Attenuated total resolution

While electron or ion beam techniques can only be applied under ultra-high vacuum, optical techniques have no specific requirements concerning sample environment and are generally easier to use. The surface information which can be obtained is, however, quite different and mostly does not contain direct chemical information. While with infra-red attenuated total reflection spectroscopy (IR-ATR) a deep surface area with a typical depth of some micrometers is investigated, other techniques like phase-measurement interference microscopy (PMIM) have, due to interference effects, a much better surface sensitivity. PMIM is a very quick technique for surface roughness and homogeneity inspection with subnanometer resolution. 

FTIR instrumentation is mature. A typical routine mid-IR spectrometer has KBr optics, best resolution of around 1cm-1, and a room temperature DTGS detector. Noise levels below 0.1 % T peak-to-peak can be achieved in a few seconds. The sample compartment will accommodate a variety of sampling accessories such as those for ATR (attenuated total reflection) and diffuse reflection. At present, IR spectra can be obtained with fast and very fast FTIR interferometers with microscopes, in reflection and microreflection, in diffusion, at very low or very high temperatures, in dilute solutions, etc. Hyphenated IR techniques such as PyFTIR, TG-FTIR, GC-FTIR, HPLC-FTIR and SEC-FTIR (Chapter 7) can simplify many problems and streamline the selection process by doing multiple analyses with one sampling. Solvent absorbance limits flow-through IR spectroscopy cells so as to make them impractical for polymer analysis. Advanced FTIR... 

An infrared spectrum is a plot of percent radiation absorbed versus the frequency of the incident radiation given in wavenumbers (cm ) or in wave length ( xm). A variation of this method, diffuse reflectance spectroscopy, is used for samples with poor transmittance, e.g. cubic hematite crystals. Increased resolution and sensitivity as well as more rapid collection of data is provided by Fourier-transform-IR (FTIR), which averages a large number of spectra. Another IR technique makes use of attenuated total reflectance FTIR (ATR-FTIR) often using a cylindrical internal reflectance cell (CIR) (e.g. Tejedor-Tejedor Anderson, 1986). ATR enables wet systems and adsorbing species to be studied in situ. 

IR spectra of starch can be obtained with an IR spectrometer such as a Digilab FTS 7000 spectrometer, Digilab USA, Randolph, MA, equipped with a thermoelectrically cooled deuterated tri-glycine sulfate (DTGS) detector using an attenuated total reflectance (ATR) accessory at a resolution of 4 cm by 128 scans. Spectra are baseline-corrected, and then deconvoluted between wavenumbers 1200 to 800 cm . A half-band width of 15 cm and a resolution enhancement factor of 1.5 with Bessel apodization are employed. Intensity measurements are performed on the deconvoluted spectra by recording the height of the absorbance bands from the baseline. 

Chan, K. L. A. and Kazarian, S. G. (2003) New opportunities in micro- and macro-attenuated total reflection infrared spectroscopic imaging spatial resolution and sampling versatility. Appl. Spectrosc. 57, 381. 

Figure 17 Phase sensitive P, Pt H PMG-HMQC spectrum of [Pt(C5H5 N)(PPh3) CI2] in THF at 295 K. A standard gradient experiment could not be used due to the large /(P-Pt). NS = 2, spin-lock pulse duration 5900 xs, 14 dB attenuation, total acquisition time 15 min. Further reductions in experiment time, or improved resolution in FI could be achieved by using a smaller spectral width in the Pt dimension. SW = 125 ppm, with 128 increments was used here. Compare the signal-to-noise achieved in the Pt spectrum with that in Section 3.1...

A Shimadzu UV-3102PC UV-VIS-NIR scanning spectrophotometer was used to record the UV-VIS spectra. Infrared spectra were recorded using a BioRad FTS 6000 spectrometer in the attenuated total reflection (ATR) mode for 200 scans at a resolution of 4 cm The BioRad Merlin software was used to analyze the spectra. 

Figure 3.13. (d) Time-resolved attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectra collected during arsenic (As) oxidation on random stacked bimessite (RSB). Peaks represent the oxidation product, arsenate, adsorbed at the RSB surface. (Z ) As oxidation kinetic data collected on RSB (O) on hexagonal bimessite (H-Bi) ( ) during a batch experiment. Inset shows the peak height versus time plot for the spectra seen in the top panel, illustrating the higher time resolution achievable with rapid-scan ATR-FUR spectroscopy. (From Borda and Sparks, unpublished data, 2006.)... 

It can be seen from Equations 1.2 and 1.3 that the spatial resolution of infrared microspectroscopy can be improved by immersing the sample in a medium of high refractive index. This exactly what is done in attenuated total reflection (ATR) spectroscopy using a single-reflection hemispherical internal reflection element (IRE). Eor example, if a germanium n = 4.0) hemispherical IRE is used, not only... 

In early work (8) we used infrared spectroscopy coupled with attenuated total reflection optics. This work was done before the availability of infrared equipment based on Fourier transform methods. Due to their relative speed these methods now permit in situ, real time measurements with a resolution of 1 sec or less (9), and continue to yield valuable data, particularly in the hands of the Battelle group in a series of studies dating from 1979 (10). In our early infrared work we had to be content to rinse and dry the surface before obtaining the infrared reflection spectrum Nevertheless the values of surface concentration were remarkably close to those determined more recently. Infrared studies of proteins suffer generally from the fact that the main features of protein spectra are similar for all proteins and therefore it is difficult to distinguish one from another. 

The IR spectra were obtained using a Nicolet Magna 550 Series II FT-IR (Midac Co., USA) equipped with 45° zinc selenide (ZnSe, =2.4) attenuated total reflectance (ATR). Spectra were collected for 32 scans at a resolution of 16 cm between 650 and 4000 cm. The spectrometer was linked to a PC equipped with Omnic E.S.P. 5.2 software to allow the automated collection of IR spectra and to integrate the peak area. 

Functional groups attached to oxidized carbon nanotubes were identified by Fourier-transformed infrared spectroscopy by attenuated total reflectance, ATR-FTIR in a Nicolet 6700 FT-IR spectrophotometer at 1068 scans, in the frequency interval of 4000 cm-i to 650 cm-i with resolution of 8 cm-i. 

IR analysis was carried out to evaluate structural changes of CMC and CFF and its grafted copolymers, by means main functional groups signals. IR spectra were recorded with a Perkin-Elmer Spectrum One Fourier Transform IR spectrophotometer, using an Attenuated Total Reflactance (ATR) accessory, with ZnSe plate, using 12 scans and resolution of 4 cm", ranging from 4000 to 600 cm-i. 

IR spectroscopic analysis was used to identify the surface modification of the wool fibres, using a Perkin - Elmo Fourier Transform infirared (FT-IR) spectrophotometer with Golden Gate attenuated total reflection (ATR) attachment. The Raman spectra were measured on die same spectrophotometer equipment with a FT-Raman module with Hd YAG lasa source. Spectra were accumulated fixrni 64 scans at a resolution of 4 cm. An optical bench alignment was performed before each Raman measurranent to ensure that the spectrometer was fine-tuned and the detector signal maximised. 

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