The [formula omitted] resonance at 6.44 MeV

Abstract

The first T = 3 2 level in 13C has been studied as an isospin-forbidden resonance in the 9Be(α, n 0), 9Be(α, n 1) and 9Be(α, α 0) reactions at an incident energy of 6443.5±2.0 keV, corresponding to an excitation energy of 15108.9±1.5 keV in 13C. Total and partial decay widths were deduced as Γ = 5.49±0.25 keV and Γ α0/Γ ≧ 0.017 . The resonance parameters are discussed along the lines of similar investigations in 17O and 21Ne and with respect to the isobaric mass multiplet equation. Combining the present value for Γ with previous measurements of Γ γ0 / Γ yields the ground-state γ-decay width Γ γ0 = 22.8±1.9 eV, which compares well with the most precise value until now known from inelastic electron scattering data. The weighted combination of all available information on the ground-state-γ-decay of the first T = 3 2 states in 13C and 13N leads to B( 13 C)/B( 13 N)−1 = −0.15±0.07 for the reduced M1 transition strengths. The charge asymmetry of the reduced M1 transition strengths is discussed with respect to a charge-dependent mixing in the initial and final states and a possible isotensor component of the M1 transition operator.