Measurement of Methane Hyperfine Structure Using Laser Saturated Absorption

Abstract

With optical resolution above ${10}^{10}$, we study hyperfine structure in the methane vibration-rotation line at 3.39 μm. Doppler-generated crossing resonances were observed in addition to the resolved $\Delta F=0\mathrm{}$ and - 1 lines. Splittings in both ground and excited states were determined. Differential saturation of such hyperfine structure will lead to an intensity-dependent shift in many molecularly stabilized lasers.