High-resolution degenerate four-wave mixing spectral profiles of OH

Abstract

High-resolution degenerate four-wave mixing spectra of the R(1)(9) A(2)Sigma(+) ? X(2)II(0,0) transition of OH have been measured in a hydrogen/oxygen flame at atmospheric pressure where the Doppler and homogeneous linewidths are of comparable magnitude. The observed sub-Lorentzian Doppler-free line profile is fit well by existing perturbative models by using homogeneous broadening consistent with two-photon absorption measurements. Power broadening of the spectral profile with increasing pump-beam intensity was observed and is compared with predictions from a nonperturbative two-level model.