拉曼学院-文献参考

二维材料是纳米和光电子领域的最新技术。在微米尺度上用无损方法表征其结构特性是非常重要的。LabRAM Soleil™ 共焦拉曼多模显微镜是表征这些材料的理想工具。

In this article, we present the combination of Raman spectroscopy, Photoluminescence and SEM-CL techniques, where the instruments weren’t physically connected. Smart nanostructured materials require a comprehensive understanding of their morphology, elemental and chemical composition. nanoGPS Suite solution allows a colocalized combination of a variety of microscopy techniques, providing a full characterization of nanostructured materials and a precise superimposition of the results obtained.

For corrosion purposes, to predict failures, optimize material lifespan, and develop effective corrosion protection strategies, ensuring durability and reliability in demanding environments, different advanced analytical solutions are needed. We will present a comprehensive range of advanced analytical solutions for the corrosion market, designed to address the complexities of corrosion processes and protection strategies.

In recent years, core-shell particles have attracted significant attention due to their smart properties. Size, morphology, and composition are the key features that strongly affect the performance and suitable applications of such structures.

Many challenges remain before the promise of 2D materials is realized in the form of practical nano-devices. An information-rich, nanoscale characterization technique is required to qualify these materials and assist in the deployment of 2D material-based applications.

Every analyst who has recorded Raman spectra is aware of the difficulties in accessing the information from the spectra when samples fluoresce. From the instrument’s point of view, the fluorescent emission is the same as the Raman emission; that is, there is an excitation laser wavelength and there is emission to the long wavelength side of the laser.

离子交换过程是在具有高非线性易感性和电光系数的晶体中制造通道波导的一种方便方法。我们的想法是创建一个通道，其中的折射率已被充分改变，以实现激光束的限制（导波），同时保留主晶体的高非线性光敏度。通过连续波导中的准相位匹配或分段波导中的平衡相位匹配，可以实现二次谐波的产生，从末端发射的近红外激光束中产生短波长的激光输出。 我们应用三维（3D）拉曼成像来了解和描述化学键和晶体结构的变化，以及测量波导段的体积结构。

The orientation of a crystal can be determined from the phase shift of the experimental P/O micro-Raman diagram relative to that calculated for a particular crystal face.

Micro-Raman spectroscopy has been used to depth-profile a waveguide produced by an ion-exchange reaction in a single crystal of a ferroelectric metal oxide, and to reveal the changes in chemical bonding and atomic structure that occur in this process.

Both TEPL and TERS images are well correlated with AFM morphological images obtained simultaneously, and all are consistent in revealing the nature (number of layers) of MoS2 flakes. Upon deconvolution, the TEPL signal is even capable of revealing local inhomogeneities within a MoS2 flake of 100 nm size. Kelvin probe measurement supports TEPL and TERS measurements and adds to the power of such tip-enhanced combinative tools.

Polarized Raman spectra are presented along with a discussion of the association of the symmetry species of the normal vibrational mode and the depolarization ratio of Raman scattering.

Segmented channel waveguides have been fabricated in single-crystal KTiOPO4 through a topotactic process of partial cation exchange. The ion-exchanged waveguides maintain the high nonlinear susceptibility of KTiOPO4 to function as frequency doubling laser light sources

Resonance and off-resonance Raman spectroscopy and imaging are used to examine the spatial variation of the solid-state structure and electronic character of few-layer MoS2 flakes. Simultaneous acquisition of photoluminescence spectra with the Raman scattering provides complementary ways of rendering Raman and photoluminescence spectral images of thin-film MoS2.

Raman bands in the low energy region of the spectrum of crystals are attributed to so-called external lattice vibrational modes. The Raman bands from these external vibrational modes (low energy phonons) are very sensitive to crystal structure and orientation with respect to the incident laser polarization and to molecular interactions within the crystal. The low energy vibrational modes of many organic molecular crystals have very high Raman scattering cross-sections. Raman spectra and images of low energy phonons in so-called two dimensional (2D) crystals such as few-layer MoS2 reveal spatial variations in the solid state structure that are not evident in the higher energy bands.

激光加工提供了一种快速、非接触和灵活的方法来修改和图案化材料，从玻璃到金属，微加工、薄层烧蚀、双光子聚合只是已经被证明的几个例子。玻璃，新一代的光学材料，可以通过改变其折射率对激光照射作出反应，这种效应已被成功地用于在块状玻璃内创建三维结构（波导、光学存储器、体布拉格光栅等）。

The recent development of side-illuminated TERS analysis even provides the possibility to investigate the behavior of graphene-based structures under device operation.

