High-order harmonic generation in non-planar molecules driven by a bicircular field

ABSTRACT

We investigate high-order harmonic generation of non-planar ammonia molecules by a bicircular field, which consists of two coplanar counter-rotating circularly polarised fields of frequencies ω and 2ω. This field possesses dynamical symmetries, which can be used together with the symmetry of the molecular Hamiltonian to obtain the selection rules for harmonic emission. We show analytically and confirm by numerical calculations that circularly polarised harmonics of order n = 3q ± 1, with q integer, as well as linearly polarised harmonics of order n = 3q are emitted. The presence of well-separated both linearly and circularly polarised harmonics in the same spectrum is unique to non-planar molecules.

KEYWORDS:

• High-order harmonic generation
• polyatomic molecules
• strong-field approximation
• bicircular field

Acknowledgments

Support by the Federal Ministry of Education and Science, Bosnia and Herzegovina, is gratefully acknowledged.

Disclosure statement

No potential conflict of interest was reported by the authors.