Giant dipole resonance in 56Fe observed via (p, γ) and (α, γ) reactions

A comparison is made between the yield curves of the measured 52Cr(α,γ0) and 55Mn(p,γ0) reactions in the giant dipole resonance region of 56Fe (E/subx/=14.0 to 21.5 MeV) to determine if the gross differences can be interpreted as being due to isospin effects. Above 18 MeV the yield of (γ,α0), determined by the principle of detailed balance, is observed to drop below the value obtained when the energy dependence of the transmission coefficients is removed. This leads to the conclusion that while the diminished yield in the (γ,α0) channel may be due to the failure to populate the isospin forbidden T/sub greater-than/ states, other effects cannot be ruled out