyuk, V.V.; Remizovich, V.S.

    2001-01-01

    The problem of influence of inelastic energy losses (ionization braking) of particles on the development of atom-atom collision cascades in infinite medium was studied theoretically. Main attention was paid to study of angular and energy distributions of primary ions and cascade atoms in the presence of braking. Analytical calculations were made in the assumption that single scattering of particles occurs by solid balls law, while the value of electron braking ability of a medium is determined by the Lindhard formula. It is shown that account of braking (directly when solving the Boltzmann transport equation) changes in principle the previously obtained angular and energy spectra of ions and cascade atoms. Moreover, it is the braking that is the determining factor responsible for anisotropy of angular distributions of low-energy primary ions and cascade atoms [ru

  6. Concerning the theory of radiation cascades of atomic collisions in a solid with an arbitrary interatomic interaction potential

    International Nuclear Information System (INIS)

    Ryazanov, A.I.; Metelkin, E.V.

    1980-01-01

    Cascades of atomic collisions created by high energy particles as a result of irradiation of solids by them are considered. The solution of the problem is based on the investigation of the Boltzmann stationary kinetic equation for moving atoms. For this equation a model scattering indicatrix is constructed with an arbitrary form of the potential of interaction of moving atoms with lattice atoms. The choice of the model scattering indicatrix of atoms is determined by the normalization, the average energy loss in a single collision and by the deviation of the energy losses really occurring in the collision from the mean value, as well as by the initial kinetic equation for moving atoms. The energy distribution of moving atoms for arbitrary interatomic interaction potentials has been obtained using the constructed model scattering indicatrix. On the basis of the theory constructed a cascade is calculated with an interatomic interaction potential in the form of the Thomas-Fermi potential and the power potential. (author)

  7. Effect of solute atoms on collision cascades in copper and molybdenum irradiated with self-ions

    International Nuclear Information System (INIS)

    English, C.A.; Eyre, B.L.; Wadley, H.; Stathopoulos, A.Y.

    1975-01-01

    An examination of the effect material purity has on the numbers and sizes of the vacancy loops formed in collision cascades produced by self-ion irradiation of copper and molybdenum is reported. It is shown that substitutional and interstitial impurities both markedly reduce the damage generated in molybdenum by 60 keV Mo + ions but little effect is seen in copper irradiated by 30 keV Cu + ions. These results are compared with recent observations of vacancy defects in type 316 stainless steel following irradiation with 40-200 keV Cr + . The comparison highlights the much lower vacancy concentration retained in visible clusters in the complex alloy

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

    International Nuclear Information System (INIS)

    Chakarova, R.; Pazsit, I.

    1997-01-01

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Chakarova, R.; Pazsit, I.

    1997-01-01

    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.

  10. Section of Atomic Collisions

    International Nuclear Information System (INIS)

    Berenyi, D.; Biri, S.; Gulyas, L.; Juhasz, Z.; Kover, A.; Orban, A.; Palinkas, J.; Papp, T.; Racz, R.; Ricz, S.

    2009-01-01

    The Section of Atomic Collisions is a research unit with extended activity in the field of atomic and molecular physics. Starting from the study of atomic processes at the beamlines of nuclear physics accelerators in the seventies, our research community became one of the centers of fundamental research in Atomki. We also have a strong connection to materials sciences especially along the line of electron and ion spectroscopy methods. Our present activity covers a wide range of topics from atomic collision mechanisms of fundamental interest, to the complex interactions of electrons, ions, photons and antiparticles with atoms, molecules, surfaces, and specific nanostructures. In the last few years, an increasing fraction of our present topics has become relevant for applications, e.g., molecular collision studies for the radiation therapy methods of tumors, or ion-nanostructure interactions for the future construction of small ion-focusing elements. Our section belongs to the Division of Atomic Physics. The other unit of the Division is the Section of Electron Spectroscopy and Materials Sciences. There are traditionally good connections and a strong collaboration between the groups of the two sections in many fields. From the very beginning of our research work in atomic collisions, external collaborations were of vital importance for us. We regularly organize international workshops in the field of fast ion-atom collisions and related small conferences in Debrecen from 1981. Recently, we organized the Conference on Radiation Damage in Biomolecular Systems (RADAM 2008, Debrecen), and coorganized the Conference on Elementary Processes in Atomic Systems (CEPAS 2008, Cluj). We have access to several large scale facilities in Europe within the framework of formal and informal collaborations. The next themes are in this article: Forward electron emission from energetic atomic collisions; Positron-atom collisions; Photon-atom interactions; Interference effects in electron

  11. The temporal development of collision cascades in the binary collision approximation

    International Nuclear Information System (INIS)

    Robinson, M.T.

    1989-07-01

    A modified binary collision approximation (BCA) was developed to allow explicit evaluation of the times at which projectiles in a collision cascade reach significant points in their trajectories, without altering the ''event-driven'' character of the model. The modified BCA was used to study the temporal development of cascades in copper and gold, initiated by primary atoms of up to 10 keV initial kinetic energy. Cascades generated with time-ordered collisions show fewer ''distant'' Frenkel pairs than do cascades generated with velocity-ordered collisions. In the former, the slower projectiles tend to move in less-damaged crystal than they do in the latter. The effect is larger in Au than in Cu and increases with primary energy. As an approach to cascade nonlinearities, cascades were generated in which stopped cascade atoms were allowed to be redisplaced in later encounters. There were many more redisplacements in time-ordered cascades than in velocity-ordered ones. Because of the additional stopping introduced by the redisplacement events, the cascades in which they were allowed had fewer defects than occurred otherwise. This effect also was larger in Au than in Cu and larger at high energies although most of the redisplacement encounters involved only low-energy particles. 13 refs., 5 figs., 4 tabs

  12. Positron-atom collisions

    International Nuclear Information System (INIS)

    Drachman, R.J.

    1984-01-01

    The past decade has seen the field of positron-atom collisions mature into an important sub-field of atomic physics. Increasingly intense positron sources are leading towards a situation in which electron and positron collision experiments will be on almost an equal footing, challenging theory to analyze their similarities and differences. The author reviews the advances made in theory, including dispersion theory, resonances, and inelastic processes. A survey of experimental progress and a brief discussion of astrophysical positronics is also included. (Auth.)

  13. Atomic cluster collisions

    Science.gov (United States)

    Korol, Andrey V.; Solov'yov, Andrey

    2013-01-01

    Atomic cluster collisions are a field of rapidly emerging research interest by both experimentalists and theorists. The international symposium on atomic cluster collisions (ISSAC) is the premier forum to present cutting-edge research in this field. It was established in 2003 and the most recent conference was held in Berlin, Germany in July of 2011. This Topical Issue presents original research results from some of the participants, who attended this conference. This issues specifically focuses on two research areas, namely Clusters and Fullerenes in External Fields and Nanoscale Insights in Radiation Biodamage.

  14. Laser-assisted atom-atom collisions

    International Nuclear Information System (INIS)

    Roussel, F.

    1984-01-01

    The basic layer-assisted atom-atom collision processes are reviewed in order to get a simpler picture of the main physical facts. The processes can be separated into two groups: optical collisions where only one atom is changing state during the collision, the other acting as a spectator atom, and radiative collisions where the states of the two atoms are changing during the collision. All the processes can be interpreted in terms of photoexcitation of the quasimolecule formed during the collisional process. (author)

  15. Collision cascades and sputtering induced by larger cluster ions

    International Nuclear Information System (INIS)

    Sigmund, P.

    1988-01-01

    Recent experimental work on larger cluster impact on solid surfaces suggests large deviations from the standard case of additive sputter yields both in the nuclear and electronic stopping regime. The paper concentrates on elastic collision cascades. In addition to very pronounced spike effects, two phenomena are pointed out that are specific to cluster bombardment. Multiple hits of cluster atoms on one and the same target atom may result in recoil atoms that move faster than the maximum recoil speed for monomer bombardment at the same projectile speed. This effect is important when the atomic mass of a beam atom is less than that of a target atom, M 1 2 . In the opposite case, M 1 >> M 2 , collisions between beam particles may accelerate some beam particles and slow down others. Some consequences are mentioned. Remarks on the nuclear stopping power of larger clusters and on electronic sputtering by cluster bombardment conclude the paper. 38 refs., 2 figs

  16. Computer simulation studies of high energy collision cascades

    International Nuclear Information System (INIS)

    Robinson, M.T.

    1991-07-01

    A modified binary collision approximation allowing the proper order of the collisions in time was used to study cascades in Cu and Au at primary kinetic energies up to 100 keV. Nonlinearities were approximated by letting already-stopped cascade atoms become targets in later collisions, using an improved method of locating potential targets to extend the calculations to energies much higher than heretofore. Beside the effect of the approximate nonlinearity, the effect of thermal disorder in the targets was examined. Target redisplacements reduce the damage in Cu by 3% at most, but in Au they reduce it by amounts up to 20% at 100 keV. Thermal disorder is also important: by disrupting crystal effects, the damage is reduced significantly. 11 refs., 4 figs

  17. Topics in atomic collision theory

    CERN Document Server

    Geltman, Sydney; Brueckner, Keith A

    1969-01-01

    Topics in Atomic Collision Theory originated in a course of graduate lectures given at the University of Colorado and at University College in London. It is recommended for students in physics and related fields who are interested in the application of quantum scattering theory to low-energy atomic collision phenomena. No attention is given to the electromagnetic, nuclear, or elementary particle domains. The book is organized into three parts: static field scattering, electron-atom collisions, and atom-atom collisions. These are in the order of increasing physical complexity and hence necessar

  18. Bremsstrahlung in atom-atom collisions

    International Nuclear Information System (INIS)

    Amus'ya, M.Y.; Kuchiev, M.Y.; Solov'ev, A.V.

    1985-01-01

    It is shown that in the collision of a fast atom with a target atom when the frequencies are on the order of the potentials or higher, there arises bremsstrahlung comparable in intensity with the bremsstrahlung emitted by an electron with the same velocity in the field of the target atom. The mechanism by which bremsstrahlung is produced in atom-atom collisions is elucidated. Results of specific calculations of the bremsstrahlung spectra are given for α particles and helium atoms colliding with xenon

  19. Time development of cascades by the binary collision approximation code

    International Nuclear Information System (INIS)

    Fukumura, A.; Ishino, S.; Sekimura, N.

    1991-01-01

    To link a molecular dynamic calculation to binary collision approximation codes to explore high energy cascade damage, time between consecutive collisions is introduced into the binary collision MARLOWE code. Calculated results for gold by the modified code show formation of sub-cascades and their spatial and time overlapping, which can affect formation of defect clusters. (orig.)

  20. Cascade Processes in Muonic Hydrogen Atoms

    International Nuclear Information System (INIS)

    Faifman, M. P.; Men'Shikov, L. I.

    2001-01-01

    The QCMC scheme created earlier for cascade calculations in heavy hadronic atoms of hydrogen isotopes has been modified and applied to the study of cascade processes in the μp muonic hydrogen atoms. The distribution of μp atoms over kinetic energies has been obtained and the yields of K-series X-rays per one stopped muon have been calculated.Comparison with experimental data indicated directly that for muonic and pionic atoms new types of non-radiative transitions are essential, while they are negligible for heavy (kaonic, antiprotonic, etc.) atoms. These processes have been considered and their probabilities have been estimated.

  1. Collision-produced atomic states

    International Nuclear Information System (INIS)

    Andersen, N.; Copenhagen Univ.

    1988-01-01

    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)

  2. 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...

  3. Cascade processes in kaonic and muonic atoms

    International Nuclear Information System (INIS)

    Faifman, M.P.; Men'shikov, L.I.

    2003-01-01

    Cascade processes in exotic (kaonic and muonic) hydrogen/deuterium have been studied with the quantum-classical Monte Carlo code (QCMC) developed for 'ab initio' - calculations. It has been shown that the majority of kaonic hydrogen atoms during cascade are accelerated to high energies E ∼ 100 eV, which leads to a much lower value for the calculated yields Y of x-rays than predicted by the 'standard cascade model'. The modified QCMC scheme has been applied to the study of the cascade in μp and μd muonic atoms. A comparison of the calculated yields for K-series x-rays with experimental data directly indicates that the molecular structure of the hydrogen target and new types of non-radiative transitions are essential for the light muonic atoms, while they are negligible for heavy (kaonic) atoms. These processes have been considered and estimates of their probabilities are presented. (author)

  4. Atomic collisions research with excited atomic species

    International Nuclear Information System (INIS)

    Hoogerland, M.D.; Gulley, R.J.; Colla, M.; Lu, W.; Milic, D.; Baldwin, K.G.H.; Buckman, S.J.

    1999-01-01

    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 CF 2 radicals formed by electron impact dissociation in a CF 4 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(2 3 S) atoms

  5. Modeling defect production in high energy collision cascades

    International Nuclear Information System (INIS)

    Heinisch, H.L.; Singh, B.N.

    1993-01-01

    A multi-model approach roach (MMA) to simulating defect production processes at the atomic scale is described that incorporates molecular dynamics (MD), binary collision approximation (BCA) calculations and stochastic annealing simulations. The central hypothesis of the MMA is that the simple, fast computer codes capable of simulating large numbers of high energy cascades (e.g., BCA codes) can be made to yield the correct defect configurations when their parameters are calibrated using the results of the more physically realistic MD simulations. The calibration procedure is investigated using results of MD simulations of 25 keV cascades in copper. The configurations of point defects are extracted from the MD cascade simulations at the end of the collisional phase, similar to the information obtained with a binary collision model. The MD collisional phase defect configurations are used as input to the ALSOME annealing simulation code, and values of the ALSOME quenching parameters are determined that yield the best fit to the post-quenching defect configurations of the MD simulations

  6. Radiations from atomic collision processes

    International Nuclear Information System (INIS)

    Bernyi, D.

    1994-01-01

    The physics of atomic collision phenomena in which only the Coulomb forces have a role is an actual field or the research of the present days. The impact energy range in these collisions is very broad,it extends from the eV or even lower region to the GeV region or higher,i.e. it spans the region of three branches of physics,namely that of the atomic,the nuclear and the particle physics.To describe and explain the collision processes themselves, different models (collision mechanisms) are used and they are surveyed in the presentation. Different electromagnetic radiations and particles are emitted from the collision processes.Their features are shown in details together with the most important methods in their detection and study.Examples are given based on the literature and on the investigations of the author and his coworkers. The applications of the radiation from atomic collisions in other scientific fields and in the solution of different practical problems are also surveyed shortly. 16 figs., 2 tabs., 76 refs. (author)

  7. Ultrarelativistic atomic collisions

    International Nuclear Information System (INIS)

    Bottcher, C.; Strayer, M.R.

    1991-01-01

    Calculations of the coherent production of free pairs and of pair production with electron capture from ultrarelativistic ion-ion collisions are discussed. Theory and experiment are contrasted, with some conjectures on the possibility of new phenomena. 29 refs., 5 figs., 1 tab

  8. Atom localization with double-cascade configuration

    International Nuclear Information System (INIS)

    Gordeev, Maksim Yu; Rozhdestvensky, Yuri V; Efremova, Ekaterina A

    2016-01-01

    We investigate the one-dimensional (1D) and two-dimensional (2D) atom localization of a four-level system in a double-cascade configuration. We demonstrate the possibility of 1D localization in the field of a standing wave, 2D localization in the field of two standing waves and 2D localization only in the field of running waves by using different configurations of driven waves on transitions. In addition, for each configuration we reached a high-precision atom localization in one of the states at scales much smaller than the wavelength of the incident optical radiation. (paper)

  9. Atomic and molecular collision processes

    International Nuclear Information System (INIS)

    Norcross, D.W.

    1991-01-01

    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 H 2

  10. Collision cascades in HTSC [high temperature superconductors] as possible pinning centres

    International Nuclear Information System (INIS)

    Kirsanov, V.V.; Musin, N.N.; Roskin, D.G.; Shamarina, E.I.

    1993-01-01

    Computer simulation was used to study the development of collision cascades in monocrystals of YBa 2 Cu 3 O 7 , YBa 2 Cu 3 O 6.5 and YBa 2 Cu 3 O 6 which were produced by primary knock-on atoms (PKAs) during fast particle irradiation. Oxygen deficit was found to have an effect on the development of cascades in these phases, with a lowering of oxygen deficit decreasing cascade sizes. The type of PKA was observed to influence the geometry of a cascade. When heavy PKAs form a cascade, the oxygen sublattice is practically undisturbed, with very little disorder; while with oxygen ions as the PKA, the main displacements fall within the oxygen subsystem. In addition, the angular dependences of the displacement threshold energy for yttrium and barium ions are given. (Author)

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

    International Nuclear Information System (INIS)

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

    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

  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. Systematics of atom-atom collision strengths at high speeds

    International Nuclear Information System (INIS)

    Gillespie, G.H.; Inokuti, M.

    1980-01-01

    The collision strengths for atom-atom collisions at high speeds are calculated in the first Born approximation. We studied four classes of collisions, distinguished depending upon whether each of the collision partners becomes excited or not. The results of numerical calculations of the collision strengths are presented for all neutral atoms with Z< or =18. The calculations are based on atomic form factors and incoherent scattering functions found in the literature. The relative contribution of each class of collision processes to the total collision cross section is examined in detail. In general, inelastic processes dominate for low-Z atoms, while elastic scattering is more important for large Z. Other systematics of the collision strengths are comprehensively discussed. The relevant experimental literature has been surveyed and the results of this work for the three collision systems H-He, He-He, and H-Ar are compared with the data for electron-loss processes. Finally, suggestions are made for future work in measurements of atom-atom and ion-atom collision cross sections

  14. Cascade in muonic and pionic atoms with Z = 1

    International Nuclear Information System (INIS)

    Markushin, V.E.

    1999-01-01

    Recent theoretical and experimental studies of the exotic atoms with Z = 1 are reviewed. An interplay between the atomic internal and external degrees of freedom is essential for a good description of the atomic cascade. The perspective of ab initio cascade calculations is outlined

  15. Cascade multiplicity inside deuteron in Π d high energy collisions

    International Nuclear Information System (INIS)

    Kisielewska, D.

    1983-01-01

    Multiplicity distribution of double scattering events is analysed using the additive quark model including the cascading effect. The mean multiplicity of particles produced in the process of cascading estimated for Π d experiments at 100, 205 and 360 GeV/c is equal to 1.15 ± .31. This value does not depend on the momentum of the incident pion. Some indications are found that the probability of cascading depends on multiplicity of the collision with the first nucleon and is smaller for low multiplicities. (author)

  16. Laser-assisted electron-atom collisions

    International Nuclear Information System (INIS)

    Mason, N.J.

    1989-01-01

    New developments in our understanding of the electron-atom collision process have been made possible by combining the use of highly monochromatic electron beams and intense CO 2 lasers. This paper reviews such experiments and discusses possible future progress in what is a new field in atomic collision physics. (author)

  17. Cascade of negative muons in atoms

    International Nuclear Information System (INIS)

    Akylas, V.R.

    1978-01-01

    A study is made of the evolution of a negative muon captured in an atom and the formalism of energy loss associated with the muonic atom. The principal goals are to calculate reliability the muon x-ray intensities, given the initial population of the muonic orbits, to invert the problem and deduce the initial distribution from the x-ray intensities, to provide a reasonably simple and convenient tool to correlate observations, and finally, to systematize some questions of theoretical interest. The early part of the history of the muon in matter, including the atomic capture and classical phase of the atomic cascade are reviewed. In the quantal treatment of the transition rates, both radiative and electron Auger transitions are considered. In general, multipolarities up to E3 and K, L, and M electronic shells are fully investigated. Multipole radiation is treated in the conventinal way and pesents no special problems. Magnetic type transitions between states with different principal quantum numbers are shown to be small. Auger electron ejection rates are more complicated and several approximations have been adopted. The basic results have been computed in terms of elemetary functions. In the Auger transitions we have shown that magnetic multipoles can be safety neglected. The relative sizes of the rates corresponding to different multipoles are systematically studied. A comparison of results is made with atomic photoelectric effect data and with the nuclear internal conversion coefficients. A general agreement is found, except around shell thresholds. The existing data of muonic x-ray intensities in iron and thallium are analyzed in a systematic way. It is found that for Fe the initial l-distribution is almost flat, whereas that for T1 is weighted towards the high l values, sharper than statistical. As a result of the investigations and in order to make our findings usable, a computer program has been developed. 36 references

  18. Energy sharing and sputtering in low-energy collision cascades

    International Nuclear Information System (INIS)

    Weller, R.A.; Weller, M.R.

    1982-01-01

    Using a non-linear transport equation to describe the energy-sharing process in an isotropic collision cascade, we have numerically calculated sputtered particle velocity spectra for several very low energy (=< 10 eV) primary recoil distributions. Our formulation of the sputtering process is essentially that used in the linear model and our equations yield the familiar linear model results in the appropriate limit. Discrepancies between our calculations and the linear model results in other cases may be understood by considering the effects of the linear model assumptions on the sputtering yield at very low energies. Our calculations are also compared with recent experimental results investigating ion-explosion sputtering. The results of this comparison support the conclusion that in insulators sputtering is initiated by very low energy recoil atoms when the energy of the incident beam is high enough that the stopping power is dominated by the electronic contribution. The calculations also suggest that energy spectra similar to those for evaporation may result from non-equilibrium processes but that the apparent temperatures of evaporation are not related in a simple way to any real temperature within the target. (author)

  19. An investigation of collision propagation in energetic ion initiated cascades in copper

    International Nuclear Information System (INIS)

    Chakarov, I.R.; Webb, R.P.; Smith, R.; Beardmore, K.

    1995-01-01

    Using simple Binary Collision simulations of energetic ion initiated collision cascades, particles are considered to undergo a series of binary collisions with their surroundings. In Molecular Dynamics simulation it is difficult to even define what is meant by a collision as the interaction potentials are infinite in nature and consequently all particles are considered to interact with all other particles. By making a suitable definition of a collision for Molecular Dynamics we are able to compare the temporal behaviour of the number of collisions occurring during the propagation of a collision cascade between the two different calculation schemes. An investigation is made of the number of collisions as a function of time occurring in collision cascades. We compare these results to the time ordered version of MARLOWE. By making further definitions about what makes a many body collision, we further investigate the numbers of many body collisions occurring during a number of collision cascades. (orig.)

  20. Relativistic Collisions of Structured Atomic Particles

    CERN Document Server

    Voitkiv, Alexander

    2008-01-01

    The book reviews the progress achieved over the last decade in the study of collisions between an ion and an atom in which both the atomic particles carry electrons and can undergo transitions between their internal states -- including continua. It presents the detailed considerations of different theoretical approaches, that can be used to describe collisions of structured atomic particles for the very broad interval of impact energies ranging from 0.5--1 MeV/u till extreme relativistic energies where the collision velocity very closely approaches the speed of light.

  1. Charge exchange in ion-atom collisions

    International Nuclear Information System (INIS)

    Bransden, B.H.

    1990-01-01

    Charge exchange reactions in which electrons are transferred from one ion (or atom) to another during a collision have been studied both as interesting examples of rearrangement collisions and because of important applications in plasma physics. This article reviews the modern theory developed for use at non-relativistic energies, but excluding the thermal and very low energy region. (author)

  2. Electron detachment in ion-atom collisions

    International Nuclear Information System (INIS)

    Vreugd, C. de.

    1980-01-01

    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.)

  3. Atomic collisions related to atomic laser isotope separation

    International Nuclear Information System (INIS)

    Shibata, Takemasa

    1995-01-01

    Atomic collisions are important in various places in atomic vapor laser isotope separation (AVLIS). At a vaporization zone, many atomic collisions due to high density have influence on the atomic beam characteristics such as velocity distribution and metastable states' populations at a separation zone. In the separation zone, a symmetric charge transfer between the produced ions and the neutral atoms may degrade selectivity. We have measured atomic excitation temperatures of atomic beams and symmetric charge transfer cross sections for gadolinium and neodymium. Gadolinium and neodymium are both lanthanides. Nevertheless, results for gadolinium and neodymium are very different. The gadolinium atom has one 5d electron and neodymium atom has no 5d electron. It is considered that the differences are due to existence of 5d electron. (author)

  4. Atomic collision experiments using pulsed synchrotron radiation

    International Nuclear Information System (INIS)

    Arikawa, Tatsuo; Watanabe, Tsutomu.

    1982-01-01

    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)

  5. Angular momentum coupling in atom-atom collisions

    International Nuclear Information System (INIS)

    Grosser, J.

    1986-01-01

    The coupling between the electronic angular momentum and the rotating atom-atom axis in the initial or the final phase of an atom-atom collision is discussed, making use of the concepts of radial and rotational (Coriolis) coupling between different molecular states. The description is based on a limited number of well-understood approximations, and it allows an illustrative geometric representation of the transition from the body fixed to the space fixed motion of the electrons. (orig.)

  6. Effects of temperature in binary-collision simulations of high-energy displacement cascades

    International Nuclear Information System (INIS)

    Heinisch, H.L.

    1981-10-01

    Several hundred cascades ranging from 1 to 500 keV were generated using the binary collision code MARLOWE for primary knock-on atoms (PKAs) with randomly chosen directions in both a non-thermal copper lattice and one having atomic displacements representative of room temperature. To simulate the recombination occurring during localized quenching of the highly excited cascade region, an effective spontaneous recombination radius was applied to reduce the number of defect pairs to be consistent with values extracted from resistivity measurements at 4 0 K. At room temperature fewer widely separated pairs are produced, thus the recombination radius is smaller, however, the recombination radii were found to be independent of energy over the entire energy range investigated for both the cold and room temperature cases. The sizes and other features of the point defect distributions were determined as a function of energy. Differences between cold and room temperature cascade dimensions are small. The room temperature cascades tend to have a greater number of distinct damage regions per cascade, with about the same frequency of widely separated subcascades

  7. 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.

  8. 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

  9. Low energy atom-atom collisions

    International Nuclear Information System (INIS)

    Child, M.S.

    1980-01-01

    The semiclassical theory of atom-atom potential scattering and of low energy inelastic atom-atom scattering is reviewed. Particular attention is given to the origin and interpretation of rainbow structure, diffraction oscillations and exchange oscillations in the potential scattering differential cross-section, and to the glory structure and symmetry oscillations in the integral cross-section. Available methods for direct inversion of the cross-section data to recover the potential are reviewed in some detail. The theory of non-adiabatic transitions is introduced by a short discussion of interaction mechanisms and of diabetic and adiabatic representations. Analytical S matrix elements are presented for two state curve-crossing (Landau-Zener-Stuckelberg), Demkov and Nikitin models. The relation between Stuckelberg oscillations in the S matrix and in the differential cross-section is discussed in terms of interference between trajectories belonging to two different classical deflection functions. The energy dependences of the inelastic integral cross-section for curve-crossing and Demkov type transitions are also discussed. Finally the theory is reviewed in relation to a recent close-coupled study of fine structure transitions in F( 2 P) + Xe( 2 S) scattering

  10. 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

  11. Case studies in atomic collision physics

    CERN Document Server

    McDaniel, Earl Wadsworth

    1972-01-01

    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

  12. Computer simulation of displacement cascade damages in metals using binary collision approximation code 'MARLOWE'

    International Nuclear Information System (INIS)

    Watanabe, Nishio; Shimomura, Yoshiharu

    1985-01-01

    The derivation of basic equations of the computer simulation code 'MARLOWE' was examined in detail, which was treated by the binary collision approximation developed by Robinson and Torrens. The 'MARLOWE' program was used for the simulation of the three dimensional structure of displacement cascade damages of Au, Cu and Al, which were generated by primary knock-on atoms (PKA) of 1 keV to 40 keV. Results were seriously affected by the selection of parameter of Frenkel defect formation E disp and ion movement E quit with the close Frenkel defect recombination criteria and E disp = E quit , it was found that E disp of 11 eV, 5 eV, 5 eV are reasonable for the simulation calculation for Au, Cu, and Al, respectively. Cascade seems to have subcascade structures even for 40 keV PKA. (author)

  13. Continuum states in ion-atom collisions

    Energy Technology Data Exchange (ETDEWEB)

    Garibotti, C.R. (Centro Atomico Bariloche and CONICET (Argentina)); Barrachina, R.O. (Centro Atomico Bariloche and CONICET (Argentina))

    1994-03-01

    We review the experimental and theoretical situation for ionization collisions of nude ions with neutral gas atoms, at intermediate and high impact energies. We consider particularly that part of the electron spectrum where emission is larger, corresponding to the joint action to the two ions. We discuss the evidence of this two-center interaction and how it is described by current theories. (orig.)

  14. Atomic collisions in fusion plasmas involving multiply charged ions

    International Nuclear Information System (INIS)

    Salzborn, E.

    1980-01-01

    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)

  15. Calibrating a multi-model approach to defect production in high energy collision cascades

    International Nuclear Information System (INIS)

    Heinisch, H.L.; Singh, B.N.; Diaz de la Rubia, T.

    1994-01-01

    A multi-model approach to simulating defect production processes at the atomic scale is described that incorporates molecular dynamics (MD), binary collision approximation (BCA) calculations and stochastic annealing simulations. The central hypothesis is that the simple, fast computer codes capable of simulating large numbers of high energy cascades (e.g., BCA codes) can be made to yield the correct defect configurations when their parameters are calibrated using the results of the more physically realistic MD simulations. The calibration procedure is investigated using results of MD simulations of 25 keV cascades in copper. The configurations of point defects are extracted from the MD cascade simulations at the end of the collisional phase, thus providing information similar to that obtained with a binary collision model. The MD collisional phase defect configurations are used as input to the ALSOME annealing simulation code, and values of the ALSOME quenching parameters are determined that yield the best fit to the post-quenching defect configurations of the MD simulations. ((orig.))

  16. Semiclassical model of atomic collisions: stopping and capture of the heavy charged particles and exotic atom formation

    International Nuclear Information System (INIS)

    Beck, W.A.

    2000-01-01

    The semiclassical model of atomic collisions, especially in different areas of the maximum stopping, when proton collides at the velocity of the boron order velocity, providing as the result for interactions of many bodies with an electron target, enabling application of the model with high degree of confidence to a clearly expressed experimental problem, such the antiproton capture on helium, is presented. The semiclassical collision model and stopping energy are considered. The stopping and capture of negatively-charged particles are investigated. The capture and angular moments of antiprotons, captures at the end of the collision cascade, are presented [ru

  17. MD simulation of atomic displacement cascades near chromium-rich clusters in FeCr alloy

    International Nuclear Information System (INIS)

    Tikhonchev, M.; Svetukhin, V.; Gaganidze, E.

    2013-01-01

    The paper reports simulation of cascades in Fe–9 at.%Cr binary alloy containing chromium-rich clusters. The simulation is performed by the molecular dynamics method at the initial temperature of 300 K and primary knock-on atom energy of 15 and 20 keV. Spherical clusters containing 95 at.% of Cr with diameter of 1–5 nm have been considered. The properties of cascade evolution in the presence of chromium-rich cluster are studied. It is shown that these clusters tend to dissolve in collision cascades. However, clusters with diameter of ⩾3 nm exhibit only slight modifications and can be considered stable. Parameters of small (1–2 nm) clusters can change significantly and, in some cases, a 1 nm cluster can be totally dissolved

  18. MD simulation of atomic displacement cascades near chromium-rich clusters in FeCr alloy

    Energy Technology Data Exchange (ETDEWEB)

    Tikhonchev, M., E-mail: tikhonchev@sv.ulsu.ru [Ulyanovsk State University, Research Institute of Technology, 42 Leo Tolstoy St., 432970 Ulyanovsk (Russian Federation); Svetukhin, V. [Ulyanovsk State University, Research Institute of Technology, 42 Leo Tolstoy St., 432970 Ulyanovsk (Russian Federation); Gaganidze, E. [Karlsruhe Institute of Technology, Institute for Applied Materials, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Karlsruhe (Germany)

    2013-11-15

    The paper reports simulation of cascades in Fe–9 at.%Cr binary alloy containing chromium-rich clusters. The simulation is performed by the molecular dynamics method at the initial temperature of 300 K and primary knock-on atom energy of 15 and 20 keV. Spherical clusters containing 95 at.% of Cr with diameter of 1–5 nm have been considered. The properties of cascade evolution in the presence of chromium-rich cluster are studied. It is shown that these clusters tend to dissolve in collision cascades. However, clusters with diameter of ⩾3 nm exhibit only slight modifications and can be considered stable. Parameters of small (1–2 nm) clusters can change significantly and, in some cases, a 1 nm cluster can be totally dissolved.

  19. Case studies in atomic collision physics

    CERN Document Server

    McDaniel, E W

    1974-01-01

    Case Studies in Atomic Physics III focuses on case studies on atomic and molecular physics, including atomic collisions, transport properties of electrons, ions, molecules, and photons, interaction potentials, spectroscopy, and surface phenomena. The selection first discusses detailed balancing in the time-dependent impact parameter method, as well as time-reversal in the impact parameter method and coupled state approximation. The text also examines the mechanisms of electron production in ion. Topics include measurement of doubly differential cross sections and electron spectra, direct Coul

  20. Comparison of many bodied and binary collision cascade models up to 1 keV

    International Nuclear Information System (INIS)

    Schwartz, D.M.; Schiffgens, J.D.; Doran, D.G.; Odette, G.R.; Ariyasu, R.G.

    1976-01-01

    A quasi-dynamical code ADDES has been developed to model displacement cascades in copper for primary knockon atom energies up to several keV. ADDES is like a dynamical code in that it employs a many body treatment, yet similar to a binary collision code in that it incorporates the basic assumption that energy transfers below several eV can be ignored in describing cascade evolution. This paper is primarily concerned with (1) a continuing effort to validate the assumptions and specific parameters in the code by the comparison of ADDES results with experiment and with results from a dynamical code, and (2) comparisons of ADDES results with those from a binary collision code. The directional dependence of the displacement threshold is in reasonable agreement with the measurements of Jung et al. The behavior of focused replacement sequences is very similar to that obtained with the dynamical codes GRAPE and COMENT. Qualitative agreement was found between ADDES and COMENT for a higher energy (500 eV) defocused event while differences, still under study, are apparent in a 250 eV high index event. Comparisons of ADDES with the binary collision code MARLOWE show surprisingly good agreement in the 250 to 1000 eV range for both number and separation of Frenkel pairs. A preliminary observation, perhaps significant to displacement calculations utilizing the concept of a mean displacement energy, is the dissipation of 300 to 400 eV in a replacement sequence producing a single interstitial

  1. Current ideas on ion-atom collisions

    International Nuclear Information System (INIS)

    Hansteen, J.M.

    1975-09-01

    A survey is given of recent developments in the understanding of ion-atom collisions, with particular emphasis on processes leading to ion-induced X-rays. The inner-shell Coulomb ionization phenomena are discussed at some length, with stress on the near-quantitative picture that appears to emerge from simple-minded models. The phenomenon of Pauli excitations and the formation of quasi-molecules leading to united atom phenomena are qualitatively reviewed together with a brief mention of target recoil effects and electron capture processes. Selected background phenomena of importance in interpreting experiments are touched upon, such as various types of bremsstrahlung production. Implications of the recently-discovered interplay between Coulomb-induced processes and united atom phenomena are especially mentioned. It is suggested that this branch of collision physics is now (1975) reaching a point where new notions and more advanced and unifying models are greatly needed. (auth)

  2. Decay of long-lived autoionization atomic states in atom collisions

    International Nuclear Information System (INIS)

    Krakov, B.G.

    1994-01-01

    Radiationless decay of long-lived autoionization states of helium atoms in atom collisions is investigated. It is shown that the states may decay in atom collisions due to softening of the selection rules

  3. Use of pseudopotentials in atom-atom (or molecule) collisions

    International Nuclear Information System (INIS)

    Pascale, J.

    1985-09-01

    Knowledge of interactions between ions, atoms or molecules is fundamental for interpretating or predicting collisional processes which may occur under various circumstances. The aim of this paper is to demonstrate the usefulness of using semiempirical effective interactions (more particularly, emphasis will be put on the pseudopotential approach) in the study of atom-atom (or molecule) collisions. We would like to show that if the semiempirical effective interactions are carefully defined, their use in molecular-structure calculations and in collision problems can give quite accurate results. We will limit our examples to one-electron systems. We consider the M-atom-He systems as a first example. For these systems, recent molecular-structure calculations have been carried out using an 1-dependent semiempirical pseudopotential approach and they have been tested against numerous experimental data in extensive calculations of cross sections for intra-and-inter-doublet transitions in the M-atom in collisions with He. Our second example will concern the M-H 2 systems, for which semiempirical pseudopotential molecular-structure calculations have been performed very recently using an one-electron two-center model. The results of these calculations are quite encouraging and we foresee the use of the pseudopotential approach in future studies of some reactive scattering processes

  4. Atomic collisions under extreme conditions in space

    International Nuclear Information System (INIS)

    Itikawa, Yukikazu

    1987-01-01

    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. Cascade statistics in the binary collision approximation and in full molecular dynamics

    International Nuclear Information System (INIS)

    Hou, M.; Pan, Z.Y.

    1995-01-01

    The Binary Collision Approximation (BCA) and Molecular Dynamics (MD) are used to simulate low energy atomic collision cascades in solids. Results are compared and discussed on the example of copper and gold self irradiation. For MD, long range N-body potentials are built, similar to those deduced from the second moment semi-empirical tight binding model. The pair interaction contribution is splined to a Moliere screened Coulomb potential at small separation distances. The BCA calculations are performed with the MARLOWE program, using the same Moliere potential as for MD, and modelling the N-body contribution by a binding of the atoms to their equilibrium lattice sites. The scattering integrals are estimated by means of a 4 points Gauss-Mehler quadrature. In MD, the NVT equations of motion are integrated with a constant time step of 2 fs. For the NVE cascade simulations, the Newton equations of motion are solved with a dynamically adjusted time step, kept lower than 2 fs. The influence of the time step on the simulated trajectories is discussed. The mean number of moving atoms with total energy above threshold values ranging from 1 to 100 eV is estimated as a function of time over 300 fs both with MARLOWE and by MD. This estimate is repeated for external primary energies ranging from 250 eV to 1 keV. In the case of copper, the BCA results are found to be in remarkable agreement with MD over about 200 fs cascade development, provided the size of the crystallite used in MD is sufficiently large in order to account for the early mechanical response of the close environment. This agreement between the two methods is found to be the best when the binding energy of the target atoms as modelled in the BCA is adjusted to a value close to the cohesive energy. In the case of gold, the agreement between BCA and MD is reasonable and the results suggest the need of an accurate modelling of linear collision sequences in the BCA. (orig.)

  6. Electron-collision excitation cross section of the silver atom

    International Nuclear Information System (INIS)

    Krasavin, A.Y.; Kuchenev, A.N.; Smirnov, Y.M.

    1983-01-01

    The cross sections for direct excitation by electron collision were measured for fifteen transitions of the silver atom. For thirteen of these transitions the optical excitation functions were recorded, varying the energy of the exciting electrons from the threshold energy to 250 eV. The operating region of the spectrum was 2000--5500 A. The excitation cross sections of the two principal lines exceeded the excitation cross sections of all the remaining lines by more than an order of magnitude. Reabsorption of the resonance lines was detected from the change in the ratio of intensities of the lines at 3280.68 and 3382.89 A, and so their intensity has been corrected relative to the intensities of the nonreabsorbed lines. All radiative transitions, with the exception of resonance transitions, participate in cascade population of the lowest resonance levels, making it possible to determine the resulting direct excitation cross sections of the 5p 2 P/sub 1/2/ and 5p 2 P/sub 3/2/ levels from the ground state of the silver atom. The part played by cascade population of the resonance levels is not large and is 2 P/sub 3/2/ level, and 10% for the 5p 2 P/sub 1/2/ level, of the excitation cross sections of the corresponding resonance transitions

  7. Molecular dynamics and binary collisions modeling of the primary damage state of collision cascades

    International Nuclear Information System (INIS)

    Heinisch, H.L.; Singh, B.N.

    1992-01-01

    The objective of this work is to determine the spectral dependence of defect production and microstructure evolution for the development of fission-fusion correlations. Quantitative information on defect production in cascades in copper obtained from recent molecular dynamics (MD) simulations is compared to defect production information determined earlier with a model based on the binary collision approximation (BCA). The total numbers of residual defects, the fractions of them that are mobile, and the sizes of immobile clusters compare favorably, especially when the termination conditions of the two simulations are taken into account. A strategy is laid out for integrating the details of the cascade quenching phase determined by MD into a BCA-based model that is practical for simulating much higher energies and longer times than MD alone can achieve. The extraction of collisional phase information from MD simulations and the correspondence of MD and BCA versions of the collisional phase demonstrated at low energy

  8. Molecular dynamics and binary collision modeling of the primary damage state of collision cascades

    DEFF Research Database (Denmark)

    Heinisch, H.L.; Singh, B.N.

    1992-01-01

    Quantitative information on defect production in cascades in copper obtained from recent molecular dynamics simulations is compared to defect production information determined earlier with a model based on the binary collision approximation (BCA). The total numbers of residual defects......, the fractions of them that are mobile, and the sizes of immobile clusters compare favorably, especially when the termination conditions of the two simulations are taken into account. A strategy is laid out for integrating the details of the cascade quenching phase determined by MD into a BCA-based model...... that is practical for simulating much higher energies and longer times than MD alone can achieve. The extraction of collisional phase information from MD simulations and the correspondence of MD and BCA versions of the collisional phase is demonstrated at low energy....

  9. Electron transfer, ionization, and excitation atomic collisions

    International Nuclear Information System (INIS)

    Winter, T.G.; Alston, S.G.

    1990-01-01

    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

  10. Account of the effect of nuclear collision cascades in model of radiation damage of RPV steels

    International Nuclear Information System (INIS)

    Kevorkyan, Yu.R.; Nikolaev, Yu.A.

    1997-01-01

    A kinetic model is proposed for describing the effect of collision cascades in model of radiation damage of reactor pressure vessel steels. This is a closed system of equations which can be solved only by numerical methods in general case

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

    International Nuclear Information System (INIS)

    1991-01-01

    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

  12. Atomic-cascade photons and quantum-mechanical nonlocality

    International Nuclear Information System (INIS)

    Bell, J.S.

    1995-01-01

    In recent years there have been several experiments on polarization correlation between photons emitted in atomic cascades. They are supposed to bear on the notion that the consequences of events do not propagate faster than light. This notion is difficult to reconcile with quantum-mechanical predictions for idealized versions of the experiments in question. The present Comment offers a brief introduction to the situation. (author)

  13. Free-parameterless model of high energy particle collisions with atomic nuclei

    International Nuclear Information System (INIS)

    Strugalski, Z.

    1982-01-01

    In result of studies, it has been discovered that: a) Intensive emission of fast nucleons of kinetic energy from 20 to 400 MeV proceeds independently of the pion production process; b) The particle production in hadron-nucleon collisions is mediated by intermediate objects produced first in a 2 → 2 type endoergic reaction and decaying after lifetime tausub(g) > or approximately 10 - 22 s into commonly known resonances and particles; c) Inside of massive enough atomic nuclei quasi-onedimensional cascades of the intermediate objects can develop; d) A definite simple connection exists between the characteristics of the secondaries appearing in hadron-nucleus collision events and corresponding hadron-nucleon collision events, the target-nucleus size and the nucleon density distribution in it. The yield of the hadron-nucleus collisions is described in a convincing manner in terms of the hadron-nucleon collision data by means of simple formulas

  14. Correlated charge changing ion-atom collisions

    International Nuclear Information System (INIS)

    Bernstein, E.M.; Tanis, J.A.

