Orientation-dependent ionization yields from strong-field ionization of fixed-in-space linear and asymmetric top molecules

TL;DR

This study investigates how the ionization yield from strong laser fields depends on molecular orientation in fixed-in-space linear and asymmetric top molecules, combining experimental measurements with theoretical modeling.

Contribution

It provides a detailed comparison of experimental and theoretical orientation-dependent ionization yields for specific molecules, highlighting agreements and discrepancies.

Findings

Ionization is maximized along the most polarizable axis for benzonitrile and naphthalene.

Experimental results for OCS show maximum ionization when perpendicular, contrary to theory.

Theoretical models incorporate Stark shifts and alignments to predict ionization behavior.

Abstract

The yield of strong-field ionization, by a linearly polarized probe pulse, is studied experimentally and theoretically, as a function of the relative orientation between the laser field and the molecule. Experimentally, carbonyl sulfide, benzonitrile and naphthalene molecules are aligned in one or three dimensions before being singly ionized by a 30 fs laser pulse centered at 800 nm. Theoretically, we address the behaviour of these three molecules. We consider the degree of alignment and orientation and model the angular dependence of the total ionization yield by molecular tunneling theory accounting for the Stark shift of the energy level of the ionizing orbital. For naphthalene and benzonitrile the orientational dependence of the ionization yield agrees well with the calculated results, in particular the observation that ionization is maximized when the probe laser is polarized along the most polarizable axis. For OCS the observation of maximum ionization yield when the probe is perpendicular to the internuclear axis contrasts the theoretical results.