Advances in Radioactive Isotope Science

Gamow-Teller Giant Resonance in $^{11}$Li neutron drip line nucleus

6 juin 2023, 16:45

15m

oral contribution reactions parallel session

Orateur

Dr László Stuhl (Center for Exotic Nuclear Studies, Institute for Basic Science)

Description

At the RIKEN Radioactive Isotope Beam Factory, the spin-isospin response of $^{11}$Li was measured in charge-exchange $(p,n)$ reaction at 182 MeV/nucleon beam energy. There is no available data for isovector spin-flip giant resonances in nuclei with large isospin asymmetry factors, where (N−Z)/A>0.25 [1]. Our work aims to investigate this unexplored region up to (N−Z)/A=0.5.
The charge-exchange $(p,n)$ reactions in inverse kinematics combined with the missing-mass technique are powerful tools to extract the B(GT) strengths of unstable isotopes up to high excitation energies, without Q-value limitation of the β decay [1]. In our previous work on $^{132}$Sn [2], we demonstrated that accurate information about giant resonances can be obtained for unstable nuclei by using this probe. The combined setup [3] of PANDORA low-energy neutron spectrometer [4] and SAMURAI large-acceptance magnetic spectrometer [5] together with a thick liquid hydrogen target allowed us to perform the experiment with high luminosity. The recoil neutrons with kinetic energy of 0.1–10 MeV were identified with PANDORA, while the SAMURAI was used for tagging the decay channels of the reaction residues.
The β decay of $^{11}$Li is complex. The $^{11}$Li β-decay involves the largest number of decay channels ever detected [6] and experimental results have been reported for cases, when the daughter breaks into fragments, and emission of one, two, and three neutrons, α particles and $^{6}$He, tritons, and deuterons has been observed in several β-decay studies [8,9]. However, the B(GT) values were not clearly deduced as these studies were effected by the Q value.
In this talk, the final results of our analysis will be presented. Deduced double differential cross section up to about 40 MeV, including the Gamow-Teller (GT) Giant Resonance region in $^{11}$Li will be reported, as well as the comparison of the obtained B(GT) values with those from β-decay studies. We will discuss the nature of several newly identified decay channels of $^{11}$Be also.
Our observation, that the GT peak occurs below the Isobaric Analog State in $^{11}$Li, will be discussed in connection with the variation of residual spin-isospin interaction in exotic nuclei.

[1] K. Nakayama, et al., Phys. Lett. B 114, 217 (1982).
[2] M. Sasano et al., Phys. Rev. Lett. 107, 202501 (2011).

[3] J. Yasuda et al., Phys. Rev. Lett. 121, 132501 (2018).
[4] L. Stuhl et al., Nucl. Instr. Meth. B 463, 189 (2020). 

[5] L. Stuhl et al., Nucl. Instr. Meth. A 866, 164 (2017).
[6] T. Kobayashi, et al., Nucl. Instr. Meth. B 317, 294 (2013).
[7] M. Madurga et al., Nucl. Phys. A 810, 1 (2008).
[8] M.J.G. Borge et al., Nucl. Phys. A 613 199 (1997).
[9] R. Raabe et al., Phys. Rev. Lett. 101, 212501 (2008).