Many-body theory for positronium-atom interactions

Abstract

A many-body-theory approach has been developed to study positronium-atom interactions. As first applications, we calculate the elastic scattering and momentum-transfer cross sections and the pickoff annihilation rate $^1Z_\text{eff}$ for Ps collisions with He and Ne. The cross section for He is in agreement with previous coupled-state calculations, and the momentum-transfer cross section for Ne agrees with available experimental data. $^1Z_\text{eff}$ is found to be 0.13 and 0.26 for He and Ne, respectively, in excellent agreement with the measured values.Comment: Accepted by Phys. Rev. Lett. (V2 contains update to text and Figs. 3 and 5. V3 contains further discussion on the calculation of pickoff annihilation rates.