Kevin Ching Wei Li

• Ekeberg, Hannah Lovise Okstad; Voyles, A.S.; Basunia, M.S.; Batchelder, J.C.; Bernstein, L.A. & Bleuel, D.L. [Vis alle 12 forfattere av denne artikkelen] (2026). Nuclear excitation functions for medical isotope production: Targeted radionuclide therapy via natIr(𝑑,𝑥)193mPt. Applied Radiation and Isotopes. ISSN 0969-8043. 229. doi: 10.1016/j.apradiso.2025.112311. Fulltekst i vitenarkiv
• Martinsen, Elise Malmer; Voyles, Andrew S.; Li, Kevin Ching Wei; Basunia, M. Shamsuzzoha; Bernstein, Lee A. & Ekeberg, Hannah Lovise Okstad [Vis alle 12 forfattere av denne artikkelen] (2025). Deuteron-induced reactions on natural Zr from threshold to 50 MeV: production of 86gY. Radiochimica Acta. ISSN 0033-8230. 114(4), s. 280–280. doi: 10.1515/ract-2025-0057. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Two stacks of thin Zr foils were irradiated with 30 and 50 MeV deuterons, respectively, using the Lawrence Berkeley National Laboratory 88-Inch Cyclotron, and 19 excitation functions for nat Zr( d , x ) reactions were measured over a beam energy range of 6.3–47.64 MeV, where the independent cross sections for nat Zr( d , x ) 88 Nb and nat Zr( d , x ) 86m,g Y were measured for the first time. The well-characterized nat Fe( d , x ) 56 Co, nat Ni( d , x ) 56 Co, nat Ni( d , x ) 58 Co, nat Ni( d , x ) 61 Cu, nat Ti( d , x ) 46 Sc and nat Ti( d , x ) 48 V monitor reactions were used to determine the deuteron beam current throughout the stacks. All cross sections were determined using High Purity Germanium (HPGe) detector γ -ray spectroscopy. A variance minimization technique was employed to simultaneously constrain the deuteron beam currents with multiple monitor reactions, thus reducing systematic uncertainties. An additional 16 channels are reported for reactions on the nickel, titanium, and iron monitor foils, leading to a total of 35 excitation functions, with seven reaction channels reported for the first time in this work. The measured excitation functions are compared to calculations provided by the reaction modeling codes TALYS – 2.0, ALICE – 2020, CoH – 3.5.3 and EMPIRE – 3.2.3, as well as the TENDL – 2023 data library. The degree of agreement between theory and experiments is discussed. The possible production of the important PET radionuclide 86g Y via the nat Zr( d , x ) route was critically examined. The physical yields for nat Zr( d , x ) 86 Y and other yttrium isotopes produced were calculated and compared to other production pathways. Due to high-level of associated radionuclide impurities, this route cannot deliver 86g Y suitable for medical applications.

• Paulsen, Wanja; Li, Kevin Ching Wei; Siem, Sunniva; Ingeberg, Vetle Wegner; Larsen, Ann-Cecilie & Eriksen, Tomas Kvalheim [Vis alle 15 forfattere av denne artikkelen] (2025). Remeasuring the γ-decay branching ratio of the Hoyle state. Physical Review C. ISSN 2469-9985. 112. doi: 10.1103/2h2s-sbyx. Fulltekst i vitenarkiv
• Bahini, A.; Neveling, R.; Neumann-Cosel, P. von; Usman, I. T.; Carter, J. & Adsley, P. [Vis alle 25 forfattere av denne artikkelen] (2024). Study of the isoscalar giant monopole resonance: Discrepancies between available experimental results. Nuovo cimento della societa italiana de fisica. C, Geophysics and space physics. ISSN 1124-1896. 2024(2). doi: 10.1393/ncc/i2024-24017-0. Fulltekst i vitenarkiv
• Bahini, A.; Neumann-Cosel, Peter von; Carter, J.; Usman, I. T.; Arsenyev, N. N. & Severyukhin, A. P. [Vis alle 29 forfattere av denne artikkelen] (2024). Fine structure of the isoscalar giant monopole resonance in 58Ni, 90Zr, 120Sn, and 208Pb. Physical Review C. ISSN 2469-9985. 109(1). doi: 10.1103/PhysRevC.109.014325. Fulltekst i vitenarkiv
• Li, Kevin Ching Wei; Neveling, R.; Adsley, P.; Fujita, H.; Papka, P. & Smit, F. D. [Vis alle 15 forfattere av denne artikkelen] (2024). Understanding the total width of the 3−1 state in 12C. Physical Review C. ISSN 2469-9985. 109(1). doi: 10.1103/PhysRevC.109.015806. Fulltekst i vitenarkiv Vis sammendrag

