Showing papers in "Applied Spectroscopy in 1989"
TL;DR: In this article, the standard normal variate (SNV) and de-trending (DT) approaches are applied to individual NIR diffuse reflectance spectra to remove the multiplicative interferences of scatter and particle size.
Abstract: Particle size, scatter, and multi-collinearity are long-standing problems encountered in diffuse reflectance spectrometry. Multiplicative combinations of these effects are the major factor inhibiting the interpretation of near-infrared diffuse reflectance spectra. Sample particle size accounts for the majority of the variance, while variance due to chemical composition is small. Procedures are presented whereby physical and chemical variance can be separated. Mathematical transformations—standard normal variate (SNV) and de-trending (DT)—applicable to individual NIR diffuse reflectance spectra are presented. The standard normal variate approach effectively removes the multiplicative interferences of scatter and particle size. De-trending accounts for the variation in baseline shift and curvilinearity, generally found in the reflectance spectra of powdered or densely packed samples, with the use of a second-degree polynomial regression. NIR diffuse NIR diffuse reflectance spectra transposed by these methods are free from multi-collinearity and are not confused by the complexity of shape encountered with the use of derivative spectroscopy.
3,062 citations
TL;DR: In this article, a method for the quantitative subtraction of water from the transmission infrared spectra of aqueous solutions of proteins is described, which eliminates the user bias encountered with interactive methods and takes into account small baseline variations due to instrument drift.
Abstract: A method is described for the quantitative subtraction of water from the transmission infrared spectra of aqueous solutions of proteins. The 2125-cm−1 association band of water is used as an internal intensity standard, and the scaling factor is determined with the use of a second-order least-squares fit. This method eliminates the user bias encountered with interactive methods and takes into account small baseline variations due to instrument drift. Statistical analysis of the results obtained demonstrates that at 10% w/w protein concentration, the error is of the order of 2% in the region of the amide I and II bands.
232 citations
TL;DR: In this article, a correlation between antisymmetric and symmetric carboxylate group infrared absorption frequencies, cationic radii, and acetate group types was developed that can be used to differentiate between ionic, unidentate, bidentate and bridging acetate groups in aqueous metal acetate solutions.
Abstract: A correlation has been developed between antisymmetric and symmetric carboxylate group infrared absorption frequencies, cationic radii, and acetate group types that can be used to differentiate between ionic, unidentate, bidentate, and bridging acetate groups in aqueous metal acetate solutions. In solutions containing the alkali metal, alkaline earth, and Mn(II), Co(II), and Ni(II) ions, the acetate group is primarily ionic. The bound acetate groups in Ce(III), Pb(II), Sm(III), Y(III), and Yb(III) systems are bidentate. A solution of Cr(III) acetate has bridging acetate groups. Cu(II), Zn(II), and Cd(II) appear to form H-bonded unidentate structures in which an acetate oxygen not coordinated to the metal is hydrogen bonded to a coordinated water molecule. Hg(II) acetate has bridging acetate groups and might also have unidentate acetate groups.
229 citations
TL;DR: In this article, the authors studied the FT-IR spectra of 24 different woods with the use of whole wood pieces and a diffuse reflectance accessory, and three absorptions were identified, the positions or relative intensities of which are characteristic of the holocellulose/lignin ratio or of the type of lignin present in the wood.
Abstract: FT-IR spectra of 24 different woods have been studied with the use of whole wood pieces and a diffuse reflectance accessory. Three absorptions have been identified, the positions or relative intensities of which are characteristic of the holocellulose/lignin ratio or of the type of lignin present in the wood. These spectral features serve as useful indicators to distinguish between "soft" or "hard" woods.
191 citations
TL;DR: A double quadrupole arrangement to remove polyatomic ions by collisions with an added target gas has been evaluated in this paper, where the ions Ar2+, ArO+, and ArN+ were attenuated by factors of 50-400 to count rates of \lesssim 100 counts s−1.
