Macroscopic properties of high-harmonic generation from molecular ions

TL;DR

This paper develops a macroscopic HHG framework integrating ab initio molecular calculations, revealing how microscopic features like Mollow sidebands manifest in macroscopic spectra and their angular emission patterns.

Contribution

It introduces a combined microscopic-macroscopic approach for HHG in molecules, demonstrating the persistence of spectral features and angular patterns in the macroscopic response.

Findings

Mollow sidebands appear in macroscopic spectra with similar intensity to main harmonics.

Sidebands are emitted at wider angles, aiding experimental isolation.

Method validated with DFT and 1D Schrödinger equation models.

Abstract

We extend the existing framework of macroscopic HHG to combine it with high-accuracy ab initio calculations for molecules as microscopic input. This approach is applied to HHG spectra exhibiting Mollow sidebands, for open shell molecules undergoing nonadiabatic dynamics. We demonstrate the details of the method and analyze how the predicted features in the microscopic HHG response unambiguously survive macroscopic response calculations, and furthermore they exhibit a interesting angular pattern in the far-field. We calculate the macroscopic harmonic spectrum by combining many single-molecule calculations at different intensities, obtained in one case from time-dependent density functional theory calculations for N+ 2 , in second case for one electron time dependent Schr\"odinger equation for a 1D double well model potential. For both cases one can observe that the resulting macroscopic spectra exhibit Mollow sidebands of approximately the same intensity as the main harmonics, while being radiated at wider angles, meaning they could be isolated more easily in an experiment.