Definition of quantum yield

1. The number of defined events which occur per photon absorbed by the system. The integral quantum yield is

   

   For a photochemical reaction,

   

   The differential quantum yield is

   

   where d[X]/dt is the rate of change of the amount of (substance) concentration of a measurable quantity, and n the amount of photons (mol or its equivalent einsteins) absorbed per unit time. can be used for photophysical processes or photochemical reactions. IUPAC PHOTOCHEMICAL GLOSSARY (1992).