Bulletin of the American Physical Society
38th Annual Meeting of the Division of Atomic, Molecular, and Optical Physics
Volume 52, Number 7
Tuesday–Saturday, June 5–9, 2007; Calgary, Alberta, Canada
Session G6: Heavy Particle Collisions and Surface Interactions |
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Chair: D. Schultz, Oak Ridge National Laboratory Room: TELUS Convention Centre Olde Scotch Room |
Thursday, June 7, 2007 8:00AM - 8:12AM |
G6.00001: ABSTRACT HAS BEEN MOVED TO P4.00013 |
Thursday, June 7, 2007 8:12AM - 8:24AM |
G6.00002: ABSTRACT HAS BEEN MOVED TO H4.00009 |
Thursday, June 7, 2007 8:24AM - 8:36AM |
G6.00003: Correlation between bound and continuous states of three identical particles Nicolas Douguet, Viatcheslav Kokoouline Study of degenerate cold gazes represents today a wide field of physics, because phenomena in cold gazes are relevant in several other fields of physics, like for instance, superconductivity or astrophysics. In this work, we discuss collisions of three identical particles in ultra-cold gazes, by considering the symmetry of the total wave function of the system. Thus, we use either laboratory-frame, hyperspherical, or Jacobian coordinates, depending on which ones are best suited to describe the different configurations of the system. Precisely, for this purpose, we describe the wave function of the system at large distances, in order to understand the states of the particles before and after the three-body collision, but also consider the wave function at short distances during the actual collision process. Then, we are able to predict the possible quantum states of the particles after collision, by using symmetry considerations. In particular, we describe the recombination of the system into one free particle and a dimer. The result can be used for example, to identify possible decay products of quasi-stationary Efimov states. [Preview Abstract] |
Thursday, June 7, 2007 8:36AM - 8:48AM |
G6.00004: ABSTRACT HAS BEEN MOVED TO H4.00013 |
Thursday, June 7, 2007 8:48AM - 9:00AM |
G6.00005: A Novel Method to Analyze Four-Body Break-Up Processes Michael Schulz, Daniel Fischer, Thomas Ferger, Robert Moshammer, Joachim Ullrich Numerous kinematically complete experiments on a variety of atomic break-up processes have been performed in recent years. The fully differential cross sections (FDCS) extracted from such measurements provide the most sensitive tests of theory. However, one drawback of the FDCS is that they do not show a comprehensive physical picture of the process, but rather only for one specific kinematical setting at a time usually covering only a small fraction of the total cross section. Less differential data can be presented in conventional one- or two-dimensional plots without losing any part of the total cross section. However, for processes involving more than two particles these spectra are integrated over at least one fragment. Recently, we demonstrated that for single ionization (three bodies) Dalitz plots are a powerful tool to present data as a function of all three fragments simultaneously in a single spectrum without loss of any part of the total cross section$^{1}$. Here, we report on a generalization of Dalitz plots to four-body break-up processes. By using a tetrahedral coordinate system it has become possible for the first time to present measured data as a function of all four fragments simultaneously. $^{1}$M. Schulz et al., J. Phys. \underline {B37}, 4055 (2004) [Preview Abstract] |
Thursday, June 7, 2007 9:00AM - 9:12AM |
G6.00006: Acoustic Desorption from a Room Temperature Ionic Liquid. Peter Harris, Eugene Tracy, William Cooke We use laser induced acoustic pulses to efficiently desorb ions from a Room Temperature Ionic Liquid (RTIL) in vacuum. Our RTIL, 1-butyl-3-methylimidazolium hexafluorophosphate, remains a stable liquid at pressures exceeding 10$^{-9}$ torr. We use the 2$^{nd}$ harmonic of a Nd:YAG laser, 2ns pulse time, to generate acoustic pulses via laser ablation of the backside of a metal foil. Both negative and positive ions are desorbed from the liquid RTIL surface on the front side of the foil. The m/q of ejected ions is detected via TOF measurements from an imaging micro-channel plate detector. We measure the time our acoustic pulse reaches the RTIL surface by detecting the ejected electron signal. We present data showing the variation of desorbed ion yield as a function of the amplitude and shape of the incident acoustic pulse. [Preview Abstract] |
Thursday, June 7, 2007 9:12AM - 9:24AM |
