High spin structure in the odd-proton nucleus 133Pr

The odd-proton nucleus 133Pr has been investigated using the 118Sn(19F,4n) and 117Sn(19F,3n) reactions. Several rotational bands could be followed up to high spins. The yrast band, built on a decoupled h112 proton, shows an upbend at (h2π)ω = 0.43 MeV when two additional h112 protons align. Two positive-parity side bands of opposite signature were established, both showing a band crossing at (h2π)ω = 0.27 MeV with a gain in alignment Δi/sub x//similar to/8(h2π) when two h112 protons align. This low crossing frequency, compared to that observed in the 132Ce core nucleus, is partly explained by a reduction in the proton pairing gap. Three ΔI = 1 bands were observed;the lowest one is believed to represent a collective rotation of an oblate shape. The shape change is induced by the alignment of a pair of h112 neutrons from the upper midshell driving the nucleus from a prolate to an oblate shape