Odd-odd Nuclei, The Energy Level Statistics

In this paper, we first introduce some basic surveys of the studies of the properties of the nuclear structure, the development of Random-Matrix Theory (RMT) in the field of nuclear physics, and some principal theories and basic ways of RMT. We also introduce the quasiparticles plus rotor model and calculate the energy levels of odd-odd nuclei MY and b in A80 mass region in detail. In order to study the statistical properties of the energy levels that we calculate based on our theoretic model, the standard statistical tests of RMT such as the distribution function p(s) of the nearest- neighbor level spacings and the spectral rigidity are used. By detailed analysis we mainly study the statistical properties of the energy levels of odd-odd nuclei 84Y and ~Nb at low spins and the effects of the Coriolis force, the recoil term, and the quasiparticle features on the spectral structure. In briefly, we give out the results of our research as follows: (1) The energy levels of odd-odd nuclei 6Nb and MY at low spins are close to chaos. We guess that the energy levels of the other odd-odd nuclei in A80 mass region are also close to chaos. (2) In our theoretic model the chaotic degree of the energy levels of ~~慛b and MY depends on the spin and there also exists a distinct phenomenon: the chaotic degree of the energy levels initially increases and reaches a maximum around 1=10, then it gradually decreases with the increasing of spin for the spins above 1=10. (3) The effects of single particle tenn and the pure rotor term on the spectral structure are much less, however the effects of the recoil term and the Coriolis force are strong and * Project supported by the National Science Foundation of China (Granted No. 19875040) 4 the latter is very important for the properties of the spectral structure of 86Nb and My (4) In this theoretic model Hamiltonian, the recoil term makes the energy levels slightly regular but the Coriolis force depending on the spin makes the energy levels tend to be chaotic. The decoupling effect of the Coriolis force plays a major role in the statistical properties of the energy levels. (5) The quasiparticle features affect the spectral structure though the recoil term and the Coriolis force in our theoretic model. The chaotic degree of the energy levels gradually decreases with the decreasing of the Femii energy and the energy-gap.