CTAMOP | Centre for Theoretical Atomic, Molecular and Optical Physics

Queen's University > School of Math. & Phys. > CTAMOP Research

Computational Atomic Structure

The major part of our work concerns the calculation of accurate oscillator strengths (or equivalently A-values), particularly but not exclusively for astrophysically important atoms and ions, using the general atomic structure code CIV3 which we developed over many years and which we upgrade on a regular basis. Increasingly we are attempting to give realistic but narrow uncertainty estimates for our data. The emphasis in our work is on obtaining oscillator strengths to high accuracy.

The analysis of new, high quality, spectroscopic observations from space-based observatories is frequently hampered by the relative inaccuracy of much existing atomic data (and particularly oscillator strengths). This underlines the continuing urgency of the calculations we undertake.

Much of our recent work has focused on the iron group elements, in particular on Fe II, Fe III, Fe IV, Mn II and more recently on Sc II. In this work, we collaborate with observational and experimental researchers as part of the FERRUM project, involving experimental groups in Stockholm and Imperial College London, and astrophysicists at Lund and in the ARC research cluster in our own School. Experimental determinations of oscillator strengths are obtained by combining lifetimes measured in Lund and Stockholm with branching fractions measured in London.

This collaboration has developed further into a combined theoretical/experimental approach to the determination of hyperfine structure, which is another aspect of our work.

More details of our work in relation to astrophysics, as well as recent publications, are given on the associated website Atomic Data for Astrophysics : http://www.am.qub.ac.uk/apa/

Other recent work has focused on the need for oscillator strength data used in the analysis of impurities in the plasmas found in tokamaks including the planned ITER for fusion research. Our particular interest is in neutral and singly ionised tin, for which very little accurate atomic data exists.

Recent observations using space-based observatories have revealed the presence of elements which previously had been undetectable. These include the lanthanides, as well as other heavy elements. In contrast to the lighter elements, relatively little theoretical work has so far been undertaken on transitions in ions of these elements. In view of the importance of these elements, we are planning to undertake a major study of such transitions, using the GRASP program; some members of our group were involved in its development.