Vibrational sum-frequency spectroscopy of the liquid/vapor interface for dilute HOD in D2O

Auer, Benjamin M.; Skinner, James

doi:10.1063/1.3012568

Cited by 104 publications

(152 citation statements)

References 73 publications

(121 reference statements)

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“…In the equations above we also used the harmonic approximation, which makes the ratio of the response functions of the fundamental and sequence transitions in HD 2D SFG spectroscopy equal, just as in 2D IR spectroscopy, because α depends linearly on the vibrational coordinate just as μ does (35). Because the experimental spectra have fundamental and sequence peaks of equal (but opposite) intensities, we conclude that the harmonic approximation is valid and that the metal surface does not appreciably weaken the Born-Oppenheimer approximation at these energies (36).…”

Section: Formalism Of Hd 2d Sfg Spectroscopymentioning

confidence: 99%

Adding a dimension to the infrared spectra of interfaces using heterodyne detected 2D sum-frequency generation (HD 2D SFG) spectroscopy

Xiong

Laaser

Mehlenbacher

et al. 2011

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

169

232

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In the last ten years, two-dimensional infrared spectroscopy has become an important technique for studying molecular structures and dynamics. We report the implementation of heterodyne detected two-dimensional sum-frequency generation (HD 2D SFG) spectroscopy, which is the analog of 2D infrared (2D IR) spectroscopy, but is selective to noncentrosymmetric systems such as interfaces. We implement the technique using mid-IR pulse shaping, which enables rapid scanning, phase cycling, and automatic phasing. Absorptive spectra are obtained, that have the highest frequency resolution possible, from which we extract the rephasing and nonrephasing signals that are sometimes preferred. Using this technique, we measure the vibrational mode of CO adsorbed on a polycrystalline Pt surface. The 2D spectrum reveals a significant inhomogenous contribution to the spectral line shape, which is quantified by simulations. This observation indicates that the surface conformation and environment of CO molecules is more complicated than the simple "atop" configuration assumed in previous work. Our method can be straightforwardly incorporated into many existing SFG spectrometers. The technique enables one to quantify inhomogeneity, vibrational couplings, spectral diffusion, chemical exchange, and many other properties analogous to 2D IR spectroscopy, but specifically for interfaces. multidimensional spectroscopy | vibrational spectroscopy | surface-sensitive | Pt catalysis | CO monolayer M olecular spectroscopies are some of the best tools for studying structures and dynamics. Two particularly useful variants are sum-frequency generation (SFG) and two-dimensional infrared (2D IR) spectroscopy. SFG spectroscopy provides a vibrational spectrum of molecular systems that lack an inversion center (1), and so has become a valuable tool for probing interfaces because no signal arises from the bulk. SFG spectroscopy has helped reveal the surface structure of liquids, characterize the surfaces of materials, and probe membrane proteins, to name only a few applications (2-5). 2D IR spectroscopy is also a vibrational spectroscopy, although not interface specific. 2D IR spectroscopy spreads the infrared spectrum into a second coordinate so that coupled vibrational modes are correlated by cross peaks, vibrational dynamics quantified by 2D line shapes, and energy transfer or chemical exchange revealed from peak intensities (6-8), in addition to many other capabilities not possible with linear one-dimensional (1D) vibrational spectroscopies like SFG spectroscopy. 2D IR spectroscopy is now being used to study protein structure and dynamics, solvent dynamics, charge transfer in semiconductors, and many other processes (9-12). These two techniques might be considered the core technologies of modern infrared spectroscopy.In this article, we combine the surface sensitivity of SFG spectroscopy with the multidimensional capabilities of 2D IR spectroscopy in a technique that we call heterodyne detected (HD) 2D SFG spectroscopy. With this technique, one obtain...

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Section: Formalism Of Hd 2d Sfg Spectroscopymentioning

confidence: 99%

Adding a dimension to the infrared spectra of interfaces using heterodyne detected 2D sum-frequency generation (HD 2D SFG) spectroscopy

Xiong

Laaser

Mehlenbacher

et al. 2011

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

169

232

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“…2 Despite its importance for disciplines such as electrochemistry, atmospheric chemistry, and membrane biophysics, the structure of interfacial water has remained highly debated. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] The challenge of specifically probing molecules at the outermost surface layers of water has been overcome with sum-frequency generation (SFG) spectroscopy of the O-H stretch vibrations of the water molecules. In an SFG experiment, infrared and visible laser pulses are overlapped in space and time on the surface, and the sum-frequency of the two laser fields can be generated, but in the top molecular layers only.…”

mentioning

confidence: 99%

Communication: Interfacial water structure revealed by ultrafast two-dimensional surface vibrational spectroscopy

Zhang

Piątkowski

Bakker

et al. 2011

The Journal of Chemical Physics

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Knowledge of the interfacial water structure is essential for a basic understanding of the many environmental, technological, and biophysical systems in which aqueous interfaces appear. Using ultrafast two-dimensional surface-specific vibrational spectroscopy we show that the structure of heavy water at the water-air interface displays short-lived heterogeneity and is very different from that at the water-lipid interface.

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“…First, all states are electronic states and the contribution from vibrational states are treated implicitly. Second, in a typical VSFG case the hyperpolarizability term corresponds to Raman transition 39 , where for ESFG, the hyperpolarizability represents two photon absorption process, as firstly pointed out by Moad and Simpson. 38 Last, the light-matter interaction sequences differ in VSFG and ESFG.…”

Section: Experimental Methods and Theoretical Backgroundmentioning

confidence: 99%

Probing Electronic Structures of Organic Semiconductors at Buried Interfaces by Electronic Sum Frequency Generation Spectroscopy

Xiong

2015

J. Phys. Chem. C

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We use Electronic Sum Frequency Generation Spectroscopy (ESFG) to study the electronic structures at a buried solid/solid interface for the first time. The system is an organic thin film, poly(3-hexylthiophene-2,5-diyl) (P3HT), supported on a silicon surface. The ESFG measurement is only in resonance with electronic (or vibronic) excitations, thus capable of yielding rich information of the band gap and electronic structures of the P3HT film at interface.We find the bandgap of P3HT in contact with silicon is 2.2 eV, with a narrowed bandwidth and Lorentzian lineshape. This is significantly distinct from the UV-Vis spectra of bulk P3HT, which contains multiple broad Gaussian peaks. Our measurement demonstrates at interfaces regioregular P3HT has a uniform electronic structure, which could improve the short circuit currents. The unique capability of ESFG to probe electronic structures at buried interface under atmosphere will be useful for investigating many buried interfaces.

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Vibrational sum-frequency spectroscopy of the liquid/vapor interface for dilute HOD in D2O

Cited by 104 publications

References 73 publications

Adding a dimension to the infrared spectra of interfaces using heterodyne detected 2D sum-frequency generation (HD 2D SFG) spectroscopy

Adding a dimension to the infrared spectra of interfaces using heterodyne detected 2D sum-frequency generation (HD 2D SFG) spectroscopy

Communication: Interfacial water structure revealed by ultrafast two-dimensional surface vibrational spectroscopy

Probing Electronic Structures of Organic Semiconductors at Buried Interfaces by Electronic Sum Frequency Generation Spectroscopy

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