Ann-Cecilie Larsen

Professor - Nuclear and Energy Physics

Norwegian version of this page

Email a.c.larsen@fys.uio.no

Phone +47 22855486

Room V104

Available hours Anytime

Username

Visiting address Physics building Sem Sælandsvei 24 0371 Oslo

Postal address Postboks 1048 Blindern 0316 Oslo

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Academic Interests

What happens if the atomic nucleus is heated to several billion degrees?

How were the elements that we know of in the Universe made?

How can nuclear physics save lives?

The nuclear physics group at the Oslo Cyclotron Laboratory (OCL) has developed a method to measure the properties of atomic nuclei at very high temperatures. At these temperatures, the most important properties are the level density, which is how many quantum states available for the nucleus at a given excitation energy, and the gamma-ray strength function, which is a measure of the probability of electromagnetic decay for a certain gamma energy. These two quantities are indispensable for estimating astrophysical reaction rates, which in turn are used for modeling the creation of the various elements in, e.g., supernovae.

New results from the OCL experiments show that some nuclei have an enhanced probability for electromagnetic decay for low-energetic gamma rays. It turns out that these discoveries might have a huge impact on the astrophysical reaction rates of the so-called r-process (rapid neutron capture), which is believed to be the mechanism behind about 50% of the heavy elements we observe in the Universe. Dependent on the models applied in the calculations, the reaction rates can increase up to a factor of 300 for the most neutron-rich nuclei [A. C. Larsen and S. Goriely, Physical Review C 82, 014318 (2010)].

Atomic nuclei may also be used for efficient and precise cancer treatment. By shooting e.g. protons (ionized hydrogen gas) or carbon ions into a tumor, the cancer cells will die while the surrounding healthy tissue will receive a minimal dose compared to conventional radiation treatment. Proton and ion therapy is now a well established method of treatment in many countries, and hopefully this method will also be available for Norwegian cancer patients soon.

Teaching

From spring 2021: FYS-MEK1110 - Mechanics https://www.uio.no/studier/emner/matnat/fys/FYS-MEK1110/index-eng.html

Lecturer, FYS4515 - Nuclear Physics I https://www.uio.no/studier/emner/matnat/fys/FYS4515/index-eng.html

Previous teaching

colloquium teacher, FYS-MEK1110 - Mechanics http://www.uio.no/studier/emner/matnat/fys/FYS-MEK1110/index-eng.html
lab teacher, KJM-FYS5920 - Nuclear measurement techniques and instruments http://www.uio.no/studier/emner/matnat/kjemi/KJM-FYS5920/index-eng.html

Higher education and employment history

Cand.mag. in Physics, Dec. 2002, Department of Physics, University of Oslo

Cand.scient. in Nuclear Physics, June 2004, Department of Physics, University of Oslo

Ph.D. in Nuclear Physics, May 2008, Department of Physics, University of Oslo

Research fellow, OCL nuclear physics group, June 2008 - Feb 2009, Department of Physics, University of Oslo

Post.doc., OCL nuclear physics group, Nov. 2009 - Feb 2011, Department of Physics, University of Oslo

Personal postdoc grant, Research Council of Norway, Nov 2011 - Oct 2014, Department of Physics, University of Oslo

Guest researcher, Université Libre de Bruxelles, spring 2013

Guest researcher, UC Berkeley/Lawrence Berkeley National Lab/Lawrence Livermore National Lab, fall 2013

Guest researcher, National Superconducting Cyclotron Laboratory/Michigan State University, summer 2014

Fulbright fellow at the National Superconducting Cyclotron Laboratory/Michigan State University, fall 2016

Fulbright fellow at UC Berkeley/Lawrence Berkeley National Lab, spring 2017

Honoraria

Fulbright Scholarship, 2016-2017

Member of the Norwegian Academy for Science and Letters, 2017-

Prize for Young, Excellent Researchers, Research Council of Norway, fall 2016

Starting Grant (STG-ERC-2014), European Research Council, Grant Agreement No. 637686, 2015-2020

Personal postdoc grant from the Research Council of Norway, Project Grant No. 205528, 2011-2014

Best poster presentation award, Zakopane Conference on Nuclear Physics, 2006

Cooperation

Oslo Syklotronlaboratorium (OCL), http://ocl.uio.no

Université Libre de Bruxelles, http://www.ulb.ac.be/index.html

National Superconducting Cyclotron Laboratory, Michigan State University, http://www.nscl.msu.edu

