Knowledge Bank

Following excitation into either the bound B state vibrational levels or into the continuum $Br2$ emits from the $v=0$ level of the $B3\Pi (0u+)$ 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 $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Pi 1$ continuum. Our results confirm the assignment of the long wavelength shoulder on the gas phase $Br2$ visible absorption spectrum to the B state. A value of $7.3\mu s$ is found for the $B3\Pi (0u+)v=0$ 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.