bluuebunny/crossref_metadata_2025 huggingface dataset:
Room-Temperature Measurement of Photoluminescence Spectra of Semiconductors Using an FT-Raman Spectrophotometer
Authors: Webb J. D. , Dunlavy D. J. , Ciszek T. , Ahrenkiel R. K. , Wanlass M. W. , Noufi R. , Vernon S. M.
Published: June 2005

This paper demonstrates the utility of an FT-Raman accessory for an FT-IR spectrophotometer in obtaining the room-temperature photoluminescence (PL) spectra of semiconductors used in photovoltaic and electro-optical devices. Sample types analyzed by FT-IR/PL spectroscopy included bulk silicon and films of gallium indium arsenide phosphide (GaInAsP), copper indium diselenide (CuInSe2), and gallium arsenide-germanium alloy on various substrates. The FT-IR/PL technique exhibits advantages in speed, sensitivity, and freedom from stray light over conventional dispersive methods, and can be used in some cases to characterize complete semiconductor devices as well as component materials at room temperature. Some suggestions for improving the spectral range of the technique and removing instrumental spectral artifacts are presented.
Evaluation of the Performance of Microwave-Induced Plasma Atomic Absorption Spectrometry (MIP-AAS)
Authors: Duan Yixiang , Hou Mingyi , Du Zhaohui , Jin Qinhan
Published: June 2005

An innovative method of MIP-AAS has been developed. The sample solution was introduced by using an ultrasonic nebulizer. The desolvation was accomplished by a heating tube and a combination of a water-cooled condenser and a concentrated sulfuric acid desiccator. Both an L-shaped and a T-shaped plasma discharge tube were used as the absorption cell in the experiment. The experimental parameters were carefully examined and optimized for the elements studied. Some comparison of properties for these two different absorption tubes was made, and the analytical performance of MIP-AAS was evaluated. The characteristic concentrations obtained in this work were shown to be around ppb under the optimized experimental conditions for 12 elements. Good repeatability and accuracy were achieved. The analytical figures of merit were found to be much better than those obtained by ICP-AAS and previous MIP-AAS experiments and comparable to or even better than the best reported values of flame AAS.
Application of FT-IR Absorption Spectroscopy for in Situ Gas Concentration and Temperature Measurements in Laboratory- and Pilot-Scale Combustion Environments
Authors: Martin Denise M. , Medvecz Patrick J. , Nichols Kenneth M.
Published: June 2005

In situ FT-IR absorption spectroscopy was used as a diagnostic tool to evaluate the gas phase above a heterogeneous reaction, black liquor char combustion. Previously developed calculation methodologies were used to determine the CO and CO2 concentrations and the CO rotational temperatures from absorption spectra. Spectroscopically obtained gas temperatures and concentrations from laboratory-scale experiments were compared to thermocouple and NDIR measurements. Quantitative evaluations of the gas phase during these experiments indicated that gas temperatures can be measured with an accuracy of 2–3% at 450–750 K and gas concentrations can be measured with accuracies of better than 10% at gas concentrations between 0.3 and 1.3%. Gas temperatures obtained during pilot-scale combustion were between 1118 and 1183 K, while concentrations were between 0.35 and 0.76%. Differences among gas concentrations and temperatures calculated from the absorption spectra, compared to NDIR measurements and thermocouples, were greater than those from laboratory combustion due to the dynamics of the gas phase. The need is exemplified for a well-characterized combustion environment for effective use of FT-IR as a diagnostic tool for pilot-scale combustion and for advancing the fundamental understanding of combustion processes.
Some Experimental Aspects of the Spectroscopy of the Emission Intensity of Simple Radicals
Authors: Stefano G. Di , Ricci A.
Published: June 2005

Experimental distributions of rotational line strength have been recently obtained for the first time in weak transitions of diatomic species [Chem. Phys. 165, 201 (1992)]. Contrary to widespread opinion, a very simple apparatus has been sufficient to achieve this goal, but certain attention must be paid to a few specific points. A description is reported, where some experimental requirements, due to the quantitative character of this spectroscopy, are emphasized.
Remote Biodetection Method Using Circular Dichroism
Authors: Rosen David L.
Published: June 2005

This paper proposes a new method for remote biodetection and simulates it with a laboratory optical table experiment. The new method, called circular polarization transmissometry, uses laser light scattered from the ground to measure the circular dichroism in an aerosol plume. In the optical table experiment, a scatter plate simulated the ground, and solutions of camphoroquinone simulated the biological aerosols. The experiment showed that this biodetection method could work even in daylight. Optical elements with inherent birefringence caused an optical artifact background that was subtracted from the signal.
Two-Dimensional Vibrational Spectroscopy II: Correlation of the Absorptions of Lignins in the Mid- and Near-Infrared
Authors: Barton F. E. , Himmelsbach D. S.
Published: June 2005

Two-dimensional (2D) statistical correlation of mid- and near-infrared spectra was used as a means to assist with qualitative spectral interpretation of the lignin carbohydrate fractions from plant materials. Cross-correlation by least-squares is used to assess changes in both regions that result from changes in the set of sample spectra. The technique has been applied to a set of specially prepared “lignin” samples that differ in lignin content, species of origin, and method of preparation. Dispersive near-infrared (NIR) and Fourier transformed mid-infrared (FT-IR) diffuse reflectance spectra (DRIFTS) were obtained on each of the samples, and point-for-point 2D cross-correlation was obtained. The technique permits the correlation of the combination and overtone bands of the NIR region with the fundamental vibrations in the mid-infrared (MIR) region. The results show a broad correlation of aromatic C-H stretch at 3022 cm−1 in the MIR to 1666-nm location in the NIR region and other locations to a lesser extent all across the NIR from 1400 to 2500 nm. A narrower region of correlation was found for the phenolic O-H stretch in the MIR at 3663 cm−1 to 1428 nm and 1938 nm in the MIR. Multiple narrow correlations occur in the area of the summation bands from 1450 to 1650 cm−1, indicative of substitution patterns and correlated areas of C-H and O-H stretch in the NIR.
Photoionization Mass Spectrometry of C60 and C70 with a Vacuum Ultraviolet Hydrogen Laser Source
Authors: Zumwalt Michael C. , Denton M. Bonner
Published: June 2005

