About isomeric transitions at high Z

[EJIn]

I wonder why at high Z, isomeric transitions with small transition energies may be 100% converted.

 

[EJIn]

I can be possible to reword the post. Thanks

 

[DrSteve]

I wonder why at high Z, isomeric transitions with small transition energies may be 100% converted.

I believe that IT rate scales as the inverse of the excited state energy to some large power (E^-5), as well as proportional to Z², thus explaining both the enhancement for small small transition energies and high-Z isotopes