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RIBF Nuclear Physics Seminar
RNC–KEK Joint Seminars：The 347h and The 348th RIBF Nuclear Physics Seminars
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Asia/Tokyo
RIBF Hall, RIBF 2nd Floor (Wako, Saitama)
RIBF Hall, RIBF 2nd Floor
Wako, Saitama
Description
【347th】
Talk given by Dr. James Cubiss, The University of Edinburgh
Title: Shifts, Shapes and Shells studied by In-Source Laser Spectroscopy at ISOLDE
Abstract:
Laser spectroscopy is a powerful technique for studying how ground and isomeric state properties across the chart of nuclides [1]. From the measuring isotope shifts and hyperfine structures we can deduce nuclear spins, changes in mean-squared charge radii and electromagnetic moments. Such data are excellent tests for theory, providing wide-ranging benchmarks to compare model predictions to [2].
I will introduce the in-source resonance ionisation technique used at CERN’s ISOLDE facility [3] – a highly efficient method, which when combined with the sensitivity of decay stations [4] or mass spectrometry devices [5], allows access to exotic nuclides with extremely low production rates. Results will be presented from recent campaigns in the neutron-rich Pb (Z=82) region, where the impact of the N=126 closure on nuclear properties, such as the “kink” in charge radii, have been explored [6,7].
[1] X. F. Yang, S. J. Wang, S. G. Wilkins, R. F. Garcia Ruiz, Prog. Part. Nucl. Phys. 129, 104005 (2023).
[2] A. R. Vernon et al., Nature 607, 260-265 (2022).
[3] M. J. Borge, B. Jonson, J. Phys. G: Nucl. Part. Phys. 44, 044011 (2017).
[4] A. N. Andreyev et al., Phys. Rev. Lett. 105, 252502 (2010).
[5] R. N. Wolf et al., Int. J. Mass Spectrom. 349-350, 123-133 (2013).
[6] Z. Yue et al., Phys. Lett. B 849, 138452 (2024)
[7] Z. Yue et al., Phys. Rev. C 110, 034315 (2024).
【348th】
Talk given by Prof. Andrei Andreyev, the University of York
Title: Approaching the dominance of electron-capture delayed fission in 234Bk and 230Am
Abstract:
The beta-delayed fission is believed to play an important role in the so-called ‘fission termination’ of the astrophysical r-process, together with spontaneous and neutron-induced fission. However, its properties are very difficult for investigations, due to the experimental problems to reach relevant regions of nuclei, with only about 25 cases of beta-delayed fission known so far, predominantly for the neutron-deficient nuclides [1].
The talk will present the result of an experiment to study electron-capture delayed fission (ECDF) in the very neutron-deficient isotope 234Bk, performed at the gas-filled recoil separator SHANS2 at the Institute for Modern Physics, IMP-Lanzhou, China. The isotope 234Bk was produced in the fusion-evaporation reaction 40Ar+197Au->237Bk*->234Bk+3n.
By using the method of temporal and position correlations, different decay channels of 234Bk and its alpha-decay product 230Am were investigated and a wealth of new experimental information was obtained. The data significantly improve over the previous investigations at the GARIS gas-filled separator [2,3].
The highest ECDF probabilities, PECDF(234Bk)=0.57(11) and PECDF(230Am)=0.34(9), among all beta- or EC-delayed fission cases known so far are reported, showing the tendency of approaching the expected saturation towards PECDF =1 [4]. The comparison of the PECDF systematics with two theoretical fission models shows significant discrepancies in respect of corresponding fission barrier values. The need for a theoretical framework that can provide realistic beta-delayed fission probabilities for astrophysical predictions is strongly underlined.
[1] A.N. Andreyev, M. Huyse, Piet Van Duppen, Reviews of Modern Physics 85 (4), 1541 (2013)
[2] D. Kaji et al., Journal of the Physical Society of Japan 85, 015002 (2016).
[3] G. L. Wilson et al., Physical Review C 96, 044315 (2017).
[4] Z. Zhang et al, submitted, March 2026
Zoom Link: Zoom link: https://riken-jp.zoom.us/j/96577967679?pwd=YmgrOW9pTmNhUkIvODFycEdRSUpuQT09