X-ray atomic absorption of cesium and xenon in theL-edge region

Abstract

X-ray absorption of atomic cesium is measured in the $L$-edge region, using a beryllium-window cell for cesium vapor. For comparison, absorption in Xe gas in the same energy region is remeasured with improved signal-to-noise ratio. By combining deconvolution and modeling, the edge profiles are studied to determine the threshold energies and the shape of the edge apex with exponential slope of the high-energy flank. In both elements, multielectron excitations show the same basic ordering in compact groups, largely independent of the core-hole subshell, following the energy sequence of coexcited valence and subvalence orbitals. The main effect of $6s$ electron in Cs, apart from $2(s,p)6s$ excitation, is the enhancement of single- as well as some multielectron resonant channels. The spectra of both elements show the ``polarization effect'': a convex basic curvature of the ${L}_{2}$ and ${L}_{3}$ segments, a concave ${L}_{1}$ segment. Previously, Kutzner demonstrated a convincing theoretical explanation of the effect on Xe in a relativistic random-phase approximation with relaxation involving overlap integrals with continuum [Rad. Phys. Chem. 70, 95 (2004)].