Comments on the paper by W. Nitsch and W. Kiefer "Coherent anti-Stokes resonance Raman spectroscopy"

It is shown that quasiresonant pumping at the frequencies of lines used in coherent anti-Stokes Raman spectroscopy (CARS) causes a change in the ratio of the absorption and emission intensities because of reversal of the sign of the real part of the Raman scattering susceptibility. The changes in the line profile with the concentration of a substance subjected to long-wavelength pumping are due to reversal of the sign of the imaginary part of the susceptibility. An expression is obtained for the dependence of the CARS line profile on the pump intensity.