Reaction Matrix Calculation for Neutron-Rich He-Isotopes

Abstract

The neutron-rich He-isotopes are investigated by carrying out the renormalized reaction matrix calculation, starting with the realistic two-body nuclear force. The single-particle wave function is assumed to be of the harmonic oscillator type which is permitted to have a different oscillator constant in each orbit. Several factors which influence the stability of the neutron-rich nuclei are discussed; the spin-orbit force, the starting-energy-dependence of the reaction matrix and the behaviour of the single-particle wave function. In recent years, study of nuclei far from stability-line (abbreviated to NFFS) has been developed with great interest in revealing new aspects of nuclei.v At present, a number of neutron- and proton-rich nuclei which are stable against particle-decay have been produced by the use of fragmentation and transfer reac­ tions, and the information on mass excess and other properties which show interest­ ing aspects of NFFS has been accumulated. Since the nuclear force has strong state dependence due to its noncentral parts and exchange character, the nuclear system may reveal various aspects under the changes of conditions, one of which is large variation in the ratio of proton­ and neutron-numbers. How many neutrons (protons) can be bound for a given number of protons (neutrons) seriously depends on the effective interactions deter­ mined as a result of the interplay between nuclear interaction and structure of nuclei under consideration. In this sense the neutron- (proton-) rich nuclei are expected to bring about further information on many facets of nuclei, and also offer a place where the nuclear many-body theory can be tested. In the theoretical study, several types of approach have been performed so far. In phenomenological approach mass formulae or mass relations are used; the Garvey-Kelson mass relation 2) is widely accepted and has been playing an important role as a standard base for the consideration of systematics and a guide of experi­ ments. Model calculations have been made mostly on the shell-model base3l by the use of some effective interactions. A more elaborate approach is the density-depend­ ent Hartree-Fock (DDHF) calculation. 4) In order to investigate the subtle matter such as the binding mechanism of NFFS, it is essentially important to take into account the substantial aspects of the binding mechanism which have been estab