Abstract: A double quadrupole arrangement to remove polyatomic ions by collisions with an added target gas has been evaluated. The ions Ar2+, ArO+, and ArN+ were attenuated by factors of 50-400 to count rates of \lesssim 100 counts s−1. Fifty to seventy percent of the analyte ions were retained. Removal of polyatomic ions and retention of analyte ions were favored by low-energy collisions with Xe or CH4 rather than typical target gases like N2 or Ar. Products of ion-molecule reactions between background ions and target gas in the first quadrupole could be observed.
142 citations
AT&T1
TL;DR: The infrared spectra of silica gels made from alkoxides are different from those made from fumed silica, and from other amorphous silicas in which the SiO2 network is relatively complete.
Abstract: The infrared spectra of silica gels made from alkoxides are different from those made from fumed silica, and from the infrared spectra of other amorphous silicas in which the SiO2 network is relatively complete. One important feature of these spectra is the occurrence of an absorption band at 960 cm−1 due to the vibration of dangling -Si-OH bonds in the alkoxide gels, which is not present in many other silicas. There also are less well-defined absorption bands due to structural defects for the alkoxide gels, but their interpretation is speculative. Dried gels made with more concentrated reactants contain more defects, and heat treatment reduces the concentration of dangling bonds, especially above 900°C. For gels containing fluorine, two absorption bands appear at 932 and 980 cm−1, and these are interpreted as arising from terminal -SiF and -SiF2 groups, respectively.
114 citations
TL;DR: In this article, X-ray diffraction studies showed that the bulk structure was not affected by the air-plasma treatment, and the XPS valence band spectra proved a more sensitive probe of the surface chemistry of the carbon fibers than XPS core studies.
Abstract: X-ray photoelectron spectroscopy has been used to monitor the surface chemical changes on DuPont high-modulus pitch-based carbon fiber surfaces brought about by microwave air-plasma treatments for different periods of time. The air-plasma treatment increased the fiber surface functionalities, but extended treatment caused fiber damage. X-ray diffraction studies showed that the bulk structure was not affected by the air-plasma treatment. XPS valence band spectra proved a more sensitive probe of the surface chemistry of the carbon fibers than XPS core studies. Air-plasma treatment of fibers promises to be an effective method of fiber treatment.
110 citations
TL;DR: In this paper, a cautionary note about three possible artifacts that may arise during in situ laser Raman microprobe analysis of graphitic material and hydrocarbon fluids in polished rock sections is presented.
Abstract: The advent of laser Raman microprobe (LRM) instruments has permitted researchers to analyze minute (≥ 1 μm) phases in situ in their rock matrix. Geologists prefer to study such samples in polished thin-sections (in which a rock wafer is fixed with a mounting medium onto a glass slide and thinned to 30 μm thickness) or in doubly polished unmounted rock wafers (≥30 μm) like those used for microthermometry. There obviously are many advantages to doing in situ LRM analysis: direct observation of the sample grain in its textural and mineralogical context, preservation of the grain for analysis by additional techniques, and lack of physical disruption and possible modification of the grain caused by physical removal from its matrix. However, there are some problems inherent in this application of the LRM technique. This brief communication is a cautionary note about three possible artifacts that may arise during in situ LRM analysis of graphitic material and hydrocarbon fluids in polished rock sections.
103 citations
TL;DR: In this article, a simple substrate for surface-enhanced Raman scattering (SERS) was investigated, which consists of a solid support, such as a microscope slide, coated with alumina and then covered with silver.
Abstract: A new and simple substrate for inducing surface-enhanced Raman scattering (SERS) was investigated. This new SERS substrate consists of a solid support, such as a microscope slide, coated with alumina and then covered with silver. The alumina used in this work is an agglomerate-free type available in several submicron nominal particle diameters and is widely used as polishing powders. Several substrate conditions, such as the silver thickness used to coat the alumina, the amount of alumina deposited on the glass support, and the particle size of the alumina, were investigated extensively to determine the optimal experimental conditions for obtaining the SERS enhancement. In addition, it was also shown that the SERS enhancement obtained from the silver-coated alumina substrate was comparable to—or even better than—that obtained with previously used substrates. The analytical figures of merit, such as spectral features, signal reproducibility, linear dynamic range, and limits of detection, were investigated to demonstrate the analytical potential of this new substrate.
