AN ANALYSIS OF THE 16 $\mu \ \nu_{3}$ Q-BRANCH ABSORPTION SPECTRUM OF $UF_{6}$
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Date
1976
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Ohio State University
Abstract
An analytical treatment of the $\nu_{3}$ band Q-branch absorption spectra of dilute concentrations of $UF_{6}$ vapor in carrier gases has been developed and results for two cases $(^{235}UF_{6}$ in He at $42.6^\circ K$ and $^{238}UF_{6}$ in $N_{2}$ at $92^\circ K$ ) will be presented. Absorption curves, obtained with a tunable $PbSn_{x}Te_{1-x}$ laser diode, were matched by a least-squares fitting routine to an absorption expression that incorporates to fourth order the molecular octahedral-field perturbation effects on the degenerate overlapping Q-branch transitions. Values for five free fitting parameters A, $\bigtriangleup \nu$, $\nu_{QQ}$, $^{\bigtriangleup B}$eff and g in the two cases have been derived. The amplitude parameter A is interpreted as defining a spontaneous emission coefficient for the $\nu_{3}$ band, and values of 8.72 $s^{-1}$ and $11.54 s^{-1}$ were found for $^{235}UF_{6}$ and $^{238}UF_{6}$, respectively. The line width parameter $\bigtriangleup \nu$ provides estimates of classical $UF_{6}-He$ and $UF_{6}-N_{2}$ collision cross sections. The parameters $\nu_{OQ}$, $^{\bigtriangleup B}$eff and g are, respectively, the $\nu_{3}$ band center, a term proportional to the difference between the ground and $\nu_{3}$ state inertial constants, and a tensor splitting factor. The frequency positions of the 4251 symmetry-identified rotational substate transitions for J = 0 to 100 have been found for the two Q-branches, Opportunities for selective excitation of collections of symmetry - sorted $UF_{6}$ molecules will be discussed.
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Author Institution: Los Alamos Scientific Laboratory, University of California