Hi, The decay constant for alpha decay is the product of the transmission probability P and the collision frequency f of the alpha with the potential barrier, where f depends on velocity of the alpha in the nucleus. My question is about this Hyperphysics page, where alpha decay is modelled. Here in both the diagram and description, the alpha seems to have the same velocity within and outside the nucleus. Is that correct? I would have thought that attenuation of the wavefunction by the potential barrier would lead to an energy difference between alpha within and outside the nucleus.