Tracing origins of asymmetric momentum distribution for polar molecules in strong linearly-polarized laser fields

TL;DR

This paper investigates the asymmetric electron momentum distribution in polar molecules like HeH$^+$ under strong laser fields, revealing the interplay of Coulomb effects and permanent dipoles as the cause.

Contribution

It introduces a model that traces electron motion in real time, explaining the origin of asymmetry in momentum distributions for polar molecules in strong laser fields.

Findings

Asymmetric momentum distributions are caused by Coulomb effects and permanent dipoles.

The model successfully explains the asymmetry observed in HeH$^+$, CO, and BF.

The structure can be used to measure molecular orientation in ultrafast experiments.

Abstract

We study the ionization dynamics of oriented HeH$^+$ in strong linearly-polarized laser fields by numerically solving the time-dependent Schr\"{o}dinger equation. The calculated photoelectron momentum distributions for parallel orientation show a striking asymmetric structure. With a developed model pertinent to polar molecules, we trace the electron motion in real time. We show that this asymmetric structure arises from the interplay of the Coulomb effect and the permanent dipole in strong laser fields. This structure can be used to probe the degree of orientation which is important in ultrafast experiments for polar molecules. we also check our results for other polar molecules such as CO and BF.