Elastic and rotational excitation of the hydrogen molecule by 1--200-eV positron impact

Pure elastic scattering (J = 0→J' = 0 and J = 1→J' = 1), rotational excitation (J = 0→J' = 2 and J = 1→J' = 3), and average elastic (pure elastic plus rotational excitation) cross sections of the hydrogen molecule by 1--200-eV positrons are computed by using the adiabatic approximation in which the Glauber-type eikonal amplitude for a fixed molecular orientation is considered as input. Both differential and total scattering cross sections are calculated. Momentum-transfer cross sections are also obtained. Two different model effective potentials for positron--hydrogen-molecule interactions have been considered. Effects of positronium formation channel are neglected. Comparison is made with the recent measurements as well as with the available theoretical calculations. Below the positronium formation threshold average total elastic-scattering cross sections are found to reproduce the experimental data quite accurately. Electron and positron scattering cross sections at intermediate energies are compared. The effects of polarization interaction are found to be significant even at 200 eV