Proton Single-Particle States In The Heaviest Actinide Nuclei.

The level structure of 249Bk has been investigated by measuring the γ-ray spectra following the α decay of a chemically and isotopically pure 253Es sample. Alpha-gamma coincidence measurement was performed using a Si detector for α particles and a 25% Ge detector for γ rays. A gamma-gamma coincidence measurement was performed with the Gammasphere spectrometer. The Es sample was obtained by extracting the 253Es which grew in a 253Cf source material produced in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. Additional information on the 249Bk levels was obtained from the study of γ rays produced in the β- decay of 249Cm. The 249Cm sample was produced by neutron irradiation of 248Cm. Using the results of the present study and the results of previous 248Cm(α,t) and 248Cm(3He,d) reaction spectra, the following single-particle states have been identified in 249Bk: 7/2+[633], 0.0 keV; 3/2-[521], 8.78 keV; 1/2+[400], 377.55 keV: 5/2+[642], 389.17 keV; 1/2-[530], 569.19 keV; 1/2-[521], 643.0 keV; 5/2-[523], 672.8 keV; 9/2+[624], 1075.1 keV. Four vibrational bands were identified at 767.9, 932.2, 1150.7 and 1223.0 keV with tentative assignments of {7/2+[633]x1-}9/2-, {7/2+[633]x0-}7/2-, {7/2+[633]x1-}5/2- and {7/2+[633]x0+}7/2+, respectively. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]