Time-domain coherent anti-Stokes Raman spectroscopy for hydrogen gas in the Dicke narrowing region

An experiment on time-domain coherent anti-Stokes Raman spectroscopy (time-domain CARS) of molecular hydrogen was performed in the pressure range 10-2--10 atm. The experimental setup had a dynamic measurement range 105 and could reliably record the signal in the gas-pressure range to 10-2 Torr. A theory of time-domain CARS is developed for an inhomogeneously broadened transition with allowance for two mechanisms that dephase the molecular vibrations, viz. collisions and the Doppler effect. The waveform of the pulsed response of a gaseous medium to an external field is calculated at arbitrary pressures. It is shown that under definite conditions the time-domain CARS technique can be used to determine the real and imaginary components of the nonlinear susceptibility of the medium, chi/sup( /3)/sup /(ω), in contrast to the frequency-domain CARS, in which Vertical Barchi/sup( /3)/sup /(ω)Vertical Bar2 is measured. The results of the theory agree with the obtained experimental data