A more detailed test of the implementation of nuclear forces that drive shell evolution in the pivotal nucleus ${}^{42}\mathrm{Si}$—going beyond earlier comparisons of excited-state energies—is important. The two leading shell-model effective interactions, SDPF-MU and SDPF-U-Si, both of which reproduce the low-lying ${}^{42}\mathrm{Si}(2_1^{+})$ energy, but whose predictions for other observables differ significantly, are interrogated by the population of states in neutron-rich ${}^{42}\mathrm{Si}$ with a one-proton removal reaction from ${}^{43}\mathrm{P}$ projectiles at $81\mathrm{MeV}/\mathrm{nucleon}$. The measured cross sections to the individual ${}^{42}\mathrm{Si}$ final states are compared to calculations that combine eikonal reaction dynamics with these shell-model nuclear structure overlaps. The differences in the two shell-model descriptions are examined and linked to predicted low-lying excited $0^{+}$ states and shape coexistence. Based on the present data, which are in better agreement with the SDPF-MU calculations, the state observed at 2150(13) keV in ${}^{42}\mathrm{Si}$ is proposed to be the ($0_2^{+}$) level.

• Received 12 March 2019
• Revised 23 April 2019

DOI:https://doi.org/10.1103/PhysRevLett.122.222501