I am learning about nuclear fissions and learned about the fission fragment distribution. It was interesting to see that the fission fragments have unequal masses.

I was wondering as to what governs which fission products are generated in each fission?

What parameters decide which fission products will have higher yield?


Fission products are generated randomly, i.e. you can't tell what nuclei will be formed as a result of particular fission process.

However, "the distribution of the fragment masses formed in fission is dependent on the mass of the fissioning nucleus and the excitation energy at which the fission occurs. At low excitation energy, the fission of such nuclides as uranium-235 or plutonium-239 is asymmetric—i.e., the fragments are formed in a two-humped probability (or yield) distribution favouring an unequal division in mass. (...) the light group of fragment masses shifts to higher mass numbers as the mass of the fissioning nucleus increases, whereas the position of the heavy group remains nearly stationary. As the excitation energy of the fission increases, the probability for a symmetric mass split increases, while that for asymmetric division decreases. Thus, the valley between the two peaks increases in probability (yield of formation), and at high excitations the mass distribution becomes single-humped, with the maximum yield at symmetry".

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