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Large Shell Model Calculations for Calcium Isotopes: Spectral Statistics and Chaos

V. R. Manfredi·J. M. G. Gomez·L. Salasnich
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Abstract

We perform large shell model calculations for Calcium isotopes in the full fp shell by using the realistic Kuo-Brown interaction. The Calcium isotopes are especially interesting because the nearest-neighbour spacing distribution P(s) of low-lying energy levels shows significant deviations from the predictions of the Gaussian Orthogonal Ensemble of random--matrix theory. This contrasts with other neighbouring nuclei which show fully chaotic spectral distributions. We study the chaotic behaviour as a function of the excitation energy. In addition, a clear signature of chaos suppression is obtained when the single-particle spacings are increased. In our opinion the relatively weak strength of the neutron-neutron interaction is unable to destroy the regular single-particle mean-field motion completely. In the neighbouring nuclei with both protons and neutrons in valence orbits, on the other hand, the stronger proton-neutron interaction would appear to be sufficient to destroy the regular mean-field motion.

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V. R. Manfredi, J. M. G. Gomez, L. Salasnich. 1998-05-27. Large Shell Model Calculations for Calcium Isotopes: Spectral Statistics and Chaos. https://arxiv.org/abs/nucl-th/9805049

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