SPECTROSCOPY AND DYNAMICS OF THE $H_{2}-CN$ VAN DER WAALS COMPLEX
Loading...
Date
1998
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
The reaction $H_{2} + CN \to H + HCN$ is of importance in the combustion of hydrocarbons in air. It is also a prototypical system for studies of polyatomic reaction dynamics. The reaction has a substantial entrance channel barrier ($\approx 1000cm^{-1}$), which raises the possibility that pre-reactive $H_{2}-CN$ van der Waals complex may be stable at low temperatures. We have recently detected $H_{2}-CN$ in a free-jet expansion, using laser excitation of the B-X and A-X transitions. The complex feature associated with the monomer B-X 0-0 transition consisted of a single broad peak. This corresponds to direct excitation to the $H_{2} + CN(B)$ dissociation continuum. From the onset of the continuum, the ground state well-depth is estimated to be $40cm^{-1}$. Bands of $H_{2}-CN$ associated with the monomer $A^{2}\Pi-X^{2}\Sigma^{+} 3-0$ transition were examined. Complex features associated with $A^{2}\Pi_{1/2}$ were found to be homogeneously broadened by the spin-orbit predissociation process $H_{2}-CN(A^{2}\Pi_{1/2},v=3)\to H_{2}+CN(A^{2}\Pi_{3/2},v=3)\qquad[\Gamma=2.5 \times 10^{11}s^{-1}]$ Excitation of the complex to the $A^{2}\Pi_{3/2}$ spin-orbit component yielded rotationally resolved bands. A preliminary analysis of the rotational structure yields an $H_{2}$ to CN separation of 3.7 {\AA}. The rotational lines are homogeneously broadened by the internal conversion predissociation process $H_{2}-CN(A^{2}\Pi_{3/2},v=3)\to H_{2}+CN(X,v=7)\qquad [\Gamma=1.3 \times 10^{10}s^{-1}]$ Double resonance techniques have been used to examine the CN fragments produced by both predissociation channels. Data for $H_{2}-CN$ and $D_{2}-CN$ (experiments in progress) will be presented and discussed.
Description
Author Institution: Department of Chemistry, Emory University