Ultrafast dynamics and dissociative ionization of CS2 molecules studied via the femtosecond pump-probe method

The ultrafast dynamics and dissociative ionization of CS2 were studied using the pump-probe method with time-of-flight mass spectroscopy. The transient behavior of both parent ion （CS2^＋） and fragment ions （S^＋ and CS^＋） was observed. It was found that all the ionic signals decay exponentially with lifetimes that were different for delay times, t〉0 and t〈0, which can be attributed to the evolution of different Rydberg states pumped by 267-nm and 400-nm laser pulses. The lifetimes of two Rydberg states were ob- tained simultaneously from one fitting of the transients. The fragment ions were produced by the dissociation of CS2^＋, and it is suggested that the final ionic state is the C2Eg＋ state of CS2^＋ based on the measured S^＋/CS^＋branching ratio. The S^＋/CS^＋ ratio is dependent on the delay time of the two lasers, indicating that the dissociation process of CS2^＋ is related to the evolution of the intermediate Rydberg state.