The probability of penetrating a rectangular barrier of height U o and width a is approximately given by, were and E is the energy of the particle.

The probability of penetrating a rectangular barrier of height Uo and width a is approximately given by, were

and E is the energy of the particle. What is the order of magnitude of the probability that a proton will tunnel through this barrier in just one collision with the barrier if it has energy 18 MeV below the top of the potential .62barrier and the barrier thickness is 2 × 10?14 m.