Real-time observation of concerted benzene formation in the infrared multiphoton dissociation of 1,4-cyclohexadiene

Abstract

The infrared-multiphoton dissociation of 1,4-cyclohexadiene opens up two dissociation channels from its ground electronic state. The major dehydrogenation channel ( > 95%) gives benzene and hydrogen whereas the retro-Diels-Alder reaction channel produces 1,3-butadiene and acetylene. The temporal evolution of benzene as a photoproduct is monitored. From the real-time formation of benzene, a unimolecular dissociation rate for 1,4-cyclohexadiene has been found to be (1.0± 0.15) × 10⁶ s^-1. The UV spectrum of nascent benzene reveals a red-shift of 8 nm. The effects of laser energy and substrate pressure on dissociation yield are also investigated.