Study of (d,2He) and (3He,t) charge exchange reactions on 14N and 64Ni
Denis De Frenne
Université de Gand
Vendredi 19/05/2006, 11:00
Bat 703, p 45, CEA Saclay, Orme des Merisiers
The charge-exchange reactions performed at intermediate energies represent a unique opportunity for studying the collective excitations in nuclei.The most simple excitation of the spin and isospin degrees of freedom of a nucleus is called a Gamow-Teller (GT) excitation (ΔJπ = 1+, ΔL = 0, ΔS = 1, ΔT = 1) It is very analoguous to similar ΔL=0 transitions in beta decay.
Its investigation is an opportunity to study a few basic features of the nuclear force due to the very simple excitation mechanism.
It is well-known that beta decay studies suffer from the Q-limitation, while the limited resolution of (p, n) or (n, p) - type charge-exchange reactions made it difficult in the past to determine the GT strength distribution for individual final levels. With the improved resolution obtained in the (n, p)-type (d, 2He) reaction (≈ 100 keV) and in the (p, n)-type (3He, t) reaction (≈ 35 keV) this goal is now achievable.
We will report here on two particular cases where the very good energy resolution obtained in these two reactions makes possible a step forward in the understanding of certain key features:
1. The GT strength distribution starting from the ground state of 14N in both β+ and β- directions reveals basic aspects of the applicability of the Shell Model and its interplay with other models.
2. The GT excitations starting from the Ni isotopes deliver important ingredients for the astrophysical models, where fp-nuclei like 64Ni play a very important role in the early stage of the collapse of supernovae and can reveal also interesting nuclear structure aspects.
Its investigation is an opportunity to study a few basic features of the nuclear force due to the very simple excitation mechanism.
It is well-known that beta decay studies suffer from the Q-limitation, while the limited resolution of (p, n) or (n, p) - type charge-exchange reactions made it difficult in the past to determine the GT strength distribution for individual final levels. With the improved resolution obtained in the (n, p)-type (d, 2He) reaction (≈ 100 keV) and in the (p, n)-type (3He, t) reaction (≈ 35 keV) this goal is now achievable.
We will report here on two particular cases where the very good energy resolution obtained in these two reactions makes possible a step forward in the understanding of certain key features:
1. The GT strength distribution starting from the ground state of 14N in both β+ and β- directions reveals basic aspects of the applicability of the Shell Model and its interplay with other models.
2. The GT excitations starting from the Ni isotopes deliver important ingredients for the astrophysical models, where fp-nuclei like 64Ni play a very important role in the early stage of the collapse of supernovae and can reveal also interesting nuclear structure aspects.