99 citations
TL;DR: In this article, a GaAlAs diode laser operating at 783 nm was combined with an unintensified charge coupled device (CCD) array detector and single grating spectrograph to obtain near-infrared (NIR) Raman spectra.
Abstract: A GaAlAs diode laser operating at 783 nm was combined with an un-intensified charge coupled device (CCD) array detector and single grating spectrograph to obtain near-infrared (NIR) Raman spectra. The spectrometer has no moving parts and retains the high sensitivity expected for multichannel, shot-noise-limited detectors. Diode laser excitation permits high-sensitivity Raman spectroscopy with reduced fluorescence interference, in comparison to that produced with conventional visible lasers. The diode laser/CCD approach should exhibit much higher sensitivity than FT-Raman systems operating at 1064 nm, at much lower laser power. The sensitivity of the system was demonstrated by an S/N ratio of 17 for the 981-cm−1 band of 0.01 M (NH4)2SO4, obtained with 30 mW of 783 nm laser power.
93 citations
TL;DR: In this article, pressure-induced correlation field splitting of the CH2 rocking mode in the infrared spectra of methylene chain systems such as polyethylene, n-alkanes, surfactants, fatty acids, and model and biomembranes provides important information concerning the interchain structural and dynamic properties.
Abstract: Pressure-induced correlation field splitting of the CH2 rocking mode in the infrared spectra of methylene chain systems such as polyethylene, n-alkanes, surfactants, fatty acids, and model and biomembranes provides important information concerning the interchain structural and dynamic properties of these systems. The pressure at which the correlation field splitting starts is a measure of the orientational disorder of methylene chains along the chain axis. Moreover, the integrated intensity ratio between the correlation field component bands of the CH2 rocking mode is a measure of the relative orientation of the zig-zag planes between neighboring methylene chains.
TL;DR: Several laser-based techniques are being developed to provide in situ determinations of size, velocity, and elemental composition for individual particulates in combustion environments as mentioned in this paper, where the detection of numerous constituent species is demonstrated, and trends observed in elemental distribution are in agreement with x-ray fluorescence measurements.
Abstract: Several laser-based techniques are being developed to provide in situ determinations of size, velocity, and elemental composition for individual particulates in combustion environments. Emphasis is placed on composition measurements using laser spark spectroscopy, and data for particulates entrained in gaseous flows are presented. Size and velocity of individual particles are determined by a colinear two-color laser scattering technique. Laser sparks (high-temperature plasmas) are produced from single particles with the use of a Q-switched Nd:YAG laser, and time-resolved emission spectra are observed. Results indicate a high sensitivity of the technique to mineral matter in coal particles. The detection of numerous constituent species is demonstrated, and trends observed in elemental distribution are in agreement with x-ray fluorescence measurements. Initial semi-quantitative results are compared with standard chemical analyses of the bulk material.
TL;DR: In this paper, a correction scheme for attenuation caused by significant absorption of the excitation or emission radiation by the fluorophore or other species was presented. But the correction scheme was tested with quinine sulfate (QS) as the analyte in the absence and presence of other chromophores (gentisic acid and methyl red).
Abstract: Fluorescence (FL) and absorbance (ABS) data are acquired simultaneously with a multiple detector spectrometer. The measured ABS is utilized in mathematical equations for automatic correction of fluorescence signals for attenuation (inner-filter effects) caused by significant absorption of the excitation or emission radiation by the fluorophore or other species. Correction equations are presented which apply to situations in which the excitation or emission beam cannot be considered monochromatic, for collection geometries involving optical fibers, and for chemiluminescence measurements. The correction scheme was tested with quinine sulfate (QS) as the analyte in the absence and presence of other chromophores (gentisic acid and methyl red). Even when conditions are such that the FL signal is attenuated by a factor of 5, the correction scheme is accurate to 2% or better. These corrections extend the linear range of the QS calibration curve by a factor of over 100, and they can improve the accuracy up to a factor of ten in cases for which polychromatic effects are important.
