HIGH RESOLUTION INFRARED STUDY OF THE $\nu_{3}+\nu_{6}\leftarrow \nu_{6}$ BAND OF $^{12}CH_{3}F^{1}$

$^{1}$ This work was supported by the U.S. National Science Foundation.Author Institution: Department of Chemistry, Michigan State UniversityThe $\nu_{3} +\nu_{6} \leftarrow \nu_{6}$ hot band of $^{12}CH_{3}F (1039 cm^{-1}, E \leftarrow E$ symmetry) has been recorded at Doppler-limited resolution by an infrared-microwave sideband laser spectrometer. More than 200 hotband transitions have been assigned in spectra taken with a sample at 0.5 Torr pressure in a White-type cell with 8-meter path. The transitions were identified by eliminating from the spectrum transitions in the $\nu_{3}$ bands of $^{12}CH_{3}$ F and $^{13}CH_{3}$ F and in the $2\mu_{3}-\nu_{3}$ band of $^{12}CH_{3}F$. The frequencies of these transitions were predicted by the use of previously-reported constants. The assignment was assisted by the results of previous infrared and microwave studies of transitions involving the $\nu_{6}$ and $\nu_{3} + \nu_{4}$ vibrational states. The spectra, which include a number of well-resolved $\ell$-doublets, were analyzed by using $\Delta k - 0$ and $\ell - 0$ selection rules. The molecular parameters determined for the ve and $\nu_{3} +\nu_{6}$ states, including the $\ell$-type doubling constants, will be discussed and compared to the values obtained in earlier work