Lawrence Berkeley National Laboratory, http://www.lbl.gov

Institute of Nuclear Physics NCSR Demokritos, http://www.inp.demokritos.gr/

Lawrence Livermore National Laboratory, https://www.llnl.gov/

CERN / ISOLDE

Tags: nuclear physics, nuclear astrophysics, detectors, Instrumentation

Naqvi, F.; Crespo Campo, Lucia; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Renstrøm, Therese & Siem, Sunniva [Show all 7 contributors for this article] (2022). Total absorption spectroscopy measurement on neutron-rich 74,75Cu isotopes. Nuclear Physics A. ISSN 0375-9474. A1018(122359). doi: 10.1016/j.nuclphysa.2021.122359.
Gjestvang, Dorthea; Siem, Sunniva; Zeiser, Fabio; Randrup, Jørgen; Vogt, Ramona & Bello Garrote, Frank Leonel [Show all 20 contributors for this article] (2021). The study of prompt fission γ rays at the Oslo Cyclotron Laboratory. The European Physical Journal Conferences. ISSN 2101-6275. doi: 10.1051/epjconf/202125600005. Full text in Research Archive
Markova, Maria; von Neumann-Cosel, Neumann-Cosel; Larsen, A.C.; Bassauer, S.; Görgen, A. & Guttormsen, Magne Sveen [Show all 25 contributors for this article] (2021). Comprehensive Test of the Brink-Axel Hypothesis in the Energy Region of the Pygmy Dipole Resonance. Physical Review Letters. ISSN 0031-9007. 127(18). doi: 10.1103/PhysRevLett.127.182501. Full text in Research Archive
Wiedeking, Mathis; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Zeiser, Fabio; Görgen, Andreas & Liddick, Sean N. [Show all 9 contributors for this article] (2021). Independent normalization for gamma-ray strength functions: The shape method. Physical Review C. ISSN 2469-9985. 104(014311). doi: 10.1103/PhysRevC.104.014311. Full text in Research Archive
Persch, C.F.; DeYoung, P.A.; Lyons, S.; Spyrou, Artemis; Liddick, Sean N. & Naqvi, F. [Show all 27 contributors for this article] (2021). Beta-decay feeding intensity distributions of 71,73Ni. Physical Review C. ISSN 2469-9985. C103(055808). doi: 10.1103/PhysRevC.103.055808. Full text in Research Archive
Görgen, Andreas; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Siem, Sunniva; Adli, Erik & Edin, Nina Frederike J [Show all 14 contributors for this article] (2021). The Oslo Cyclotron Laboratory. The European Physical Journal Plus. ISSN 2190-5444. 136, p. 1–13. doi: 10.1140/epjp/s13360-021-01150-3. Full text in Research Archive
Guttormsen, Magne Sveen; Alhassid, Yoram; Ryssens, Wouter; Ay, K.o.; Ozgur, Mustafa & Algin, Emel [Show all 22 contributors for this article] (2021). Strong enhancement of level densities in the crossover from spherical to deformed neodymium isotopes. Physics Letters B. ISSN 0370-2693. 816. doi: 10.1016/j.physletb.2021.136206. Full text in Research Archive
Gjestvang, Dorthea; Siem, Sunniva; Zeiser, Fabio; Randrup, Jørgen; Vogt, Ramona & Wilson, Jonathan Nicholas [Show all 19 contributors for this article] (2021). Excitation energy dependence of prompt fission γ-ray emission from 241Pu*. Physical Review C. ISSN 2469-9985. 103(3). doi: 10.1103/PhysRevC.103.034609. Full text in Research Archive Show summary
Prompt fission γ rays (PFGs) resulting from the 240Pu(d,pf) reaction have been measured as a function of fissioning nucleus excitation energy Ex at the Oslo Cyclotron Laboratory. We study the average total PFG multiplicity per fission, the average total PFG energy released per fission, and the average PFG energy. No significant changes in these characteristics are observed over the range 5.75
Malatji, Kgashane Leroy; Beckmann, Kristine Sønstevold; Wiedeking, Mathis; Siem, Sunniva; Goriely, Stephane & Larsen, Ann-Cecilie [Show all 21 contributors for this article] (2021). Statistical properties of the well deformed 153,155Sm nuclei and the scissors resonance. Physical Review C. ISSN 2469-9985. 103(1). doi: 10.1103/PhysRevC.103.014309. 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
Zeiser, Fabio; Tveten, Gry Merete; Bello Garrote, Frank Leonel; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie & Ingeberg, Vetle Wegner [Show all 8 contributors for this article] (2021). The gamma-ray energy response of the Oslo Scintillator Array OSCAR. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 985. doi: 10.1016/j.nima.2020.164678. Full text in Research Archive
Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Spyrou, Artemis & Liddick, Sean N. (2020). Experimentally constrained (n, γ) reaction rates relevant to r- and i-process nucleosynthesis. Acta Physica Polonica B. ISSN 0587-4254. 56(3), p. 667–676. doi: 10.5506/APhysPolB.51.667. Full text in Research Archive
Scholz, P.; Guttormsen, Magne Sveen; Heim, F.; Larsen, Ann-Cecilie; Mayer, J. & Savran, D. [Show all 12 contributors for this article] (2020). Primary γ-ray intensities and γ-strength functions from discrete two-step γ-ray cascades in radiative proton-capture experiments. Physical Review C. ISSN 2469-9985. doi: 10.1103/PhysRevC.101.045806. Full text in Research Archive
Kibédi, T.; Alshahrani, B.; Stuchbery, A.E.; Larsen, Ann-Cecilie; Görgen, Andreas & Siem, Sunniva [Show all 20 contributors for this article] (2020). Radiative Width of the Hoyle State from γ -Ray Spectroscopy. Physical Review Letters. ISSN 0031-9007. 125(18). doi: 10.1103/PhysRevLett.125.182701. Full text in Research Archive
Ingeberg, Vetle Wegner; Siem, Sunniva; Wiedeking, Mathis; Sieja, Kamila; Bleuel, D.l. & Brits, C.P. [Show all 29 contributors for this article] (2020). First application of the Oslo method in inverse kinematics. European Physical Journal A. ISSN 1434-6001. 56. doi: 10.1140/epja/s10050-020-00070-7. Full text in Research Archive Show summary
