Issue 42, 2023

High-order harmonic generation by aligned homonuclear diatomic cations

Abstract

We introduce the theory of high-order harmonic generation by aligned homonuclear diatomic cations using a strong-field approximation. The target cation is represented as a system which consists of two atomic (ionic) centres and one active electron, while the driving field is either a monochromatic or bichromatic field. For a linearly polarised driving field, we investigate the differences between the harmonic spectra obtained with a neutral molecule and the corresponding molecular cation. Due to the larger ionisation potential, the molecular cations can withstand much higher laser-field intensity than the corresponding neutral molecule before the saturation effects become significant. This allows one to produce high-order harmonics with energy in the water-window interval or beyond. Also, the harmonic spectrum provides information about the structure of the highest-occupied molecular orbital. In order to obtain elliptically polarised harmonics, we suggest that an orthogonally polarised two-colour field is employed as a driving field. In this case, we analyse the harmonic ellipticity as a function of the relative orientation of the cation in the laser field. We show that the regions with large harmonic ellipticity in the harmonic energy-orientation angle plane are the broadest for cations whose molecular orbital does not have a nodal plane. Finally, we show that the molecular cations exposed to an orthogonally polarised two-colour field represent an excellent setup for the production of elliptically polarised attosecond pulses with a duration shorter than 100 as.

Graphical abstract: High-order harmonic generation by aligned homonuclear diatomic cations

Article information

Article type
Paper
Submitted
27 Mot 2023
Accepted
06 Mph 2023
First published
06 Mph 2023

Phys. Chem. Chem. Phys., 2023,25, 28848-28860

High-order harmonic generation by aligned homonuclear diatomic cations

D. B. Milošević and D. Habibović, Phys. Chem. Chem. Phys., 2023, 25, 28848 DOI: 10.1039/D3CP02447D

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