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The detection of a Gaussian-like distribution of the nearest level spacings for simple neutron resonances in 28Si, 32S, 40Ca, 52Cr and 96Zr points to the existence of phonons and permits the nucleus to be represented by a three dimensional multiple harmonic oscillator system. The degrees of freedom which determine the nuclear spectra are therefore nucleons and phonons. A clustered lattice model of the nucleus is proposed, containing the property of independent motion of nucleons. The spin-orbit term in the Nilsson model is replaced by a phonon-nucleon term. The experimental results support this model and explain shell effects by ordered clusters in the nucleus. The following aspects are discussed: - the validity of the Bethe level density expression - the existence of unbound shape collective states - changes in the level density parameter with the excitation energy - the possible disappearance of the so-called shell effect with changes in the excitation energy - predictions of the level density of states

Additional information

Authors: ROHR G, JRC Geel, B-2440 Geel (BE)
Bibliographic Reference: Paper presented: Specialists Meeting on Nuclear Level Densities, Bologna (IT), Nov. 15-17, 1989
Availability: Text not available
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