High-resolution laser spectroscopy in molecular beams

The application of high-resolution gas-phase spectroscopy has for a long time remained limited to the study of small molecules. Recent years have witnessed remarkable advances in experimental and computational techniques. These now allow us to meet the challenges in exploring the structural and dynamical properties of the ground and electronically excited states of large, conformationally complex, molecular systems. We employ new methods like laser desorption to seed nonvolatile compounds in supersonic expansions, and helium nanodroplet spectroscopy to study them at even lower temperatures. New double- and triple-resonance techniques are developed that enable us to analyze and interpret complicated spectra. And solvation by one solvent molecule at a time provides us with a powerful means to rationalize the influence of intermolecular interactions, and understand phenomena such as self-organization and molecular recognition.

Our experiments use a number of home-built spectrometers. These are based on detection of emission (LIF), mass-resolved ion detection (REMPI), and kinetic-energy-resolved electron detection (PES). Apart from the spectrometers at the UvA, an advanced facility for vibrational studies of conformational dynamics has been constructed at FELIX together with FOM Rijnhuizen and supported by a NWO-Middelgroot grant.

Our current interests are in areas like molecular nanotechnology where we study and control the structural dynamics of molecular motors. For photoactive proteins we are interested in the structural and dynamic properties of excited states involved in the primary steps of light-induced signal transduction. Conformational isomerization is at the basis of complex phenomena such as protein folding. We therefore study conformational dynamics in flexible (bio)molecular systems to understand the fundamental steps of such processes. In a similar way, multichromophoric systems are of interest to us in the context of energy and charge transport.  

Contact: Wybren Jan Buma, e-mail: w.j.buma@uva.nl
Molecular Photonics (UvA) 
Buma1 
Infrared absorption spectra of the complex of a mechanically interlocked molecule (a [2] rotaxane) with one (black) and five (blue) methanol molecules. The orange band is associated with the binding interactions between thread and macrocycle. Its disappearance in the penta-solvated cluster provides a direct view on the uncoupling of the separate components from each other (Angew. Chem. Int. Ed. 2010, 49, 3896-3900).