Impact of intense laser pulses on the autoionization dynamics of the 2s2p doubly-excited state of He

TL;DR

This study investigates how intense, short laser pulses influence the autoionization dynamics of the 2s2p doubly-excited state in helium, demonstrating control over Fano-interferences through pulse parameters.

Contribution

It introduces a numerical approach using TD-RASCI to show how laser pulse intensity and duration can manipulate autoionization and Fano interference profiles in helium.

Findings

Fano-interferences can be controlled by a single high-frequency pulse.

Varying pulse intensity affects the Fano profile.

Weak-field asymmetric profile can be transformed into a window-type interference.

Abstract

The photoionization of a helium atom by short intense laser pulses is studied theoretically in the vicinity of the $2s2p\,^1P$ doubly-excited state with the intention to investigate the impact of the intensity and duration of the exciting pulse on the dynamics of the autoionization process. For that purpose, we solve numerically the corresponding time-dependent Schr\"{o}dinger equation by applying the time-dependent restricted-active-space configuration-interaction method (TD-RASCI). The present numerical results clearly demonstrate that the Fano-interferences can be controlled by a single high-frequency pulse. As long as the pulse duration is comparable to the autoionization lifetime, varying the peak intensity of the pulse enables manipulation of the underlying Fano-interference. In particular, the asymmetric profile observed for the $2s2p\,^1P$ doubly-excited state of He in the weak-field ionization can be smoothly transformed to a window-type interference profile.