    1990-02-01

    This report summarizes the progress and accomplishments in accelerator atomic physics research supported by DOE grant FG02-87ER13778 from August 15, 1987 through February 15, 1990. 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, for the most part, coincidence techniques in which projectile charge-changing events are associated with x-ray emission, target recoil ions, or electron emission. Measurements were conducted using accelerators at the Lawrence Berkeley Laboratory (LBL), Argonne National Laboratory (ANL), Hahn-Meitner-Institut, Berlin (HMI), and Western Michigan University (WMU). The research described here has resulted in 34 published papers, 14 invited presentations at national and international meetings, and 31 contributed presentations. Brief summaries of work completed and work in progress are discussed in this paper

  15. Storage ring to investigate cold unidimensional atomic collisions

    International Nuclear Information System (INIS)

    Marcassa, L. G.; Caires, A. R. L.; Nascimento, V. A.; Dulieu, O.; Weiner, J.; Bagnato, V. S.

    2005-01-01

    In this paper we employ a circulating ring of trapped atoms, that we have named the atomotron, to study cold collisions. The atomotron is obtained from a conventional magneto-optical trap when the two pairs of normally retroreflecting Gaussian laser beams in the x-y plane are slightly offset. Circulating stable atomic orbits then form a racetrack geometry in this plane. The circulating atom flux behaves similarly to an atomic beam with an average tangential velocity much greater than the transverse components, and is therefore suitable for one-dimensional atomic collision studies. Using the atomotron, we have investigated the polarization dependence of ultracold photoassociation collisions between Rb atoms circulating in the racetrack. The ability to investigate collisions in ultracold circulating atomic rings reveals alignment and orientation properties that are averaged away in ordinary three-dimensional magneto-optical trap collision processes

  16. Cascaded two-photon spectroscopy of Yb atoms with a transportable effusive atomic beam apparatus

    Energy Technology Data Exchange (ETDEWEB)

    Song, Minsoo; Yoon, Tai Hyun [Department of Physics, Korea University, Anam-dong, Seongbuk-gu, Seoul 136-713 (Korea, Republic of)

    2013-02-15

    We present a transportable effusive atomic beam apparatus for cascaded two-photon spectroscopy of the dipole-forbidden transition (6s{sup 2} {sup 1}S{sub 0}{r_reversible} 6s7s {sup 1}S{sub 0}) of Yb atoms. An ohmic-heating effusive oven is designed to have a reservoir volume of 1.6 cm{sup 3} and a high degree of atomic beam collimation angle of 30 mrad. The new atomic beam apparatus allows us to detect the spontaneously cascaded two-photons from the 6s7s{sup 1}S{sub 0} state via the intercombination 6s6p{sup 3}P{sub 1} state with a high signal-to-noise ratio even at the temperature of 340 Degree-Sign C. This is made possible in our apparatus because of the enhanced atomic beam flux and superior detection solid angle.

  17. Cascaded two-photon spectroscopy of Yb atoms with a transportable effusive atomic beam apparatus

    International Nuclear Information System (INIS)

    Song, Minsoo; Yoon, Tai Hyun

    2013-01-01

    We present a transportable effusive atomic beam apparatus for cascaded two-photon spectroscopy of the dipole-forbidden transition (6s 2 1 S 0 ↔ 6s7s 1 S 0 ) of Yb atoms. An ohmic-heating effusive oven is designed to have a reservoir volume of 1.6 cm 3 and a high degree of atomic beam collimation angle of 30 mrad. The new atomic beam apparatus allows us to detect the spontaneously cascaded two-photons from the 6s7s 1 S 0 state via the intercombination 6s6p 3 P 1 state with a high signal-to-noise ratio even at the temperature of 340 °C. This is made possible in our apparatus because of the enhanced atomic beam flux and superior detection solid angle.

  18. Alignment and orientation in ion/endash/atom collisions

    International Nuclear Information System (INIS)

    Kimura, M.; Lane, N.F.

    1987-01-01

    Recent progress in the theoretical study of alignment and orientation in atom-atom and ion-atom collisions at intermediate energies is reviewed. Recent systematic studies of the alignment and orientation of electronic charge cloud distributions of excited states resulting from such collisions clearly have provided more detailed information about the underlying collision dynamics. However, since accurate determination of these parameters is quite difficult, both theoretically and experimentally, a close collaboration between theory and experiment is necessary for a deeper understanding of the collision dynamics. A more complete approach, where the full density matrix is determined, is also discussed

  19. The relationship between vacuum and atomic collisions in solids

    International Nuclear Information System (INIS)

    Carter, G.; Armour, D.G.

    1980-01-01

    Atomic collision events in solids are frequently stimulated by external irradiation with energetic heavy ions. This requires production, acceleration and manipulation of ion beams in vacuum system with ensuing problems arising in perturbations to ion beam quality from gas phase collisions. In addition the dynamic interaction between the gas phase and any surfaces at which atomic collisions are under investigation can lead to perturbation to the collision events by adsorbed contaminant. This review discusses both gas phase requirements for ion accelerators to minimize deleterious effects and outlines some of the processes which occur in atomic collisions due to the presence of adsorbed impurities. Finally it is shown how certain atomic collision processes involving elastic scattering may be employed to investigate surface adsorption and related effects. (author)

  20. On the utility and ubiquity of atomic collision physics

    International Nuclear Information System (INIS)

    Datz, S.

    1989-01-01

    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

  1. Polarization, alignment, and orientation in atomic collisions

    CERN Document Server

    Andersen, Nils

    2017-01-01

    This book covers polarization, alignment, and orientation effects in atomic collisions induced by electron, heavy particle, or photon impact. The first part of the book presents introductory chapters on light and particle polarization, experimental and computational methods, and the density matrix and state multipole formalism. Examples and exercises are included. The second part of the book deals with case studies of electron impact and heavy particle excitation, electron transfer, impact ionization, and autoionization. A separate chapter on photo-induced processes by new-generation light sources has been added. The last chapter discusses related topics and applications. Part III includes examples of charge clouds and introductory summaries of selected seminal papers of tutorial value from the early history of the field (1925 – 1975). The book is a significant update to the previous (first) edition, particularly in experimental and computational methods, the inclusion of key results obtained during the pas...

  2. Correlation effects in electron-atom collisions

    International Nuclear Information System (INIS)

    Water, W. van de.

    1981-01-01

    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.)

  3. Entropy lowering in ion-atom collisions

    International Nuclear Information System (INIS)

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

    2005-01-01

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

  4. Complete experiments in electron-atom collisions

    International Nuclear Information System (INIS)

    Anderson, N.; Bartschat, K.

    1996-01-01

    This paper addresses the advances up to the present in complete electron-atom collision experiments. The aim is to present a series of key examples for fundamental scattering processes, together with the experimental techniques that have been used. The purpose is not a full presentation of all processes studied, nor of all data that have been accumulated; rather, it is to select examples of the most recent theoretical and experimental results that will enable the reader to assess the present level of achievement. We hope that the power of this approach will become evident along the way, in the sense that it provides an efficient framework for a systematic, and complete test of the current theoretical understanding. In addition, it may produce specific recipes for ways to select experimental geometries that most efficiently test theoretical predictions, and it may reveal connections between apparently unrelated observables from often very different and highly sophisticated experiments, thus providing valuable consistency checks. The presentation is structured in the following way. To begin with, a general analysis of scattering amplitude properties concludes in a recipe for determination of the number of independent parameters necessary to define a complete experiment for a given process. We then proceed to analyze in a systematic way a string of specific cases of elastic and inelastic collisions, with gradually increasing levels of sophistication. Finally, we comment on directions in which future studies could fruitfully be pursued. 77 refs., 53 figs

  5. Deterministic Role of Collision Cascade Density in Radiation Defect Dynamics in Si

    Science.gov (United States)

    Wallace, J. B.; Aji, L. B. Bayu; Shao, L.; Kucheyev, S. O.

    2018-05-01

    The formation of stable radiation damage in solids often proceeds via complex dynamic annealing (DA) processes, involving point defect migration and interaction. The dependence of DA on irradiation conditions remains poorly understood even for Si. Here, we use a pulsed ion beam method to study defect interaction dynamics in Si bombarded in the temperature range from ˜-30 ° C to 210 °C with ions in a wide range of masses, from Ne to Xe, creating collision cascades with different densities. We demonstrate that the complexity of the influence of irradiation conditions on defect dynamics can be reduced to a deterministic effect of a single parameter, the average cascade density, calculated by taking into account the fractal nature of collision cascades. For each ion species, the DA rate exhibits two well-defined Arrhenius regions where different DA mechanisms dominate. These two regions intersect at a critical temperature, which depends linearly on the cascade density. The low-temperature DA regime is characterized by an activation energy of ˜0.1 eV , independent of the cascade density. The high-temperature regime, however, exhibits a change in the dominant DA process for cascade densities above ˜0.04 at.%, evidenced by an increase in the activation energy. These results clearly demonstrate a crucial role of the collision cascade density and can be used to predict radiation defect dynamics in Si.

  6. A metastable helium trap for atomic collision physics

    International Nuclear Information System (INIS)

    Colla, M.; Gulley, R.; Uhlmann, L.; Hoogerland, M.D.; Baldwin, K.G.H.; Buckman, S.J.

    1999-01-01

    Full text: Metastable helium in the 2 3 S 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 (2 3 S 1 - 2 3 P2 1 ) 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 He 2 + 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 2 3 S 1 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

  7. Spectroscopic studies of hydrogen atom and molecule collisions: Performance report

    International Nuclear Information System (INIS)

    Kielkopf, J.

    1986-01-01

    This research is concerned with spectroscopic measurements of collisions in atomic and molecular hydrogen in order to clarify the basic physical processes that take place during radiative collisions and to provide experimental values for systems where the theoretical analysis is tractable. To this end, we proposed to measure from the cores to the far wings the profiles of the spectral lines of atomic hydrogen broadened by molecular hydrogen and noble gases, and to study energy transfer in the atom and molecule

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

    International Nuclear Information System (INIS)

    Duinker, W.

    1981-01-01

    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 26 Mg and 27 Al. (Auth./C.F.)

  9. Three-dimensional atom localization via probe absorption in a cascade four-level atomic system

    Directory of Open Access Journals (Sweden)

    Zeng Wei

    2018-03-01

    Full Text Available For an atomic system with cascade four-level type, a useful scheme about three-dimensional (3D atom localization is proposed. In our scheme the atomic system is coherently controlled by using a radio-frequency field to couple with two-folded levels under the condition of the existence of probe absorption. Our results show that detecting precision of 3D atom localization may be obviously improved by properly adjusting the frequency detuning and strength of the radio-frequency driving field. So our scheme could be helpful to realize 3D atom localization with high-efficiency and high-precision . In the field of laser cooling or the atom nano-lithography, our studies provide potential applications.

  10. Three-dimensional atom localization via probe absorption in a cascade four-level atomic system

    Science.gov (United States)

    Zeng, Wei; Deng, Li; Chen, Aixi

    2018-03-01

    For an atomic system with cascade four-level type, a useful scheme about three-dimensional (3D) atom localization is proposed. In our scheme the atomic system is coherently controlled by using a radio-frequency field to couple with two-folded levels under the condition of the existence of probe absorption. Our results show that detecting precision of 3D atom localization may be obviously improved by properly adjusting the frequency detuning and strength of the radio-frequency driving field. So our scheme could be helpful to realize 3D atom localization with high-efficiency and high-precision . In the field of laser cooling or the atom nano-lithography, our studies provide potential applications.

  11. Monte Carlo event generator MCMHA for high energy hadron-nucleus collisions and intranuclear cascade interactions

    International Nuclear Information System (INIS)

    Iga, Y.; Hamatsu, R.; Yamazaki, S.

    1988-01-01

    The Monte Carlo event generator for high energy hadron-nucleus (h-A) collisions has been developed which is based on the multi-chain model. The concept of formation zone and the cascade interactions of secondary particles are properly taken into account in this Monte Carlo code. Comparing the results of this code with experimental data, the importance of intranuclear cascade interactions becomes very clear. (orig.)

  12. 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

  13. Collision cascades enhanced hydrogen redistribution in cobalt implanted hydrogenated diamond-like carbon films

    International Nuclear Information System (INIS)

    Gupta, P.; Becker, H.-W.; Williams, G.V.M.; Hübner, R.; Heinig, K.-H.; Markwitz, A.

    2017-01-01

    Highlights: • This paper reports for the first time redistribution of hydrogen atoms in diamond like carbon thin films during ion implantation of low energy magnetic ions. • The results point towards new routes of controlling the composition and distribution of elements at the nanoscale within a base matrix without using any heat treatment methods. • Exploring these opportunities can lead to a new horizon of materials and device engineering needed for enabling advanced technologies and applications. - Abstract: Hydrogenated diamond-like carbon films produced by C_3H_6 deposition at 5 kV and implanted at room temperature with 30 keV Co atoms to 12 at.% show not only a bimodal distribution of Co atoms but also a massive redistribution of hydrogen in the films. Resonant nuclear reaction analysis was used to measure the hydrogen depth profiles (15N-method). Depletion of hydrogen near the surface was measured to be as low as 7 at.% followed by hydrogen accumulation from 27 to 35 at.%. A model is proposed considering the thermal energy deposited by collision cascade for thermal insulators. In this model, sufficient energy is provided for dissociated hydrogen to diffuse out of the sample from the surface and diffuse into the sample towards the interface which is however limited by the range of the incoming Co ions. At a hydrogen concentration of ∼35 at.%, the concentration gradient of the mobile unbounded hydrogen atoms is neutralised effectively stopping diffusion towards the interface. The results point towards new routes of controlling the composition and distribution of elements at the nanoscale within a base matrix without using any heat treatment methods. Exploring these opportunities can lead to a new horizon of materials and device engineering needed for enabling advanced technologies and applications.

  14. Collision cascades enhanced hydrogen redistribution in cobalt implanted hydrogenated diamond-like carbon films

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, P. [National Isotope Centre, GNS Science, Lower Hutt (New Zealand); The MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington (New Zealand); Becker, H.-W. [RUBION, Ruhr-University Bochum (Germany); Williams, G.V.M. [The MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington (New Zealand); Hübner, R.; Heinig, K.-H. [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf (Germany); Markwitz, A., E-mail: a.markwitz@gns.cri.nz [National Isotope Centre, GNS Science, Lower Hutt (New Zealand); The MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington (New Zealand)

    2017-03-01

    Highlights: • This paper reports for the first time redistribution of hydrogen atoms in diamond like carbon thin films during ion implantation of low energy magnetic ions. • The results point towards new routes of controlling the composition and distribution of elements at the nanoscale within a base matrix without using any heat treatment methods. • Exploring these opportunities can lead to a new horizon of materials and device engineering needed for enabling advanced technologies and applications. - Abstract: Hydrogenated diamond-like carbon films produced by C{sub 3}H{sub 6} deposition at 5 kV and implanted at room temperature with 30 keV Co atoms to 12 at.% show not only a bimodal distribution of Co atoms but also a massive redistribution of hydrogen in the films. Resonant nuclear reaction analysis was used to measure the hydrogen depth profiles (15N-method). Depletion of hydrogen near the surface was measured to be as low as 7 at.% followed by hydrogen accumulation from 27 to 35 at.%. A model is proposed considering the thermal energy deposited by collision cascade for thermal insulators. In this model, sufficient energy is provided for dissociated hydrogen to diffuse out of the sample from the surface and diffuse into the sample towards the interface which is however limited by the range of the incoming Co ions. At a hydrogen concentration of ∼35 at.%, the concentration gradient of the mobile unbounded hydrogen atoms is neutralised effectively stopping diffusion towards the interface. The results point towards new routes of controlling the composition and distribution of elements at the nanoscale within a base matrix without using any heat treatment methods. Exploring these opportunities can lead to a new horizon of materials and device engineering needed for enabling advanced technologies and applications.

  15. X-ray fluorescence/Auger-electron coincidence spectroscopy of vacancy cascades in atomic argon

    International Nuclear Information System (INIS)

    Arp, U.

    1996-01-01

    Argon L 2.3 -M 2.3 M 2.3 Auger-electron spectra were measured in coincidence with Kα fluorescent x-rays in studies of Ar K-shell vacancy decays at several photon energies above the K-threshold and on the 1s-4p resonance in atomic argon. The complex spectra recorded by conventional electron spectroscopy are greatly simplified when recorded in coincidence with fluorescent x-rays, allowing a more detailed analysis of the vacancy cascade process. The resulting coincidence spectra are compared with Hartree-Fock calculations which include shake-up transitions in the resonant case. Small energy shifts of the coincidence electron spectra are attributed to post-collision interaction with 1s photoelectrons

  16. 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.

  17. Some time dependent aspects of fast neutron induced atomic cascades

    International Nuclear Information System (INIS)

    Williams, M.M.R.

    1976-01-01

    Analytical results are obtained for the time-energy distribution of neutrons and the associated displaced atoms slowing down in an amorphous medium according to a general force law. Explicit results are given for the inverse power law, and applications to hard-sphere and Coulomb scattering are discussed. Complete results are obtained for the steady state energy distribution of particles arising from a primary knock-on, and from a neutron initiated cascade. The speed of the slowing down process is assessed by calculating the slowing down time of particles. Two different concepts of slowing down time are discussed, one based upon a density average and the other on a slowing down density average. It is shown that the latter definition is physically more realistic and mathematically simpler. (author)

  18. Positron collisions with helium and alkaline earth-like atoms

    International Nuclear Information System (INIS)

    Campbell, C.P.

    1998-09-01

    This doctoral thesis is subdivided into: 1. Theory of positron collisions with helium and alkaline earth-like atoms, 2. Positron collisions with helium, magnesium, calcium, zinc, 3. Intercomparison of positron scattering by all those elements. The appendix of this work gives details of the numerical calculations and expands on the wavefunctions used

  19. Collision assisted Zeeman cooling with multiple types of atoms

    Science.gov (United States)

    Hamilton, Mathew S.; Wilson, Rebekah F.; Roberts, Jacob L.

    2014-01-01

    Through a combination of spin-exchange collisions in a magnetic field and optical pumping, it is possible to cool a gas of atoms without requiring the loss of atoms from the gas. This technique, collision assisted Zeeman cooling (CAZ), was developed theoretically assuming a single atomic species [G. Ferrari, Eur. Phys. J. D 13, 67 (2001)]. We have extended this cooling technique to a system of two atomic species rather than just one and have developed a simple analytic model describing the cooling rate. We find that the two-isotope CAZ cooling scheme has a clear theoretical advantage in systems that are reabsorption limited.

  20. Inelastic collisions of medium energy atomic elements. Qualitative model of energy losses during collisions

    International Nuclear Information System (INIS)

    Pustovit, A.N.

    2006-01-01

    A new approach to the theoretical description of energy losses of atomic particle of medium energy during their interaction with the substance is proposed. The corner-stone of this approach is the supposition that all of the collision processes have inelastic nature during particle movement through the substance, while the calculation of the atomic particles braking is based on the law of their dispersion and the laws of energy and momentum conservation at the inelastic collisions. It is shown that inelastic atomic collision there are three dispersion zones for the only potential interaction with different laws, which characterize energy losses. The application conditions of this approach are determined [ru

  1. Effect of collision cascades on dislocations in tungsten: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Fu, B.Q., E-mail: bqfu@scu.edu.cn [Key Laboratory for Radiation Physics and Technology, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610065 (China); Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Fitzgerald, S.P. [Department of Applied Mathematics, University of Leeds, Leeds LS2 9JT (United Kingdom); Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Hou, Q.; Wang, J.; Li, M. [Key Laboratory for Radiation Physics and Technology, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610065 (China)

    2017-02-15

    Highlights: • A cascde near a dislocation promotes climb motion. • Kinks induced by cascade facilitate the dipoles motion toward the cascade. • Shearing of dipole is dependent on PKA energy, position, direction, and dipole width. - Abstract: Tungsten (W) is the prime candidate material for the divertor and other plasma-facing components in DEMO. The point defects (i.e. vacancies and self-interstitials) produced in collision cascades caused by incident neutrons aggregate into dislocation loops (and voids), which strongly affect the mechanical properties. The point defects also interact with existing microstructural features, and understanding these processes is crucial for modelling the long term microstructural evolution of the material under fusion conditions. In this work, we performed molecular dynamics simulations of cascades interacting with initially straight edge dislocation dipoles. It was found that the residual vacancy number usually exceeds the residual interstitial number for cascades interacting with vacancy type dipoles, but for interstitial type dipoles these are close. We observed that a cascade near a dislocation promotes climb, i.e. it facilitates the movement of point defects along the climb direction. We also observed that the dislocations move easily along the glide direction, and that kinks are formed near the centre of the cascade, which then facilitate the movement of the dipoles. Some dipoles are sheared off by the cascade, and this is dependent on PKA energy, position, direction, and the width of dipole.

  2. Comparison of universal potentials for atomic collisions in solids

    International Nuclear Information System (INIS)

    Cupini, E.; Ventura, A.

    1984-01-01

    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

  3. 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

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

    International Nuclear Information System (INIS)

    Sellin, I.A.

    1990-01-01

    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

  5. Vibronic excitation in atom molecule collisions

    International Nuclear Information System (INIS)

    Kleyn, A.W.

    1980-01-01

    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 + O 2 collisions (3-6000 eV); another to measure differential cross sections for neutral scattering and positive ion formation in K, Cs + O 2 and K + Br 2 collisions (20 - 150 eV); and a third to measure energy-loss spectra for neutral K scattered at a certain angle after a collision with O 2 or Br 2 (20 - 150 eV). (Auth.)

  6. Feshbach resonances in cold collisions of potassium atoms

    International Nuclear Information System (INIS)

    Bambini, A.; Geltman, S.

    2002-01-01

    In this paper we briefly review the basic steps that allow the calculation of the scattering length in the collision of two alkali-metal atoms in a well defined magnetic polarization state, and in the presence of a static magnetic field. Calculations are actually done for the low-field seeking state F=1, μ F =-1 of bosonic potassium atoms. The electrostatic potentials obtained through Rydberg-Klein-Rees data are connected to a dispersive, long range tail in which the dominant dipole-dipole C 6 term may take different values within a specified range. We show the occurrence of Feshbach resonances in the ultra cold collision of two identical atoms, belonging either to the bosonic species 39 K or 41 K. Our results demonstrate that there is a range of C 6 values for which the collision of two 39 K atoms displays a single resonance, while for other values of C 6 no resonance occurs. On the other hand, Feshbach resonances are present in the collision of two 41 K atoms for almost all values of the dispersion coefficient C 6 in that range. We also show the origin of the different types of Feshbach resonances that occur in the cold collision of two 41 K atoms. The detection of such resonances can help establish the actual value of the dispersive coefficient

  7. Multiple-electron processes in fast ion-atom collisions

    International Nuclear Information System (INIS)

    Schlachter, A.S.

    1989-03-01

    Research in atomic physics at the Lawrence Berkeley Laboratory Super-HILAC and Bevalac accelerators on multiple-electron processes in fast ion-atom collisions is described. Experiments have studied various aspects of the charge-transfer, ionization, and excitation processes. Examples of processes in which electron correlation plays a role are resonant transfer and excitation and Auger-electron emission. Processes in which electron behavior can generally be described as uncorrelated include ionization and charge transfer in high-energy ion-atom collisions. A variety of experiments and results for energies from 1 MeV/u to 420 MeV/u are presented. 20 refs., 15 figs

  8. Mechanisms of defect production and atomic mixing in high energy displacement cascades: A molecular dynamics study

    International Nuclear Information System (INIS)

    Diaz de la Rubia, T.; Guinan, M.W.

    1991-01-01

    We have performed molecular dynamics computer simulation studies of displacement cascades in Cu at low temperature. For 25 keV recoils we observe the splitting of a cascade into subcascades and show that cascades in Cu may lead to the formation of vacancy and interstitial dislocation loops. We discuss a new mechanism of defect production based on the observation of interstitial prismatic dislocation loop punching from cascades at 10 K. We also show that below the subcascade threshold, atomic mixing in the cascade is recoil-energy dependent and obtain a mixing efficiency that scales as the square root of the primary recoil energy. 44 refs., 12 figs

  9. Analytic cross sections for collisions of H, H2, He and Li atoms and ions with atoms and molecules. 3

    International Nuclear Information System (INIS)

    Ito, Rinsuke; Tabata, Tatsuo; Shirai, Toshizo; Phaneuf, R.A.

    1995-07-01

    Analytic expressions fitted to Barnett's recommended data are given for the collision cross sections of H, H 2 , He, and Li atoms and ions colliding with atoms and molecules. The collisions treated are ionization collisions, charge-production collisions, electron-loss collisions, and electron detachment collisions. The analytic expressions use the semiempirical functional forms proposed by Green and McNeal and some modified forms to make it possible not only to interpolate but also to extrapolate the recommended data. (author)

  10. MARLOWE 15b, Computer Simulation of Atomic Collisions in Crystalline Solids

    International Nuclear Information System (INIS)

    2007-01-01

    1 - Description of problem or function: The MARLOWE program simulates atomic collisions in crystalline targets using the binary collision approximation. It follows out the consequences of launching an energetic atomic projectile, from either an external beam or an interior site, into a target. The targets may have many material regions, each with its own arbitrary (triclinic) crystal structure and with many kinds of atoms. The program follows the slowing-down of the primary particle and, if desired, that of all target particles which are displaced from their lattice sites, until they either leave the target or fall below a selected low kinetic energy. All cascades may be initiated in undamaged material or damage may be accumulated from one cascade to another; cascades may be run in groups of a selected size. The User's Guide contains a detailed listing of changes in Version 15 and a summary of changes in earlier versions. Version 15b of MARLOWE, dated 5 December 2002, includes some error corrections for the previous release. The new package includes Version 3 of TABULA, a program which uses MARLOWE interatomic potential energy functions to tabulate the classical elastic scattering integrals and related data. News about Marlowe will be posted on the developer's web site from time-to-time http://www.ssd.ornl.gov/Programs/Marlowe/Marlowe.htm. 2 - Method of solution: The particle trajectories are constructed as series of binary encounters between the projectiles and the initially stationary target atoms. Elastic scattering is governed by one of several interatomic potentials. The interactions which bind atoms into crystals are modelled by including binding energies between atoms and their original lattice sites as well as binding to the entire crystal. Inelastic (electron excitation) effects are included in a low-energy (< ∼25 keV/amu) approximation. Provision is made for users to supply alternative interatomic potential functions, inelastic energy-loss functions

  11. Energy dependence of the ionization of highly excited atoms by collisions with excited atoms

    International Nuclear Information System (INIS)

    Shirai, T.; Nakai, Y.; Nakamura, H.

    1979-01-01

    Approximate analytical expressions are derived for the ionization cross sections in the high- and low-collision-energy limits using the improved impulse approximation based on the assumption that the electron-atom inelastic-scattering amplitude is a function only of the momentum transfer. Both cases of simultaneous excitation and de-excitation of one of the atoms are discussed. The formulas are applied to the collisions between two excited hydrogen atoms and are found very useful for estimating the cross sections in the wide range of collisions energies

  12. Computer codes for simulating atomic-displacement cascades in solids subject to irradiation

    International Nuclear Information System (INIS)

    Asaoka, Takumi; Taji, Yukichi; Tsutsui, Tsuneo; Nakagawa, Masayuki; Nishida, Takahiko

    1979-03-01

    In order to study atomic displacement cascades originating from primary knock-on atoms in solids subject to incident radiation, the simulation code CASCADE/CLUSTER is adapted for use on FACOM/230-75 computer system. In addition, the code is modified so as to plot the defect patterns in crystalline solids. As other simulation code of the cascade process, MARLOWE is also available for use on the FACOM system. To deal with the thermal annealing of point defects produced in the cascade process, the code DAIQUIRI developed originally for body-centered cubic crystals is modified to be applicable also for face-centered cubic lattices. By combining CASCADE/CLUSTER and DAIQUIRI, we then prepared a computer code system CASCSRB to deal with heavy irradiation or saturation damage state of solids at normal temperature. Furthermore, a code system for the simulation of heavy irradiations CASCMARL is available, in which MARLOWE code is substituted for CASCADE in the CASCSRB system. (author)

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

    International Nuclear Information System (INIS)

    1992-01-01

    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

  14. Role of atom--atom inelastic collisions in two-temperature nonequilibrium plasmas

    International Nuclear Information System (INIS)

    Kunc, J.A.

    1987-01-01

    The contribution of inelastic atom--atom collisions to the production of electrons and excited atoms in two-temperature (with electron temperature T/sub e/, atomic temperature T/sub a/, and atomic density N/sub a/), steady-state, nonequilibrium atomic hydrogen plasma is investigated. The results are valid for plasmas having large amounts of atomic hydrogen as one of the plasma components, so that e--H and H--H inelastic collisions and interaction of these atoms with radiation dominate the production of electrons and excited hydrogen atoms. Densities of electrons and excited atoms are calculated in low-temperature plasma, with T/sub e/ and T/sub a/≤8000 K and 10 16 cm -3 ≤N/sub a/≤10 18 cm -3 , and with different degrees of the reabsorption of radiation. The results indicate that inelastic atom--atom collisions are important for production of electrons and excited atoms in partially ionized plasmas with medium and high atomic density and temperatures below 8000 K

  15. The morphology of collision cascades as a function of recoil energy

    International Nuclear Information System (INIS)

    Heinisch, H.L.; Singh, B.N.

    1989-09-01

    An analytical method based on defect densities has been devised to determine the threshold energies for subcascade formation in computer simulated collision cascades. Cascades generated with the binary collision code MARLOWE in Al, Cu, Ag, Au, Fe, Mo and W were analyzed to determine the threshold energy for subcascade formation, the number of subcascades per recoil per unit energy and the average spacing of subcascades. Compared on the basis of reduced damage energy, metals of the same crystal structure have subcascade thresholds at the same reduced energy. The number of subcascades per unit reduced damage energy is about the same for metals of the same crystal structure, and the average spacing of subcascades is about the same in units of lattice parameters. Comparisons between subcascade threshold energies and average recoil energies in fission and fusion neutron environments show the spectral sensitivity of the formation of subcascades

  16. Applied atomic collision physics. Vol. 2

    International Nuclear Information System (INIS)

    Barnett, C.F.; Harrison, M.F.A.

    1984-01-01

    This volume brings together papers on atomic processes that have been important in fusion research during the past 30 years. Topics include: Atomic radiation from low density plasma; Properties of magnetically confined plasmas in tokomaks; Diagnostics and; Heating by energetic particles. Each chapter includes references

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

    International Nuclear Information System (INIS)

    Gallagher, J.W.

    1983-01-01

    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

  18. Non vertical vibronic transitions in atom molecule collisions

    International Nuclear Information System (INIS)

    Klomp, U.C.

    1982-01-01

    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-N 2 collisions, and in Cs-NO and Cs-O 2 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 O 2 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.)

  19. Multiple electron capture in close ion-atom collisions

    International Nuclear Information System (INIS)

    Schlachter, A.S.; Stearns, J.W.; Berkner, K.H.

    1989-01-01

    Collisions in which a fast highly charged ion passes within the orbit of K electron of a target gas atom are selected by emission of a K x-ray from the projectile or target. Measurement of the projectile charge state after the collision, in coincidence with the K x-ray, allows measurement of the charge-transfer probability during these close collisions. When the projectile velocity is approximately the same as that of target electrons, a large number of electrons can be transferred to the projectile in a single collision. The electron-capture probability is found to be a linear function of the number of vacancies in the projectile L shell for 47-MeV calcium ions in an Ar target. 18 refs., 9 figs

  20. ECR-based atomic collision physics research at ORNL

    International Nuclear Information System (INIS)

    Meyer, F.W.; Bannister, M.E.; Hale, J.W.; Havener, C.C.

    1997-01-01

    After a brief summary of the present capability and configuration of the ORNL Multicharged Ion Research Facility (MIRF), and of upcoming upgrades and expansions, the presently on-line atomic collisions experiments are described. In the process, the utility of intense, cw ion beams extracted from ECR ion sources for low-signal rate experiments is illustrated

  1. Recent investigations on electronic capture in atomic collisions

    International Nuclear Information System (INIS)

    Rivarola, R.D.

    1988-01-01

    In this work, electron capture processes in ion-atom collisions at various impact energy ranges are dicussed: i) intermediate non-relativistic energy; ii) high energy; iii) high relativistic energy. Much attention is given to the development and use of distorted wave models. (A.C.A.S.) [pt

  2. Anisotropy in electron-atom collisions

    International Nuclear Information System (INIS)

    Linden van den Heuvel, H.B. van.

    1982-01-01

    Most of the work described in this thesis deals with studies using coincidence experiments, particularly for investigating the electron impact excitation of the 2 1 P and 3 1 D states in helium. A peculiarity is that in the 3 1 D studies the directly emitted 3 1 D → 2 1 P photons are not observed but the 2 1 P → 1 1 S photons resulting from the 3 1 D → 2 1 P → 1 1 S 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 (2p 2 ) 3 P state of helium by electrons is studied. In chapter III the anisotropy parameters for the electron impact excitation of the 2 1 P state of helium in the energy range from 26.6 to 40 eV and in the angular range from 30 0 to 110 0 are determined. Chapter IV contains a description of a scattered electron cascaded-photon coincidence experiment on the electron impact excitation of helium's 3 1 D state. The measurement of complex scattering amplitudes for electron impact excitation of the 3 1 D and 3 1 P states of helium is discussed in Chapter V. (Auth./C.F.)

  3. Positronium collisions with atoms and molecules

    Science.gov (United States)

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

    2017-11-01

    We review recent theoretical efforts to explain observed similarities between electron-atom and positronium(Ps)-atom scattering which also extends to molecular targets. In the range of the projectile velocities above the threshold for Ps ionization (break-up) this similarity can be explained in terms of quasi-free electron scattering and impulse approximation. However, for lower Ps velocities more sophisticated methods should be developed. Our calculations of Ps scattering by heavy noble-gas atoms agree well with experiments at Ps velocities above the Ps ionization threshold. However, in contrast to electron scattering cross sections, at lower velocities they exhibit maxima whereas the experimental cross sections tend to decrease toward lower velocities indicating the same similarity with electron scattering cross section observed above the threshold. Our preliminary results for Ps-N2 scattering confirm experimental observation of a resonance similar to the ∏ g resonance in electron-N2 scattering.

  4. Electronic excitation in ion-atom collisions

    International Nuclear Information System (INIS)

    Rodriguez, V.D.; Miraglia, J.E.

    1988-01-01

    Theoretical calculations for excitation of hydrogen-like atoms by ion impact at high and intermediate energies, are presented. Impulsive and eikonal wave functions are employed, both normalized. It is studied the dependence on energy and projectil charge (saturation) of cross sections, compared to experimental results. (A.C.A.S.) [pt

  5. Single Atoms Preparation Using Light-Assisted Collisions

    Directory of Open Access Journals (Sweden)

    Yin Hsien Fung

    2016-01-01

    Full Text Available The detailed control achieved over single optically trapped neutral atoms makes them candidates for applications in quantum metrology and quantum information processing. The last few decades have seen different methods developed to optimize the preparation efficiency of single atoms in optical traps. Here we review the near-deterministic preparation of single atoms based on light-assisted collisions and describe how this method can be implemented in different trap regimes. The simplicity and versatility of the method makes it feasible to be employed in future quantum technologies such as a quantum logic device.

  6. Mesonic atom production in high-energy nuclear collisions

    International Nuclear Information System (INIS)

    Wakai, M.; Bando, H.; Sano, M.

    1987-08-01

    The production probability of π-mesonic atom in high-energy nuclear collisions is estimated by a coalescence model. The production cross section is calculated for p + Ne and Ne + Ne systems at 2.1 GeV/A and 5.0 GeV/A beam energy. It is shown that nuclear fragments with larger charge numbers have the advantage in the formation of π-mesonic atoms. The cross section is proportional to Z 3 and of the order of magnitude of 1 ∼ 10 μb in all the above cases. The production cross sections of K-mesonic atoms are also estimated. (author)

  7. Atom capture and loss in ion molecule collisions

    International Nuclear Information System (INIS)

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

    1985-01-01

    Progress is reported in measuring the energy and angular distribution of protons emerging with velocity close to the beam velocity from the target region when Ar + beams collide with a CH 4 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

  8. Atom collisions in a strong electromagnetic field

    International Nuclear Information System (INIS)

    Smirnov, V.S.; Chaplik, A.V.

    1976-01-01

    It is shown that the long-range part of interatomic interaction is considerably altered in a strong electromagnetic field. Instead of the van der Waals law the potential asymptote can best be described by a dipole-dipole R -3 law. Impact broadening and the line shift in a strong nonresonant field are calculated. The possibility of bound states of two atoms being formed in a strong light field is discussed

  9. Charge changing collision cross sections of atomic ions

    International Nuclear Information System (INIS)

    Bliman, S.; Dousson, S.; Geller, R.; Jacquot, B.; Van Houtte, D.

    1980-05-01

    A device has been built to measure charge changing cross sections of atomic ions. It consists of an E.C.R. ion source (Micromafios) that delivers oxygen ions up to charge + 8, argon ions up to charge + 13. The ion source potential may be varied from 1 up to 10 kVolts. A first magnet is used to charge analyze the extracted beam. For a given charge state, the ion beam is passed in a collision cell whose pressure may be varied. The ions undergoing collisions on the target are analyzed by a second magnet and collected. The single collision condition is checked. Different collisions are considered: 1- Charge exchange collisions of argon ions with charge 2<=Z<=12 on argon. Cross sections for capture of 1, 2 and 3 electrons are given. 2- Stripping of argon ions (1<=Z<=4) on argon atoms. 3- Charge exchange of oxygen ions (2<=Z<=8) colliding on deuterium. One and two electron capture cross sections are presented

  10. Ion-atom collisions for materials study

    International Nuclear Information System (INIS)

    Loaiza S, N.S.

    1976-01-01

    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 40 0 C, 80 0 C, 110 0 C and 160 0 C 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)

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

    International Nuclear Information System (INIS)

    Moeller, W.; Eckstein, W.

    1988-05-01

    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)

  12. Long term simulation of point defect cluster size distributions from atomic displacement cascades in Fe70Cr20Ni10

    International Nuclear Information System (INIS)

    Souidi, A.; Hou, M.; Becquart, C.S.; Domain, C.; De Backer, A.

    2015-01-01

    We have used an Object Kinetic Monte Carlo (OKMC) model to simulate the long term evolution of the primary damage in Fe 70 Cr 20 Ni 10 alloys. The mean number of Frenkel pairs created by different Primary Knocked on Atoms (PKA) was estimated by Molecular Dynamics using a ternary EAM potential developed in the framework of the PERFORM-60 European project. This number was then used to obtain the vacancy–interstitial recombination distance required in the calculation of displacement cascades in the Binary Collision Approximation (BCA) with code MARLOWE (Robinson, 1989). The BCA cascades have been generated in the 10–100 keV range with the MARLOWE code and two different screened Coulomb potentials, namely, the Molière approximation to the Thomas–Fermi potential and the so-called “Universal” potential by Ziegler, Biersack and Littmark (ZBL). These cascades have been used as input to the OKMC code LAKIMOCA (Domain et al., 2004), with a set of parameters for describing the mobility of point defect clusters based on ab initio calculations and experimental data. The cluster size distributions have been estimated for irradiation doses of 0.1 and 1 dpa, and a dose rate of 10 −7 dpa/s at 600 K. We demonstrate that, like in the case of BCC iron, cluster size distributions in the long term are independent of the cascade energy and that the recursive cascade model suggested for BCC iron in Souidi et al. (2011) also applies to FCC Fe 70 Cr 20 Ni 10. The results also show that the influence of the BCA potential is sizeable but the qualitative correspondence in the predicted long term evolution is excellent

  13. Atomic-Scale Simulations of Cascade Overlap and Damage Evolution in Silicon Carbide

    International Nuclear Information System (INIS)

    Gao, Fei; Weber, William J.

    2003-01-01

    In a previous computer simulation experiment, the accumulation of damage in SiC from the overlap of 10 keV Si displacement cascades at 200 K was investigated, and the damage states produced following each cascade were archived for further analysis. In the present study, interstitial clustering, system energy, and volume changes are investigated as the damage states evolve due to cascade overlap. An amorphous state is achieved at a damage energy density of 27.5 eV/atom (0.28 displacements per atom). At low dose levels, most defects are produced as isolated Frenkel pairs, with a small number of defect clusters involving only 4 to 6 atoms; however, after the overlap of 5 cascades (0.0125 displacements per atom), the size and number of interstitial clusters increases with increasing dose. The average energy per atom increases linearly with increasing short-range (or chemical) disorder. The volume change exhibits two regimes of linear dependence on system energy and increases more rapidly with dose than either the energy or the disorder, which indicate a significant contribution to swelling of isolated interstitials and anti-site defects. The saturation volume change for the cascade-amorphized state in these simulations is 8.2%, which is in reasonable agreement with the experimental value of 10.8% in neutron-irradiated SiC

  14. Learning from numerical calculations of ion-atom collisions

    International Nuclear Information System (INIS)

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

    1981-01-01

    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

  15. Learning from numerical calculations of ion-atom collisions

    International Nuclear Information System (INIS)

    Reading, J.F.; Ford, A.L.; Martir, M.

    1982-01-01

    Violent collisions of two independent many-particle systems, victims, are discussed in the atomic sphere. The asymmetric region where the charge of the projectile Zsub(p) is less than the target nuclear charge Zsub(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 (Zsub(p) approx. equal to Zsub(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. (orig.)

  16. Atomic-orbital expansion model for describing ion-atom collisions at intermediate and low energies

    International Nuclear Information System (INIS)

    Lin, C.D.; Fritsch, W.

    1983-01-01

    In the description of inelastic processes in ion-atom collisions at moderate energies, the semiclassical close-coupling method is well established as the standard method. Ever since the pioneering work on H + + H in the early 60's, the standard procedure is to expand the electronic wavefunction in terms of molecular orbitals (MO) or atomic orbitals (AO) for describing collisions at, respectively, low or intermediate velocities. It has been recognized since early days that traveling orbitals are needed in the expansions in order to represent the asymptotic states in the collisions correctly. While the adoption of such traveling orbitals presents no conceptual difficulties for expansions using atomic orbitals, the situation for molecular orbitals is less clear. In recent years, various forms of traveling MO's have been proposed, but conflicting results for several well-studied systems have been reported

  17. Three-particle correlations from parton cascades in Au+Au collisions

    International Nuclear Information System (INIS)

    Ma, G.L.; Ma, Y.G.; Zhang, S.; Cai, X.Z.; Chen, J.H.; He, Z.J.; Huang, H.Z.; Long, J.L.; Shen, W.Q.; Shi, X.H.; Zhong, C.; Zuo, J.X.

    2007-01-01

    We present a study of three-particle correlations among a trigger particle and two associated particles in Au+Au collisions at s NN =200 GeV using a multi-phase transport model (AMPT) with both partonic and hadronic interactions. We found that three-particle correlation densities in different angular directions with respect to the triggered particle ('center', 'cone', 'deflected', 'near' and 'near-away') increase with the number of participants. The ratio of 'deflected' to 'cone' density approaches to 1.0 with the increasing of number of participants, which indicates that partonic Mach-like shock waves can be produced by strong parton cascades in central Au+Au collisions

  18. Formulating analytic expressions for atomic collision cross sections

    International Nuclear Information System (INIS)

    Tabata, Tatsuo; Kubo, Hirotaka; Sataka, Masao

    2003-08-01

    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)

  19. Laser-induced charge exchange in ion-atom collisions

    International Nuclear Information System (INIS)

    Riera, A.

