Pre-formation Probability of ^5He Cluster in Pre-equilibrium Mechanism

The possibility of ^5He cluster emission has been affirmed theoretically. In order to describe the emission probability of SHe cluster, the pre-formation probability of ^5He cluster in pre-equilibrium emission process is needed to be established. In terms of Iwamoto-Harada model, the theoretical formula of pre-formation probability of ^5He cluster including lp shell nucleon in pre-equilibrium mechanism has been established and calculated. In the case of low incident energies, the configuration of 1, m] for ^5He cluster is the dominant part in the nuclear reaction. The calculated results indicate that pre-formation probability of configuration 1, m] for the unstable SHe duster is much smaller than those of d, t, ^3He, and ^4He, i.e. the light stable composite particles, which are consisted of only ls shell nucleons. However, it is propitious to the emission of ^5He from the point of view on threshold energies, since the binding energies of ^5He are generally lower than that of 3He in compound nucleus. The corresponding model formula has been given in this paper for described pre-formation probability of ^5He cluster in pre-equilibrium mechanism.