TL;DR: In this article, the emission characteristics of laser-induced plasma, with the use of a Q-switched ruby laser of 1.5 J, were studied in argon atmosphere at reduced pressure.
Abstract: The emission characteristics of laser-induced plasma, with the use of a Q-switched ruby laser of 1.5 J, were studied in argon atmosphere at reduced pressure. The time- and spatially resolved emission profiles were measured. In argon atmosphere at reduced pressure, the emission period of plasma is elongated to over a hundred microseconds, and the emissive region expands to more than a few tens of millimeters above the sample surface. The emission intensities of atomic lines increase severalfold in an argon atmosphere, in comparison with those obtained in air at the same pressure. Moderate confinement of plasmas and a resultant increase of emission intensities are achieved at 50 Torr. These results are explained by the chemical inertness and the thermal characteristics of the argon atmosphere and the decrease in absorption of the laser pulse by the plasma plume. The re-excitation of emissive species by collisions with metastable argon atoms seems to be less important.
TL;DR: In this article, a near-infrared Fourier transform (near-IR FT) Raman spectroscopy was used to predict mass percentages of liquid fuel mixtures without the use of an internal standard.
Abstract: Near-infrared Fourier transform (near-IR FT) Raman spectroscopy was used to predict mass percentages of liquid fuel mixtures without the use of an internal standard. The 29 mixtures making up the calibration set were composed of varying mass percentages of unleaded gasoline, super-unleaded gasoline, and diesel. Predictions were made with the use of classical least-squares with the pure components. Root mean square error (RMSE) values for all samples were 13.5, 13.8, and 5.2% (absolute error) for unleaded, superunleaded, and diesel, respectively. Using an estimate of the pure spectra determined by calibration gave RMSE values of 13.3% for unleaded, 12.2% for superunleaded, and 5.0% for diesel. A partial least-squares (PLS) model was able to partially compensate for matrix effects. Using different portions of the Raman spectra reduced the RMSE to 5.7% for unleaded, 5.2% for superunleaded, and 1.3% for diesel.
TL;DR: A 0.1 M sodium dodecyl sulfate (SDS) micellar mobile phase and C-18 stationary phase were used to separate triethyltin bromide, tripropyltin trichloride, trimethyltrin chloride, and triptin chloride with a 0.02 M SDS mobile phase as mentioned in this paper.
Abstract: Inductively coupled plasma mass spectrometry has been used as a detector for several organotin compounds which were separated with the use of micellar liquid chromatography. Trimethyltin chloride, triethyltin bromide, and tripropyltin chloride were separated with a 0.1 M sodium dodecyl sulfate (SDS) micellar mobile phase and C-18 stationary phase. Detection limits for the three were 27, 51, and 111 picograms tin, respectively. A 0.02 M SDS mobile phase was used to separate mono-methyltin trichloride, dimethyltin dichloride, and trimethyltin chloride. Detection limits for these compounds were 46, 26, and 126 picograms tin, respectively. Preliminary separation of those five organotin compounds was obtained by gradient elution. Calibration curves were linear over 3.5 orders of magnitude. The relative standard deviation for ten 100-μL injections containing 4 ng tin ranged from 1.3 to 1.9% with a 0.1 M SDS mobile phase and from 3.4 to 4.8% with a 0.02 M SDS mobile phase.
TL;DR: In this paper, surface-enhanced Raman spectra (SERS) on copper and gold metal colloids were obtained with a Fourier transform Raman Spectrometer using a Nd:YAG laser (1.064 μm).
Abstract: Near-infrared (NIR) surface-enhanced Raman spectra (SERS) on copper and gold metal colloids were obtained with a Fourier transform Raman spectrometer using a Nd:YAG laser (1.064 μm) for excitation. Enhanced spectra were observed for pyridine and 3-chloropyridine (CP) on copper colloids and for tris(orthophenanthroline)ruthenium(II), Ru(o-phen)32+, on copper and gold colloids. The copper-colloid surface-enhanced Raman spectra of pyridine and CP were compared with spectra measured for these molecules on copper electrodes. NIR-SERS enhancements on the metal colloids were at least as large as for visible-wavelength excited SERS. Good-quality spectra of Ru(o-phen)32+ were obtained at solution concentrations as low as 0.025 mM.
