  Starting from constrained Skyrme-mean-field calculations, the low-energy
excitation spectrum of 16O is calculated by configuration mixing of
particle-number and angular-momentum projected mean-field states in the
framework of the Generator Coordinate Method. Without any adjustable
parameters, this approach gives a very good description of those states and
their transition moments that can be described with our restriction to axially
and reflection-symmetric shapes. The structure of low-lying 0+ states is
analyzed in terms of self-consistent 0p-0h, 2p-2h, and 4p-4h Hartree-Fock
states.
