Relationship between x-ray spectra from some metal chlorides and their ionicity

The $K\beta$-emission and $K$-absorption spectra of chlorine in CsCl, Ba${\mathrm{Cl}}_2$, La${\mathrm{Cl}}_3$, and Ce${\mathrm{Cl}}_3$ have been reported. From an analysis of these data and those for other metal chlorides reported previously, it is found that the energy of a prominent peak of the Cl $K$-absorption spectrum measured relative to the bottom of the conduction band as well as the halfwidth of the $K{\beta }_1$ band, and the peak separation between the $K{\beta }_1$ band and its subband $K{\beta }_x$ are correlated to the amounts of ionic character of the bond of these chlorides. The $K$- and $L_3$-absorption spectra of chlorine in CsCl have been discussed on the basis of the energy band-structure calculation by Donato et al. The band gaps estimated from the x-ray spectra are compared with those obtained from the optical spectra.