$Br_{2} B^{3} {\Pi}(O_{u}^{+})$ EXCITATION SPECTRA AND RADIATIVE LIFETIMES IN SOLID RARE GASES

Abstract

Following excitation into either the bound B state vibrational levels or into the continuum $Br_{2}$ emits from the $v = 0$ level of the $B_{3}{\Pi}(0_{u}^{+})$ electronic 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 $^{1}{\Pi}_{1}$ continuum. Our results confirm the assignment of the long wavelength shoulder on the gas phase $Br_{2}$ visible absorption spectrum to the B state. A value of $7.3 {\mu} s$ is found for the $B^{3}{\Pi}(0_{u}^{+}) v = 0$ emission lifetime in solid argon. Extrapolation based on the matrix data leads to an estimate of $12 \pm 2 {\mu}s$ for the radiative lifetime of the gas phase molecule.