NUCLEAR INSTABILITY, dN/dt = -λN = -N/τ
The fission barrier Ef is the energy
needed to deform the nucleus to the scission point. For heavy
nuclei, Ef decreases as Z2/A1/3
increases. When Z2/A1/3 is large enough,
the barrier height is comparable to the system energy and the
quantum tunneling probability for SF becomes significant. The
natural log of the spontaneous fission half life goes like the
exponential of Ef divided by the square root of Z2/A.
For 238U, with Z2/A about 36, the half
life is about 1016 years, whereas for 256Fm
with Z2/A about 39, the half life is about 10-4
years, roughly one hour.
Chart of the Nuclides
Another Chart of the Nuclides
An isotope with huge numbers of medical
applications (example)
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