The 20F and 20Na NUCLEI and the 19Ne(p, γ) 20Na reaction in a microscopic three-cluster model

Abstract

The generator coordinate method is applied to a three-cluster description of the 19Ne(p,γ) 20Na reaction. Different 19Ne+p and 17F+ 3He configurations are included in the model. The 19Ne nucleus is described by an 16O + 3He cluster structure with J π = 1 2 + , 3 2 + , 5 2 + , 1 2 − , 3 2 − and 17 F by an 16O + p cluster structure with J π = 1 2 + , 3 2 + , 5 2 + . We find a good qualitative agreement with exper for the level scheme of the mirror nucleus 20F. The spin assignments of the experimental 20F levels are discussed; the 3.17 MeV state of 20F is suggested to be a possible 1 − state. The experimental El, E2 and Ml reduced transition probabilities in 20F are however not well reproduced by the model. This problem is shown to arise from the cluster structure adopted here. In the 20Na spectrum, the first 19nc+p resonance is suggested to be the analog of the 3.17 MeV of 20F and therefore a possible 1 − state, in contradiction with the 1 + assignment of Kubono et at. With this assumption, we compute the resonant and non-resonant 19Ne(p, γ) 20Na reaction rates, and find results larger by about a factor of three than those of Kubono et al.