Absolute frequency measurement and spectroscopy of gas laser transitions in the far infrared.

Absolute frequencies of the 311‐μ and the 337‐μ transitions of the CN gas laser are measured to within a few parts in 107. This is achieved by mixing the laser frequencies with high order harmonics of a microwave signal in a silicon diode. The beat frequencies of these two transitions which falls at 73.5 GHz is also measured directly. The Zeeman effect of these two laser transitions is studied. Based on a detailed analysis, it is found that the existing identification of these transitions is inconsistent with our observations.