Jakub Skowronski · Postdoctoral Researcher, Experimental Nuclear Astrophysics
Nuclear astrophysics, measured under 1.4 km of rock.
Stars shine because atomic nuclei fuse in their cores. I measure those nuclear reactions in the laboratory, at the low energies at which they happen inside stars. At those energies the reactions are so rare that the experiments must be shielded from cosmic rays, under 1.4 km of rock at LUNA, the underground accelerator beneath the Gran Sasso mountain in Italy. I also develop the software that turns such measurements into the reaction rates astrophysicists use.
Next: open, FAIR data from underground experiments, a shared database of R-matrix evaluations, and new observables — γ-ray tracking and polarization — at LUNA. What comes next →
- a proton is captured
- β⁺ decay: a proton turns into a neutron
- proton in, helium out: back to carbon
Resources for the community
Open, versioned and citable resources for anyone working on these reactions.
Reaction atlas
75 reactions of stellar burning and the Big Bang, the main measurements listed with their references, and the whole atlas downloadable as one JSON file.
CC BY 4.0 licenceversion 2026-10-12How to cite
Rate explorer
The pp chains, CNO, NeNa, MgAl and the s-process. Find the slowest step at a stellar site, change a rate and see how the abundances change, computed in your browser from JINA REACLIB.
CC BY 4.0 licenceJINA REACLIB · pynucastroSources21 curiosities
Nuclear data explorer
What has been measured, and where the measurements stop: 89 804 datasets of the world's nuclear-reaction logbook (EXFOR) and the levels of each nucleus (ENSDF), linked to the 75 reactions of the atlas.
Data: EXFOR (IAEA/NRDC), snapshot of 28 September 2026, CC BY 4.0Levels: ENSDF (NNDC)How to cite
The s-process
How stars make about half the nuclei heavier than iron, on the chart from iron to bismuth.
R-matrix evaluations
8 R-matrix evaluations running AZURE2 in the browser: 2 reproduce published fits, 2 are preliminary models of published analyses, 3 are not yet published and 1 is in progress. Each comes with its input files, to download and run locally.
How to cite: on each evaluation's pageWhere these rates end up: the rate explorer
LunaSRIM
SRIM-2013 in pure Python, validated against SRIM-2013 output
version 1.0.0MIT licencePyPI
Notes
5 notes on R-matrix theory, each with a worked example on a real reaction (in English).
Glossary
49 terms of nuclear astrophysics in plain language, in English and Italian.
The atlas, the glossary and the evaluations are also in Italian, for students and the public as well as specialists. Outreach has included Stelle sulla Terra, nuclear astrophysics for children with disabilities (2024), and courses on nuclear astrophysics for high-school students (PCTO, 2021–2022); see Outreach in the CV.
What's new
All newsRoles and recognition
Full CVResearch
Underground, the flux of cosmic-ray muons drops a millionfold and cross sections of picobarns become measurable. A measurement, though, is only ever a handful of points in a narrow window of energy. Turning those points into the quantity astrophysics needs — a rate at stellar temperatures, often far below anything measurable — is R-matrix theory's job.
Since June 2025 I have been the maintainer and lead developer of AZURE2, a widely used R-matrix code, and I am a member of the IAEA INDEN network for light elements (INDEN-LE), which evaluates their cross sections. This site puts both to work: notes on the theory, and evaluations you can open, change and rerun in your browser.
2020–present
LUNA — proton capture, deep underground
Working Group Leader (19F + p, since 2024) · DAQ Coordinator (since 2024)
Direct cross-section measurements at stellar energies, where the signal is so faint that the experiment has to be buried to see it at all.
Jun 2025 – present
AZURE2 — R-matrix code
Maintainer and Lead Developer
A widely used R-matrix code for nuclear astrophysics, IAEA nuclear-data evaluation and materials analysis.
2023–present
AGATA — a sub-femtosecond lifetime in 15O
Spokesperson
Measuring how long a nuclear state lives when the answer is a fraction of a femtosecond, and what that says about the Sun.
2024–present
CRYRING — electron screening in inverse kinematics
Participant
Testing how atomic electrons distort a nuclear cross section measured in the laboratory, in a regime where the effect is largest.
Selected papers
PublicationsPhys. Rev. Lett. 131, 162701 (2023)
Proton-capture rates on carbon isotopes and their impact on the astrophysical 12C/13C ratio
First author
Phys. Rev. C 107, L062801 (2023)
Improved S-factor of the 12C(p,γ)13N reaction at E = 320–620 keV and the 422 keV resonance
First author
Phys. Rev. C 111, 064611 (2025)
Improved S factor of the 13C(p,γ)14N reaction at Eₚ = 330–740 keV and parameters of resonances at 448 keV and 551 keV
First author
Phys. Rev. C 111, 035802 (2025)
A comparative analysis of R-matrix fitting: 12C(p,γ)13N as test case
First author
Notes
All notesWhen a reduced width stops being measurable
R-matrix theory · 16 minAn R-matrix fit can describe the data well and still contain a parameter the data cannot see. Why that happens, why the channel radius controls it, and how to tell before trusting an uncertainty.
Polarization observables in R-matrix theory
R-matrix theory · 15 minWhat a polarized beam measures, why it carries information no cross section can, and how the calculation adapts to the spins of the particles involved. Two worked examples: protons on carbon-12 and on nitrogen-15.
From a cross section to a stellar reaction rate
Nuclear astrophysics · 8 minThe integral that turns a laboratory cross section into the quantity a stellar model consumes, why it samples an energy window no experiment can reach, and a regime in which the standard perturbative treatment of radiative capture fails without any obvious warning.