Nucleon transfer reactions accompanied by the formation of a compound system of complex nuclei

Abstract

An experimental study of the dependence of the angular distributions for the (p+n) pick-up and (p+3n) stripping reactions upon the energy of Ne 22 ions has been made. The measurements were performed for the range of angles 0°–180° and for an energy interval 90–140 MeV (laboratory system). The target was Au 197 and a catcher-foil method was applied. The results obtained for the reaction Au 197(Ne 22, +d)Na 24 emphasize the tunneling mechanism for the deuteron transfer into the incident nucleus. The contribution of the “grazing” process of the (p+n) transfer is found to be much smaller. The behaviour of the total cross section for the generation of Na 24 at energies near the Coulomb barrier is found to be close to that of the excitation function of single neutron transfers, in agreement with what one may expect in the case of transfer of an associated (p+n) group. The energy dependence of the angular distribution of final products in the reaction Au 197(Ne 22, −p−3n)F 18 shows, that in the stripping of (p+3n) from the Ne 22 nucleus, the prevalent reaction mechanism is the transfer of nucleons in grazing collisions. In this case the degree of association in the transfer process seems to be low. In the range of angles 90–180° for the obtained angular distribution of the differential cross section for the (p+3n) stripping and (p+n) pick-up reactions several maxima are observed, the number and position of which change with the incident particle energy. It is proposed that the observed effects are connected with formation of a very short-lived compound system of the interacting nuclei. On the basis of the performed analysis of the measured angular distributions, the conclusion was drawn that the compound system of two nuclei (in the investigated case) has an angular momentum of about 15 ħ.