Spectra statistics for the odd-odd nucleus Nb-86

The energy levels of the add-odd nucleus Nb-86 at low spins are calculated by using quasi-particles plus a rotor model. The distribution of the neares t-neighbour spacing and the spectral rigidity are studied. We find that the chaotic degree of the energy spectra increases with the increasing spin an d reaches a maximum at I = 10; then it decreases gradually for spins above I = 10. The recoil term in the model Hamiltonian makes the energy spectra s lightly regular. The Coriolis force, however, makes the spectra chaotic and plays a major role in the spectral statistics of the odd-odd nucleus Nb-86 .