The γ-ray strength function of 56Fe has been measured from proton-γ coincidences for excitation energies up to ≈11  MeV. The low-energy enhancement in the γ-ray strength function, which was first discovered in the (3He,αγ)56Fe reaction, is confirmed with the (p,p'γ)56Fe experiment reported here. Angular distributions of the γ rays give for the first time evidence that the enhancement is dominated by dipole transitions.

The γ -ray strength function in the quasicontinuum has been measured for [231][232][233] 232,233 Pa, and 237-239 U using the Oslo method. All eight nuclei show a pronounced increase in γ strength at ω SR ≈ 2.4 MeV, which is interpreted as the low-energy M1 scissors resonance (SR). The total strength is found to be B SR = 9-11 μ 2 N when integrated over the 1-4 MeV γ -energy region. The SR displays a double-hump structure that is theoretically not understood. Our results are compared with data from (γ , γ ) experiments and theoretical sum-rule estimates for a nuclear rigid-body moment of inertia.

The level densities and γ-ray strength functions of 105,106,111,112 Cd have been extracted from particle-γ coincidence data using the Oslo method. The level densities are in very good agreement with known levels at low excitation energy. The γ-ray strength functions display no strong enhancement for low γ energies. However, more low-energy strength is apparent for 105,106 Cd than for 111,112 Cd. For γ energies above ≈ 4 MeV, there is evidence for some extra strength, similar to what has been previously observed for the Sn isotopes. The origin of this extra strength is unclear; it might be due to E1 and M1 transitions originating from neutron skin oscillations or the spin-flip resonance, respectively.

The orbital M1 scissors resonance has been measured for the first time in the quasicontinuum of actinides. Particle-γ coincidences are recorded with deuteron and (3)He-induced reactions on (232)Th. The residual nuclei (231,232,233)Th and (232,233) Pa show an unexpectedly strong integrated strength of B(M1)=11-15μ(n)(2) in the E(γ)=1.0-3.5 MeV region. The increased γ-decay probability in actinides due to scissors resonance is important for cross-section calculations for future fuel cycles of fast nuclear reactors and may also have an impact on stellar nucleosynthesis.

The level density and γ -ray strength function in the quasicontinuum of 238 Np have been measured using the Oslo method. The level-density function follows closely the constant-temperature level-density formula and reaches 43 × 10 6 levels per MeV at S n = 5.488 MeV of excitation energy. The γ -ray strength function displays a two-humped resonance at low-energy as also seen in previous investigations of Th, Pa, and U isotopes. The structure is interpreted as the scissors resonance and has an average centroid of ω SR = 2.26(5) MeV and a total strength of B SR = 10.8(12)μ 2 N , which is in excellent agreement with sum-rule estimates. The scissors resonance is shown to have an impact on the 237 Np(n,γ ) 238 Np cross section.