Strength of the scissors mode in odd-mass Gd isotopes from the radiative capture of resonance neutrons

Radiative neutron capture reaction was measured in the resolved resonance region for Gd-152,Gd-154,Gd-156,Gd-158 targets with the Detector for Advanced Neutron Capture Experiments gamma-ray calorimeter at the Los Alamos Neutron Science Center. The gamma-ray energy spectra for different multiplicities were obtained for several s-wave resonances in each nucleus. These spectra were analyzed within the extreme statistical model to provide unique information on the photon strength functions and especially on the scissors mode in odd Gd isotopes. The main result of this analysis is that in all nuclei scissors-mode resonances are built on excited levels and not only on their ground states. The strength of the mode found in Gd-153 and Gd-155 is comparable to the strength observed in well-deformed even-even Gd isotopes while it is substantially higher in Gd-157,Gd-159. The difference in observed strengths of the scissors mode indicates an existence of an even-odd effect in this quantity.