Same Period Emission and Recombination in Non-Sequential Double Recombination High-Harmonic Generation in H$_2$

TL;DR

This paper investigates non-sequential double recombination high-harmonic generation in molecules, revealing a unique two-electron effect with higher energy cutoffs than atomic cases, influenced by molecular potential and same period electron emission.

Contribution

It introduces the concept of same period emission and recombination (SPEaR) in molecular NSDR HHG, highlighting its dependence on molecular potential and nuclear distance.

Findings

Higher energy cutoff observed in molecular NSDR HHG.

Effect persists at intermediate nuclear distances ($R \,\gtrsim\, 8.0$ a.u.).

Classical model confirms sensitivity to molecular potential.

Abstract

Non-sequential double recombination (NSDR) high-order harmonic generation (HHG) is studied in a molecular system. We observe a unique molecular two-electron effect with a characteristic cutoff in the HHG spectrum at higher energies than what was previously seen for NSDR HHG in atoms. The effect is corroborated with a classical model where it is found that the effect is sensitive to the molecular potential and originates from same period emission and recombination (SPEaR) of two electrons. The effect persists for intermediate nuclear distances of $R \gtrsim 8.0$ a.u.