bluuebunny/crossref_metadata_2025 huggingface dataset:
Photothermal Deflection Densitometer with Pulsed-UV Laser Excitation
Authors: Fotiou Fotios K. , Morris Michael D.
Published: July 2005

First application of pulsed photothermal deflection spectroscopy to solid samples is demonstrated. A new densitometer for thin layer chromatography based on this method is described. The technique is suitable for direct measurements in the ultraviolet region. A pulsed excimer laser is used to produce a transient thermal refractive index gradient. The laser delivers pulses of 1–2 mJ at 10–22 pulses/s, at 351 nm. With this system the detection limit for 2,4-dinitroaniline is 750 pg. The signal is linear with amount of analyte for about three orders of magnitude.
Real-Time Acquisition and Preprocessing of Kinetic and Spectroscopic Data in Laser Flash Photolysis
Authors: Longoni A. , Ponterini G.
Published: July 2005

An automatic flash photolysis system for the measurement of absorption decays and transient difference spectra is described. The apparatus performs a digital measurement of the light transmitted by the sample and a few on-line preprocessing operations on the measured data, such as the digital averaging of the signal and the computation of the change in absorbance. A boxcar averager, used as a gated integrator, constitutes the sampling head of the apparatus. A microprocessor-based acquisition and control unit performs a digital conversion of the value sampled by the boxcar, provides an on-line preprocessing of the data, and supervises every operation required by the measurement process. This unit is interfaced to a personal computer which allows a friendly interaction with the operator as well as the on-line display of the data. The electronic instrumentation features a time resolution of a few nanoseconds, with a boxcar averager as input head, and of a few hundreds of picoseconds, with a sampling oscilloscope as input head.
A Novel Light-Scattering Technique to Study Gas-Flow Dynamics in an ICP Torch
Authors: Childers Alfred G. , Hieftje Gary M.
Published: July 2005

A new technique for studying gas-flow dynamics in unlit ICP torches is presented. This technique allows direct visualization of the gas-flow pattern of any one of the three argon flows employed by an ICP torch. The gas-flow patterns are observed by introducing a light-scattering medium into one of the argon flows and passing a thin plane of light through the gas above the torch. Because a thin plane of light is employed for visualization, direct radial and vertical gas-flow patterns can be observed in a direction perpendicular to the plane. Flow patterns for the coolant, plasma, and central gases were studied, as was the effect of argon flow rates in conventional and low-argon-consumption torches.
Hyperfine Relaxation of an Optically Pumped Cesium Vapor
Authors: Tornos J. , Amare J. C.
Published: July 2005

The relaxation of hyperfine orientation indirectly induced by optical pumping with σ-polarized D1-light in a cesium vapor in the presence of Ar is experimentally studied. The detection technique ensures the absence of quadrupole relaxation contributions in the relaxation signals. The results from the dependences of the hyperfine relaxation rate on the temperature and argon pressure are: diffusion coefficient of C s in Ar, D0 = 0.101 ± 0.010 cm2 s−1 at 0°C and 760 Torr; relaxation cross section by Cs-Ar collisions, σc = (104 ± 5) × 10−23 cm2; relaxation cross section by Cs-Cs (spin exchange) collisions, σex = (1.63 ± 0.13) × 10−14 cm2.
The Chemical Interaction of Organic Materials with Metal Substrates. Part II: FT-IR Studies of Organic Phosphate Films on Steel
Authors: Carter R. O. , Gierczak C. A. , Dickie R. A.
Published: July 2005

Reflection-absorption spectroscopy at grazing incidence has been shown to be a useful tool for investigation of thin organic films on gold and steel substrates. No artifacts related to the technique were identified for films thinner than 250 Å. The spectra obtained for films of an organic phosphate on polished steel substrates are consistent with reaction of the organic phosphate with the steel to produce a metal salt. The organic phosphate studied in this work was the reaction product of the diglycidyl ether of bisphenol-A (DGEBA), and comprised the mono- and diphosphoric acid adducts of DGEBA. The spectrum of the organic phosphate films formed on steel was indicative of a specific complex rather than the random product formed by bulk precipitation: the P-O stretching vibrations occurred as a pair of bands, while the spectrum of the salt formed from solution contained but a single band. No chemical interaction of the organic phosphate with the gold substrate was observed. The spectra have relative intensity changes with thickness which indicate the presence of ordering for the thinnest films studied.
Continuous, On-Line Interface for Reverse-Phase Microbore High-Performance Liquid Chromatography/Diffuse Reflectance Infrared Fourier Transform Analysis
Authors: Castles M. A. , Azarraga L. V. , Carreira L. A.
Published: July 2005

An ultrasonic nebulizer with a piezo-electric transducer and a newly designed and constructed continuous on-line collection station have been adapted as an interface between a reverse-phase microbore high-performance liquid Chromatograph (RP-μHPLC) and a diffuse reflectance infrared Fourier transform spectrometer. The collection station incorporates a directional vacuum port for confinement of the nebulized material onto a small area (3 to S mm i.d.) of the diamond powder. The inherent desolvation that occurs upon nebulization of the reverse-phase eluant, along with the vacuum collection system and the diamond powder diffuse reflectance substrate, makes possible the continuous on-line collection and FT-IR analysis of the compounds separated by a RP-μHPLC without any type of initial solute extraction.
A Modified Sum Cauchy-Gauss Function to Fit Nonsymmetrical Bands to Infrared Internal-Reflectance Spectra
Authors: Janik L. J.
Published: July 2005