    1986-01-01

    The theory of laser-induced charge transfer (LICT) in ion-atom collisions is presented for the range of impact energies in which a quasimolecular description is appropriate. For each relative orientation of the AC field, LICT cross sections can be obtained with trivial modifications of standard programs. Simpler, perturbative expressions for the orientation-averaged cross sections are accurate for I v -1 6 W s cm -3 , and the analytical Landau-Zener perturbative expression often provides good estimates for these cross sections. The practical advantages of the dressed state formalism as an alternative approach are critically examined, and the general characteristics of LICT cross sections in multicharged ion-atom collisions are shown with the help of an example. (Auth.)

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

    International Nuclear Information System (INIS)

    Schultz, D.R.

    1997-01-01

    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

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

    International Nuclear Information System (INIS)

    2010-01-01

    This Book contains the abstracts of invited and contributed talks submitted for presentation at the 24 th 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.

  2. Ionization and charge exchange in atom collision with multicharged ion

    International Nuclear Information System (INIS)

    Presnyakov, L.P.; Uskov, D.B.

    1984-01-01

    Single-electron ionization and charge exchange are considered in collisions of an atom with an ion of charge Z> or =3 and at velocities v>Z -1 /sup // 3 . The approach is based on the Keldysh quasiclassical method. The ionization and charge exchange processes are described within the framework of a single formalism. Effects of rotation and translation are taken into account. The calculated total and partial cross sections agree well with the available experimental data. OFF

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

    International Nuclear Information System (INIS)

    1981-01-01

    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

  4. Theoretical treatment of electron capture and excitation in two-electron system ion-atom, atom-atom collisions at low to intermediate energy

    International Nuclear Information System (INIS)

    Kimura, M.

    1986-01-01

    A review of various theoretical treatments which have been used to study electron-capture and excitation processes in two-electron-system ion-atom, atom-atom collisions at low to intermediate energy is presented. Advantages as well as limitations associated with these theoretical models in application to practical many-electron ion-atom, atom-atom collisions are specifically pointed out. Although a rigorous theoretical study of many-electron systems has just begun so that reports of theoretical calculations are scarce to date in comparison to flourishing experimental activities, some theoretical results are of great interest and provide important information for understanding collision dynamics of the system which contains many electrons. Selected examples are given for electron capture in a multiply charged ion-He collision, ion-pair formation in an atom-atom collision and alignment and orientation in a Li + + He collision. (Auth.)

  5. Progress of research on the mechanism of microstructure evolution during irradiation with collision cascades

    International Nuclear Information System (INIS)

    Kiritani, Michio

    1997-01-01

    Progress of the research on microstructural evolution during radiation damage accompanied with collision cascades, particularly by neutrons, is summarized from the researches reported in 1995 and 1996. The major part of irradiation was performed with JMTR (Japan Material Testing Reactor), and comparisons were made with the result of D-T fusion neutron irradiation with RTNS-II (Rotating Target Neutron Source, LLNL). The subjects concerned are: (1) Microstructure evolution during irradiation, (2) Processes controlling the accumulation of defects during cascade damage, (3) Subcascades from the viewpoint of point defect cluster formation, (4) Mechanism of suppression of microstructure evolution during temperature cycle neutron irradiation of nickel, (5) Identification of the nature of neutron-irradiation-induced point defect clusters in copper by means of electron irradiation, (6) Easy one-dimensional motion of small interstitial clusters, (7) Identification of the nature of small point defect clusters in neutron irradiated Fe-16Ni-15Cr, (8) Spatial distribution of nucleation of point defect clusters by high energy particle irradiation, (9) Crystallographic orientation dependence of dislocation structures in neutron irradiated metals, (10) Examination of defect accumulation mode with multi-section-removable-irradiation-rig in Japan Material Testing Reactor, (11) Estimation of freely migrating point defects during cascade damage by the growth of helical dislocations, (12) Identification of the nature of neutron-irradiation-induced small point defect clusters in Nickel by means of electron irradiation, (13) Thermal stability of point defect clusters in neutron irradiated Fe-16Ni-15Cr. (author)

  6. Photoionization and cold collision studies using trapped atoms

    International Nuclear Information System (INIS)

    Gould, P.L.

    1996-01-01

    The authors have used laser cooling and trapping techniques to investigate photoionization and cold collisions. With laser-trapped Rb, they have measured the photoionization cross section from the first excited (5P) level by observing the photoionization-induced loss rate of neutral atoms from the trap. This technique has the advantage that it directly measures the photoionization rate per atom. Knowing the ionizing laser intensity and the excited-state fraction, the measured loss rate gives the absolute cross section. Using this technique, the Rb 5P photoionization cross section at ∼400 nm has been determined with an uncertainty of 9%. The authors are currently attempting to extend this method to the 5D level. Using time-ordered pulses of diode-laser light (similar to the STIRAP technique), they have performed very efficient two-photon excitation of trapped Rb atoms to 5D. Finally, they will present results from a recent collaboration which combines measurements form conventional molecular spectroscopy (single photon and double resonance) with photoassociation collisions of ultracold Na atoms to yield a precise (≤1 ppm) value for the dissociation energy of the X Σ g+ ground state of the Na 2 molecule

  7. Discussion of the origin of secondary photon and secondary ion emission during energetic particle irradiation of solids. I. The collision cascade

    International Nuclear Information System (INIS)

    Wright, R.B.; Gruen, D.M.

    1980-01-01

    Secondary photon and secondary ion emission during energetic particle irradiation of solid surfaces is assumed to arise due to excitation and de-excitation of sputtered particles originating from a collision cascade induced by the incident projectile. The excitation is postulated to occur by two alternative mechanisms: path (a), where excitation occurs at or very near the surface of the solid due to atom--atom or atom--electron collisions; and path (b), where excitation occurs as the sputtered particle leaves the solid, but is still under its influence so that electron exchange processes are permitted. Once the excited and/or ionized sputtered particle is formed nonradiative de-excitation processes are then included in the discussion which allow the excited and/or ionized particle to be de-excited and/or neutralized. The result of these nonradiative de-excitation processes is shown to provide a possible channel for the formation of new excited ''daughters'' by the de-excitation of the initial excited ''parent''. Depending on the initial excitation probability of the parent the new excited daughters are shown to contribute to various energy regions of the excited and/or ionized secondary particle energy distribution. A mathematical formalism is developed based on the neutral sputtered atom energy and velocity distributions assuming a collision cascade origin for these sputtered particles. By including various models for the excitation probability, and the survival probability for excited particles once formed to not undergo nonradiative de-excitation the resulting energy and velocity distributions of the sputtered excited and/or ionized secondary particles are calculated. These distributions are found to be a function of the emission angle depending on the model assumed for the initial excitation. From this formalism the total excited secondary particle yield may be calculated

  8. Fine structures of atomic excited states: precision atomic spectroscopy and electron-ion collision process

    International Nuclear Information System (INIS)

    Gao Xiang; Cheng Cheng; Li Jiaming

    2011-01-01

    Scientific research fields for future energies such as inertial confinement fusion researches and astrophysics studies especially with satellite observatories advance into stages of precision physics. The relevant atomic data are not only enormous but also of accuracy according to requirements, especially for both energy levels and the collision data. The fine structure of high excited states of atoms and ions can be measured by precision spectroscopy. Such precision measurements can provide not only knowledge about detailed dynamics of electron-ion interactions but also a bench mark examination of the accuracy of electron-ion collision data, especially incorporating theoretical computations. We illustrate that by using theoretical calculation methods which can treat the bound states and the adjacent continua on equal footing. The precision spectroscopic measurements of excited fine structures can be served as stringent tests of electron-ion collision data. (authors)

  9. Correlated charge-changing ion-atom collisions

    International Nuclear Information System (INIS)

    Tanis, J.A.

    1992-04-01

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

  10. Effect of temperature on atom-atom collision chain length in metals

    International Nuclear Information System (INIS)

    Makarov, A.A.; Demkin, N.A.; Lyashchenko, B.G.

    1981-01-01

    Focused atom-atom collision chain lengths are calculated for fcc-crystals with account of thermal oscillations. The model of solid spheres with the Born-Merier potential has been used in the calculations. The dependence of chain lengths on the temperature, energy and movement direction of the first chain atom for Cu, Au, Ag, Pb, Ni is considered. The plot presented shows that the chain lengths strongly decrease with temperature growth, for example, for the gold at T=100 K the chain length equals up to 37 interatomic spacings, whereas at T=1000 K their length decreases down to 5 interatomic distances. The dependence of the energy loss by the chain atoms on the atom number in the chain is obtained in a wide range of crystal temperature and the primary chain atom energy [ru

  11. Accelerator-based atomic and molecular collision physics

    International Nuclear Information System (INIS)

    Datz, S.

    1993-01-01

    Accelerators have been shown to have great utility in addressing a broad range of problems in experimental atomic physics. There are, of course, phenomena such as inner-shell MO promotion which can occur only at high collision energies. At much higher energies, large transient Coulomb fields can be generated which lead to copious production electron-positron pairs and to capture of electrons from the negative continuum. But in addition, many advantages can be gained by carrying out low-energy (center-of-mass) collisions at high laboratory energies, specifically in a single pass mode or in multi-pass modes in ion storage rings in which, e.g., collision in the milli-electron volt region can be achieved for electron-molecule reactions. Certain advantages also accrue using open-quotes reverse kinematicsclose quotes in which high velocity ions collide with almost open-quotes stationaryclose quotes electrons as in resonant transfer and excitation (RTE) and collisions of energetic ions in the dense open-quotes electron gasclose quotes found in crystal channels

  12. Collisions involving energy transfer between atoms with large angular moments

    International Nuclear Information System (INIS)

    Vdovin, Yu.A.; Galitskij, V.M.

    1975-01-01

    Study is made of the collisions of excited and nonexcited atoms with a small resonance defect, assuming that the excited and ground states of each atom are bound via an allowed dipole transition and that intrinsic moments of states are great. In such an approximation the atomic interaction is defined by a dipole-dipole interaction operator. Equations for amplitudes are derived for two cases: (1) the first atom is in an excited state while the second is in the ground state and (2) the first atom is in the ground state while the second is in an excited state. The problem is solved in the approximation that the moments of the excited and ground states of each atom are equal. An expression for the excitation transfer cross section is written down. Analysis of this expression shows that the excitation transfer cross section at first increases with removal from the exact resonance and reaches resonance at lambda approximately 0.1 (lambda is a dimensionless parameter which is equal to the ratio of the resonance defect Δ to the interaction at spacings of the order of the Weisskopf radius). Only at lambda >0.16 does the cross section become smaller than the resonance one. This effect is due to the interaction Hamiltonian approximation adopted in the present study

  13. Microwave multiphoton excitation of helium Rydberg atoms: The analogy with atomic collisions

    International Nuclear Information System (INIS)

    van de Water, W.; van Leeuwen, K.A.H.; Yoakum, S.; Galvez, E.J.; Moorman, L.; Bergeman, T.; Sauer, B.E.; Koch, P.M.

    1989-01-01

    We study multiphoton transitions in helium Rydberg atoms subjected to a microwave electric field of fixed frequency but varying intensity. For each principal quantum number in the range n=25--32, the n 3 S to n 3 (L>2), n=25--32, transition probability exhibits very sharp structures as a function of the field amplitude. Their positions could be reproduced precisely using a Floquet Hamiltonian for the interaction between atom and field. Their shapes are determined by the transients of field turn-on and turn-off in a way that makes a close analogy with the theory of slow atomic collisions

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

    International Nuclear Information System (INIS)

    Kvale, T.J.

    1991-01-01

    This research project is designed to provide measurements of various scattering processes which occur in H - collisions with atomic targets at intermediate energies. The immediate goal is to study elastic scattering, single electron detachment, and target excitation/ionization in H - scattering from noble gas targets. For the target inelastic processes, these cross sections are unknown both experimentally and theoretically. The present measurements 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 collisions. This series of experiments required the construction of a new facility, and significant progress toward its operation has been realized during this period. The proposed research is described in this report. The progress on and the status of the apparatus is also detailed in this report

  15. The screening length of interatomic potential in atomic collisions

    International Nuclear Information System (INIS)

    Yamamura, Y.; Takeuchi, W.; Kawamura, T.

    1998-03-01

    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)

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

    International Nuclear Information System (INIS)

    Winter, T.G.; Alston, S.G.

    1992-01-01

    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

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

    International Nuclear Information System (INIS)

    Melezhik, V.S.

    1995-01-01

    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

  18. Multivariable hypergeometric functions for ion-atom collisions

    Energy Technology Data Exchange (ETDEWEB)

    Gasaneo, G.; Colavecchia, F.D.; Garibotti, C.R

    1999-06-03

    In this work we present a correlated wave function for a three-body continuum Coulomb problem. This state is described by the two-variables PHI{sub 2} hypergeometric function. We examine the properties of this function and their differences with previous uncorrelated models. The PHI{sub 2} wave function can be considered as a final state of ion-atom ionizing collisions, giving rise to both undistorted (Born-PHI{sub 2}) and distorted (EIS-PHI{sub 2}) models. We obtain double differential cross sections with the Born-PHI{sub 2} theory for proton-helium collisions in the intermediate to high energy regime. They exhibit all the main features of the electronic emission process and agree with the experimental data.

  19. Design and performance of a high intensity copper atom beam source nozzle for use in inelastic atom--atom collision experiments

    International Nuclear Information System (INIS)

    Santavicca, D.A.

    1975-01-01

    The research was aimed at developing a neutral copper atom beam source which could be used to study the collision cross sections for electronic excitation of neutral copper atoms in collision with neutral argon atoms. Of particular interest is the excitation from the ground state to the two upper laser levels at 3.80 and 3.82 electron volts

  20. Probing Efimov discrete scaling in an atom-molecule collision

    Science.gov (United States)

    Shalchi, M. A.; Yamashita, M. T.; Hadizadeh, M. R.; Garrido, E.; Tomio, Lauro; Frederico, T.

    2018-01-01

    The discrete Efimov scaling behavior, well known in the low-energy spectrum of three-body bound systems for large scattering lengths (unitary limit), is identified in the energy dependence of an atom-molecule elastic cross section in mass-imbalanced systems. That happens in the collision of a heavy atom with mass mH with a weakly bound dimer formed by the heavy atom and a lighter one with mass mL≪mH . Approaching the heavy-light unitary limit, the s -wave elastic cross section σ will present a sequence of zeros or minima at collision energies following closely the Efimov geometrical law. Our results, obtained with Faddeev calculations and supplemented by a Born-Oppenheimer analysis, open a perspective to detecting the discrete scaling behavior from low-energy scattering data, which is timely in view of the ongoing experiments with ultracold binary mixtures having strong mass asymmetries, such as lithium and cesium or lithium and ytterbium.

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

    International Nuclear Information System (INIS)

    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 - 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 - 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

  2. Production of dimeson atoms in high-energy collisions

    Energy Technology Data Exchange (ETDEWEB)

    Afanasyev, L.; Gevorkyan, S.; Voskresenskaya, O. [Joint Institute for Nuclear Research, Dubna (Russian Federation)

    2017-04-15

    The production of two-meson electromagnetic bound states and free meson pairs π{sup +}π{sup -}, K{sup +}K{sup -}, π{sup +}K{sup -+} in relativistic collisions has been considered. It is shown that using of exact Coulomb wave functions for dimeson atom (DMA) allows one to calculate the yield of discrete states with the desired accuracy. The relative probabilities of production of DMA and meson pairs in the free state are estimated. The amplitude of DMA transition from 1S to 2P state, which is essential for the pionium Lamb shift measurements, has been obtained. (orig.)

  3. Delta-electron emission in fast heavy ion atom collisions

    International Nuclear Information System (INIS)

    Schmidt-Boecking, H.; Ramm, U.; Berg, H.; Kelbch, C.; Feng Jiazhen; Hagmann, S.; Kraft, G.; Ullrich, J.

    1991-01-01

    The δ-electron emission processes occuring in fast heavy ion atom collisons are explained qualitatively. The different spectral structures of electron emission arising from either the target or the projectile are explained in terms of simple models of the kinetics of momentum transfer induced by the COULOMB forces. In collisions of very heavy ions with matter, high nuclear COULOMB forces are created. These forces lead to a strong polarization of the electronic states of the participated electrons. The effects of this polarization are discussed. (orig.)

  4. Superradiant cascade emissions in an atomic ensemble via four-wave mixing

    Energy Technology Data Exchange (ETDEWEB)

    Jen, H.H., E-mail: sappyjen@gmail.com

    2015-09-15

    We investigate superradiant cascade emissions from an atomic ensemble driven by two-color classical fields. The correlated pair of photons (signal and idler) is generated by adiabatically driving the system with large-detuned light fields via four-wave mixing. The signal photon from the upper transition of the diamond-type atomic levels is followed by the idler one which can be superradiant due to light-induced dipole–dipole interactions. We then calculate the cooperative Lamb shift (CLS) of the idler photon, which is a cumulative effect of interaction energy. We study its dependence on a cylindrical geometry, a conventional setup in cold atom experiments, and estimate the maximum CLS which can be significant and observable. Manipulating the CLS of cascade emissions enables frequency qubits that provide alternative robust elements in quantum network. - Highlights: • Superradiance from a cascade atomic transition. • Correlated photon pair generation via four-wave mixing. • Dynamical light–matter couplings in a phased symmetrical state. • Cooperative Lamb shift in a cylindrical atomic ensemble.

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

    Science.gov (United States)

    Stancil, P. C.; Turner, A. R.; Cooper, D. L.; Schultz, D. R.; Rakovic, M. J.; Fritsch, W.; Zygelman, B.

    2001-06-01

    Charge transfer processes due to collisions of ground state S4+(3s2 1S) 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.

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

    International Nuclear Information System (INIS)

    Watanabe, T.; Hino, K.

    1985-01-01

    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)

  7. Diabatic and adiabatic representations for atomic collision processes

    International Nuclear Information System (INIS)

    Delos, J.B.; Thorson, W.R.

    1979-01-01

    A consistent general definition of diabatic representations has not previously been given, even though many practical examples of such representations have been constructed for specific problems. Such a definition is provided in this paper. Beginning with a classical trajectory formulation, we describe the form and behavior of velocity-dependent couplings in slow collisions, including the effects of electron-translation factors (ETF's). We compare the couplings arising from atomic representations and atomic ETF's with those arising from molecular representations and ''switching function'' ETF's. We show that a unique set of switching functions makes the two descriptions identical in their effects. We then show that an acceptable general definition of a diabatic representation is provided by the condition P+A=0, where P is the usual nonadiabatic coupling matrix and A represents corrections to it arising from electron translation factors (ETF's). Two distinct types of diabatic representation result, depending on the definition taken for A. States that undergo no deformation are called F diabatic; those that have no velocity-dependent couplings are called M diabatic. Finally, we discuss the properties of representations that are partially diabatic and partially adiabatic, and we give some rules for the construction of representations that should be nearly optimal for describing many types of collision processes

  8. Electron-atom collisions in a laser field

    International Nuclear Information System (INIS)

    Ehlotzky, F.

    1998-01-01

    The present work is a report on recent progress made in our understanding of electron-atom collisions in a laser field. To some extent it is a continuation of a previous review covering a somewhat larger subject (Can. J. Phys. 63 (1985)). We shall discuss the present status of investigations in this field from the theoretical as well as experimental point of view but most of the report will be devoted to an analysis of the various approximation schemes used at present in this field to describe the different aspects of laser-assisted electron-atom interactions. As the table of contents shows, most of the work done so far is treating the atom as a spectator, described by a potential and only very little has been achieved over the years to include the atomic structure into consideration since the inclusion of these structure effects poses considerable computational problems. Since, for example, multiphoton ionization and its inverse process laser-assisted recombination may be considered as one half of a scattering process, it is quite natural that some of the theoretical techniques described here are also of interest for the treatment of other multiphoton processes not considered here since there are several other recent reviews available on these topics. (orig.)

  9. Stochastic theory of molecular collisions. II. Application to atom--vibrotor collisions

    International Nuclear Information System (INIS)

    Augustin, S.D.; Rabitz, H.

    1977-01-01

    In this work stochastic theory is applied to the treatment of atom--vibrotor collisions. This is an extension of a previous paper which described molecular collisions by a Pauli master equation or a Fokker--Planck equation. In this framework an energy conserving classical path model is explored, and methods for solving the equations numerically are discussed. The coefficients of the Fokker--Planck equation are shown to be expressible as simple functions of the interaction potential. Estimates of the computational labor are also discussed. Finally as a followup on the initial work, numerical solutions of the master equation for the collinear vibrational excitation problem of Secrest and Johnson are presented in an Appendix

  10. Gamma techniques for IAEA [International Atomic Energy Agency] safeguards at centrifuge enrichment cascades

    International Nuclear Information System (INIS)

    Aaldijk, J.K.; de Betue, P.A.C.; van der Meer, K.; Harry, R.J.S.

    1987-01-01

    On February 4, 1983, the Hexapartite Safeguards Project (HSP) concluded that the safeguards approach involving limited frequency unannounced access (LFUA) by International Atomic Energy Agency (IAEA) inspectors to cascades areas together with inspection activities outside the cascade areas meets the IAEA safeguards objectives in an effective and efficient way. In this way, the risks of revealing sensitive information were also minimized. The approach has been defined clearly and unambiguously, and it should be applied equally to all technology holders. One of the conclusions of the HSP was that a nondestructive assay go/no-go technique should be used during the LFUA inspections in the cascade areas of centrifuge enrichment plants. The purpose is to verify that the enrichment of the product UF 6 gas is in the range of low-enriched uranium (LEU), i.e., the enrichment is below 20%

  11. Studies on low energy ion-atom collisions by means of electron-spectroscopy

    International Nuclear Information System (INIS)

    Hirosi Suzuki

    1991-01-01

    The typical results of studies on autoionization processes produced by low energy ion-atom collisions are given by means of the ejected electron spectroscopy, which have been performed by Atomic Physics Group of Sophia University

  12. MD simulation of atomic displacement cascades in Fe-10 at.%Cr binary alloy

    International Nuclear Information System (INIS)

    Tikhonchev, M.; Svetukhin, V.; Kadochkin, A.; Gaganidze, E.

    2009-01-01

    Molecular dynamics simulation of atomic displacement cascades up to 20 keV has been performed in Fe-10 at.%Cr binary alloy at a temperature of 600 K. The N-body interatomic potentials of Finnis-Sinclair type were used. According to the obtained results the dependence of 'surviving' defects amount is well approximated by power function that coincides with other researchers' results. Obtained cascade efficiency for damage energy in the range from 10 to 20 keV is ∼0.2 NRT that is slightly higher than for pure α-Fe. In post-cascade area Cr fraction in interstitials is in range 2-5% that is essentially lower than Cr content in the base alloy. The results on size and amount of vacancy and interstitial clusters generated in displacement cascades are obtained. For energies of 2 keV and higher the defect cluster average size increases and it is well approximated by a linear dependence on cascade energy both for interstitials and vacancies.

  13. MD simulation of atomic displacement cascades in Fe-10 at.%Cr binary alloy

    Energy Technology Data Exchange (ETDEWEB)

    Tikhonchev, M., E-mail: tikhonchev@sv.ulsu.r [Ulyanovsk State University, Leo Tolstoy Str., 42, Ulyanovsk 432970 (Russian Federation); Joint Stock Company, ' State Scientific Center Research Institute of Atomic Reactors' , 433510 Dimitrovgrad-10 (Russian Federation); Svetukhin, V.; Kadochkin, A. [Ulyanovsk State University, Leo Tolstoy Str., 42, Ulyanovsk 432970 (Russian Federation); Gaganidze, E. [Forschungszentrum Karlsruhe, IMF II, 3640, D-76021 Karlsruhe (Germany)

    2009-12-15

    Molecular dynamics simulation of atomic displacement cascades up to 20 keV has been performed in Fe-10 at.%Cr binary alloy at a temperature of 600 K. The N-body interatomic potentials of Finnis-Sinclair type were used. According to the obtained results the dependence of 'surviving' defects amount is well approximated by power function that coincides with other researchers' results. Obtained cascade efficiency for damage energy in the range from 10 to 20 keV is approx0.2 NRT that is slightly higher than for pure alpha-Fe. In post-cascade area Cr fraction in interstitials is in range 2-5% that is essentially lower than Cr content in the base alloy. The results on size and amount of vacancy and interstitial clusters generated in displacement cascades are obtained. For energies of 2 keV and higher the defect cluster average size increases and it is well approximated by a linear dependence on cascade energy both for interstitials and vacancies.

  14. Mechanisms of cascade collapse

    International Nuclear Information System (INIS)

    Diaz de la Rubia, T.; Smalinskas, K.; Averback, R.S.; Robertson, I.M.; Hseih, H.; Benedek, R.

    1988-12-01

    The spontaneous collapse of energetic displacement cascades in metals into vacancy dislocation loops has been investigated by molecular dynamics (MD) computer simulation and transmission electron microscopy (TEM). Simulations of 5 keV recoil events in Cu and Ni provide the following scenario of cascade collapse: atoms are ejected from the central region of the cascade by replacement collision sequences; the central region subsequently melts; vacancies are driven to the center of the cascade during resolidification where they may collapse into loops. Whether or not collapse occurs depends critically on the melting temperature of the metal and the energy density and total energy in the cascade. Results of TEM are presented in support of this mechanism. 14 refs., 4 figs., 1 tab

  15. 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…

  16. Adiabatic translation factors in slow ion-atom collisions

    International Nuclear Information System (INIS)

    Vaaben, J.; Taulbjerg, K.

    1981-01-01

    The general properties of translation factors in slow atomic collisions are discussed. It is emphasised that an acceptable form of translation factors must be conceptually consistent with the basic underlying assumption of the molecular model; i.e. translation factors must relax adiabatically at intermediate and small internuclear separations. A simple physical argument is applied to derive a general parameter-free expression for the translation factor pertinent to an electron in a two-centre Coulomb field. Within the present approach the adiabatic translation factor is considered to be a property of the two-centre field independently of the molecular state under consideration. The generalisation to many-electron systems is therefore readily made. (author)

  17. Collision-induced polarizabilities of inert gas atoms

    International Nuclear Information System (INIS)

    Clarke, K.L.; Madden, P.A.; Buckingham, A.D.

    1978-01-01

    The use of polarizability densities to calculate collision-induced polarizabilities is investigated. One method for computing polarizabilities of inert gas diatoms employs atomic polarizability densities from finite-field Hartree-Fock calculations, together with classical equations for the polarization of dielectrics. It is shown that this model gives inaccurate values for both the local fields and the local response to non-uniform fields. An alternative method incorporating the same physical effects is used to compute the pair polarizabilities to first order in the interatomic interaction. To first order the pair contribution to the trace of the polarizability is negative at short range. The calculated anisotropy does not differ significantly from the DID value, whereas the polarizability density calculation gives a substantial reduction in the anisotropy. (author)

  18. 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...

  19. Simultaneous electron capture and excitation in ion-atom collisions

    International Nuclear Information System (INIS)

    Tanis, J.A.; Bernstein, E.M.; Graham, W.G.; Clark, M.; Shafroth, S.M.; Johnson, B.M.; Jones, K.; Meron, M.

    1982-01-01

    A review of recent efforts to observe simultaneous electron capture-and-K-shell excitation in ion-atom collisions is presented. This process which has been referred to as resonant-transfer-and-excitation (RTE), is qualitatively analogous to dielectronic recombination (inverse Auger transition) in free-electron-ion collisions, and, hence, is expected to be resonant. Experimentally, events having the correct signature for simultaneous capture-and-excitation are isolated by detecting projectile K x rays in coincidence with ions which capture a single electron. In a recent experiment involving 70-160 MeV S 13+ ions incident on Ar, a maximum was observed in the yield of projectile K x rays associated with electron capture. This maximum is attributed to simultaneous capture - and excitation. The position (120 MeV) and width (60 MeV) of the observed maximum are in good agreement with theoretical calculations. The data indicate that RTE is an important mechanism for inner-shell vacancy production in the energy range studied

  20. Thermal relaxation of molecular oxygen in collisions with nitrogen atoms

    Energy Technology Data Exchange (ETDEWEB)

    Andrienko, Daniil A., E-mail: daniila@umich.edu; Boyd, Iain D. [Department of Aerospace Engineering, University of Michigan, 1320 Beal Ave., Ann Arbor, Michigan 48108 (United States)

    2016-07-07

    Investigation of O{sub 2}–N collisions is performed by means of the quasi-classical trajectory method on the two lowest ab initio potential energy surfaces at temperatures relevant to hypersonic flows. A complete set of bound–bound and bound–free transition rates is obtained for each precollisional rovibrational state. Special attention is paid to the vibrational and rotational relaxations of oxygen as a result of chemically non-reactive interaction with nitrogen atoms. The vibrational relaxation of oxygen partially occurs via the formation of an intermediate NO{sub 2} complex. The efficient energy randomization results in rapid vibrational relaxation at low temperatures, compared to other molecular systems with a purely repulsive potential. The vibrational relaxation time, computed by means of master equation studies, is nearly an order of magnitude lower than the relaxation time in N{sub 2}–O collisions. The rotational nonequilibrium starts to play a significant effect at translational temperatures above 8000 K. The present work provides convenient relations for the vibrational and rotational relaxation times as well as for the quasi-steady dissociation rate coefficient and thus fills a gap in data due to a lack of experimental measurements for this system.

  1. 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

  2. Dark states and interferences in cascade transitions of ultracold atoms in a cavity

    International Nuclear Information System (INIS)

    Arun, R.; Agarwal, G.S.

    2002-01-01

    We examine the competition among one- and two-photon processes in an ultracold, three-level atom undergoing cascade transitions as a result of its interaction with a bimodal cavity. We show parameter domains where two-photon transitions are dominant, and we also study the effect of two-photon emission on the mazer action in the cavity. The two-photon emission leads to the loss of detailed balance and therefore we obtain the photon statistics of the cavity field by the numerical integration of the master equation. The photon distribution in each cavity mode exhibits sub- and super-Poissonian behaviors depending on the strength of atom-field coupling. The photon distribution becomes identical to a Poisson distribution when the atom-field coupling strengths of the modes are equal

  3. Modeling of cascade and sub-cascade formation at high PKA energies in irradiated fusion structural materials

    International Nuclear Information System (INIS)

    Ryazanov, A.I.; Metelkin, E.V.; Semenov, E.V.

    2009-01-01

    A new theoretical model is developed for the investigations of cascade and sub-cascade formation in fusion structural materials under fast neutron irradiation at high primary knock-on atom energies. Light fusion structural materials: such as Be, C and SiC under 14 MeV neutron irradiation in fusion reactor will have the primary knock-on atoms with the energies up to 1 MeV. It is very difficult to use at such high energies the Monte-Carlo or molecular dynamic simulations [H.L. Heinisch, B.N. Singh, Philos. Mag. A67 (1993) 407; H.L. Heinisch, B.N. Singh, J. Nucl. Mater. 251 (1997) 77]. The developed model is based on the analytical consideration of elastic collisions between displaced moving atoms produced by primary knock-on atoms with some kinetic energies obtained from fast neutrons and crystal lattice atoms. The Thomas-Fermi interaction potential is used here for the description of these elastic atomic collisions. The suggested model takes into account also the electronic losses for moving atoms between elastic collisions. The self-consistent criterion for sub-cascade formation is suggested here which is based on the comparison of mean distance of primary knock-on atoms between consequent collisions of them with the target atoms and a size of sub-cascade produced by moving secondary knock-on atoms produced in such collisions. The analytical relations for the most important characteristics of cascades and sub-cascades are determined including the average number of sub-cascades per one primary knock-on atom in the dependence on its energy, the distance between sub-cascades and the average cascade and sub-cascade sizes. The developed model allows determining the total numbers, distribution functions of cascades and sub-cascades in dependence on their sizes and generation rate of cascades and sub-cascades for the different fusion neutron energy spectra. On the basis of this developed model the numerical calculations for main characteristics of cascades and sub-cascades

  4. Disalignment rate coefficient of neon excited atoms due to helium atom collisions at low temperatures

    International Nuclear Information System (INIS)

    Seo, M; Shimamura, T; Furutani, T; Hasuo, M; Bahrim, C; Fujimoto, T

    2003-01-01

    Disalignment of neon excited atoms in the fine-structure 2p i levels (in Paschen notation) of the 2p 5 3p configuration is investigated in a helium-neon glow discharge at temperatures between 15 and 77 K. At several temperatures, we plot the disalignment rate as a function of the helium atom density for Ne* (2p 2 or 2p 7 ) + He(1s 2 ) collisions. The slope of this dependence gives the disalignment rate coefficient. For both collisions, the experimental data for the disalignment rate coefficient show a more rapid decrease with the decrease in temperature below 40 K than our quantum close-coupling calculations based on the model potential of Hennecart and Masnou-Seeuws (1985 J. Phys. B: At. Mol. Phys. 18 657). This finding suggests that the disalignment cross section rapidly decreases below a few millielectronvolts, in disagreement with our theoretical quantum calculations which predict a strong increase below 1 meV. The disagreement suggests that the long-range electrostatic potentials are significantly more repulsive than in the aforementioned model

  5. Low energy collisions of spin-polarized metastable argon atoms with ground state argon atoms

    Science.gov (United States)

    Taillandier-Loize, T.; Perales, F.; Baudon, J.; Hamamda, M.; Bocvarski, V.; Ducloy, M.; Correia, F.; Fabre, N.; Dutier, G.

    2018-04-01

    The collision between a spin-polarized metastable argon atom in Ar* (3p54s, 3P2, M = +2) state slightly decelerated by the Zeeman slower-laser technique and a co-propagating thermal ground state argon atom Ar (3p6, 1S0), both merged from the same supersonic beam, but coming through adjacent slots of a rotating disk, is investigated at the center of mass energies ranging from 1 to 10 meV. The duration of the laser pulse synchronised with the disk allows the tuning of the relative velocity and thus the collision energy. At these sub-thermal energies, the ‘resonant metastability transfer’ signal is too small to be evidenced. The explored energy range requires using indiscernibility amplitudes for identical isotopes to have a correct interpretation of the experimental results. Nevertheless, excitation transfers are expected to increase significantly at much lower energies as suggested by previous theoretical predictions of potentials 2g(3P2) and 2u(3P2). Limits at ultra-low collisional energies of the order of 1 mK (0.086 μeV) or less, where gigantic elastic cross sections are expected, will also be discussed. The experimental method is versatile and could be applied using different isotopes of Argon like 36Ar combined with 40Ar, as well as other rare gases among which Krypton should be of great interest thanks to the available numerous isotopes present in a natural gas mixture.

  6. Dynamic effect of collision failure of phase in gas of cold dark atoms

    International Nuclear Information System (INIS)

    Il'ichev, L.V.

    2005-01-01

    In a gas of slow atoms exhibiting the effect of coherent population trapping (CPT) on the sublevels of the ground state in a spatially nonuniform light field, rare collisions destroying the CPT state initiate the irreversible exchange of momentum between radiation and atoms. This exchange is manifested as an additional force that acts on the particles. The force is of geometric origin, being determined only by the structure of the field of local CPT states. When this force is not masked by the standard collision change in atomic momentum, the observation of the kinetics of the particles may provide information on the physics of the collisions [ru

  7. Autoionic microscopy of damage regions of single atom displacement cascades in metals

    International Nuclear Information System (INIS)

    Suvorov, A.L.

    1981-01-01

    The defect region formation characterized by zones of depletion with atoms and interstitial halos arizing during displacement cascade development in an irradiated metal is considered. in experimental autoionmicroscopic analysis technique is used. The analysis procedure is briefly discussed: the experiment, the defect identification on autoionic image microphotos, computer data processing. The technique was applied for pure tungsten irradiated with 12 and 5.8 MeV deuterons and fission neutrons, and for tungsten-1.5% ThO 2 alloy irradiated with fast neutrons from fission fragments

  8. PREFACE: XXVIth International Conference on Photonic, Electronic and Atomic Collisions

    Science.gov (United States)

    Orel, Ann; Starace, Anthony F.; Nikolić, Dragan; Berrah, Nora; Gorczyca, Thomas W.; Kamber, Emanuel Y.; Tanis, John A.

    2009-12-01

    The XXVIth International Conference on Photonic, Electronic and Atomic Collisions was held on the campus of Western Michigan University (WMU) in Kalamazoo during 22-28 July 2009. Kalamazoo, the home of a major state university amid pleasant surroundings, was a delightful place for the conference. The 473 scientific participants, 111 of whom were students, had many fruitful discussions and exchanges that contributed to the success of the conference. Participants from 43 countries made the conference truly international in scope. The 590 abstracts that were presented on the first four days formed the heart of the conference and provided ample opportunity for discussion. This change, allowing the conference to end with invited talks, was a departure from the format used at previous ICPEAC gatherings in which the conferences ended with a poster session. The abstracts were split almost equally between the three main conference areas, i.e., photonic, electronic, and atomic collisions, and the posters were distributed across the days of the conference so that approximately equal numbers of abstracts in the different areas were scheduled for each day. Of the total number of presented abstracts, 517 of these are included in this proceedings volume, the first time that abstracts have been published by ICPEAC. There were 5 plenary lectures covering the different areas of the conference: Paul Corkum (University of Ottawa) talked on attosecond physics with atoms and molecules, Serge Haroche (Collège de France) on non-destructive photon counting, Toshiyuki Azuma (Tokyo Metropolitan University) on resonant coherent excitation of highly-charged ions in crystals, Eva Lindroth (Stockholm University) on atomic structure effects, and Alfred Müller (Justus Liebig University) on resonance phenomena in electron- and photon-ion collisions. Two speakers gave very illuminating public lectures that drew many people from the local area, as well as conference participants: Patricia Dehmer

  9. Collision processes of highly excited hydrogen atom, 1

    International Nuclear Information System (INIS)

    Toshima, Nobuyuki

    1977-01-01

    The cross sections for the transitions 5S sub(1/2) → 5P sub(1/2), 5S sub(1/2) → 5P sub(3/2), 5P sub(1/2) → 5D sub(3/2), 5S sub(1/2) → 5D sub(3/2) and 5S sub(1/2) → 5D sub(5/2) in the hydrogen atom by proton impact are calculated on the basis of the impact parameter method. Distant collisions are dominant and the couplings among the sub-levels belonging to the same n are important at low energies, but the couplings with the levels belonging to different n's are negligibly small. The Glauber and the Born approximations are also applied to the same problem and the Glauber approximation gives a good agreement with the impact parameter method over a wide energy range down to at least about 100 eV. (auth.)

  10. Fast numerical calculations of ion-atom collisions

    International Nuclear Information System (INIS)

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

    1979-01-01

    When an ion impinges on an atom, the cross sections for electronic transitions can be described in the independent electron model by functions of single electron amplitudes. A single centered expansion of the time-dependent wave function of an electron about the heavier nucleus, with charge Z/sub N/, is shown to be moderately successful in explaining the dependence of K-shell hole production on the charge, Z/sub p/, of the projectile. However, capture of electrons by the projectile is important for a complete understanding and can be incorporated, in principle, in the single-center approach by evaluation of a transition matrix element involving a final state on the projectile. This is not an easy theoretical problem even in an asymmetric (Z/sub p/ much less than Z/sub N/) collision, because long times are involved which aggravate the inadequacies of a coupled-state calculation where the continuum is replaced by a discrete set of pseudostates. Nevertheless a method was devised which allows convergence in the truncated expansion of Hilbert states. Comparisons are made to experiment. Future developments are discussed

  11. Propensity rules for orientation in singly-charged ion-atom collisions

    International Nuclear Information System (INIS)

    Nielsen, S.E.; Dubois, A.; Hansen, J.P.

    1990-01-01

    Orientation effects for electron capture and excitation in singly-charged ion-atom collisions are analysed using the atomic basis impact parameter method with full inclusion of electron translational factors. We find that the orientation preferences previously predicted for excitation in terms of propensity rules may still be observed when capture is present in ion-atom collisions. Furthermore, in spite of intricate behaviour of the direct capture couplings during the collision, we draw some parallel conclusions for the orientation of the capture states. We illustrate these perturbative predictions by close-coupling calculations for H + -Na(3s) collisions where clear propensity for orientation of the H(2p) capture state is demonstrated in impact parameter and velocity dependences. Finally we predict pronounced orientation effects for H(2s) and H(2p) capture in collisions of H + with initially oriented Na(3p) states. (author)

  12. The time-energy distribution of atoms in a radiation damage cascade

    International Nuclear Information System (INIS)

    Williams, M.M.R.

    1976-01-01

    The time-energy distribution of atoms in a cascade induced by a primary knock-on is obtained by solving the Boltzmann equation. A more general scattering law is used than has hitherto been possible which is based upon a rational approximation to the Thomas-Fermi model of atomic scattering. The virtue of this scheme is that it remains possible to obtain an exact, closed form solution but allows a more realistic description of the scattering process. Time moments of the distribution are obtained from which the slowing down time and associated variance can be calculated. It is shown that the complete time-energy distribution may be reconstructed from the moments. (author)

  13. Quadripartite cluster and Greenberger–Horne–Zeilinger entangled light via cascade interactions with separated atomic ensembles

    International Nuclear Information System (INIS)

    Li Xing; Hu Xiangming

    2012-01-01

    It has been known that two-mode entangled light can possibly be generated by employing near-resonant interaction with an ensemble of two-level atoms. The responsible mechanism is the absorption of two photons from the strong driving field and the emission of two new photons into the cavity field. Here, we generalize such a mechanism to three separated atomic ensembles and establish cascade interactions for four nondegenerate fields. It is shown that the quadripartite cluster and Greenberger–Horne–Zeilinger entangled states occur for continuous variables. The advantage of the present scheme for the multipartite entanglement lies in that the coupling strengths are much larger due to the near resonances than for far-off-resonance-based parametric processes. (paper)

  14. On the extension of (e,2e) theory to coincidence studies of ion-atom collisions

    International Nuclear Information System (INIS)

    Godunov, A.L.; Kampp, Marco; Sulik, B.; Walters, H.R.J.; Whelan, Colm T.

    2007-01-01

    The extension of (e,2e) theory to the coincidence studies of ion-atom collisions is considered. The simultaneous ionization of projectile and target is discussed and results are presented for transfer ionization

  15. Mimicing Charged Particle-Atom Collisions Using Half-Cycle Electromagnetic Pulses

    National Research Council Canada - National Science Library

    Jones, Robert

    2000-01-01

    .... Demonstration and preliminary studies of free electron-ion recombination in mock collisions. Identified Stark wave packets, coherent superpositions of "stretched" atomic states as potentially useful sources of short-pulses...

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

    International Nuclear Information System (INIS)

    Tawara, H.

    1993-04-01

    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

  17. Collision-induced absorption intensity redistribution and the atomic pair polarizabilities

    International Nuclear Information System (INIS)

    Bulanin, M. O.

    1997-01-01

    A modified relation between the trace polarizability of a diatom and the S(-2) dipole sum is proposed that accounts for the effect of atomic collisions on the dipole oscillator strength distribution. Contribution to the collision-induced trace due to redistribution in the ionization continuum of Ar is evaluated and is found to be significant

  18. VNI version 4.1. Simulation of high-energy particle collisions in QCD: Space-time evolution of e+e-... A + B collisions with parton-cascades, cluster-hadronization, final-state hadron cascades

    International Nuclear Information System (INIS)

    Geiger, K.; Longacre, R.

