Photochemical dynamics of 79Br2 in Xe matrices

The photochemical dynamics of Br2 trapped in a Xe matrix have been investigated. Following excitation into either the B 3Pi(0+/sub u/) or 1Pi(1u) states, emission occurs in the far red and infrared region. Analysis of the emission allows the emitting states to be characterized as B 3Pi(0+/sub u/) v' = 0→X 1Σ+/sub g/, and (tentatively) the A' 3Pi(2u)→X1Σ+/sub g/. The spectrum of the B→X emission was recorded and exhibited unusually broad vibronic emission lines when compared with Ar spectra. The B→X emission lifetime was measured to be 3.6 +- 0.5 μs and is in excellent agreement with the expected value for the radiative lifetime. The risetime of the B signal was found to be limited by the detection system (approx.15 ns). The tentatively identified A'→X emission has a lifetime of 4 +- 1 ms. The A3Pi(1u)→X 1Σ+/sub g/ emission resolved clearly in Ar and Kr matrices is altogether absent from Br2 isolated in Xe. Experiements were performed to measure the relative intensities of the B/A' emissions in Xe and compare them with earlier results from Ar matrices. The Xe B/A' ratio was found to be nearly 100 times greater in Xe then in Ar. The observations were found to be independent of temperature from 12 to 60 K and independent of concentrations from 1:500 to 1:10 000, Br2 in Xe