Polarisation effects in low-energy positron-molecule scattering

The UK molecular R-matrix method has been adapted to treat positron collisions from polyatomic targets. A simple empirical enhancement factor which corrects for the underestimation of electron-positron polarisation and correlation effects in the calculations performed with the static-plus-polarization model at low scattering energies is presented. Application of this model to positron scattering from carbon dioxide at energies below 8 eV is discussed. Introduction of the enhancement factor improves the integral cross sections significantly and introduces structures in the differential cross sections consistent with other studies. The prospects for a fully ab initio treatment of this problem are discussed. (c) 2007 Elsevier B.V. All rights reserved.