Matrix spectroscopy has the advantage that the atoms or molecules being probed can be isolated and cooled, but the matrix holding the "sample"

usually has a significant effect on the spectra.  These effects can be minimized by using superfluid helium-4 as matrix.  Therefore, spectroscopy of helium-4 nanodroplets doped with single atoms or molecules or clusters of them has become a versatile experimental tool.

Interpretation of spectra obtained in this quantum matrix require knowledge about the influence of helium on the dynamics of the probed atom or molecule.  In my presentation, I will give an overview of calculation methods for this non-trivial quantum many-body system, based on Monte Carlo simulations, but also on traditional many-body techniques.  I present some results on rotational spectra of neutral and ionic molecules inside and on the surface of helium clusters, and on the formation of alkali-helium exciplexes, and discuss the influence of superfluidity of helium on molecule rotation spectra.  Experiments of large organic molecules and of metal clusters in helium-4 have gotten much less attention from the theoretical physics and chemistry community since accurate interactions potential are not known in this case.  We are tackling this problem with a phenomenological approach to obtain the all-important interactions between the dopant and the He atoms.

Coffee/tea and cake will be served from 15:05