A possible correlation between a Jahn-Teller coupling and a Raman scattering

Abstract

It has been shown how the Raman line of a degenerate vibration can be caused by a vibronic coupling in a degenerate electronic excited state. Such a vibronic coupling is known to cause a distortion in the equilibrium conformation of the molecule (Jahn-Teller distortion) from the symmetrical conformation, and the Raman scattering tensor is found to be calculated by the use of the amount (δ) of this distortion as an empirical parameter. It has been suggested that some of the Raman lines for the degenerate stretching vibrations, which become stronger with the exciting frequency, in some molecules, are caused by such Jahn-Teller couplings. For the intensity of the Raman line at 887 cm −1 of the degenerate stretching vibration of chromate anion, a slightly more detailed examination has been made, and the amount of the Jahn-Teller distortion in a B ̃ ( T 2) electronic state has been estimated to be 0.2 0 Å amu 1/2 along the normal coordinate of this vibration.