Gordon Godfrey Theoretical Seminar 2006

Isotope shift, relativistic shift, and the hunt for alpha-variation.

Julian Berengut
UNSW

Date
12 pm, Tuesday, 14 March, 2006
School of Physics,
Room 5

Abstract:
This work is motivated by recent studies of quasar absorption spectra designed to probe the fine-structure constant, alpha, in the distant past. Atomic transition frequencies depend on alpha, and by comparing frequencies on earth with those in quasar absorption spectra, one can deduce whether or not alpha was different in the early universe. While some studies have revealed a significant deviation from zero, other groups using a different telescope have not.

In order to measure any variation in alpha, the alpha-dependence (relativistic shift) of every transition used in the analysis must be calculated ab initio. Furthermore isotope shifts are needed to resolve systematic effects. These isotope shifts can also be used to measure isotopic abundances in gas clouds in the early universe, which are needed to study nuclear reactions in stars and supernovae and test models of chemical evolution.

In this talk I will present a method for the precise calculation of relativistic shifts and isotope shifts, based on an energy calculation involving combination of the configuration interaction method and many-body perturbation theory.

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