Femtosecond predissociation dynamics of the methyl radical from the 3pz Rydberg state

Abstract

The real time dynamics of electronic predissociation of the CH radical (and its deuterated variant CD) from selected vibrational states of the 3p Rydberg state have been measured for the first time using a novel methodology based on a femtosecond three-color experiment to generate, two-photon excite and ionize methyl radicals as a function of time in combination with velocity map imaging detection. Subpicosecond lifetimes have been measured, showing a decreasing trend as vibrational excitation in the symmetric stretch and bending umbrella modes increases for both species. High-level ab initio calculations have been carried out in order to elucidate the CH 3p predissociation mechanism and support the lifetime measurements. The observed lifetimes are relevant for the understanding of the resonance enhanced multiphoton ionization spectroscopy of this radical.