Systematics of the pygmy resonance in keV neutron capture γ-ray spectra of nuclei with N ≈ 82–126

Igashira, M.; Kitazawa, H.; Shimizu, M.; Komano, Hiroshi; Yamamuro, Nobuhiro

doi:10.1016/0375-9474(86)90380-5

Cited by 88 publications

(57 citation statements)

References 20 publications

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“…The present spectrum of 141 Pr at 550 ke V was in good agreement with our previous resultC 14 ) at 540 ke V, and an anomalous bump was clearly observed around l.5MeV. The anomalous bump was also observed around 1.5 MeV in the spectra of 14°C e, as was predicted by the systematics obtained in our previous workC 14 l. The origin of the anomalous bump should be investigated from various aspects such as the pygmy resonance in the El 1 -ray strength function and the excitation of the Ml scissors mode. The reduced multiplicity of observed capture I rays was calculated, and compared with those for other nuclides.…”

Section: Discussionsupporting

confidence: 93%

Measurement of keV-Neutron Capture Cross Sections and Capture Gamma-Ray Spectra of¹⁴⁰Ce and¹⁴¹Pr

HARNOOD¹,

Igashira²,

Matsumoto³

et al. 2000

Journal of Nuclear Science and Technology

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The neutron capture cross sections and capture ')'-ray spectra of 14°C e and 141 Pr were measured in the neutron energy region of 10 to lOOkeV and at 550keV. Prompt 1' rays from a capture sample were detected with a large anti-Compton NaI(Tl) spectrometer, employing a neutron time-of-flight method with a 1.5-ns pulsed neutron source by the 7 Li(p, n)7Be reaction. A pulse-height weighting technique was applied to observed capture ')'-ray pulse-height spectra to extract capture yields. The capture cross sections were derived with the error of about 5% by using the standard capture cross sections of 197 Au. The present results were compared with evaluated values in JENDL-3.2 and previous measurements. The capture ')'-ray spectra were obtained by unfolding the observed capture ')'-ray pulse-height spectra. An anomalous bump was observed around 1.5 MeV in each ')'-ray spectrum of 14°C e and 141 Pr, and its energy position was consistent with the systematics obtained in our previous work. The multiplicities of the observed capture 1' rays were derived from the ')'-ray spectra.

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Section: Discussionsupporting

confidence: 93%

Measurement of keV-Neutron Capture Cross Sections and Capture Gamma-Ray Spectra of¹⁴⁰Ce and¹⁴¹Pr

HARNOOD¹,

Igashira²,

Matsumoto³

et al. 2000

Journal of Nuclear Science and Technology

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“…Experimentally, resonances in the low E γ region have long been observed, commonly termed as pygmy dipole resonances and attributed to the enhancement of the E1 strength function [8], partly due to the presence of a neutron skin. Recent studies in rare earth nuclei have shown [9,10] that bumps in the E γ ≈ 3 MeV region are of M1 character.…”

Section: Introductionmentioning

confidence: 99%

Low energy magnetic radiation enhancement in thef7/2shell

Karampagia¹,

Brown²,

Zelevinsky³

2017

Phys. Rev. C

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Studies of the γ-ray strength functions can reveal useful information concerning underlying nuclear structure. Accumulated experimental data on the strength functions show an enhancement in the low γ energy region. We have calculated the M1 strength functions for the 49,50 Cr and 48 V nuclei in the f 7/2 shell-model basis. We find a low-energy enhancement for gamma decay similar to that obtained for other nuclei in previous studies, but for the first time we are also able to study the complete distribution related to M1 emission and absorption. We find that M1 strength distribution peaks at zero transition energy and falls off exponentially. The height of the peak and the slope of the exponential are approximately independent of the nuclei studied in this model space and the range of initial angular momenta. We show that the slope of the exponential fall off is proportional to the energy of the T = 1 pairing gap.

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“…However, the situation is more complex. Further studies [5][6][7] reveal fine structures in the RSF, which are commonly called pygmy resonances. This name does not refer to specific structures: the E1 pygmy resonance in the E γ = 5 − 7 MeV region of gold to lead nuclei could be due to neutron skin oscillations [8], whereas bumps in the 3 MeV region of rare earth nuclei are now determined to be of M1 character [9,10].…”

Section: Introductionmentioning

confidence: 99%

Radiative strength functions inMo93−98

et al. 2005

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Radiative strength functions (RSFs) in 93−98 Mo have been extracted using the ( 3 He,αγ) and ( 3 He, 3 He ′ γ) reactions. The RSFs are U-shaped as function of γ energy with a minimum at around Eγ = 3 MeV. The minimum values increase with neutron number due to the increase in the lowenergy tail of the giant electric dipole resonance with nuclear deformation. The unexpected strong increase in strength below Eγ = 3 MeV, here called soft pole, is established for all 93−98 Mo isotopes. The soft pole is present at all initial excitation energies in the 5 − 8 MeV region.

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Systematics of the pygmy resonance in keV neutron capture γ-ray spectra of nuclei with N ≈ 82–126

Cited by 88 publications

References 20 publications

Measurement of keV-Neutron Capture Cross Sections and Capture Gamma-Ray Spectra of¹⁴⁰Ce and¹⁴¹Pr

Measurement of keV-Neutron Capture Cross Sections and Capture Gamma-Ray Spectra of¹⁴⁰Ce and¹⁴¹Pr

Low energy magnetic radiation enhancement in thef7/2shell

Radiative strength functions inMo93−98

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Systematics of the pygmy resonance in keV neutron capture γ-ray spectra of nuclei with N ≈ 82–126

Cited by 88 publications

References 20 publications

Measurement of keV-Neutron Capture Cross Sections and Capture Gamma-Ray Spectra of140Ce and141Pr

Measurement of keV-Neutron Capture Cross Sections and Capture Gamma-Ray Spectra of140Ce and141Pr

Low energy magnetic radiation enhancement in thef7/2shell

Radiative strength functions inMo93−98

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Measurement of keV-Neutron Capture Cross Sections and Capture Gamma-Ray Spectra of¹⁴⁰Ce and¹⁴¹Pr

Measurement of keV-Neutron Capture Cross Sections and Capture Gamma-Ray Spectra of¹⁴⁰Ce and¹⁴¹Pr