Infrared Spectroscopy—Mid-infrared, Near-infrared, and Far-infrared/Terahertz Spectroscopy

Ozaki, Yukihiro

doi:10.2116/analsci.20r008

Cited by 66 publications

(42 citation statements)

References 67 publications

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“…The primary motions of mode A 1 -1 are the translations of Li and O octahedron with comparable strengths. As shown in Figure S2, Nb and Li undergo antiphase translations with the O octahedron in the z axis, consistent with the simulation result of Sanna et al. , It is worth noting that Kojima et al in 1993 deduced that Li atoms make a trivial contribution to mode A 1 -1, based on the observation that the isotope substitution of Li by Li did not change its Raman frequency at all . In our calculation, this isotope substitution leads to a frequency shift from 234 to 238 cm –1 .…”

Section: Resultssupporting

confidence: 91%

“…Nonlinear optical crystals represent one of the primary sources emitting free-space propagating terahertz (THz) radiation via either optical rectification or difference-frequency generation. − In the linear interaction regime between THz radiation and matter, we have witnessed the widespread applications of THz technologies in molecule identification, trace chemistry, industrial diagnostics, biomedical imaging, and nanoscience. − The recent development of tabletop strong-field THz sources has further given access to the nonlinear interaction regime between THz radiation and matter, − opening the doorway to the THz control of matter . Among many nonlinear optical crystals, including ionic solids, semiconductors, and organic crystals, LiNbO 3 is exceptional. ,, In the early 1970s, the first demonstration of generating THz signal via optical rectification was performed in LiNbO 3 by Shen and colleagues. , Compared with most semiconductors, LiNbO 3 has more significant second-order nonlinear optical coefficients with the largest element d 33 ≈ 30 pm/V .…”

Section: Introductionmentioning

confidence: 99%

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Origins of THz Modes and Their IR Intensities in LiNbO₃

et al. 2022

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LiNbO 3 crystals have been essential materials for generating freely propagating terahertz (THz) pulses among other materials because of their excellent nonlinear optical properties and high damage thresholds. However, one of their dielectric properties�the huge IR intensities of THz modes�has been impeding their practical applications. Such IR intensities produce additional contributions to the refractive index, making the phase-matching between the optical pump and THz radiation difficult. The large IR intensities also lead to strong THz absorptions, reducing the conversion coefficient. Although a couple of techniques have been applied to solve or avoid the relevant problems, a more fundamental question regarding the atomic mechanism of generating the huge IR intensities of THz modes in LiNbO 3 has not been discussed so far. We performed a rigorous analysis of the nature of THz modes in terms of the contributions from the constituent atoms Li, Nb, and O using a quantitative approach originally developed in the previous studies. We further clarified the roles played by the motions of the constituent atoms in generating IR intensities by calculating the associated Born charge vectors. We revealed that the librations of the O octahedra, despite their prominent presence in some THz modes, are IR-silent motions. The translations of the O octahedra and Nb cations are the leading contributors to IR intensities, while the internal vibrations of the O octahedra play a destructive role. We propose two mechanisms for reducing the IR intensities of THz modes in LiNbO 3 based on the analyzed results.

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Section: Resultssupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Origins of THz Modes and Their IR Intensities in LiNbO₃

et al. 2022

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“…Infrared spectroscopy has several advantages for hydrogen bonding studies of compounds including C=O and/or OH groups. [1][2][3][4][5][6][7][8][9][10][11][12]14 First of all, IR spectroscopy gives a very intense C=O stretching band whose frequency is very sensitive to the strength of a hydrogen bond. In the OH stretching region IR bands due to strong hydrogen bonds such as OHÁÁÁOH oligomer and C=OÁÁÁHO hydrogen bonds appear strongly, although there are overlappings of these bands.…”

Section: Introductionmentioning

confidence: 99%

A Study of C=O…HO and OH…OH (Dimer, Trimer, and Oligomer) Hydrogen Bonding in a Poly(4-vinylphenol) 30%/Poly(methyl methacrylate) 70% Blend and its Thermal Behavior Using Near-Infrared Spectroscopy and Infrared Spectroscopy

