Field isotope shifts in the 6s-6p and 4f-5d transitions from the 4f^6 6s^2 ^7F_J ground multiplet of Sm I

Abstract

Multiconfiguration Dirac-Fock (MCDF) calculations are used to interpret the field shift contributions to isotope shifts of Sm I in visible and near-UV transition lines. The investigated lines correspond to the transitions between the ground configuration 4f^6 6s^2 and the excited configurations 4f^6 6s6p and 4f^5 5d6s^2. For the 6s-6p transition the field shift is negative as a result of the reduced 6s electron occupation, whereas for the 4f-5d transition the field shift is positive because of the decreased screening of 6s and inner-shell electrons. MCDF calculations for the electron charge density at the origin that include the configuration mixing effect agree well with the electronic factor ratios derived from experimental data with the exception of a few cases of 6s-6p transitions.