Relaxation in {\AA} $^{\prime}A_{2} \nu_{4} = 1 D_{2}CO$: Evidence for Coupling to a Lumpy Continuum from Single State Depopulation Rates, and a Reversible Intersystem Crossing Interpretation of Fluoresence Decay
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Date
1990
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Ohio State University
Abstract
We have performed two types of experiments in {\AA} $^{1}A_{2} \nu_{4} = 1 D_{2}CO$: He and self-broadened population decay measurements by transient gain spectroscopy (TGS) on several single rotational levels (SRL's), self-broadened undispersed fluorescence decay measurements on the $^{\prime}R_{0}$ head. The SRL depopulation measurements allow a comparison between collisional inclastic rotational or vibrational relaxation, enhanced in self-broadening, and collisional electronic quenching, which is a larger fraction of the He-broadened rate. The large irregular variation in He-broadened SRI. depopulation rates indicates that collisional electronic quenching rates vary strongly in a way consistent with the large range of $S_{1}-S_{0}$ matrix elements found by Polik et. al [1]. The fluorescence decay curves at low pressures between 0.9 m Torr and 13.0 m Torr are accurately modeled by single exponential curves with a decay rate linear in pressure, in disagreement with Ref. [2]. At high pressures. the decays become strongly non-exponential. In light of recent measurements on V-V transfer in $\nu_{2} = 1 NH_{3}$ (a comparable non-planar system) [3], and of other V-V measurements, we interpret this data with a reversible intersystem crossing model, rather than the V-V model of Ref [4]
Description
$^{1}$. W.F. Polik, C.B. Moore, W.H. Miller, J. Chem. Phys. 89,3584 (1988). $^{2}$. J.Weisshaar, A.Baronavski, A.Cabello, C.B.Moore, J.Chem. Phys. 69, 4720 (1978). $^{3}$. M.Shultz, J. Wei, to be published in J. Chem. Phys. $^{4}$. J.Weisshaar, D.Bamford, E.Specht, C.B.Moore. J.Chem. Phys. 74, 226 (1981).
Author Institution: Dept. of Chemistry, MIT; Dept. of Chemistry, MIT; Dept. of Chemistry, Rice U.
Author Institution: Dept. of Chemistry, MIT; Dept. of Chemistry, MIT; Dept. of Chemistry, Rice U.