A three-laser heterodyne system was used to measure the frequencies of twel
ve optically pumped laser emissions far-infrared (FIR) region. These emis-f
rom (CH3OH)-C-13 in the far sions, ranging from 54 to 142 mum, are reported
with fractional uncertainties up to +/-2 x 10(-7) along with their polariz
ation relative to the CO2 pump. Using the 9P32 and 10R14 CO2 lines, complet
e spectroscopic assignments for two laser systems were confirmed.