Re: only holds true at the very low temperatures ...
I don't think these are true isomers in the chemistry sense either, it usually implies a different configuration of atoms. These are actually going to be different quantum states but with the same configuration. Interesting they may have different reactivity though.
Nuclear spin in water tends to reach equilibrium quite easily, NMR and MRI rely on this. In a magnetic field you have spin up and spin down states and they can only be kept out of equilibrium for short periods of time, the excess energy is lost or absorbed through interactions with surrounding nuclei over a couple of seconds at 3 tesla. Without an external field the only source of energy difference is the interaction between the spin states of the two nuclei, which is much smaller and therefore any inequality can decay much faster.
Biting the hand that feeds IT
