The Participation of Excited Oxygen in a Chemiluminescent Reaction†

Some properties of silica gel adsorbates of the acridine dye, acriflavine, have been investigated in the presence of oxygen and inert gases. In addition to its well‐known quenching of phosphorescence, oxygen stimulates additional luminescence, a chemi‐luminescence, at high concentrations of the dye triplet state molecules. The dependence of the chemiluminescence and of oxygen consumption on experimental variables have been explained in terms of a mechanism in which O2*, formed in the act of quenching of one photoexcited dye molecule by oxygen, diffuses to a second excited dye molecule where it may cause an irreversible oxidation. This oxidation may be accompanied by chemi‐luminescence. Both the intensity of the chemiluminescence and the rate of oxygen consumption were found to be reduced specifically by inert gases having vibrational frequencies close to the vibrational spacings of oxygen. It was concluded that O2* is probably vibrationally excited oxygen and that it is deactivated principally by resonance energy transfer processes.