# Hannover 2013 – wissenschaftliches Programm

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# A: Fachverband Atomphysik

## A 33: Interaction with strong or short laser pulses III

### A 33.3: Vortrag

### Donnerstag, 21. März 2013, 11:30–11:45, B 302

**Decay of autoionizing states in time-dependent density functional and reduced density matrix functional theory** — •Varun Kapoor, Martins Brics, and Dieter Bauer — Institut für Physik, Universität Rostock, 18051 Rostock

Autoionizing states are inaccessible to time-dependent density functional theory (TDDFT) using known, adiabatic Kohn-Sham (KS) potentials. We determine the exact KS potential for a numerically exactly solvable model Helium atom interacting with a laser field that is populating an autoionizing state. The exact single-particle density of the population in the autoionizing state corresponds to that of the energetically lowest quasi-stationary state in the exact KS potential. We describe how this exact potential controls the decay by a barrier whose height and width allows for the density to tunnel out and decay with the same rate as in the ab initio time-dependent Schrödinger calculation. However, devising a useful exchange-correlation potential that is capable of governing such a scenario in general and in more complex systems is hopeless. As an improvement over TDDFT, time-dependent reduced density matrix functional theory has been proposed. We are able to obtain for the above described autoionization process the exact time-dependent natural orbitals (i.e., the eigenfunctions of the exact, time-dependent one-body reduced density matrix) and study the potentials that appear in the equations of motion for the natural orbitals and the structure of the two-body density matrix expanded in them.