Tomas Kvalheim Eriksen

• Markova, Maria; Larsen, Ann-Cecilie; Tveten, Gry Merete; von Neumann-Cosel, Peter; Eriksen, Tomas Kvalheim & Bello Garrote, Frank Leonel [Show all 16 contributors for this article] (2023). Nuclear level densities and γ -ray strength functions of Sn 111,112,113 isotopes studied with the Oslo method. Physical Review C. ISSN 2469-9985. 108(1). doi: 10.1103/PhysRevC.108.014315. Full text in Research Archive
• Markova, Maria; Larsen, Ann-Cecilie; von Neumann-Cosel, Peter; Bassauer, Sergej; Görgen, Andreas & Guttormsen, Magne Sveen [Show all 23 contributors for this article] (2022). Nuclear level densities and γ -ray strength functions in Sn 120,124 isotopes: Impact of Porter-Thomas fluctuations. Physical Review C. ISSN 2469-9985. 106(3). doi: 10.1103/PhysRevC.106.034322. Full text in Research Archive
• Pogliano, Francesco; Larsen, Ann-Cecilie; Markova, Maria; Bello Garrote, Frank Leonel; Bjørøen, Marianne Møller & Eriksen, Tomas Kvalheim [Show all 17 contributors for this article] (2022). Indirect measurement of the (n,γ) Sb 127 cross section. Physical Review C. ISSN 2469-9985. 106(1). doi: 10.1103/PhysRevC.106.015804. Full text in Research Archive
• Cook, K.J.; Chevis, A.; Eriksen, Tomas Kvalheim; Simpson, E.C.; Kibédi, T. & Bezzina, L.T. [Show all 17 contributors for this article] (2021). High-precision proton angular distribution measurements of C 12 (p,p′) for the determination of the E0 decay branching ratio of the Hoyle state. Physical Review C. ISSN 2469-9985. 104(2). doi: 10.1103/PhysRevC.104.024620.
• 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
• 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
• Evitts, Lee J.; Garnsworthy, Adam B.; Kibédi, Tibor; Smallcombe, James; Reed, Matthew W. & Stuchbery, Andrew E. [Show all 24 contributors for this article] (2019). E0 transition strength in stable Ni isotopes. Physical Review C. ISSN 2469-9985. 99:024306(2), p. 1–11. doi: 10.1103/PhysRevC.99.024306.
• McCormick, Brendan P.; Stuchbery, A.E.; Brown, BA; Georgiev, G; Coombes, BJ & Gray, TJ [Show all 18 contributors for this article] (2019). First-excited state g factors in the stable, even Ge and Se isotopes. Physical Review C. ISSN 2469-9985. 100(4). doi: 10.1103/PhysRevC.100.044317. 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
• 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.

