Three lowest S states of B9 e+ calculated with including nuclear motion and relativistic and QED corrections

We have performed high-accuracy quantum mechanical calculations for the three lowest S states of the beryllium ion (B9 e+). The nonrelativistic part of the calculations was done with the variational approach and explicitly included the nuclear motion (i.e., the finite-nuclear-mass approach). The nonrelativistic wave functions were expanded in terms of explicitly correlated Gaussian functions. These nonrelativistic functions were subsequently used to calculate the leading α2 relativistic corrections (α=1/c) and the α3 and α4 QED (quantum electrodynamics) corrections. In the α4 QED correction we only accounted for its dominant component typically contributing about 80% of the correction. With those the present results are the most accurate ever obtained for B9 e+. They also agree with the experimentally measured transitions within less than 0.1 cm-1.