Showing papers in "Applied Spectroscopy in 1984"
TL;DR: In this article, a laser-generated spark was used to analyze liquids spectroscopically for elemental constituents, and limits of detection for Li, Na, K, Rb, Cs, Be, Mg, Ca, B, and Al were established with the use of a 10 Hz repetitive single spark (RSS).
Abstract: A laser-generated spark was used to analyze liquids spectroscopically for elemental constituents. The spark was produced directly in liquids by a focused laser pulse of 15 ns duration and an energy of about 45 mJ/pulse. The size, temperature, and electron density of the spark are reported. Emissions from once-ionized and neutral atoms and simple molecules were observed. Limits of detection for Li, Na, K, Rb, Cs, Be, Mg, Ca, B, and Al in aqueous solutions were established with the use of a 10 Hz repetitive single spark (RSS). Most of these elements were only detectable at levels above 1 μg/mL, although the detection limit for Li was 0.006 μg/mL. The relative standard deviation for replicate sample analysis was 4-8%. The detectability of some species was enhanced with the use of a 10 Hz repetitive spark pair (RSP): a pair of sparks separated in time by about 18 μs. The detection limits for B/H2O with the RSP and the RSS were 80 and 1200 μg/mL, respectively. Species were also detected in organic solvents and in flowing samples. The laser spark method of liquid analysis would be useful in situations requiring noninvasive monitoring of species at high or moderate concentrations.
406 citations
TL;DR: In this paper, a new tunable optical filter has been developed which rejects a narrow wavelength interval ( 90%). This filter will be useful in optics, in spectroscopy, and for laser applications.
Abstract: A new tunable optical filter has been developed which rejects a narrow wavelength interval ( 90%). This filter will be useful in optics, in spectroscopy, and for laser applications. The active element of the filter is a crystalline colloidal array of polystyrene spheres. The rejected wavelengths are Bragg diffracted from this ordered array. For a particular sphere concentration and scattering from a particular set of lattice planes, tunability can be achieved by the altering of the angle between the filter and incident light beam. Bragg diffraction and light rejection of these filters are monitored by transmission measurements. The utility of this filter for spectroscopic measurements is demonstrated for Raman spectroscopy. Raman measurements are shown for polypropylene, a highly scattering material with numerous low-frequency modes. The filter selectively attenuates the elastically scattered light and allows the low frequency peaks to be observed. Use of this wavelength rejection filter to reject the Rayleigh scattered light simplifies the instrumentation, decreases the cost, and increases the sensitivity of Raman spectral measurements. This filter also has the potential to replace dispersive elements such as gratings and prisms in a variety of spectroscopic and optical applications.
197 citations
TL;DR: In this paper, a new technique using Kossel rings is described which simultaneously measures structure, lattice spacings, and crystallite orientation, and the experimental determination of the bulk modulus is further illustrated.
Abstract: Bragg diffraction of laser light from crystalline aqueous colloids of polystyrene spheres is examined to determine crystal structure, orientation, and elasticity. A new technique using Kossel rings is described which simultaneously measures structure, lattice spacings, and crystallite orientation. The monodisperse polystyrene sphere latex dispersions crystallize into large single crystals, which, depending on sphere concentration, are either face-centered or body-centered cubic. The interparticle spacings in the crystals are many times larger than the sphere diameter (0.109 μm). The use of tunable lasers to easily determine crystal structure is described, and the technique is further illustrated by the experimental determination of the bulk modulus. The bulk modulus is a macroscopic physical constant which can be used to monitor intersphere potentials and the screening of the particle charges by electrolytes in the solution. Data are presented which suggest that crystallite orientation occurs with the closest packed sphere layers parallel to the sample cell quartz walls.
174 citations
TL;DR: In this paper, nonlinear least squares curve fitting is used to analyze Ni 2p spectra obtained from various nickel-oxygen compounds and Ni/Al2O3 catalysts.
Abstract: Nonlinear least-squares curve fitting is used to analyze Ni 2p spectra obtained from various nickel-oxygen compounds and Ni/Al2O3 catalysts. Apart from NiO, which shows a characteristic discrete satellite peak 2 eV from the main 2p3/2 peak, all other spectra exhibit variable peak asymmetry assigned to multiplet splitting effects. By the use of a single extra peak to describe this asymmetry, the relative satellite/main peak intensity ratio can be used as an indication of the chemical state of nickel. Results for Ni/Al2O3 catalysts agree with reduction studies from previous work about the nature of nickel species on the surfaces of these catalysts at various nickel loadings.
