Low-lying structure of 15C: Information on the N=8 shell gap

Abstract

The low-lying structure of 15C has been investigated via the neutron-removal d(16C, t) reaction. The experiment was performed at GANIL using a secondary 16C beam produced by fragmentation in the LISE spectrometer at 17.2 MeV/nucleon with an intensity of 5 × 104 pps and 100% purity. The angle and energy of the light ejectile were detected by three MUST2 telescopes. The missing mass technique was used to reconstruct the excitation energy of 15C. In this spectrum, two bound states were observed (gs and the first excited state) and two unbound resonant states above the neutron separation threshold (S n = 1.218 MeV). From the differential cross sections, information on the angular momentum of the transferred nucleon and spectroscopic factors were deduced. The excitation energies and the deduced spectroscopic factors of the negative parity states placed above the neutron separation energy are an important measurement of the 2p-1h configurations in 15C. Our results show good agreement with shell-model calculations with the YSOX interaction and show a sensitivity to the N=8 shell gap.