Electronic band structure of the alkali halides. I. Experimental parameters

Experimental work on the electron energy-band structures of the alkali halides is reviewed in order to obtain a set of basic parameters (band gap $E_g$, threshold energy $E_t$, and electron affinity $\chi$) that are used subsequently (paper II) to assess the merits of various theoretical band calculations. Included is a summary of our recent ultraviolet photoelectron spectroscopic studies of the alkali halides. Various experimental and interpretational difficulties are discussed and a number of systematic trends delineated.