I know that particles don't have much mass and that the "force" of gravity is weaker than elecromagneitic or nuclear force, but gravity isn't really a force, it's a warping of space time related to energy density. Particles are quite dense so they should significantly warp space on a small scale and even if a particle is in high energy space it will be scrunched in so it's energy density will be higher. Also, when I look at the distribution of electrons around an atom, it makes me think of a spereical diffraction pattern. Accordingly, I think that the energy density of the nucleus is actually distributed in rings, so that space is scrunced in at the nucleas and at each of the rings, but it is expanded in the inbetween spaces so that the energy of any wave that passes by the atom will tend to concentrate in the rings as well as the nucleus. Passing electromagnetic waves should have a tendency to circle around an electron reinforcing the enrgy distribution and sort cirling the atom around the atom and making it pulse inward, although it wouldn't be an actual acceleration unless the photon interacted with the electron/atom.