Optical properties of KPb_2Cl_5 and RbPb_2Cl_5 single crystals in the far ultraviolet spectral region

摘要

Electronic structure properties of undoped single crystals of KPb_2Cl_5 (KPC) and RbPb_2Cl_5 (RPC) have been studied using low-temperature (T = 8°K) far ultraviolet (3.7-24 eV) synchrotron radiation spectroscopy. Dispersions of optical functions have been calculated. The electronic transitions at 4.4-5.0 eV were ascribed to the excitation of cationic excitons. The energy region of 5-9 eV was associated with the transitions from the valence band to the conduction band: 6~1S_0 → 6~1P_1 at 6.28 eV, 6~1S_0 → 6~3P_2 at 5.94 eV. The complex band at 7.87 eV was attributed to the excitation of anionic excitons. The 19-24 eV peaks were associated with the 5d → 6p transitions in Pb~(2+) ions.