Third-order isotope-shift constants for alkali-metal atoms and ions - art.no. 052501

We derive expressions for third-order matrix elements of one- and two-parti cle operators within the framework of relativistic many-body perturbation t heory and use these formulas to evaluate specific-mass isotope shifts and i sotope field shifts in atoms and ions with one valence electron. Third-orde r corrections to isotope-shift constants for 3s, 3p, and 3d levels in sodiu m and sodiumlike ions with Z=12-18 and Z=26 are given. Applications to 4s, 4p, 3d, and 4d levels in K and 4s, 4p, and 3d levels in Ca+ are also given. Comparisons are made with previous calculations and with experiment. Inclu ding third-order corrections improves the agreement between theoretical and experimental values of the specific-mass isotope-shift constants for the c ases considered.