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Background: An unexpected enhancement in the γ-ray strength function, as compared to the low-energy tail of the giant dipole resonance (GDR), has been observed for Sc, Ti, V, Fe, and Mo isotopes for Eγ < 4 MeV. This enhancement was not observed in subsequent analyses on Sn isotopes, but a pygmy dipole resonance (PDR) centered at Eγ ≈ 8 MeV was however detected. The γ-ray strength functions measured for Cd isotopes exhibit both features over the range of isotopes, with the low-energy enhancement decreasing and PDR strength increasing as a function of neutron number. This suggests a transitional region for the onset of low-energy enhancement, and also that the PDR strength depends on the number of neutrons. Purpose: The γ-ray strength functions of 105-108Pd have been measured in order to further explore the proposed transitional region. Method: Experimental data were obtained at the Oslo Cyclotron Laboratory by using the charged particle reactions (³He,³He'γ) and (³He,αγ) on 106,108Pd target foils. Particle-γ coincidence measurements provided information on initial excitation energies and the corresponding γ-ray spectra, which were used to extract the level densities and γ-ray strength functions according to the Oslo method. Results: The γ-ray strength functions indicate a sudden increase in magnitude for Eγ > 4 MeV, which is interpreted as a PDR centered at Eγ ≈ 8 MeV. An enhanced γ-ray strength at low energies is also observed for 105Pd, which is the lightest isotope measured in this work. Conclusions: A PDR is clearly identified in the γ-ray strength functions of 105-108Pd, and a low-energy enhancement is observed for Pd105. Further, the results correspond and agree very well with the observations from the Cd isotopes, and support the suggested transitional region for the onset of low-energy enhancement with decreasing mass number. The neutron number dependency of the PDR strength is also evident. [ABSTRACT FROM AUTHOR]

The γ-ray strength functions and level densities of 73,74Ge have been extracted up to the neutron-separation energy Sn from particle-γ coincidence data using the Oslo method. Moreover, the γ-ray strength function of 74Ge above Sn has been determined from photoneutron measurements; hence these two experiments cover the range of Eγ≈1-13 MeV for 74Ge. The obtained data show that both 73,74Ge display an increase in strength at low γ energies. The experimental γ-ray strength functions are compared with M1 strength functions deduced from average B(M1) values calculated within the shell model for a large number of transitions. The observed low-energy enhancements in 73,74Ge are adopted in the calculations of the 72,73Ge(n,γ) cross sections, where there are no direct experimental data. Calculated reaction rates for more neutron-rich germanium isotopes are shown to be strongly dependent on the presence of the low-energy enhancement. [ABSTRACT FROM AUTHOR]