  Background: Recent measurements indicate that the previously established upper limit for the 𝛾-decay branch of the 3− 1 resonance in 12C at 𝐸𝑥=9.641⁢(5) MeV may be incorrect. As a result, the 3−1 resonance has been suggested as a significant resonance for mediating the triple-𝛼 reaction at high temperatures above 2 GK. Accurate estimations of the 3−1 contribution to the triple-𝛼 reaction rate require accurate knowledge of not only the radiative width, but also the total width. Purpose: In anticipation of future measurements to more accurately determine the 𝛾-decay branch of the 3−1 resonance, the objective of this work is to accurately determine the total width of the 3−1 resonance. Method: An evaluation was performed on all previous results considered in the current ENSDF average of 46(3) keV for the physical total width (FWHM) of the 3−1 resonance in 12C. A new 𝐑-matrix analysis for the 3−1 resonance was performed with a self-consistent, simultaneous fit of several high-resolution 12C excitation-energy spectra populated with direct reactions. Results: The global analysis performed in this work yields a formal total width of Γ⁡(𝐸𝑟)=46⁢(2) keV and an observed total width of Γobs⁡(𝐸𝑟)=38⁢(2) keV for the 3−1 resonance. Conclusions: Significant unaccounted-for uncertainties and a misstated result were discovered in the previous results employed in the ENSDF for the physical (or observed) total width of the 3−1 resonance. These previously reported widths are fundamentally different quantities, leading to an invalid ENSDF average. An observed total width of Γobs⁡(𝐸𝑟)=38⁢(2) keV is recommended for the 3−1 resonance in 12C. This observed total width should be employed for future evaluations of the observed total radiative width for the 3−1 resonance and its contribution to the high-temperature triple-𝛼 reaction rate.

• Molaeng, R. E.; Donaldson, L. M.; Pellegri, L.; Usman, I. T.; Bahini, A. & Brümmer, J. W. [Vis alle 13 forfattere av denne artikkelen] (2023). Development of (p,p'γ) detection capabilities at iThemba LABS through the study of low-lying E1 strength in 58Ni. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. doi: 10.1088/1742-6596/2586/1/012069. Fulltekst i vitenarkiv
• Donaldson, L. M.; Adsley, P.; Banu, A.; Bassauer, S.; Bastin, B. & Bertulani, C. A. [Vis alle 45 forfattere av denne artikkelen] (2023). Nuclear-structure experiments at iThemba LABS to investigate discrepancies between (p, p') and (γ, xn) data. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. doi: 10.1088/1742-6596/2586/1/012068. Fulltekst i vitenarkiv
• Tamii, A.; Pellegri, L.; Söderström, P.-A.; Allard, D.; Goriely, S. & Inakura, T. [Vis alle 82 forfattere av denne artikkelen] (2023). PANDORA Project for the study of photonuclear reactions below A= 60. European Physical Journal A. ISSN 1434-6001. 59(9). doi: 10.1140/epja/s10050-023-01081-w. Fulltekst i vitenarkiv Vis sammendrag