• Tveten, Gry Merete; Spyrou, Artemis; Schwengner, Ronald; Naqvi, Farheen; Larsen, Ann-Cecilie & Renstrøm, Therese [Show all 22 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
• Kheswa, Bonginkosi Vincent; Wiedeking, Mathis; Brown, Joshua A.; Larsen, Ann-Cecilie; Goriely, Stéphane & Guttormsen, Magne Sveen [Show all 24 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 23 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
• Tveten, Gry Merete; Spyrou, Artemis; Schwengner, Ronald; Naqvi, Farheen; Larsen, Ann-Cecilie & Renstrøm, Therese [Show all 22 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.
• 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
• Tveten, Gry Merete; Spyrou, A; Schwengner, R; Naqvi, F; Larsen, Ann-Cecilie & Eriksen, Tomas Kvalheim [Show all 22 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
• Larsen, Ann-Cecilie; Guttormsen, Magne Sveen; Schwengner, Ronald; Bleuel, Darren L.; Goriely, Stephane & Harrisopulos, Sotirios [Show all 20 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
• 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
• Kheswa, Bonginkosi Vincent; Wiedeking, Mathis; Giacoppo, Francesca; Goriely, Stephane; Guttormsen, Magne Sveen & Larsen, Ann-Cecilie [Show all 18 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 15 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 26 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.
• Bello Garrote, Frank Leonel; Görgen, Andreas; Mierzejewski, Jan; Mihai, Corina Mihaela; Delaroche, Jean Paul & Girod, Michel [Show all 23 contributors for this article] (2015). Lifetime measurement for the 21+ state in Sm 140 and the onset of collectivity in neutron-deficient Sm isotopes. Physical Review C. Nuclear Physics. ISSN 0556-2813. 92:024317(2). doi: 10.1103/PhysRevC.92.024317. Full text in Research Archive
• Tveten, Gry Merete; Bello Garrote, Frank Leonel; Crespo Campo, Lucia; Eriksen, Tomas Kvalheim; Giacoppo, Francesca & Guttormsen, Magne Sveen [Show all 17 contributors for this article] (2015). The statistical properties of 111,112,113Sn studied with the Oslo method. The European Physical Journal Conferences. ISSN 2101-6275. 93. doi: 10.1051/epjconf/20159304004. Full text in Research Archive
• Larsen, Ann-Cecilie; Goriely, Stephane; Bernstein, L. A.; Bleuel, D. L.; Bracco, A. & Brown, B. A. [Show all 25 contributors for this article] (2015). Upbend and M1 scissors mode in neutron-rich nuclei — consequences for r-process (n,gamma) reaction rates . Acta Physica Polonica B. ISSN 0587-4254. 46(3), p. 509–512. doi: 10.5506/APhysPolB.46.509. Full text in Research Archive
• Kheswa, Bonginkosi Vincent; Wiedeking, Mathis; Giacoppo, Francesca; Goriely, Stephan; Guttormsen, Magne Sveen & Larsen, Ann-Cecilie [Show all 18 contributors for this article] (2015). Galactic production of 138La: Impact of 138,139La statistical properties. Physics Letters B. ISSN 0370-2693. 744, p. 268–272. doi: 10.1016/j.physletb.2015.03.065. Full text in Research Archive
• Larsen, Ann-Cecilie; Blasi, Nives; Bracco, Angela; Bürger, Arnold; Camera, Franco & Eriksen, Tomas Kvalheim [Show all 23 contributors for this article] (2014). Low-energy enhancement of nuclear γ strength and its impact on astrophysical reaction rates. The European Physical Journal Conferences. ISSN 2101-6275. 66:07014. doi: 10.1051/epjconf/20146607014. Full text in Research Archive
• Giacoppo, Francesca; Bello Garrote, Frank Leonel; Bernstein, L. A.; Bleuel, D. L.; Eriksen, Tomas Kvalheim & Firestone, Richard [Show all 17 contributors for this article] (2014). Level densities and thermodynamical properties of Pt and Au isotopes. Physical Review C. Nuclear Physics. ISSN 0556-2813. 90(5). doi: 10.1103/PhysRevC.90.054330. Full text in Research Archive
• Eriksen, Tomas Kvalheim; Nyhus, Hilde-Therese; Guttormsen, Magne Sveen; Görgen, Andreas; Larsen, Ann-Cecilie & Renstrøm, Therese [Show all 11 contributors for this article] (2014). Pygmy resonance and low-energy enhancement in the γ-ray strength functions of Pd isotopes. Physical Review C. Nuclear Physics. ISSN 0556-2813. 90(044311). doi: 10.1103/PhysRevC.90.044311.
• Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Bello Garrote, Frank Leonel; Eriksen, Tomas Kvalheim; Giacoppo, Francesca & Görgen, Andreas [Show all 15 contributors for this article] (2014). Shell-gap-reduced level densities in 89,90Y. Physical Review C. Nuclear Physics. ISSN 0556-2813. 90(044309). doi: 10.1103/PhysRevC.90.044309.
• Tornyi, Tamas Gabor; Guttormsen, Magne Sveen; Eriksen, Tomas Kvalheim; Görgen, Andreas; Giacoppo, Francesca & Hagen, Trine Wiborg [Show all 11 contributors for this article] (2014). Level density and gamma-ray strength function in the odd-odd 238Np nucleus. Physical Review C. Nuclear Physics. ISSN 0556-2813. 89(4). doi: 10.1103/PhysRevC.89.044323.
• Larsen, Ann-Cecilie; Blasi, Nives; Bracco, Angela; Camera, Franco; Eriksen, Tomas Kvalheim & Görgen, Andreas [Show all 18 contributors for this article] (2013). Evidence for the dipole nature of the low-energy γ enhancement in 56Fe. Physical Review Letters. ISSN 0031-9007. 111(24). doi: 10.1103/PhysRevLett.111.242504. Full text in Research Archive
• Larsen, Ann-Cecilie; Bürger, Alexander; Goriely, Stephane; Guttormsen, Magne Sveen; Görgen, Andreas & Eriksen, Tomas Kvalheim [Show all 14 contributors for this article] (2013). Astrophysical reaction rates and the low-energy enhancement in the γ strength. Acta Physica Polonica B. ISSN 0587-4254. 44(3), p. 563–566. doi: 10.5506/APhysPolB.44.563.

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• Paulsen, Wanja; Li, Kevin Ching Wei; Siem, Sunniva; Ingeberg, Vetle Wegner; Larsen, Ann-Cecilie & Eriksen, Tomas Kvalheim [Show all 20 contributors for this article] (2023). Remeasuring the gamma-decay branching ratio of the Hoyle state.
• Tveten, Gry Merete; Spyrou, Artemis; Schwengner, Ronald; Naqvi, Farheen; Larsen, Ann-Cecilie & Eriksen, Tomas Kvalheim [Show all 22 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.

• Tveten, Gry Merete; Campo, L.C.; Eriksen, Tomas Kvalheim; Giacoppo, Francesca; Guttormsen, Magne Sveen & Görgen, Andreas [Show all 16 contributors for this article] (2014). The statistical properties of Sn-isotopes studied with the Oslo-method.
• Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Blasi, N; Bracco, A; Camera, F & Eriksen, Tomas Kvalheim [Show all 18 contributors for this article] (2014). Recent results using large LaBr3 detectors and future perspectives.
• Larsen, Ann-Cecilie; Bürger, Alexander; Eriksen, Tomas Kvalheim; Görgen, Andreas; Guttormsen, Magne Sveen & Hagen, Trine Wiborg [Show all 28 contributors for this article] (2011). Experiments of reaction model inputs: level density and gamma strength.
• Larsen, Ann-Cecilie; Guttormsen, Magne Sveen; Bürger, Alexander; Eriksen, Tomas Kvalheim; Görgen, Andreas & Hagen, Trine Wiborg [Show all 15 contributors for this article] (2011). Level density and gamma strength - achievements and challenges.

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