Chemiluminescence of Cigarette Smoke: Salient Features of the Phenomenon

The study disclosed herein provides for the first time a detailed experimental support for the general mechanism of the cigarette‐smoke‐derived chemiluminescence, as an example par excellence of the excited‐state generation in a chemically complex aerosol medium. The mechanism involves chemiexcitation in a unimolecular transformation of the smoke‐borne free radical species. However, the concentration of these radicals, [r∙], obeys a bimolecular (second‐order) kinetics and depends on a particulate‐phase content (total particulate matter, TPM) of the cigarette smoke. The decrease in [r∙] with increasing the TPM amount manifests radical‐scavenging propensity of the smoke particulate phase. Astonishingly, no energy transfer takes place from the primary excited light‐emitting species to luminophoric molecules abundant in the smoke. The reported results build up fundamentals of a facile chemiluminescence assay for free radical properties of the smoke. The experimental approaches developed for this study are of general scope and may be used for mechanistic elucidation of the excited‐state generation in chemical systems and environments of an arbitrary complexity. Chemiluminescence of cigarette smoke comes about from an excited‐state generation in a unimolecular transformation of the smoke‐borne free radical species, while a predominant disappearance of the latter is bimolecular. The particulate phase (tar) of the smoke exhibits remarkable antiradical propensity manifested by the decrease in the α value upon increasing the smoke tar content.