Optical and transport studies of atomic hydrogen and chalcogen impurities in alkali metals

Atomic hydrogen and chalcogen (0 and Te) impurities in alkali metal thin films have been studied. Their optical properties were determined by transmission measurements in the vacuum ultraviolet and transport properties were probed by means of electrical resistance. The observed optical absorption and small residual resistivities of Hand 0 indicate unambiguously that these elements enter alkali metals as interstitial atoms much as in bcc transition metals. The optical spectra lack prominent features other than a very sharp peak at ~11.5 eV induced by the interstitial (but not by substitutional) atoms in Cs. This important monitor of impurity structure apparently arises from the perturbation by the interstitial impurities of the O2 ,3 core absorption edge of neighboring Cs atoms. It probably occurs near the outer core optical threshold for all alkali metals. Te impurity spectra lack this feature and their substitutional location is confirmed by a tenfold increase in resistivity over that of O. The resistance data indicate that it exists mainly as a Te--ion in alkali metal host lattices, and the observed energy width and concentration dependence of the optical profile confirms this deduction.U of I OnlyThesi