X-ray-Induced Fluorescent Emission

Why bombarding an atom with X-rays knocks out a core electron and triggers the emission of a second, characteristic X-ray as the atom relaxes, identifying that specific element.

References

• Criss, J.W., Birks, L.S. "Calculation of Fluorescence." Analytical Chemistry 40, no. 7 (1968): 1080–1086.