bluuebunny/crossref_metadata_2025 huggingface dataset:
Nondestructive Optical Depth Profiling in Thin Films through Robust Inversion of the Laser Photopyroelectric Effect Impulse Response
Authors: Power J. F. , Prystay M. C.
Published: May 2005

The laser photopyroelectric effect measures an optical absorption depth profile in a thin film through the spatial dependence of a heat flux source established below the film surface by light absorption from a short optical pulse. In this work, inverse depth profile reconstruction was achieved by means of an inverse method based on the expectation-minimum principle (as reported in a companion paper), applied in conjunction with a constrained least-squares minimization, to invert the photopyroelectric theory. This method and zero-order Tikhonov regularization were applied to the inversion of experimental photopyroelectric data obtained from samples with a variety of discrete and continuous depth dependences of optical absorption. While both methods were found to deliver stable and accurate performance under experimental conditions, the method based on the constrained expectation-minimum principle was found to exhibit improved resolution and robustness over zero-order Tikhonov regularization.
Evaluation of the Potential of a Charge-Injection Device for DNA Sequencing by Multiplexed Capillary Electrophoresis
Authors: Li Qingbo , Yeung Edward S.
Published: May 2005

Despite the rapid growth in the use of imaging detectors in spectroscopy, the charge-injection device (CID) has unique features that have not been fully exploited. The advantages of the CID as a two-dimensional array detector for laser-induced fluorescence detection in highly multiplexed capillary electrophoresis are evaluated. In such a system, the CID maintains both high sensitivity and high sampling rate, which are usually difficult to achieve simultaneously with other array detectors. Applying the electronic windowing function significantly improves the scan rate and greatly reduces the volume of data generated. With 1-s exposure time and 488-nm excitation, the detection limit of the system is 10−12 M fluorescein with the device cryogenically cooled and 10−11 M fluorescein at ambient temperature. The low dark current of the CID imager allows operation at room temperature without significantly affecting sensitivity when combined with moderate laser powers. We demonstrate that the CID is well suited for high-speed, high-throughput DNA sequencing based on multiplexed capillary electrophoresis with on-column laser-induced fluorescence detection.
High-Resolution Quadrature Photopyroelectric Spectroscopy of a-Si:H Thin Films Deposited on Silicon Wafers
Authors: Shen Jun , Mandelis Andreas , Othonos Andreas , Vanniasinkam Joseph
Published: May 2005

The recently developed photothermal technique of quadrature photopyroelectric spectroscopy (Q-PPES) has been applied to measurements of amorphous Si thin films deposited on crystalline Si substrates. Direct, meaningful comparisons have been made between purely optical transmission in-phase (IP-PPES) spectra, and purely thermal-wave sub-gap spectra with the use of a novel noncontacting PPES instrument to record lock-in in-phase and quadrature spectra, respectively. FT-IR transmission spectra have also been obtained for a comparison with this IP-PPES optical method. The results of the present work showed that the FT-IR method performs the worst in terms of spectral resolution of thin films and sub-bandgap defect/impurity absorptions inherent in the Si wafer substrate. The optical IP-PPES channel, however, albeit more sensitive than the FT-IR technique, fails to resolve spectra from surface films thinner than 2100 Å, but is sensitive to sub-bandgap absorptions. The thermal-wave Q-PPES channel is capable of resolving thin-film spectra well below 500 Å thick and exhibits strong signal levels from the crystalline Si sub-bandgap absorptions. Depending on the surface thin-film orientation toward, or away from, the direction of the incident radiation, the estimated minimum mean film thickness resolvable spectroscopically by Q-PPES is either 40 Å or 100 Å, respectively.
Analysis of Underground Storage Tank Waste Simulants by Fourier Transform Infrared Photoacoustic Spectroscopy
Authors: Bajic Stanley J. , Luo Siquan , Jones Roger W. , McClelland John F.
Published: May 2005

Underground storage tank waste sludge from nuclear fuel processes is difficult to analyze because of the extreme heterogeneity, chemical reactivity, and radioactivity of the waste. Conventional methods of analysis typically require extensive sample handling procedures either to thin the sample or to separate components prior to analysis. These procedures are time consuming, require radiation containment cells, and increase the risk of radiation exposure to lab personnel as a result of the extensive handling. In this paper a method utilizing Fourier transform infrared photoacoustic spectroscopy to analyze hazardous underground storage tank waste with a minimal amount of sample and sample handling is discussed. The method was developed with the use of waste tank simulants that were obtained from the Westinghouse Hanford Company. Emphasis was placed on the determination of disodium nickel ferrocyanide, sodium nitrate, and sodium nitrite because of the concern for the potential of exothermic reactions occurring between oxidizers and ferrocyanide-containing compounds. This method also allows for the analysis of other ions of interest in waste processes such as sodium sulfate. A simple sample preparation method is also discussed which uses freeze drying to remove water from the simulants while maintaining a uniform sample for analysis.
Pilot Study of the Analytical Performance of the Pulsed Hollow Cathode Discharge Emission Source
Authors: Cai Xiangjun , Williams J. C.
Published: May 2005