  Photonuclear reactions of light nuclei below a mass of A = 60 are planned to be studied experimentally and theoretically with the PANDORA (Photo-Absorption of Nuclei and Decay Observation for Reactions in Astrophysics) project. Two experimental methods, virtual photon excitation by proton scattering and real photo absorption by a high-brilliance γ-ray beam produced by laser Compton scattering, will be applied to measure the photoabsorption cross sections and decay branching ratio of each decay channel as a function of the photon energy. Several nuclear models, e.g. anti-symmetrized molecular dynamics, mean-field and beyond-mean-field models, a large-scale shell model, and ab initio models, will be employed to predict the photonuclear reactions. The uncertainty in the model predictions will be evaluated based on the discrepancies between the model predictions and experimental data. The data and predictions will be implemented in the general reaction calculation code, TALYS. The results will be applied to the simulation of the photo-disintegration process of ultra-high-energy cosmic rays in inter-galactic propagation.

• Jivan, H.; Pellegri, Luna; Adsley, P; Bahini, A.; Brummer, J.W. & Donaldson, L. [Vis alle 29 forfattere av denne artikkelen] (2023). Pygmy Dipole Response in Samarium isotopes. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. doi: 10.1088/1742-6596/2586/1/012088. Fulltekst i vitenarkiv Vis sammendrag

  Abstract The influence of nuclear shape deformation on the Pygmy Dipole Response (PDR) was investigated using (α,α′γ) scattering on 144 Sm and 154 Sm. Experiments were conducted at iThemba LABS, coupling for the first time the K600 magnetic spectrometer with the BaGeL (Ball of Germanium and LaBr detectors) array. Preliminary results showcasing the efficacy of the facility and set-up for performing these 0° scattering experiments to investigate the PDR region are presented.

• Pogliano, Francesco; Larsen, Ann-Cecilie; Goriely, Stéphane; Siess, Lionel; Markova, Maria & Görgen, Andreas [Vis alle 17 forfattere av denne artikkelen] (2023). Experimentally constrained Ho 165,166 (n,γ) rates and implications for the s process. Physical Review C. ISSN 2469-9985. 107(6). doi: 10.1103/PhysRevC.107.064614. Fulltekst i vitenarkiv
• Brümmer, J. W.; Adsley, P.; Rauscher, T.; Smit, F. D.; Brits, C. P. & Köhne, M. [Vis alle 18 forfattere av denne artikkelen] (2023). Proton decays from 𝛼-unbound states in 22Mg and the 18Ne(𝛼,𝑝0)21⁢Na cross section. Physical Review C. ISSN 2469-9985. 107(5). doi: 10.1103/PhysRevC.107.055802. Fulltekst i vitenarkiv
• Binda, S. D.; Adsley, P.; Long, A. M.; Berg, G.; Couder, M. & Görres, J. [Vis alle 25 forfattere av denne artikkelen] (2023). Study of the 44Ti(α, p)47V reaction rate using high-precision 50Cr(p, t)48Cr measurements. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. doi: 10.1088/1742-6596/2586/1/012106. Fulltekst i vitenarkiv
• Pogliano, Francesco; Larsen, Ann-Cecilie; Markova, Maria; Garrote, Frank Leonel Bello; Bjørøen, Marianne Møller & Eriksen, Tomas Kvalheim [Vis alle 17 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Li, Kevin Ching Wei; Adsley, P; Neveling, R; Papka, P; Smit, F. D & Nikolskii, E [Vis alle 28 forfattere av denne artikkelen] (2022). Multiprobe study of excited states in 12 C : Disentangling the sources of monopole strength between the energy of the Hoyle state and E x = 13 MeV. Physical Review C. ISSN 2469-9985. doi: 10.1103/PhysRevC.105.024308. Fulltekst i vitenarkiv Vis sammendrag

