Branching and Fragmentation of Dipole Strength in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi>Ta</mml:mi></mml:mrow><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>181</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math>in the Region of the Scissors Mode

Angell, C. T.; Hajima, Ryoichi; Shizuma, T.; Ludewigt, B.; Quiter, Brian J.

doi:10.1103/physrevlett.117.142501

Cited by 13 publications

(12 citation statements)

References 21 publications

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“…It was suggested that the SR was rather weak and splits into two parts. From our work, it can be concluded that a weak SR is observed with split centroids located at 2.16 MeV ± 0.04 MeV and 2.91 MeV ± 0.05 MeV, in agreement with NRF measurements [67,68]. The case of 182 Ta is similar to that of 197,198 Au [76] where no SR is observed.…”

Section: Scissors Resonancesupporting

confidence: 88%

“…8), which are found in the typical energy range for the SR [20]. From this work the distinction between M1 and E 1 is not possible but the assignment to the SR and its location in 181 Ta is corroborated by previous measurements [67,68].…”

Section: Scissors Resonancesupporting

confidence: 83%

“…Low-lying excitations of 181 Ta were investigated using NRF experiments [67,68]. It was suggested that the SR was rather weak and splits into two parts.…”

Section: Scissors Resonancementioning

confidence: 99%

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Nuclear level densities and γ -ray strength functions of Ta180,181,182

Brits¹,

Malatji²,

Wiedeking³

et al. 2019

Phys. Rev. C

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Particle-γ coincidence experiments were performed at the Oslo Cyclotron Laboratory with the 181 Ta(d, X) and 181 Ta(3 He, X) reactions to measure the nuclear level densities (NLDs) and γ-ray strength functions (γ SFs) of 180,181,182 Ta using the Oslo method. The back-shifted Fermi-gas, constant temperature plus Fermi gas, and Hartree-Fock-Bogoliubov plus combinatorial models were used for the absolute normalizations of the experimental NLDs at the neutron separation energies. The NLDs and γ SFs are used to calculate the corresponding 181 Ta(n, γ) cross sections and these are compared to results from other techniques. The energy region of the scissors resonance strength is investigated and from the data and comparison to prior work it is concluded that the scissors strength splits into two distinct parts. This splitting may allow for the determination of triaxiality and a γ deformation of 14.9 • ± 1.8 • was determined for 181 Ta.

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Section: Scissors Resonancesupporting

confidence: 88%

Section: Scissors Resonancesupporting

confidence: 83%

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Nuclear level densities and γ -ray strength functions of Ta180,181,182

Brits¹,

Malatji²,

Wiedeking³

et al. 2019

Phys. Rev. C

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“…(8). In experiments with quasi-monochromatic photon beams, a so-called 'average branching ratio' [42][43][44][45][46][47][48][49] of photoexcited states is often accessible, if discrete states cannot be resolved any more. It is defined as:…”

Section: A Definitionsmentioning

confidence: 99%

Experimental M1 response of Ar40 as a benchmark for neutrino-nucleus scattering calculations

et al. 2019

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The excitation of atomic nuclei via magnetic dipole transitions is closely related to the inelastic neutral-current neutrino-nucleus (NC-νA) scattering process due to the similarity of the transition operators. NC-νA-scattering serves for the detection of supernova neutrinos and poses a significant source of background in modern liquid-argon based high-energy neutrino detection experiments. In order to enable tests of the reliability of predictions for neutrino-nucleus scattering, the magnetic dipole response of 40 Ar below 7.7 MeV was characterized in a nuclear resonance fluorescence experiment using quasi-monoenergetic gamma-ray beams. The linear polarization of the beams allowed for assignments of electric or magnetic character to previously known dipole excitations. A total magnetic dipole strength of 0.36 +0.04 −0.05 µ 2 N was identified in the energy range of the present experiment. Combined with data from previous measurements, the full magnetic dipole strength of 40 Ar below the neutron separation threshold was investigated. Due to the low background in the energy range within the bandwidth of the gamma-ray beams, the previous sensitivity limit was improved. A large-scale nuclear shell model calculation in the sd-f p space satisfactorily agrees with the data in terms of excitation energies and strengths of the observed 1 + states. CONTENTS

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“…However, there are a number of experimental results which indicate violations of the BA hypothesis in the low-energy region. For example, the GSF in heavy deformed nuclei at excitation energies of 2 − 3 MeV is dominated by the orbital M1 scissors mode [16] and potentially large differences in B(M1) strengths are observed between γ emission and absorption experiments [17][18][19]. At very low energies (< 2 MeV) an increase of GSFs is observed in Oslo-type experiments [20,21], which for even-even nuclei cannot have a counterpart in ground state absorption experiments because of the pairing gap.…”

Section: Introductionmentioning

confidence: 99%

Gamma Strength Functions and Level Densities from High-Resolution Proton Scattering under 0°

et al. 2018

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Abstract. Inelastic proton scattering at energies of a few 100 MeV and forward angles including 0• provides a novel method to measure gamma strength functions (GSF) in nuclei in an energy range of about 5 -20 MeV. The experiments provide not only the E1 but also the M1 part of the GSF. The latter is poorly known in heavy nuclei. Comparison with gamma decay data (e.g. from the Oslo method) allows to test the generalised BrinkAxel (BA) hypothesis in the energy region of the pygmy dipole resonance (PDR) crucial for the modelling of (n,γ) and (γ,n) reactions in astrophysical reaction networks. From the two test cases studied, 208 Pb remains inconclusive in the energy region of the PDR because of large Porter-Thomas fluctuations due to the small level density (LD), while the BA hypothesis seems to hold in case of 96 Mo. A fluctuation analysis of the high-resolution data also provides a direct measure of the LD in the energy region of the isovector giant dipole resonance (IVGDR) well above the neutron threshold, where hardly any experimental information is available. This permits an independent test of the decomposition of GSF and LD in Oslo-type experiments.

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Branching and Fragmentation of Dipole Strength inTa181in the Region of the Scissors Mode

Cited by 13 publications

References 21 publications

Nuclear level densities and γ -ray strength functions of Ta180,181,182

Nuclear level densities and γ -ray strength functions of Ta180,181,182

Experimental M1 response of Ar40 as a benchmark for neutrino-nucleus scattering calculations

Gamma Strength Functions and Level Densities from High-Resolution Proton Scattering under 0°

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