Microwave-infrared double resonance of CH4 using 3.39μ He–Ne laser line

Abstract

The rotational transition between the F1(2) and F2(2) components of the 67 v3 = 1 level of CH4 has been observed at 6895 MHz by double resonance experiments in the 3.39 μm He–Ne laser cavity. When the microwave radiation is applied the Lamb dip signal is observed to decrease markedly in size because of the double resonance coherence splitting phenomenon. A double resonance signal is also observed over the Doppler width of the CH4 absorption because the population shift caused by the microwave transition reduces the saturation of the CH4 absorption by the laser. The frequency of the transition was measured as 6895.3 ± 0.3 MHz.