Optical Potential Calculations of Positron--H₂ Elastic Collision

We report the calculations of the elastic scattering differential cross section for positron--H₂ collisions with the impact energy below the positronium formation threshold. Our calculation is based on the static-exchange-optical model which has obtained great success in the case of electron scattering. The effective potential used here includes the static and optical potentials. The optical method can completely include the second-order effect arising from real and virtual excitation of target states, which is important for the scattering. A comparison is made with the available theoretical calculations.