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Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. [5] They are generally produced in the process of alpha decay but may also be produced in other ways. Alpha particles are named after the first letter in the Greek alphabet, α.
Passing alpha particles through a very thin glass window and trapping them in a discharge tube allowed researchers to study the emission spectrum of the captured particles, and ultimately proved that alpha particles are helium nuclei. Other experiments showed beta radiation, resulting from decay and cathode rays, were high-speed electrons.
Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or "decays" into a different atomic nucleus, with a mass number that is reduced by four and an atomic number that is reduced by two.
Alpha radiation is dangerous when alpha-emitting radioisotopes are inhaled or ingested (breathed or swallowed). This brings the radioisotope close enough to sensitive live tissue for the alpha radiation to damage cells. Per unit of energy, alpha particles are at least 20 times more effective at cell-damage than gamma rays and X-rays.
210 Po is an alpha emitter that has a half-life of 138.376 days; [1] it decays directly to stable 206 Pb. The majority of the time, 210 Po decays by emission of an alpha particle only, not by emission of an alpha particle and a gamma ray; about one in 100,000 decays results in the emission of a gamma ray. [10]
Jiří Hála claims in his textbook "Radioactivity, Ionizing Radiation and Nuclear Energy" [6] that cattle only pass a minority of the strontium, caesium, plutonium and americium they ingest to the humans who consume milk and meat. Using milk as an example, if the cow has a daily intake of 1000 Bq of the preceding isotopes then the milk will ...
The global average exposure of humans to ionizing radiation is about 3 mSv (0.3 rem) per year, 80% of which comes from nature. The remaining 20% results from exposure to human-made radiation sources, primarily from medical imaging. Average human-made exposure is much higher in developed countries, mostly due to CT scans and nuclear medicine.
Today some of these formerly extinct isotopes are again in existence as they have been manufactured. Thus they again take their places in the chain: plutonium-239, used in nuclear weapons, is the major example, decaying to uranium-235 via alpha emission with a half-life 24,500 years.