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arXiv 1609.06128nucl-ex
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~(87)Br、~(88)Br和~(94)Rb β缓发中子发射体的全吸收Gamma-Ray谱

Total Absorption Gamma-Ray Spectroscopy of 87Br, 88Br and 94Rb Beta-Delayed Neutron Emitters

E. Valencia, J. L. Tain, A. Algora, J. Agramunt, B. Rubio, S. Rice, W. Gelletly, P. Regan, A. -A. Zakari-Issoufou, M. Fallot, A. Porta, J. Rissanen, T. Eronen, … 展开作者

E. Valencia, J. L. Tain, A. Algora, J. Agramunt, B. Rubio, S. Rice, W. Gelletly, P. Regan, A. -A. Zakari-Issoufou, M. Fallot, A. Porta, J. Rissanen, T. Eronen, J. Aysto, L. Batist, M. Bowry, V. M. Bui, R. Caballero-Folch, D. Cano-Ott, V. -V. Elomaa, E. Estevez, G. F. Farrelly, A. R. Garcia, B. Gomez-Hornillos, V. Gorlychev, J. Hakala, M. D. Jordan, A. Jokinen, V. S. Kolhinen, F. G. Kondev, T. Martinez, E. Mendoza, I. Moore, H. Penttila, Zs. Podolyak, M. Reponen, V. Sonnenschein, A. A. Sonzogni

摘要:

我们用全吸收γ谱研究了~(87)Br、~(88)Br和~(94)Rb的衰变。这些重要的裂变产物是β-缓发中子发射体。我们的数据显示了相当大的伽马强度,迄今为止在高分辨率伽马射线光谱学中未观察到,从高激发能的状态。我们还发现显着差异的β强度,可以推断出从现有的测量β光谱。我们评估的影响,目前的数据对反应堆衰变热求和计算。虽然这种影响相对较小,但它有助于减少冷却时间在1至100 s范围内的235 U裂变光子分量的计算和积分测量之间的差异。我们还使用求和计算来评估目前的数据对反应堆反中微子光谱的影响。我们发现在5至9兆电子伏的范围内的反中微子能量的显着效果。此外,我们观察到一个意想不到的强概率γ辐射中子非束缚态填充的子核。伽马分支相比,豪泽-Feshbach计算,使一个解释的大值溴同位素由于原子核结构。然而,94 Rb的分支虽然小得多,但暗示需要将辐射宽度增加一个数量级。这导致了一个类似的增加,在计算的(n,伽玛)截面,这个非常丰富的中子核与r-过程丰度计算的潜在影响。

英文摘要:

We investigate the decay of 87Br, 88Br and 94Rb using total absorption gamma-ray spectroscopy. These important fission products are beta-delayed neutron emitters. Our data show considerable gamma-intensity, so far unobserved in high-resolution gamma-ray spectroscopy, from states at high excitation energy. We also find significant differences with the beta intensity that can be deduced from existing measurements of the beta spectrum. We evaluate the impact of the present data on reactor decay heat using summation calculations. Although the effect is relatively small it helps to reduce the discrepancy between calculations and integral measurements of the photon component for 235U fission at cooling times in the range 1 to 100 s. We also use summation calculations to evaluate the impact of present data on reactor antineutrino spectra. We find a significant effect at antineutrino energies in the range of 5 to 9 MeV. In addition, we observe an unexpected strong probability for gamma emission from neutron unbound states populated in the daughter nucleus. The gamma branching is compared to Hauser-Feshbach calculations which allow one to explain the large value for bromine isotopes as due to nuclear structure. However the branching for 94Rb, although much smaller, hints of the need to increase the radiative width by one order-of-magnitude. This leads to a similar increase in the calculated (n,gamma) cross section for this very neutron-rich nucleus with a potential impact on r-process abundance calculations.

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