Excitation vibrationnelle non linéaire des fullerènes par une source laser à électrons libres

Abstract

We used a free electron laser source (Felix) for investigating the non linear optical response of C60 in the infrared. In addition to the infrared active lines, we measured a relatively important absorption related to the excitation of Raman, silent and combination modes. However, it has not been possible to observe such a non linear optical response, as second or third harmonic generation. Sum-frequency generation experiments were carried out by mixing a free electron laser beam (CLIO 1000 - 1500 cm-1) with the beam of a YAG laser at the surface of an Ag single crystal covered with a C60 thin film. The unexpected detection of the Raman active Ag(2) mode points out to a symmetry breaking of the molecule at the silver interface. Finally, we mention the importance of possible non linear response of standard optical components used in such experiments. Such effects could be demonstrated in the case of a sapphire filter.

Date of Award	1995
Original language	French
Supervisor	Paul THIRY (Supervisor), Andre Peremans (Jury), Ghislain Blanquet (Jury) & Jean-Marie Gilles (Jury)