Most of the helium in the Earth's atmosphere comes from alpha decay, since helium is lighter than air and naturally escapes out out of the atmosphere.
As a result of that law, alpha particles have relatively little energy variation around 5 MeV or a speed of about 5% of the speed of light for any element, because the energy is inversely exponentially proportional to half-life. This is because:
- if the energy is much larger, decay is very fast and we don't have time to study the isotope
- if the energy is much smaller, decay is very rare and we don't have enough events to observe at all
Caused by weak interaction TODO why/how.
Most commonly known as a byproduct radioactive decay.
Gamma rays are pretty cool as they give us insight into the energy levels/different configurations of the nucleus.