Elastic scattering of electrons (or positrons) from positronium and the photodetachment of the positronium negative ion

Abstract

The authors report accurate variational calculations of the 1,3S and 1,3P phaseshifts for the elastic scattering of electrons (or positrons) by positronium up to the n=2 threshold. Higher-order phaseshifts are evaluated both in a static-exchange model and in an adiabatic-exchange model to give the total elastic, momentum transfer, ortho-para conversion and elastic differential cross sections. The positions of the minima in the elastic differential cross section are given for several values of k2. New 3P resonances are reported. The 1P continuum wavefunction is used together with an accurate variational wavefunction for the ground state of Ps- to obtain the photodetachment cross section of Ps-, and both length and velocity results are checked by evaluating the sum rule S-1.