Regular ArticleDelayed-Neutron Branching Ratios of Precursors in the Fission Product Region
Abstract
Delayed-neutron branching ratios in the fission product region have been tabulated, and average values have been determined. In order to provide data complementary to published values an experiment covering the mass range 79-150 has been carried out at the OSIRIS isotope-separator on-line facility at Studsvik. This experiment has resulted in branching ratios for some precursors (84Ge, 133Sn, and 150La) for which such data have not been reported before. In several other cases the new results are more accurate than older determinations.
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Nuclear Structure and Decay Data for A=76 Isobars
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Nuclear Data Sheets for A=141
2023, Nuclear Data SheetsThe experimental results published before August 2022 from the various reaction and decay studies leading to nuclides of Z=51 to Z=67, 141Sb, 141Te, 141I, 141Xe, 141Cs, 141Ba, 141La, 141Ce, 141Pr, 141Nd, 141Pm, 141Sm, 141Eu, 141Gd, 141Tb, 141Dy, 141Ho in the A=141 mass chain have been reviewed and the data are presented together with adopted level schemes and properties. This work supersedes the previous evaluation of the A=141 nuclides by published by N. Nica in Nuclear Data Sheets 122, 1 (2014).
Nuclear Structure and Decay Data for A=149 Isobars
2022, Nuclear Data SheetsExperimental nuclear structure and decay data are evaluated for all the 17 known nuclides of mass 149 (Xe, Cs, Ba, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb). Detailed compiled and evaluated spectroscopic information is presented for each reaction and decay dataset, and recommended values are provided for level properties, α, β and γ radiations, and other spectroscopic parameters, based on an evaluation of all the available experimental data for A=149 isobaric nuclides. Although large amounts of nuclear spectroscopic data are available for nuclides of A=149, yet large gaps in knowledge exist, as described below. For the lowest atomic number nuclide 149Xe, only the isotopic identification has been made, with no data for its ground-state half-life. For 149Cs, 149Tm and 149Yb information is available for only the respective ground states. For 149Ba, 149La and 149Er, limited data exist for excited states. Many of the decay schemes of radioactive nuclei of A=149 are considered as incomplete, either due to large energy differences between the highest observed excited states in daughter nuclides and the respective Q-values, or due to the lack of confirmed γ-ray data, as listed below: 149Cs → 149Ba, 149Ba → 149La, 149La → 149Ce, 149Ce → 149Pr, 149Pr → 149Nd, 149Tb(4.17 min) → 149Gd, 149Ho(21.0 s and 56 s) → 149Dy, 149Er(4 s and 9.6 s) → 149Ho, and 149Tm → 149Er. No data exist for the decay of 149Yb to 149Tm. Data for half-lives of the excited states in this mass chain are generally lacking as given below by the number of excited levels of known half-life / approximate number of known levels in a nuclide: 2/17 for 149Ba, 0/18 for 149La, 3/53 for 149Ce, 3/44 for 149Pr, 17/110 for 149Nd, 9/90 for 149Pm, 10/210 for 149Sm, 2/125 for 149Eu, 6/270 for 149Gd, 5/200 for 149Tb, 3/80 for 149Dy, 3/90 for 149Ho, and 3/14 for 149Er. This work supersedes earlier evaluations of A=149 nuclides published by 2004Si16, 1994Si18, 1985Sz01 and 1976Ho17.
Nuclear Data Sheets for A=147
2022, Nuclear Data SheetsThis work represents an update of the previous evaluation of the nuclear data on the A=147 nuclides (2009Ni02). The experimental data from reaction and decay studies leading to the following nuclides have been reviewed: 147I, 147Xe, 147Cs, 147Ba, 147La, 147Ce, 147Pr, 147Nd, 147Pm, 147Sm, 147Eu, 147Gd, 147Tb, 147Dy, 147Ho, 147Er, 147Tm. These data are presented, together with the adopted level schemes and their properties. 147Pm nuclide and half-life of 147Nd were evaluated by Balraj Singh (McMaster University; [email protected]). All the other nuclei were evaluated by Ninel Nica (Texas A&M University; [email protected]).
Nuclear Data Sheets for A=126
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Development of a Reference Database for Beta-Delayed Neutron Emission
2021, Nuclear Data SheetsBeta-delayed neutron emission is important for nuclear structure and astrophysics as well as for reactor applications. Significant advances in nuclear experimental techniques in the past two decades have led to a wealth of new measurements that remain to be incorporated in the databases.
We report on a coordinated effort to compile and evaluate all the available β-delayed neutron emission data. The different measurement techniques have been assessed and the data have been compared with semi-microscopic and microscopic-macroscopic models. The new microscopic database has been tested against aggregate total delayed neutron yields, time-dependent group parameters in 6-and 8-group re-presentation, and aggregate delayed neutron spectra. New recommendations of macroscopic delayed-neutron data for fissile materials of interest to applications are also presented. The new Reference Database for Beta-Delayed Neutron Emission Data is available online at: http://www-nds.iaea.org/beta-delayed-neutron/database.html.