  Background: The Hoyle state is the archetypal α-cluster state which mediates the 3α reaction to produce 12C and is of great interest for both nuclear structure and astrophysics. Recent theoretical calculations predict a breathing-mode excitation of the Hoyle state at Ex≈9 MeV. Its observation is hindered by the presence of multiple broad states and potential interference effects. An analysis with Gaussian line shapes of measurements at the Research Center for Nuclear Physics (Osaka University) with the Grand Raiden spectrometer suggested that additional strength was needed at Ex≈9 MeV to reproduce the data; this analysis did not account for the well-known threshold effects observed in 12C. Nevertheless, various theoretical studies have since concluded that this additional strength corresponds to the predicted breathing-mode excitation of the Hoyle state. To meaningfully identify a new source of monopole strength in this astrophysically significant region, a more appropriate phenomenological analysis which accounts for penetrability and interference effects must be used to determine whether the data can be explained with previously established states. Purpose: We aim to investigate the monopole strength in the astrophysically important excitation-energy region of 12C between Ex=7 and 13 MeV to determine whether the previously established sources of monopole strength are able to reproduce the data. Method: The 12C(α,α′)12C and 14C(p,t)12C reactions, which are expected to exhibit contrasting selectivity towards different monopole excitations, were employed at various detection angles and beam energies to populate states in 12C. The inclusive excitation-energy spectra were simultaneously analyzed with multilevel, multichannel line shapes. Various scenarios with different sources of monopole strength and interference effects were considered to determine whether the ghost of the Hoyle state and the previously established broad 0+3 state at Ex≈10 MeV are able to reproduce the observed monopole strength. Results: Clear evidence was found for excess monopole strength at Ex≈9 MeV, particularly in the 12C(α,α′)12C reaction at 0∘. This additional strength cannot be reproduced by the previously established monopole states between Ex=7 and 13 MeV. Coincident charged-particle decay data suggest that the strength at Ex≈9 MeV is dominantly monopole, with no evidence of a J>0 contribution. Conclusions: The data support a new source of monopole strength at Ex≈9 MeV, which cannot be described with a phenomenological parametrization of all previously established states. An additional 0+ state at Ex≈9 MeV yielded a significantly improved fit of the data and is a clear candidate for the predicted breathing-mode excitation of the Hoyle state. Alternatively, the results may suggest that a more sophisticated, physically motivated parametrization of the astrophysically important monopole strengths in 12C is required.

• Li, Kevin Ching Wei; Smit, F. D.; Adsley, P.; Neveling, R.; Papka, P. & Nikolskii, E. [Vis alle 28 forfattere av denne artikkelen] (2022). Investigating the predicted breathing-mode excitation of the Hoyle state. Physics Letters B. ISSN 0370-2693. doi: 10.1016/j.physletb.2022.136928. Fulltekst i vitenarkiv

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• Ingeberg, Vetle Wegner; Görgen, Andreas; Inoue, Azusa; Kumar, Neeraj; Larsen, Ann-Cecilie & Li, Kevin Ching Wei [Vis alle 9 forfattere av denne artikkelen] (2026). OSCAR at ISOLDE. Fulltekst i vitenarkiv Vis sammendrag

  For the next run period at ISOLDE, the Nuclear Physics group at the University of Oslo are considering proposing a longer experimental campaign with the Oslo SCintillator ARay (OSCAR). The main aims of such a campaign will be to measure the nuclear level density and -ray strength function of key nuclei relevant for nuclear structure and nuclear astrophysics (e.g. i-process nucleosynthesis). Other cases of interest could be spectroscopy of resonances in light exotic nuclei or rare event searches. In addition, we would also invite other interested groups to propose experiments with the setup while it is present at HIE-ISOLDE. The OSCAR array is the largest LaBr:Ce detector array in the world (at least in terms of detector volume). It offers exceptional efficiency for high-energy -rays without compromising on either energy or time resolution. It consists of 30 large 3.5x8-inch large volume LaBr3:Ce detectors, an icosahedron frame with six rings covering polar angles from to . Detectors can be mounted in a distance of 16.3 to 22 cm from the target, resulting in solid angle coverage of 57%. This translates to about 15% full energy efficiency at 1332 keV and close to 5% at 10 MeV in the closest configuration. In this presentation I will present the physics cases and our preliminary plans for such a campaign.

