Determination of proton and neutron contributions to the 0_g.s.⁺ → 2₁⁺ excitations in ⁴²Si and ⁴⁴S using inelastic proton scattering in inverse kinematics and intermediate energy Coulomb excitation

2025/08/01 by Riley, L. A., Conroy, I., Himmelreich, A. M. +26
#FOS: Physical sciences #Nuclear Experiment (nucl-ex)

paper · doi:10.48550/arxiv.2508.00703

Abstract

We have measured the 0_g.s.⁺ → 2₁⁺ transition in the neutron rich N=28 isotope ⁴²Si using the probes of intermediate energy Coulomb excitation and inelastic proton scattering in inverse kinematics at the Facility for Rare Isotope Beams with beam particle rates of ≈ 5 particles/s. The results of these two measurements allowed us to determine M_n/M_p, the ratio of the neutron and proton transition matrix elements for the 0_g.s.⁺ → 2₁⁺ transition. In addition, we have measured the 0_g.s.⁺ → 2₁⁺ transition in the isotone ⁴⁴S using inverse kinematics inelastic proton scattering. By comparing the ⁴⁴S proton scattering result with a recent intermediate energy Coulomb excitation result on the same transition, we were able to determine M_n/M_p for the 0_g.s.⁺ → 2₁⁺ transition in this nucleus as well. This work strengthens the evidence that ⁴²Si has a stable quadrupole deformation in its ground state and that ⁴⁴S does not. Both conclusions are further supported by shell model calculations carried out with the FSU interaction.

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