# Correlation enhancement of high-order harmonics generation in Xe

## TL;DR

This paper investigates how inter-shell electron correlation in xenon enhances high-order harmonic generation, providing a simplified model that aligns well with experimental spectra from single and two-color laser sources.

## Contribution

The authors introduce a simplified approach using enhancement factors based on photoionization cross-sections to model HHG spectra in xenon, capturing inter-shell correlation effects.

## Key findings

- The model accurately reproduces experimental HHG spectra in xenon.
- Inter-shell correlation significantly enhances high-order harmonic generation.
- The approach is effective for both single and two-color laser-driven HHG.

## Abstract

We consider the process of high-order harmonics generation (HHG) in the xenon atom enhanced by the inter-shell correlation between the valence 5p and inner 4d shells. We derive the HHG spectrum from a numerical solution of the one-electron time-dependent Schr\"odinger equation multiplied by the enhancement factor taken as the photoionization cross-sections ratio calculated with and without the inter-shell correlation. Such a simplified approach is adequate to describe the experimental HHG spectrum reported by Shiner et al [Nat. Phys. 7, 464 (2011)] generated by a single color IR laser. Similarly, we find good agreement when applied to the two-color driven HHG spectra reported by Facciala et al [Phys. Rev. Lett. 117, 093902 (2016)].