bluuebunny/crossref_metadata_2025 huggingface dataset:
Nondestructive Analysis of Biological Materials by FT-IR-ATR. Method I: Direct Evidence for the Existence of Collagen Helix Structure in Lens Capsule
Authors: Ozaki Y. , Kaneuchi F. , Iwamoto T. , Yoshiura M. , Iriyama K.
Published: June 2005

FT-IR spectra were measured in situ for an albino rabbit lens capsule by use of the ATR method, and the spectrum of water was subtracted. The obtained difference spectra resemble the spectrum of purified Type IV collagen in aqueous solution and show intense bands at 1637 and 1553 cm−1 assignable to the amide I and II modes, respectively. These frequencies are very close to those of the amide I and II bands of a 31 helix. This is direct evidence for the existence of the so-called collagen helix (a slightly modified 31 helix) in the lens capsule. FT-IR spectra were also measured by the diffuse reflectance method for the dried capsule stripped from a dried lens. IR frequencies of the amide I and II bands of the capsule collagen shift from 1637 and 1553 cm−1 to 1654 and 1540 cm−1, respectively, upon going from the intact capsule to the dried one, showing that the collagen helix is converted to a random coil structure upon drying.
Ion Enhancement by Dual-Laser Ionization in an Acetylene/Air Flame
Authors: Lin King-Chuen , Duh Yih-Shing
Published: June 2005

A technique of dual-laser ionization (DLI) is employed to detect Na trace released in an acetylene/air flame. In comparison with laser-enhanced ionization (LEI), a measurement of ion enhancement by the DLI method is found to be as large as two orders of magnitude. The ratio of DLI/LEI depends upon various factors, such as the second-step transition probability, the laser intensity, the transition linewidth, and the collisional ionization rate involved in the LEI mechanism. However, the relative ion enhancement with respect to the various second-step excitations is largely dominated by the ratio of the corresponding second-step transition probability. On the basis of this factor, a comparison between observation and estimation is found to be in satisfactory agreement.
Microsecond Time-Resolved Infrared Spectroscopy of a Thin Film of τ-Form Metal-Free Phthalocyanine Fine Particles
Authors: Iwata Koichi , Kato Chihiro , Hamaguchi Hiro-O
Published: June 2005

A microsecond time-resolved infrared spectrometer has been constructed. It is based on a dispersive infrared spectrometer modified for fast gated detection with a boxcar integrator synchronized with the photoexcitation by a high-repetition-rate cw Q-switched Nd: YAG laser. Time-resolved infrared spectra of τ-form metal-free phthalocyanine (τ-H2Pc) fine particles have been obtained with a gate width of 0.5 μs . It is most probable that the triplet exciton of τ-H2Pc and its bimolecular decay process (triplet-triplet annihilation) have been observed.
Fourier-Domain Analysis of Complex Line Shapes
Authors: Bostick J. M. , Carreira L. A.
Published: June 2005

The development of a method of phase correction is discussed. Previous phase-correction methods have often required the input of an operator in order to extract phase information from the target spectrum. The use of this Fourier-domain phase-correction technique is discussed specifically in terms of its application to coherent anti-Stokes Raman spectra. The extraction of phase information and subsequent phase correction are discussed.
Raman Spectroscopic Observation of Laser-Induced Oxidation of Transition-Metal Borides, Carbides, and Nitrides
Authors: Begun G. M. , Bamberger C. E.
Published: June 2005

Laser Raman microprobe examination in air of small-particle-sized (powders and whiskers) TiN, TiB2, TiC, WC, ZrN, and NbN revealed the formation of surface oxides, which were induced by laser heating. The rate of oxide formation varied with the particle size of the samples and the laser power density applied. The oxides produced were characterized by their Raman spectra. Thus, the Raman spectra obtained with a microprobe should always be carefully analyzed to ascertain whether oxidation or decomposition of so-called inert materials, especially in powder form, has occurred.
The Use of Fourier Deconvolution to Correct for Instrument Slit Function Differences in Measured Spectra
Authors: Mann Charles K. , Vickers Thomas J.
Published: June 2005

The need may arise to use spectral data with a sample interval and slit width that differ from those used when the data were recorded. Results are presented of an examination of the quantitative accuracy of conversion of these parameters using Raman spectra. Assuming adequate sampling in the original set, the interval can be changed by forward and inverse Fourier transform with zero-filling. This procedure only permits expansion by powers of two, but by overexpansion of the original data set, points can be selected to achieve or very closely approximate other factors. Expansion by a factor of ten is demonstrated. The effect of varying slit function is compensated for by deconvoluting the data against the slit function originally used and then convoluting with that which corresponds to the desired condition. Conditions for carrying out this conversion with less than 0.1% error are described.
Total Internal Reflection Fluorescence for Adsorbed Probe Molecule Studies of Liquid/Solid Interfacial Environments
Authors: Hartner K. C. , Carr J. W. , Harris J. M.
Published: June 2005

Total internal reflection fluorescence (TIRF) is developed as a surface selective method to allow the environment of a liquid/solid interface to be probed by fluorescent molecules which are adsorbed from solution. The method has been used to detect pyrene sorbed to an octadecylsilane-derivatized fused-silica plate and resolve its spectral emission so that vibronic intensity ratios can be calculated and the surface environment characterized. Adsorption equilibria of the fluorescent probe to the surface and the depth of penetration of the evanescent excitation beam provide the basis for predicting interference from probe molecules in the solution phase. These predictions were validated by replacing the solution overlaying the alkylated silica interface with saturated vapor and comparing the apparent surface environments.
Infrared and Raman Spectra of Phthalimide-15N-H and Phthalimide-15N-D
Authors: Arenas J. F. , Marcos J. I. , Ramírez F. J.
Published: June 2005

