Quantum-mechanical and impact-parameter treatment ofHe2+-H collisions

Abstract

Charge-transfer (sublevel) cross sections for He~++H collisions have been calculated in the 20-eV -to -10-keV center-of-mass energy region. Both a time-independent quantum-mechanical closecoupling method (ZO -500 eV) and a semiclassical impact-parameter method (0.1 -10 keV) were used. The close-coupling formalism is developed in terms of a molecular-state description of the HeH + system and is extended to include both radial and rotational couplings. The potentials and radial and rotational couplings for the Zso. , Zpo. , 3do, and Zpm molecular states were computed by expressing the molecular orbitals as variationally determined linear combinations of Slater-type orbitals centered at the atoms. ' Common molecular-electron translation factors were introduced to ensure proper asymptotic behavior of the wave functions and were found to be crucial for agreement between calculated and experimental cross sections. The usual practice of compensating for the neglect of these factors by using couplings evaluated at an atomic origin rather than at the center of mass of the nuclei is analyzed. Quantum-mechanical and semiclassical results are compatible only if Coulomb trajectories instead of straight-line trajectories are used. In particular the sublevel cross section for He+(Zp+l ) production is found to be extremely sensitive to the trajectory. At all energies above 50 eV radial and rotational couplings are about equally important. Below 100 eV cross sections fall off rapidly, and radiative charge transfer becomes the dominant process below 25 eV.

Laser-field-induced modifications of electron-transfer processes in ion-atom collisions

“…We observe good agreement with the present calculation except for very low projectile energies where the results of Ref. [26] decrease much more steeply. The reason for this behavior is that a curved instead of a straight-line trajectroy was used in Ref.…”

“…5 as functions of the projectile energy. The field-free results are compared with experimental data [24,25] and with two state-of-the-art calculations based on molecular expansions [23,26]. Detailed comparisons with other theoretical (and experimental) data can be found in the latter works and in Refs.…”

Non-adiabatic quantum molecular dynamics: basic formalism and case study

“…(1), has been already suggested by Mott [41] as early as 1931. It has been used and applied in different fields of physics (e. g. nuclear heavy-ion collisions [42], ion-atom scattering [43,44], molecular processes [27], etc.). We adopt this approximation here also from the very beginning.…”

Uncertainty estimates for theoretical atomic and molecular data

“…integrated over projectile scattering angle) cross sections only, the semiclassical approximation amounts to reducing the full scattering problem to a timedependent Schrödinger equation (TDSE) for the electronic motion in the field of classically 28 moving nuclei. The classical trajectories can be determined by considering the nonadiabatic coupling of the electronic and the nuclear motion as is done in the electron nuclear dynamics (END) method [157,158], or by using Coulomb or model scattering potentials [159][160][161][162].…”