Boundary-condition-determined wave function for the ground state of positronium ion (e)over-bar-ee

We have developed a one-parameter, model wave function for the positronium ion (e)over-bar-ee, which incorporates the correct cusp and coalescence properties when two particles are close to each other, and the asymptotic property when one of the electrons is far away. The predicted values for the energy and other properties are close to the exact values and generally superior to the values from a 13-parameter wave function