A study of the infrared and Raman spectra of previously synthesized phthalimide-15N-H and phthalimide-15N-D has been carried out. With the new data obtained, the vibrational spectra of the phthalimide molecule in a C2 v* symmetry has been reassigned, but taking into account that the molecule in the solid state forms dimers bonded by intermolecular hydrogen bonds; these dimers have a Ci symmetry. On the other hand, a semi-empiric calculation of the force fields of this molecule has been carried out by the MINDO/3-FORCE method, which required a prior optimization of the molecular geometry; the force field was transformed to the space of internal coordinates.
The Use of Reverse Mirage Spectroscopy to Determine the Absorption Coefficient of Liquid Methanol at CO2 Laser Wavelengths
Authors: Bićanić Dane , Krüger Siegfried , Torfs Paul , Bein Bruno , Harren Frans
Published: June 2005

An experimental setup for performance of reverse mirage spectroscopy at CO2 laser wavelengths on liquid samples having high values of absorption coefficients is described. One and the same liquid is used as both the absorbing and deflecting medium. The Rosencwaig-Gersho theory has been applied, and the choice of experimental conditions that would enable determination of absorption coefficient β from the magnitude of photothermal signals measured at two different probe beam distances (probing locations) is discussed. The usefulness of this technique (essentially not inhibited by the requirements imposed on the sample's thickness) is tested on methanol having absorption coefficients β close to 300 cm−1 in the wavelength region covered by CO2 laser emission.
Detailed Investigation of Fluoromethyl 1,1,1,3,3,3-Hexafluoro-2-Propyl Ether (Sevoflurane) and its Degradation Products. Part II: Two-Dimensional Fluorine-19 NMR Characterization of Fluoromethyl 1,1,3,3,3-Pentafluoro-2-Propenyl Ether
Authors: Cholli A. L. , Huang C. , Venturella V. , Pennino D. J. , Vernice G. G.
Published: June 2005

One- and two-dimensional 19F NMR spectroscopy has been used to elucidate the molecular structure of a novel compound: fluoromethyl 1,1,3,3,3-pentafluoro-2-propenyl ether. A detailed investigation has provided a means of understanding the complex nature of the one-dimensional 19F NMR spectrum of this compound. In addition, J values are used to predict the molecular conformation.
Radial Emission Profiles for a Hollow Cathode Glow Discharge in an Axial Magnetic Field
Authors: Simonneau Regis , Sacks Richard
Published: June 2005

Spatially resolved emission measurements are used to characterize the changes in plasma structure resulting from the application of an external magnetic field to an Ar hollow cathode plasma. The field is generated by ring-shaped permanent magnets which are coaxial with the cathode. The magnetic field is normal to the cathode surface and thus forms electron traps which reduce the rate of electron transport normal to the cathode surface. At lower lamp pressure, the magnetic field dramatically changes the spatial distribution of the continuum background and Ar ion radiation. Radiation from neutral-atom cathode material also is affected by the field. The magnetic field has less influence at higher pressure where collisional effects are larger.
Radial Profile of the Spectral Width of the Ar 7d[5/2]3–4p[3/2]2 Line inside the Cathode Fall Region of Ar Hollow Cathode Discharges
Authors: Hirose Chiaki , Masaki Takashi , Wada Akihide , Adachi Yukio
Published: June 2005

The spatial variation of the spectral width of the Ar 7 d[5/2]3–4 p[3/2]2 transition inside the cathode fall region of hollow cathode discharges was examined by laser optogalvanic spectroscopy at various discharge currents and gas pressures. A close yet complicated correlation with the spatial distribution of the electric field was found to be present, and attempts were made to acquire and summarize qualitative understanding of the observation. The spectral width at the cathode surface, Δ ωc (in cm−1), was found to be related to the corresponding Stark shift, Δ νc (in cm−1), by Δ ωc = (0.0021 ± 0.0002)Δ νc in cm−1.
The Infrared Analysis of Polyethylene Terephthalate Fibers and of Their Strength as Related to Sample Preparation and to Particle Size
Authors: Carter R. O. , Carduner K. R. , Peck M. C. Paputa , Motry D. H.
Published: June 2005

An explanation is presented for the broadening of intense spectral features observed in the infrared spectra of polyethylene terephthalate fibers prepared as KBr pellets. Since band broadening occurs in the spectra of stronger, undegraded fiber, it is proposed that, the stronger the fiber, the more the difficulty one has in pulverizing the sample. Larger particles result from undegraded polyester, which lead to broader bands for intense features. The local sample pathlength in the region of the large particles is greater than that for small particles, which can be more homogeneously mixed. Fiber samples can also be presented to an infrared microscope either “as is” or flattened. Striking differences exist between spectra for flattened and round fibers that were otherwise similar.
Hollow Cathode Plasma Emission Determination of F, Cl, and Br in Gas Streams
Authors: Puig Lourdes , Sacks Richard
Published: June 2005

