CALCULATED LINEWIDTHS FOR $CH_{4}$ BROADENED BY $N_{2}$ AND $O_{2}$

This research was supported by the U.S. Air Force Cambridge Research Laboratories under Contract No. F19628-72-C-0111. $^{1}$ P.W. Anderson, Phys. Rev. 76, 647 (1949); C.J. Tsao and B. Curnutte, J. Quant. Spectry. Radiat. Transfer 2, 41 (1962). $^{2}$ G.D.T. Tejwani, Ph.D. dissertation, State University of New York at Stony Brook (1971); G.D.T. Tejwani and P. Varanasi, J. Chem. Phys. 55, 1075 (1971). $^{3}$ K. Fox, Phys. Rev. Letters 27, 233 (1971); J.K.G. Watson, J. Mol. Spectrosc. 40, 536 (1971); I. Ozier, Phys. Rev. Letters 27, 1329 (1971).Author Institution: Earth Resource and Astrophysics Laboratory, Department of Physics and AstronomyThe Anderson-Tsao-$Curnutte^{1}$ theory of collision-broadened spectral lines, as extended by $Tejwani^{2}$ for octopolar interactions, has been used to compute linewidths for methane broadened by molecular nitrogen and oxygen. Width of vibration-rotation lines in the infrared-active fundamental bands $\nu_{2}, \nu_{3}$, and $\nu_{4}$; the overtone bands $2\nu_{3}, 2\nu_{4}$, and $3\nu_{3}$; and the combination bands $\nu_{2} + \nu_{3}$ and $\nu_{3} + \nu_{4}$ have been calculated for the symmetry species A, E, and F separately, for the range of angular momentum quantum number 0 $\leq$ J $\leq$ 30. The contribution of the dipole $moment^{3}$ of $CH_{4}$ has been found to be essentially negligible. The temperature dependence of the calculated linewidths has been obtained for the range $200^{\circ} K \leq T \leq 300^{\circ} K$ . Finally, these results have been used to compute corresponding air-broadened line-widths