No abstract

In order to study the physics responsible for a hmitation in angular momentum in heavy-ion fusion reactions, fusion cross sections for the reactions 2sSi+isSi, '60+~Ca, 3tS+s Si, and ' C+' Cr have been measured at several incident energies covering lower and higher energy regions by detecting the yields of the fusion-evaporation residues. The limiting angular momenta for fusion are extracted from the measured fusion cross sections and compared with calculations based upon several models. Through the systematic study of different entrance channels forming the same compound nucleus, a strong entrance channel effect has been observed for very asymmetric systems. Our conclusion is that the entrance channel is significant in limiting the fusion cross section in the higher energy region.

Equilibrium charge distributions have been measured for 18 kinds of ions passing through a carbon foil in the energy region of 1 -6 MeV/u for light ions and of 0.2 -1 MeV/u for heavy ions. By combining the data obtained at present with those reported for other energies or ion species, an attempt is made to find the systematics for charge fraction F(q), mean charge q, and distribution width d over the wide range of ion species Z and energy E. Strong correlation has been found between the shell structure of ions and the variation of q or d with Z or E. The analysis for this correlation enables the evaluation of rather reliable values of q, d, or F(q) for ion species 4~Z~9 2 in carbon foils from 0.02 to 6 MeV/u.