Br₂ B³Π(O_u⁺) excitation spectra and radiative lifetimes in rare gas solids

Following excitation into either the bound B³Π(O _u⁺) vibrational levels or into the continuum, Br ₂ emits from the ν=0 level of this state. Study of the excitation spectrum in the continuous region permits direct measurement of the B state contribution to the visible absorption and its separation from the stronger overlying ¹Π₁ continuum and confirms the assignment of the long wavelength shoulder on the visible absorption spectrum to the B state. A value of 7.3 μs is found for the B³Π(O_u ⁺) ν=0 emission lifetime in solid argon. Extrapolation based on the matrix data leads to an estimate of 12±2 μs for the radiative lifetime of the gas phase molecule.