In XRF analysis, what is produced when the sample is bombarded by X-rays?

• A. Only characteristic x-rays
• B. Gamma rays
• C. A shower of electrons, Bremsstrahlung x-rays, and characteristic x-rays, including backscattered x-rays
• D. Neutrons

Answer: (C)

When X-rays hit a sample in XRF, several interactions occur that produce a mix of radiation and particles. The atoms can eject inner-shell electrons (photoelectric effect), and as the atom relaxes, it emits characteristic X-rays that reveal the elements present. The ejected electrons and other secondary processes also generate Bremsstrahlung, a continuous X-ray spectrum as electrons decelerate in the material. Scattering of photons and electrons adds backscattered X-rays, which travel toward the detector. So the overall output is a shower of electrons, Bremsstrahlung X-rays, and characteristic X-rays, including backscattered X-rays. This combination explains both the characteristic peaks used for analysis and the background radiation seen in XRF spectra.