Energy levels of Cf251 populated in the α decay of 100255Fm and EC decay of 99251Es

I. Ahmad, J. P. Greene, E. F. Moore, F. G. Kondev, R. R. Chasman, C. E. Porter, and L. K. Felker
Phys. Rev. C 72, 054308 – Published 16 November 2005

Abstract

Gamma-ray singles spectra of extremely pure (chemically and isotopically) samples of Fm255, with strengths of ~1 mCi, have been measured with a high-resolution 2-cm2×10-mm germanium LEPS detector and with a 25% Ge spectrometer. Gamma rays with intensities as low as 1.0×106% per Fm255 α decay have been identified. The electron spectrum of a mass-separated Es251 source was measured with a cooled Si(Li) electron spectrometer. The spectrum provided the conversion coefficients of low-energy transitions in Cf251 and thereby their multipolarities. The present measurements confirm the previous assignments of single-particle states in Cf251. These include 1/2+[620], 0.0 keV; 7/2+[613], 106.30 keV; 3/2+[622], 177.59 keV; 11/2[725], 370.47 keV; 9/2[734], 433.91 keV; 5/2+[622], 543.98 keV; 1/2[750], 632.0 keV; 9/2+[615], 683 keV; and 9/2+[604], 974.0 keV. A vibrational band was identified in previous studies at 981.4 keV and given an assignment of {7/2+[613]2}3/2. Three new vibrational bands are identified in the present work at 942.5, 1086.5, and 1250.0 keV with tentative assignments {7/2+[613]1}5/2,{7/2+[613]1}9/2, and {7/2+[613]0+}7/2+, 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.

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  • Received 10 June 2005

DOI:https://doi.org/10.1103/PhysRevC.72.054308

©2005 American Physical Society

Authors & Affiliations

I. Ahmad*, J. P. Greene, E. F. Moore, F. G. Kondev, and R. R. Chasman

  • Argonne National Laboratory, Argonne, Illinois 60439, USA

C. E. Porter and L. K. Felker

  • Nuclear Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

  • *Electronic address: ahmad@phy.anl.gov

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Vol. 72, Iss. 5 — November 2005

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