Photodissociation of oxalyl bromide by using cavity ring down spectroscopy

Cavity Ring-Down Spectroscopy (CRDS) has been widely applied in the studies of spectroscopy, kinetics, dynamics, and photochemistry in the condensed or gas phases. The method is based on the measurement of the decay rate of a pulse light trapped in an optical cavity which is formed by a pair of highly reflective(R>99.9%) mirrors.
By using cavity ring-down spectroscopy technique, we have observed the channel leading to Br2 molecular elimination following photodissociation of oxalyl bromide at 248 nm. Power dependence measurements are examined, supporting that Br2 molecule were created by the following photodissociation of C2O2Br2, via a single-photon process. The nascent vibrational populations for v” = 0,1, and 2 levels are obtained with a population ratio of 1:(0.65 ± 0.09):(0.34 ± 0.07), corresponding to a Boltzmann-like vibrational temperature of 893 ± 31 K. The quantum yield of the ground state Br2 elimination reaction is determined to be 0.06 ± 0.03.