摘要 :
Coherent Anti-Stokes Raman Spectroscopy (CARS) is a recently developed method that shows great promise for extending and complementing the applicability of standard Raman spectroscopic techniques. An apparatus to observe the nonli...
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Coherent Anti-Stokes Raman Spectroscopy (CARS) is a recently developed method that shows great promise for extending and complementing the applicability of standard Raman spectroscopic techniques. An apparatus to observe the nonlinear generation of coherent anti-Stokes Raman beams was constructed. Three different types of nitrogen lasers were built and each was critically evaluated. One type, which provided the highest power, was used to simultaneously pump two tunable dye lasers. The backgrounds and design features of each of the laser types are discussed. When two dye laser beams were crossed and focused in a Raman active material, the sample emitted higher frequency anti-Stokes radiation. Due to system limitations, this radiation was diffuse rather than a collimated beam. The theory of Coherent Anti-Stokes Raman Spectroscopy (CARS) is also discussed.
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Recent advances in semiconductor laser technology have produced a reliable lightweight device ideally suited for a spacecraft high resolution molecular spectrometer. Lead-salt tunable diode lasers (TDL) emit in several spectral mo...
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Recent advances in semiconductor laser technology have produced a reliable lightweight device ideally suited for a spacecraft high resolution molecular spectrometer. Lead-salt tunable diode lasers (TDL) emit in several spectral modes, each with a very narrow linewidth of -0.0003/cm. This spectral resolution is much narrower than typical Doppler broadened molecular linewidths in the mid-IR range. Thus it is possible to detect individual rotational lines within the vibrational band and measure their intensity, which can be used to determine gas concentration. The narrow spectral lines of any impurity gas tend to lie between the narrow lines of the gas of interest. This represents a major advantage over the accepted gas chromatograph mass spectrometer (GCMS) technique for measuring gas concentrations and isotope ratios. The careful and extensive gas purification procedures required to remove impurities for reliable GCMS measurements will not be required for an IR laser gas analysis. The infrared laser gas analysis technique is being developed to measure stable isotopic ratios of gases such as CO2, CH4, N2O, and NH3. This will eventually lead to development of instruments capable of in situ istopic measurements on planets such as Mars. The carbon (C-12, C-13) isotope ratio is indicative of the type of carbon fixation mechanisms (e.g., photosynthesis, respiration) in operation on a planet, while the nitrogen (N-14, N-15) isotope ratio can probably be used to date nitrogen-bearing Martian samples. The absorbance ratio of two adjacent lines of CO2 in the 2300/cm (4.3 micron) region of the spectrum was measured. The precision of the measurement is presently better than 1 percent and significant improvement is anticipated as rapid sweep-integration techniques and computer controlled data acquistion capabilities are incorporated.
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Twelve laser-excited atomic fluorescence methods suitable for absolute temperature measurements in flames and other atomic and/or ionic reservoirs are reviewed and summarized. The different characteristics of the techniques are di...
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Twelve laser-excited atomic fluorescence methods suitable for absolute temperature measurements in flames and other atomic and/or ionic reservoirs are reviewed and summarized. The different characteristics of the techniques are discussed. Several important parameters that need to be evaluated experimentally and the assumptions that need to be made in order to obtain meaningful temperature data from the selected method are emphasized.
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A new Nd:YAG laser was purchased using AFOSR-DURIP funds and this laser was incorporated into a new infrared laser spectroscopy system based on emerging OPO/OPA technology. This laser is now employed in the study of the IR spectro...
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A new Nd:YAG laser was purchased using AFOSR-DURIP funds and this laser was incorporated into a new infrared laser spectroscopy system based on emerging OPO/OPA technology. This laser is now employed in the study of the IR spectroscopy of size-selected metal ion complexes. Initial results have been obtained for Mg(+) and Fe(+) ions in complexes with CO2 and in mixed CO2/Ar complexes. The initial results are quite promising, and they suggest that this IR spectroscopy methodology will become a general way to determine the structures of clusters and to investigate their growth dynamics.
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The solvent extraction of metal ions from an aqueous solution to a nonpolar organic phase is a separation operation of major technological significance in the hydrometallurgical and nuclear industries. It is now recognized that th...
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The solvent extraction of metal ions from an aqueous solution to a nonpolar organic phase is a separation operation of major technological significance in the hydrometallurgical and nuclear industries. It is now recognized that the interrface plays a key role in the extraction process. However, the interfacial chemistry which occurs in the solvent extraction of metal ions is still very incompletely understood. Although investigations of the interfacial behavior of extraction reagents, in the past, have provided valuable information, progress is becoming more difficult in obtaining new fundamental information from classical surface-chemical approaches. The application of more sophisticated and recently developed techniques, such as laser techniques, holds promise for significant advances in understanding the molecular principles underlying the interfacial behavior of extractant molecules and thier interactions with metal ions. This paper will discuss recent advances in laser light-scattering and laser fluorescence techniques and their application to liquid/liquid interfacial systems. (ERA citation 12:016384)
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A coherent anti-Stokes Raman scattering (CARS) experiment has been assembled and used to determine temperatures in various flame experiments. Using the Q-branch rotational-vibrational cars signal from the N2 molecule, temperature ...
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A coherent anti-Stokes Raman scattering (CARS) experiment has been assembled and used to determine temperatures in various flame experiments. Using the Q-branch rotational-vibrational cars signal from the N2 molecule, temperature profiles in Ch4/air and Ch4/NeO premixed flames have been obtained. Additionally temperatures have been determined for H2 and CH4 diffusion flames using the CARS signal from the Q-branch of H2. Several possible experiments in ballistics (muzzle flash and propellant strand burning) are discussed in the report.
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