THEORETICAL STUDIES OF COLLISION-BROADENED LINEWIDTHS IN $METHANE^{*}$

Author Institution: University of TennesseeOne of the more challenging problems in the theory of vibration-rotation transitions in gas-phase molecules is the prediction or calculation of shapes of spectral lines. An understanding of collision-broadened line shapes, widths and shifts is important in a variety of contexts, including planetary $atmospheres.^{1}$ For example, in the atmospheres of Jupiter and Earth, the systems $CH_{4}-H_{2},CH_{4}-He$, and $CH_{4}-N_{2}$, respectively, are of considerable $interest.^{2}$ High resolution laboratory spectra have been $measured^{3}$ for the $v=0\rightarrow 3,\Delta J=1$ transitions of both $^{12}CH_{4}$ and $^{13}CH_{4}$. These data will be analyzed with a view toward developing the theory of collision-broadened line widths of spherical-top molecules, including their isotopic dependence. $^{*}$This research is supported by the Planetary Atmospheres Program of the National Aeronautics and Space Administration, under Grant NAGW-125. $^{1}$See, e.g., J. J. Gelfand, in ``Vibrational-Rotational Spectroscopy for Planetary Atmospheres’’ (M. J. Mumma, K. Fox and J. Hornstein, eds.) NASA 1982. $^{2}$ See, e. g., K. Fox in ``Molecular Spectroscopy: Modern Research’’ (K. Narahari Rao and C. W. Mathews), Academic 1972. $^{3}$ J. W. Brault, K, Fox, D. E. Jennings, J. S. Margolis, and L. R. Brown, preceding Abstract, this Symposium