Intensity-selective, field-induced dissociative ionization of CS2 by femtosecond-duration light pulses

Intensity-selective time-of-flight (TOF) spectrometry has been applied to p robe the morphology of the dissociative ionization (DI) pattern obtained wh en linear triatomic, carbon disulfide, is irradiated by 100 fs long laser p ulses over a range of intensifies (10(13)-10(15) W cm(-2)). The measured DI pattern is very different to that obtained when measurements are made in t he spatially averaged (intensity-averaged) mode conventionally used in TOF spectrometry. Our results indicate that single ionization of the parent mol ecule occurs predominantly in the wings of the focus; the most intense part s of the focal region have a preponderance of highly charged atomic fragmen ts as compared to the wings. Correlation is established between the kinetic energy release (KER) accompanying dissociation of multiply charged molecul ar ions and the spatial region at which such ion production has occurred. A nisotropic angular distributions of S+ and S2+ fragment ions are used to de duce that CS2 is geometrically aligned along the direction of the laser pol arization vector due to the dependence of the ionization rate on the polari zation angle. Evidence was sought, but not found, for dynamic alignment due to reorientation of the S-C-S axis along the laser polarization vector.