Critical points, which represent minima in differential scattering cross sections as a function of scattering angle and incident projectile energy, are theoretically predicted for elastic scattering of low-energy positrons by Ar, Kr, and Xe. It is demonstrated that these points arise due to low-energy positron diffraction effects.
Wadehra JM, Stein TS, Kauppila WE. Critical points in low-energy positron-atom scattering. Phys. Rev. A. 1984;29(5):2912-2914. doi: 10.1103/PhysRevA.29.2912