Excited states of F centres in alkali halides resonant with the conduction band

With magnetic circular dichroism of the optical absorption (MCDA) and MCDA-detected electron paramagnetic resonance (MCDA-EPR) it is possible to unambiguously identify the higher absorption bands (L-1-L-3) of F centres. In CsBr, similarly as found earlier for example KCl, there are several transitions beyond the K band to states resonant in the conduction band up to about 1.5 eV It is observed that the peak-to-peak separation of the MCDA increases with increasing transition energy indicating the dominant role played by lifetime effects additionally to the spin-orbit coupling in the resonance states. In RbBr similar bands and features have been observed. However, the phase of the derivative-like MCDA-L band structures is opposite to that in CsBr. A preliminary theoretical approach to explain the resonance states is presented.