, Z50

of a photochromic system
https://doi.org/10.1351/goldbook.ZT07501
Number of cycles required to reduce by 50% the initial absorbance of the coloured form of a photochromic compound at a specific wavelength.
Source:
PAC, 2007, 79, 293. (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 441 [Terms] [Paper]