Multiconfigurational pseudo-Hartree approach for the „t , t8... propagator of a molecule in short laser fields

A method to study the rotational dynamics of a molecule interacting with a single short laser pulse or a train of pulses is proposed. The method is based on the observation that for such pulses the time propagator, in the st , t8d formalism, can be expressed as a function of approximate Floquet states given by eigenstates of the one-period time-averaged rotational Hamiltonian multiplied by appropriate Fourier functions for the t8 coordinate. Each zeroth-order eigenstate can be improved by diagonalizing a small configuration-interaction matrix formed from virtual Hartree-type wave functions. The resulting approximate propagators are more efficient than the usual sudden propagator as they allow one to obtain, in a single step, the propagated wave function at the end of the last pulse of a pulse train.