High-resolution experimental and theoretical study of singly and doubly excited resonances in ground-state photoionization of neon

An experimental and theoretical study of ground-state photoionization of neon is presented in the photon energy range between 44 and 53 eV. This portion of the spectrum is characterized by a singly excited Rydberg series 2s2${\mathit{p}}^6$np, and by overlapping doubly excited Rydberg series 2${\mathit{s}}^2$2${\mathit{p}}^4$3snp and 2${\mathit{s}}^2$2${\mathit{p}}^4$3pnl (l=s,d). With the use of synchrotron radiation of ≃3 meV spectral resolution, numerous hitherto unobserved resonances were resolved, including some which exhibit relativistic effects. To identify resonances observed here and in earlier works, we employed numerical calculations, which combine the eigenchannel R-matrix method, multichannel quantum defect theory, and the recoupling frame transformation. These nearly ab initio methods account for most of the observed features in the spectrum, including a class of spin-induced relativistic effects. © 1996 The American Physical Society.