Experimental determination of core relaxation and screening effects on the wavefunction at a nucleus for stable isotopes of –

In this work results of the measurements of the isotope shifts and the hyperfine structure of 3 levels of singly ionized europium, which were hitherto not investigated (or investigated with lower precision), are presented. In the measurements laser induced fluorescence method in a hollow cathode lamp was applied for 9 spectral lines of europium ion. The perspective aim of the investigations was the search for the sources of discrepancy between the value of the wave function modulus at the nucleus resulting from ab initio calculations and the value obtained in parametrization of isotope shifts, in particular for configuration 4f65d6s and 4f65d2. This discrepancy may result both from an incorrect classification of the levels and from a larger value of specific mass shift than the one resulting from calculations, or from the effects of core relaxation and screening. On the basis of the results obtained in this work and those available in the literature parametrization of isotope shifts for odd configurations of Eu II was performed, wherein angular coefficients calculated with semi-empirical method were applied. Further the parameters obtained were compared to the results of ab initio calculations, both available in the literature, and performed by the authors with the use of a nonrelativistic code (MCHF-Froese Fischer) and a relativistic code (MCDF-Desclaux). Results of the work, after completion of the measurements for even levels of Eu II, constitute the basis for parametrization of isotope shifts for even configurations and determination of the sources of discrepancies discussed