This thesis is dedicated to the study of C60 fullerene cooling mechanisms after a nanosecond laser excitation. In this temporal mode, absorbed energy is redistributed to all cluster's degrees of freedom causing a fragmentation cascade by emission of C2 molecules. A process of delayed ionisation is highlighted for each size of produced clusters. Then the formed cations can fragment by emission of C2. Our experimental device is made of a time-resolved velocity-map imaging spectrometer combined with a Wiley-McLaren time-of-flight mass spectrometer. It allows extracting the kinetic energy spectra from the photoelectrons or photoions that result from the C60 relaxation chain. These spectra are compared with a statistical model based on Weisskopf's formalism. A Monte Carlo algorithm was developed in order to rebuild the C60 time-of-flight spectrum. The information extracted from simulations, like the internal energies or the branching ratios at each decay stage, perfectly complete the analysis of the involved processes.
