HIGH-SPIN STATES IN TI-50, CR-52 AND FE-54

The even N = 28 isotones 50Ti, 52Cr and 54Fe 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 50Ti at 6135, 6539, 6769, 7570 and 8790 keV having, respectively, Jπ = 7+, 8+, 9+, 10+ and (11)+, and in 52Cr at 6454, 7238 and 8217 keV having, respectively, (9)+, (10)+ and (11+). Other new levels were also observed in 50Ti at 3975, 4148, 7539 and 8257 keV, in 52Cr at 6365 keV, and in 54Fe at 7507 and 8023 keV. In addition, definite Jπ values of 8+, 6+, 7+ and 8+ were assigned to the levels at 4750, 4806, 5397 and 5825 keV, respectively in 52Cr, while the mean lifetime of the (10+), 6529 keV level in 54Fe 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 50Ti and 52Cr. The interpretation of the experimental result is consistent with configuration mixing of about 20 % for the low-lying f 7 2 states. © 1979.