Theoretical studies of high-harmonic generation: Effects of symmetry, degeneracy and orientation

Abstract

Using a quantum mechanical three-step model we present numerical calculations on the high-harmonic generation from four polyatomic molecules. Ethylene (C${}_2$H${}_4$) serves as an example where orbital symmetry directly affects the harmonic yield. We treat the case of methane (CH${}_4$) to address the high-harmonic generation resulting from a molecule with degenerate orbitals. To this end we illustrate how the single orbital contributions show up in the total high-harmonic signal. This example illustrates the importance of adding coherently amplitude contributions from the individual degenerate orbitals. Finally, we study the high-harmonic generation from propane (C${}_3$H${}_8$) and butane (C${}_4$H${}_{10}$). These two molecules, being extended and far from spherical in structure, produce harmonics with non-trivial orientational dependencies. In particular, propane can be oriented so that very high-frequency harmonics are favorized, and thus the molecule contains prospects for the generation of UV attosecond pulses.

arXiv comment9 pages, 6 figures, 1 table

References in corpus (5)

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• High-harmonic generation from arbitrarily oriented diatomic molecules including nuclear motion and field-free alignment
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• High-order harmonic generation from diatomic molecules in elliptically polarized driving fields: a generalized interference condition
• Laser-induced bound-state phases in high-order harmonic generation
• Shifting nodal-plane suppressions in high-order harmonic spectra from diatomic molecules in orthogonally polarized driving fields