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Nuclei in the 135I region have been identified as being a possible bottleneck for the i process. Here we present an indirect measurement for the Maxwellian-averaged cross section of 126Sb(n,γ). The nuclear level density and the γ-ray strength function of 127Sb have been extracted from 124Sn(α,pγ)127Sb data using the Oslo method. The level density in the low-excitation-energy region agrees well with known discrete levels, and the higher-excitation-energy region follows an exponential curve compatible with the constant-temperature model. The strength function between Eγ≈1.5–8.0 MeV presents several features, such as an upbend and a possibly double-peaked pygmy-like structure. None of the theoretical models included in the nuclear reaction code talys seem to reproduce the experimental data. The Maxwellian-averaged cross section for the 126Sb(n,γ)127Sb reaction has been experimentally constrained by using our level-density and strength-function data as input to talys. We observe a good agreement with the jina reaclib, tendl, and bruslib libraries, while the endf/b-viii.0 library predicts a significantly higher rate than our results.

Nuclear level densities (NLDs) and γ-ray strength functions (GSFs) of 120,124Sn have been extracted with the Oslo method from proton-γ coincidences in the (p,p′γ) reaction. The functional forms of the GSFs and NLDs have been further constrained with the Shape method by studying primary γ-transitions to the ground and first excited states. The NLDs demonstrate good agreement with the NLDs of 116,118,122Sn isotopes measured previously. Moreover, the extracted partial NLD of 1− levels in 124Sn is shown to be in fair agreement with those deduced from spectra of relativistic Coulomb excitation in forward-angle inelastic proton scattering. The experimental NLDs have been applied to estimate the magnitude of the Porter-Thomas (PT) fluctuations. Within the PT fluctuations, we conclude that the GSFs for both isotopes can be considered to be independent of initial and final excitation energies, in accordance with the generalized Brink-Axel hypothesis. Particularly large fluctuations observed in the Shape-method GSFs present a considerable contribution to the uncertainty of the method and may be one of the reasons for deviations from the Oslo-method strength at low γ-ray energies and low values of the NLD (below ≈1×103–2×103MeV−1).

We report on spectroscopic information and lifetime measurements of even-even neutron-rich Te isotopes. Excited states were populated in fast-neutron induced fission of 238U at the ALTO facility of IJCLab with the LICORNE neutron source and detected using the hybrid ν-ball spectrometer. We provide first results on lifetimes of the 6+1 state in 136Te and the (6+1), (4+1), and (2+1) states in 138Te and discuss the results in the context of large-scale shell-model calculations. The level schemes of 136Te and 138Te are revised in terms of lifetimes of their 2+1,4+1 states and updated information on the (4+2) state in 136Te is presented. In addition, previously reported data on spectroscopy and lifetimes in 134Te are reexamined. This work provides new insights into the evolution of collectivity for Te isotopes with N=82,84,86.

The study of prompt fission γ rays (PFGs) is crucial for understanding the energy and angular momentum distribution in fission, and over the last decade there has been an revived interest in this aspect of fission. We present the new experimental setup at the Oslo Cyclotron Laboratory for detecting PFGs resulting from charged particle-induced fission. Additionally, PFGs from the reaction 240Pu(d,pf) were measured in April 2018, and the fission gated proton-γ coincidence spectrum is shown. In order to explore the dependence of the PFG emission on the excitation energy and angular momentum of the compound nucleus, we plan several experiments where charged particle reactions are used to induce fission in various plutonium isotopes. The final results will be compared to predictions made by the Fission Reaction Event Yield Algorithm (FREYA) in an upcoming publication, to benchmark the current modelling of both the PFGs and the fission process.

Prompt and delayed γ-ray spectroscopy of the neutron-rich 94Kr was performed, as part of the fission campaign at the ALTO facility of the IPN Orsay, using the fast-neutron-induced fission reaction 238U(n,f) in combination with the ν-Ball array, a novel hybrid γ spectrometer for energy and lifetime measurements. Several new yrast and nonyrast transitions were observed for the first time, extending the previously known level scheme. Additionally, we report on the observation of a new short-lived isomer at 3444 keV with a half-life of 32(3) ns. The analysis of the Nilsson orbitals obtained from Gogny cranked Hartree-Fock-Bogoliubov calculations suggests a (9−) spin and an oblate deformation for this isomer corresponding to a two-quasineutron state, indicating an isomeric structure very similar to that of the neighboring isotones 96Sr and 92Se.