TL;DR: In this paper, general principles for the selection of samples in the calibration of near-infrared (NIR) spectrophotometers are discussed, and suggestions of alternative strategies are illustrated by examples.
Abstract: General principles for the selection of samples in the calibration of near-infrared (NIR) spectrophotometers are discussed. The discussion ends with suggestions of alternative strategies, which are illustrated by examples.
TL;DR: In this article, the fundamentals of NMR imaging are described, providing a platform for application of nMR imaging to diffusion processes in polymers, as well as examples of the diffusion process that NMR Imaging is uniquely qualified to study.
Abstract: Nuclear magnetic resonance (NMR) imaging is sensitive to the mobile protons of solvent molecules and, as such, is well suited for studying the solvent diffusion in polymers. The fundamentals of NMR imaging are described, providing a platform for application of NMR imaging to diffusion processes in polymers. The constraints on the imaging experiment imposed by the diffusion process are discussed with respect to sample geometry and the rate of diffusion. A fast imaging scheme known as FLASH is described as an alternative method which reduces the influence of the diffusion rate and NMR relaxation parameters. Example images are given with regard to each of the constraints. An example of the successful application of NMR imaging to the study of Case II diffusion in PMMA is also given. The advantages and disadvantages of NMR imaging as applied to diffusion in polymers, as well as examples of the diffusion process that NMR imaging is uniquely qualified to study, are given in the conclusion.
TL;DR: In this article, the second derivative of the sum of an appropriate number of component curves is used to deconvolve the spectral component profile by fitting it with the second-derivative transformation.
Abstract: Most curve-fitting procedures deal with an unknown, variable baseline by modeling it with a function involving a number of parameters. In view of the facts that (1) there is often no analytically relevant information in the baseline, and (2) there is usually no functional form known, a priori, for the baseline, we have chosen to eliminate it by means of the. second-derivative transformation. The resulting profile is deconvoluted by fitting it with the second derivative of the sum of an appropriate number of component curves. The utility of this procedure is demonstrated on simulated data with typical baselines and noise levels, and on real FT-IR data. Peak parameters (such as position, width, and area) obtained from this technique are comparable to those obtained by fitting the original spectrum with Lorentzian curves and a simple baseline. The major advantage of this procedure is the reduction in the number of parameters that must be optimized in the fitting method. Applications of the technique could eliminate contributions from other complex baseline profiles in the quantitative analysis of spectral components.
TL;DR: In this paper, it was shown that the presence of concomitant species enhances the fraction of ions that are excited and that therefore emit light in the ICP at some heights in ICP, matrix induced depressions of the emission intensity in the center are equal to enhancements off-center.
Abstract: Changes in analyte emission intensities occur when either easily or non-easily ionizable elements are present as concomitant species at a concentration of 0.05 M. The direction (enhancement or depression of emission signals) and magnitude of the matrix effect are strongly dependent on radial and vertical location in the plasma. At some heights in the ICP, matrix-induced depressions of the emission intensity in the center are equal to enhancements off-center. As a result, no change in the line-of-sight emission intensity is observed. Initial fluorescence measurements suggest that the number of analyte ions in the normal analytical zone decreases in the presence of each of the concomitant species studied. However, it appears that the presence of concomitant species enhances the fraction of ions that are excited and that therefore emit light. The presence of Na and K resulted in larger enhancements in the fraction of ions excited than did the presence of Fe, Ni, or Ba.
TL;DR: In this paper, a linear relationship was found between the carbonyl stretching frequency (vC=O) and the carbon-13 chemical shift data [δ(13C = O)] for the carbinar group of 0.345 mole % acetone in a mixed solvent solution ranging from 1.5 to 70.8 mole % CHCl3/CCl4.
