Knowledge Bank

Femtosecond deep uv (near 200 nm) pulses were used to directly measure excited slate lifetimes for $CS2$ and NO in the gas phase. The lifetime of the $S3$ state of $CS2$ at 205 nm directly measured using femtosecond ultraviolet 1+1 multiphoton ionization spectroscopy is compared to previous indirect lifetime measurements for this state. The deep UV laser pulses have also been used in a time-resolved (2+1) multiphoton ionization study of the two-photon state of NO at 102 nm via a one-photon resonance with the $A2\Sigma +(3s\sigma )(\nu =2)$ state. The two-photon excited state lifetime exhibits a strong pressure dependence from which the collisionless lifetime and the bimolecular depopulation or quashing rate constant were obtained. The large quenching rate constant strongly suggests that the state is a medium {n} Rydberg level in the series converging to the ground slate of $NO+$, The subnanosecond collisionless lifetime implies that this state is subject to predissociation and/or autoionization.