Coupled Raman

Key Features of Fiber-Coupled Raman Sampling Probes... 

N Everall, K Davis, H Owen, MJ Pelletier, J Slater. Density mapping in poly(ethylene terephthal-ate) using a fiber-coupled Raman microprobe and partial least-squares calibration. Appl Spectrosc 50 388-393, 1996. 

IR Lewis, JM Shaver, ML Samford. Advances in fiber-coupled Raman microprobes and chemical mapping. In DB Williams, R Shimizu, eds. Institute of Physics Conference Series No. 165. Philadelphia Institute of Physics, 2000, pp 91-92. 

In an article published in 1996, Nave [124] described a need to measure hydrogen concentrations. He noted that hydrogen is an important gas used in a number of chemical processes, but also noted that it can be dangerous if not handled properly. Nave [124] coupled a 532-nm-excitation fiber-coupled Raman spectrometer and a pressurizing loop to measure hydrogen to a sensitivity of 0.1%. 

Bimetal thermometer Vortex-shedding — diaphragm coupled Raman spectroscopy... 

Similarly, Raman spectroscopy has been coupled with DSC. Instmmental and experimental details and application examples in the field of inorganic materials and polymorphism studies of organic compounds of this hyphenation technique have been summarized by Jayasooriya. However, so far applications to polymers are rare. This situation may change in the near future in view of a recendy introduced light-fiber-coupled Raman-DSC system for which first polymer applications have been reported. 

Infrared and Raman spectroscopy each probe vibrational motion, but respond to a different manifestation of it. Infrared spectroscopy is sensitive to a change in the dipole moment as a function of the vibrational motion, whereas Raman spectroscopy probes the change in polarizability as the molecule undergoes vibrations. Resonance Raman spectroscopy also couples to excited electronic states, and can yield fiirtlier infomiation regarding the identity of the vibration. Raman and IR spectroscopy are often complementary, both in the type of systems tliat can be studied, as well as the infomiation obtained. 

Time-resolved spectroscopy has become an important field from x-rays to the far-IR. Both IR and Raman spectroscopies have been adapted to time-resolved studies. There have been a large number of studies using time-resolved Raman [39], time-resolved resonance Raman [7] and higher order two-dimensional Raman spectroscopy (which can provide coupling infonuation analogous to two-dimensional NMR studies) [40]. Time-resolved IR has probed neutrals and ions in solution [41, 42], gas phase kmetics [42] and vibrational dynamics of molecules chemisorbed and physisorbed to surfaces [44]- Since vibrational frequencies are very sensitive to the chemical enviromnent, pump-probe studies with IR probe pulses allow stmctiiral changes to... 

The key for optimally extracting infonnation from these higher order Raman experiments is to use two time dimensions. This is completely analogous to standard two-dimensional NMR [136] or two-dimensional 4WM echoes. As in NMR, tire extra dimension gives infonnation on coherence transfer and the coupling between Raman modes (as opposed to spins in NMR). 

Wang C, Mohney B K, Williams R, Hupp J T and Walker G C 1998 Solvent control of vibronic coupling upon intervalence charge transfer excitation of (NC)gFeCNRu(NH3)g- as revealed by resonance Raman and near-infrared absorption spectroscopies J. Am. Chem. Soc. 120 5848-9... 

The section on Spectroscopy has been retained but with some revisions and expansion. The section includes ultraviolet-visible spectroscopy, fluorescence, infrared and Raman spectroscopy, and X-ray spectrometry. Detection limits are listed for the elements when using flame emission, flame atomic absorption, electrothermal atomic absorption, argon induction coupled plasma, and flame atomic fluorescence. Nuclear magnetic resonance embraces tables for the nuclear properties of the elements, proton chemical shifts and coupling constants, and similar material for carbon-13, boron-11, nitrogen-15, fluorine-19, silicon-19, and phosphoms-31. 

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