Alpha particle (α (or He²⁺, ⁴₂He²⁺))

Alpha radiation consists of alpha particles, which are the nuclei of helium-4 atoms (two protons and two neutrons), highly ionizing and energetic but with very low penetration—they are stopped by a few centimeters of air or by the outer layer of human skin. Internally, alpha emitters are hazardous: if radioactive material emitting alpha particles is inhaled, ingested, or enters a wound, severe, localized DNA and tissue damage can result, raising the risk for cancer and other pathology. These properties also make alpha emitters promising for targeted cancer therapy, where their destructive power is directed specifically to tumor cells (targeted alpha therapy).

Other names

alpha particlealpha raysα radiationhelium-4 nucleusHe²⁺

Induces dense ionization and double-strand DNA breaks (cytotoxicity) when internalized into tissues. High linear energy transfer (LET) leads to complex/catastrophic DNA lesions, immune activation.