The use of TERS to reveal the defects density in the structure of CNTs is of interest for a better understanding of the electrical properties of the devices made with such nano-objects. Not only defects concentration but also local chirality changes from the different radial breathing modes, pressure effect and strain distribution can be studied at the single carbon nanotube level through TERS.

The application of vibrational selection rules is usually taught with respect to the vibrational motions of individual molecules. However, many of the materials studied by infrared or Raman spectroscopy are solids and even single crystals. Furthermore, some materials such as covalent or ionic solids have no molecular species associated with them. Consequently, there is a need to understand the application of group theory for the determination of spectroscopically active vibrational modes of crystals. The correlation method is ideal for that purpose.

Were it not for the problem of photoluminescence, only one laser excitation wavelength would be necessary to perform Raman spectroscopy. Here, we examine the problem of photoluminescence from the material being analyzed and the substrate on which it is supported. Selecting an excitation wavelength that does not generate photoluminescence reduces the noise level and yields a Raman spectrum with a superior signal-to-noise ratio. Furthermore, we discuss the phenomenon of resonance Raman spectroscopy and the effect that laser excitation wavelength has on the Raman spectrum.

Photoluminescence can provide information about the composition and solid state structure of a material. The high spectral resolution of a Raman spectrometer can be useful in performing photoluminescence spectroscopy of solid state materials, particularly when the emission spectra consist of narrow bands or even lines. Having the capability to perform photoluminescence and Raman spectroscopies simultaneously with the same instrument is advantageous, especially when studying 2D crystals. When used to perform photoluminescence spectroscopy, the Raman spectrometer becomes two instruments in one.

碳纳米管已广泛用于汽车、电池、运动装备等领域，但大规模制备高性能单壁碳纳米管仍具挑战。拉曼光谱是表征碳纳米管特性的关键技术，但常规方法受限于远场光学。TERS 纳米拉曼光谱技术弥补了这一不足，提供了纳米级空间分辨率，对单壁碳纳米管等纳米材料的深入表征至关重要，助力其在微电子、光电子及医疗设备中的集成应用。

Raman spectroscopy can be used to determine the temperature of a material when other more direct means are either impractical or not possible. The material’s temperature can affect the peak position of Raman bands. When a Raman band shifts significantly with temperature, the monitoring of the peak position can be the most straightforward manner of determining temperature provided the Raman spectrometer has sufficient spectral resolution. Another method is to determine the temperature from the ratio of the Stokes and anti-Stokes signal strengths of a given Raman band. The latter method requires the ability to detect light at wavelengths longer and shorter than that of the laser and an accurate measurement of the wavelength dependent instrument response function.

The Raman spectra of crystalline and amorphous solids of the same chemical composition can be significantly different primarily because of the presence or absence of spatial order and long range translational symmetry, respectively. The purpose or goal of this installment of Molecular Spectroscopy Workbench is to help readers understand the underlying physics that affect the Raman spectra of crystalline and amorphous solids. Wave vector, reciprocal space, and the Brillouin zone are explained with respect to Raman spectroscopy of solids.

The Raman spectra of a particular face of a single crystal can be significantly different if acquired with different microscope objectives. This article explains the underlying physics of changes in relative intensity and even peak position of certain Raman bands depending on the microscope objective used to acquire the spectrum.

Raman spectroscopy is a convenient method for probing the chemical bonding and solid state structure of crystals, and it is sensitive to the presence of dopants, impurities, and crystal defects in the host-crystal lattice. Here is what you need to know about how a hostcrystal Raman spectrum is affected by dopants and impurities.

Resonance Raman spectroscopy demonstrates up to 106 signal enhancement. In this overview a detailed description of how resonance Raman spectroscopy differs from normal Raman spectroscopy is given with some specific examples explained.

与所有层状结构一样，MoS2中存在两种类型的振动模式：层内振动模式和完整层（层间）运动产生的振动模式。 层内振动模式主要与一层（或多层）的化学成分有关；但是，这些振动模式可能会受到层数的轻微影响。由于完整层的质量大，层间振动模式在非常低的频率下观察到，它们的位置取决于层的数目。因此，这两种类型的模式都可用于确定层数。

The differentiation of polymorphs is important, particularly in the pharmaceutical industry. We demonstrate the practicality of using Raman spectroscopy to differentiate crystal forms for polymorph characterization and screening, and explain aspects of chemical bonding and solid state structure that affect the Raman spectra of crystal lattice vibrational modes.