This paper describes an empirical model in which a derivative term is added to the usual sum Cauchy-Gauss function. The modified function introduces asymmetry into the band profile enabling it to fit bands to distorted infrared spectra, such as infrared attenuated total reflectance (ATR) spectra. The model uses 3 M + 5 parameters (for M bands). Parameters for each band are height, position, and half-width, with additional parameters for the Cauchy proportion, derivative scaling, half-width scaling, and baseline. The model has been applied to the splitting of the ATR spectra of liquid benzene and appears to give a good fit to the experimental data.
Thermal Lens Absorption Measurements in Binary Liquid Mixtures near the Consolute Critical Point
Authors: Hardcastle F. D. , Harris J. M.
Published: July 2005

Binary liquid mixtures near their consolute critical points are shown to possess desirable thermophysical properties for thermal lens absorption measurements. By use of a 2,6-dimethylpyridine/water mixture near critical composition and temperature, sensitivity was found to be enhanced relative to pure liquids by the Soret effect in which a concentration gradient is created between the two solvent components by thermally induced mass diffusion within the laser-excited temperature gradient. A 35-fold increase in sensitivity relative to a thermal expansion lens effect in pure water was obtained. A mechanism of phase separation unique to the critical point region known as spinodol decomposition was observed, as the sample temperature was driven above the critical point by laser excitation. This phenomenon was also found to be a potentially useful spectrophotometric technique for the thermooptical detection of small absorbances.
Fundamental Chemical Processes in a Low-Density 27-MHz Helium ICP
Authors: Miller D. C. , Fannin H. B. , Fleitz P. A. , Seliskar C. J.
Published: July 2005

A variable-pressure 27-MHz helium plasma was investigated in order to study the physical chemical nature of the inductive coupling and the microscopic atomic and molecular state variations which attend regular manipulations of plasma power and of helium pressure. Two modes of helium plasma excitation, the E- and H-plasma modes, are identified by widely differing capacities to effect ionization of other plasma species such as argon atoms. The switch from the helium E- to the H-plasma is abrupt and dependent on the gas pressure. The results presented suggest that it is the production of He+ and electrons and subsequent interactions in the plasma (electron recombination, collisions, etc.) which primarily determine the microscopic atomic and molecular behavior which we observe.
Determination of Subnanosecond Fluorescence Lifetimes with a UHF Television Tuner and a cw or Mode-Locked Laser
Authors: Bright Frank V. , Wilson Daniel A. , Hieftje Gary M.
Published: July 2005

An inexpensive ultra-high-frequency (UHF) television tuner and an argon-ion laser are employed for the determination of excited-state lifetimes of a series of common fluorophores. Fluorescence lifetimes are determined in the frequency domain; the results are in good agreement with previously reported values and demonstrate the utility of the new approach for subnanosecond measurements. Binary mixtures of rhodamine 6G and rose bengal can also be resolved with the use of this novel instrument design.
Laser-Excited Fluorescence of Diatomic Molecules of Copper and Lead in Glow Discharge Sputtering
Authors: Patel B. M. , Winefordner J. D.
Published: July 2005

Cathodic sputtering within a low-pressure inert gas discharge provides a simple and convenient means for atomic spectroscopic studies of the atomic vapor produced from cathode material. However, the vapor consists of not only the atomic species but also the molecular species. These species were investigated by probing the vapors sputtered from the copper-lead cathode in the glow discharge source using a nitrogen laser pumped dye laser to excite the fluorescence. The laser-induced fluorescence spectral characteristics were used to identify the molecular species in the vapors. The identification and assignment of the spectral band systems revealed the presence of Cu2, CuO, and Pb2 species in the sputtered vapors. It is important to be aware of the reduced number density of atoms due to clustering and the possibility of spectral interferences from molecular species while using the glow discharge sputtering sources in atomic spectroscopic applications.
Spectral Line-Diode Registry Effects with Photodiode Array Detectors
Authors: Winge R. K. , Fassel V. A. , Eckels D. E.
Published: July 2005

A limitation of photodiode array detectors for spectroscopic intensity measurements relates to the spacing of the diodes and the errors generated when a spectral line is not in exact registry with the diode or diodes from which its intensity is being measured. These misregistry intensity errors, which may be as high as 25 to 30%, are documented for a range of spectral bandwidths and for single diode (pixel) intensities and multiple diode summations of intensities.
Spectroscopic Temperatures of a Moderate-Power Argon Microwave-Induced Plasma
Authors: Brown P. G. , Workman J. M. , Haas D. L. , Fleitz P. A. , Miller D. C. , Seliskar C. J. , Caruso J. A.
Published: July 2005