A time-of-flight mass spectrum of the C60 and C70 fullerenes with the use of a vacuum ultraviolet H2 laser photoionization source is presented. The photon energy is 7.8 eV, approximately 0.2 eV above the reported ion thresholds of both molecules. This relatively low excess energy is believed to be insufficient for fragmentation, as demonstrated by production of only parent ions.
Efficient Source-To-Fiber Coupling Method Using a Diamond Rod: Theory and Application to Multimode Evanescent-Wave IR Absorption Spectroscopy
Authors: Jonas Roy E. , Braiman Mark S.
Published: June 2005

The use of a diamond rod to couple a blackbody source optically to a chalcogenide glass fiber is described and shown to be useful for evanescent-wave IR absorbance measurements. One end of a short 0.5-mm-diameter diamond rod abuts an optical fiber of the same diameter; the other end is in direct contact with a glowing silicon carbide IR source. The close match of the refractive indices of SiC, diamond, and AsSeTe fiber reduces optical losses at the interfaces, allowing a high overall throughput as well as transmission into the fiber of a wider range of transverse optical modes than is available with the use of through-air focusing methods. Use of the higher-order modes for evanescent-wave spectroscopy leads to increases in sensitivity, due both to increased evanescent pathlength and to a larger number of internal reflections per unit length.
Solid-State Transition Mechanisms of Ammonium Nitrate Phases IV, III, and II Investigated by Simultaneous Raman Spectrometry and Differential Scanning Calorimetry
Authors: Harju Mauno E. E.
Published: June 2005

The solid-state transition mechanisms of ammonium nitrate IV, III, and II were studied by measuring samples simultaneously by Raman spectrometry and differential scanning calorimetry (DSC). The Raman instruments were a Fourier transform Raman spectrophotometer and triple monochromator Raman spectrophotometer with charge-coupled-device (CCD) detector. The spectral data of the transitions were collected simultaneously with the calorimetric data in the temperature-scanning mode of the calorimeter and then isothermally between transitions. The phase transition from phase IV to phase III occurred through an intermediate phase II*, whose lifetime was seven minutes maximum when the onset temperature of the reaction was close to the phase-transition IV → II onset temperature. It is concluded that there is always an intermediate phase II* between IV and III. Simultaneous Raman measurements are shown to be an effective tool for interpreting complex DSC curves.
LIF Measurements on the C2Σ+–X2IIr Transitions of the CD Radical
Authors: Hummernbrum F. , Kempkens H. , Ruzicka A. , Schiffer C. , Uhlenbusch J. , Winter J.
Published: June 2005

Laser-induced fluorescence (LIF) measurements are made on the C2Σ+- X2II r (λ = 314 nm) transition of CD, which is produced by a microwave-excited Ar/CD4 process plasma. The experiment is realized by using a frequency-doubled cw ring dye laser as the tunable light source. Due to the small bandwidth (≈3 MHz) of the exciting UV laser, the exact line positions of spin-doubled rotational lines in the P-branch ( N” = 2 to 5 and N” = 8 to 13) of the first vibrational band ( v’ = v” = 0) could be determined. The resolution is limited only by Doppler broadening, which amounts in our plasma ( T = 450 K) to about 4 GHz. With these new values of line positions, a modified spin-splitting constant of γ = 0.051 ± 0.006 cm−1 is calculated.
High-Performance Raman Spectroscopic System Based on a Single Spectrograph, CCD, Notch Filters, and a Kr+ Laser Ranging from the Near-IR to Near-UV Regions
Authors: Kim Munsok , Owen Harry , Carey Paul R.
Published: June 2005

We describe the performance of a high-throughput system for detecting Raman spectra excited in the range from 320 to 750 nm. The system utilizes notch filters to reject Rayleigh scattering, a single polychromator as the dispersive element, and photon detection via a charge-coupled device. The filters, mirrors, and grating are changed to maximize performance in each excitation region. The excitation source consists of a Kr+ ion laser. Good-quality Raman data are reported for rhodamine 6G at 0.1 mM in methanol with the use of 752.5-nm excitation, and 0.2 mM flavin adenine dinucleotide (FAD) in tris buffer with the use of 647.1-nm excitation. High-quality resonance Raman data for 0.1 mM N-acetyl-glycine ethyl dithio ester in 5% CH3CN/H2O are also reported with the use of 324.0-nm excitation.
Composition and Particle Diameter for Styrene/Methyl Methacrylate Copolymer Latex Using UV and NIR Spectroscopy
Authors: Gossen Paul D. , Macgregor John F. , Pelton Robert H.
Published: June 2005

