Abstract : Two models are designed in order to contribute to the interpretation of the physicochemistry of organometallics ions in gas phase.
Potential energy surfaces associated with reactivity are designed using effective hamiltonian theory with a special emphasis on the oxydative addition of an LnM+ ion into a H-H bond. The principle is to build an effective hamiltonian associated with the active electrons, i.e. with the insertion of M+ into H-H link, then to use an approach similar to the ligand field theory to treat the effect of the spectator ligands (Ln). The construction of the effective Hamiltonian associated with M+ + H-H constitutes the novelty of our approach. It is constructed from two-body potentials (M+-H or H-H), derived from ab.initio calculations on the valence electronic states of these fragments. Using a correction to account for three-body terms, geometry of the stationary points of M+ + H2 are located with a good precision, and the error associated to their relative energies is about 20 kJ/mol.
The second part is devoted to the development of a kinetic model to interpret the fragmentation yield of mass-selected ions induced by an Infra-Red MultiPhotonic Dissociation (IRMPD) process in gas phase, which are used to derive IR spectrum of ions prepared in a mass spectrometer. A first set of parameters is associated to the focusing and the temporal structure of the laser, the second one to the trajectory and the physicochemical parameters of the ions. The very accurate simulation of several experiments allows for a better understanding of the relative IRMPD intensities observed and will constitute a usefull guide for future experiments.