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 open-shell type wave functions and the shifts of the resonance lines of 7 Li relative to 6 Li and of 11 B 2+ relative to 10 B 2+ are estimated to be 0.100 cm -1 and 0.688 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). The results are also compared with the values obtained using an alternative form of the mass polarization operator.