Bulletin of the American Physical Society
66th Annual Gaseous Electronics Conference
Volume 58, Number 8
Monday–Friday, September 30–October 4 2013; Princeton, New Jersey
Session LW5: Heavy-Particle Collisions |
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Chair: Tom Kirchner, York University Room: Village Square |
Wednesday, October 2, 2013 3:30PM - 4:00PM |
LW5.00001: Heavy particle collisions in astrophysical, fusion, and other plasmas Invited Speaker: David Schultz Contemporary computational methods to treat few-body, atomic-scale interactions have opened opportunities to study them at a new level of detail to both uncover unexpected phenomena and to create data of unprecedented accuracy and scope for applications. Such interactions within gaseous, plasma, and even material environments are fundamental to such diverse phenomena as low temperature plasma processing of semiconductors, collapsing giant molecular clouds forming stars, fluorescent lighting, radiation treatment of disease, and the chemistry of earth's atmosphere. I will illustrate progress using examples from recent work treating heavy particle collision systems, for which our knowledge has been both subtly refined and significantly changed. Examples will include elastic and transport-related processes in fusion and solar-system plasmas, charge transfer leading to diagnostic light emission in planetary atmospheres and fusion plasmas, and excitation and ionization processes needed for plasma modeling and diagnostics. [Preview Abstract] |
Wednesday, October 2, 2013 4:00PM - 4:15PM |
LW5.00002: Student Award Finalist - Interference in Recoil-Ion Momentum Spectra for ionization in p $+$ H$_{2}$ Collisions Sachin Sharma, Thusitha Arthanayaka, Ahmad Hasan, Basu Lamichhane, Juan Remolina, Alyson Smith, Michael Schulz We have performed a kinematically complete experiment on ionization in 75 keV p $+$ H$_{2}$ collisions. The double differential cross sections (DDCS) for fixed projectile energy loss as a function of the recoil momentum reveal interference due to indistinguishable diffraction of the projectile from the two atomic centers in the molecule. Earlier, we observed such structures in the projectile scattering angle dependent DDCS. In the present data the oscillations are more pronounced because the phase factor depends only on the recoil momentum, but not on the electron or projectile momentum. Recently, we found that interference structures are not present for an incoherent beam. However, it is not easy to unambiguously distinguish the coherence properties from projectile resolution effects, which both depend on the beam profile. Since the recoil momentum resolution is independent of the beam profile, the present measurement is not affected by this problem. While the experiment has not been completed yet for an incoherent beam, we anticipate that we will be able to present such data by the time of the meeting. [Preview Abstract] |
Wednesday, October 2, 2013 4:15PM - 4:30PM |
LW5.00003: Manipulating state-selective charge exchange in laser-assisted collisions of He$^{2+}$ with atomic H F. Javier Dom\'Inguez-Guti\'errez, R. Cabrera-Trujillo We solve the time-dependent Schr\"odinger equation within a finite-differences approach and the propagation Crank-Nicolson method to calculate the n = 2, 3, and total electron capture cross section of He$^{2+}$ colliding with atomic H in the energy collision range 0.25-35 keV/amu. We use a laser pulse of 3, 2, and 1 fs at FHWM, wavelength of 800 nm and intensity 3.15 $\times 10^{12}$ W/cm$^{2}$. We demonstrate that the laser assistance in the collision increases an order of magnitude the electron charge capture in the 0.25-2 keV/amu energy collision range. We compare our numerical results with those obtained experimentally for the laser-free case to asses the validity of our method. Also, we study the effect of the laser pulse in the excitation cross-section for n =2 states of the hydrogen atom and the dependence of the charge exchange as function of the FWHM of the laser pulse. [Preview Abstract] |
Wednesday, October 2, 2013 4:30PM - 5:00PM |
LW5.00004: Antiproton-Impact Single and Double Ionization of He and H$_2$ Invited Speaker: Michael S. Pindzola A time-dependent close-coupling (TDCC) method has been used to calculate total cross sections for the antiproton-impact single and double ionization of He and H$_2$ for incident energies up to 100 keV. One active electron TDCC-3D calculations for the single ionization of He and H$_2$ yield cross sections at low energies higher than CERN experiments. On the other hand, two active electron TDCC-6D calculations for the single ionization of He and H$_2$ yield cross sections at low energies in reasonable agreement with CERN experiments. The TDCC-6D calculations also yield double ionization cross sections for He and H$_2$. Work is in progress on the calculation of fully differential cross sections for antiproton-impact ionization of a variety of atoms and diatomic molecules. [Preview Abstract] |
Wednesday, October 2, 2013 5:00PM - 5:15PM |
LW5.00005: Student Awards Finalist - Time-dependent convergent close-coupling approach to antiproton-impact ionization of molecular hydrogen A.S. Kadyrov, I.B. Abdurakhmanov, D.V. Fursa, I. Bray A time-dependent convergent close-coupling approach to the calculation of $\bar{p}$-H$_2$ collisions has been developed and applied to study single ionization. All possible orientations of the molecular target have been accounted for using an analytic orientation-averaging technique. Results for the total single ionisation cross section are compared with experimental data over the energy range of 1 keV to 2 MeV and good agreement is found. The approach provides the first theoretical confirmation of the experimentally observed phenomenon [H. Knudsen {\em et al.}, Phys. Rev. Lett. 105, 213201 (2010)] of target structure-induced suppression of the ionization cross section for low-energy antiproton-molecular hydrogen collisions. [Preview Abstract] |
Wednesday, October 2, 2013 5:15PM - 5:30PM |
LW5.00006: ABSTRACT WITHDRAWN |
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