The influence of multiple ionization thresholds on harmonic generation: Ar+

TL;DR

This study uses time-dependent R-matrix theory to analyze how multiple ionization thresholds affect harmonic generation in Ar+ ions, revealing the dominant role of the 3s(2)3p(4) (1)D threshold and comparing yields with helium.

Contribution

It provides a detailed assessment of the influence of multiple ionization thresholds on harmonic generation in Ar+ using advanced theoretical methods.

Findings

The 3s(2)3p(4) (1)D threshold dominates harmonic generation.

Higher 3s3p(5) thresholds affect harmonic yields.

Ar+ produces higher harmonic yields than He under similar conditions.

Abstract

We apply time-dependent R-matrix theory to investigate harmonic generation from ground state Ar+ with M=0 at a wavelength of 390 nm. Contributions associated with the different 3s(2)3p(4) ionization thresholds are assessed, including the interference between these. The dominant contribution originates from the second ionization threshold, 3s(2)3p(4) (1)D. Changes to the harmonic yields arising from the higher 3s3p(5) thresholds are also assessed. We further confirm that Ar+ has a higher harmonic yield than He for the same laser pulse, despite having a higher ionization threshold.