Fourier transform infrared resolution

Chemical Gas Detection. Spectral identification of gases in industrial processing and atmospheric contamination is becoming an important tool for process control and monitoring of air quaUty. The present optical method uses the ftir (Fourier transform infrared) interference spectrometer having high resolution (<1 cm ) capabiUty and excellent sensitivity (few ppb) with the use of cooled MCT (mercury—cadmium—teUuride) (2) detectors. 

In this chapter, three methods for measuring the frequencies of the vibrations of chemical bonds between atoms in solids are discussed. Two of them, Fourier Transform Infrared Spectroscopy, FTIR, and Raman Spectroscopy, use infrared (IR) radiation as the probe. The third, High-Resolution Electron Enetgy-Loss Spectroscopy, HREELS, uses electron impact. The fourth technique. Nuclear Magnetic Resonance, NMR, is physically unrelated to the other three, involving transitions between different spin states of the atomic nucleus instead of bond vibrational states, but is included here because it provides somewhat similar information on the local bonding arrangement around an atom. 

The growth and decay of all other species (including O3) were monitored by Fourier transform infrared (FT-IR) spectroscopy at a total pathlength of 460 meters and a spectral resolution of 1 cm". At this pathlength, the intense absorptions of H2O and CO limit the usable IR spectral windows to the approximate regions 750-1300, 2000-2300, and 2400-3000 cm". Each spectrum (700-3000 cm" ) was adequately covered by the response of the Cu Ge detector. Approximately 40 seconds were required to collect the 32 interferograms co-added for each spectrum. 

Recent work in our laboratory has shown that Fourier Transform Infrared Reflection Absorption Spectroscopy (FT-IRRAS) can be used routinely to measure vibrational spectra of a monolayer on a low area metal surface. To achieve sensitivity and resolution, a pseudo-double beam, polarization modulation technique was integrated into the FT-IR experiment. We have shown applicability of FT-IRRAS to spectral measurements of surface adsorbates in the presence of a surrounding infrared absorbing gas or liquid as well as measurements in the UHV. We now show progress toward situ measurement of thermal and hydration induced conformational changes of adsorbate structure. The design of the cell and some preliminary measurements will be discussed. 

Fourier-transform infrared (IR) spectra (resolution 2 cm- ) were recorded with a Perkin Elmer 1750 instrument in a quartz cell connected to grease-free evacuation and gas manipulation lines. The self-supporting disk technique was used. Before recording the spectra, the samples were treated with O2 at 450°C (Ih), then cooled down to r.t. before evacuating the O2. The sample was then evacuated at 400°C. Evacuation at higher temperatures lead to a drastic cut off of IR trasparency. All reactants were purified prior to the adsorption experiments. Due to the better resolution of the spectra, only results for Sb V=1.0 are reported here, however the IR data for Sb V=3.0 were not significantly different. 

In the present study, we synthesized in zeolite cavities Co-Mo binary sulfide clusters by using Co and Mo carbonyls and characterized the clusters by extended X-ray absorption fine structure (EXAFS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and high resolution electron microscopy (HREM). The mechanism of catalytic synergy generation in HDS is discussed. 

For infrared spectroscopy, 20-50 mg of the cobalt-exchanged zeolite was pressed into a self-supporting wafer and placed into an infrared cell similar to that described by Joly et al. [21], Spectra were recorded on a Digilab FTS-50 Fourier-transform infrared spectrometer at a resolution of 4 cm-i. Typically, 64 or 256 scans were coadded to obtain a good signal-to-noise ratio. A reference spectrum of Co-ZSM-5 in He taken at the same temperature was subtracted from each spectrum. 

F. C. Sanchez, T. Hancewicz, B.G.M. Vandeginste and D.L. Massart, Resolution of complex liquid chromatography Fourier transform infrared spectroscopy data. Anal. Chem., 69 (1997) 1477-1484. 

The infrared spectra of the different samples were taken with a Fourier Transform infrared spectrometer (Digilab FTS-14) using the double beam mode vs. air as reference. 150 scans per sample and 100 scans per reference, at a resolution of 4 cm-l, were taken for every sample. All spectra were stored on tape, and a digital substraction of the after- and- before UV exposure (or any other sample treatment) spectra was performed, whenever needed, by an on-line computer, thus permitting a better visualization of the spectral changes in the polymer by UV- photooxidation. 

Transmission infrared spectra of species adsorbed on the catalyst were taken with a Digilab FTS-10M Fourier-transform infrared spectrometer, using a resolution of 4 cm-l. To improve the signal-to-noise ratio, between 10 and 100 interferograms were co-added. Spectra of the catalyst taken following reduction in H2 were subtracted from spectra taken in the presence of NO to eliminate the spectrum of the support. Because of the very short optical path through the gas in the reactor and the low NO partial pressures used in these studies, the spectrum of gas-phase NO was extremely weak and did not interfere with the observation of the spectrum of adsorbed species. 

Fourier transform infrared spectroscopy provides higher-resolution capabilities without undue sacrifices in energy throughput or signal-to-noise ratios. 

