Spin–isospin excitations probed by strong, weak and electro-magnetic interactions

Fujita, Y.; Rubio, B.; Gelletly, W.

doi:10.1016/j.ppnp.2011.01.056

Cited by 180 publications

(183 citation statements)

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“…Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. structure [9][10][11][12][13]. This relationship is particularly strong for nuclei close to shell closures.…”

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confidence: 93%

Evidence for Gamow-Teller Decay ofNi78Core from Beta-Delayed Neutron Emission Studies

et al. 2016

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The β-delayed neutron emission of 83;84 Ga isotopes was studied using the neutron time-of-flight technique. The measured neutron energy spectra showed emission from states at excitation energies high above the neutron separation energy and previously not observed in the β decay of midmass nuclei. The large decay strength deduced from the observed intense neutron emission is a signature of Gamow-Teller transformation. This observation was interpreted as evidence for allowed β decay to 78 Ni core-excited states in 83;84 Ge favored by shell effects. We developed shell model calculations in the proton fpg 9=2 and neutron extended fpg 9=2 þ d 5=2 valence space using realistic interactions that were used to understand measured β-decay lifetimes. We conclude that enhanced, concentrated β-decay strength for neutron-unbound states may be common for very neutron-rich nuclei. This leads to intense β-delayed high-energy neutron and strong multineutron emission probabilities that in turn affect astrophysical nucleosynthesis models. DOI: 10.1103/PhysRevLett.117.092502 β-delayed neutron emission from fission fragments was first observed in 1939 following the neutron bombardment of uranium salts [1]. It was recognized that the delayed neutron energies and emission probabilities, P n , are important parameters to model environments that involve neutron-rich isotopes. Two of the main applications are in nuclear reactor physics [2] and r-process nucleosynthesis [3]. Because β-delayed neutron precursors are neutron rich and far from stability, they are always relatively difficult to produce and study. Advances in detector capabilities allowed for pioneering measurements of neutron emission spectra of fission fragments [4,5]. In these experiments, resonancelike behavior was observed in the neutron emission spectrum [4,6].These efforts were halted in the following decade by several factors. First, it became increasingly difficult to produce species with larger neutron excess. Second, the very influential work by Hardy, Johnson, and Hansen on "pandemonium" attributed the features of the neutron spectra to purely statistical effects and warned against overinterpretation of the measurements [7]. Misinterpretations of their work attributed decay observables of all heavy nuclei to gross features of the decay strength and statistical fluctuations of the level density. A more accurate depiction of their work is that neutron emission characteristics cannot be interpreted without considering the effects of high level density. The pandemonium controversy [8] arose partly from the fact that, at the time, there was no capability to compute nuclear properties using a sufficiently complete microscopic model of the nucleus.State-of-the-art models are now capable of computing decay properties of atomic nuclei, such as lifetimes and branching ratios. It has become increasingly clear that the β-decay observables are profoundly influenced by nuclearPublished by the American Physical Society under the terms of the Creative Commons Attribution 3.0 Lic...

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confidence: 93%

Evidence for Gamow-Teller Decay ofNi78Core from Beta-Delayed Neutron Emission Studies

et al. 2016

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“…Only a few configurations are involved in GT transitions caused by the GT operator στ having no radial or angular momentum component [5,6]. In a SM picture, where the nucleons are in an orbit with angular momentum l and spin s ¼ AE1=2, GT transitions can connect only the orbits with the j > (¼ l þ 1=2) and j < (¼ l − 1=2) values, where the former is energetically lower than the latter due to the L · S force.…”

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confidence: 99%

“…The accessible excitation energy (E x ), however, is limited by the decay Q value [6]. In the 1980s, it was found that charge-exchange (CE) reactions at intermediate incident energies (E > 100 MeV=nucleon) and the scattering angle Θ ¼ 0°are good tools for the study of GT excitations [4].…”

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confidence: 99%

“…It is well established that the ERIs among the p-h configurations in IVexcitations, such as the GT or IV dipole excitations, have a repulsive nature, and thus, IV GRs are pushed up relative to the unperturbed p-h energies [4]. On the contrary, in lighter nuclei with mass number A ≤ 40, prominent high-energy GTRs are not observed; the GT strength is mainly carried by states at lower energies [6,7]. This raises a question of how these two features of GT strength distributions can be understood consistently.…”

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confidence: 99%

“…The orbits f 5=2 and f 7=2 with l ¼ 3 represent the j < and j > orbits, respectively, where the single particle energy of the former is about 6 MeV higher than that of the latter [1]. For a systematic study, we selected target nuclei with even Z and N numbers and neutron excesses of two, i.e., T z ¼ þ1, where T z ¼ ðN − ZÞ=2 is the z component of isospin T. It has been shown that GT excitations dominate the spectra of the ( 3 He, t), CE reaction at 0°and an intermediate beam energy of 140 MeV=nucleon [6]. In addition, although there were exceptions, a close proportionality between the cross sections at 0°and the BðGTÞ values σð0°Þ ≃σ GT ð0°ÞBðGTÞ; (1) has been empirically established [6,[9][10][11][12][13], whereσ GT ð0°Þ is the unit GT cross section at 0°.…”

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confidence: 99%

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Observation of Low- and High-Energy Gamow-Teller Phonon Excitations in Nuclei

Fujita¹,

Fujita²,

Adachi³

et al. 2014

Phys. Rev. Lett.

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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 ¼ 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.

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Expanding Nuclear Physics Horizons with the Gamma Factory

et al. 2022

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The Gamma Factory (GF) is an ambitious proposal, currently explored within the CERN Physics Beyond Colliders program, for a source of photons with energies up to ≈400 MeV and photon fluxes (up to ≈1017 photons s−1) exceeding those of the currently available gamma sources by orders of magnitude. The high‐energy (secondary) photons are produced via resonant scattering of the primary laser photons by highly relativistic partially‐stripped ions circulating in the accelerator. The secondary photons are emitted in a narrow cone and the energy of the beam can be monochromatized, down to 10−3–10−6 level, via collimation, at the expense of the photon flux. This paper surveys the new opportunities that may be afforded by the GF in nuclear physics and related fields.

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Spin–isospin excitations probed by strong, weak and electro-magnetic interactions

Cited by 180 publications

References 203 publications

Evidence for Gamow-Teller Decay ofNi78Core from Beta-Delayed Neutron Emission Studies

Evidence for Gamow-Teller Decay ofNi78Core from Beta-Delayed Neutron Emission Studies

Observation of Low- and High-Energy Gamow-Teller Phonon Excitations in Nuclei

Expanding Nuclear Physics Horizons with the Gamma Factory

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