LASER PHOTOACOUSTIC SPECTROSCOPY OF $Br_{2}$ VAPOUR IN THE EXTREME RED REGION $(13800-15000 Cm^{-1})$

Abstract

Electronic bands belonging to the $A{^{3}\Pi_{1u}} \leftarrow X^{1}{\sum^{+}}_{g}$ transitions in the $Br_{2}$ vapour have been recorded photoacoustically in the wave length region 665-720nm. The vibronic levels involved in these trasitions are $3 \leq v^{\ast} \leq 2l$ and relative photoacoustic band intensities have been used in estimating the non-radiative relaxation rates from upper vibronic levels of $A{^{3}\Pi_{1u}}$ state. The nonradiative rate constant is found to be a nonfinear function of the upper state vibrational quantum number. A comparison of the calculated radiative rate constants as a function of excited $A{^{3}\Pi_{1u}}$ state vibronic levels does not quite reflect the expected complementry behavior of the nonradiative rate constants.