Comparison of phase shifts and cross sections as a function of velocity for positron, electron and positronium elastic scattering from helium*

Previously, it has been shown that there is a remarkable degree of similarity between the total cross section for electron-helium and positronium-helium scattering as a function of velocity [1]. Using the Kohn and inverse Kohn variational methods we have computed S-, P-, D- and F-wave phase shifts for positron-helium scattering [2, 3]. Using the inverse Kohn phase shifts we have computed the partial-wave, elastic-differential, elastic-integrated and momentum-transfer cross sections for positron-helium scattering in the energy range where the only open channel is elastic scattering (ignoring positron annihilation) [3]. Also, using phase shifts from the literature for electron scattering and positronium scattering from helium [4-6], we have computed the corresponding cross sections. Recently, we have compared the phase shifts and cross sections as a function of velocity for the three projectiles (positron, electron and Ps) [3]. We plan to present at the GEC 2021 meeting this comparison.

[1] S. J. Brawley, S. Armitage, J. Beale, D. E. Leslie, A. I. Williams, G. Laricchia, Science 330, 789 (2010).

[2] P. Van Reeth and J. W. Humberston, J. Phys. B 32, 3651 (1999).

[3] C. M. DeMars, S. J. Ward and P. Van Reeth, http://meetings.aps.org/Meeting/DAMOP21/Session/V01.17

[4] Nirmal K Sarkar et al 1999 J. Phys. B: At. Mol. Opt. Phys. 32 1657

[5] A. L. Sinfailam and R K Nesbet Phys. Rev. A 6, 2118 (1972)

[6] R. K. Nesbet Phys. Rev. A 20, 58 (1979)