The present study reports rotational and excitation temperatures for a moderate-power Ar microwave-induced plasma (MIP) operating at 500 W forward power and zero W reflected power (as measured at the generator). We report rotational and excitation temperatures as a function of position in the plasma using both axial and lateral viewing modes with, and without, solution nebulization. For the sake of comparison, rotational temperatures ( Trot) were determined both by the fundamental, or slope, method and by the isointensity method as described by Dieke and Crosswhite (see text for references). A discussion of rotational state distributions as they are related to local thermodynamic equilibrium and rotational temperature determinations is included. In determining Trot the principal spectral region of interest is the well-known 3064 Å band characteristic of OH radical. With the use of isointensity method of calculation the temperature in the central region of this plasma was determined to be 3580 K. The excitation temperature ( Texc) was determined by the “slope” method with the use of the Ar plasma support gas excited-state emission lines. The excitation temperature at the center of this Ar MIP was found to be approximately 14,200 K by this method. These values for Trot and Texc suggest that this plasma is more thermal than those MIPs of low power.
On the Electronic Structure of Azolides. Part II: Electronic Absorption Spectra of N-Acylimidazoles. A MO Approach to Cross- and Linear Conjugation
Authors: Hilal Rifaat , Basahel Sulaiman , Aziz Saadullah
Published: July 2005

The electronic absorption spectra of a number of N-acylimidazoles have been investigated with special emphasis on the type and extent of interaction across the carbonyl group. Quantitative discussion of substituent and solvent effects is presented, based on the results of MO Computation and energy partitioning analysis. The results of the present analysis enabled a quantitative definition of the classical and frequently used terminology of cross- and linear conjugation.
Time-Domain Filtering of Two-Dimensional Fluorescence Data
Authors: Vicsek Maria , Neal Sharon L. , Warner Isiah M.
Published: July 2005

Four time-domain filtering methods are applied to simulated and experimental two-dimensional fluorescence data in order to evaluate their performance. The methods that were evaluated are (1) moving average, (2) Savitsky-Golay polynomial smoothing, (3) Chebyshev filtering, and (4) bicubic spline filtering. The methods are compared with the use of mean square error analysis and the difference in the amplitudes of the filtered noisy and ideal data. The two-dimensional version of the Savitzky-Golay filtering and the spline method produced the best overall results.
Carbon13 NMR of Z- and E-Doxepin Hydrochloride
Authors: Wyatt Dorothy K. , Roscher Nina M. , Grady Lee T.
Published: July 2005

Carbon13 chemical shift assignments are reported for Z- and E-doxepin hydrochloride [ Z- and E-N,N,-dimethyl-dibenz[b,e]oxepin-delta-11(6H)], gamma-propylamine hydrochloride, and related model compounds. Doxepin hydrochloride, a mixture of approximately 85% E- and 15% Z-isomer is of clinical importance as an antidepressant drug. Previous proton NMR studies indicated that the dibenz(b,e,)oxepin ring exists in two conformations. This study indicates that one conformation may be favored for each isomer with alkylamino olefinic substituent orientation above the most adjacent aromatic ring. Homoand heteronuclear shift-correlated 2D NMR, selective INEPT, selective and off-resonance decoupling, and inversion-recovery ( T1) experiments as well as model compound comparisons were used in assignments.
Determination of the Orientation of Silanes on Silica Surfaces by Fourier Transform Infrared Photoacoustic Spectroscopy
Authors: Urban Marek W. , Koenig Jack L.
Published: July 2005

Fourier transform infrared photoacoustic spectroscopy has been used for quantitative surface analysis of silica treated with trifunctional coupling agents such as γ-Methacryloxypropyltriethoxysilane (γ-MPS), γ-Glycidoxypropyltrimethoxysilane (γ-GPS), and γ-Aminopropyltri-ethoxysilane (γ-APS). The calibration curves are obtained for several characteristic bands of the coupling agents. Using a highly polarizable gas in the photoacoustic cell and comparing the spectra with a nonpolarizable coupling gas, it is possible to evaluate orientation of the coupling agents on the silica surface. The type of orientation is a function of the extent of surface coverage. At low surface coverage, coupling agents tend to take a perpendicular orientation with respect to the surface, and increasing surface coverage leads to parallel orientation. Increasing the coupling agent concentration also causes orientational changes of the species which form chemical bonds with the silica surface (hydroxyl, water, and carbonyl groups).
1H NMR Spectral Simplification with Achiral and Chiral Lanthanide Shift Reagents. Part II: Ethosuximide, 3-Ethyl-3-Methyl-2,5-Pyrrolidinedione, and Comparisons with Analogs
Authors: Avolio John , Eberhart Suzanne Thomson , Rothchild Robert , Simons Paul
Published: July 2005

The 60 MHz 1H NMR spectra of racemic ethosuximide, 1, have been studied in detail with the achiral shift reagent, tris(6,6,7,7,8,8,8-hepta-fiuoro-2,2-dimethyl-3,5-octanedionato)europium(III), 2, and the chiral tris(3-trifluoromethylhydroxymethylene)- d-camphorato]europium(III), 3. Enantiomeric shift differences, ΔΔδ, were clearly observed for the CH3 of the ethyl group of 1 at molar ratios of 3:1 as low as 0.0385, with ΔΔδ valaues of about 12 Hz seen at a 3:1 ratio of 0.340 for CDCl3 solutions at 28°, 0.634 molal in 1. Smaller ΔΔδ values were also seen for the quaternary methyl and for one of the hydrogens at C-4. Parallel studies with 2 were performed to support assignments. Results are compared with a group of important drugs that are structurally related, including ethotoin, mephenytoin, glutethimide, methsuximide, phensuximide, and paramethadione, in terms of steric and basicity effects. Correlations of both lanthanide-induced shift (Δδ) and ΔΔδ could generally be made from simple electronic considerations related to infrared carbonyl stretching frequencies. Of the 28 sets of Δδ values assigned for the substrates, 3 gave significantly larger values than 2 in only two cases.
Polarization Modulation Fourier Transform Infrared Ellipsometry of Thin Polymer Films
Authors: Graf R. T. , Eng F. , Koenig J. L. , Ishida H.
Published: July 2005