    1999-01-01

    VNI is a general-purpose Monte-Carlo event-generator, which includes the simulation of lepton-lepton, lepton-hadron, lepton-nucleus, hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions. It uses the real-time evolution of parton cascades in conjunction with a self-consistent hadronization scheme, as well as the development of hadron cascades after hadronization. The causal evolution from a specific initial state (determined by the colliding beam particles) is followed by the time-development of the phase-space densities of partons, pre-hadronic parton clusters, and final-state hadrons, in position-space, momentum-space and color-space. The parton-evolution is described in terms of a space-time generalization of the familiar momentum-space description of multiple (semi)hard interactions in QCD, involving 2 → 2 parton collisions, 2 → 1 parton fusion processes, and 1 → 2 radiation processes. The formation of color-singlet pre-hadronic clusters and their decays into hadrons, on the other hand, is treated by using a spatial criterion motivated by confinement and a non-perturbative model for hadronization. Finally, the cascading of produced prehadronic clusters and of hadrons includes a multitude of 2 → n processes, and is modeled in parallel to the parton cascade description. This paper gives a brief review of the physics underlying VNI, as well as a detailed description of the program itself. The latter program description emphasizes easy-to-use pragmatism and explains how to use the program (including simple examples), annotates input and control parameters, and discusses output data provided by it

  19. Influence of stacking fault energies on the size distribution and character of defect clusters formed by collision cascades in face-centered cubic metals

    Directory of Open Access Journals (Sweden)

    Y. Yang

    2016-12-01

    Full Text Available Molecular dynamics simulations are performed to evaluate the influence of the stacking fault energy (SFE as a single variable parameter on defect formation by collision cascades in face-centered cubic metals. The simulations are performed for energies of a primary knock-on atom (EPKA up to 50keV at 100K by using six sets of the recently developed embedded atom method–type potentials. Neither the number of residual defects nor their clustering behavior is found to be affected by the SFE, except for the mean size of the vacancy clusters at EPKA=50keV. The mean size increases as the SFE decreases because of the enhanced formation of large vacancy clusters, which prefer to have stacking faults inside them. On the other hand, the ratio of glissile self-interstitial atom (SIA clusters decreases as the SFE increases. At higher SFEs, both the number of Frank loops and number of perfect loops tend to decrease; instead, three-dimensional irregular clusters with higher densities appear, most of which are sessile. The effect of SFE on the number of Frank loops becomes apparent only at a high EPKA of 50keV, where comparably large SIA clusters can be formed with a higher density.

  20. 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.

  1. Electron capture in proton collisions with alkali atoms as a three-body problem

    International Nuclear Information System (INIS)

    Avakov, G.V.; Blokhintsev, L.D.; Kadyrov, A.S.; Mukhamedzhanov, A.M.

    1992-01-01

    A previous paper proposed an approach to the calculation of electron transfer reactions in ion-atomic collisions based on the Faddeev three-body equations written in the Alt-Grassberger-Sandhas form. In the present work this approach is used to describe the electron capture in proton collisions with alkali atoms. The results of calculation of the total and partial cross sections for charge exchange in proton collisions with Li, Na, K and Rb atoms are presented. The calculated total cross sections are in good agreement with experiment for light target atoms. In going over to heavier targets, the theoretical total cross sections, while agreeing in form, tend to be larger than the experimental ones. The calculated partial cross sections for electron capture into the 2s state of the H atom are also in agreement with experiment. Some other partial cross sections were also calculated. (author)

  2. Suppression of Zeeman relaxation in cold collisions of 2P1/2 atoms

    International Nuclear Information System (INIS)

    Tscherbul, T. V.; Dalgarno, A.; Buchachenko, A. A.; 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 2 P atoms in the presence of an external magnetic field. We show that collision-induced Zeeman relaxation of Ga( 2 P 1/2 ) and In( 2 P 1/2 ) atoms in cold 4 He gas is dramatically suppressed compared to atoms in 2 P 3/2 states. Using rigorous quantum-scattering calculations based on ab initio interaction potentials, we demonstrate that Zeeman transitions in collisions of atoms in 2 P 1/2 electronic states occur via couplings to the 2 P 3/2 state induced by the anisotropy of the interaction potential. Our results suggest the feasibility of sympathetic cooling and magnetic trapping of 2 P 1/2 -state atoms, such as halogens, thereby opening up exciting areas of research in precision spectroscopy and cold-controlled chemistry.

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

    International Nuclear Information System (INIS)

    Janev, R.K.

    1983-05-01

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

  4. Charge exchange and ionization of atoms in collisions with multicharged ions

    International Nuclear Information System (INIS)

    Presnyakov, L.P.; Uskov, D.B.

    1987-01-01

    Single-electron transition in continuous and discrete spectra, induced by A atom and B +2 multicharged ion collision with the charge Z>3 are investigated. A theory of quantum transitions in multilevel systems with ion-atom collisions is considered. Main results on charge exchange in slow (v 0 Z 1/2 ) collisions are presented. For analysis of charge exchange analytical method, being generalization of decay model and of approximation of nonadiabatic coupling of two states, that are included into a developed approach as limiting cases, is developed. The calculation results are compared with the available experimental data

  5. Dissociative excitation of lithium atom in electron collisions with LiBr molecules

    International Nuclear Information System (INIS)

    Smirnov, Yu.M.

    1998-01-01

    Effective cross sections of the lithium atom dissociative excitation in electron collisions with the LiBr molecules are measured. The measurement error equals 5-12%. The optical functions of the lithium atom dissociative excitation are calculated on the basis of the data obtained

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

    International Nuclear Information System (INIS)

    Montenegro, E.C.; Pinho, A.G. de; Souza, G.G.B. de.

    1988-01-01

    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.) [pt

  7. Database for inelastic collisions of lithium atoms with electrons, protons, and multiply charged ions

    NARCIS (Netherlands)

    Schweinzer, J; Brandenburg, R; Bray, [No Value; Hoekstra, R; Aumayr, F; Janev, RK; Winter, HP

    New experimental and theoretical cross-section data for inelastic collision processes of Li atoms in the ground state and excited states (up to n = 4) with electrons, protons, and multiply charged ions have been reported since the database assembled by Wutte et al. [ATOMIC DATA AND NUCLEAR DATA

  8. ''Atomic'' Bremsstrahlung or polarizational radiation in collision of many-electron ions

    International Nuclear Information System (INIS)

    Amusia, M.Ya.; Solov'yov, A.V.

    1991-01-01

    In this work the so-called ''Atomic'' bremsstrahlung (AB) or polarizational radiation, created in collisions of atoms or ions, is discussed. This kind of radiation arises due to the polarization of the electron shell of colliding particles. It is created by the structured projectiles and targets if the constituents are electrically charged. 6 refs, 2 figs

  9. Multiple electron capture in close ion-atom collisions

    International Nuclear Information System (INIS)

    Schlachter, A.S.

    1987-10-01

    Multiple electron capture is reported for Ca 17+ 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

  10. Adatom Bond Dissociation in the Collision Between an Adsorbed Atom and Incident Diatomic Molecule: A Classical Trajectory Study

    International Nuclear Information System (INIS)

    Bayhan, U.

    2004-01-01

    The collisional dissociation of the Atom-Surface bond in the diatomic molecule (gas) / atom (ads) collision taking place on a bcc-structure surface have been studied by classical trajectory methods over the collision energy ranges and the attractive well depth of the diatomic molecule (gas) / atom (ads) interactions

  11. Electron loss from heavy heliumlike projectiles in ultrarelativistic collisions with many-electron atomic targets

    International Nuclear Information System (INIS)

    Mueller, C.; Gruen, N.; Voitkiv, A.B.

    2002-01-01

    We study single- and double-electron loss from heavy heliumlike projectiles in ultrarelativistic collisions with neutral many-electron target atoms. The simultaneous interaction of the target with two projectile electrons is found to be the dominant process in the double-electron loss provided the atomic number of the projectile, Z p , that of the target, Z t , and the collision velocity, v, satisfy the condition Z p Z t /v>0.4. It is shown that for a wide range of projectile and target atomic numbers the asymptotic double-to-single loss ratio strongly depends on the target atomic number but is nearly independent of the nuclear charge of the projectile. It is also demonstrated that many-photon exchange between the target and each of the projectile electrons considerably influences the double loss in collisions with very heavy targets

  12. Selective Production of Renewable para-Xylene by Tungsten Carbide Catalyzed Atom-Economic Cascade Reactions.

    Science.gov (United States)

    Dai, Tao; Li, Changzhi; Li, Lin; Zhao, Zongbao Kent; Zhang, Bo; Cong, Yu; Wang, Aiqin

    2018-02-12

    Tungsten carbide was employed as the catalyst in an atom-economic and renewable synthesis of para-xylene with excellent selectivity and yield from 4-methyl-3-cyclohexene-1-carbonylaldehyde (4-MCHCA). This intermediate is the product of the Diels-Alder reaction between the two readily available bio-based building blocks acrolein and isoprene. Our results suggest that 4-MCHCA undergoes a novel dehydroaromatization-hydrodeoxygenation cascade process by intramolecular hydrogen transfer that does not involve an external hydrogen source, and that the hydrodeoxygenation occurs through the direct dissociation of the C=O bond on the W 2 C surface. Notably, this process is readily applicable to the synthesis of various (multi)methylated arenes from bio-based building blocks, thus potentially providing a petroleum-independent solution to valuable aromatic compounds. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Double differential distributions of electron emission in ion-atom and electron-atom collisions using an electron spectrometer

    International Nuclear Information System (INIS)

    Misra, Deepankar; Thulasiram, K.V.; Fernandes, W.; Kelkar, Aditya H.; Kadhane, U.; Kumar, Ajay; Singh, Yeshpal; Gulyas, L.; Tribedi, Lokesh C.

    2009-01-01

    We study electron emission from atoms and molecules in collisions with fast electrons and heavy ions (C 6+ ). The soft collision electrons (SE), two center electron emission (TCEE), the binary encounter (BE) events and the KLL Auger lines along with the elastically scattered peaks (in electron collisions) are studied using a hemispherical electrostatic electron analyzer. The details of the measurements along with description of the spectrometer and data acquisition system are given. The angular distributions of the low energy (few eV) electrons in soft collisions and the binary encounter electrons at keV energies are compared with quantum mechanical models based on the first Born (B1) and the continuum distorted wave-Eikonal initial state approximation (CDW-EIS).

  14. Outer-shell transitions in collisions between multiply charged ions and atoms

    International Nuclear Information System (INIS)

    Bloemen, E.W.P.

    1980-01-01

    The study of collisions between multiply charged ions and atoms (molecules) is of importance in different areas of research. Usually, the most important process is capture of an electron from the target atom into the projectile ion. In most cases the electron goes to an excited state of the projectile ion. These electron capture processes are studied. The author also studied direct excitation of the target atom and of the projectile ion. (Auth.)

  15. Vibrational and cascade dissociation of H{sub 2}{sup +} ions by collision with gas molecules; Dissociation vibrationnelle et dissociation en cascade d'ions H{sub 2}{sup +} par collisions avec les molecules d'un gaz

    Energy Technology Data Exchange (ETDEWEB)

    Verveer, P [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1966-07-01

    Protons produced by collisional dissociation of H{sub 2}{sup +} ions have an energy spectrum with a narrow central peak. For a part the protons in this peak are produced by vibrational dissociation and for another part by a cascade of two collisions. For H{sub 2}{sup +} ions of 50 to 150 keV the cross section for vibrational dissociation is about 4.1 10{sup -19} cm{sup 2}/molecule in hydrogen and 1.1 10{sup -18} cm{sup 2}/molecule in argon. (author) [French] Les protons resultant de la dissociation par collisions d'ions H{sub 2}{sup +} dans un gaz ont un spectre d'energie qui presente un pic central tres etroit. Les protons dans ce pic proviennent, pour une part de la dissociation vibrationnelle et pour l'autre part d'une suite de deux collisions. Dans le domaine d'energie des ions H{sub 2}{sup +} de 50 a 150 keV la section efficace de dissociation vibrationnel vaut 4.1 10{sup -19} cm{sup 2}/molecule pour l'hydrogene et 1,1 10{sup -18} cm{sup 2}/molecule pour l'argon.

  16. Application of the Faddeev-Watson expansion to thermal collisions of Rydberg atoms with neutral particles

    International Nuclear Information System (INIS)

    de Prunele, E.

    1983-01-01

    The Faddeev-Watson expansion (FWE) for the T operator is applied to the study of thermal collisions between Rydberg atom and neutral atom. These collisions are considered as a three-body problem (the perturber, the Rydberg electron, and its parent core) and it is assumed, as already done in most theoretical works dealing with Rydberg-atom--atom collisions, that the core-perturber interaction can be neglected. Then the evaluation of the FWE first- and second-order terms is made tractable by using an appropriate separable potential for the Rydberg-electron--perturber interaction. The evaluation of the second-order term allows us to estimate the importance of taking into account explicitly the Rydberg-electron--core interaction in the expression of the (three-body) T operator for the thermal collisions considered. Detailed calculations for the process Rb(n, l = 0)+He →Rb(n',l')+He are presented and discussed. The FWE second-order term has been evaluated for the first time by taking the (two-body) t operator associated with the Rydberg atom (valence electron plus parent core) as the Coulomb potential. The contribution of the FWE second-order term to the scattering amplitude decreases as n increases and is found especially significant when both the momentum transfers involved in the collision are large and the values of l and l' are small

  17. Systematics in Rydberg state excitations for ion-atom collisions

    International Nuclear Information System (INIS)

    Andresen, B.; Jensen, K.; Petersen, N.B.; Veje, E.

    1976-01-01

    Rydberg state excitations in the Ne + , Mg + -He collisions have been studied in the projectile energy range 10-75 keV by means of optical spectrometry in a search for systematic trends. The relative excitation cross sections for levels of a Rydberg term series are found to follow a general (nsup(x))sup(P) behaviour with P < approximately -3 varying with collision energy and particles, regardless of whether the excited state population results from direct excitation, single electron transfer, or double electron transfer. At higher collision energies P is approximately -3 as predicted by theory. Polarization of the emitted line radiation indicates that there is no general rule for the relative excitation of the different magnetic substates of the same level. A statistical distribution of excitation is found for levels within the same term when the fine structure splitting is small. (Auth.)

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

    International Nuclear Information System (INIS)

    Frank, W.; Kaun, K.-H.; Manfrass, P.

    1981-01-01

    The continuum consisting of an intensive low-energy and a high-energy components in heavy-ion atom collision systems with atomic numbers Z 1 , Z 2 > 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 Z 1 , Z 2 [ru

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

    International Nuclear Information System (INIS)

    Grimpe, A.

    2006-01-01

    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 LiH 2 and LiD 2 show a pronounced oscillatory structure, which for the first time is observed for atom-molecule optical collisions. (orig.)

  20. n l -> n' l' transition rates in electron and proton - Rydberg atom collision

    Science.gov (United States)

    Vrinceanu, Daniel

    2017-04-01

    Electrons and protons drive the recombination dynamics of highly excited Rydberg atoms in cold rarefied plasmas found in astrophysical conditions such as primordial recombination or star formation in H-II clouds. It has been recognized that collisions induce both energy and angular momentum transitions in Rydberg atoms, although in different proportions, depending on the initial state, temperature and the given species considered in the collision (electron or proton). Most studies focused on one collision type at a time, under the assumption that collision types are independent or their effects are not competing. The classical Monte-Carlo trajectory simulations presented in this work calculate the rates for both energy and angular momentum transfers and show their interdependence. For example, energy transfer with small angular momentum change are more efficient for target states with initial large angular momentum. The author acknowledges support received from the National Science Foundation through a Grant for the Center for Research on Complex Networks (HRD-1137732).

  1. Atomic population redistribution in a dense Ga vapour proceeding via energy pooling ionization induced by resonant laser-assisted collisions

    International Nuclear Information System (INIS)

    Barsanti, S; Bicchi, P

    2002-01-01

    In this paper we report on the atomic population redistribution originating from the ionization that takes place in a dense Ga vapour kept in quartz cells and resonantly excited by laser radiation, in the collisions between two excited atoms. This ionization process is known as energy-pooling ionization (EPI). The electron/ion recombination that takes place in the low density plasma produced gives rise to population in the atomic Rydberg levels and from the latter via cascade transitions to lower lying ones. We have monitored the fluorescences relative to the radiative emissions from such levels, namely those corresponding to the nP → 5S 1/2 series, with 9 ≤ n ≤ 26, and the 4D → 4P 1/2,3/2 transitions. Their characteristics testify to their origin as being due to the EPI process. Further confirmation is obtained by performing a time-resolved analysis of such fluorescences, whose appearance and time evolution is strongly influenced by the dynamics of the process. The effect of the introduction of a few Torr of buffer gas inside the quartz cell, resulting in the quenching of all the fluorescences for n ≥ 12, is also discussed

  2. Computer simulation of atomic collision processes in solids

    International Nuclear Information System (INIS)

    Robinson, M.T.

    1992-11-01

    Computer simulation is a major tool for studying the interactions of swift ions with solids which underlie processes such as particle backscattering, ion implantation, radiation damage, and sputtering. Numerical models are classed as molecular dynamics or binary collision models, along with some intermediate types. Binary collision models are divided into those for crystalline targets and those for structureless ones. The foundations of such models are reviewed, including interatomic potentials, electron excitations, and relationships among the various types of codes. Some topics of current interest are summarized

  3. Modeling of cascade and sub-cascade formation at high pka energies in irradiated fusion structural materials

    International Nuclear Information System (INIS)

    Ryazanov, A.; Metelkin, E.V.; Semenov, E.A.

    2007-01-01

    Full text of publication follows: A new theoretical model is developed for the investigations of cascade and sub-cascade formation in fusion structural materials under fast neutron irradiation at high primary knock atom (PKA) energies. Under 14 MeV neutron irradiation especially of light fusion structural materials such as Be, C, SiC materials PKA will have the energies up to 1 MeV. At such high energies it is very difficult to use the Monte Carlo or molecular dynamic simulations. The developed model is based on the analytical consideration of elastic collisions between displaced moving atoms into atomic cascades produced by a PKAs with the some kinetic energy obtained from fast neutrons. The Tomas-Fermy interaction potential is used for the describing of elastic collisions between moving atoms. The suggested model takes into account also the electronic losses for moving atoms between elastic collisions. The self consistent criterion for sub-cascade formation is suggested here which is based on the comparison of mean distance between two consequent PKA collisions and size of sub-cascade produced by PKA. The analytical relations for the most important characteristics of cascades and sub-cascade are determined including the average number of sub-cascades per one PKA in the dependence on PKA energy, the distance between sub-cascades and the average cascade and sub-cascade sizes as a function of PKA energy. The developed model allows determining the total numbers, distribution functions of cascades and sub-cascades in dependence on their sizes and generation rate of cascades and sub-cascades for different fusion neutron energy spectra. Based on the developed model the numerical calculations for main characteristics of cascades and sub-cascades in different fusion structural materials are performed using the neutron flux and PKA energy spectra for fusion reactors: ITER and DEMO. The main characteristics for cascade and sub-cascade formation are calculated here for the

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

    International Nuclear Information System (INIS)

    Murakami, I.; Janev, R.K.; Kato, T.; Yan, J.; Sato, H.; Kimura, M.

    2004-08-01

    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 Li 3+ 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)

  5. Offsetting the difficulties of the molecular model of atomic collisions in the intermediate velocity range

    International Nuclear Information System (INIS)

    Errea, L.F.; Mendez, L.; Riera, A.

    1991-01-01

    To offset the defective behavior of the molecular method of atomic collisions at intermediate energies, we propose a method to approximate the probability flux towards continuum and discrete states not included in the molecular basis. We check the degree of accuracy and limitations of the method for a model case where transition probabilities can be calculated exactly. An application to the benchmark case of He + +H + collisions is also presented, and yields complementary information on the properties of this approach

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

    OpenAIRE

    KHABIBULLAEV, P. K.

    2014-01-01

    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.

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

    International Nuclear Information System (INIS)

    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)

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

    International Nuclear Information System (INIS)

    Tawara, H.

    1990-08-01

    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

  9. Non-Markovian decay of a three-level cascade atom in a structured reservoir

    International Nuclear Information System (INIS)

    Dalton, B.J.; Garraway, B.M.

    2003-01-01

    The dynamics of a three-level atom in a cascade (or ladder) configuration with both transitions coupled to a single structured reservoir of quantized electromagnetic field modes is treated using Laplace transform methods applied to the coupled amplitude equations. In this system two-photon excitation of the reservoir occurs, and both sequences for emitting the two photons are allowed and included in the theory. An integral equation is found to govern the complex amplitudes of interest. It is shown that the dynamics of the atomic system is completely determined in terms of reservoir structure functions, which are products of the mode density with the coupling constant squared. This dependence on reservoir structure functions rather than on the mode density or coupling constants alone, shows that it may be possible to extend pseudomode theory to treat multiphoton excitation of a structured reservoir--pseudomodes being introduced in one-one correspondence with the poles of reservoir structure functions in the complex frequency plane. A general numerical method for solving the integral equations based on discretizing frequency space, and applicable to different structured reservoirs such as high-Q cavities and photonic band-gap systems, is presented. An application to a high-Q-cavity case with identical Lorentzian reservoir structure functions is made, and the non-Markovian decay of the excited state shown. A formal solution to the integral equations in terms of right and left eigenfunctions of a non-Hermitian kernel is also given. The dynamics of the cascade atom, with the two transitions coupled to two separate structured reservoirs of quantized electromagnetic field modes, is treated similarly to the single structured reservoir situation. Again the dynamics only depends on reservoir structure functions. As only one sequence of emitting the two photons now occurs, the integral equation for the amplitudes can be solved analytically. The non-Markovian decay of the

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

    International Nuclear Information System (INIS)

    Kuzminski, J.

    1980-01-01

    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)

  11. 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...

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

    International Nuclear Information System (INIS)

    Crandall, D.H.; Hafford, P.M.; Itikawa, Y.

    1981-04-01

    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

  13. Interaction of primary cascades with different atomic grain boundaries in α-Zr: An atomic scale study

    Energy Technology Data Exchange (ETDEWEB)

    Hatami, F.; Feghhi, S.A.H., E-mail: a.feghhi@gmail.com; Arjhangmehr, A., E-mail: ms.arjangmehr@gmail.com; Esfandiarpour, A.

    2016-11-15

    In this paper, we investigate interaction of primary cascades with grain boundaries (GBs) in α-Zr using the atomistic-scale simulations, and intend to study the influence of different GB structures on production and evolution of defects on picosecond timescale. We observe that, contrary to the previous results in cubic metals, GBs in α-Zr are not necessarily biased toward interstitials, and can preferentially absorb vacancies. Further, in terms of energetic and kinetic behavior, we find that GBs act as defect sinks due to the substantial reduction of defect formation energies and migration barriers in close vicinity of the GB center, with either a preference toward interstitials or vacancies which depends on the atomic structure of the boundaries. Finally, using continuous ion bombardment, we investigate the stability of GBs in sever irradiation environment. The results indicate that the sink strength and efficiency of boundaries varies with increasing accumulated defects in GB region. - Highlights: • GBs in hcp Zr are not necessarily biased toward interstitials. • Defect content within bulk depends on PKA energy, PKA distance, and GB texture. • Defect formation energies and diffusion barriers decrease in close vicinity of GBs. • GBs become locally unstable due to absorption of excess defects in ion bombardment.

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

    International Nuclear Information System (INIS)

    Valentini, J.J.

    1991-01-01

    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 → H 2 R reactions where RH is CH 4 , C 2 H 6 , or C 3 H 8 , (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

  15. Assessment of ion-atom collision data for magnetic fusion plasma edge modelling

    International Nuclear Information System (INIS)

    Phaneuf, R.A.

    1990-01-01

    Cross-section data for ion-atom collision processes which play important roles in the edge plasma of magnetically-confined fusion devices are surveyed and reviewed. The species considered include H, He, Li, Be, C, O, Ne, Al, Si, Ar, Ti, Cr, Fe, Ni, Cu, Mo, W and their ions. The most important ion-atom collision processes occurring in the edge plasma are charge-exchange reactions. Excitation and ionization processes are also considered. The scope is limited to atomic species and to collision velocities corresponding to plasma ion temperatures in the 2-200 eV range. Sources of evaluated or recommended data are presented where possible, and deficiencies in the data base are indicated. 42 refs., 1 fig., 4 tabs

  16. Absorption of resonant electromagnetic radiation in electron-atom collisions

    International Nuclear Information System (INIS)

    Arslanbekov, T.U.; Pazdzerskii, V.A.; Usachenko, V.I.

    1986-01-01

    Nonrelativistic quantum theory is used to study the possibility of amplification of electromagnetic radiation in forced braking scattering of an electron beam on atoms. The interaction of the atom with the electromagnetic field is considered in the resonant approximation. Cases of large and small detuning from resonance are considered. It is shown that for any orientation of the electron beam relative to the field polarization vector, absorption of radiation occurs, with the major contribution being produced by atomic electrons

  17. Pseudo potentials and model potentials in atomic collisions

    International Nuclear Information System (INIS)

    Reyes, O.; Jouin, H.; Fuentealba, P.

    1988-01-01

    In this work, it is discussed the main differences between the use of pseudo-potentials and model potentials in collision problems . It is shown the potential energy curves for distinct systems obtained with both kinds of potentials. (A.C.A.S.) [pt

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

    International Nuclear Information System (INIS)

    Garibotti, C.R.

    1988-01-01

    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.) [pt

  19. Emission of H- fragments from collisions of OH+ ions with atoms and molecules

    International Nuclear Information System (INIS)

    Juhasz, Z.; Sulik, B.

    2010-01-01

    Compete text of publication follows. Detailed measurement of the kinematics of positive fragment ions from molecular collisions pro-vide useful information about the collision dynamics (see e.g. and references therein). In the present work, we turn our attention to negative fragments. Double differential emission spectra of negative charged particles have been measured in collisions of OH + ions with gas jets of Ar atoms and acetone (CH 3 -CO-CH 3 ) molecules at 7 keV impact energy. Among the emitted electrons, a relatively strong contribution of H - ions has been observed in both collision systems. According to a kinematic analysis, the observed H - ions were produced in close atom-atom collisions. For acetone, these ions originated from both the projectile and the target. The present ion impact energy range falls in the distal region of the Bragg peak. Therefore, a non negligible H - production in biological tissues could be relevant for ion therapy and for radiolysis in general. The present experiments were conducted at the 14.5 GHz Electron Cyclotron Resonance (ECR) ion source of the ARIBE facility, at the Grand Accelerateur National d'Ions Lourds (GANIL) in Caen, France. The molecular OH + ions were produced by introducing water vapor in the ECR plasma chamber. The extracted ions were collimated to a diameter of 2.5 mm before entering the collision chamber. In its center, the OH + projectiles crossed an effusive gas jet of either argon atoms or acetone molecules. In the collision area, the density of the gas target was typically of 10 13 cm -3 . The electrons and negative ions produced in the collision were detected by means of a single-stage spectrometer consisting of an electrostatic parallel-plate analyzer. Spectra taken at 30 deg observation angle are shown in Figure 1. Contributions from H - appear in clearly visible peaks. Kinematics shows that the peak at 410 eV in both panels is due emission of H - ions moving with nearly the projectile velocity. An H

  20. Atomic rubidium, the workhorse of theoretical collision physics

    NARCIS (Netherlands)

    Verhaar, B.; van Kempen, E.; Kokkelmans, S.J.J.M.F.

    2008-01-01

    Since the first realizations of Bose-Einstein condensates in ultracold atomic gases in 1995, the 85Rb and 87Rb atomic species have acted as the workhorses of experimental developments in this field. Parallel to and partly preceding this work the same isotopes figured also as workhorses for

  1. Orbital alignment effects in near-resonant Rydberg atoms-rare gas collisions

    International Nuclear Information System (INIS)

    Isaacs, W.A.; Morrison, M.A.

    1993-01-01

    Recent experimental and theoretical studies of near-resonant energy transfer collisions involving rare-gas atoms and alkali or alkaline earth atoms which have been initially excited to an aligned state via one or more linearly polarized rasters have yielded a wealth of insight into orbital alignment and related effects. We have extended this inquiry to initially aligned Rydberg states, examining state-to-state and alignment-selected cross sections using quantum collision theory augmented by approximations appropriate to the special characteristics of the Rydberg state (e.g., the quasi-free-electron model and the impulse approximation)

  2. Charge transfer and excitation in high-energy ion-atom collisions

    International Nuclear Information System (INIS)

    Schlachter, A.S.; Berkner, K.H.; McDonald, R.J.

    1986-11-01

    Coincidence measurements of charge transfer and simultaneous projectile electron excitation provide insight into correlated two-electron processes in energetic ion-atom collisions. Projectile excitation and electron capture can occur simultaneously in a collision of a highly charged ion with a target atom; this process is called resonant transfer and excitation (RTE). The intermediate excited state which is thus formed can subsequently decay by photon emission or by Auger-electron emission. Results are shown for RTE in both the K shell of Ca ions and the L shell of Nb ions, for simultaneous projectile electron loss and excitation, and for the effect of RTE on electron capture

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

    International Nuclear Information System (INIS)

    Roberts, David C.

    2002-01-01

    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

  4. Atomic collisions by neutrons-induced charged particles in water, protein and nucleic acid

    International Nuclear Information System (INIS)

    Bergman, R.

    1976-01-01

    The action of slow charged particles is peculiar in that atomic collisions are commonly invlolved. In atomic collisions, which are rare events when fast particles interact with matter, displacement of atoms and chemical bond-breakage is possible. Sufficiently energetic neutrons generate charged recoil particles in matter. Some of these are slow as compared to orbital electrons, but the energy transferred to such slow particles is generally relatively small. Yet, it contributes significantly to the dose absorbed from 0.1-30 keV neutrons. In tissue all recoils induced by neutrons of less than 30 keV are slow, and above 0.1 keV the absorbed dose due to collisiondominates over that due to capture reactions. The aim of the present paper is to identify those intervals of neutron energy in which atomic collision damage is most probable in living matter. The results of calculations presented here indicate that atomic collisions should be most significant for 0.5-3 keV neutrons. (author)

  5. Binary encounter electron production in ion-atom collisions

    International Nuclear Information System (INIS)

    Grabbe, S.; Bhalla, C.P.; Shingal, R.

    1993-01-01

    The binary encounter electrons are produced by hard collisions between the target electrons and the energetic projectiles. Richard et al. found the measured double differential cross section for BEe production at zero degree laboratory scattering angle, in collisions of F q+ with H 2 and He targets, to increase as the charge state of the projectile was decreased. The binary encounter electron production has recently been a subject of detailed investigations. We have calculated the differential elastic scattering cross sections of electrons from several ions incorporating the exchange contribution of the continuum and the bound orbitals in addition to the static potential. The double differential binary encounter electron production cross sections are presented using the impulse approximation

  6. Double electron transfer in ion-atom collisions

    International Nuclear Information System (INIS)

    Martinez, A.E

    1990-01-01

    Continuum distorted wave (CDW) and CDW-EIS (electron-ion scattering) approximations are used to study the resonant double capture by collision of alpha particles on He targets for intermediate and high energies. Calculations of total cross-sections based on the Independent Event Approximation are presented. A good agreement with experimental results was found, even without the inclusion of the dynamic and angular correlation of captured electrons. (Author). 11 refs., 1 fig

  7. Nonlinear effect of pion production in collisions of atomic nuclei

    International Nuclear Information System (INIS)

    Grin', Yu.T.

    1982-01-01

    The phenomenon of pion production in relativistic nucleon-nucleus and nucleus-nucleus interactions is investigated. The present experimental data are analyzed. It is shown that average multiplicity of pions in the (p, C), (C, C) collision reactions with the momentum p=4.2 GeV/cA and (p, Ar), (Ar, KCl) with the momentum p=2.3 GeV/cA non-linearly depends on the nucleon number. The calculated values of average multiplicity of negative pions per one nucleon of nucleus-pro ectile, probability of pion production and number of nucleon interactions for the investigated reactions are presented as a table. A comparative analysis of average multiplicities of pions per nucleon-participant in the nucleon-nucleus and nucleus-nucleus reactions at the p=2.3 GeV/cA momentum for argon and at the p=4.2 GeV/cA for carbon reveals that decrease of multiplicity by 30-35% is observed in nucleus-nucleus collision. Non-linearity is associated with decrease of effective interaction of each incident nucleon in the collision of nuclei as compared with the number of nucleon interactions in the ''elementary'' nucleon-nucleus reaction. Knock-out of nucleons from the colliding nuclei is the most probable reason for the decrease of the number of interactions

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

    Energy Technology Data Exchange (ETDEWEB)

    Paul, H; Bauer, P; Semrad, D [ed.; Johannes Kepler Univ., Linz (Austria). Inst. fuer Experimentalphysik

    1996-12-31

    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).

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

    International Nuclear Information System (INIS)

    Paul, H.; Bauer, P.; Semrad, D.

    1995-01-01

    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)

  10. Charge exchange of excited mesic atoms of hydrogen isotopes in triple collisions with molecules

    International Nuclear Information System (INIS)

    Men'shikov, L.I.; Ponomarev, L.I.

    1985-01-01

    At high densities of deuterium-tritium mixture the probability for the occurrence of the isotope-exchange reaction (dμ)/sub n/+t → d+(tμ)/sub n/ from the excited states of n mesic atoms of deuterium is high in the triple collisions of mesic atoms with the molecules of hydrogen isotopes. This reaction should be taken into account in describing the kinetics of muon catalysis

  11. Correlations and polarization in electronic and atomic collisions and (e,2e) reactions

    International Nuclear Information System (INIS)

    Teubner, P.J.O.; Weigold, E.

    1992-01-01

    This volume contains the invited papers presented at the Sixth International Symposium on Correlations and Polarization in Electronic and Atomic collisions and (e,2e) Reactions held at Flinders University, Adelaide, Australia from 18-21 July, 1991. This symposium was a satellite meeting to the XVII International Conference on the Physics of Electronic and Atomic Collisions (ICPEAC) held in Brisbane, Australia. It follows a tradition of satellite meetings on (e,2e) collisions and on correlation and polarization in electronic and atomic collisions held in association with previous ICPEACs. The subject matter of this symposium covered that of the previous meeting at Hoboken, USA (1989) on correlation and polarization phenomena as well as that of the previous meeting at the University of Maryland (1989) on (e,2e) collisions. In addition it extended the scope to include some discussion of (e,3e), (γ,eγ) and (γ,2γ) coincidence measurements. The discussion of the current rapid advances in coincidence experiments, correlations and polarization measurements and related theoretical developments brought together 100 scientist from many countries with broad interdisciplinary backgrounds. The symposium stressed the common threads weaving through all these areas of research. (Author)

  12. Few electron transitions in atomic collisions. Final report, September 1, 1992--December 31, 1995

    Energy Technology Data Exchange (ETDEWEB)

    McGuire, J.

    1997-04-01

    During the past three years we have evaluated probabilities and cross sections for few and multiple electron transitions in atomic collisions. Our studies included interactions of atoms and molecules with incident protons, bare ions, electrons, positrons, anti-protons, ions carrying electrons and photons. We also: studied the inter-relation between collisions with charged particles and collisions involving various processes with photons. This work has complemented various studies of collisions of atoms with charged particles and with photons as well as more general efforts to understand the nature of multi-electron systems. Our aim has been to begin with relatively simple two electron systems and to focus on fast processes in which there is too little time for complicated processes to occur. We have used a variety of computational techniques, but we emphasize those appropriate for fast collisions in which we hope to obtain insight into the physical nature of the process itself. We generally considered systems in which experimental data was available.

  13. Hyperthermal (10-500 eV) collisions of noble gases with Ni(100) surface. Comparison between light and heavy atom collisions

    International Nuclear Information System (INIS)

    Kim, C.

    1995-01-01

    Collisional events between 10-500 eV atomic beams (He, Ne, Ar, Kr, and Xe) and a Ni(100) surface are investigated by the classical trajectory method. The calculation employs a molecular dynamics approach combined with a Langevin method for treating energy dissipation to infinite solid. We find that low energy collisions of heavy atoms (Xe and Kr) are characterized by extensive many-body interactions with top layer surface atoms. On the other hand, light atom (Ne and He) collisions can be approximated as a sequence of binary collisions even at these energies. Such a difference in the collisional nature gives rise to the following consequences. Low energy heavy atoms transfer energy mostly to the surface atoms during 45 angle collision. They scatter from the surface with a narrow angular distribution centered in a supraspecular direction. The ratio of the scattered to incident particle energy rapidly decreases with increasing beam energy of heavy atoms. The sputtering yield for Ni atoms by heavy atom bombardment increases quite linearly with beam energy, which is attributed to a linear proportionality between the beam energy and the energy transfered to a surface. Near the threshold energy sputtering can occur more efficiently by light atom bombardment. The energy transfer ratio to solid continuously increases with beam energy for light atoms. For heavy projectiles, on the other hand, this ratio reaches a maximum at the energy of ca, 100 eV, above which it stays nearly constant but slightly decreases. ((orig.))

  14. Direct excitation in heavy atom collisions: A propensity rule for charge cloud orientation

    International Nuclear Information System (INIS)

    Andersen, N.; Aarhus Univ.; Nielsen, S.E.; Royal Danish School of Pharmacy, Copenhagen)

    1985-01-01

    The Massey Criterion prescribes maximum electronic excitation of atoms in heavy particle collisions for collision velocities v where Δε a/ℎv ≅ π. Here Δε is the energy defect and a is the effective interaction length. Experiments with planar symmetry have revealed a preferred way of rotation of the excited charge cloud in this velocity region. We demonstrate by analysis of a simple, yet realistic model why excitation favors states with a specific orientation. A general propensity rule is derived and its validity evaluated for a specific case, the Na-He system. Implications for future experiments are pointed out. In particular, the propensity rule predicts very different collisions behaviors of oppositely oriented atoms, as prepared e.g. by circular polarized laser light. (orig.)

  15. Negative ion formation in collisions involving excited alkali atoms

    International Nuclear Information System (INIS)

    Cheret, M.

    1988-01-01

    Ion-pair production is considered as the prototype of the crossing problem between potential energy curves. In general an alkali atom is one of the reactants the other being an halogen, hydrogen atom or molecule. Experimental results are generally analyzed in the framework of the Landau-Zener-Stuekelberg theory, ionization potential and electron affinity, being the most important parameters. In order to vary these parameters over a wide range two experimental works have been devoted to systems of excited alkali atoms colliding with ground state alkali atoms. In the first study Rb atoms are excited to various ns or nd states from Rb(5d) to Rb(9s) in a cell. The second study is devoted to the Na(3p)-Na(3s) system, in this study also the possibility of creating excited negative ions (Na - (3s3p)) has been investigated. These results are presented and analyzed. Finally further developments of the subject are suggested. 17 refs.; 8 figs.; 1 table

  16. Application of a distorted wave model to electron capture in atomic collisions

    International Nuclear Information System (INIS)

    Deco, G.R.; Martinez, A.E.; Rivarola, R.D.

    1988-01-01

    In this work, it is presented the CDW-EIS approximation applied to the description of processes of electron capture in ion-atom collisions. Differential and total cross sections are compared to results obtained by other theoretical models, as well as, to experimental data. (A.C.A.S.) [pt

  17. New analytical treatment for a kind of two dimensional integrals in ion-atom collisions

    International Nuclear Information System (INIS)

    Yang Qifeng; Kuang Yurang

    1994-01-01

    A kind of two-dimensional integrals, separated from two-center matrix elements in ion-atom collisions, is analytically integrated by introducing the Laplace transform into the integrals and expressed by the modified Bessel functions. The traditional Feynman transform is very complicated for this kind of more general integrals related to the excited state capture

  18. 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,

  19. Electron capture in slow collisions of multicharged ions with hydrogen atoms using merged beams

    International Nuclear Information System (INIS)

    Havener, C.C.; Nesnidal, M.P.; Porter, M.R.; Phaneuf, R.A.

    1991-01-01

    Absolute total electron-capture cross-section mesurements are reported for collisions of O 3+ and O 4+ with atomic hydrogen in the energy range 1-1000 eV /amu using merged beams. The data are compared with available coupled-states theoretical calculations. (orig.)

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

    International Nuclear Information System (INIS)

    Woerlee, P.H.

    1979-01-01

    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.)

  1. Electron capture in ion atom and ion-ion collisions

    International Nuclear Information System (INIS)

    Barat, M.

    1986-01-01

    Electron capture (EC) by positive ions in collision with various targets has remained one of the most important subjects of research since the early 30's. From a theoretical point of view, EC is obviously a coupled 3-body problem: at least two cores and an active electron that jumps between them. Practical interest in EC arose in a variety of fields. Recently a renewed interest arose from the physics of thermonuclear fusion, where capture by highly charged ionic impurities were found to be an important process in tokamak devices. For that reasons, a number of reviews were devoted to this subject during the past years, including lectures given in various NATO advanced science institutes. The aim of this lecture is not at all to add a new review to this list, but (i) to summarize the very basis of the present theoretical approaches at low and moderate collision energy, (ii) to pinpoint some crucial difficulties in the theoretical treatment, (iii) to select specific examples which, to the taste of the author, reflect some present practical interest, or some significant advances. 48 references, 38 figures, 1 table

  2. Positron production in heavy ion-atom collisions

    International Nuclear Information System (INIS)

    Kienle, P.

    1985-08-01

    Following an introduction into the concept of an atom with an overcritical field, established by a nucleus with a charge larger than 173, the spontaneous positron emission from such an atom with an 1s binding energy exceeding 2mc 2 is presented. Such a process, in which an electron is bound and a monoenergetic positron emitted turns the neutral into a charged vacuum. In a U-U di-nuclear system (Z=184) the spontaneous positron emission proceeds with an energy of about 300 keV corresponding to a decay time of 3x10 -19 sec. (orig./WL)

  3. Formation of Rydberg states in fast ion-atom collisions

    International Nuclear Information System (INIS)

    Schneider, D.; Kanter, E.P.; Vager, Z.; Gemmell, D.; Koch, P.; Mariani, D.; Van de Water, W.

    1983-01-01

    Previous results from beam-foil spectroscopy and from experiments using field ionization techniques have shown that a significant fraction of fast ionic projectiles traversing solid targets can be excited to high Rydberg states. We report an experimental investigation of Rydberg states formed in atomic and molecular ion beams (MeV) emerging from thin-carbon foils. Different field arrangements, including μ-wave fields, have been applied to study the effects of field ionization. The yields of electrons produced via field ionization are compared for different projectile atoms and molecules

  4. Ionization in positron- and positronium- collisions with atoms and molecules

    Energy Technology Data Exchange (ETDEWEB)

    Laricchia, G; Brawley, S; Cooke, D A; Murtagh, D J; Williams, A I [UCL Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Koever, A [permanent address: ATOMKI, Institute for Nuclear Research, Debrecen (Hungary)

    2009-11-15

    Recent progress in the experimental study of positron- and positronium-induced ionization of atoms and molecules is outlined. Investigations include integral and differential cross-sections, as well as formation of positronium in the first excited state. Future prospects are discussed.

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

    International Nuclear Information System (INIS)

    Combes, J.M.; Tip, A.

    1983-02-01

    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

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

    CERN Multimedia

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

  7. Reactive Collisions and Interactions of Ultracold Dipolar Atoms

    Science.gov (United States)

    2014-10-29

    Kotochigova Department of Physics, Temple University, Philadelphia, PA 19122-6082 I. COLLISIONAL INTERACTIONS OF RARE- EARTH MAGNETIC ATOMS The breakthroughs...technologies, it was not previously implemented, possibly owing to the misconception that molecular ions predominantly undergo charge-exchange reactions leading

  8. Coupled-channels calculations of excitation and ionization in ion-atom collisions

    International Nuclear Information System (INIS)

    Martir, M.H.

