Rotational spectroscopy of weakly bound complexes

Abstract

The first indication of the formation of complexes between molecules came from investigations of the equation of state of real gases through the work of van der Waals. During collisions, molecules or rare gas atoms may form short-lived complexes which are likely to be dissociated by the next collision. The binding energy of such complexes between stable closed shell molecules or rare gas atoms is small, much smaller than that for a typical chemical bond. Weakly bound molecular complexes can now be investigated with different spectroscopic techniques. They are produced most efficiently in supersonic expansions where the strong adiabatic cooling favours their formation. The spectroscopic characterization is then performed in the collision-free region of the emerging jet or molecular beam.