Bulletin of the American Physical Society
63rd Annual Gaseous Electronics Conference and 7th International Conference on Reactive Plasmas
Volume 55, Number 7
Monday–Friday, October 4–8, 2010; Paris, France
Session UF2: Heavy-Particle Collisions |
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Chair: Tom Kirchner, York University Room: 262 |
Friday, October 8, 2010 2:00PM - 2:30PM |
UF2.00001: Doubly differential spectra of scattered protons in ionization of atomic hydrogen Invited Speaker: We have measured and calculated doubly differential cross sections for ionization of atomic hydrogen using~75-keV proton impact for fixed projectile energy losses as a function of projectile scattering angle. This collision system represents a pure three-body system and thus offers a very sensitive and accurate test of the theoretical description of the few-body dynamics without any complications presented by electron correlation in many-electron targets. Comparison between experiment and several theoretical models reveals that the projectile-target nucleus (PT) interaction is best described by the operator of a second-order term of the transition amplitude. Higher-order contributions in the projectile-electron interaction, on the other hand, are more appropriately accounted for in the final-state wave function. Furthermore, the comparison between experiment and theory reveals that in the well-known focusing of the ejected electrons due to the post-collision interaction (PCI) the PT interaction plays a crucial role. [Preview Abstract] |
Friday, October 8, 2010 2:30PM - 2:45PM |
UF2.00002: Four-Body Charge Transfer Processes in proton-helium Collisions Uttam Chowdhury, Allison Harris, Jerry Peacher, Don Madison Recent advancements in experimental techniques now allow for the study of fully differential cross sections for four-body collisions. The simplest four-body problem is a charged particle collision with a helium atom, in which both atomic electrons change state. This type of collision can result in many different outcomes, such as double excitation, excitation-ionization, double ionization, transfer-excitation, transfer-ionization, and double charge transfer. Theoretical fully differential cross sections will be presented and compared with absolute experimental data for transfer-excitation and double charge transfer proton-helium collisions. The model used is a fully quantum mechanical, first order perturbative model that includes all relevant two particle interactions. Numerically, this requires a full nine-dimensional integral, and is quite computationally expensive. The role of different scattering mechanisms will be discussed. [Preview Abstract] |
Friday, October 8, 2010 2:45PM - 3:15PM |
UF2.00003: Differential cross sections for ion-impact ionization of helium Invited Speaker: An overview is given of the recent progress made in applying the time-dependent close-coupling (TDCC) approach to the treatment of ion-impact collisions with small atoms and molecules. In the last several years, the TDCC method has been used to compute cross sections for the single and double ionization of helium by alpha particles, protons, and anti-protons. We have also recently extended our approach to examine proton-impact single and double ionization of the hydrogen molecule. Recent work has also examined the differential cross sections arising from the single and double ionization of helium by protons and fully stripped carbon ions. Although the TDCC approach assumes a straight-line trajectory (impact-parameter method) for the incoming projectile, it is possible to extract cross sections differential in projectile scattering angle from such an approach. These calculations are made to compare with the recent intense experimental efforts in this area. We will report on our progress, including detailed comparisons with the C$^{6+}$ single ionization of helium measurements, at the conference. [Preview Abstract] |
Friday, October 8, 2010 3:15PM - 3:30PM |
UF2.00004: Ionization and Spin Exchange Processes with Spin-Polarized Metastable Helium Atoms in Gas Discharge Plasma Victor Kartoshkin, George Klementiev At the interaction between the spin-polarized excited atom and paramagnetic ground state atom or molecule in gas discharge, elastic and inelastic processes can take place simultaneously. It means that besides the chemo-ionization of the atom or molecule at the expense of atom's excitation energy (inelastic process), an exchange of electrons is possible without a great depolarization (elastic process, or spin exchange). In such a case these two processes give rise to a remarkable spin polarization transfer between colliding particles. Influencing each other, these two processes result in a change in the spin exchange and frequency shift cross section values. [Preview Abstract] |
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