Isotope shift and nuclear charge radii of barium isotopes

Abstract

Relativistic coupled-cluster calculations of hyperfine structure and field isotope shift constants for the 6s and 6p states in Ba⁺ have been performed. Comparison with experimental hyperfine structures shows agreement within a few per cent and the authors assign a similar uncertainty to the electronic factor for the field shift: F(6s to 6p₃2/)=-4.20 (13) GHz fm^-2. This value, which is about 18% smaller than semi-empirical estimates used in earlier works, has been used to extract revised values for the changes delta (r²) in nuclear charge radii using optical isotope shifts for ^122-148Ba and muonic results for the stable isotopes ^134-138Ba. Also the factor B/Q, relating the observed quadrupole hyper-fine structure to the nuclear quadrupole moment, was calculated, giving B/Q=374 (4) MHz b^-1.