Direct determination of the astrophysical reaction rate of ¹⁴¹Pr(γ, n)¹⁴⁰Pr at the SSRF-SLEGS

¹ Sino-French Institute of Nuclear Engineering and Technology, Sun Yat-sen University, Zhuhai 519082, China
² Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China
³ Key Laboratory of Nuclear Physics and Ion-beam Application (MOE), Institute of Modern Physics, Department of Nuclear Science and Technology, Fudan University, Shanghai 200433, China
⁴ Shanghai Research Center for Theoretical Nuclear Physics, NSFC and Fudan University, Shanghai 200438, China
⁵ Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, China
⁶ School of Nuclear Science and Technology, University of South China, Hengyang 421001, China
⁷ School of Physics, East China Normal University, Shanghai 200241, China

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Received: 5 December 2025
Accepted: 27 February 2026

Abstract

Context. The ¹⁴¹Pr(γ, n) cross-section is critical to the nucleosynthesis of p-nuclides ^136,138Ce in thermonuclear supernovae and in massive stars. The photonuclear reaction of ¹⁴¹Pr(γ, n) provides a new method for producing ¹⁴⁰Pr radioisotopes for positron emission tomography tracing in nuclear medicine.

Aims. We aim to perform an accurate measurement of the ¹⁴¹Pr(γ, n)¹⁴⁰Pr cross-section over a sufficiently wide range of gamma energies of the p-process and deduce the ¹⁴⁰Pr(n, γ)¹⁴¹Pr cross-section with γSF and TALYS-SMLO models. We determined the astrophysical reaction rate of ¹⁴¹Pr(γ, n)¹⁴⁰Pr at the temperature range of 0.2–10 GK based on the new measurement cross-section of the ¹⁴¹Pr(γ, n)¹⁴⁰Pr reaction.

Methods. We performed a new measurement of the ¹⁴¹Pr photoneutron cross-section at the Shanghai Laser Electron Gamma Source of the Shanghai Synchrotron Radiation Facility using quasi-monoenergetic laser Compton scattered γ-ray beams. The neutrons emitted by the ¹⁴¹Pr target were detected by the flat-efficiency detector array, while the γ beam transmitted by the ¹⁴¹Pr target were attenuated by a copper absorber and then measured by a bismuth germanate detector in order to reconstruct the γ spectrum incident on the target.

Results. The cross-section data of ¹⁴¹Pr(γ, n) were acquired using an unfolding iteration method with an uncertainty of less than 4%, and the inconsistencies between the available experimental data and evaluation libraries were discussed. The inverse reaction cross-section of ¹⁴⁰Pr(n, γ) and the reaction rates for the ¹⁴¹Pr(γ, n) reaction were derived over the astrophysically relevant temperature range of the p-process nucleosynthesis model. The photodisintegration decay constants of the ¹⁴¹Pr(γ, n) reaction for stellar temperatures between 0.2 GK and 10 GK are provided in a tabular form and by an analytical fitting expression. The λ_γn(¹⁴¹Pr) = 0.013 ± 0.001 s⁻¹ at a typical p-process temperature of T = 2.5 GK was also computed.

Conclusions. The photodisintegration decay constants of the ¹⁴¹Pr(γ, n) reaction deviate significantly from previous theoretical predictions, and the uncertainties are significantly reduced in the direct measurement.