The γ-ray strength function (SF) and nuclear level density (NLD) have been extracted for the first time from inverse kinematic reactions with the Oslo method. This novel technique allows measurements of these properties across a wide range of previously inaccessible nuclei. Proton–γ coincidence events from the d(⁸⁷Kr,p)⁸⁶Kr reaction were measured at iThemba LABS and the γSF and NLD in ⁸⁶Kr was obtained. The low-energy region of the γSF is compared to shell-model calculations, which suggest this region to be dominated by M1 strength. The γSF and NLD are used as input parameters to Hauser–Feshbach calculations to constrain (n,γ) cross sections of nuclei using the TALYS reaction code. These results are compared to ⁸⁶Kr(n,γ) data from direct measurements.
Wrzosek-Lipska, K.; Rezynkina, K.; Bree, N.; Zielińska, M.; Gaffney, L.P. & Petts, A. [Show all 70 contributors for this article] (2019). Electromagnetic properties of low-lying states in neutron-deficient Hg isotopes: Coulomb excitation of 182Hg, 184Hg, 186Hg and 188Hg. European Physical Journal A. ISSN 1434-6001. 55(8), p. 1–23. doi: 10.1140/epja/i2019-12815-2.
Krzysiek, Mateusz; Utsunomiya, Hiroaki; Gheorghe, Ioana; Filipescu, Dan Mihai; Renstrøm, Therese & Tveten, Gry Merete [Show all 19 contributors for this article] (2019). Photoneutron cross-section measurements for 165HO by the direct neutron-multiplicity sorting at Newsubaru . Acta Physica Polonica B. ISSN 0587-4254. 50(3), p. 487–494. doi: 10.5506/APhysPolB.50.487.
Midtbø, Jørgen E.; Larsen, Ann-Cecilie; Renstrøm, Therese; Bello Garrote, Frank Leonel & 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 978-3-030-13875-2. p. 405–407. doi: 10.1007/978-3-030-13876-9.
Larsen, Ann-Cecilie; Liddick, Sean N.; Spyrou, Artemis; Guttormsen, Magne Sveen; Bello Garrote, Frank Leonel & Midtbø, Jørgen E. [Show all 7 contributors for this article] (2019). The Beta-Oslo Method: ExperimentallyConstrained (n,γ) Reaction RatesRelevant to ther-Process. In Formicola, Alba; Junker, Matthias; Gialanella, Lucio & Imbriani, Gianluca (Ed.), Nuclei in the Cosmos XV. Springer. ISSN 978-3-030-13875-2. p. 137–140. doi: 10.1007/978-3-030-13876-9_22.
Guttormsen, Magne Sveen; Goriely, Stephane; Larsen, Ann-Cecilie; Görgen, Andreas; Hagen, Trine Wiborg & Renstrøm, Therese [Show all 13 contributors for this article] (2019). Indirect(n,γ)91,92Zr Cross SectionMeasurements for the s-Process. In Formicola, Alba; Junker, Matthias; Gialanella, Lucio & Imbriani, Gianluca (Ed.), Nuclei in the Cosmos XV. Springer. ISSN 978-3-030-13875-2. p. 359–362. doi: 10.1007/978-3-030-13876-9_65.
Voinov, Alexander; Renstrøm, Therese; Bleuel, D.l.; Grimes, S.M.; Guttormsen, Magne Sveen & Larsen, Ann-Cecilie [Show all 23 contributors for this article] (2019). Level densities of 74,76Ge from compound nuclear reactions. Physical Review C. ISSN 2469-9985. 99(5). doi: 10.1103/PhysRevC.99.054609. Full text in Research Archive
Brits, C.P.; Malatji, Kgashane L.; Wiedeking, M.; Kheswa, BV; Goriely, S. & Bello Garrote, Frank Leonel [Show all 27 contributors for this article] (2019). Nuclear level densities and γ-ray strength functions of 180,181,182Ta. Physical Review C. ISSN 2469-9985. 99(5). doi: 10.1103/PhysRevC.99.054330. Full text in Research Archive
Zeiser, Fabio; Tveten, Gry Merete; Potel, Gregory; Larsen, Ann-Cecilie; Guttormsen, Magne Sveen & Laplace, Thibault A. [Show all 22 contributors for this article] (2019). Restricted spin-range correction in the Oslo method: The example of nuclear level density and γ-ray strength function from 239Pu(d, pγ) 240Pu. Physical Review C. ISSN 2469-9985. 100:024305(2), p. 1–9. doi: 10.1103/PhysRevC.100.024305. Full text in Research Archive
Lyons, Stephanie; Spyrou, Artemis; Liddick, Sean N.; Naqvi, Farheen; Crider, Benjamin P. & Dombos, Alexander C. [Show all 25 contributors for this article] (2019). 69,71Co β-decay strength distributions from total absorption spectroscopy. Physical Review C. ISSN 2469-9985. 100(2), p. 1–10. doi: 10.1103/PhysRevC.100.025806. Full text in Research Archive
Liddick, Sean N.; Larsen, Ann-Cecilie; Guttormsen, Magne Sveen; Spyrou, Artemis; Crider, Benjamin P. & Naqvi, Farheen [Show all 30 contributors for this article] (2019). Benchmarking the extraction of statistical neutron capture cross sections on short-lived nuclei for applications using the β-Oslo method . Physical Review C. ISSN 2469-9985. 100:024624(2), p. 1–12. doi: 10.1103/PhysRevC.100.024624. Full text in Research Archive
Larsen, Ann-Cecilie; Spyrou, Artemis; Liddick, Sean N. & Guttormsen, Magne Sveen (2019). Novel techniques for constraining neutron-capture rates relevant for r-process heavy-element nucleosynthesis. Progress in Particle and Nuclear Physics. ISSN 0146-6410. 107, p. 69–108. doi: 10.1016/j.ppnp.2019.04.002. Full text in Research Archive
Kullmann, Ina Kristine Berentsen; Larsen, Ann-Cecilie; Renstrøm, Therese; Beckmann, Kristine Sønstevold; Bello Garrote, Frank Leonel & Crespo Campo, Lucia [Show all 13 contributors for this article] (2019). First experimental constraint on the 191Os(n,γ) reaction rate relevant to s-process nucleosynthesis . Physical Review C. ISSN 2469-9985. 99(6). doi: 10.1103/PhysRevC.99.065806. Full text in Research Archive Show summary
