536 Matching Results

Search Results

Advanced search parameters have been applied.

ICPEAC XX: A Retro- and Pro-Spective Analysis

Description: There is something magical about ``round birthdays.`` They make one stop and think about where he is, how he got there, and where he is going. The same is apparently true of conferences, especially those like ICPEAC which represent the periodic coming together of a broad range of scientists in a reasonably well-defined discipline. This Vienna conference is the 20th in the ICPEAC series, and a retro- and pro-spective analysis seems appropriate. At the first ICPEAC in New York (1958), there were about 50 participants. In Vienna (1997), there were more than 800 participants. How do we account for this growth? ICPEAC is one of the most democratic conferences of its size. For example, input from a general committee of 50 representing the many geographic and sub- disciplinary areas gives continuous refreshment of ideas for the invited program. And, as in any democracy, there is a constant state of turmoil and self doubt. After all, atomic collisions is a ``mature`` field, and was a ``mature`` field at the time of the first ICPEAC in 1958, 50 what can one expect in new developments? This self doubt is best expressed in the comment of Ben Bederson (the ``Father of ICPEAC``) following the second in Boulder, Colorado, in 1961: ``This conference is the second in a series of informal meetings organized by a group of workers in the general field of electronic and atomic collisions. The first such meeting was held at New York University in 1958, and we will probably continue to meet at irregular intervals in the future....`` As part of my ``keynote`` talk at the New York ICPEAC XVI in 1989, I gave a brief history of the conference which we can build on to round things off for our twentieth.
Date: December 31, 1997
Creator: Datz, S.
Partner: UNT Libraries Government Documents Department

Theoretical atomic collision physics. Final report, July 1, 1987-- June 30, 1995

Description: This is the final report of research activities supported by the most recent grant to the theoretical atomic collision physics program at Rice University. For this most recent 3-year grant, the focus has been the study of excitation and charge-transfer in atom-atom and ion-atom collisions. Emphasis has been placed on low-velocity collision processes involving initially excited atoms, including ``low Rydberg`` atoms. Two particular objectives of this research were to examine the dependence of state-changing collision cross sections and other observables on the orientation and alignment of the initial excited orbitals and to look for ``intracollisional interference`` effects, speculated to arise from spatially separated interactions during a collision involving a highly excited atom. A number of radiative and non-radiative charge transfer studies involving ground-state atoms and ions were continued from the previous grant period. Several unanticipated personnel changes prevented execution of some of the proposed research, including the studies of collisions involving negative ions and electron-attaching atoms and the development of new theoretical techniques for handling the ``strong coupling`` regime. These remain challenging and fundamentally important research topics. Research highlights briefly described in the report deal with: spherical and non-spherical low-Rydberg atom collisions; alignment effects in collisions of Na(3p) with He{sup +} ions; near-resonant electron capture at very low energies; ion-atom and ion-molecule collisions, including electron capture; and low- energy processes involving collisions of H{sup +} with He, Na, and K atoms. The report also lists publications since 1991 reporting on the grant work.
Date: December 1, 1995
Creator: Walters, G.K.
Partner: UNT Libraries Government Documents Department

Autoionizing states in the alkalis

Description: Autoionization measurements are presented for collisionally excited states of lithium, sodium, magnesium, and potassium. Excitation was accomplished by passing a 70 keV beam of the alkali ions through a gas cell containing helium. Details of the experimental apparatus are given and electron spectra of the excited atoms are shown. 6 figs, 4 tables, 26 refs (GHT)
Date: January 1, 1975
Creator: Pegg, D. J.
Partner: UNT Libraries Government Documents Department

Measurements of Scattering Processes in Negative Ion- Atom Collisions

Description: The main research activity is to study various scattering processes which occur in H{sup -} collisions with atomic (specifically, noble gas and atomic hydrogen) targets in the intermediate energy region. These processes include: elastic scattering, single- and double-electron detachment, and target excitation/ionization.
Date: December 22, 2000
Creator: Kvale, T. J.
Partner: UNT Libraries Government Documents Department

Standing wave solutions to the inhomogeneous equation for identical particle scattering

