X-ray-photoelectron spectroscopy has been used to investigate the valence bands of AgF, AgCl, AgBr, $\beta -\mathrm{A}\mathrm{g}\mathrm{I}$, and $\alpha -\mathrm{A}\mathrm{g}\mathrm{I}$. Assignments of the photoemission peaks are made by using the point-charge electrostatic model of Citrin and Thomas. Density-of-states maxima from the halogen $p$ levels are clearly resolved from those of the silver $4d$ states. Additional splittings due to $k$-space symmetry are observable, and in the case of AgCl and AgBr, give excellent confirmation of existing band-structure calculations. The spectrum of AgF shows the inversion of silver $4d$ and halogen $2p$ levels suggested by the optical-absorption spectra and predicted by several recent band calculations. A new interpretation for the AgF optical spectrum is proposed.

• Received 10 December 1973

DOI:https://doi.org/10.1103/PhysRevB.11.5094