DIELECTRONIC RECOMBINATION OF U28+ ATOMIC IONS

Dielectronic recombination cross sections for U28+ are calculated in t he distorted-wave approximation and compared with measurements obtaine d using an electron-ion merged beams apparatus. Although the experimen t covered energies between 0 and 420 eV, the theoretical calculations were restricted to energies below 180 eV, where the most important res onance structures occur. The theoretical cross sections involving Delt a n=0 excitations from the 5s(2)5p(2) ground configuration are found t o be equally well described using either semirelativistic wave functio ns, as found in the AUTOSTRUCTURE codes, or fully relativistic wave fu nctions, as found in the HULLAC codes. The main features of the experi mental spectrum are well identified for the 80-180 eV energies, althou gh complicated by the possible presence of unknown fractions of metast able levels. However, the resonance structures observed at the energie s less than 80 eV, in the vicinity of a huge zero-energy peak, remain largely unexplained.