石墨烯作为二维晶体明星材料，引领单层至多层结构新材料潮流。MoS2、MoSe2 等新型无机二维材料，因层数变化展现独特电学、光学特性，备受瞩目。科学家利用光学显微镜捕捉2D晶体颜色变化，快速识别层数。我们曾报道利用共振拉曼光谱与光致发光技术精准成像 MoS2 层数与应变，现聚焦于 WS2 晶体的拉曼与 PL 成像表征，推动二维材料研究深入发展。

A Raman spectrometer’s spectral resolution is determined by its spectral dispersion in conjunction with the entrance slit width. We explain the instrument design parameters involved.

Group theory in conjunction with Raman polarization selection rules may be applied to the study and characterization of crystalline materials. The Polarization–Orientation (P-O) Raman method employs this relationship, and is useful for the identification of a material’s crystal class, orientation, degree of disorder, and determination of the symmetry species to which the Raman bands in a spectrum belong.

Combined Raman and photoluminescence (PL) spectroscopy and imaging are used to examine the spatial variation of solid-state structure and electronic character of two-dimensional (2-D) tungsten disulfide (WS2) crystals. Simultaneous mapping acquisition of PL and Raman scattering from the same spatial locations provide complementary structural information and a way of rendering combinative Raman and PL spectral images of thin film 2-D crystals in general, and WS2 in particular.

Peak-fitting software is frequently written to offer the user a choice of automated peak fitting or one that allows the user to enter specific values of peak shape, amplitude, and width. The shapes are most often presented as a choice of percent Gaussian or Lorentzian profile contributions to the peak. To better understand these spectral profiles, we briefly explain the physical basis of the so-called spectral line shapes. Furthermore, we discuss and model the spectral shape, bandwidth, and broadening to help the reader see how the percentage of Gaussian and Lorentzian components contribute to overall peak shape and how two closely spaced and unresolved peaks of different amplitudes or bandwidths can affect the maximum position and overall appearance of the convolved peak.

We investigated in detail the Raman scattering of barium fluorohalides BaFX (X = Cl, Br, I) in an effort to characterize changes in structure and chemical bonding. The overall picture that emerges from the BaFX Raman data is that with the compositional change from X = Cl → Br → I, electron density shifts from the axial Ba-X bond to the equatorial Ba-X bonds with compositional change to the heavier halide, and that the charge distribution becomes more delocalized in the halide layers. This change in electron density indicates an increase in covalency of the Ba-X bonds from Cl to I.

In the last 30 to 40 years, various new types of carbon materials have been engineered for multiple industrial uses. It is now well-known that the Raman spectrum is sensitive to the structure, even though the spectrum is rather uncomplicated. Because Raman spectroscopy now has a reputation for providing good information, potential users of Raman equipment can request information on the quality of their sample.

Depth profiles of a laminar material have been measured on a confocal Raman microscope with a selection of microscope objectives. It is well known that the quality of the profiles will depend on the quality of the focus, which requires matching the objective’s engineered properties with the properties of the material, particularly the effects of the indices of refraction. Depth profile comparisons performed with a series of objectives will illustrate how better matching improves the spatial resolution and chemical speciation in the depth profile.

We recorded the Raman spectra of NodaxTM (PHBHx-copolymer of hydroxybutyrate) biopolymer class with varying amounts of comonomer hydroxyhexanoate (Hx). The properties of Nodax is controlled by the amount of Hx added. Engineering the polymer for specific applications requires understanding the effects of Hx on the physical and chemical properties, and vibrational spectra provide a window on this information. Inspection of the structure of PHBHx indicates that the addition of Hx only replaces the methyl group with a propyl group on the hydroxyhexanoate segments of the polymer chains.

与大多数金属相反，我们知道金属氧化物很容易通过其特有的拉曼光谱来区分；它们的存在可以用拉曼光谱在微米的范围内检测出来。

The study of vibrational spectra of linear alkanes has been used in the past to model the structure of polyethylenes. In particular, from these studies it has become clear that, in polyethylene, the longitudinal acoustic mode (LAM) frequency is inversely related to the length of polymer units between folds (lamellae), which is determined by sample history. This relationship had been developed by studying a series of linear alkanes. Spectra of samples of (C44H90), (C20D42), (C24D50), and (C36D74) are reported here. Although full spectra were recorded, we were more interested in the behavior in the low frequency region.

