Nuclear structure of 157Gd

Abstract The energy levels of 157 Gd have been investigated using the (n,  γ ) and (n, n′ γ ) reactions. As a result of the analysis of the γ -ray spectra from 16 isolated neutron resonances, a level scheme with a complete set of levels with spins J =1/2, 3/2 has been established up to 1.86 MeV excitation energy. A part of the level scheme is interpreted in more detail on the basis of Coriolis and Δ N =2 coupled Nilsson configurations. Slightly different sets of shape parameters are deduced for negative- and positive-parity levels. A large excess of unassigned 1/2 and 3/2 levels evidently requires an explanation in terms of inclusion of new additional degrees of freedom.