ADOPTED LEVELS, GAMMAS for 251Bk

Authors: E. Browne, J. K. Tuli |  Citation: Nucl. Data Sheets 114, 1041 (2013) |  Cutoff date: 1-Jan-2012 

 Full ENSDF file | Adopted Levels (PDF version) 


Q(β-)=1093 keV 10S(n)= 5794 keV 11S(p)= 5049 keV 15Q(α)= 5650 keV SY
Reference: 2012WA38

References:
  A  251Cm β- decay  B  255Es α decay

General Comments:

Calculations, compilations:

g.s. properties: 1997Mo25, 1995Mo29

Single-particle Nilsson levels: 1994Cw02, 2004Pa40

2004Pa40: Calculated deformation, pairing.

1994Cw02 calculated the following single-particle level sequence: g.s. 3/2[521], 0.13 MeV 7/2[633], 0.31 MeV 5/2[642], 0.47 MeV 1/2[660], 0.62 MeV 3/2[651].

Calculated Q(α), T1/2: 2011Sa40, 2010Ni02, 2011Zh36, 2008Do12.

2004Pa40 calculated the following single-particle level sequence: g.s. 3/2[521], 0.03 MeV 7/2[633], 0.20 MeV 5/2[642], 0.30 MeV 1/2[400], 0.44 MeV 3/2[402], 0.47 MeV 1/2[521].

Assignment: daughter of 255Es (1967Fi03).

Levels: For Jπ and band assignments based on analogy to 249Bk level scheme, see 251Cm β- decay (1978Lo13).

Gammas: γ-ray data are from 251Cm β- decay, unless otherwise noted.

Q-value: Estimated ΔQ(α)=101 (2012Wa38)










E(level)
(keV)
XREFJπ(level) T1/2(level)E(γ)
(keV)
I(γ)M(γ)Final Levels
    0AB (3/2-) 55.6 m 11 
% β- = 100
     
   32.5 8 A  (5/2-)      32.5S
 

    0
(3/2-)
   35.5 13 AB (7/2+) 58 µs 4     35.5S
  100
[M2]
    0
(3/2-)
   70 3  B (9/2+)        
  124 B (11/2+)        
  269.1 10 AB (5/2+)     233.6
  269.1
  100
 


   35.5
    0
(7/2+)
(3/2-)
  311.7 10 A  (1/2+)     311.7
 

    0
(3/2-)
  422.2 8 A  (3/2-)     389.7
  422.3
  100 7 
   56 7 


   32.5
    0
(5/2-)
(3/2-)
  438.2 10 A  (1/2-)     438.2
 

    0
(3/2-)
  542.6 8 A  (3/2-)     542.7
 

    0
(3/2-)
  562.5 8 A  (3/2-)     530.0
  562.5
  100 7 
   63 20 


   32.5
    0
(5/2-)
(3/2-)
  978.4 7 A  (1/2-,3/2)     415.9
  435.8
  945.9
  978.2
   16 6 
   15 5 
   15 7 
  100 13 




  562.5
  542.6
   32.5
    0
(3/2-)
(3/2-)
(5/2-)
(3/2-)

E(level): From least-squares fit to Eγ (uncertainty in Eγ has been assumed |+1 keV) for levels seen in 251Cm β- decay. Uncertainties for levels seen in 255Es α decay only are from Q(α) and Eα.

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Band Transitions:

E(level)
(keV)
Jπ(level) T1/2(level)E(γ)I(γ)M(γ)Final Levels
Band 1 - 3/2[521].
    0 (3/2-) 55.6 m 11 
% β- = 100
     
   32.5 8  (5/2-)      32.5S
 

    0
(3/2-)
E(level)
(keV)
Jπ(level) T1/2(level)E(γ)I(γ)M(γ)Final Levels
Band 2 - 7/2[633].
   35.5 13  (7/2+) 58 µs 4       
   70 3  (9/2+)     
  124 (11/2+)     

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Additional Gamma Data:













E(level)
(keV)
Jπ(level)T1/2(level)E(γ)
(keV)
MultipolarityConversion
Coefficient
Additional Data
   35.5 (7/2+) 58 µs 4     35.5[M2]1.231×104B(M2)(W.u.)=0.019 3, α=1.231×104, α(L)=8.71E3 13, α(M)=2.62E3 4, α(N)=752 11, α(O)=192 3, α(P)=35.1 5, α(Q)=1.97 3, α(N+)=982 14

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Additional Level Data and Comments:

E(level)Jπ(level)T1/2(level)Comments
    0(3/2-) 55.6 m 11 
% β- = 100
E(level): 3/2[521]. From 255Es α decay.
   32.5(5/2-)   E(level): 3/2[521]. From 255Es α decay.
   35.5(7/2+) 58 µs 4  E(level): 7/2[633].
   70(9/2+)   E(level): 7/2[633].
  124(11/2+)   E(level): 7/2[633].
  422.2(3/2-)   Jπ(level): log ft<7.2, log f1ut<7.6 from (1/2+) 251Cm rule out J|>5/2.
  438.2(1/2-)   Jπ(level): log ft<7.2, log f1ut<7.6 from (1/2+) 251Cm rule out J|>5/2.
  542.6(3/2-)   Jπ(level): log ft<7.2, log f1ut<7.6 from (1/2+) 251Cm rule out J|>5/2.
  562.5(3/2-)   Jπ(level): log ft<7.2, log f1ut<7.6 from (1/2+) 251Cm rule out J|>5/2.
  978.4(1/2-,3/2)   Jπ(level): log ft<7.2, log f1ut<7.6 from (1/2+) 251Cm rule out J|>5/2.

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