Alignment-Dependent Ionization of Molecular Hydrogen in Intense Laser Fields

TL;DR

This study investigates how the orientation of molecular hydrogen affects its ionization behavior under intense laser fields, revealing orientation-dependent ionization yields and spectral features through detailed quantum simulations.

Contribution

It provides a comprehensive ab initio analysis of alignment-dependent ionization in H₂, comparing full quantum solutions with strong-field approximation predictions.

Findings

Parallel molecules are generally easier to ionize than perpendicular ones at most intensities.

The full quantum results do not confirm the simple interference pattern predicted by the strong-field approximation.

Ionization yields and electron spectra depend strongly on molecular orientation and laser intensity.

Abstract

The alignment dependence of the ionization behavior of H$_2$ exposed to intense ultrashort laser pulses is investigated on the basis of solutions of the full time-dependent Schr\"odinger equation within the fixed-nuclei and dipole approximation. The total ionization yields as well as the energy-resolved electron spectra have been calculated for a parallel and a perpendicular orientation of the molecular axis with respect to the polarization axis of linear polarized laser pulses. For most, but not all considered laser peak intensities the parallel aligned molecules are easier to ionize. Furthermore, it is shown that the velocity formulation of the strong-field approximation predicts a simple interference pattern for the ratio of the energy-resolved electron spectra obtained for the two orientations, but this is not confirmed by the full ab initio results.