18 research outputs found
Complete Break Up of Ortho Positronium (Ps)- Hydrogenic ion System
The dynamics of the complete breakup process in an Ortho Ps - He+ system
including electron loss to the continuum (ELC) is studied where both the
projectile and the target get ionized. The process is essentially a four body
problem and the present model takes account of the two centre effect on the
electron ejected from the Ps atom which is crucial for a proper description of
the ELC phenomena. The calculations are performed in the framework of Coulomb
Distorted Eikonal Approximation. The exchange effect between the target and the
projectile electron is taken into account in a consistent manner. The proper
asymptotic 3-body boundary condition for this ionization process is also
satisfied in the present model. A distinct broad ELC peak is noted in the fully
differential cross sections (5DCS) for the Ps electron corroborating
qualitatively the experiment for the Ps - He system. Both the dynamics of the
ELC from the Ps and the ejected electron from the target He+ in the FDCS are
studied using coplanar geometry. Interesting features are noted in the FDCS for
both the electrons belonging to the target and the projectile.Comment: 14 pages,7 figure
Collisions of positronium with atoms and molecules
Positronium, Ps, is the atom-like bound state of an electron and its antimatter counterpart, the
positron. This work encompasses the experimental techniques required to produce a collimated
beam of Ps atoms and recent investigations of Ps collisions on a variety of atomic and molecular
targets to determine Ps total and fragmentation cross-sections. For the former experiment, the
present work is compared to theory - for which there is now very good agreement for low energy
Ps–He collisions - and to other projectiles where the present data shows that total cross-sections
for equivelocity Ps and electrons are nearly identical for a wide range of targets and velocities.
The Ps fragmentation measurements proceed via the detection of ejected electrons or positrons
for Ps collisions on Xe at 18 and 30 eV. Detection of ejected positrons is a unique signature of
Ps fragmentation and the recent integrated measurements for this process agree well with theory,
as do the shapes of the differential cross-sections with respect to the longitudinal energy of the
ejected positrons. Concerning these, the energy dependence of the positron distributions appear
similar for the present measurements on Xe and those previously measured for a He target. When
detecting ejected electrons, the experiment is sensitive to reactions in which the projectile and/or
target are ionised, and the integrated cross-sections indicate that target-ionisation is significant at
only ∼3 eV above threshold in Xe