165 citations
TL;DR: In this paper, it was shown that inelastic scattering from the substrate which supports the particle for measurement must be avoided in order to keep spectral interference with the Raman spectrum of interest to a minimum.
Abstract: Recently, there has been a rapid development in Raman microprobe spectroscopy [1]. It was shown that Raman spectra can be obtained from micrometer-size particles with reasonable signal-to-noise ratio. In these techniques specific precaution has to be taken into account to minimize spectral contributions arising from elastic and inelastic scattering from all possible sources other than the particle of interest. Particularly, inelastic scattering from the substrate which supports the particle for measurement must be avoided in order to keep spectral interference with the Raman spectrum of interest to a minimum.
135 citations
TL;DR: In this article, the cause of sample degradation in three different x-ray photoelectron spectrometers (AEI-ES200, LHS-10, and HP-5950A) was investigated.
Abstract: Six Cu compounds were analyzed in three different x-ray photoelectron spectrometers (AEI-ES200, LHS-10, and HP-5950A), each equipped with a different type of AI Kα x-ray source, to determine the cause of reduction of copper salts in photoelectron spectrometers. The monochromatic source used in the HP 5950A spectrometer did not cause sample degradation. Significant sample degradation was observed in the AEI ES200, which was attributed to the radiative heating from the x-ray gun. The LHS-10 spectrometer, which utilizes a water-cooled x-ray housing, afforded significantly less sample reduction than the AEI ES200 spectrometer.
132 citations
TL;DR: In this article, the problem of nonlinear detector response in FT-IR spectroscopy is discussed, and a convenient method for detection of the nonlinear response is given, with the use of synthetic data.
Abstract: The problem of nonlinear detector response in FT-IR spectroscopy is discussed. The effects of nonlinearity are demonstrated with the use of synthetic data, and a convenient method for detection of the nonlinear response is given. The interaction between phase correction and nonlinear response is also shown with the use of synthetic data.
97 citations
TL;DR: In this article, the authors improved the reported assignments of the vibrational frequencies in several organosilicon monomers and oligomers, and assigned the frequencies of polydimethylsiloxane (PDMS) to its other physical properties.
Abstract: This work had three objectives: to improve the reported assignments of the vibrational frequencies in several organosilicon monomers and oligomers; to assign the vibrational frequencies of polydimethylsiloxane (PDMS); and to relate the vibrational spectra of PDMS to its other physical properties, especially at sub-ambient temperatures, Infrared and Raman spectra were obtained on the title compounds, and five sets of low-temperature IR spectra were obtained on PDMS. Some low-temperature spectra were also taken on the cyclosiloxanes. Assignment of all frequencies was accomplished, although in some cases, e.g., the methyl rocking frequencies at 650-870 cm−1 and the skeletal deformations below 400 cm−1, our confidence in their correctness is less than complete. The low-temperature study showed striking changes in the IR spectrum of PDMS below its glass transition temperature Tg, Bands became sharper and in some cases showed splitting. This behavior is consistent with the concept of polymer motion being frozen below Tg, Except for the appearance of a strong, sharp band at 662 cm−1, not much change was seen in the spectrum at the "cold crystallization" point. Possibly the expected spectral changes were swamped by absorption from the more plentiful amorphous portion of the polymer matrix.
95 citations
TL;DR: The effect of compressing powdered samples on their diffuse reflectance infrared spectra is discussed in this paper, where the scattering coefficient decreases with applied pressure, the magnitude of the increase being dependent on the nature of the sample.
Abstract: The effect of compressing powdered samples on their diffuse reflectance infrared spectra is discussed. The scattering coefficient decreases with applied pressure, the magnitude of the increase being dependent on the nature of the sample. For pure powdered organic samples, such as caffeine, the increase in f(R∞) can be dramatic. By subjecting powdered samples to a pressure which is not enough to cause them to become transparent, the packing density becomes more uniform and band intensities become more reproducible. The relative intensity of neighboring bands in any region of the spectrum does not change appreciably with applied pressure.
77 citations
TL;DR: In this paper, a method for displaying this implicit information is developed and evaluated, and a comparison is made of this new spectral reconstruction technique to established methods such as spectral stripping and factor analysis.
