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What is radioluminescence and how do radioactive particles cause it?

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energy levels of a luminescent centre — luminescence Figure 1: Energy levels of a luminescent centre (see text).

Radioluminescence is a form of luminescence that occurs when a material is excited to emit light through exposure to radioactive substances.12

Radioactive elements emit high-energy particles and radiation, including alpha particles, electrons, and gamma rays. When these radioactive particles strike an appropriate material—typically a crystal phosphor—they transfer energy to the material's atoms. This excitation process causes the phosphor to emit visible light.1

This phenomenon is utilized in self-luminous paints found on watch dials and other instruments, which combine a phosphor with a radioactive source like tritium or radium. Historically, the impact of alpha particles on crystal phosphors was used by Ernest Rutherford to demonstrate the existence of the atomic nucleus. Additionally, the aurora borealis serves as a natural example, where particles from the Sun interact with the Earth's upper atmosphere to produce light.1