STATE-SELECTIVE SINGLE-ELECTRON CAPTURE BY AR4+ IN HE, NE AND AR

Translational energy spectra have been obtained for single-electron ca pture by 8 keV Ar4+ ions in He, Ne and Ar. The spectra for He and Ne t argets display eight well-resolved peaks, the majority of which corres pond to capture involving a rearrangement of the electron core configu ration. By contrast, the five channels observed in the spectrum for th e Ar target are all associated with core-conserved electron-capture pr ocesses. One pronounced peak in the spectra for He and Ne cannot be ex plained on the basis of capture from the ground P-3 Or metastable D-1 and S-1 states of the Ar4+ ions, and appears to originate from capture by Ar4+ in the hitherto unidentified metastable S-5(0)-state at simil ar to 7.5 eV above the ground state. All observed channels are spin-co nserved.