Vibration-rotation bands of methyl fluoride and methyl fluoride- d 3

Abstract

Four parallel vibration-rotation bands of CD 3 F have been measured, and much of their fine structure has been resolved. In some of these bands, the K splitting of the central Q branches has been measured, and in one case the P and B lines of the subbands, corresponding to different K values, have been analysed. Eight perpendicular type bands of CD 3 F have been measured, and seven have been analysed. One of these, v 4 , shows much P-R structure of the subbands. Values have been derived for the rotational constants, Coriolis coefficients, and the α values which relate the rotational constants in different vibrational levels. The value found for A o is 2.56 1 cm -1 . One parallel and two perpendicular bands of methyl fluoride have been analysed, and the results have been considered with previous data on this molecule to estimate the molecular constants. The band v 5 shows an unusual type of perturbation which appears to affect the two sides of the band in different ways. The value found for A 0 is 5.08 1 cm -1 . The results show again, as found with other methyl halides, that interactions between energy levels often lead to perturbations which complicate the determination of the molecular constants.