A hollow cathode lamp system for the determination of F, Cl, and Br in flowing gas streams is described. The lamp uses a relatively small cathode cavity diameter. The sample vapor in a He carrier is introduced at one end of the cathode cavity. Radiation is viewed at the other end. Relatively intense emission lines from F, Cl, Cl+, Br, and Br+ are observed when 100 ppm CClF3 and CBrF3 in He are introduced. The effects on the lamp emission characteristics of He pressure in the range of 15 to 40 Torr, with current in the range 10 to 100 mA, and the cathode cavity diameter in the range 0.8 to 3.2 mm are presented. Potential applications for GC detection are considered.
Absorption-Corrected Spectral Studies of the Lucigenin Chemiluminescence Reaction
Authors: Yappert M. Cecilia , Ingle J. D.
Published: June 2005

With a spectrometer based on two multichannel detectors, luminescence and absorption spectra are acquired simultaneously during the reaction between lucigenin and H2O2 in a basic solution. Alterations in the fluorescence and chemiluminescence spectral contours occur during the reaction, due to time-dependent inner filter effects caused by the changing absorption of the emission radiation by reactants, intermediates, or products. The spectrometer uses the measured absorbances and appropriate equations for automatic correction of luminescence spectra for inner filter effects. The corrected spectra demonstrate that the primary fluorescent product of the reaction, N-methyl acridone, is not the primary chemiluminescent emitting species.
Correction of Polychromatic Luminescence Signals for Inner-Filter Effects
Authors: Yappert M. Cecilia , Ingle J. D.
Published: June 2005

Fluorescence (FL) and absorbance (ABS) data are acquired simultaneously with a multiple detector spectrometer. The measured ABS is utilized in mathematical equations for automatic correction of fluorescence signals for attenuation (inner-filter effects) caused by significant absorption of the excitation or emission radiation by the fluorophore or other species. Correction equations are presented which apply to situations in which the excitation or emission beam cannot be considered monochromatic, for collection geometries involving optical fibers, and for chemiluminescence measurements. The correction scheme was tested with quinine sulfate (QS) as the analyte in the absence and presence of other chromophores (gentisic acid and methyl red). Even when conditions are such that the FL signal is attenuated by a factor of 5, the correction scheme is accurate to 2% or better. These corrections extend the linear range of the QS calibration curve by a factor of over 100, and they can improve the accuracy up to a factor of ten in cases for which polychromatic effects are important.
Approaching Single Atom Detection with Atomic Fluorescence in a Glow Discharge Atom Reservoir
Authors: Smith B. W. , Womack J. B. , Omenetto N. , Winefordner J. D.
Published: June 2005

A commercial hollow cathode lamp is used as an atom reservoir for the atomic fluorescence of lead excited by a copper laser pumped dye laser. The glow discharge source is nearly an ideal atom cell for such measurements, having very low background emission and excellent atomization characteristics. A detection limit of 1.8 ag of lead within the laser beam is easily obtained.
Laser Photolytic Fragmentation-Fluorescence Spectrometry of Ammonia and Aliphatic Amines
Authors: Jinkins Jane G. , Wehry E. L.
Published: June 2005

Ammonia and eight aliphatic amines (ranging in alkyl chain length from C1 to C16) are photolyzed at 193 nm, producing fluorescent molecular fragments (NH from ammonia; CN, CH, and NH from the amines). Fluorescence from NH is used to quantify ammonia; CN fluorescence is used to quantify the amines. Limits of detection in the 10–50 pmol regime, precision of ∼6% RSD, and linear dynamic ranges of 1–3 decades in quantity of parent compound are observed. A small but discernible “large molecule effect” exists; as the size of the alkyl chain in RNH2 increases, the limit of detection increases, and the dependence of the fragment fluorescence signal on photolysis laser fluence also increases. Attempts to enhance fragment fluorescence intensities via “probe-laser” excitation of ground-state fragments were unsuccessful; it is inferred that, at the photolysis fluences employed (∼2 × 1018 photons/cm2), few ground-state fragments are formed.
Standard Normal Variate Transformation and De-Trending of Near-Infrared Diffuse Reflectance Spectra
Authors: Barnes R. J. , Dhanoa M. S. , Lister Susan J.
Published: June 2005

Particle size, scatter, and multi-collinearity are long-standing problems encountered in diffuse reflectance spectrometry. Multiplicative combinations of these effects are the major factor inhibiting the interpretation of near-infrared diffuse reflectance spectra. Sample particle size accounts for the majority of the variance, while variance due to chemical composition is small. Procedures are presented whereby physical and chemical variance can be separated. Mathematical transformations—standard normal variate (SNV) and de-trending (DT)—applicable to individual NIR diffuse reflectance spectra are presented. The standard normal variate approach effectively removes the multiplicative interferences of scatter and particle size. De-trending accounts for the variation in baseline shift and curvilinearity, generally found in the reflectance spectra of powdered or densely packed samples, with the use of a second-degree polynomial regression. NIR diffuse reflectance spectra transposed by these methods are free from multi-collinearity and are not confused by the complexity of shape encountered with the use of derivative spectroscopy.
Microwave-Induced Plasma as an Elemental Detector for Packed-Column Supercritical Fluid Chromatography
Authors: Motley Curtis B. , Ashraf-Khorassani Mehdi , Long Gary L.
Published: June 2005

