FREE-ELECTRON LASER INFRARED IRRADIATION OF MOLECULES ISOLATED IN MATRICES AS A TOOL FOR MOLECULAR RELAXATION STUDIES

The selective excitation of different vibrational modes of the CH2D-CH 2D molecule isolated in a xenon matrix at 7 K has been performed using the free electron laser source CLIO. The aim of these experiments was to test the selectivity of the different intramolecular couplings inv olved in the isomerization induced by the infrared irradiation. Kineti cs measurements have been recorded using FT-IR spectroscopy as a probe of the sample composition and the modifications of the quantum yield with the excited mode have been obtained. Preliminary results show tha t the local environment strongly influences the reaction rate. Althoug h the overall behavior of the quantum yield with energy is consistent with a RRKM process, a non statistical redistribution of the energy am ong the different modes is observed in some cases.