# Heidelberg 2015 – wissenschaftliches Programm

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# A: Fachverband Atomphysik

## A 16: Interaction with strong or short laser pulses I

### A 16.6: Vortrag

### Dienstag, 24. März 2015, 15:45–16:00, C/kHS

**Nonsequential double ionization and radiation/absorption spectra with time-dependent renormalized-natural-orbital theory** — •Martins Brics, Julius Rapp, and Dieter Bauer — Universität Rostock, Rostock, Germany

Time-dependent renormalized-natural-orbital theory (TDRNOT) is a promising approach to describe correlated electron quantum dynamics, even beyond linear response. It has been shown in [1] that TDRNOT with only two renormalized natural orbitals (RNOs) per spin is capable of describing correlated phenomena such as doubly excited states, autoionization, and Fano profiles in the photoelectron spectra for He. Here we go one step further and investigate the performance of TDRNOT for processes which involve more than two RNOs.

As the first test case we consider nonsequential double ionization (NSDI) as it is a very correlated process and therefore many RNOs are needed to describe it. Our two main observables for NSDI are the double-ionization probability and correlated photoelectron spectra. It is found that TDRNOT reproduces the celebrated NSDI “knee,” i.e., a many-order-of-magnitude enhancement of the double-ionization yield (as compared to purely sequential ionization) with only the ten most significant natural orbitals (NOs) per spin. Correlated photoelectron spectra—as “more differential” observables—require more NOs [2].

The second test case is radiation/absorption spectra. Here we look at absorption line-shapes showing Lorentz/Fano profiles and ATI spectra.

[1] M. Brics, D. Bauer, Phys. Rev. A **88**, 052514 (2013).

[2] M. Brics, J. Rapp, D. Bauer, Phys. Rev. A **90**, 053418 (2014).