Nuclear levels in 233Th excited by neutron capture

doi:10.1016/0375-9474(79)90487-1

Nuclear Physics A

Volume 317, Issues 2–3, 9 April 1979, Pages 363-387

https://doi.org/10.1016/0375-9474(79)90487-1 Get rights and content

Abstract

The excited levels in ²³³Th have been studied using thermal and average resonance neutron capture in ²³²Th. 2 keV and 24 keV neutron capture has been investigated at the Brookhaven HFBR filtered beam facility. Conversion electrons and low energy γ-rays following thermal neutron capture have been measured at the ILL, Grenoble. From the combination of these data a level scheme of ²³³Th is proposed, which includes all low-spin states up to about 900 keV. Nine Nilsson configurations have been identified. Several rotational bands are explained as β, γ and octupole vibrational excitations. β-vibrational bands coupled to the [631 ↓] Nilsson states could be identified from the observation of transitions having strong E0 admixtures.

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Cited by (18)

Nuclear Data Sheets for A=233
2020, Nuclear Data Sheets
The present evaluation of the known A=233 nuclides (²³³Fr, ²³³Ra, ²³³Ac, ²³³Th, ²³³Pa, ²³³U, ²³³Np, ²³³Pu, ²³³Am, ²³³Cm) and ²³³Bk represents an update and revision, after 15 years of the previous evaluation of A=233 published by B. Singh and J.K. Tuli (2005Si15). Laboratory identification of ²³³Bk nuclide is still considered as tentative. Various decay and reaction data are evaluated and compared. Adopted data, levels, gammas, level half-lives, spins, parities, and configuration assignments are provided. For ²³³Fr, ²³³Ra, ²³³Ac, ²³³Pu, ²³³Am and ²³³Cm, information is available for the respective ground states only. The decay schemes from β⁻ decays of ²³³Fr and ²³³Ra, and from ε decay of ²³³Am and ²³³Cm are unknown, while those from β⁻ decay of ²³³Ac, and from ε decay of ²³³Np are considered incomplete. The α decay of ²³⁷Np to ²³³Pa has been studied in detail by many investigators, yet the decay scheme is considered incomplete as several very low-energy transitions are involved, without the knowledge of their intensities, resulting in mismatch of directly measured α feedings and those deduced from γ-transition intensity balances. The decay schemes from α decays of ²³⁷Am, ²³⁷Cm and ²³⁷Cf to respective A=233 daughters are considered incomplete. Particle-transfer and high-spin data are available for ²³³Th, ²³³Pa and ²³³U nuclei, which remain the most extensively studied in this mass chain. However, data for half-lives for the excited states are available only for one level in ²³³Pa, and for five levels in ²³³U, thus limiting the knowledge of reduced transition probabilities in this mass chain.
Nuclear data sheets for A = 233
2005, Nuclear Data Sheets
The available nuclear structure information for nine known nuclei (Ra,Ac,Th,Pa,U,Np,Pu,Am,Cm) with mass number A = 233 is presented. Various decay and reaction data are evaluated and compared. Adopted data, levels, gammas, level half-lives, spins, parities, and configuration assignments are given. No excited states are yet known in ²³³Ra, ²³³Ac, ²³³Pu, ²³³Am and ²³³Cm. The present work supersedes earlier evaluations of A = 233 by Y.A. Akovali published in Nuclear Data Sheets (1990Ak02,1978El04,1971El13), covering literature up to December 1988.
Persistence of octupole correlations in 231Ra
2001, Nuclear Physics A
The structure of $^{231}$ Ra, the heaviest odd Ra nucleus currently accessible for detailed spectroscopic investigation, has been studied in the $β^{−}$ decay of $^{231}$ Fr. The main purpose has been to verify whether fast $B$ (E1) rates and significant octupole correlations recently established in $^{229}$ Ra persist in $^{231}$ Ra. The excited states in $^{231}$ Ra have been determined for the first time. Spins and parities have been deduced from conversion electron measurements, while level half-lives in the ps and ns ranges have been measured with the Advanced Time Delayed $βγγ$ (t) method. The moderately fast $B$ (E1) rates found for transitions connecting the lowest-lying $K^{π} =5/2^{±}$ and $K^{π} =1/2^{±}$ bands, reveal the persistence of octupole collective effects in $^{231}$ Ra, although the $B$ (E1) rates are lower than in $^{229}$ Ra. These findings reinforce the differences in the $B$ (E1) systematics between isotonic Ra and Th nuclei.
Nuclear Data Sheets for A=233
1990, Nuclear Data Sheets
Nuclear level densities and level spacing distributions: Part II
1988, Nuclear Physics, Section A
Extensive and complete nuclear level schemes and neutron resonance densities of 75 nuclides have been used to determine parameters of level density formulae, the spacing distribution of levels with equal spins and parities, and spacing correlations. The dependences of the level density parameters on A, on pairing energies and on shell effects are discussed. The spacing distribution is found to lie between a Poisson and Wigner distribution indicating a transitional character between regular and chaotic properties of the nuclear quantum system near the ground state.
Nuclear level densities and level spacing distributions from 20F to 244Am
1986, Nuclear Physics, Section A
The parameters of nuclear level density formulae have been determined from extensive and complete level schemes and neutron resonance densities for 24 nuclei between ²⁰F and ²⁴⁴Am. The constant temperature level-density formula and the Bethe formula are compared with the experimental level densities. Both formulae reproduce experimental densities equally well. The same nuclei have been used to obtain an A-dependent spin cut-off parameter for low-lying levels. The spacing distribution of levels with equal spins and parities at lower excitation energies is found to be much closer to an exponential distribution than to the Wigner distribution especially for even-even nuclei. This is at variance with previous theoretical expectations and interpretations of nuclear data compilations. It gives evidence for a further good quantum number at low excitation energies in addition to spin and parity or for very different structures.

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^☆: Work supported in part by the US Energy Research and Development Administration.

^††: Present address: CENG/LETI, 38041 Grenoble Cédex, France.

^†††: Supported by KFA Jülich, Germany.

^‡: Permanent address: Idaho National Engineering Laboratory, EG & G Idaho, Inc., Idaho Falls, Idaho 83401, USA.

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Nuclear Physics A

Abstract

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Nuclear Data Sheets for A=233

Nuclear data sheets for A = 233

Persistence of octupole correlations in <sup>231</sup>Ra

Nuclear Data Sheets for A=233

Nuclear level densities and level spacing distributions: Part II

Nuclear level densities and level spacing distributions from <sup>20</sup>F to <sup>244</sup>Am

Nuclear levels in 233Th excited by neutron capture☆

Abstract

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Nuclear levels in ²³³Th excited by neutron capture☆