Sciencemadness Discussion Board

Why Gold (Au-197) doesn't decay with alpha particle?

radioboy - 14-4-2016 at 03:08

What conditions are neccessary for some element to decay? I've been watching these so-called q-values (energies) for each isotope and found values for neutron separation energy, proton separation energy, energy of beta and alpha and mixed decays... Shouldn't some element decay if it has positive energy for something (as Au-197) has for alpha decay? Here is link:

Joe Skulan - 15-4-2016 at 09:39

All nuclei heavier than 56Fe (except 62Ni) are thermodynamically unstable and might be expected to decay given long enough, just as, given long enough, all lighter nuclei might be expected to fuse into 56Fe or 62Ni. But just as in regular chemistry in nuclear chemistry there are kinetic inhibitions to what is thermodynamically favored that control whether a process actually will happen, and at what rate. Kinetic effects tend to be idiosyncratic and difficult to model. There is no master theory of radioactive decay that allows us to accurately predict the half lives of nuclei. That needs to be worked out empirically. Alpha decay is especially problematic. Alpha decay is not possible under classical mechanics because it is impossible for an alpha particle to get the kinetic energy it needs to overcome the binding forces of the nucleus and leave it. It's like trying to get out of a glass phone booth with a baseball bat-- you don't have enough room to swing hard enough to break the glass. Alpha decay requires quantum tunneling.