Vibration-rotation bands of methyl fluoride

Abstract

The vibration-rotation bands of methyl fluoride between 2⋅5 and 5 μ 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 D J , 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.