Some of the most innovative aspects of the Action deal with the observation of molecules at the attosecond time scale. At this time scale it is possible to observe the movement of electrons inside the molecule and their evolution during a chemical reaction providing the ultimate picture of the different factors governing a reaction, since up to now if was only possible to observe the nuclear movements at the femtosecond time scale.

Several aspects will be covered by this WG:

– Track of the electron/hole movements in molecules with femto- or attosecond laser pulses generated by XFEL or HHG. Imaging of electrons moving in small diatomic molecules, tunnelling through energy barriers or crossing conical intersections has been possible in the last years using these techniques. These methods will be used to observe intramolecular charge migration and intermolecular charge transfers in larger molecules, as biomolecules where charge transfer play a key role in their chemical activity.

– To develop the theoretical background needed to describe the ultrafast chemistry induced by ions and light in molecules. The first challenge is to have accurate methods to describe the interaction of a molecule with an ultrashort and ultraintense laser pulse. A second challenge is the treatment of the electron dynamics in the attosecond scale inside the molecules. The third one is to describe simultaneously the electronic and nuclear degrees of freedom, since in this kind of ultrafast processes, the traditional Born-Oppenhemeir approach in which the nuclei are supposed to move more slowly than electrons is no longer valid.

– Establish the use of ultrahigh resolution spectroscopies and of multicoincidence techniques as one of the techniques of choice to probe not only ultrafast electronic and nuclear wave packet dynamics, but also as probes of molecular structure and reactivity following interaction with short wavelength radiation and multicharged ions. Diffraction of the ejected electrons by the molecular centers will be used to determine the structure of isolated molecules or to obtain a temporal mapping of the electron and nuclear dynamics

– Describe the complex dynamics that starts when electrons are removed from deep inner electronic shells. Pure electronic processes are triggered by these excitations. Auger decay will produce the emission of a second electron and will leave the molecule in an excited and doubly charged state that will evolve very rapidly to fragmentation. There are several techniques that can produce these excitations (X-ray synchrotron radiation, laser pulses or collisions with ions) and it is possible to detect in coincidence the emitted electrons (photoelectron and Auger electrons) and the molecular ionic fragments, thus providing an insight into the fragmentation dynamics and a direct test of the methodologies used. The existing expertise in small molecules will be the starting point to extend the studies to treat medium-sized (CH4, SF6, C2H2, etc.) and larger molecules, such as aminoacids, PAHs, nucleic acids, etc.