The effect of the one-body Hamiltonian on the statistical fluctuations of the nuclear energy spectrum in ¹³⁸Ba using the context of the nuclear shell model

The effect of the one-body Hamiltonian on the statistical fluctuations of the nuclear energy spectrum in ¹³⁸Ba is examined via the framework of the nuclear shell model, using an effective interaction of N82K for six valence protons in the N82-model space with a ¹³²Sn core. The level density for considered class of states is seen to have a Gaussian shape. The spectral fluctuations (i.e., the nearest-neighbors level spacing distribution and the Δ₃ statistic) formed with normal value of single-particle energies are well described by the Gaussian orthogonal ensemble of random matrices. An obvious quantum sign of breaking the chaoticity is seen with doubling the value of single-particle energies. (author)