ELECTRONIC ABSORPTION AND MAGNETIC CIRCULAR-DICHROISM SPECTRA OF CO2+ IN CDI2

Abstract The electronic absorption and magnetic circular dichroism spectra of Co 2+ doped CdI 2 were measured at temperatures from 1.6 to 300 K and in magnetic fields up to 5 T. The absorption bands could be assigned to magnetic dipole and vibronically-induced electric dipole d-d transitions of Co 2+ . From the positions of the bands the Racah parameters B = 680 cm -1 , C = 2720 cm -1 and the cubic crystal field splitting 10 D q = 5200 cm -1 were calculated. The trigonal calculated cry field is small, as indicated by the isotropic g = 4.3 value obtained from EPR measurements. Zeeman measurements on sharp lines make it possible to determine g values of excited states. The fine structure of spin-forbidden d-d transitions is due to vibronic coupling with phonons of CdI 2 and with a local mode of 47 cm -1 . The temperature dependence and polarization of the absorption band at 18000 cm -1 indicates that it is due to a charge-transfer transition.