Optical properties of KPb sub(2)Cl sub(5) and RbPb sub(2)Cl sub(5) single crystals in the far ultraviolet spectral region

Electronic structure properties of undoped single crystals of KPb sub(2) Cl sub(5) (KPC) and RbPb sub(2) Cl sub(5) (RPC) have been studied using low-temperature (T = 8[degrees]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 super(1)S sub(0) arrow right 6 super(1)P sub(1) at 6.28 eV, 6 super(1)S sub(0) arrow right 6 super(3)P sub(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 arrow right 6p transitions in Pb super(2+) ions.