Polarization modulation infrared ellipsometric spectra were collected on an FT-IR spectrometer, with the use of two linear polarizers and a photoelastic modulator. Samples consisted of thin poly(vinyl acetate) and poly(methyl methacrylate) films on gold substrates. The relative phase retardation (delta) and relative amplitude (psi) were derived from these measurements. These spectra were superior to those from static infrared ellipsometry measurements on the same samples. The thickness and optical constants of the films were calculated from the ellipsometric measurements and compared with reference optical constant spectra.
Time-Resolved Infrared Spectroelectrochemistry
Authors: Daschbach John , Heisler Dale , Pons Stanley
Published: July 2005

The generation of time-resolved infrared spectra of species formed at the electrode-solution interface is reported. The methodology involves electronic pre- or post-coupling of the electrochemical experiment to the interferometer retardation timing. By the sorting of the data points in each of the resulting sets of interferograms, which are accumulated over finite intervals of time after initiation of the electrochemical experiment, spectra representing very short integrated time periods are obtained. These time discretized spectra represent the time evolution of the vibrational structure at the electrode surface.
Signal Enhancement by Data Domain Averaging
Authors: Mann Charles K. , Vickers Thomas J.
Published: July 2005

A technique has been described which minimizes the effects of random noise on quantitative spectroscopic measurements. It is applicable to cases in which a reference spectrum of the analyte compound is available and consists of repeated comparisons of sections of the reference spectrum with corresponding segments of the unknown. It has been demonstrated that the average of these replicate measurements is less affected by noise than is a measurement based on peak height, area, cross correlation, or least-squares fitting. Application to infrared measurements has been demonstrated.
Red/Near-Infrared Atomic Analysis for H, C, N, O, S, Cl, and Br with a Fourier Transform Inductively Coupled Plasma Emission Spectrometer
Authors: Schleisman A. J. J. , Pivonka D. E. , Fateley W. G. , Fry R. C.
Published: July 2005

Medium resolution (0.25 cm−1) Fourier transform atomic emission reference spectra of H, C, N, O, S, Cl, Br, and Ar are presented in the red/near-infrared (15,800–8300 cm−1) region for a “pure” argon inductively coupled plasma. A silicon photodiode detector provided the red response needed to measure atomic hydrogen emissions simultaneously with near-infrared lines of the other nonmetals. Several new ICP excited lines of sulfur and carbon are reported. A list of relative intensities for all observed lines in this region is presented, and an 84-page appendix containing labelled medium resolution plots of the entire spectral region for seven elements and the argon background is available upon request. Transparent master overlays of the appendix are also available. Phase error with single-sided interferograms is studied, and the application of standard correction methods prior to power spectrum plotting is explored for red/near-infrared atomic emissions. The interaction between spectral line intensity and resolution is studied in this region.
Factors Affecting Calibration for Phase-Modulation Fluorescence Lifetime Determinations
Authors: Nithipatikom Kasem , McGown Linda B.
Published: July 2005

The effects of several instrumental and experimental factors on phase-modulation fluorescence lifetime determinations of dimethyl POPOP, 9,10-diphenylanthracene, and benzo(a)pyrene were evaluated with the use of both a scattering solution and dimethylPOPOP as references for phase and modulation calibration. For the scattering solution reference, best results were obtained when the scatterer was measured within a few nanometers of the resonance peak corresponding to the excitation wavelength used for measuring the sample. Intensity matching of the reference (either scatterer or dimethylPOPOP) to the sample solution does not appear to be required as long as the sample solution exhibits lifetime homogeneity and the sample and reference are measured with the same voltage applied to the photomultiplier tube detector. Intensity matching to within 10–20% does appear to be indicated for samples with lifetime heterogeneity. When intensity matching is used, the intensities should be matched by adjustment of the reference solution concentration rather than by changing the wavelengths used to measure the reference.
Prominent Spectral Lines for Analytical Atomic Emission Spectrometry with an Ar-N2 Inductively Coupled Plasma
Authors: Montaser Akbar , Chan Shi-Kit , Huse G. R. , Vieira P. A. , Van Hoven R. L.
Published: July 2005

Atomic emission signal-to-background ratios of prominent spectral lines of 45 elements are reported in order to estimate the detection limit capabilities of a relatively low power (1200 W) Ar-N2 ICP.
An X-Ray Photoelectron Spectroscopic Study of Some Ammonium Uranates
Authors: Paul Alan J. , Sherwood Peter M. A.
Published: July 2005

X-ray photoelectron and infrared spectroscopy have been used to investigate the chemical composition of some ammonium uranates, all of which were prepared by the direct titration of uranyl nitrate solution with ammonia. Some correlation is found between the U(4f) binding energy and the pH of the solution used to prepare the uranates, and the v3 asymmetric stretching frequency for the uranyl (UO22+) ion. All samples showed the presence of ammonium ions and possibly two types of hydroxide species. Strong retention of nitrate ions was also observed for all samples.
Laser Optogalvanic Monitoring of SiH in a Chemical Vapor Deposition Glow Discharge
Authors: Tong William G. , Shaw Robert W.
Published: July 2005

