Nonadiabatic coupling in the (p)over-bar-He+ system

Metastable states of the (p)over-bar-He+ system are studied in the adiabati c and in the united-atom representations. The upper and lower bounds on the energy shifts with respect to the Born-Oppenheimer approximation are obtai ned by taking into account the nonadiabatic coupling of the states that bel ong both to the discrete and to the continuous parts of the electron spectr um. The limits within which the Born-Oppenheimer picture can be used to des cribe the metastable states are established. An efficient scheme for calcul ating the energy levels and wave functions is implemented.