Effectively infinite thickness

{
  "id": "MLC-T-CHM-003595",
  "term": "Effectively infinite thickness",
  "field": "Chemistry",
  "definition": "The condition in X-ray fluorescence and related X-ray spectroscopy in which a sample is thick enough that the intensity of a characteristic line no longer changes measurably when the thickness increases further, because radiation from deeper layers is absorbed before it leaves the sample. The thickness needed depends on the line energy and the matrix, from a few micrometres for soft X-rays in heavy matrices to centimetres for hard X-rays in light matrices.",
  "subject": "Analytical Chemistry",
  "see_also": [
    "X-ray spectroscopy",
    "bulk sample",
    "gram"
  ],
  "references": [
    "Orange Book, 2nd ed., p. 182 (https://media.iupac.org/publications/analytical_compendium/)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/effectively-infinite-thickness/"
}