Proper conditioning of the hollow cathode by sputtering is critical to the analytical performance of the hollow cathode. A pulsed discharge procedure was developed to condition the 1.5- × 5-mm stainless steel cathode. A scanning electron microscope was used to study the surface structure resulting from the conditioning. The resulting hollow bottom was bulb-shaped and the surface was mirror-like, very smooth, and shiny. The emission intensities from smooth cathodes were greater that those from the rough ones. The precision obtained here was 3–5% for Na, 5–8% for Li, and 4–10% for K. Three working curves for each element were made on different days with different cathodes that had been conditioned in the same manner for 4 h by sputtering. The three working curves virtually coincided when plotted in the same figure, demonstrating the precision and reproducibility from day to day of the hollow cathode discharge method as developed in this laboratory. The 3-σ detection limits calculated from slopes of working curves are 0.32 pg, 0.35 pg, and 3.2 pg for Na, Li, and K, respectively.
Comparison of Pattern Recognition Techniques for Sample Classification Using Elemental Composition: Applications for ICP-AES
Authors: Branagh Wayne , Yu Huinan , Salin Eric D.
Published: May 2005

Pattern recognition is very important for many aspects of data analysis and robotic control. Three pattern recognition techniques were examined— k-Nearest Neighbors, Bayesian analysis, and the C4.5 inductive learning algorithm. Their abilities to classify 71 different reference materials were compared. Each training and test example consisted of 79 different elemental concentrations. Different data sets were generated with relative standard deviations of 1, 3, 5, 10, 30, 100, and 500%. Each data set consisted of 2000 examples. These sets were used in both the training stages and in the test stages. It was found that C4.5's inductive learning algorithm had a higher classification accuracy than either Bayesian or k-Nearest Neighbors techniques, especially when large amounts of noise were present in the systems.
Submicrosecond Preliminary Process of Electric-Field-Induced Reorientation of a Ferroelectric Liquid Crystal, 5-(2-Fluoroalkoxy)-2-(4-n-Alkylphenyl)-Pyrimidine, Studied by Time-Resolved Infrared Spectroscopy
Authors: Katayama Norihisa , Sato Takashi , Ozaki Yukihiro , Murashiro Katsuyuki , Kikuchi Makoto , Saito Shinichi , Demus Dietrich , Yuzawa Tetsuro , Hamaguchi Hiro-O
Published: May 2005

Pulsed electric-field-induced reorientation of a ferroelectric liquid crystal (FLC), 5-(2-fluorooctyloxy)-2-(4-hexylphenyl)-pyrimidine, has been investigated by using a dispersive submicrosecond time-resolved infrared spectroscopic technique. The observed absorbance decay for a band at 1440 cm−1 due to a ring-stretching mode of the phenylpyrimidine group indicates that the FLC molecule reorients from a stationary state with a slight delay (less than 1 μs) just after the upswing of the electric field, while counter-reorientation occurs with a delay time of a microsecond after the reverse of the electric field. The delay time for the counter-reorientation changes with temperature, indicating that the viscosity has a strong influence on the delay time. It is also indicated in the present study that the whole FLC molecule reorients simultaneously as a rigid rod in both the preliminary and the counter-reorientation process.
Confocal Image Properties of a Confocal Scanning Laser Visible Light FT-Raman Microscope
Authors: Brenan Colin J. H. , Hunter Ian W.
Published: May 2005

The confocal Raman microscope is an instrument designed for acquisition of high-contrast volumetric Raman spectral images of three-dimensional chemical structures. Little effort, however, has gone into the investigation of the spatial imaging properties of this class of confocal microscope. In this paper we present experimental results, obtained with a confocal scanning laser visible light FT-Raman microscope we built, that demonstrates the high depth resolution and enhanced Raman image contrast intrinsic to the confocal Raman microscope design. We explore these microscope properties through a combination of experimental measurement and theory based on a paraxial wave diffraction model.
Matrix Isolation/Fourier Transform Infrared Spectrometry of Laser-Desorbed Species
Authors: Carr B. L. , Brown R. S.
Published: May 2005

Initial results are presented for a novel experimental arrangement which allows the successful study of laser-desorbed neutral species under matrix isolation conditions. In the current work, a pulsed carbon dioxide laser (10.6 μm) is employed for laser desorption. With the combination of a previously described cryogenic trapping technique with coaxial matrix isolation gas (xenon or argon) introduction, laser-desorbed neutrals have been matrix isolated and their Fourier transform infrared spectra recorded. Two different cinnamic acid derivatives ( p-coumaric acid and sinapinic acid) typically employed for matrix-assisted laser ionization (MALDI) mass spectrometry were utilized to demonstrate this new technique. Experimental conditions were determined for optimal matrix isolation of the laser-desorbed species. Two different desorption geometries were examined with respect to their effectiveness for matrix isolation of desorbed neutrals. A covalent dimer of p-coumaric acid produced in an external UV photoreactor and thought to be a possible photoreaction product in UV MALDI was studied by this technique. Thermal degradation of this dimer is shown to occur above threshold irradiance for laser desorption.
Absorbance-Corrected Synchronous Fluorescence with a Fiber-Optic-Based Fluorometer
Authors: Victor Mark A. , Crouch Stanley R.
Published: May 2005

Synchronous fluorescence spectroscopy is frequently used to resolve multiple components in mixtures without separation. However, uncompensated inner-filter effects can lead to unexpected and/or large quantitative errors. An instrument and a method that correct for primary and secondary inner-filter effects in synchronous fluorescence spectroscopy have been designed and characterized. A bifurcated fiber-optic-based diode array fluorometer that simultaneously measures front-surface fluorescence and absorbance was constructed. A transfer function that mathematically describes the coupling efficiency between the excitation and emission legs of the fiber optics is defined and characterized. Once characterized, such a fluorometer is capable of calculating what the fluorescence measurement would be in the absence of inner-filter effects. Several experimental procedures for determining the instrument's transfer function are compared and discussed. Applications of the various procedures to experimental fluorescence inner-filter corrections to problematic samples are demonstrated.
Near-Infrared Spectroscopy as an Alternative to Biological Testing for Quality Control of Hyaluronan: Comparison of Data Preprocessing Methods for Classification
Authors: Carlsson Annika E. , Janné Kjell L.-R.
Published: May 2005

An alternative method to biological testing on animals has been studied. The method is based on pattern recognition by combination of near-infrared spectroscopy and multivariate classification. The pharmaceutical product under study is based on a high-molecular-weight carbohydrate, Hyaluronan, used as a medical device for eye surgery. The effect of data preprocessing on classification performance of approved and rejected samples was evaluated by use of principal components models for each class. With the use of multiplicative scatter correction techniques, the class discrimination was enhanced 10 times in comparison to uncorrected data. From a leave-one-out procedure including a total of 29 samples, 80% of the samples were classified in agreement with the biological reference data and the remaining 20% were classified as non-members. With the use of partial least-squares discriminant analysis, 90% of the predicted samples were in accordance with the biological assay.
Evaluation of Alternative Plasma Gases for Radio-Frequency Glow Discharge Mass Spectrometry (rf GD-MS)
Authors: Giglio Jeffrey J. , Caruso Joseph A.
Published: May 2005

Interferences are a major consideration in all forms of plasma mass spectrometry. Investigations into the use of He, Ne, N2, and Kr in radio-frequence glow discharge mass spectrometry (rf GD-MS) have been undertaken to study their potential as alternative plasma gases. All gases exhibited expected behavior with respect to pressure and power. Background species are discussed for each gas, along with the effect of each gas on analyte intensities in Standard Reference Material (SRM) copper 500. A helium plasma yields the highest intensities for analytes (Cr, Fe, Ni, Co, Zn, As, Se, Ag, Au, Pb, and Bi) of all gases investigated. Kr was not a practical alternative gas since analyte intensities were extremely low, severe memory effects were present, and the UHP Kr is very expensive. Relative sensitivity factors are presented for each of the gases for the same copper SRM 500. Argon has the highest sputter rate, with Ne and He being similar and N2 being the lowest. Isotope abundances are given for Se, Fe, Br, and Cl in a He plasma.
Investigation of the Vaporization and Atomization of Boron in a Graphite Furnace Using Digital Imaging Techniques
Authors: Goltz Douglas M. , Chakrabarti Chuni L. , Sturgeon Ralph E. , Hughes Dianne M. , Grégoire D. Conrad
Published: May 2005

The distributions of atomic and molecular species of boron inside a graphite furnace were investigated with a charge-coupled device (CCD) camera. Extensive spatial nonuniformity of the distributions at high temperatures was observed for both species. Digital imaging by the CCD camera showed that molecular boron species are preferentially formed at the top of the graphite tube at 1800–2000°C and their concentrations increase toward the center of the tube. The lowest concentrations of molecular boron species occur at the furnace walls and especially at the bottom of the graphite furnace. The highest concentrations of boron atoms occur along the graphite tube walls, at the bottom. The absence of significant concentrations of molecular species desorbing from the initial site of analyte deposition suggests that the analyte boron species, which do not absorb light at 254 nm, are vaporized. Since the highest concentrations of the molecular boron species were detected away from the graphite tube wall, desorption of molecular boron species is not likely. A gas-phase thermal dissociation of boron oxide species, resulting in the formation of BO (g), is suggested at temperatures below the atomization temperature. Pre-atomization loss of boron as molecular boron species is clearly evident from the CCD images. The high appearance temperature (2300°C) and high concentrations of atomic boron at the graphite tube wall suggest that much of the atomic boron signal is probably the result of desorption of boron atoms from the decomposition of boron carbide (solid).
Comparison of Vibrational Spectroscopic Techniques for the Characterization of Human Gallstones
Authors: Wentrup-Byrne E. , Rintoul L. , Smith J. L. , Fredericks P. M.
Published: May 2005

A suite of human gallstones was investigated by vibrational spectroscopic techniques with a view to developing an effective characterization procedure. Using infrared microscopy, microspectroscopic mapping, infrared photoacoustic spectroscopy (PAS), and FT-Raman spectroscopy, we have examined both the chemical composition and the microstructure of the different categories of human gallstones. We show how infrared microscopy can be used to determine the chemical identity of particular microstructural features of a stone. Infrared mapping produces functional group maps of the surface of a gallstone and shows the actual distribution of the different chemical components. Good fluorescence-free FT-Raman spectra were obtained from all categories of stones except black stones, which gave a fluorescence background with no observable Raman spectrum. Of the vibrational techniques studied, PAS proved the most suited to the spectroscopic categorization of gallstones because data for the whole stone can be obtained with minimal sample preparation. The advantages and disadvantages of each technique are discussed.
Atomic Line Profiles in Hollow Cathode Lamps and a Glow Discharge Atomizer Determined by Fourier Transform Spectroscopy
Authors: Pavski Victor , Chakrabarti Chuni L.
Published: May 2005

