Time-Resolved Dissociation Dynamics of Iodomethane Resulting from Rydberg and Valence Excitation

Rydberg excitations in the vacuum ultraviolet spectral range may open upmolecular photoreaction pathways not accessible from lower-lying valence states. Here,single-shot UV/VUV pump−probe spectroscopy was used to study the photodissociationdynamics of iodomethane after 268 nm excitation in the A-band and excitation of the 6p(2E3/2) Rydberg state at 161 nm. By combining weak-field VUV single-photon ionizationwith sub-10 fs temporal resolution and the superior statistical accuracy of the single-shottechnique, sub-30 fs wave packet dynamics upon excitation in the A-band by a UV pumppulse were disclosed. Population transfer from the Rydberg state to the 2 1A1 valencestate leading to 100 fs dissociation dynamics was observed by utilizing the same methodologyin a VUV-pump/UV-probe scheme