We search for low-lying resonances in the ${}^8\mathrm{B}$ and ${}^8\mathrm{Li}$ nuclei using a microscopic cluster model and a variational scattering method, which is analytically continued to complex energies. After fine-tuning the nucleon-nucleon interaction to get the known $1^{+}$ state of ${}^8\mathrm{B}$ at the right energy, we reproduce the known spectra of the studied nuclei. In addition, our model predicts a $1^{+}$ state at 1.3 MeV in ${}^8\mathrm{B},$ relative to the ${}^7\mathrm{Be}+p$ threshold, whose corresponding pair is situated right at the ${}^7\mathrm{Li}+n$ threshold in ${}^8\mathrm{Li}.$ Lacking any experimental evidence for the existence of such states, it is presently uncertain whether these structures really exist or whether they are spurious resonances in our model. We demonstrate that the predicted state in ${}^8\mathrm{B},$ if it exists, would have important consequences for the understanding of the astrophysically important ${}^7\mathrm{Be}(p,\gamma {)}^8\mathrm{B}$ reaction.

• Received 10 August 1999

DOI:https://doi.org/10.1103/PhysRevC.61.024311