Is the Structure of ^{42}Si Understood?

Area of Science:

• Nuclear physics
• Nuclear structure theory

Background:

• Shell evolution in atomic nuclei is crucial for understanding nuclear forces.
• Previous studies compared excited-state energies of silicon-42.
• Two shell-model interactions, SDPF-MU and SDPF-U-Si, exist but yield different predictions.

Purpose of the Study:

• To perform a detailed test of nuclear forces driving shell evolution in silicon-42.
• To differentiate between the SDPF-MU and SDPF-U-Si shell-model effective interactions.
• To investigate the nature of low-lying excited states and shape coexistence in silicon-42.

Main Methods:

• A one-proton removal reaction from phosphorus-43 projectiles at 81 MeV/nucleon was used.
• Measured cross sections to individual silicon-42 final states were analyzed.
• Calculations combined eikonal reaction dynamics with shell-model nuclear structure overlaps.

Main Results:

• The measured cross sections showed better agreement with the SDPF-MU calculations.
• The study provides new insights into the population of states in neutron-rich silicon-42.
• The observed state at 2150(13) keV in silicon-42 is proposed to be the (0_2+) level.

Conclusions:

• The SDPF-MU interaction is favored based on the experimental data.
• The findings support the role of nuclear forces in shell evolution.
• The proposed assignment of the (0_2+) level advances the understanding of shape coexistence in silicon-42.