    1981-01-01

    A numerical method has been used to compute excitation and ionization cross sections for ion-atom collisions. The projectile is treated classically and follows a straight line, constant velocity path (unless indicated otherwise). The wave function that describes the atom is expanded about the target in a truncated Hilbert space. The interaction between the projectile and the target atom is treated as a time dependent perturbation. A unitary time development operator, U, propagates the wave function from a time prior to the collision to a time after the collision in small time steps. Contrary to first-order theories, coupling between states is allowed. This method has been improved so that any number of partial waves can be included in the wave function expansion. This method has been applied to study negatively charged projectiles. Cross sections are obtained for collisions of antiprotons on atomic hydrogen (30 keV to 372 keV) and compared with cross sections of protons on atomic hydrogen to explore the Z/sub P/ dependence. The antiproton-hydrogen results were converted into electron-hydrogen values with E/sub e/ = E/sub P/(m/sub e//m/sub P/) (15 eV to 200 eV) and compared to experimental values. The method is then applied to study vacancy production from the L-shell. The partial wave convergence of the cross sections was carefully studied for s through g waves. Collisions between protons (and alpha-particles) and argon are studied to explore the Z/sub P/ dependence of the cross sections. The cross section ratio sigma(α)/(4sigma(p)) is compared to experiment

  9. Projectile ionization in fast heavy-ion--atom collisions

    International Nuclear Information System (INIS)

    Schneider, D.; Prost, M.; Stolterfoht, N.; Nolte, G.; Du Bois, R.

    1983-01-01

    Electron emission following the ionization of projectile ions has been investigated systematically in collisions with Ne/sup q/+ and Ar/sup q/+ ions at several hundred MeV incident on different target gases. The projectile electrons are concentrated within one maximum, the electron-loss peak (ELP). The variation of the shape and intensity of the ELP with the projectile energy, its charge state, the observation angle, and the target gas has been measured. Theoretical predictions which are based on the binary-encounter approximation show, in general, good agreement with the experimental data. The contributions of the different subshells to the ELP are deduced. It is shown that electronic screening of the target nucleus plays an important role in the ionization process of the projectile ions

  10. Auto transfer to Rydberg states during ion-atom collisions

    International Nuclear Information System (INIS)

    Bachau, H.; Harel, C.; Barat, M.; Roncin, P.; Bordenave-Montesquieu, A.; Moretto-Capelle, P.; Benoit-Cattin, P.; Gleizes, A.; Benhenni, M.

    1993-01-01

    Electron capture by slow multiply charged ions colliding on rare-gas targets is known to populate highly excited states of the projectile. On the basis of experimental measurement of energy and angle differential cross-sections we have shown that capture to a resonant doubly excited state may lead to Autoionizing Double Capture (ADC) as well as to True Double Capture (TDC). In this model TDC appears as a two step post-collisional process, the state populated by the collision decays to (or delutes into) a dense adjacent Rydberg series, followed by radiative deexcitation of the inner electron of the (3,n) Rydberg states. We report here new experimental observations in electron spectra measured in N 7+ +He. Auto transfer to Rydber states has also important consequences on the determination of the lifetime of the autoionizing states, some discrepancies between theoretical width values for low N 5+ (4,4) resonant states will be discussed and partially resolved

  11. Photon emission spectroscopy of ion-atom collisions

    International Nuclear Information System (INIS)

    Nystroem, B.

    1995-10-01

    Emission cross sections for the 1snp 1 P 1 -levels have been measured by photon emission spectroscopy for the collision systems He + + He at 10 keV and He 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 q+ (q=7-9) and Xe q+ (q=5-9) colliding with Helium and Argon. The Lifetimes of 3p 2 P-levels in Na-like Nb are reported together with lifetime for the 3s3p 3 P 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

  12. 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.

  13. Resonance effects in projectile-electron loss in relativistic collisions with excited atoms

    International Nuclear Information System (INIS)

    Voitkiv, A B

    2005-01-01

    The theory of electron loss from projectile-ions in relativistic ion-atom collisions is extended to the case of collisions with excited atoms. The main feature of such collisions is a resonance which can emerge between electron transitions in the ion and atom. The resonance becomes possible due to the Doppler effect and has a well-defined impact energy threshold. In the resonance case, the ion-atom interaction is transmitted by the radiation field and the range of this interaction becomes extremely long. Because of this the presence of other atoms in the target medium and the size of the space occupied by the medium have to be taken into account and it turns out that microscopic loss cross sections may be strongly dependent on such macroscopic parameters as the target density, temperature and size. We consider both the total and differential loss cross sections and show that the resonance can have a strong impact on the angular and energy distributions of electrons emitted from the projectiles and the total number of electron loss events

  14. First-principles dynamics treatment of light emission in collisions between alkali-metal atom and noble-gas atom collisions at 10keV

    Science.gov (United States)

    Pacheco, Alexander B.; Reyes, Andrés; Micha, David A.

    2006-12-01

    Collision-induced light emission during the interaction of an alkali-metal atom and a noble-gas atom is treated within a first-principles, or direct, dynamics approach that calculates a time-dependent electric dipole for the whole system, and spectral emission cross sections from its Fourier transform. These cross sections are very sensitive to excited diatomic potentials and a source of information on their shape. The coupling between electronic transitions and nuclear motions is treated with atomic pseudopotentials and an electronic density matrix coupled to trajectories for the nuclei. A recently implemented pseudopotential parametrization scheme is used here for the ground and excited states of the LiHe system, and to calculate state-to-state dipole moments. To verify the accuracy of our new parameters, we recalculate the integral cross sections for the LiHe system in the keV energy regime and obtain agreement with other results from theory and experiment. We further present results for the emission spectrum from 10keV Li(2s)+He collisions, and compare them to experimental values available in the region of light emitted at 300-900nm .

  15. 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.

  16. Muon transfer rates in collisions of hydrogen isotope mesic atoms on 'bare' nuclei. Multichannel adiabatic approach

    International Nuclear Information System (INIS)

    Korobov, V.I.; Melezhik, V.S.; Ponomarev, L.I.

    1992-01-01

    A numerical scheme for solving the problem of slow collisions in the three-body adiabatic approach is applied for calculation of muon transfer rates in collisions of hydrogen isotope atoms on bare nuclei. It is demonstrated that the multichannel adiabatic approach allows one to reach high accuracy results (∼3%) estimating the cross sections of charge transfer processes which are the best ones up to date. The method is appliable in a wide range of energies (0.001-50 eV) which is of interest for analysis of muon catalysed fusion experiments. 20 refs.; 3 figs.; 5 tabs

  17. Measurement of product rotational alignment in associative-ionization collisions between polarized Na(3p) atoms

    International Nuclear Information System (INIS)

    Wang, M.; de Vries, M.S.; Weiner, J.

    1986-01-01

    We have studied the effect of reactant Na(3p) polarization on the rotational angular momentum alignment of product Na 2 + ions arising from associative-ionization (AI) collisions. Our results show that sensitivity of the AI rate constant to initial atomic polarization persists even when all hyperfine states are populated with broadband (3 cm -1 ) pulsed laser excitation of Na( 2 P/sub 3/2/) and that the spatial distribution of product rotational angular momentum vectors is anisotropic. We discuss a qualitative description of the collision process consistent with our measurements which indicates that sigma-orbital symmetry is preferred to π-orbital symmetry as the colliding partners approach

  18. Influences of atom Ar on Ar at C60 + Ar at C60 collisions

    International Nuclear Information System (INIS)

    Zhao Qiang; Zhou Hongyu; Zhang Fengshou

    2007-01-01

    A semi-emperical molecular dynamics model was developed. The central collisions of C 60 + C 60 and Ar at C 60 + Ar at C 60 at the same incident energy were investigated within this model. The fullerene dimers could be formed by a self-assembly of C 60 fullerene, and the new fullerene structure like 'peanut' could be formed by a self-assembly of Ar at C 60 . It was found that atom Ar had a great effect on the collision of Ar at C 60 + Ar at C 60 . (authors)

  19. Comment on the classical-trajectory Monte Carlo method for ion-atom collisions

    International Nuclear Information System (INIS)

    Cohen, J.S.

    1982-01-01

    It is shown that the procedure described by Olson and Salop for classical-trajectory Monte Carlo treatment of ion-atom collisions does not provide a uniform statistical distribution of all the parameters defining the initial conditions of a trajectory. Impact-ionization and charge-transfer cross sections for collisions of H + with H at H energies between 25 and 600 keV are recalculated eliminating this failing and compared with those obtained using the procedure of Olson and Salop and with experimental results

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

    International Nuclear Information System (INIS)

    Runge, Serge.

    1980-12-01

    The relative cross-sections of ionizing collisions between He + He and He + Ne atoms, have been studied, the helium being excited in a state (3 1 p) by a laser beam. The results obtained made it possible (a) to reveal in a direct manner the production of molecular ions He 2 + 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 (3 1 P) + Ne collision, despite the very short life of the He (3 1 P) excited state (1.7 ns). The production of He 2 + ions from an He (3 1 P) + He collision sets an upper limit to the appearance potential of these ions. The experimental study of the associative ionization in the He (3 1 P) + 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 [fr

  1. Auto transfer to Rydberg states during ion-atom collisions

    Energy Technology Data Exchange (ETDEWEB)

    Bachau, H.; Harel, C. (Laboratoire des Collisions Atomiques, Unite Propre de Recherche 260 du CNRS, Universite Bordeaux I, 351 Cours de la Liberation, 33405 Talence (France)); Barat, M.; Roncin, P. (Laboratoire des Collisions Atomiques et Moleculaires, Unite associee 281 du CNRS, Universite de Paris Sud, Batiment 351, 91405 Orsay (France)); Bordenave-Montesquieu, A.; Moretto-Capelle, P.; Benoit-Cattin, P.; Gleizes, A.; Benhenni, M. (IRSAMC, Unite associee 770 du CNRS, Universite Paul Sabatier, 118 route de Narbonne, 31062 Toulouse (France))

    1993-06-05

    Electron capture by slow multiply charged ions colliding on rare-gas targets is known to populate highly excited states of the projectile. On the basis of experimental measurement of energy and angle differential cross-sections we have shown that capture to a resonant doubly excited state may lead to Autoionizing Double Capture (ADC) as well as to True Double Capture (TDC). In this model TDC appears as a two step post-collisional process, the state populated by the collision decays to (or delutes into) a dense adjacent Rydberg series, followed by radiative deexcitation of the inner electron of the (3,n) Rydberg states. We report here new experimental observations in electron spectra measured in [ital N][sup 7+]+[ital He]. Auto transfer to Rydber states has also important consequences on the determination of the lifetime of the autoionizing states, some discrepancies between theoretical width values for low [ital N][sup 5+](4,4) resonant states will be discussed and partially resolved.

  2. Benchmark Calculations for Electron Collisions with Complex Atoms

    International Nuclear Information System (INIS)

    Zatsarinny, Oleg; Bartschat, Klaus

    2014-01-01

    The B-spline R-matrix (BSR) approach [1,2] is based on the non-perturbative close-coupling method. As such it is, in principle, based on an exact expansion of the solution of the time-independent Schrödinger equation, as an infinite sum/integral of N-electron target states coupled to the wave function of the scattering projectile. The N-electron target states, again, can in principle be calculated with almost arbitrary accuracy using sufficiently large configuration-interaction expansions and the correct interaction hamiltonian. In practice, of course, the infinite expansions have to be cut off in some way and the exact hamiltonian may not be available. In the collision part of the BSR method, the integral over the ionization continuum and the infinite sum over high-lying Rydberg states are replaced by a finite sum over square-integrable pseudo-states. Also, a number of inner shells are treated as (partially) inert, i.e., a minimum number of electrons are required in those subshells.

  3. Many-electron model for multiple ionization in atomic collisions

    International Nuclear Information System (INIS)

    Archubi, C D; Montanari, C C; Miraglia, J E

    2007-01-01

    We have developed a many-electron model for multiple ionization of heavy atoms bombarded by bare ions. It is based on the transport equation for an ion in an inhomogeneous electronic density. Ionization probabilities are obtained by employing the shell-to-shell local plasma approximation with the Levine and Louie dielectric function to take into account the binding energy of each shell. Post-collisional contributions due to Auger-like processes are taken into account by employing recent photoemission data. Results for single-to-quadruple ionization of Ne, Ar, Kr and Xe by protons are presented showing a very good agreement with experimental data

  4. Many-electron model for multiple ionization in atomic collisions

    Energy Technology Data Exchange (ETDEWEB)

    Archubi, C D [Instituto de AstronomIa y Fisica del Espacio, Casilla de Correo 67, Sucursal 28 (C1428EGA) Buenos Aires (Argentina); Montanari, C C [Instituto de AstronomIa y Fisica del Espacio, Casilla de Correo 67, Sucursal 28 (C1428EGA) Buenos Aires (Argentina); Miraglia, J E [Instituto de AstronomIa y Fisica del Espacio, Casilla de Correo 67, Sucursal 28 (C1428EGA) Buenos Aires (Argentina)

    2007-03-14

    We have developed a many-electron model for multiple ionization of heavy atoms bombarded by bare ions. It is based on the transport equation for an ion in an inhomogeneous electronic density. Ionization probabilities are obtained by employing the shell-to-shell local plasma approximation with the Levine and Louie dielectric function to take into account the binding energy of each shell. Post-collisional contributions due to Auger-like processes are taken into account by employing recent photoemission data. Results for single-to-quadruple ionization of Ne, Ar, Kr and Xe by protons are presented showing a very good agreement with experimental data.

  5. Effects of the electron-phonon coupling activation in collision cascades

    Energy Technology Data Exchange (ETDEWEB)

    Zarkadoula, Eva, E-mail: zarkadoulae@ornl.gov [Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Samolyuk, German [Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Weber, William J. [Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Department of Materials Science & Engineering, University of Tennessee, Knoxville, TN 37996 (United States)

    2017-07-15

    Using the two-temperature (2T-MD) model in molecular dynamics simulations, we investigate the condition of switching the electronic stopping term off when the electron-phonon coupling is activated in the damage production due to 50 keV Ni ion cascades in Ni and equiatomic NiFe. Additionally, we investigate the effect of the electron-phonon coupling activation time in the damage production. We find that the switching condition has negligible effect in the produced damage, while the choice of the activation time of the electron-phonon coupling can affect the amount of surviving damage. - Highlights: •The electron-phonon interactions in irradiation affect the energy dissipation. •The resulting damage depends on the electron-phonon interaction activation time. •The electronic stopping acts on the ions before the electron-phonon interactions.

  6. Charge-exchange collisions of multiply charged ions with atoms

    International Nuclear Information System (INIS)

    Grozdanov, T.P.; Janev, R.K.

    1978-01-01

    The problem of electron transfer between neutral atoms and multiply charged ions is considered at low and medium energies. It is assumed that a large number of final states are available for the electron transition so that the electron-capture process is treated as a tunnel effect caused by the strong attractive Coulomb field of the multicharged ions. The electron transition probability is obtained in a closed form using the modified-comparison-equation method to solve the Schroedinger equation. An approximately linear dependence of the one-electron transfer cross section on the charge of multicharged ion is found. Cross-section calculations of a number of charge-exchange reactions are performed

  7. Contribution to the theoretical study of collisions between highly excited atom and a neutral particle (atom or molecule)

    International Nuclear Information System (INIS)

    Prunele, Eugene de.

    1979-01-01

    The problem of the collision between an atom in the Rydberg state and a neutral atom (or molecule) is considerably simplified if it is considered as the collision of a B particle with a system of two linked particles A + and e - . If the interaction between these two particles is described by a potential and if the three-body interaction is approximated by a potential equal to the sum of the two-body interaction potentials, the problem is theoretically solvable exactly within the framework of quantum mechanics but, its explicit solution is very complicated, even for very simple potentials. Various types of approaches are then necessary. The choice of interaction potentials is already an approximation, for it is obviously not known how to describe exactly the interaction between the electron and atom B for example. The fact that the electron is, on average, very far from core A + has enabled an interaction potential to be simulated between B and e - when the latter is linked to A + , by utilizing the scattering data between free e - and B. (Fermi's pseudopotential). A second approach consists in utilizing the scattering data between free e - and B, without bringing in an interaction potential between e - and B. The first approach is more satisfactory from the theoretical point of view; the second and less ambitious one is more useful [fr

  8. Electron-ion collision rates in atomic clusters irradiated by femtosecond laser pulses

    International Nuclear Information System (INIS)

    Moll, M; Hilse, P; Schlanges, M; Bornath, Th; Krainov, V P

    2010-01-01

    In atomic clusters irradiated by femtosecond laser pulses, plasmas with high density and high temperature are created. The heating is mainly caused by inverse bremsstrahlung, i.e. determined by electron-ion collisions. In the description of the scattering of electrons on noble gas ions in such plasmas, it is important to account for the inner structure of the ions and the screening by the surrounding plasma medium which can be accomplished by using suitable model potentials. In the wide parameter range met in experiments, the Born approximation is not applicable. Instead, the electron-ion collision frequency is calculated on the basis of classical momentum transport cross sections. Results are presented for xenon, krypton and argon ions in different charge states. A comparison of these results to those for the scattering on Coulomb particles with the same charge shows an enhancement of the collision frequency. The Born approximation, however, leads to an overestimation.

  9. Applications of beam-foil spectroscopy to atomic collisions in solids

    Science.gov (United States)

    Sellin, I. A.

    1976-01-01

    Some selected papers presented at the Fourth International Conference on Beam-Foil Spectroscopy, whose results are of particular pertinence to ionic collision phenomena in solids, are reviewed. The topics discussed include solid target effects and means of surmounting them in the measurement of excited projectile ion lifetimes for low-energy heavy element ions; the electron emission accompanying the passage of heavy particles through solid targets; the collision broadening of X rays emitted from 100 keV ions moving in solids; residual K-shell excitation in chlorine ions penetrating carbon; comparison between 40 MeV Si on gaseous SiH4 targets at 300 mtorr and 40 MeV Si on Al; and the emergent surface interaction in beam-foil spectroscopy. A distinct overlap of interests between the sciences of beam-foil spectroscopy and atomic collisions in solids is pointed out.

  10. Differential electron emission in multi-charged ion atom collisions: Systematics for distant and close collisions

    International Nuclear Information System (INIS)

    DuBois, R.D.; Toburen, L.H.; Middendorf, M.E.; Jagutzki, O.

    1992-09-01

    Absolute doubly differential cross sections for electron emission are presented for 0.5 MeV/u multi-charged ion impact on helium, neon, and argon targets. For the helium target, Bq+, Cq+ (q = 2--5) and Oq+, Fq+ (q = 3--6) projectiles were studied; for neon and argon, only Cq+ (q = 2--5) projectiles were used. Electron emission for 10 degrees ≤ Θ ≤ 60 degrees was studied. The measured cross sections were assumed to scale as the square of an effective projectile charge, Z eff , which was determined as a function of emitted electron energy and angle. For distant collisions (low emitted electron energies), we find that Z eff ∼ q for small q and Z eff eff > Z and increases as q decreases. This is true for all angles and targets investigated

  11. Correlated charge-changing uion-atom collisions. Final Technical Report

    International Nuclear Information System (INIS)

    John Tanis

    2005-01-01

    This document comprises the final technical report for atomic collisions research supported by DOE grant No. DE-FG02-87ER13778 from September 1, 2001 through August 31, 2004. The research involved the experimental investigation of excitation and charge-changing processes occurring in ion-atom and ion-molecule collisions. Major emphases of the study were: (1) interference effects resulting from coherent electron emission in H2, (2) production of doubly vacant K-shell (hollow ion) states due to electron correlation, and (3) formation of long-lived metastable states in electron transfer processes. During the period of the grant, this research resulted in 23 publications, 12 invited presentations, and 39 contributed presentations at national and international meetings and other institutions. Brief summaries of the completed research are presented below

  12. Two-body loss rates for reactive collisions of cold atoms

    Science.gov (United States)

    Cop, C.; Walser, R.

    2018-01-01

    We present an effective two-channel model for reactive collisions of cold atoms. It augments elastic molecular channels with an irreversible, inelastic loss channel. Scattering is studied with the distorted-wave Born approximation and yields general expressions for angular momentum resolved cross sections as well as two-body loss rates. Explicit expressions are obtained for piecewise constant potentials. A pole expansion reveals simple universal shape functions for cross sections and two-body loss rates in agreement with the Wigner threshold laws. This is applied to collisions of metastable 20Ne and 21Ne atoms, which decay primarily through exothermic Penning or associative ionization processes. From a numerical solution of the multichannel Schrödinger equation using the best currently available molecular potentials, we have obtained synthetic scattering data. Using the two-body loss shape functions derived in this paper, we can match these scattering data very well.

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

    International Nuclear Information System (INIS)

    Shevelko, V.P.; Tolstikhina, I.Yu.; Kato, D.; Tawara, H.; Song, M-.Y.; Yoon, J-.S.

    2009-12-01

    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(1s 2 , 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)

  14. High-resolution measurements of x rays from ion-atom collisions

    International Nuclear Information System (INIS)

    Knudson, A.R.

    1974-01-01

    High resolution measurements of K x-ray spectra produced by ion-atom collisions at MeV energies are presented. These measurements indicate that a distribution of L-shell vacancies accompanies K-shell excitation. The variation of these spectra as a function of incident ion energy and atomic number is discussed. Difficulties in the analysis of these spectra due to rearrangement of vacancies between the time of the collision and the time of x-ray emission are considered. The use of high resolution x-ray measurements to obtain information on projectile ion vacancy configurations is demonstrated by data for Ar ions in KCl. X-ray spectra from Al projectiles in a variety of targets were measured and the effect of target composition on these spectra is discussed

  15. Pauli blocking and laser manipulation of the electron dynamics in atomic collisions

    International Nuclear Information System (INIS)

    Kirchner, T.

    2004-01-01

    Full text: The dynamics of ion-atom collisions are governed primarily by the Coulomb interactions between the active electrons and the projectile and target nuclei. This contribution is devoted to the question whether and how other phenomena can modify the outcome of atomic scattering experiments. Firstly, the role of the Pauli exclusion principle on electronic transitions will be considered. Supported by experimental data it will be argued that Pauli blocking may have an important influence on electron transfer processes if collision systems with electrons on target and projectile in the initial channel are addressed [1]. Secondly, it will be discussed to which extent the electron dynamics can be modified and manipulated by an external interaction, namely by a suitable laser field [2]. The prototype scattering system He 2+ -H will be considered in the framework of the semiclassical approximation, i.e., projectile and laser interactions are described in terms of time-dependent external potentials which govern the quantum dynamics of the electron. The focus will be on slow collisions, in which electron transfer dominates, and on relatively short wavelengths such that both time dependent potentials vary on comparable time scales. A strong enhancement of laser-assisted electron transfer is found at collision energies below 1 keV/amu [3]. Its origin and its disappearance at higher energies as well as implications for planned experiments will be discussed

  16. 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.

  17. Atomic excitation and molecular dissociation by low energy electron collisions

    International Nuclear Information System (INIS)

    Weyland, Marvin

    2016-01-01

    In this work, momentum imaging experiments have been conducted for the electron impact excitation of metastable states in noble gases and for dissociative electron attachment (DEA) in polyatomic molecules. For the electron impact excitation study a new experimental technique has been developed which is able to measure the scattering angle distribution of the electrons by detection of the momentum transfer to the atoms. Momentum transfer images have been recorded for helium and neon at fixed electron impact energy close to the excitation threshold and good agreement with current R-matrix theory calculations was found. A new momentum imaging apparatus for negative ions has been built for the purpose of studying DEA in biologically relevant molecules. During this work, DEA was investigated in the molecules ammonia, water, formic acid, furan, pyridine and in two chlorofluorocarbons. Furthermore, the change of DEA resonance energies when molecules form clusters compared to monomers was investigated in ammonia and formic acid. The experimental results of most studied molecules could be compared to recent theoretical calculations and they support further development in the theoretical description of DEA. The new apparatus built in this work also delivered a superior momentum resolution compared to existing setups. This allows the momentum imaging of heavier fragments and fragments with lower kinetic energy.

  18. Slow Collisions of Si3+ with Atomic Hydrogen

    Science.gov (United States)

    Joseph, D. C.; Gu, J.-P.; Saha, B. C.; Liebermann, H. P.; Funke, P.; Buenker, R. J.

    2010-03-01

    Low energy electron capture from hydrogen atom by multi-charged ions continues to be of interest and applications include both magnetically confined fusion and astrophysical plasmas. The charge exchange process reported here, Si^3+ + H -> Si^2+ + H^+ is an important destruction mechanism of Si^3+ in photo-ionized gas. The soft X-ray emission from comets has been explained by charge transfer of solar wind ions, among them Si^3+, with neutrals in the cometary gas vapor. The state selective cross sections are evaluated using the full quantum [1] and semi-classical molecular orbital close coupling (MOCC) [2] methods. Adiabatic potentials and wave functions for a number of low-lying singlet and triplet states of and symmetry are calculated wing the MRD-CI package [3]. Details will be presented at the conference. [4pt] [1] L. B. Zhao, D. C. Joseph, B. C. Saha, H. P. Liebermann, P. Funke and R. J. Buenker, Phys. Rev A, 79, 034701 (1009).[0pt] [2] M. Kimura and N. F. Lane, At. Mol. Opt. Phys 26, 79 (1990).[0pt] [3] R. J. Buenker, ``Current Aspects of Quantum Chemistry 1981, Vol 21, edited by R. Carbo (Elsevier, Amsterdam) p 17.

  19. Atomic excitation and molecular dissociation by low energy electron collisions

    Energy Technology Data Exchange (ETDEWEB)

    Weyland, Marvin

    2016-11-16

    In this work, momentum imaging experiments have been conducted for the electron impact excitation of metastable states in noble gases and for dissociative electron attachment (DEA) in polyatomic molecules. For the electron impact excitation study a new experimental technique has been developed which is able to measure the scattering angle distribution of the electrons by detection of the momentum transfer to the atoms. Momentum transfer images have been recorded for helium and neon at fixed electron impact energy close to the excitation threshold and good agreement with current R-matrix theory calculations was found. A new momentum imaging apparatus for negative ions has been built for the purpose of studying DEA in biologically relevant molecules. During this work, DEA was investigated in the molecules ammonia, water, formic acid, furan, pyridine and in two chlorofluorocarbons. Furthermore, the change of DEA resonance energies when molecules form clusters compared to monomers was investigated in ammonia and formic acid. The experimental results of most studied molecules could be compared to recent theoretical calculations and they support further development in the theoretical description of DEA. The new apparatus built in this work also delivered a superior momentum resolution compared to existing setups. This allows the momentum imaging of heavier fragments and fragments with lower kinetic energy.

  20. Electron removal from H and He atoms in collisions with C q+ , O q+ ions

    Science.gov (United States)

    Janev, R. K.; McDowell, M. R. C.

    1984-06-01

    Cross sections for electron capture and ionisation in collision of partially and completely stripped C q+ , N q+ and O q+ ions with hydrogen and helium atoms have been calculated at selected energies. The classical trajectory Monte Carlo method was used with a variable-charge pseudopotential to describe the interaction of the active electron with the projectile ion. A scalling relationship has been derived for the electron removal (capture and ionisation) cross section which allows a unifield representation of the data.

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

    International Nuclear Information System (INIS)

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

    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. Atomic collisions in the presence of laser radiation - Time dependence and the asymptotic wave function

    Science.gov (United States)

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

    1982-01-01

    A time-dependent, wave-packet description of atomic collisions in the presence of laser radiation is extracted from the more conventional time-independent, stationary-state description. This approach resolves certain difficulties of interpretation in the time-independent approach which arise in the case of asymptotic near resonance. In the two-state model investigated, the approach predicts the existence of three spherically scattered waves in this asymptotically near-resonant case.

  3. 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....

  4. Charge exchange and ionization in atom-multiply-charged ion collisions

    International Nuclear Information System (INIS)

    Presnyakov, L.P.; Uskov, D.B.

    1988-01-01

    This study investigates one-electron transitions to the continuous and discrete spectra induced by a collision of atom A and multiply-charged ion B +Z with nuclear charge Z > 3. An analytical method is developed the charge-exchange reaction; this method is a generalization of the decay model and the approximation of nonadiabatic coupling of two states that are used as limiting cases in the proposed approach

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

    International Nuclear Information System (INIS)

    Voitkiv, A.B

    2007-01-01

    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 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 a ∼ a is the atomic nuclear charge

  6. Electron-hydrogen atom collisions in the presence of a laser field

    International Nuclear Information System (INIS)

    Brandi, H.S.; Koiller, B.; Barros, H.G.P.L. de

    1978-01-01

    The collision of an electron and a hydrogen atom in the presence of a laser field is studied within a previously proposed approximation (based on the space translation approximation) for the bound states of the hydrogen atom. Fhe Green's function formalism is applied to derive an expression for the scattering amplitude associated to multiphoton processes. The Born-Oppenheimer approximation is obtained and numerical calculations are performed for the ls→2s inelastic excitation. It is shown as expected that exchange effects are important only for scattering processes involving low energy electrons [pt

  7. Absolute single electron loss in collisions of Ar+ with various atoms

    Science.gov (United States)

    Reyes, P. G.; Martínez, H.; Castillo, F.

    2001-07-01

    Absolute differential and total cross sections for single electron loss were measured for Ar+ ions on various atoms in the energy range of 1.5 to 5.0 keV. The laboratory angular scan for the distributions ranged from -2.5 to 2.5 degrees. The measured differential cross sections have been integrated over the experimental angular range providing absolute total cross sections. The behavior of the total electron loss cross sections with the target atomic number, Zt, shows different dependences as the collision energy increases. In all cases it displays a saturation as Zt increases.

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

    International Nuclear Information System (INIS)

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

    1980-03-01

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

  9. Atomic collision experiments at the border line between classical and quantum mechanics

    International Nuclear Information System (INIS)

    Aquilanti, V.

    1984-01-01

    In order to understand atomic and molecular interactions, one has to learn how to live with the wave-particle duality, considering classical nuclei and quantum electrons. A better way, illustrated by reference to experiments, is by quasiclassical (or semi-classical) mechanics, governing a world with a quasi-zero Planck's constant. One thus explains optical analogs (shadows, rainbows, glories) as interference effects in atomic collisions. Reference is also made to Wheeler's 'black bird' on the inversion problem from spectroscopy and scattering to molecular structure. The paper concludes outlining a journey in the hyperspace to escape from Einstein's torus and to find interferences and resonances in three body scattering and reactions. (Auth.)

  10. 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

  11. Quantum chaos in ultracold collisions of gas-phase erbium atoms.

    Science.gov (United States)

    Frisch, Albert; Mark, Michael; Aikawa, Kiyotaka; Ferlaino, Francesca; Bohn, John L; Makrides, Constantinos; Petrov, Alexander; Kotochigova, Svetlana

    2014-03-27

    Atomic and molecular samples reduced to temperatures below one microkelvin, yet still in the gas phase, afford unprecedented energy resolution in probing and manipulating the interactions between their constituent particles. As a result of this resolution, atoms can be made to scatter resonantly on demand, through the precise control of a magnetic field. For simple atoms, such as alkalis, scattering resonances are extremely well characterized. However, ultracold physics is now poised to enter a new regime, where much more complex species can be cooled and studied, including magnetic lanthanide atoms and even molecules. For molecules, it has been speculated that a dense set of resonances in ultracold collision cross-sections will probably exhibit essentially random fluctuations, much as the observed energy spectra of nuclear scattering do. According to the Bohigas-Giannoni-Schmit conjecture, such fluctuations would imply chaotic dynamics of the underlying classical motion driving the collision. This would necessitate new ways of looking at the fundamental interactions in ultracold atomic and molecular systems, as well as perhaps new chaos-driven states of ultracold matter. Here we describe the experimental demonstration that random spectra are indeed found at ultralow temperatures. In the experiment, an ultracold gas of erbium atoms is shown to exhibit many Fano-Feshbach resonances, of the order of three per gauss for bosons. Analysis of their statistics verifies that their distribution of nearest-neighbour spacings is what one would expect from random matrix theory. The density and statistics of these resonances are explained by fully quantum mechanical scattering calculations that locate their origin in the anisotropy of the atoms' potential energy surface. Our results therefore reveal chaotic behaviour in the native interaction between ultracold atoms.

  12. Removal of nonorthogonality in the Born theory used for study of electron capture in high energy ion-atom collisions

    International Nuclear Information System (INIS)

    Kimura, M.

    1989-01-01

    We show the complete removal of the nonorthogonality of wave functions between initial and final states in the Born theory. Hence, this treatment offers more realistic electron capture cross sections in high energy ion-atom collisions. Representative results for resonant electron capture in H + + H collision are discussed in conjunction with other perturbative results. 10 refs., 1 fig

  13. A quantum-mechanical study of atom-diatom collisions in a laser field

    International Nuclear Information System (INIS)

    Chang, Sintarng.

    1989-01-01

    A quantum-mechanical formalism, in both space-fixed (SF) and body-fixed (BF) coordinate systems, is developed for describing an S-state structureless atom (A) colliding with a Estate vibrating rotor diatomic molecule (BC) in the presence of a laser field. The additional Hamiltonians H rad and H int , which describe the laser field and its interaction with the atom-diatom collision system, have been added to the field-free Hamiltonian Ho. And the collision problem can be solved by this extended Hamiltonian. The laser field Hamiltonian is represented by the number state representation. The interaction Hamiltonian is expressed by rvec μ BC . rvec ε, where rvec μ BC is the dipole moment of the diatomic molecule BC, and rvec ε is the electric field strength of the laser field. Since the field-free total angular momentum J is coupling with the laser field, J and its z-axis projection M are no longer conserved. To facilitate the collision problem, the laser field is restricted to a single mode, and its interaction with the collision only involves dipole allowed transitions in which a single photon is absorbed or emitted. For convenience, the coupled-channel equations are solved by the real boundary conditions instead of the complex boundary conditions. On applying the real boundary conditions, the author obtains the K-matrix, which is related to the S-matrix by S = (I + iK)(I - iK) -1 . A model calculation is discussed for the Ar + CO collision system in a laser intensity of 10 9 W/cm 2

  14. Properties of atomic pairs produced in the collision of Bose-Einstein condensates

    Science.gov (United States)

    Ziń, Paweł; Wasak, Tomasz

    2018-04-01

    During a collision of Bose-Einstein condensates correlated pairs of atoms are emitted. The scattered massive particles, in analogy to photon pairs in quantum optics, might be used in the violation of Bell's inequalities, demonstration of Einstein-Podolsky-Rosen correlations, or sub-shot-noise atomic interferometry. Usually, a theoretical description of the collision relies either on stochastic numerical methods or on analytical treatments involving various approximations. Here, we investigate elastic scattering of atoms from colliding elongated Bose-Einstein condensates within the Bogoliubov method, carefully controlling performed approximations at every stage of the analysis. We derive expressions for the one- and two-particle correlation functions. The obtained formulas, which relate the correlation functions to the condensate wave function, are convenient for numerical calculations. We employ the variational approach for condensate wave functions to obtain analytical expressions for the correlation functions, whose properties we analyze in detail. We also present a useful semiclassical model of the process and compare its results with the quantum one. The results are relevant for recent experiments with excited helium atoms, as well as for planned experiments aimed at investigating the nonclassicality of the system.

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

    International Nuclear Information System (INIS)

    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)

  16. Excitation and charge transfer in low-energy hydrogen atom collisions with neutral iron

    Science.gov (United States)

    Barklem, P. S.

    2018-05-01

    Data for inelastic processes due to hydrogen atom collisions with iron are needed for accurate modelling of the iron spectrum in late-type stars. Excitation and charge transfer in low-energy Fe+H collisions is studied theoretically using a previously presented method based on an asymptotic two-electron linear combination of atomic orbitals model of ionic-covalent interactions in the neutral atom-hydrogen-atom system, together with the multi-channel Landau-Zener model. An extensive calculation including 166 covalent states and 25 ionic states is presented and rate coefficients are calculated for temperatures in the range 1000-20 000 K. The largest rates are found for charge transfer processes to and from two clusters of states around 6.3 and 6.6 eV excitation, corresponding in both cases to active 4d and 5p electrons undergoing transfer. Excitation and de-excitation processes among these two sets of states are also significant. Full Tables and rate coefficient data are only 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/612/A90

  17. Correlated charge changing ion-atom collisions. Progress report, March 15, 1985-March 14, 1986

    International Nuclear Information System (INIS)

    Bernstein, E.M.; Tanis, J.A.

    1986-04-01

    X-ray emission associated with projectile charge-changing events in ion-atom collisions has been used to isolate and investigate excitation, ionization, and charge transfer, as well as combinations of these processes. New measurements were made of K-shell and L-shell resonant transfer and excitation (RTE) for 210 to 300 MeV 20 Ca/sup 10,11+/ + H 2 collisions and 230 to 610 MeV 41 Nb 31+ + H 2 collisions, respectively. Nonresonant transfer and excitation (NTE) was studied for 40 to 160 MeV S 13+ + Ne. Single-electron capture and loss measurements, requiring accel-decel techniques, were made for 2.5 to 200 MeV S 13+ on He. In the case of Ca/sup 16,17,18,19 + / + H 2 collisions the single capture cross cross sections exhibit a nonmonotonic energy dependence which we attribute to RTE. Double-electron capture in single collisions was investigated for S 13+ + He and Ne and Ar 15+ + Ne and the cross sections were found to be 10 to 100 times smaller than the single-capture cross sections. Measured two-electron loss cross sections for Ca/sup q + / ions incident on H 2 vary with charge state and depend strongly on whether L- or K-shell electrons are removed. Measurements of simultaneous projectile excitation and electron loss for several collision systems indicate that K-vacancy production occurs primarily through excitation rather than loss of the 1s electron. 13 refs

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

    International Nuclear Information System (INIS)

    Fawcett, B.C.; Mason, H.E.

    1989-02-01

    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)

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

    International Nuclear Information System (INIS)

    Luehr, Armin

    2010-01-01

    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 H 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 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 2 + , and H 2 as well as with He and alkali-metal atoms Li, Na, K, and Rb. Additionally, data are obtained for p collisions with H 2 , 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

  20. Vibrational deactivation and atom exchange in O(3P)+CO(X 1Σ+) collisions

    International Nuclear Information System (INIS)

    Kelley, J.D.; Thommarson, R.L.

    1977-01-01

    A quasiclassical Monte Carlo averaged trajectory study of the ground-state O, CO collision system is presented. An ''effective'' adiabatic potential surface is constructed using pertinent theoretical and experimental data. Vibrational deactivation rates for CO(v=1, 3) and atom exchange rates for CO(v=0, 1, 3) are calculated and compared with experimental data. The high-temperature (400 K< T<2000 K) and low-temperature (270 K< T<400 K) CO deactivation data, and the low-temperature (300 K< T<400 K) atom exchange data are all fit reasonably well by the calculation. However, comparison of the deactivation data to the atom exchange data suggests that at temperatures below 400 K an additional nonadiabatic mechanism may be contributing to the overall deactivation rate

  1. Low-energy charge transfer for collisions of Si3+ with atomic hydrogen

    Science.gov (United States)

    Bruhns, H.; Kreckel, H.; Savin, D. W.; Seely, D. G.; Havener, C. C.

    2008-06-01

    Cross sections of charge transfer for Si3+ ions with atomic hydrogen at collision energies of ≈40-2500eV/u were carried out using a merged-beam technique at the Multicharged Ion Research Facility at Oak Ridge National Laboratory. The data span an energy range in which both molecular orbital close coupling (MOCC) and classical trajectory Monte Carlo (CTMC) calculations are available. The influence of quantum mechanical effects of the ionic core as predicted by MOCC is clearly seen in our results. However, discrepancies between our experiment and MOCC results toward higher collision energies are observed. At energies above 1000 eV/u good agreement is found with CTMC results.

  2. Ab initio study of charge transfer in B2+ low-energy collisions with atomic hydrogen

    Science.gov (United States)

    Turner, A. R.; Cooper, D. L.; Wang, J. G.; Stancil, P. C.

    2003-07-01

    Charge transfer processes due to collisions of ground state B2+(2s 2S) ions with atomic hydrogen are investigated using the quantum-mechanical molecular-orbital close-coupling (MOCC) method. The MOCC calculations utilize ab initio adiabatic potentials and nonadiabatic radial and rotational coupling matrix elements obtained with the spin-coupled valence-bond approach. Total and state-selective cross sections and rate coefficients are presented. Comparison with the existing experiments shows our results to be in good agreement. When EMOCC cross sections with and without rotational coupling are small (400 eV/u, inclusion of rotational coupling increases the total cross section by 50% 80%, improving the agreement between the current calculations and experiments. For state-selective cross sections, rotational coupling induces mixing between different symmetries; however, its effect, especially at low collision energies, is not as important as had been suggested in previous work.

  3. Low Energy Charge Transfer for Collisions of Si3+ with Atomic Hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Bruhns, H. [Columbia University; Kreckel, H. [Columbia University; Savin, D. W. [Columbia University; Seely, D. G. [Albion College; Havener, Charles C [ORNL

    2008-01-01

    Cross sections of charge transfer for Si{sup 3+} ions with atomic hydrogen at collision energies of {approx} 40-2500 eV/u were carried out using a merged-beam technique at the Multicharged Ion Research Facility at Oak Ridge National Laboratory. The data span an energy range in which both molecular orbital close coupling (MOCC) and classical trajectory Monte Carlo (CTMC) calculations are available. The influence of quantum mechanical effects of the ionic core as predicted by MOCC is clearly seen in our results. However, discrepancies between our experiment and MOCC results toward higher collision energies are observed. At energies above 1000 eV/u good agreement is found with CTMC results.

  4. Ab initio study of charge transfer in B2+ low-energy collisions with atomic hydrogen

    International Nuclear Information System (INIS)

    Turner, A.R.; Cooper, D.L.; Wang, J.G.; Stancil, P.C.

    2003-01-01

    Charge transfer processes due to collisions of ground state B 2+ (2s 2 S) ions with atomic hydrogen are investigated using the quantum-mechanical molecular-orbital close-coupling (MOCC) method. The MOCC calculations utilize ab initio adiabatic potentials and nonadiabatic radial and rotational coupling matrix elements obtained with the spin-coupled valence-bond approach. Total and state-selective cross sections and rate coefficients are presented. Comparison with the existing experiments shows our results to be in good agreement. When E 400 eV/u, inclusion of rotational coupling increases the total cross section by 50%-80%, improving the agreement between the current calculations and experiments. For state-selective cross sections, rotational coupling induces mixing between different symmetries; however, its effect, especially at low collision energies, is not as important as had been suggested in previous work

  5. US-Japan workshop on atomic collisions in solids: Abstracts of lectures

    International Nuclear Information System (INIS)

    1990-03-01

    This report contains abstracts on the following topics: techniques of scanning probe microscopy; new types of radiation; a search for wake-riding electrons using slow antiproton beams; antiproton wake: theory; bending of swift ion beams by graphite foils; angular momentum distribution of autoionizing rydberg states: produced by 64 MeV S ions in collisions with C foils; multiphonon energy exchange in atom-surface collisions; plans for positron experiments; resonant coherent excitation: experiment; line shapes in resonant coherent excitation: theory; MUSE experiments and Monte Carlo simulation; inelastic interactions of electrons and positrons with solids; density fluctuation detection; cluster-impact fusion; a model for cluster-impact fusion; thoughts on cold fusion; and plasmon decay

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

    International Nuclear Information System (INIS)

    Andersen, H.H.

    1986-01-01

    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

  7. Excitation and charge transfer in low-energy hydrogen atom collisions with neutral oxygen

    Science.gov (United States)

    Barklem, P. S.

