Energy levels of {sup 251}Cf populated in the {alpha} decay of {sub 100}{sup 255}Fm and EC decay of {sub 99}{sup 251}Es
- Argonne National Laboratory, Argonne, Illinois 60439 (United States)
Gamma-ray singles spectra of extremely pure (chemically and isotopically) samples of {sup 255}Fm, with strengths of {approx}1 mCi, have been measured with a high-resolution 2-cm{sup 2}x10-mm germanium LEPS detector and with a 25% Ge spectrometer. Gamma rays with intensities as low as 1.0x10{sup -6}% per {sup 255}Fm {alpha} decay have been identified. The electron spectrum of a mass-separated {sup 251}Es source was measured with a cooled Si(Li) electron spectrometer. The spectrum provided the conversion coefficients of low-energy transitions in {sup 251}Cf and thereby their multipolarities. The present measurements confirm the previous assignments of single-particle states in {sup 251}Cf. These include 1/2{sup +}[620], 0.0 keV; 7/2{sup +}[613], 106.30 keV; 3/2{sup +}[622], 177.59 keV; 11/2{sup -}[725], 370.47 keV; 9/2{sup -}[734], 433.91 keV; 5/2{sup +}[622], 543.98 keV; 1/2{sup -}[750], 632.0 keV; 9/2{sup +}[615], 683 keV; and 9/2{sup +}[604], 974.0 keV. A vibrational band was identified in previous studies at 981.4 keV and given an assignment of {l_brace}7/2{sup +}[613]x2{sup -}{r_brace}3/2{sup -}. Three new vibrational bands are identified in the present work at 942.5, 1086.5, and 1250.0 keV with tentative assignments {l_brace}7/2{sup +}[613]x1{sup -}{r_brace}5/2{sup -},{l_brace}7/2{sup +}[613]x1{sup -}{r_brace}9/2{sup -}, and {l_brace}7/2{sup +}[613]x0{sup +}{r_brace}7/2{sup +}, respectively. A level was identified at 1185.5 keV with spin of 5/2 or 7/2 but it was not given any configuration assignment. Another level was identified at 1077.5 keV and given a spin of 9/2. Again, no configuration could be assigned to this level.
- OSTI ID:
- 20699113
- Journal Information:
- Physical Review. C, Nuclear Physics, Vol. 72, Issue 5; Other Information: DOI: 10.1103/PhysRevC.72.054308; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2813
- Country of Publication:
- United States
- Language:
- English
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