Elastic alpha-particle resonances as evidence of clustering at high excitation in 40Ca

The elastic-scattering reaction Ar-36 + alpha was studied using the Thick Target Inverse Kinematics technique. Data were taken at a beam energy of 150MeV in a reaction chamber filled with He-4 gas, corresponding to the excitation region of 12-20MeV in Ca-40. Using a simplified R-matrix method of analysis energies, widths and spin assignments were obtained for 137 resonances. The structure is discussed within the concept of alpha-cluster structure in the quasi-continuum of Ca-40 and is compared to other nuclei in the same mass region.