The nuclear level density and γ -decay strength of 192 Os have been extracted using particle- γ coincidence data from the 192 Os ( α , α ′ γ ) 192 Os 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 E 1 and M 1 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 E γ ≈ 1.5 – 6 MeV . 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 191 Os ( n , γ ) 192 Os 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 k B T = 30 keV , ⟨ σ ⟩ n , γ = 1134 ± 375 mb , 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.
Utsunomiya, Hiroaki; Renstrøm, Therese; Tveten, Gry Merete; Goriely, Stéphane; Ari-izumi, Takashi & Filipescu, Dan Mihai [Show all 14 contributors for this article] (2019). γ-ray strength function for thallium isotopes relevant to the 205Pb−205Tl chronometry. Physical Review C. ISSN 2469-9985. 99(2), p. 024609-1–023609-8. doi: 10.1103/PhysRevC.99.024609. Full text in Research Archive
Malatji, Kgashane Leroy; Wiedeking, Mathis; Goriely, Stephane; Brits, Christiaan Petrus; Kheswa, Bonginkosi Vincent & Bello Garrote, Frank Leonel [Show all 22 contributors for this article] (2019). Re-estimation of 180Ta nucleosynthesis in light of newly constrained reaction rates. Physics Letters B. ISSN 0370-2693. 791, p. 403–408. doi: 10.1016/j.physletb.2019.03.013. Full text in Research Archive
Lewis, Rebecca; Liddick, Sean N.; Larsen, Ann-Cecilie; Spyrou, Artemis; Bleuel, Darren L. & Couture, Aaron J. [Show all 17 contributors for this article] (2019). Experimental constraints on the 73Zn(n,γ)74Zn reaction rate. Physical Review C. ISSN 2469-9985. 99(3). doi: 10.1103/PhysRevC.99.034601. Full text in Research Archive
Midtbø, Jørgen E.; Larsen, Ann-Cecilie; Renstrøm, Therese; Bello Garrote, Frank Leonel & 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
Larsen, Ann-Cecilie; Midtbø, Jørgen E.; Guttormsen, Magne Sveen; Renstrøm, Therese; Liddick, Sean N. & Spyrou, Artemis [Show all 22 contributors for this article] (2018). Enhanced low-energy γ-decay strength of 70Ni and its robustness within the shell model. Physical Review C. ISSN 2469-9985. 97(5), p. 1–9. doi: 10.1103/PhysRevC.97.054329. Full text in Research Archive
Jones, M.D.; Macchiavelli, Augusto Oswaldo; Wiedeking, Mathis; Bernstein, Lee A.; Crawford, Heather L. & Campbell, C.M. [Show all 30 contributors for this article] (2018). Examination of the Low-Energy Enhancement of the gamma-ray Strength Function of 56Fe. Physical Review C. ISSN 2469-9985. 97(2). doi: 10.1103/PhysRevC.97.024327. Full text in Research Archive
Crespo Campo, Lucia; Guttormsen, Magne Sveen; Bello Garrote, Frank Leonel; Eriksen, Tomas Kvalheim; Giacoppo, Francesca & Görgen, Andreas [Show all 15 contributors for this article] (2018). Test of the generalized Brink-Axel hypothesis in 64,65Ni. Physical Review C. ISSN 2469-9985. 98, p. 054303-1–054303-10. doi: 10.1103/PhysRevC.98.054303. Full text in Research Archive Show summary
Previously published particle-γ coincidence data on the 64Ni(p,p′γ)64Ni and 64Ni(d,pγ)65Ni reactions were further analyzed to study the statistical properties of γ decay in 64,65Ni. To do so, the γ decay to the quasicontinuum region and discrete low-lying states was investigated at γ-ray energies of 2.0–9.6 and 1.6–6.1 MeV in 64 Ni and 65 Ni, respectively. In particular, the dependence of the γ -strength function with initial and final excitation energy was studied to test the validity of the generalized Brink-Axel hypothesis. Finally, the role of fluctuations in transition strengths was estimated as a function of γ-ray and excitation energy. The γ -strength function is consistent with the hypothesis of the independence of initial excitation energy, in accordance with the generalized Brink-Axel hypothesis. The results show that the γ decay to low-lying levels displays large fluctuations for low initial excitation energies.
Renstrøm, Therese; Utsunomiya, H.; Nyhus, Hilde-Therese; Larsen, Ann-Cecilie; Guttormsen, Magne Sveen & Tveten, Gry Merete [Show all 16 contributors for this article] (2018). Verification of detailed balance for γ absorption and emission in Dy isotopes. Physical Review C. ISSN 2469-9985. 98(5), p. 1–14. doi: 10.1103/PhysRevC.98.054310. Full text in Research Archive Show summary
The photoneutron cross sections of 162,163Dy have been measured for the first time in an energy region from the neutron threshold (Sn) up to ≈13MeV. The (γ,n) reaction was induced with quasimonochromatic laser Compton-scattered γ rays, produced at the NewSUBARU laboratory. The corresponding γ -ray strength functions (γ SF) have been calculated from the photoneutron cross sections. The data are compared to reanalyzed γSFs of 160–164Dy, which are measured below Sn. The excellent agreement with the photoneutron data at Sn confirms the principle of detailed balance. Thus, a complete γ SF is established covering in total the energy regionof1 Eγ 13MeV.Thesemid-shellwell-deformeddysprosiumisotopesallshowscissorsresonances with very similar structures. We find that our data predict the same integrated scissors strength as (γ,γ′) data when integrated over the same energy range, which shows that the scissors mode very likely is consistent with the generalized Brink hypothesis. Finally, using the γSFs as input in the reaction code TALYS, we have deduced radiative neutron-capture cross sections and compared them to direct measurements. We find a very good agreement within the uncertainties, which gives further support to the experimentally determined γ SFs.
Utsunomiya, Hiroaki; Renstrøm, Therese; Tveten, Gry Merete; Goriely, Stéphane; Katayama, Seitaro & Ari-Izumi, Takashi [Show all 22 contributors for this article] (2018). Photoneutron cross sections for Ni isotopes: Toward understanding (n, γ ) cross sections relevant to weak s-process nucleosynthesis. Physical Review C. ISSN 2469-9985. 98(5), p. 1–9. doi: 10.1103/PhysRevC.98.054619. Full text in Research Archive Show summary
