We examine an effective way to apply high level quantum chemical computations towards quantum dynamics when several electronic states are coherently excited. We describe the coupled nuclear wave packets, one on each adiabatic electronic state, on a grid of internuclear distances with non-adiabatic coupling terms explicitly taken into account. Accurate quantum chemical computations provide the necessary matrix elements of the electronic Hamiltonian at each grid point – potentials, dipoles and non-adiabatic couplings. Computing of the nuclear dynamics is on the fly as if we are running a classical trajectory while retaining full quantum coherence. This is realized within a localized form of the momentum and kinetic energy operator for the nuclear dynamics via a Finite difference approximation. We propagate only along few grid points relevant at this particular time and extend the grid by a finite number of points in the direction of the wave packets motion. Thereby the very time demanding quantum chemical computations for each grid point are used only for the physically relevant regions of the internuclear distances. To illustrate the benefits and high accuracy of the current approach we use several examples of early time (100fs) dynamics in homo- and hetero-nuclear diatomic molecules pumped by an attosecond pulse.

On-the-fly approach for the attosecond quantum dynamics on multiple electronic potentials of diatomic molecules

256th National Meeting (2018)

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