J-dependence of optical isotope shifts in Sm II

Isotope shift measurements in 18 optical transitions between 8 samarium isotopes ASm have been taken (A=144, 146, 147, 148, 149, 150, 152, 154) using collinear laser ion beam spectroscopy. For the even-A isotopes, a direct-measurement technique was developed. A multidimensional King plot served to evaluate the term-related isotope shifts in the fine-structure multiplet 4f6(7F)5d8HJ. These shifts should show a linear dependence on J(J+1) in accordance with a crossed second-order approximation. A closer correlation is found between the isotope shifts and the fine-structure energies. Field shift and mass shift can be separated in order to calculate changes of mean-square charge radii delta (r2).