Theoretical study on ClL23NEXAFS and UV absorption data for metal chlorides

An effective iterative decomposition procedure for separating the $L_{23}$ NEXAFS line shape into the $L_2$ and $L_3$ components for the alkali halides has been developed. This decomposition allows a direct comparison of one of the components with UV spectral data, density of states (DOS), or with results from theoretical curved-wave multiple scattering cluster calculations (FEFF6 results). The derived Cl $L_3$ (or $L_2$) experimental component agrees reasonably well with the calculated DOS and with the FEFF6 results except in the excitonic region. Comparison with the UV spectra reveals a strong similarity between the Cl $L_3$ (or $L_2$) component and the UV (Cl $M_{23}$) spectrum. Through this similarity, we account for peaks in the UV with a one-electron theory, which were previously attributed to two-electron excitations. The excitonic peaks in the UV spectra at the alkali metal edge are similarly analyzed, resulting in assignments different from those previously given in the literature.