Threshold behavior of positronium formation in positron–alkali-metal scattering

Near-threshold behavior of positronium-antiproton scattering

Enhancement of positron-atom annihilation near the positronium formation threshold.

The behavior of the positron- 2 gamma annihilation rate on an atomic target near the positronium (Ps) formation threshold is determined. When the positron energy epsilon approaches the threshold epsilon(thr) from below, the effective number of electrons contributing to the annihilation, Z(eff), grows as Z(eff) approximately A/square root of [epsilon(thr)-epsilon], where A is related to the size...

Evidence for positronium molecule formation at a metal surface

We have observed a reduction in the amount of positronium emitted from an atomically clean Al 111 surface that depends on the incident positron beam density. We interpret this as evidence for the formation of molecular positronium, created following interactions between two pseudopositronium atoms trapped in a surface state. We find that this process is highly sensitive to the condition of the ...

Resonances in positronium-rubidium and positronium-cesium scattering

Scattering of ortho positronium (Ps) by cesium and rubidium atoms has been investigated employing a three-Ps-state coupled-channel model with Ps(1s,2s,2p) states using a time-reversal-symmetric regularized electronexchange model potential. We find a narrow S-wave singlet resonance at 5.057 eV of width 0.003 eV in the Ps-Rb system and at 5.067 eV of width 0.003 eV in the Ps-Cs system. Singlet P-...

Positronium-positronium interaction: Resonance, scattering length, and Bose-Einstein condensation

The low-energy scattering of ortho positronium (Ps) by ortho Ps has been studied in a full quantum mechanical coupled-channel approach. In the singlet channel (total spin sT = 0) we find Sand P-wave resonances at 3.35 eV (width 0.02 eV) and 5.05 eV (width 0.04 eV), respectively and a binding of 0.43 eV of Ps2. The scattering length for sT = 0 is 3.95 Å and for sT = 2 is 0.83 Å. The small sT = 2...