Spectroscopy and reaction dynamics of molecular and cluster ions

Informacje na temat projektu

Identyfikator umowy o grant: INTAS-93-1128

Data rozpoczęcia 1 Czerwca 1995

Data zakończenia 31 Maja 1996

Finansowanie w ramach

• International Association for the promotion of cooperation with scientists from the independent states of the former Soviet Union (INTAS), 1993-

Koszt całkowity € 0,00

Wkład UE € 25 000,00

Koordynowany przez

Università degli Studi di Trento
Italy

Exploitable results

Spectroscopy and reaction dynamics of molecular and cluster ions

The goal of this project was the investigation of ion/neutral reactions, considering - in particular - the interaction of simple atomic and molecular ions with polar neutral molecules and the formation of ion/dipole collisional complexes. Most of the experiments have been devoted to the study of the acetonitrile molecule (CH3CN) which has a large dipole moment (about 4 Debye) producing strong alignment effects during the collision process The flow-tube mass spectrometer at the IEPCP has been upgraded, a new ion-optics has been installed, overcoming previous mass discrimination effects. Now, the Moscow apparatus may be used for the accurate measurement of rate constants for the production of secondary and ternary ions A detailed study of the association and charge-transfer reaction of Xe+ and O2+ with acetonitrile has been carried out in cooperation with the Innsbruck group. Charge-transfer process are slightly endoergic and show a very low efficiency at collision energies below about 0.3 eV. At low collision energies, association becomes the dominant channel. This correspond to a relatively long lifetime of the collisional ion/dipole complex which is estimated to be about 10-7 s An investigation of the kinetics of secondary ion complexes [CH3CN-Xe+] and [CH3CN-O2+] has shown the formation of nonprotonated dimers of acetonitrile (CH3CN)2+ which has been ascribed to a switching reaction of the ion complex with acetonitrile. Further information about the reaction mechanism, and the role of molecular vibrations have been obtained by means of experiments based on the use of deuterated acetonitrile Detailed studies have been devoted to the characterization of isomerisation processes. Semi-empirical theoretical calculations and experiments carried out by means of the Innsbruck Selected Ion Flow Drift Tube (SIFDT) apparatus have demonstrated the production of two different CH3CN+ isomers in the charge transfer reaction of Xe+, Kr+ , O2+, and O+ ions with acetonitrile. The relative populations of these two isomers depend on both the recombination energy of the reactant ions and the collision energy.