Photoneutron cross sections were measured for 58Ni, 60Ni, 61Ni, and 64Ni at energies between the one-neutron and two-neutron thresholds using quasimonochromatic γ -ray beams produced in laser Compton scattering at the NewSUBARU synchrotron radiation facility. These photoneutron data are used to extract the γ -ray strength function above the neutron threshold, complementing the information obtained by the Oslo method below the threshold. We discuss radiative neutron-capture cross sections and the Maxwellian-averaged cross sections for Ni isotopes including 63Ni, a branching point nucleus along the weak s-process path. The cross sections are calculated with the experimentally constrained γ-ray strength functions from the Hartree-Fock-Bogolyubov plus quasiparticle–random-phase approximation based on the Gogny D1M interaction for both E1 and M1 components and supplemented with the M1 upbend.
Utsunomiya, Hiroaki; Renstrøm, Therese; Tveten, Gry Merete; Gheorghe, Ioana; Filipescu, Dan Mihai & Belyshev, Sergey [Show all 22 contributors for this article] (2018). Photoneutron Reaction Data for Nuclear Physics and Astrophysics. The European Physical Journal Conferences. ISSN 2101-6275. 178. doi: 10.1051/epjconf/201817806003. Full text in Research Archive
Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Midtbø, Jørgen E.; Crespo Campo, Lucia; Görgen, Andreas & Ingeberg, Vetle Wegner [Show all 11 contributors for this article] (2018). Gamma-widths, lifetimes and fluctuations in the nuclear quasi-continuum. The European Physical Journal Conferences. ISSN 2101-6275. 178(06001). doi: 10.1051/epjconf/201817806001. Full text in Research Archive
Wiedeking, Mathis; Bernstein, Lee A.; Bleuel, Darren L.; Brits, Christiaan Petrus; Sowazi, Khanyisa & Görgen, Andreas [Show all 16 contributors for this article] (2017). Statistical gamma-ray decay studies at iThemba LABS. The European Physical Journal Conferences. ISSN 2101-6275. 146:05006, p. 1–4. doi: 10.1051/epjconf/201714605006.
Brits, C.P.; Wiedeking, M.; Bello Garrote, Frank Leonel; Bleuel, D. L.; Giacoppo, F. & Görgen, Andreas [Show all 22 contributors for this article] (2017). Resonances in odd-odd 182Ta. The European Physical Journal Conferences. ISSN 2101-6275. 146. doi: 10.1051/epjconf/201714605012. Full text in Research Archive
Malatji, Kgashane L.; Kheswa, Bonginkosi Vincent; Wiedeking, M.; Bello Garrote, Frank Leonel; Brits, C.P. & Bleuel, D. L. [Show all 21 contributors for this article] (2017). Nuclear level densities and γ-ray strength functions of 180,181Ta and neutron capture cross sections. The European Physical Journal Conferences. ISSN 2101-6275. 146. doi: 10.1051/epjconf/201714601010. Full text in Research Archive
Larsen, Ann-Cecilie; Spyrou, Artemis; Liddick, Sean N.; Guttormsen, Magne Sveen; Ingeberg, Vetle Wegner & Siem, Sunniva [Show all 25 contributors for this article] (2017). Novel Techniques for Constraining Neutron-capture Rates relevant to Heavy-element Nucleosynthesis. Proceedings of Science (PoS). ISSN 1824-8039. INPC2016. doi: 10.22323/1.281.0360. Full text in Research Archive
Tveten, Gry Merete; Spyrou, Artemis; Schwengner, Ronald; Naqvi, Farheen; Larsen, Ann-Cecilie & Renstrøm, Therese [Show all 23 contributors for this article] (2017). The Statistical Properties Of 92Mo And Implications For The p-process. Proceedings of Science (PoS). ISSN 1824-8039. INPC2016. Full text in Research Archive Show summary
A particularly challenging part of the question of how elements heavier than iron are created in extreme, astrophysical environments is the creation of the so-called p-nuclei, which are believed to be mainly produced in the O-Ne layer of type II supernovae or type Ia supernovae. The lack of needed nuclear data presents an obstacle in nailing down the precise site and astrophysical conditions for the production of these isotopes. Astrophysical model calculations are able to reproduce abundance patterns of most p-isotopes reasonably well, with some pivotal exceptions. In particular, p-isotopes of mass 92 ≤ A ≤ 98 are underproduced in calculations compared to the actual abundance of these isotopes. The p-isotope 92Mo represents one of the most severe cases of underproduction. State-of-the-art p-process calculations systematically underestimate the observed solar abundance of this isotope. The main destruction mechanism of this isotope in the standard description of the p-process is through the 92Mo(γ, p)91Nb reaction. Measurements on the nuclear level density and average gamma strength function of 92Mo have been carried out at the Oslo Cyclotron Laboratory. TALYS cross section and reaction rate calculations where the experimental results are used as input will be presented. The data provide stringent constraints on the 91Nb(p, γ)92Mo (and consequently the inverse) reaction rate. The reaction rate extracted in this work was used in reaction network calculations for the scenario of a p-process taking place in a type II supernova explosion as the shock front passes through the O-Ne layer of a 25 solar mass star.
Crespo Campo, Lucia; Larsen, Ann-Cecilie; Bello Garrote, Frank Leonel; Eriksen, Tomas Kvalheim; Giacoppo, Francesca & Görgen, Andreas [Show all 13 contributors for this article] (2017). Investigating the gamma decay of Ni 65 from particle-gamma coincidence data. Physical Review C. ISSN 2469-9985. 96(1). doi: 10.1103/PhysRevC.96.014312. Full text in Research Archive
