High-lying collective rotational states in nuclei

A review of the latest works concerning the γ decay of high-lying collective rotational states is given. The study of warm rotating nuclei is based on several experiments made with large γ-spectroscopy arrays, including EUROBALL. The analysis techniques, mainly based on the fluctuations of counts of γ-coincidence spectra, are briefly described, while the obtained results are discussed in detail. The work presented here focuses on several properties of nuclei in the order to chaos transition region, such as (i) the importance of the two-body residual interaction in the description of the warm rotation; (ii) the collectivity of the excited rotational states; (iii) the conservation of quantum number with thermal energy; (iv) the dependence of the band mixing process on mass and deformation. Altogether, the results discussed in this review show a consistent picture of the problem of excited rotation in the regime of strongly interacting bands. The present limits and perspectives are also briefly given.