In an attempt to understand the implications of using glow discharge atomizers in atomic absorption spectrometry (AAS), line profiles and kinetic (Doppler) temperatures were measured in commercial hollow cathode lamps and a laboratory-constructed, jet-assisted dc glow discharge atomizer using a high-resolution Bomem Fourier transform spectrometer. Line profiles were measured in the hollow cathode lamps as current was increased from 1 to 30 mA for three resonance atomic lines (Mg 285.21 nm, Al 308.22 nm, and Pb 283.31 nm) having distinctly different hyperfine structure. Although the Al 308.22-nm line was largely unaffected by self-absorption as the lamp current was increased, the Pb 283.31-nm and Mg 285.21-nm lines exhibited pronounced self-absorption broadening at relatively low lamp currents. Kinetic temperatures in the hollow cathode lamps ranged from 320 ± 20 K at low lamp currents to 840 ± 20 K at high currents. With the use of the Ar(I) 415.86-nm line from the argon discharge gas as a thermometric species, kinetic temperatures of 460 ± 20 K to 620 ± 20 K were measured in the glow discharge atomizer under typical analytical operating conditions. These low atomizer gas temperatures imply that the sensitivity and linear dynamic range of analytical calibration curves will be more strongly affected by the lamp current of the primary radiation source and the spectral properties of the analysis line in glow discharge AAS than in flame or furnace AAS, and that operation at low lamp current is essential for optimal analytical performance. The degrees to which the linear dynamic range and the slope of the analytical calibration curve would be affected by the hyperfine structure of the analysis line, the extent of self-absorption in the hollow cathode lamp, the hollow cathode kinetic temperature, and the glow discharge kinetic temperature are considered separately for each atomic line investigated. The kinetic temperatures in the hollow cathode lamps and the glow discharge atomizer were so close that it was possible to obtain absorption line profiles for the three resonance atomic lines in the glow discharge atomizer with the use of hollow cathode lamps as primary radiation sources, i.e., without the necessity of using a continuum source of radiation.
Chinese Greenware Raw Materials: Principal Component Analysis of Major and Minor Chemical Constituents
Authors: Yap Choon-Teck , Hua Younan
Published: May 2005

Principal component analysis is used in the study of 24 raw materials for the production of Chinese greenware porcelains, known as Yue ware, Longquan ware, Southern Song Guan ware, Ge ware, Ru ware, Linru ware, Jun ware, and Yaozhou ware. The results of this study give reasonably good indications of the possible raw materials used in the production of these greenwares.
Periodic Nature of Metal-Noble Gas Adduct Ions in Glow Discharge Mass Spectrometry
Authors: Barshick C. M. , Smith D. H. , Johnson E. , King F. L. , Bastug T. , Fricke B.
Published: May 2005

The observation that ZnAr+ ion currents in a glow discharge can measure as high as 30% of those of Zn+ prompted a systematic study of metal-noble gas diatomic species. Twenty-four elements in combination with neon, argon, and krypton were included. Periodicity of behavior was observed from one row to the next with all three noble gases; periodicity was also observed as the identity of the noble gas was changed. The diatomic noble gas adduct ions of zinc, cadmium, and mercury (group 12) each displayed a concentration relative to the corresponding metal ion that was well above that of other elements in their respective rows. Investigation of the cause of this phenomenon eliminated glow discharge pressure and power conditions. Binding energies of the various species were qualitatively consistent with the observation of relative abundances of metal-noble gas diatomic ions as they varied with the identity of the noble gas, but did not explain why Zn X+, Cd X+, and Hg X+ form in what seem to be anomalously high abundance. Variations in the sputtering rates of the transition metals (Zn > Cu > Ni > Fe) are consistent with the observation that Zn X+ > Cu X+ > Ni X+ > Fe X+, the resulting increase in collision frequency (with increasing sputtering rate) is believed to account for the relative abundances of these adduct ions in the discharge.
Dual Fluorescence of p-Dimethylaminobenzoic Acid in Cetyltrimethylammonium Bromide (CTAB)/1-Heptanol/Water Reverse Micelle
Authors: Jiang Yun-Bao , Lin Li
Published: May 2005

Dual fluorescence of p-dimethylaminobenzoic acid (DMABOA), typical of excited-state twisted intramolecular charge transfer (TICT), in the cetyltrimethylammonium (CTAB)/1-heptanol/H2O reverse micelle has been monitored as a function of a number of factors such as the water pool size, the bulk concentrations of DMABOA and CTAB, and the pH and [KF]/[KBr] ratio in the water pool. Two fluorescence parameters, i.e., the wavelength of the TICT emission band and the intensity ratio of the TICT band to the LE (locally excited state) band, Ia/ Ib, are employed to measure the effects of these factors. The position of the DMABOA molecule in the reverse micelle is ascertained to be among the hydrocarbon chains close to the water pool with its (CH3) 2N group towards the bulk 1-heptanol while the carboxylic group interacts with the polar head of the surfactant electrostatically. The TICT of DMABOA at this position is shown to be similar to that in an organic solvent, and the reverse micelle exerts a restriction on the TICT of DMABOA. It seems that the water molecules in the water pool do not penetrate into the hydrocarbon region of the reverse micelle.
Routine Wavenumber Calibration of an FT-Raman Spectrometer
Authors: Fountain Augustus W. , Mann Charles K. , Vickers Thomas J.
Published: May 2005

A readily automated procedure for testing and calibrating the wavenumber shift scale of an FT-Raman spectrometer is described. The procedure uses atomic lines as wavenumber standards. An apodization procedure is used in accurately determining the line positions to a fraction of the sampling interval. A fiber-optic bundle conveniently couples the output from a hollow cathode lamp to the collection optics of the Raman accessory. Results are reported and compared for both thorium and neon atomic lines. Acetonitrile is suggested as a wavenumber shift standard, and peak shifts have been measured for its major features. Peak shift values are reported for 11 lines of cyclohexane.
Raman Spectroscopy Studies of Metabolic Concentrations in Aqueous Solutions and Aqueous Humor Specimens
Authors: Wicksted James P. , Erckens Roel J. , Motamedi Massoud , March Wayne F.
Published: May 2005

Individual concentrations of glucose, lactic acid, and urea down to 0.1 wt % have been investigated in aqueous solutions by the Raman scattering technique. These measurements have been conducted with three different laser excitation wavelengths at 514.5, 632.8, and 751.8 nm in conjunction with a single-grating spectrometer and a liquid nitrogen-cooled charge-coupled device (CCD). Rabbit and human aqueous humor specimens have also been studied by this method. In addition to a water background, the large fluorescence structure in the Raman spectra resulting from these aqueous humor specimens has been subtracted out by being fitted to a first-degree polynomial. Raman peaks similar to the stretching vibrations of methylene and methyl groups associated with glucose and lactate, respectively, were observed in the human specimens within the region from 2800 to 3050 cm−1. Similar structure was observed from the rabbit specimens. In addition, a Raman peak, indicative of the carbon-nitrogen stretching mode of urea and various amino acids, was observed at 1006 cm−1 in all aqueous humor specimens. However, some of the Raman peaks in the rabbit specimens may have resulted from the euthanasia process.
Mass Diffusion Transport Studies of Lithium Sulfate in Aqueous Solutions Using Raman Spectroscopy
Authors: Martinez A. Rodriguez , Grañón F. Sobron , Pérez F. Rull , Colorado A. C. Prieto , Edwards And H. G. M.
Published: May 2005

The diffusivity coefficients of lithium sulfate solutions in water and water and silica gels over the concentration range 0.2 to 2.5 molal have been measured for the first time with micro-Raman spectroscopy for a horizontal-tube capillary, conventional 90° Raman scattering for a narrow-bore vertical-tube system, and FT-Raman spectroscopy for the gels. Data were obtained for axial concentration profiles as function of the distance and for time elapse at fixed positions on the tube axis with the use of integrated intensity measurements of the v1 (SO4) symmetric stretching band at 980 cm−1. The use of computer model calculations to fit the experimental data yielded values of DA = 0.4 × 10−5 cm2 s−1 for the vertical system and 0.3 × 10−5 cm−2 s−1 for the gel system. Discrepancies observed for the horizontal system have been ascribed to the presence of convective flow. A convective flow rate of 5.10−2 cm h−1 was calculated in this case with the use of computer simulation and used in the fitting of the experimental data through a general form of the second Fick's law. Under these conditions, a DA value of 0.2 × 10−5 cm2 s−1 was obtained.
Optoacoustic Lead-Salt Diode Laser Detection of Trace Species in a Flow System
Authors: Olsson Bo E. R. , Davidsson Jan , Hallquist Mattias , Ljungström Evert
Published: May 2005

An experimental setup for kinetic and product studies in a flow system has been developed. For detection, a nonresonant optoacoustic technique combined with a tunable lead-salt diode laser has been employed. The performance of the system was tested on ammonia in argon, and a detection limit (S/N = 2) of 8 × 1012 molecules cm−3 (corresponding to 320 ppb at atmospheric pressure) was obtained at a pressure of about 7 kPa when frequency modulation was employed. At 1.5 kPa the detection limit was about 2 × 1014 molecules cm−1. With a multipass cell the sensitivity was increased by a factor of four.
Inverse Problem in Diffuse Reflectance Spectroscopy: Accuracy of the Kubelka-Munk Equations
Authors: Loyalka S. K. , Riggs C. A.
Published: May 2005

In diffuse reflectance spectroscopy the Kubelka-Munk equations have been used extensively. These equations provide simple solutions to the inverse problem of obtaining information on the scattering and absorption cross sections from reflected light. Proof is provided that the basic Kubelka-Munk equation

[Formula: see text]

should be replaced by the equation

[Formula: see text]

and that the Kubelka-Munk function

[Formula: see text]

should be replaced by the function

[Formula: see text]

Here r( x) is the reflectance; s is the scattering cross section (cm−1); a = ( k + s)/ s, where k is the absorption cross section (cm−1); and R∞ is the reflection coefficient of an infinitely thick sample. We note, however, that because of a redefinition of a carried out by Kubelka and Munk in the process of their calculations, the scattering cross section s calculated from their expression

[Formula: see text]

is correct. But the Kubelka-Munk theory still overestimates k by a factor of two.
Transient in Situ Infrared Methods for Investigation of Adsorbates in Catalysis
Authors: Chuang Steven S. C. , Brundage Mark A. , Balakos Michael W. , Srinivas Girish
Published: May 2005

This paper reports the details of a high-pressure and -temperature in situ transmission infrared reactor cell and experimental approaches for investigation of the nature of adsorbates in CO hydrogenation and NO-CO reaction on Rh/SiO2 catalyst. The infrared cell used in this study allows easy assembling and reliable operation up to 773 K and 6.0 MPa. The structure and coverage of adsorbates during reaction are determined by an infrared spectrometer, and the composition of gaseous effluent from the infrared cell is monitored by a mass spectrometer. The steady-state 13CO step transient shows that gaseous CO rapidly exchanges with adsorbed CO, which is slowly converted to CH4 during CO hydrogenation at 513 K and 0.1 MPa. The pulsing CO study reveals that linear CO is more reactive than bridged CO during methane and CO2 formation, and bridged CO sites are blocked from CO disproportionation. Steady-state 13CO pulse transients show that the CO2 response leads the CO response, and Rh-NCO and Si-NCO are not involved in the formation of CO2 from CO during NO-CO reaction. The advantages and limitations of the in situ infrared and transient approaches for catalysis research will be discussed.
Dynamic Two-Dimensional Infrared Spectroscopy. Part I: Melt-Crystallized Nylon 11
Authors: Singhal Anu , Fina Leslie J.
Published: May 2005

Two-dimensional FT-IR spectroscopy has been used to study the N-H stretching and amide I/amide II region of melt-crystallized nylon 11 thin films on Teflon® substrates. Samples are dynamic mechanically oscillated at room temperature at a frequency of 11 Hz. A two-dimensional correlation analysis on the dynamic spectra indicates that the N-H stretching region splits into two peaks. Analysis of two-dimensional crossplots between the N-H stretching region and the amide I/amide II region shows that the prominent peak in the N-H stretching region (∼3300 cm−1) is similar in morphological character to the ordered peak of the amide I region. The amide II region resolves into two-ordered and one-disordered peak.
Detection of Chlorinated Hydrocarbons in Aqueous Surfactant Solutions by Near-IR Raman Spectroscopy
Authors: Shi Xuelong , Parus Stephen J. , Pennell Kurt D. , Morris Michael D.
Published: May 2005

Near-IR Raman spectroscopy is used to detect chlorinated hydrocarbons under surfactant-enhanced solubilization conditions. The Raman bands of tetrachloroethylene (PCE) and 1,2-dichlorobenzene (DCB) in micelle solutions could be observed in the presence of humic acid when a 784-nm diode laser was used. With 532- or 632.8-nm excitation, humic acid fluorescence obscured the Raman signals. For quantification, the integrated area of the carbon-chlorine stretch mode (PCE) or the phenyl ring-breathing mode (DCB) was used. Test results for samples with unknown concentrations based on linear calibration curves were in agreement with results from an accepted gas chromatography method. Detection limits were calculated to be 240 ppm for tetrachloroethylene and 500 ppm for 1,2-dichlorobenzene. Our study has shown the feasibility of this technique for field applications.
FT-IR and 13C-NMR Correlations for Some N-Substituted Azoles and Benzazoles
Authors: Elguero José , Gil Manuel , Iza Nerea , Pardo Carmen , Ramos Mar
Published: May 2005

The FT-IR (in carbon tetrachloride) and 13C-NMR (in deuterochloroform) spectra of six p-substituted aniline derivatives, as reference compounds, and nine 1- p-aminophenyl-azoles and benzazoles were recorded. The measured spectral parameters from FT-IR were symmetric, vs(NH2), and antisymmetric, vas(NH2), stretching fundamentals and their band intensity ratio, A( vas)/ A( vs), while the corresponding 13C-NMR parameters were C-1 to C-4 chemical shifts of 1- p-aminophenyl carbons. Different IR and 13C-NMR spectral parameters and Hammett constants σp (or σp-) were correlated, and statistic analysis of the results permitted an estimation of σp values of the nine (azol-1-yl) substituents. An empirical equation to calculate the Hammett constants of new azoles and benzazoles is proposed.
Investigation of the Influence of Mode Polarizations on Mode-Crossing Resonances
Authors: Fellman Tomas
Published: May 2005

The magneto-optic effect called mode-crossing is investigated. The crossings are produced with a polarization-stabilized two-mode 633-nm He-Ne laser. The beam from the laser interacts with a thermal neon gas absorber placed outside the laser. The absorber is in a tunable longitudinal magnetic field. The investigations are focused on the behavior of the crossing signals when the laser mode polarizations are varied. Both linearly and circularly polarized modes are used. The results are compared with conclusions that are drawn from couplings between the Zeeman sublevels in J = 1 to J = 0 systems. It is found that the number and the strength of mode-crossings can be controlled by selections of the mode polarizations.
Aqueous Dissolved Gas Measurements Using Near-Infrared Raman Spectroscopy
Authors: Berger Andrew J. , Wang Yang , Sammeth David M. , Itzkan Irving , Kneipp Katrin , Feld Michael S.
Published: May 2005

Near-infrared Raman spectra of several gases dissolved in an aqueous medium have been acquired and analyzed for the first time. Spectra of dissolved and gaseous CO2, SO2, N2O, dimethyl ether, and O2 are presented and compared. Raman-forbidden bands in the spectrum of gaseous dimethyl ether are observed in the dissolved spectrum; this result can be explained by relaxed selection rules due to lowered symmetry. Raman scattering enhancements in the dissolved phase are measured and shown to compare well with a theoretical prediction accounting for internal field enhancements in water. Dissolved CO2 is measured quantitatively at concentrations from 0 to 250 Torr with the use of the method of partial least-squares, with an average prediction error of 12 Torr.
Design and Characterization of a Visible-Light Fourier Transform Raman Spectrometer
Authors: Brenan Colin J. H. , Hunter Ian W.
Published: May 2005

