(α,2α) Reaction onBe9at 42.8 and 49.2 MeV and onO16at 49.2 and 52.5 MeV

The ($\alpha ,2\mathrm{}\alpha$) reactions on ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ at 42.8 and 49.2 MeV and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ at 46.0 and 52.5 MeV have been studied in order to test the validity of the impulse approximation. The experimental data are consistent with this approximation, but the over-all agreement is much worse than in the case of the ($\alpha ,2\mathrm{}\alpha$) reaction on ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$.