The recent production of atoms of antihydrogen as well as advances in
particle trap and beam technologies have generated considerable interest in
the interaction of antiparticles with regular matter and with each other.
Though it is tempting to think of a positron as just a "positive electron"
in terms of its interaction with atoms and molecules, there are significant
differences that are most apparent at low and intermediate energies. One of
the most interesting phenomena in the field of positron collisions with
matter---and one that has no electron-scattering counterpart---is the
formation of real and virtual positronium (Ps) and the manner in which this
charge-exchange process affects the elastic scattering. There is also keen
interest in making and trapping "exotic" systems, such as antihydrogen and
positronium hydride, for use in basic research, and potentially, as an
extremely compact energy storage mechanism.
The goal of the current research is to modify and extend existing quantum
chemistry technologies so that accurate interaction potential surfaces can
be used to compute integrated total and differential cross sections (DCS) for a variety of
positron-atom and positron-molecule systems.
Some of the distinguishing features of this research include:
- The use of concurrent computers
and algorithms to extend what is
- A new treatment of
short-range correlation between the positron and the
electrons of the target.
- Downloadable results for
positron collisions with various target atoms and molecules.
The Paper Chase
If you are interested in obtaining more information about this topic, try
J. Franz , F. A. Gianturco, K. L. Baluja, J. Tennyson, R. Carey, R.
Montuoro, R. R. Lucchese, T. Stoecklin, P. Nichols, T. L. Gibson,
"Correlation-Polarization Effects In Electron/Positron Scattering From
Acetylene: A Comparison Of Computational Models," Nucl. Instrum. Methods
Phys. Res. B 266, 425-434 (2008).
F.A. Gianturco, P. Nichols, T.L. Gibson, and R.R. Lucchese,
"Metastable Trapping of Low-Energy Positrons by Cubane: A Computational
Experiment," Phys. Rev. A 72, 032724 (2005).
F.A. Gianturco, T.L. Gibson, P. Nichols, R.R. Lucchese, and T. Nishimura,
"Modelling Dynamical Correlation Forces In Low-Energy Positron Scattering
From Polyatomic Gases: A Comparison for CH4," Radiat. Phys. Chem. 68,
673-680 (2003). [Link].
Preprint: [pdf] (217 KB).
- Book Chapter:
Robert R. Lucchese, F. A. Gianturco, P. Nichols, and Thomas L. Gibson,
"A Test Calculation on SF6 of Model Potentials for Correlation and
Polarization Effects in Positron Scattering from Molecules," Chapter 25 in
New Directions in Antimatter Physics and Chemistry, edited by
Clifford M. Surko and Franco A. Gianturco (Kluwer Academic, Dordrecht, 2001). Preprint:
[gzipped ps] (494 KB);
[zipped ps] (494 KB); [pdf] (700 KB).
Thomas L. Gibson, "Low-Energy Positron-H2 Collisions in the
Distributed Positron Model," J. Phys. B 25, 1321-1336 (1992).
Thomas L. Gibson, "A Modified Adiabatic Approach to Positron-Atom and
Positron-Molecule Polarization Potentials: Application to Positron-He
Scattering," J. Phys. B 23, 767-776 (1990).
Brian K. Elza, Thomas L. Gibson, Michael A. Morrison, and Bidhan C. Saha,
"Non-Adiabaticity and Other Aspects of Polarisation in Positron-Molecule
Scattering," J. Phys. B 22, 113-130 (1989).
Michael A. Morrison, Thomas L. Gibson, and David Austin,
"Polarization Potentials for Positron-Molecule Collisions:
Positron-H2 Scattering," J. Phys. B 17, 2725-2745
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