New Computational Methods for Attosecond Molecular processes
Current laser technology is able to provide intense ultrashort pulses with a wide range of applications in physics, chemistry and even biology. The generation and characterization of coherent light pulses with durations as short as a few tens of attoseconds (1 as = 10-18 seconds) give access to monitor and manipulate electronic motion in matter at its natural time scale. It is now possible to examine in real time light-induced electron and charge transfer processes producing excitons (electron-hole pairs) that can separate along a given material, or producing ionized molecular species leading to fragmentation. These mechanisms eventually generate electronic currents, which are the underlying mechanisms for fundamental processes that occur in nature such as photooxidation, electronic transport or radiation damage, and are at the focus of research in the recently born field of Attosecond Chemistry (see, e.g, recent reviews by the applicants [1,2]). The potential of this field is recognized by the European Research Council and COST Action association, with the recently awarded Synergy Grant TOMATTO (“The ultimate time scale in organic molecular opto-electronics, the attosecond”) with € 11,7 million (GA nº 951224) or the AttoChem network , both chaired by one of the organizers. This new field is being further boosted by the large worldwide investments in new facilities that generate these coherent ultrashort intense pulses, namely the high-harmonic generation sources (ELI-ALPS, international laser user facility in Europe) and X-ray free electron lasers (European XFEL, SwissFEL, FERMI-Italy, LCSL-USA, XFEL-SCALA-Japan). Ongoing and forthcoming experiments using these sources require of a solid theoretical background to obtain real insights on the light-induced electron dynamics, which can also be tightly coupled with the nuclear of degrees of freedom in complex molecular targets. A reliable theoretical description of these processes goes beyond the capabilities of commercially available quantum-chemistry packages, in particular, when ionization processes come into play, as it occurs as long as XUV and X-ray frequencies or large laser intensities are employed. The goal of the school is to provide a solid theoretical background to describe these attosecond light-induced ionization processes. This discipline requires of accurate theoretical modelling, which must describe the coherent superposition of electronic continuum states created by such pulses, which are not available in standard quantum-chemistry or molecular-physics packages. For this reason, new theoretical methods have been developed during the last decade [1,2]. The lectures of the school are structured to introduce these methods in increasing complexity: state-of-the-art ab-initio and hybrid time-dependent systems, as well as more advanced methods that can cope with the electronic continuum of molecules, with an emphasis on unbound states in strong-fields and on the need to go beyond single-active-electron models to properly account for electron correlation (see recent applications of these novel methods introduced in the school in references -). The school is directed to advanced PhD students and post-doctoral researchers in atomic and molecular physics, theoretical chemistry and applied mathematics, with an interest in developing new software for coherent control of electronic dynamics in systems of chemical interest.
 M. Nisoli, P. Decleva, F. Calegari, A. Palacios, and F. Martín, Chem. Rev. 117, 10760 (2017).
 A. Palacios and F. Martín, WIREs Comp. Mol. Sci., e1430 (2020).
 L. Cattaneo et al, Nature Physics 14, 733 (2018)
 F. Calegari et al, Science 346, 336 (2014)
 O. Smirnova, Nature Physics 16, 241 (2020)
 A.W. Bray, U. Eichmann and S. Patchkovskii, Phys. Rev. Lett. 124, 23302 (2020)
Fernando Martin (Universidad Autonoma de Madrid) - Organiser
Alicia Palacios (Universidad Autónoma de Madrid) - Organiser
Wilson Rodríguez (Universidad Autónoma de Madrid) - Organiser