  We study numerically the interaction between an intense circularly polarized
laser field and an electron moving in a potential which has a discrete
cylindrical symmetry with respect to the laser pulse propagation direction.
This setup serves as a simple model, e.g., for benzene and other aromatic
compounds. From general symmetry considerations, within a Floquet approach,
selection rules for the harmonic generation [O. Alon Phys. Rev. Lett. 80 3743
(1998)] have been derived recently. Instead, the results we present in this
paper have been obtained solving the time-dependent Schroedinger equation ab
initio for realistic pulse shapes. We find a rich structure which is not always
dominated by the laser harmonics.
