title: Coupling between positron-atom scattering channels above the first inelastic threshold.
abstract: Experimentally determined cross sections for the elastic scattering of positrons by argon and xenon atoms have been found to exhibit a steplike increase at the first inelastic threshold energy--i.e., that for positronium formation. Rather than supporting the existence of a cusplike behavior predicted theoretically, this feature, which is more pronounced for xenon, suggests the existence of an intermediate virtual positronium state which enhances the elastic interaction probability.
authors.affiliation: Department of Physics, University of Bath, Bath BA2 7AY, United Kingdom.
authors.forename: P G
authors.initials: PG
authors.lastname: Coleman
authors.forename: N
authors.initials: N
authors.lastname: Cheesman
authors.forename: E R
authors.initials: ER
authors.lastname: Lowry