The pure rotational spectrum of NaCH3 (X̃1A1)

The pure rotational spectrum of NaCH3 and NaCD3 in their X̃1A1 states has been recorded using millimeter/sub-mm direct absorption techniques in the 300–510 GHz range. This work is the first gas-phase detection of sodium monomethyl, which was created by the reaction of sodium vapor with tetramethyl tin. Ten rotational transitions were measured for NaCH3 for the K=0 through K=5 components and, in select cases, up to K=10, and four transitions (K=0–7) for NaCD3. Rotational constants have been accurately determined for both isotopomers, suggesting a sodium–carbon bond length of 2.30 Å and an H–C–H bond angle of 107.3°.