Even-parity autoionizing levels of atomic uranium and their total angular momenta

Employing three-colour three-step resonance ionization spectroscopy, photoionization spectra of atomic uranium have been investigated extensively in the energy region 49,959-51,504 cm(-1). A detailed analysis of the photoionization spectra has resulted in the observation of 346 even-parity autoionizing levels including 199 new levels and a Rydberg series converging to the second-lowest ionic level (L-6(11/2)o) of uranium. Using the method of laser polarization combinations as well as the method of total angular momentum (J) selection rules, the J values of 72 of these autoionizing levels have been assigned unambiguously. Out of these 72 levels, the unique J values of 56 autoionizing levels have been determined for the first time, while it has been confirmed for the remaining 16 reported previously.