Coupled-cluster treatment of molecular strong-field ionization

TL;DR

This paper uses coupled-cluster methods to accurately compute ionization rates and Stark shifts of various molecules in static electric fields, highlighting the importance of electron correlation and proposing a criterion to distinguish ionization mechanisms.

Contribution

It introduces a coupled-cluster approach with complex scaling for molecular ionization in strong fields, emphasizing electron correlation effects and a new criterion for ionization mechanism distinction.

Findings

Electron correlation significantly affects ionization rates and Stark shifts.

A simple criterion is proposed to distinguish tunnel and barrier suppression ionization.

Computed ionization properties agree with experimental trends.

Abstract

Ionization rates and Stark shifts of H$_2$, CO, O$_2$, H$_2$O, and CH$_4$ in static electric fields have been computed with coupled-cluster methods in a basis set of atom-centered Gaussian functions with complex-scaled exponent. Consideration of electron correlation is found to be of great importance even for a qualitatively correct description of the dependence of ionization rates and Stark shifts on the strength and orientation of the external field. The analysis of the second moments of the molecular charge distribution suggests a simple criterion for distinguishing tunnel and barrier suppression ionization in polyatomic molecules.