Electron collisions with Fe-peak elements: Forbidden transitions between the low lying valence states 3d6, 3d54s, and 3d54p of Fe III:

Effective collision strengths are presented for the Fe-peak element Fe III at electron temperatures (Te in degrees Kelvin) in the range 2 × 103 to 1 × 106. Forbidden transitions results are given between the 3d6, 3d54s, and the 3d54p manifolds applicable to the modeling of laboratory and astrophysical plasmas.

Electron/positron collisions with positronium

We report results for e(+/-)-Ps(Is) scattering in the energy range up to 80 eV calculated in 9-state and 30-state coupled pseudostate approximations. Cross-sections are presented for elastic scattering, ortho-para conversion, discrete excitation, ionization and total scattering. Resonances associated with the Ps(n = 2) threshold are also examined and their positions and widths determined. Very good agreement is obtained with the variational calculations of Ward et al. [J. Phys. B 20 (1987) 127] below 5.1 eV. (C) 2004 Elsevier B.V. All rights reserved.

Positronium formation in positron-noble gas collisions

Distorted-wave Born approximation calculations for Ps formation in positron impact on He, Ne, Ar, Kr and Xe are reported for the energy range up to 200 eV. Capture into the n = 1, 2 and 3 states of Ps is calculated explicitly and 1/n(3) scaling is used to estimate capture into states with n > 3. The calculations for the heavier noble gases allow for capture not only from the outer np(6) shell of the atom but also from the first inner ns(2) shell. However, the inner shell capture is found to be very small. Although by no means unambiguous, the calculations provide some support to the conjecture of Larrichia et al. [J. Phys. B 35 (2002) 2525] that the double peak and shoulder structures observed experimentally for Ps formation in Ar, Kr and Xe arise from formation in excited states. (C) 2004 Elsevier B.V. All rights reserved.

Atomic collisions involving positrons

In this short review we look at bound states, positron-atom scattering. positronium-atom scattering. positronium-positronium scattering, cold antihydrogen and annihilation. (c) 2005 Published by Elsevier B.V.

Positronium-atom collisions

New results are presented for Ps(1s) scattering by H(1s), He(1(1)S) and Li(2s). Calculations have been performed in a coupled state framework, usually employing pseudostates, and allowing for excitation of both the Ps and the atom. In the Ps(1s)-H(1s) calculations the H- formation channel has also been included using a highly accurate H- wave function. Resonances resulting from unstable states in which the positron orbits H- have been calculated and analysed. The new Ps(1s)-He(1(1)S) calculations still fail to resolve existing discrepancies between theory and experiment at very low energies. The possible importance of the Ps(-) formation channel in all three collision systems is discussed. (C) 2004 Elsevier B.V. All rights reserved.