TY - JOUR

T1 - Determination and applications of enhancement factors for positron and ortho-positronium annihilations

AU - Mitroy, James

PY - 2005

Y1 - 2005

N2 - 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.

AB - 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.

KW - Carrier concentration

KW - Electron scattering

KW - Electrons

KW - Helium

KW - Electron-positron annihilation rates

KW - Electron-positron interactions

KW - Ortho-positronium annihilations

KW - Positrons

M3 - Article

SN - 1050-2947

VL - 72

SP - 62707

EP - 62713

JO - Physical Review A - Atomic, Molecular, and Optical Physics

JF - Physical Review A - Atomic, Molecular, and Optical Physics

IS - 6

ER -