Events
Spectroscopy of complex molecular systems: Physics on an exciton cake-walk
November 29, 2011 at 3pm/36-428
Jasper Knoester
Zernike Institute for Advanced Materials, University of Groningen, Netherlands
Abstract:
The concept of excitons, collective excited states, is well-known in solid-state physics. It was first developed by Frenkel in the 1930’s to explain the absorption spectrum of perfect molecular crystals, in which case the excitons are simple Bloch waves of excitation. Over the years, it has become apparent that also less regular structures carry delocalized excitations, which are responsible for many of their electromagnetic properties and energy transport characteristics. In this presentation, I will address two classes of such systems. The first class are molecular J-aggregates, large self-assembled structures containing up to 1000’s of molecules, which play a role in opto-electronic applications and natural photosynthetic systems. The second class are polypeptides and proteins, in which case collective vibrations are the excitations of interest. The irregular nature of these systems and the occurrence of fluctuations in their host, provide a complex and dynamic landscape in which the excitons are created, evolve, and decay. I will address the basic physics of these systems, some of their intriguing properties, and the theoretical tools used by us to analyse and predict (ultrafast) spectroscopic experiments in the visible and the infrared used to probe these properties.
Bio:
Jasper Knoester received his MSc and PhD in Theoretical Physics at the University of Utrecht, The Netherlands, in 1983 and 1987, respectively. Currently, he is the Dean of Faculty of Mathematics and Natural Sciences and Professor of Theoretical Physics at the University of Groningen, The Netherlands. He conducts his research in the Theory of Condensed Matter Group at the Zernike Institute for Advanced Materials in optical and electronic properties of condensed phases, in particular of (bio)molecular aggregates and conjugated polymers; vibrational dynamics and infrared spectroscopy of polypeptides and proteins; low-dimensional systems; spin systems; disorder and localization; QED near dielectric interfaces; light scattering on photonic crystals, plasmonics.
