Inner-shell and double-excitation spectrum of rubidium involving 4p and 5s subshells

Abstract

New high resolution observations of the 4p inner shell and of the doubly excited states of rubidium covering the spectral region between 500 and 700 AA are reported. The spectra were recorded in the first order of a 3-meter spectrograph equipped with a 5000 line/mm holographic grating and synchrotron radiation emitted by the 500 MeV electron accelerator as the background source of radiation. More than 130 new levels of Rb I are reported which are interpreted as inner-shell transitions 4p6582S12,1/2 to 4p55s(3P2,1,0,1P1)ns,nd and the doubly excited transitions 4p65s2S1/2 to 4p54d(3P0.1.2)nl. All the observed levels lie well above the first ionization threshold and are arranged into Rydberg series converging onto seven conspicuous limits. The inter-channel interactions between the overlapping series have been parameterized using multichannel quantum defect theory.