One further detail - on the importance of having a light source of some kind, which apparently does not have to be coherent – like a laser. But having a laser probably helps, if it is the right wavelength of light.
As I recall, Letts and Cravens spent many months trying to find laser light which worked --- and ended up using two different WLs. The reason that light is important most likely relates to SPP. It could very well be the case that the SPP are necessary to further reduce the f/H atoms, which first form in contact with the iron/potassium catalyst, but can only shrink part of the way. The intense magnetic field of SPP could then finish off the job.