The properties of a polymer latex were measured over the course of a semi-batch polymerization with the use of ultraviolet (UV) and near-infrared (NIR) spectroscopy. The spectra were very complex, and their characteristics changed dramatically throughout the course of a batch, so linear calibration models were constructed for groups of similar spectra using Partial Least-Squares (PLS). Principal Component Analysis (PCA) was used as a pattern recognition tool to group spectra before calibration or prediction. UV spectra from 190 to 800 nm were taken of diluted latex. The weight fractions of styrene monomer and poly(styrene) were predicted with a standard error less than 0.5 wt%. NIR spectra from 900 to 1800 nm were taken of undiluted latex with a transflectance fiber-optic probe. Calibrations could predict the concentrations of all the major components [water, poly(styrene), poly(methyl methacrylate), styrene, methyl methacrylate] with a standard error of less than 0.5 wt%. Mean particle size was also well predicted for some of the calibration sets.
Empirically Minimax Affine Mineralogy Estimates from Fourier Transform Infrared Spectrometry Using a Decimated Wavelet Basis
Authors: Stark Philip B. , Herron Michael M. , Matteson Abigail
Published: June 2005

The Fourier transform infrared (FT-IR) spectrum of a rock contains information about its constituent minerals. Using the wavelet transform, we roughly separate the mineralogical information in the FT-IR spectrum from the noise, using an extensive set of training data for which the true mineralogy is known. We ignore wavelet coefficients that vary too much among repeated measurements on rocks with the same mineralogy, since these are likely to reflect analytical noise. We also ignore those that vary too little across the entire training set, since they do not help to discriminate among minerals. We use the remaining wavelet coefficients as the data for the problem of estimating mineralogy from FT-IR data. For each mineral of interest, we construct an affine estimator ◯ of the mass fraction x of the mineral of the form [Formula: see text], where [Formula: see text] is a vector, [Formula: see text] is the vector of retained wavelet coefficients, and b is a scalar. We find [Formula: see text] and b by minimizing the maximum error of the estimator over the training set. When applying the estimator, we “truncate” to keep the estimated mineralogy between 0 and 1. The estimators typically perform better than weighted nonnegative least-squares.
Simultaneous Analysis of Gas Phase and Intermediates in the Hydrogenation of Carbon Oxides by DRIFTS
Authors: Benitez J. J. , Carrizosa I. , Odriozola J. A.
Published: June 2005

In this work the experimental details and some examples of applications of diffuse reflectance infrared technique are described. Special interest has been devoted to a correct determination of the temperature of the sample, to gas-phase analysis, and to quantitative aspects in a DRIFTS controlled environmental cell. Applications to the analysis of the gas phase during catalytic hydrogenation and to the obtainment of kinetic parameters for the catalytic decomposition of adsorbates are included.
Trace Detection of Nitrocompounds by ArF Laser Photofragmentation/Ionization Spectrometry
Authors: Simeonsson Josef B. , Lemire George W. , Sausa Rosario C.
Published: June 2005

A new method for detecting trace vapors of NO2-containing compounds near atmospheric conditions has been demonstrated with the use of one-color-laser photofragmentation/ionization spectrometry. An ArF laser is employed to both photolytically fragment the target molecules in a collision-free environment and ionize the characteristic NO fragments. The production of NO is hypothesized to result from a combination of two NO2 unimolecular fragmentation pathways, one yielding NO in its X2II electronic ground state and the other in its A2Σ+ excited state. Ionization of ground-state NO molecules is accomplished by resonance-enhanced multiphoton ionization processes via its A2Σ+ ← X2II (3, 0), B2II ← X2II (7, 0) and/or D2Σ+ ← X2II (0, 1) bands at 193 nm. The analytical utility of this method is demonstrated in a molecular beam time-of-flight apparatus. Limits of detection range from the parts-per-million (ppm) to parts-per-billion (ppb) level for NO, NO2, CH3NO2, dimethylnitramine (DMNA), ortho- and meta-nitrotoluene, nitrobenzene, and trinitrotoluene (TNT). Under effusive beam experimental conditions, discrimination between structural isomers, ortho-nitrotoluene and meta-nitrotoluene, has been demonstrated with the use of their characteristic photofragmentation/ionization mass spectra.
Raman Spectroscopic Study of Ba2+-Surfactant Interactions in Aqueous Monodisperse Alkylpolyoxyethylene Surfactant Solutions
Authors: Siew Diana C. W. , Cooney Ralph P. , Taylor Michael J.
Published: June 2005

Aqueous monodisperse alkylpolyoxyethylene surfactant-Ba2+ systems were investigated to clarify the coordination effects between the polyether chain and the cation which have been previously identified in polydisperse alkylphenoxy- and alkypolyoxyethylene surfactant systems. The coordination effects are simplified in the present study due to the presence of only a single polyether chain component. Formation of the surfactant complex resulted in conformational changes of the polyether chain which were monitored by Raman difference spectroscopy and curve fitting. The present studies confirm that surfactant-complex formation is dependent upon the polyether chain adopting the TGT-TĜT conformation and that the stability of the complex increases with the number of filled chain sites. The length of the polyether chain is also an influencing factor.
Intensity Calibration and Sensitivity Comparisons for CCD/Raman Spectrometers
Authors: Fryling Mark , Frank Christopher J. , McCreery Richard L.
Published: June 2005

A calibrated tungsten source combined with a fiber optic was used to correct Raman spectra for instrumental response. With the placement of the fiber output at the Raman sample position, the product of throughput, collection efficiency, quantum efficiency, and sampled area could be assessed. This product is related to a spectrometer figure of merit, which provides a quantitative comparison of spectrometer sensitivity and signal-to-noise ratio. Four spectrometer configurations were compared to illustrate the approach. An additional feature of the white light calibration is correction of relative Raman peak intensities. This issue is particularly important due to the substantial differences between CCD quantum efficiency curves and those of photomultipliers or intensified photodiode arrays.
Infrared Emission Spectroscopy with Transient Cooling
Authors: Pell Randy J. , Miller Charles E. , Kowalski Bruce R. , Callis James B.
Published: June 2005

