High-spin states in 50Ti, 52Cr and 54Fe

Abstract The even N = 28 isotones 50 Ti, 52 Cr and 54 Fe have been investigated using (α, 2nγ) reactions. The experiments involved the measurement of γ-ray angular distributions and correlations, linear polarizations, excitation functions and γ-γ coincidences. Spin-parity values were established for new levels observed in 50 Ti at 6135, 6539, 6769, 7570 and 8790 keV having, respectively, J π = 7 + , 8 + , 9 + , 10 + and (11) + , and in 52 Cr at 6454, 7238 and 8217 keV having, respectively, (9) + , (10) + and (11 + ). Other new levels were also observed in 50 Ti at 3975, 4148, 7539 and 8257 keV, in 52 Cr at 6365 keV, and in 54 Fe at 7507 and 8023 keV. In addition, definite J π values of 8 + , 6 + , 7 + and 8 + were assigned to the levels at 4750, 4806, 5397 and 5825 keV, respectively in 52 Cr, while the mean lifetime of the (10 + ), 6529 keV level in 54 Fe was measured to be 517 ± 45 ns, using a γ-γ delayed coincidence technique. Shell-model calculations, including excitations of one particle from the N = 28 core, successfully account for the newly observed states and indicate their 2p 3 2 neutron character in 50 Ti and 52 Cr. The interpretation of the experimental result is consistent with configuration mixing of about 20 % for the low-lying f 7 2 states.