Laser-driven electron dynamics in molecules

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Ultrashort, often tailored, laser pulses have been very successful for unravelling dynamical details of electronic motion in atoms, small molecules and at surfaces, on the electrons' natural timescale of attoseconds. In an attempt to contribute towards "attosecond chemistry'', in this project we wish to apply and improve explicitly correlated, time-dependent wavefunction-based methods to probe and control, the many-electron dynamics in laser-pulse excited molecules: from small to large ones.Specifically, we wish to apply Time-Dependent Configuration Interaction (TD-CI) expressed in an Atomic Orbital (AO) basis and in the fixed-nuclei approximation as the main working horse. This ansatz is efficient and at the same time readily available for treating quantum chemically difficult cases such as long-range charge transfer and static correlation. For refinement, various approaches towards treating ionization losses, nuclear motion and effects of an environment will be applied. Also, TD-CI will be benchmarked against density functional based methods on the one-hand side (for larger molecules), and against numerically "exact" solutions of the molecular Schrödinger equation on the other (for small molecules). We shall use either analytic pulses, or shaped ultrashort femtosecond laser pulses constructed by various automated strategies, notably Optimal Control Theory (OCT) and Stochastic Pulse Optimization (SPO).Two main lines of applications will be followed: 1. The creation and control of electronic wavepackets and 2. the non-linear response of molecules to lasers and its active control.The control of electronic wavepackets by laser pulses serves the purpose of steering electronic motion in molecules. Specific goals are to enforce directed, long-range charge transfer in molecular systems, or, as a so far purely hypothetical concept, to de-correlate electrons. Concerning non-linear responses, we are particularly interested in High Harmonic Generation (HHG) in molecules. Specifically, we wish to investigate the performance of HHG as a spectroscopic tool to discriminate between organic isomers, or to create ultrashort laser pulses. For smaller systems, we shall try to actively control HHG signals and investigate their dependence on ionization losses and nuclear motion.