Infrared spectroscopy specular reflection

Infrared spectroscopy, including Fourier-transform infrared (FTIR) spectroscopy, is one of the oldest techniques used for surface analysis. ATR has been used for many years to probe the surface composition of polymers that have been surface-modified by an etching process or by deposition of a film. RAIR has been widely used to characterize thin films on the surfaces of specular reflecting substrates. FTIR has numerous characteristics that make it an appropriate technique for... 

A powerful characteristic of RAIR spectroscopy is that the technique can be used to determine the orientation of surface species. The reason for this is as follows. When parallel polarized infrared radiation is specularly reflected off of a substrate at a large angle of incidence, the incident and reflected waves combine to form a standing wave that has its electric field vector (E) perpendicular to the substrate surface. Since the intensity of an infrared absorption band is proportional to / ( M), where M is the transition moment , it can be seen that the intensity of a band is maximum when E and M are parallel (i.e., both perpendicular to the surface). / is a minimum when M is parallel to the surface (as stated above, E is always perpendicular to the surface in RAIR spectroscopy). 

The most important methods used in in-situ studies of electrode surfaces are various modifications of reflection spectroscopy in the ultraviolet through infrared regions. For electrochemical applications, the specular reflection (at smooth electrode surfaces) is much more important than the diffuse reflection from matt surfaces. The reflectivity, R, of the electrode/ electrolyte interface is defined by ... 

Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) is used to obtain spectra of powders and rough polymeric surfaces such as textiles and paper. IR radiation is focused onto the surface of the sample in a cup resulting in both specular reflectance (which directly reflects off the surface having equal angles of incidence and reflectance) and diffuse reflectance (which penetrates into the sample subsequently scattering in all angles). Special mirrors allow the specular reflectance to be minimized. 

Unlike classical analytical spectroscopy performed on liquids or dilute solutions of analytes, diffuse reflectance measurement in the near-infrared must deal with a composite effect of spectroscopic absorption and scattering from the analyte and the matrix in which it is found. Differences in refractive indices of the sample material, specular reflection and observance of relatively small differences are all dealt with in this technique. 

Specular reflectance spectroscopy — Spectroscopic techniques using light in the UV-Vis and the infrared range impinging on the electrode surface and reflected away from the surface at the angle of incidence are called specular reflectance spectroscopies (see -> UV-Vis spectroscopy, -> infrared spectroscopy). 

Many types of spectroscopy have been coupled with electrochemistry including electronic absorption spectroscopy, X ray (see X-Ray Absorption Spectroscopy), infrared (IR) (see Vibrational Spectroscopy), or Raman spectroscopy, eUipsometry, specular reflectance, and electron spin resonance (ESR). Electronic absorption spectroscopy, one of the most prominent electrochemistry coupled with spectro-electrochemical techniques, will be discussed here as will... 

Fourier transform infrared spectroscopy (FT-IR) is useful for identifying organic and inorganic compounds by comparison with library references. Perkin Elmer System 2000 offers near IR, mid IR, far IR 15,000-15,030 cm, transmittance (T), specular reflectance (SR Ref. 6) and diffuse reflectance (DR), horizontal and vertical attenuated total reflectance (ATR) microscope (>10-gm spot, 10,000-10,580 cmy ... 

The technique developed by Bewick for use with a dispersive IR spectrometer is termed electrically modulated infrared spectroscopy (EMIRS) and is essentially a direct development of the UV-VIS specular reflectance technique [50], modulated specular reflectance spectroscopy (MSRS). As in MSRS, radiation is specularly reflected form a polished electrode surface while the electrode potential is modulated with a square wave between a base potential and the working potential at which the process of interest occurs the wavelength range of interest is then slowly scanned. Only that... 

One of the major sample-handling problems in FTIR analysis of carbonaceous materials is that many of them are effective blackbody absorbers and thus are too opaque for direct transmission analysis in the midinfrared spectral region. Addition of KBr intensifies the signal to obtain transmission infrared spectra. It is time consuming, and grinding conditions and moisture are known to affect the spectrum of the sample [238]. Alternative techniques such as specular reflectance, diffuse reflectance (DRIFT), photoacustic spectroscopy (FTIR-PAS), and total... 

First, we will examine the various ways of examining samples using the traditional transmission methods of infrared spectroscopy. In the second part of this ch ter we will examine the more modem reflectance methods that arh now available, such as the attenuated total reflectance, diffuse and specular reflectance methods. We ml also look at a number of more specialist techniques which you might encounter, such as photoacoustic spectroscopy, gas chromatography-infrared spectroscopy, and the use of temperature and raicrosampling cells. 

The various reflectance methods which are now widely available, such as attenuated total reflectance, specular reflectance, and diffuse reflectance spectroscopy, were also introduced. Photoacoustic spectroscopy, gas chromatography-infrared spectroscopy, temperature studies and microsampling techniques were also described. 

Specular reflection Fourier transform infrared spectroscopy, performed with the beam striking the sample at 45- from the surface normal, was also used for in situ studies of the catalytic reaction. This technique makes it possible to observe changes in the gasphase composition [4-5]. The broad band reflectivity of the overlayer can be used to obtain the composition of a thin oxide film [6], Infrared spectra have been obtained from polycrystalline samples and from Cu(llO). The former samples are akin to the ones used for mass spectrometric studies. Distinguished from those studies our FTIR work was performed with a reaction vessel at room temperature. The sample was in this case resistively heated by tantalum wires. This combination separates the gas temperature from the temperature of the catalyst. The temperature of the impinging molecules is a... 

IR spectroscopy is one of the few analytical techniques that can be used for the characterization of solid, liquid, and gas samples. The choice of sampling technique depends upon the goal of the analysis, qualitative identification or quantitative measurement of specific analytes, upon the sample size available, and upon sample composition. Water content of the sample is a major concern, since the most common IR-transparent materials are soluble in water. Samples in different phases must be treated differently. Sampling techniques are available for transmission (absorption) measurements and, since the advent of FTIR, for several types of reflectance (reflection) measurements. The common reflectance measurements are attenuated total reflectance (ATR), diffuse reflectance or diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and specular reflectance. The term reflection may be used in place of reflectance and may be more accurate specular reflection is actually what occurs in that measurement, for example. However, the term reflectance is widely used in the literature and will be used here. 

No.17, 1995,p.3385-92 ORIENTATION AND CONFORMATION IN POLY(ETHYLENE TEREPHTHALATE) WITH LOW DRAW RATIOS AS CHARACTERISED BY SPECULAR REFLECTION INFRARED SPECTROSCOPY... 

Another aspect of morphology characterization is spectroscopic analyses of the molecular orientation. The simplest and most often used method is infrared (IR) spectroscopy. Although IR techniques cannot investigate the multilayered texture, they can readily provide vivid one- or two-dimensional profiles of molecular orientation vs. position. Bensaad et al. [17] used normal incidence specular reflection to characterize the orientation profile on the surface of an injection molded plaque (6 cm X 6 cm x 0.4 cm) made of a wholly aromatic thermotropic... 

---