Exploring photoelectron angular distributions emitted from molecular dimers by two delayed intense laser pulses

TL;DR

This study combines experiments and simulations to analyze how intense laser pulses influence photoelectron angular distributions emitted from molecular dimers, revealing effects of neighboring molecules on ionization pathways and opening avenues for studying electronic dynamics.

Contribution

It introduces a method using two delayed laser pulses and coincidence imaging to distinguish ionization steps and analyze photoelectron scattering in molecular dimers.

Findings

Scattering causes deformation and rotation of photoelectron angular distributions.

Separation of electron momentum space allows insight into ionization pathways.

Variable delay pulses enable investigation of light-induced electronic dynamics.

Abstract

We describe the results of experiments and simulations performed with the aim of extending photoelectron spectroscopy with intense laser pulses to the case of molecular compounds. Dimer frame photoelectron angular distributions generated by double ionization of N$_2$-N$_2$ and N$_2$-O$_2$ van der Waals dimers with ultrashort, intense laser pulses are measured using four-body coincidence imaging with a reaction microscope. To study the influence of the first-generated molecular ion on the ionization behavior of the remaining neutral molecule we employ a two-pulse sequence comprising of a linearly polarized and a delayed elliptically polarized laser pulse that allows distinguishing the two ionization steps. By analysis of the obtained electron momentum distributions we show that scattering of the photoelectron on the neighbouring molecular potential leads to a deformation and rotation of the photoelectron angular distribution as compared to that measured for an isolated molecule. Based on this result we demonstrate that the electron momentum space in the dimer case can be separated, allowing to extract information about the ionization pathway from the photoelectron angular distributions. Our work, when implemented with variable pulse delay, opens up the possibility of investigating light-induced electronic dynamics in molecular dimers using angularly resolved photoelectron spectroscopy with intense laser pulses.