Resonant Auger decay of the core-excited C$^\ast$O molecule in intense X-ray laser fields

TL;DR

This paper presents a theoretical study of resonant Auger decay in core-excited CO molecules under intense X-ray laser fields, revealing complex interactions, interference effects, and the influence of light-induced non-adiabatic couplings on electron spectra.

Contribution

It introduces a comprehensive theoretical model accounting for conical intersections, decay, and photoionization processes in intense X-ray fields, highlighting new non-adiabatic effects in molecular dynamics.

Findings

Strong coupling between electronic, vibrational, and rotational states due to light-induced conical intersections.

Dramatic increase in direct photoionization and decay processes with field intensity.

Distinct interference patterns in electron spectra from combined ionization and decay channels.

Abstract

The dynamics of the resonant Auger (RA) process of the core-excited C$^\ast$O(1s$^{-1}\pi^\ast,v_r=0$) molecule in an intense X-ray laser field is studied theoretically. The theoretical approach includes the analogue of the conical intersections of the complex potential energy surfaces of the ground and `dressed' resonant states due to intense X-ray pulses, taking into account the decay of the resonance and the direct photoionization of the ground state, both populating the same final ionic states coherently, as well as the direct photoionization of the resonance state itself. The light-induced non-adiabatic effect of the analogue of the conical intersections of the resulting complex potential energy surfaces gives rise to strong coupling between the electronic, vibrational and rotational degrees of freedom of the diatomic CO molecule. The interplay of the direct photoionization of the ground state and of the decay of the resonance increases dramatically with the field intensity. The coherent population of a final ionic state via both the direct photoionization and the resonant Auger decay channels induces strong interference effects with distinct patterns in the RA electron spectra. The individual impact of these physical processes on the total electron yield and on the CO$^+(A^2\Pi)$ electron spectrum are demonstrated.