Description: The standing wave solution to the inhomogeneous equation describing identical particle scattering is re-examined. Although the form of that solution is correct, its content is shown to be incorrect. A paradigm for constructing the correct solution, based on unitarity, is discussed, and the proper solution is then obtained. A comparison of different standing wave solutions with differing K operators is given. The results are shown to be an extension to the multi-channel case of those derived previously for the potential well case. (auth)
Date: January 1, 1973
Creator: Kouri, D.J. & Levin, F.S.
Partner: UNT Libraries Government Documents Department

Coherent excitation of autoionizing resonances

Description: An electron-electron coincidence [or (e,2e)] technique was used to investigate atomic ionization by electron impact in the neighborhood of autoionizing resonances. Differing binary (I{sup +}) and recoil (I{sup -}) lobe intensities in coplanar (e,2e) ejected-electron angular distributions were analyzed in terms of interference cross-terms, between opposite parity final-state continua, that change sign when {theta}{sub ej} {yields} {theta}{sub ej} + 180{sup o} in the angular distributions. The magnitude of these cross-terms varies rapidly with ejected-electron energy across overlapping autoionizing resonances. The energy variation in the interference terms may be examined by obtaining the sum (I{sup +} + I{sup -}) and difference (I{sup +} - I{sup -}) of (e,2e) energy spectra measured at ejected-electron angles 180{sup o} apart.
Date: October 3, 2002
Creator: Martin, N.L.S.
Partner: UNT Libraries Government Documents Department

1984 Bibliography of atomic and molecular processes

Description: This annotated bibliography includes papers on atomic and molecular processes published during 1984. Sources include scientific journals, conference proceedings, and books. Each entry is designated by one or more of the 114 categories of atomic and molecular processes used by the Controlled Fusion Atomic Data Center, Oak Ridge National Laboratory to classify data. Also indicated is whether the work was experimental or theoretical, what energy range was covered, what reactants were investigated, and the country of origin of the first author. Following the bibliographical listing, the entries are indexed according to the categories and according to reactants within each subcategory.
Date: April 1, 1985
Creator: Barnett, C.F.; Gilbody, H.B.; Gregory, D.C.; Griffin, P.M.; Havener, C.C.; Howard, A.M. et al.
Partner: UNT Libraries Government Documents Department

Multiphoton processes: conference proceedings

Description: The chapters of this volume represent the invited papers delivered at the conference. They are arranged according to thermatic proximity beginning with atoms and continuing with molecules and surfaces. Section headings include multiphoton processes in atoms, field fluctuations and collisions in multiphoton process, and multiphoton processes in molecules and surfaces. Abstracts of individual items from the conference were prepared separately for the data base. (GHT)
Date: January 1, 1984
Creator: Lambropoulos, P. & Smith, S.J. (eds.)
Partner: UNT Libraries Government Documents Department

1982 bibliography of atomic and molecular processes

Description: This annotated bibliography includes papers on atomic and molecular processes published during 1982. Sources include scientific journals, conference proceedings, and books. Each entry is designated by one or more of the 114 categories of atomic and molecular processes used by the Controlled Fusion Atomic Data Center, Oak Ridge National Laboratory to classify data. Also indicated is whether the work was experimental or theoretical, what energy range was covered, what reactants were investigated, and the country of origin of the first author. Following the bibliographical listing, the entries are indexed according to the categories and according to reactants within each subcategory.
Date: May 1, 1984
Creator: Barnett, C.F.; Crandall, D.H.; Gilbody, H.B.; Gregory, D.C.; Kirkpatrick, M.I.; McDaniel, E.W. et al.
Partner: UNT Libraries Government Documents Department

Theoretical investigation of electron-positive ion/atom interactions. Progress report, November 15, 1991--July 14, 1992

Description: Very brief summaries are given on three research topics. Electron impact elastic, excitation, and total cross sections for K were investigated by using elaborate Cl target wave functions in the close-coupling approximation. Photoionization cross sections from ground-state Na were calculated near the 2s{sup 2}2p{sup 5}3s and 2s2p{sup 6}3s inner-shell thresholds; also, the photoionization cross sections of excited 3p {sup 2}P{sup o} and 3d {sup 2}D states were calculated with the R-matrix methodology near the 2s2p{sup 6}3s thresholds. A numerical approach was developed to calculate the charge transfer matrix elements for ion-atom(ion) collisions; this was used for the proton-hydrogen collision problem as an illustration.
Date: December 31, 1992
Creator: Msezane, A. Z.
Partner: UNT Libraries Government Documents Department

