Variational expansion for antiprotonic helium atoms

A very accurate variational expansion is suggested for calculation of nonrelativistic energies of the metastable antiprotonic helium atoms He⁺p̄. This expansion reflects the dual atomic-molecular nature of the system. Convergence of the results as a function of the increasing sets of basis functions shows an accuracy better than 10^-10a.u., two orders of magnitude better than in our previous calculations.