Positron Scattering and Annihilation from the Hydrogen Molecule at Zero Energy

The confined variational method is used to generate a basis of correlated Gaussians to describe the interaction region wave function for positron scattering from the H-2 molecule. The scattering length was approximate to-2.7a(0) while the zero energy Z(eff) of 15.7 is compatible with experimental values. The variation of the scattering length and Z(eff) with internuclear distance was surprisingly rapid due to virtual state formation at R approximate to 3.4a(0).