Electron-ion collision spectroscopy: Lithium-like xenon ions

Abstract

The resonant process of dielectronic recombination (DR) has been applied as a spectroscopic tool to investigate intra-$L$-shell excitations $2s\ensuremath{-}2{p}_{j}$ in Li-like ${}^{136}{\text{Xe}}^{51}+$. The experiments were carried out at the electron cooler of the Experimental Storage Ring of the GSI-Helmholtzzentrum f\"ur Schwerionenforschung, Darmstadt, Germany. The observed center-of-mass energy range (0--505 eV) covers all resonances associated with the $2s+{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{(2{p}_{1/2}n{l}_{j})}_{J}$ and ${(2{p}_{3/2}n{l}_{j})}_{J}$ DR processes. Energies and strengths of isolated $2{p}_{1/2}n$ and $2{p}_{3/2}n$ DR-resonance groups were obtained for principal quantum numbers $n$ up to 43 and 36, respectively. The $2s\ensuremath{-}2{p}_{1/2}$ and $2s\ensuremath{-}2{p}_{3/2}$ excitation energies were deduced to be 119.816(42) eV and 492.174(52) eV. The excitation energies are compared with previous measurements of other groups and with recent QED calculations. In addition, the experimental spectra and extracted resonance strengths are compared with multiconfiguration Dirac-Fock calculations. Measurements and theory are found to be in good agreement with each other.