Spin-Orbit Splitting of \(\) Exciton Bands in RbI and KI

The exciton absorption bands in RbI and KI are studied by means of magnetic circular dichroism spectra, and their effective g -values are obtained. From the sign of the g eff -values, it is concluded that the lowest two sharp absorption bands, E 1 and E 2 , are (\(⁻₈\); \(⁺₆\)) and (\(⁻₆\); \(⁺₆\)) excitons, respectively, which are split by the spin-orbit interaction of iodine 5 p electrons. The higher energy bands, E 3 and E 4 , are probably the exciton bands produced by excitation of halogen 5 p electrons to the d -like conduction bands at X and L points in the Brillouin zone.