Positron scattering and annihilation on noble-gas atoms is studied ab initio using many-body theory methods for positron energies below the positronium formation threshold. We show that in this energy range, the many-body theory yields accurate numerical results and provides a near-complete understanding of the positron–noble-gas atom system. It accounts for positron-atom and electron-positron correlations, including the polarization of the atom by the positron and the nonperturbative effect of virtual positronium formation. These correlations have a large influence on the scattering dynamics and result in a strong enhancement of the annihilation rates compared to the independent-particle mean-field description. Computed elastic scattering cross sections are found to be in good agreement with recent experimental results and Kohn variational and convergent close-coupling calculations. The calculated values of the annihilation rate parameter Zeff (effective number of electrons participating in annihilation) rise steeply along the sequence of noble-gas atoms due to the increasing strength of the correlation effects, and agree well with experimental data.
|Number of pages||19|
|Journal||Physical Review A (Atomic, Molecular, and Optical Physics)|
|Publication status||Published - 10 Sep 2014|
Green, D. G., Ludlow, J. A., & Gribakin, G. F. (2014). Positron scattering and annihilation on noble-gas atoms. Physical Review A (Atomic, Molecular, and Optical Physics), 90, 032712. . https://doi.org/10.1103/PhysRevA.90.032712