et al. 2022

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Inter- and intramolecular hydrogen bondings and their temperature-dependent changes in a poly(4-vinylphenol)/poly(methyl methacrylate)(PVPh30%/PMMA70%) blend were investigated using near-infrared (NIR) and infrared (IR) spectroscopy. Band assignments of the fundamentals and first overtones of the OH stretching mode of a free OH group and OH groups in C=O…HO and OH…OH (dimer, trimer, and oligomer) hydrogen bondings of PVPh30%/PMMA70% were carried out by comparison between its NIR and IR spectra and comparison with NIR and IR spectra of phenol. The comparison of the NIR spectra of the PVPh30%PMMA70% blend (hereafter, we denote it as PVPh30%) with the corresponding IR spectra reveals that to observe bands arising from the free OH and OH…OH dimer, which is a weaker hydrogen bonding, NIR is better while to investigate bands originating from OH groups in the OH…O=C and OH…OH (oligomer) hydrogen bonds, which are stronger hydrogen bondings, IR is better. Thus, a combination of IR and NIR spectroscopy has provided convincing results for the hydrogen bondings of PVPh30%. The relative intensity of the two bands at 7058 and 6921 cm-1 (I7058/I6921) due to the first overtones of the OH stretching modes of the free OH group and the OH group in the dimer, respectively, increases significantly above 90℃, which is close to Tg of PVPh. In concomitance with the intensity increase in the relative intensity of the free OH band, the intensity of a band at 1706 cm-1 due to the C=O stretching mode of the C=O…HO hydrogen bond of PVPh30% decreases above 90℃. These results suggest that above the Tg of PVPh the C=O…HO hydrogen bond is broken gradually and that the free OH increases. Of note is that below Tg the intensities of NIR bands due to the OH first overtones of free OH group and OH groups in the OH…OH dimer gain intensity in parallel with temperature increase, and above Tg the intensity of the band derived from the OH…OH group increases linearly much slower than that of the band due to the free OH. Moreover, a band due to an OH…OH oligomer decreases linearly. Hence, it is very likely that the OH…OH oligomers dissociate into free OH groups. Anharmonicity of O-H bonds, which is sensitive to a hydrogen bond, was estimated for the free OH and OH bonds in the C=O…HO and OH…OH (dimer, trimer, and oligomer) hydrogen bondings by comparison between the NIR and IR spectra in the OH stretching band regions.

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“…9 In the case of ATR-IR spectroscopy, the penetration depth of the evanescent light generated at the surface of an internal reflection element (IRE) is from 1.5 to 4.0 μm. 10 In contrast, the penetration depth of the evanescent wave is approximately 40–20 nm in the case of the FUV region, suggesting that ATR-FUV can explore the electronic structure of a very surface of solutions and solids. For example, Goto et al 11 observed surface of water on sapphire IRE and revealed that the FUV spectra of interfacial water exhibited a blueshift and a red-tailing of the first electronic ( Ã ← X̃) transition relative to the bulk water.…”

Section: Introductionmentioning

confidence: 99%

Attenuated Total Reflection Far-Ultraviolet (ATR-FUV) Spectroscopy is a Sensitive Tool for Investigation of Protein Adsorption

et al. 2022

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Attenuated total reflection-far-ultraviolet (ATR-FUV) spectra in the 145 – 250 nm region were studied for four kinds of proteins (two α-helix rich proteins; bovine serum albumin (BSA) and lysozyme, and two β-sheet rich proteins; concanavalin A and γ-globulin) in different solutions (pure water and phosphate buffered saline (PBS)) with different concentrations. All the spectra show a band at 191 nm due to the π－π* transition of amide bonds of the proteins. The wavelength of the band does not change with their second structures, suggesting that the corresponding electronic transition mode is localized and polarized in the direction that is not affected by the difference in the peptide folding. The intensity of the 191 nm band differs with the concentration of salt in the solution, suggesting that the band intensity reflects the adsorption density of a protein on the internal reflection element (IRE) made of a sapphire glass prism. According to the intensity changes of the band at 191 nm, it is revealed that the properties in adsorption are different from one protein to another. It is assumed that there are two types of forces on the protein adsorption; one is that among the molecules, and the other is that between a molecule and a substrate. The origin of force includes localized electrostatic polarity and affinity to water. The ions in the solvent give a marked effect on these forces, resulting in the difference in the response to adsorption density against the salt concentration in the solvent.

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Infrared Spectroscopy—Mid-infrared, Near-infrared, and Far-infrared/Terahertz Spectroscopy

Cited by 66 publications

References 67 publications

Origins of THz Modes and Their IR Intensities in LiNbO₃

Origins of THz Modes and Their IR Intensities in LiNbO₃

A Study of C=O…HO and OH…OH (Dimer, Trimer, and Oligomer) Hydrogen Bonding in a Poly(4-vinylphenol) 30%/Poly(methyl methacrylate) 70% Blend and its Thermal Behavior Using Near-Infrared Spectroscopy and Infrared Spectroscopy

Attenuated Total Reflection Far-Ultraviolet (ATR-FUV) Spectroscopy is a Sensitive Tool for Investigation of Protein Adsorption

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Infrared Spectroscopy—Mid-infrared, Near-infrared, and Far-infrared/Terahertz Spectroscopy

Cited by 66 publications

References 67 publications

Origins of THz Modes and Their IR Intensities in LiNbO3

Origins of THz Modes and Their IR Intensities in LiNbO3

A Study of C=O…HO and OH…OH (Dimer, Trimer, and Oligomer) Hydrogen Bonding in a Poly(4-vinylphenol) 30%/Poly(methyl methacrylate) 70% Blend and its Thermal Behavior Using Near-Infrared Spectroscopy and Infrared Spectroscopy

Attenuated Total Reflection Far-Ultraviolet (ATR-FUV) Spectroscopy is a Sensitive Tool for Investigation of Protein Adsorption

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Origins of THz Modes and Their IR Intensities in LiNbO₃

Origins of THz Modes and Their IR Intensities in LiNbO₃