Isomeric Transitions occur when a nucleus is in an energetically excited state, and decays to discrete energy isomeric states and a ground state can occur following a radioactive half-life. A prior thread references variability of up to 3% in that half-life under certain conditions involving the electron-cloud density (chemical state) of the element. How does the electron-cloud density interact with the nucleus to effect the half-life? Also, isomeric transitions are also reportedly effected when the nucleus absorbs entangled gamma-photons. http://www.freepatentsonline.com/y2008/0078961.html How does this occur?
Just like in a laser where an external photon serves as a trigger for the normally spontaneous decay of an excited electron configuration to a less excited state, so can the electromagnetic/electroweak environment potentially serve as a trigger or path for normally spontaneous decay of an excited nucleon configuration to a less excited state. A detailed answer of "how" would require precise modeling of specific nuclear states with the electron cloud added, but the principle has been clear for a while. Here is a speculative idea to exactly use the laser analogy. B. Balko. "An investigation into the possibility of lasing directly from an isomeric level" Journal of Quantitative Spectroscopy and Radiative Transfer 40:6, 751-762 (December 1988).