Abstrakt
The experimental spectra of gamma rays following radiative neutron capture on isolated resonances of stable Gd-152,Gd-154-158 targets were measured by the DANCE calorimeter installed at the Los Alamos Neutron Scattering Center in New Mexico, USA. These spectra were analyzed within the extreme statistical model to get new information on the photon strength functions.
Special emphasis was put on study of the scissors vibrational mode present in these isotopes. Our data show that the scissors-mode resonances are built not only on the ground states but also on the excited levels of all studied Gd isotopes.
The scissors mode strength observed in Gd-157,Gd-159 products is significantly higher than in neighboring even-even nuclei Gd-156,Gd-158. Such a difference indicates the existence of an odd-even effect in the scissors mode strength.
Moreover, there exists no universal parameter-free model of the electric dipole photon strength function describing the experimental data in all of the Gd isotopes studied. The results for the scissors mode are compared with the (gamma,gamma') data for the ground-state transitions and with the results from He-3-induced reactions.