LASER INDUCED FLUORESCENCE STUDY OF THE EFFECT OF PERTURBATIONS ON THE RADIATIVE LIFETIMES AND COLLISIONAL RELAXATION OF THE CO($a^{3}\Sigma^{+}, v'=31$ AND 35) $STATES^{*}$
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Date
1996
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Ohio State University
Abstract
The CO(a $^{3}\Sigma^{+}$, $v^{\prime}$=31,35) valence and CO(b $^{3}\Sigma^{+}, v^{\prime}=0,1$) Rydberg states were selectively excited from the CO($a^{3}\Pi$) metastable molecules that were produced in a $CO_{2}+He$ discharge afterglow. Excitation was accomplished by a 10 ns dye laser pulse and fluorescence was observed through a 0.3 m monochromator. The extended vibrational progressions of the CO($a^{3}\Pi$) and CO(b) states back to CO($a^{3}\Pi$), and the fluorescence waveforms from particular bands were studied to understand the effect of the interaction between the CO($a^{3}\Pi$) and CO(b) states on their radiative lifetimes, vibrational band intensities, and the collisional transfer rates He and Ar bath gases. The radiative lifetimes of the CO(b, $v^{\prime}$=0,1) states were measured as 55$\pm$5 ns and those of the deperturbed CO($a^{\prime}$, v=31,35) states as $3\pm 1 \mu$s. Intensity borrowing by the CO($a^{\prime}$) states results in a mixed character of their Franck-Condon factors, as demonstrated by the band intensities of the emission spectra. The rotational quantum number dependent interaction gives strongly decreasing perturbation strengths with increasing J, which affects the rotational line intensities within a given vibrational band. Analysis of the electronic and rotational relaxation rates among the $CO^{+}$ states at this energy and estimations of the corresponding rate constants in He will be presented. It was demonstrated that collisional transfer rates between the interacting CO($a^{\prime}$, v=35 and b, v=1) and $CO(a^{\prime}$, v=31 and b,v=0) pairs were not the fastest relaxation rates.
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$^{*}$Supported by US National Science Foundation
Author Institution: Department of Chemistry, Kansan State University; Laboratoire de Spectrometrie Physique, Universite Joseph Fourier-Grenoble
Author Institution: Department of Chemistry, Kansan State University; Laboratoire de Spectrometrie Physique, Universite Joseph Fourier-Grenoble