Rose, Sunniva Johanne; Zeiser, Fabio; Wilson, JN; Oberstedt, A; Oberstedt, S & Siem, Sunniva [Show all 25 contributors for this article] (2017). Energy dependence of the prompt gamma-ray emission from the (d,p)-induced fission of U-234 and Pu-240. Physical Review C. ISSN 2469-9985. 96(1). doi: 10.1103/PhysRevC.96.014601. Full text in Research Archive
Guttormsen, Magne Sveen; Goriely, Stephan; Larsen, Ann-Cecilie; Görgen, Andreas; Hagen, Trine Wiborg & Renstrøm, Therese [Show all 13 contributors for this article] (2017). Quasicontinuum γ decay of 91,92Zr: Benchmarking indirect (n,γ ) cross section measurements for the s process. Physical Review C. ISSN 2469-9985. 96(2). doi: 10.1103/PhysRevC.96.024313. Full text in Research Archive
Spyrou, Artemis; Larsen, Ann-Cecilie; Liddick, Sean N.; Naqvi, Farheen; Crider, Benjamin P. & Dombos, Alexander C. [Show all 19 contributors for this article] (2017). Neutron-capture rates for explosive nucleosynthesis: the case of 68Ni(n, γ)69Ni. Journal of Physics G: Nuclear and Particle Physics. ISSN 0954-3899. 44. doi: 10.1088/1361-6471/aa5ae7. Full text in Research Archive
Kheswa, Bonginkosi Vincent; Wiedeking, Mathis; Brown, Joshua A.; Larsen, Ann-Cecilie; Goriely, Stéphane & Guttormsen, Magne Sveen [Show all 25 contributors for this article] (2017). 137,138,139La(n,γ) cross sections constrained with statistical decay properties of 138,139,140La nuclei. Physical Review C. ISSN 2469-9985. 95(4). doi: 10.1103/PhysRevC.95.045805. Full text in Research Archive
Larsen, Ann-Cecilie; Guttormsen, Magne Sveen; Blasi, Nives; Bracco, Angela; Camera, Franco & Crespo Campo, Lucia [Show all 24 contributors for this article] (2017). Low-energy enhancement and fluctuations of γ-ray strength functions in 56,57Fe: test of the Brink–Axel hypothesis. Journal of Physics G: Nuclear and Particle Physics. ISSN 0954-3899. 44(6). doi: 10.1088/1361-6471/aa644a. Full text in Research Archive
Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Görgen, Andreas; Renstrøm, Therese; Siem, Sunniva & Tornyi, Tamas Gabor [Show all 7 contributors for this article] (2016). Is the generalized Brink-Axel hypothesis valid? Proceedings of Science (PoS). ISSN 1824-8039. 2016-September, p. 1–8. doi: 10.22323/1.281.0062. Full text in Research Archive
Larsen, Ann-Cecilie; Spyrou, Artemisia; Liddick, Sean N.; Guttormsen, Magne Sveen; Ingeberg, Vetle Wegner & Siem, Sunniva [Show all 25 contributors for this article] (2016). Novel techniques for constraining neutron-capture rates relevant to heavy-element nucleosynthesis. Proceedings of Science (PoS). ISSN 1824-8039. 2016-September:360, p. 1–9. Full text in Research Archive
Tveten, Gry Merete; Spyrou, Artemis; Schwengner, Ronald; Naqvi, Farheen; Larsen, Ann-Cecilie & Renstrøm, Therese [Show all 23 contributors for this article] (2016). The statistical properties of 92Mo and implications for the p-process. Proceedings of Science (PoS). ISSN 1824-8039. 2016-September:163.
Clement, E; Zielinska, Magdalena; Péru, Sophie; Goutte, Héloïse; Hilaire, Stephane & Görgen, Andreas [Show all 51 contributors for this article] (2016). Low-energy Coulomb excitation of 96,98Sr beams. Physical Review C. Nuclear Physics. ISSN 0556-2813. 94(5). doi: 10.1103/PhysRevC.94.054326. Full text in Research Archive
Crespo Campo, Lucia; Bello Garrote, Frank Leonel; Eriksen, Tomas Kvalheim; Görgen, Andreas; Guttormsen, Magne Sveen & Hadynska-Klek, Katarzyna [Show all 14 contributors for this article] (2016). Statistical γ -decay properties of Ni 64 and deduced (n,γ) cross section of the s -process branch-point nucleus Ni 63. Physical Review C. Nuclear Physics. ISSN 0556-2813. 94(4). doi: 10.1103/PhysRevC.94.044321. Full text in Research Archive
Ay, K.o.; Ozgur, Mustafa; Algin, Emel; Guttormsen, Magne Sveen; Bello Garrote, Frank Leonel & Crespo Campo, Lucia [Show all 20 contributors for this article] (2016). Nuclear level densities and gamma-ray strength functions of 145,149,151Nd isotopes. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. 766(012027). doi: 10.1088/1742-6596/766/1/012027.
Negi, D; Wiedeking, M; Lanza, EG; Litvinova, E; Vitturi, A & Bark, RA [Show all 35 contributors for this article] (2016). Nature of low-lying electric dipole resonance excitations in Ge 74. Physical Review C. Nuclear Physics. ISSN 0556-2813. 94(2). doi: 10.1103/PhysRevC.94.024332. Full text in Research Archive
Ducasse, Q; Jurado, B; Aiche, M; Marini, P; Mathieu, L & Görgen, Andreas [Show all 29 contributors for this article] (2016). Investigation of the U 238 (d,p) surrogate reaction via the simultaneous measurement of γ -decay and fission probabilities. Physical Review C. Nuclear Physics. ISSN 0556-2813. 94(2). doi: 10.1103/PhysRevC.94.024614. Full text in Research Archive
Tveten, Gry Merete; Spyrou, A; Schwengner, R; Naqvi, F; Larsen, Ann-Cecilie & Eriksen, Tomas Kvalheim [Show all 23 contributors for this article] (2016). Completing the nuclear reaction puzzle of the nucleosynthesis of Mo 92. Physical Review C. Nuclear Physics. ISSN 0556-2813. 94(2). doi: 10.1103/PhysRevC.94.025804. Full text in Research Archive
Marini, P.; Ducasse, Q; Jurado, B; Aiche, M; Mathieu, L & Barreau, G. [Show all 33 contributors for this article] (2016). First simultaneous measurement of fission and gamma probabilities of 237U and 239Np via surrogate reactions. The European Physical Journal Conferences. ISSN 2101-6275. 122. doi: 10.1051/epjconf/201612212004.
