We present a new heuristic model which describes the diffusion of noble gas atoms inside a polymer matrix. The motion of the gas atoms consists of movements inside small areas called traps and of hops between different traps. Whether an atom enters another trap during a molecular dynamics (MD) simulation is determined by observing a new quantity called cage overlap. This criterion is independent of size, time, and temperature scales of the system. The resulting motions are quantitatively described by probability distributions and correlation functions. We measure these distributions for three example systems of helium, argon, and krypton atoms inside a polyethylene matrix using MD simulations. Then we verify the model by comparing results from direct simulations of the hopping model with initial results from the MD.