KINETICS OF DISSOCIATIVE RECOMBINATION OF H3O-ELECTRONS IN PREMIXED FLAMES( IONS WITH FREE)

Mass-spectrometric measurements have been made of the axial concentrat ions of the positive ions along premixed, flat flames of H-2, O-2 and N-2, either with or without trace amounts of acetylene added to the un burned gases. In each case the principal positive ion is H3O+, whereas the sole negatively charged species is the free electron. The main re action governing the concentration of H3O+ in the burned gases of such a flame without acetylene added is: H3O+ + e(-) reversible arrow H H + OH However, with acetylene in the burner supplies, chemi-ionisatio n in a flame's reaction zone produces amounts of H3O+ far in excess of those for equilibrium. Thus H3O+ disappears via the forward step of ( 1) in the burned gases, enabling its rate constant to be measured betw een 1820 and 2400 K. This ion-electron recombination coefficient was f ound to vary with temperature, T, according to: k(1) = (3.6 +/- 0.5) T --21+0.7 ion(-1) ml s(-1). The magnitude of k(1) at 2000 K is (4.2 +/- 0.6) x 10(-7) ion(-1) ml s(-1): theoretical considerations indicate t hat k(1) is proportional to T--1.5.