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The distribution of E1 and M1 strength in " Gd compound nucleus has been studied. An investigation of capture of 2 and 24 keV neutrons in a " Gd target resulted in resonance-averaged intensities of primary gamma rays between 3.7 and 6.4 MeV. From these intensities the gamma-ray strength functions have been derived for E1 and M1 radiation. We compare several formulations of strength functions to these resonance capture and/or photoabsorption data. Further we use these prescriptions in calculations of the total average radiation width, radiative capture cross sections, and gamma-ray spectra, and compare them to available experimental information. By analyzing these results strong evidence was found for an E1 strength function which is based on a generalized Lorentzian, enhanced compared to spherical nuclei, with an energy-dependent spreading width and a nonzero limit as the energy tends to zero. For M1 radiation the giant resonance spin-flip mode is favored. PACS number(s): 25.40.Lw, 23.20.Lv, 24.60.Dr, 21.10.Pc

The neutron capture cross sections of 152 Gd, 154 Gd, 155 Gd, 156 Gd, 157 Gd, and 158 Gd were measured in the energy range from 3 to 225 keV at the Karlsruhe 3.75 MV Van de Graaff accelerator. Neutrons were produced via the 7 Li(p,n)1Be reaction by bombarding metallic Li targets with a pulsed protori beam. Capture events were registered with the Karlsruhe 47r Barium Fluoride Detector, which was improved by replacing crystals with high a background and by introducing a pierced crystal at zero degrees with respect to the beam axis. These changes resulted in a significantly increased efficiency for capture events. The main experimental problern was that the samples of the two s-only isotopes 152 Gd and 154 Gd showed only relatively low enrichment, but the spectroscopic quality of the BaF 2 detector allowed to determine the resulting corrections for isotopic impurities reliably. The cross section ratios could be determined with an overall uncertainty of typically 1%, an improvement by factors of five to ten compared to existing data. Severe discrepancies were found with respect to previous results. Maxwellian averaged neutron capture cross sections were calculated forthermal energies between kT = 10 keV and 100 keV. The new stellar cross sections were used for an updated analysis of the s-process reaction flow in the mass region between samarium and gadolinium, which is characterized by branchings at 151 Sm, 154 Eu, and 155 Eu. With the classical approach, the s-process temperature could be constrained corresponding to a range of thermal energies between kT=28 ke V and 33 keV. The 152 Gd production in low mass starswas found to depend strongly on the neutron freeze-out at the end of the heliumshell burning episodes.

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