Review the band assignments of a protein spectrum, pointing out why it can be useful to know the band assignments when attempting to use the Raman spectra to understand the functionality of proteins. In fact, the American Chemical Society (ACS) has just issued a virtual issue of Journal of Physical Chemistry entitled “Protein Crowding and Stability,” discussing how the protein conformation impacts its biological functionality. I address how the Raman spectra can help with the determination of protein structure.

Stress and strain are terms that are often used interchangeably when discussing the characteristics of materials. Nevertheless, their meanings are different. Stress is a force per unit area applied to an object, and strain is the effect on the object from the stress.

Raman measurements can be used to infer the temperature of a material based on the Stokes and anti-Stokes band signal strengths, and by applying a predefined mathematical relationship. In reality, the temperature, Raman shift, and laser excitation wavelength all interact, and should be considered to better understand these measurements.

碳纳米管作为新型材料，在工程领域备受瞩目。其结构源自石墨层卷曲成管，直径与轴向决定其物理特性，涵盖绝缘、半导体至金属性。多层卷曲则形成多壁碳纳米管。独特的共振现象与拉曼光谱对 CNT 结构的敏感性，使光谱展现强烈波长依赖性，成为识别 CNT 类型的关键工具，特征显著，助力深入研究。

Raman imaging provides detailed crystal orientation information for two-dimensional MoS2 prepared by chemical vapor deposition on silicon substrates. These two-dimensional crystals consist of individual atomic layers of sulfur, molybdenum, and sulfur atoms.

纯碳可以以多种形式出现，这些形式由最近的邻接键以及固体的中程和长程排序反映出来，不同形式的碳正在新的工程应用中被利用。拉曼光谱已被证明对许多形式的碳有独特的诊断作用，即使材料是以少量或薄膜形式存在，本文档的讨论应该有助于在设计、监测和控制生产过程中使用拉曼光谱来描述碳的特性。

石墨烯，2004年《科学》首报的高新材料，由单层高结晶石墨构成，是碳材料基础。研究石墨烯需精确识别层数与无序度，显微拉曼光谱技术因其高选择性、分辨率及非破坏性，成为石墨烯领域理想的表征工具，助力石墨烯基器件发展。

拉曼光谱以其对碳材料多晶型的敏感性，在硬碳膜研究中发挥关键作用，能精准分离 G 带石墨碳与 D 带无序碳，预测薄膜硬度、耐久性等多项物理特性。硬盘业广泛采用硬碳涂层保护磁介质，DiskRam 系统应运而生，加速光谱采集并自动分析涂层性能，通过 D、G 带及氮带拟合，简化测试流程，本文档将详细阐述其光谱还原技术。

激光共聚焦显微拉曼光谱为宝石学分析标配，亦探究发光特性。研究聚焦天然与人工着色宝石在紫外光下的光致发光差异，以鉴别钻石的天然色彩与HPHT处理，并探讨辐照、退火等处理对钻石色彩增强的效果。

Any product used for medical purposes has to follow the adage “do no harm.” In the current work, we assess if and how Raman microscopy, in combination with X-ray fluorescence (XRF), can aid in the characterization of material leached from several implantable devices. The results show both the presence of metal oxides and organic compounds. In one case, two crystalline forms of an identical oxide existed simultaneously, and we suggest that such information may be useful in characterizing the oxidation of the metal. One of the samples was tinged pink, and its spectrum was consistent with a resonance Raman (RR) spectrum of a pigment.

Raman 2D-COS spectral data provide information on conformational changes of polymers. Here, Raman spectra of ethylene vinyl acetate and vinyl acetate copolymer are measured and interpreted, enabling a description of morphological changes related to the vinyl acetate group.

The spectral behavior of water is studied using Raman with an NIR spectrograph and dual wavelength lasers for measurements of both the fingerprint and the OH stretching regions. Raman spectra are recorded between 5 ⁰C and 80 ⁰C, and treated with both band-fitting and the 2D-COS algorithm revealing improved insights into the spectral behavior of water.

