Differential, state-to-state, and total-charge-transfer cross sections for H⁺ colliding with Ar

Differential, direct, state-to-state, and summed charge-transfer cross sections in collisions of protons with argon atoms have been studied at collision energies ranging from 10 eV to 100 keV by means of two different methods: a semiclassical coupled-channel and a nonadiabatic electron-nuclear dynamics approach. Our results for the direct differential cross section show excellent agreement between theory and the available experimental data. We discuss the effect of the interference in the differential cross sections caused by different projectile trajectories that have the same scattering angle. A comparison of the methods shows that the repulsive and attractive parts of the interaction potential are required in the trajectory dynamics for the correct description of the deflection of the projectile and the electron capture probability at the low-intermediate energies and intermediate to low impact parameter region. For energies greater than ∼4 keV, the theoretical methods follow the trend of the experimental data. We find that the 2s, 2p, and total cross sections change about three orders of magnitude for energies below 1 keV down to 0.01 keV. We also find that the electron capture probability into the 1s orbital as a function of the projectile energy and impact parameter forms a ridge that extends toward the high impact parameter region and low projectile energies.