Molecular symmetry effects in the ionization of CS₂ by intense few-cycle laser pulses

Abstract

Few-cycle pulses of 800 nm light cause ionization and dissociation of CS₂ in the intensity and temporal regime where, by contemporary wisdom, rescattering is expected to dominate laser-molecule interactions. However, our experiments indicate that in the case of laser-CS₂ interactions in the strong-field regime, the wave packet of the rescattered electron destructively interferes with the antibonding π orbital of CS₂⁺ such that rescattering is essentially "switched off." Consequently, dissociation becomes an almost nonexistent channel; long-lived singly, doubly, and triply charged molecular ions dominate the mass spectrum in the few-cycle regime, revealing the importance of molecular symmetry in strong-field ionization. Comparison with CS₂ ionization spectra that we measure in the 700 attosecond domain using fast, highly charged ions corroborates that rescattering is not of importance when CS₂ ionization is caused by intense laser light. Direct signature of enhanced ionization being "switched off" in the few-cycle domain is also obtained in our measurements.