Experimental evidence of large collective enhancement of nuclear level density and its significance in radiative neutron capture

The collective enhancement of nuclear level density and its fade out with excitation in the deformed 171Yb nucleus has been inferred through an exclusive measurement of neutron spectra. The statistical model analysis of neutron spectra demonstrated a large collective enhancement factor of 40±3, a value consistent with recent microscopic model predictions but is an anomalous result compared with the measurements in the nearby deformed nuclei. The complete picture of the energy dependent collective enhancement has been obtained by combining the present results with those obtained with the Oslo method below neutron binding energy. The signature of a large collective enhancement in radiative neutron capture cross section of astrophysical interest is highlighted.