Vibration-rotation bands of methyl fluoride

Abstract

Abstract The vibration-rotation bands of methyl fluoride between 2⋅5 and 5μ have been measured with higher resolution than previously. Three parallel bands have been analyzed, providing three independent values for B", the rotational constant in the ground state. Each of these values is close to that obtained from the microwave spectrum (0⋅8518 cm-1), and some earlier values deduced from infra-red bands are shown to be incorrect. A value of 2⋅28 x 10-6 cm-1 has also been obtained for DJ, the centrifugal stretching constant, which is shown to be more satisfactory than that previously deduced from the microwave spectrum. A perpendicular type band has been resolved fairly completely, and it has been possible to measure the P and R lines of the sub-bands in addition to the strong Q branches. An analysis has been made which accounts satisfactorily for most of the lines in the entire band, and this provides the first example of such a complete analysis of a perpendicular band of a symmetrical top molecule.