dorsal/arxiv
View SchemaMultichannel Formalism for Positron-Hydrogen Scattering and Annihilation
| Authors | S L Yakovlev, C-Y Hu, D Caballero |
|---|---|
| Categories | |
| ArXiv ID | physics/0612123 |
| URL | https://arxiv.org/abs/physics/0612123 |
| DOI | 10.1088/0953-4075/40/10/003 |
| Journal | , J. Phys. B: At. Mol. Opt. Phys. 40 (2007) 1675-1693 |
Abstract
A problem to account for the direct electron-positron annihilation in positron-hydrogen scattering above the positronium formation threshold has been resolved within the time independent formalism. The generalization of the optical theorem is derived for the case when an absorption potential is present in the Hamiltonian. With this theorem the annihilation cross section is fully determined by scattering amplitudes. This allows us to separate out analytically the contribution of the positronium formation from the overall annihilation cross section. The rest is determined as the direct annihilation cross section. It is done uniformly below as well as above the positronium formation threshold. The multichannel three-body theory for scattering states in the presence of an imaginary absorption potential is developed in order to compute the direct $e^+ e^-$ annihilation amplitude. Special attention has been paid to an accurate definition of the coordinate part of the absorption potential as the properly constructed zero-range potential, which corresponds to the delta-function originated from the first order perturbation theory. The calculated direct annihilation cross section below the positronium formation threshold is in good agreement with results of other authors. The direct annihilation cross section computed with the formalism of the paper shows nonsingular behavior at the positronium formation threshold and is in good agreement with existing data. A number of $e^+ e^-$ direct annihilation cross sections and positronium formation cross sections in the energy gap between Ps$(1s)$ and H$(n=2)$ thresholds are reported. A sharp increase in the calculated direct annihilation cross section across the resonant energy is found for all first S and P-wave Feshbach resonances.
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"abstract": "A problem to account for the direct electron-positron annihilation in\npositron-hydrogen scattering above the positronium formation threshold has been\nresolved within the time independent formalism. The generalization of the\noptical theorem is derived for the case when an absorption potential is present\nin the Hamiltonian. With this theorem the annihilation cross section is fully\ndetermined by scattering amplitudes. This allows us to separate out\nanalytically the contribution of the positronium formation from the overall\nannihilation cross section. The rest is determined as the direct annihilation\ncross section. It is done uniformly below as well as above the positronium\nformation threshold. The multichannel three-body theory for scattering states\nin the presence of an imaginary absorption potential is developed in order to\ncompute the direct $e^+ e^-$ annihilation amplitude. Special attention has been\npaid to an accurate definition of the coordinate part of the absorption\npotential as the properly constructed zero-range potential, which corresponds\nto the delta-function originated from the first order perturbation theory. The\ncalculated direct annihilation cross section below the positronium formation\nthreshold is in good agreement with results of other authors. The direct\nannihilation cross section computed with the formalism of the paper shows\nnonsingular behavior at the positronium formation threshold and is in good\nagreement with existing data. A number of $e^+ e^-$ direct annihilation cross\nsections and positronium formation cross sections in the energy gap between\nPs$(1s)$ and H$(n=2)$ thresholds are reported. A sharp increase in the\ncalculated direct annihilation cross section across the resonant energy is\nfound for all first S and P-wave Feshbach resonances.",
"arxiv_id": "physics/0612123",
"authors": [
"S L Yakovlev",
"C-Y Hu",
"D Caballero"
],
"categories": [
"physics.atom-ph",
"physics.atm-clus"
],
"doi": "10.1088/0953-4075/40/10/003",
"journal_ref": ", J. Phys. B: At. Mol. Opt. Phys. 40 (2007) 1675-1693",
"title": "Multichannel Formalism for Positron-Hydrogen Scattering and Annihilation",
"url": "https://arxiv.org/abs/physics/0612123"
},
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