Influence of asymmetry and nodal planes on high-harmonic generation in heteronuclear molecules

TL;DR

This study explores how molecular orbital geometry, especially nodal planes, influences high-harmonic generation spectra in heteronuclear molecules, revealing potential for molecular imaging based on spectral suppression patterns.

Contribution

It identifies how nodal planes affect harmonic suppression in heteronuclear molecules and proposes a method for molecular imaging using spectral shifts as indicators.

Findings

Nodal planes cause strong suppression in harmonic spectra at specific angles.

Different types of nodal planes lead to distinct suppression angle behaviors.

Heteronuclear molecules show shifted suppression angles compared to homonuclear counterparts.

Abstract

The relation between high-harmonic spectra and the geometry of the molecular orbitals in position and momentum space is investigated. In particular we choose two isoelectronic pairs of homonuclear and heteronuclear molecules, such that the highest occupied molecular orbital of the former exhibit at least one nodal plane. The imprint of such planes is a strong suppression in the harmonic spectra, for particular alignment angles. We are able to identify two distinct types of nodal planes. If the nodal planes are determined by the atomic wavefunctions only, the angle for which the yield is suppressed will remain the same for both types of molecules. In contrast, if they are determined by the linear combination of atomic orbitals at different centers in the molecule, there will be a shift in the angle at which the suppression occurs for the heteronuclear molecules, with regard to their homonuclear counterpart. This shows that, in principle, molecular imaging, which uses the homonuclear molecule as a reference and enables one to observe the wavefunction distortions in its heteronuclear counterpart, is possible.