PROSPECTS FOR INCREASING THE PRECISION OF OPTICAL FREQUENCY STANDARD BASED ON TRANSITIONS IN THE METHANE MOLECULE

An analysis is made of the feasibility of increasing further the preci sion of the 3-mu m frequency standards in which lines in the nu(3) ban d of the methane molecule are used as the reference points. It is prop osed to use stronger absorption lines of methane, cooled to cryogenic temperatures, as new reference lines. Numerical estimates are obtained of the absorption coefficients of lines in the nu(3) band as a functi on of temperature. Experimental observations, made with a colour-centr e laser of lines in the R branch (lambda = 3.2-3.3 mu m) at loom and l iquid nitrogen temperatures are reported.