Nuclear Data Sheets最新文献

Experimental 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.

Most evaluated elemental fission product yield distributions are not experimentally measured. Instead, the majority of evaluated distributions are based on analytic expressions of the Zp-model for relevant cumulative yields. Here we report independent elemental fission product yield distributions of a ²³⁵U target for incident neutron energies ranging from 0.11 MeV through 92.4 MeV. Atomic numbers are calculated by an approach that combines a 2E analysis with a stopping force analysis method, developed within this paper. These analyses are applied to more than 6.1 × 10⁶ fission fragment ionization tracks captured within the NIFFTE (Neutron Induced Fission Fragment Tracking Experiment) collaboration fission time projection chamber (fissionTPC). A 3-Z resolution was obtained with the fissionTPC spatial and energy resolutions. Tabulated results are presented for the atomic yield and experimentally derived Zp values as a function of pre-neutron-emission fragment masses for the complete range of incident neutron energies. The stopping-force-derived Zp values tend to support the unchanged charge distribution theory within uncertainty.

Experimental nuclear spectroscopic data are evaluated for 11 known nuclides of mass 31 (F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K). Detailed evaluated information is presented for each reaction and decay experiment. Combining all the available data, recommended values are provided for energies, spins and parities, and half-lives of levels, with energies, branching ratios and multipolarities of γ radiations, and characteristics of β and α radiations in radioactive decays. ³¹P is the most extensively studied one among all nuclides via various reactions and decays, followed by ³¹S, ³¹Si, ³¹Mg and ³¹Al. Information for excited states in ³¹Ne, ³¹Na, ³¹Cl, ³¹Ar and ³¹K are limited; no excited states have yet been identified in ³¹F, even its ground-state half-life is unknown. Significant new data have become available for the structure of ³¹S, with its relevance to astrophysical applications. This work supersedes the earlier evaluation of A=31 by 2013Ou01, with literature cutoff date of Feb 15, 2013.

Evaluated spectroscopic data and level schemes from radioactive decay and nuclear reaction studies are presented for ¹⁸⁶Lu, ¹⁸⁶Hf, ¹⁸⁶Ta, ¹⁸⁶W, ¹⁸⁶Re, ¹⁸⁶Os, ¹⁸⁶Ir, ¹⁸⁶Pt, ¹⁸⁶Au, ¹⁸⁶Hg, ¹⁸⁶Tl, ¹⁸⁶Pb, ¹⁸⁶Bi, and ¹⁸⁶Po. This evaluation for A=186 supersedes the earlier evaluation 2003Ba44 by C. M. Baglin. Highlights of this evaluation are the following: ¹⁸⁶Re: Revised %ε and %β⁻ branches. New values are almost same as of the earlier ones. Adopted improved level energy for the long-lived (8⁺) isomer at 148.2 keV 5 based on the study reported in 2015Ma60 (¹⁸⁷Re(n, 2nγ)) compared to 149 keV 7 in previous evaluation (2003Ba44). ¹⁸⁶Hg: Discrepancies in the level schemes between 1992Po01 and 1993Ma02 remain to resolve experimentally, arise primarily due to the assigned multipolarity of the ≈607 keV γ transition between the 1228 keV bandhead and the 2⁺ 621 keV level. See general comments in Adopted Levels, Gammas dataset. ¹⁸⁶Tl: From α decay studies, 2020St11 propose spin-parity (2⁻) for the g.s. and (7⁺) for the excited level at 0.0+x of level energy of 77 keV 56. From mass measurements, 2014Bo26 propose the (7⁻) level energy of 20 keV 40 earlier.

Information on the production, identification, half-lives and decay modes for experimentally known nuclides with mass numbers of 267, 271, 275, 279, 283, 287, and 291, along with attempts to observe nuclides with mass numbers of 295 and 299, are presented along with the recommended values. Data here supersede data from the previous evaluation in this region, 2005Gu33. Since the previous evaluation many new and conclusive experiments have explored the region of superheavy nuclei, thus significantly expanding our knowledge of the nuclear chart in this area.