Observation and assignment of torsional transitions in FIR emission from optically pumped CH3OH

Using output coupling by reststrahlen reflection from NaCl we have observed 14 new FIR lines in the wavelength range between 30 μm and 60 μm. Two of them have been identified as torsional n=1→0 transitions in the CO stretch vibration. Together with lines previously reported in the literature they are the basis for an identification of 41 FIR lines associated with torsionally excited states.