Positron attachment to helium in the³S state

Abstract

A generalized Hylleraas trial function, properly antisymmetrized in the electron coordinates, is used to investigate positron attachment to 3S helium. A state lying below the ground state of the 3S system (-4.35 Ryd) and which would also be stable against dissociation into He+ and Ps in their ground states (-4.5 Ryd) is searched for (unsuccessfully). When the mass of the positron (and hence the energy of ground-state Ps) is allowed to vary, however, such a stable state is obtained for m<or=0.94; this critical mass is so close to the physical value that further calculations with improved trial functions are indicated.