Alpha–proton elastic scattering cross sections for ERDA in the resonance region

We have investigated alpha–proton elastic scattering for He-ERDA. The broad maximum of the elastic scattering resonance around E He =8.8 MeV is most important for hydrogen profiling with good sensitivity, since the cross section is more than hundredfold enhanced relative to Rutherford at the peak of the resonance. We present measurements covering the resonant energy region from 1.2 to 5.2 MeV of the inverse proton backscattering reaction at a laboratory backscattering angle of 129°. The present data and previous literature values found around the resonance were analysed by using the R -matrix theory. Comparison between the analysis of this work and an earlier work by Dodder et al. [Phys. Rev. C 15 (1977) 518] indicate the need of modified R -matrix parameters responsible for the shape of the resonance. Cross sections lower by 10–15% at the peak of the resonance and a new parameter set for calculating the cross sections for ERDA are suggested.