Z₅₀

{
  "id": "MLC-T-CHM-012790",
  "term": "Z₅₀",
  "field": "Chemistry",
  "definition": "A measure of the fatigue resistance of a photochromic compound, given as the number of colouring and bleaching cycles after which the absorbance of the coloured form at a chosen wavelength has fallen to half its initial value. A larger Z50 means a more durable photochromic system. Diarylethenes are known for particularly high values, surviving many thousands of cycles, whereas many spiropyrans fatigue after far fewer.",
  "subject": "Organic and Biomolecular Chemistry",
  "see_also": [
    "absorbance",
    "wavelength"
  ],
  "references": [
    "PAC, 2007, 79, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 441 (https://doi.org/10.1351/pac200779030293)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/z50/"
}