Determination of Hyperfine Constants and Nuclear Shielding in Methyl Fluoride and Comparison with Other Molecules

The molecular-beam electric resonance spectrum of methyl fluoride (CH3F) was measured in several rotational states. From analysis of the spectra the hyperfine structure of the molecule was determined. The hyperfine constants are (kilohertz): ζα=0.8±1.5, ζβ=14.66±0.7 for the spin—rotation interactions of the hydrogen nuclei, and cα=4.0±1.9, cβ=−51.1±1.3 for the spin—rotation at the fluorine. These results are combined with nuclear shielding data to calculate contributions to shielding and the electrostatic potential at the nucleus. Quantitative comparison is made with other molecules.