Structure and Total Strength of the Magnetic Dipole Resonance on Excited States in sd-Shell Nuclei

Abstract

The gamma-decay of resonance-like structures observed in the reaction of the radiative capture of protons by ²²Ne, ²⁶Mg, ³⁰Si, ^34,36S, and ³⁸Ar nuclei in the 7–12 MeV region of excitation energies is studied. The excitation functions of this reaction are measured. The resonance strengths of states in energy range E_p = 1.0–3.0 MeV of accelerated protons are determined. The discrete distributions of magnetic dipole γ-transitions between the ground and excited states for sd-shell nuclei are of a resonance nature. A magnetic dipole resonance is identified for the ground and excited states in the above nuclei. The position of the magnetic dipole resonance on the excited states coincides with the one predicted by the Brink–Axel hypothesis for nuclei at the beginning of a subshell.