My research

I do research simply because I like to have an answer to the question “why” – or “how come”. This question came over me already when I started to use a hobby telescope I got at twelve years of age. This was also the reason that I as a fresh PhD student in experimental physics started to get involved in molecular calculations – I could not give up the hope to explain ALL the bands in the X-ray emission spectrum of the water molecule I just had recorded. Over the years this ambition to ask “why” has given thrilling revelations, but also some disappointment. As somebody said, the art of being researcher is to cope with disappointment, to learn and to move on from that. Thus the road is winding, but has, I think, led to a situation in my research field that is more promising and inspiring than ever before. Most of the work still lies ahead !

I now try to answer the question “why” using theoretical models where every electron, atom or molecule can make a difference, or, at a different scale, I try to interpret modeling results in terms of chemical structure, properties and dynamics. Here I struggle with the problem that while Quantum Mechanics is the deepest and widest description of nature we have available today, it is limited to small (OK, maybe not that small) systems and to zero temperature. I try to deal with this situation by using models that combine quantum and classical physics, where we join the accuracy of the former with the applicability of the latter. Here classical physics can mean molecular Newtonain dynamics, Maxwellian wave mechanics, statistical mechanics or dielectric principles. In this realm we apply the Scandinavian style of property calculations (response, propagators, inner projections) to search for and understand light- matter interaction at larger scales in space and time. We use that understanding to explore molecular properties and spectroscopy and to design molecular probes in different wavelength regions, for instance spin-labels building on magnetic resonance effects in the radio-frequency region – vibrational fingerprints given by the Raman effect - optical absorption and fluorescence relying on the two-photon principle - all the way down to the X-ray wavelength region, where I once started, but where theory now touches on the fantastic opportunities offered by modern synchrotron radiation sources and X-ray free electron lasers. These quantum-classical approaches have secure applications in a wide variety of applied research areas, in chemistry, biotechnology, biomedicine and material science. Thus, in addition to interpreting experiment by answering “why”, we have now come close to the point of true predictive modeling.

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