Effects of a single water molecule on the OH + H2O2 reaction

The catalytic effect of water, water dimers and water trimers on H2S +3O2formation by the HO2+ HS reaction under tropospheric conditions

Catalyst X (X = H₂O, (H₂O)₂and (H₂O)₃) is incorporated into the channel of H₂S +³O₂formation and the catalytic effect of water, water dimers and water trimers is mainly taken from the contribution of a single water vapor molecule.

Can a single water molecule really affect the HO2 + NO2 hydrogen abstraction reaction under tropospheric conditions?

During the HO₂ + NO₂ reaction, hydrogen abstraction by a single water molecule not only changes the branching ratio of HONO and HNO₂ formation, but also introduces different features with respect to the naked reaction, acting as a reactant that leads to the production of HNO₃.

Formation of hydrogen polyoxides as constituents of peroxy radical condensate upon low-temperature interaction of hydrogen atoms with liquid ozone

The composition of low-temperature condensates obtained by the reaction of hydrogen atoms with liquid ozone has been determined from the Raman spectra and data on the molar ratio of O2 to H2O2 in the decomposition products. The main constituents are hydrogen tetroxide H2O4, trioxide H2O3, and peroxide H2O2 in comparable amounts and also water H2O. The mechanism and quantitative kinetic model of their formation have been proposed. H2O4, H2O3, and H2O2 are formed in the diffusion-controlled reactions between OH and HO2 in the liquid ozone layer and stabilized by transfer to the solid phase. OH and HO2 radicals are generated via a sequence of the reactions initiated by the interaction H + O3(liq). The model adequately reproduces the properties of the real condensates.

Water formation at low temperatures by surface O2 hydrogenation III: Monte Carlo simulation

Water is the most abundant molecule found in interstellar icy mantles. In space it is thought to be efficiently formed on the surfaces of dust grains through successive hydrogenation of O, O2 and O3. The underlying physico-chemical mechanisms have been studied experimentally in the past decade and in this paper we extend this work theoretically, using Continuous-Time Random-Walk Monte Carlo simulations to disentangle the different processes at play during hydrogenation of molecular oxygen. CTRW-MC offers a kinetic approach to compare simulated surface abundances of different species to the experimental values. For this purpose, the results of four key experiments-sequential hydrogenation as well as co-deposition experiments at 15 and 25 K-are selected that serve as a reference throughout the modeling stage. The aim is to reproduce all four experiments with a single set of parameters. Input for the simulations consists of binding energies as well as reaction barriers (activation energies). In order to understand the influence of the parameters separately, we vary a single process rate at a time. Our main findings are: (i) The key reactions for the hydrogenation route starting from O2 are H + O2, H + HO2, OH + OH, H + H2O2, H + OH. (ii) The relatively high experimental abundance of H2O2 is due to its slow destruction. (iii) The large consumption of O2 at a temperature of 25 K is due to a high hydrogen diffusion rate. (iv) The diffusion of radicals plays an important role in the full reaction network. The resulting set of 'best fit' parameters is presented and discussed for use in future astrochemical modeling.