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The Oslo method has been applied to particle-γ coincidences following the 239Pu(d, p) reaction to obtain the nuclear level density (NLD) and γ-ray strength function (γ SF) of 240Pu. The experiment was conducted with a 12 MeV deuteron beam at the Oslo Cyclotron Laboratory. The low spin transfer of this reaction leads to a spin-parity mismatch between populated and intrinsic levels. This is a challenge for the Oslo method as it can have a significant impact on the extracted NLD and γ SF. We have developed an iterative approach to ensure consistent results even for cases with a large spin-parity mismatch, in which we couple Green's function transfer calculations of the spin-parity dependent population cross-section to the nuclear decay code rainier. The resulting γ SF shows a pronounced enhancement between 2-4 MeV that is consistent with the location of the low-energy orbital M1 scissors mode. [ABSTRACT FROM AUTHOR]

The level density and y-ray strength function in the quasicontinuum of 238Np have been measured using the Oslo method. The level-density function follows closely the constant-temperature level-density formula and reaches 43 × 106 levels per MeV at Sn = 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 ωSR = 2.26(5) MeV and a total strength of BSR = 10.8(12)μ²N, which is in excellent agreement with sum-rule estimates. The scissors resonance is shown to have an impact on the 237Np(n.y)238Np cross section. [ABSTRACT FROM AUTHOR]

163,164Dy nuclei have been measured by use of the Oslo method on data from pick-up (3He, &agr;) and inelastic scattering (3He,3Hé) reactions, respectively. The level densities for these dysprosium isotopes together with previously measured 160-162Dy are extracted in the region below the neutron binding energy. Thermodynamic properties are deduced within both micro-canonical and canonical ensemble theories. A phase transition from the pair-correlated state at low energies to a less correlated or uncorrelated state is studied in both ensembles. It is investigated whether the temperature of the nucleus is constant or a varying function of excitation energy. It is found that above an excitation energy of 3 MeV the temperature of all five dysprosium nuclei have a constant value within the experimental uncertainties. The impact of a constant-temperature level density versus a Fermi gas level density is discussed with respect to the canonical heat capacity. [ABSTRACT FROM AUTHOR]

Primary &ggr;-ray spectra for a wide excitation-energy range have been extracted for 44Ti from particle-y coincidence data of the 46Ti(p,t&ggr;)44Ti reaction. These spectra reveal information on the &ggr;-decay pattern of the nucleus and may be used to extract the level density and radiative strength function applying the Oslo method. Models of the level density and radiative strength function are used as input for cross-section calculations of the 40Ca(&agr;,&ggr;)44Ti reaction. Acceptable models should reproduce data on the 40Ca(&agr;,&ggr;)44Ti reaction cross section as well as the measured primary &ggr;-ray spectra. This is only achieved when a coherent normalization of the slope of the level density and radiative strength function is performed. Thus, the overall shape of the experimental primary &ggr;-ray spectra puts a constraint on the input models for the rate calculations. [ABSTRACT FROM AUTHOR]

The nuclear level density and γ-decay strength of 192Os have been extracted using particle-γ coincidence data from the 192Os(α,α′γ)192Os reaction by means of the Oslo method. The level density is found to be a rather smooth function of excitation energy, approximately following the constant temperature model. The γ-decay strength is compared to photoneutron cross-section data above the neutron separation energy, and to E1 and M1 strengths for nuclei in this mass region derived from primary transitions following neutron capture. Our results are in good agreement with these previous data and draw a consistent picture of the γ-strength function in the range Eγ≈1.5-6MeV. Using the measured nuclear level density and γ-decay strength as input to the nuclear-reaction code talys, we provide the first experimentally constrained Maxwellian-averaged cross section (MACS) for the 191Os(n,γ)192Os reaction relevant to s-process nucleosynthesis. The systematic uncertainties introduced by the normalization procedure of the level density and γ-strength function were investigated and propagated to the calculated Maxwellian-averaged cross section. The obtained result of the Maxwellian-averaged cross section at kBT=30keV, 〈σ〉n,γ=1134±375mb, is in very good agreement with the theoretical estimate provided by the KADoNiS project, giving experimental support to the adopted KADoNiS value. Good agreement is also found with MACS values obtained from other libraries, such as TENDL-2017, ENDF/B-VII.0, and JEFF. [ABSTRACT FROM AUTHOR]

The γ decay of 65 Ni has been studied from particle-γ coincidence data on the 64Ni(d,pγ) 65Ni reaction. γ-ray spectra at excitation energies below Ex ≈ 2 MeV have been studied and compared with previous measurements. Coincidences corresponding to Ex ≈ 4.4-6.1 MeV have been used to constrain the shape of the nuclear level density and γ-strength function of 65 Ni by means of the Oslo method. The experimental γ-strength function presents an enhancement at γ energies below Eγ ≈ 3 MeV. In addition, a resonance-like structure centered at E γ ≈ 4.6 MeV is seen together with accumulated strength at Eγ ≈ 2.6-3.6 MeV. The obtained results contribute to the systematic study of γ decay in the Ni isotopes, which is of great interest for the understanding of both single-particle and collective nuclear structure phenomena. [ABSTRACT FROM AUTHOR]

The nuclear level density and the γ-ray strength function have been extracted for 89Y by using the Oslo method on 89Y(p,p'γ)89Y coincidence data. The γ-ray strength function displays a low-energy enhancement consistent with previous observations in this mass region (93-98Mo). Shell-model calculations support the conclusion that the observed enhancement is due to strong, low-energy M1 transitions at high excitation energies. The data were further used as input for calculations of the 88Sr(p,γ)89Y and 88Y(n,γ)89Y cross sections with the talys reaction code. Comparison with cross-section data, where available, as well as with values from the BRUSLIB library, shows a satisfying agreement. [ABSTRACT FROM AUTHOR]