Scientists working at the Relativistic Heavy Ion Collider have announced that they have detected the heaviest known particle of antimatter to date - an anti-helium nucleus, or anti-alpha particle ...

Demonstration of alpha particle confinement capability in helical fusion plasmas. National Institutes of Natural Sciences. Journal Nuclear Fusion DOI ...

When a radioactive atom emits an alpha particle the mass number decreases by four and the atomic number drops by two. Here is the equation for the alpha decay of radon-219 into polonium.