High-lying levels in uranium atomic vapor near the ionization limit

This paper comments on the recent observation of Rydberg "progressions" in atomic uranium. A multichannel quantum-defect analysis shows that the observed ion peaks are unresolved groups of levels with different total angular momenta $J$ and approximately the same effective quantum number ${\nu }_{\ln }$, and configuration interactions are apparent. The possible number of channels and their assignment are outlined.