Frequency Measurement of Far-Infrared Laser Emissions Generated by Methanol Isotopologues

An optically pumped molecular laser system has been used to generate far-infrared (FIR) radiation with a variety of methanol isotopologues as its laser medium. Once detected, the frequencies of these laser emissions were measured using a heterodyne technique to a one-sigma fractional uncertainty of ±5 parts in 10⁷. In total, 68 FIR laser frequencies, ranging from 0.417 to 2.611 THz, have been measured for the first time. These laser emissions were generated by six isotopic forms of methanol, CD₃OH, CH₃OD, CH₂DOH, CHD₂OH, CD₃OD, and CH₃¹⁷OH. Two of these laser emissions were discovered during this investigation and are reported with their optimal operating pressure, polarization with respect to the CO₂ pump laser, and output power.