  We study the dynamics of non interacting thermal atoms embedded in structured
optical lattices with non trivial geometry. The lattice would be generated by
two counter propagating modes with parabolic cylindrical symmetry and we
concentrate on the quasi conservative red detuned far-off-resonance regime. The
system exhibits quasi periodic and chaotic behaviors whose probability can be
controlled by varying the intensity of the beams. The spectral density of the
trajectories is used as a chaos signature. An analysis of permanency times for
chaotic trajectories that visit more than one potential well reveals a
distribution with a long tail.
