Elastic electron scattering off Si-30 and P-31 was studied in an effec
tive momentum-transfer range of 1.8-3.0 fm(-1). The form-factor data w
ere analyzed together with existing data sets for these nuclei and for
S-32 in a model-independent Fourier-Bessel expansion. For P-31 the M1
contribution was subtracted following an established parametrization.
Results of Hartree-Fock (HF) calculations, performed for these three
nuclei in a spherical basis and in an axially deformed basis, are comp
ared to experiment. Occupancies have been determined which, when used
in the spherical-basis HF calculations, lead to a good description of
the elastic form-factor data. The deformed-basis calculations have bee
n used to study the influence of the deformation on the calculated bin
ding energies and ground-state charge densities. In all calculations t
he influence of using different effective nucleon-nucleon interactions
was investigated. The resulting differences in 2s(1/2) in occupancy a
re combined with results from previous existing (e,e'p) experiments to
yield ''absolute occupancies'' for the 2s(1/2) orbital. The deduced 2
s(1/2) occupancies for Si-30 and S-32 are 0.24(4) and 1.35(19), respec
tively.