Mimicking solvent shells in the gas phase. II. Solvation of K+

Miller, Dorothy J.; Lisy, James M.

doi:10.1063/1.2155386

Cited by 35 publications

(46 citation statements)

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“…In order to fully solvate an ion in the solvation shell, usually six water molecules are needed. [70,71,72,75] At such high bulk concentration as 5M the cations and anions are very close to each other. However, our SHG data of the five salts KF, KCl, KBr, NaBr and NaCl did not show the same ion pairing or association effects as the NaF salt.…”

Section: Resultsmentioning

confidence: 96%

“…Studies showed that these different behaviors were largely due to their different hydration number and hydration free energies. [69,70,71,72] Recently, using SFG vibrational spectroscopy, Cremer and co-workers investigated the ion effects on the water molecules at the polymer surfactant aqueous interfaces. [73,74] In these studies, significant anion effects and insignificant cation effect were observed.…”

Section: Resultsmentioning

confidence: 99%

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Specific Na+ and K+ cation effects on the interfacial water molecules at the air/aqueous salt solution interfaces probed with nonresonant second harmonic generation

Bian

Feng

Guo

et al. 2009

The Journal of Chemical Physics

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Here we report the polarization dependent non-resonant second harmonic generation (SHG) measurement of the interfacial water molecules at the aqueous solution of the following salts: NaF, NaCl, NaBr, KF, KCl, and KBr. Through quantitative polarization analysis of the SHG data, the orientational parameter D,(D= cosθ / cos 3 θ ) value and the relative surface density of the interfacial water molecules at these aqueous solution surfaces were determined. From these results we found that addition of each of the six salts caused increase of the thickness of the interfacial water layer at the surfaces to a certain extent. Noticeably, both the cations and the anions contributed to the changes, and the abilities to increase the thickness of the interfacial water layer were in the following order: KBr > NaBr > KCl > NaCl ∼ NaF > KF. Since these changes can not be factorized into individual anion and cation contributions, there are possible ion pairing or association effects, especially for the NaF case. We also found that the orientational parameter D values of the interfacial water molecules changed to opposite directions for the aqueous solutions of the three sodium salts versus the aqueous solutions of the three potassium salts. These findings clearly indicated unexpected specific Na + and K + cation effects at the aqueous solution surface.These effects were not anticipated from the recent molecular dynamics (MD) simulation results, which concluded that the Na + and K + cations can be treated as small non-polarizable hard ions and they are repelled from the aqueous interfaces. These results suggest that the electrolyte aqueous solution surfaces are more complex than the currently prevalent theoretical and experimental understandings.2

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Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

Specific Na+ and K+ cation effects on the interfacial water molecules at the air/aqueous salt solution interfaces probed with nonresonant second harmonic generation

Bian

Feng

Guo

et al. 2009

The Journal of Chemical Physics

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“…In this cooperative process, the movement of the water molecule at the short end leads to the formation of a cyclic structure, where the two water molecules and the HONO species act as hydrogen-bond acceptors and form a complete solvation shell around the H 3 O + ion. The formation of such a solvation shell can effectively stabilize the central H 3 O + ion, a well-established fact in the gas-phase reaction involving ionic clusters (23)(24)(25)(26). Due to the stabilization effect, the formation of HONO-containing isomer 4-ii, from the highly populated isomer 4E, entails a low-energy barrier of ∼2.1 kcal/mol.…”