• Paulsen, Wanja; Li, Kevin Ching Wei; Siem, Sunniva; Ingeberg, Vetle Wegner; Larsen, Ann-Cecilie & Eriksen, Tomas Kvalheim [Vis alle 15 forfattere av denne artikkelen] (2026). CLUSTER'26. Fulltekst i vitenarkiv
• Paulsen, Wanja; Li, Kevin Ching Wei; Siem, Sunniva; Ingeberg, Vetle Wegner; Larsen, Ann-Cecilie & Eriksen, Tomas Kvalheim [Vis alle 20 forfattere av denne artikkelen] (2023). Remeasuring the gamma-decay branching ratio of the Hoyle state. Fulltekst i vitenarkiv
• Paulsen, Wanja; Görgen, Andreas; Siem, Sunniva & Li, Kevin Ching Wei (2021). Studies of shape coexistence in 140Sm. Fulltekst i vitenarkiv Vis sammendrag

  The shape of atomic nuclei can vary vastly, several shapes can even coexist within the same nucleus in certain regions of the nuclear chart. Shape coexistence is believed to be present at higher excitation energies in the N=78 isotones 140Sm and 142Gd [1], where the nucleus of interest is 140Sm in this case. 140Sm has previously been studied in a coulomb excitation experiment performed by M. Klintefjord et. al. [2] at REX-ISOLDE where results showed considerable gamma-softness and the resulting level scheme follows the theoretical prediction of a triaxial nucleus [3], but further investigation is needed to conclude. A new coulomb experiment on 140Sm has been performed using HIE-ISOLDE, yielding data of incredible quality which has also let us vastly improve the level scheme of this nucleus. Preliminary results from this dataset will be presented as well as a deeper look into gamma-softness as well as the possibility of 140Sm having shape coexistence. [1] W. Starzecki et al., Phys. Lett. B 200, 419 (1988). [2] M. Klintefjord et al. Phys. Rev. C 93, 054303 (2016) [3] F. Iachello, Phys. Rev. Lett. 85, 3580 (2000)

• Paulsen, Wanja; Siem, Sunniva; Li, Kevin Ching Wei & Eriksen, Tomas Kvalheim (2025). A saga on the γ-decay branching ratio of the Hoyle state at the Oslo Cyclotron Laboratory. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  The triple-α process is a fundamental cornerstone of stellar nucleosynthesis, facilitating the production of 12C, a vital building block for life. Through the triple-α process, three helium nuclei can fuse to ultimately produce a stable 12C nuclide. At medium stellar temperatures between 0.1–2.0 GK, the Hoyle state in 12C mediates the triple-α reaction, making a comprehensive understanding of its properties essential for accurately modeling the stellar production of 12C, as well as the subsequent stellar nucleosynthesis. Numerous measurements of the decay modes of the Hoyle state have been conducted since its discovery, yielding a relatively well-constrained value of for it’s radiative branching ratio, describing the probability of producing 12C through the triple-α process. However, a recent measurement published by Kibédi et al. [Phys. Rev. Lett. 125, 182701 (2020)] reported a highly discrepant value of Γrad/Γ = 6.2(6) × 10−4 for the radiative branching ratio from the Hoyle state. Given the astrophysical significance of the Hoyle state, resolving this conflict is crucial. This study seeks to address this discrepancy through a new measurement of the γ-decay branching ratio of the Hoyle state, together with a comprehensive reanalysis of the data published by Kibédi et al. [Phys. Rev. Lett. 125, 182701 (2020)].

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