Identification of Surface Molecular Hydrates on Solid Sulfuric Acid Films

Couling, Suzanne B.; Nash, Karen L.; Fletcher, John S.; Henderson, Alex; Vickerman, John C.; Horn, Andrew B.

doi:10.1021/ja036384l

Cited by 7 publications

(7 citation statements)

References 10 publications

(13 reference statements)

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“…Vibrational sum frequency generation studies have also provided evidence for the presence of unionized species on the surface of low-temperature liquid sulfuric acid. 25 One such species, a sulfuric acid/water 1:1 complex with the H 2 O molecule bridging the O and OH groups, gives predicted bond vibrations in good agreement with a species observed by Horn et al 26 in a number of ATR-IR experiments. The species was most easily observed in the ATR-IR experiments where the films had been deposited under extremely H 2 Odeficient conditions.…”

Section: Resultssupporting

confidence: 75%

ToF-SIMS Studies of Sulfuric Acid Hydrate Films

et al. 2004

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A variety of sulfuric acid hydrate films, formed by the co-deposition of SO3 and H2O on a cooled substrate, have been analyzed using time-of-flight secondary ion mass spectrometry (ToF-SIMS). The films were produced using procedures developed in recent infrared spectroscopic studies. Spectra have been shown to consist of a series of identifiable fragments, the change in intensities of which can be related to changes in temperature and the relative abundance of H2O during the deposition of the film under UHV conditions. Depth profiling of the films shows clear evidence of separate surface species on some films and supports the existence of surface molecular hydrates over a stable bulk hydrate film.

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Section: Resultssupporting

confidence: 75%

ToF-SIMS Studies of Sulfuric Acid Hydrate Films

et al. 2004

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“…Table 1 compares the peak positions of the major features in the three forms of MSSAH. There is very good agreement between the three forms, if systematic differences in the measurements methods are taken into account (also, the SAM surface MSSAH spectrum is very thin ((0.01 mm) and is obtained by subtraction of spectra of relatively thick films 24 ). Closer scrutiny reveals the presence of an additional poorly resolved features at ca.…”

Section: Mssah: Metastable Sulfuric Acid Hydratementioning

confidence: 80%

“…6b shows the spectrum of a thin surface layer of MSSAH recently identified as being on the surface on a thin film of SAM at ca. 200 K by Couling et al, 24 whilst Fig. 6c shows a condensed film consisting entirely of the same material at 190 K. Detailed assignment of the absorption bands of this material are presented elsewhere.…”

Section: Mssah: Metastable Sulfuric Acid Hydratementioning

confidence: 80%

First detection of molecular hydrate complexes in sulfuric acid aerosols

Couling

Fletcher²,

Horn

et al. 2003

Phys. Chem. Chem. Phys.

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Two un-ionised molecular hydrate complexes, previously observed by Fourier-transform spectroscopy in flat films of vapour deposited sulfuric acid, have been identified directly in aerosols nucleated from SO 3 and H 2 O in a 75 dm 3 coolable spectroscopic cell. Aerosols of a 1 : 1 complex H 2 SO 4 ÁH 2 O have been generated at 195 K and have also been formed in cooled liquid sulfuric acid aerosols. A second polymeric metastable hydrate of the type (H 2 SO 4 .2H 2 O) n has been identified as the initial material formed during the nucleation process of sulfuric acid aerosol at 195 K. These metastable species are likely to play an important role in the formation of sulfuric acid aerosols at the low temperatures found in the upper troposphere and the lower stratosphere.

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“…1 Molecular hydrate complexes have been detected in sulfate aerosolsandtheirstabilityhasbeencorroboratedinexperiments. [15][16][17][18] In year 2004, the high polarity of H 2 SO 4 hydrates was predicted by Natsheh et al 19 Two years later, this finding has received an experimental conformation in the work of Leopold with coauthors, 13 who have reported dipole moment of 3.05 debyes for the most stable isomer of hydrogen-bonded (H 2 SO 4 )(H 2 O) at T ) 3 K.…”

Section: Introductionmentioning

confidence: 90%

Anomalously Large Difference in Dipole Moment of Isomers with Nearly Identical Thermodynamic Stability

Nadykto

2008

J. Phys. Chem. A

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Sulfuric acid is a primary atmospheric nucleation precursor, with the ability to form stable aqueous hydrogen-bonded clusters/complexes. The electrical dipole moment of such clusters/complexes is important for ion-induced nucleation, largely controlled by dipole-charge interaction of airborne ions with vapor monomers and pre-existing clusters. Although experiments typically trace a single lowest energy conformer at low temperatures, the present study shows that the immediate vicinity (<1 kcal mol (-1)) of the global minima may be populated with a number of isomers of nearly identical spectral characteristics and drastically different dipole moments. The difference in the dipole moment of mono-, di-, and trihydrates of the sulfuric acid exceeds 1.3-1.5 Debyes ( approximately 50-60%), 1.4-2.6 Debyes ( approximately 50-90%), and 3.8-4.2 Debyes ( approximately 370-550%), respectively. Being driven by the temperature dependence of the Boltzmann distribution, the difference between the Boltzmann-Gibbs average dipole moment and the dipole moment of the most stable isomer increases with the ambient temperature, leading to large variations in the dipole-ion interaction strength, which may have important implications for the ion-mediated production of ultrafine aerosol particles associated with various climatic and health impacts.

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Identification of Surface Molecular Hydrates on Solid Sulfuric Acid Films

Cited by 7 publications

References 10 publications

ToF-SIMS Studies of Sulfuric Acid Hydrate Films

ToF-SIMS Studies of Sulfuric Acid Hydrate Films

First detection of molecular hydrate complexes in sulfuric acid aerosols

Anomalously Large Difference in Dipole Moment of Isomers with Nearly Identical Thermodynamic Stability

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