Extreme Ultraviolet Absorption Spectra of K–Rb and K–Cs alloys

Abstract

The optical conductivities of K–Rb and K–Cs alloys have been measured at liquid nitrogen temperature using synchrotron radiation from a 0.4 GeV electron storage ring over the photon energy range from 10 to 30 eV. The spectra of the alloys have the profiles given by the proportional sums of the spectra of pure alkali metals and this feature suggests the localization of the excitation of outer-most p-shell electrons. The critical exponent of the Fermi edge singularity is altered by alloying. Its concentration-dependence is interpreted as indicating that the shape of spikes at the edge is affected not by the density of states but by the size of the core hole. The energy positions of the edge are shifted by alloying. The amount of the shift is dependent on the concentration and increases for increasing atomic number. This, along with the change in the exponent, may be ascribed to charge transfer effects due to alloying.