特征X射线又称为二次特征X射线或荧光X射线。光子激发原子所发生的激发和辐射过程称为光电效应，被击出的电子称为光电子。 ---**Diagram Description:** The diagram shows a Bohr model of an atom. At the center is the nucleus, labeled "Mg" (Magnesium). Concentric circles represent electron shells, labeled K, L, and M from inner to outer. Electrons are depicted as colored dots (some gray, some green, one blue). An arrow labeled "入射X射线" (Incident X-ray) points towards an electron in the K shell (gray dot). An arrow points away from this K shell electron towards an outer shell electron (green dot in L shell), and another arrow points outwards from the atom starting from an electron in the M shell (blue dot). The outgoing arrow from the M shell electron is labeled as an emitted electron, while the arrow between the K and L shells likely indicates an electron dropping from L to K shell after the K shell electron is ejected. **Text Extraction:** 入射X射线 Mg K L M 特征X射线又称为二次特征X射线或荧光X射线。 光子激发原子所发生的激发和辐射过程称为光电效应，被击出的电子称为光电子。