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Ultrafast vibrational coupling between C H and C O band of cyclic amide 2-Pyrrolidinone revealed by 2DIR spectroscopy
摘要： Coupling between C–H and C=O vibrational modes play an essential role on determination of biological structure and dynamics. However, due to the weakness of the C–H absorption and strong absorption of the C=O vibrational band make such experiments less straightforward than those with transitions of nearly the same strength. In this communication the characteristics of the C–H and C=O coupling has been studied using dual frequency two dimensional infrared spectroscopy. 2-Pyrrolidinone has been used as a model molecule of biological system. The coherent and incoherent couplings between C–H and C=O vibrational bands have been observed. The cross peaks dynamics have been discussed and time constant of the cross peak intensity has been calculated.
关键词： dual frequency,vibrational coupling,vibrational spectroscopy,Molecular structure,2DIR spectroscopy,vibrational dynamics
更新于2025-09-12 10:27:22
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Formation of Highly Ordered Terminal Alkyne Self-Assembled Monolayers on the Au{111} Surface through Substitution of 1-Decaboranethiolate
摘要： The reaction aimed at completing and closing the open cages of 1-decaboranethiol self-assembled monolayers (SAMs) on Au{111} with 4-phenyl-1-butyne results in highly ordered monolayers of 4-phenyl-1-butyne. The initially disordered 1-decaboranethiolate changed into ordered (√3×√3)R 30° lattices on Au{111} typical of alkyne SAMs, indicating the complete substitution of 1-decaboranethiolate moieties, as determined by nanoscale imaging with scanning tunneling microscopy and X-ray photoelectron spectroscopy. Vibrational spectroscopy results indicate that the process happens gradually and that alkynyl groups are not totally oxidized in the ordered 4-phenyl-1-butyne monolayer.
关键词： Au{111},self-assembled monolayers,vibrational spectroscopy,scanning tunneling microscopy,X-ray photoelectron spectroscopy,4-phenyl-1-butyne,1-decaboranethiol
更新于2025-09-11 14:15:04
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Measurements, Mechanisms, and Models of Heat Transport || Macroscopic Analysis of the Flow of Energy Into and Through Matter From Spectroscopic Measurements and Electromagnetic Theory
摘要： That light (what we see) and heat (what we feel) traveling through air or vacuum are the same phenomena is now well-known. However, heat transfer within a solid is treated differently: most researchers consider elastic waves as the main carrier of interior heat, after Debye (1914). This situation in part stems from the vibrations of molecules or ions in condensed matter, which are connected with the heat capacity of a solid, not being probed by spectroscopy until B1930 due to instrumental limitations (Sawyer, 1963).
关键词： radiative transfer,spectroscopy,infrared,heat transfer,light,vibrational spectroscopy
更新于2025-09-10 09:29:36
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Photoexcitation Dynamics of Thiocyanate-Bound Heme Proteins Using Femtosecond Infrared Spectroscopy
摘要： Myoglobin (Mb) and hemoglobin (Hb) have been used as model systems to understand the relationships between protein function, structure, and dynamics. These studies have primarily been carried out by observing the (re)binding between ferrous heme proteins and neutral ligands. Ferric heme proteins also bind to various anionic ligands, such as CN?, N3?, OCN?, and SCN?. Only a few anion-bound ferric heme proteins have been investigated for ligand-binding dynamics.1–4 Although CN?-bound Mb (MbCN) was reported to be photostable, i.e., not photodeligated by a visible photon, recent study using Raman spectroscopy claimed a photodeligation quantum yield for MbCN of 0.75.5 Thus, the photostability of ?-bound MbCN is still in question. At room temperature, N3?-bound Mb (MbN3) exists in both high spin (HS) and low spin (LS) complexes. When MbN3 absorbs a visible photon, the ligand is not dissociated; instead the excited MbN3 undergoes a thermal relaxation process involving a spin transition.3 Recently, we have shown that photoexcited OCN?-bound Mb and OCN?-bound Hb are also photostable, losing their excess energy via thermal relaxation after rapid electronic relaxation.4 Here, to determine the general excitation properties of anion-bound heme proteins after absorption of a visible photon, we have extended our study of photoexcitation dynamics to SCN?-bound ferric Mb (MbNCS) and Hb (HbNCS).
