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A new-type of $\gamma$-ray spectroscopy in search of mediating states in $^{180}$Ta
Hiroaki Utsunomiya$^{a,b}$, Gongtao Fan$^c$, Xiangai Deng$^b$, Yifan Liu$^d$, Zirui Hao$^c$, Liyong Zhang$^e$, Baohua Sun$^f$, Jianjun He$^b$, Hongwei Wang$^c$, Yugang Ma$^b$, Dan Filipescu$^g$, Ioana Gheorghe$^g$, Taka Kajino$^f$, Stephane Goriely$^h$
$^a$ Konan University, Kobe, Japan
$^b$ Fudan University, Shanghai, China
$^c$ SARI, Shanghai, China
$^d$ Shanghai Tech University, Shanghai, China
$^e$ Beijing Normal University, Beijing, China
$^f$ Baijing University of Aeronautics and Astronautics, Beijing, China
$^g$ IFIN-HH, Bucharest-Magurele, Romania
$^h$ ULB, Brussels, Belgium
Intermediate states that connect the short-lived ground 1$^+$ state and long-lived isomeric 9$^-$ state by ${\gamma}$-transitions have remained an unveiled mystery in the nucleosynthesis of $^{180}$Ta. The thermalization of $^{180}$Ta during the s-, ${\nu}$-, or p-process nucleosynthesis requires the identification of mediating states[1-3]. The conventional ${\gamma}$-spectroscopy with heavy-ion reactions has failed to detect the mediating states primarily because large angular-momentum ($J$) and excitation-energy ($E_x$) inputs to the reaction resulted in ${\gamma}$-transitions dominated by the yrast transitions [4,5]. We propose a new-type of ${\gamma}$-spectroscopy with the small $J$ and $E_x$ input which is unique to the nucleosynthesis of $^{180}$Ta. The detector dedicated to the new spectroscopy experiment called the p-process chaser detector [6] is under construction and a test measurement is scheduled in the fall of 2025.
References
[1] K. Yokoi and K. Takahashi, Nature (London) 305, 198 (1983).
[2] S. E. Woosley et al., Astrophys. J. 356, 272 (1990).
[3] N. Prantzos et al., Astron. Astrophys. 238, 455 (1990).
[4] G. D. Dracoulis et al., Phys. Rev. C 58, 1444 (1998); Phys. Rev. C62, 037301 (2000).
[5] T.R. Saitoh et al., Nucl. Phys. A660, 121 (1999).
[6] H. Utsunomiya et al., Nucl. Inst. and Meth. in Phy. Res. A 1034, 166819 (2022)
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