Positron–molecule scattering experiments

Abstract

We have extended our measurements of the relative elastic differential cross sections (DCSs) and positronium formation cross sections ( Q Pss) for positron scattering to include molecules of varying complexity and symmetry. Diffraction effects observed in our earlier e +–Ar and e +–CH 4 DCS measurements [Phys. Rev. A 55 (1997) 4244] are shown to have disappeared for a linear tri-atomic molecule, CO 2. In contrast to the structureless, bell-shaped Ps-formation curves of H and H 2 [Phys. Rev. A 55 (1997) 361], the Ps-formation cross section curves for CH 4, CO 2, and SF 6 show structure which may be associated with electron transfer of inner orbital electrons of the molecule.