Photodissociation of Molecular Bromine in Solid H2 and D2: Spectroscopy of the Atomic Bromine Spin-Orbit Transition

We report 355 nm photodissociation studies of molecular bromine (Br-2) trapped in solid parahydrogen (pH(2)) and orthodeuterium (oD(2)). The product Br atoms are observed via the spin-orbit transition (P-2(1/2)<- P-2(3/2)) of atomic bromine. The quantum yield (0) for Br atom photoproduction is measured to be 0.29(3) in pH(2) and 0.24(2) in oD(2), demonstrating that both quantum solids have minimal cage effects for Br-2 photodissociation. The effective Br spin-orbit splitting increases when the Br atom is solvated in solid pH(2) (+1.1%) and oD(2) (+ 1.5%); these increases are interpreted as evidence that the solvation energy of the Br ground fine structure state (P-2(3/2)) is significantly greater than the excited state ((2)p(1/2)). Molecular bromine induced H-2 infrared absorptions are detected in the Q(1)(0) and S-1(0) regions near 4150 and 4486 cm(-1), respectively, which allow the relative Br-2 concentration to be monitored as a function of 355 nm photolysis.