Ion Chemistry Mediated by Water Networks

Siefermann, Katrin R.; Abel, Bernd

doi:10.1126/science.1184555

Cited by 11 publications

(16 citation statements)

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“…To achieve HONO formation, the lowest-lying isomers of tetrahydrates must first be converted to the highly populated critical isomer 4E in a dynamic fashion at 220 K. Subsequently, the critical isomer 4E can be converted to the HONO-containing product with encountering very low barriers at 220 K, consistent with previous experiment (11,17). We also confirmed another experimental finding (18) that the 3γ trihydrate cluster is a highly stable nonreactive cluster, even at 220 K (Fig.…”

supporting

confidence: 80%

“…The charge transfer observed for clusters with n ≥ 3 suggests the possible formation of HONO from the NO + (H 2 O) n clusters. However, the population of water clusters decreases rapidly with increasing n because of the scarcity of the water molecules in the D layer of the ionosphere (17). Therefore, the trihydrate, tetrahydrate, and pentahydrate clusters are most likely the prevailing reactive species for HONO formation in the ionosphere and thus constitute the focus of our AIMD simulations.…”

mentioning

confidence: 99%

“…The chemical equilibrium between highly populated 5Λ or 5Y and 5Γ corresponds to the second dynamic channel for HONO formation in the ionosphere. The discovery of these two dynamic channels brings previously unidentified insights into the HONO formation in the 200-220-K temperature range, a key reaction in the D layer of the ionosphere (17).…”

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Resolving the HONO formation mechanism in the ionosphere via ab initio molecular dynamic simulations

Zhong

et al. 2016

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

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Solar emission produces copious nitrosonium ions (NO + ) in the D layer of the ionosphere, 60 to 90 km above the Earth's surface. NO + is believed to transfer its charge to water clusters in that region, leading to the formation of gaseous nitrous acid (HONO) and protonated water cluster. The dynamics of this reaction at the ionospheric temperature (200-220 K) and the associated mechanistic details are largely unknown. Using ab initio molecular dynamics (AIMD) simulations and transition-state search, key structures of the water hydrates-tetrahydrate NO + (H 2 O) 4 and pentahydrate NO + (H 2 O) 5 -are identified and shown to be responsible for HONO formation in the ionosphere. The critical tetrahydrate NO + (H 2 O) 4 exhibits a chainlike structure through which all of the lowest-energy isomers must go. However, most lowest-energy isomers of pentahydrate NO + (H 2 O) 5 can be converted to the HONO-containing product, encountering very low barriers, via a chain-like or a three-armed, star-like structure. Although these structures are not the global minima, at 220 K, most lowest-energy NO + (H 2 O) 4 and NO + (H 2 O) 5 isomers tend to channel through these highly populated isomers toward HONO formation.ionosphere | HONO | mechanism | water | clusters T he ionosphere is the largest layer in the Earth's atmosphere, ranging in altitude from ∼60 to 1,000 km and includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere contains a high concentration of electrons and ions because of the ionization of gases in that region by short wavelength radiation from the Sun. Therefore, these species play an important role in atmospheric electricity, influencing radio propagation to different regions on the Earth's surface and space-based navigational systems (1). The D layer is the innermost layer of the ionosphere, ranging from 60 to 90 km in altitude, where Lyman series-α hydrogen radiation from the Sun gives rise to abundant nitrosonium ions (NO + ). In addition to the ionospheric reaction between NO + and water, explorations of the chemical reactivity of NO + and water clusters (2-4) have implications for understanding the mechanisms of atmospherically relevant reactions in water clusters (5-9).Over the past two decades, several experimental and theoretical studies (10-13) have focused on understanding the chemical and physical properties of the small-sized hydrated nitrosonium ion NO + (H 2 O) n , where n = 1-5. Two key processes have been proposed for HONO formation: NO + ðH 2 OÞ n + H 2 O → fðHONOÞH + ðH 2 OÞ n É → H + ðH 2 OÞ n + HONO .[1]Lee and coworkers (14) used vibrational spectroscopy to obtain clear evidence of the rearrangement of the NO + (H 2 O) n cluster by observing the appearance of new hydrogen (H)-bonded OH stretching lines. Using quantum molecular dynamics, Ye and Cheng (15) suggested possible structures and corresponding IR spectra for NO + (H 2 O) n (n = 1-3) clusters. In a major experimental breakthrough, Relph et al. (16) showed that the extent to which reaction 1 produces HONO ...

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Resolving the HONO formation mechanism in the ionosphere via ab initio molecular dynamic simulations

Zhong

et al. 2016

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

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“…148,149 These experimental and theoretical studies find subtle changes in the hydration environment leading to significant structural and chemical effects. [159][160][161][162][163][164] An outstanding example of significance in the D region of the ionosphere emerged from the vibrational spectroscopy of ionic water complexes in the study of the reaction of NO + with water to form HONO and H + (H 2 O) n . 165 This chemistry depends sensitively on the geometry of the water network in promoting charge delocalization providing evidence for isomer specific reactivity in ionic water clusters.…”

Section: Cluster Models For Condensed Phases Aerosols and Interfacesmentioning

confidence: 99%

Perspective: Water cluster mediated atmospheric chemistry

Vaida

2011

The Journal of Chemical Physics

269

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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“…Examples are ion chemistry in the atmosphere [1,2], in space [3,4,5] where it leads to the formation of complex molecules [6,7] in a very cold and dilute environment, or the ubiquitous role played by ions in aqueous solutions [8,9,10,11], including biological systems [12]. For experimental studies of the interaction with radiation, ionic molecules and clusters in well-defined initial states constitute a special group of targets, often only accessible using discharge sources or other dedicated ion preparation techniques.…”

Section: Introductionmentioning

confidence: 99%

Soft-x-ray fragmentation studies of molecular ions

Wolf¹,

Pedersen²,

Lammich³

et al. 2010

J. Phys. B: At. Mol. Opt. Phys.

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Abstract. Imaging of photofragments from molecular ions after irradiation by soft X-ray photons has been realized at the ion beam infrastructure TIFF set up at the FLASH facility. Photodissociation of the two-electron system HeH + at 38.7 eV revealed the electronic excitations and the charge-state ratios for the products of this process, reflecting the non-adiabatic dissociation dynamics through multiple avoided crossings among the HeH + Rydberg potential curves. Dissociative ionization of the protonated water molecules H 3 O + and H 5 O + 2 at 90 eV revealed the main fragmentation pathways after the production of valence vacancies in these ionic species, which include a strong three-body channnel with a neutral fragment (OH + H + + H + ) in H 3 O + photolysis and a significant two-body fragmentation channel (photolysis. The measurements yield absolute cross sections and fragment angular distributions. Increased precision and sensitivity of the technique was realized in recent developments, creating a tool for exploring X-ray excited molecular states under highly controlled target conditions challenging detailed theoretical understanding.

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Ion Chemistry Mediated by Water Networks

Abstract: The reaction of ions such as NO + with networks of only a few water molecules has implications for understanding chemistry in the ionosphere.

Cited by 11 publications

References 10 publications

Resolving the HONO formation mechanism in the ionosphere via ab initio molecular dynamic simulations

Resolving the HONO formation mechanism in the ionosphere via ab initio molecular dynamic simulations

Perspective: Water cluster mediated atmospheric chemistry

Soft-x-ray fragmentation studies of molecular ions

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