Rotational transitions of the alkali metal fluorides CsF, ${\mathrm{Rb}}^{87}$F, ${\mathrm{Rb}}^{85}$F, ${\mathrm{K}}^{39}$F, NaF, and ${\mathrm{Li}}^7$F have been measured in the millimeter- and submillimeter-wave regions where no previous measurements existed. The work was accomplished with a high-resolution molecular-beam absorption spectrometer, previously utilized for study of the other alkali halides. A more reliable oven was constructed and used to vaporize the alkali fluorides at temperatures up to 1100°C. Measurements on rotational transitions as high as $J=27\mathrm{}\to 28$ in the first three vibrational states gave $Y_{01}$, $Y_{11}$, and $Y_{21}$ more accurately, for the most part, than they were previously known, and gave $Y_{02}$ and $Y_{12}$ for the first time. From these Dunham rotational constants were derived potential coefficients, moments of inertia, internuclear distances, and vibrational constants.

• Received 14 January 1965

DOI:https://doi.org/10.1103/PhysRev.138.A1303