Low-lying Gamow-Teller transitions in spherical nuclei
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NUCLEI Theory
Low-lying Gamow–Teller Transitions in Spherical Nuclei* 1)** ¨ u¨ 2) , and C. Selam3) N. Cakmak ¸ , S. Unl
Received July 14, 2011
Abstract—The Pyatov Method has been used to study the low-lying Gamow–Teller transitions in the mass region of 98 A 130. The eigenvalues and eigenfunctions of the total Hamiltonian have been solved within the framework of proton–neutron quasiparticle random-phase approximation. The low-lying β decay log(f t) values have been calculated for the nuclei under consideration. DOI: 10.1134/S106377881201005X
been used, while for β + decay and electron capture [9] both particle–hole (ph) and particle–particle (pp) terms have been taken into account. The pp force is known to be important in reproducing the observed suppression of the GT strength in the β + direction [10–13]. The results of [8, 9] have good agreement with the experimental values of β-decay half-lives. Kuzmin and Soloviev [14] have calculated the log(f t) values for the GT β + decay of the neutron-deficit spherical nuclei and obtained good agreement with the corresponding experimental values for nuclei in the mass region of A ∼ = 94–150. In [15], using a deformed Nilsson single-particle model the strengths of the ph and pp forces have been determined in such a way that the calculation reproduces β-decay halflives of a wide range of nuclei. In [16], using the same parameter values, the log(f t) values for some deformed nuclei (125 A 131 and 159 A 181) have been calculated within the Woods–Saxon basis, and it has been shown that the calculations are in good agreement with the corresponding experimental values. In [17], authors search for deformed neutron-rich nuclei in which peaks with a considerable amount of the GT strength may be present in the excitation energy below a few MeV. The study is based on the Skyrme type Hartree–Fock calculation plus Tamm–Dancoff Approximation (TDA) or Random Phase Approximation (RPA). In pnQRPA calculations, the separable GT forces in the pp channel have played an important role in reproducing the observed suppression of the β + -transition strength, since the pp-interaction constant has been adjusted in such a way that the calculated values of the β + transition strength are in good agreement with the corresponding experimental data. The extended versions of the pnQRPA method have been used to decrease the influence of the pp interaction on the β + transition amplitude. In fact, these higher versions of the pnQRPA method have been developed to solve
1. INTRODUCTION One of the most important ways to test the properties of the nuclear structure and weak interaction is the calculation of the low-lying β-decay matrix elements or decay rates. The rates of weak interaction in nuclei far from the stability valley provide good information about the estimation of their βdecay properties. For this purpose, several authors have performed β-decay rate calculations [1–9]. The gross theory [1] was used for these calculations. This statistical model describes the average properties of the
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