Speaker
Description
High-$\ell$ single-particle configurations provide critical information on nuclear structure and place important constraints on theoretical models but are typically difficult to access experimentally due to their weak population in commonly used experimental methods such as low-energy transfer and knockout reactions. Intermediate-energy one-neutron pickup reactions in inverse kinematics are uniquely suited to this problem as due to poor angular momentum matching the population of high-$\ell$ ($\ell$ $\geq$3) states are drastically enhanced whilst also suppressing low-$\ell$ transfer [1,2]. When applied to nuclei with high-lying high-$\ell$ orbitals these reactions provide selective access to states that have remained unobserved in previous $\gamma$-ray spectroscopy studies, even in otherwise well-studied systems.
Here, one-neutron pickup reaction experiments performed at the former NSCL will be discussed. Beams delivered by the Coupled Cyclotron Facility were impinged on a $^{12}$C target to induce one-neutron pickup reactions. Prompt $\gamma$ rays were detected with the Gamma-Ray Energy in-beam Nuclear Array (GRETINA), while reaction residues were subsequently identified in the S800 magnetic spectrometer. These measurements build on earlier one-neutron pickup studies performed at the NSCL which first demonstrated the strong selectivity of one-neutron pickup reactions [3,4]. Results from the $^{12}$C($^{46}$Ca,$^{47}$Ca+ $\gamma$)X reaction will be discussed, which provided new insight into the placement and strength of the ν(0f$_{5/2}$) and ν(0g$_{9/2}$) orbitals in $^{47}$Ca [5], including the population of states not previously observed in $\gamma$-ray spectroscopy. In addition, preliminary results from the ongoing analysis of the $^{12}$C($^{44}$Ar,$^{45}$Ar+$\gamma$)X reaction will be presented, further demonstrating the strong selectivity of one-neutron pickup reactions and their potential to probe high-$\ell$ structure in neutron-rich nuclei.
[1] D. Brink, Phys. Lett. B 40, 37 (1972)
[2] W. R. Phillips, Rep. Prog. Phys. 40, 345 (1977)
[3] A. Gade, J. A. Tostevin et al, Phys. Rev. C 93, 031601 (2016)
[4] A. Gade, J. A. Tostevin et al, Phys. Rev. C 93, 054315 (2016)
[5] T. Parry, A. Gade, B. A. Brown et al, Phys. Rev. C 112, 014328 (2026)