An analysis and model calculations are presented to clarity how both the electronic and vibrational inhomogeneities with no correlation between them influence the most relevant resonant steady-state third-order nonlinear optical mixing processes (CARS, CSRS, polarization spectroscopy and Raman gain (loss)).It is shown that all these processes may be divided into three groups: 1) processes yielding almost homogeneous spectra: both inhomogeneities are greatly reduced; 2) processes yielding quasihomo- geneous spectra: inhomogeneities are present, but the electronic one is not manifest in the spectrum; 3) processes yielding completely inhomogeneous spectra.The suppression of inhomogeneous broadening allows to study the excited electronic states and the ultrafast relaxation processes in inhomogeneous media more effectively than in linear spectroscopy. * About another steady-state frequency domain technique byhot luminescence measurements for the study of ultrafast energy relaxation see.e. g. f l4 ].ЁЁЗТТ NSV TEADUSTE AKADEEMIA TOIMETISED.30.
We explain the utility of third-order nonlinear susceptibility, χ (3) (ω 2 ; ±ω 1 ,
∓ω1, ω 2 ), for the observation of resonances with homogeneous widths from inhomogeneously broadened distributions in three-level systems related to Raman or two-photon allowed electronic transitions. The line narrowing and high resolution capabilities are demonstrated theoretically using a model for inhomogeneous distributions of transitions in which we regard an absorption spectrum as the composition of some inhomogeneously broadened substructures. The experimental methods to separate a signal having frequency ω 2 from ingoing beam at the same frequency are outlined.