THE Cl+H$_2 \rightarrow$ HCl+H REACTION INDUCED BY $IR+UV$ IRRADIATION OF Cl$_2$ IN SOLID PARA-\\HYDROGEN
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Date
2009
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Ohio State University
Abstract
Matrix isolation spectroscopy is a technique which enables highly reactive species to be trapped in a host environment and studied spectroscopically. Solid parahydrogen ($p$H$_2$) has been employed as a matrix host because of its interesting quantum mechanical properties and also because of its general inertness towards trapped dopants. However, in some cases $p$H$_2$ can react with impurities yielding new product molecules and providing insight into non-classical reaction pathways. In this talk I will present the results from a series of experiments where molecular chlorine (Cl$_2$) doped $p$H$_2$ crystals were exposed to two different irradiation schemes (namely $UV$ only or $IR + UV$ conditions) that gave rise to very different products. Cl$_2$ doped $p$H$_2$ crystals irradiated with $355\: \:nm$ $UV$ light produced almost exclusively ($99\%$) isolated Cl-atom photofragments, indicating the reaction Cl+H$_2(\nu=0, J=0)\rightarrow$ HCl+H is not readily occurring. Cl$_2$ doped $p$H$_2$ exposed simultaneously to $355\: \:nm$ $UV$ irradiation and broadband $cw\: IR$ light yielded HCl photoproducts indicating that the following reaction is playing a significant ($15\%$) role in the \emph{in situ} photochemistry: Cl+H$_2(\nu=1, J=0)\rightarrow$ HCl+H. The kinetic analysis of these experiments with two very different reaction pathways for $UV$ only or $IR + UV$ conditions will be presented. Further, the results of current investigations involving spin-orbit excited Cl-atoms generated using $416\: \:nm\: \:UV$ photons will be discussed in order to explore the intriguing possibility of non-Born Oppenheimer reaction dynamics in the simple Cl+H$_2$ reaction.
Description
Author Institution: Department of Chemistry, University of Wyoming, Laramie, WY 82071-3838, USA; Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada