bluuebunny/crossref_metadata_2025 huggingface dataset:
Excited Species from a Pulsed Discharge in Helium at One Atmosphere Pressure
Authors: Wentworth Wayne E. , Qin Yang , Wiedeman Sophie , Stearns Stanley D. , Madabushi Janardhan
Published: May 2005

The relative intensities of atomic emission lines have been analyzed in regard to a Boltzmann distribution of the electronic levels in the pulsed discharge. The analysis confirms a Boltzmann distribution with an excitation temperature of 3200 ± 220 K, a relatively low temperature compared with that for other excitation sources, such as microwave and radio-frequency discharges. The analysis also suggests that little ionization occurs via direct excitation in the discharge. The emission spectra from excited diatomic helium states have been analyzed and confirm the formation of a32σu+) and the Hopfield emission He2( A1σu+ → 2He(11 S) continuum in the range 72 to 92 nm. Emission intensity-time profiles have been obtained for both atomic and diatomic helium emissions. Analysis of these profiles indicates that excited He2 states are obtained by two reactions: (1) an excited atomic helium reacting with a ground-state helium atom, and (2) recombination of He2+ with electrons. The study concludes that excitation in a discharge through helium at atmospheric pressure yields the following predominant species: He(23S), He2( a3σu+), Hopfield emission continuum 72–92 nm, and He2+.
Observations on the Measurement of Vibrational Circular Dichroism with Rapid-Scan and Step-Scan FT-IR Techniques
Authors: Wang Baoliang , Keiderling Timothy A.
Published: May 2005

Extensive tests to determine an optimal method for using a Bio-Rad FTS-60A spectrometer for measurement of vibrational circular dichroism (VCD) in both step-scan and rapid-scan modes are reported. In the latter case, results of “fast-scan” and “slow-scan” experiments are also presented for comparison. In step-scan mode, phase modulation (PM) during the polarization-modulation measurements is found to be detrimental to the signal-to-noise ratio (S/N), but is very useful for the normal IR measurements at slow step speeds. VCD S/N is improved by doing sequential spectral collection of the polarization-modulated spectrum without PM and the instrument response spectra with phase modulation. Systematic comparative studies are used to identify optimal parameter sets for doing the step-scan VCD measurements. These conditions use more rapid data collection with faster steps than previously suggested, which permits a more realistic evaluation of S/N and reproducibility of the spectra through comparison of spectra collected in blocks. Example VCD spectra are presented for small molecules in nonaqueous solution measured in short times and for proteins in aqueous solution measured over longer times scales. Near-IR FT-VCD measured in step-scan mode at both moderate resolution and high S/N are presented. At this stage, fast-scan, slow-scan, and step-scan techniques are shown to be virtually equivalent in the mid-IR, but the reduction in frequency dependence of the phase correction and the new capability for VCD measurement in the near-IR favor continued development of step-scan techniques.
Measurement of Aromatic Hydrocarbons with the DOAS Technique
Authors: Axelsson Håkan , Eilard Anders , Emanuelsson Annika , Galle Bo , Edner Hans , Ragnarson Pär , Kloo Henrik
Published: May 2005

Long-path DOAS (differential optical absorption spectroscopy) in the ultraviolet spectral region has been shown to be applicable for low-concentration measurements of light aromatic hydrocarbons. However, because of spectral interferences among different aromatics as well as with oxygen, ozone, and sulfur dioxide, the application of the DOAS technique for this group of components is not without problems. This project includes a study of the differential absorption characteristics, between 250 and 280 nm, of twelve light aromatic hydrocarbons representing major constituents in technical solvents used in the automobile industry. Spectral overlapping between the different species, including oxygen, ozone, and sulfur dioxide, has been investigated and related to the chemical structure of the different aromatics. Interference effects in the DOAS application due to spectral overlapping have been investigated both in quantitative and in qualitative terms, with data from a field campaign at a major automobile manufacturing plant.
Nondestructive Inspection of Graphite-Epoxy Composites for Heat Damage Using Laser-Induced Fluorescence
Authors: Fisher W. G. , Storey J. M. E. , Sharp S. L. , Janke C. J. , Wachter E. A.
Published: May 2005

Laser-induced fluorescence has been applied to the nondestructive inspection of graphite-fiber-reinforced polymer-matrix composites. Upon curing, the epoxy resin in these materials forms a highly cross-linked network of aromatic sub-units. This result yields a material with significant absorptivity from the ultraviolet through the near-infrared and a fluorescence bandwidth covering 200 to 300 nm. When subjected to temperatures beyond the recommended upper service temperature, these materials experience thermally induced degradation and a reduction in mechanical strength. Furthermore, these heat-damaged materials exhibit significant changes in fluorescence intensity and in the wavelength of maximum fluorescence intensity. These spectroscopic changes can be correlated with the extent of heat damage. An imaging approach has been developed to monitor these fluorescence signatures, allowing rapid nondestructive inspection of large surface areas. This capability provides qualitative and quantitative information about the location and severity of damage.
Quantitative Two-Dimensional Infrared (2D IR) Spectroscopy: Theoretical Development for General and Specific Cases
Authors: Ekgasit Sanong , Ishida Hatsuo
Published: May 2005

A quantitative two-dimensional correlation analysis for various spectroscopic techniques is introduced. Normalization of the spectral intensities enables two-dimensional infrared (2D IR) spectroscopy to be used for quantitative purposes. As a result of the normalization, the correlation strengths are characterized by the dynamic parameters of the correlated spectral intensities. Relationships between the chemical species associated with peak positions in 2D IR spectra are characterized by both the magnitude and the sign of the correlation strength. The magnitude describes the degree of harmonization, while the sign shows the relationship between the dynamic behaviors of the correlated spectral intensities. The phase spectrum, which indicates the quantitative relationship among the dynamic behavior of the spectral intensities, is also introduced.
Microscopic Raman Line-Imaging with Principal Component Analysis
Authors: Drumm Charlene A. , Morris Michael D.
Published: May 2005

Reconstructed Raman images of the distribution of polystyrene and polyethylene were obtained by line-imaging, with the use of univariate and multivariate processing of the spectral data. Multiple sets of microscopic Raman spectral line-images were acquired with line-focused illumination, a motorized translation stage to move the sample perpendicular to the illumination line, and a holographic imaging spectrograph equipped with a 2D detector. The line-imaged raw spectral data were processed with the use of both a simple univariate method (single-band integration) and a more sophisticated multivariate method (principal component analysis with eigenvector rotation) to generate two-dimensional Raman images representing spatial distribution of the polymers. In the spectral range employed (900–1700 cm−1), suitable bands could be found for univariate processing of the polystyrene and polyethylene images. The principal component analysis method gave equivalent separation of the images, but only if the entire spectral window was employed to generate the eigenvectors.
ATR/FT-IR Study of Vanadium Pentoxide Gel Films on Semiconductor Substrates
Authors: Bay Nguyen Thi Be , Tien Pham Minh , Badilescu Simona , Djaoued Yahia , Bader G. , Girouard Fernand E. , Truong Vo-Van
Published: May 2005

Deposition of the vanadium pentoxide on a KRS-5 ATR crystal by dip-coating has led to the formation of a thallium bronze. ATR spectroscopy is used to study the changes in the spectral pattern induced by the heat treatment of the films. The results show that both the spectrum of the xerogel and its evolution depend on the precursors and the method of preparation. The spectra of the heated thin films suggest an irreversible structural change taking place at a temperature around 220°C.
FT-IR Optical Fiber Remote Detection of Aluminum Hydroxide by Evanescent Wave Absorption Spectroscopy
Authors: Namkung Juock S. , Hoke Michael , Rogowski Robert S. , Albin Sacharia
Published: May 2005

Remote detection of very small amounts of aluminum hydroxide has been achieved with the use of evanescent wave absorption spectroscopy. Aluminum hydroxide is a principal corrosion product of aluminum. Five absorption bands have been recorded in the spectral range from 3350 to 3650 cm−1. The recorded positions, transition strengths, and widths of the absorption bands are in qualitative agreement with reference spectral data. A four-wavenumber-resolution Michelson interferometer and decoated 200-μm-core-diameter multimode chalcogenide optical fibers were combined to make the evanescent wave absorption measurements. One-to four-meter lengths of fiber were used with 15 to 25 cm of the fibers decoated. The technique is very sensitive and can detect a very small amount of aluminum hydroxide in contact with the decoated fiber core. This study is a valuable step in the development of a technique for monitoring industrial corrosion of aluminum alloys.
Solvation of Lauric Acid Studied by Vibrational Spectroscopies
Authors: Picquart Michel , Lefèvre Thierry , Lacrampe Georgette
Published: May 2005

Solvation of lauric acid [CH3(CH2)10COOH] has been investigated in different solvents (apolar, polar-aprotic, and protic solvents) by infrared absorption and Raman scattering in a large molar ratio range in order to investigate the intermolecular interactions between fatty acids and molecules of different types of solvents. Temperature effects on these mixtures have also been investigated between 24 and 95°C. We have especially concentrated on the carbonyl stretching region (between 1600 and 1800 cm−1), the hydroxyl stretching region (between 2500 and 3600 cm−1), and the C-H stretching region (2800–3000 cm−1). Chloroform behaves, with respect to lauric acid, almost as an apolar solvent. In acetone and in DMSO, a dynamical equilibrium between both cyclic dimers and H-bonded lauric acid molecules with solvent molecules seems to occur, the proportion of the two species depending on the lauric acid concentration. Cyclic dimers appear for a lauric acid: DMSO molar ratio x > 0.5 ( x > 0.2 in acetone). In alcohols, cyclic dimers are present from x &thkap, 0.2. For x < 0.2, two different complexes exist, in contrast with results from recent literature. These may be monosolvate and disolvate complexes. When the alcohol is deuterated, exchange between hydroxyl groups of both components is observed. Finally, Raman scattering appears as a powerful tool to clarify IR spectra in the case of solvated carboxylic acids.
Measurement of Fluid Film Thickness on Curved Surfaces by Raman Spectroscopy
Authors: Hutchinson Erik J. , Shu Darren , Laplant Fred , Ben-Amotz Dor
Published: May 2005

The Raman scattering intensity from a polyphenylether fluid film entrapped between a diamond window and a one-inch-diameter steel ball is found to correlate linearly with fluid film thickness over a 0.1 to 10 μm thickness range. The calibration and precision of the technique, as well as comparisons with other methods, are discussed.
Factors Influencing the Quantitative Determination of Trace Elements in Soils by Glow Discharge Mass Spectrometry
Authors: Teng Jiuwei , Barshick Christopher M. , Duckworth Douglas C. , Morton Shelby J. , Smith David H. , King Fred L.
Published: May 2005

The influence of oxygen content, conducting host matrix, and soil composition on the quantitative determination of trace elements in soils by glow discharge mass spectrometry was examined. Oxygen content and conducting host matrix identity influenced relative sensitivity factors employed in the quantitative interpretation of the glow discharge mass spectra. Soil composition did not influence these relative sensitivity factors. Unknown soils taken from the field were analyzed with the use of a set of relative sensitivity factors obtained from standard soils with certified compositions. The quantitative results from glow discharge mass spectrometry of these unknowns compared favorably with quantitative results from inductively coupled plasma atomic emission spectrometry and laser ablation solid sampling inductively coupled plasma mass spectrometry.
Waveguide CARS: A Method to Determine the Third-Order Polarizability of Thin Layers Applied to a SiOxNy Waveguide
Authors: Ranger Johannes S. , Otto Cees , Greve Jan
Published: May 2005

Waveguide coherent anti-Stokes Raman spectroscopy (WCARS) can be used to measure Raman-active vibrations of thin (mono, submono) layers deposited on dielectric waveguides. In these experiments, surface sensitivity and background-free spectra are obtained by using asymmetric mode combinations. The degree of suppression then depends upon the waveguide parameters (thicknesses, refractive indices, and third-order polarizabilities), the wavelengths used, and the selected propagating modes. With knowledge of the refractive indices and the third-order polarizabilities, the other parameters can be used to tune into a background-free region. The refractive indices of many waveguide materials are known or can easily be measured. Unfortunately, the third-order polarizabilities are most often not known and should therefore be determined experimentally. In this paper a method is outlined to measure the third-order susceptibility ( X(3)NR) of a waveguide with the use of WCARS experiments. The value X(3)NR of SiO xN y is determined experimentally and is found to be 0.22 ± 0.03 10−12 electrostatic units.
Study of Laser-Induced Plasma Emission Spectra of N2, O2, and Ambient Air in the Region 350 nm to 950 nm
Authors: Nordstrom Robert J.
Published: May 2005

Laser-induced breakdown spectroscopy (LIBS) is a technique where the output from a pulsed laser is focused onto a sample to create an intense plasma. The emission spectrum from the plasma contains quantitative information on the composition of the sample in the region of the breakdown. Growing applications of this technique include remote or in situ measurements where the atmosphere, primarily nitrogen and oxygen, may present spectral interferences. This study was undertaken to evaluate the spectral characteristics of the interference from the nitrogen and oxygen components in air. Of primary interest in this study is the atomic and molecular origin of the emission features. Comparison of the LIBS spectra with NIST atomic emission data is presented.
Analyte Transport Studies of Aqueous Solutions and Slurry Samples Using Electrothermal Vaporization ICP-MS
Authors: Fonseca R. W. , Miller-Ihli N. J.
Published: May 2005

Analyte transport of both aqueous solutions and slurry samples was studied with the use of ultrasonic slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry (USS-ETV-ICP-MS). The elements studied included V, Mn, Ni, Cu, and Pb, and the materials analyzed included NIST SRM 1548 Total Diet, SRM 1632a Coal, SRM 1566a Oyster Tissue, and NRCC LUTS-1 Lobster Hepatopancreas. The effect of microgram amounts of Pd as well as the effect of oxygen ashing on analyte transport were studied. Slurry samples were found to have better analyte transport in comparison to aqueous solutions when no physical carriers were added. Under these experimental conditions, the determined slurry concentrations were apparently high when quantified with the use of external calibration. Microgram amounts of Pd were used to investigate whether it was possible to reduce the difference in analyte transport between slurry samples and aqueous standards. The use of microgram amounts of Pd resulted in signal intensity suppression. Such a signal reduction could be related to the presence of space charge effects or losses of analyte due to condensation of the physical carrier together with the analyte on different parts of the ETV cell or the transfer line. On the other hand, quantitation for slurry samples was improved by the use of Pd as a physical carrier. Pd by itself was not completely effective for samples with high carbon content; therefore the effect of oxygen ashing combined with Pd was studied. An enhancement of signal intensities was observed when oxygen ashing was used, as well as a shift in the carbon signal to earlier times. In this case, signal enhancement was associated with an improvement in analyte transport caused by an increased number of carbon particles leaving the furnace at the same time as the analytes studied. With oxygen ashing, slurry samples behaved more similarly to aqueous solutions, facilitating quantitation with aqueous standards.
Photoacoustic FT-IR Spectroscopy of Natural Copper Patina
Authors: Salnick Alex O. , Faubel Werner
Published: May 2005

Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) has proved to be a useful tool for nondestructive testing of copper corrosion layer (patina) formed in the atmosphere. The samples cut from a piece of the roof of the Stockholm City Hall were examined without any additional pretreatment. The components of the patina—brochantite Cu4(OH)6SO4, antlerite Cu3(OH)4SO4, and basic cupric carbonate Cu2CO3(OH)6 · H2O—as well as some other minerals were identified. The photothermal beam deflection (PBD) method was used for independent photoacoustic characterization of the samples. The depth profiling capability of FT-IR/PAS was used to determine the degree of photoacoustic saturation of the spectral bands and to evaluate the depth distribution of the main patina components. The technique thus compares favorably with more common approaches of patina examination which are more expensive and require special sample preparation.
Simple Two-Color Base-Calling Schemes for DNA Sequencing Based on Standard Four-Label Sanger Chemistry
Authors: Li Qingbo , Yeung Edward S.
Published: May 2005

Two base-calling schemes for DNA sequencing are evaluated. Both are based on data collected from two broad-band emission channels derived from either one- or two-excitation channels. Standard four-dye Sanger reaction products are used in conjunction with capillary electrophoretic separation in a polymer matrix. Data acquisition is compatible with high light-throughput imaging and minimal data storage. In one scheme, commercial chromatographic software provides peak recognition and peak heights. The peak-height ratios from the two channels provide base-calling accuracies of 99.3% and 97.1% through 330 bp and 350 bp, respectively. In another scheme, ratiograms are derived from the two channels. The resulting step-like functions permit the calling of bases even when successive peaks are not resolved. The base-calling accuracy is 99% through 340 bp. Because of simplicity in implementation, either scheme should be readily applicable to high-speed, high-throughput DNA sequencing in capillary arrays.
Shipborne FT-IR Measurements of Atmospheric Trace Gases on a South (33°S) to North (53°N) Atlantic Traverse
Authors: Notholt J. , Beninga I. , Schrems O.
Published: May 2005

For the first time solar and lunar IR absorption measurements have been performed by means of an FT-IR spectrometer on a lengthy ship cruise. These measurements were performed in May and June 1994 on board the German research vessel Polarstern between Cape Town (33°S) and Bremerhaven (53°N). Spectral analysis of the obtained spectra allowed retrieval of the total zenith columns of a number of trace gases in the atmosphere and study of the latitudinal dependence of the column densities of these trace gases.
Two-Temperature Model for the Simulation of Atmospheric-Pressure Helium ICPs
Authors: Cai Mingxiang , Montaser Akbar , Mostaghimi Javad
Published: May 2005

A two-temperature model (2-T model) was used to predict fundamental properties of pure helium inductively coupled plasmas (He ICPs). Plasma characteristics with the use of the 2-T model were compared to those obtained by the local thermodynamic equilibrum (LTE) model for the He ICP, to those of an Ar ICP, and to the existing experimental data. The distributions of electron and heavy-particle temperatures, electron number density, and electric and magnetic fields were obtained as a function of the internal diameters of the torch, the gas flow rates, the gap between the plasma tube and the MACOR insert, the generator frequency, and the active power. Overall, the He ICP was predicted to have a much higher electron temperature (> 12,000 K) in the load coil region, but its axial heavy-particle and electron temperatures (∼2000 K) at the analytical zone were lower than those of the Ar ICP (4000–6000 K). The high-temperature region in the He ICP was constricted to a smaller region close to the wall of the plasma confinement tube as compared to that in the Ar ICP. Most of the input power in the He ICP was lost through the plasma quartz tube. The magnetic and electric fields inside the induction coil in the helium plasma were approximately one order of magnitude higher than those in the argon plasma.
Quasi-Continuous Wave Stimulated Raman Technique for Local Methane Concentration Measurements at Atmospheric Pressure
Authors: Pinette Thomas C. , Yin Huiqi , Laurendeau Normand M.
Published: May 2005

We report the application of quasi-continuous wave (cw) inverse stimulated Raman spectroscopy (SRS) to the quantitative measurement of methane concentrations in atmospheric mixtures near room temperature. The quasi-cw SRS signal, with the use of the v1, fundamental of methane (2916 cm−1), is shown to be proportional to the powers of both the pump and probe lasers as well as to the methane concentration. The current minimum detectable signal corresponds to ∼200 ppm (v/v).
Imaging Fluorometer to Detect Pathological and Physiological Change in Plants
Authors: Ning Li , Edwards Gerald E. , Strobel Garry A. , Daley Larry S. , Callis James B.
Published: May 2005

Fluorescence signals from plant leaves have considerable potential for improving agricultural investigations; however, to fully interpret these signals, which are distributed unevenly across the leaf, it is necessary to image the signal distribution. Leaf tissues generate complex, two-dimensional, changing, time-dependent patterns of fluorescence that occur immediately after illumination of a dark-adapted leaf. These patterns are very sensitive measures of plant photosynthetic function. Thus, we built a novel, fully computer-interfaced instrument which provides two-dimensional images of time-dependent fluorescence in photosynthetic tissue. The instrument was built with the use of parts of our recently constructed imaging spectrophotometer. This instrument employs a charge-coupled device (CCD) camera, which can acquire spectra for 31,680 positions per sample. Two simple filters remove excitation emission overlap. Software based on a novel approximation allows imaging of time-dependent fluorescence of photosystem II across the surface of a leaf. A simple reconfiguration of this instrument to image at a distance of seven meters was used to test potential remote sensing applications. The instrument's use in agriculture is demonstrated by very early determination of freeze damage, herbicide effects, and invasion by fungal pathogens.
Residual Hydrogen Determination in Perfluoropolyalkylethers Using Fourier Transform Infrared and Proton Nuclear Magnetic Resonance Spectroscopies
Authors: Liang Jim , Roselius Mark , Johnson David W.
Published: May 2005

The residual hydrogen content of several perfluoropolyalkylether base fluids has been determined with the use of proton nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR) spectroscopies. The analysis of standard samples gives a linear calibration curve for hydrogen concentrations between 0.5 and 500 ppm for both FT-IR and NMR. The two methods have similar detection limits of about 1 ppm. Analysis of identical samples of Krytox 143 AC and Krytox 143 AZ by both methods gives results which are in excellent agreement. The two methods also provide information about the chemical environment in which the hydrogen is located. In both of the Krytox samples, the hydrogen is located in CFH groups within the polymer chain.
Spectroscopic Studies of the Migration of Vanadium in the Model Fluid Catalytic Cracking Process
Authors: Cao Hui , Suib Steven L.
Published: May 2005

In order to help eliminate the deleterious effects of vanadium metals (from crude oil) on fluid cracking catalysts (FCCs) during the FCC process, spectroscopic studies on the migration of vanadium metal poisons on model FCCs have been carried out. Fresh samples of Eu-Y zeolite and AAA (aluminosilicate gel: 25% SiO2 and 75% Al2O3) matrix have been impregnated separately with vanadyl naphthenate [V(n)], vanadium(3+) acetylacetonate [V(acac)], and vanadyl tetraphenylporphine [V(TPP)]. Also, mixtures of vanadium-impregnated Eu-Y with an AAA matrix or vanadium-impregnated AAA matrix with Eu-Y were prepared, respectively. The mixtures were calcined at 540°C in flowing dry air or steamed at 730°C under hydrothermal conditions after calcination. Spectroscopic studies by energy-dispersive X-ray (EDX) analysis, scanning electron microscopy (SEM), surface area analysis [Brunauer-Emmett-Teller (BET)], electron paramagnetic resonance (EPR) spectroscopy, and luminescence were used for the study of vanadium migration between the FCC components, for the detection of the vanadium intermediates on each component during the FCC process and also to generalize the migration behavior of different vanadium precursors under calcination and steaming conditions. Vanadium species from three vanadium precursors migrated from the AAA matrices to Eu-Y or vice versa during the steaming stage. During calcining, vanadium species from V(acac) or V(n) impregnated into Eu-Y or AAA did not migrate, while small amounts of migration of V(TPP) on Eu-Y or AAA could be detected occasionally, indicating that migration during calcination, unlike migration during steaming, depended on the vanadium species. These observations and spectroscopic information may be useful for vanadium poison passivation.
Micro-Volume Time-Resolved Fluorescence Spectroscopy Using a Confocal Synchrotron Radiation Microscope
Authors: Van Der Oord Cornelis J. R. , Gerritsen Hans C. , Rommerts Focko F. G. , Shaw David A. , Munro Ian H. , Levine Yehudi K.
Published: May 2005

The confocal microscope SYCLOPS (SYCLOPS is not an acronym although the first syllable is derived from its main light source, a synchrotron radiation source) at the Daresbury Science and Engineering Research Council (SERC) Laboratory, U.K., has been designed to facilitate fluorescence decay measurements on microscopic volume elements. SYCLOPS utilizes the Daresbury Synchrotron Radiation Source (SRS) as a pulsed light source. Visible or UV excitation light is selected from the white synchrotron radiation spectrum with a bandpass filter matching the absorption band of the fluorophores. Decay curves of fluorescence intensity emitted by a pre-selected micro-volume in the sample can be acquired with standard time-correlated single-photon counting techniques. The fluorescence intensity was collected from a confocal spot with a volume of 3 μm3. The first lifetime measurements done with the instrument were carried out on a coumestrol l]benzopyran-6-one) solution and on different cellular compartments of living cells incubated with coumestrol.
Spectral Observation of Defects in Space-Use Polymer Chain Irradiated by Ultraviolet Light
Authors: Yokota Toshiaki , Sasaki Susumu , Ota Masahiro , Yoshida Hirohisa , Kawashima Nobuki
Published: May 2005

We discuss some effects of the optical damages to polymer, on the basis of infrared spectroscopic, electron spin resonance (ESR), and dynamic viscoelastic data analysis related to the study of the effect of the space medium in space. It is revealed that UV light from the sun has a strong influence on the surface of spacecraft, as does atomic oxygen. After the irradiation of space-use polymer in the laboratory for several days, which corresponds to more than two years of use in space, the spectral change was observed by using the attenuated total reflectance (ATR) method. The IR spectra due to CO2, C=O, and alphatic CH, groups ( n = 1–3) appeared to indicate that the surface of the polymer was oxidized. The viscoelastic spectra revealed a cut in the polyimide chain. The radical intermediates in the breakdown of the polymer were observed by means of ESR spectroscopy.
Determination of the Equilibrium Constant and Resolution of the HOD Spectrum by Alternating Least-Squares and Infrared Analysis
Authors: Libnau Fred O. , Christy Alfred A. , Kvalheim Olav M.
Published: May 2005

The equilibrium between H2O, D2O, and HOD in the liquid phase has been analyzed for different concentrations of the reactants by using the attenuated total internal reflectance (ATR) technique. The infrared spectroscopic profiles of the equilibrium mixtures were broken down into the contributing components by the alternating least-squares (ALS) curve resolution technique. Furthermore, the concentration profiles of H2O, D2O, and HOD were determined together with the equilibrium constant. Band assignment of the resolved HOD spectrum was further carried out. The equilibrium constant determined in this work agrees excellently with values determined by both theoretical calculations and experiments.
Use of Normalized Relative Line Intensities for Qualitative and Semi-Quantitative Analysis in Inductively Coupled Plasma Atomic Emission Spectrometry Using a Custom Segmented-Array Charge-Coupled Device Detector. Part I: Principle and Feasibility
Authors: Soudier Luc , Mermet Jean-Michel
Published: May 2005

A procedure is described to conduct qualitative analysis in inductively coupled plasma atomic emission spectrometry even in the presence of spectral interferences. This procedure is based on the use of both line correlation and normalized relative line intensities of given elements. When spectral interferences due to a major element are observed for an analyte, use of multiple linear regression of the normalized relative line intensities of both the analyte and the major element provides information about the certainty of the presence of the analyte and the relative concentration between the major element and the analyte. Direct peaking and automatic background correction are required for this procedure. In this instance, no information is necessary about the shape of the line profile. This procedure has been tested with an echelle grating-based dispersive system equipped with a custom segmented-array charge-coupled device detector.
Multivariate Fluorescence Imaging of Gel on Nylon 66 Production Pack Screens
Authors: Stellman Christopher M. , Booksh Karl S. , Myrick Michael L.
Published: May 2005

Fluorescence microscopy is an established technique for qualitative and quantitative surface imaging. Because many “real world” surfaces of interest are optically rough (vertical variations on the order of 100 μm or more) it is of great interest to minimize the amount of spectral information lost because of depth-of-focus variations. Multivariate statistics on normalized spectra provide an ideal method for extracting information from such data. The following study examines nylon 66 gel on production pack screens via multivariate fluorescence imaging.
FT-near-IR and FT-IR Studies of Cis-9-Octadecen-1-ol: Molar Absorption Coefficient of a Band Due to the First Overtone of the Stretching Mode of the Terminal OH Group and Comparison of Anharmonicity of an OH Stretching Mode among the Monomeric and Associated Species
Authors: Liu Yongliang , Maeda Hisashi , Ozaki Yukihiro , Czarnecki Mirosław A. , Suzuki Masao , Iwahashi Makio
Published: May 2005

Fourier transform near-infrared (FT-near-IR) and FT-IR spectra have been measured for cis-9-octadecen-1-ol in CCl4 solutions at various concentrations and temperatures partly to investigate its self-association and partly to explore its near-IR spectrum. Both spectra have demonstrated the appearances of bands due to free terminal OH groups of the linear dimer (open-chain dimer) and oligomer of the alcohol. They are observed at 3621 and 7070 cm−1 in the IR and near-IR regions, whose frequencies are lower by 16 and 34 cm−1, respectively, than those of the corresponding bands due to a free OH group of the monomer. The spectral changes in both regions suggest that (1) at concentrations below 0.10 M, the alcohol exists mostly as the monomer and dimer, and with increasing temperature the dimer dissociates into the monomer; and (2) as the concentration is increased, it associates to form aggregates (such as tetramer), and with temperature increase the aggregates dissociate into the dimer and monomer. The molar absorption coefficient of the band due to the first overtone of the stretching mode of the terminal OH groups has been determined to be 0.139 dm3 mol−1 cm−1. It is approximately 8% of that of the first overtone of the monomeric OH group (1.63 dm3 mol−1 cm−1). The anharmonicity of an OH stretching mode of the alcohol has been investigated for various OH groups, free, terminal, and hydrogen-bonded, by comparing the frequencies of the bands due to the OH stretching modes with those of the bands due to the corresponding first overtones. The anharmonicity of the stretching mode of the terminal OH groups of the associated species is very similar to that for the free OH group of the monomer.
Discrimination of Organic Solvents Using an Infrared-Emitting Diode-Based Analyzer. Part I: Feasibility
Authors: Bonanno Anthony S. , Griffiths Peter R.
Published: May 2005

This report demonstrates the feasibility of discriminating organic solvents on the basis of short-wave near-infrared spectra (from 0.7 to 1.1 μm). Both library searching and multivariate statistical methods were applied to 8-cm−1 spectra and to spectra de-resolved to the point achievable with an analyzer using discrete infrared-emitting diode sources. Library searching performed satisfactorily if the unknown and library spectra were collected under reasonably similar conditions, but performed poorly if the temperature of hydrogen-bonding solvents was varied. A multivariate discrimination technique based on Mahalanobis distance computation was capable of discriminating between several alcohols while allowing for a temperature variation of 20°C. These results indicate that a very low resolution (on the order of 100 cm−1) short-wave near-infrared analyzer can achieve successful discrimination between similar solvents under variable conditions.
Elimination of Mode Hopping and Frequency Hysteresis in Diode Laser Raman Spectroscopy: The Advantages of a Distributed Bragg Reflector Diode Laser for Raman Excitation
Authors: Cooper John B. , Flecher Philip E. , Albin Sacharia , Vess Thomas M. , Welch William T.
Published: May 2005

A comparison is made between an index-guided (Fabry-Perot type) diode laser and a distributed Bragg reflector (DBR) diode laser as excitation sources for fiber-optic Raman spectroscopy utilizing charge-coupled device (CCD) detection and an image-corrected spectrograph. The DBR diode laser was superior to the index-guided diode laser for elimination of mode hopping, elimination of frequency hysteresis as a function of both temperature and current changes, and reduction in laser broadband emission. These advantages may allow the DBR laser to be used in industrial process control applications which are too demanding for index-guided diode lasers.
Laser-Excited Fluorescence of Dityrosine
Authors: Mahmoud Sahar F. , Bialkowski Stephen E.
Published: May 2005

In this research, laser-excited fluorescence was examined for sensitive detection of aqueous dityrosine. Samples were excited with a 6.3-mW, 325-nm helium-cadmium laser focused into a small volume-fluorescence cell with a 10-cm lens. The resulting fluorescence emission was collected perpendicular to the excitation and detected with two different schemes. An optical bandpass filter was used with a photomultiplier tube for sensitive quantitative measurement, while a photodiode array detector was used in conjunction with a spectrograph for qualitative characterization of fluorescence emission spectra. Dityrosine detection on the order of 2 × 10−11 M was obtained with the use of the photomultiplier tube with bandpass optical filter. The dityrosine fluorescence yield is found to vary with the solution pH, the relative concentrations of ferric and ferrous iron, and the amount of dissolved oxygen. A maximum fluorescence yield is observed for iron-free, oxygen-free alkaline solutions. Fluorescence quenching by oxygen is a cumulative photolysis effect that diminished fluorescence yield with increased irradiation time. Flowing the solutions minimized photolysis effects in oxygenated solutions. Quenching by ferrous and ferric iron is found to be due primarily to complex formation. The ferrous iron complex appears to have a fluorescence efficiency of ∼20% of the free dityrosine. The ferric iron dityrosine complex appears to have two ferric ions per molecule at low iron concentration. Other complexes may form at different concentrations. Solvent effects on dityrosine absorption and fluorescence spectra were also investigated. A red shift in dityrosine fluorescence maximum was observed in 1 M trichloroacetic acid and in N, N-dimethylformamide. The fluorescence emission maximum was shifted to the blue in acetonitrile and glacial acetic acid. These shifts were attributed to typical solvochromic behavior.
Infrared Microspectroscopy of Bauxitic Pisoliths
Authors: Rintoul Llewellyn , Fredericks Peter M.
Published: May 2005

Bauxite ore in the deposit at Weipa, Queensland, Australia occurs as pisoliths which are small, approximately spherical, pebbles with diameters in the range 0.5 to 2 cm. The distribution of various mineral species within the pisoliths has been determined by the use of reflectance infrared microspectroscopy of a large suite of pisoliths obtained from different parts of the Weipa orebody. The method allows the significant minerals of the bauxite to be analyzed including gibbsite (aluminium trihydroxide), boehmite (aluminium oxyhydroxide), quartz, and the clay, kaolinite. These minerals are readily distinguished by their IR spectrum. The iron minerals, present in small amounts, could not be detected. Specular reflectance spectra of sectioned pisoliths were measured, and the spectrum was utilized directly without the application of the Kramers–Kronig transformation. Polished pisolith sections were also mapped at a spatial resolution of 100 μm with the use of a computer-controlled microscope stage, and the mineral composition at any point was estimated by measuring relevant areas of the spectrum. Semi-quantitative results were obtained by relating the reflectance spectra for a particular pisolith thin section to the transmittance spectra for the same points. The transmittance spectra of the pisoliths were correlated with spectra of pure standards by application of a multicomponent Q-matrix approach. Principal component analysis of the mineral distribution data allowed the suite of pisoliths to be subdivided into groups with similar mineralization.
Study of Analyte Diffusion into a Silicone-Clad Fiber-Optic Chemical Sensor by Evanescent Wave Spectroscopy
Authors: Blair Dianna S. , Burgess Lloyd W. , Brodsky Anatol M.
Published: May 2005

The diffusion rates of various polar and nonpolar analytes in dimethylsiloxane were examined with the use of a commercially available 200-μm silica-core/300-μm silicone-clad fiber as the optical element for evanescent wave spectroscopy in the near-infrared spectral region. An analytical solution to Fick's second law was used to model the time-dependent analyte concentration at the core/cladding interface. Successful fit of the analytical solutions to infrared data verifies the assumption of constant diffusion coefficients that is necessary to solve the equation. Transport rates of polar analytes in silicone can be estimated with the use of a single-parameter model that results in diffusion coefficients of 3.2 × 10−1, 1.6 × 10−1, 8.1 × 10−7, and 3.9 × 10−7 cm2/s for methanol, ethanol, 2-propanol, and n-butanol, respectively. Estimating the transport of larger nonpolar analytes in the silicone cladding requires a two-parameter model that includes a diffusion coefficient and an interfacial conductance term. For pentane, hexane, heptane, and cyclohexane the resultant diffusion coefficients and interfacial conductance parameters are 6.9 × 10−7, 4.6 × 10−7, 4.4 × 10−7, and 2.3 × 10−7 cm2/s and 2500, 2000, 2000, and 600 μm−1, respectively.
Laser-Induced Breakdown Spectra in a Coal-Fired MHD Facility
Authors: Zhang Hansheng , Singh Jagdish P. , Yueh Fang-Yu , Cook Robert L.
Published: May 2005

A study of laser-induced breakdown spectroscopy (LIBS) has been performed in a particle-loaded methane/air flame and in the Diagnostic Instrumentation and Analysis Laboratory/Mississippi State University (DIAL/MSU) test stand to evaluate its application for practical environments. The LIBS spectra collected from different observational directions and spectral regions are compared. The forward LIBS technique has been chosen to characterize the upstream region of a large magnetohydrodynamics (MHD) coal-fired flow facility (CFFF). The relative concentrations of several species are inferred by fitting the observed CFFF LIBS spectra with computer-simulated spectra. This paper reports the first LIBS experiments in a harsh, turbulent, and highly luminous coal-fired MHD combustion environment.
Determination of Sulfur Content in Steel by Laser-Produced Plasma Atomic Emission Spectroscopy
Authors: Gonzcález Ana , Ortiz Montserrat , Campos José
Published: May 2005

Sulfur content in steel samples has been determined by laser-produced plasma atomic emission spectroscopy with the use of a Q-switch Nd: YAG laser. With the use of time-resolved spectroscopy employing an OMA III (EG&G) as detector, a detection limit of 70 ppm and a precision of 7% have been obtained. Calibration curves are linear, and no noticeable matrix effects have been observed.
Discrimination of Organic Solvents Using an Infrared-Emitting Diode-Based Analyzer. Part II: Practical Demonstration
Authors: Bonanno Anthony S. , Griffiths Peter R.
Published: May 2005

It is demonstrated that a short-wave near-infrared analyzer equipped with a small number of discrete infrared-emitting diode sources can provide the spectral information required to discriminate organic solvents. Discrimination models were developed and validated for a large variety of compounds with the use of as few as six data points, and were, in most cases, quite successful. Additionally, the effect of added impurities on the discrimination model for methanol was investigated. As expected, the model developed for pure methanol was relatively insensitive to the presence of impurities at levels below about 5%.
Infrared Absorption Spectra and Their Correlation with the Ti-O Bond Length Variations for TiO2 (Rutile), Na-Titanates, and Na-Titanosilicate (Natisite, Na2TiOSiO4)
Authors: Peng Gow-Weng , Chen Shou-Kang , Liu Hok-Shing
Published: May 2005

The mid-infrared absorption spectra (400–1200 cm−1) of four TiO2-bearing crystalline solids, in the form of rutile (TiO2), Na-titanates (Na2Ti6O13/ Na2Ti3O7), and natisite (Na2TiOSiO4), are presented, providing a clear illustration of their differences in IR band structure (band pattern). Two sharp characteristic peaks of IR absorption bands of natisite have been noted at 725 and 624 cm−1, representing the internal vibration modes of TiO5 (normal) and SiO4 structural units, respectively, and obtainable by comparison with that of Ca-titanosilicate (CaTiOSiO4), NTS glass (Na2O-TiO2-SiO2), and low-cristobalite (SiO2). The tested series of TiO2-bearing crystalline solids has been helpful in presenting a case study in support for the generalization of IR spectra/structure correlations, showing that vibrational spectroscopy can be useful for understanding the crystal chemistry of crystalline solids in terms of the geometric setting of molecular structural units and chemical bonds. It has been qualitatively demonstrated that the Ti-O bond length variations may be broadly correlated with the complexity of IR absorption bands of four TiO2-bearing solids having great diversity in both chemical composition and crystalline structure.
Quantitative Determination of Sulfur Oxide Species in White Liquor by FT-IR
Authors: Bandekarc Jagdeesh , Sethna Rustam , Kirschner Mark
Published: May 2005

The Circle® cell has made possible the quantitative analysis of samples by infrared spectroscopy in aqueous solutions. With the use of this technique, which makes use of an FT-IR spectrometer, a novel analytical method is presented for the quantitative determination of sulfur oxide anions in white liquor. The method is appropriate only for oxidized sulfur species. However, it is shown that when Na2S concentrations are determined by another technique (e.g., ion chromatography or ion-selective electrode), the results can be used to carry out material/species balance on the unoxidized as well as oxidized samples of white liquor. The method is fast, straightforward, and convenient to use, and it does not require further treatments of white liquor solutions. Another advantage of this method is that it lends itself to in situ analysis. It is also general enough to be used for the quantitative analysis of other aqueous solutions. Linear regressions carried out on the SO=4, S20=3, and SO=3 species (in concentration ranges of 0–70, 0–45, and 0–42 g/L as salts, respectively) led to correlation coefficients of higher than 0.99; respective minimum detection limits of 0.01, 0.02, and 0.02 g/L were obtained. The latter can be further improved upon by employing longer-pathlength crystals. The method provides a way of carrying out material species balances, and studying reactions and their kinetics. The process does not use any toxic materials or environmentally unfriendly bleaching agents; it makes use of a combination of temperature, pressure, and molecular oxygen to oxidize white liquor to sulfate.
Compact, Self-Contained Optical Spectrometer
Authors: Baird William , Nogar Nicholas S.
Published: May 2005

We describe the construction and performance of a self-contained, battery-operated, hand-held optical spectrometer. This unit contains an on-board optical excitation source, miniaturized monochromator, CCD detector, Peltier cooler, LCD display module, and microprocessor control. We demonstrate capabilities for qualitative fluorescence determinations and semiquantitative fluorescence and absorption measurements. Resolution is λ/δλ ≈ 1200 at 434 nm.