Laser Raman microprobe

Laser Raman Microprobe. A more sophisticated microscope is the Laser Raman Microprobe, sometimes referred to as MOLE (the molecular orbital laser examiner). This instmment is designed around a light microscope to yield a Raman spectmm (45) on selected areas or particles, often <1 ia volume. The data are related, at least distantly, to iafrared absorption, siace the difference between the frequency of the exciting laser and the observed Raman frequency is the frequency of one of the IR absorption peaks. Both, however, result from rotational and vibrational states. Unfortunately, strong IR absorption bands are weak Raman scatterers and vice versa hence there is no exact correspondence between the two. 

Thomas R. (2000) Determination of water contents of granite melt inclusions by confocal laser Raman microprobe spectroscopy. Am. Mineral. 85, 868-872. 

Aerosol Heterogeneity. The variation of the chemical composition from particle to particle within an aerosol size class has been probed in a number of ways. Single-particle chemical analysis has been achieved by using the laser Raman microprobe (25) and analytical scanning electron microscopy (26). With the electron microscope techniques, the particle can be sized as well as analyzed chemically, so the need for classification prior to sample collection is reduced. Analyzing hundreds to thousands of particles provides the information necessary to track the particles back to their different sources but is extremely time consuming. 

The Laser Raman microprobe constitutes a physical method of microanalysis based on the vibration spectra characteristic of polyatomic structures. A focused laser beam excites the sample. The light diffused by the Raman effect is used for identification and localisation of the molecular constituents present in the sample. An optical microscope allows a survey of the interesting structures and the placing of the laser beam. The spectra obtained from fossil organic particles generally match well the corresponding IR-spectra, but the features in particular yield additional information, which will be discussed below with the given examples (Fig. 23, p. 36). 

Applications of IR and Raman spectroscopy to the study of clinkers and unhydrated cements have been reviewed (B39,B40). The laser Raman microprobe, with which regions of micrometre dimensions on a polished surface may be examined, has been used to investigate structure and crystallinity, especially of the alite and belite (Cl9). Spectroscopic methods for studying the surface structures and compositions of cements are considered in Section 5.6.2. 

The single crystal of gas hydrate prepared from H2 + CO2 and H2 + CO2 + THF mixtures was analyzed by in situ Raman spectroscopy using a laser Raman microprobe spectrophotometer with multichannel CCD detector. In the present study, the single crystal was defined as the gas hydrate crystal for which the Raman peak of the intermolecular 0-0 vibration mode can be detected. The argon ion laser beam (wavelength 514.5 nm, power 100 mW) or He-Ne laser beam (wavelength 632.8 nm, power 35 mW) condensed to 2 pm in spot diameter was irradiated to the sample through the upper sapphire (or quartz) window. The backscatter of the opposite direction was taken in with the same lens. The spectral resolution was about 1 cm ... 

Raman Spectroscopy Measurements. The methane molecules in hydrate were analyzed by Raman spectroscopy by use of a laser Raman microprobe spectrometer (JASCO NSR-1000). The temperature of hydrate crystal was kept constant at 253 K during Raman measurements and heating the sample F by use of a freezing stage (Linkam LK-FDCSI). 

Brooker (1997) measured the Raman spectra using a Laser Raman Microprobe Renishaw and a conventional spectrometer Coderg PHO. A super-notch filter served as a monochromator in front of the entrance slit of a single grating, which in turn disperses the Raman beam onto a 400 x 600 CCD detector. The Laser Raman Microprobe was equipped with a 632.8 nm helium-neon laser of 10 mW power and a 514.5nm argon ion laser of 50 mW power with the appropriate super-notch filters. The laser beam was focused into the sample by a lens with an Olympus microscope and the back-scattered Raman light was collected by the same lens. Samples of molten salts were sealed in capillary tubes under dry nitrogen or vacuum. 

The surface morphology, thickness and quality of the deposited carbon films are analyzed by scanning electron microscopy (SEM), by energy dispersive x-ray (EDx) and by Raman spectroscopy (RS). The Raman spectrum was recorded using an argon ion laser Raman microprobe. The exciting laser wavelength is 632.81 nm with a laser power equal to 1.75 mW. The instrument was operated in the multi-channel mode with the beam focused to a spot diameter of approximately 2 pm. 

Pasteris, J. D., B. Wopenka J. C. Seitz, 1988. Practical aspects of quantitative laser Raman microprobe spectroscopy for the study of fluid inclusions. Geoch. Cosmoch. Acta. 52 979-988. Petrichenko, 0. I., 1973. Methods of Study of Inclusions in Minerals of Saline Deposits. Naukova dumka, Kiev, p. 98 (in Ukrainian transl. In Fluid Inclusion Research Proc. COFFI, 12 214-... 

Laser Raman Microprobe This allows information to be collected from small samples via the use of a VLM, which allows the region to be selected from which the Raman spectrum will be obtained. Surface-Enhanced Raman Scattering (SERS) This is used to examine surfaces, oxidation, catalysis, and thin films. 

LE Jurdana, KP Ghiggino, KW Nugent, IH Leaver. Confocal laser Raman microprobe studies of keratin fibers. Textile Res J 65 593-600, 1995. 

In addition the laser Raman microprobe has been used in combination with HPTLC/SERS spectroscopy for the investigation of HPTLC spots down to 1 in size or other forms of microsamples approaching the femtogram level in mass. 

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