DOPPLER-LIMITED SPECTROSCOPY OF THE $3\nu_{3}$ BAND OF $SF_{6}^{*}$
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Date
1979
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Ohio State University
Abstract
The $\nu_{3}$ overtone ladder in $SF_{6}$ has come under close scrutiny recently in an attempt to understand the isotope selective excitation mechanism in collisionless multiple photon ionization of $SF_{6}$. The $F_{lu}$ symmetry modes of the $3\nu_{3}$ vibration are directly accessible from the ground state and some low resolution gas and liquid phase spectra have prompted much speculation about the roles played by anharmonic splittings, rotational structure, selection rules and hot hands to interpret the second overtone band envelope and the multiphoton excitation process. We have recorded the Doppler-limited rotationally-resolved spectrum of $^{3}\nu_{3}$ from 2831.7 to $2821.0 cm^{-1}$ at 295 and 140 K using a tunable difference-frequency laser. The intensity of nearly all of the rotational structure observed at 295 K is enhanced by at least a factor of 3 at 140 K indicating that none of this structure is due to hot bands. The continuum background at room temperature is drastically reduced upon cooling. The alternating intensity pattern of some of the rotational structure resembles the cluster sub-hands previously $observerd^{1}$ in the Q-branch of the fundamental $\nu_{3}$ band of $SF_{6}$.
Description
$^{1}$ R.S. McDowell, H.W. Galbraith, C.D. Cantrell, N.G. Nerenson, and E.D. Hinkley, J. Mol. Spectrosc. 68, 288-298 (1977). $^{*}$ This work was sponsored by the Department of the Air Force.
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