Two-center interference and ellipticity in high-order harmonic generation from H$_2^+$

TL;DR

This paper theoretically explores how two-center interference affects high-order harmonic generation in aligned H$_2^+$, revealing effects on harmonic intensity, phase, polarization, and ellipticity, influenced by electronic trajectories and Coulomb potential.

Contribution

It provides new insights into the role of multiple electronic trajectories and Coulomb effects on two-center interference in HHG from H$_2^+$, including polarization and ellipticity.

Findings

Interference minimum occurs at the same angle for different Gaussian wave packets.

Multiple trajectories influence the interference minimum position.

Significant ellipticity observed near the interference minimum.

Abstract

We present a theoretical investigation into the two-center interference in aligned H$_2^+$. The influence of the laser field on the recombination step is investigated by comparing laser-induced harmonic generation with harmonic generation from field-free collisions of Gaussian wave packets with the core. We find that for different Gaussian wave packets colliding with the molecule, the interference minimum occurs at the same alignment angle. The same result is obtained for the laser-induced spectrum when only a single electronic trajectory per harmonic contributes. When multiple electronic trajectories contribute, we find an effect on the minimum position because the interference between short and long trajectories is alignment-dependent. The two-center interference and the influence of the Coulombic potential are clearly seen not only in the harmonic intensity and phase but also in the polarization direction and ellipticity. We observe significant ellipticity of the emitted radiation around the two-center interference minimum.