    2018-02-01

    Excitation and charge transfer in low-energy O+H collisions is studied; it is a problem of importance for modelling stellar spectra and obtaining accurate oxygen abundances in late-type stars including the Sun. The collisions have been studied theoretically using a previously presented method based on an asymptotic two-electron linear combination of atomic orbitals (LCAO) model of ionic-covalent interactions in the neutral atom-hydrogen-atom system, together with the multichannel Landau-Zener model. The method has been extended to include configurations involving excited states of hydrogen using an estimate for the two-electron transition coupling, but this extension was found to not lead to any remarkably high rates. Rate coefficients are calculated for temperatures in the range 1000-20 000 K, and charge transfer and (de)excitation processes involving the first excited S-states, 4s.5So and 4s.3So, are found to have the highest rates. Data are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/vizbin/qcat?J/A+A/610/A57. The data are also available at http://https://github.com/barklem/public-data

  8. Cascade Problems in Some Atomic Lifetime Measurements at a Heavy-Ion Storage Ring

    Energy Technology Data Exchange (ETDEWEB)

    Trabert, E; Hoffmann, J; Krantz, C; Wolf, A; Ishikawa, Y; Santana, J

    2008-10-09

    Lifetimes of 3s{sup 2}3p{sup k} ground configuration levels of Al-, Si-, P-, and S-like ions of Be, Co, and Ni have been measured at a heavy-ion storage ring. Some of the observed decay curves show strong evidence of cascade repopulation from specific 3d levels that feature lifetimes in the same multi-millisecond range as the levels of the ground configuration.

  9. Effective stopping of relativistic structural heavy ions at collisions with atoms

    International Nuclear Information System (INIS)

    Matveev, V.I.

    2002-01-01

    One develops the unperturbed theory of energy losses at collision of atoms with structural high-charged heavy ions moving with relativistic velocity. One derived a simple formula for efficient braking. The structural ions in terms of this paper are considered to mean partially ionized ions of heavy elements compressing ion nucleus and some bound electrons compensating partially for ion nucleus charge. Account of ion charge magnitude is determined to result in essential increase of efficient braking of ion in contrast to braking of point nucleus of Z* charge [ru

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

    International Nuclear Information System (INIS)

    Watson, R.L.

    1991-01-01

    Much of the work this year has been directed toward studies of charge exchange and ionization in single collisions of heavy ions with gaseous atoms and molecules. A study of the double ionization of He by high energy N 7+ ions, which began last year, was extended up in energy to 40 MeV/amu. These measurements verified the deviations from the predictions of theory observed in our previous work and indicated that the energy required to reach the limiting value of the ratio of double-to-single ionization cross sections may be as high as 70 MeV/amu

  11. Correlated double electron capture in slow, highly charged ion-atom collisions

    Energy Technology Data Exchange (ETDEWEB)

    Stolterfoht, N.; Havener, C.C.; Phaneuf, R.A.; Swenson, J.K.; Shafroth, S.M.; Meyer, F.W.

    1986-01-01

    Recent measurements of autoionization electrons produced in slow, highly charged ion-atom collisions are reviewed. Mechanisms for double electron capture into equivalent and nonequivalent configurations are analyzed by comparing the probabilities for the creation of L/sub 1/L/sub 23/X Coster Kronig electrons and L-Auger electrons. It is shown that the production of the Coster-Kronig electrons is due to electron correlation effects whose analysis leads beyond the independent-particle model. The importance of correlation effects on different capture mechanisms is discussed. 28 refs., 6 figs.

  12. Correlated double electron capture in slow, highly charged ion-atom collisions

    International Nuclear Information System (INIS)

    Stolterfoht, N.; Havener, C.C.; Phaneuf, R.A.; Swenson, J.K.; Shafroth, S.M.; Meyer, F.W.

    1986-01-01

    Recent measurements of autoionization electrons produced in slow, highly charged ion-atom collisions are reviewed. Mechanisms for double electron capture into equivalent and nonequivalent configurations are analyzed by comparing the probabilities for the creation of L 1 L 23 X Coster Kronig electrons and L-Auger electrons. It is shown that the production of the Coster-Kronig electrons is due to electron correlation effects whose analysis leads beyond the independent-particle model. The importance of correlation effects on different capture mechanisms is discussed. 28 refs., 6 figs

  13. Potentials and scattering cross sections for collisions of He atoms with adsorbed CO

    International Nuclear Information System (INIS)

    Liu, W.K.; Gumhalter, B.

    1986-05-01

    Ab initio calculations of the total scattering cross section for the collision system He → CO/Pt(111) within the renormalized distorted wave Born approximation are reported. The interaction potential for this atom-adsorbate system consists of the usual two-body gas phase-like potential as well as two additional substrate mediated van de Waals contributions, all with similar long range behaviour. Comparison of the calculated cross sections for various incident velocities and angles with available experimental data is made without using any adjustable parameters to fit the data, and the importance of including the substrate-mediated forces is emphasized. (author)

  14. Radiative double electron capture in fast heavy ion-atom collisions

    International Nuclear Information System (INIS)

    Yakhontov, V.L.; Amusia, M.Ya.

    1996-01-01

    Two-electron capture with emission of a single photon (TESP) in collisions of highly charged ions with light atoms is considered. Such a process is actually a time-reversed double photoionization but occurring at specific kinematics. In the lowest order in the inter-electron interaction, the TESP probability is determined by two diagrams which are evaluated analytically by means of the Coulomb Green function. The calculated ratio of the TESP and single recombination cross sections is in fair agreement with the data obtained in the recent experimental study of this phenomena. (orig.)

  15. Impulse approximation treatment of electron-electron excitation and ionization in energetic ion-atom collisions

    International Nuclear Information System (INIS)

    Zouros, T.J.M.; Lee, D.H.; Sanders, J.M.; Richard, P.

    1993-01-01

    The effect of electron-electron interactions between projectile and target electrons observed in recent measurements of projectile K-shell excitation and ionization using 0 projectile Auger electron spectroscopy are analysed within the framework of the impulse approximation (IA). The IA formulation is seen to give a good account of the threshold behavior of both ionization and excitation, while providing a remarkably simple intuitive picture of such electron-electron interactions in ion-atom collisions in general. Thus, the applicability of the IA treatment is extended to cover most known processes involving such interactions including resonance transfer excitation, binary encounter electron production, electron-electron excitation and ionization. (orig.)

  16. Discussion of electron capture theories for ion-atom collisions at high energies

    Energy Technology Data Exchange (ETDEWEB)

    Miraglia, J E [Instituto de Astronomia y Fisica del Espacio, Buenos Aires (Argentina); Piacentini, R D [Consejo Nacional de Investigaciones Cientificas y Tecnicas, Buenos Aires (Argentina); Rivarola, R D [Rosario Univ. Nacional (Argentina). Dept. de Fisica; Salin, A [Bordeaux-1 Univ., 33 - Talence (France)

    1981-03-14

    Different theories of charge exchange processes in ion-atom collisions at high energies for the H/sup +/-H system are considered. Large discrepancies are found in the differential cross sections obtained from the various models. The validity of Dettmann's peaking approximation is analysed by comparison with exact values for the first- and second-order Oppenheimer-Brinkman-Kramers (OBK 1 and OBK 2) theories. It is also shown that for energies up to a few MeV the OBK 2 differential cross sections are higher than the corresponding OBK 1 ones. Total cross sections in the OBK 2 approximation are given.

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

    International Nuclear Information System (INIS)

    Mueller-Nehler, U.

    1993-11-01

    The properties of strongly bound electrons in superheavy quasimolecular systems with combined nuclear charge numbers Z = Z P + Z T ≥ 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.)

  18. The fifth international symposium ''atomic cluster collisions''. ISACC 2011. Book of Abstracts

    International Nuclear Information System (INIS)

    2011-01-01

    The Fifth International Symposium ''Atomic Cluster Collisions'' (ISACC 2011) will take place in July 21-25, 2011 in Berlin, Germany. The venue of the meeting will be the St.-Michaels-Heim a lovely place located within a garden area of Berlin-Grunewald. The ISACC 2011 is organized by the Fritz-Haber-Institute of the Max- Planck Society along with the King Saud University, Rhiyadh and by the Frankfurt Institute for Advanced Studies (FIAS), Frankfurt am Main, Germany. ISACC started as the international symposium on atomic cluster collisions in St. Petersburg, Russia in 2003. The second ISACC was held at the GSI, Darmstadt, Germany in 2007. Both first and second symposia were satellites of the International Conferences on Photonic Electronic and Atomic Collisions (ICPEAC). The third ISACC has returned to St. Petersburg, Russia in 2008. The last ISACC took place in Ann Arbor, again as a satellite meeting of the ICPEAC. Initially the symposium was mainly focused on dynamics of atomic clusters, especially in atomic cluster collisions, but since then its scope has been widened significantly to include dynamics of nanosystems, biomolecules, and macromolecules with the emphasis on the similarity of numerous essential clustering phenomena arising in different branches of physics, chemistry, and biology. After the four ISACC meetings it has become clear that there is a need for an interdisciplinary conference covering a broad range of topics related to the Dynamics of Systems on a Nanoscale. Therefore in 2010 it was decided to expand upon this series of meetings with a new conference organized under the new title ''Dynamics of Systems on the Nanoscale'', the DySoN Conference, since this title better reflects the interdisciplinary character of the earlier ISACC meetings embracing all the topics of interest under a common theme. The first DySoN Conference took place in Rome, Italy in 2010. The fifth ISACC symposium will be again a satellite of the ICPEAC. The ISACC 2011 will

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

    International Nuclear Information System (INIS)

    Choi, B.H.; Poe, R.T.

    1985-01-01

    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

  20. Charge exchange cross sections in slow collisions of Si3+ with Hydrogen atom

    Science.gov (United States)

    Joseph, Dwayne; Quashie, Edwin; Saha, Bidhan

    2011-05-01

    In recent years both the experimental and theoretical studies of electron transfer in ion-atom collisions have progressed considerably. Accurate determination of the cross sections and an understanding of the dynamics of the electron-capture process by multiply charged ions from atomic hydrogen over a wide range of projectile velocities are important in various field ranging from fusion plasma to astrophysics. The soft X-ray emission from comets has been explained by charge transfer of solar wind ions, among them Si3+, with neutrals in the cometary gas vapor. The cross sections are evaluated using the (a) full quantum and (b) semi-classical molecular orbital close coupling (MOCC) methods. Adiabatic potentials and wave functions for relavent singlet and triplet states are generated using the MRDCI structure codes. Details will be presented at the conference. In recent years both the experimental and theoretical studies of electron transfer in ion-atom collisions have progressed considerably. Accurate determination of the cross sections and an understanding of the dynamics of the electron-capture process by multiply charged ions from atomic hydrogen over a wide range of projectile velocities are important in various field ranging from fusion plasma to astrophysics. The soft X-ray emission from comets has been explained by charge transfer of solar wind ions, among them Si3+, with neutrals in the cometary gas vapor. The cross sections are evaluated using the (a) full quantum and (b) semi-classical molecular orbital close coupling (MOCC) methods. Adiabatic potentials and wave functions for relavent singlet and triplet states are generated using the MRDCI structure codes. Details will be presented at the conference. Work supported by NSF CREST project (grant #0630370).

  1. Direct processes in ion-atom collisions at intermediate and high energies

    International Nuclear Information System (INIS)

    Rodriguez Chariarse, V.D.

    1990-01-01

    This thesis deals with direct processes induced by Zp charge ion impact on one or two electron atoms and ions at intermediate energies. At a first step, a one-dimensional collision model is used in order to prove the different theoretical methods available to study collisions at such energy range, such as: perturbative and related variational principles, and distorted wave methods. The best description of both, symmetric and asymmetric collision type, is achieved by the distorted wave methods, particularly the ones using the exact impulsive wave function. As a next step, the appropriate formulations of the wave functions employed in the one-dimensional model to describe the real 3-dimensional Coulomb interaction case are examined by using the Eikonal and impulse hypothesis. In this way, the VPS and Eikonal wave functions are reviewed, and furtherly, the Eikonal form of the extended impulse wave function is derived. The Eikonal impulse approximation (EIA) is introduced. This is a distorted wave method using the Eikonal and extended impulse wave functions. The choice of the EIA prior version, i.e., the one using extended impulse wave function in the final channel for excitation is widely discussed and justified. (Author) [es

  2. Electron-electron interaction and transfer ionization in fast ion-atom collisions

    International Nuclear Information System (INIS)

    Voitkiv, A B

    2008-01-01

    Recently it was pointed out that electron capture occurring in fast ion-atom collisions can proceed via a mechanism which earlier was not considered. In the present paper we study this mechanism in more detail. Similarly as in radiative capture, where the electron transfer occurs due to the interaction with the radiation field and proceeds via emission of a photon, within this mechanism the electron capture is caused by the interaction with another atomic electron leading mainly to the emission of the latter. In contrast to the electron-electron Thomas capture, this electron-electron (E-E) mechanism is basically a first-order one having similarities to the kinematic and radiative capture channels. It also possesses important differences with the latter two. Leading to transfer ionization, this first-order capture mechanism results in the electron emission mainly in the direction opposite to the motion of the projectile ion. The same, although less pronounced, feature is also characteristic for the momenta of the target recoil ions produced via this mechanism. It is also shown that the action of the E-E mechanism is clearly seen in recent experimental data on the transfer ionization in fast proton-helium collisions.

  3. Forward electron production in heavy ion-atom and ion-solid collisions

    International Nuclear Information System (INIS)

    Sellin, I.A.

    1984-01-01

    A sharp cusp in the velocity spectrum of electrons, ejected in ion-atom and ion-solid collisions, is observed when the ejected electron velocity vector v/sub e/ matches that of the emergent ion vector v/sub p/ in both speed and direction. In ion-atom collisions, the electrons originate from capture to low-lying, projectile-centered continuum states (ECC) for fast bare or nearly bare projectiles, and from loss to those low-lying continuum states (ELC) when loosely bound projectile electrons are available. Most investigators now agree that ECC cusps are strongly skewed toward lower velocities, and exhibit full widths half maxima roughly proportional to v/sub p/ (neglecting target-shell effects, which are sometimes strong). A close examination of recent ELC data shows that ELC cusps are instead nearly symmetric, with widths nearly independent on v/sub p/ in the velocity range 6 to 18 a.u., a result only recently predicted by theory. Convoy electron cusps produced in heavy ion-solid collisions at MeV/u energies exhibit approximately velocity-independent widths very similar to ELC cusp widths. While the shape of the convoy peaks is approximately independent of projectile Z, velocity, and of target material, it is found that the yields in polycrystalline targets exhibit a strong dependence on projectile Z and velocity. While attempts have been made to link convoy electron production to binary ECC or ELC processes, sometimes at the last layer, or alternatively to a solid-state wake-riding model, our measured dependences of cusp shape and yield on projectile charge state and energy are inconsistent with the predictions of available theories. 10 references, 8 figures, 1 table

  4. Cross-sections for inelastic collisions of fast charged particles with atoms and molecules

    International Nuclear Information System (INIS)

    Inokuti, M.

    1987-01-01

    Despite the long history of research, the current experimental data of the cross-sections, required for solving problems of radiological physics and dosimetry, are far from being complete or even satisfactory for tentative applications. Calculations are, in general, difficult and only in exceptional situations lead to reliable results. Thus, one practical approach to the cross-section determination is to test experimental data with general criteria. This is possible because cross-sections for various processes are related among themselves and with many other properties of atoms and molecules. For example, the Bethe theory indicates a close connection between photoabsorption and energy absorption by glancing collisions and puts many other useful constraints on the cross-section data. Development and use of these data constraints, first advanced by Platzman, can now be demonstrated in many examples. More recent studies concern the determination of the analytic expression most suitable for fitting the data on the oscillator strength distribution or the energy distribution of secondary electrons from ionizing collisions of charged particles. There are three areas to which major efforts should be directed: (1) Methods of absolute cross-section measurements, both for electron and ionic collisions, must be thoroughly reviewed so that sources of systematic errors may be identified and corrected. (2) Efforts should be devoted to the understanding of the data systematics, viz. the trends of cross-sections for a series of molecules. This is especially important because the variety of molecules relevant to radiological physics and radiation biology is so enormous that even the data presentation for each molecule will be impractical. (3) Electron and ionic collisions with molecules in condensed phases will be an important topic of study for years to come. Initial reports on efforts in this direction are encouraging. 49 refs

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

    International Nuclear Information System (INIS)

    Mokler, P.H.; Hoffmann, D.H.H.; Schoenfeldt, W.A.; Maor, D.

    1984-01-01

    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 Kr 33+ to U 66+ 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.)

  6. Experimental study on the kinetically induced electronic excitation in atomic collisional cascades

    International Nuclear Information System (INIS)

    Meyer, S.

    2006-01-01

    the present thesis deals with the ion-collision-induced electronic excitation of metallic solids. For this for the first time metal-insulator-metal layer systems are used for the detection of this electronic excitation. The here applied aluminium/aluminium oxide/silver layer sytems have barrier heights of 2.4 eV on the aluminium respectively 3.3 eV on the silver side. With the results it could uniquely be shown that the electronic excitation is generated by kinetic processes, this excitation dependenc on the kinetic energy of the colliding particles, and the excitation dependes on the charge state of the projectile

  7. Parametric amplification and cascaded-nonlinearity processes in common atomic system.

    Science.gov (United States)

    Zheng, Huaibin; Zhang, Xun; Zhang, Zhaoyang; Tian, Yaling; Chen, Haixia; Li, Changbiao; Zhang, Yanpeng

    2013-01-01

    For the first time, we study the parametric amplification process of multi-wave mixing (PA-MWM) signal and cascaded-nonlinearity process (CNP) in sodium vapors both theoretically and experimentally, based on a conventional phase-conjugate MWM and a self-diffraction four-wave mixing (SD-FWM) processes, which are pumped by laser or amplified spontaneous emission (ASE), respectively. For laser pumping case, SD-FWM process serves as a quantum linear amplifier (a CNP) out (inside) of the resonant absorption region. While for ASE case, only the CNP occurs and the output linewidth is much narrower than that of the MWM signal due to the second selected effect of its electromagnetically induced transparency window. In addition, the phase-sensitive amplifying process seeded by two MWM processes is discussed for the first time. Theoretical fittings agree well with the experiment. The investigations have important potential applications in quantum communication.

  8. Radiation damage in materials. Primary knock-on atom energy analyses of cascade damage

    International Nuclear Information System (INIS)

    Sekimura, Naoto

    1995-01-01

    To understand cascade damage formation as a function of primary recoil energy, thin foils of gold were irradiated with 20 - 400 keV self-ions to 1.0 x 10 14 ions/m 2 at 300 K. Yield of groups of vacancy clusters saturated at ion energy higher than 100 keV. Number of clusters in a group had variation even from the same energy ions. Size distribution of the clusters was not strongly dependent on number of clusters in a group and ion energy. Density of vacancy clusters in a group formed near the specimen surface was calibrated to estimate vacancy cluster formation in neutron-irradiated material. A model was proposed to predict distribution of defect clusters in the irradiated materials based on a primary recoil spectrum. Examples of recomposed distribution of vacancy clusters in a group in irradiated gold were compared with the measured data. (author)

  9. Atomic-scale simulation of dust grain collisions: Surface chemistry and dissipation beyond existing theory

    Science.gov (United States)

    Quadery, Abrar H.; Doan, Baochi D.; Tucker, William C.; Dove, Adrienne R.; Schelling, Patrick K.

    2017-10-01

    The early stages of planet formation involve steps where submicron-sized dust particles collide to form aggregates. However, the mechanism through which millimeter-sized particles aggregate to kilometer-sized planetesimals is still not understood. Dust grain collision experiments carried out in the environment of the Earth lead to the prediction of a 'bouncing barrier' at millimeter-sizes. Theoretical models, e.g., Johnson-Kendall-Roberts and Derjaguin-Muller-Toporov theories, lack two key features, namely the chemistry of dust grain surfaces, and a mechanism for atomic-scale dissipation of energy. Moreover, interaction strengths in these models are parameterized based on experiments done in the Earth's environment. To address these issues, we performed atomic-scale simulations of collisions between nonhydroxylated and hydroxylated amorphous silica nanoparticles. We used the ReaxFF approach which enables modeling chemical reactions using an empirical potential. We found that nonhydroxylated nanograins tend to adhere with much higher probability than suggested by existing theories. By contrast, hydroxylated nanograins exhibit a strong tendency to bounce. Also, the interaction between dust grains has the characteristics of a strong chemical force instead of weak van der Waals forces. This suggests that the formation of strong chemical bonds and dissipation via internal atomic vibration may result in aggregation beyond what is expected based on our current understanding. Our results also indicate that experiments should more carefully consider surface conditions to mimic the space environment. We also report results of simulations with molten silica nanoparticles. It is found that molten particles are more likely to adhere due to viscous dissipation, which supports theories that suggest aggregation to kilometer scales might require grains to be in a molten state.

  10. Recent measurements of low energy charge exchange cross sections for collisions of multicharged ions on neutral atoms and molecules

    International Nuclear Information System (INIS)

    Havener, Charles C.

    2001-01-01

    At ORNL Multicharged Ion Research Facility (MIRF), charge exchange (CX) cross sections have been measured for multicharged ions (MCI) on neutral atoms and molecules. The ORNL ion-atom merged-beam apparatus was used to measure single electron capture by MCI from H at eV/amu energies. A gas cell was used to measure single and double electron capture by MCI from a variety of molecular targets at keV collision energies. The merged-beams experiment has been successful in providing benchmark total electron capture measurements for several collision systems with a variety of multicharged ions on H or D

  11. 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

    2001-02-05

    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.

  12. Cross-sections for dissociative excitation of lead atom in collisions of slow electrons with PbI2 molecules

    International Nuclear Information System (INIS)

    Smirnov, Yu.M.

    2006-01-01

    The dissociative excitation of the lead atom in e-PbI 2 collisions has been studied experimentally. 27 excitation cross-sections are measured at an exciting-electron energy of 100 eV. Nine optical excitation functions are recorded at the electron energy varying in the 0-100 eV range. The most possible reaction channels at low electron energies along with the relation of the dissociative-excitation cross-sections of the lead atom both in e-PbI 2 and e-PbCl 2 collisions are discussed. (authors)

  13. Cascade calculation of K--p and K--d atoms

    International Nuclear Information System (INIS)

    Koike, T.; Harada, T.; Akaishi, Y.

    1995-09-01

    X-ray yields of K - -p and K - -d atoms are calculated as a function of the target density in order to find an optimum condition for experiments. The dependence of the yields on the energy level shift and absorption width due to the strong interaction is systematically investigated. (author)

  14. Semiclassical study of the collision of a highly excited Rydberg atom with the molecules HF and HCl

    International Nuclear Information System (INIS)

    Kimura, M.; Lane, N.F.

    1990-01-01

    The semiclassical impact-parameter method is applied to the processes of state changing and energy transfer in the collision of a highly excited Rydberg atom (n≥20) with the polar molecules HF and HCl. The relative motion of the molecule and atomic nucleus is taken to be rectilinear; the electron-molecule and ion core-molecule interactions are represented by cutoff dipole forms. Cross sections for transitions involving quantum numbers n and l of the atom and rotational quantum number j of the molecule are obtained for a range of collision energies and initial atomic and molecular states. Comparisons are made with the results of earlier classical studies and with the quantum-mechanical impulse approximation. Collision rates are calculated and compared with experimental values for l mixing and n and j changing. The agreement between experiment and theory is shown to be satisfactory, within the uncertainties of both the measurements and the theory. Cases of agreement and disagreement between various theories are examined. One finding of the present work is that the quantum-mechanical impulse approximation appears to significantly overestimate the values of various state-changing cross sections when the internal energy defect is small. The validity of the impulse approximation for collisions of Rydberg atoms with polar molecules is discussed

  15. 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...

  16. Effect of the nuclear charge of a fast structural ion on its internal effective stopping in collisions with atoms

    Energy Technology Data Exchange (ETDEWEB)

    Gusarevich, E. S., E-mail: gusarevich@gmail.com [Lomonosov Nothern (Arctic) Federal University (Russian Federation)

    2017-02-15

    The energy losses of fast structural ions in collisions with atoms have been considered in the eikonal approximation. The structural ions are ions consisting of a nucleus and a certain number of electrons bound to it. The effect of nuclear charge Z of the ion on its effective deceleration κ{sup (p)} (energy losses associated with excitation of only intrinsic ion shells) has been analyzed. It is shown that the allowance for the interaction of an atom with the ion nucleus for Z{sub a}Z/v > 1, where Z{sub a} is the charge of the atomic nucleus and v is the velocity of collisions in atomic units, considerably affects the value of κ{sup (p)}, which generally necessitates taking into account nonperturbatively the effect of both charges Z{sub a} and Z on κ{sup (p)}.

  17. 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...

  18. Correlated charge changing ion-atom collisions: Progress report for the period March 15, 1988--March 14, 1989

    International Nuclear Information System (INIS)

    Bernstein, E.M.; Tanis, J.A.

    1989-04-01

    This report summarizes the progress and accomplishments in accelerator atomic physics research supported by DOE grant FG02-87ER13778 from March 15, 1988 through atomic interactions in collisions of highly charged projectiles with neutral targets. Processes involving excitation, ionization, and charge transfer are investigated using coincidence techniques to isolate and identify specific interaction mechanisms. New measurements were conducted using accelerators at the Lawrence Berkeley Laboratory, Argonne National Laboratory, and Western Michigan University. The principal new results are summarized

  19. Electron loss from hydrogen-like highly charged ions in collisions with electrons, protons and light atoms

    Science.gov (United States)

    Lyashchenko, K. N.; Andreev, O. Yu; Voitkiv, A. B.

    2018-03-01

    We consider electron loss from a hydrogen-like highly charged ion (HCI) in relativistic collisions with hydrogen and helium in the range of impact velocities v min ≤ v ≤ v max (v min and v max correspond to the threshold energy ε th for electron loss in collisions with a free electron and to ≈5 ε th, respectively) where any reliable data for loss cross sections are absent. In this range, where the loss process is characterized by large momentum transfers, we express it in terms of electron loss in collisions with equivelocity protons and electrons and explore by performing a detailed comparative study of these subprocesses. Our results, in particular, show that: (i) compared to equivelocity electrons protons are more effective in inducing electron loss, (ii) the relative effectiveness of electron projectiles grows with increase in the atomic number of a HCI, (iii) collisions with protons and electrons lead to a qualitatively different population of the final-state-electron momentum space and even when the total loss cross sections in these collisions become already equal the spectra of the outgoing electrons still remain quite different in almost the entire volume of the final-state-electron momentum space, (iv) in collisions with hydrogen and helium the contributions to the loss process from the interactions with the nucleus and the electron(s) of the atom could be rather well separated in a substantial part of the final-state-electron momentum space.

  20. Eikonal calculation of electron-capture cross sections in collisions of H atoms with fast projectiles

    International Nuclear Information System (INIS)

    Ho, T.S.; Lieber, M.; Chan, F.T.

    1981-01-01

    We have employed the eikonal method to calculate the cross section for the capture of an electron into an arbitrary nl subshell in collisions between hydrogen atoms and fast projectiles. the projectiles were protons, C 6+ , O 8+ , and Fe 24+ . The energy ranges considered were 20--100 keV in the proton case, and 40--200 keV per nucleon in the other cases. These projectiles were selected because of their importance in fusion plasmas. For the highly charged case of Fe 24+ we found that our formulas, while exact, involved a high degree of cancellation and produced unreliable numerical results, so that a numerical integration of the penultimate formula was substituted. In the proton case agreement with recent experimental data is excellent

  1. Description of ionization in the molecular approach to atomic collisions. II

    International Nuclear Information System (INIS)

    Errea, L.F.; Mendez, L.; Riera, A.; Sevila, I.; Harel, C.; Jouin, H.; Pons, B.

    2002-01-01

    We complement a previous article [Harel et al., Phys. Rev. A 55, 287 (1997)] that studied the characteristics of the description of ionization by the molecular approach to atomic collisions, by comparing the wave functions with accurate counterparts. We show how the failure of the basis to describe the phase of the ionizing wave function results in a trapping of the corresponding population in some molecular channels. The time evolution of the molecular wave function then departs from the exact one and the ionization and capture mechanisms appear as interlocked. We thus elucidate the question of the 'natural' boundary of the molecular approach and draw further consequences as to the choice of pseudostates and the use of translation factors

  2. 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)

  3. Excited-state positronium formation from positron--atomic-hydrogen collisions

    International Nuclear Information System (INIS)

    Mandal, C.R.; Mandal, M.; Mukherjee, S.C.

    1991-01-01

    Positronium formation into ground and n=2 levels has been studied in collisions of positrons with atomic hydrogen in the framework of an approximation called the boundary-corrected continuum-intermediate-state (BCCIS) approximation in the energy range of 0.08--2 keV. The conventional continuum-intermediate-state approximation does not satisfy the correct boundary condition. It has been shown that, with a suitable choice of the distorting potential, the boundary condition may be satisfied with a proper account of the intermediate continuum states. It has also been shown that the BCCIS approximation leads to the same transition amplitude as may be derived using the Vainshtein-Presnyakov-Sobelman approximation. The results obtained here are found to be in good agreement when compared with other theoretical results

  4. 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.

  5. Correlated electron capture and inner-shell excitation measurements in ion-atom collisions

    International Nuclear Information System (INIS)

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

    1985-01-01

    In an ion-atom collision projectile excitation and charge transfer (electron capture) may occur together in a single encounter. If the excitation and capture are correlated, then the process is called resonant transfer and excitation (RTE); if they are uncorrelated, then the process is termed nonresonant transfer and excitation (NTE). Experimental work to date has shown the existence of RTE and provided strong evidence for NTE. Results presented here provide information on the relative magnitudes of RTE and NTE, the charge state dependence of RTE, the effect of the target momentum distribution on RTE, the magnitude of L-shell RTE compared to K-shell RTE, and the target Z dependences of RTE and NTE. 15 refs., 5 figs

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

    International Nuclear Information System (INIS)

    Harada, Kichinosuke; Ozawa, Kunio; Kamitsubo, H.; Nomura, T.; Awaya, Y.; Watanabe, T.

    1982-11-01

    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)

  7. Time ordering of two-step processes in energetic ion-atom collisions: Basic formalism

    International Nuclear Information System (INIS)

    Stolterfoht, N.

    1993-01-01

    The semiclassical approximation is applied in second order to describe time ordering of two-step processes in energetic ion-atom collisions. Emphasis is given to the conditions for interferences between first- and second-order terms. In systems with two active electrons, time ordering gives rise to a pair of associated paths involving a second-order process and its time-inverted process. Combining these paths within the independent-particle frozen orbital model, time ordering is lost. It is shown that the loss of time ordering modifies the second-order amplitude so that its ability to interfere with the first-order amplitude is essentially reduced. Time ordering and the capability for interference is regained, as one path is blocked by means of the Pauli exclusion principle. The time-ordering formalism is prepared for papers dealing with collision experiments of single excitation [Stolterfoht et al., following paper, Phys. Rev. A 48, 2986 (1993)] and double excitation [Stolterfoht et al. (unpublished)

  8. Annealing and cluster formation of defects in a cascade

    International Nuclear Information System (INIS)

    Martynenko, Yu.V.

    1975-01-01

    The behaviour of radiative defects after a dynamic cascade of atomic collisions caused by irradiation by neutrons or accelerated heavy ions if theoretically investigated. In investig.ation, apart from processes of vacancy recombination, cluster formation and interstitial atoms the diffusive ''spreading'' of point defects from the initial region is taken into account. Since interstitial atoms are more mobile, all the processes are divided into two stages: at the first stage only interstitial atoms diffuse, and vacancies are stationary; at the second stage vacancies are mobile, and interstitial atoms are either ''spread'' over the whole volume, or are united into stable clusters. The number of defects and clusters is calculated depending on energy of cascade, atomic number of the material and temperature

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

    International Nuclear Information System (INIS)

    Blieck, J.

    2008-10-01

    87 Rb 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)

  10. The production of collimated beams of o-Ps atoms using charge exchange in positron-gas collisions

    International Nuclear Information System (INIS)

    Laricchia, G.; Charlton, M.; Davies, S.A.; Beling, C.D.; Griffith, T.C.

    1987-01-01

    Using positron-gas collisions in a short scattering cell it is demonstrated that, at certain impact energies, approximately 4% of the scattered positrons can be detected as o-Ps atoms collimated in a 6 0 cone about the incident positron direction. (author)

  11. Strong isotope effects on the charge transfer in slow collisions of He2+ with atomic hydrogen, deuterium, and tritium

    NARCIS (Netherlands)

    Stolterfoht, N.; Cabrera-Trujillo, R.; Oehrn, Y.; Deumens, E.; Hoekstra, R.; Sabin, J. R.

    2007-01-01

    Probabilities and cross sections for charge transfer by He2+ impact on atomic hydrogen (H), deuterium (D), and tritium (T) at low collision energies are calculated. The results are obtained using an ab initio theory, which solves the time-dependent Schrodinger equation. For the H target, excellent

  12. Collision cross sections and equilibrium fractions of ions and atoms in metal vapor targets. Project progress report, June 1, 1979-May 31, 1980

    International Nuclear Information System (INIS)

    Morgan, T.J.

    1980-01-01

    The objective of this program is to measure atomic collision cross sections and equilibrium fractions of ions and atoms in metal vapor targets. The goal is to obtain experimental information on atomic collision processes relevant to the Magnetic Fusion Energy Program. In particular, in connection with the development of double charge exchange D - ion sources, we are measuring D - formation cross sections in alkaline-earth metal vapor targets. During the period covered in this report we have measured electron transfer cross sections for 3-40 keV D + ions and D 0 atoms in collision with calcium vapor

  13. Superheavy nuclei and quasi-atoms produced in collisions of transuranium ions

    International Nuclear Information System (INIS)

    Zagrebaev, V.; Oganessian, Y.; Itkis, M.; Greiner, W.

    2005-01-01

    , may remain in contact rather long time. This time delay (up to 10 -19 s) could significantly increase the yield of the so-called spontaneous positron emission from super-strong electric field of quasi-atoms by a static QED process (transition from neutral to charged QED vacuum). This effect was searched sometime ago at GSI but no clear evidences of it have been found. New experiments may be performed now based on our new knowledge of collision dynamics of these nuclei. About twenty years ago damped collisions of very heavy nuclei have been used also for production of chemically separated long-lived actinides. The cross sections were found to be exponentially decreasing with increase of a charge number of heavier fragment, up to the level of 0.1 μb for production of Md isotopes in U + Cm collisions. A new effect, which we found here, is the 'inverse quasi-fission' process. In this process a superheavy nuclear system, say Th + Cf, travelling over the multidimensional potential energy surface, changes its mass asymmetry and may fall into the so-called lead valley. If Th comes to Pb, then Cf grows to the element 106. In spite of rather high excitation energy and low survival probability of residual fragments, this effect significantly increases the yield of nuclei complementary to lead and give us a new way for production of neutron rich (more close to the island of stability) superheavy elements in addition to the extensively used complete fusion reactions. These and some other prospects of subsequent theoretical and experimental studies along with possible collaborations in the field will be discussed in the talk

  14. Electron capture in collisions of S{sup 4+} with atomic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Stancil, P.C. [Department of Physics and Astronomy, University of Georgia, Athens, GA (United States)]. E-mail: stancil@physast.uga.edu; Turner, A.R. [Department of Chemistry, University of Liverpool, Liverpool (United Kingdom)]. E-mail: art@liv.ac.uk; Cooper, D.L. [Department of Chemistry, University of Liverpool, Liverpool (United Kingdom)]. E-mail: dlc@liv.ac.uk; Schultz, D.R. [Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States)]. E-mail: schultz@mail.phy.ornl.gov; Rakovic, M.J. [Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States)]. E-mail: milun@mail.phy.ornl.gov; Fritsch, W. [Abteilung Theoretische Physik, Hahn-Meitner-Institut Berlin, Berlin (Germany)]. E-mail: fritsch@hmi.de; Zygelman, B. [Department of Physics, University of Nevada, Las Vegas, NV (United States)]. E-mail: bernard@physics.unlv.edu

    2001-06-28

    Charge transfer processes due to collisions of ground state S{sup 4+}(3s{sup 2} {sup 1}S) ions with atomic hydrogen are investigated for energies between 1 meV u{sup -1} and 10 MeV u{sup -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 S{sup 3+} excited classical states. Hydrogen target isotope effects are explored and rate coefficients for temperatures between 100 and 10{sup 6} K are also presented. (author)

  15. Displacement cascades in diatomic materials

    International Nuclear Information System (INIS)

    Parkin, D.M.; Coulter, C.A.

    1981-01-01

    A new function, the specified-projectile displacement function p/sub ijk/ (E), is introduced to describe displacement cascades in polyatomic materials. This function describes the specific collision events that produce displacements and hence adds new information not previously available. Calculations of p/sub ijk/ (E) for MgO, Al 2 O 3 and TaO are presented and discussed. Results show that the parameters that have the largest effect on displacement collision events are the PKA energy and the mass ratio of the atom types in the material. It is further shown that the microscopic nature of the displacement events changes over the entire recoil energy range relevant to fusion neutron spectra and that these changes are different in materials whose mass ratio is near one than in those where it is far from one

  16. PREFACE: XXVIII International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC 2013)

    Science.gov (United States)

    Xiao, Guoqing; Cai, Xiaohong; Ding, Dajun; Ma, Xinwen; Zhao, Yongtao

    2014-04-01

    The 28th International Conference on Photonic, Electronic and Atomic Collisions (XXVIII ICPEAC) was held by the Institute of Modern Physics, Chinese Academy of Sciences (IMP) on 24-30 July, 2013 in Lanzhou, China. The 444 conference participants came from 37 countries and/or regions. Five plenary lectures, more than 80 progress reports and special reports had been arranged according to the decision of the ICPEAC International General Committee. Meanwhile, more than 650 abstracts were selected as poster presentations. Before the conference, three highly distinguished scientists, Professor Joachim Burgdöorfer, Professor Hossein Sadeghpour and Professor Yasunori Yamazaki, presented tutorial lectures with the support of the IMP Branch of Youth Innovation Promotion Association, CAS (IMP-YIPA). During the conference, Professor Jianwei Pan from University of Sciences and Technology in China presented an enlightening public lecture on quantum communication. Furthermore, 2013 IUPAP Young Scientist Prize was awarded to Dr T Jahnke from Johann Wolfgang Goethe University of Germany. The Sheldon Datz Prize for an Outstanding Young Scientist Attending ICPEAC was awarded to Dr Diogo Almeida from University of Fribourg of Switzerland. As a biannual academic conference, ICPEAC 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, atomic, ionic, molecular, cluster collisions with matter. With a history back to 1958, ICPEAC came to China for the very first time. IMP has been preparing the conference six years before, ever since the ICPEAC International General Committee made the decision to hold the XXVIII ICPEAC in Lanzhou. This proceedings includes the papers of the two plenary lectures, 40 progress reports, 17 special reports and 337 posters, which were reviewed and revised according to the comments of the referees. The Local Organizing Committee would like to

  17. Two-electron excitation in slow ion-atom collisions: Excitation mechanisms and interferences among autoionizing states

    International Nuclear Information System (INIS)

    Kimura, M.; Rice Univ., Houston, TX

    1990-01-01

    The two-electron capture or excitation process resulting from collisions of H + and O 6+ ions with He atoms in the energy range from 0.5 keV/amu to 5 keV/amu is studied within a molecular representation. The collision dynamics for formation of doubly excited O 4+ ions and He** atoms and their (n ell, n'ell ') populations are analyzed in conjunction with electron correlations. Autoionizing states thus formed decay through the Auger process. An experimental study of an ejected electron energy spectrum shows ample structures in addition to two characteristic peaks that are identified by atomic and molecular autoionizations. These structures are attributable to various interferences among electronic states and trajectories. We examine the dominant sources of the interferences. 12 refs., 5 figs

  18. TDHF study of the He+ collision on atomic He targets at the 8Be ground state energy

    International Nuclear Information System (INIS)

    Cai, J.; Shoppa, T.D.; Langanke, K.

    1997-01-01

    Experimentally the 8 Be ground state resonance has been studied in He + collisions on atomic He atoms. The nuclear resonance manifests itself by satellite resonance lines corresponding to different electron configurations of the Be ion. Experimentally a large probability for the emission of one electron has been deduced. We study the atomic He + +He collision within a model in which the evolution of the electron wavefunction is treated dynamically in the TDHF scheme, and the motion of the nuclei is treated classically. In agreement with experiment we find a large probability for one electron to be emitted into the continuum during the lifetime of the 8 Be ground state resonance. (orig.). With 2 figs., 1 tab

  19. VNI version 4.1. Simulation of high-energy particle collisions in QCD: Space-time evolution of e{sup +}e{sup {minus}}...A + B collisions with parton-cascades, cluster-hadronization, final-state hadron cascades

    Energy Technology Data Exchange (ETDEWEB)

    Geiger, K.; Longacre, R. [Brookhaven National Lab., Upton, NY (United States). Physics Dept.; Srivastava, D.K. [Variable Energy Cyclotron Centre, Calcutta (India)

    1999-02-01

    VNI is a general-purpose Monte-Carlo event-generator, which includes the simulation of lepton-lepton, lepton-hadron, lepton-nucleus, hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions. It uses the real-time evolution of parton cascades in conjunction with a self-consistent hadronization scheme, as well as the development of hadron cascades after hadronization. The causal evolution from a specific initial state (determined by the colliding beam particles) is followed by the time-development of the phase-space densities of partons, pre-hadronic parton clusters, and final-state hadrons, in position-space, momentum-space and color-space. The parton-evolution is described in terms of a space-time generalization of the familiar momentum-space description of multiple (semi)hard interactions in QCD, involving 2 {r_arrow} 2 parton collisions, 2 {r_arrow} 1 parton fusion processes, and 1 {r_arrow} 2 radiation processes. The formation of color-singlet pre-hadronic clusters and their decays into hadrons, on the other hand, is treated by using a spatial criterion motivated by confinement and a non-perturbative model for hadronization. Finally, the cascading of produced prehadronic clusters and of hadrons includes a multitude of 2 {r_arrow} n processes, and is modeled in parallel to the parton cascade description. This paper gives a brief review of the physics underlying VNI, as well as a detailed description of the program itself. The latter program description emphasizes easy-to-use pragmatism and explains how to use the program (including simple examples), annotates input and control parameters, and discusses output data provided by it.

  20. 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)

  1. The energy-deposition model. Electron loss of heavy ions in collisions with neutral atoms at low and intermediate energies

    International Nuclear Information System (INIS)

    Shevelko, V.P.; Litsarev, M.S.; Kato, D.; Tawara, H.

