Threshold Singularities of <i>p</i>-shell Absorption in Potassium, Rubidium and Cesium Metals

Abstract

The extreme ultraviolet absorption spectra of K, Rb, and Cs show spikes at the thresholds of outermost- p -shell absorption. With inclusion of the data on Nareported by Haensel et al. , it is concluded that the occurrence of a spike at the edge of the absorption spectrum of outermost- p -shell electrons is a commoncharacteristic of alkali metals. In Rb and Cs no definite spike is found at the onset of the high-energy-component-absorption, L II , produced by the spin-orbit splitting of the levels of core holes. The sharpness of the spike decreases in the order of Na, K, Rb, and Cs. The threshold exponent α 0 for the transition to the s -symmetric state, obtained by neglecting the contribution from the transition to the d -symmetric state, decreases as the electron gas parameter, r s , increases in contrast with the prediction from the electron gas theory.