COLLISIONAL RELEASE OF $Br_{2}$

$^{\ast}$ Staff member, Quantum Physics Division, National Bureau of Standards. Address of Smedley and Leone: Joint Institute for Laboratory Astrophysics and Department of Chemistry, Boulder, Colorado 80309-0440. Address of Haugen: Department of Physics, University of Toronto, Toronto, Ontario, Canada, M5S 1A7.Author Institution:The process of collisional dissociation of highly vibrationally excited B-state $Br_{2}$ is investigated in this study. A pulsed laser excites specific rovibrational levels which lie 1-5 kt below the B-state dissociation limit. Collisions ``pump'' the molecules up to form $Br(^{2}P_{3/2}) + Br^{\ast}(^{2}P_{1/2})$ products, which are detected by IR fluorescence and/or transient absorption-gain probing with an F-center laser at $2.7 \mu m$. The yield of $Br^{\ast}$ is measured as a function of the energy of the prepared state below the dissociation limit, for both $Br_{2}$ and rate gas collision partners. Quenching by predissociation, both collision-induced and collision free, is a competing process. These rates are also presented. Ground state $Br_{2}$ is an especially effective collisional release partner. The implications of this result with respect to possible mechanisms for collisional release are discussed