Wavelength dependence of the quantum efficiencies of the primary processes in formaldehyde photolysis at 25°C

Horowitz, A.; Calvert, Jack G.

doi:10.1002/kin.550100803

Cited by 56 publications

(41 citation statements)

References 22 publications

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“…(7). and Warneck, 1979;Horowitz and Calvert, 1978;Moortgat et al, 1983). The present fit and the theoretical curve from Troe (2007) are given by full lines.…”

Section: The Quantum Yield Of the Molecular Channelmentioning

confidence: 97%

“…Most publications on the formaldehyde photolysis deal with the radical channel (R3) -notably: Horowitz and Calvert (1978), Moortgat et al (1983), Smith et al (2002), Gorrotxategi Carbajo et al (2008, and Tatum Ernest et Figure 1. Spectrum of the quantum yield of the radical channel of the CH 2 O photolysis at room temperature.…”

Section: The Quantum Yield Of the Radical Channelmentioning

confidence: 99%

“…Spectrum of the quantum yield of the radical channel of the CH 2 O photolysis at room temperature. Measured data used for the fit are indicated by the large filled symbols (Horowitz and Calvert, 1978;Moortgat et al, 1983;Smith et al, 2002;Gorrotxategi Carbajo et al, 2008). The present fit and the theoretical curve from Troe (2007) are given by full lines.…”

Section: The Quantum Yield Of the Radical Channelmentioning

confidence: 99%

“…Figure 1 also contains the recommended wavelength dependences of rad given in the evaluations by JPL (Sander et al, 2011) and IUPAC (2006, 2013. The reason for the inclusion of IUPAC (2006) is that these data, which were first published in 2002 and remained on the internet until 2012, had many users in the past and possibly still have users at present.…”

Section: The Quantum Yield Of the Radical Channelmentioning

confidence: 99%

“…The quantum yield mol of the molecular branch R2 was usually measured by monitoring the H 2 production while scavenging the H atoms to prevent their contribution to the H 2 production (e.g., Moortgat et al, 1978;Horowitz and Calvert, 1978). The formation of the molecular products via the reaction path of a roaming H atom (see e.g., Bowman and Shepler, 2011;Christoffel and Bowman, 2009) was not known then and is not included explicitly in our list of reactions but it is included in R2, and its quantum yield is part of the measured mol .…”

Section: Introductionmentioning

confidence: 99%

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A simple formulation of the CH<sub>2</sub>O photolysis quantum yields

Röth¹,

Ehhalt²

2015

Atmos. Chem. Phys.

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Abstract. New expressions for the wavelength-dependent photolysis quantum yields of CH 2 O, j , are presented. They are based on combinations of functions of the typeThe parameters A i , b i , and λ 0i which have a physical meaning, are obtained by fits to the measured j data available from literature. The altitude dependence of the photolysis frequencies resulting from the new quantum yield expressions are compared to those derived from the j recommended by JPL and IUPAC.

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“…(7). and Warneck, 1979;Horowitz and Calvert, 1978;Moortgat et al, 1983). The present fit and the theoretical curve from Troe (2007) are given by full lines.…”

Section: The Quantum Yield Of the Molecular Channelmentioning

confidence: 97%

Section: The Quantum Yield Of the Radical Channelmentioning

confidence: 99%

Section: The Quantum Yield Of the Radical Channelmentioning

confidence: 99%

Section: The Quantum Yield Of the Radical Channelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A simple formulation of the CH<sub>2</sub>O photolysis quantum yields

Röth¹,

Ehhalt²

2015

Atmos. Chem. Phys.

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A smog chamber and modeling study of the gas phase NO_x–air photooxidation of toluene and the cresols

Atkinson

Carter

Darnall

et al. 1980

Int J of Chemical Kinetics

180

135

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An experimental and modeling study of irradiated toluene-NO,-air, toluene-benzaldehyde-NO,-air, and cresol-NO,-air mixtures a t part-per-million concentrations has been carried out. These mixtures were irradiated a t 303 f 1 K in a 5800-liter Teflon-lined, evacuable environmental chamber, with temperature, humidity, light intensity, spectral distribution, and the concentrations of 0 3 , NO, NOz, toluene, PAN, formaldehyde, benzaldehyde, o-cresol, m-nitrotoluene, and methyl nitrate being monitored as a function of time. For the toluene and toluene-benzaldehyde-NO,-air runs a variety of initial reactant concentrations were investigated. Cresol-NO,-air runs were observed to be much less reactive in terms of 0 3 formation and NO to NO2 conversion rates than toluene-NO,-air runs, with the relative reactivity of the cresol isomers being in the order meta >> ortho > para. The addition of benzaldehyde to toluene-NO,-air mixtures decreased the reactivity, in agreement with previous studies. Alternative mechanistic pathways for the NO, photooxidations of aromatic systems in general are discussed, and the effects of varying these mechanistic alternatives on the model predictions for the toluene and o-cresol-NO,-air systems are examined. Fits of the calculations to most of the experimental concentration-time profiles could be obtained to within the experimental uncertainty for two of the mechanistic options considered. In both cases it is assumed that (1) 0 2 adds to the OH-toluene adduct -75% of the time forming, after a further addition of 0 2 , a C7 bicyclic peroxy radical, and (2) this C7 bicyclic peroxy radical reacts with NO -75% of the time to ultimately form a-dicarbonyls and conjugated y-dicarbonyls (e.g., methylglyoxal + 2-butene-1,4-dial) and -25% of the time to form organic nitrates.The major uncertainties in the mechanisms concern (1) the structure of the bicyclic peroxy intermediate, and (2) the y-dicarbonyl photooxidation mechanism. Good fits to the o-cresol concentration-time profiles in the toluene-NO, runs are obtained if it is assumed that o-cresol

