Rovibrational state distributions for H 2 photoeliminated from 1,3-butadiene. Evidence for a symmetric transition state

Abstract

The rovibrational distributions of H 2 photoeliminated from 1,3-butadiene upon excitation at 212.8 nm have been measured via 1 + 1 resonance-enhanced two-photon ionization. The measured rotational distributions are in reasonable agreement with a prior distribution, while the experimental vibrational distribution is substantially hotter than the prior. These results indicate that the photoelimination occurs via a concerted mechanism through a symmetric transition state in which the HH distance is greater than the equilibrium H 2 value.