Search

High-energy $\ensuremath{\gamma}$ rays emitted by the decay of the hot compound nucleus ${}^{194}\mathrm{Hg}$, formed in the reaction ${}^{30}\mathrm{Si}(142 \mathrm{MeV}{)+}^{164}\mathrm{Dy}$, have been measured in coincidence with different residual nuclei. The measured spectra and the relative residual-nucleus cross sections were simultaneously analyzed with the statistical model. Calculations assuming contributions from a GDR in superdeformed states were also made. No clear evidence was found that superdeformed shapes seen at $T=0$ survive at average nuclear temperature $〈T〉\ensuremath{\simeq}1.3 \mathrm{MeV}$. Instead, an average nuclear deformation corresponding to $〈\ensuremath{\beta}〉=0.3$ constant with spin has been deduced for $20lIl38 \ensuremath{\Elzxh}$ by comparing the measured width to that predicted by the model of thermal shape fluctuations.