Bulletin of the American Physical Society
2013 Joint Meeting of the APS Division of Atomic, Molecular & Optical Physics and the CAP Division of Atomic, Molecular & Optical Physics, Canada
Volume 58, Number 6
Monday–Friday, June 3–7, 2013; Quebec City, Canada
Session B5: Invited Session: Atomic Collisions Underpinning Astrophysics |
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Chair: Hossein Sadeghpour, Harvard-Smithsonian Center for Astrophysics Room: 301 |
Tuesday, June 4, 2013 10:30AM - 11:00AM |
B5.00001: Proton-hydrogen collisions for Rydberg n,l-changing transitions in the early Universe Invited Speaker: Daniel Vrinceanu Cosmic Microwave Background (CMB) is a vestige radiation generated during the Recombination era, some 390,000 years after the Big Bang, when the Universe had become transparent for the first time. Initial observations of CMB made by the Wilkinson Microwave Anisotropy Probe (WMAP) led to determining the age of the Universe. The mechanisms that drove the recombination have been discovered by using modeling of the primordial plasma and seeking agreement with the observations. The new Plank Surveyor Instrument launched in 2009 is expected to produce data about the recombination era of an unprecedented accuracy, that require including better information regarding the basic atomic physics processes into the present models. In this talk, I will review the results for various Rydberg atom - charge particle collisions and establish their relative importance during the stages of recombination era, with respect to each other and to radiative processes. Energy changing and angular momentum changing collisions with electrons and ions are considered. [Preview Abstract] |
Tuesday, June 4, 2013 11:00AM - 11:30AM |
B5.00002: Three-body recombination in primordial star formation Invited Speaker: Robert C. Forrey Three-body recombination and its importance to first star formation will be discussed. Published rates for molecular hydrogen formation disagree by several orders of magnitude at temperatures relevant to primordial gas. This uncertainty limits the reliability of gravitational collapse models at high densities. An overview of various approaches for calculating three-body recombination rates and the status of current efforts to improve these rates for H and He will be presented. [Preview Abstract] |
Tuesday, June 4, 2013 11:30AM - 12:00PM |
B5.00003: Gas-Phase Theoretical Kinetics for Astrochemistry Invited Speaker: Stephen Klippenstein We will survey a number of our applications of ab initio theoretical kinetics to reactions of importance to astrochemistry. Illustrative examples will be taken from our calculations for (i) interstellar chemistry, (ii) Titan's atmospheric chemistry, and (iii) the chemistry of extrasolar giant planets. For low temperature interstellar chemistry, careful consideration of the long-range expansion of the potential allows for quantitative predictions of the kinetics. Our recent calculations for the reactions of H$_{\mathrm{3}}^{\mathrm{+}}$ with O($^{\mathrm{3}}$P) and with CO suggest an increase of the predicted destruction rate of H$_{\mathrm{3}}^{\mathrm{+\thinspace }}$by a factor of 2.5 to 3.0 for temperatures that are typical of dense clouds. Further consideration of the interplay between spin-orbit and multipole terms for open-shell atomic fragments allows us to predict the kinetics for a number of the reactions that have been listed as important reactions for interstellar chemical modeling [V. Wakelam, I. W. M. Smith, E. Herbst, J. Troe, W. Geppert, et al. Space Science Rev., 156, 13-72, 2010]. Our calculations for Titan's atmosphere demonstrate the importance of radiative emission as a stabilization process in the low-pressure environment of Titan's upper atmosphere. Theory has also helped to illuminate the role of various reactions in both Titan's atmosphere and in extrasolar planetary atmospheres. Comparisons between theory and experiment have provided a more detail understanding of the kinetics of PAH dimerization. High level predictions of thermochemical properties are remarkably accurate, and allow us to provide important data for studying P chemistry in planetary atmospheres. Finally, our study of O($^{\mathrm{3}}$P) $+$ C$_{\mathrm{3}}$ provides an example of a case where theory provides suggestive but not definitive results, and further experiments are clearly needed. [Preview Abstract] |
Tuesday, June 4, 2013 12:00PM - 12:30PM |
B5.00004: High resolution X-ray emission measurements toward understanding low energy charge exchange important to astrophysics Invited Speaker: Charles Havener From the discovery of X-ray emission from Comet Hyakutake to the more detailed observations provided by Chandra, XMM-Newton, Suzaku, etc., charge exchange (CX) is of increasing importance for NASA missions. The University of Wisconsin and Goddard Space Center X-ray micro calorimeter which is used in sounding rocket observations of the diffuse X-ray background, has a dedicated beam line at ORNL and has measured X-ray emission due to CX from a variety of solar wind ions interacting with He, Kr and H${_2}$ at typical solar wind velocities. A proposed modification to the X-ray calorimeter and cryogenic shields will allow for the first merged-beam measurements with atomic H, the remaining elusive benchmark needed for CX modeling of a variety of astrophysical objects. Measured line ratios for the gas targets are compared to a variety of available theoretical predictions. Research supported by the NASA Solar \& Heliospheric Physics Program NNH07ZDA001N, the Office of Fusion Energy Sciences and Division of Chemical Sciences, Geosciences, and Biosciences, the Office of Basic Energy Sciences of the US Department of Energy. VA is supported by the National Science Foundation through Grant No. PHY-106887. [Preview Abstract] |
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