Low-Energy Enhancement in the Photon Strength of 
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi>Mo</mml:mi><mml:mprescripts /><mml:none /><mml:mn>95</mml:mn></mml:mmultiscripts></mml:math>

Wiedeking, M.; Bernstein, L. A.; Krtička, M.; Bleuel, D. L.; Allmond, J. M.; Basunia, M. S.; Burke, J. T.; Fallon, P.; Firestone, R. B.; Goldblum, B. L.; Hatarik, R.; Lake, Peter T.; Lee, IY; Lesher, Shelly; Paschalis, S.; Petri, M.; Phair, L.; Scielzo, N. D.

doi:10.1103/physrevlett.108.162503

Cited by 77 publications

(66 citation statements)

References 27 publications

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“…This low-energy enhancement or upbend has been seen in a wide mass range of nuclei, including 60,64 Ni [30][31][32][33][34][35][36][37][38][39][40][41]. The physical mechanisms underlying this upbend are still not well understood, and theoretical investigations propose different interpretations.…”

Section: Introductionmentioning

confidence: 98%

Investigating the γ decay of Ni65 from particle- γ coincidence data

et al. 2017

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The γ decay of 65 Ni has been studied from particle-γ coincidence data on the 64 Ni(d,pγ ) 65 Ni reaction. γ -ray spectra at excitation energies below E x ≈ 2 MeV have been studied and compared with previous measurements. Coincidences corresponding to E x ≈ 4.4-6.1 MeV have been used to constrain the shape of the nuclear level density and γ -strength function of 65 Ni by means of the Oslo method. The experimental γ -strength function presents an enhancement at γ energies below E γ ≈ 3 MeV. In addition, a resonance-like structure centered at E γ ≈ 4.6 MeV is seen together with accumulated strength at E γ ≈ 2.6-3.6 MeV. The obtained results contribute to the systematic study of γ decay in the Ni isotopes, which is of great interest for the understanding of both single-particle and collective nuclear structure phenomena.

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Section: Introductionmentioning

confidence: 98%

Investigating the γ decay of Ni65 from particle- γ coincidence data

et al. 2017

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“…One of the most surprising features observed in the γ -strength function is the increased probability of γ decay with γ energies below 2-4 MeV, first seen in 56,57 Fe in 2004 [11]. Since then, this low-energy enhancement or upbend has been measured for several nuclei from Sc to Sm [11][12][13][14][15][16][17][18][19] and confirmed with an independent method for 95 Mo [20]. The physical mechanisms underlying this enhancement are still not clarified.…”

Section: Introductionmentioning

confidence: 99%

Statistical γ -decay properties of Ni64 and deduced ( n,γ ) cross section of the
Campo
¹
,
Garrote
²
,
Eriksen
³

et al. 2016
Phys. Rev. C

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Particle-γ coincidence data have been analyzed to obtain the nuclear level density and the γ -strength function of 64 Ni by means of the Oslo method. The level density found in this work is in very good agreement with known energy levels at low excitation energies as well as with data deduced from particle-evaporation measurements at excitation energies above E x ≈ 5.5 MeV. The experimental γ -strength function presents an enhancement at γ energies below E γ ≈ 3 MeV and possibly a resonancelike structure centered at E γ ≈ 9.2 MeV. The obtained nuclear level density and γ -strength function have been used to estimate the (n,γ ) cross section for the s-process branch-point nucleus 63 Ni, of particular interest for astrophysical calculations of elemental abundances.

