Studying Correlated Electron Dynamics in Molecules and Materials with Isolated Attosecond Pulses

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Electrons play a fundamental role in most natural and laboratory phenomena. These elementary particles are extremely light and agile--they can move inside atoms, molecules and materials on the timescale of "attoseconds," which is a billionth of a billionth of a second. To understand the functioning of physical, chemical, and biological processes, it is important to be able to resolve and control the underlying fast electronic motion. Newly devised attosecond techniques provides exactly such an opportunity, using light pulses to strobe the dynamics of electrons. However, most initial studies in this field have been conducted on simple systems like atoms and small molecules. The researchers supported by this program will develop and extend attosecond techniques to the study of complex molecules and materials, where one or more electrons are interacting with each other. Success along these directions will open up opportunities for direct investigation of many biochemical and nanomaterial processes relevant for light harvesting and energy storage. The proposed program will therefore advance the state of science by building bridges between the field of physics, and those of chemistry, biology, and material sciences. The project will also train the next generation of scientists belonging to diverse backgrounds in this emerging and interdisciplinary research field.Electronic correlation often dominates the excitation and relaxation dynamics of photo-excited molecules and nanomaterials, manifesting itself in the energy and charge redistribution mechanisms in important natural and laboratory processes, such as photosynthesis, repair and damage or DNA, energy storage at molecule-semiconductor interfaces etc. This research project aims at the investigation of correlation-driven physical and chemical phenomena using various types of ultrafast spectroscopy. The high temporal resolution required for these studies will be achieved through the generation of isolated attosecond pulses using double optical gating or similar schemes. The scientific objectives of this program will be to: (1) investigate coherent charge migration dynamics in polyatomic molecules, such as those consisting of a phenyl group, (2) study the coherence in electron wavepacket dynamics and the origin of decoherence mechanisms, and (3) probe the generation and dynamics of high energy excitons in carbon nanomaterials (e.g. graphene). These objectives will be achieved while training graduate and undergraduate students in the field of attosecond physics. Two powerful experimental techniques will be utilized in the proposed measurements: velocity map imaging and attosecond transient absorption. The investigations outlined in the proposal will provide the building blocks for developing a better understanding of the inner-workings of natural and practically relevant phenomena. Collaborations with theorists will play crucial role in the interpretation of results obtained in this unchartered territory, potentially leading to the development of new theoretical models.