Measurement and Spectroscopic Assignment of Far-Infrared Laser Frequencies Generated by 13CD3OH and CH3 18OH

The frequencies for thirty one far-infrared laser emissions, generated by an optically pumped molecular laser with either
¹³
CD3OH or CH3
¹⁸
OH as its laser medium, have been measured for the first time. The frequencies, ranging from 0.443 to 3.243 THz, were measured with a heterodyne technique to a one-sigma fractional uncertainty no less than ± 5 parts in 10
⁷
. Approximately half of the frequencies measured during this investigation have been used to either confirm or propose new spectroscopic assignments associated with these methanol isotopologues.