Low-Energy Positronium Scattering from O2

The total cross-section of positronium scattering from molecular oxygen has been measured in the velocity range 0.27 − 1.50 a.u. (energy range 2 − 61 eV) and found to be close to the corresponding equivelocity electron cross-section above 0.87 a.u. (20 eV), as previously found by Brawley et al. Science 330 789 (2010). However, below this value the cross-section for positronium is observed to exceed that for electrons by up to a factor of 4 at the lowest energy. Measurements are compared to the predictions of low-energy resonant peaks in the elastic scattering cross-section calculated within a free-electron-gas model refined by applying corrections to the correlation energy for the interaction between Ps and the electron gas. Additionally, cross-sections for O− 2 formation and positronium break-up have been calculated using a classical trajectory Monte Carlo approach. Comparisons are made with earlier calculations and discussed in terms of both experimental and theoretical uncertainties

Roadmap on photonic, electronic and atomic collision physics: II. Electron and antimatter interactions

We publish three Roadmaps on photonic, electronic and atomic collision physics in order to celebrate the 60th anniversary of the ICPEAC conference. In Roadmap II we focus on electron and antimatter interactions. Modern theoretical and experimental approaches provide detailed insight into the many body quantum dynamics of leptonic collisions with targets of varying complexity ranging from neutral and charged atoms to large biomolecules and clusters. These developments have been driven by technological progress and by the needs of adjacent areas of science such as astrophysics, plasma physics and radiation biophysics. This Roadmap aims at looking back along the road, explaining the evolution of the field, and looking forward, collecting contributions from eighteen leading groups from the field

Ionization cross-sections for positron collisions with N2

The total and direct ionization cross-sections for positron impact on molecular nitrogen have been measured in the energy range from 5 eV to 850 eV. The results are compared with other experimental and theoretical determinations.ISSN:1434-6060ISSN:1434-607

Collimated positronium production from gases

New data for positronium beam production efficiency are presented. As a converter of positrons to forward-going positronium, O2 has been found to be as good as CO2 from ~250 to 400 eV. Preliminary data is also presented for the production efficiency from Ar at 2.8 eV