Nuclear Data Sheets for A = 227

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• 作者：Filip Kondev^a ; Elizabeth McCutchan^b ; Balraj Singh^c ; ^{balraj@mcmaster.ca" class="auth_mail" title="E-mail the corresponding author} ; Jagdish Tuli^d
• 刊名：Nuclear Data Sheets
• 出版年：2016
• 出版时间：February 2016
• 年：2016
• 卷：132
• 期：Complete
• 页码：257-354
• 全文大小：565 K

文摘

The evaluated spectroscopic data are presented for ten known nuclides of mass 227 (Po, At, Rn, Fr, Ra, Ac, Th, Pa, U, Np). For ²²⁷Po, ²²⁷At, ²²⁷Rn, ²²⁷Pa, ²²⁷U and ²²⁷Np nuclei, only the ground-state information is available. Their decay characteristics are mostly unknown. Levels in ²²⁷Fr are known only from the decay of ²²⁷Rn to ²²⁷Fr. This decay scheme at present cannot be normalized to deduce γ intensities per 100 decays due to lack of knowledge about multipolarities of many low-energy transitions. The levels in ²²⁷Ra, ²²⁷Ac and ²²⁷Th are known from several decays and reactions, including particle-transfer data for ²²⁷Ra and ²²⁷Ac. The decay scheme of ²²⁷Ra to ²²⁷Ac was last studied in 1971 using small Ge detectors. Improved γ-ray intensity data need to be obtained with a better γ-detection system. The datasets for ²²⁷Ac have undergone extensive revisions, including detailed data for 231Pa α decay from 1986BaYK report, and single-proton transfer data from 1986MaYU thesis. High-spin (J>13/2 or so) structures are known only for 227Th. Level lifetime data are quite scarce for all the nuclides in this mass chain, thus limiting the knowledge of reduced transition probabilities.

Band structures for ²²⁷Fr, ²²⁷Ra, ²²⁷Ac and ²²⁷Th are known in detail, together with evidence of weak octupole deformation and consequent parity-doublet structures.

This evaluation was carried out as part of a joint IAEA-ICTP workshop for Nuclear Structure and Decay Data, organized and hosted by the IAEA, Vienna and ICTP, Trieste, March 24–28, 2014. The evaluation work was coordinated by B. Singh (McMaster). This work supersedes previous A=227 evaluation (2001Br31) published by E. Browne which covered literature before May 2001.