Isotope shift in Li and B²⁺

The mass polarization or specific isotope shift of the 1s 2 2s 2 S and 1s 2 2p 2 P levels of Li and B 2+ is calculated using the 45-parameter wave functions of Weiss. The specific shifts of the resonance lines of 7 Li relative to 6 Li and of 11 B 2+ relative to 10 B 2+ are calculated to be 0 186 cm -1 and 0.843 cm -1 respectively, compared with the observed values 0.157 cm -1 , 0 930 cm -1 (Δ J = 0) and 0.970 cm -1 (Δ J = 1) of Burke and of Hughes.