G6.00007: Internuclear separation dependence of dipole-dipole interactions between excited sodium atoms Brian Ricconi, Yan Xiao, J. Gary Eden Wavepackets and parametric four-wave mixing (PFWM) was used to probe excited Na atoms with mean internuclear separations between 700 and 1100 {\AA}. A pump-probe technique employing a nonlinear parametrically amplified oscillator to coherently probe the 4d and 5s energy states was used to observe the quantum beating at a frequency of 1348.1 cm$^{-1}$. Frequency analysis of the PFWM signal indicated the energy defect between the Na 5s-4d levels was perturbed and sidebands to the main frequency appeared. By monitoring the frequency difference between the perturbed and unperturbed oscillations, the sum of the interaction energies between one atom and all surrounding atoms may be obtained. Although two-body dipole-dipole interactions qualitatively account for the frequency spread, quantitative analysis shows that many-body interactions must be considered to be consistent with the observed splitting. [Preview Abstract] |
Thursday, June 7, 2007 9:24AM - 9:36AM |
G6.00008: Particle, Energy and Rovibrational Spectra of Molecules Chemically Sputtered of Carbon Surfaces Predrag Krstic, Carlos Reinhold, Steven Stuart We perform classical molecular dynamics simulations of the chemical sputtering of deuterated amorphous carbon surfaces by deuterium atoms and molecules at impact energies from threshold to 50 eV/D. Particular attention is paid to the preparation of the target surfaces for varying impact projectile fluence, energy and species [1]. The spectra of hydrocarbon molecules C$_{x}$D$_{y}$, with x in range 1 to 5 are observed, and spectral distributions of their translational, rotational and vibrational energies are analyzed. Angular spectra of the sputtered molecules are also analyzed. Our results show good agreement with existing experimental data. [1] P. S. Krstic, C. O. Reinhold, and S. J. Stuart, Europhysics Letters 77, 33002(2007). [Preview Abstract] |
Thursday, June 7, 2007 9:36AM - 9:48AM |
G6.00009: Dielectric Spectroscopy Analysis of Aged EVOH films with Application to Deterioration of Food Packaging Materials Timothy Hoeller Samples of EVOH films from compositions of 29 - 44 mol\% ethylene content were exposed to thermal aging with and without light exposure. The results of Dielectric Spectroscopy on select samples showed Cole-Cole plots of skewed dielectric constant indicating multiple distributions of dipole relaxation times. The onset for decreases in dielectric response occurs earlier in samples exposed to elevated temperature under light exposure. Lower permittivity is exhibited in samples of higher ethylene content. Results from heat exposed samples are presented. Colorimetric analysis indicates only a slight film yellowing in one case. Raman spectroscopy on untreated films discerns changes in the C-C-O stretch associated with the alcohol. The effects of aging on microstructure may cause hindrance of molecular motion from moisture desorption. Slight material degradation occurs from film hardening presumably due to crosslinking. An electrical circuit model of the conduction processes associated with the EVOH films is presented. Dielectric analysis shows promise for monitoring material changes related to deterioration. We are also using these methods to understand Fluorescence Imaging which has been recently released for paper and plastic materials analysis. Future work may include refinement of these techniques for identification of changes in material properties correlated to packaging material barrier resistance. [Preview Abstract] |
Thursday, June 7, 2007 9:48AM - 10:00AM |
G6.00010: Application of Laser Induced Electron Impact Ionization to the SiH$_{4}$-NH$_{3}$ Hot Wire Chemical Vapor Deposition System. Brett Eustergerling, Martin Heden, Yujun Shi The application of a laser induced electron ionization (LIEI) source in studying the gas phase chemistry of the SiH$_{4}$ -- NH$_{3}$ hot wire chemical vapor deposition system has been investigated. By directing an unfocused laser beam containing 118 and 355 \textit{nm} radiation to the repeller plate in a Wiley-McLaren type time-of-flight mass spectrometer, photoelectrons were successfully liberated from the stainless steel plate. The large electric field in the ion optics region accelerated these photoelectrons, resulting in the ionization of species which are unavailable by the 118 \textit{nm} single-photon ionization route (SPI, 10.5 \textit{eV}). In all mixtures studied, it was found that any species with an ionization potential below 10.5 \textit{eV} , e.g. Si$_{2}$H$_{6}$ and NH$_{3}$, were observed most strongly when pure SPI was used, whereas peaks corresponding to those species with IP's above 10.5 \textit{eV}, e.g. H$_{2}$, N$_{2}$ and He, were strongest when LIEI was employed. Further investigations using a custom built, variable-energy photoelectron source will also be presented. [Preview Abstract] |
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