Knowledge Bank

Van der Waals molecules formed by rare gas atoms bound to halogen molecules are simple molecular systems on which fundamental theories of chemical dynamics may be tested. Vibrational predissociation of $NeBr2$ occurs in the reaction \begin{equation}NeBr_{2}(X,v^{\prime\prime}, J^{\prime}) \to hu \to NeBr_{2}(B,v^{\prime},J^{\prime})\end{equation} \begin{equation}NeBr_{2}(B,v^{\prime},J^{\prime})\to Ne \to Br_{2}(B,v^{\prime}-n,J)\end{equation} Here X and B indicate the electronic states of $NeBr2$ corresponding to the associated electronic states of free $Br2$ and v is the vibrational quantum number of the Br-Br stretching mode. $NeBr2(B,v\prime )$ has a lifetime of typically much less than one nanosecond. High resolution laser induced fluorescence studies have yielded accurate structural information about the X and B electronic states of $NeBr2$ as well as vibrational state dependent rates for (2). The radiative lifetime of $Br2(B)$ is several orders of magnitude greater than the predissociation lifetime of $NeBr2$. By dispersing the fluorescence of the $Br2$ fragment the vibrational and rotational state distributions of the reaction products are obtained, giving quantum state to state understanding of the reaction dynamics. Further analysis of the spectra allows indirect determination of the depth of the van der Waals potential. Preliminary results show evidence of rotational excitation of the $Br2$ fragment and the loss of multiple vibrational quanta upon excitation of the higher $v\prime$ states.