The pure rotational spectrum of LiCH3 (X̃ 1A)

The pure rotational spectrum of lithium monomethyl, LiCH3, in its X̃ 1A ground electronic state has been measured using millimeter/sub-millimeter direct absorption techniques. Spectra of LiCD3 and 6LiCH3 have been recorded as well. These species were synthesized in the gas phase by the reaction of lithium vapor, produced in a Broida-type oven, and (CH3)4Sn, (CH3)2Hg or CH3I. Transitions were recorded in the 90–505 GHz range for J=2←1 to J=11←10 and K=0 up to K=10. Rotational and centrifugal distortion constants have been determined for each isotopomer, as well as an ro structure for LiCH3.