Resonance reactions

Abstract

The experimental conditions are discussed for the observation of reactions proceeding through narrow isolated resonances. This includes a survey of gamma-ray resonant scattering or absorption techniques, making use of accelerator produced radiation.

This general introduction is followed by some examples of recent Utrecht work on resonance reactions. The 23Na(p,γ)24Mg reaction has been investigated at six resonance levels in the Ep = 300–800 keV region. The gamma-ray branching has been determined of these levels and of twelve lower levels in 24Mg. Gamma-ray angular distributions have been measured at nine resonances in the 24Mg(α,γ)28Si reaction, from which resonance spins and parities can be determined in a unique way. Isotopic spin selection rules explain the relative weakness of observed E1 and M1 transitions compared to E2 transitions. From yield measurements in the 27Al(p,γ)28Si, 27Al(p,α)24Mg, and 24Mg(α,γ)28Si reactions the partial widths have been obtained for the decay of the relevant 28Si resonance levels.