Search

The γ-decay from excited nuclei is used to study the interplay between rotational motion and compound nucleus formation in deformed nuclei. A new analysis technique is presented which allows for the first time to directly measure the rotational and compound damping widths Γrot and Γμ from γ-coincidence spectra. The method is first tested on simulated spectra and then applied to high-statistics EUROBALL data on the nucleus 163Er. Experimental values of ≈200 and 20 keV are obtained for Γrot and Γμ, respectively, in the spin region I ≈ 30–40 h, in good agreement with microscopic cranked shell model calculations for the specific nucleus. A dependence of rotational damping on the K-quantum number of the nuclear states is also observed, both in experiment and theory, resulting in a ≈30% reduction of Γrot for high-K states. This points to a delayed onset of rotational damping in high-K configurations. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The high-energy and discrete γ-ray spectra, as well as the charged particle angular distribution have been measured in the reaction 105 MeV 18O+28Si using the EUROBALL IV, HECTOR and EUCLIDES arrays in order to investigate the predicted Jacobi shape transition in light nuclei. A comparison of the GDR line shape data with the predictions of the thermal shape fluctuation model, based on the most recent rotating liquid drop LSD calculations, shows evidence for such Jacobi shape transition in hot, rapidly rotating 46Ti. The found narrow low-energy component in the GDR line shape is interpreted as the consequence both of the elongated shape and of the Coriolis effect. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

High-energy γ rays emitted in the symmetric reaction [sup 90]Zr + [sup 89]Y have been measured at the Argonne National Laboratory using the LEPPEX array coupled to the Fragment Mass Analyzer (FMA). The high-energy γ-ray spectra emitted by the giant dipole resonance built on excited states and associated with the evaporation of 0, 1 and 2 nucleons have been measured. The statistical model analysis indicates that the radiative-fusion process, namely the 0 particle emission channel, can be well described as a compound nucleus decay channel. In addition, the analysis of the highenergy γ-ray spectra associated with the different evaporation channels provides the first evidence that shell effects still play a role in determining the nuclear shapes of [sup 179]Au in the temperature interval 0.5-1 MeV. [ABSTRACT FROM AUTHOR]