Proceedings of the Workshop on Electronic and Ionic Collision Cross Sections Needed in the Modeling of Radiation Interactions with Matter, Held at Argonne National Laboratory December 6-8, 1983

Description: The term modeling in the Workship title refers to the mathematical analysis of the consequences of many collision processes for characterizing the physical stage of radiation actions. It requires as input some knowledge of collision cross sections. Traditionally, work on cross sections and work on the modeling are conducted by separate groups of scientists. It was the purpose of the Workshop to bring these two groups together in a forum that would promote effective communication. Cross-section workers described the status of their work and told what data were available or trustworthy. Modeling workers told what kind of data were needed or were most important. Twenty-two items from the workshop were prepared separately for the data base.
Date: May 1984
Creator: Argonne National Laboratory
Partner: UNT Libraries Government Documents Department

Time-dependent, lattice approach to atomic collisions

Description: Recent progress in developing and applying methods of direct numerical solution of atomic collision problems is described. Various forms of the three-body problem are used to illustrate these techniques. Specifically, the process of ionization in proton-, antiproton-, and electron-impact of atomic hydrogen is considered in applications ranging in computational intensity from collisions simulated in two spatial dimensions to treatment of the three-dimensional, fully correlated two-electron Schroedinger equation. These examples demonstrate the utility and feasibility of treating strongly interacting atomic systems through time-dependent, lattice approaches.
Date: December 1995
Creator: Schultz, D. R.
Partner: UNT Libraries Government Documents Department

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

Description: 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.
Date: April 1, 1997
Creator: McGuire, J.
Partner: UNT Libraries Government Documents Department

Relevant ion time scales for electron impact processes of atoms in dense plasmas

Description: In this paper a new model for treating collisional atomic processes has been presented. This model simultaneously and self-consistently treats electron and ion processes. For transitions frequencies above the ion plasma frequency, it is argued that little ion motion occurs although the interaction is still strong; the ion microfield perturbs the atom. The electron impact processes may still be described by a DSF between levels of the perturbed atoms, suggesting the name Microfield Stochastic Model (MSM) for this method. Future work will be directed towards refining some of the approximations used here for application to realistic systems.
Date: December 31, 1997
Creator: Murillo, M.S.
Partner: UNT Libraries Government Documents Department

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

Description: 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.
Date: May 1, 1983
Creator: Janev, R.K.
Partner: UNT Libraries Government Documents Department

Theory of electron transfer in ion-atom collisions

Description: Current development of the theory of electron transfer in ion-atom collisions is summarized. Preliminary results indicate that K-K capture cross sections at lower energies are sensitive to the proper treatment of the atomic model. It was shown that electron capture from outer shells of multielectron atoms can be calculated using the present method, in conjunction with the simple independent electron model. Some recent research is summarized. 8 references. (JFP)
Date: January 1, 1979
Creator: Lin, C D
Partner: UNT Libraries Government Documents Department

Correlation holography: imaging of atoms when sigma/sub inelastic//sup >>sigma/elastic

Description: Atomic-scale resolution of details is possible with this method, even if protons interact with the atoms overwhelmingly inelastically, i.e. when sigma/sub inelastic/ >>sigma/sub elastic/. Observation of small objects is compatible with quantum mechanics even if the disturbance of the object caused by the observation process is arbitrarily small.
Date: January 1, 1979
Creator: Csonka, P.L.
Partner: UNT Libraries Government Documents Department

Atomic phenomena in dense plasmas

Description: The following chapters are included: (1) the plasma environment, (2) perturbations of atomic structure, (3) perturbations of atomic collisions, (4) formation of spectral lines, and (5) dielectronic recombination. (MOW)
Date: March 1, 1981
Creator: Weisheit, J.C.
Partner: UNT Libraries Government Documents Department

Theoretical triply differential cross section of electron-impact ionization of atoms

Description: The triply differential cross section of electron-impact ionization of atoms is given in a parameterized form, suitable for theoretical computations or for semi-empirical fittings. Application of the present formulation is demonstrated. Merits of coplanar measurements are discussed. It is also shown that the coplanar up-down asymmetry of the ejected electron is linear in the scattering angle, or the momentum transfer, of the incident electron for small momentum transfers.
Date: January 1, 1983
Creator: Huang, K.N.
Partner: UNT Libraries Government Documents Department