Independent normalization for gamma-ray strength functions: The shape method

The shape method, a novel approach to obtain the functional form of the gamma-ray strength function (gamma SF), is introduced. In connection with the Oslo method the slope of the nuclear level density (NLD) and gamma SF can be obtained simultaneously even in the absence of neutron resonance spacing data. The foundation of the shape method lies in the primary gamma-ray transitions which preserve information on the functional form of the gamma SF. The shape method has been applied to Fe-56, Zr-92, and Dy-164, which are representative cases for the variety of situations encountered in typical NLD and gamma SF studies. The comparisons of results from the shape method to those from the Oslo method demonstrate that the functional form of the gamma SF is retained regardless of nuclear structure details or J(pi) values of the states fed by the primary transitions.