Molecules in the cold environment of a supersonic free-jet beam: from spectroscopy of neutral-neutral interactions to test of Bell's inequality

The supersonic free-jet expansion technique has been used in different fields
of research in physics, physical chemistry and chemistry to study vibrational
and rotational molecular structures in ground and excited electronic energy
states as well as in cold chemistry to study chemical reactions in a unique
environment. The supersonic beam technique, as a widely used method in
laser spectroscopy of molecules, exploits a source of monokinetic, rotationally
and vibrationally cold molecules, that are very weakly bound in their ground
electronic states (van der Waals molecules). In experiments at Jagiellonian
University the supersonic free-jet beam serves as a source of ground-state van
der Waals objects in studies of neutral–neutral interactions between group 12
metal (M = Zn, Cd, Hg) and noble gas (NG) atoms. Recently, the method has
been applied as a source of entangled 199Hg atom pairs in order to test Bell’s
inequality in an experiment at Texas A&M University.