Lifetimes of High Spin Yrast States in Odd-Proton Nucleus ¹³¹Pr

Lifetimes of the high spin yrast states in the odd-proton nucleus ¹³¹Pr have been determined by analysing the Doppler broadened line shapes for the de-exciting γ-rays following the ¹¹⁶Sn(¹⁹F, 4n)¹³¹Pr reaction at a bombarding energy of 95 MeV. The transition quadrupole moments extracted from the measured lifetimes exhibit a considerable reduction near the rotational frequency of 0.42 MeV, at which the J⁽¹⁾ and J⁽²⁾ moments of inertia indicate a band crossing. The experimental result demonstrates occurrence of the nuclear shape change induced by band crossing associated with the alignment of a pair of h_11/2 protons.