INFRARED ABSORPTION SPECTRUM OF $CH_{4}$ at $7500 cm^{-1}$

Support by NASA Contract NAS7-100 is acknowledged by John E. Beckman. Support (in part) by NASA Research Grant NSG-539 is acknowledged by Kenneth Fox. $^{1}$ K. Fox, J. Mol. Spectry. 9, 381 (1962).Author Institution: Space Sciences Division Jet Propulsion Laboratory; Physics Department, The University of TennesseeA high resolution ($0.06 cm^{-1}$) infrared absorption spectrum, obtained using a multi-pass absorption cell and a scanning Ebert spectrometer, is presented for the region in which the combination band $\nu_{2}+2_{\nu 3}$ of methane is expected to appear. A well-defined Q- and R-branch is observed. The R-branch consists of fine structure components in groups separated by about 10 to $11 cm^{-1}$. An analysis of the R-branch is made, assuming it belongs to $\nu_{2}+2_{\nu 2}$, and an explanation based on a successful analysis of other methane bands$^{1}$ is given for the unexpectedly regular structure. The fine structure components arising from tetrahedral vibration-rotation interactions are examined and compared with other bands of methane