We demonstrate the feasibility of Fourier transform (FT) Raman spectroscopy with visible wavelength excitation through design, construction, and characterization of a visible-light FT-Raman spectrometer. Our motivation to explore this approach stemmed from the need for a versatile Raman spectrometer for use in a confocal scanning laser Raman microscope we built. We discuss the spectrometer design features which contribute to efficient and reliable microscope operation and evaluate the spectrometer performance on the basis of a series of measurements chosen because of their impact on confocal microscope function. The measurements include the acquisition of representative Raman spectra from both solids and liquids, a demonstration of the independence of resolving power from input aperture diameter, the measurement of the absolute spectrometer optical efficiency curve, and an evaluation of the short- and long-term spectrometer noise processes.
Polymer-Coated, Tapered Cylindrical ATR Elements for Sensitive Detection of Organic Solutes in Water
Authors: Ertan-Lamontagne Marc C. , Lowry Stephen R. , Seitz W. Rudolf , Tomellini Sterling A.
Published: May 2005

Commercially available tapered chalcogenide fibers have been coated with poly(vinyl chloride) (PVC) plasticized with 47% (w/w) chloroparaffin containing 60% Cl by weight. The coating procedure involves applying a drop of a solution containing PVC and the plasticizer in tetrahydrofuran along the fiber while allowing the solvent to evaporate. The coated fibers were exposed to 0.15% (v/v) benzene in water (1479-cm−1 band), 0.40% (v/v) chloroform in water (1216-cm−1), and 0.10% (v/v) nitrobenzene in 1.5% (w/v) methanol/water (1348-cm−1). All three organic solutes gave readily detectable signals with the coated fibers but were not observable when the aqueous solution was sampled with the use of an uncoated, tapered fiber. Detection limits for benzene, chloroform, and nitrobenzene were calculated to be 0.02%, 0.11%, and 0.006% by volume, respectively. These data show that the advantage of using a polymer coating to concentrate the analyte and reduce the water background may be combined with the advantages of using a tapered optical fiber to yield a sensitive method for detecting nonpolar organic solutes in water.
Characterization of a Modified, Low-Power Argon Microwave Plasma Torch (MPT) as an Atomization Cell for Atomic Fluorescence Spectrometry
Authors: Duan Yixiang , Du Xiaoguang , Li Yimu , Jin Qinhan
Published: May 2005

A microwave plasma torch (MPT) has been newly modified and used as an atomization cell for atomic fluorescence spectrometry (AFS). The analytical performance of the MPT-AFS system has been characterized with hollow cathode lamps (HCLs) working in the pulsed mode as an excitation source and a pneumatic nebulizer for aqueous sample introduction. The method exhibits a relatively large dynamic range over at least three orders of magnitude in concentration and fairly good precision in a range from 0.42% (Zn) to 4.9% (Ag). It was found that observation height, microwave power, and plasma support-gas flow rate have an important influence on the performance of MPT-AFS. The detection limits obtained by the new MPT-AFS system are in a range from 0.25 (Cd) to 121 (As) ng/mL for ten elements examined. A comparison of MPT-AFS with other plasma AFS approaches suggests several advantages of the MPT source as an atomizer for AFS.
Rapid Normal Raman Spectroscopy of Sub-Ppm Oxy-Anion Solutions: The Role of Electrophoretic Preconcentration
Authors: Kowalchyk Will K. , Walker Patrick A. , Morris Michael D.
Published: May 2005

Normal Raman spectroscopy is used as an on-line detector for capillary electrophoresis (CE) to detect sub-ppm mixtures of nitrate and perchlorate in water. Field-amplified injection, a form of sample stacking, into a running electrolyte of 0.1 M KCl increases the analyte concentration at the detection window by up to 1800 times its starting value. Raman bands of nitrate (1047 cm−1) and perchlorate (934 cm−1) are measured in a total separation time of less than 3 min, with only 1-s integration times. The Raman spectroscopy of solutions originally 1 × 10−5 M nitrate (620 ppb) and perchlorate (1 ppm) is demonstrated.
DRIFTS Chamber for in Situ and Simultaneous Study of Infrared and Electrical Response of Sensors
Authors: Benítez José J. , Centeno Miguel A. , Merdrignac Odile M. , Guyader Jean , Laurent Yves , Odriozola José A.
Published: May 2005

A diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) chamber suitable for in situ and simultaneous analysis of the infrared and electrical response of sensors is tested and described in detail. Experiments on a CdGeON sensor show some results about its reversible/ irreversible behavior in terms of temperature and under N2 atmosphere. A direct relationship between the conductivity and the elimination of DRIFTS peaks at 810,780, and 580 cm−1 is observed. From both DRIFTS spectra and conductivity measurements, an explanation involving the presence and filling of vacancies in the solid framework is proposed.
Raman Imaging Using a Tunable Dual-Stage Liquid Crystal Fabry-Perot Interferometer
Authors: Christensen Kenneth A. , Bradley Nancy L. , Morris Michael D. , Morrison Robert V.
Published: May 2005

A 11 12 cm−1 bandpass electronically tunable liquid crystal dual-stage Fabry-Perot filter (DFPF) has been developed for use in Raman and fluorescence microscopic imaging. The imaging performance of the filter was demonstrated in the fluorescence and Raman modes. In the fluorescence mode, the filter was shown to give sharpened images using the nearest-neighbors deblurring algorithm. In the Raman imaging mode, background subtraction was shown to be useful for removal of the fluorescence from Raman images. With the use of a 100 × /1.25 objective, no significant decrease in the spatial resolution of the microscope was observed when the DFPF was inserted in the optical system.
Investigation of the Morphological Composition of Cimetidine by FT-Raman Spectroscopy
Authors: Jalsovszky George , Egyed Orsolya , Holly Sándor , Hegedus Béla
Published: May 2005