Abstract: In near-infrared reflectance analysis (NIRA), a computer is trained to recognize and quantitate the relationship between the near-infrared spectrum of a sample and the concentrations of one or more of the sample constituents. During this training process the computer implicitly generates the spectrum of the constituents in question, although this spectrum is ordinarily not available for operator inspection. In the present study, a method for displaying this implicit information is developed and evaluated. The resulting "reconstructed spectrum" can be of a specific chemical constituent in a sample or can be a composite spectrum of those components that collectively contribute to specific sample properties such as material strength or processing temperature, or to sensory characteristics such as the "hotness" of peppers. A comparison is made of this new spectral reconstruction technique to established methods such as spectral stripping and factor analysis.
73 citations
TL;DR: Fluorescence studies of hematoporphyrin derivative in normal and tumor tissue of rat were performed with nitrogen laser excitation and optical multi-channel detection and should have implications for practical human HPD endoscopy.
Abstract: Fluorescence studies of hematoporphyrin derivative (HPD) in normal and tumor tissue of rat were performed with nitrogen laser excitation and optical multi-channel detection. Fifteen types of tissue including inoculated tumor were investigated for rats at different delays after HPD injection. Optimum contrast functions and other criteria for discriminating tumor tissue from normal tissue are discussed. The results should have implications for practical human HPD endoscopy.
TL;DR: In this article, the authors describe the forms, symmetries, and selection rules for the normal modes of vibration of a number of examples of surface-adsorbed species, both on isolated sites and in regular arrays of surface sites such as are occupied at higher coverage.
Abstract: In this paper we describe systematically the forms, symmetries, and selection rules for the normal modes of vibration of a number of examples of surface-adsorbed species. The chosen cases are discussed for adsorption both on isolated sites and in regular arrays of surface sites such as are occupied at higher coverage. For this purpose the Site Group and Factor Group (Correlation Field) approach to the vibrations of regular 3-dimensional lattices is adapted to the 2-dimensional systems. For simplicity the examples chosen are mainly monatomic and diatomic species adsorbed in various ways on specific sites of (111), (100), or (110) planes of metals with face-centered cubic lattices. The selection rules discussed refer to activities in infrared, Raman, or electron energy loss spectroscopy (dipolar and impact scattering mechanisms) and distinguish between adsorption on insulating and conducting (metal) surfaces. The examples chosen for regular arrays all refer to cases where experimental results (mainly from electron energy loss spectroscopy) are available in the literature, where they have been discussed mainly at the site group level.
TL;DR: The investigation of various types of window functions shows that the selection of the window function does not directly affect the performance of adaptive smoothing, and the signal-to-noise ratio is maximized at any local section of the entire spectrum.
Abstract: An adaptive smoothing method based on a least mean-square estimation is developed for noise filtering of spectroscopic data. The algorithm of this method is nonrecursive and shift-varying with the local statistics of data. The mean and the variance of the observed spectrum at an individual sampled point are calculated point by point from its local mean and variance. By this method, in the resultant spectrum, the signal-to-noise ratio is maximized at any local section of the entire spectrum. Experimental results for the absorption spectrum of ammonia gas demonstrate that this method distorts less amount of signal components than the conventional smoothing method based on the polynomial curve-fitting and suppresses noise components satisfactorily. The computation time of this algorithm is rather shorter than that of the convolution algorithm with seven weighting coefficients. The a priori information for the estimation of the signal by this method are: the variance of noise, which can be attainable in the experiment; and the window function which gives the local statistics. The investigation of various types of window functions shows that the selection of the window function does not directly affect the performance of adaptive smoothing.
TL;DR: In this paper, the Fourier coefficients computed from the NIR spectra of pulverized tobacco samples can be used to estimate certain chemical constituents in the samples, which can reduce the computation time for calibration by 96% and reduce the magnetic storage space requirements by 98%.
Abstract: Fourier coefficients computed from the NIR spectra of pulverized tobacco samples can be used to estimate certain chemical constituents in the samples. As few as 11 coefficients from the Fourier domain used in a stepwise multiple linear regression (SMLR) model provide results equivalent to a 7-term SMLR model using log I/R from the wavelength domain. The Fourier model reduces the computation time for calibration by 96% compared to the wavelength model, and reduces the magnetic storage space requirements by 98%. Removing the mean term from the Fourier model partially corrects the particle size anomaly encountered in pulverized samples.
