Excitation profile of coherent anti-Stokes Raman scattering from the MnO−4 ion doped in a KClO4 crystal at low temperature

Abstract

We have performed polarized resonance coherent anti-Stokes Raman experiments on the permanganate ion doped in potassium perchlorate single crystals at temperature T=15 K. At this temperature the m (Cs) site splitting of the excited degenerate 1T2-electronic level of the permanganate ion and the vibronic structure are well resolved. We report on the A′-ν1 coherent anti-Stokes Raman excitation profile which shows a strong dependence on the frequency of the pump laser. The simulation of the experimental results is performed by using the transform theory, which enables one to calculate the resonance Raman excitation profile solely from the measured absorption spectrum. According to the well known relation between the third-order nonlinear susceptibility and the Raman polarizability the coherent anti-Stokes excitation profile is given by a simple product of two Raman excitation profiles which are shifted relative to each other. The linear and the quadratic electron-phonon coupling as well as the influence of non-Condon terms were taken into account. Since the transform theory is mode selective in case there are no mode mixing effects the results derived from the description of the Raman excitation profiles and the coherent anti-Stokes excitation profiles are more definite. For this purpose one only needs the model parameters of the mode of interest. The simulation of the A′-ν1 coherent anti-Stokes profile shows that a small amount of non-Condon coupling yields to a better agreement with the experiment.

Transform relations for CARS excitation profiles

“…1, left side). However, there are cases, when the measured CEP is remarkably shifted from the absorption maximum [8,10,11]. It indicates a violation of the basic model.…”