Measuring the beta-decay properties for exotic rare-earth isotopes

Sep 28, 2022, 12:20 PM
Sestri Levante

Sestri Levante

Grand Hotel dei Castelli, Via Penisola Levante, 26, 16039 Sestri Levante (GE), Italy
Oral contribution Session 5


Sándor Kovács (University of Debrecen)


S. Kovács$^1$, G. G. Kiss$^2$, Y. Saito$^3$, A. Vitéz-Sveiczer$^{1,2}$, A. Tarifeno-Saldivia$^4$, on behalf of the BRIKEN collaboration
$^1$ University of Debrecen, H-4032 Debrecen, Egyetem tér 1, Hungary
$^2$ Institute for Nuclear Research (ATOMKI), H-4026 Debrecen, Bem tér 18/c, Hungary
$^3$ TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia V6T 2A3, Canada
$^4$ Universitat Politècnica de Catalunya (UPC), E-08028 Barcelona, Spain

The rapid neutron capture (so-called r-) process produces about half the heavy isotopes beyond the iron peak. The solar r-process abundance distribution has a local maximum around A $\approx$ 160 which originates from freeze-out during the late phases after neutron exhaustion. This rare-earth abundance peak (REP) provides a unique probe of the astrophysical conditions in the latter stages of the r-process [1-4].

According to the most recent sensitivity study the most influential nuclei to the REP formation can be found in the 55 ≤ Z ≤ 64 neutron rich region [3]. To constrain the peak formation models, in recent measurements at RIKEN Nishina Center using the BRIKEN array [5], the beta-decay parameters (delayed neutron emission probability and half-life) of 28 exotic neutron-rich Pm-Sm-Eu and Gd isotopes were measured. The half-life values and the neutron emission probabilities of the isotopes were obtained by fitting the time distribution of implantation-beta (i-$\beta$) and implantation-beta-neutron (i-$\beta$-n) correlation events using a sum of Bateman formulae. Furthermore, two CLOVER-type HPGe detectors are also mounted in the BRIKEN array, that are used to measure $\gamma$-spectra, thus the half-life results could be verified by exponential fitting the time distribution of implantation-beta-gamma (i-$\beta$-$\gamma$) correlation events [6]. The experimental results and astrophysical interpretation will be presented [7].

[1] M. R. Mumpower et al., ApJ. 752, 117 (2012).
[2] M. R. Mumpower et al., PRC 85, 045801 (2012).
[3] M. R. Mumpower et al., PRC 86, 035803 (2012).
[4] A. Arcones and G. Martínez-Piendo, PRC 83, 045809 (2011).
[5] A. Tolosa-Delgado et al., Nucl. Instr. Meth. 925, 133 (2019).
[6] A. Vitéz-Sveiczer et al., in preparation
[7] G. G. Kiss et al., submitted to The Astrophysical Journal

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