Search for Motional Narrowing Effects in Nuclearγ-Ray Spectra

At moderate temperatures in nuclei (≅0.5 MeV), there is evidence for damping effects in the rotational behavior. Instead of normal rotational bands, each state can emit any one of a distribution of $\gamma$-ray energies whose FWHM is called the damping width. At higher temperatures, there are expected to be motional narrowing effects, where the damping widths decrease with further increases in temperature. We do not find such a narrowing in the experimental damping widths.