FARADAY ROTATION STUDIES OF AN R-LIKE CENTER IN NEUTRON-IRRADIATED MGO .2. THEORY

The experimental results of the preceding paper have shown that the R-like center associated with the zero-phonon transition at 5233 in neutron-irradiated MgO is paramagnetic (spin-1/2). In addition, these results indicate that the orbital angular momentum that is to be associated with the degenerate E ground state is highly quenched. It is believed that this quenching arises primarily from two sources: (i) splitting of the E ground state by the random strain field of the bulk crystal, and (ii) a coupling of this E state to a pair of degenerate vibrational modes through the Jahn-Teller effect. In this paper an expression for the Faraday angle will be developed which will incorporate these two quenching mechanisms. The observed temperature and magnetic field dependence as well as the spectral pattern of the Faraday angle will be explained on the basis of the assumed model. Finally, the experimental results of the preceding paper will be used to make the following estimates: 1 cm-1 λcm-1, and aΛ0.07, where λR and aΛ are the spin-orbit splitting and reduced orbital angular momentum, respectively, associated with the degenerate ground state. © 1969 The American Physical Society.