Electron, Positron and Photon Collisions with Atoms and Molecules

Photoionization and photodetachment

In the area of photon collisions, our non-relativistic and relativistic calculations have helped to analyse the ocillator strengths and role of metastable states in the strong 4d-4f transition region in Xe ions

[A. Aguilar, J. D. Gillaspy, G. F. Gribakin, R. A. Phaneuf, M. F. Gharaibeh, M. G. Kozlov, J. D. Bozek, and A. L. D. Kilcoyne, "Absolute photoionization cross sections for Xe4+, Xe5+, and Xe6+ near 13.5 nm: Experiment and theory", Phys. Rev. A 73, 032717 (2006)]. We also used random-phase approximation to study the role of inner-shell photodetachment in the negative fluorine ion, and aid the analysis of experimetal data obtained using modern synchrotron radioation sources [V. T. Davis, A. Aguilar, A. M. Covington, J. S. Thompson, D. Calabrese, C. Cisneros, M. S. Gulley, M. Halka, D. Hanstorp, J. Sandström, B. M. McLaughlin, G. F. Gribakin and D. J. Pegg, "Photo-double detachment from the F- ion", J. Phys. B 38, 2579 (2005)].

Inner-shell photon processes

We work with theoretical physics colleagues in Meudon (France) and Atlanta (Georgia,USA) to undertake calculation of inner-shell photoionisation and photodetachment processes. Our collaborations involve experimental groups in Orsay (France), Dublin (Ireland) and Kalamazoo (Michigan, USA).

Early work focused on calculations of photoionisation cross sections of hollow lithium and photodetachment of the Li negative ion, and included the first joint experimental/theoretical study of these newly observed phenomena. As the range of experimental work extended, so did our calculations, to inner-shell photoionisation of carbon, sodium and copper, and the photodetachment of He-, Be- and B-.

Photodetachment

Until recently all experimental and theoretical photodetachment studies have been concerned with the photodetachment of outer and near-outer electrons only. For deep inner shells, such as the 1s shell, however, photodetachment cross sections whether experimental or theoretical are much more scarce. To explore the differing effects of correlation in inner as opposed to outer shell photodetachment pioneering calculations for photodetachment across the K-shell threshold of the negative beryllium ion have been completed (Carlin et al (2003)). These projects are timely in that experimentalists have recently managed to measure, for the first time, the absolute cross section for inner-shell photodetachment of the negative lithium ion near the 1s threshold.