Observation of the recoil effect in saturated dispersion resonances in methane

The results are given of an experimental investigation of the structure of the λ= 3.39 μ methane line by recording saturated dispersion resonances. A method is described for reducing the intensity of the laser field in the absorbing medium to a value of < 10^-6 W/cm² and thus ensuring that the resolving power of the method is determined mainly by the collisional and field broadening of the lines, and exceeds considerably the transit limit. A 2.2 kHz doublet line splitting, resulting from the recoil effect, was recorded using a laser having a 3-cm diameter beam.