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When produced in standard alpha radioactive decay, alpha particles generally have a kinetic energy of about 5 MeV and a velocity in the vicinity of 4% of the speed of light. They are a highly ionizing form of particle radiation , with low penetration depth (stopped by a few centimetres of air , or by the skin ).
Ionizing subatomic particles include alpha particles, beta particles, and neutrons. These particles are created by radioactive decay , and almost all are energetic enough to ionize. There are also secondary cosmic particles produced after cosmic rays interact with Earth's atmosphere, including muons , mesons , and positrons .
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.
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 ...
These particles continue to decay, emitting alpha particles, which can damage cells in the lung tissue. [11] The death of Marie Curie at age 66 from aplastic anemia was probably caused by prolonged exposure to high doses of ionizing radiation, but it is not clear if this was due to alpha radiation or X-rays.
Particle radiation can be emitted by an unstable atomic nucleus (via radioactive decay), or it can be produced from some other kind of nuclear reaction. Many types of particles may be emitted: protons and other hydrogen nuclei stripped of their electrons; positively charged alpha particles (α), equivalent to a helium-4 nucleus
Beta particles are electrons or positrons and can travel farther than alpha particles in air. They are in the middle of the scale in terms of ionizing potential and penetrating power, being stopped by a few millimeters of plastic. This radiation is a small portion of the total emitted during radium 226 decay.
The picture shows how the stopping power of 5.49 MeV alpha particles increases while the particle traverses air, until it reaches the maximum. This particular energy corresponds to that of the alpha particle radiation from naturally radioactive gas radon (222 Rn) which is present in the air in minute amounts.