I wrote: I did not intend the earlier description to preclude the possibility of > some kind of electromagnetic stimulation coming along and nudging the > isomer out of its excited level into a lower one. I'd be interested if > someone knows of something like this. >
In the paper that Harry linked to [1], there was mention at the end of a claim in 1999 of being able to stimulate the 2.4 MeV decay of hafnium-178m2 with x-rays with less than 100 keV. This is a controversial result, for the energy needed to stimulate the transition is very low, and the result hasn't been confirmed yet. Eric [1] http://epubs.surrey.ac.uk/469/1/fulltext.pdf
