Observation of delayed alignment in N=Z nuclei 72Kr, 76Sr and 80Zr

Excited states of the N = Z nuclei Kr-72, S-76 and Zr-80 have been studied in a series of experiments involving Gammasphere plus Microball, and Gammasphere plus the Argonne Fragment Mass Analyzer. The ground state band of Kr-72 has been extended to a spin of (26(+)), and a very pronounced delay in the alignment of g(9/2) particles is evident. The ground state bands of Sr-76 and Zr-80 have been observed to spins 14(+) and 12(+), respectively, and also show evidence for delayed alignments. This delay in alignment may be a signature for neutron-proton pairing correlations.