The scientific activity, documented by more than 430 papers, concerns experimental and theoretical aspects in the fields of radiation chemistry, of the ionic reactions in the gas phase, of elastic, inelastic and reactive collisions, between atoms and simple molecules of atmospheric and astrophysical interest, of quantum and semi-classical physical chemistry. His experimental activity was initiated in Rome in the Sixties, with the study of the role of the reactions involving ions in radiation chemistry and of the mechanisms of ion-molecule reactions. The construction in Perugia in the Seventies of an original experimental apparatus, where coupling the technique of crossed atomic and molecular beams with the spectroscopic emission detection has led to the discovery of phenomena of polarization and interference in atomic and molecular collisions. A variant of such an apparatus is still operative in Barcelona. In the 80s, through an original technique of magnetic analysis of type Stern-Gerlach for the orbital states of polarization of spin and electronic angular momentum of atoms, such as halogens, oxygen, sulphur, he has obtained an ample phenomenology on the interactions of these species by molecular-beams scattering. These interactions provide remarkable information on the initial phases of chemical reactions, that involve long range forces determined by their open shell structure. From the Nineties, following the discovery of effects of rotational alignment in molecules in supersonic expansions, he has established a technology for the study of collisions of aligned molecules, obtaining the characterization of intermolecular forces and of their anisotropy. In the last years, he is developing, in the Perugia, Trieste, Taipei and Osaka laboratories, experimental instrumentations for the study of the collisional origin of molecular chirality. The theoretical activity is being developed in parallel to the experimental one, a fundamental theme being the quantum treatment of phenomena such asthose observed in the study of elementary chemical processes, where the motion of nuclei enters into play: their behaviour is at the borderline of classical mechanics . On this theme he has studied non-adiabatic processes, the role of singularities , the chaotic regime, and has also contributed to the historical – epistemological debate. His major theoretical effort has concerned the formulation and implementation of the treatment of the dynamics of processes involving few bodies, that encounter as a quantum mechanical principal obstacle the necessity to explicitly treat the coupling of angular momenta and spin, with electronic, rotational and orbital momenta. He has contributed in this area to the introduction of hyperspherical coordinates and harmonics, developing analytical tools and original algorithms. In the last years, he has also focused on the stuy of the deviations from the Arrhenius law.
