The second spectrum of niobium: I. Accurate fine structure study of even-parity levels

For the first time, a parametric analysis of the fine and hyperfine structure for even-parity levels of Nb II, involving 17 configurations, has been performed. The interpretation has been carried out based on a linked-parameter method of level-fitting calculations in a large multiconfiguration basis. The sets of fine structure parameters, the leading eigenvector percentages of levels, as well as their calculated magnetic Lande g-factors are newly given. Furthermore, we confirm on the whole the validity of the attributions to term designations, previously proposed. The single-electron hyperfine structure parameters are determined in their entirety for Nb-93 II for the model space (4d + 5s)(4) with a good accuracy and confirmed by ab initio calculations. Finally, a complete list of the predicted magnetic hyperfine structure constants A of all levels of this model space was generated.