    2010-09-01

    Single- and multiple-electron loss processes in collisions of heavy many-electron ions (positive and negative) in collisions with neutral atoms at low and intermediate energies are considered using the energy-deposition model. The DEPOSIT computer code, created earlier to calculate electron-loss cross sections at high projectile energies, is extended for low and intermediate energies. A description of a new version of DEPOSIT code is given, and the limits of validity for collision velocity in the model are discussed. Calculated electron-loss cross sections for heavy ions and atoms (N + , Ar + , Xe + , U + , U 28+ , W, W + , Ge - , Au - ), colliding with neutral atoms (He, Ne, Ar, W) are compared with available experimental and theoretical data at energies E > 10 keV/u. It is found that in most cases the agreement between experimental data and the present model is within a factor of 2. Combining results obtained by the DEPOSIT code at low and intermediate energies with those by the LOSS-R code at high energies (relativistic Born approximation), recommended electron-loss cross sections in a wide range of collision energy are presented. (author)

  2. Lane fuzzy collision in channel with potential deformation by photon-phonon-electron excitation and sub-atomic control

    International Nuclear Information System (INIS)

    Shen Jing

    1998-01-01

    Collision between μ + and the μ - beams in the crystal are forbidden due to the two beams having different ''lanes'' in a channel. A laser pulse of ps-fs shocks lattice kernel vibration and dilates lattice electron distribution. It deforms the Lindhard's potential which is then expressed in a quantized form as the Huang-Zhu's potential[1]. The dynamic lanes can be made to overlap in a channel to allow collision without ductile fracture. This raises a new technology of sub-atomic information and control, which has been raised by T. D. Lee

  3. INCAS: an analytical model to describe displacement cascades

    Energy Technology Data Exchange (ETDEWEB)

    Jumel, Stephanie E-mail: stephanie.jumel@edf.fr; Claude Van-Duysen, Jean E-mail: jean-claude.van-duysen@edf.fr

    2004-07-01

    REVE (REactor for Virtual Experiments) is an international project aimed at developing tools to simulate neutron irradiation effects in Light Water Reactor materials (Fe, Ni or Zr-based alloys). One of the important steps of the project is to characterise the displacement cascades induced by neutrons. Accordingly, the Department of Material Studies of Electricite de France developed an analytical model based on the binary collision approximation. This model, called INCAS (INtegration of CAScades), was devised to be applied on pure elements; however, it can also be used on diluted alloys (reactor pressure vessel steels, etc.) or alloys composed of atoms with close atomic numbers (stainless steels, etc.). INCAS describes displacement cascades by taking into account the nuclear collisions and electronic interactions undergone by the moving atoms. In particular, it enables to determine the mean number of sub-cascades induced by a PKA (depending on its energy) as well as the mean energy dissipated in each of them. The experimental validation of INCAS requires a large effort and could not be carried out in the framework of the study. However, it was verified that INCAS results are in conformity with those obtained from other approaches. As a first application, INCAS was applied to determine the sub-cascade spectrum induced in iron by the neutron spectrum corresponding to the central channel of the High Flux Irradiation Reactor of Oak Ridge National Laboratory.

  4. INCAS: an analytical model to describe displacement cascades

    Science.gov (United States)

    Jumel, Stéphanie; Claude Van-Duysen, Jean

    2004-07-01

    REVE (REactor for Virtual Experiments) is an international project aimed at developing tools to simulate neutron irradiation effects in Light Water Reactor materials (Fe, Ni or Zr-based alloys). One of the important steps of the project is to characterise the displacement cascades induced by neutrons. Accordingly, the Department of Material Studies of Electricité de France developed an analytical model based on the binary collision approximation. This model, called INCAS (INtegration of CAScades), was devised to be applied on pure elements; however, it can also be used on diluted alloys (reactor pressure vessel steels, etc.) or alloys composed of atoms with close atomic numbers (stainless steels, etc.). INCAS describes displacement cascades by taking into account the nuclear collisions and electronic interactions undergone by the moving atoms. In particular, it enables to determine the mean number of sub-cascades induced by a PKA (depending on its energy) as well as the mean energy dissipated in each of them. The experimental validation of INCAS requires a large effort and could not be carried out in the framework of the study. However, it was verified that INCAS results are in conformity with those obtained from other approaches. As a first application, INCAS was applied to determine the sub-cascade spectrum induced in iron by the neutron spectrum corresponding to the central channel of the High Flux Irradiation Reactor of Oak Ridge National Laboratory.

  5. INCAS: an analytical model to describe displacement cascades

    International Nuclear Information System (INIS)

    Jumel, Stephanie; Claude Van-Duysen, Jean

    2004-01-01

    REVE (REactor for Virtual Experiments) is an international project aimed at developing tools to simulate neutron irradiation effects in Light Water Reactor materials (Fe, Ni or Zr-based alloys). One of the important steps of the project is to characterise the displacement cascades induced by neutrons. Accordingly, the Department of Material Studies of Electricite de France developed an analytical model based on the binary collision approximation. This model, called INCAS (INtegration of CAScades), was devised to be applied on pure elements; however, it can also be used on diluted alloys (reactor pressure vessel steels, etc.) or alloys composed of atoms with close atomic numbers (stainless steels, etc.). INCAS describes displacement cascades by taking into account the nuclear collisions and electronic interactions undergone by the moving atoms. In particular, it enables to determine the mean number of sub-cascades induced by a PKA (depending on its energy) as well as the mean energy dissipated in each of them. The experimental validation of INCAS requires a large effort and could not be carried out in the framework of the study. However, it was verified that INCAS results are in conformity with those obtained from other approaches. As a first application, INCAS was applied to determine the sub-cascade spectrum induced in iron by the neutron spectrum corresponding to the central channel of the High Flux Irradiation Reactor of Oak Ridge National Laboratory

  6. Atomic data on inelastic processes in low-energy manganese-hydrogen collisions

    Science.gov (United States)

    Belyaev, Andrey K.; Voronov, Yaroslav V.

    2017-10-01

    Aims: The aim of this paper is to calculate cross sections and rate coefficients for inelastic processes in low-energy Mn + H and Mn+ + H- collisions, especially, for processes with high and moderate rate coefficients. These processes are required for non-local thermodynamic equilibrium (non-LTE) modeling of manganese spectra in cool stellar atmospheres, and in particular, for metal-poor stars. Methods: The calculations of the cross sections and the rate coefficients were performed by means of the quantum model approach within the framework of the Born-Oppenheimer formalism, that is, the asymptotic semi-empirical method for the electronic MnH molecular structure calculation followed by the nonadiabatic nuclear dynamical calculation by means of the multichannel analytic formulas. Results: The cross sections and the rate coefficients for low-energy inelastic processes in manganese-hydrogen collisions are calculated for all transitions between 21 low-lying covalent states and one ionic state. We show that the highest values of the cross sections and the rate coefficients correspond to the mutual neutralization processes into the final atomic states Mn(3d54s(7S)5s e 6S), Mn(3d54s(7S)5p y 8P°), Mn(3d54s(7S)5s e 8S), Mn(3d54s(7S)4d e 8D) [the first group], the processes with the rate coefficients (at temperature T = 6000 K) of the values 4.38 × 10-8, 2.72 × 10-8, 1.98 × 10-8, and 1.59 × 10-8 cm3/ s, respectively, that is, with the rate coefficients exceeding 10-8 cm3/ s. The processes with moderate rate coefficients, that is, with values between 10-10 and 10-8 cm3/ s include many excitation, de-excitation, mutual neutralization and ion-pair formation processes. In addition to other processes involving the atomic states from the first group, the processes from the second group include those involving the following atomic states: Mn(3d5(6S)4s4p (1P°) y 6P°), Mn(3d54s(7S)4d e 6D), Mn(3d54s(7S)5p w 6P°), Mn(3d5(4P)4s4p (3P°) y 6D°), Mn(3d5(4G)4s4p (3P°) y 6F

  7. The rate coefficients for the processes of (n - n')-mixing in collisions of Rydberg atoms H*(n) with H(1s) atoms

    Energy Technology Data Exchange (ETDEWEB)

    Mihajlov, A A [Institute of Physics, PO Box 57, 11001 Belgrade (Serbia and Montenegro); Ignjatovic, Lj M [Institute of Physics, PO Box 57, 11001 Belgrade (Serbia and Montenegro); Djuric, Z [Silvaco Data Systems, Compass Point, St Ives PE27 5JL (United Kingdom); Ljepojevic, N N [Silvaco Data Systems, Compass Point, St Ives PE27 5JL (United Kingdom)

    2004-11-28

    This paper presents the results of semi-classical calculations of rate coefficients of (n - n')-mixing processes in collisions of Rydberg atoms H*(n) with H(1s) atoms. These processes have been modelled by the mechanism of the resonant energy exchange within the electron component of the H*(n) + H collisional system. The calculations of the rate coefficients, based on this model, were performed for the series of principal quantum numbers, n and n', and atomic, T{sub a}, and electronic, T{sub e}, temperatures. It was shown that these processes can be of significant influence on the populations of Rydberg atoms in weakly ionized plasmas (ionization degree {approx}<10{sup -4}), and therefore have to be included in appropriate models of such plasmas.

  8. The rate coefficients for the processes of (n - n')-mixing in collisions of Rydberg atoms H*(n) with H(1s) atoms

    International Nuclear Information System (INIS)

    Mihajlov, A A; Ignjatovic, Lj M; Djuric, Z; Ljepojevic, N N

    2004-01-01

    This paper presents the results of semi-classical calculations of rate coefficients of (n - n')-mixing processes in collisions of Rydberg atoms H*(n) with H(1s) atoms. These processes have been modelled by the mechanism of the resonant energy exchange within the electron component of the H*(n) + H collisional system. The calculations of the rate coefficients, based on this model, were performed for the series of principal quantum numbers, n and n', and atomic, T a , and electronic, T e , temperatures. It was shown that these processes can be of significant influence on the populations of Rydberg atoms in weakly ionized plasmas (ionization degree ∼ -4 ), and therefore have to be included in appropriate models of such plasmas

  9. Collisions of halogen (2P) and rare gas (1S) atoms

    International Nuclear Information System (INIS)

    Becker, C.H.

    1978-12-01

    Differential cross sections I (THETA) at several collision energies measured in crossed molecular beam experiments are reported for several combinations of halogen atoms ( 2 P) scattered off rare gas-rare gas atoms ( 1 S 0 ), namely, F + Ne, F + Ar, F + Kr, F + Xe, C1 + Xe. The scattering is described by an elastic model appropriate to Hund's case c coupling. With the use of this model, the X 1/2, I 3/2, and II 1/2 interaction potential energy curves are derived by fitting calculated differential cross sections, based on analytic representations of the potentials, to the data. The F - Xe X 1/2 potential shows a significant bonding qualitatively different than for the other F-rare gases. The I 3/2 and II 1/2 potentials closely resemble the van der Waals interactions of the one electron richer ground state rare gas-rare gas systems. Coupled-channel scattering calculations are carried out for F + Ar, F + Xe, and C1 + Xe using the realistic potential curves derived earlier. The results justify the use of the elastic model, and give additional information on intramultiplet and intermultiplet transitions. The transitions are found to be governed by the crossing of the two Ω = 1/2 potentials in the complex plane. The measured I (theta) and I (THETA) derived from the coupled-channel computations show small oscillations or perturbations (Stueckelberg oscillations) though quantitative agreement is not obtained.The nature of the anomalous F - Xe X 1/2 potential is discussed as is the approximation of a constant spin orbit coupling over the experimentally accessible range of internuclear distances for these open shell molecules. 55 references

  10. Molecular dynamics studies of displacement cascades

    International Nuclear Information System (INIS)

    Averback, R.S.; Hsieh, Horngming; Diaz de la Rubia, T.

    1990-02-01

    Molecular-dynamics simulations of cascades in Cu and Ni with primary-knock-on energies up to 5 keV and lattice temperatures in the range 0 K--700 K are described. Interatomic forces were represented by either the Gibson II (Cu) or Johnson-Erginsoy (Ni) potentials in most of this work, although some simulations using ''Embedded Atom Method'' potentials, e.g., for threshold events in Ni 3 Al, are also presented. The results indicate that the primary state of damage produced by displacement cascades is controlled by two phenomena, replacement collision sequences during the collisional phase of the cascade and local melting during the thermal spike. As expected, the collisional phase is rather similar in Cu and Ni, however, the thermal spike is of longer duration and has a more pronounced influence in Cu than Ni. When the ambient temperature of the lattice is increased, the melt zones are observed to both increase in size and cool more slowly. This has the effect of reducing defect production and enhancing atomic mixing and disordering. The implications of these results for defect production, cascade collapse, atomic disordering will be discussed. 34 refs., 7 figs., 2 tabs

  11. Inelastic collisions of atomic particles at mean energies. Pt.1. Qualitative model of energy losses during a collision

    International Nuclear Information System (INIS)

    Pustovit, A.N.

    2005-01-01

    A new approach is proposed for description of the energy losses of mean-energy atomic particles during their interactions with atomic particles of solids. It is shown that all these interactions are inelastic ones and are determined by different scattering zones with different laws of energy loss dependences [ru

  12. Charge Transfer Processes in Collisions of Si4+ Ions with He Atoms at Intermediate Energies

    Science.gov (United States)

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

    Charge transfer in collisions of Si4+ ions with He atoms below 100 keV/u is studied by using a molecular orbital representation within both the semiclassical and quantal representations. Single transfer reaction Si4++He →Si3++He+ has been studied by a number of theoretical investigations. In addition to the reaction (1), the first semiclassical MOCC calculations are performed for the double transfer channel Si4++HE→Si2++He2+ Nine molecular states that connect both with single and double electron transfer processes are considered in the present model. Electronic states and corresponding couplings are determined by the multireference single- and double- excitation configuration interaction method. The present cross sections tie well with the earlier calculations of Stancil et al., Phys. Rev. A 55, 1064 (1997) at lower energies, but show a rather different magnitude from those of Bacchus-Montabonel and Ceyzeriat, Phys. Rev. A 58, 1162 (1998). The present rate constant is found to be significantly different from the experimental finding of Fang and Kwong, Phys. Rev. A 59, 342 (1996) at 4,600 K, and hence does not support the experiment.

  13. Electron capture in collisions of Si3+ ions with atomic hydrogen from low to intermediate energies

    Science.gov (United States)

    Liu, C. H.; Liu, L.; Wang, J. G.

    2014-07-01

    The electron capture process for the Si3+(3s) + H(1s) collisions is investigated by the quantum-mechanical molecular orbital close-coupling (MOCC) method and by the two-center atomic orbital close-coupling (AOCC) method in the energy range of 10-5-10 keV/u and 0.8-200 keV/u, respectively. Total and state-selective cross sections are presented and compared with the available theoretical and experimental results. The present MOCC and AOCC results agree well with the experimental measurements, but show some discrepancy with the calculations of Wang et al. [Phys. Rev. A 74, 052709 (2006), 10.1103/PhysRevA.74.052709] at E > 40 eV/u because of the inclusion of rotational couplings, which play important roles in the electron capture process. At lower energies, the present results are about three to five times smaller than those of Wang et al. due to the difference in the molecular data at large internuclear distances. The energy behaviors of the electron capture cross sections are discussed on the basis of identified reaction mechanisms.

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

    International Nuclear Information System (INIS)

    Chacon, A.D.

    1989-01-01

    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 56 Fe + Fe, 1.82 · A GeV 40 Ar + KCl and 1.54 · A GeV 93 Nb + 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

  15. Near-threshold effects in ionization of atoms (post collision interaction)

    International Nuclear Information System (INIS)

    Amus'ya, M.Ya.; Kuchiev, M.Yu.; Shejnerman, S.A.

    1979-01-01

    The special class of phenomena of the post collision interaction PCI taking place in case of inelastic electron scattering on atoms, when the incident electron energy is close to the excitement threshold of an autoionization state, is studied. The quantitative quantum-mechanical theory of the PCI is developed. The theory is based only on the supposition that the change of the field in which a slow electron moves takes place in such a small time interval that the interaction of a fast and slow electron can be neglected. The possibility of carrying out calculations giving the direct comparison with the experimental results are shown in the concrete examples. All possible PCI effects such as the shift of the maximum in the energy distribution of fast (or slow) electrons, the asymmetry of the contour form and its broadening, the change of the angular distribution of slow electrons, have been practically illustrated. It is shown that the interaction of a slow electron and a vacancy in the final state essentially affects the process characteristics. Taking into account PCI in the concrete process calculations made it possible to get an acceptable agreement with the available experimental data

  16. Target continuum distorted-wave theory for collisions of fast protons with atomic hydrogen

    International Nuclear Information System (INIS)

    Crothers, D.S.F.; Dunseath, K.M.

    1990-01-01

    By considering the target continuum distorted-wave (TCDW) theory as the high-energy limit of the half-way house variational continuum distorted-wave theory, it is shown not only that there is no intermediate elastic divergence but also that the second-order amplitude based on a purely elastic intermediate state is of order υ -6 and is thus negligible. The residual inelastic TCDW theory is developed to second-order at high velocities. It is used to describe charge exchange during collisions of fast protons with atomic hydrogen. Using an on-shell peaking approximation and considering 1s-1s capture it is shown that the residual purely second-order transition amplitude comprises two terms, one real term of order υ -6 and one purely imaginary term of order υ -7 ln υ. At 5 MeV laboratory energy, it is shown that these are negligible. It is also shown that the υ -5 first-order term gives a differential cross section in very good agreement with an experiment at all angles including forward, interference minimum, Thomas maximum and large angles, particularly having folded our theory over experimental resolution. (author)

  17. Three-body dynamical interference in electron and positron collision with positronium atom

    Directory of Open Access Journals (Sweden)

    E Ghanbari Adivi

    2010-12-01

    Full Text Available In this project, the Faddeev-Watson-Lovelace (FWL formalism is generalized to large scattering angles. The angular range includes 0-180 degrees. Using this method, the charge transfer differential cross-sections are calculated, in a second-order approximation, for collision of energetic positrons and electrons with neutral positronium atoms. In this approximation, the rearrangement amplitude contains two first-order and three second-order partial amplitudes. The first first-order term is the Born amplitude in a first-order approximation. The second one corresponds to capturing the transferred particle without perturbing the state of this particle. This term, in fact, describes a knock-on process. Since the masses of the particles and the absolute values of their charges are equal, one expects that the second-order terms be similar in magnitude. This aspect causes the instructive interference of the partial amplitudes in some angles and destructive interference in some others. However, it is predicted that these amplitudes have local maxima in direction of the recoiling of the projectile. In order to investigate this situation, the second-order partial amplitudes are calculated and their relations with the parity of the initial and final states of the scattering system are analyzed. In particular, the role of dynamical interference of these partial amplitudes in creation of the kinematical peak and the peak corresponding to the knock-on scattering in angular distribution of the differential cross sections is investigated.

  18. Measurement of cross-sections for step-bystep excitation of inert gas atoms from metastable states by electron collisions

    International Nuclear Information System (INIS)

    Mityureva, A.A.; Penkin, N.P.; Smirnov, V.V.

    1989-01-01

    Excitation of argon atoms by electron collisions from metastable (MS) to high-lying states of inert gases (the so-called step-by-step excitation) is investigated. Formation of MS atoms m and their further step-by-step excitation up to k level is carried out by an electron beam with energy from 1 up to 40 eV. Time distribution of forming metastable and step-by-step electron collisions is used. The method used permits to measure the functions of step-by-step excitation and the absolute values of cross sections. Absolute values of cross-sections and functions of step-by-step excitation of some lines and argon levels are obtained

  19. Correlated charge-changing ion-atom collisions. Progress report, 16 February 1993--15 April 1994

    International Nuclear Information System (INIS)

    Tanis, J.A.

    1994-04-01

    This report summarizes the progress and accomplishments of research supported by DOE. This work involves the experimental investigation of fundamental atomic processes in collisions of few-electron, charged projectile ions with neutral gas targets or electrons. The major emphasis is the study of collision processes involving two active electrons, and particularly those in which the electron-electron interaction plays a role. New results have been obtained for studies involving (1) continuum-electron emission, (2) double ionization of helium and Li + , and (3) resonant recombination of atomic ions. Experiments were conducted using accelerators at Western Michigan University, Michigan State University, Indiana University, Lawrence Livermore Laboratory, and the Institute of Nuclear Research, Debrecen, Hungary. Brief summaries of work completed and work in progress are given

  20. Improved adiabatic calculation of muonic-hydrogen-atom cross sections. I. Isotopic exchange and elastic scattering in asymmetric collisions

    International Nuclear Information System (INIS)

    Cohen, J.S.; Struensee, M.C.

    1991-01-01

    The improved adiabatic representation is used in calculations of elastic and isotopic-exchange cross sections for asymmetric collisions of pμ, dμ, and tμ with bare p, d, and t nuclei and with H, D, and T atoms. This formulation dissociates properly, correcting a well-known deficiency of the standard adiabatic method for muonic-atom collisions, and includes some effects at zeroth order that are normally considered nonadiabatic. The electronic screening is calculated directly and precisely within the improved adiabatic description; it is found to be about 30% smaller in magnitude than the previously used value at large internuclear distances and to deviate considerably from the asymptotic form at small distances. The reactance matrices, needed for calculations of molecular-target effects, are given in tables

  1. A quasi-classical study of energy transfer in collisions of hyperthermal H atoms with SO2 molecules.

    Science.gov (United States)

    da Silva, Ramon S; Garrido, Juan D; Ballester, Maikel Y

    2017-08-28

    A deep understanding of energy transfer processes in molecular collisions is at central attention in physical chemistry. Particularly vibrational excitation of small molecules colliding with hot light atoms, via a metastable complex formation, has shown to be an efficient manner of enhancing reactivity. A quasi-classical trajectory study of translation-to-vibration energy transfer (T-V ET) in collisions of hyperthermal H( 2 S) atoms with SO 2 (X̃ 1 A ' ) molecules is presented here. For such a study, a double many-body expansion potential energy surface previously reported for HSO 2 ( 2 A) is used. This work was motivated by recent experiments by Ma et al. studying collisions of H + SO 2 at the translational energy of 59 kcal/mol [J. Ma et al., Phys. Rev. A 93, 040702 (2016)]. Calculations reproduce the experimental evidence that during majority of inelastic non-reactive collision processes, there is a metastable intermediate formation (HOSO or HSO 2 ). Nevertheless, the analysis of the trajectories shows that there are two distinct mechanisms in the T-V ET process: direct and indirect. Direct T-V processes are responsible for the high population of SO 2 with relatively low vibrational excitation energy, while indirect ones dominate the conversion from translational energy to high values of the vibrational counterpart.

  2. Scheme for the implementation of a universal quantum cloning machine via cavity-assisted atomic collisions in cavity QED

    International Nuclear Information System (INIS)

    Zou Xubo; Pahlke, K.; Mathis, W.

    2003-01-01

    We propose a scheme to implement the 1→2 universal quantum cloning machine of Buzek and Hillery [Phys. Rev. A 54, 1844 (1996)] in the context of cavity QED. The scheme requires cavity-assisted collision processes between atoms, which cross through nonresonant cavity fields in the vacuum states. The cavity fields are only virtually excited to face the decoherence problem. That's why the requirements on the cavity quality factor can be loosened

  3. Shape of electron lines emitted by a fast particle in atomic collisions. Influence of the acceptance function

    International Nuclear Information System (INIS)

    Bordenave-Montesquieu, A.; Gleizes, A.; Benoit-Cattin, P.; Boudjema, M.

    1980-01-01

    In order to explain the large energy broadening of the lines observed in energy spectra of electrons emitted by fast particles, an accurate knowledge of the angular acceptance function of the electron energy analyser is necessary. A simple method is proposed which can give an accurate function for most atomic collisions: the various approximations are discussed. It is also shown that the analyser transmission depends on the acceptance angle. (author)

  4. 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

  5. International Symposium on (e, 2e), Double Photoionization, and Related Topics and the Thirteenth International Symposium on Polarization and Correlation in Electronic and Atomic Collisions

    CERN Document Server

    Lohmann, Birgit; Nieuwenhuizen, Theo M; 13th International Symposium on Polarization and Correlation in Electronic and Atomic Collisions; Ionization, correlation and polarization in atomic collisions

    2006-01-01

    All papers were peer-reviewed. This proceedings volume contains the invited talks presented at two atomic physics symposia held jointly in Buenos Aires, Argentina from 28-30 July 2005. They represent the latest research in dynamics of collision systems involving collisions between photons, electrons, and ions and a diverse range of target species: atoms, molecules, clusters, and surfaces. There is a particular emphasis on correlation and many-body effects in excitation and ionization.

  6. Electronic and Atomic Collisions. Abstracts of Contributed Papers. International Conference on the Physics of Electronic and atomic Collisions (14th) Held at Palo Alto, California in 1985,

    Science.gov (United States)

    1985-01-01

    Atomoic Collisions, (Berlin, to the insufficient energy resolution, to the 1983). coincidence signal can be neglected at this energy. In 2 J.P.M...DECAY RATES FOR % MULTIPLY IONIZED ATOMO . F. Lombet Farnoux Laboratoire Spectroscopic Atomique et lonique - Batiment 350 - vUniversite Paris-Sud...and atomo oeanis was constructed.The accompanied to 1-shell ionization X-ray emission was reristrated by 0 an Si(Li) semiconductor detector in the

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

    International Nuclear Information System (INIS)

    Watson, R.L.

    1992-01-01

    This report discusses research of multicharged nitrogen, oxygen and carbon monoxide molecular ions produced with collision with multicharged argon ions. Properties like ionization, dissociation, and excitation are investigated

  8. 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

  9. 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)

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

    International Nuclear Information System (INIS)

    Lattouf, Elie

    2013-01-01

    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 + + H 2 O 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) [fr

  11. On the impact parameter probability distribution in atomic collisions for Monte Carlo simulations

    International Nuclear Information System (INIS)

    Katardjiev, I.V.; Berg, S.; Nender, C.; Miteva, V.

    1992-01-01

    The collision statistics of ion-solid interactions in Monte Carlo simulations is discussed. The models for structureless targets are shown to be inadequate at low energies and a model for amorphous targets based on the short range ordering in amorphous solids is presented. This model clearly shows the correlation between successive collisions due to the amorphous target structure. It is shown that the new model approximates to a certain extent the collision statistics of the MARLOWE type of programs in the ''amorphous'' mode

  12. Multiple H3+ fragment production in single collision of fast Hn+ clusters with He atoms

    International Nuclear Information System (INIS)

    Farizon, B.; Farizon, M.; Gaillard, M.J.; Gerlic, E.; Ouaskit, S.

    1994-09-01

    The production of H 3 + ions resulting from single collisions of mass-selected ionic hydrogen clusters, H n + (n=9,25,31), with helium at high velocity (1.55 times the Bohr velocity) has been studied. A strong double H 3 + ion production resulting from one incident cluster is observed. Moreover, evidence for a triple H 3 + fragment production is presented for n=25 and 31. Thus, in this energy range, the collision gives rise to multifragmentation processes. The formation of H 3 + ions takes place in the fragmentation of the multicharged cluster resulting from the collision. (authors)

  13. 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...... of the de Broglie wavelength lambda(dB) = 150 fm at a velocity v = 0.20 au and the effective atomic diameter for electron capture 2R = 20 au. Parallel AO and MO semiclassical coupled-channel calculations of the Na(3s, 3p) --> Li(2s, 2p) state-to-state collision amplitudes have been performed, and quantum...

  14. Observation of double resonant laser induced transitions in the $v = n - l - 1 = 2$ metastable cascade of antiprotonic helium-4 atoms

    CERN Document Server

    Hayano, R S; Tamura, H; Torii, H A; Hori, Masaki; Maas, F E; Morita, N; Kumakura, M; Sugai, I; Hartmann, F J; Daniel, H; Von Egidy, T; Ketzer, B; Pohl, R; Horváth, D; Eades, John; Widmann, E; Yamazaki, T

    1997-01-01

    A new laser-induced resonant transition in the $v=n-l-1=2$ metastable cascade of antiprotonic $^4$He atoms has been found by using a double resonance technique. This was done by setting the first laser to the already known 470.724 nm resonance ($(n,l)=(37,34)\\rightarrow (36,33)$), while the $(38,35)\\rightarrow (37,34)$ transition was searched for with the second laser. The resonant transition was found at wavelength of 529.622$\\pm$0.003 nm, showing excellent agreement with a recent prediction of Korobov.

  15. A crossed-beam experiment on intramultiplet mixing collisions with short-lived Ne** {(2p)5(3p)} atoms

    NARCIS (Netherlands)

    Manders, M.P.I.; Ruyten, W.M.J.; van de Beucken, F..J.H.M.; Driessen, J.P.J.; Veugelers, W.J.T.; Kramer, P.H.; Vredenbregt, E.J.D.; van Hoek, W.B.M.; Sandker, G.J.; Beijerinck, H.C.W.; Verhaar, B.J.

    1988-01-01

    We describe the design, operation, and calibration of a crossed-beam experiment for the study of intramultiplet mixing collisions of short-lived electronically excited Ne{(2p)5(3p)}≡{α} atoms with ground-state atoms/molecules. The excellent performance of almost 1 kHz/Å2 (number of counts per unit

  16. [Electron transfer, ionization, and excitation in atomic collisions]. Final technical report, June 15, 1986 - June 14, 1998

    International Nuclear Information System (INIS)

    1998-01-01

    The research on theoretical atomic collisions that was funded at The Pennsylvania State University's Wilkes-Barre Campus by DOE from 1986 to 1998 was carried out by Winger from 1986 to 1989 and by Winter and Alston from 1989 to 1998. The fundamental processes of electron transfer, ionization, and excitation in ion-ion, ion-atom, and, more recently, ion-molecule collisions were addressed. These collision processes were treated in the context of simple one-electron, quasi-one-electron, or two-electron systems in order to provide unambiguous results and reveal more clearly the collisional mechanisms. Winter's work generally focused on the intermediate projectile-energy range corresponding to proton energies from about ten to a few hundred keV. In this velocity-matching energy range, the electron-transfer cross section reaches a peak, and many states, including electron-transfer and ionization states, contribute to the overall electron-cloud distribution and transition probabilities; a large number of states are coupled, and therefore perturbative approaches are generally inappropriate. These coupled-state calculations were sometimes also extended to higher energies to join with perturbative results. Alston concentrated on intermediate-energy asymmetric collision systems, for which coupling with the projectile is weaker, but many target states are included, and on high energies (MeV energies). Thus, while perturbation theory for electron transfer is valid, it is not adequate to first order. The studies by Winter and Alston described were often done in parallel. Alston also developed formal perturbative approaches not tied to any particular system. Materials studied included He + , Li 2+ , Be 3+ , B 4+ , C 5+ , and the H + + Na system

  17. 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.)

  18. Quasi-four-body treatment of charge transfer in the collision of protons with atomic helium: I. Thomas related mechanisms

    Science.gov (United States)

    Safarzade, Zohre; Fathi, Reza; Shojaei Akbarabadi, Farideh; Bolorizadeh, Mohammad A.

    2018-04-01

    The scattering of a completely bare ion by atoms larger than hydrogen is at least a four-body interaction, and the charge transfer channel involves a two-step process. Amongst the two-step interactions of the high-velocity single charge transfer in an anion-atom collision, there is one whose amplitude demonstrates a peak in the angular distribution of the cross sections. This peak, the so-called Thomas peak, was predicted by Thomas in a two-step interaction, classically, which could also be described through three-body quantum mechanical models. This work discusses a four-body quantum treatment of the charge transfer in ion-atom collisions, where two-step interactions illustrating a Thomas peak are emphasized. In addition, the Pauli exclusion principle is taken into account for the initial and final states as well as the operators. It will be demonstrated that there is a momentum condition for each two-step interaction to occur in a single charge transfer channel, where new classical interactions lead to the Thomas mechanism.

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

    International Nuclear Information System (INIS)

    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 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.)

  20. 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.)

  1. Measurements of scattering processes in negative ion-atom collisions: Progress report, 1 September 1988--31 August 1989

    International Nuclear Information System (INIS)

    Kvale, T.J.

    1989-01-01

    The main emphasis of this research effort is the simultaneous study of several of the scattering processes that occur in negative ion-atom collisions. These include: elastic scattering, target excitation/ionization, single electron detachment, and double electron detachment. The measurements will provide absolute total and differential cross sections for the aforementioned processes. These are extremely valuable in providing stringent tests of the approximations used in the various theoretical calculations. This period covers the first year of the grant and the vast majority of the activity was directed toward construction of the apparatus needed to carry out the proposed measurements. Progress toward these goals are summarized. 2 refs., 1 fig

  2. Energy dependence of the anisotropy of noncharacteristic x-rays emitted in fast ion-atom collisions

    International Nuclear Information System (INIS)

    Thoe, R.S.; Sellin, I.A.; Brown, M.D.; Forester, J.P.; Griffin, P.M.; Pegg, D.J.; Peterson, R.S.

    1974-01-01

    The effect of beam velocity and K-shell binding energy on the angular distributions of the noncharacteristic x-radiation emitted for various collision pairs. The results are in general agreement with the calculations of Mueller and Greiner, in that the anisotropy increases rapidly with energy, provided that the ions are still moving slowly, compared to the velocity of the K-shell electrons of the separated atoms. The anisotropy in some cases exceeds the maximum permitted by the Mueller--Greiner model for the zero alignment case, implying that strong alignment phenomena also occur

  3. CDW-EIS model for single-electron capture in ion-atom collisions involving multielectronic targets

    International Nuclear Information System (INIS)

    Abufager, P N; MartInez, A E; Rivarola, R D; Fainstein, P D

    2004-01-01

    A generalization of the continuum distorted wave eikonal initial state (CDW-EIS) approximation, for the description of single-electron capture in ion-atom collisions involving multielectronic targets is presented. This approximation is developed within the framework of the independent electron model taking particular care of the representation of the bound and continuum target states. Total cross sections for single-electron capture from the K-shell of He, Ne and Ar noble gases by impact of bare ions are calculated. Present results are compared to previous CDW-EIS ones and to experimental data

  4. The fifth international symposium ''atomic cluster collisions''. ISACC 2011. Book of Abstracts

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2011-07-01

    The Fifth International Symposium ''Atomic Cluster Collisions'' (ISACC 2011) will take place in July 21-25, 2011 in Berlin, Germany. The venue of the meeting will be the St.-Michaels-Heim a lovely place located within a garden area of Berlin-Grunewald. The ISACC 2011 is organized by the Fritz-Haber-Institute of the Max- Planck Society along with the King Saud University, Rhiyadh and by the Frankfurt Institute for Advanced Studies (FIAS), Frankfurt am Main, Germany. ISACC started as the international symposium on atomic cluster collisions in St. Petersburg, Russia in 2003. The second ISACC was held at the GSI, Darmstadt, Germany in 2007. Both first and second symposia were satellites of the International Conferences on Photonic Electronic and Atomic Collisions (ICPEAC). The third ISACC has returned to St. Petersburg, Russia in 2008. The last ISACC took place in Ann Arbor, again as a satellite meeting of the ICPEAC. Initially the symposium was mainly focused on dynamics of atomic clusters, especially in atomic cluster collisions, but since then its scope has been widened significantly to include dynamics of nanosystems, biomolecules, and macromolecules with the emphasis on the similarity of numerous essential clustering phenomena arising in different branches of physics, chemistry, and biology. After the four ISACC meetings it has become clear that there is a need for an interdisciplinary conference covering a broad range of topics related to the Dynamics of Systems on a Nanoscale. Therefore in 2010 it was decided to expand upon this series of meetings with a new conference organized under the new title ''Dynamics of Systems on the Nanoscale'', the DySoN Conference, since this title better reflects the interdisciplinary character of the earlier ISACC meetings embracing all the topics of interest under a common theme. The first DySoN Conference took place in Rome, Italy in 2010. The fifth ISACC symposium will be again a

  5. Analytic cross sections for collisions of H, H2, He and Li atoms and ions with atoms and molecules, 1

    International Nuclear Information System (INIS)

    Ito, Rinsuke; Tabata, Tatsuo; Shirai, Toshizo; Phaneuf, R.A.

    1993-06-01

    Analytic expressions fitted to Barnett's recommended data are given for the cross sections of the following reactions: (1) electron capture by H, H + , H 2 + , He + , and He 2+ colliding with atoms, molecules, and ions and (2) electron capture into excited states by H + , He + , and He 2+ colliding with atoms and molecules. The latter category includes cross sections for photon emission due to electron capture. The expressions use the semiempirical functional forms proposed by Green and McNeal and some modified forms to make it possible not only to interpolate but also to extrapolate the recommended data. (author)

  6. Calculation of the positronium formation differential cross section for collision of electron with anti-hydrogen atoms

    International Nuclear Information System (INIS)

    Ghanbari Adivi, E.; Kanjuri, F.; Bolorizadeh, M.

    2006-01-01

    The positronium formation differential cross sections in collision of the high-energy but non-relativistic electrons with anti-hydrogen atoms are calculated by using the three-body Faddeev-Watson-Lovelace formalism. In a second-order approximation, the inter-nuclear and nuclear-electronic partial amplitudes therein the Faddeev-Watson series are calculated, analytically, in the range of 0-180 degrees of the scattering angles. The presence of the T homas peak a t 45 d egree i s investigated. The results are discussed for 1 and 10 keV impact energies and for electron transition from anti-hydrogen ground state into the different states therein the K-, L- and M- shells of the positronium atoms.

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

    International Nuclear Information System (INIS)

    Kvale, T.J.

    1994-01-01

    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 - 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 - 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)

  8. Ion-atom collisions with laser-prepared target: High resolution study of single charge exchange process

    International Nuclear Information System (INIS)

    Leredde, Arnaud

    2012-01-01

    Single charge transfer in low-energy Na"++"8"7Rb(5s,5p) collisions is investigated using magneto-optically trapped Rb atoms and high-resolution recoil-ion momentum spectroscopy. The three-dimensional reconstruction of the recoil-ion momentum provides accurate relative cross-sections for the active channels and the projectile scattering angle distributions. Thanks to the high experimental resolution, scattering structures such as diffraction-like oscillations in angular distributions are clearly observed. The measurements are compared with molecular close-coupling calculations and an excellent agreement is found. To go further in the test of the theory, the target is prepared in an oriented state. It is the first time that such collision experiments with oriented target is performed with such a high resolution. The right-left asymmetry expected for the scattering angle distribution is evidenced. The agreement between MOCC calculations and experiments is very good. Simple models developed for collisions with oriented target are also discussed. (author) [fr

  9. Coincident Auger electron and recoil ion momentum spectroscopy for low-energy ion-atom collisions

    International Nuclear Information System (INIS)

    Laurent, G.; Tarisien, M.; Flechard, X.; Jardin, P.; Guillaume, L.; Sobocinski, P.; Adoui, L.; Bordenave-Montesquieu, A.; Bordenave-Montesquieu, D.; Chesnel, J.-Y.; Fremont, F.; Hennecart, D.; Lienard, E.; Maunoury, L.; Moretto-Capelle, P.; Cassimi, A.

    2003-01-01

    The recoil ion momentum spectroscopy (RIMS) method combined with the detection of Auger electrons has been used successfully to analyse double electron capture following O 6+ + He collisions at low impact velocities. Although RIMS and Auger spectroscopies are known to be efficient tools to obtain details on the primary processes occurring during the collision, the conjunction of both techniques provides new insights on the electron capture process. In the present experiment, triple coincidence detection of the scattered projectile, the target recoil ion and the Auger electron allows for a precise identification of the doubly excited states O 4+ (1s 2 nln ' l ' ) populated after double electron-capture events

  10. Search for Fermi shuttle mechanisms in electron emission from atomic collision sequences

    International Nuclear Information System (INIS)

    Suarez, S.; Jung, M.; Rothard, H.; Schosnig, M.; Maier, R.; Clouvas, A.; Groeneveld, K.O.

    1994-01-01

    In electron spectra induced by slow heavy ion bombardment of solids a high energy tail can be observed, which is suggested to be explained by multiple collision sequences. In order to find those multiple collision effects like the ''Fermi shuttle'' acceleration mechanism we measured doubly differential electron emission cross sections for H + (33.5-700 keV) impact on different targets (He, Ne, C and Au) as a function of projectile energy and electron emission angle. We observed a surprising target dependence of the electron emission within the range of electron energies close to that of the binary encounter electrons for all observed angles of emission. (orig.)

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

    International Nuclear Information System (INIS)

    Jardin, P.

    1995-01-01

    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 => Xe 44 + Ar q+ +qe - (q ranging from 1 to 7); Xe 44+ (6.7 MeV/A) + He => Xe 44+ He 1+,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)

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

    OpenAIRE

    Cooper, D. L.; Stancil, P. C.; Turner, A. R.; Wang, J. G.; Clarke, N. J.; Zygelman, B.

    2002-01-01

    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...

  13. Ifluence of the collisions of electrons and ions with atoms and molecules on the dynamic form-factors of bounded many-particle systems

    International Nuclear Information System (INIS)

    Yakimenko, I.P.; Zagorodny, A.G.

    1980-01-01

    The kinetic theory of fluctuations is used to investigate the influence of the collisions of charged particles with atoms and molecules on the dynamic form-factors of semi-infinite weakly ionized plasma. It is shown that the collisions between the electrons and neutral particles and the diffuse processes connected with them lead to a much increased influence of the boundary on correlations in a plasma [ru

  14. 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)

    Fawcett, B.C.; Hibbert, A.

    1989-11-01

    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)

  15. Sensitized fluorescence in thallium induced in collisions with Hg(6/sup 3/P/sub 1/) atoms

    Energy Technology Data Exchange (ETDEWEB)

    Wade, M K; Czajkowski, M; Krause, L [Windsor Univ., Ontario (Canada). Dept. of Physics

    1978-07-01

    The transfer of excitation from excited mercury atoms to ground-state thallium atoms was investigated using techniques of sensitized fluorescence. A Hg-Tl vapor mixture contained in a quartz cell was irradiated with Hg 2537 A resonance radiation which caused the mercury atoms to become excited to the 6/sup 3/P/sub 1/ state. Subsequent collisions between the Hg(6/sup 3/P/sub 1/) and Tl(6/sup 2/Psub(1/2)) atoms resulted in the population of the 8/sup 2/Ssub(1/2), 6/sup 2/D, and 7/sup 2/Ssub(1/2) thallium states, whose decay gave rise to sensitized fluorescence of wavelengths 3231, 3520, 3776, and 5352 A. Intensity measurements on the sensitized fluorescence and on the Hg 2537 A resonance fluorescence, observed at right angles to the direction of excitation, yielded cross sections of 3.0, 0.3, and 0.05 A/sup 2/ for collisional excitation transfer from Hg(6/sup 3/P/sub 1/) to the 8/sup 2/Ssub(1/2), 6/sup 2/D, and 7/sup 2/Ssub(1/2) states in thallium, respectively. The results are fully consistent with previously determined cross sections for excitation transfer in other binary metallic vapor systems.

  16. 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.

  17. Analytic cross sections for collisions of H, H2, He and Li Atoms and ions with atoms and molecules. 2

    International Nuclear Information System (INIS)

    Ito, Rinsuke; Tabata, Tatsuo; Shirai, Toshizo; Phaneuf, R.A.

    1994-07-01

    Analytic expressions fitted to Barnett's recommended data are given for the cross sections of excitation and spectral line emission by H, H + , He + , He, and He 2+ colliding with atoms and molecules. The expressions use the semiempirical functional forms proposed by Green and McNeal and some modified forms to make it possible not only to interpolate but also to extrapolate the recommended data. (author)

  18. Free hydrogen atom collision cross sections of interest in controlled thermonuclear research

    Energy Technology Data Exchange (ETDEWEB)

    Fite, W L [John Jay Hopkins Laboratory for Pure and Applied Science, General Atomic Division of General Dynamics Corporation, San Diego, CA (United States)

    1958-07-01

    The present paper summarizes the results of measurements of the cross sections of hydrogen atoms for: (1) ionization, (2) excitation of Lyman alpha radiation on electron impact, and (3) elastic scattering of electrons of energy less than 10 eV; and also describes the approach of measurements now in progress on (4) charge-exchange between deuterons and deuterium atoms and (5) ionization of the hydrogen atom on proton impact.

  19. Electron emission induced by atomic collisions in gaseous targets and solids

    International Nuclear Information System (INIS)

    Meckbach, W.

    1988-01-01

    In this work, it is considered only the process of single collision with gaseous targets. The possible inelastic processes are: excitation and ionization of both, target and incident beam. The attention was concentrated to the processes of direct ionization which may give rise to electron emission. (A.C.A.S.) [pt

  20. Recoil ion momentum spectroscopy in atomic and nuclear physics: applications to low energy ion-atom/molecule collisions and to beta-neutrino angular correlation in beta decay

    International Nuclear Information System (INIS)

    Flechard, X.

