The Infrared Spectrum of Formyl Fluoride

Nine bands were observed in HOOF and thirteen DCOF. A rotational analysis was completed on five of the fundamental bands in each molecule. The ground state moments of inertia are internally consistent. The value of B which is quoted is actually B̅ = 1/2 (B+C). As the symmetric top approximation is used throughout, no information was obtained about the actual values of B and C themselves. We know, however, that they cannot differ by very much because symmetric top approximation gives consistent results.

The moment of inertia were used to determine the approximate position of the hydrogen atom. The moments of inertia, however, are relatively insensitive to the position of the hydrogen atom.

The band centers were used to determine some of the vibrational constants. Several ω_i°'s were calculated, but none of the ω_i's could be determined. If the combination band ν₂+ν₄ could be observed, it would then be possible to find ω₄.

A rotational analysis could probably be completed on several of the combination bands. It seems likely that some of these, notably 2ν₄, in both molecules, might require that the symmetric top approximation be abandoned.

The results quoted here might be improved considerably if some of the bands could be examined under higher resolution. It seemed that the parallel component of ν₅ (in both molecules) could be resolved with only a slight improvement in resolution. The unresolved regions in ν₂, apparently caused by interference between the lines, might also be cleared up.

It seems likely that higher resolution would force one to give up the symmetric top approximation entirely. In any case, in a complete analysis of these molecules, it would be desirable to consider their asymmetry. Tables^1,2 have been made by machine calculation which may be used to calculate the rotational energy levels of the asymmetric top for J up to 40. These tables would allow the asymmetry to be considered with a minimum of labor.