### Abstract

Electron-positron annihilation rates calculated directly from the electron and positron densities are known to underestimate the true annihilation rate. A correction factor, known as the enhancement factor, allows for the local increase of the electron density around the positron caused by the attractive electron-positron interaction. Enhancement factors are given for positrons annihilating with the 1s electron in H, He+, He, Li2+, and Li+. The enhancement factor for a free positron annihilating with He+ and He is found to be close to that of ortho-positronium (i.e., Ps in its triplet state) annihilating with these atoms. The enhancement factor for Ps-He scattering is used in conjunction with the known annihilation rate for pickoff annihilation to derive a scattering length of 1.47 a0 for Ps-He scattering. Further, enhancement factors for e+ -Ne and e+ -Ar annihilation are used in conjunction with the pickoff annihilation rate to estimate scattering lengths of 1.46 a0 for Ps-Ne scattering and 1.75 a0 for Ps-Ar scattering. � 2005 The American Physical Society.

Original language | English |
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Pages (from-to) | 62707-62713 |

Number of pages | 7 |

Journal | Physical Review A - Atomic, Molecular, and Optical Physics |

Volume | 72 |

Issue number | 6 |

Publication status | Published - 2005 |

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## Cite this

Mitroy, J. (2005). Determination and applications of enhancement factors for positron and ortho-positronium annihilations.

*Physical Review A - Atomic, Molecular, and Optical Physics*,*72*(6), 62707-62713.