Atomic core-polarization effects in metastable hadronic helium atoms

Abstract

A theoretical consideration is presented concerning the atomic core-polarization effect on the E1 transitions of large-l circular orbitals in hadronic helium atoms (${\mathit{e}}^{\mathrm{-}}$ ${\mathit{X}}^{\mathrm{-}}$ ${\mathrm{He}}^{2+}$), where the ${\mathit{e}}^{\mathrm{-}}$ occupies the 1s orbital and the negative hadron (${\mathit{X}}^{\mathrm{-}}$) occupies a large-l circular orbital. The first-order mixing of the 2p electron configuration due to the repulsive ${\mathit{e}}^{\mathrm{-}\mathrm{-}}$ ${\mathit{X}}^{\mathrm{-}}$ interaction gives rise to a substantial suppression (∼1/3) of the E1 transitions, compared with a single-particle estimate, since the slowly moving particle (${\mathit{X}}^{\mathrm{-}}$) polarizes the electron cloud in the opposite direction. Recently discovered metastable states of antiprotonic helium atoms are discussed.