Calculations of capture cross sections and gamma-ray spectra with different strength function models

We studied the impact of different models for the E1 and M1 gamma-ray strength function on the results of neutron capture cross sections calculations for spherical and deformed target nuclei with mass numbers between 55 and 197. Assuming an M1 strength based on a standard Lorentzian we found in many cases strong support for an E1 strength in terms of a generalized Lorentzian with an energy dependent width and a non-zero limit as the energy tends to zero. These features are founded in microscopic models. For some of the investigated deformed nuclei, namely 151,153Eu, 156Gd and 175Lu, an enhancement of the width is required in order to reproduce the experimental data. (author). 18 refs.; 1 fig