Abstract. The authors have investigated various aspects of polarisation/correlation effects at low energies for the prototypical positron-N₂ system. First, they have found that, like positron-H₂ cross sections, those for this system are highly sensitive to terms in the (adiabatic) polarisation potential that explicitly depend on the sign of the charge of the projectile. Insight into the nature of these sign-dependent distortions is afforded by three-dimensional graphs of polarised N₂ density functions. Second, they have explored and characterised nonadiabatic (correlation) effects in this system using a simple two-parameter model, they have found that the onset of these effects in the near-target region in positron scattering is much more gradual than in electron scattering. By including in scattering calculations adiabatic and non-adiabatic effects, they obtain theoretical positron-N₂ cross sections in good agreement with recent experimental data.

Print publication: Issue 1 (14 January 1989)