Alpha decay helium produced on Earth is the result of the alpha decay of underground deposits of minerals containing uranium or thorium. The helium is brought to the surface as a by-product of natural gas production. Alpha particles were first described in the investigations of radioactivity by Ernest Rutherford in 1899, and by 1907 they were identified as He ions. By 1928, George Gamow had solved the theory of alpha decay via tunneling. The alpha particle is trapped in a potential well by the nucleus. Classically, it is forbidden to escape, but according to the (then) newly discovered principles of quantum mechanics,
Alpha particle glass wall of an evacuated tube, thus capturing a large number of the hypothesized helium ions inside the tube. They then caused an electric spark inside the tube, which provided a shower of electrons that were taken up by the ions to form neutral atoms of a gas. Subsequent study of the spectra of the resulting gas showed that it was helium and that the alpha particles were indeed the hypothesized helium ions. Because alpha particles occur naturally, but can have energy high enough to participate in a nuclear reaction, study of them led to much early knowledge of nuclear