Positron scattering and annihilation from hydrogenlike ions

Abstract

The Kohn variational method is used with a configuration-interaction-type wave function to determine the J = 0 and J = 1 phase shifts and annihilation parameter Z eff for positron-hydrogenic ion scattering. The phase shifts are within 1 -2% of the best previous calculations. The values of Z eff are small and do not exceed unity for any of the momenta considered. At thermal energies Z eff is minute with a value of order 10 −50 occurring for He + at k = 0.05a 0 −1 . In addition to the variational calculations, analytic expressions for the phase shift and annihilation parameters within the Coulomb wave Born approximation are derived and used to help elucidate the dynamics of positron collisions with positive ions.

Transport theory for low-energy positron thermalization and annihilation in helium

“…The G 1 value of 3.96 is 30% larger than G 0 . The tendency for the p-wave enhancement factor to be significantly larger than the s-wave enhancement factor has been noticed for other systems [34][35][36]46].…”

“…Since there have been no values of Z 2,eff (v) published, recourse is made to recent calculations of the He + ion [35,36]. The d-wave enhancement factor is 20% larger than the p-wave enhancement factor.…”

“…This means that the errors in using an energy-independent enhancement factor should not be too large [31,32]. There have been a number of investigations that have shown that a single multiplicative factor (for each L) can adequately represent the magnitude and energy dependence over the energy range below the first excitation threshold [15,[33][34][35][36].…”

Positron Annihilation In Xe Atoms

“…This has been the subject of extensive experimental and theoretical work [1][2][3][4][5][6][7][8][9][10][11]. This has been the subject of extensive experimental and theoretical work [1][2][3][4][5][6][7][8][9][10][11].…”

Comment on “Multireference configuration-interaction calculations for positronium halides” [J. Chem. Phys. 122, 054302 (2005)]

“…6 The number of natural orbitals ͑NOs͒ used by Saito is different for electrons and positrons at ᐉ = 8. It has been found in all our calculations [6][7][8][9][10] that the optimized Laguerretype orbital ͑LTO͒ basis sets used to represent the positron and electron orbitals become identical as ᐉ increases. The high-ᐉ orbitals needed in mixed electron-positron systems arise due to the tendency of the electron and positron to coalesce into something that resembles the Ps ground state.…”