Thanks for the link, kith. I have had a closer look now and feel a bit closer to understanding this. I am curious because I have read that in principle there is no lower limit, but it seems that testing at very low energies merely results in infinetessimal perturbations.
In the case of a beam of atoms passing between opposed magnets in a Stern Gerlach device and being deflected by the field into two different directions with 50:50 probability, could someone please clarify for me if there is a lower limit of magnetic field strength for this sorting effect to...