  The proton-rich nucleus $^{23}$Al has a ground state just 123 keV below the
proton drip-line, and as a result comparatively little is known experimentally
about its properties, as with many such nuclei. Theoretical investigations have
tended to model exclusively the ground and first one to three excited states
known. In this paper, we theoretically model most of the known spectrum, and
predict what states may as yet be unobserved. We use the multichannel algebraic
scattering (MCAS) method to describe states as resonances of a valence proton
coupled to a $^{22}$Mg rotor core. Six states with low-excitation energies and
defined $J^\pi$ are matched, and we make the first prediction of the properties
of four others and propound the possible existence of several more.
