Igor M Savukov
Los Alamos National Laboratory, USA
Title: Applications of many-body perturbation theory to actinide atoms
Biography
Biography: Igor M Savukov
Abstract
There are three main challenges for accurate applications of atomic theory to calculations of energy levels and other properties of Actinide atoms. First, the valence-valence interaction is strong and requires a large confi guration space to account for this interaction. Various methods have implemented small configuration space and cannot account for the interaction with highly excited states and continuum. Second, the valence-core interaction is also strong and second-order MBPT, which is usually implemented in the confi guration-interaction (CI) many-body perturbation theory (MBPT) method, is not adequate. Finally, the relativistic eff ects are signifi cant breaking the LS-coupling scheme and making the transition amplitudes sensitive to these corrections. Th e approach of relativistic CI-MBPT is quite promising. It proved to give quite accurate results in light atoms, where the valence-core interaction can be described well in the second order and relativistic eff ects can be accounted for by employing Dirac-Fock basis and adding dominant Breit interactions. However, ab initio CI-MBPT completely fails in actinides. Still, signifi cant improvement in accuracy can be achieved by introducing adjustable parameters. In particular, seven such parameters can be used to correct the single-valence energy, while additional two parameters can be used to improve the Coulomb screening. With 9-parameter CI-MBPT approach it is possible to reproduce energy levels in as complex an atom as U I. In this talk, I will show examples of CI-MBPT calculations with adjustable parameters for complex atoms. The work is in progress and some future directions will be also discussed.