Abstract: A linear relationship is found to exist between the carbonyl stretching frequency (vC=O) and the carbon-13 chemical shift data [δ(13C=O)] for the carbonyl group of 0.345 mole % acetone in a mixed solvent solution ranging from 1.5 to 70.8 mole % CHCl3/CCl4. The correlation shows that as vC=O decreases in frequency δ(13C=O) increases in frequency as the concentration of CHCl3 increases in the acetone/CHCl3/CCl4 solutions. However, the relationship between vC=O and the mole % CHCl3/CCl4 and between δ(13C=O) and the mole % CHCl3/CCl4 is not linear over the concentration range studied. Both hydrogen bonding and bulk dielectric effects most likely contribute to the change in both the IR and NMR data with change in the CHCl3/CCl4 ratio.
TL;DR: In this paper, a phase-resolved two-dimensional fluorescence measurement system using an image dissector tube (IDT) has been developed, where gain control characteristics of the blanking electrode (located between the aperture plate and the first dynode of the IDT) are utilized to allow heterodyne detection with lowvoltage control signals.
Abstract: A new phase-resolved two-dimensional fluorescence measurement system using an image dissector tube (IDT) has been developed. The gain control characteristics of the blanking electrode (located between the aperture plate and the first dynode of the IDT) are utilized to allow heterodyne detection with low-voltage control signals. Heterodyning the modulated fluorescence and reference signals at the blanking electrode of the IDT provides high-frequency response up to 1 GHz, in contrast to the 20 MHz bandwidth of the dynode chain due to electron transit time spread. Significant improvement of time resolution is observed. Fluorescence intensity and lifetime data are derived from the dc and ac components of the phase-resolved signals respectively. Two-dimensional measurements can be performed by electronically scanning images within the IDT. Details of the instrumental system and typical fluorescence lifetime distribution measurements are presented.
TL;DR: In this article, the capabilities of a step-scan Fourier transform spectrometer for obtaining time-resolved spectra from a pulsed fluorescent lamp are reported. But the authors focus on the potential of the stepscan interferometry for time-resolution infrared measurements of a variety of transient phenomena.
Abstract: The capabilities of a step-scan Fourier transform spectrometer of obtaining time-resolved spectra are reported. As a demonstration of the method, time-resolved spectra from a pulsed fluorescent lamp are presented. The potential of step-scan interferometry for time-resolved infrared measurements of a variety of transient phenomena is discussed.
TL;DR: In this paper, the mechanical denaturation process of silk fibroin is examined by Raman spectroscopy and the effect of water content in liquid silk on this conformational transition process is revealed and discussed.
Abstract: The mechanical denaturation process of silk fibroin is examined by Raman spectroscopy. The fresh silk fibroins from the middle gland of mature silkworms are drawn to various ratios on a tensile tester (R = ldrawn/linitial, where l is length) and their conformations are measured with Raman spectroscopy. Undrawn silk fibroin is mainly in the random coil structure with some α-helical conformation, the characteristic bands appearing at 1252 and 1660 (random coil) and at 942, 1106, and 1270 cm−1 (α-helix). When the samples are drawn up to R = 4 at an extension rate of 500 mm/min, two peaks at 1233 cm−1 (the amide III band) and 1085 cm−1 appear; it is shown that the β-sheet conformation is then formed. With an increase in drawing ratios, the intensities of these β-sheet bands increase and those of the random coil and α-helical bands decrease gradually. These changes indicate that, under the action of stress, the conformation of fibroin is altered from random coil and α-helix to β-sheet structures. This result is quite similar to the results achieved by the spinning of the silkworm. The effect of the water content in liquid silk on this conformational transition process is revealed and discussed.
TL;DR: In this article, the electron acceptor number (AN) values for each solvent versus the vC=O frequencies for acetone and tetramethylurea in solution with these solvents suggests that the AN values are not a precise measure of solute/solvent interaction for all solute-solvent systems.
