Possible observation of the 1/2(+)[880] orbital in Cm-249(96)

The position of the k(17/2) Shell orbital plays a significant role in deter mining the shell correction energy and hence the stability of the superheav y elements. A deformed component of this orbital, 1/2(+) [880], comes down in energy with increasing prolate deformation, and is expected to have an e xcitation energy of less than 2 MeV in nuclei with N = 153. We have perform ed the reaction Cm-248(He-4,He-3) using 98.5-MeV alpha particles from the I UCF cyclotron to populate high-e states in Cm-249. This reaction preferenti ally excites high-e states because of the angular momentum mismatch. The em erging He-3 ions were momentum analyzed with the K600 magnetic spectrometer , Spectra were measured at theta(cm) = 4.1 degrees, 6.1 degrees, 10.2 degre es, 12.2 degrees, and 16.2 degrees. The spectrometer was calibrated with th e Pb-208(He-4,He-3) and( 232)Th(He-4,He-3) reactions at the same incident e nergy. Three strong peaks were identified in the Cm-248(He-4,He-3) spectrum and these have been given tentative assignments: 593 keV, 15/2 11/2(-)[725 ]; 1560 keV and 1898 keV, 17/2 1/2(+)[880], 15/2 13/2(-) [716]. Our data do not distinguish between the 17/2(+) and 15/2(-) assignments. (C) 1999 Publ ished by Elsevier Science B.V.