Optical multichannel Raman spectrometers

Multichannel Raman spectrometers are similar to the conventional systems except that the photomultiplier tube is replaced with an optical multichannel detector... 

Structural characterization of the surface metal oxide species was obtained by laser Raman spectroscopy under ambient and dehydrated conditions. The laser Raman spectroscope consists of a Spectra Physics Ar" " laser producing 1-100 mW of power measured at the sample. The scattered radiation was focused into a Spex Triplemate spectrometer coupled to a Princeton Applied Research DMA III optical multichannel analyzer. About 100-200 mg of... 

Raman spectra were obtained with a Spex Triplemate spectrometer(Model 1877) coupled to an EG G intensiTied photodiode array detector cooled thermoelectrically to -40°C, and interTaced with an EG G DMA III Optical Multichannel Analyzer(Mode1 1463). The samples were... 

The molecular structures of the surface vanadium oxide species on the different supports were examined with Raman spectroscopy. The Raman spectrometer system possessed a Spectra-Physics Ar+ laser (model 2020-05) tuned to the exciting line at 514.5 nm. The radiation intensity at the samples was varied from 10 to 70 mW. The scattered radiation was passed through a Spex Triplemate spectrometer (Model 1877) coupled to a Princeton Applied Research OMA III optical multichannel analyzer (Model 1463) with an intensified photo diode array cooled to 233 K. Slit widths ranged from 60 to 550 m. The overall resolution was better than 2 cm l. For the in situ Raman spectra of dehydrated samples, a pressed wafer was placed into a stationary sample holder that was installed in an in situ cell. Spectra were recorded in flowing oxygen at room temperature after the samples were dehydrated in flowing oxygen at 573 K. 

A tunable pulsed laser Raman spectrometer for time resolved Raman studies of radiation-chemical processes is described. This apparatus utilizes the state of art optical multichannel detection and a-nalysis techniques for data acquisition and electron pulse radiolysis for initiating the reactions. By using this technique the resonance Raman spectra of intermediates with absorption spectra in the 248-900 nm region, and mean lifetimes > 30 ns can be examined. This apparatus can be used to time resolve the vibrational spectral o-verlap between transients absorbing in the same region, and to follow their decay kinetics by monitoring the well resolved Raman peaks. For kinetic measurements at millisecond time scale, the Raman technique is preferable over optical absorption method where low frequency noise is quite bothersome. A time resolved Raman study of the pulse radiolytic oxidation of aqueous tetrafluoro-hydroquinone and p-methoxyphenol is briefly discussed. 

In summary, we have combined state of the art optical multichannel analysis techniques with the well established method of electron pulse radiolysis to construct a pulsed laser Raman spectrometer for time resolved studies of transient intermediates in solution. This apparatus can be applied to time resolve the vibrational spectral overlap between transients decaying at differ-... 

For the in situ Raman measurements, the UHV system is optically aligned with a triple monochromator Raman spectrometer (Dilor XY) equipped with a CCD camera for multichannel detection [1]. The samples were excited with the 488 nm (2.54 eV) Ar laser line that lies in the first absorption maximum of both organic molecules and thus ensures resonance conditions for the Raman process. 

The measurements were performed with an usual setup for siuface-enhanced Raman spectroscopy The Raman spectra were measured with a Spex 1406 spectrometer, the samples were illmninated with a Spectroscopy Instruments argon ion laser (A = 514 nm, 30 mW) and the spectra were detected by a Princeton Instruments optical multichannel analyzer imder computer control. All experiments were performed in an electrochemical cell containing an inert platinum working electrode mechanically... 

The absence of a, phase-matching condition means that it is also possible to use a fixed frequency pump laser with a broadband probe laser. This gives a complete Raman spectrum over the bandwidth of the probe laser (- 1000 cm l) which can be analysed using a spectrometer placed after the blocking polarizer, followed by an optical multichannel analyzer. 

Sample handling and preparation is very easy, as in the case of IR spectroscopy. Commercial instruments belong to two main types, conventional scanning and optical multichannel analysers. The main difference between both types is that, in scanning spectrometers, the scattered light is collected and analysed, usually at 1 cm intervals (channels), whereas in optical multichannel analysers a 300-600 cm section of the Raman spectrum, projected on to the detector, is rapidly recorded in a computer memory without... 

More recently, charge-transfer devices, such as charge-coupled devices (CCDs) and charge-injection devices (ClDs), have been employed in Raman spectrometers. Figure 18-11 shows a fiber-optic Raman spectrometer that uses a CCD as a multichannel detector. Here, high-quality bandpass and band-rejection (notch) filters provide good stray light rejection. The CCD array can be a two-dimensional array or in some cases a linear array. 

Figure 40 CCD detector image for a four-channel multichannel Raman analyzer based on an axial transmissive spectrometer with a multiplex grating. The eight stripes relating to the four lower-wavenumber ranges and four high-wavenumber ranges can be clearly observed. (Reproduced with permission from Kaiser Optical Systems, Inc.)...

Figure 1 Optical path of the Madrid dual Raman spectrometer, (a) PMT mode with a single-channel subtractive dispersion configuration (b) CCD mode with a multichannel configuration. (From Ref. 53, with permission.)...

The micro-Raman spectra (Fig. la) were measured by a triple multichannel spectrometer Microdil 28 (Dilor) equipped with an optical microscope (objective xlOO and numerical aperture NA=0.95) for focusing the incident laser beam (Ar+ laser, X=488.O nm, PL 10 mW, focus spot diameter of about 2 pm). The scattered light was collected in a backscattering configuration (A). 

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