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To study the Gamow-Teller (GT) transitions from the Tz = +1 nucleus 42Ca to the Tz = 0 nucleus 42Sc, where Tz is the z component of isospin T, we performed a (p,n)-type (³He,t) charge-exchange reaction at 140 MeV/nucleon and scattering angles around 0°. With an energy resolution of 29 keV, states excited by GT transitions (GT states) could be studied accurately. The reduced GT transition strengths B(GT) were derived up to the excitation energy of 13 MeV, assuming the proportionality between the cross sections at 0° and B(GT) values. The main part of the observed GT transition strength is concentrated in the lowest 0.611-MeV, Jπ = 1+ GT state. All the other states at higher energies are weakly excited. Shell-model calculations could reproduce the gross feature of the experimental B(GT) distribution, and random-phase-approximation calculations including an attractive isoscalar interaction showed that the 0.611-MeV state has a collective nature. It was found that this state has all of the properties of a "low-energy super-Gamow-Teller state." It is expected that low-lying Jπ = 1+ GT states have T = 0 in the Tz = 0 nucleus 42Sc. However, T = 1 states are situated in a higher energy region. Assuming an isospin-analogous structure in A = 42 isobars, analogous T = 1, 1+ states are also expected in 42Ca. Comparing the 42Ca(³He,t) 42Sc and 42Ca(p,p') spectra measured at 0°, candidates for T = 1 GT states could be found in the 10-12-MeV region of 42Sc. They were all weakly excited. The mass dependence of the GT strength distributions in Sc isotopes is also discussed. [ABSTRACT FROM AUTHOR]

Gamow-Teller (GT) strength distributions have been investigated in a high-resolution (³He,T) charge-exchange experiment on the double-ß (ßß ) decaying nuclei 128Te and l30Te. The experiment was carried out at the Research Center for Nuclear Physics, Osaka, with a 420-MeV incident 3He beam and the Grand Raiden magnetic spectrometer. A final-state energy resolution of 35 keV was achieved. The extracted GT strength distributions at low excitation energies in the final nuclei l28I and 130I are presented and discussed in the context of the ßß decay matrix elements for the two tellurium nuclei. The additional neutron pair in l30Te seems to produce a moderate increase in the fragmentation of the low-energy GT distribution. [ABSTRACT FROM AUTHOR]

Gamow-Teller (GT) transitions starting from the Tz=+2 nucleus 64Zn to the Tz=+1 nucleus 64Ga were studied in a (p,n)-type (3He,t) charge-exchange reaction at a beam energy of 140 MeV/nucleon and scattering angles close to 0°. Here, Tz is the z component of the isospin T. The experiment was conducted at the Research Center for Nuclear Physics (RCNP) in Osaka, Japan. An energy resolution of ≈34 keV was achieved by applying beam matching techniques to the Grand Raiden magnetic spectrometer system. With our good resolution, we could observe GT strength fragmented in many states up to an excitation energy of ≈11 MeV. By performing angular distribution analysis, we could identify states in 64Ga excited by GT transitions. The reduced GT transition strengths [B(GT) values] were calculated assuming the proportionality between the cross sections and the B(GT) values. Shell-model calculations using the GXPF1J interaction reproduced the B(GT) strength distribution throughout the spectrum. States with isospin T=3 were identified by comparing the 64Zn(³He,t)64Ga spectrum with a 64Zn(d,²He)64Cu spectrum. Relative excitation energies of the corresponding structures are in good agreement, supporting the robustness of isospin symmetry in the mass number A=64 nuclei. [ABSTRACT FROM AUTHOR]

We report the observation of a very exotic decay mode at the proton drip line, the β-delayed γ-proton decay, clearly seen in the β decay of the T_{z}=-2 nucleus ^{56}Zn. Three γ-proton sequences have been observed after the β decay. Here this decay mode, already observed in the sd shell, is seen for the first time in the fp shell. Both γ and proton decays have been taken into account in the estimation of the Fermi and Gamow-Teller strengths. Evidence for fragmentation of the Fermi strength due to strong isospin mixing is found.

Gamow-Teller (GT) transitions in atomic nuclei are sensitive to both nuclear shell structure and effective residual interactions. The nuclear GT excitations were studied for the mass number A = 42, 46, 50, and 54 "f-shell" nuclei in ((3)He, t) charge-exchange reactions. In the (42)Ca → (42)Sc reaction, most of the GT strength is concentrated in the lowest excited state at 0.6 MeV, suggesting the existence of a low-energy GT phonon excitation. As A increases, a high-energy GT phonon excitation develops in the 6-11 MeV region. In the (54)Fe → (54)Co reaction, the high-energy GT phonon excitation mainly carries the GT strength. The existence of these two GT phonon excitations are attributed to the 2 fermionic degrees of freedom in nuclei.