Computational investigation of positron scattering from C-60

The low-energy (0-6-eV) behavior of positrons scattering from gaseous C-60 molecules is examined through a computational study which employs a nonempi rical modeling of all the relevant interaction forces (static, correlation, and polarization potentials). There is uncertainty concerning the most app ropriate correlation-polarization potential to use in the study of positron -molecule scattering. Hei-e we have considered two such potentials which ar e representative of the potentials which have been proposed for this purpos e. The coupled quantum scattering equations are solved in the body-fixed fr ame of reference, and the fixed-nuclei approximation is used to decouple th e nuclear motion during the collision. The elastic integral cross sections without positronium formation exhibit strong one-particle resonances in the very-low-energy region up to similar to 4 eV. The low-angular-momentum sca ttering components are shown to be the dominant contributions to trapped st ate wave functions. The existence of resonances in positron scattering from molecules is unusual. In the system studied here there are two types of re sonances. First there are angular-momentum barrier resonances with the posi tron trapped outside of the C-60 cage. Second, there are resonances of low angular momentum (l less than or equal to 2) with the positron trapped insi de of the C-60 cage by the repulsive interaction between the positron and t he nuclei. The possibility of the experimental observation of these resonan ces is also discussed. [S1050-2947(99)08511-X].