Far infrared laser lines and assignments of Ch3OJ: a review

Methyl alcohol is the molecule with the largest number of FIR laser lines, and one of the most efficient (the most powerful and efficient known FIR laser line is the 119 p.m of CH3OH pumped by the 9P36 CO2 laser line). Therefore it is also the standard molecule used to test new apparatus and new pump sources. Under this condition new laser lines are steadily discovered and reported in many papers. In the 1984 review [1] we reported at least 331 optically pumped laser lines. A few other lines were considered as synonym of others, because were sharing the same pump line and the same wavelength within the experimental error. Laser lines with close wavelengths can be obtained from different pump lines separated in frequency by less than the Doppler linewidth. Only when the frequency of the laser line is measured directly, or the the pump frequency is accurately determined by the Transferred Lamb Dip technique, we can count the laser lines with confidence.