Pulse Fourier-Transform Optical Spectroscopy

The optical analog of pulse Fourier-transform NMR spectroscopy is demonstrated. Doppler-free infrared spectra are obtained for a set of closely spaced ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$H${}_3{}^{}{}_{}{}^{}\mathrm{F}$ transitions at 9.66 μm from two-pulse echo and free-induction decay transients. The effects of elastic or inelastic collisions on the decay rate are obtained for each transition, and the long-range force laws are deduced from the dependence of the scattering cross section on molecular velocity.