ADOPTED LEVELS for 254Rf

Author: Balraj Singh |  Citation: Nucl. Data Sheets 156, 1 (2019) |  Cutoff date: 31-Jan-2019 

 Full ENSDF file | Adopted Levels (PDF version) 


S(n)= 8430 keV SYS(p)= 2670 keV SYQ(α)= 9210 keV SY
Reference: 2017WA10

General Comments:

This dataset uses a compiled dataset from 2015Da12 by J. Chen (NSCL, MSU) available in the XUNDL database

1997He29: 254Rf produced and identified in 206Pb(50Ti,2n) reaction, followed by measurement of T1/2 from SF decay.

Later measurements of half-lives: 2008Dr05, 2015Da12

2008Dr05: 208Pb(48Ti,2n),E=4.6-4.8 MeV/nucleon; the beam provided by 88-Inch cyclotron at LBNL. Detected charged particles using a focal plane detector and a double-sided silicon strip detector. Half-life of 254Rf and production cross section measured based on subsequent α decay of 254Rf.

2015Da12: two experiments were performed using 206Pb(50Ti,2n) reaction: 1. E=242.5 MeV 50Ti beam produced at ATLAS-ANL facility was incident on a 0.5 mg/cm2 99.948% enriched 206Pb target. Recoiling residues were separated and selected using the Fragment Mass Analyzer (FMA) and implanted into a 100 μm-thick, double-sided silicon strip detector (DSSD) at the focal plane. Spontaneous-fission (SF) events were identified based on spatial and temporal correlations between implanted residues and high-energy (>100 MeV) decay events in DSSD. Measured energies of reaction products, conversion electrons, implant-decay correlations. 2. E=244 MeV 50Ti beam produced at the LBNL cyclotron facility was incident on a 0.5 mg/cm2 206Pb target. Recoiling residues were separated and selected by the Berkeley Gas-filled Separator (BGS) and implanted into three 1-mm-thick, double-sided silicon-strip detectors (DSSDs), with emitted γ rays detected with a clover HPGe detector behind each DSSD. Measured energies of reaction products, Eγ, Iγ, conversion electrons, implant-decay correlations. Deduced evidence and T1/2 for two isomers in 254Rf using a novel approach involving a pulse-shape analysis of data acquired with a digital data acquisition system. Comparison with multi-quasiparticle calculations. α total of 28 and 723 SF events from 254Rf were identified in the two experiments, respectively. The two isomers were identified based on observed electron-SF and/or electron-electron-SF correlations following the decay of the isomers, with 82 electrons associated with the shorter-lived 2-qp isomer and 11 electrons with the longer-lived 4-qp isomer. The absence of sizable fission branches from either of the isomers implies unprecedented fission hindrance relative to the ground state

Theoretical studies: consult the NSR database at www.nndc.bnl.gov for 42 references dealing with theoretical calculations of half-lives for different decay modes, binding energies, fission characteristics, and other nuclear structure aspects.

Q-value: Estimated uncertainties (2017Wa10): 500 for S(n), 350 for S(p), 200 for Q(α)

Q-value: S(2n)=15810 (theory,1997Mo25). S(2p)=4250 280, Q(εp)=1550 280 (syst,2017Wa10)





E(level)
(keV)
Jπ(level) T1/2(level)
  0.0 0+ 23.2 µs 11 
% SF ≈ 100
% α < 1.5
  X (8-) 4.7 µs 11 
% IT ≈ 100
% SF < 10
  Y (16+) 247 µs 73 
% IT ≈ 100
% SF < 40

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Additional Level Data and Comments:

E(level)Jπ(level)T1/2(level)Comments
  0.00+ 23.2 µs 11 
% SF ≈ 100
% α < 1.5
Only the SF-decay mode has been detected. An upper limit of 1.5% was given by 1997He29 from non-observation of α particles and the total number of 155 SF events detected.
E(level): Only the SF-decay mode has been detected. An upper limit of 1.5% was given by 1997He29 from non-observation of α particles and the total number of 155 SF events detected.
  X(8-) 4.7 µs 11 
% IT ≈ 100
% SF < 10
α cluster of three counts at 853 keV and two counts at 829 keV is seen in the spectrum of γ rays coincident with electrons, indicating two other possible transitions associated with the 2-qp isomer (2015Da12).
E(level): α cluster of three counts at 853 keV and two counts at 829 keV is seen in the spectrum of γ rays coincident with electrons, indicating two other possible transitions associated with the 2-qp isomer (2015Da12).
  Y(16+) 247 µs 73 
% IT ≈ 100
% SF < 40
%SF<40%, deduced by 2015Da12, assuming that all the six fission events in the time interval of the 4-qp isomer decays originated from this isomer, although these six fission events could also be associated with the ground-state fission events following decays of the 4-qp isomer which may have escaped detection.
E(level): %SF<40%, deduced by 2015Da12, assuming that all the six fission events in the time interval of the 4-qp isomer decays originated from this isomer, although these six fission events could also be associated with the ground-state fission events following decays of the 4-qp isomer which may have escaped detection.

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