Variational expansion for antiprotonic helium atoms

A very accurate variational expansion is suggested for calculation of nonrelativistic energies of the metastable antiprotonic helium atoms ${\mathrm{He}}^{+}\overline{p}.$ 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 ${10}^{-10}\mathrm{a}.\mathrm{u}.\mathrm{},$ two orders of magnitude better than in our previous calculations.