6s electron screening in isotope shifts of configurations 4f75d6s, 4f76s6d and 4f76s7d in europium

In the experimental part of this work, measurement results of isotope shifts and the hyperfine structure of nine electronic levels in europium atoms, obtained using the laser induced fluorescence method, are presented. In the case of five levels, these results were obtained for the first time and have no counterparts in the literature. Most of the levels measured are classified as belonging to configuration 4f76s7d. From the results obtained, on the basis of the sharing rule and the wavefunctions for the levels investigated, known from the literature, isotope shifts for pure configurations 4f76s7d and 4f76p2 were determined for the first time using the semi-empirical method, and the isotope shift values for configurations 4f76s6d, 4f75d2 and 4f76s8s were verified. Wavefunction values at the nucleus for all three configurations and contributions from individual electrons s and p* were calculated ab initio with the use of programs MCHF and MCDF, and compared to experimental results of isotope shifts. (paper)