Theoretical study of vibrational energy transfer of free OH groups at the water-air interface

Zheng, Ren-Hui; Wei, Wen-mei; Sun, Yuanyuan; Song, Kai; Shi, Qiang

doi:10.1063/1.4945424

Cited by 4 publications

(3 citation statements)

References 47 publications

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“…Thus, we used IRRAS to spectrally probe the OH stretching (ν(OH), ∼3000–3800 cm –1 ) modes of the headgroups and their hydration shells as well as the HOH bending (δ(HOH), ∼1500–1800 cm –1 ) modes of the hydrating water molecules. We also probed the ν(OD) modes of dilute HOD to remove resonant vibrational excitation transfer, a Förster transfer mechanism mediated by transition dipole moment coupling; the ν(OD) modes thus act as uncoupled local modes for more reliable reporting of water structure. ,,− All spectra were collected at 21.0 ± 0.5 and 1.0 ± 1.0 °C. Shifts in the OH and OD stretching region spectra as a function of temperature were quantified by Gaussian peak fitting (Figures S3, S4, S7, S8).…”

Section: Resultsmentioning

confidence: 99%

“…More specifically, changes in temperature alter the transition dipole moment strengths and hydrogen-bonding configurations of the interfacial water molecules, thereby shifting the distribution of resonant vibrational frequencies. Others have shown that an increase in temperature induces a frequency mismatch between the stretch fundamental and the bending overtone of bulk water, leading to a decrease in the Fermi resonance intramolecular coupling at ∼3250 cm –1 . − Intramolecular coupling dominates the vibrational relaxation pathways in interfacial water. ,− Thus, intramolecular coupling is possibly driving the temperature-dependent spectral shifts observed in Figure a, but the exact mechanisms responsible for these spectral shifts are currently unknown. Vibrational coupling to octadecanol- d 37 vibrational modes is also possible. , Additionally, it is nontrivial to distinguish between peak intensity contributions caused by changes in hydration shell number density and structure versus changes in transition dipole moment strength as a function of temperature, further complicating the spectral interpretation.…”

Section: Resultsmentioning

confidence: 99%

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Hydration and Hydrogen Bond Order of Octadecanoic Acid and Octadecanol Films on Water at 21 and 1 °C

et al. 2021

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The temperature-dependent hydration structure of long-chain fatty acids and alcohols at air−water interfaces has great significance in the fundamental interactions underlying ice nucleation in the atmosphere. We present an integrated theoretical and experimental study of the temperature-dependent vibrational structure and electric field character of the immediate hydration shells of fatty alcohol and acid headgroups. We use a combination of surface-sensitive infrared reflection−absorption spectroscopy (IRRAS), surface potentiometry, and ab initio molecular dynamics simulations to elucidate detailed molecular structures of the octadecanoic acid and octadecanol (stearic acid and stearyl alcohol) headgroup hydration shells at room temperature and near freezing. In experiments, the alcohol at high surface concentration exhibits the largest surface potential; yet we observe a strengthening of the hydrogen-bonding for the solvating water molecules near freezing for both the alcohol and the fatty acid IRRAS experiments. Results reveal that the hydration shells for both compounds screen their polar headgroup dipole moments reducing the surface potential at low surface coverages; at higher surface coverage, the polar headgroups become dehydrated, which reduces the screening, correlating to higher observed surface potential values. Lowering the temperature promotes tighter chain packing and an increase in surface potential. IRRAS reveals that the intra-and intermolecular vibrational coupling mechanisms are highly sensitive to changes in temperature. We find that intramolecular coupling dominates the vibrational relaxation pathways for interfacial water determined by comparing the H 2 O and the HOD spectra. Using ab initio molecular dynamics (AIMD) calculations on cluster systems of propanol + 6H 2 O and propionic acid + 10H 2 O, a spectral decomposition scheme was used to correlate the OH stretching motion with the IRRAS spectral features, revealing the effects of intra-and intermolecular coupling on the spectra. Spectra calculated with AIMD reproduce the red shift and increase in intensity observed in experimental spectra corresponding to the OH stretching region of the first solvation shell. These findings suggest that intra-and intermolecular vibrational couplings strongly impact the OH stretching region at fatty acid and fatty alcohol water interfaces. Overall, results are consistent with ice templating behavior for both the fatty acid and the alcohol, yet the surface potential signature is strongest for the fatty alcohol. These findings develop a better understanding of the complex surface potential and spectral signatures involved in ice templating.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Hydration and Hydrogen Bond Order of Octadecanoic Acid and Octadecanol Films on Water at 21 and 1 °C

et al. 2021

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“…From a theoretical point of view, the SFG spectrum is a second-order susceptibility that arises from the interactions between the incident electric fields and the molecules. Both the real and imaginary parts of the appropriate susceptibility can be obtained using the Fourier–Laplace transform of a time-correlation function ( 11 , 14 , 16 , 17 , 27 – 33 ). Often, the water structures for deriving the susceptibility are calculated using a molecular dynamics (MD) simulation.…”

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confidence: 99%

Sum rule comparison of narrowband and broadband sum frequency generation spectra and comparison with theory

Niu,

Wang,

Marcus

2024

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

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Earlier sum frequency generation (SFG) experiments involve one infrared and one visible laser, and a measurement of the intensity of the response, yielding data on the surface sensitive properties of the sample. Recently, both the real and imaginary components of the susceptibility were measured in two different sets of experiments. In one set, a broadband infrared laser was used, permitting observations at very short times, while in another set the infrared laser was narrowband, permitting higher spectral resolution. The differences in the spectrum obtained by the two will be most evident in studying narrow absorption bands, e.g., the band due to dangling OH bonds at a water interface. The direct comparisons in the integrated amplitude (sum rule) of the imaginary part of the dangling OH bond region differ by a factor of 3. Due to variations in experimental setup and data processing, corrections were made for the quartz reference, Fresnel factors, and the incident visible laser wavelength. After the corrections, the agreement differs now by the factors of 1.1 within broadband and narrowband groups and the two groups now differ by a factor of 1.5. The 1.5 factor may arise from the extra heating of the more powerful broadband laser system on the water surface. The convolution from the narrowband SFG spectrum to the broadband SFG spectrum is also investigated and it does not affect the sum rule. Theory and narrowband experiments are compared using the sum rule and agree to a factor of 1.3 with no adjustable parameters.

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Energy relaxation pathways and their isotope effects of water bending mode in liquid phase: A nonequilibrium ab initio molecular dynamics simulation study

Ishiyama

2024

Chemical Physics

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Theoretical study of vibrational energy transfer of free OH groups at the water-air interface

Cited by 4 publications

References 47 publications

Hydration and Hydrogen Bond Order of Octadecanoic Acid and Octadecanol Films on Water at 21 and 1 °C

Hydration and Hydrogen Bond Order of Octadecanoic Acid and Octadecanol Films on Water at 21 and 1 °C

Sum rule comparison of narrowband and broadband sum frequency generation spectra and comparison with theory

Energy relaxation pathways and their isotope effects of water bending mode in liquid phase: A nonequilibrium ab initio molecular dynamics simulation study

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