Firm spin and parity assignments for high-lying, low-spin levels in stable Si isotopes

A natural silicon target was investigated in a nat Si( γ , γ ′ ) photon-scattering experiment with fully linearly-polarised, quasi-monochromatic γ rays in the entrance channel. The mean photon energies used were ⟨ E γ ⟩ = 9.33, 9.77, 10.17, 10.55, 10.93, and 11.37 MeV, and the relative energy spread (full width at half maximum) of the incident beam was Δ E γ / ⟨ E γ ⟩ ≈ 3.5–4 %. The observed angular distributions for the ground-state decay allow firm spin and parity assignments for several levels of the stable even-even silicon isotopes.