Analysis of effects of macroscopic propagation and multiple molecular orbitals on the minimum in high-order harmonic generation of aligned CO$_{2}$

TL;DR

This paper presents theoretical analysis of how macroscopic propagation and multiple molecular orbitals influence the minimum in high-order harmonic generation spectra of aligned CO₂, aligning well with recent experimental observations.

Contribution

It introduces a comprehensive theoretical model that includes macroscopic propagation effects and multiple orbital contributions to explain the minima in HHG spectra of CO₂.

Findings

Good agreement with experimental data on HHG minima dynamics

Minima position depends on molecular alignment and laser focusing

Alignment-dependent ionization rates affect spectral minima

Abstract

We report theoretical calculations on the effect of the multiple orbital contribution in high-order harmonic generation (HHG) from aligned CO$_2$ with inclusion of macroscopic propagation of harmonic fields in the medium. Our results show very good agreements with recent experiments for the dynamics of the minimum in HHG spectra as laser intensity or alignment angle changes. Calculations are carried out to check how the position of the minimum in HHG spectra depends on the degrees of molecular alignment, laser focusing conditions, and the effects of alignment-dependent ionization rates of the different molecular orbitals. These analyses help to explain why the minima observed in different experiments may vary.