The calculation of p-wave phaseshifts for positron-helium scattering

Elastic scattering of low-energy positron by atom

“…The elastic scattering crosssection (both total, Figures 3 and 4, where they are compared with some experimental [5,6] and theoretical results [6,7,8,9,10]. Our previous results (RPA (1) ) [7] are different from the present results (RPA (imp) ).…”

“…In the case of e + -He scattering, accurate results have been obtained by the variational methods [4,5,6], and the optical potential method [6,7,8,9].…”

“…2. Total cross section for e + -He: solid line our result, dash [7], dot-dash [8], dots [9], black square [5] In order to introduce the effect of virtual positronium formation VPF (the results of the summation of an infinite sequence of the diagrams which represents the VPF terms are presented in Figure 1g) it is suggested [7] the "energy shift'' technique by replacing the binding energy hole ε β in the denominator of Eq. (5) by ε β HF − E p (where E p = −0.5Ryd).…”

Large Basis Calculation of Positron?Hydrogen Scattering at Low Energies

“…In kinematic regions with only a few open channels, variational techniques have frequently been used to compute the most accurate cross sections for electron-atom scattering. This is also true for positron-hydrogen scattering and there have been a number of calculations of phase shifts in the elastic scattering region below the positronium formation threshold at 6·8 eV (Schwartz 1961;Armstead 1968;Bhatia et ale 1971Bhatia et ale , 1974Humberston and Wallace 1972;Humberston and Campeanu 1980;Register and Poe 1975). Of these calculations, the phase shifts of Bhatia et ale (1971,1974) are generally regarded as the most accurate for the J == 0 and J == 1 partial waves.…”

“…A series of high quality variational calculations for the elastic and positronium formation cross sections have been performed by Humberston and collaborators (Humberston 1982(Humberston , 1984(Humberston , 1986Brown and Humberston 1985) for the J == 0, J == 1 and J == 2 partial waves. While the cross sections reported for the J == 0 and J == 1 waves are regarded as being close to exact, the calculations for the J == 2 partial wave did not achieve the same degree of precision and the J == 2 cross sections are expected to be accurate to only 10%.…”