Abstract: Variation in the correlations obtained between electron acceptor number (AN) values for each solvent versus the vC=O frequencies for acetone and tetramethylurea in solution with these solvents suggests that the AN values are not a precise measure of solute/solvent interaction for all solute/solvent systems. Factors such as intermolecular hydrogen bonding between solute and solvent and the differences between molecular geometry of the solutes and solvents most likely account for differences in the solute/solvent interaction for different solutes in the same solvents.
TL;DR: In this article, the dependence of enhancement of the infrared bands by thin Ag films on the molecular structure of the organic compound was investigated and a different enhancement behavior for the three isomers (ortho-, meta-, and paranitrobenzoic acids) was observed and accounted for by structural features.
Abstract: The dependence of enhancement of the infrared bands by thin Ag films on the molecular structure of the organic compound was investigated. A different enhancement behavior for the three isomers—ortho-, meta-, and paranitrobenzoic acids—was observed and accounted for by structural features. The presence of the ionized species of the acids in the monolayer bonded to Ag was found, and the spectral features of the monolayer and bulk compound were compared. The splitting of the antisymmetric stretching band of the nitro group for metanitro benzoic acid strongly interacting with Ag was observed. The correlation of the morphology of the Ag surface to the magnitude of the achieved enhancement is discussed.
TL;DR: In this paper, a general method based upon reflectance and transmittance measurements in the infrared region has been developed for the determination of the optical constants n(v and k(v) of thin films deposited on any substrate (transparent or not).
Abstract: A general method based upon reflectance and transmittance measurements in the infrared region has been developed for the determination of the optical constants n(v) and k(v) of thin films deposited on any substrate (transparent or not). The corresponding computer program, written in FORTRAN 77, involves three main parts: (1) a matrix formalism to compute reflection and transmission coefficients of multilayered systems; (2) an iterative Newton-Raphson method to estimate the optical constants by comparison of the calculated and experimental values; and (3) a fast Kramers-Kronig transform to improve the accuracy of calculating the refractive index. The first part of this program can be used independently to simulate reflection and transmission spectra of any multilayered system using various experimental conditions. Two practical examples are given for illustration. Simulation of reflection spectra at grazing incidence for thin films deposited on a metal surface and determination of the optical constants for thin CaF2 layers deposited on a silicon substrate are presented.
TL;DR: In this article, a gas chromatograph was coupled with a helium microwave-induced plasma mass spectrometer for the detection of halogenated hydrocarbons and the linear dynamic ranges were found to be 2.5-3 orders of magnitude.
Abstract: A gas chromatograph was coupled to a helium microwave-induced plasma mass spectrometer for the detection of halogenated hydrocarbons. The absolute detection limits for the chlorinated compounds investigated ranged from 9.2 to 21 picograms, while the detection limits for brominated and iodinated compounds ranged from 0.92 to 1.05 picograms. The linear dynamic ranges were found to be 2.5-3 orders of magnitude. The results obtained are compared with optical emission from this and other laboratories.
TL;DR: In this paper, a He high-efficiency microwave-induced plasma, He-HEMIP, utilizing direct sample introduction with pneumatic nebulization for atomic emission and atomic fluorescence spectrometry is presented.
Abstract: Characterization studies of a He high-efficiency microwave-induced plasma, He-HEMIP, utilizing direct sample introduction with pneumatic nebulization for atomic emission and atomic fluorescence spectrometry are presented. These studies include diagnostic measurements and analytical characterization of the 150-W He-HEMIP. Diagnostic measurements include excitation temperatures with the use of aqueous and organic nebulized thermometric species, electron number densities, and ionization temperatures for the plasma. The effect of sample uptake rate on the emission intensity is investigated. Ionization interferences are minimal, and phosphate interferences were found not to occur. In addition, the He-HEMIP is characterized as an atom source for metals and nonmetals with the use of atomic emission spectrometry and atomic fluorescence spectrometry. With AES, detection limits for metals and nonmetals are in the sub-ppm range. With AFS, detection limits for metals were determined to be in the low to sub-ppb range and were found to be not statistically different from those reported for HCL-ICP-AFS. Linear ranges for AES and AFS ranged from four up to five and one-half orders of concentrative magnitude.