Spectral changes revealed by two-dimensional correlation spectroscopy can be used to interpret structural changes in polymers determined by processing conditions, so that materials can be rationally engineered for particular applications with known mechanical requirements.

Because of the structural use of polymers, it is important to understand the origin of their strength, elongation to break, elasticity, flexibility, and so on. It is in the very low frequency region (the so called “terahertz” range) where it is believed that the real indicators for crystallinity appear.

This introduction to two-dimensional correlation spectroscopy (2D COS) illustrates how to understand the structural changes occurring in polyester molecules in the fibers as they are annealed under tension.

We show Raman spectra of polymeric fibers acquired as a function of increasing stress and temperature. With knowledge of Raman band assignments, it becomes possible to understand, in detail, the molecular changes that are responsible for polymer orientation and crystallization.

The resonance Raman spectra of carotenoids vary with subtle changes on the functional side groups, making these spectra useful for identifying and characterizing carotenoids. Carotenoids serve multiple uses in biological systems ranging from visual pigments to antioxidants. Because the resonance Raman spectrum varies with subtle chemical changes on the functional side groups, the spectra of carotenoids have been used for identification and characterization.

Controlling the orientation of the laser and Raman polarization relative to the sample orientation can provide a wealth of information in the Raman spectrum that would be difficult to achieve by other methods. Presentation of the spectra makes these effects appear straightforward, but because of multiple instrumental factors, and experimental design, it is easy to produce erroneous results. This column is going to explain what instrumental components affect the polarization effects that are observed, and how the sample setup itself affects the Raman signal.

Raman spectra of celluloses modified for use in the pharmaceutical, food, and materials industries will be compared and analyzed, with the goal of determining spectroscopic features that can be of use in aiding in the determination of physical and chemical properties.

The use of Raman spectroscopy to produce material images whose contrast is derived from chemical or crystallographic species has been seen as quite useful since the introduction of the Raman microscope in 1976, but particularly, more recently, with the development of more sensitive and easier-to-use instruments. When the various species in the field of view have spectra with non-overlapping analytical bands, simple univariate analysis can provide good images. When overlapping bands are present, multivariate techniques, especially MCR (Multivariate Curve Resolution), have been successfully applied. However, there are cases where even MCR results may be problematic. We will look at some maps of a ceramic composite containing SiC, Si, B4C, and Carbon, where each of these species has non-unique spectra to see what type of results flexible software can produce. What is the goal in this type of exercise? For some of us, creating images is like a teenager’s computer game. But really what we are trying to do is to extract information about a sample from its Raman image. A beautiful rendition is nice, but it must yield information. The following will show how Raman maps can provide useful information on a sample.

Metal oxides often occur in crystals where there are no molecular units. Here, we provide an introduction to the concepts that need to be understood when analyzing metal oxides in materials such as paint, ceramic pigments, corrosion films, catalysts, and minerals.

We examine vapor-phase Raman spectroscopy through the acquisition of spectra from gas molecules confined to the headspace of sealed containers. Studying the Raman spectra of the liquid and vapor phases of compounds with different functional groups, degrees of hydrogen bonding, and polarity provides insight into the energetics of molecular interactions.

The performance of a Raman spectrograph for a particular application will depend, among other things, on its sensitivity and spectral resolution. The sensitivity will determine how long it will take to record a spectrum with a given signal-to-noise ratio. In turn, the grating reflectivity will determine the optical throughput of the instrument. The spectral resolution will determine how easy it will be to extract subtle information from a spectrum.

The presence of electronic transitions in the visible part of the spectrum can provide enormous enhancement of the Raman signals, if these electronic states are not luminescent. In some cases, the signals can increase by as much as six orders of magnitude. How much of an enhancement is possible depends on several factors, such as the width of the excited state, the proximity of the laser to that state, and the enhancement mechanism. The good part of this phenomenon is the increased sensitivity, but the downside is the nonlinearity of the signal, making it difficult to exploit for analytical purposes.

Here, we discuss the use of Raman spectroscopy to characterize oil shale, particularly black shale, which consists of kerogen (fossilized organic matter) trapped in sedimentary rock consisting of clays, calcites, silicates, and titanium dioxides among other inorganic minerals. We show that Raman spectroscopy is useful for characterizing the varieties of kerogen structure (chemical bonding and solid state), differentiating shales with different relative amounts of kerogen to inorganic mineral, and differentiating polymorphs of naturally occurring inorganic oxides.

