  We investigate the coexistence of spherical, deformed and superdeformed
states at low spin in S32, Ar36, Ar38 and Ca40. The microscopic states are
constructed by configuration mixing of BCS states projected on good particle
number and angular momentum. The BCS states are themselves obtained from
Hartree-Fock BCS calculations using the Skyrme interaction SLy6 for the
particle-hole channel, and a density-dependent contact force in the pairing
channel. The same interaction is used within the Generator Coordinate Method to
determine the configuration mixing and calculate the properties of even-spin
states with positive parity. Our calculations underestimate moments of inertia.
Nevertheless, for the four nuclei, the global structural properties of the
states of normal deformation as well as the recently discovered superdeformed
bands up to spin 6 are correctly reproduced with regard to both the energies
and the transition rates.
