Rapid scanning spectroscopy applications

When the heterogeneous electron transfer is followed by a chemical step, the registration of spectral data becomes more complicated unless the rate of the chemical reaction is very low. Rapidly reacting species—for instance, radical ions—can be characterized spectroscopically by the application of rapid scan spectroscopy (RSS), modulated specular reflectance spectroscopy (MSRS) and, more recently, diode array spectrometers. 

Rapid-scanning spectroscopy (RSS) is a method in which a selected portion of the ultraviolet, visible, or near-infrared spectrum is scanned on a time scale ranging from several sec to a few /isec. The applications of this technique to systems in which short-lived transient species exist or large reaction rates are encountered are numerous... 

Results of a comprehensive study of the absolute spectral radiance of the infrared emissions from methane—air expins have been reported (Ref 44). The spectral growth of these expanding flames was recorded with a time resolution of one msec in the spectral range 1.7— 5.0 microns. Time resolved spectra were obtained as a function of stoichiometry, nitrogen dilution and Halon dilution. Similar data are also available for coal dust-air explns. Additional applications of rapid scan IR spectroscopy are discussed in Ref 50. In this work, flare spectra (Mk45, LUU-2B and LUU-2B/B) in the 1.7-4.7 and 9—14 micron regions were studied. The Mk-45 and LUU-2B/B showed similar spectral character with Na and C02 emissions superimposed on a gray body continuum, while LUU-2B flares demonstrated variable emittance properties... 

FTIR spectroscopy to a particular pesticide, the methods have general applications to numerous compounds. Most of these utilize the high sensitivity of FTIR, and the data manipulation capability of the system. In several of the gas evolution studies, spectra were acquired at less than one-minute intervals. While this is not really "rapid scanning," the high resolution required for vapor phase spectra would not have been possible with a normal dispersive instrument. Several other techniques using FTIR show promise in the area of pesticide analysis. 

Because it is widely recognized that a significant amount of reactivity takes places rapidly during sorption processes, it has become necessary to employ new experimental techniques that can adequately measure these processes with high temporal sensitivity. Techniques such as rapid-scan infrared spectroscopy and quick-EXAFS have shown great promise in the early stages of their development and application in our field. It will be over the next decade(s) that these... 

Applications of Rapid-Scanning, Stopped-Flow (RSSF) UV-Visible Spectroscopy to the Study of Biological Systems... 

The limited availability of affordable commercial RSSF instruments has been an important factor that has prevented the widespread application of RSSF spectroscopy to the study of biological systems. However, in the past year, a significant change in the availability of commercial instrumentation hats come about. There currently are at least five manufacturers of computerized rapid-scanning detector systems. The choices in commercial instrumentation range from a mechanically scanned system with a single photomultiplier detector to photodiode array detector systems. This review includes descriptions of the currently available commercial systems. Because the authors experience in the field of RSSF spectroscopy is limited to the use of diode array detector systems and because most of the commercial instruments have appeared on the market just within the past 12 months, it has not been possible to make detailed performance evaluations and comparisons of the new commercial systems. 

APPLICATIONS OF RAPID-SCANNING, STOPPED-FLOW (RSSF) UV-VISIBLE SPECTROSCOPY TO THE STUDY OF BIOLOGICAL SYSTEMS... 

Thus, this paper gives tantalising glimpses of the possible applications of in-situ rapid-scan time-resolved FTIR spectroscopy. Unlike the digital time-resolved technique, the rapid-scan method does not require reaction reversibility and may thus have wider application. The technique does have its limitations, however. 

Johnson T J, Simon A, Weil J M and Harris G W1993 Applications of time-resolved step-scan and rapid-scan FT-IR spectroscopy dynamics from ten seconds to ten nanoseconds Appl. Spectrosc. 47 1376-81... 

If the investigation of the chemical mechanisms of enzyme-catalyzed reactions is to be successful, then detection and identification of transient intermediates along the reaction path are essential components. The application of rapid-scanning stopped-flow (RSSF) UV/visible spectroscopy to the study of enzyme catalysis may be of considerable significance in certain instances as a tool for both the direct detection and the identification of transient chemical intermediates. 

Significant Applications Use of Rapid-Scanning Stopped-Flow Spectroscopy to Investigate Enzyme Structure-Function Relationships... 

The advent of rapid-scanning FTIR systems has tremendously expanded the application of vibrational spectroscopy in the field of rheo-optics and will certainly stimulate further progress in this research area. A similar developm t can presently be observed for X-ray diffraction since the availability of synchrotron... 

Ori ally ai lied jH edominantly as an analytical tool in the field of polymer characterization infrared spectroscopy has bem increasingly utilized in the last decades for the ducidation of the diysical structure of polymers. However, with the advent of rapid-scanning FTIR instruments and the development of the iheo-optical FTIR technique infrared spectro py has been launched into a completely new ex of polymer ph ical applications. 

A polymeric material coated onto, for example, aluminum is easily measured by an attenuated total reflectance attachment. Vibrational spectroscopy, IR, or NIR may be used for this application. A possible postproduction reaction, polymerization, or coating each may be followed by a surface probe. The reaction requires only a moderately fast instrument, such as a rapid scanning IR or NIR. Monitoring a continuous process, e.g., a lamination of two or more layers, requires a rapidly scanning device. In this case, an interferometric IR/NIR or accoustooptic device is able to scan hundreds to thousands of sample points per minute. 

Rapid reversible processes can be studied by FT-IR spectrometry in at least four ways, two using rapid-scan interferometers and two using step-scan interferometers. Three of these approaches, asynchronous sampling and stroboscopic measurements with a rapid-scan interferometer and time-resolved spectroscopy with a step-scan interferometer, were described in Sections 19.2 and 19.3. The fourth approach involves the use of a step-scan interferometer and some type of sample modulation. We have seen one application in the earlier part of this chapter, and two other applications will now be described. The reorientation of liquid crystals induced by rapid switching of the electric field to which they are being subjected has been studied by at least three of these approaches. Results have been summarized in an excellent article by Czamecki [17]. In this section we discuss the application of sample-modulation FT-IR spectrometry to this problem. 

A rapid scan version of two-dimensional spectroscopy is introduced and applied to study the phases of an acrylonitrile-butadiene-styrene polymer system. Some recent advances in the application of computational chemistry to the evaluation of vibrational spectra are presented. Some specific applications are discussed. 31 refs. 

One of the major advantages of FTIR spectroscopy is its rapid scanning capability, which has opened new applications of IR spectroscopy. These new applications require continuous monitoring in short time intervals and extremely small differences between spectra. With currently available commercial instrumentation, inter-... 

Both instrument design and capabilities of fluorescence spectroscopy have greatly advanced over the last several decades. Advancements include solid-state excitation sources, integration of fiber optic technology, highly sensitive multichannel detectors, rapid-scan monochromators, sensitive spectral correction techniques, and improved data manipulation software (Christian et al., 1981 Lochmuller and Saavedra, 1986 Cabaniss and Shuman, 1987 Lakowicz, 2006 Hudson et al., 2(X)7). The cumulative effect of these improvements have pushed the limits and expanded the application of fluorescence techniques to numerous scientific research fields. One of the more powerful advancements is the ability to obtain in situ fluorescence measurements of natural waters (Moore, 1994). 

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