A demountable hollow cathode discharge cell that is useful for studies of plasmas relevant to chemical vapor deposition (CVD) was assembled and demonstrated. Direct current glow discharge decomposition of 10% silane in helium in this cell at 20 Torr produced silicon-containing cathodic thin films that were subsequently examined with the use of Raman and x-ray fluorescence spectroscopy. A pulsed dye laser-excited optogalvanic detection technique was used to monitor the presence of a transient molecular intermediate—silicon hydride—in this decomposition plasma. An optogalvanic spectrum of the SiH A2δ -X2τ transition near 420 nm is presented. This electronic absorption technique complements other spectroscopic methods for mechanistic studies and optimization of glow discharge CVD plasmas that are currently used for the commercial preparation of technologically important thin film materials such as hydrogenated amorphous silicon. It will be particularly useful for detection of nonluminescent plasma intermediates.
Infrared Intensities of Liquids III: The Photometric Accuracy of FT-IR Transmission Spectra of C5H10, CH3NO2, CH2Cl2, C6H6, C6H5·CH3, and C6H5Cl in the Liquid State at 25°C in 11- to 500-μm Cells
Authors: Bertie John E. , Jones R. Norman , Behnam Victor
Published: July 2005

This paper completes the report of our FT-IR measurements of transmission spectra of organic liquids. These measurements were undertaken in order to estimate the photometric accuracy of our FT-IR spectrometer for transmission spectra by comparing the results with those measured previously [Applied Spectroscopy 34, 657 (1980)] by a calibrated dispersive spectrometer. We have studied 97 bands of chlorobenzene, toluene, and dichloromethane, in 500-μm cells and 54 bands of benzene, chlorobenzene, toluene, cyclopentane, and dichloromethane, in cells 11 to 53 μm thick. The average value of the imaginary refractive index at the band peak, kmax, is reported for each band and compared with the calibrated value. When averaged over the 184 bands that are reported in this work and our earlier paper [Applied Spectroscopy 39, 401 (1985)], our measurements agree with the calibrated values to about 3% of kmax, and have a 90% confidence limit of about 0.7 to 1% of kmax, The calibrated values themselves have an estimated error of about 6%, so to obtain better knowledge of the accuracy of our measurements we need better standards and we need measurements to be made on other FT-IR instruments. We plan to publish simplified procedures that will encourage others to make such measurements. Our 90% confidence limit includes effects due to the use of different cells, daily realignment of the fixed mirror of the interferometer, realignment of the optics of the detector and sample compartments, change of beamsplitter, and a day-to-day variation of uncertain origin, in addition to the error sources that always contribute to typical analytical precision. Our data do not show these additional error sources to be systematic, so it is appropriate to include their effect in the evaluation of the confidence limit. We believe the main source of error to be the effect of the infrared cell on the path of the light beam through the instrument. The day-to-day variation of uncertain origin is thought to be due to very small changes in the beam path through the instrument, which in turn cause the effect of the infrared cell on the beam to vary.
Time-Resolved Laser-Induced Breakdown Spectrometry for the Rapid Determination of Beryllium in Beryllium-Copper Alloys
Authors: Millard John A. , Dalling Robert H. , Radziemski Leon J.
Published: July 2005

Time-resolved laser-induced breakdown spectrometry has been combined with the long spark technique and applied to the rapid determination of beryllium in beryllium-copper alloys. A calibration curve was developed which related the beryllium concentration in a solid copper matrix to the Be(I) 234.9-nm to Cu(II) 235.7-nm intensity ratio. The beryllium concentrations ranged from 0.001 to 0.22%. For the lowest concentration the relative standard deviation of replicate samples was 7%, implying a detection limit of 0.0002% (2 ppm) at a signal-to-noise ratio of 3. The excitation temperature was determined from Boltzmann plots on Cu(I) and Cu(II), assuming local thermodynamic equilibrium. The values from the two spectra agreed well, and averaged to 13,850 K at 1 μS into the plasma lifetime.
Multisample System for Raman Difference Spectroscopy
Authors: Savoie Rodrigue , Alex Serge , Langlais Marc
Published: July 2005

A new type of sample holder suitable for Raman difference spectroscopy is described. It can accommodate up to six different samples (∼10 μL) contained in capillary cells such as those commonly used in conventional Raman spectroscopy. This system can be readily incorporated in an instrument equipped with a conventional computerized control system and it provides a differential frequency accuracy (±0.03 cm−1) which is comparable to that of other existing devices.
Phase Interference in the Two-Photon Excitation of Phenanthrene
Authors: Koskelo A. C. , Curtin D. L. , Wirth M. J.
Published: July 2005

Two-photon polarization measurements are shown to provide an incorrect symmetry assignment for the first excited state of phenanthrene, both in solution and in the vapor phase. Published assignments from one-photon, single-crystal measurements indicate a totally symmetric state, while the assignment from two-photon measurements indicates an antisymmetric state. Possible reasons for the failure of the two-photon symmetry assignment are low-frequency vibronic overlap, and interference among the diagonal tensor elements. Experimental evidence points to interference as the origin of the discrepancy.
Background Spectral Features in Inductively Coupled Plasma/Mass Spectrometry
Authors: Tan S. H. , Horlick G.
Published: July 2005

