Fusion is, in most cases (stars, etc.), considered probabilistic. The Gamow-Sommerfeld factor is used to calculate the probability that two colliding nuclei will undergo fusion, considering the fact that the particles have a chance of fusing by quantum tunneling. However, one can calculate an energy (and corresponding speed) that a particle must have to overcome the coloumb barrier and approach within a set distance of the target nuclei, using only classical mechanics. This energy is 1.44 MeV•Z(1)•Z(2)/D, where D is the set distance in fermis, aka 10^-15 meters. If a particle is incoming onto a target nucleus enough energy to come close enough to fuse, even by classical mechanics, is fusion guaranteed or is there still a probabilistic nature to it?