Erlend Lima

• Larsen, Ann-Cecilie; Tveten, Gry Merete; Renstrøm, Therese; Utsunomiya, H.; Algin, E. & Ari-Izumi, T. [Show all 31 contributors for this article] (2023). New experimental constraint on the W 185 (n,γ) W 186 cross section. Physical Review C. ISSN 2469-9985. 108(2). doi: 10.1103/PhysRevC.108.025804. Full text in Research Archive
• Midtbø, Jørgen E.; Zeiser, Fabio; Lima, Erlend; Larsen, Ann-Cecilie; Tveten, Gry Merete & Guttormsen, Magne Sveen [Show all 9 contributors for this article] (2021). A new software implementation of the Oslo method with rigorous statistical uncertainty propagation. Computer Physics Communications. ISSN 0010-4655. 262. doi: 10.1016/j.cpc.2020.107795. Full text in Research Archive Show summary

  The Oslo method comprises a set of analysis techniques designed to extract nuclear level density and average -decay strength function from a set of excitation-energy tagged -ray spectra. Here we present a new software implementation of the entire Oslo method, called OMpy. We provide a summary of the theoretical basis and derive the essential equations used in the Oslo method. In addition to the functionality of the original analysis code, the new implementation includes novel components such as a rigorous method to propagate uncertainties throughout all steps of the Oslo method using a Monte Carlo approach. The resulting level density and -ray strength function have to be normalized to auxiliary data. The normalization is performed simultaneously for both quantities, thus preserving all correlations. The software is verified by the analysis of a synthetic spectrum and compared to the results of the previous implementation, the oslo-method-software.

• Midtbø, Jørgen E.; Larsen, Ann-Cecilie; Renstrøm, Therese; Garrote, Frank Leonel Bello & Lima, Erlend (2019). Systematic Low-Energy Enhancementof the Gamma-Ray Strength Function. In Formicola, Alba; Junker, Matthias; Gialanella, Lucio & Imbriani, Gianluca (Ed.), Nuclei in the Cosmos XV. Springer. ISSN 9783030138752. p. 405–407. doi: 10.1007/978-3-030-13876-9. Full text in Research Archive
• Midtbø, Jørgen E.; Larsen, Ann-Cecilie; Renstrøm, Therese; Garrote, Frank Leonel Bello & Lima, Erlend (2018). Consolidating the concept of low-energy magnetic dipole decay radiation. Physical Review C. ISSN 2469-9985. 98(6), p. 064321-1–064321-12. doi: 10.1103/PhysRevC.98.064321. Full text in Research Archive Show summary

  We have made a thorough study of the low-energy behavior of the γ -ray strength function within the framework of the shell model. We have performed large-scale calculations spanning isotopic and isotonic chains over several mass regions, considering 283 nuclei in total, with the purpose of studying the systematic behavior of the low-energy enhancement (LEE) for M1 transitions. There are clear trends in the calculations: From being nearly absent in the lowest mass region, the LEE becomes steeper and more pronounced as the mass number increases, and for a given mass region it further increases toward shell closures. Moreover, the LEE is found to be steeper in regions near doubly magic nuclei where proton particles couple to neutron holes. These trends enable us to consolidate several previous works on the LEE into a single, consistent concept. We compare the inferred trends to the available experimental data from the Oslo method and find support for the systematic behavior. Lastly, we have compared the calculations to strength functions compiled from discrete, experimental lifetimes and find excellent agreement; the discrete data are consistent with an LEE and indicate that the slope varies as function of mass number.

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• Zeiser, Fabio; Midtbø, Jørgen E. & Lima, Erlend (2019). A new approach to uncertainty estimation for nuclear level densities and gamma-ray strength functions in the Oslo Method. Full text in Research Archive

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