The energy dependence of the positronium formation cross section in helium
- 14 November 1993
- journal article
- Published by IOP Publishing in Journal of Physics B: Atomic, Molecular and Optical Physics
- Vol. 26 (21) , 3951-3957
- https://doi.org/10.1088/0953-4075/26/21/027
Abstract
The total cross section for positronium formation in helium for positrons of energies E from threshold (17.8 eV) to 250 eV has been measured using a gas cell transmission method. The results indicate that the cross section above E=60 eV is satisfactorily described by 0.5e-0.02E pi a02, tending to zero at energies close to 200 eV. The approximate description of the cross section at intermediate energies, falling as E-2.5, is consistent with a number of theoretical predictions but is in conflict with earlier experiments, which show an E-1 behaviour. The implications of these measurements are discussed, with particular reference to the observed merging of the total cross sections for positron- and electron-helium scattering at intermediate energies.Keywords
This publication has 19 references indexed in Scilit:
- Positronium formation in then=1 andn=2 states in-He scatteringPhysical Review A, 1992
- Positronium formation in positron-helium collisionJournal of Physics B: Atomic, Molecular and Optical Physics, 1990
- Single-electron–removal processes in collisions of positrons and protons with helium at intermediate velocitiesPhysical Review A, 1988
- Partial-Cross-Section Measurements for Ionization of Helium by Positron ImpactPhysical Review Letters, 1986
- Absence of energy loss in positron emission from metal surfacesPhysical Review B, 1985
- Positronium Formation in Collisions of Positrons with He, Ar, andPhysical Review Letters, 1983
- Positronium formation cross sections in the inert gasesJournal of Physics B: Atomic and Molecular Physics, 1983
- Measurements of total scattering cross sections for intermediate-energy positrons and electrons colliding with helium, neon, and argonPhysical Review A, 1981
- Positron-helium collisions: Positronium formation into an arbitrary excitedstatePhysical Review A, 1980
- A reappraisal of the experimental cross sections for low-energy positron-helium scatteringJournal of Physics B: Atomic and Molecular Physics, 1978