    2012-12-01

    Since the early 1990's, Recoil Ion Momentum Spectroscopy is an ideal tool for ion-atom and ion-molecule collisions study. We detail here the development of this experimental technique during the last twenty years, illustrated with some of the most striking results obtained at GANIL (Caen) and J.R. Mac Donald Laboratory (Kansas State University). Recoil Ion Momentum Spectroscopy is also particularly well suited for β-ν angular correlation measurements in nuclear β decay. The LPCTrap experiment, installed at GANIL, is based on this technique, coupled to the use of a Paul trap for the radioactive ions confinement. The precise measurements performed with this setup allow both, to test specific aspects of the Standard Model of elementary particles, and to study the electron shake-off process following β decay. (author)

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

    International Nuclear Information System (INIS)

    Bielschowsky, C.E.

    1984-01-01

    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 m 2 S and m 2 P excitations are obtained, as well as numerical results for several excitations processes in alkali atoms. (Author) [pt

  2. Transitions between the fine structure components of C+ in collision with atomic hydrogen

    International Nuclear Information System (INIS)

    Bazet, J.F.; Harel, C.; McCarroll, R.; Riera, A.

    1975-01-01

    The cross section for excitation of the 2 Psub(1/2)- 2 Psub(3/2) transition in thermal C + ( 2 P)-H( 2 S) collisions is calculated in the framework of the semiclassical approximation using the potential energy curves of the 1 Σ, 1 π, 3 π, 3 Σ states of CH + , determined by an exchange perturbation method. Full account is taken of the exchange interaction and of the trajectory effects induced by the long range polarization potential. For low energies E, such that E/k 350 K, sigma depends on the exchange interaction. The cross section, which presents a maximum of 130a 2 0 for E/k approximately equal to 180 K, is lower by about 50% than that calculated by Weisheit and Lane. The cooling function due to C + -H collisions in the interstellar clouds is computed as a function of the kinetic temperature of the medium. (orig.) [de

  3. Coincident Auger electron and recoil ion momentum spectroscopy for low-energy ion-atom collisions

    Energy Technology Data Exchange (ETDEWEB)

    Laurent, G. E-mail: glaurent@ganil.fr; Tarisien, M.; Flechard, X.; Jardin, P.; Guillaume, L.; Sobocinski, P.; Adoui, L.; Bordenave-Montesquieu, A.; Bordenave-Montesquieu, D.; Chesnel, J.-Y.; Fremont, F.; Hennecart, D.; Lienard, E.; Maunoury, L.; Moretto-Capelle, P.; Cassimi, A

    2003-05-01

    The recoil ion momentum spectroscopy (RIMS) method combined with the detection of Auger electrons has been used successfully to analyse double electron capture following O{sup 6+} + He collisions at low impact velocities. Although RIMS and Auger spectroscopies are known to be efficient tools to obtain details on the primary processes occurring during the collision, the conjunction of both techniques provides new insights on the electron capture process. In the present experiment, triple coincidence detection of the scattered projectile, the target recoil ion and the Auger electron allows for a precise identification of the doubly excited states O{sup 4+} (1s{sup 2}nln{sup '}l{sup '}) populated after double electron-capture events.

  4. Studies of electron correlation effects in multicharged ion atom collisions involving double capture

    Energy Technology Data Exchange (ETDEWEB)

    Stolterfoht, N.; Sommer, K.; Griffin, D.C.; Havener, C.C.; Huq, M.S.; Phaneuf, R.A.; Swenson, J.K.; Meyer, F.W.

    1988-01-01

    We review measurements of L-Coster Kronig and Auger electron production in slow, multicharged collision systems to study electron correlation effects in the process of double electron capture. The n/sup /minus/3/ law was confirmed for the production of the Coster-Kronig configurations 1s/sup 2/2pn/ell/ (n greater than or equal to 6) in O/sup 6 +/ + He collisions. Enhancement of high angular momentum /ell/ in specific 1s/sup 2/2pn/ell/ configurations was observed by means of high-resolution measurements of the Coster-Kronig lines. The importance of electron correlation effects in couplings of potential energy curves leading to the 1s/sup 2/2pn/ell/ configurations is verified by means of Landau-Zener model calculations. 32 refs., 4 figs.

  5. Studies of electron correlation effects in multicharged ion atom collisions involving double capture

    International Nuclear Information System (INIS)

    Stolterfoht, N.; Sommer, K.; Griffin, D.C.; Havener, C.C.; Huq, M.S.; Phaneuf, R.A.; Swenson, J.K.; Meyer, F.W.

    1988-01-01

    We review measurements of L-Coster Kronig and Auger electron production in slow, multicharged collision systems to study electron correlation effects in the process of double electron capture. The n/sup /minus/3/ law was confirmed for the production of the Coster-Kronig configurations 1s 2 2pn/ell/ (n ≥ 6) in O 6+ + He collisions. Enhancement of high angular momentum /ell/ in specific 1s 2 2pn/ell/ configurations was observed by means of high-resolution measurements of the Coster-Kronig lines. The importance of electron correlation effects in couplings of potential energy curves leading to the 1s 2 2pn/ell/ configurations is verified by means of Landau-Zener model calculations. 32 refs., 4 figs

  6. Multiple ionization effects in atomic collisions in the K-L matching region

    International Nuclear Information System (INIS)

    Piticu, I.; Ciortea, C.; Dumitriu, D.; Enulescu, A.; Fluerasu, D.; Szilagyi, S.Z.; Zoran, V.; Bucur, B.I.

    1994-01-01

    The multiple ionization effect in the determination of 3dσ vacancy production cross sections and sharing probabilities in asymmetric quasimolecular collisions near K-L level matching, for the collision systems Fe, Co, Ni, and Cu + Bi in the energy range 0.25 - 1.75 MeV/u have been studied. The experimental energy and intensity shifts of some projectile and target X-ray lines, as well as Dirac-Hartree-Fock calculations, have been used to estimate average single particle probabilities for multiple ionization of projectile L- and target M-shells. Using these estimates and a standard procedure, the experimental 3dσ vacancy production cross sections and sharing probabilities have been corrected for multiple ionization. The influence of the multiple ionization-induced increase in binding energy of the molecular orbitals implied in vacancy sharing is discussed. (Author)

  7. About the close collisions of the fast positrons and electrons with the string atoms

    International Nuclear Information System (INIS)

    Kudrin, V.V.; Vorobiev, S.A.

    1975-01-01

    The penetration behaviour of 20 MeV electron in MgO single crystal was studied. In the calculations the early described version of the binary collision model based on the classical mechanics was used. The classical theory has been shown to be valid for the scattering of the fast electrons in the crystal lattice. For the comparison with the behaviour of the positive particles the scattering of 20MeV positrons under the same conditions was simulated

  8. Diffraction structures in delta electron spectra emitted in heavy-ion atom collisions

    International Nuclear Information System (INIS)

    Liao, C.; Bhalla, C.; Shingal, R.; Schmidt-Boecking, H.; Shinpaugh, J.; Wolf, W.; Wolf, H.

    1992-01-01

    We have measured doubly differential cross sections DDCS for projectiles between F and Au and find evidence for strong diffraction structure in the Binary Encounter region of the emitted electron spectra for Au(Z=79), I(Z=53) and Cu(Z=29) projectiles, however not for F projectiles in the collision energy range between 0.2 and 0.5 MeV/u. (orig.)

  9. Excitation of Li and Na atoms in collisions with He and Ne

    International Nuclear Information System (INIS)

    Olsen, J.Oe.; Andersen, T.; Andersen, N.

    1977-01-01

    Total emission cross sections and polarizations have been measured for the 2 2 S - 2 2 P, 2 2 P - 3 2 D and 2 2 P - 3 2 S LiI multiplets in Li - He,Ne collisions, and the 3 2 S - 3 2 P and 3 2 P - 3 2 D NaI multiplets in Na - He,Ne collisions in the 0.6 - 60 keV energy range. The excitation of the alkali resonance multiplet is found to be the dominant inelastic process for all four collision systems. The behaviour is very similar to the previously investigated Be + - He,Ne and Mg + - He,Ne systems. The results are compared with recent calculations by Manique et al based on a quasi-one electron description using various model potentials. Good agreement is found for Li - He with a simple Hartree-Fock frozen-core potential. The agreement is fair for Li,Na - He calculations with a Baylis type potential but poor for calculations based on Bottcher model potentials. For Ne as target all three potentials by far overestimate the size of the cross section. (Auth.)

  10. Quasiclassical treatment of the Auger effect in slow ion-atom collisions

    Science.gov (United States)

    Frémont, F.

    2017-09-01

    A quasiclassical model based on the resolution of Hamilton equations of motion is used to get evidence for Auger electron emission following double-electron capture in 150-keV N e10 ++He collisions. Electron-electron interaction is taken into account during the collision by using pure Coulombic potential. To make sure that the helium target is stable before the collision, phenomenological potentials for the electron-nucleus interactions that simulate the Heisenberg principle are included in addition to the Coulombic potential. First, single- and double-electron captures are determined and compared with previous experiments and theories. Then, integration time evolution is calculated for autoionizing and nonautoionizing double capture. In contrast with single capture, the number of electrons originating from autoionization slowly increases with integration time. A fit of the calculated cross sections by means of an exponential function indicates that the average lifetime is 4.4 ×10-3a .u . , in very good agreement with the average lifetime deduced from experiments and a classical model introduced to calculate individual angular momentum distributions. The present calculation demonstrates the ability of classical models to treat the Auger effect, which is a pure quantum effect.

  11. On the Lippmann--Schwinger equation for atom--diatom collisions: A rotating frame treatment

    International Nuclear Information System (INIS)

    Kouri, D.J.; Heil, T.G.; Shimoni, Y.

    1976-01-01

    The use of a rotating frame description of molecular collisions is reconsidered within the framework of the Lippmann--Schwinger equation for the transition or T operator. The present approach explicitly displays the proper boundary conditions which apply to descriptions of such collisions in the rotating frame whose Z axis follows the scattering vector. The resulting body frame equations are shown to lead naturally to the introduction of ''body frame Bessel and Hankel functions,'' J/subJ//subj//sup lambda//sup lambda//sup prime/ and H/subJ//subj//sup lambda//sup lambda//sup prime/ (BFBF), which are solutions of the unperturbed Hamiltonian for the collision transformed to the rotating frame. It is found that the BFBF can be defined in several ways differing by phase factors that affect their asymptotic form. Two particular choices are examined, one of which leads to a simple asymptotic form of the wavefunction, and the other leads to a somewhat more complicated form. Both are shown to yield the j/subz/-conserving coupled states equations of McGuire and Kouri but slightly different approximations are required in the two cases. The implication of these results as to the accuracy of the j/subz/CCS method are discussed

  12. Investigation of cascade regions of damage in alpha iron by a computer simulation method (crystal model). Issledovaniye kaskadnykh oblastey povrezhdeniya v. cap alpha. -zheleze metodom mashinnogo modelirovaniya (kristallicheskaya model)

    Energy Technology Data Exchange (ETDEWEB)

    Kevorkyan, Yu R

    1974-01-01

    A SPIKE program is used to study regions of structural damage that arise as a result of cascades of atomic collisions in single-crystal alpha iron. The model of the cascade process realized in the program uses a pair collision approximation and accounts for the influence of the crystal structure of the material. The following characteristics of regions of damage are found as a function of the energy of the primary knock-on atom: volume of the region, displacement effectiveness, size distribution of complexes of vacancies and injections. The results are compared with data in the literature. An appendix gives the text of the SPIKE program in FORTRAN.

  13. Populations and lifetimes in the $v=n-l-1=2$ and 3 metastable cascades of $\\overline{p} He^{+}$ measured by pulsed and continuous antiproton beams

    CERN Document Server

    Hori, Masaki; Widmann, E; Yamazaki, T; Hayano, R S; Ishikawa, T; Torie, H A; Von Egidy, T; Hartmann, F; Ketzer, B; Maierl, C; Pohl, R; Kumakura, M; Morita, N; Horváth, D; Sugai, I

    2004-01-01

    Using the laser spectroscopy, the time evolution of the state population in the v equivalent n-l=2 and 3 metastable cascades of antiprotonic helium atoms were studied. The effects of the collision between antiprotonic helium and the ordinary helium atoms on the atomic cascade were also analyzed. The measurements were done using the pulsed and continuous types of antiproton beams supplied by the Low Energy Antiproton Ring. The studies revealed five phases in the life history of the metastable antiprotonic helium. (Edited abstract) 71 Refs.

  14. 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.

  15. Chapter 6 Quantum Mechanical Methods for Loss-Excitation and Loss-Ionization in Fast Ion-Atom Collisions

    Science.gov (United States)

    Belkic, Dzevad

    Inelastic collisions between bare nuclei and hydrogen-like atomic systems are characterized by three main channels: electron capture, excitation, and ionization. Capture dominates at lower energies, whereas excitation and ionization prevail at higher impact energies. At intermediate energies and in the region of resonant scattering near the Massey peak, all three channels become competitive. For dressed or clothed nuclei possessing electrons, such as hydrogen-like ions, several additional channels open up, including electron loss (projectile ionization or stripping). The most important aspect of electron loss is the competition between one- and two-electron processes. Here, in a typical one-electron process, the projectile emits an electron, whereas the target final and initial states are the same. A prototype of double-electron transitions in loss processes is projectile ionization accompanied with an alteration of the target state. In such a two-electron process, the target could be excited or ionized. The relative importance of these loss channels with single- and double-electron transitions involving collisions of dressed projectiles with atomic systems is also strongly dependent on the value of the impact energy. Moreover, impact energies determine which theoretical method is likely to be more appropriate to use for predictions of cross sections. At low energies, an expansion of total scattering wave functions in terms of molecular orbitals is adequate. This is because the projectile spends considerable time in the vicinity of the target, and as a result, a compound system comprised of the projectile and the target can be formed in a metastable molecular state which is prone to decay. At high energies, a perturbation series expansion is more appropriate in terms of powers of interaction potentials. In the intermediate energy region, atomic orbitals are often used with success while expanding the total scattering wave functions. The present work is focused on

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

    International Nuclear Information System (INIS)

    Marbach, Johannes

    2012-01-01

    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.

  17. Inelastic collisions between an atom and a diatomic molecule. I. Theoretical and numerical considerations for the close coupling approximation

    International Nuclear Information System (INIS)

    Choi, B.H.; Tang, K.T.

    1975-01-01

    The close coupled differential equations for rotational excitation in collisions between an atom and a diatomic molecule are reformulated. Although it is equivalent to other formulations, it is computationally more convenient and gives a simpler expression for differential cross sections. Questions concerning real boundary conditions and the unitarity of the S matrix are discussed. Stormer's algorithm for solving coupled differential equations is introduced for molecular scatterings. This numerical procedure, which is known to be very useful in nuclear scattering problems, has to be modified for molecular systems. It is capable of treating the case where all channels are open as well as the case where some of the channels are closed. This algorithm is compared with other typical procedures of solving coupled differential equations

  18. Formation of H(2s) atoms by excitation in 10-100 keV H+-H collisions

    International Nuclear Information System (INIS)

    Higgins, D.P.; Geddes, J.; Gilbody, H.B.

    1996-01-01

    Cross sections for 2s excitation of H atoms in 10-100 keV H + -H collisions have been determined using a modulated crossed-beam technique. The measurements have been based on observations of the Lyman alpha radiation emitted during electric-field-induced decay of the metastable H(2s) collision products. The results extend the range of the 5-26 keV cross sections measured by Morgan and co-workers to intermediate energies where theoretical predictions based on close-coupling methods are known to be strongly dependent on the choice of the expansion basis. The present cross sections pass through a broad maximum at about 40 keV. Over the range 5-100 keV the available experimental data exhibit an undulatory structure similar to that predicted by some close-coupling calculations but good quantitative agreement is very limited. Close-coupling calculations which employ large basis sets and include a large number of projectile states at the expense of target states are shown to agree less satisfactorily with experiment than those which include only the dominant 1s capture projectile channel. (Author)

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

    International Nuclear Information System (INIS)

    Poel, M van der; Nielsen, C V; Rybaltover, M; Nielsen, S E; Machholm, M; Andersen, N

    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. This setup yields a momentum resolution of 0.12 au, an order of magnitude better angular resolution than previous measurements on this system. This enables us to clearly resolve Fraunhofer-type diffraction patterns in the angle DCS. In particular, the angular width of the ring structure is given by the ratio of the de Broglie wavelength λ dB = 150 fm at a velocity v = 0.20 au and the effective atomic diameter for electron capture 2R = 20 au. Parallel AO and MO semiclassical coupled-channel calculations of the Na(3s, 3p) → Li(2s, 2p) state-to-state collision amplitudes have been performed, and 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

  20. Quantum-mechanical theory for electronic-vibrational-rotational energy transfer in atom--diatom collisions: Analysis of the Hamiltonian

    International Nuclear Information System (INIS)

    Bellum, J.C.; McGuire, P.

    1983-01-01

    We investigate forms of the molecular system Hamiltonian valid for rigorous quantum-mechanical treatments of inelastic atom--diatom collisions characterized by exchange of energy between electronic, vibrational, and rotational degrees of freedom. We analyze this Hamiltonian in terms of various choices of independent coordinates which unambiguously specify the electronic and nuclear positions in the context of space-fixed and body-fixed reference frames. In particular we derive forms of the Hamiltonian in the context of the following four sets of independent coordinates: (1) a so-called space-fixed set, in which both electronic and nuclear positions are relative to the space-fixed frame; (2) a so-called mixed set, in which nuclear positions are relative to the body-fixed frame while electronic positions are relative to the space-fixed frame; (3) a so-called body-fixed set, in which both electronic and nuclear positions are relative to the body-fixed frame; and (4) another mixed set, in which nuclear positions are relative to the space-fixed frame while electronic positions are relative to the body-fixed frame. Based on practical considerations in accounting for electronic structure and nonadiabatic coupling of electronic states of the collision complex we find the forms of the Hamiltonian in the context of coordinate sets (3) and (4) above to be most appropriate, respectively, for body-fixed and space-fixed treatments of nuclear dynamics in collisional transfer of electronic, vibrational, and rotational energies

  1. Need for reaction coordinates to ensure a complete basis set in an adiabatic representation of ion-atom collisions

    Science.gov (United States)

    Rabli, Djamal; McCarroll, Ronald

    2018-02-01

    This review surveys the different theoretical approaches, used to describe inelastic and rearrangement processes in collisions involving atoms and ions. For a range of energies from a few meV up to about 1 keV, the adiabatic representation is expected to be valid and under these conditions, inelastic and rearrangement processes take place via a network of avoided crossings of the potential energy curves of the collision system. In general, such avoided crossings are finite in number. The non-adiabatic coupling, due to the breakdown of the Born-Oppenheimer separation of the electronic and nuclear variables, depends on the ratio of the electron mass to the nuclear mass terms in the total Hamiltonian. By limiting terms in the total Hamiltonian correct to first order in the electron to nuclear mass ratio, a system of reaction coordinates is found which allows for a correct description of both inelastic channels. The connection between the use of reaction coordinates in the quantum description and the electron translation factors of the impact parameter approach is established. A major result is that only when reaction coordinates are used, is it possible to introduce the notion of a minimal basis set. Such a set must include all avoided crossings including both radial coupling and long range Coriolis coupling. But, only when reactive coordinates are used, can such a basis set be considered as complete. In particular when the centre of nuclear mass is used as centre of coordinates, rather than the correct reaction coordinates, it is shown that erroneous results are obtained. A few results to illustrate this important point are presented: one concerning a simple two-state Landau-Zener type avoided crossing, the other concerning a network of multiple crossings in a typical electron capture process involving a highly charged ion with a neutral atom.

  2. Electron Capture in Slow Collisions of Si4+ With Atomic Hydrogen

    Science.gov (United States)

    Joseph, D. C.; Gu, J. P.; Saha, B. C.

    2009-10-01

    In recent years the charge transfer involving Si4+ and H at low energies has drawn considerable attention both theoretically and experimentally due to its importance not only in astronomical environments but also in modern semiconductor industries. Accurate information regarding its molecular structures and interactions are essential to understand the low energy collision dynamics. Ab initio calculations are performed using the multireference single- and double-excitation configuration-interaction (MRD-CI) method to evaluate potential energies. State selective cross sections are calculate using fully quantum and semi-classical molecular-orbital close coupling (MOCC) methods in the adiabatic representation. Detail results will be presented in the conference.

  3. Classical description of the electron capture to the continuum cusp formation in ion-atom collisions

    International Nuclear Information System (INIS)

    Illescas, Clara; Pons, B.; Riera, A.

    2002-01-01

    Classical calculations are used to describe the dynamics of the electron capture to the continuum (ECC) cusp formation in H + +He collisions. We illustrate the frontier character of the ECC electrons between capture and ionization, and confirm that it is a temporary capture, through projectile focusing, that is responsible for the ECC cusp. Furthermore, the cusp is not a divergence smoothed by the experiment, and is slightly shifted from the impact-velocity value because of the residual pull from the target after ionization. This shift is larger the smaller the nuclear velocity

  4. Quantum-mechanical study of ionization in slow collisions of antiprotons with hydrogen atoms

    International Nuclear Information System (INIS)

    Sakimoto, Kazuhiro

    2004-01-01

    The cross sections for the ionization p+H→p+p+e at low collision energies are computed with a complete quantum-mechanical method of time-dependent wave-packet propagation, which was applied to the protonium formation (→pp+e) by the present author [Phys. Rev. A 65, 012706 (2002)]. The ionization process shows very large cross sections even near threshold energy. An impact-parameter semiclassical method, in which the trajectory bending is taken into account by the introduction of the adiabatic potential, is also examined for the calculation of the ionization cross section. The semiclassical results are in good agreement with the quantum-mechanical results

  5. Monte Carlo calculation of collisions of directionally-incident electrons on highly excited hydrogen atoms

    International Nuclear Information System (INIS)

    Kawakami, Kazuki; Fujimoto, Takasi

    2001-01-01

    We treat classically the n-, l- and m r -changing transitions and ionization. Excitation cross sections against the final state energy continue smoothly to the 'ionization cross sections'. The steady state populations determined by elastic collisions among the degenerate states in the same n level show higher populations in the m 1 =0 states, suggesting positive polarizations of Lyman lines emitted from plasmas having directional electrons. For ionization, the two outgoing electrons have large relative angles, suggesting reduced three body recombination rates for these plasmas. (author)

  6. Multiple-electron excitation, ionization, and transfer in high-velocity atomic and molecular collisions

    International Nuclear Information System (INIS)

    McGuire, J.H.

    1992-01-01

    This paper reports that the many-body and many-electron problem is common in various areas of physics as well as in chemistry and biology. Basic understanding of phenomena ranging from the nature of matter at the creation of time to the properties of useful materials in the human environment is limited by the boundaries of our knowledge of the many-body problem. There is an advantage in studying the many-body problem in atomic physics since the two-body and parts of the three-body problem are understood. Furthermore, both the mystery of the meanings of quantum mechanics and the mystery of the transition from microscopic time-reversible atomic processes to the dynamics of macroscopic time-irreversible aggregates of atomic particles is inherent in the many-body problems of atomic interactions. Thus, by studying the many-body problem in atomic physics we are able to develop effective tools to discover insights that provide both meaning and utility in our lives

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

    International Nuclear Information System (INIS)

    Renwick, S.P.

    1992-01-01

    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 N 2 , Ar, and SF 6 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 N 2 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 N 2 but not in Ar. This represents the first measurement of a breakdown of the Independent Particle Model for fast Rydberg atom scattering

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

    NARCIS (Netherlands)

    Chen, T.; Gatchell, M.; Stockett, M. H.; Alexander, J. D.; Zhang, Y.; Rousseau, P.; Domaracka, A.; Maclot, S.; Delaunay, R.; Adoui, L.; Huber, B. A.; Schlathölter, T.; Schmidt, H. T.; Cederquist, H.; Zettergren, H.

    2014-01-01

    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

  9. An investigation of antiprotons collisions with positronium atom in Debye plasma environments

    International Nuclear Information System (INIS)

    Pandey, M. K.; Lin, Y.-C.; Ho, Y. K.

    2015-01-01

    The effects of Debye plasmas on antihydrogen formation and ionization processes are investigated in antiprotons (p ¯ ) and positronium (Ps) collisions. The classical trajectory Monte Carlo method with Debye Hückel potentials has been used for cross section calculations. In this process, antihydrogen formation and ionization cross sections have been calculated in unscreened as well as in Debye plasmas conditions in energies ranging from 1 to 500 keV. Partial cross sections for antihydrogen formation are also calculated which show the largest cross sections correspond to production of antihydrogen in the n = 2 (2s, 2p) states. Comparative study has been carried out to determine the differences of cross sections in screening and unscreening cases. The results show that the cross sections for both antihydrogen formation and positronium ionization depend on Debye screening lengths as well as on collision energies. The effects of plasmas conditions on antihydrogen formation and positronium ionization are explained in terms of classical trajectory framework. Our results for the unscreened case are in agreement with previously reported results

  10. An investigation of antiprotons collisions with positronium atom in Debye plasma environments

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, M. K., E-mail: pandey@pub.iams.sinica.edu.tw; Lin, Y.-C.; Ho, Y. K., E-mail: ykho@pub.iams.sinica.edu.tw [Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 106, Taiwan (China)

    2015-05-15

    The effects of Debye plasmas on antihydrogen formation and ionization processes are investigated in antiprotons (p{sup ¯}) and positronium (Ps) collisions. The classical trajectory Monte Carlo method with Debye Hückel potentials has been used for cross section calculations. In this process, antihydrogen formation and ionization cross sections have been calculated in unscreened as well as in Debye plasmas conditions in energies ranging from 1 to 500 keV. Partial cross sections for antihydrogen formation are also calculated which show the largest cross sections correspond to production of antihydrogen in the n = 2 (2s, 2p) states. Comparative study has been carried out to determine the differences of cross sections in screening and unscreening cases. The results show that the cross sections for both antihydrogen formation and positronium ionization depend on Debye screening lengths as well as on collision energies. The effects of plasmas conditions on antihydrogen formation and positronium ionization are explained in terms of classical trajectory framework. Our results for the unscreened case are in agreement with previously reported results.

  11. 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.)

  12. 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

    the 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...... previously. Inelastic contributions to the energy loss can easily be included. The oscillator forces binding lattice atoms turn out to influence the scattering process only at very small energies. The validity of the so-called momentum approximation and a related perturbation method are also investigated....

  13. Spontaneous electromagnetic radiation caused by binary ion-atom collisions in the quasiresonant case

    International Nuclear Information System (INIS)

    Mihajlov, A.A.; Popovic, M.M.

    1981-01-01

    The process of spontaneous electromagnetic radiation in the reaction A + + B → A + B + + hω is studied. Here A and B are the same kind of atoms or atoms with small differences in ionization potentials (quasiresonant case). Differential cross section, energy spectrum of the emitted photons, and total intensity of electromagnetic radiation are determined for thermal velocities of relative motion. Results are applicable in a wide range of temperatures: 500< or = T< or = 50,000 K. It is shown that the radiation spectrum is very broad and the radiation intensity is considerable

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

    International Nuclear Information System (INIS)

    Garcia de Abajo, F.J.; Pitarke, J.M.

    1994-01-01

    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.)

  15. A simple algorithm for calculating the scattering angle in atomic collisions

    International Nuclear Information System (INIS)

    Belchior, J.C.; Braga, J.P.

    1996-01-01

    A geometric approach to calculate the classical atomic scattering angle is presented. The trajectory of the particle is divided into several straight-lines and changing in direction from one sector to the other is used to calculate the scattering angle. In this model, calculation of the scattering angle does not involve either the direct evaluation of integrals nor classical turning points. (author)

  16. Understanding Molecular-Ion Neutral Atom Collisions for the Production of Ultracold Molecular Ions

    Science.gov (United States)

    2014-02-03

    SECURITY CLASSIFICATION OF: This project was superseded and replaced by another ARO-funded project of the same name, which is still continuing. The goal...cooled atoms," IOTA -COST Workshop on molecular ions, Arosa, Switzerland. 5. E.R. Hudson, "Sympathetic cooling of molecules with laser cooled

  17. Collision between two ortho-positronium (Ps) atoms: A four-body ...

    Indian Academy of Sciences (India)

    The theory includes the non-adiabatic short-range effects due to exchange. ... S = 2 when both the atoms are aligned in the same direction (e.g. polarized beam) and ..... The plot of k cot δ0 vs. k2 in a.u. for both the singlet (+) and triplet (−).

  18. Population of Rydberg states by electron capture in fast-ion--atom collisions

    International Nuclear Information System (INIS)

    Burgdoerfer, J.; Dube, L.J.

    1985-01-01

    The l,m-substate distribution in low-lying Rydberg manifolds (nroughly-equal10) following electron capture H + +H(1s)→H(n)+H + is calculated at high velocities (v>1 a.u.) in the continuum-distorted-wave (CDW) approximation. The standard CDW approximation is modified to account for final-state Stark mixing of the Rydberg manifold in the exit channel using the post-collision-interaction model. The influence of multiple-scattering contributions is analyzed and comparison is made with sigma/sub l/m predicted by the Born approximation. We find that the double-scattering contribution, closely connected with the classical Thomas process, becomes visible in the CDW approximation at surprisingly low nonasymptotic velocities

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

    International Nuclear Information System (INIS)

    Stoehlker, T.; Kozhuharov, C.; Mokler, P.H.; Warczak, A.; Bosch, F.; Geissel, H.; Moshammer, R.; Scheidenberger, C.; Eichler, J.; Shirai, T.; Stachura, Z.; Rymuza, P.

    1994-08-01

    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 sin 2 θ 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. Radiative electron capture studied in relativistic heavy-ion--atom collisions

    International Nuclear Information System (INIS)

    Stoehlker, T.; Kozhuharov, C.; Mokler, P.H.; Warczak, A.; Bosch, F.; Geissel, H.; Moshammer, R.; Scheidenberger, C.; Eichler, J.; Ichihara, A.; Shirai, T.; Stachura, Z.; Rymuza, P.

    1995-01-01

    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 analyzed 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 sin 2 θ 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 nonrelativistic dipole approximation. The agreement between these different theoretical approaches must be regarded as fortuitous, but it lends support to the use of the nonrelativistic approach for practical purposes

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

    International Nuclear Information System (INIS)

    Lohmann, Bernd; Grum-Grzhimailo, Alexei N.; Kleinpoppen, Hans

    2013-01-01

    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, until today, hardly to perform

  2. 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

  3. Cross sections for energy transfer in collisions between two excited sodium atoms

    International Nuclear Information System (INIS)

    Huennekens, J.; Gallagher, A.

    1983-01-01

    We have measured cross sections, sigma/sub n/L, for the excitation transfer process Na(3P)+Na(3P)→Na(3S)+Na(nL), where nL is the 4D or 5S level. Our results are sigma/sub 4D/ = 23 A 2 +- 35% and sigma/sub 5S/ = 16 A 2 +- 35% at Tapprox.600 K. To obtain these cross sections we have used pulsed excitation and measured the intensities of 4D, 5S, and 3P fluorescence emissions, and the spatial distribution of excited atoms resulting from radiation diffusion, as well as the excited atom density as a function of time. Additionally, we have accounted for (time-dependent) radiation trapping of 3P and nL level radiation and for the resulting anisotropies of these fluorescence emissions. Comparisons of our results with theory have been made, and their relevance to other experiments is discussed

  4. Implementation of exterior complex scaling in B-splines to solve atomic and molecular collision problems

    International Nuclear Information System (INIS)

    McCurdy, C William; MartIn, Fernando

    2004-01-01

    B-spline methods are now well established as widely applicable tools for the evaluation of atomic and molecular continuum states. The mathematical technique of exterior complex scaling has been shown, in a variety of other implementations, to be a powerful method with which to solve atomic and molecular scattering problems, because it allows the correct imposition of continuum boundary conditions without their explicit analytic application. In this paper, an implementation of exterior complex scaling in B-splines is described that can bring the well-developed technology of B-splines to bear on new problems, including multiple ionization and breakup problems, in a straightforward way. The approach is demonstrated for examples involving the continuum motion of nuclei in diatomic molecules as well as electronic continua. For problems involving electrons, a method based on Poisson's equation is presented for computing two-electron integrals over B-splines under exterior complex scaling

  5. Charge exchange in slow collisions of multiply charged ions with atoms

    International Nuclear Information System (INIS)

    Presnyakov, L.P.; Uskov, D.B.; Janev, R.K.

    1982-01-01

    Single-electron charge exchange between ions having a charge Z>6 and atoms is considered at relative velocities v< Z/sup 1/2/. An analytic method is developed for the solution of a multilevel problem that is a generalization of the decay model and of the approximation of nonadiabatic coupling between two states. Expressions are obtained for the reaction-product distributions in the principal and angular quantum numbers. The calculated total cross sections agree well with the experimental data on charge exchange of hydrogen atoms and molecules with nuclei. The theory describes the oscillations of the total cross section against the background of a monotonic growth as the charge is increased

  6. GEANT4 hadronic cascade models analysis of proton and charged pion transverse momentum spectra from p plus Cu and Pb collisions at 3, 8, and 15 GeV/c

    CERN Document Server

    Abdel-Waged, Khaled; Uzhinskii, V V

    2011-01-01

    We describe how various hadronic cascade models, which are implemented in the GEANT4 toolkit, describe proton and charged pion transverse momentum spectra from p + Cu and Pb collisions at 3, 8, and 15 GeV/c, recently measured in the hadron production (HARP) experiment at CERN. The Binary, ultrarelativistic quantum molecular dynamics (UrQMD) and modified FRITIOF (FTF) hadronic cascade models are chosen for investigation. The first two models are based on limited (Binary) and branched (UrQMD) binary scattering between cascade particles which can be either a baryon or meson, in the three-dimensional space of the nucleus, while the latter (FTF) considers collective interactions between nucleons only, on the plane of impact parameter. It is found that the slow (p(T) 0.3 GeV/c) proton spectra are not strongly affected by the differences between the FTF and UrQMD models. It is also shown that the UrQMD and FTF combined with Binary (FTFB) models could reproduce both proton and charged pion spectra from p + Cu and Pb...

  7. Inelastic Transitions in Slow Collisions of Anti-Hydrogen with Hydrogen Atoms

    Science.gov (United States)

    Harrison, Robert; Krstic, Predrag

    2007-06-01

    We calculate excited adiabatic states and nonadiabatic coupling matrix elements of a quasimolecular system containing hydrogen and anti-hydrogen atoms, for a range of internuclear distances from 0.2 to 20 Bohrs. High accuracy is achieved by exact diagonalization of the molecular Hamiltionian in a large Gaussian basis. Nonadiabatic dynamics was calculated by solving MOCC equations. Positronium states are included in the consideration.

  8. Destruction of fast H(2S) atoms in collisions with neon, krypton, xenon, and molecular hydrogen

    International Nuclear Information System (INIS)

    Roussel, F.; Pradel, P.; Spiess, G.

    1977-01-01

    Measurements are reported for the total quenching of metastable hydrogen atoms by neon, krypton, xenon, and molecular hydrogen, in the energy range 0.052--3 keV. The cross sections are found to be on the order of 5 x 10 -15 cm 2 at the lowest energies, and decrease to approximately 2 x 10 -15 cm 2 at the highest energies. The data at low energy are analyzed using a simple theoretical model

  9. An apparatus for measuring the energy and angular distribution of electrons in ion-atom collisions

    International Nuclear Information System (INIS)

    Gibson, D.K.; Petersen, M.C.E.

    1978-07-01

    There is a need for further data on the energy and angular distribution of electrons ejected from atoms and molecules by ion impact. An apparatus in which simultaneous measurements can be made of the energy and angular distributions of such electrons is described. The advantages of the apparatus are the possibility of fast data collection and the ability to make measurements over the whole range of scattering angle. Preliminary tests and a trial measurement with the apparatus are described

  10. Understanding Molecular Ion-Neutral Atom Collisions for the Production of Ultracold Molecular Ions

    Science.gov (United States)

    2016-06-06

    2012): 0. doi: 10.1103/PhysRevLett.109.223002 Kuang Chen, Scott T. Sullivan, Wade G. Rellergert, Eric R. Hudson. Measurement of the Coulomb Logarithm...or fellowships for further studies in science, mathematics, engineering or technology fields: Student Metrics This section only applies to graduating...clouds of Ba+ ions and Ca atoms. Due to the strong Coulomb interaction, the Ba+ ions quickly cool the molecular ion translation motion, while the

  11. All-optical atom trap as a target for MOTRIMS-like collision experiments

    Science.gov (United States)

    Sharma, S.; Acharya, B. P.; De Silva, A. H. N. C.; Parris, N. W.; Ramsey, B. J.; Romans, K. L.; Dorn, A.; de Jesus, V. L. B.; Fischer, D.

    2018-04-01

    Momentum-resolved scattering experiments with laser-cooled atomic targets have been performed since almost two decades with magneto-optical trap recoil ion momentum spectroscopy (MOTRIMS) setups. Compared to experiments with gas-jet targets, MOTRIMS features significantly lower target temperatures allowing for an excellent recoil ion momentum resolution. However, the coincident and momentum-resolved detection of electrons was long rendered impossible due to incompatible magnetic field requirements. Here we report on an experimental approach which is based on an all-optical 6Li atom trap that—in contrast to magneto-optical traps—does not require magnetic field gradients in the trapping region. Atom temperatures of about 2 mK and number densities up to 109 cm-3 make this trap ideally suited for momentum-resolved electron-ion coincidence experiments. The overall configuration of the trap is very similar to conventional magneto-optical traps. It mainly requires small modifications of laser beam geometries and polarization which makes it easily implementable in other existing MOTRIMS experiments.

  12. Quenching of the resonance 5s({sup 3}P{sub 1}) state of krypton atoms in collisions with krypton and helium atoms

    Energy Technology Data Exchange (ETDEWEB)

    Zayarnyi, D A; L' dov, A Yu; Kholin, I V [P N Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

    2014-11-30

    The processes of collision quenching of the resonance 5s[3/2]{sub 1}{sup o}({sup 3}P{sub 1}) state of the krypton atom are studied by the absorption probe method in electron-beam-excited high-pressure He – Kr mixtures with a low content of krypton. The rate constants of plasmochemical reactions Kr* + Kr + He → Kr*{sub 2} + He [(4.21 ± 0.42) × 10{sup -33} cm{sup 6} s{sup -1}], Kr* + 2He → HeKr* + He [(4.5 ± 1.2) × 10{sup -36} cm{sup 6} s{sup -1}] and Kr* + He → products + He [(2.21 ± 0.22) × 10{sup -15} cm{sup 3} s{sup -1}] are measured for the first time. The rate constants of similar reactions are refined for krypton in the metastable 5s[3/2]{sub 2}{sup o} ({sup 3}P{sub 2}) state. (laser applications and other topics in quantum electronics)

  13. Rapidity distributions of secondary particles in hadron-nucleus collisions

    International Nuclear Information System (INIS)

    Alaverdyan, G.B.; Pak, A.S.; Tarasov, A.V.; Tseren, Ch.; Uzhinsky, V.V.

    1979-01-01

    In the framework of the cascade model of a leading particle the rapidity distributions of secondary particles in the hadron-nucleus interactions are considered. The energy loss fluctuations of leading particles in the successive collisions have been taken into account. It is shown that the centre of rapidity distribution is displaced towards small rapidity with target nucleus atomic number A growth. The model well reproduces the energy and A dependences of the rapidity distributions

  14. Charge-transfer cross sections of H+ ions in collisions with noble gas atoms in the energy range below 4.0 keV

    International Nuclear Information System (INIS)

    Kusakabe, Toshio; Sakaue, Hiroyuki A.; Tawara, Hiroyuki

    2011-01-01

    Charge-transfer cross sections in collisions of H + ions with the ground state He, Ar, Kr, and Xe atoms have been measured in the energy range below 4.0 keV with the initial growth rate method. These observed cross sections are also compared with previously published experimental data and theoretical predictions. In the He and Ar targets, it is found that some previous experimental data deviate significantly from the present observed cross sections as the collision energy decreases. It has been found that in the Kr and Xe targets, the energy dependence of the present observed cross sections behaves as “near-resonant” charge transfer. (author)

  15. 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)

    Barklem, Paul S

    2012-01-01

    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.

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

    International Nuclear Information System (INIS)

    Watson, R.L.

    1993-01-01

    A study of the double ionization of He by high-energy N 7+ ions was extended up in energy to 40 MeV/amu. Coincidence time-of-flight studies of multicharged N 2 , O 2 , and CO molecular ions produced in collisions with 97-MeV Ar 14+ ions were completed. Analysis of the total kinetic energy distributions and comparison with the available data for CO 2+ and CO 3+ from synchrotron radiation experiments led to the conclusion that ionization by Ar-ion impact populates states having considerably higher excitation energies than those accessed by photoionization. The dissociation fractions for CO 1+ and CO 2+ molecular ions, and the branching ratios for the most prominent charge division channels of CO 2+ through CO 7+ were determined from time-of-flight singles and coincidence data. An experiment designed to investigate the orientation dependence of dissociative multielectron ionization of molecules by heavy ion impact was completed. Measurements of the cross sections for K-shell ionization of intermediate-Z elements by 30-MeV/amu H, N, Ne, and Ar ions were completed. The cross sections were determined for solid targets of Z = 13, 22, 26, 29, 32, 40, 42, 46, and 50 by recording the spectra of K x rays with a Si(Li) spectrometer

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

    International Nuclear Information System (INIS)

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

    1983-01-01

    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 S 6 - 16 + on He and Ar at 6-20 MeV and P(b) measurements for MO x-rays produced in Cl 16 + + Ar collisions at 20, 10 and 5 MeV have demonstrated the usefulness of highly-stripped, low-velocity projectiles. These experiments and a few possibilities for future experiments are discussed

  18. Effect of nuclear shielding in collision of positive charged helium ions with helium atoms

    Science.gov (United States)

    Ghavaminia, Hoda; Ghavaminia, Shirin

    2018-03-01

    Differential in angle and absolute cross sections in energy of the scattered particles are obtained for single charge exchange in ^3He^+-^4He collisions by means of the four body boundary-corrected first Born approximation (CB1-4B). The quantum-mechanical post and prior transition amplitudes are derived in terms of two-dimensional real integrals in the case of the prior form and five-dimensional quadratures for the post form. The effect of the dynamic electron correlation through the complete perturbation potential and the nuclear-screening influence of the passive electrons on the electron capture process is investigated. The results obtained in the CB1-4B method are compared with the available experimental data. For differential cross sections, the present results are in better agreement with experimental data than other theoretical data at extreme forward scattering angles. The integral cross sections are in excellent agreement with the experiment. Also, total cross sections for single electron capture, has been investigated using the classical trajectory Monte Carlo method. The present calculated results are found to be in an excellent agreement with the experimental data.

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

    International Nuclear Information System (INIS)

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

    1982-01-01

    Intense beams of highly-stripped ions are now routinely produced at low velocities using the Brookhaven dual MP-tandens in a unique four-stage accel/decel mode. This mode of operation combines three stages of acceleration, stripping at high energy, and one stage of deceleration to near-zero velocity. To date, experiments have used 10-100 nA beams of bare and few-electron heavy ions at energies as low as 0.2 MeV/amu, and upgrades of the facility should push the lower limit below 0.1 MeV/amu. Recent experiments, such as measurements of charge transfer and x-ray production for S/sup 6-16+/ on He and Ar at 6 to 20 MeV and P(b) measurements for MO x-rays produced in Cl 16 + + Ar collisions at 20, 10, and 5 MeV have demonstrated the usefulness of highly-stripped, low-velocity projectiles. These experiments and a few possibilities for future experiments are discussed

  20. 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.