Structure and population of ²¹⁰Po and ²¹²Po isotopes produced by transfer reactions

Several light nuclei, as ¹⁸O, display a 'core + α' structure. ²¹²Po is the only heavy one where this phenomenon has been highlighted. In this thesis, we combined the measurement of the excitation energy of levels populated via transfer reaction from a ¹²C nucleus on a ²⁰⁸Pb nucleus, and the measurement of the γ decaying of these levels. A first experiment has been performed in inverse kinematic, using the AGATA Germanium array and a thick silicon detector. A second experiment, in direct kinematic has been done at Tokai's Tandem using a telescope of silicon detectors, 4 HPGe and 4 LaBr₃ crystals. We describe the principle of these detectors, the data reduction up to the kinematical reconstruction, and the simulations used to build the experimental set-up and to validate the data analysis. We have studied 1p, 2p, 2p 1n and α transfer reactions leading to ²⁰⁹Bi, ²¹⁰Po, ²¹¹Po et ²¹²Po at energies around the Coulomb barrier. From the comparison of these reactions channels, we firmly established that the 4 nucleons are transferred simultaneously to produce ²¹²Po. Evolution of the excitation energy with the beam energy has shown that the ²¹²Po states including a strong 'core + α' component lie much preferentially at high excitation energy (E* ≥ 3 MeV). Seven new energy levels of ²¹²Po have been discovered, for which spin and parity attributions are proposed. We also measured the partial cross-sections to several levels to characterize their cluster components. We confirmed the large 'core + α' components of the 4^-₃ and 7^-₂ states, and the weak 'core + α' components of the 2⁺₁ and 2⁺₂ states. Five new levels of ²¹⁰Po have been discovered. Shell model calculations allowed us to firmly assign spins and parities. (author)