An original three-dimensional detector, which allows the precise measurement of the kinetic energy release and angular distributions of charged fragments, has been used to investigate the kinematics of the charge separation reaction SO23+-->S++O++O+ after core excitation in the S 2p threshold region. Kinetic energy release distributions and angular distributions are reported at various photon energies. The role of bending and stretching of the molecule in the repartition of the kinetic energies in the dissociative kinematics is demonstrated by means of a simple, parameter free, Coulomb repulsion model. At certain photon energies different geometries of SO23+ have been observed experimentally. An nb initio study, at the multireference single- and double-excitation configuration interaction level, of the potential curves corresponding to the neutral core-excited SO2 molecule is presented. This theoretical approach demonstrates that it is possible to explain this observation from the nuclear dynamics of the neutral core-excited molecule before the Auger decay occurs.