Continuum Spectra from theBe9 (He3, α)2He4Reaction

Abstract

Alpha particles from the ${\mathrm{Be}}^9({\mathrm{He}}^3, \alpha )2\mathrm{}{\mathrm{He}}^4$ reaction were recorded at observation angles from 5 to 140 deg using a broad-range spectrograph. Bombarding energies were 3.00 and 4.00 MeV. The alpha continuum was measured from the reaction threshold up to a corresponding excitation energy of 15.5 MeV in the ${\mathrm{Be}}^9({\mathrm{He}}^3, \alpha ){\mathrm{Be}}^8$ reaction. The continuum is analyzed in terms of two possible decay modes involving spontaneous three-alpha disintegration of ${\mathrm{C}}^{12*}$ or stepwise two-body decay through states in ${\mathrm{Be}}^{8*}$. When Coulomb barrier effects are taken into account, qualitative agreement with the data is obtained by assuming the reaction proceeds via the three-body process. The low-energy anomaly seen in the reactions ${\mathrm{B}}^{11}(p, \alpha ){\mathrm{Be}}^8$ and ${\mathrm{Be}}^9(p, d){\mathrm{Be}}^8$ was not observed.