Superexcited State Dynamics of OCS: An Experimental Identification of Three Competing Decay Channels among Autoionization, Internal Conversion, and Neutral Predissociation.

The 7sσ and 6pσ superexcited Rydberg states of OCS belonging to series converging onto the B̃Σ ionic limit have been successfully prepared by three-photon UV excitation, and their ensuing competing relaxation processes have been probed by a time-delayed IR ionization pulse. The time profiles of S ions, which encode their fragmentation mechanism, are only observable at high pump intensities, thus providing unique experimental identification of the neutral predissociation channel producing S* atoms. Benefiting from this feature and by comparison with the time behavior of OCS ions, three competing relaxation channels are identified: autoionization associated with both X̃Π and ÃΠ ionic states; internal conversion to isoenergetic R states, the deactivation of which manifests as a picosecond decay in the time profile of OCS ions; picosecond neutral predissociation appearing as a nondecaying plateau in the time profiles of S ions.

Real-time observation of cascaded electronic relaxation processes in p-Fluorotoluene.

Ultrafast electronic relaxation processes following two photoexcitation of 400nm in p-Fluorotoluene (pFT) have been investigated utilizing time-resolved photoelectron imaging coupled with time-resolved mass spectroscopy. Cascaded electronic relaxation processes started from the electronically excited S state are directly imaged in real time and well characterized by two distinct time constants of ~85±10fs and 2.4±0.