Nuclear Data Sheets最新文献

Surrogate reactions are a powerful tool to access neutron-induced reaction cross sections of short-lived nuclei. However, to infer neutron-induced reaction cross sections from measured deexcitation probabilities requires a consistent and rigorous theoretical framework describing both charged-particle and neutron-induced reactions. This work presents the first practical application of the new approach developed in O. Bouland, Phys. Rev. C 100, 064611 (2019) to Pu fissile isotopes, ^{237,238,240,242,244}Pu*. Average neutron-induced reaction cross sections and deexcitation probabilities measured in surrogate reactions are simultaneously analyzed with an efficient Monte Carlo $R$-matrix-extended theory algorithm using a unique set of nuclear-structure parameters to describe both observables. Fission probabilities allow one to estimate fission-barrier heights, not otherwise accessible in fissile isotopes. The theoretical framework is here extended to model 'giant' resonance structures observed in the fission probabilities of some nuclides. A careful study of the impact of the uncertainties on nuclear parameters and on the populated compound system angular distribution has been carried out. This study raises questions on the normalization of some fission probabilities measured in the 70's in ($t,p$) reactions, that could not have been pointed out without the use of the here-presented complex technique. This finding is especially important for the peculiar ²⁴⁰Pu* system. In addition, our study reveals for the ²³⁷Pu* compound system a 10 to 30 % too high value of the only-performed low-energy neutron-induced fission cross section measurement (Gerasimov et al., JINR-E–3-97-213 (1997)) and, subsequently of the evaluated fission cross section below 50 keV for the ²³⁶Pu.

Evaluated data are presented for 11 known $A=222$ nuclides (Bi, Po, At, Rn, Fr, Ra, Ac, Th, Pa, U, and Np), and relevant J^π and T_1/2 data for $A=226$ nuclei decaying by α-decay to $A=222$ nuclei. For ²²²Bi, only the isotopic identification is established with no measurement of its half-life. For ²²²Po, ²²²At, ²²²Fr, ²²²U, and ²²²Np, data are available only for the ground states, with static magnetic dipole and electric quadrupole moments, and charge radius measurements for the ²²²Fr ground state. For ²²²Ac and ²²²Pa, two low-lying levels are known from ²²⁶Pa α decay, and ²²⁶Np decay, respectively, but with no information about J^π assignments and γ decays of these levels. For ²²²Pa, a long-lived isomeric state is known, decaying dominantly by α decay. ²²²Rn, ²²²Ra, and ²²²Th have been investigated in detail, the low-spin states by α decay and the high-spin studies of ground-state and octupole bands by in-beam γ-ray studies for all the three nuclei, as well as by Coulomb excitation for ²²²Rn and ²²²Ra. Low-spin levels in ²²²Ra have been investigated also through the ${\beta }^{-}$ decay of ²²²Fr. Half-lives of the excited states are known for 7 levels in ²²²Rn, 12 levels in ²²²Ra, and 3 levels in ²²²Th. Octupole deformations, with the presence of alternating-parity bands up to (16⁺) and (${21}^{-}$) in ²²²Rn, (20⁺) and (${19}^{-}$) in ²²²Ra, and (26⁺) and (${25}^{-}$) in ²²²Th, and with interband E1 transitions, have been established in these three nuclei. The present evaluation supersedes the previous $A=222$ ENSDF evaluations: (2011Si24), (1996El01), (1987El06) and (1977To14).

Evaluated nuclear structure and decay data for all nuclei with mass number $A=200$ (²⁰⁰Os, ²⁰⁰Ir, ²⁰⁰Pt, ²⁰⁰Au, ²⁰⁰Hg, ²⁰⁰Tl, ²⁰⁰Pb, ²⁰⁰Bi, ²⁰⁰Po, ²⁰⁰At, ²⁰⁰Rn, and ²⁰⁰Fr), are presented. All available experimental data are compiled and evaluated, and best values for level and γ-ray energies, quantum numbers, lifetimes, γ-ray intensities and transition probabilities, as well as other nuclear properties, are recommended. Inconsistencies and discrepancies that exist in the literature are discussed. A number of computer codes (https://www-nds.iaea.org/public/ensdf_pgm/) developed by members of the NSDD network were used during the evaluation process. This work supersedes the earlier evaluation by F.G. Kondev and S. Lalkovski (2007Ko42), published in Nuclear Data Sheets 108, 1471 (2007).

Experimental nuclear spectroscopic data are compiled and evaluated for 17 known nuclides of mass 167 (Sm, Eu, Gd, Tb, Dy, Ho, Er Tm, Yb, Lu, Hf, Ta, W, Re, Os, Ir, Pt), 23 years after the previous full evaluation by 2000Ba65. Detailed 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. The α decays of A=171 nuclei to A=167 daughters are included in this work, while for α decays of A=167 nuclei to A=163 daughters, consult Nuclear Data Sheets (2010Re03) or the ENSDF database for A=163. ¹⁶⁷Er, ¹⁶⁷Tm, ¹⁶⁷Yb, ¹⁶⁷Lu and ¹⁶⁷Ta are among the most extensively studied nuclides via decay and high-spin gamma-ray spectroscopy measurements, followed by ¹⁶⁷Ho, ¹⁶⁷Hf, ¹⁶⁷W, and ¹⁶⁷Os. Information for excited states in ¹⁶⁷Dy, ¹⁶⁷Re, and ¹⁶⁷Ir are limited; no excited states have yet been identified in ¹⁶⁷Sm, ¹⁶⁷Eu, ¹⁶⁷Gd, ¹⁶⁷Tb and ¹⁶⁷Pt, with the ground-state half-life of ¹⁶⁷Sm remaining unknown. This work supersedes the earlier evaluation of A=167 nuclei by 2000Ba65.

Experimental nuclear spectroscopic data are evaluated for 12 known nuclides of mass number A=44 (Si, P, S, Cl, Ar, K, Ca, Sc, Ti, V, Cr, Mn). Detailed evaluated information are presented for each reaction and decay. Recommended values combining all available data are provided for all spectroscopic properties of each level, γ-ray, and decay radiation. No excited states have yet been identified in ⁴⁴Si, ⁴⁴P, ⁴⁴Cr, and ⁴⁴Mn. Information for excited states in ⁴⁴Cl and ⁴⁴V are limited. Nuclides of ⁴⁴S, ⁴⁴Ar and ⁴⁴K have been studied via only a few reactions and decays, while ⁴⁴Ca, ⁴⁴Sc and ⁴⁴Ti are the most investigated nuclides through various reactions and decays. Evaluators note that the half-life of the g.s. of ⁴⁴S has been measured independently, with fairly good statistics, in three references, most precise being 100 ms 1 by 2004Gr20, but this value is in disagreement with the values of 125.5 ms 25 and 119 ms 6 by 2022Tr03, and 123 ms 10 by 1995So03. We adopted the unweighted average of this discrepant dataset. Another outstanding issue is that of the β⁺-delayed proton decay of ⁴⁴Cr g.s. to ⁴⁴V, where the T=2, 0⁺ IAS state in ⁴⁴V is expected to be strongly populated by a superallowed β transition, but has not been definitely identified as discussed in detail by 2020Fu05. A detailed study of ⁴⁴Cr decay is required to unravel the status of the T=2, 0⁺ IAS state in ⁴⁴V. This work supersedes earlier ENSDF evaluations of A=44 by 2011Ch39 and 1999Ca45.