Decay Kinetics for Isotropic Radicals in Carbonates

Electron spin resonance (ESR) signals of isotropic CO3- and CO2- radicals are frequently encountered in irradiated carbonates. These centers are thought to be surrounded by water molecules. Until now, their thermal annealing curves were generally described in terms of several simultaneous first order-reaction kinetics. A reinvestigation of some recent data allows us to conclude that, at sufficiently low temperatures, a second-order equal concentration dispersive kinetics suffices to reproduce satisfactorily the decays. When the annealing temperature approaches that of the water departure, this mechanism becomes inadequate. Mixed first-and second-order classical reaction and 1.5-order reaction kinetics have then been tentatively used.