Speaker
Description
The one-neutron (1n) and $\alpha$-transfer reactions have been widely explored for weakly bound stable nuclei [1,2]. Similar investigations with radioactive nuclei are relatively scarce [1,3]. In this work, we report the first simultaneous measurement of both 1n and $\alpha$-transfer processes in the reaction $^{12}\mathrm{C}(^{7}\mathrm{Be},{}^{8}\mathrm{Be}^{*})^{11}\mathrm{C}^{*}$. The experiment was carried out at HIE-ISOLDE, CERN, using a 5 MeV/u $^{7}\mathrm{Be}$ beam [4]. An earlier study of the $^{9}\mathrm{Be} + {}^{12}\mathrm{C}$ system at $E \approx 2.2$ MeV/u [5] reported that 1n transfer dominates at forward angles, while $\alpha$ transfer is more prominent at backward angles. Data also exist for 1n transfer in the $^{7}\mathrm{Li} + {}^{13}\mathrm{C}$ reaction at $E \approx 5$ MeV/u [6]. Both channels lead to the formation of the proton-rich nucleus $^{11}\mathrm{C}$ (half-life = 20.4 min), populating its ground state ($3/2^{-}$) and excited states at 2.00 MeV ($1/2^{-}$), 4.31 MeV ($5/2^{-}$), and 4.80 MeV ($3/2^{-}$). The unbound $^{8}\mathrm{Be}$ produced in the exit channel is populated in its known excited states at 3.03, 11.35, and 16.62 MeV, and promptly decays into two $\alpha$-particles. Preliminary calculations show that neutron transfer dominates at forward angles and $\alpha$-transfer dominates at backward angles for the 3.03 and 11.35 MeV states in $^{8}\mathrm{Be}^{*}$. In contrast, for the 16.62 MeV state, $\alpha$-transfer dominates at all angles while the neutron-transfer contribution is negligible. The neutron and $\alpha$-spectroscopic factors can be extracted from this work. The ground-state spectroscopic factor for the $^{7}\mathrm{Be} + \alpha$ configuration in $^{11}\mathrm{C}$ can be used to constrain the direct-capture component of the $^{7}\mathrm{Be}(\alpha, \gamma)^{11}\mathrm{C}$ astrophysical S-factor [7] and would be useful in nuclear astrophysics.
References
[1] A. Pakou et al., Eur. Phys. J. A 58 (2022) 8.
[2] N. Oulebsir et al., Phys. Rev. C 85 (2012) 035804.
[3] A. Chatterjee et al., Phys. Rev. Lett. 101 (2008) 032701.
[4] Sk M. Ali et al., Phys. Rev. Lett. 128 (2022) 252701.
[5] L. Jarczyk et al., J. Phys. G: Nucl. Phys. 5 (1979) 565.
[6] J. Cook et al., Nucl. Phys. A 466 (1987) 168.
[7] M. Hartos et al., Astrophys. J. 862 (2018) 62.