Anisotropic forces and molecular dynamics

The focus of the present work is on the detailed characterization of the most relevant components of the intermolecular interaction, which determine anisotropic force fields driving the molecular dynamics under a variety of conditions. This target is here achieved by combining in a unifying picture the results of different type of experiments, probing complementary aspects of the intermolecular interactions involved. In particular, the analysis of high-resolution scattering data led to an accurate evaluation of the strength and anisotropy of non-covalent interaction components, due to the balance of size (or Pauli) repulsion with dispersion and induction attraction, to which electrostatic contributions must be added. Moreover, for the complete representation of the intermolecular interaction other components of covalent (chemical) nature, mostly affected by charge (electron) transfer effects, must be properly taken into account. Particular attention has been recently devoted to some experimental findings probing in detail the strength, range, anisotropy and role of the charge transfer effects. Obtained results have been important to develop suitable analytical representations for the potential energy surfaces (PESs), tested and improved by exploiting also the comparison with results of ab initio calculations, useful to provide an internally consistent description of the intermolecular interaction both in the most and less stable configurations of the interacting system. The complete and appropriate formulation of the PESs must be then considered crucial not only to describe the dynamics of elementary processes occurring in interstellar medium and in planetary atmospheres, but also to control equilibrium and non-equilibrium phenomena of applied interest, as those occurring in combustion, flames and plasmas.