Aniline-CH4 S1 vibrational dynamics studied with picosecond photoelectron spectroscopy

Abstract

Intramolecular vibrational energy redistribution (IVR) and vibrational predissociation (VP) are measured for a number of vibronic states in the S1 electronic state of the aniline-CH4 complex. The detailed dynamics are monitored using picosecond threshold photoelectron spectroscopy which is shown to be a sensitive probe of van der Waals molecule dynamics. For the lowest vibrational states accessed, the 6a10 and 6a10+24 cm−1 bands, both IVR and VP are observed and their rates are independently determined. At higher excess energy, IVR becomes the rate limiting step and the rate for VP cannot be measured independently. The results are interpreted using a serial dissociation mechanism with a simple kinetic model description. The rates of the reaction are modeled using standard Rice–Ramsperger–Kassel–Marcus (RRKM) theory which qualitatively predicts rates consistent with the experimental observations.