Spyrou, Artemis; Liddick, Sean N.; Naqvi, Farheen; Crider, Benjamin P.; Dombos, Alexander C. & Bleuel, Darren L. [Show all 21 contributors for this article] (2016). Strong Neutron-γ Competition above the Neutron Threshold in the Decay of 70Co. Physical Review Letters. ISSN 0031-9007. 117(14). doi: 10.1103/PhysRevLett.117.142701. Full text in Research Archive
Liddick, Sean N.; Spyrou, Artemisia; Crider, Benjamin P.; Naqvi, Farheen; Larsen, Ann-Cecilie & Guttormsen, Magne Sveen [Show all 21 contributors for this article] (2016). Experimental Neutron Capture Rate Constraint Far from Stability. Physical Review Letters. ISSN 0031-9007. 116:242502(24). doi: 10.1103/PhysRevLett.116.242502. Full text in Research Archive
Renstrøm, Therese; Nyhus, Hilde-Therese; Utsunomiya, Hiroaki; Schwengner, Ronald; Goriely, Stephane & Larsen, Ann-Cecilie [Show all 25 contributors for this article] (2016). Low-energy enhancement in the γ-ray strength functions of Ge73,74. Physical Review C. Nuclear Physics. ISSN 0556-2813. 93(6). doi: 10.1103/PhysRevC.93.064302. Full text in Research Archive
Wiedeking, Mathis; Krtička, M.; Bernstein, L. A.; Allmond, J. M.; Basunia, M. S. & Bleuel, Darren L. [Show all 21 contributors for this article] (2016). γ-ray decay from neutron-bound and unbound states in Mo 95 and a novel technique for spin determination. Physical Review C. Nuclear Physics. ISSN 0556-2813. 93(2). doi: 10.1103/PhysRevC.93.024303. Full text in Research Archive
Larsen, Ann-Cecilie; Guttormsen, Magne Sveen; Schwengner, Ronald; Bleuel, Darren L.; Goriely, Stephane & Harrisopulos, Sotirios [Show all 21 contributors for this article] (2016). Experimentally constrained (p,γ) y 89 and (n,γ) y 89 reaction rates relevant to p -process nucleosynthesis. Physical Review C. Nuclear Physics. ISSN 0556-2813. 93(4). doi: 10.1103/PhysRevC.93.045810. Full text in Research Archive
Klintefjord, Malin; Hadynska-Klek, Katarzyna; Görgen, Andreas; Bauer, C; Bello Garrote, Frank Leonel & Bönig, S [Show all 44 contributors for this article] (2016). Structure of low-lying states in Sm140 studied by Coulomb excitation. Physical Review C. Nuclear Physics. ISSN 0556-2813. 93(5). doi: 10.1103/PhysRevC.93.054303.
Simon, Anna; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Beausang, Con W.; Humby, Peter & Burke, Jason T. [Show all 17 contributors for this article] (2016). First observation of low-energy γ -ray enhancement in the rare-earth region. Physical Review C. Nuclear Physics. ISSN 0556-2813. 93:034303. doi: 10.1103/PhysRevC.93.034303. Full text in Research Archive
Laplace, Thibault A.; Zeiser, Fabio; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Bleuel, Darren L. & Bernstein, Lee A. [Show all 27 contributors for this article] (2016). Statistical properties of Pu 243, and Pu 242 (n,γ) cross section calculation. Physical Review C. Nuclear Physics. ISSN 0556-2813. 93(1). doi: 10.1103/PhysRevC.93.014323. Full text in Research Archive
Clément, Emmanuel; Zielińska, Magdalena; Görgen, Andreas; Körten, Wolfram; Péru, Sophie & Libert, Jacques J. [Show all 51 contributors for this article] (2016). Spectroscopic Quadrupole Moments in Sr 96,98: Evidence for Shape Coexistence in Neutron-Rich Strontium Isotopes at N=60. Physical Review Letters. ISSN 0031-9007. 116:022701(2). doi: 10.1103/PhysRevLett.116.022701. Full text in Research Archive
Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Görgen, Andreas; Renstrøm, Therese; Siem, Sunniva & Tornyi, Tamas Gabor [Show all 7 contributors for this article] (2016). Validity of the Generalized Brink-Axel Hypothesis in Np 238. Physical Review Letters. ISSN 0031-9007. 116(1). doi: 10.1103/PhysRevLett.116.012502. Full text in Research Archive
Moretto, Luciano; Larsen, Ann-Cecilie; Guttormsen, Magne Sveen & Siem, Sunniva (2015). The little hagedorn that could. Proceedings of Science (PoS). ISSN 1824-8039. 26-30-January-2015:058. Full text in Research Archive
Schwengner, Ronald; Frauendorf, Stefan & Larsen, Ann-Cecilie (2015). Low-energy enhancement of M1 strength. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. 580:012020, p. 1–7. doi: 10.1088/1742-6596/580/1/012020. Full text in Research Archive
Renstrøm, Therese; Nyhus, Hilde-Therese; Utsunomiya, Hiroaki; Larsen, Ann-Cecilie; Siem, Sunniva & Guttormsen, Magne Sveen [Show all 25 contributors for this article] (2015). First evidence of low energy enhancement in Ge isotopes. The European Physical Journal Conferences. ISSN 2101-6275. 93. doi: 10.1051/epjconf/20159304003. Full text in Research Archive
Kheswa, Bonginkosi Vincent; Wiedeking, Mathis; Giacoppo, Francesca; Goriely, Stephane; Guttormsen, Magne Sveen & Larsen, Ann-Cecilie [Show all 19 contributors for this article] (2015). Statistical nuclear properties and synthesis of La-138. The European Physical Journal Conferences. ISSN 2101-6275. 93. doi: 10.1051/epjconf/20159304005.
Giacoppo, Francesca; Bello Garrote, Frank Leonel; Eriksen, Tomas Kvalheim; Görgen, Andreas; Guttormsen, Magne Sveen & Hagen, Trine Wiborg [Show all 16 contributors for this article] (2015). Observation of low-lying resonances in the quasicontinuum of Pt-195,Pt-196 and enhanced astrophysical reaction rates. The European Physical Journal Conferences. ISSN 2101-6275. 93. doi: 10.1051/epjconf/20159301039.
Guttormsen, Magne Sveen; Aiche, M; Bello Garrote, Frank Leonel; Bernstein, Lee; Bleuel, D.l. & Byun, Y. [Show all 27 contributors for this article] (2015). Experimental level densities of atomic nuclei. European Physical Journal A. ISSN 1434-6001. 51(12), p. 1–8. doi: 10.1140/epja/i2015-15170-4.