The direct introduction of supercritical fluid chromatography effluent from a packed DeltaBond 300 phenyl column with the MIP as an elemental detector, using a high efficiency TM010 cavity, has been employed for SFC separations. A toroidal plasma is sustained in the cavity by using an ICP type torch and an argon auxiliary flow (2 L/min) over all pressures (1500–5000 psi). Methanol modifier concentrations (0–5%) have also been studied. Studies of the effects of CO2 on excitation temperature, electron number density, and analyte emission signals are presented. In addition, the background broad-band emission signal with 100% CO2 and a methanol modifier up to 5% are presented.
The Resolution of Laser-Induced Europium(III) Ion Excitation Spectra through the Use of the Marquardt Nonlinear Regression Method
Authors: McNemar Charles W. , Horrocks William Dew.
Published: June 2005

The ability to resolve a 7 F0 → 5 D0 spectrum into individual peaks is important in the study of Eu(III) complexes where the wavelength of the transition is sensitive to the environment of the ion. This paper describes a computer program, based upon the Marquardt nonlinear regression algorithm, developed to resolve such spectra. Several different line shapes were examined, with the Lorentzian function providing the most accurate description for solid complexes and the Lorentzian-Gaussian product function being the most acceptable for species in solution. The program can resolve a spectrum into as many as five peaks with the option to hold any of the parameters constant. The best fit is determined by evaluation of the sum of the squares of the differences between the calculated and the experimental values.
Identification of Quinacridone Pigment Mixtures Using Resonance Raman Microspectrometry
Authors: Binant C. , Lautie A.
Published: June 2005

Vibrational bands of each quinadridone pigment have been attributed in two mixtures: PO48 and PR206. The amounts of the PV19 and quinacridone quinone components have been estimated by preresonance Raman microspectrometry.
Direct Use of Second Derivatives in Curve-Fitting Procedures
Authors: Holler Farida , Burns David H. , Callis James B.
Published: June 2005

Most curve-fitting procedures deal with an unknown, variable baseline by modeling it with a function involving a number of parameters. In view of the facts that (1) there is often no analytically relevant information in the baseline, and (2) there is usually no functional form known, a priori, for the baseline, we have chosen to eliminate it by means of the second-derivative transformation. The resulting profile is deconvoluted by fitting it with the second derivative of the sum of an appropriate number of component curves. The utility of this procedure is demonstrated on simulated data with typical baselines and noise levels, and on real FT-IR data. Peak parameters (such as position, width, and area) obtained from this technique are comparable to those obtained by fitting the original spectrum with Lorentzian curves and a simple baseline. The major advantage of this procedure is the reduction in the number of parameters that must be optimized in the fitting method. Applications of the technique could eliminate contributions from other complex baseline profiles in the quantitative analysis of spectral components.
Near- and Mid-Infrared Transmission Cells for the Study of Reverse Micelle Phases in Supercritical Fluids
Authors: Blitz J. P. , Fulton J. L. , Smith R. D.
Published: June 2005

The design and construction of near- and mid-infrared transmission cells for the study of liquid, gaseous, and fluid systems at elevated pressures and temperatures are described. The cells can be used to pressures as high as 800 bar and temperatures exceeding 100°C. Typical spectra of reverse micelle phases in liquid propane and supercritical xenon through the near- and mid-infrared range are presented. The utility of applying FT-IR spectroscopy, and the transmission cells described here, to study reverse micelle and microemulsion phases in supercritical fluids is clearly demonstrated.
A Pulsed Photoacoustic Microcalorimeter for the Detection of Upper Excited-State Processes and Intersystem Crossing Yields
Authors: Lynch Daniel , Endicott John F.
Published: June 2005

A photoacoustic detection system is described that has excellent linearity and limits of detection, and which is simple to implement. This system has been applied to the determination of intersystem crossing yields, φisc, of a series of Cr(NN)33+ complexes. The results are in excellent agreement with the literature values for two of these complexes. Results for two other complexes determined that there are long-lived (τ < 15 ns) upper excited states or other high-energy species produced that prevent rapid relaxation to the lowest energy excited state of these complexes. Without the need to resort to deconvolution techniques, this method can be used on systems that have rapid relaxation (τ < 1 ns) of the upper excited states and lifetimes <5 μs for the lowest energy excited state, with the application of a 5 MHz piezoelectric transducer.
Modification of IBM-PC Data Acquisition and Control Adaptor for Versatile Data Acquisition and Control System
Authors: Kim Haidong , Zabik Matthew J. , Crouch Stanley R.
Published: June 2005

An inexpensive but versatile data acquisition system has been developed with the use of a modified IBM-DACA (IBM Personal Computer Data Acquisition and Control Adaptor). With the modification described, the IBM-DACA can be operated in more various modes of operation. Data can be read either by software trigger or by hardware trigger mode. Also, all the three channels of the on-board timer/counter can be fully utilized for complex or accurate timing and experiment control. This allows gated data acquisition with user-specified timing and a maximum A/D throughput to memory of up to 18520 samples/s in a single channel. With its menu-driven software, this system can be used in various scientific data acquisition environments with minimal expense.
Colorimetric Detection of Alkali Metals by Ion-Pair Extraction
Authors: Roe J. N. , Szoka F. C. , Verkman A. S.
Published: June 2005

An optical absorbance method was developed to measure the concentration of alkali metal ions in aqueous solution at neutral pH. The method was based on the formation of a ternary complex between an ionophore/metal ion complex and the anionic form of 7-( n-decyl)-2-methyl-4-(3′,5′-dichlorophen-4′-one)-indonapthl-1-ol (MEDPIN). Detection of the ternary complex was made in the organic phase after ion-pair extraction. Concentrations of sodium and potassium in the aqueous phase were detectable with high sensitivity and selectivity. The absorbance spectrum of MEDPIN in octanol was strongly dependent upon the potassium concentration in the aqueous phase when the octanol contained the potassium ionophore valinomycin; the absorbance at 610 nm increased by 159% upon addition of 4 mM potassium with an isosbestic point at 501 nm. Potassium was detected with a sensitivity of 0.1 mM and a standard error of 3.4% at concentrations below 25 mM. In chloroform, 80 mM sodium in the aqueous phase caused the absorbance of MEDPIN at 620 nm to increase by 830% in the presence of the sodium ionophore hemisodium. From studies of the spectroscopic properties of MEDPIN in various solvents, at varying concentrations of MEDPIN, and at different pH values in the aqueous solvent, it was concluded that the mechanism of MEDPIN sensitivity to a cation/ionophore complex involves an ionexchange transfer reaction in the organic phase, resulting in deprotonation of MEDPIN.
Thermal Lens Measurements in Liquids on a Submicrosecond Time Scale
Authors: Isak Stefan J. , Komorowski Stanislaw J. , Merrow Clifton N. , Poston P. E. , Eyring Edward M.
Published: June 2005

The use of the thermal lens method is shown to be quite suitable for kinetic studies of quenching on a submicrosecond time scale. The lower limit of time resolution that can be achieved is determined by the acoustic transit time, τa in the medium. A thermal lens signal with a 100-ns time constant due to the quenched triplet state of benzophenone is readily measured. The thermal lens method is superior to the photoacoustic (PA) method in the breadth of the accessible time range, and in the significantly fewer measurements required to obtain accurate data, including no requirement for a reference sample; it is also less sensitive to geometrical and laser power requirements than is the PA method.
Infrared Spectra of Organic Monolayers on Mica
Authors: Carson George , Granick Steve
Published: June 2005

A method is described for obtaining infrared spectra of an organic monolayer film on muscovite mica. This task is normally difficult because mica is not metallic, and it has biaxial optical properties and produces large interference fringes when analyzed in transmission or reflection because of reflections off the front and back of a sheet. The method involves the transmission of parallel-polarized light, incident at the Brewster's angle, through a mica sheet that is oriented along one of its principal optical directions.
A New Desolvation System for Use with Capacitatively Coupled Microwave Plasma and Inductively Coupled Plasma-Atomic Emission Spectrometry
Authors: Uchida H. , Masamba W. R. , Uchida T. , Smith B. W. , Winefordner J. D.
Published: June 2005

A compact and highly efficient desolvation system with a pneumatic nebulizer was applied to capacitatively coupled microwave plasma and inductively coupled plasma-atomic emission spectrometry. Approximately 50% of the analyte (Mn) was introduced to the plasma, and 50 (CMP) and 16 (ICP) times improvement of the sensitivity could be achieved. In spite of slightly poorer stability caused by larger aerosol size, detection limits were 17 (CMP) and 10 (ICP) times superior to results achieved with conventional pneumatic nebulization.
A Mixed Linear/Nonlinear Least-Squares Method for Determining Line Parameters from Noisy Spectra
Authors: Premoli Amedeo , Rastello Maria Luisa
Published: June 2005

The determination of the parameters characterizing line profiles embedded in a noisy spectrum is an important task in IR and Raman spectroscopy. A direct analysis from an inspection of the spectrum is often difficult in the presence of overlapped profiles and/or considerable background. This paper presents an algorithm based on alternate stages of linear and nonlinear optimization for extracting Lorentzians or Gaussians from the measured data, taking into account the presence of a frequency-dependent background superimposed onto white noise. The analysis of several experimental spectra shows the capability of the algorithm in discriminating noisy and partially overlapped profiles.
On the Spectral Subtraction of Water from the FT-IR Spectra of Aqueous Solutions of Proteins
Authors: Dousseau Françoise , Therrien Marie , Pézolet Michel
Published: June 2005

A method is described for the quantitative subtraction of water from the transmission infrared spectra of aqueous solutions of proteins. The 2125-cm−1 association band of water is used as an internal intensity standard, and the scaling factor is determined with the use of a second-order least-squares fit. This method eliminates the user bias encountered with interactive methods and takes into account small baseline variations due to instrument drift. Statistical analysis of the results obtained demonstrates that at 10% w/w protein concentration, the error is of the order of 2% in the region of the amide I and II bands.
A Multichannel Data Acquisition and Processing System for Laser Spectroscopic Experiments
Authors: Rutherford Michael L. , Clouthier Dennis J. , Holler F. James
Published: June 2005

A microcomputer-controlled data acquisition and processing system, developed to carry out a variety of pulsed-laser spectroscopic experiments, is described. The hardware consists of largely off-the-shelf spectroscopic instrumentation in conjunction with an IBM personal computer. Versatile software with interactive graphics has been written with the use of Turbo BASIC. The software and hardware components are discussed in detail. As an example of the system performance, the LIF spectrum of S2O has been acquired with the use of an Nd:YAG pumped dye laser as the excitation source. Examples of interactive screen displays and a publication-quality spectrum are presented.
Enhanced Infrared ATR Spectra of O-, m-, and p-Nitrobenzoic Acid with Ag Films
Authors: Badilescu Simona , Ashrit P. V. , Truong Vo-Van , Badilescu I. I.
Published: June 2005

