Yield ratios and directed flows of light particles from proton-rich nuclei-induced collisions

The neutron-to-proton and3 H-to-3 He yield ratios, and the directed flows of particles dependent on a reduced rapidity, the transverse momentum per nucleon,and a reduced impact parameter are investigated for ^(28)S+^(28)Si and ^(32)S+^(28)Si systems at 50 and 400 MeV/u using an isospin-dependent quantum molecular dynamics model.The results show that these yield ratios of projectile-like fragments are approximately equal to the constituent neutron-to-proton ratio of the projectile. There are clear differences of the directed flows for isospin-related fragments neutron and proton,~3H and ~3He from ^(28)S+^(28)Si collisions.The differences in directed flows for neutrons and protons and ~3H–~3He from a proton-rich nucleus ^(28)S- induced collisions are noticeably larger than those from a stable nucleus ^(32)S- induced reactions under medium impact parameters. Thus, the yield ratios and differences in directed flows for the neutrons and protons and ~3H–~3He under medium impact parameters are proposed as possible observable items for studying isospin physics.

Proton and Two-proton Emissions from Proton-rich Nuclei with 10 ≤ Z ≤ 20

Proton(p) and two-proton(2p) emissions from the proton-rich nuclei with 10≤Z≤20 have been explored by the in-fight decay and implantation decay methods, respectively, in a series of experiments at the HIRFL-RIBLL facility. The in-flight 2p emissions from the excited states of ^(28,29)S/^(26,27)P and ^(17,18)Ne were studied by complete-kinematics measurements. Mechanisms of 2p decay and related p-p correlations have been explored. Obvious 2p correlated emissions have been observed in the cases of ^(28,29)S but not in ^(27,28)P, indicating the 2p halo plays an important role in the diproton emission. In the ^(17,18)Ne cases, a small 2p opening angles were deduced by the HBT analyses, implying the BCS-BEC crossover may occur in the dilute nuclear matter. Moreover,^(27)S/^(26)P/^(25)Si,^(22)Si/^(20)Mg,^(23)Si/^(22)Al/^(21)Mg,^(24)Si/^(23)Al, and ^(36,37)Ca were implanted in a thin double-sided-silicon-strip detector and their β-delayed p and 2p decays have been measured by a surrounding silicon detector array under the continuous-beam mode. Important information on the nuclear spectroscopy, such as energy, lifetime, branching-ratio, and so on, has been extracted, which helps us to understand the nuclear structures of proton-rich exotic nuclei close to the drip-line.

Collective multipole excitations of exotic nuclei in relativistic continuum random phase approximation

The isoscalar and isovector collective multipole excitations in exotic nuclei are studied in the framework of a fully self-consistent relativistic continuum random phase approximation （RCRPA）. In this method the contri- bution of the continuum spectrum to nuclear excitations is treated exactly by the single particle Green＇s function. Different from the cases in stable nuclei, there are strong low-energy excitations in neutron-rich nuclei and proton-rich nuclei. The neutron or proton excess pushes the centroid of the strength function to lower energies and increases the fragmentation of the strength distribution. The effect of treating the contribution of continuum exactly is also discussed.