Acceleration effects in slow ion-atom collisions from a first-principles dynamics

Slow ion-atom collisions can be described within a first-principles molecular dynamics based on eikonal wave functions for the nuclei and the time- dependent Hartree-Fock (TDHF) approximation for electrons that self-consistently couples the electronic and nuclear degrees of freedom. By expanding the molecular Orbitals in traveling atomic orbitals containing electron translation factors, it is possible to eliminate spurious couplings between same-center orbitals at asymptotic distances, and this generates a term in the density matrix equations proportional to the nuclear accelerations. We examine the effect of this acceleration term on Löwdin atomic populations for H⁺ + H(1s) and He²⁺ + H(1s) collisions, for varying collision energies and impact parameters. We find significant increases in atomic populations for an intermediate range of energies going from several tens to several hundreds of electron volts, and for low impact parameters, in the case of the H⁺ + H(1s) collision.