关键词： Femtosecond vibrational spectroscopy,Thiocyanate-bound myoglobin,Electronic relaxation,Ferric heme proteins,Thermal relaxation
更新于2025-09-10 09:29:36
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Sum Frequency Generation Vibrational Spectroscopy using Evanescent Waves - towards Probing Irregular and Complex Surfaces of Mesoscopic-scale Materials
摘要： With rapid development of materials science, on-demand techniques are highly needed with the capability to characterize materials in the micrometer and nanometer scales. In this article, we show that, by employing a prism geometry, total internal reflection (TIR) sum frequency generation (SFG) vibrational spectroscopy allows for characterizing mesoscopic materials with irregular or complex surfaces. Four representative examples were presented. First, we reveal that, mechanical grinding can subtly alter the surface molecular structures of original materials. Second, spin coating can substantially change the surface molecular structures of particle samples. Third, surface restructuring of carboxylated multi-walled carbon nanotubes (c-MWCNTs) can happen in response to the surrounding environment. Fourth, surface adsorption and desorption dynamics of toluene on activated charcoal can be traced. Such experiments demonstrate, there are still a broad range of research fields ahead SFG can be directed to, where materials in mesoscopic scales with irregular or complex surfaces can be studied.
关键词： Surface Characterization,Sum Frequency Generation,Vibrational Spectroscopy,Mesoscopic-scale Materials,Evanescent Waves
更新于2025-09-10 09:29:36
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Infrared Investigations of the Neutral-Ionic Phase Transition in TTF-CA and Its Dynamics
摘要： The neutral-ionic phase transition in TTF-CA was investigated by steady-state and time-resolved infrared spectroscopy. We describe the growth of high-quality single crystals and their characterization. Extended theoretical calculations were performed in order to obtain the band structure, the molecular vibrational modes and the optical spectra along all crystallographic axes. The theoretical results are compared to polarization-dependent infrared reflection experiments. The temperature-dependent optical conductivity is discussed in detail. We study the photo-induced phase transition in the vicinity of thermally-induced neutral-ionic transition. The observed temporal dynamics of the photo-induced states is attributed to the random-walk of neutral-ionic domain walls. We simulate the random-walk annihilation process of domain walls on a one-dimensional chain.
关键词： domain-wall motion,neutral-ionic phase transition,steady-state and transient infrared spectroscopy,TTF-CA,charge-transfer salts,characterization,random-walk simulations,light-induced phase transition,vibrational spectroscopy,crystal growth
更新于2025-09-09 09:28:46
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Encyclopedia of Spectroscopy and Spectrometry || Spatially Offset Raman Spectroscopy
摘要： Spatially offset Raman spectroscopy (SORS) is a type of vibrational spectroscopy that provides a means to obtain chemically specific information from below the surfaces beneath materials, up to several millimeters have been demonstrated. The chemical identification of materials represents a fundamental analytical requirement that spans the physical, biological, and medical sciences. In manufacturing, it is utilized in methods to ensure product quality (including purity), usually under governmental legislation, and in healthcare to differentiate between a healthy and diseased state. For many applications there may be a strict protocol to ensure that the sample suffers no damage and this limits the type of analysis that can be performed. Generally most spectroscopic methods fit the non-destructive criteria but all-too-often to perform an analysis there is a need to perform some preliminary sample preparation and recovery wet chemistry and this may not be advisable, particularly when the environment the sample is in is difficult to get at and/or, as for example in medical applications performing a biopsy may lead to unwanted complications and stress to patients. Raman spectroscopy provides a unique capability in terms of every chemical’s spectral signature is a unique fingerprint that can allow its identification. However, there are certain limitations to Raman spectroscopy. For example, Raman scattering cross sections are very small, typically 10 orders of magnitude weaker than typical organic molecules UV–Visible absorption cross section. The advent of lasers coupled with the development of excellent transmission optics and modern CCD cameras has revolutionized Raman spectroscopy in the last 20 years, to the point that samples can be examined be-they gas, liquid or solid, animal, vegetable, or mineral. However, for solid systems standard Raman methods are confined to characterization of the surface. This includes confocal Raman microscopy regularly used to study solids that is restricted to depths of the order of 100 mm below material surface. However, this limitation has recently been overcome using SORS and this new technology is being applied to a range of systems to characterize subsurface diffusely scattering materials, including tissue.
