Doubly excited resonances in the photoionization spectrum of Li⁺: experiment and theory

Abstract

Absolute cross-section measurements for resonant double photoexcitation of Li+ ions followed by autoionization have been performed at high resolution in the photon energy range from 148 eV, just below the (2s2p, 2(0, 1)n+) resonance, to 198 eV (the region of the double ionization threshold). The measurements have been made using the photon–ion merged-beam endstation at the Advanced Light Source, Lawrence Berkeley National Laboratory, USA. The absolute cross-section measurements show excellent agreement with theoretical results from the R-matrix plus pseudo-state (RMPS) method. Comparisons between theory and experiment for the Auger resonance energies, autoionization linewidth (Γ) and the Fano line profile index q for several members of the principal (2snp, 2(0, 1)n+) and (3snp, 3(1, 1)n+) Rydberg series found in the photoionization spectra for the 1Po symmetry show satisfactory accord.