$R$-matrix formulas are used to derive information about levels of ${}^8\mathrm{Be}$ and reactions involving ${}^8\mathrm{Be}.$ Data from the ${}^4\mathrm{He}(\alpha {,p)}^7\mathrm{Li},$ ${}^4\mathrm{He}(\alpha {,n)}^7\mathrm{Be},$ and ${}^7\mathrm{Li}(p,\alpha {)}^4\mathrm{He}$ reactions and from $\alpha +\alpha$ elastic scattering are fitted, and a value obtained for the zero-energy S factor for ${}^7\mathrm{Li}(p,\alpha {)}^4\mathrm{He}:$ $S\left(0\right)=58\mathrm{}$ keV b. Recent measurements and analyses of the ${}^7\mathrm{Li}(d,\alpha \alpha )n$ and ${}^7\mathrm{Li}(p,{\gamma }_0{)}^8\mathrm{Be}$ reactions, and calculations concerned with low-lying intruder states in ${}^8\mathrm{Be},$ are discussed with reference to R-matrix fits.

• Received 30 March 2000

DOI:https://doi.org/10.1103/PhysRevC.62.044607