Dependence of Gamow-Teller? +-decay of80Zr,76Sr and72Kr on nuclear shape

Abstract

Abstract. The Gamow-Teller (GT)/3 +-decay probability is estimated for three neutron-deficient N = Z nuclei, 76 8OZr ~Kr36, 38Sr38, and 4o 4o, using a quasiparticle TammDancoff approximation (TDA) based on a Skyrme-type deformed Hartree-Fock (HF) calculation. The distribution of the GT strength is found to depend sensitively on the nuclear shape, namely, a spherical shape or a prolate or an oblate deformation of the obtained HF minima. At the shape of the lowest HF minimum about a half of the calculated total GT strength lies below the ground state of those N = Z mother nuclei, and there seems to be a good chance to observe/?-delayed proton emission. PACS: 21.10.Re; 21.60.Jz; 23.40.Hc The giant resonances (GR) of spin-isospin excitation modes of /~-stable nuclei have been studied since the eighties, using charge exchange reactions such as (p, n) and (3He, t). See, for example, in [1,2]. The isopin-dependent properties of nuclei far from fl-stability may show a dramatic difference from that of stable nuclei and are currently of broad interests, especially because the recent development of experimental facilities as well as currently planned projects may give an actual chance of measuring them. The quantitative information on the isospin-dependent modes in nuclei far from the/~-stability line is also of great interests in nuclear astrophysics. It was pointed out in [3,4] that in very light neutron-drip-line and in medium-heavy proton-drip-line nuclei the GT GR might be reached by ]~-decay and by fl+ decay, respectively. Namely, the major strength of GT GR may be placed below the ground state of respective mother nuclei. The deformation and pair correlation, which were neglected in the calculation of [3,4], can be important in some of nuclei studied there. Thus, in this letter we present the calculated result of three nuclei, 72 76 36Kr36, 38Sr38 and 4S~ using the deformed HF calculation together with the quasiparticle TDA. Those neutron-deficient N = Z nuclei are chosen here, especially because we are stimulated by learning the possibility [5] of having experimental information on the part of GT GR strength expected to lie at higher excited states of daughter nuclei, which are populated by /~+-decay. Some experimental result of the GT/~+ decay of 76Sr to lower-lying states of the daughter nucleus, 76 37Rb39, can be found in [6]. The observed small excitation energy [7] of the first 2 + state, 709, 261 and 290 keV in 72Kr, 76Sr and 8~ respectively, already suggests that these nuclei are deformed, though a direct experimental information on the shape is not yet available. Those nuclei are predicted to be deformed according to various theoretical calculations [8,9]. The/~-decay half-lives of 76Sr and 8~ were estimated in [10] without introducing the possibility of deformed shape.First, we perform deformed HF calculations using Skyrme interactions [11]. In order to obtain a HF minimum at a reasonable deformation, pair correlations have to be included. We use the BCS approximation with a given pairing-gap parameter, ...

Symmetry-unrestricted Skyrme–Hartree–Fock–Bogoliubov calculations for exotic shapes in nuclei from 64Ge to 84Mo

“…These gross features are consistent with available experimental data [60][61][62][63][64][65][66] and previous theoretical calculations [19,21,22,49,[67][68][69][70][71][72][73][74][75][76][77].…”

“…[21,22]. The oblate shape of 76 84 Mo with a finite equilibrium value of β 30 is reported in [21]. Although such details differ depending on the treatment of the pairing correlations, the basic features, i.e., the softness to both β 32 and β 33 of the oblate shape of 76 Sr and the softess to β 30 of the spherical shape of 84 Mo are in common between the present HFB calculations and those of [21,22].…”

“…Fig. 1) of the quadrupole deformation energies for 64 Ge, 68 Se, 72 Kr, 76 Sr, 80 Zr and 84 Mo. The effective interactions used are the same as in Fig.…”

Mass measurements on neutron-deficient Sr and neutron-rich Sn isotopes with the ISOLTRAP mass spectrometer

“…Following the concept of valence nucleons and mirror nuclei this region is still a unique test bench for investigating the forces between individual nucleons as well as their interactions with the residual nuclear core [5,6]. Furthermore, strong deformations among the upper fp-shell N ≈ Z nuclei have particularly triggered development of new methods for deducing the nature of ground-state deformations [7,8]. It is of central relevance whether the theoretical predictions remain valid when extending them into formerly unknown regions far from the valley of β-stability.…”

Beta decay studies of the N=Z and waiting point nucleus72Kr

“…Hartree-Fock (HF) calculations [5] predict that the GT distribution depends on the shape for nuclei in the mass region A≈70-80. These predictions have been supported by calculations performed by P. Sarriguren [6] where several nearby minima in potential energy at different quadrupole deformations are predicted.…”