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Departmental Colloquium

High Quality Computation of Selective Atomic and Molecular Processes  
Guest Speaker
Brendan M. McLaughlin  
Guest Affiliation
Centre for Theoretical Atomic, Molecular and Optical Physics, Queen’s University of Belfast  
Thursday, December 1, 2016 3:30 pm - 4:30 pm  
CSP Conference Room (322)  
Photoionization of atomic and molecular species is an important process in determining the ionization balance and hence the abundances of elements in astrophysical nebulae. It has recently become possible to detect neutron-capture elements (atomic number Z>30) in a large number of ionized nebulae. Accurate assessment of elemental abundances in astrophysical nebulae can be made from the direct comparison of the observed spectra with synthetic non-local thermodynamic equilibrium (NLTE) spectra, if the atomic data for electron and photon interaction processes are known with sufficient accuracy. Experiments on light systems, trans-Fe elements and molecules at third generation synchrotron radiation source, such the Advanced Light Source (ALS) in Berkeley, California, USA, SOLEIL in Saint-Aubin, France, ASTRID II in Aarhus, Denmark and PETRA III, in Hamburg, Germany, require high quality theoretical studies to interpret experimental results. Results will be presented from recently developed ab initio R-matrix methods for atomic and molecular systems using parallel computing architectures. Photoionization cross sections will be presented for a variety of atomic species; Se, Kr, Ar, Xe, W, Si, S, Cl, C, N, and O, in neutral or low stages of ionization. Comparison of our theoretical results with experiments performed at leading synchrotron light sources serve as the ultimate benchmark for theory, in order to have confidence in the atomic and molecular data being incorporated into astrophysical modelling codes such as CLOUDY, XSTAR, CHIANTI and ATOMDB.