A new approach for collection of infrared spectral data from optically opaque materials is explored. This approach has previously been introduced in the literature and is known as transient infrared transmission spectroscopy (TIRTS). The front surface of a hot sample is transiently cooled with a jet of cold gas, and the ratio of the spectrum measured after cooling to that measured before cooling is shown to closely resemble a transmission spectrum. This report provides for a more theoretical understanding of the experiments than provided by previous workers, making use of unsteady-state heat flow calculations, harmonic oscillator modeling, and radiation transfer theory. Experimental data are collected from a solid polymer sample and two viscous liquid samples. The position of the spectral features for the emission measurements corresponds with transmission measurements, with some saturation of the more intense spectral features noted. Faster scanning instrumentation, proper pulse scan synchronization, or rotation of solid samples, as demonstrated by previous workers, may resolve the saturation problem.
Time-Resolved Luminescence Spectroscopy: Computer Interfacing and Software Development for a Boxcar-Based Laser-Luminescence Spectrometer
Authors: Novo João B. Marques , Pessine Francisco B. T.
Published: June 2005

The undesirable resistance-capacitance (RC) distortion coming from the exponential moving averaging process of a boxcar integrator/averager acquisition system in kinetic and spectral luminescence measurements could be effectively eliminated by interfacing it to a microcomputer. Accurate acquisition of luminescence decay curves and time-resolved spectra was provided by a developed software that allows synchronous scan control of the gate delay time in the boxcar integrator with the emission wavelength in the monochromator. Some simple mathematical calculation routines, including excited-state lifetime extraction from luminescence decay curves and normalization of time-resolved spectra, were added. The main characteristics of both the software and the interfacing hardware are reported.
Theoretical Studies in EDXRF on a New Linear Relation: In(Fluorescent Intensity Ratio of Analyte to Pure Analyte/Concentration of Analyte) versus In(Fluorescent Energy)
Authors: Yap C. T. , Hua Younan
Published: June 2005

The inaccuracies and validity of the approximate linear relation between In(fluorescent intensity/concentration) and In(fluorescent energy) are presented and discussed. We then present the derivation of a new linear relation between In(fluorescent intensity ratio of analyte to pure analyte/concentration of analyte) and In(fluorescent energy) which is valid for all elements that can be excited by radiation sources, whether by tube x-ray or by radioisotope sources.
Uranium Determination by Remote Time-Resolved Laser-Induced Fluorescence
Authors: Moulin Christophe , Rougeault Stephane , Hamon Dominique , Mauchien Patrick
Published: June 2005

Uranium measurements taken in a hostile environment are required in the nuclear fuel cycle. Current trends are leading toward development of better sensitivity and rapidity as well as remote measurements. Time-Resolved Laser-Induced Fluorescence (TRLIF) is a very selective and sensitive method that has been widely used for uranium determinations in complex matrices. This technique evolved from analysis in a cell located in a glove box to remote measurements via fiber optics in a shielded cell. The setup of Remote Time-Resolved Laser-Induced Fluorescence (RTRLIF) includes an excitation laser focused in the excitation fiber, with the fluorescence collection fibers concentrically positioned around the excitation fiber at the optrode tip, which dips into the solution; the signal is analyzed by a pulsed intensified multichannel spectrofluorimeter. This analyzer allows for the elimination of the unwanted parasital fluorescence (organic, Raman) by the placement of a gate a few microseconds after the laser pulse. Special care is taken in terms of laser focalization, fiber-optic parameters (numerical aperture, diameter, and arrangement), parasital fluorescence, time delay, and width of the gate. Results obtained with RTRLIF in terms of limits of detection (LOD ∼ 10−10 M) are presented and compared with the results obtained by TRLIF.
Raman Spectroscopic Characterization of the Oxidation of Nuclear-Grade Graphites
Authors: Nikiel Leszek , Jagodzinski Paul W.
Published: June 2005

Nuclear-grade graphites were characterized with the use of laser Raman spectra collected between 1100 and 2800 cm−1. Significant band broadening and wavenumber shifts were observed for the D band (1317 cm−1), the G band (1578 cm−1), and the D' band (1612 cm−1) for samples treated at 1100°C in helium- or nitrogen-enriched atmospheres. Significant decreases in the domain sizes were calculated on the basis of these data. Very intense, broad bands located between 1700 and 2500 cm−1 were observed for samples treated at high temperature in a nitrogen-enriched atmosphere. These bands have been assigned to oxidation products adsorbed on the graphite surface, and their appearance has been correlated with trace element analysis for all investigated graphites. It is proposed that silicon atoms inhibit metal-catalyzed oxidation of the graphites studied in this work.
Quantitative Infrared Spectroscopy of Interstitial Oxygen in Silicon Wafers Using Multivariate Calibration
Authors: Linn J. H. , Hanley K. L.
Published: June 2005

A PLS multivariate calibration method is used to create a reliable means for the determination of the interstitial oxygen content in silicon wafers. The multivariate calibration, derived from silicon standards with various backside treatments, provides similar precision measurement capability when compared to peak area calibration curves established from individual backside treatments. In this case, the significant advantage of the multivariate calibration is that a single calibration can yield interstitial oxygen results that correlate favorably with vendor values over a wide range (20 to 40 ppma), regardless of the backside condition of the wafers.
Overtone Spectra of CHD3 with an FT-IR Spectrometer Aided by Infrared Double Resonance
Authors: Mizugai Yoshihiro , Klaassen Jody J. , Roche Christine , Steinfeld Jeffrey I.
Published: June 2005

