Reconsideration of second-harmonic generation from isotropic liquid interface: Broken Kleinman symmetry of neat air/water interface from dipolar contribution

Zhang, Wen-kai; Dong, Zheng; Xu, Yanyan; Bian, Hongtao; Guo, Yuan; Wang, Hong‐fei

doi:10.1063/1.2136875

Cited by 57 publications

(53 citation statements)

References 92 publications

(172 reference statements)

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“…Non-resonant SHG provides orientational measurement of the non-straddle-type of interfacial water molecules (Zhang et al, 2005). We are working far from any resonant second-order susceptibility χ NR effect is ignored since we do not track ion adsorption at the interface (Ong et al, 1992).…”

Section: Materials and Setupmentioning

confidence: 99%

Probing ice-nucleation processes on the molecular level using second harmonic generation spectroscopy

2015

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Abstract. We present and characterize a novel setup to apply second harmonic generation (SHG) spectroscopy in total internal reflection geometry (TIR) to heterogeneous freezing research. It allows to monitor the evolution of water structuring at solid surfaces at low temperatures prior to heterogeneous ice nucleation. Apart from the possibility of investigating temperature dependence, a major novelty in our setup is the ability of measuring sheet-like samples in TIR geometry in a direct way. As a main experimental result, we find that our method can discriminate between good and poor ice nucleating surfaces. While at the sapphire basal plane, which is known to be a poor ice nucleator, no structural rearrangement of the water molecules is found prior to freezing, the basal plane surface of mica, an analogue to ice active mineral dust surfaces, exhibits a strong change in the nonlinear optical properties at temperatures well above the freezing transition. This is interpreted as a pre-activation, i.e. an increase in the local ordering of the interfacial water which is expected to facilitate the crystallization of ice at the surface. The results are in line with recent predictions by molecular dynamics simulations on a similar system.

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Section: Materials and Setupmentioning

confidence: 99%

Probing ice-nucleation processes on the molecular level using second harmonic generation spectroscopy

2015

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“…Then, one has [35,40] In the previous study, we showed that the contributions from the ions and from the electric field induced SHG were negligible for the non resonant SHG signal from the electrolyte aqueous solution surface. Therefore, only the contribution from the interfacial water molecules need to be considered.…”

Section: Theoretical Background For the Shg Data Treatmentmentioning

confidence: 99%

“…For molecules with the C 2v symmetry, such as the water molecule, there are seven nonzero microscopic polarizability tensor elements β ijk (i, j, k = a, b, c) in molecular coordinates system (a, b, c): namely, β ccc , β caa , β cbb , β aca , β aac , β bcb and β bbc , with β aca = β aac and β bcb = β bbc for the SHG process. When the optical frequency is far below the resonance, β ccc is usually negligible, by defining R = (β caa + β cbb )/(β aca + β bcb ), one has, [35,40] …”

Section: Theoretical Background For the Shg Data Treatmentmentioning

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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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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“…[23,52] In these studies, we demonstrated that the non-resonant SHG signal was originated only from the electronic responses of the hydrogen bonded water molecules with the orientationally ordered structures at these electrolyte aqueous surfaces. [53] In the SFG-VS measurement, surface water molecules with different hydrogen bonding structures exhibit clearly different vibrational spectral features. However, the non-resonant SHG signal from these surfaces is the measurement of the whole water surface layer without discrimination on the surface water molecules in different hydrogen-bonding configurations.…”

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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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Reconsideration of second-harmonic generation from isotropic liquid interface: Broken Kleinman symmetry of neat air/water interface from dipolar contribution

Cited by 57 publications

References 92 publications

Probing ice-nucleation processes on the molecular level using second harmonic generation spectroscopy

Probing ice-nucleation processes on the molecular level using second harmonic generation spectroscopy

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

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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