« on: 16/05/2022 17:16:37 »
Is it possible to slow the decay down by other methods? A few years ago, school-level physics would have stated that nuclear reactions are unlike chemical reactions - nuclear decay is a random process and the decay rates are un-affected by environmental conditions like pressure and temperature. The general explanation being that the nucleus is dominated by the effects of nuclear forces (the strong and weak force) and effectively independent from whatever else is going on outside the nucleus. It was a good explanation but like the semolina pudding they served at school lunchtime, it was just so wrong.
This belief was seriously adjusted in my life time when a type of nuclear change called electron capture was studied. ( https://en.wikipedia.org/wiki/Electron_capture ). In electron capture it is possible to adjust the nuclear reaction rates just by ionising the atom (for example the nuclear change 74Be+ → 73Li+ proceeds more slowly than 74Be → 73Li ). You can get a smaller (but statistically significant) difference just by bonding the atom to certain things.
I've not seen any information about it - but it begs the question that you might be able to adjust the rates of other nuclear changes. For example, alpha emission may be reduced if the unstable nucleus can be surrounded with ligands that are positively charged and create a potential barrier against the emission of another positively charged particle. Maybe just putting the unstable nuceii under pressure is enough to slow the decay (since the appearance of more particles tends to increase pressure PV = nRT etc). I don't know and It's important to point out that this is just speculation: I have a personal belief that nuclear reactions are much more like chemical reactions than we had first imagined (just in terms of their reaction kinetics, obviously chemistry goes on outside the nucleus but nuclear change doesn't).
Neutrinos can also influence the rate of reverse electron capture (https://iopscience.iop.org/article/10.1086/305343/fulltext/34468.text.html)
And, obviously, nuclear fission chain reactions such as those crucial (critical?!? sorry...) to atomic bombs, show that nuclear decay can be influenced by the environment.
That said, because of the great energies typically involved in nuclear reactions, I don't think that most changes in pressures and temperatures that could be highly influential for chemical reactions would do much for nuclear ones. But the stability of neutrons in neutron stars is significantly greater than for lonely neutrons—and I think it might be due to the insane pressures within a neutron star that favor single neutrons over proton/electron pairs (and neutrinos!).
I think the case of electron capture in 74Be+ vs 74Be can be explained by looking at how much electron density is within the cross-section of the electron capture of the nucleus. However, I am not so sure that adding positive ligands around an atom would significantly reduce α decay. The electric field at the "surface" of the nucleus will be almost entirely dominated by the protons within the nucleus For example, a 210Po nucleus, which typically undergoes α-decay with a half-life of about 140 days, has 84 protons in a sphere with a radius on the order of a few femtometers—adding a handful of singly (or doubly) positively charged ligands at a radius of 150 picometers (almost 1 million times as far away) likely won't change much. In terms of the electric potential at the nucleus, I think this will be a similar story, but might have a greater effect (but, I would expect it to be the opposite of your prediction—more positive ligands leads to a more positive potential at the nucleus, making it more favorable for the nuclear charge to decrease).