We have used a time-resolved double-resonance (pump-probe) method to assign the CHD3 spectra taken by an FT-IR spectrometer at high resolution. The spectra of 2ν3, ν3 + ν6, and 2ν6 around 2000 cm−1 were investigated. Collisional processes in the molecule were investigated by the time evolution of the signal and double-resonance spectra.
Trace-Level Quantitation via Time-Resolved Two-Photon-Excited Fluorescence
Authors: Lytle Fred E. , Dinkel Debora M. , Fisher Walter G.
Published: June 2005

With the use of a cavity-dumped, synchronously pumped dye laser for excitation, two-photon fluorescence cross sections are approximately eight orders of magnitude smaller than those for one-photon excitation. Thus, examination of dilute solutions has been achieved only with great difficulty. Any successful instrumentation will require that the blank be essentially eliminated. To this end, time-filtered detection has been combined with two-photon excitation and spatial filtering to produce fluorometric detection limits of 38 pM for 9,10-diphenylanthracene and 8.6 pM for α-NPO. It is believed that this latter value is the lowest concentration yet reported for two-photon spectroscopy in fluid solution. The instrumentation and data processing are described. Additionally, a comparison is made with the performance of other recent alternative approaches involving spatial filtering and second harmonic detection.
Quantitative Study of the Dissociation of Dimeric cis-9, cis-12-Octadecadienoic Acid in Pure Liquid by the FT-IR Liquid Film Technique
Authors: Czarnecki Mirosław Antoni , Ozaki Yukihiro , Suzuki Masao , Iwahashi Makio
Published: June 2005

The study of the infrared spectra of neat cis-9, cis-12-octadecadienoic acid in the liquid phase has been carried out over a temperature range of 31 to 110°C. In the region of 1710 cm−1 a strong absorption band accompanied by two weaker bands appears. The strong band is assigned to a C=O stretching vibration due to the dimeric form of the acid, and the weaker bands near 1750 and 1650 cm−1 are attributed to a C=O stretching vibration due to its monomer and to C=C stretching modes arising from both forms, respectively. The shape of the band envelope strongly depends on temperature. Making a curve fitting, one can determine spectral parameters of the individual bands, and from them it is possible to calculate the degree of dissociation of the acid. The obtained values of the degree of dissociation enable us to determine enthalpy (Δ H) and entropy (Δ S) for the process of dissociation of dimeric species into free molecules, and the results seem to be reasonable as compared with the literature data for other fatty acids.
Use of a Mono-Fiber Optrode in Remote and in Situ Measurements by the Raman/Laser/Fiber Optics (RLFO) Method
Authors: Huy Nguyen Quang , Jouan Michel , Dao Nguyen Quy
Published: June 2005

A new versatile mono-fiber optrode based on the combined use of a dual-fiber optrode and a short mono-fiber is proposed. The quantitative analytical possibility of this optrode configuration is tested on benzene/heptane mixtures with the use of a PLS procedure, and good results are obtained. The new all-purpose mono-fiber optrode is extremely simple and user friendly and can be used for in situ and in vivo detection.
Effect of Cultural Conditions on Deep UV Resonance Raman Spectra of Bacteria
Authors: Manoharan R. , Ghiamati E. , Chadha S. , Nelson W. H. , Sperry J. F.
Published: June 2005

Bacteria grown on trypticase soy agar (TSA), trypticase soy broth (TSB), and Davis minimal media, and harvested at times ranging from 4.5 to 48 h have been excited at 242.54 and 222.65 nm for the purpose of generating resonance Raman spectra. When excitation with 242.54-nm light occurs, simple spectra of tyrosine and tryptophan and various nucleic acids are observed. Large changes in the relative intensities of major nucleic acid peaks at 1485 and 1575 cm−1, on the one hand, as compared to a prominent protein tyrosine + tryptophan peak at 1616 cm−1, on the other, have been attributed to very large variations in the RNA content of bacterial cells from culture to culture. The spectral changes are observed whenever differences in growth rates or variations in cultural media result in substantial changes in the amount of ribosomal RNA. In spite of very large cultural effects on peak intensities it has been possible to obtain bacterial G + C/A + T ratios from these spectra. Specifically, the ratio of the intensity of the C (1530 cm−1) peak to the intensity of the A + G peak (1485 cm−1) when plotted against the known molar percent G + C of the corresponding bacterial DNA produces a straight line. Plots have been shown to be very nearly growth-time and media independent for fourteen different types of bacteria, which range in DNA G + C content from 32 to 66%. Spectra obtained with 222.65-nm light, in contrast with spectra obtained with 242.54-nm excitation, have been found to be nearly growth-rate and media independent. The excitation wavelength, 222.65 nm, appears to be the best yet found for use in rapid Raman identification of bacteria. All strong peaks which have been assigned have been attributed to protein modes. Relative intensities of 1556-cm−1 tryptophan and 1616-cm−1 tryptophan + tyrosine bands have been found to be strongly correlated with bacterial Gram type and nearly independent of cultural media or stage of growth.
Design Parameters for an Optimized Flame/Furnace Infrared Emission (FIRE) Radiometer
Authors: Busch Kenneth W. , Busch Marianna A. , Ythier Renaud Mercier , Kuehn Arvie J.
Published: June 2005