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Sørbø, Solveig & Larsen, Ann-Cecilie (2022). Ann-Cecilie Larsen om kjerneastrofysikk, løping og musikk. [Radio]. radiOrakel og podcast. Show summary
Ann-Cecilie Larsen er på en måte en spesielt speisa gjest siden hun forsker på space!!! I denne episoden snakker vi om musikk som har hjulpet henne tenke klart når hun skulle kna kjerneastrofysiske data eller "bare" løpe halvmaraton! Tung musikk, tunge metaller. Eller heavy metal, heavy metals. Masse sexy vitenskap.
Larsen, Ann-Cecilie (2021). Solveigs speisa musikk https://radiorakel.no/author/solveigs-speisa-musikk/ Ann-Cecilie Larsen Om Kjerneastrofysikk, Løping Og Musikk. [Radio]. Podkast og radio.
Larsen, Ann-Cecilie (2021). Abels tårn - om gull og protoner. [Radio]. NRK P2 Ekko.
Larsen, Ann-Cecilie (2021). Abels tårn - om fusjon. [Radio]. NRK P2 Ekko.
Larsen, Ann-Cecilie (2021). The quest for the origin of heavy elements.
Larsen, Ann-Cecilie (2020). A bright-matter mystery: the quest for the origin of the elements.
Larsen, Ann-Cecilie (2020). Experimentally constrained neutron-capture rates for the intermediate and rapid neutron-capture processes.
Larsen, Ann-Cecilie (2019). Indirect, experimental constraints of (n,γ) reaction rates for the i- and r-process.
Larsen, Ann-Cecilie (2019). Constraining neutron-capture rates relevant to r-process and i-process nucleosynthesis.
Larsen, Ann-Cecilie (2019). Leading an ERC StG research team - some experiences and thoughts.
Larsen, Ann-Cecilie (2019). Mysteriet i hjertet av atomet - hvor lenge overlever nøytroner på avveie?
Larsen, Ann-Cecilie (2018). Constraining neutron-capture rates for r-process scenarios.
Larsen, Ann-Cecilie (2018). The beta-Oslo method: experimentally constrained (n,gamma) reaction rates relevant to the r-process.
Midtbø, Jørgen E.; Larsen, Ann-Cecilie & Renstrøm, Therese (2018). Extracting γ-strength functions from shell model calculations.
Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Midtbø, Jørgen E.; Crespo Campo, Lucia; Görgen, Andreas & Ingeberg, Vetle Wegner [Show all 11 contributors for this article] (2017). Gamma-widths, lifetimes and fluctuations in the nuclear quasi-continuum.
Larsen, Ann-Cecilie (2017). Alkymisten. [Newspaper]. Magasinet, Dagbladet.
Larsen, Ann-Cecilie (2017). Stjernestøv, supernovaer og atomkjerner – hvordan ble grunnstoffene til?
Larsen, Ann-Cecilie (2016). Programdeltagelse, Abels tårn. [Radio]. Radio, nettradio (NRK P2).
Tveten, Gry Merete; Spyrou, Artemis; Schwengner, Ronald; Naqvi, Farheen; Larsen, Ann-Cecilie & Eriksen, Tomas Kvalheim [Show all 23 contributors for this article] (2016). The Statistical Properties Of 92Mo And Implications For The p-process. Show summary
A particularly challenging part of the question of how elements heavier than iron are created in extreme, astrophysical environments is the creation of the so-called p-nuclei, which are believed to be mainly produced in the O-Ne layer of type II supernovae or type Ia supernovae. The lack of needed nuclear data presents an obstacle in nailing down the precise site and astrophysical conditions for the production of these isotopes. Astrophysical model calculations are able to reproduce abundance patterns of most p-isotopes reasonably well, with some pivotal exceptions. In particular, p-isotopes of mass 92 ≤ A ≤ 98 are underproduced in calculations compared to the actual abundance of these isotopes. The p-isotope 92Mo represents one of the most severe cases of underproduction. State-of-the-art p-process calculations systematically underestimate the observed solar abundance of this isotope. The main destruction mechanism of this isotope in the standard description of the p-process is through the 92Mo(γ, p)91Nb reaction. Measurements on the nuclear level density and average gamma strength function of 92Mo have been carried out at the Oslo Cyclotron Laboratory. TALYS cross section and reaction rate calculations where the experimental results are used as input will be presented. The data provide stringent constraints on the 91Nb(p, γ)92Mo (and consequently the inverse) reaction rate. The reaction rate extracted in this work was used in reaction network calculations for the scenario of a p-process taking place in a type II supernova explosion as the shock front passes through the O-Ne layer of a 25 solar mass star.
Larsen, Ann-Cecilie (2016). Novel techniques for constraining neutron-capture rates relevant to heavy-element nucleosynthesis.
Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Görgen, Andreas; Renstrøm, Therese; Siem, Sunniva & Tornyi, Tamas Gabor [Show all 7 contributors for this article] (2016). Is the generalized Brink-Axel hypothesis valid?
Larsen, Ann-Cecilie (2016). Paneldeltager Abels tårn, Ekko P2. [Radio]. Realfagsbiblioteket, UiO.
Larsen, Ann-Cecilie (2016). Experimental level densities and gamma strength functions for nuclear astrophysics.
Larsen, Ann-Cecilie (2015). Workshop on the (beta-)Oslo method, NSCL/MSU.
Larsen, Ann-Cecilie (2015). Applying for an ERC Starting Grant - some experiences and thoughts.

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Published Nov. 4, 2010 12:22 PM - Last modified Sep. 24, 2020 10:36 AM

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Nuclear and Energy Physics