Attosecond spectroscopy of ultrafast charge dynamics in biomolecules

Zusammenfassung

Electron motion is a ubiquitous physical phenomenon of paramount importance in physical, chemical and biological sciences. It is responsible for the emission and detection of light and it also dictates the formation or dissociation of molecular bonds, driving the changes in the chemical composition and function of biological systems. The characteristic time scale of the electron motion is the attosecond, which is related to a second as a second is related to the age of the universe. Such short time scale is now accessible owing to the development of novel coherent light sources which have permitted the observation and control atomic-scale electron motion in real time. Although there are already a few applications of this technology to ultrafast electron transfer in large molecules, its huge potential to understand a large variety of chemical processes is still to be realized. Indeed, electron dynamics play a pivotal role in many photoinduced molecular processes, such as photosynthesis or radiation damage of biologically relevant molecules. This thesis is devoted to the theoretical description of the coupledelectron nuclear dynamics induced and probed by ultrashort laser pulses in amino acids. First, we present a theoretical study of molecular photoionization with ultrashort pulses and analyze the electronic wave packet created by an extreme ultraviolet pulse in the ionic manifold of a large molecule. In this context, we have also studied the role of the ejected photoelectron on the subsequent cationic dynamics and explored the possibility of modifying the purely electron dynamics through shaping of the driving pulse. It is further shown how the correlated treatment of electron and nuclear motion aects the electronic dynamics upon photoionization within the TDDFT-Ehrenfest formalism. We have applied this method to provide theoretical support to a recent experiment on sub-femtosecond charge dynamics in the tryptophan molecule. Finally, we report a theoretical framework of an XUV-XUV pump-probe scheme applied to image the coupled electron-nuclear dynamics of an aminoacid by extracting the resulting photoelectron spectra and analyzing the possible fragmentation channels.