ADOPTED LEVELS, GAMMAS for 254Fm

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

 Full ENSDF file | Adopted Levels (PDF version) 


Q(β-)=-2550 keV SYS(n)= 6514 keV 4S(p)= 5396.7 keV 23Q(α)= 7307.5 keV 19
Reference: 2017WA10

References:
  A  254Es β- decay (275.7 d)  B  254Es β- decay (39.3 H)

General Comments:

Both the known activities of 254Md decay almost 100% by β+,ε decays, but no experimental data are available to elucidate the level structure in 254Fm. Based on particle plus rotor model phenomenological calculations, 2017So07 analyzed β++ε decays of the 10-min and 28-min activities of 254Md to 254Fm, and concluded that 10-min activity, assigned as π1/2[521]~#ν1/2[620], Kπ=0-, Jπ=1- is the ground state, and the 28-min activity, assigned as π7/2[514]~#ν1/2[620],Kπ=3-, is a Jπ=3- isomer lying within a few keV of the 10-min ground state. The authors further estimated decays to the excited states in 254Fm, and surmised that the 10-min, 1- ground state would populate the known g.s. and the first 2+ state in 254Fm, and the 28-min 3- isomer would feed the known 2+ and 3+ members of the gamma-vibrational band at 694 and 793, respectively.

Theoretical studies: consult the NSR database at www.nndc.bnl.gov for 172 references dealing with theoretical calculations of half-lives for different decay modes, binding energies, fission characteristics, and other nuclear structure aspects.

Q-value: Estimated ΔQ(β-)=100 (2017Wa10)

Q-value: S(2n)=12055 6, S(2p)=9710 3 (2017Wa10)










E(level)
(keV)		XREFJπ(level) T1/2(level)E(γ)
(keV)		I(γ)M(γ)Final Levels
    0.0 B 0+ 3.240 h 2 
% α = 99.9408 3
% SF = 0.0592 3
     
   44.992 10  B 2+      44.992 10 
  100
E2
    0.0
0+
  149.349 16  B 4+     104.356 12 
  100
E2
   44.992
2+
  693.66 4  B 2+     544.28 10 
  648.69 7 
  693.67 7 
    3.1 3 
  100 7 
   86 6 
E2
E2(+M1)
E2
  149.349
   44.992
    0.0
4+
2+
0+
  733.54 4  B 3+      39.881 10 
  584.18 10 
  688.68 2 
 
   23.2 16 
  100 7 
(E2)
E2(+M1)
E2(+M1)
  693.66
  149.349
   44.992
2+
4+
2+

Jπ(level): From band assignments, and other supporting comments as given.

Back to top

Band Transitions:

E(level)
(keV)		Jπ(level) T1/2(level)E(γ)I(γ)M(γ)Final Levels
Band 1 - Ground-state band
    0.0 0+ 3.240 h 2 
% α = 99.9408 3
% SF = 0.0592 3
     
   44.992 10  2+      44.992 10 
  100
E2
    0.0
0+
  149.349 16  4+     104.356 12 
  100
E2
   44.992
2+
E(level)
(keV)		Jπ(level) T1/2(level)E(γ)I(γ)M(γ)Final Levels
Band 2 - Kπ=2+ γ-vibrational band
  693.66 4  2+        
  733.54 4  3+      39.881 10 
  584.18 10 
  688.68 2 
 
   23.2 16 
  100 7 
(E2)
E2(+M1)
E2(+M1)
  693.66
  149.349
   44.992
2+
4+
2+

Back to top

Additional Gamma Data:















E(level)
(keV)		Jπ(level)T1/2(level)E(γ)
(keV)		MultipolarityMixing
Ratio		Conversion
Coefficient		Additional Data
   44.992 2+      44.992 10 E2 1172α=1172
  149.349 4+     104.356 12 E2 21.7α=21.7
  693.66 2+     544.28 10 E2 0.0612α=0.0612
2+     648.69 7 E2(+M1)9 GT0.0427α=0.0427 13
2+     693.67 7 E2 0.0359α=0.0359
  733.54 3+      39.881 10 (E2) 2.10×103α=2.10×103
3+     584.18 10 E2(+M1)9 GT0.0538α=0.0538 17
3+     688.68 2 E2(+M1)8 GT0.0378α=0.0378 13

Back to top

Additional Level Data and Comments:

E(level)Jπ(level)T1/2(level)Comments
    0.00+ 3.240 h 2 
% α = 99.9408 3
% SF = 0.0592 3
%α/%SF=1689 8, weighted average of 1695 8 and 1664 17, measured by 1967Fi03. Other measurements: 1956Jo09.
E(level): %α/%SF=1689 8, weighted average of 1695 8 and 1664 17, measured by 1967Fi03. Other measurements: 1956Jo09. Ground-state band.
   44.9922+   E(level): Ground-state band.
  149.3494+   E(level): Ground-state band.
  693.662+   E(level): Kπ=2+ γ-vibrational band.
  733.543+   E(level): Kπ=2+ γ-vibrational band.

Back to top