Optical Absorption Spectra of MnCl2 and MnBr2

Optical absorption spectra of MnCl 2 and MnBr 2 have been obtained for photon energies between 3 and 7 eV at room and liquid nitrogen temperatures. The spectra show long tails near the onset of the fundamental absorption. Weak but sharp peaks are found at 5.40, 5.85, 6.37, and 6.7 eV in MnCl 2 , and at 5.47, 5.81, and 6.36 eV in MnBr 2 . The long tails are interpreted as being due to the indirect interband transitions between the valence band arising from p electrons of halogen and the conduction band arising from 4s electrons of manganese. The sharp peaks are assigned to the excitonic transition from the 3d orbitals to the 4s orbitals of manganese ions.