Post-ionization dynamics of the polar molecule OCS in asymmetric laser fields

Endo, Tomoyuki, Ziems, Karl Michael, Richter, Martin, Fröbel, Friedrich G., Hishikawa, Akiyoshi, Gräfe, Stefanie, Légaré, François and Ibrahim, Heide (2022) Post-ionization dynamics of the polar molecule OCS in asymmetric laser fields. Frontiers in Chemistry, 10, [859750]. (doi:10.3389/fchem.2022.859750).

Abstract

We have investigated the dissociation mechanisms of the prototypical heavy polar molecule OCS into the two break-up channels of the dication, OCS²⁺ → O⁺ + CS⁺ and OC⁺ + S⁺, in phase-locked two-color intense laser fields. The branching ratio of the breaking of the C–O and C–S bonds followed a pronounced 2π-oscillation with a modulation depth of 11%, depending on the relative phase of the two-color laser fields. The fragment ejection direction of both break-up channels reflects the anisotropy of the tunneling ionization rate, following a 2π-periodicity, as well. The two dissociation pathways in the C–S bond breaking channel show different phase dependencies of the fragment ejection direction, which are assigned to post-ionization dynamics. These observations, resulting from the excitation with asymmetric two-color intense laser fields, supported by state-of-the-art theoretical simulations, reveal the importance of post-ionization population dynamics in addition to tunneling ionization in the molecular fragmentation processes, even for heavy polar molecules.

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Contributors

Author: Karl Michael Ziems

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