The Raman spectra of six polymorphic crystal forms of N-cyano- N′-methyl- N″-{2-[(5-methyl-1H-imidazol-4-yl)methylthio]ethyl}-guanidine (Cimetidine) have been studied to investigate the possibility of quantitative analysis of polymorphic mixtures. Characteristic Raman bands of the various polymorphs have been found, some of which proved to be appropriate for quantitative analysis. The applicability of various mathematical techniques has been investigated, of which partial least-squares (PLS) has been found to be the best.
Chemometric Study of the Fluorescence of Dental Calculus by Trilinear Decomposition
Authors: Ferreira Marcia M. C. , Brandes Mary Lou , Ferreira Inês M. C. , Booksh Karl S. , Dolowy William C. , Gouterman Martin , Kowalski Bruce R.
Published: May 2005

Chemometric techniques have been applied to the unresolved second-order porphyrinic emission-excitation fluorescent spectra of several animal dental calculus deposits dissolved in HCl. A singular value decomposition (SVD) procedure was used for preliminary indication of the number of fluorescent species present in the samples. The trilinear decomposition (TLD) method was applied to resolve component spectra, resulting in three porphyrinic spectral profiles for both canines and felines.
Simple Near-Infrared Spectrometric Sorption-Based Vapor Sensor
Authors: Fong Andrew , Hieftje Gary M.
Published: May 2005

A new class of near-IR sensors has been devised which relies on spectroscopic near-IR detection of analytes sorbed on a preconcentrating layer. The new sensors furnish both qualitative and quantitative information by detection of molecular vibrational overtone and combination absorption bands and by measurement of changes in the scattering of the silica-gel medium. A silica-gel thin-layer chromatography (TLC) plate was used as the adsorbent medium. This method is responsive to vapors ranging from water to carbon tetrachloride. Ethyl- and octylderivatized TLC plates were also tested and generally exhibited a weaker response and different spectral features than the original plate. The optical nature of these sensors opens up the possibility of remote analysis by coupling the technique with fiber optics and/or near-IR light-emitting diodes and lasers. Detection limits ranged from 4.1 to 210 ppm by volume. Polar compounds able to hydrogen bond to the surface exhibited lower detection limits than nonpolar compounds.
Application of a Magnetron Glow Discharge to Direct Solid Sampling for Mass Spectrometry
Authors: Shi Zhan , Brewer Stephen , Sacks Richard
Published: May 2005

The behavior of a planar magnetron glow discharge used as a sampling device and ion source for mass spectrometry of conducting solids is examined. Low-pressure operation of the magnetron allows efficient sputtering and ion production from conducting samples. Interfacing the magnetron with the mass spectrometer is simplified by low-pressure magnetron operation. A special sample holder allows up to five sample plugs to be analyzed without the source chamber vacuum being broken. Sample ion current is not found to be a simple function of discharge current, but is a strong function of sample axial position relative to the mass spectrometer sampling cone. The mass spectrometer sampling cone orifice diameter may be varied from 0.5 to 5.0 mm. A cone orifice diameter of 2.0 mm yields optimum analytical conditions. Determination of Al at the 3–5% level in a series of NIST Zn-base alloy standards yields a straight-line analytical curve, suggesting the potential application of the device to high-precision analyses of alloys.
Design and Performance of a Hadamard Transform Infrared Spectrometer with No Moving Parts
Authors: Tilotta David C. , Zhou Zhou
Published: May 2005

The development of an improved Hadamard transform infrared HT-IR) spectrometer with no moving optical parts is described. This spectrometer is based on a thermo-optic array for the stationary encoding of radiation (TOASTER) fabricated from Nichrome resistance wire. The TOASTER HT-IR instrument utilizes a reversed Czerny-Turner optical mount and relies on entrance focal plane modulation for operation. This design allows the dedispersion optics to be eliminated while still providing for a multiplex advantage. In addition, a conventional mechanical chopper is not needed in this instrument because the TOASTER is used as a natural modulator. The TOASTER HT-IR spectrometer can acquire an infrared spectrum in the range of 2.5 to 11 μm (4000 to 910 cm−1). Its spectral resolution is 0.07 μm (∼7 cm−1 at 1000 cm−1), and, for fifteen spectral resolution elements, the observation window is 0.5 μm (∼48 cm−1 at 1000 cm−1). In addition to the design of the instrument, this communication also examines the thermo-optic switching properties of the Nichrome wire used in the prototype TOASTER. Although the maximum switching speed of the Nichrome wire is governed by its thermal decay time, we show that the TOASTER can be operated faster than this limit by employing a preheating step.
Quantification of Raman Spectra for the Primary Atmospheric Corrosion Products of Lead
Authors: Black Leon , Allen Geoffrey C. , Frost Paul C.
Published: May 2005

In this study laser Raman spectra were recorded for eight lead compounds commonly reported as products from the atmospheric corrosion of lead. The spectra obtained demonstrated that this technique is well suited for the characterization of lead compounds. Moreover, when mixtures of these compounds are being studied, a good correlation can be obtained between sample composition and a characteristic Raman band intensity. This correlation should permit an estimate of the quantity of various compounds present in corrosion products.