The torsion-rotation microwave spectrum of 12CH318OH and the structure of methanol

The microwave and millimeter wave spectrum of ¹²CH₃¹⁸OH has been observed in the frequency region 7.9–200 GHz. Both a- and b-type transitions have been assigned and measured. This spectrum was analyzed using the method of Lees and Baker, and rotational constants, torsional constants, centrifugal distortion constants, the barrier to internal rotation and moments of inertia have been evaluated. The barrier has been found to be 374.91 ± 0.18 cm^?1, in good agreement with that of ¹²CH₃¹⁶OH. The moments of inertia were combined with those of other isotopic species to give a full substitution structure. To assist searches for this molecule in interstellar space a table of predicted frequencies of astrophysically interesting transitions is presented.