Several design aspects of an optimized flame/furnace infrared emission (FIRE) radiometer are discussed. For a source in thermal equilibrium, the optimum excitation temperature for CO2 is predicted to be 2500 K, based on the stability of the molecule and the population of excited states as functions of temperature. The influence of spectral bandpass on the magnitude of flame background was studied for several wavelengths within the profile of the 4.4-µm emission band of CO2. For the dispersive FIRE radiometer used in this study, the system was found to be detectornoise limited over the range of spectral bandwidths accessible by the instrument (0.01–0.08 µm). When a hydrogen/air flame was used as the excitation source, the maximum signal-to-background ratio was obtained at 4.40 µm with a spectral bandpass of 0.08 µm. For this same experimental arrangement, a mathematical model was used to predict that the maximum signal-to-noise ratio would occur at 4.40 µm with a spectral bandpass of about 0.25 µm. The influence of chopping frequency on detector noise was determined for two different types of wavelength isolation. When a room-temperature bandpass filter was employed, a modulation frequency of 600–1000 Hz was satisfactory for avoiding 1/ f noise from the PbSe detector. However, when a monochromator was employed, chopping frequencies beyond 1000 Hz produced some additional reduction in 1/ f noise. The specific detectivity for the PbSe detector (6.2 × 108 cm Hz0.5 W−1), calculated from the measured noise at a modulation frequency of 600 Hz, is in good agreement with values reported in the literature for 4.40 µm under the same experimental conditions.
Laser Ablation of Metals: A New Method for Preparing SERS Active Colloids
Authors: Neddersen John , Chumanov George , Cotton Therese M.
Published: June 2005

Laser ablation of metals is a new and very powerful method for preparation of surface-enhanced Raman scattering (SERS) active colloids. The method is characterized by its simplicity and versatility. Stable Ag, Au, Pt, Pd, and Cu colloids are prepared by ablation of the metal for ∼10 min in water and organic solvents. An important advantage of this approach over conventional chemical procedures is that the colloids are free of organic or ionic species. Consequently, the chemical and physical effects of ions or other adsorbates can be studied under carefully controlled conditions. The SERS activity of colloidal metals prepared by laser ablation is comparable or superior to that of chemically prepared colloids.
Improved Vacuum Ultraviolet Supersonic Jet Absorption Spectrometer
Authors: Steadman Jhobe , Syage Jack A.
Published: June 2005

We report on design changes that have significantly improved the performance of our supersonic jet ultraviolet and vacuum ultraviolet absorption spectrometer. We incorporated the following three features: (1) direct detection of VUV photons rather than scintillator detection; (2) a triple-pass mirror arrangement; and (3) a larger-pathlength monochromator and a finer grating. These upgrades have yielded about an order-of-magnitude improvement in sensitivity and greater than fivefold improvement in resolution.
Microsecond Time-Resolved Infrared Study of the Electric-Field-Induced Reorientation of Nematic Liquid Crystals. Part II: Dependence of the Motion of Liquid Crystals on the Applied Electric Field
Authors: Urano Taeko I. , Hamaguchi Hiro-O
Published: June 2005

The electric-field dependence of the reorientation motion of a nematic liquid crystal, 5CB (4- n-pentyl-4'-cyanobiphenyl), has been studied by microsecond time-resolved infrared spectroscopy. A rectangular pulsed electric field with a short pulse duration (2 ms) and a low repetition rate (5 Hz) was used to examine the liquid crystal (LC) response in a silicon cell. The motion of the rigid core part (the cyanobiphenyl group) of 5CB was monitored by the CN stretch band and that of the flexible part (the pentyl group) by the pentyl CH stretch band. The response of the LC to the pulsed electric field consists of two components, the slow component and the fast component. The slow component is common to the rigid core and the flexible parts of SCB. The voltage dependence of the slow component exhibits a clear threshold, indicating that this component corresponds to a cooperative motion of the 5CB molecules. The fast component is specific to the flexible part and shows exponential rise and decay behavior patterns. This observation suggests that the fast component corresponds to some noncooperative motions which are characteristic of the pentyl group. It is most likely that the internal rotation around the C(biphenyl)-C(pentyl) bond is responsible for the fast component. It is suggested that the LC molecules near the cell interface play a key role in the primary stage of the reorientation motion under an applied electric field.
Compact Table for the Publication of Infrared Spectra That are Quantitative on Both Intensity and Wavenumber Axes
Authors: Bertie John E. , Jones R. Norman , Apelblat Yoram
Published: June 2005

A Compact Table format is presented for the publication of infrared spectra that are quantitative on both intensity and wavenumber axes. The format is illustrated with a molar absorption coefficient spectrum, Em(ν˜) vs. ν˜, and with infrared real and imaginary refractive index spectra, n(ν˜) vs. ν˜ and k(ν˜) vs. ν˜, respectively. The algorithm consists of two steps: first, the number of spectral points is reduced by using larger wavenumber spacings than appear in the original spectrum; second, the resulting spectral points are presented in a compressed table format. The Compact Table is about one tenth the size required for the original spectrum to be presented in a conventional XY table. The essential criterion for increasing the wavenumber spacing is that it must be possible to recover the original spectrum by interpolation to an accuracy better than that of the original spectrum. Nearly all the recovered imaginary refractive index and molar absorption coefficient values are within 1% of the original values, and for each quantity the average of the magnitudes of the accuracies of recovery is 0.2%. The real refractive index spectrum is most accurately recovered by Kramers-Kronig transformation of the recovered imaginary refractive index spectrum. Nearly all the recovered real refractive index values are within 0.02% of the original values, and the average of the magnitudes of the accuracies of recovery is 0.005%. The real and imaginary infrared dielectric constant spectra, ɛ′(ν˜) vs. ν˜ and ɛ″(ν˜) vs. ν˜, can be calculated from the recovered data with an accuracy in ɛ′ that is about one half of that of the real refractive index and an accuracy in ɛ″ that is approximately that of the imaginary refractive index. The detailed method is outlined and is applied to infrared intensities of chlorobenzene. Computer programs are presented for the construction of the Compact Table and for the recovery of the full spectrum from the tabulated information.
Portable Laser Spectrofluorimeter System for in Vivo Human Tissue Fluorescence Studies
Authors: Brennan James F. , Zonios George I. , Wang Thomas D. , Rava Richard P. , Hayes Gary B. , Dasari Ramachandra R. , Feld Michael S.
Published: June 2005

