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.
Wiki mentions that alpha decay is well modelled as a quantum tunnelling event, see also Geiger-Nuttall law.
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:
- youtu.be/_f8zeEI0oys?t=796 George Gamow and Edward Condon proposed the quantum tunnelling explanation
- youtu.be/_f8zeEI0oys?t=1725 worked out example that predicts the half-life of polonium-210 based on its emission energy
They are stopped by:Therefore, alpha emitters are not too dangerous unless ingested.
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Alpha decay is radioactive decay emitting an alpha particle, a bound group of two protons and two neutrons. The daughter atomic nucleus therefore has atomic number reduced by two and mass number reduced by four.
A released alpha particle must escape the Coulomb barrier outside the short-range nuclear attraction. Quantum tunnelling explains how emission can occur even when the alpha particle's measured kinetic energy is below the barrier's classical height. The strong sensitivity of tunnelling to energy helps explain widely differing decay lifetimes.
For a specified transition from a parent initially at rest, the alpha particle and daughter share the available Q value through two-body recoil. Different daughter nuclear energy levels can produce distinct alpha lines. Their line energies and populations provide information beyond simply counting the sample's total radioactive activity.
Alpha decay is a type of radioactive decay in which an unstable atomic nucleus releases an alpha particle and transforms into a lighter nucleus. An alpha particle consists of two protons and two neutrons, essentially making it identical to a helium nucleus. During alpha decay, the original nucleus (parent nucleus) loses these two protons and two neutrons, causing the atomic number to decrease by 2 and the mass number to decrease by 4.