Ruan Ming

Possible Experimental Evidence of a Moderate Proton Halo in29S

The total reaction cross sections (TRCSs) of 29S+28Si have been measured at intermediate energies. An obvious enhancement in TRCS of 29S is observed as compared with its neighbouring nuclei. The TRCSs of 29S+28Si are calculated with the modified Glauber theory in the optical limit and few-body approaches. The different factor d as a possible measure of halo appearance is deduced from the experimental and theoretical data. It is well accepted that 27P is a proton halo nucleus. Although not as anomalous as 27P, the different factor d of 29S is obviously larger than that of its neighbouring isotones of N = 13. This result indicates that a moderate proton halo may exist in 29S nucleus. We calculate the total reaction cross sections for 29S with the modified Glauber theory as a function of incident energy and compare the results with those for 27Si which is a core nucleus of 29S. The measured TRCSs of 27Si+28Si can be described to be satisfactory by the modified Glauber theory of the optical limit approach. Although a diffused nuclear density distribution is used, the theories still inadequately predict the experimental TRCSs of 29S+28Si, which further indicates the possibility of proton halo in 29S.

Unusual Threshold Anomaly in the 6Li+208Pb System

The angular distributions of elastic scattering for the 6Li +208Pb system have been measured at several energies around the Coulomb barrier. The parameters of optical potential are extracted by means of a phenomenological optical model analysis. It is found that the real and imaginal potentials show a pronounced energy dependence. The behaviour of the potential at the nearly especially sub-barrier energies in the 6Li+208Pb system is quite different from the results of some previous reports observed in other systems, such as 19F+208Pb and 16O+208Pb. This unusual threshold phenomenon indicates that breakup channel is strongly coupled with the elastic channel and has obvious effects on optical potential.

Dynamical Effects on Sub-barrier Fusion of 40,48Ca+90,96Zr

We have measured the fusion cross sections for 48Ca+90,96Zr around the Coulomb barrier and presented them along with the experimental data of 40Ca+90,96Zr. The experimental results are compared with the improved quantum molecular dynamics model calculations. It is shown in comparison that the dynamical effects play an important role in the sub-barrier fusion reactions.