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The mechanisms of elementary physicochemical processes: An introductory report

Re¹,

Barone²,

Lelj³

1984

Int J of Quantum Chemistry

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Most of the work of theoretical physical chemists and chemical physicists relates at least indirectly to the mechanisms of physicochemical processes. Therefore it is important to examine the meaning and the scope of that notion in the context of recent developments in computational studies. After a brief mention of the meaning of the expression "elementary" physicochemical processes (EPCP), the authors adopt as a definition of mechanism a cause-effect description of an EPCP based on metastable and transient states corresponding to minima and saddle points of the potential energy surface; these states transform into one another according to appropriate selection rules. The so-called reaction-path Hamiltonian can be seen as the starting point for a quantum interpretation of the mechanism concept. On this basis the reaction coordinate, the mechanism profile, and the transition state can be fitted into the same framework. Selection rules are illustrated on the symmetry rules, with a few recent examples of applications which also show their limitations. "Propensity" rules allowing surmises on the nature of a transition state from a static picture of the initial state are also considered and their connection with "reactivity indices" emphasized. Processes involving excitation of electronic states as well as environmental effects are briefly examined. Finally, a specific example taken from surface studies is described in some detail to provide the grounds for further reflection. What Is a Mechanism?The meaning and scope of the concept of mechanism of a physicochemical process such as-a chemical reaction requires a careful discussion because it can be introduced at various levels and because there is much confusion in the literature especially as regards its relation with the detailed description in spacetime of the given process. This report is intended as a contribution to that general discussion. The realm of physicochemical processes, however, is so vast that a preliminary restriction of the field to be covered is mandatory. We shall only consider processes involving stable or metastable states separated by energy barriers which are passed by modifications of the relative positions of atoms in molecules, groups of molecules, or admolecule-substrate complexes. We further assume that these processes can be described in terms of energy hypersurfaces defined in the framework of the Born-Oppenheimer [l] or equivalent approximations, so that for a given electronic state of the system the energy may be represented as a function of the nuclear positions. Within this approximation the considerations presented here will be mostly limited to continuous and smooth surfaces ; this presupposes the definition of suitable domains [2], which exclude points where the energy is not diff erentiable-typically at the intersection of energy hypersurfaces [3,4]-as well as physically meaningless points like

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Wavelength dependence of the quantum efficiencies of the primary processes in formaldehyde photolysis at 25°C

Abstract: The quantum efficiencies of the primary processes in formaldehyde photolysis (61 and &z) were determined as a function of wavelength in the range from 2890 to 3380 A and a t 25OC:

Cited by 56 publications

References 22 publications

A simple formulation of the CH<sub>2</sub>O photolysis quantum yields

A simple formulation of the CH<sub>2</sub>O photolysis quantum yields

A smog chamber and modeling study of the gas phase NO_x–air photooxidation of toluene and the cresols

The mechanisms of elementary physicochemical processes: An introductory report

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Wavelength dependence of the quantum efficiencies of the primary processes in formaldehyde photolysis at 25°C

Abstract: The quantum efficiencies of the primary processes in formaldehyde photolysis (61 and &z) were determined as a function of wavelength in the range from 2890 to 3380 A and a t 25OC:

Cited by 56 publications

References 22 publications

A simple formulation of the CH&lt;sub&gt;2&lt;/sub&gt;O photolysis quantum yields

A simple formulation of the CH&lt;sub&gt;2&lt;/sub&gt;O photolysis quantum yields

A smog chamber and modeling study of the gas phase NOx–air photooxidation of toluene and the cresols

The mechanisms of elementary physicochemical processes: An introductory report

Contact Info

Product

Resources

About

A simple formulation of the CH<sub>2</sub>O photolysis quantum yields

A simple formulation of the CH<sub>2</sub>O photolysis quantum yields

A smog chamber and modeling study of the gas phase NO_x–air photooxidation of toluene and the cresols