Internal Conversion:radiationless transition to lower state when vibrational energy levels "match" External Conversion:radiationless transition to lower state by collisional deactivation Intersystem Crossing:transition with spin change (e.g.S to T) Fluorescence emission not involving spin change (e.g. S→S,T-→T),efficient,short-lived<l0-5s Phosphorescence emission involving spin change (T->S), improbable,long-lived >10-5 s Dissociation excitation to vibrational state with enough energy to break bond Predissociation relaxation to state with enough energy to break bond CEM 333 page 5.6Internal Conversion: radiationless transition to lower state when vibrational energy levels "match" External Conversion: radiationless transition to lower state by collisional deactivation Intersystem Crossing: transition with spin change (e.g. S to T) Fluorescence: emission not involving spin change (e.g. S®S, T®T), efficient, short-lived <10-5 s Phosphorescence: emission involving spin change (T®S), improbable, long-lived >10-5 s Dissociation: excitation to vibrational state with enough energy to break bond Predissociation: relaxation to state with enough energy to break bond CEM 333 page 5.6