HYPERFINE-STRUCTURE STUDIES OF ZR-II - EXPERIMENTAL AND RELATIVISTIC CONFIGURATION-INTERACTION RESULTS

We report an experimental and theoretical study of the hyperfine struc ture (hfs) in various metastable levels in Zr-91 II. Hyperfine structu res in 11 levels arising from the 4d3 and 4d(2)5S Configurations were measured using the laser-rf double-resonance method in a collinear las er-ion-beam geometry. The hfs A and B constants were measured to a pre cision of 4 and 11 kHz, respectively. Less precise values for hfs cons tants for nine upper levels in the 4d(2)5p configuration were derived from optical spectra. Theoretically, the A and B constants for the met astable levels having J = 0.5 and 1.5 were calculated using a relativi stic configuration-interaction (RCI) approach. The final many-body wav e function produced energy gaps between the five J = 0.5 levels which differ from experiment by an average of 0.050 eV, whereas the correspo nding value for the ten J = 1.5 levels is 0.087 eV. For the two J = 0. 5 levels measured and calculated, the average error in A is 31.8 %. Fo r the three J = 1. 5 levels, the situation is better, with the average error in A being 9.2%. For comparison, the average errors in A using independent-particle Dirac-Fock (DF) wave functions were 88% and 136% for J =0.5 and 1.5, respectively. In all cases, the many-body (RCI) re sult represents a vast improvement from the DF result for the A values . The value for the electric-quadrupole moment of Zr-91 obtained from a comparison of the experimental B values and theoretical matrix eleme nts is 0.257(0.013) b. In addition, the calculations confirm a previou s report that the level at 17614.00 cm-1 reported in Moore's Atomic En ergy Levels, Vol. II (U.S. Government Printing Office, Washington, D.C ., 1971) is spurious.