Positively charged particles composed of two protons and two neutrons, i.e., helium nuclei, emitted during disintegration of very heavy isotopes; a beam of alpha particles or an alpha ray has very strong ionizing power, but weak penetrability.
A particle, identical to the nucleus of a helium atom, emitted by some radioactive materials.
A particle emitted from an atom following one form of radioactive decay. An alpha particle consists of two protons and two neutrons.
A charged particle emitted from a radioactive substance made up of a helium nucleus consisting of two protons and two electrons. The particle has very low penetrability, but an extremely high linear energy transfer.
The nucleus of a helium atom, which carries a positive charge and consists of two protons and two neutrons. Alpha particles are emitted spontaneously during the radioactive decay of certain substances as they undergo a transformation from one element to another.