The building blocks of 3D models of barred galaxies

We make an orbital study of a Milky Way-like model of a barred galaxy of three degrees of freedom, with a relatively small bar perturbation (12% in forces). We find the planar PL1, 2 family of orbits, which is the continuation of the Lagrangian equilibrium points, L1, 2, for energy levels above EnL1, 2, and study its stability indices, b1, b2. Then with the help of the 4D Poincaré surfaces of section (PSSs) of the 6D phase space in several energy levels, we find 3D sticky chaotic orbits lying above (having a small third dimension) the planar PL2 orbits, as well as above other planar unstable periodic orbits, outside corotation, that behave like regular ones and support ring structures of R1 and R1R2 type (on the plane of rotation) for a very long time compared to the Hubble time. We find that these sticky chaotic orbits quickly get diffused outside the system after tens or hundreds of Hubble times through a superdiffusing procedure that lasts for a certain time period, and that they will finally escape from the system through an Archimedean spiral converging to ballistic motion.