TL;DR: In this article, the utility of diffuse reflectance FT-IR (DRIFT) spectroscopy is explored to study the surfaces of clean E-glass fibers and e-glass/coupling agent systems.
Abstract: The utility of diffuse reflectance FT-IR (DRIFT) spectroscopy is explored to study the surfaces of clean E-glass fibers and E-glass/coupling agent systems. The ability to use a non-destructive sampling procedure is an important benefit for the study of these systems. However, the nature of the fiber samples leads to several experimental difficulties. We solve these problems through the use of a KBr overlayer. Using this sample-preparation procedure, we increase the information derivable from the spectra. The inherent surface sensitivity of the DRIFT technique is demonstrated by the study of small amounts of the silane coupling agent γ-aminopropyltriethoxysilane (γ-APS) on the surface of E-glass fibers.
TL;DR: In this paper, the Fourier transform infrared spectroscopic ATR (FT-IR-ATR) method has been applied to quantitative determination of chemical composition of thin surface layers.
Abstract: The Fourier transform infrared spectroscopic ATR (FT-IR-ATR) method has been applied to quantitative determination of chemical composition of thin surface layers. The powerful capability of the FT-IR-ATR spectral subtraction method was proved to determine poly(dimethylsiloxane) content in the surface layer of Cardiothane 51, which consists of poly(urethane) and poly(dimethylsiloxane) as a minor component, showing the detection limit of 0.2% of the content. An absorbance ratio of a selected band of poly(dimethylsiloxane) relative to a selected band of poly(urethane) was determined by FT-IR-ATR measurements on the pure samples of each of the constituting components that have the same area contacted onto the internal reflection element of Ge. Consideration was also given to the thickness of the surface layer that can be analyzed by the present method, and one half of the penetration depth dp was considered to better represent the thickness of the surface layer measured than dp.
TL;DR: In this paper, FT-IR spectra obtained as a function of time revealed many changes in spectral content, providing new information about anomer characteristic bands in aqueous media.
Abstract: FT-IR spectral investigations on carbohydrates were undertaken in aqueous media in order to facilitate the assignments of vibrational bands. For pure anomeric forms of glucose, FT-IR spectra obtained as a function of time revealed many changes in spectral content, providing new information about anomer characteristic bands in aqueous media. It was also found that fructose, which is known to undergo complex mutarotation, exhibits two types of spectral changes, whereas glucose, which undergoes simple mutarotation, shows a single type of spectral change. Thus FT-IR spectral investigations in aqueous carbohydrates should be able to distinguish between simple and complex mutarotation cases. As a vibrational spectroscopic technique, the importance of FT-IR spectroscopy is further emphasized by showing that Raman spectroscopy is not sensitive enough to reveal the structural changes of carbohydrates in aqueous media.
TL;DR: In this paper, several methods of preparing mixtures of powdered samples for diffuse reflectance infrared spectrometry are described, including ground separately and then mixed and shaken together vigorously using a mechanical device such as a Wig-L-Bug.
Abstract: Several methods of preparing mixtures of powdered samples for diffuse reflectance infrared spectrometry are described. Simply grinding two materials together does not usually lead to a homogeneous mixture because the softer material will adhere to the walls of the vessel holding the mixture. The components should be ground separately and then mixed and shaken together vigorously, preferably using a mechanical device such as a Wig-L-Bug.
TL;DR: In this article, the effect of a contaminant overlayer on solid gold gives rise to a background which increases as the separation from the main photoelectron peak, ΔE, increases.
Abstract: Analysis of the Au 4f ESCA spectra of thin gold films deposited over a graphite base shows that as the separation from the main photoelectron peak, ΔE, increases the background decreases. Conversely, the effect of a contaminant overlayer on solid gold gives rise to a background which increases as ΔE increases. There is, therefore, a considerable variety of background profiles which can be encountered in real samples, which depends markedly on the element, its concentration, and its distribution in the sample. Over the region of the photoelectron line signal itself, the simple integral description which assumes that the background is proportional to the number of electrons of higher kinetic energy is reasonably valid and is suggested for peak area measurement when a nonlinear profile is needed. Direct integration and curve fitting techniques constitute the two main methods of peak area measurement. Simulated Ni 2p spectra are used to compare the effectiveness of the simple integral and linear background profiles for producing the correct peak areas. Although the simple integral profile shows more consistency and is to be preferred in general, certain fortuitous cancellation effects, particularly with nonmonochromatized spectra, make areas using the linear background fairly accurate in some instances. Curve fitting can overcome many of the problems of direct integration resulting from severe peak overlap. Two types of Gaussian/Lorentzian functions with a suitable exponential tailing function, which has a finite area over reasonable integration limits, are discussed with regard to their use in non-linear least-squares curve fitting methods. Also discussed is the usefulness of composite and difference spectra as simpler methods of determining the relative areas of overlapping peaks.
