Conservation of the K-quantum number in warm nuclei

The selection rules on the K-quantum number in rapidly rotating warm nuclei are investigated analyzing quasi-continuum spectra feeding into low-K and high-K bands in 163Er. The data are compared to simulated spectra obtained using the band mixing model predictions including the residual interaction and a term representing the effect of the K-quantum number on the rotational energy. K-selection rules are found to be obeyed by the decay along excited unresolved rotational bands of heat energy up to around 1.2 MeV and angular momentum 30ℏ⩽I⩽40ℏ. In contrast, the results corresponding to higher heat energy of 1.2 to 2.5 MeV indicate that the selection rules are only partially satisfied.