Self-absorption in XRF is most pronounced under which condition?

Prepare for the NRCan XRF Analyzer Operator Certification Level 1 Exam. Utilize flashcards and multiple-choice questions with detailed hints and explanations. Ready yourself for a successful examination!

Self-absorption in XRF happens when the X-rays produced inside the sample have to travel through the sample material to reach the detector, and the material itself absorbs some of those photons. This effect is strongest when the sample is thick or dense because the photons have a longer path through material and thus a higher chance of being absorbed before escaping. The attenuation depends on the X-ray energy, so lower-energy (lighter element) lines are absorbed more readily than higher-energy lines, making the effect more evident for those lines. Because of this, the detected peak intensities drop as depth increases, and quantitative results can be biased if not corrected. This phenomenon reduces peak signals, rather than increasing them, and it is especially pronounced in thick samples or when the take-off angle increases the photon path length.