Basic background mass spectra of the inductively coupled plasma are presented in this report. The background spectral features were measured for the nebulization of water and for 5% solutions of nitric acid, hydrochloric acid, and sulfuric acid. Background spectra are presented for all these solutions for the mass range 1 to 84 amu, and extensive tables are presented for observed species and their isotopic combinations.
Resolution-Enhanced FT-IR Spectra of Soil Constituents: Humic Acid
Authors: Gerasimowicz Walter V. , Byler D. Michael , Susi Heino
Published: July 2005

Fourier deconvolution and second-derivative spectroscopy have been used to enhance the resolution of infrared spectra of humic acid (HA) extracted from dried municipal waste. The results demonstrate the extent to which the use of such resolution enhancement techniques can disclose new valuable information concerning the composition of complex heterogeneous samples. The findings are in good agreement with previously obtained solid-state NMR results.
Laser-Based Instrument for Electric Dichroism Spectroscopy of Small Molecules
Authors: Jansen K. L. , Harris J. M.
Published: July 2005

While the chemical information provided by electric dichroism spectroscopy can be useful for studying the conformation and electronic structures of molecules in solution, the dichroism signals produced at fields approaching the dielectric strength of organic solvents are extremely small and difficult to detect. A double-beam, laser-based instrument for electric dichroism measurements is described which allows detection of dichroism signals corresponding to changes in absorbance of less than 10−6 with only a 1.2-kV high-voltage source.
FT-IR Photothermal Beam Deflection Spectroscopy of Black Inks on Paper
Authors: Varlashkin P. G. , Low M. J. D.
Published: July 2005

Infrared spectra of several different black inks on paper were obtained by FT-IR photothermal beam deflection spectroscopy (PBDS). Even though the manuscript samples contained about 0.1–0.5 μg of ink solid, spectra of sufficient quality were obtained to enable us to tell which inks contain carbon and to permit some differentiation between similar black inks to be made. However, the identification of an unknown ink is not feasible at present. Spectra of the ink printed on two stamps, and of the black print of a dollar bill, were also recorded. IR/PBDS studies of manuscript and print are totally nondestructive, and may prove to be useful in the fields of forensics and art history.
Oxide, Hydroxide, and Doubly Charged Analyte Species in Inductively Coupled Plasma/Mass Spectrometry
Authors: Vaughan M. A. , Horlick G.
Published: July 2005

In inductively coupled plasma/mass spectrometry analyte, M may be distributed among several species forms including doubly charged ions (M2+), singly charged ions (M+), mono-oxide ions (MO+), and hydroxide ions (MOH+). Detailed data are presented for Ba to illustrate the dependence of the ion count of these species and their ratios (M2+/M+, MO+/M+, and MOH+/M+) on nebulizer flow rate, plasma power, and sampling depth. Although these data are representative of most elements, many form oxides to a much greater degree than Ba; data are presented for Ti, W, and Ce to illustrate this fact. These various analyte species are important in that serious interelement interferences can occur because of spectral overlap. An extensive pair of tables indicating potential spectral interferences caused by element oxide, hydroxide, and doubly charged ions is presented.
Determination of Silicon Dioxide in Silicon Carbide by Diffuse Reflectance Infrared Fourier Transform Spectrometry
Authors: Tsuge Akira , Uwamino Yoshinori , Ishizuka Toshio
Published: July 2005

Diffuse reflectance infrared Fourier transform spectrometry was applied to the determination of SiO2 in SiC powders. The main peaks of SiO2 were observed in the 1000–1250 cm−1 region. The peak intensities were estimated from the peak height at 1150 cm−1. The intensities were little affected by the particle sizes of SiC powders in the 1–9–μm region. The linear relationship between peak intensity and concentration was obtained in the concentration range of 0–5 wt% SiO2. The analytical curve was successfully used for the determination of SiO2 in a few commercial SiC powders.
Carbon13 NMR Shift Assignments for E- and Z-Dothiepin Hydrochloride and 6H-Dibenzo[b,e]thiepin-11-One
Authors: Wyatt Dorothy K. , Roscher Nina Matheny , Grady Lee T.
Published: July 2005

Carbon13 chemical shift assignments are reported for Z- and E-dothiepin hydrochloride (N,N-dimethyldibenzo[b,e]thiepin- delta-11(6H)′, gamma-propylamine hydrochloride). The commercial product, a mixture of approximately 95% E-isomer, is of clinical importance as an antidepressant drug. The precursor and degradation product, 6H-dibenzo[b,e]thiepin-11-one, and related model compounds were also studied. Homo- and heteronuclear shift-correlated 2D NMR, selective INEPT, selective and off-resonance decoupling, and inversion-recovery ( T1) experiments as well as model compound comparisons were used in assignments.
A Comparative Study of the Photoacoustic Spectra of Lanthanide and Actinide Oxides
Authors: Heinrich G. , Güsten H. , Ache H. J.
Published: July 2005

