Two and three dimensional gamma ray correlations in rotational nuclei

Several new methods for the study of nuclear structure at low temperature are reviewed. The methods analyze the fluctuations of the intensity of Eγ1 · Eγ2 spectra, and the shape and width Γrot of the correlated patterns with different characteristics of the rotational motion in cold and warm nuclei. New results are given for the rotational damping width, and the number of 2-step-paths below and above U0 ≈ 800 keV, considered to be the energy of the borderline between undamped and damped rotational motion. The rotational damping width Γrot is studied as function of rotational frequency for selected regions of entry states in 163Tm , and found to be rather constant ≈ 80 keV, significantly smaller than current theoretical predictions. The fluctuation analysis supports the damping picture in general, and confirms that a strong branching of the transition strength for each step in the E2 cascades exists at high spin. This can be taken as evidence for damping of the rotational motion in warm nuclei.