Raman Spectroscopy optical detection systems

Picosecond spectroscopy provides a means of studying ultrafast events which occur in physical, chemical, and biological processes. Several types of laser systems are currently available which possess time resolution ranging from less than one picosecond to several picoseconds. These systems can be used to observe transient states and species involved in a reaction and to measure their formation and decay kinetics by means of picosecond absorption, emission and Raman spectroscopy. Technological advances in lasers and optical detection systems have permitted an increasing number of photochemical reactions to be studied in. greater detail than was previously possible. Several recent reviews (1-4) have been written which describe these picosecond laser systems and several applications of them... 

Since there are a large number of different experimental laser and detection systems that can be used for time-resolved resonance Raman experiments, we shall only focus our attention here on two common types of methods that are typically used to investigate chemical reactions. We shall first describe typical nanosecond TR spectroscopy instrumentation that can obtain spectra of intermediates from several nanoseconds to millisecond time scales by employing electronic control of the pnmp and probe laser systems to vary the time-delay between the pnmp and probe pnlses. We then describe typical ultrafast TR spectroscopy instrumentation that can be used to examine intermediates from the picosecond to several nanosecond time scales by controlling the optical path length difference between the pump and probe laser pulses. In some reaction systems, it is useful to utilize both types of laser systems to study the chemical reaction and intermediates of interest from the picosecond to the microsecond or millisecond time-scales. 

Bruckner (2001) combined UV-vis with EPR spectroscopy, using online gas chromatography for product analysis. For many transition metal ions, EPR and optical spectra are complementary, in that some states are detectable or distinguishable with only one of the methods. The UV-vis facility was added to a previously described flow reactor system for EPR spectroscopy (Bruckner et al., 1996). A fiber optical probe (Avantes, AVS-PC-2000 plug-in spectrometer) was inserted directly into the reactor via a Teflon -sealed feedthrough and placed in the catalyst bed. UV-vis spectra were reported for temperatures up to 810 K. The design was later expanded to include a third method, Raman spectroscopy (Bruckner, 2005 Bruckner and Kondratenko, 2006). A hole in the... 

Because Raman signals are typically weak, intense lasers in combination with sophisticated tight collection must be used. Although intense laser radiation can potentially harm the delicate structures in the visual system, ocular tissue has been found to be a very suitable target for Raman spectroscopy for two reasons. First, the ocular media (cornea, lens and vitreous) generally have good optical clarity, which enables high penetration of laser excitation and optical detection of scattered... 

Abstract Thin and flexible probes made with hollow-optical fibers may be useful for remote spectroscopy. Experimental results showed that these probes are useful for endoscopic measurements of infrared and Raman spectroscopy. A hollow-fiber probe has been used for remote FT-IR spectroscopy in the form of endoscopic measurement of infrared reflectometry spectra inside the body. This measurement was made possible by the hollow-fiber probe s flexibility, durability, nontoxicity, and low transmission loss. A hoUow-fiber probe with a ball lens at the end works as a confocal system for Raman spectroscopy. It can thus detect the molecular structure of biotissues with a high signal-to-noise ratio. Owing to their small diameter, the probes are useful for in vivo, noninvasive analysis using a flexible endoscope. 

Reduction of sulfur in DM SO gives two waves in the (CV). It was shown by reflection spectroelectrochemistry that the first reduction gives Sg , which rapidly decomposes by follow-up reactions to S6 , S4 , S3 , and S . Three of these, Sg , Se , and S are further reduced at the second wave [52]. The reduction to S3 has also been studied in dimethyl formamide (DMF) using time-resolved spectroscopy/DVCA using reflection with fiber-optic/CCD detection [54], and Raman spectroscopy [70], as has the corresponding Se system [71]. Further refinements to the sulfur mechanism have appeared [70]. 

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