The absorption spectra of thirteen sintered trivalent lanthanide oxides (La to Lu) and six actinide dioxides (Th to Cm) have been measured by photoacoustic spectroscopy. Though both series of elements have in common successive filling of the 4f and 5f shells, respectively, the absorption spectra of the two classes of oxides are very different. While absorption spectra of the thirteen trivalent lanthanide oxides show narrow weak absorption bands and lines in the uv, visible, and near-IR wavelength ranges due to internal 4f n → 4f n transitions between the numerous energy levels of the Xe 4f n configuration, the absorption spectra of the actinide oxides display very intense and broad absorption bands extending from the ultraviolet to the visible and sometimes to the infrared. In the absorption spectra of the lanthanide oxides of higher valencies, such as Tb4O7 or Pr6O11, the sharp absorption lines cannot be detected, as the much stronger 4f n → 4f n–15d transitions overlap the weak 4f n → 4f n transitions. The conclusion is that the 5f n electrons in the actinide oxides are not as well localized as the 4f n electrons of the lanthanide sesquioxides. The 5f electrons probably participate in bonding, e.g., in electron transfer processes from a molecular oxygen orbital to a partly filled or empty 5f electron state of the oxidizing central atom which gives rise to intensive broad absorption bands in the ultraviolet and visible.
Measurement of Phase Transitions by Photothermal Radiometry: The Semiconductor-To-Metal Transition of Vanadium(IV) Oxide, VO2
Authors: Pekker Sandor , Eyring Edward M.
Published: July 2005

A new experimental method of investigating phase transitions of solids, photothermal radiometry, is described. The effects of modulation frequency, laser intensity, and heating-cooling rates on the first-order semiconductor-to-metal phase transition of a microcystalline vanadium dioxide sample have been studied. The PTR signal increases with temperature in both phases, and a negative peak occurs at the phase transition. The intensity of signal is inversely proportional to the square root of frequency at laser-beam chopping frequencies lower than 100 Hz, indicating that the sample is thermally thick, and the signal is controlled by the thermal conductivity and the heat capacity and is independent of the optical properties of the material. The relative peak intensity decreases slightly in the low-frequency range with increasing frequency and more sharply at higher frequencies. The measured temperature of the phase transition decreases linearly with the intensity of illuminating light, from which the static component of the temperature rise at the surface can be determined. From the increase of linewidth with the laser intensity one may estimate the amplitude of the temperature modulation at the surface. The measured temperature of the phase transition increases with increasing heating rate and decreases with increasing cooling rates. The effects of variable light intensity and heating-cooling rates can be eliminated by extrapolation, and the exact temperature of the phase transition is obtained.
Factors Affecting Infrared Group Frequencies: Carbonyl Stretching Absorption Bands
Authors: Nyquist Richard A.
Published: July 2005

The data presented show that infrared group frequencies are only applicable for specific spectra structure identification when the infrared spectrum of the unknown material is recorded in the same manner as that used to record the infrared spectra used to build the IR group-frequency data base. IR spectra recorded of compounds in different phases such as the liquid, solution, and vapor phase are useful in helping one to determine whether a compound exists in more than one rotational molecular configuration such as rotation of a CHCl2 group about a C-C=O single bond in compounds of form CHCl2-C=O.
Near-Infrared Reflectance Determination of Sensory Quality of Peas
Authors: Martens M. , Martens H.
Published: July 2005

Rapid, precise, and relevant methods for predicting the sensory quality of frozen peas were sought. Pea batches chosen to span many different types of quality variations were analyzed by a consumer test, sensory laboratory analysis, and traditional chemical and physical measurements as well as by near-infrared reflectance analysis (NIR). Partial least-squares (PLS) regression was used to reveal the relationships between the different types of measurements. A noise-compensated value, relative ability of prediction (RAP), was used to express the degree of prediction (1.0 = perfect prediction). NIR was found to predict the sensory texture variables (RAP = 0.79) better than the flavor variables (RAP = 0.67). Average consumer preference was less well predicted (RAP = 0.48) by NIR. This was interpretable since NIR gave a better description of the chemical and physical methods relevant for texture (e.g., dry matter (RAP = 0.93)) than the flavor-related variables (e.g., sucrose (RAP = 0.45)) that apparently determine the consumer preference. However, NIR was found to describe the average variation in sensory quality better than the traditional tenderometer value (TV). The highest prediction of sensory variables was obtained by a combination of NIR, TV, and chemical measurements (RAP = 0.87 and 0.80 for texture and flavor variables, respectively). We discuss the predictive validity and the meaning of the present predictive abilities in practice, leading to a conclusion that NIR has a potential for predicting the sensory quality of peas.
Simultaneous Determination of C, H, N, O, F, Cl, Br, and S in Gas Chromatographic Effluent by Fourier Transform Red/Near-Infrared Atomic Emission Spectroscopy
Authors: Pivonka Don E. , Fateley William G. , Fry Robert C.
Published: July 2005

A high-powered, atmospheric-pressure, helium microwave-induced plasma (MIP) is used as the interface between a gas chromatograph (GC) and a Fourier transform near-infrared (FT-NIR) emission spectrometer. By the collection of a series of time-resolved interferograms when organic compounds elute from the GC into the plasma, a complete account of both spectral and chromatographic activity is recorded. Computer-generated, element-specific chromatographic reconstructions for each of eight different nonmetals are obtained from a single injection of a chemical mixture. Atomic emission intensity vs. chromatographic retention time is plotted for each of eight or more optical frequencies chosen from the 15,700–7900 cm−1 region. The frequencies are preselected to coincide with spectral lines of C, H, N, O, F, Cl, Br, and S emitting from the helium MIP. This unique GC/MIP/FT-NIR emission spectrometer provides simultaneous multielement-specific chromatographic detection of a variety of nonmetals important to synthetic organic chemistry.
A New Accessory for Infrared Emission Spectroscopy Measurements
Authors: Handke M. , Harrick N. J.
Published: July 2005

