THE STRUCTURE OF EXOTIC ATOMS CONTAINING POSITRONS AND POSITRONIUM

The structures of a number of exotic atoms with an attached positron o r positronium atom are studied using a large-scale variational expansi on in terms of a basis of explicitly correlated Gaussian functions. Th e binding energies and annihilation rates for seven exotic species wit h electronically stable ground states, namely HPs, Lie(+), LiPs, Bee(), Nae(+), NaPs and Mge(+) have been predicted. The binding energy for HPs, 0.038 1944 Hartree, is the largest attained so far. Two of the s pecies, Lie(+) and Nae(+), with approximate binding energies of 0.0024 and 0.0005 Hartree respectively, are seen to have structures best des cribed as a positronium atom orbiting a residual Li+ or Na+ positively charged core. The Bee(+) atom with an approximate binding energy of 0 .0028 Hartree is best characterized as a positron orbiting a polarized Be core. The binding energy of the Mge(+) ground state, 0.014 Hartree , is larger than that of any other positronic atom (a neutral atom wit h an attached positron). The LiPs and NaPs atoms, with approximate bin ding energies of 0.012 and 0.0072 Hartree respectively, have structure s similar to HPs although the binding energies are smaller and the val ence electrons and the positron are found at larger distances from the nucleus.