Accurate frequency of the 119 mu m methanol laser from tunable far-infrared absorption spectroscopy

High-accuracy absorption spectroscopy of CH/sub 3/OH in the far infrared is discussed. In addition to 22 transitions in the ground state, the frequency of the (n, tau , J, K), (0, 1, 16, 8) to (0, 2, 15, 7) transition in the nu /sub 5/ excited vibrational level, which is responsible for the laser emission at 119 mu m, was measured. The measured frequency is 2,522,782.57(10) MHz at zero pressure, with a pressure shift of 6.1(32) kHz/Pa (0.805