Time-Dependent Many-Electron Treatment of Electronic Energy and Charge Transfer in Atomic Collisions

Abstract

Electronic energy and charge transfer in atomic collisions are described within a first principles molecular dynamics including an explicit treatment of electronic motions, in terms of time-dependent many-electron wavefunctions. Following an overview of treatments in the literature based on expansions in sets of adiabatic and diabatic electronic states, this article emphazises the use of time-dependent molecular orbitals and timedependent Hartree-Fock states. Three fundamental problems are identified in a first principles dynamics, relating to the calculation of state-to-state transition probabilities and expectation values, to the translational motion of electrons moving with nuclei, and to the coupling of fast electronic transitions and slow nuclear motions. Solutions to these problems are described on the basis of an eikonal representation of wavefunctions and sums over initial conditions, of the use of traveling atomic functions to expand molecular orbitals, and of a relax-and-drive propagation procedure for electrons and nuclei. Examples are presented of applications in ion-atom and ion-surface collisions, relating to electronic excitation and charge transfer, orbital polarization, and light emission during collisions.

Numerical Simulation of Nonadiabatic Electron Excitation in the Strong Field Regime. 2. Linear Polyene Cations

“…62,63 To characterize the behavior of a molecule in an intense field, several properties are useful. The effective charge on atom R can be computed by using the Löwdin population analysis, where Z R is the charge on the nucleus, P ii are the diagonal elements of the density matrix in the orthonormal basis, and the sum is over basis functions on atom R. Orbital occupation numbers are obtained by projecting the time-dependent density matrix onto the initial, field-free orbitals where C k (0) is the kth eigenvector of the converged Fock matrix at t ) 0.…”

A correlated-polaron electronic propagator: Open electronic dynamics beyond the Born-Oppenheimer approximation

“…12 In the many-electron case, there has also been some recent pioneering work toward developing random-phase approximation equations. 2,3 The electronic structure community has also produced some related work, [13][14][15][16][17][18] including phenomenologically damped 19 response theory.…”

Chemical reactions in the gas phase and in condensed matter: From wavefunctions to density operators

“…And thermal averages are inevitable when the reactions occur in condensed phases, such as on surfaces or in liquid solutions. In these cases, it is possible to obtain useful results within a quantum-classical treatment where electronic states are yet quantized, but atomic motions are treated as classical and evolving under effective potentials [13][14][15]. A treatment in terms of the statistical density operator ⌫ (t) of quantum mechanics provides a powerful tool for quantum-classical studies in many-atom systems, because it is the basis of a rigorous treatment of quantum-classical interactions, and also provides a way to impose the correct initial conditions, possibly involving temperature and densities of a medium in a condensed phase reaction [16,17].…”