Possible observation of the 12+[880] orbital in 96249Cm

Abstract The position of the K 17 2 shell orbital plays a significant role in determining the shell correction energy and hence the stability of the superheavy elements. A deformed component of this orbital, 1 2 + [880] , comes down in energy with increasing prolate deformation, and is expected to have an excitation energy of less than 2 MeV in nuclei with N = 153. We have performed the reaction 248 Cm( 4 He, 3 He) using 98.5-MeV alpha particles from the IUCF cyclotron to populate high-l states in 249 Cm. this reaction preferentially excites high-l states because of the angular momentum mismatch. The emerging 3 He ions were momentum analyzed with the K600 magnetic spectrometer. Spectra were measured at θ cm = 4.1°, 6.1°, 10.2°, 12.2°, and 16.2° The spectrometer was calibrated with the 208 Pb( 4 He, 3 He) and 232 Th( 4 He, 3 He) reactions at the same incident energy. Three strong peaks were identified in the 248 Cm( 4 He, 3 He) 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.