Super-heavy Quarkonia as a probe of the QCD Vacuum

The phenomenon of gluon condensation is under vital discussion since more than fifteen years now [1]. The gluon condensate is an important quantity not only in the sum rule approach but also in high-energy hadron scattering and phenomenological models of confinement. Despite many indications of a non-trivial vacuum the quantitative picture is still vague [3]. Quarkonia are the simplest hadronic systems that allow to test the vacuum structure of QCD. Heavy quarks can be treated as non-relativistic objects in a gluonic vacuum making them tangible to numerical simulations and perturbative calculations.