The Jahn-Teller effect for the 3P-term of Ni2+ impurity ions in CdS crystals

The piezo spectroscopic investigation of the absorption spectrum caused by the optical transition onto spin-orbital components of the excited 3T1 (3P)-term of Ni2+ impurity ions in CdS crystals is performed. It is shown that the structure of the spectrum is due to the vibronic (Jahn-Teller) coupling with low-frequency pseudo local vibrations (PLV) and phonons of the crystal, that give rise to a Jahn-Teller polaron. The value of such a coupling is estimated. The tunnel splitting of vibronic levels is found. The significant influence of PLV and the trigonal component of the crystalline field upon the intensity, polarization, and spectral composition of absorption is established. Based on the obtained results, the microstructure of the impurity center taking into account the decreasing of elastic constants nearby the impurity is established