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

Slow ion-atom collisions can be described within a first-principles molecul ar dynamics based on eikonal wave functions for the nuclei and the time-dep endent Hartree-Fock (TDHF) approximation for electrons that self-consistent ly couples the electronic and nuclear degrees of freedom. By expanding the molecular orbitals in traveling atomic orbitals containing electron transla tion factors, it is possible to eliminate spurious couplings between same-c enter orbitals at asymptotic distances, and this generates a term in the de nsity matrix equations proportional to the nuclear accelerations. We examin e the effect of this acceleration term on Lowdin atomic populations for H+ H(1s) and He2+ + H(1s) collisions, for varying collision energies and impa ct parameters. We find significant increases in atomic populations for an i ntermediate range of energies going from several tens to several hundreds o f electron volts, and for low impact parameters, in the case of the H+ + H( 1s) collision. (C) 1999 John Wiley & Sons, Inc. Int J Quant Chem 75: 361-36 6, 1999.