Multidimensional Intermolecular Potential Surfaces from Vibration- Rotation-tunneling (vrt) Spectra of Van Der Waals Complexes

The role of intermolecular forces in modern science is becoming ever more prominent, as increasing numbers of chemists and physicists turn to the investigation of condensed matter phenomena and biological systems. Although thee subject is hardly novel, the state of our knowledge of intermolecular forces and their associated potential energy surfaces is, nevertheless, remarkably primitive. For example, isotropic descriptions of the pairwise interactions between most of the common small molecules have existed for many years, but the anisotropy of these interactions still remains largely uncharacterized--even after nearly two decades of investigation with the most sophisticated experimental and theoretical techniques available! Furthermore, anisotropy is a dominant feature of systems that have the most significance, viz. those exhibiting hydrogen bonding. This state of affairs seems all the more surprising when one considers that detailed theoretical formulations have been developed (1) for describing the three types of weak attractive interactions that occur between a pair of molecules, viz. electrostatic, induction, and dispersion forces, and that at least the low-order parameters that describe these interactions (polarizabilities, dipole moments, quadrupole moments) are generally wellknown. However, as we elaborate upon in this review, it is our lack of