Positron annihilation in the positronium negative ion Ps−

The energy and other bound state properties of the positronium negative ion Ps− (or e−e+e−) are determined to high accuracy with the use of extremely accurate variational wave functions. The determined total energy of the ground state in the Ps− ion E=−0.26200507023298010776885a.u. is the lowest variational value obtained for this system. The two-, three- and one-photon annihilation rates are determined with the highly accurate wave functions. We also consider the computation of the lowest order relativistic and QED corrections.