Abstract
The structure of
72Kr has been investigated at GASP through the
40Ca(
40Ca,2α) reaction at a beam energy of 160 MeV using the 4π ISIS Si-ball for reaction channel selection. The level scheme has been extended up to an excitation energy of ≈ 8.5 MeV. The spins and parties of the observed levels are assigned tentatively. The observed band shows the predicted change from oblate to prolate shape. The four quasi-particle
g
9
2
alignment is found to be significantly delayed in rotational frequency with respect to the heavier Kr isotopes. Such a delay contradicts the predictions of standard mean-field calculations and may reflect either additional correlations in the T = 0 pairing channel or coupling to vibrational degrees of freedom or both.