[en] For the last ten years, the Ultra High Intensity Lasers offer the opportunity to produce accelerated particle beams which contain more than 10¹² electrons, protons accelerated into a few ps. We have simulated and developed some diagnostics based on nuclear activation to characterize both the angular and the energy distributions of the particle beams produced with intense lasers. The characterization methods which are presented are illustrated by means of results obtained in different experiments. We would use the particle beams produced to excite nuclear state in a plasma environment. It can modify intrinsic characteristics of the nuclei such as the half-life of some isomeric states. To prepare this kind of experiments, we have measured the nuclear reaction cross section (gamma,n) to produce the isomeric state of the ⁸⁴Rb, which has an excitation energy of 463 keV, with the electron accelerator ELSA of CEA/DIF in Bruyeres-le-Chatel (France). (author)