Decay channels of the discrete and continuum Xe 4d resonances.

Abstract

Excitations of the Xe 4d subshell to discrete np and continuum \ensuremath{\epsilon}f states have been studied by photoemission. The resonant photoelectron spectra provide the first direct evidence that the emission of continuously distributed shakeoff electrons is one of the dominant decay modes of the 4d\ensuremath{\rightarrow}np resonances. The same effect is proposed to account for the missing 4d intensity in the 4d\ensuremath{\rightarrow}\ensuremath{\epsilon}f shape resonance compared to the absorption cross section. The fraction of direct recombination in the decay of the 4d\ensuremath{\rightarrow}np resonances was determined quantitatively by partial cross-section and branching-ratio measurements of the 5s and 5p main lines in the photon-energy range from 60 to 70 eV. The modified Fano theory for partial cross sections was applied to nearly Lorentzian-type profiles in order to derive partial decay widths. The decay into the 5s and 5p photoemission channels amounts to less than 0.5% of the total decay rate. The 5${p}_{3/2}$:5${p}_{1/2}$ branching ratio was measured over a broad range (17--140 eV) in order to test details of relativistic random-phase approximation calculations concerning intershell correlations between the 4d and 5p subshells.