Photodissociation Dynamics of C2H4BrCl: Nonadiabatic Dynamics with Intrinsic Cs Symmetry

The photodissociation dynamics of 1,2-bromochloroethane (C2H4BrCl) was investigated near 234 nm. A two-dimensional photofragment ion-imaging technique coupled with a [2+1] resonance-enhanced multiphoton ionization scheme was utilized to obtain speed and angular distributions of the nascent Br(P-2(3/2)) and Br*(P-2(1/2)) atoms. The total translational energy distributions for the Br and Br* channels were well characterized by Gaussian functions with average translational energies of 100 and 84 kJ/mol, respectively. The recoil anisotropies for the Br and Br* channels were measured to be beta = 0.49 +/- 0.05 for Br and 1.55 +/- 0.05 for Br*. The relative quantum yield for Br* was found to be Phi(Br*) = 0.33 +/- 0.03. The probability of nonadiabatic transition between A' states was estimated to be 0.46. The relevant nonadiabatic dynamics is discussed in terms of interaction between potential energy surfaces in symmetry.