Test of the Brink-Axel Hypothesis for the Pygmy Dipole Resonance

The gamma strength function and level density of 1(-) states in Mo-96 have been extracted from a high-resolution study of the ((p)over-right-arrow, (p)over-right-arrow') reaction at 295 MeV and extreme forward angles. By comparison with compound nucleus gamma decay experiments, this allows a test of the generalized Brink-Axel hypothesis in the energy region of the pygmy dipole resonance. The Brink-Axel hypothesis is commonly assumed in astrophysical reaction network calculations and states that the gamma strength function in nuclei is independent of the structure of the initial and final state. The present results validate the Brink-Axel hypothesis for Mo-96 and provide independent confirmation of the methods used to separate gamma strength function and level density in y decay experiments.