The principal problem in measurement of emission IR spectra is the low signal-to-noise ratio resulting from the large background radiation relative to sample emission. One method of increasing the signal is to collect the emitted radiation over a very large solid angle using an ellipsoidal mirror. In this method, placing the sample at the short focal length of the ellipsoid both increases the amount of radiation collected for an improved signal-to-noise ratio as well as facilitates sampling of small areas. For locating the area of interest, a microscope is mounted on the emission accessory. The results of testing this emission accessory under different operating conditions such as different samples, emission angles, temperatures, etc., are presented.
Infrared Spectra of Intumescent Chars
Authors: Varlashkin P. G. , Low M. J. D.
Published: July 2005

The utility of infrared Fourier transform photothermal beam deflection spectroscopy (PBDS) for the examination of intumescent systems was explored. Infrared spectra were recorded of a model system consisting of a mixture of pentaerythritol and (NH4)2HPO4, and of a film of a commercial fire-retardant paint painted on sheet metal, at various stages before, at, and after intumescence. Although the morphology of the materials changes greatly during the thermal decompositions, infrared spectra can be recorded which can provide useful information about the systems and intumescent chars.
Spectral and Noise Characteristics of a Xenon Microwave-Induced Plasma Lamp
Authors: Beauchemin D. , Hubert J. , Moisan M.
Published: July 2005

Xenon lamps, filled at various pressures from 0.9 to 5 atmospheres and activated by an electromagnetic-surface-wave-produced plasma, are evaluated for their optical spectrum characteristics in the uv-visible region. The influence of several operating parameters on their optical emission spectrum and noise characteristics is reported. These microwave-induced lamps are compared with a commercial 150 W high-pressure xenon short-arc lamp in regard to their use as continuous sources of uv-visible radiation. They are more stable but are less intense than the short arc. Furthermore, the intensity of the line spectrum that is superimposed on the continuum is comparatively larger than with the short arc. The results obtained indicate, however, that it is possible to decrease the line intensities with respect to the continuum intensity as well as to improve the signal-to-noise ratio and to increase the total emitted intensity by increasing the gas pressure and/or the microwave power. These lamps may thus be considered as potential highly stable, low-noise spectrometric continuum sources.
Solids Formation from Synthetic Fuel Reprocessing Solutions: Characterization of Zirconium Molybdate by ICP, XRF, and Raman Microprobe Spectroscopy
Authors: Rao B. S. M. , Gantner E. , Müller H. G. , Reinhardt J. , Steinert D. , Ache H. J.
Published: July 2005

Raman microprobe, ICP, and XRF techniques have been applied to characterize the solids precipitated from HNO3 solutions containing Zr and Mo under different solution conditions. The saturation yields of precipitation decrease linearly—in almost all cases—with increasing acid strength, and nearly complete precipitation of Mo occurs in 3-M HNO3 solutions; ionic strength does not seem to affect the yields. Raman spectra of the microparticles indicate that hydrated zirconium molybdate is the main product, except in solutions with large excess of Mo relative to Zr. Identification of the species formed in these solutions is made by comparison of the Raman spectra with the spectra of known compounds. X-ray diffraction patterns of hydrated and thermally treated zirconium molybdate are in accord with the reported crystallographic data.
Performance of a Direct Sample Insertion System for the Inductively Coupled Plasma
Authors: Shao Youbin , Horlick Gary
Published: July 2005

A new design for a direct sample insertion system is presented. It is a mechanical system that allows precise movement of the sample cup into the ICP discharge and it can be readily attached to standard commercial ICP spectrometers. Good quantitative results can be obtained for volatile elements with reasonable precision and low detection limits with the use of 10 μL of solution or 10 mg of powdered samples.
FT-IR Studies of Langmuir-Blodgett Thin Protein Films: Albumin
Authors: Jakobsen R. J. , Cornell D. G.
Published: July 2005

FT-IR/ATR spectra were obtained on films deposited on a 45° Ge ATR crystal by Langmuir-Blodgett techniques. Two thicknesses (33 Å and 59 Å) were investigated. The ATR spectra showed that the albumin molecules attached directly to the germanium surface were more ordered than and different from the albumin molecules adsorbed on other albumin molecules. These ordered albumin films rearranged with time to more closely resemble conventional albumin films.
Optical Properties of Thin Layers of Bovine Serum Albumin, γ-Globulin, and Hemoglobin*
Authors: Arwin H.
Published: July 2005

We have used spectroscopic ellipsometry to determine the dielectric functions of thin films of γ-globulin, bovine serum albumin, and hemoglobin in the visible and near-uv photon energy range. We show that both thickness and dielectric function can be resolved for monomolecular films adsorbed on substrates with relatively low polarizability. The data which we consider to be closest to the intrinsic dielectric response of the protein films were obtained on HgTe and HgCdTe substrates. Less resolution was obtained on silicon substrates. For a density-deficient film, we were able to model the dielectric response with effective medium theories, and the void fraction could be determined.