Gas-Phase Models for Catalysis:  Alkane Activation and Olefin Epoxidation by the Triatomic Cation Ag2O+

The homogeneous gas phase models of relaxation kinetics (application of the gas phase effective coefficients to represent surface losses) are applied for the study of charged and neutral active particles decay in neon afterglow. The experimental data obtained by the breakdown time delay measurements as a function of the relaxation time td (?) (memory curve) is modeled in early, as well as in late afterglow. The number density decay of metastable states can explain neither the early, nor the late afterglow kinetics (memory effect), because their effective lifetimes are of the order of milliseconds and are determined by numerous collision quenching processes. The afterglow kinetics up to hundreds of milliseconds is dominated by the decay of molecular neon Ne2 + and nitrogen ions N2 + (present as impurities) and the approximate value of N2 + ambipolar diffusion coefficient is determined. After the charged particle decay, the secondary emitted electrons from the surface catalyzed excitation of nitrogen atoms on the cathode determine the breakdown time delay down to the cosmic rays and natural radioactivity level. Due to the neglecting of number density spatial profiles, the homogeneous gas phase models give only the approximate values of the corresponding coefficients, but reproduce correctly other characteristics of afterglow kinetics from simple fits to the experimental data.

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Understanding Energy Transfer in Gas–Surface Collisions from Gas-Phase Models

The Journal of Physical Chemistry C ◽

10.1021/jp4117134 ◽

2014 ◽

Vol 118 (5) ◽

pp. 2609-2621 ◽

Cited By ~ 10

Author(s):

Juan J. Nogueira ◽

William L. Hase ◽

Emilio Martínez-Núñez

Keyword(s):

Energy Transfer ◽

Gas Phase ◽

Phase Models

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Radical loss in the atmosphere from Cu-Fe redox coupling in aerosols

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-27053-2012 ◽

2012 ◽

Vol 12 (10) ◽

pp. 27053-27076 ◽

Cited By ~ 7

Author(s):

J. Mao ◽

S. Fan ◽

D. J. Jacob ◽

K. R. Travis

Keyword(s):

Gas Phase ◽

Atmospheric Chemistry ◽

Tropospheric Ozone ◽

Catalytic Mechanism ◽

Transition Metal Ions ◽

Hydroperoxyl Radical ◽

Model Predictions ◽

Atmospheric Observations ◽

Gas Standard ◽

Phase Models

Abstract. The hydroperoxyl radical (HO2) is a major precursor of OH and tropospheric ozone. OH is the main atmospheric oxidant, while tropospheric ozone is an important surface pollutant and greenhouse gas. Standard gas-phase models for atmospheric chemistry tend to overestimate observed HO2 concentrations, and this has been tentatively attributed to heterogeneous uptake by aerosol particles. It is generally assumed that HO2 uptake by aerosol involve conversion to H2O2, but this is of limited efficacy as an HO2 sink because H2O2 can photolyze to regenerate OH and from there HO2. Joint atmospheric observations of HO2 and H2O2 suggest that HO2 uptake by aerosols may in fact not produce H2O2. Here we propose a catalytic mechanism involving coupling of the transition metal ions (TMI) Cu(I)/Cu(II) and Fe(II)/Fe(III) to rapidly convert HO2 to H2O in aerosols. The implied HO2 uptake significantly affects global model predictions of tropospheric OH, ozone, and other species, improving comparisons to observations, and may have a major and previously unrecognized impact on atmospheric oxidant chemistry.

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Nitrogen Sulfide (NS) in Star Forming Regions

Symposium - International Astronomical Union ◽

10.1017/s0074180900090070 ◽

1992 ◽

Vol 150 ◽

pp. 227-230 ◽

Cited By ~ 1

Author(s):

Douglas Mcgonagle ◽

William Irvine ◽

Young Minh

Keyword(s):

Star Formation ◽

Gas Phase ◽

Molecular Clouds ◽

Massive Star ◽

Interstellar Molecules ◽

Good Test ◽

Star Forming ◽

Star Forming Regions ◽

Phase Models ◽

Sulfur Containing

Gas phase models of ion molecule chemistry have been rather successful in matching the observed abundances of small interstellar molecules containing carbon, hydrogen, and oxygen. However, the situation is somewhat less clear for nitrogen-containing species, partly because the important initiating reaction N+ + H2 is slightly endothermic; and for sulfur-containing molecules, where it remains uncertain whether it is necessary to invoke surface reactions on grains to match the observed abundances. As a relatively simple species, the abundance of nitrogen sulfide should provide a good test of the models of the coupled chemistry of nitrogen and sulfur. Until very recently only two molecules containing both these elements were known in the interstellar medium, NS and HNCS, and both have been observed only in Sgr B2. We have therefore undertaken a survey for interstellar NS in Galactic molecular clouds using the FCRAO 14-meter telescope. The 2Π1/2, J = 5/2 → 3/2, transition has in fact been detected in many regions of massive star formation (see table).

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