We study the energy systematics in light mirror nuclei of the unbound states having predominant single-particle character. For many levels in the mass range A=9–17, the observed Thomas-Ehrmann shift is described very well by a simple potential model. We speculate that the missing partner in ${}_{}{}^9{}_{}{}^{}\mathrm{B}$ of the ${\mathrm{}(1/2)\mathrm{}}^{+}$ state in ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ is observable as a broad continuum with a peak at 0.9 MeV.

• Received 22 July 1985

DOI:https://doi.org/10.1103/PhysRevC.32.1809