Rotational spectrum of the NH3–He van der Waals complex

The interaction between ammonia and helium has attracted considerable interest over many years, partly because of the observation of interstellar ammonia. The rate coefficients of NH3 –He scattering are an important ingredient for numerical modeling of astrochemical environments. Another, though quite different application in which the NH3 –He interaction can play an important role is the doping of helium clusters with NH3 molecules to perform high-resolution spectroscopy. Such experiments are directed on the detection of non-classical response of molecular rotation in helium clusters addressing fundamental questions related to the microscopic nature of superfluidity. High-resolution spectroscopy on the NH3–He complex is an important tool for increasing our understanding of intermolecular forces between NH3 and He.