The 18th International Symposium on Origin of Matter and Evolution of Galaxies (OMEG18)

Experimental studies of β-decay properties of very neutron-rich nuclei relevant to the r process

Oct 23, 2026, 2:05 PM

25m

Headquarters Building 2F (RIKEN)

Invited Presentation Experimental nuclear physics for astrophysics Scientific Session

Speaker

Vi Phong (Radioactive Isotope Physics Laboratory, RIKEN Nishina Center)

Description

The search for the limits of nuclear existence at extreme isospin toward the neutron drip line is at the forefront of modern nuclear physics. Along this line, the astrophysical rapid neutron capture process (r-process), which is responsible for the synthesis of about half of the elements heavier than iron [1], provides one of the strongest motivations. The β-decay properties of very neutron-rich nuclei are key inputs to r-process calculations, and where direct data are missing, they serve as essential constraints on the theoretical models employed [2]. In particular, half-lives (T₁/₂) set the timescale of the reaction flow toward heavier masses, while β-delayed neutron emission probabilities (Pₓₙ) control the availability of late-time neutrons and shape the final abundance pattern.
In this talk, we will present a variety of experiments focusing on the β-decay properties of very neutron-rich nuclei, namely half-lives, β-delayed neutrons, and delayed γ rays, covering wide regions of the nuclear chart [3–5]. These measurements were performed at the RIBF facility using intense radioactive-isotope beams produced by in-flight fission and separated by BigRIPS, combined with complementary experimental apparatus: the high-efficiency neutron counter BRIKEN [6], high-efficiency γ-ray detector arrays, and the decay station coupled with multi-reflection time-of-flight (MRTOF) mass spectrographs [7]. Recent results, including new decay rates in the A ≈ 110 region [8] and β-decay half-lives beyond the N = 126 shell closure [9], will be discussed together with their impact on r-process calculations and prospects for reaching further toward the drip line.
[1] J. J. Cowan et al., Rev. Mod. Phys. 93, 015002 (2021).
[2] M. R. Mumpower et al., Prog. Part. Nucl. Phys. 86, 86 (2016).
[3] S. Nishimura et al., Phys. Rev. Lett. 106, 052502 (2011).
[4] G. Lorusso et al., Phys. Rev. Lett. 114, 192501 (2015).
[5] V. H. Phong et al., Phys. Rev. Lett. 129, 172701 (2022).
[6] A. Tolosa-Delgado et al., Nucl. Instrum. Methods Phys. Res. A 925, 133 (2019).
[7] M. Rosenbusch et al., Nucl. Instrum. Methods Phys. Res. A 1047, 167824 (2023).
[8] V. H. Phong, S. Nishimura et al., submitted.
[9] V. H. Phong, S. Nishimura et al., in preparation.