Two-proton relative momentum (q pp ) and opening angle (θ pp ) distributions from the three-body decay of two excited proton-rich nuclei, namely 23 Al → p + p + 21 Na and 22 Mg → p + p + 20 Ne, have been measured with the projectile fragment separator (RIPS) at the RIKEN RI Beam Factory. An evident peak at q pp ∼ 20 MeV/c as well as a peak in θ pp around 30 • are seen in the two-proton break-up channel from a highly-excited 22 Mg. In contrast, such peaks are absent for the 23 Al case. It is concluded that the two-proton emission mechanism of excited 22 Mg is quite different from the 23 Al case, with the former having a favorable diproton emission component at a highly excited state and the latter dominated by the sequential decay process.

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Anisotropic flows ($v_1$, $v_2$ and $v_4$) of light nuclear clusters are studied by a nucleonic transport model in intermediate energy heavy ion collisions. The number-of-nucleon scalings of the directed flow ($v_1$) and elliptic flow ($v_2$) are demonstrated for light nuclear clusters. Moreover, the ratios of $v_4/v_2^2$ of nuclear clusters show a constant value of 1/2 regardless of the transverse momentum. The above phenomena can be understood by the coalescence mechanism in nucleonic level and are worthy to be explored in experiments.Comment: Invited talk at "IX International Conference on Nucleus-Nucleus Collisions", Rio de Janeiro, Aug 28- Sept 1, 2006; to appear on the proceeding issue in Nuclear Physics