The processes involved in creating fibers from organic polymers — either man-made or natural — have the potential to orient the molecules in the fibers. Examination of a number of fibers confirms that orientation is a more or less ubiquitous phenomenon that can be detected and quantified by Raman microscopy. In addition, the presence of molecular orientation can mediate the crystallization process which can also be followed with the Raman signatures.

It is common for overlapping spectral lines to occur in Raman spectra. To the extent that analytical bands can provide physical or chemical meaning relevant to the material being studied, it becomes necessary to follow these spectral lines separately as sample parameters change. Anyone who has band-fitted spectra knows that the results are fraught with pitfalls. The most common one is to add a spectral component in order to improve the overall fit. The problem with this approach is that there may not be physical or chemical meaning to this extra component.

In several of my earlier columns I discussed the interpretation of Raman spectra. This column continues that theme, examining the spectra of a series of functionalized celluloses. It is interesting to see what is consistent from material to material, and what is different. In particular, it is useful to identify marker bands for the various functional groups. In addition, when identifying an unknown, it is important to identify a collection of functional group bands that would all be present when that functional group is part of a molecule.

Polarization/orientation (P/O) micro-Raman spectroscopy can be used to identify vibrational modes, determine crystal structure, distinguish allotropes and polymorphs, differentiate single from polycrystalline materials, and determine orientation of the crystal and degree of disorder, all on a micrometer scale. P/O micro-Raman spectroscopy promises to be an important analytical tool because of its complementarity to micro-X-ray diffraction.

Raman is usually thought of as a tool for studying molecular and crystalline structure; in this context it also can differentiate the amorphous phase from any number of crystalline phases. However, it is also known that Raman spectra of a crystalline phase can be acquired under conditions where X-ray crystallography indicates that the sample is amorphous. With the development of nanophase materials, Raman is exhibiting a unique capability for characterizing materials that are between crystalline and amorphous.

How can you navigate the maze of choices for detecting molecular vibrations with mid-infrared (IR), near IR (NIR), and visible (Raman)? Understanding what is being measured, how it is measured, and the advantages and disadvantages of each technique, will help.

Raman spectroscopy can be used to measure the vibrational spectra of both organic and inorganic materials. It is now well understood that Raman spectroscopy can provide information that is not available by other analytical means. This fact has sparked interest in the technique, yet many analysts remain uneasy because of their lack of knowledge or experience.

Graphene has potential applications ranging from computer monitors to solar cells, and Raman spectroscopy is a useful method for its characterization. Graphene, which consists of single layers of perfectly crystalline graphite, was first reported in Science in 2004 (1). It was were created by the "highly sophisticated" technique of peeling off layers of highly oriented pyrolytic graphite (HOPG). One might imagine that Geim and Novoselov and their colleagues were simply searching for a new interesting material, interesting due to the physical properties resulting from its two-dimensional nature.

Raman microscopy has been attractive because of its ability to characterize materials on a spatial scale commensurate with optical microscopy. Typically, the lateral spatial resolution is quoted as determined by the Airy disk (1), which is 1.22λ/NA. λ is the wavelength of the illuminating light, and NA is the numerical aperture, which is equal to nsinθ, where n is the index of refraction of the medium (1.0 in the case of air) and θ is the angle subtended by the optics. However, it is interesting to this aging Raman spectroscopist that in recent years, the quoted spatial resolution of a Raman microscope has been getting smaller and smaller as more instrument manufacturers enter into the business of Raman microscopy.

With the coming shortages in fuel, the issues of high carbon dioxide emissions, and the problems in waste disposal, society is now searching for alternative, sustainable energy sources. Biological materials are being targeted as attractive feedstocks. They are available in industrial and urban waste streams, in lumber and prairie grasses, and in agricultural products including agricultural waste. The major constituents of plant biomass from these sources are polysaccharides and lignin. To capture high-energy products from these materials, useful chemical forms have to be identified and isolated.

Vibrational spectra are of interest to analytical and materials scientists because of their potential to yield nondestructively detailed information on materials. This is because the vibrations quite sensitively reflect interatomic bonding. There are several spectroscopies in which vibrational transitions can be detected. The simplest is infrared (IR) absorption. In this case, when a molecule is irradiated with photons whose energy corresponds to the energy of one of its vibrations (which is in the mid- and far-IR part of the electromagnetic spectrum), those photons will be absorbed.