The dependence of enhancement of the infrared bands by thin Ag films on the molecular structure of the organic compound was investigated. A different enhancement behavior for the three isomers—ortho-, meta-, and paranitrobenzoic acids—was observed and accounted for by structural features. The presence of the ionized species of the acids in the monolayer bonded to Ag was found, and the spectral features of the monolayer and bulk compound were compared. The splitting of the antisymmetric stretching band of the nitro group for metanitro benzoic acid strongly interacting with Ag was observed. The correlation of the morphology of the Ag surface to the magnitude of the achieved enhancement is discussed.
Real-Time Electron Diffraction. Part III: Image Transfer via Fiber Optics
Authors: Ewbank John D. , Paul David W. , Schäfer Lothar , Bakhtiar Reza
Published: June 2005

Improvements are described in photodiode-array real-time data recording for gas electron diffraction (GED). When the conventional glass window and lens optics in a previously reported detector configuration are replaced by fiber optic components, two significant effects arise: (1) detector gain is enhanced to the extent that it is now possible to detect nanoliter samples in combined GED-GC (gas chromatography) experiments, and (2) for the first time since the development of the real-time recording scheme, molecular mean amplitudes of vibration are within error limits of literature values. Thus the method now affords full molecular structure determinations, including bond distances and angles, and their associated mean vibrational properties.
A Comprehensive Table of Atomic Fluorescence Detection Limits and Experimental Conditions
Authors: Smith Benjamin W. , Glick Mark R. , Spears Ken N. , Winefordner James D.
Published: June 2005

A comprehensive table of atomic fluorescence spectrometry results has been compiled and arranged by element. Data tabulated include excitation and fluorescence wavelengths, atom reservoir, excitation source, limits of detection, and comments concerning experimental peculiarities and types of samples analyzed.
Nitrogen Determination in Argon by Surface-Wave-Induced Plasma Atomic Emission Spectrometry
Authors: Boudreau Denis , Laverdure Chantal , Hubert Joseph
Published: June 2005

An on-line analyzer for traces of nitrogen in argon was developed with the use of microwave-induced plasma/atomic emission spectrometry (MIP-AES). The plasma is generated with a surface wave launcher called “Surfatron.” The emission spectra of the major impurities of argon were characterized in the spectral region from 600 to 900 nm. Effects on analyte emission of parameters such as observation height in the plasma, gas flow and pressure, applied power, and discharge tube geometry were studied. A charge-coupled device (CCD) was used as the multichannel detector for this analyzer. The automation of the CCD by a microcomputer allowed fast, unaided data acquisition and analysis, and the overall system had the compactness, ruggedness, and stability essential for on-line use. We measured a 0.4-ppm detection limit for nitrogen, and the system's long-term stability is greater than 99%. Also, comparative work with a commercial photodiode array (PDA) system was conducted, and a 0.05-ppm detection limit for nitrogen was obtained.
Applications of Fourier Transform Raman Spectroscopy in an Industrial Laboratory
Authors: Bergin F. J. , Shurvell H. F.
Published: June 2005

In the past, the usefulness of laser Raman spectroscopy as an analytical technique in industrial laboratories has been greatly reduced by problems of laser-induced fluorescence. One method of circumventing this problem is to use near-infrared excitation coupled with a modified FT-IR spectrometer. In this paper, we report the results of some initial exploratory experiments which indicate that significant fluorescence rejection can be achieved. This fluorescence rejection opens up new areas of application for Raman spectroscopy. The advantages and limitations of FT-Raman spectroscopy are discussed. In addition, some initial experiments are outlined on Fourier transform Raman microscopy using a conventional microscope.
Near-Infrared Surface-Enhanced Raman Spectroscopy. Part II: Copper and Gold Colloids
Authors: Angel S. M. , Katz L. F. , Archibald D. D. , Honigs D. E.
Published: June 2005

Near-infrared (NIR) surface-enhanced Raman spectra (SERS) on copper and gold metal colloids were obtained with a Fourier transform Raman spectrometer using a Nd:YAG laser (1.064 μm) for excitation. Enhanced spectra were observed for pyridine and 3-chloropyridine (CP) on copper colloids and for tris(orthophenanthroline)ruthenium(II), Ru(o-phen)32+, on copper and gold colloids. The copper-colloid surface-enhanced Raman spectra of pyridine and CP were compared with spectra measured for these molecules on copper electrodes. NIR-SERS enhancements on the metal colloids were at least as large as for visible-wavelength excited SERS. Good-quality spectra of Ru(o-phen)32+ were obtained at solution concentrations as low as 0.025 mM.
The Variable-Temperature FT-IR Study of the Secondary Structure of γ-Globulin, Chymotrypsin, Serum Albumin, and β-Lactoglobulin in Aqueous Solution
Authors: Kirsch Joseph L. , Koenig Jack L.
Published: June 2005

The FT-IR spectra of γ-globulin, chymotrypsin, serum albumin, and β-lactoglobulin were collected in aqueous buffer solutions at different temperatures. A least-squares subtraction algorithm was used to subtract the interfering water bands in the amide I, II, and III frequency regions. The spectra of the protein amide I and II bands were deconvoluted with the use of Fourier self-deconvolution and a Lorentzian curve fit process, and band assignments were made for the α helix, β pleated sheet, and disordered or turns structures of the proteins. Factor analysis was applied to the variable-temperature protein spectra, and the compositions with respect to the different types of secondary structures were calculated.
Characterization of a High-Efficiency Helium Microwave-Induced Plasma as an Atomization Source for Atomic Spectrometric Analysis
Authors: Perkins Larry D. , Long Gary L.
Published: June 2005

