Characterizing Sub-Cycle Electron Dynamics of Polar Molecules by Asymmetry in Photoelectron Momentum Distributions

TL;DR

This paper introduces a strong-field model that uses asymmetries in photoelectron momentum distributions to resolve sub-cycle electron dynamics in polar molecules with attosecond precision.

Contribution

It develops a novel approach to distinguish complex electron processes in polar molecules by analyzing asymmetries in PMDs in orthogonal two-color laser fields.

Findings

PMDs asymmetry reveals sub-cycle electron dynamics

Time differences in electron escape are identified

Method achieves attosecond-scale resolution

Abstract

Strong-field ionization of polar molecules contains rich dynamical processes such as tunneling, excitation, and Stark shift. These processes occur on a sub-cycle time scale and are difficult to distinguish in ultrafast measurements. Here, with a developed strong-field model considering effects of both Coulomb and permanent dipole, we show that photoelectron momentum distributions (PMDs) in orthogonal two-color laser fields can be utilized to resolve these processes with attosecond-scale resolution. A feature quantity related to the asymmetry in PMDs is obtained, with which the complex electron dynamics of polar molecules in each half laser cycle is characterized and the subtle time difference when electrons escaping from different sides of the polar molecule is identified.