Structure elucidation of semiochemicals by modern NMR-techniques (including HPLC/NMR) is often hampered by the very small amounts of available material and problems in the isolation of pure compounds from the complex mixtures they are embedded in. Thus, the combination of gas chromatography and mass spectrometry, GC/MS, is frequently the method of choice. Determination of the molecular mass of the target compound (by chemical ionisation) and its atomic composition (by high resolution mass spectrometry) as well as a careful use of MS-Ubraries (mass spectra of beetle pheromones and their fragmentation pattern have been described [27]) and gas chromatographic retention indices will certainly facihtate the identification procedure. In addition, the combination of gas chromatography with Fourier-transform infrared spec-... 

Table 5.2 Summary of selected analytical methods for molecular environmental geochemistry. AAS Atomic absorption spectroscopy AFM Atomic force microscopy (also known as SFM) CT Computerized tomography EDS Energy dispersive spectrometry. EELS Electron energy loss spectroscopy EM Electron microscopy EPR Electron paramagnetic resonance (also known as ESR) ESR Electron spin resonance (also known as EPR) EXAFS Extended X-ray absorption fine structure FUR Fourier transform infrared FIR-TEM Fligh-resolution transmission electron microscopy ICP-AES Inductively-coupled plasma atomic emission spectrometry ICP-MS Inductively-coupled plasma mass spectrometry. Reproduced by permission of American Geophysical Union. O Day PA (1999) Molecular environmental geochemistry. Rev Geophysics 37 249-274. Copyright 1999 American Geophysical Union...

The most recent advance in VCD instrumentation has been its adaptation to Fourier transform infrared (FTIR) measurement (23-25). The details of this technique involve a new method of FTIR measurement termed double-modulation FTIR spectroscopy. Thus spectra of very high quality and resolution have been obtained using a standard VCD modulator and detector, a glower source, and a commercially available FTIR spectrometer system. In fact an entire FTIR-VCD spectrometer can be assembled from a few commercially available components. It is found that the major advantages of resolution, throughput, and... 

Fourier Transform Infrared (FTIR) Spectroscopy A 5DXB Nicolet system with a TGDS detector was used at a resolution of 4 cm-1. The samples were mixed with pure KBr at a concentration of 2% w/w and 64 scans were collected. 

XANES and EXAFS were conducted at BL-lOB in the Photon Factory of the National Laboratory for High Energy Physics (KEK-PF)[12]. s Fe Nttssbauer spectra were recorded with a Shimadzu MEG-2 spectrometer(13]. Isomer shifts were given relative to a-Fe. Infrared spectra were recorded by a Shimadzu Fourier-transform infrared spectrometer(FTIR-4100) with a resolution of 2 cm i. Diffuse reflectance UV-VIS spectra were obtained on a Hitachi 330 spectrophotometer. 

Fourier-transform infrared (FT-IR) spectra (resolution 2 cm" ) were recorded with a Perkin-Elmer 1750 instrument in a cell connected to grease-free evacuation and gas manipulation lines. The self-supporting disk technique was used. The usual pretreatment of the samples was evacuation at 500 C. 

We conclude this chapter by presenting several examples of deconvolution of real data. Most of these examples represent deconvolutions of data that were used as part of a spectral analysis rather than generated as deconvolution examples or tests. The examples include high-resolution grating spectra, tunable-diode-laser (TDL) spectra, a Fourier transform infrared spectrum (FTIR), laser Raman spectra, and a high-resolution y-ray spectrum. 

This article will review the impact of two powerful new techniques for characterizing epoxy resins at the molecular level — Fourier transform infrared spectroscopy (FT-IR) and high resolution nuclear magnetic resonance (NMR) of solids. Fortunately, these two techniques are not inhibited appreciably by the insoluble nature of the cured resin. Consequently, substantial structural information at the molecular level can be obtained. In this article, the basis of the methods will be briefly described in order to appreciate the nature of the methods followed by a description of the work on epoxies to date and finally some indication will be given of the anticipated contributions of these methods in the future. 

Measurements either from the ground or from satellites have been a major contribution to this effort, and satellite instruments such as LIMS (Limb Infrared Monitor of the Stratosphere) on the Nimbus 7 satellite (I) in 1979 and ATMOS (Atmospheric Trace Molecular Spectroscopy instrument), a Fourier transform infrared spectrometer aboard Spacelab 3 (2) in 1987, have produced valuable data sets that still challenge our models. But these remote techniques are not always adequate for resolving photochemistry on the small scale, particularly in the lower stratosphere. In some cases, the altitude resolution provided by remote techniques has been insufficient to provide unambiguous concentrations of trace gas species at specific altitudes. Insufficient altitude resolution is a handicap particularly for those trace species with large gradients in either altitude or latitude. Often only the most abundant species can be measured. Many of the reactive trace gases, the key species in most chemical transformations, have small abundances that are difficult to detect accurately from remote platforms. 

The concept of isotopic labeling for distinguishing pseudo enantiomers in the kinetic resolution of chiral compounds and in the desymmetrization of prochiral substrates bearing reactive enantiotopic groups (Sections 9.2 and 9.3) can also be applied when Fourier transform infrared spectroscopy (FTIR) is used as the detec-... 

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