Alpha particle cluster structure is known experimentally to persist throughout the mass range 16≤A≤20, and has been very successfully described in this region in terms of the Buck-Dover-Vary local potential cluster model. It is argued that an analogous cluster structure should be present in nuclei at the beginning of the fp shell, and the available experimental data are examined to determine likely alpha particle cluster state candidates in the mass range 40≤A≤44. Calculations of the cluster state spectra and mean square cluster-core separation distances (which may be readily used to evaluate E2 electromagnetic transition rates) for ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{42}{}_{}{}^{}\mathrm{Sc}$, ${}_{}{}^{43}{}_{}{}^{}\mathrm{Sc}$, ${}_{}{}^{43}{}_{}{}^{}\mathrm{Ti}$, and ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$ using the above-mentioned model are presented, and compared with experimental measurements where possible. The agreement between theory and experiment is generally good (although inferior to that obtained in the sd shell), and points to the desirability of an extension and improvement of the measurements of the properties of the excited states in these nuclei.

• Received 16 March 1987

DOI:https://doi.org/10.1103/PhysRevC.36.778