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arXiv · 2408.14148

Electron recollisional excitation of OCS$^+$ in phase-locked $\omega + 2\omega$ intense laser fields

Tomoyuki Endo·Tomohito Otobe·Ryuji Itakura
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Abstract

Photoelectron-photoion coincidence momentum imaging has been performed to investigate excitation processes on dissociative ionization of OCS, OCS $\to$ OCS$^+$ + e$^-$ $\to$ OC + S$^+$ + e$^-$, in phase-locked $\omega + 2\omega$ intense laser fields. The electron kinetic energy spectra depend on coincidentally produced ion species, OCS$^+$ or S$^+$. The observed electron momentum distribution shows clear asymmetry along the laser polarization direction with a 2$\pi$-oscillation period as a function of the phase difference between the $\omega$ and $2\omega$ laser fields. The asymmetry of electron emission in the OCS$^+$ channel flips at the electron kinetic energy of 8.2 eV where the dominant scattering direction switches from forward to backward. In the S$^+$ channel, the asymmetry flips at the lower kinetic energy of 4.2 eV. In comparison with a classical trajectory Monte Carlo simulation, it has been clarified that this energy shift between the OCS$^+$ and S$^+$ channels corresponds to the excitation energy of the parent ion and that electron recollisional excitation takes place to form the fragment ion in intense laser fields.

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Tomoyuki Endo, Tomohito Otobe, Ryuji Itakura. 2024-08-26. Electron recollisional excitation of OCS$^+$ in phase-locked $\omega + 2\omega$ intense laser fields. https://doi.org/10.1039/d5cp04819b

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