Energy levels of 36Ar and 38Ar from alpha capture in sulphur and proton capture in chlorine

Abstract

The reactions 32S(α, γ)36Ar and 34S(α, γ)38Ar were investigated in the energy range Eα = 2.2−3.2 MeV. Five resonance states in 36Ar (Ex = 8.9−9.5 MeV) and six in 38Ar(Ex = 9.6−;10.1 MeV) were found. The excitation energies and resonance strengths are reported. The spins and parities of most resonances showing a ground-state transition were determined from angular distribution measurements. The relative strengths of the Jπ = 1− resonances in 36Ar and 38Ar indicate that the isobaric-spin selection rule for electric dipole transitions in self-conjugate nuclei is still effective in this mass region. The slowing-down factor for these transitions amounts to about ten.

The 35Cl(p, γ)36Ar reaction for Ep = 0.4−;1.0 MeV, leads to twenty 36Ar levels in the excitation range covered in the 32S(α, γ)36Ar experiment. The yield curves of the two reactions are compared. Three 36Ar resonance levels are excited in both the (p, γ) and the (α, γ) reaction.