Initiation • Oxygen raised to excited state (1O2) by light energy – called photooxidation – promoted by pigments called sensitizers sens sens* sens* + 3O2 sens + 1O2 – e.g. chlorophyll, riboflavin lightInitiation • Oxygen raised to excited state (1O2) by light energy – called photooxidation – promoted by pigments called sensitizers sens sens* sens* + 3O2 sens + 1O2 – e.g. chlorophyll, riboflavin light