Probing the Jacobi shape transition in hot and rotating Sc 43

The evolution of the hot and rotating $^{43}\mathrm{Sc}$ nucleus to a highly deformed shape has been studied by measuring the high-energy $\ensuremath{\gamma}$ rays from the decay of the giant dipole resonance. The compound nucleus was populated at two initial excitation energies and average angular momenta of $\ensuremath{\approx}26$ and $31\ensuremath{\hbar}$ by using $^{16}\mathrm{O}$ beam of energies ${E}_{\mathrm{lab}}$ = 120 and 142 MeV, respectively. The evaporated neutron energy spectra have been measured for proper determination of nuclear level density. The angular momentum has been determined by measuring the low-energy $\ensuremath{\gamma}$-ray multiplicities. The high-energy $\ensuremath{\gamma}$-ray and neutron spectra were analyzed simultaneously. At $\ensuremath{\langle}J\ensuremath{\rangle}\ensuremath{\approx}26\ensuremath{\hbar}$ a near-oblate shape is observed, whereas at $\ensuremath{\langle}J\ensuremath{\rangle}\ensuremath{\approx}31\ensuremath{\hbar}$ a sharp peak is observed at ${E}_{\ensuremath{\gamma}}\ensuremath{\approx}10\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}$ pointing towards the transition to the Jacobi shape with quadruple deformation parameter $\ensuremath{\beta}\ensuremath{\approx}0.7$. The results have been corroborated by the theoretical calculations based on the rotating liquid drop model framework.