Ultrafast electron dynamics following outer-valence ionization: The impact of low-lying relaxation satellite states

TL;DR

This study investigates ultrafast electron dynamics after outer-valence ionization in a molecular system, revealing rapid charge redistribution driven by low-lying relaxation satellite states using ab initio simulations.

Contribution

It demonstrates the significant impact of relaxation satellite states on ultrafast electron dynamics following ionization, with real-time ab initio analysis of charge redistribution.

Findings

Charge remains stationary initially after ionization.

Ultrafast pi-pi* excitation occurs within sub-femtosecond timescale.

Charge delocalization and localization happen within about 1.4 fs.

Abstract

Low-lying relaxation satellites give rise to ultrafast electron dynamics following outer-valence ionization of a molecular system is studied. To demonstrate the impact of such satellites, the evolution of the electronic cloud after sudden removal of an electron from the highest occupied molecular orbital (HOMO) of the organic unsaturated nitroso compound 2-Nitroso[1,3]oxazolo[5,4-d][1,3]oxazole is traced in real time and space using ab initio methods only. Our results show that the initially created hole charge remains stationary but on top of it the system reacts by an ultrafast pi-pi* excitation followed by a cyclic excitation-deexcitation process which leads to a redistribution of the charge. The pi-pi* excitation following the removal of the HOMO electron takes place on a sub-femtosecond time scale and the period of the excitation-deexcitation alternations is about 1.4 fs. In real space the processes of excitation and de-excitation represent ultrafast delocalization and localization of the charge. The results are analyzed by a simple two- and three-state model.