MECHANISM OF OXYGEN (P-3) ATOM REACTION WITH TETRAFLUOROETHYLENE AND QUENCHING PROCESSES OF THE EMISSION OF CF2(B-3(1)

The reaction mechanism of ground state oxygen atoms with tetrafluoroethylene was elucidated in terms of kinetic analysis of the emission from CF2(3B1) produced in N2O-Hg-C2F4 mixtures on irradiation with a low-pressure mercury lamp. The exciting lamp was operated in a repetitive pulse mode, and the emission was monitored by means of a boxcar mode photon-counting system to determine its time profile after excitation. The emission intensity was found to be proportional to the exciting light intensity. The emission showed a first-order decay soon after an initial rise. The decay constant was proportional to the pressure of C2F4, from which the bimolecular rate constant for the reaction of O(3P) with C2F4 was derived to be (7.1 ± 0.2) × 10-13 cm3 molecule-1 s-1 (293-303 K). The time profile of the emission could be satisfactorily reproduced in terms of a proposed reaction model, where the principal reaction produced CF2(3B1) and CF2O. Assuming that no long-lived intermediate was formed in the above elementary reaction, the radiative decay constant of CF2(3B1) multiplied by its quantum yield was estimated to be around 1 s-1. The quenching rate constant by O2 was 4.1 × 10-12 (±20%) cm3 molecule-1 s-1; relative quenching rates by O2, Xe, NO, C3H8, i-C4H10, C2H4, C3H6, and C2F4 were 1:≤0.017:≥12:0.16:0.45:2.2:5.4:0.1. If some long-lived intermediates were formed, the above quantities should be interpreted differently. Systems with C2F3H and with NO in place of C2F4 were also investigated. © 1979 American Chemical Society.