Algebraic coupled-state method for positron-ion collisions

Abstract

The Harris-Nesbet variational method has been considered for an accurate calculation of positron collisions with hydrogen-like ions. We applied our newly developed computer code for positron collisions with hydrogen-like ions to a benchmark calculation at energies below the first excitation threshold of the ions. Very accurate results of phase shift have been obtained for the first time for partial-wave scattering from various hydrogen-like ion targets, with L equal up to 6. The accuracy of the results has been double-checked by carrying out calculations using different large coupling schemes. Our results were compared with those calculated by other research groups who had employed different numerical methods for their calculations.

Positron scattering and annihilation from hydrogenlike ions

“…The phase shifts agree very well with those of a previous variational calculation by Gien [5,6] for those ions and momenta common to both calculations and demonstrate that the CI-Kohn approach is capable of obtaining phase shifts comparable in accuracy to calculations which explicitly include the electron-positron distance in the scattering wave function. Indeed, we believe that the present phase shifts are marginally more accurate than those of Gien since they are slightly more positive.…”

“…The CIKOHN ϱ p-wave phase shifts are also in reasonable agreement with the variational phase shifts of Gien [5,6]. The size of the L max → ϱ correction is less than 1% at all momenta listed in Table III.…”

“…The comparison with the phase shifts of Gien [6] for Li 2+ and B 4+ is generally very good with agreement at the 1 -2% level being typical. Once again, the CIKOHN ϱ phase shifts are slightly more positive than those of Gien, which suggests that they may be slightly more accurate.…”

“…The present phase shifts are compared with those of Bransden, Noble, and Whitehead (BNW) [4] and the Harris-Nesbet variational results of Gien [5,6]. The results of the Gien E6PS basis are presented.…”

“…More recently, Bransden et al [4] solved the Lippmann-Schwinger equation in a mixed basis of e + -He + and Ps-He 2+ channels to obtain relatively accurate phase shifts for the positron-He + system. Most recently, the Harris-Nesbet variational method has been applied by Gien to give phase shifts for positron scattering for the various ions (He + , Li 2+ , Be 3+ , and B 4+ ) in the elastic-scattering region [5,6].…”