A compact, portable spectrofluorimeter which measures broad-band fluorophores with high sensitivity is described. This instrument is specifically designed for acquisition of human tissue autofluorescence spectra in vivo. Pulsed excitation laser light at 337 nm and in the 370–700 nm wavelength range is provided, and the resulting fluorescence can be measured with 10-nm resolution. The system produces single-pulse spectra in human artery wall tissues with a signal-to-noise ratio of 100:1. An optically shielded fiber-optic probe for light delivery and collection permits calibrated intensity information to be obtained.
Spectroscopic Study of the Ternary Complex of Beta-Cyclodextrin, Pyrene, and Triton X-100
Authors: Cummings Elizabeth A. , Ndou Thilivhali T. , Smith Vonda K. , Warner Isiah M.
Published: June 2005

The increased fluorescence intensity of pyrene due to indirect excitation by the nonionic surfactant Triton X-100 is discussed. Sensitization is quantitatively shown to occur in mixed solutions of pyrene, Triton X-100, and β-cyclodextrin (β-CD). A ternary complex is formed below the critical micelle concentration (CMC). Above the CMC, pyrene is displaced from the β-CD cavity. This is accompanied by a subsequent incorporation of pyrene into the interior of the micelle. Evidence is given that ternary complexation occurs among pyrene, CD, and TX-100.
Direct Detection of Vacuum Ultraviolet Radiation for Nonmetal Determinations with a Helium Microwave-Induced Plasma
Authors: Alvarado Jorge , Carnahan Jon W.
Published: June 2005

A study of the determination of metals, nonmetals, and metalloids (F, Cl, Br, I, S, P, Se, As, Sb, and Pb) in the vacuum-ultraviolet spectral region with a kilowatt-plus helium microwave-induced plasma is presented. A spectrometer system similar to that used for far-ultraviolet optical sampling with an inductively coupled plasma was designed and implemented. This arrangement was produced by using an optical sampler to couple the plasma discharge with a helium-purged monochromator. Monitoring was performed at wavelengths less than 200 nm with no N2 or O2 in the optical path. Helium was chosen as the purge gas because it is transparent in the wavelength region of interest (>58 nm). Sample introduction was accomplished with ultrasonic nebulization. Limits of detection, linear ranges, and matrix effects caused by group IA and IIA elements were studied. Analytical calibration plots were linear over a range of 2–3 orders of magnitude. Detection limits ranged from 0.06 μg/mL for sulfur to 5 μg/mL for selenium.
Polarization-Sensitive CARS of Excited-State Rhodamine 6G: Induced Anisotropy Effects on Depolarization Ratios
Authors: Lucassen Gerald W. , De Boeij Wim P. , Greve Jan
Published: June 2005

Resonance polarization-sensitive coherent anti-Stokes Raman scattering (PS CARS) spectra of the electronic ground state and excited singlet S1 state of rhodamine 6G in ethanol were obtained with the use of the pump-probe technique with nanosecond time resolution. Variation of the polarization orientation of the pump laser beam showed differences in the excited-state spectra due to optically induced anisotropy. The pure electronic susceptibility of ground-state rhodamine 6G was shown to be small in comparison with nonresonant susceptibility of the solvent, and was neglected in further analyses. The pure electronic susceptibility of excited rhodamine 6G was examined by coherent ellipsometry. The complex third-order susceptibility was analyzed by means of a nonlinear least-squares fit program that provides detailed information on the Raman vibration parameters, including depolarization ratios and phases. In the isotropic case the measured depolarization ratios are close to 1/3, whereas in the anisotropic case, ground-state depolarization ratios are 0.5–0.65 and in the excited state 0.17–0.22. Estimated depolarization ratio changes in ground-state and excited-state rhodamine 6G are in agreement with theoretically predicted values in the case of induced anisotropy under the assumption of parallel dipole moments of the CARS process. The effects of possible changed molecular structure or symmetry and changed enhancement of different electronic transitions cannot be determined without making some assumptions about one of these effects. The obtained phase differences reflect different enhancements and vibronic coupling for ground-state and excited-state vibrations. The ground-state and excited-state hyperpolarizabilities, [Formula: see text], of rhodamine 6G were estimated to be 3.8·10−35 esu and 27.4·10−35 esu, respectively.
Comparison of Fluorescence-to-Phosphorescence Quantum Yield Ratios in Solid-Matrix Luminescence as a Function of Temperature
Authors: Hurtubise R. J. , Ramasamy S. M.
Published: June 2005

