Abstract
We propose a schematic model of nucleons moving in spin–orbit partner levels, j=l±12, to explain Gamow–Teller and two-nucleon transfer data in N=Z nuclei above 40Ca. Use of the LS coupling scheme provides a more transparent approach to interpret the structure and reaction data. We apply the model to the analysis of charge-exchange, 42Ca(3He,t)42Sc, and np-transfer, 40Ca(3He,p)42Sc, reactions data to define the elementary modes of excitation in terms of both isovector and isoscalar pairs, whose properties can be determined by adjusting the parameters of the model (spin–orbit splitting, isovector pairing strength and quadrupole matrix element) to the available data. The overall agreement with experiment suggests that the approach captures the main physics ingredients and provides the basis for a boson approximation that can be extended to heavier nuclei. Our analysis also reveals that the SU(4)-symmetry limit is not realized in 42Sc.
Highlights
We propose a schematic model of nucleons moving in spin–orbit partner levels, j = l ± 1/2, to explain Gamow–Teller and two-nucleon transfer data in N = Z nuclei above 40Ca
In this letter we propose an explanation of these observations, assuming that the nucleons occupy two orbitals with radial quantum number n, orbital angular momentum l and total angular momentum j = l ± 1/2
Since the properties of the nuclear interaction are more transparent in LS coupling, we analyze the problem in this basis instead of the more usual jj coupling
Summary
They lead to a description of structural properties in terms of three essential quantities: the spin–orbit splitting ∆ , and the isoscalar and isovector pairing strengths V0110 and V0001, which we denote on as g0 and g1, respectively. To calculate various properties in the LSJT basis, we consider a general one-body operator with definite tensor character λl under SOL(3), λs under SOS(3), coupled to total λj, and λt under SOT (3). With this expression one can calculate matrix elements of the M1 operator (λj = 1), which has spin (λl, λs) = (0, 1), orbital (λl, λs) = (1, 0) and tensor (λl, λs) = (1, 1) parts of both isoscalar (λt = 0) and isovector (λt = 1) character.
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