FRFC : Control of attosecond dynamics

Abstract



In the past 10 years a radically different field of chemical dynamics has opened up with the experimental development of attosecond optical pulses.
These pulses are so short and intense that they excite the electrons into non-stationary and complex states, giving the potential to use the electronic wavepacket to control the dynamics leading to the reaction products. The practical benefits will cover catalysis, chemical analysis, charge directed reactivity or charge transfer in photovoltaics and nano-electronics.
This project will develop new theoretical tools and methodologies for the control of chemical reactivity and electron dynamics under ultrashort optical pulses. It is a joint venture between chemistry and physics: we will simultaneously exploit the high precision of multi-configurational quantum chemistry to calculate and analyze electron and nuclear dynamics, and the high efficiency of time dependent density functional (TDDFT) based methods for large molecules and nanostructures, and for long simulation times (up to picoseconds for final reaction products). The crux of the project is the transfer of knowledge and insight from accurate but costly quantum chemical methods to new functionals and algorithms for TDDFT.
Benchmarking and development will be carried out on progressively more complex systems, which aim at applications in the fields mentioned above.

Objectives


Our project aims to develop the theory and modeling tools necessary for controlling reactivity in molecules and nanostructures, based on the attosecond excitation of non-equilibrium states. The project focuses on non-equilibrium, multi-timescale, electron and ion dynamics, going all the way from the shortest time scale attainable (the atto to few fs (or subfs) range needed to excite a non-stationary state for the electrons) up to the time scale describing the targeted physicochemical outcomes of the excited system, which is longer by up to four orders of magnitude when the atoms have to move substantially.

The central objectives of the project are to explore new schemes and examine new ideas, based on the control of electron dynamics,

The achievement of these objectives requires developing a better understanding of :

·                the correlation between electronic and nuclear motion. We need to understand how the non-equilibrium electron dynamics is expressed as the forces on atomic nuclei in molecular systems, and we need to do it for systems of increasing size. Several electronic states are typically involved in the dynamics during and after an ultrafast excitation, which requires using explicitly multiconfigurational approaches. These are feasible for small molecules but are too costly for larger systems. The question is how well mean-field approaches, that are currently being developed and used, perform for larger systems of practical interest.

·                the correlation between electron and hole dynamics in ionization processes and for charge-directed reactivity. For both processes, one needs a better understanding of hole-electron dynamics upon ultrafast excitation of the electron density.

·                the interplay of multiple time scales (from atto- to picosecond) and how to control the dynamics of molecules subject to rapidly varying fields. Attosecond electronic motion, the slower electron-ion coupling, and the final chemical reaction need to be treated seamlessly within a unifying and accurate framework.