alpha (alpha) particle
(redirected from alpha a particle)al·pha (α) par·ti·cle
(al'fă pahr'ti-kĕl)A particle consisting of two neutrons and two protons, with a positive charge (2e+); emitted energetically from the nuclei of unstable isotopes of high atomic number (elements of mass number from 82 up); identical to the helium nucleus.