Elastic and inelastic alpha scattering on Ar-36 at Ealpha=40, 48, and 54 MeV

Differential cross sections for elastic and inelastic α- scattering on Ar36 have been measured at 40, 48, and 54 MeV. The data have been analyzed in the coupled-channel approach using double-folded optical α−36Ar potentials considering the model of the symmetric rotator and the harmonic vibrator. The octupole transition probability deduced in the harmonic-vibrator model is almost identical to the value obtained from electromagnetic probes. In the symmetric-rotator model only the choice of negative β2 and β4 deformation parameters results in consistent fits to the data at all incident energies. This unambiguously proves the oblate shape of Ar36. The volume integrals and rms radii of the extracted optical potentials fit well into the systematics obtained for lighter sd-shell nuclei.