When this complex absorbs light, it immediately returns to the fundamental state without emitting any photons. Static quenching involves the interaction of the ground Figure 1: Stern-Volmer plot for fluorescence quenching. Fig: Quenching of quinine fluorescence in presence of chloride ions QUENCHING It is a process that decrease the fluorescence intensity of given substance. Rational design of novel photoinduced electron transfer type fluorescent probes for sodium cation. [3] found that photo-induced electron transfer plays an important role in this type of quenching. The order of quenching efficiency is G