Al27and the Excited-Core Model

The nuclear properties of the low-lying levels in ${\mathrm{Al}}^{27}$ are discussed in terms of a model in which a proton hole is coupled to the observed levels of ${\mathrm{Si}}^{28}$. The calculated electric $E2\mathrm{}$ transition probabilities are found to be in good agreement with the experimental values, but the agreement between theory and experiment for $M1\mathrm{}$ transition probabilities does not appear to be so good. It is found that the core-particle interaction required to fit the observed levels of ${\mathrm{Al}}^{27}$ contains multipoles of order up to four. A possible explicit form for this interaction is suggested.