Atmospheric Photochemistry via Vibrational Overtone Absorption

Donaldson, D. J.; Tuck, A. F.; Vaida, Veronica

doi:10.1021/cr0206519

Cited by 100 publications

(157 citation statements)

References 61 publications

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“…One of the consequences of this gas-phase water-mediated chemistry is a change in the electronic state of the molecule, eliminating the n → π Ã transition of the aldehyde carbonyl which is well known to undergo near-UV photochemistry (52)(53)(54). Instead, the OH vibrational chromophore of the diol may react through excitation of the OH vibrational overtone in the near IR to form new products by dehydration, decarboxylation, and decarbonylation, as suggested recently for a number of alcohols and acids (32,(55)(56)(57)(58). Using MG and MGD spectral features, we determine the gas-phase water-mediated equilibrium K P .…”

Section: Resultsmentioning

confidence: 96%

Gas-phase water-mediated equilibrium between methylglyoxal and its geminal diol

Axson

Takahashi

Haan

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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106

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In aqueous solution, aldehydes, and to a lesser extent ketones, hydrate to form geminal diols. We investigate the hydration of methylglyoxal (MG) in the gas phase, a process not previously considered to occur in water-restricted environments. In this study, we spectroscopically identified methylglyoxal diol (MGD) and obtained the gas-phase partial pressures of MG and MGD. These results, in conjunction with the relative humidity, were used to obtain the equilibrium constant, K P , for the water-mediated hydration of MG in the gas phase. The Gibbs free energy for this process, ΔG°, obtained as a result, suggests a larger than expected gas-phase diol concentration. This may have significant implications for understanding the role of organics in atmospheric chemistry.hydration | equilibrium constant | water clusters

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Section: Resultsmentioning

confidence: 96%

Gas-phase water-mediated equilibrium between methylglyoxal and its geminal diol

Axson

Takahashi

Haan

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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106

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“…Atmospheric measurements 70 found evidence of chemistry initiated by red rather than UV light and suggested that excitation of OH stretching vibrational overtone transitions in the ground electronic state might be of importance in atmospheric photochemistry. 7,70 Examples relevant to atmospheric chemistry have recently been discussed in the literature 7,[71][72][73] renewing interest in vibrational overtone initiated chemistry. 3,74 Cross-sections for absorption to vibrational overtone levels which are formally forbidden are several orders of magnitude smaller than cross sections of electronic states; nevertheless, in circumstances where electronic state chemistry is unfavorable, ground state sunlight initiated chemistry can be important in the atmosphere.…”

Section: Role Of Water In Sunlight Driven Reactionsmentioning

confidence: 99%

“…For example, light absorption by the OH stretching vibrational overtone transitions in oxidized atmospheric chromophores such as HNO 3 , HNO 4 , H 2 O 2 may lead to dissociation of the weak (e.g., N-O or O-O) bond in these molecules to produce "anomalously high" concentrations of radicals when the sun is near horizon. 71,72 Light-initiated ground electronic state reactions of this type can initiate endothermic reactions and induce photochemistry in acids and alcohols which have electronic states too high in energy to undergo atmospheric excited electronic state photochemistry. 7,71,72,[75][76][77][78] Water can potentially modify the rates of unimolecular light-initiated reactions on the ground electronic state.…”

Section: Role Of Water In Sunlight Driven Reactionsmentioning

confidence: 99%

Perspective: Water cluster mediated atmospheric chemistry

Vaida

2011

The Journal of Chemical Physics

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274

249

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The importance of water in atmospheric and environmental chemistry initiated recent studies with results documenting catalysis, suppression and anti-catalysis of thermal and photochemical reactions due to hydrogen bonding of reagents with water. Water, even one water molecule in binary complexes, has been shown by quantum chemistry to stabilize the transition state and lower its energy. However, new results underscore the need to evaluate the relative competing rates between reaction and dissipation to elucidate the role of water in chemistry. Water clusters have been used successfully as models for reactions in gas-phase, in aqueous condensed phases and at aqueous surfaces. Opportunities for experimental and theoretical chemical physics to make fundamental new discoveries abound. Work in this field is timely given the importance of water in atmospheric and environmental chemistry.

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“…Another effect to be considered in future simulations is the near infrared photolysis of HO 2 NO 2 via excitation of purely vibrational modes at wavelengths larger than 760 nm, which works also at low sun conditions in high latitude winter. It turned out to be important for the partitioning of reactive nitrogen in the lower stratosphere and upper troposphere and to reduce discrepancies between observations and models (Salawitch et al, 2002;Evans et al, 2003;Donaldson et al, 2003).…”

Section: Discussionmentioning

confidence: 99%

Impact of large solar zenith angles on lower stratospheric dynamical and chemical processes in a coupled chemistry-climate model

Lamago¹,

Dameris²,

Schnadt³

et al. 2003

Atmos. Chem. Phys.

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Abstract. Actinic fluxes at large solar zenith angles (SZAs) are important for atmospheric chemistry, especially under twilight conditions in polar winter and spring. The results of a sensitivity experiment employing the fully coupled 3D chemistry-climate model ECHAM4.L39(DLR)/CHEM have been analysed to quantify the impact of SZAs larger than 87.5 • on dynamical and chemical processes in the lower stratosphere, in particular their influence on the ozone layer.Although the actinic fluxes at SZAs larger than 87.5 • are small, ozone concentrations are significantly affected because daytime photolytic ozone destruction is switched on earlier, especially at the end of polar night the conversion of Cl 2 and Cl 2 O 2 into ClO in the lower stratosphere. Comparing climatological mean ozone column values of a simulation considering SZAs up to 93 • with those of the sensitivity run with SZAs confined to 87.5 • total ozone is reduced by about 20% in the polar Southern Hemisphere, i.e., the ozone hole is "deeper" if twilight conditions are considered in the model because there is about 4 weeks more time for ozone destruction. This causes an additional cooling of the polar lower stratosphere (50 hPa) up to −4 K with obvious consequences for chemical processes. In the Northern Hemisphere the impact of large SZAs cannot be determined on the basis of climatological mean values due to the pronounced dynamic variability of the stratosphere in winter and spring. This study clearly shows the necessity of considering large SZAs for the calculation of photolysis rates in atmospheric models.

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Atmospheric Photochemistry via Vibrational Overtone Absorption

Cited by 100 publications

References 61 publications

Gas-phase water-mediated equilibrium between methylglyoxal and its geminal diol

Gas-phase water-mediated equilibrium between methylglyoxal and its geminal diol

Perspective: Water cluster mediated atmospheric chemistry

Impact of large solar zenith angles on lower stratospheric dynamical and chemical processes in a coupled chemistry-climate model

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