OPTICALLY PUMPED CHEMILUMINESCENCE OF INDOLE-3-ACETIC-ACID

Optically pumped chemiluminescence of indole-3-acetic acid (IAA) was o bserved and studied. Rose Bengal (RB) was used as a photosensitizer. L ong-lived chemiluminescence (CL) appeared after irradiation of the IAA /RB reaction mixture by monochromatic light at 550 nm (the maximum of RB absorption) or by visible light. The CL spectrum had a maximum at 4 80 nm. The kinetics of the CL decay were single exponential. Single-ex ponential kinetics were characterized by two experimentally measured v alues: initial CL intensity and exponential lifetime of the CL decay. We studied the influence of five parameters: (1) the rate of irradiati on fluence, (2) the time of irradiation, (3) RB concentration, (4) IAA concentration and (5) buffer pH on the initial CL intensity and the C L lifetime. Initial CL intensity was proportional to the rate of irrad iation fluence and the concentration of RB. Saturation was observed in dependencies of initial CL intensity on the time of irradiation, the concentration of IAA and the buffer pH. The lifetime of the CL decay d ecreased with increasing pH and did not depend on the other four param eters. The mechanism explaining the experimental results was suggested and detailed kinetic analysis was performed to prove the proposed mec hanism. Quantum yield of the CL and five rate constants that are invol ved in the mechanism were determined.