Gamov-Teller Transitions Research Articles

Negative parity states ofB11andC11and the similarity withC12

The negative parity states of $^{11}\mathrm{B}$ and $^{11}\mathrm{C}$ were studied based on the calculations of antisymmetrized molecular dynamics (AMD). The calculations reproduced well the experimental strengths of Gamov-Teller (GT), $M1$, and monopole transitions. We especially focused on the $3/{2}_{3}^{\ensuremath{-}}$ and $5/{2}_{2}^{\ensuremath{-}}$ states for which GT transition strengths were recently measured. The weak $M1$ and GT transitions for $3/{2}_{3}^{\ensuremath{-}}$ in $^{11}\mathrm{B}$ and $^{11}\mathrm{C}$ are described by a well-developed cluster structure of $2\ensuremath{\alpha}+t$ and $2\ensuremath{\alpha}{+}^{3}$He, respectively, while the strong transitions for $5/{2}_{2}^{\ensuremath{-}}$ is characterized by an intrinsic spin excitation with no cluster structure. It was found that the $3/{2}_{3}^{\ensuremath{-}}$ state is a dilute cluster state, and its features are similar to those of ${}^{12}\mathrm{C}({0}_{2}^{+})$ which is considered to be a gas state of $3\ensuremath{\alpha}$ clusters.

BETA DECAY MODES AND THE STRUCTURE OF A=96, A=98 AND A=100 NUCLEI

The Gamov–Teller transitions were investigated within the boson model based on the idea of proton–neutron interaction and describing the 0+ and 1+ levels of A = 96 - 100 nuclei.

Weak interaction processes in supernovae: New probes using charge exchange reaction at intermediate energies

Spin-isospin-flip excitations in nuclei at vanishing momentum transfer are generally referred to as Gamov-Teller (GT) transitions. They are being studied because the simplicity of the excitation makes them an ideal probe for testing nuclear structure models. In astrophysics, GT transitions provide an important input for model calculations and element formation during the explosive phase of a massive star at the end of its life-time. GT transitions in the β − direction (also referred to as isospin lowering T < transitions) have extensively been studied through (p,n) and ( 3 He,t) charge-exchange reactions [B.D. Anderson et al., Phys. Rev. C 36 (1987) 2195, B.D. Anderson et al., Phys. Rev. C 43 (1991) 50, J. Rapaport et al., Phys. Rev. C 24 (1981) 335, H. Akimune et al., Nucl. Phys. A 569 (1994) 245c, Y. Fujita et al., Phys. Lett. B 365 (1996) 29]. The generally good resolution allows easy extraction of the GT distribution and the total B(GT − ) strength in the final nucleus. On the other hand, determination of B(GT + ) strength through a charge-exchange reaction in the T > direction were mostly done with secondary neutron beams, and as such, they come with significant experimental difficulties. TRIUMF has pioneered this field in the late 80's and early 90's with a rich and highly successful (n,p) program using a several hundred MeV neutron beam from a 7 Li(p,n) 7 Be reaction [R. Helmer, Can. J. Phys. 65 (1987) 588]. In this paper we present the ( d , 2 He) reaction at intermediate energies as another and potentially even more powerful tool for charge-exchange reactions in the T > , resp. β + direction. The key issue here will be the high resolution of order 100 keV, which provides new and sometimes unexpected insight into nuclear structure phenomena. This program has been launched at the AGOR Superconducting Cyclotron Facility at the KVI Groningen. By now, it covers a wide field of physics questions ranging from few-body physics, the structure of halo-nuclei, to questions pertaining to the dynamics of supernova explosions and nuclear synthesis, and more recently to the measurements of ( ββ ) decay matrix elements and the determination of half-lives of ( ββ ) decaying nuclei.

On the limit of nuclear stability — The region of double magic100Sn and bound-state β-decay of187Re75+

Experiments which led to the discovery of the heaviest, self-conjugated double magic nucleus100Sn and the bound-state β-decay of completely ionized187Re are presented.100Sn was produced by fragmentation of 1.1 A GeV124Xe beams, separated and implanted in a 4π Si-stack detector. From its decay a half-lifeT1/2=0.94(+0.54, −0.27) s and a β+ endpoint energy ofEβ=3.4(+0.7, −0.3) MeV were determined for the 0+−1+ Gamov-Teller transition. Completely stripped187Re75+ was produced and stored in a coolerring with an energy of 351 A MeV for several hours. The products of bound-state β-decay of187Re75+ were detected by two independent methods, which allowed to determine a half-life ofT1/2=33±6 y for this decay, which is of importance for the calibration of the Re/Os nucleosynthesis chronometer.