Characterization studies of a He high-efficiency microwave-induced plasma, He-HEMIP, utilizing direct sample introduction with pneumatic nebulization for atomic emission and atomic fluorescence spectrometry are presented. These studies include diagnostic measurements and analytical characterization of the 150-W He-HEMIP. Diagnostic measurements include excitation temperatures with the use of aqueous and organic nebulized thermometric species, electron number densities, and ionization temperatures for the plasma. The effect of sample uptake rate on the emission intensity is investigated. Ionization interferences are minimal, and phosphate interferences were found not to occur. In addition, the He-HEMIP is characterized as an atom source for metals and nonmetals with the use of atomic emission spectrometry and atomic fluorescence spectrometry. With AES, detection limits for metals and nonmetals are in the sub-ppm range. With AFS, detection limits for metals were determined to be in the low to sub-ppb range and were found to be not statistically different from those reported for HCL-ICP-AFS. Linear ranges for AES and AFS ranged from four up to five and one-half orders of concentrative magnitude.
Quantitative Characterization of Raman Spectra of Vanadium Oxides Layered on SiO2
Authors: Miyata H. , Tokuda S. , Yoshida T.
Published: June 2005

The Raman spectra of vanadium oxides layered on Aerosil have been quantitatively investigated. First, the number of peaks and three parameters of each peak were estimated in a self-generating initial parameter estimation using the B-spline functions. These parameters were refined by a nonlinear optimization technique using the Simplex method. For a series of V2O5/SiO2, three types of vanadium oxide—such as a small cluster vanadate, surface polyvanadate, and crystalline vanadium oxide—were identified and quantitated by Raman spectroscopy. The small cluster surface species is shown to increase with vanadium loadings up to 6.6 wt % V2O5 and to convert into surface polyvanadate species at higher vanadium loadings or heat treatment.
Near-Infrared Raman Spectroscopy with a 783-nm Diode Laser and CCD Array Detector
Authors: Williamson James M. , Bowling Robert J. , McCreery Richard L.
Published: June 2005

A GaAlAs diode laser operating at 783 nm was combined with an unintensified charge coupled device (CCD) array detector and single grating spectrograph to obtain near-infrared (NIR) Raman spectra. The spectrometer has no moving parts and retains the high sensitivity expected for multichannel, shot-noise-limited detectors. Diode laser excitation permits high-sensitivity Raman spectroscopy with reduced fluorescence interference, in comparison to that produced with conventional visible lasers. The diode laser/CCD approach should exhibit much higher sensitivity than FT-Raman systems operating at 1064 nm, at much lower laser power. The sensitivity of the system was demonstrated by an S/N ratio of 17 for the 981-cm−1 band of 0.01 M (NH4)2SO4, obtained with 30 mW of 783 nm laser power.
Beating the Multiplex Disadvantage in Shot-Noise-Limited Interferometry with Self-Adaptive Filtering
Authors: Williams Ron
Published: June 2005

A new data acquisition scheme is presented which produces interferograms with constant standard deviations from shot-noise-limited signals. This is accomplished by tuning the frequency response of the data acquisition system in real time in response to the noise in the interferogram. A constant amount of shot noise is recorded with each datum, regardless of signal intensity, so that the multiplex disadvantage is nullified for these data.
A Hadamard Transform Raman Microprobe
Authors: Treado Patrick J. , Morris Michael D.
Published: June 2005

The design of a Hadamard transform Raman microprobe is presented. The spatially multiplexed imaging system provides true spectroscopic microscopy. Near-diffraction limited resolution, 1.3 µm, is demonstrated with Raman images of polycrystalline materials.
Time-Resolved Spectroscopy Using Step-Scan Fourier Transform Interferometry
Authors: Palmer Richard A. , Manning Christopher J. , Rzepiela Jeffrey A. , Widder Jeffrey M. , Chao James L.
Published: June 2005

The capabilities of a step-scan Fourier transform spectrometer of obtaining time-resolved spectra are reported. As a demonstration of the method, time-resolved spectra from a pulsed fluorescent lamp are presented. The potential of step-scan interferometry for time-resolved infrared measurements of a variety of transient phenomena is discussed.
Atomic Emission Characteristics of Laser-Induced Plasmas in an Argon Atmosphere at Reduced Pressure
Authors: Iida Yasuo
Published: June 2005

The emission characteristics of laser-induced plasma, with the use of a Q-switched ruby laser of 1.5 J, were studied in argon atmosphere at reduced pressure. The time- and spatially resolved emission profiles were measured. In argon atmosphere at reduced pressure, the emission period of plasma is elongated to over a hundred microseconds, and the emissive region expands to more than a few tens of millimeters above the sample surface. The emission intensities of atomic lines increase severalfold in an argon atmosphere, in comparison with those obtained in air at the same pressure. Moderate confinement of plasmas and a resultant increase of emission intensities are achieved at 50 Torr. These results are explained by the chemical inertness and the thermal characteristics of the argon atmosphere and the decrease in absorption of the laser pulse by the plasma plume. The re-excitation of emissive species by collisions with metastable argon atoms seems to be less important.
Attomole Amino Acid Analysis: Capillary-Zone Electrophoresis with Laser-Based Thermo-Optical Detection
Authors: Yu Margaret , Dovichi Norman J.
Published: June 2005