An equation that relates the ratio of fluorescence to phosphorescence quantum yields as function of temperature to basic photophysical parameters is considered. The quantum yields were obtained from three compounds on three different solid matrices. Fluorescence quantum yields did not change much with temperature, while phosphorescence quantum yields changed more substantially with temperature. For some of the systems considered, it was possible to show that, as the temperature was lowered, the quantum yield ratio was only a function of the phosphorescence lifetime of the phosphor. However, with other systems, the quantum yield ratio was dependent on both the rate constant of intersystem crossing from the singlet state to the triplet state and the phosphorescence lifetime. The equation discussed is important in defining the fundamental parameters that cause the luminescence quantum yield ratio to change as temperature is lowered.
Application of NMR Spectroscopy to the Study of Piperidine Derivatives. Part III: Molecular Dynamics Study of N-Benzyl-4-[N-Benzyloxyacetyl)-(2-Fluorophenyl)]Amino-3-Methyl Piperidine
Authors: Cholli A. L. , Lau M. L.
Published: June 2005

High-resolution 1H NMR has been used to study the molecular dynamics of the piperidine derivative. Detailed analysis of variable temperature NMR data allowed the identification of the origin of two sets of methyl resonance peaks with unequal intensities in the room-temperature proton NMR spectrum of the compound.
Analysis of Urinary Calculi of Mixed and Unusual Composition: Raman Spectroscopic Investigation
Authors: Kodati Venkata Ramana , Tu Anthony T. , Nath Ravindra , Turumin Jacob L.
Published: June 2005

Raman spectroscopic analysis of kidney stones of mixed composition and of unusual stones is presented. Raman spectroscopy was used to analyze the chemical composition of kidney stones without extraction. A kidney stone sample was irradiated by laser light of 514.5 nm, and the scattered light was analyzed by a Raman spectrometer. The first stone was determined to be a mixture of calcium oxalate dihydrate and hydroxyapatite and the second one to be a mixture of calcium oxalate monohydrate, uric acid, and hydroxyapatite. The third and fourth stones were not mixed-composition stones, but rather stones with unusual composition. One was concluded to be carboxyapatite, and the other was mucoprotein-type stone. The present investigation indicates that Raman spectroscopy is a useful tool for direct analysis of kidney stone without going through the usual procedure of crushing, extracting, and carrying out tedious wet chemical analysis.
Spectroscopic Properties of Polycyclic Aromatic Compounds. Part III: Fluorescence Emission and Quenching Behavior of Periodic Table Group 16 Hetero-Atom Derivatives
Authors: Tucker Sheryl A. , Acree William E. , Zander Maximilian , Demerseman Pierre , Buisson Jean-Pierre
Published: June 2005

Fluorescence emission spectra are reported for benzo[b]naphtho[2,3d]furan, dinaphtho[l,2b:l′,2′d]furan, dinaphtho[2,lb:l′,2′d]furan, dibenzo[2,3:10,11]perylo[l,12bcd]furan, dibenzo[2,3:10,ll]perylo-(l,12bcd]thiophene, naphtho[l,8bc:5,4b′c′]dipyran (also called 1,6-dioxapyrene), and naphtha[l,8bc:4,5b′c′]dipyran (also called 1,8-dioxapyrene) in organic nonelectrolyte solvents of varying polarity. Results of these measurements indicate that dinaphtho[l,2b:l′,2′d]furan exhibits slight signs of probe character as evidenced by changing emission intensity ratios; however, the dynamic range was much too small to classify this molecule as a polycyclic aromatic compound probe. The effect of nitromethane and 1,2,4-trimethoxybenzene as selective quenching agents was also examined. Nitromethane was found to quench fluorescence emission of all the aforementioned compounds except benzo[b]naphtho[2,3d]furan.
Near-IR Identification of Woods for Restoration of Historic Buildings and Furniture
Authors: Nair Prakash , Lodder Robert A.
Published: June 2005

Frank Lloyd Wright is perhaps the most widely known of American architects. Wright's Prairie period, devoted mostly to residential architecture, is characterized in part by the use of indigenous woods that were neither planed nor painted (though they were sometimes stained). Residences are more likely to be altered over time than are other buildings, often without good documentation of the changes that were made. This research seeks to aid restoration efforts by providing a means of identifying the original woods used in construction.
Analysis of Polymer-Dispersed Liquid Crystals by Infrared Spectroscopy
Authors: McFarland Coleen A. , Koenig Jack L. , West John L.
Published: June 2005

FT-IR microspectroscopy is used to compare the polymer and liquid crystal droplet regions within polymer-dispersed liquid crystal (PDLC) films. Thermoplastic polymer matrix PDLCs contain a higher amount of liquid crystal within the polymer regions than do thermoset polymer matrix films. IR functional group images of a droplet show characteristic textures corresponding to the visual images of the same droplet. The textures in the IR images change with IR polarization and with an applied electric field. Analysis by conventional IR spectroscopy shows that the C=N and the pentyl CH2 groups require an equivalent voltage to switch in the IR region. However, the phenyl C=C group does not exhibit changes under the same voltage conditions. Hysteresis also is seen in the infrared region as a function of voltage and temperature.
Simple Refraction Law for Uniaxial Anisotropic Absorbing Media
Authors: Hasegawa Takeshi , Umemura Junzo , Takenaka Tohru
Published: June 2005

In anisotropic media, there exist ordinary and extraordinary rays. Until now, there has been no simple refraction law like Snell's law for the extraordinary ray. In this study, with the Fresnel model, we made a simple refraction law applicable to both ordinary and extraordinary rays, though it is limited for uniaxial media. The obtained formula could explain the differences between the two rays and would be very useful in extending the traditional isotropic electromagnetic theories to the uniaxial anisotropic electromagnetic theories.