Group of theoretical chemistry, Laboratoire de Spectrométrie Ionique et Moléculaire- Lyons

Dr. Marie-Christine Bacchus
Dr. Y.Suzanne Tergiman, Marta Łabuda, Katarzyna Piechowska

The activity of the group is mainly devoted towards two thematics:

Charge transfer in collisional processes: we have developed a complete treatment including ab-initio molecular calculations followed by semi-classical or quantal dynamical calculations which has shown its efficiency in a large number of cases. This field is now oriented to charge transfer in ion/biomolecule, and as a first example we treat the Cq+ + uracyl collisional system in relation with the work of the group in Gröningen.

Non-adiabatic effects in photodissociation processes: wave-packet time-dependent collisional approaches have been developed in the framework of the reduced dimensionality approximation in order to treat such problems involving a great number of degrees of freedom. An interesting situation appears in the analysis of competitive dissociation after photonic excitation in time-resolved femtosecond pomp-probe spectroscopy experiments. Important non-adiabatic effects around the avoided crossings have been shown in particular to drive the competitive C-Cl and C-Br bond breaking in the bromoacetyl chloride photodissociation process. Conical intersection behaviour is now investigated in the photodissociation of the vinoxy radical CH₂CHO in ketene.

In the action of radiation or ions on biomolecular systems, the mechanism could generally be separated into two steps, a first step, very rapid and localised, which involves elementary processes as charge transfer, followed by the relaxation of the molecule. Information on initial mechanisms intervening in such reactions, or life-time of excited species could then be provided by approaches we have developed previously for rapid processes as photodissociation or charge transfer reactions.

COST P9 Workings group(s) of interest: WG4