TL;DR: Raman spectra of three readily available C-type stoichiometric rare-earth sesquioxide powders of composition Ln2O3 are presented in this article, where correlations of spectra with body-cell structure and infrared absorption spectra have been made.
Abstract: Raman spectra of three readily available C-type stoichiometric rare-earth sesquioxide powders of composition Ln2O3 are presented. Some correlations of spectra with body-cell structure and infrared absorption spectra have been made. Spectra of Eu2O3, Dy2O3, and Tm2O3 display several new peaks that have not as yet been reported. Assignments of certain peaks to electronic Raman and resonance Raman transitions are discussed.
TL;DR: In this paper, the authors report FT-IR-VCD recorded under improved conditions of signal-to-noise ratio, resolution, and spectral range (to 800 cm−1).
Abstract: We report FT-IR-VCD recorded under improved conditions of signal-to-noise ratio, resolution, and spectral range (to 800 cm−1). Detailed descriptions are provided in the areas of artifact suppression, phase correction procedures, and comparison of FT-IR to dispersive VCD measurements. Spectral evidence supports the proposition that VCD absorbance artifacts are a surface effect originating at the optical window–solution interface.
TL;DR: In this article, the authors performed a model study using multilayer polymer films in order to understand the optimal applicability of DRIFT to these measurements, and found that the relative contribution of the surface to the spectra can be adjusted by varying the amount and/or particle size of the KBr powder overlayer.
Abstract: Diffuse reflectance FT-IR (DRIFT) is described as a tool for the study of polymer surfaces. The high sensitivity (particularly to surfaces) and nondestructive sample preparation procedure used for DRIFT experiments are valuable characteristics of the technique. By the use of an overlayer of a nonabsorbing powder such as KBr, the quality of the spectra of coatings and surface species on absorbing substrates is improved. We performed a model study using multilayer polymer films in order to understand the optimal applicability of DRIFT to these measurements. The relative contribution of the surface to the spectra can be adjusted by varying the amount and/or particle size of the KBr powder overlayer. Correlations between particle size, overlayer amount, and nature of the spectra of the
TL;DR: The three Gaussian components of the IR stretching band of OH for reverse micelles of egg yolk Lα-phosphatidylcholine in benzene have been characterized in frequency, bandwidth, and extinction coefficient.
Abstract: The three Gaussian components of the IR stretching band of OH for reverse micelles of egg yolk L-α-phosphatidylcholine in benzene have been characterized in frequency, bandwidth, and extinction coefficient. The different types of water identified inside the micelles correspond to hydration layers around the phospholipid polar heads, the first containing up to ~11 water molecules per polar head, the second with a maximum of 10–12 water molecules per polar head.
TL;DR: In this paper, the development and design of instrumentation used to generate a microwave-induced plasma (MIP) is reviewed and a complete analysis of the widely used TM010 cavity is also presented.
Abstract: The development and the design of instrumentation used to generate a microwave-induced plasma (MIP) is reviewed. Microwave power generators, coupling devices, discharge tubes, and their influence on the spectrochemical utility of the MIP are described. A complete analysis of the widely used TM010 cavity is also presented.
TL;DR: In this article, the use of B-splines for smoothing and differentiation of spectroscopic curves has been investigated, and various schemes for automatic selection of knots used in fitting experimental curves have been investigated and some schemes have been applied to data obtained by Raman spectroscopy.
Abstract: The use of B-splines for smoothing and differentiation of spectroscopic curves has been investigated. The theory of B-splines and their use are outlined. For single Lorentzian and Gaussian curves, optimal spline functions of degrees 3-7 inclusive, based on symmetric arrangements of 5, 6, and 7 knots, have been computed. Various schemes for the automatic selection of knots used in fitting experimental curves have been investigated and some schemes have been applied to data obtained by Raman spectroscopy.