关键词： chemical identification,subsurface analysis,Spatially offset Raman spectroscopy,SORS,vibrational spectroscopy
更新于2025-09-09 09:28:46
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[Topics in Current Chemistry Collections] Multidimensional Time-Resolved Spectroscopy || Multidimensional Vibrational Coherence Spectroscopy
摘要： Multidimensional vibrational coherence spectroscopy has been part of laser spec-troscopy since the 1990s and its role in several areas of science has continuously been increasing. In this contribution, after introducing the principals of vibrational coherence spectroscopy (VCS), we review the three most widespread experimen-tal methods for multidimensional VCS (multi-VCS), namely femtosecond stimu-lated Raman spectroscopy, pump-impulsive vibrational spectroscopy, and pump-degenerate four wave-mixing. Focus is given to the generation and typical analysis of the respective signals in the time and spectral domains. Critical aspects of all multidimensional techniques are the challenges in the data interpretation due to the existence of several possible contributions to the observed signals or to opti-cal interferences and how to overcome the corresponding difficulties by exploiting experimental parameters including higher-order nonlinear effects. We overview how multidimensional vibrational coherence spectroscopy can assist a chemist in under-standing how molecular structural changes and eventually photochemical reactions take place. In order to illustrate the application of the techniques described in this chapter, two molecular systems are discussed in more detail in regard to the vibra-tional dynamics in the electronic excited states: (1) carotenoids as a non-reactive system and (2) stilbene derivatives as a reactive system.
关键词： Excited states,Photoisomerization,Multidimensional spectroscopy,Coherence spectroscopy,Vibronic coupling,Ultrafast laser spectroscopy,Raman,Vibrational spectroscopy
更新于2025-09-04 15:30:14
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Direct Observation of Ion Pairing in Aqueous Nitric Acid Using 2D Infrared Spectroscopy
摘要： Ion-ion interactions and ion pairing play an important role in the properties of concentrated electrolyte solutions, yet remain difficult to study due to the heterogeneous and highly dynamic behavior of these systems. In concentrated acid solutions these questions take on a further level of complexity, because the structure of the aqueous proton itself is uncertain, and may be influenced by the counterion. Here, we address these questions by studying the IR spectra of nitric acid as a function of concentration in H2O, and comparing these to the spectra of several alkali nitrate salts. We show how the close proximity between cations and NO3– ions in solution at high concentration affect the IR spectra, and therefore the molecular structures. Using 2D IR spectroscopy, we demonstrate the formation of contracted ion pair configurations in nitric acid solutions between NO3– ions and H+(aq) via the observation of a distinct anisotropic intermolecular crosspeak between these species. By studying the concentration dependence of this spectral feature, we show that this ion-paired configuration exists in solution at concentrations as low as 2M, and suggests that the structure of H+(aq) solvation complex in these ion pairs differs from the structure in bulk solution.
关键词： 2D IR spectroscopy,Proton hydration,Aqueous nitric acid,Ion pairing,Vibrational spectroscopy
更新于2025-09-04 15:30:14
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Structure and Properties of Gallium-Rich Sodium Germano-Gallate Glasses
摘要： Glass compositions in the gallium-rich region of the ternary GaO3/2-GeO2-NaO1/2 vitreous system are studied as a function of the Na/Ga cationic ratio (ranging from 1.30 to 1.61) for a fixed GeO2 content. Glass structures are investigated by 71Ga MAS-NMR, infrared and Raman spectroscopies, and the thermal, optical and physical properties are characterized. Vibrational spectra are interpreted with the help of density functional theory (DFT) calculations. Gallium oxide generally enters the germania network in four-fold coordination, however for Na/Ga ratio below unity, gallium cations tend to charge balance with the formation of 5- or 6-fold coordination units. When the amount of sodium is greater than gallium, non-bridging oxygens (NBOs) are formed preferably on germanate tetrahedral units. These structural descriptions are used to understand the evolution of glass properties such as glass transition temperature, density and refractive index.
关键词： germano-gallate glasses,infrared,vibrational spectroscopy,glass structure,71Ga NMR spectroscopy
更新于2025-09-04 15:30:14