Neutron-capture gamma-ray study of levels in Ba135 and description of nuclear levels in the interacting-boson-fermion model

We have performed neutron-capture gamma-ray studies on natural and enriched targets of Ba-134 in order to investigate the nuclear levels of Ba-135. The low-energy level spectra were compared with the calculations using the interacting-boson-fermion model (IBFM) and the cluster-vibration model. The level densities up to 5 MeV that are calculated within the IBFM are in accordance with the constant temperature Fermi gas model. From the spin distribution we have determined the corresponding spin cutoff parameter sigma and compared it to the prediction from nuclear systematics.