Millimeter-Wave Spectra and Molecular Constants ofLi6D andLi7D

The $J=0\mathrm{}\to 1$ rotational line of LiD has been measured in the ground vibrational state and in the first excited state. The measurements have provided values of the frequencies and the spectral constants. The value of ${\mathcal{r}}_e$, which is independent of isotopic substitution, is found to be 1.594 90 ± 0.000 02 Å. From these constants the corresponding values for the LiH species are derived.