Raman microscope spectrometer

Fletcher, RD.L, Haswell, S.J., and Zhang, X.L., Monitoring of chemical reactions within microreactors using an inverted Raman microscopic spectrometer. Electrophoresis, 24, 3239-3245, 2003. 

The test equipment of crystal type of gas hydrates consists of a laser Raman spectrometer, gas supply system, jacketed cooling type high-pressure visual cell, temperature control system, data acquisition and other parts. The experiment using a laser Raman spectrometer for the JY Co. in French produced Lab RAM HR-800 type visible confocal Raman microscope spectrometer. Laboratory independently designed a cooled jacket visible in situ high-pressure reactor, reactor with sapphire window to ensure full transparency of laser, and high pressure performance, visual reactor effective volume 3 ml, compression 20 MPa effective volume, to achieve characteristics of gas hydrate non-destructive and accurate measurement. The schematic representation of equipment is shown in Eigure 1. 

Figure 7.27 Confocal Raman microscope spectrometer. The sample is illuminated by a laser light reflected on a dielectric mirror (DM) combined with a highly selective Notch filter. The Raman signals scattered from the sample are detected by highly selective avalanche photo diodes (APD) or via a monochromator on a CCD detector. The sample is scanned in two or three dimensions and the...

Bruker has introduced an FT-Raman microscope which is an accessory to an FT-IR spectrometer (42). The coupling between the microscope and the Raman module is made by NIR-fiber optics. In the wavelength range of the Raman experiment excited by a Nd YAG laser, the fiber optics transmission is at a maximum, thus allowing the experiment to be successful (43). Spatial resolution down to 5//m can be achieved. The technique appears to be a capable adjunct to FT-IR microscopy. 

Delhaye and Dhamelincourt (1975) were the first to combine a Raman spectrometer with a microscope. Kiefer (1988) described the Raman spectroscopy of single particles of aerosols by the optical levitation technique, an approach which is even possible with a compact spectrometer (Hoffmann et al., 1992). Raman spectra recorded with NIR FT Raman microscopes have proven the value of this technique (Messerschmidt and Chase, 1989 Bergin and Shurwell, 1989 Simon and Sawatzki, 1991). Examples of micro Raman spectra obtained from different spots on certain biological samples have been published (Schrader, 1990 Puppels et al., 1991). 

A different approach to liquid crystal filters led to the development of a nondispersive Raman spectrometer used commercially in a Raman microscope... 

Raman spectroscopy requires highly monochromatic light, which can be provided only by a laser source. The laser source is commonly a continuous-wave laser, not a pulsed laser. The laser source generates laser beams with the wavelengths in the visible light range or close to the range. In a Raman microscope, sample illumination and collection are accomplished in the microscope. The microscope s optical system enables us to obtain a Raman spectrum from a microscopic area this is the main difference between the micro-Raman and conventional Raman spectrometers. 

Raman microspectroscopy was not a completely new concept. In 1966, Delhaye and Migeon [35] showed that a laser beam could be hghtly focused at a sample, and that Raman-scattered light could be collected and transferred to a spectrometer, with minimal loss. Their calculahons showed that the increased irradiance more than compensated for the decrease in the size of the irradiated volume. The first Raman microscope was reported by Delhaye and Dhamelincourt in 1975 [36], and an instrument based on these principles (the MOLE) was introduced by Jobin Yvon at about the same time. However, the optical scheme used for imaging, which employed global illumination, was inefHcient and it was not until the advent of CCD-Raman spectrometers that the advantages of Raman microscopy became apparent. 

FT-Raman spectra were recorded using a Bruker IFS66 spectrometer with FRA 106 Raman module attachment and dedicated microscope. The wavelength excitation was at 1064 nm, using a Nd +/YAG laser. The spectral resolution was 4cm and from 2000 to 4000 scans were accumulated over about 30-60 minutes to improve the spectral signal-to-noise ratios. For analyses with 785, 633, 514.5 and 488 nm laser excitation a Renishaw InVia Reflex Raman Microscope coupled to a Leica DMLM microscope with 5X, 20X, and 50X objective lenses were utilized. 30-70 accumulations at 10 s exposure time for each scan with a laser power between 0.5 to 50 mW were typically used to collect spectra. 

There are three types of Raman spectrometers in general use today for the characterization of protein or nucleic acid structure (a) the classic laser Raman spectrometer,(b) the laser Raman microscope, " and (c) the ultraviolet resonance Raman spectrometer. In the classical system... 

Variable temperature spectroscopy, both IR and Raman, can be achieved either by using a variable temperature cell or chamber in a standard spectrometer or by including a variable temperature stage when using an IR or Raman microscope. Variable temperature cells for FT-IR use DRIFTS... 

Silver deposition is an example of a metal deposition, which can be monitored by Raman spectroscopy. A Raman spectrometer is now usually a Raman microscope using confocal... 

Raman Microscope Raman microscopy [41, 42] is a hybrid of optical microscopy and Raman spectroscopy and, in consequence, has all the concomitant advantages of both techniques. The main purpose of the microscope is to excite, collect, and couple the Raman radiation very efficiently from the sample to the Raman spectrometer, and to provide a means for sample positioning and viewing at high magnification. The Raman microscope can analyze the vibrational frequency shift at different points of a surface, so as to resolve areas with different chemical composition, which is referred to as chemical imaging. 

A Renishaw inVia Raman Microscope was utilized for scratch induced residual mechanical stress measurements. Using a Si-laser (532 nm), Raman spectra were collected from several SiC particles present within the scratch grooves. The laser spot size used was around I pm. For comparison purposes, Raman spectra were also collected from several SiC particles residing outside the scratch grooves. All the Raman measurements were performed at room temperature. The Raman spectrometer was calibrated with a Si standard using a Si band position at 520.3 cm". ... 

The sample interface brings together the laser illumination and the spectrometer field of view at the desired location on the sample. The three most common sample interfaces are a sample compartment, a fiber optic probe, and a Raman microscope. Common to all three interfaces are the needs to condition the laser beam that illuminates the sample and to collect light from the sample. 

The development of Raman spectroscopy began with direct coupled systems, which are used today in many research laboratories, particularly in imaging Raman microscopes [3] and FT-Raman spectrometers [1,2]. Fiber-coupled sampling is also quite commonly... 

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