Contribution of the exact Breit operator plus the electron state-dependent screening to the multiplet and fine structure of muon-electron atoms

We investigate for very general cases the multiplet and fine structure splitting of muonelectron atoms arising from the coupling of the electron and muon angular momenta, including the effect of the Breit operator plus the electron state-dependent screening. Although many conditions have to be fulfilled simultaneously to observe these effeets, it should be possible to measure them in the 6h- 5g muonic transition in the Sn region.

State-dependent volume isotope shifts of low-lying states of group-IIa and -IIb elements

Results of relativistic multiconfiguration Dirac-Fock calculations with an extended nucleus are used to analyze the volume isotope shifts of the resonance transitions in the group-IIa and -IIb elements as well as in Yb. This is done together with a review of the isotope shift theory, including a critical evaluation and comparison of the semiempirical calculation of volume isotope shifts commonly used today. Electronic factors F_i, proportional to differences of electronic densities over the nuclear volume, are discussed within various approximations and compared with experimental results.

State dependent volume isotope shift analysis of the low lying states of Ba I and Ba II

Relativistic multi-configuration Dirac-Fock wavefunctions, coupled to good angular momentum J, have been calculated for low lying states of Ba I and Ba II. The resulting electronic factors show good agreement with data derived from recent high-resolution laser spectroscopy experiments and results from a comparison of muonic and optical data.