Isotope-shift analysis with the 4f^146s^2~¹S₀- 4f^135d6s^2 (J=2) transition in ytterbium

Measurements of isotope shifts have recently been attracting considerable attention due to their potentials in searching for new forces. We report on the isotope shifts of the 4f^146s^2~¹S₀- 4f^135d6s^2 (J=2) transition at 431 nm in Yb, based on absolute frequency measurements with an accuracy of 10 kHz. With these data, the hyperfine constants for ^173Yb are determined. To analyze these data further, electronic structure of ytterbium is theoretically calculated. The nuclear charge radii are estimated together with some previously reported isotope-shift data for other transitions. An analysis of the King plot for the 4f^146s^2~¹S₀- 4f^135d6s^2 (J=2) transition shows a good consistency with other transitions, resulting in a constraint on the existence of new bosons mediating the force between an electron and a neutron. The analysis motivates further precision measurements on isotope shifts of the narrow-linewidth transitions in ytterbium, not only for the even-mass isotopes but also for the odd-mass isotopes.