Mechanism of dark decomposition of iodine donor in the active medium of a pulsed chemical oxygen — iodine laser

A scheme is proposed that describes the dark decomposition of iodide – the donor of iodine – and the relaxation of singlet oxygen in the chlorine-containing active medium of a pulsed chemical oxygen – iodine laser (COIL). For typical compositions of the active media of pulsed COILs utilising CH₃I molecules as iodine donors, a branching chain reaction of the CH₃I decomposition accompanied by the efficient dissipation of singlet oxygen is shown to develop even at the stage of filling the active volume. In the active media with CF₃I as the donor, a similar chain reaction is retarded due to the decay of CF₃ radicals upon recombination with oxygen. The validity of this mechanism is confirmed by a rather good agreement between the results of calculations and the available experimental data. The chain decomposition of alkyliodides accompanied by an avalanche production of iodine atoms represents a new way of efficient chemical production of iodine for a COIL.