Heterogeneous quenching of O-2((1)Delta(g)) molecules in H-2 : O-2 mixtures

Quenching of O-2((1)Delta(g)) molecules both in the gas phase and on a reac tor surface has been investigated in binary mixtures of hydrogen and oxygen by using the fast-flow quartz reactor and infrared emission spectroscopy. Rate constants of the O-2((1)Delta(g)) deactivation by H-2 and O-2 at room temperature have been determined to be (1.5 +/- 0.5) 10(-18) cm(3) s(-1) an d (1.6 +/- 0.2) 10(-18) cm(3) s(-1), respectively. Heterogeneous quenching of O-2((1)Delta(g)) on quartz walls has been studied both in pure oxygen an d in H-2:O2 mixtures. A model of O-2((1)Delta(g)) heterogeneous quenching i n binary mixtures has been developed and has allowed us to describe all obs erved features of singlet oxygen kinetics. Active surface complexes formed by 'chemisorbed' atomic oxygen and 'physadsorbed' molecules of O-2 and H-2 are assumed to be responsible for the O-2((1)Delta(g)) heterogeneous deacti vation. It has been shown that the higher rate of O-2((1)Delta(g)) quenchin g in pure oxygen is connected with a quasi-resonant transfer of the O-2((1) Delta(g)) electronic excitation to physadsorbed oxygen molecules. The obser ved effect of the wall passivation by hydrogen is conditioned both by the a bsence of the similar resonance in the hydrogen surface complex and by the higher bond energy of H-2 in this complex. Bond energies of O-2 (3750 +/- 4 50 K) and H-2 (4050 +/- 450 K) in the surface complexes have been determine d from the model parameters by fitting calculations to experimental results .