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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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“…According to this picture, it shall be hard to imagine how such longrange interactions can be so different for the Na + and the K + cations, since people already knew that the solvation of the Na + and the K + cations hardly go beyond the second solvation shell. [57,58] On the other hand, in the currently prevalent paradigm, the adsorption of the more polarizable anions to the aqueous solution surfaces should be enhanced, but not the less polarizable anions, such as the F − , and the cations, such as the Na + and the K + cations.Then the difficulties shall be the same as in the classical picture on how the significantly different Na + and the K + cation effects are originated.Richmond and co-workers observed the change of the SFG spectra for the NaF aqueous solution surfaces, [24] which is further confirmed in our measurement as reported here.They concluded that even though the F − anion concentration was 'diminished' in the top surface water layers, the presence of F − anion in the surface region can still affect the hydrogen bonding structure of the water molecules in the surface region in different ways from the larger and more polarizable Br − and I − anions. According to the same reasoning as Richmond and co-workers proposed for the F − anion, the presence of the Na + and the K + cations in the surface layers, even though diminished from the bulk concentration, can also be expected.…”

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Spectroscopic evidence for the specific Na+ and K+ interactions with the hydrogen-bonded water molecules at the electrolyte aqueous solution surfaces

Feng

Bian

Guo

et al. 2009

The Journal of Chemical Physics

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Sum frequency generation vibrational spectra of the water molecules at the NaF and KF aqueous solution surfaces showed significantly different spectral features and different concentration dependence. This result is the first direct observation of the cation effects of the simple alkali cations, which have been believed to be depleted from the aqueous surface, on the hydrogen bonding structure of the water molecules at the electrolyte solution surfaces. These observations may provide important clue to understand the fundamental phenomenon of ions at the air/water interface. † Also Graduate University of the Chinese Academy of Sciences.* To whom correspondence should be addressed. E-mail: hongfei@iccas.ac.cn; Tel: 86-10-62555347; Fax:86-10-62563167. 1In this letter we would like to report the significantly different sum-frequency generation vibrational spectra of the NaF and KF aqueous solution surfaces. These results suggested that the ion effects on the interfacial water hydrogen bonding structure are quite different for the NaF and KF salts. These results may provide direct counterexamples to the physical picture based on the currently prevalent molecular dynamics (MD) simulations with the polarizable force field, which have predicted that the adsorption of the more polarizable anions, such as the I − and Br − anions, are significantly enhanced at the electrolyte aqueous solution surfaces, while the less polarizable anions, such as the F − and Cl − anions, and the non polarizable cations, such as the Na + and K + cations, are repelled from the electrolyte aqueous solution surfaces. [1,2,3,4,5] Recently, there have been a great deal of theoretical and experimental studies on the ion solvation and ion effects at the electrolyte aqueous solution surfaces. [1,2,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29] It has been well established that the ssp SFG spectra for the neat air/water interface has two prominent features, one is the narrow peak centered at 3700cm −1 and the other is the fairly broad band in the 3000-3600cm −1 . The former is the signature of the non hydrogenbonded O-H group which sticks out of the liquid phase, i.e. the so called 'free O-H'; while the latter is the signature of the O-H stretching vibrations of the differently hydrogen-bonded water molecules on the liquid side in the vicinity of the air/water interface. [38,39,40,41,42] These signatures of the interfacial water molecules can be observed in the SFG-VS because the water molecules at the air/water interface are orientationally ordered. [38,39,40,41,42,46] It has been known that addition of the electrolytes into the bulk aqueous phase can introduce changes in the ssp SFG spectra in the hydrogen-bonded water region, i.e. 3000- [3,6,17,18,24,39,47] In order to systematically investigate the anion effects on the hydrogen-bonded water molecules at the electrolyte aqueous solution surfaces, the ssp 3 SFG-VS spectra of the NaF, NaCl, NaBr and NaI slat solution surfaces were measured by two independent groups. [17...

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Mimicking solvent shells in the gas phase. II. Solvation of K+

Cited by 35 publications

References 25 publications

Specific Na+ and K+ cation effects on the interfacial water molecules at the air/aqueous salt solution interfaces probed with nonresonant second harmonic generation

Specific Na+ and K+ cation effects on the interfacial water molecules at the air/aqueous salt solution interfaces probed with nonresonant second harmonic generation

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

Spectroscopic evidence for the specific Na+ and K+ interactions with the hydrogen-bonded water molecules at the electrolyte aqueous solution surfaces

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