Which statement correctly identifies background sources that include scattering from the sample matrix?

• A. Compton and Rayleigh scattering from the sample matrix.
• B. Bremsstrahlung from the X-ray tube.
• C. Ambient radiation.
• D. All of the above.

Answer: (A)

In XRF, the background seen in the spectrum includes signals created when X-rays interact with the atoms in the sample itself. The two relevant scattering processes inside the sample matrix are Compton scattering (an inelastic interaction where photons lose energy to electrons) and Rayleigh scattering (elastic scattering where photons change direction but keep their energy). Both of these within the sample contribute to a broad, continuous background beneath the characteristic peaks as scattered photons appear at many energies.

Bremsstrahlung, on the other hand, comes from the X-ray tube as a continuous spectrum produced by decelerating electrons; it’s not a result of scattering within the sample matrix. Ambient radiation is external environmental radiation, not related to the sample’s scattering processes. Therefore, the statement that correctly identifies background sources that include scattering from the sample matrix is the one listing Compton and Rayleigh scattering from the sample matrix.