Variational calculation of positron-atom scattering using configuration-interaction-type wave functions
- Faculty of SITE, Northern Territory University, Darwin, Northern Territory 0909 (Australia)
The Kohn variational method is used with a configuration-interaction (CI)-type wave function to determine the phase shifts and Z{sub eff} for positron-copper scattering. The method is first tested for positron-hydrogen scattering and it is found to give phase shifts and Z{sub eff} within 1-2% of the best previous calculations. Although the phase shift for Cu converged more slowly with L{sub max} (the maximum angular momentum of the electron and positron orbitals included in the short-range basis), it was still possible to get reliable estimates of the phase shifts by including orbitals with l{<=}18 and the use of an extrapolation technique. Calculation of Z{sub eff} was more problematic since the convergence of Z{sub eff} with respect to L{sub max} was very slow. Despite the uncertainties, it was clear that the p-wave phase shift was showing signs of forming a shape resonance at about 0.5 eV incident energy. This resulted in a p-wave contribution to Z{sub eff} that was larger than that of the s wave for k{>=}0.1a{sub 0}{sup -1}. Speculative calculations based upon a model potential suggest that a p-wave shape resonance centered at thermal energies, e.g., about 0.025 eV, could result in a thermally averaged Z{sub eff} exceeding 10,000.
- OSTI ID:
- 20639760
- Journal Information:
- Physical Review. A, Vol. 67, Issue 6; Other Information: DOI: 10.1103/PhysRevA.67.062709; (c) 2003 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
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