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“…Widely different shapes for the photon strength function (PSF), representing the decay strength as a function of γ -ray energy, have resulted from various measurements [1][2][3]. In addition, the enhancement in strength at low γ -ray energies reported for molybdenum isotopes [1,2] has been called into question [4,5], although more recent data [6] strongly support its existence. There is also disagreement about the nature of γ decay following neutron capture on molybdenum isotopes.…”

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“…Neutron capture measurements were made at a source-to-sample distance of 40.12 m with a pair of C 6 D 6 detectors using the pulseheight-weighting technique, and were normalized via the saturated 4.9 eV resonance in the 197 Au(n,γ ) reaction. Total neutron cross sections were measured on a separate flight path via transmission using a 6 Li-loaded glass scintillator − , 2 − , 3 − , and 4 − , respectively. Resonance spins and parities were determined using information contained in the γ -ray cascade following neutron capture, as described in Ref.…”

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confidence: 99%

Extreme nonstatistical effects inγdecay of95Mo neutron resonances

et al. 2013

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We demonstrate that high-quality total radiation width ( γ ) data are a virtually untapped resource for testing and improving nuclear models. To this end, we obtained unprecedentedly large sets of γ values for all six sand p-wave J π values for 95 Mo neutron resonances. We show that γ distributions simulated in the framework of the nuclear statistical model are in sharp disagreement with the data. Simulations modified to include doorway effects resulted in much better agreement. These results call into question the reliability of the nuclear statistical model. There has been significant controversy surrounding γ decay of molybdenum isotopes below the neutron separation energy. Widely different shapes for the photon strength function (PSF), representing the decay strength as a function of γ -ray energy, have resulted from various measurements [1][2][3]. In addition, the enhancement in strength at low γ -ray energies reported for molybdenum isotopes [1,2] has been called into question [4,5], although more recent data [6] strongly support its existence. There is also disagreement about the nature of γ decay following neutron capture on molybdenum isotopes. On the basis of a very few measured total radiation widths γ , it was suggested [7] that significant nonstatistical effects affected this decay. In contrast, it was found that the extreme statistical model was in very good agreement with two-step cascade γ spectra following thermal neutron capture [4] as well as coincidence-pulse-height spectra and other data for neutron-resonance capture [5].Resolving these controversies is of central importance for applications such as advanced nuclear fuel cycles [8] and astrophysical nucleosynthesis studies. For example, the PSF shape can have substantial impact on astrophysical reaction rates [9] in explosive environments, and therefore significantly impact the resulting nucleosynthesis. In addition, as the nuclear statistical model is used to calculate almost all rates for nuclides beyond the reach of current experiments, it is important to test basic assumptions of this model.Total radiation widths of neutron resonances represent a virtually untapped source of data in this endeavor. Due to the very large number of levels below the neutron binding energy B n , there are thousands of channels by which γ decay can occur following resonance neutron capture, a few of which are schematically illustrated in Fig. 1. Hence, energies E γ of these transitions span the entire range of level density (LD) and PSF below B n . The total radiation width γ is the sum of all the partial widths for the initial (primary) γ transitions from the resonance.According to the statistical model, strengths of each of these primary transitions follow the Porter-Thomas distribution (PTD) [10], with average strength proportional to the PSF * Corresponding author.(with an appropriate energy factor, which is E 3 γ for dipole transitions) at the corresponding energy. It is further assumed that all, or at least the vast majority, of the channels are indepen...

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Low-Energy Enhancement in the Photon Strength of Mo95

Cited by 77 publications

References 27 publications

Investigating the γ decay of Ni65 from particle- γ coincidence data

Investigating the γ decay of Ni65 from particle- γ coincidence data

Statistical γ -decay properties of Ni64 and deduced ( n,γ ) cross section of the
Campo
¹
,
Garrote
²
,
Eriksen
³

et al. 2016
Phys. Rev. C

Extreme nonstatistical effects inγdecay of95Mo neutron resonances

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Low-Energy Enhancement in the Photon Strength of Mo95

Cited by 77 publications

References 27 publications

Investigating the γ decay of Ni65 from particle- γ coincidence data

Investigating the γ decay of Ni65 from particle- γ coincidence data

Statistical γ -decay properties of Ni64 and deduced ( n,γ ) cross section of the Campo1, Garrote2, Eriksen3 et al. 2016Phys. Rev. C

Extreme nonstatistical effects inγdecay of95Mo neutron resonances

Contact Info

Product

Resources

About

Statistical γ -decay properties of Ni64 and deduced ( n,γ ) cross section of the
Campo
¹
,
Garrote
²
,
Eriksen
³

et al. 2016
Phys. Rev. C