Vacuum Ultraviolet Reflection Spectra of KDP and ADP

The reflection spectra of KDP and ADP are studied in the vacuum ultraviolet region up to 35 eV. Polarized light is used in the study of low energy part below 13 eV. Some peaks in the spectra are found to show remarkable dependence on the polarization of the incident light. The energy levels of PO 4 3- , H 2 PO 4 - and H 4 PO 4 + are calculated by the extended Hückel method. By comparing the peak energies in the reflection spectra with the energy levels and taking the polarization characteristics into consideration, tentative assignment is given to the bands observed.