Helium nucleus

WordNet Word definitions in WordNet
n. a positively charged particle that is the nucleus of the helium atom; emitted from natural or radioactive isotopes

Wikipedia Word definitions in Wikipedia
Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus . They are generally produced in the process of alpha decay , but may also be produced in other ways. Alpha particles are named after the ...

Wiktionary Word definitions in Wiktionary
n. A positively charged nucleus of a helium-4 atom (consisting of two protons and two neutrons), emitted as a consequence of radioactivity; α-particle

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
alpha particle \alpha particle\ (Physics & Chem.) a particle emitted at high velocity from certain radioactive substances. It is identical to the helium nucleus, consisting of two protons and two neutrons. Rays of such particles are called alpha rays .