A team of UK researchers will build instruments that can capture the movement of individual electrons inside molecules and materials, tracking events that last just 100 attoseconds—a hundred times faster than current techniques allow. This matters because a fundamental process called charge migration—where an electric charge shifts across a molecule in less than a femtosecond after it absorbs energy—has been predicted but never directly observed. Existing methods are too slow to see it. Without that observation, scientists cannot understand how the very first moments of electronic excitation trigger the nuclear motions that ultimately control chemical reactions. If successful, the programme will reveal how charge moves in large molecules and condensed materials, including the building blocks of biomolecules. This is primarily fundamental science—exploring a previously invisible layer of reality. But the knowledge could eventually guide the design of more efficient artificial light-harvesting systems, molecular electronic components, and new approaches to biomolecular analysis. Past leaps in measurement capability have repeatedly led to unexpected breakthroughs, and the researchers expect this one to be no different.
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This is a programme of advanced research with potential for extremely high scientific impact and applications to areas of great strategic importance to the UK, such as renewable energy and biomolecular technology. The aim is to develop and apply a combination of cutting-edge experimental and theoretical tools to observe and model dynamics in molecules and condensed phase matter with 100 attosecond temporal and nanometre spatial resolutions. The temporal resolution we will achieve is two orders of magnitude beyond the current state-of-the-art for measurements in larger molecules and condensed matter. The history of science shows that whenever such large improvements in measurement capability occur major new breakthroughs are inevitable. For instance, it has recently emerged that sudden electronic excitation in key molecular building blocks of matter is followed by a universal primary event - sub-femtosecond to few femtosecond migration of electric charge across nanometres. This charge migration, expected to be extremely important in triggering subsequent nuclear dynamics and so controlling chemical change, is too fast to be observed with existing methods. The proposed research programme will apply the world-leading experimental and theoretical tools developed by the assembled team to study the nature of charge migration and other previously unexplored attosecond-scale processes. We will pioneer the investigation in both condensed phase matter and large molecules including the building blocks of biomolecules. The knowledge gained from this research will lead to a new understanding of the first moments in the electronic excitation of matter and ultimately to, for example, new approaches for optimising artificial light harvesting, molecular electronic devices and biomolecular analysis.Imaging and controlling dynamics of matter at the level of electrons, especially far from equilibrium, and understanding the role of quantum coherence in molecules and nanoscale assemblies have been identified by the US Department of Energy as key components of five grand scientific challenges to basic energy sciences (Phys.Today, July 2008, p28-33). Our programme will enable the concerted effort and close linking of experiment and theory needed to address these questions. The UK has a unique opportunity for world leadership in this area, as we have assembled an exceptional team that commands all of the technical and theoretical tools required to lead this new and important area of science.Our programme will exploit two new types of measurements that we have already begun to develop: high harmonic generation (HHG) spectroscopy and attosecond pump-probe spectroscopy, and will apply them to the measurement of attosecond electron dynamics in large molecules and the condensed phase. This is a formidable challenge that will open new frontiers both experimentally and theoretically. This challenge will be met by our coordinated and balanced programme that will bring together theoretical and experimental expertise in attosecond physics, quantum chemistry, molecular structure and dynamics, ultrafast and intense-field science, nanoscale and plasma physics.The programme is structured into 4 interlinked projects, each of which makes a major contribution to the eventual research outcomes: Project 1: High harmonic generation (HHG) spectroscopy Project 2: Attosecond pump-probe spectroscopy Project 3: Coupling of charge migration and nuclear dynamics Project 4: Probing attosecond dynamics in the condensed phase .
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