To analyze minute samples of complex biological mixtures, it is necessary to utilize an analytical technique which combines high selectivity and sensitivity. In the analysis of attomole quantities of amino acids, we combine capillary-zone electrophoresis for high-resolution separation with laser-induced thermo-optical measurements for high-sensitivity detection. Capillary-zone electrophoresis provides theoretical plate counts greater than 200,000 within a 40-minute separation. However, to achieve this separation efficiency, it is necessary to utilize a detector with subnanoliter volume. Crossed-beam thermo-optical detection directly on the 50-µm-diameter capillary tube results in high-sensitivity detection with minimal detector volume. Detection limits of 40 attomoles of methionine, injected onto the column, are obtained with a 130-mW argon-ion pump laser.
Direct Laser Ionization in Analytically Useful Flames
Authors: Seltzer M. D. , Green R. B.
Published: June 2005

Direct laser ionization (DLI) proceeds by resonant excitation of analyte followed by photoionization of the excited-state atoms. Photoionization is accomplished with the use of off-resonant radiation, which is usually obtained from the dye laser pumping source. DLI has been shown to enhance ionization yields, relative to laser-enhanced ionization (LEI), in low-temperature atom reservoirs where collisional ionization is inefficient. In the present study, DLI has been demonstrated in high-temperature, analytically useful flames, with similar results. DLI detection limits and spectral interferences, as well as the effects of photoionizing laser power on ionization yield, have been evaluated.
Capacitive Discharge Circuit for Controlled Heating of Anisotropic Graphite Tubes: Part I
Authors: McCaffrey John T. , Michel Robert G.
Published: June 2005

Circuitry suitable for capacitive discharge heating of anisotropic graphite tubes for atomic absorption and atomic fluorescence is detailed and initial calibration data are presented.
Tunable Diode Laser Quantification of Isomeric Partially Deuterated Cyclobutanes and Ethenes
Authors: Glenar David A. , Lewis David K.
Published: June 2005

A specially designed tunable diode laser (TDL) absorption spectrometer which operates near 900 and 1300 cm−1 has been constructed in order to identify and measure very low concentrations of product gases extracted from a single-pulse shock-tube experiment. The ultra-high-frequency resolution of the TDL spectrometer (5 to 10 MHz) shows the rotational fine structure in an absorption spectrum, clearly distinguishing between isomers of the same compound. The spectrometer features dual-beam detection in order to simultaneously acquire source and reference gas spectra for unambiguous labeling of the product gases, and rapid sweep averaging, which minimizes the effects of low-frequency mechanical vibrations and achieves very high signal-to-noise ratio. Cis and trans isomers of 1,2-d2-cyclobutane were detected and measured in quantities of shock-tube products as small as 75 cm3-Torr. Several conformations of deuterated ethenes were also detected in samples smaller than 1 cm3-Torr.
Surface-Enhanced Raman Spectroscopy of CrO3/H2SO4-Etched Polyethylene Films
Authors: Siperko Lorraine M.
Published: June 2005

The effects of chromic/sulfuric acid etchant on thin polyethylene films are being studied by Raman spectroscopy. The functional groups on the surface of the etched films were found to differ from those present in the bulk. Cr-O bands appeared in both the bulk and SERS spectra, and sulfate species were detected on the surface only. The ability to differentiate between the surface and bulk polymer chemistry of CrO3/H2SO4-etched polyethylene using surface-enhanced Raman spectroscopy is demonstrated.
Photothermal Beam Deflection and Photoaction Spectroscopic Study of CdS Photoelectrodes in Polysulfide Electrolyte
Authors: Wagner Robert E. , Mandelis Andreas
Published: June 2005

A number of experimental photothermal deflection, ac photovoltage, and ac photocurrent spectra for CdS photoelectrochemical cells are presented. The spectra were obtained under various conditions, with the use of modulated light: open circuit and short circuit, and with a dc bias applied across the working and counter electrodes. The measurement of both the photothermal deflection and the photoaction signals allows one to monitor two energy conversion channels, namely optical-to-thermal, and optical-to-electrical. The photothermal deflection technique was found to provide useful information regarding the surface condition of the electrodes, with respect to polishing or corrosion damage. Finally, the effect of a current-induced species gradient at the working electrode/electrolyte interface upon the photothermal deflection signal is also examined.
Depth Profiling and Signal Saturation in Photoacoustic FT-IR Spectra Measured with a Step-Scan Interferometer
Authors: Michaelian K. H.
Published: June 2005

A commercial step-scan FT-IR spectrometer has been used to obtain photoacoustic spectra of carbon black, coals, polymers, and clays. Variation of the external modulation frequency from 40 to 400 Hz shows that saturation affects many of the spectra. Nevertheless, comparison of spectra of oxidized coal with spectra of fresh coal obtained at the corresponding modulation frequencies yields results implying successful depth profiling. Several suggestions for further experiments are also presented.
Spectroscopy of Matrices and Thin Films with an Integrating Sphere
Authors: Berger E. , Griffith D. W. T. , Schuster G. , Wilson S. R.
Published: June 2005

The paper describes a novel experimental approach to improving sensitivity to weak absorption in matrix isolation and thin film spectroscopy. The matrix or film is grown on the surface of an integrating sphere, in which the multiply reflected light correspondingly multipasses the sample film. The quantitative photometric behavior of the sphere is satisfactorily described by extending standard theory. Enhancement of absorption by a factor of at least 20 is possible and is demonstrated. The sphere has a number of useful advantages over other multipass techniques, particularly in matrix isolation spectroscopy.