The number of CO2 laser lines available for optical pumping of far-infrared (FIR) lasers has been significantly increased by the development of a new continuous wave (cw) CO2 laser at the Time and Frequency Division of the National Institute of Standards and Technology in Boulder, Colorado. This system operates on very high-J lines of the normal bands as well as on sequence and new hot-band lines, and has generated numerous new FIR laser transitions in CH3OH. These include the new 123 μm world-record holder, pumped by the 9HP(20) hot-band CO2 line, which is now the most efficient known FIR laser line. Assignments are given for a number of the IR pump – FIR laser energy level and transition systems, based on our high-resolution Fourier transform studies of the FIR and IR spectra of CH3OH. Features of the transition system for the 123 μm line and wave numbers for several further potential FIR laser lines are presented.