TL;DR: In this article, the minimum number of training samples required for near-infrared reflectance spectroscopy has been evaluated and a working procedure for objectively calculating the minimum required training samples has been described.
Abstract: Near-infrared reflectance spectroscopy uses a learning algorithm to derive a set of weighting coefficients from the reflectance spectra of a reference sample set. These coefficients, when applied to the reflectance values of an unknown sample at specific wavelengths, can be used to calculate constituent concentrations. Having enough samples in the training set and enough wavelengths in the calculation procedures is essential, but there are severe drawbacks to picking too large a number. This paper describes the principles and implementation of a working procedure for objectively calculating the minimum number of training samples required.
TL;DR: In this paper, a transient absorption, maximizing at 510 nm, was observed for microcrystalline benzil, by diffuse reflectance laser flash photolysis, and its decay appears to be a mixture of first-and second-order processes.
Abstract: Following pulsed excitation at 354 nm, a transient absorption, maximizing at 510 nm, is readily observed for microcrystalline benzil, by diffuse reflectance laser flash photolysis. The transient absorption reduces the level of diffusely reflected analyzing light by 80%, and its decay appears to be a mixture of first- and second-order processes. Decay constants obtained from the slope of the first-order plot vary over a factor of about 2.5, with an initial slope = 0.18 × 105 (±0.01 × 105) s−1, and a final slope = 0.66 × 104 (±0.04 × 104) s−1. Laser excitation also induces phosphorescence in microcrystalline benzil, which has a similar kinetic decay. It is confirmed that in diffuse reflectance mode the percentage transient absorption is directly proportional to the excited state concentration.
TL;DR: In this paper, the authors used the vibrational frequency location of broad infrared Si-N antisymmetrical stretching absorption in the spectra of various plasma deposited Si3N4 films to identify hydrogen-containing impurities.
Abstract: Deposited films of amorphous silicon nitride, Si3N4, which are used for surface protection or as an insulating interlayer in microelectronic devices, have been studied by IR. The observed changes in the vibrational frequency location of the broad infrared Si-N antisymmetrical stretching absorption in the spectra of various plasma deposited Si3N4 films indicate the formation and inclusion of impurities within the silicon nitride network. The deposited films are composed principally of amorphous Si3N4, but trace amounts of hydrogen-, oxygen-, and nitrogen-containing moieties were found which contributed to the displacement of the Si-N absorption. The associated functional groups were identified as Si-H, NH, SiOx, and Si-O-Nx. IR was used to measure quantitatively the hydrogen-containing impurities. The method provides a means of identifying and correlating impurity levels with properties of the films.
IBM1
TL;DR: In this article, a liquid analyzer was used for infrared spectroscopy of aqueous solutions of penicillin VK, sodium oxacillin and sodium methicillin.
Abstract: Infrared spectra of aqueous antibiotic solutions were obtained using a new Liquid Analyzer accessory in a Fourier transform infrared (FT-IR) spectrometer. Based on a cylindrical internal reflectance element, the Liquid Analyzer accessory provides a sufficiently short (~0.015 mm) effective pathlength for infrared spectroscopy of aqueous solutions from 3200 to 800 cm−1. Spectra of aqueous solutions of penicillin VK, sodium oxacillin and sodium methicillin are shown. By measuring the absorbance of the beta-lactam carbonyl band, FT-IR spectroscopy with the accessory exhibits analytical sensitivity to less than 0.1% concentration by weight of antibiotic both in aqueous solution and in an actual fermentation broth.
TL;DR: In this article, a collection of photoacoustic spectra of several readily available stoichiometric rare earth oxide powders is presented, and the J levels of these spectra are assigned.
Abstract: A collection of photoacoustic spectra of several readily available stoichiometric rare earth oxide powders is presented. J levels of these spectra are assigned. In addition to the traditional applications of photoacoustic spectroscopy (chemical, physical, and analytical investigations), the technique is useful for studying the kinetics and thermodynamics of intermediate phases of rare earth oxides and surface photochemical reactions of rare earth oxides. The spectra may also reveal information on the lattice structure of powder grains. The need for additional work in rare earth oxide spectroscopy is pointed out.