Photodissociation dynamics of C_2H_5Br and n-C_3H_7Br in UV region

摘要

The photodissociation of C_2H_5Br and n-C_3H_7Br at 234 and 267 nm was investigated utilizing time-of-flight (TOF) mass spectrometry coupled with resonance-enhanced multiphoton ionization (REMPI) scheme. The experiment found that the branching ratio Br~*(2P_(1/2))/Br(2P_(3/2)) of C_2H_5Br decreased, and that of n-C3H7Br increased with the laser changing from 267 to 234 nm. In order to interpret the experimental results, ab initio calculations were performed to get potential energy surface (PES) curves of the compounds. The calculations predicted an avoided crossing between the PES curves of C_2H_5Br, which would result in non-adiabatic dissociation of C_2H_5Br, while no curve crossing among the PES curves of n-C_3H_7Br, leading to adiabatic dissociation of n-C_3H_7Br. The calculated results matched the experimental findings very well.