Application of the Rapid Scan Fourier Transform Infrared Spectrometer to KineticsLephardt, J. O.; Vilcins, G.
doi: 10.1366/000370275774455996pmid: N/A
The properties of a rapid scanning Fourier transform infrared spectrometer (FT-IR) which permit its effective utilization in acquiring kinetics information are described. Experiments which would be lengthy and difficult to perform by conventional infrared procedures can be performed quickly and more reliably with an FT-IR system. The detection of all spectral frequencies simultaneously, inherent to the interferometer spectrometer, enables these advances to be achieved. The computer, which is essential for Fourier transformation, can also be utilized to provide absorbance profiles, differential profiles, and other display formats which can simplify the analysis and improve the reliability of kinetic measurements. Spectra and profiles obtained for a gas-solid adsorption process and a gas phase reaction of butadiene with an NO2-N2O4 mixture are presented to illustrate the potentials of an FT-IR system.
A Comparison of Two Discriminant Functions for Classifying Binary Infrared DataWoodruff, H. B.; Lowry, S. R.; Isenhour, T. L.
doi: 10.1366/000370275774456021pmid: N/A
Some form of information compression is essential if one is to be able to utilize effectively the increasingly large data compilations. One approach is to eliminate the intensity information, leaving spectra packed in a peak/no peak format. This paper reports the comparison of two simple discriminant functions for classifying binary infrared data. For the multicategory problem of 13 classes used in this investigation, random guessing would achieve about 8% correct classification. A dot product calculation produces 49.1% correct classification, while a distance measurement produces 58.7%. The results from this investigation are also qualitatively compared to previous work using infrared data which retained some intensity information. It is found that the binary packing of spectral data shows great promise in the area of infrared analysis.
Slitwidth Dependence of Depolarization RatiosFini, Giancarlo; Mirone, Paolo
doi: 10.1366/000370275774456120pmid: N/A
The dependence of the depolarization ratio on the slitwidth has been investigated for some polarized Raman bands. It is found that the ratio of the peak intensities depends on the slitwidth, whereas the ratio of the integrated strengths does not. This behavior is explained in a general way by considering the different contributions of the isotropic and the anisotropic spectrum to the two terms of the depolarization ratio.
Spectrographic Analysis of Geological Materials with an Argon Plasma JetGolightly, D. W.; Harris, J. L.
doi: 10.1366/000370275774456111pmid: N/A
An argon plasma jet source of recent design is applied to multiple element spectrographic analysis of geological materials. The source is characterized in terms of accuracy of analysis and repeatability of measurements obtained from spectra from a large region of the plasma. Results of analyses for Al, Ca, Fe, Mg, Si, and Ti in geochemical reference samples, for Ti in lunar basalts, gabbros, and soils, and for the SiO2/Al2O3 ratio in mordenite from geodes are presented. The effective temperature of the plasma region used for analytical measurements is 4670 ± 50°K. Use of control samples is recommended to improve accuracy of analysis.
A Miniature, Low Energy Spark Discharge System for Emission Spectrochemical Analysis of SolutionsZynger, J.; Crouch, S. R.
doi: 10.1366/000370275774456030pmid: N/A
A miniature spark discharge system is described for solution analysis by emission spectroscopy. Samples are introduced as dry particles formed by nebulization into a heated desolvation chamber. The spark is formed by the discharge of a coaxial capacitor through a stream of argon which transports the desolvated aerosol. A photoelectric, time-resolved detection system for mechanistic studies and analytical applications is described. The detection system consists of a synchronous integrator controlled by a digital timing and sequencing system. The time-resolved spectral characteristics of the source are discussed, and time resolution is shown to provide enhanced sensitivity. Analytical results are reported for a variety of elements.
Study of the Excitation Mechanism in the Low Current Carbon Arc in Argon and HeliumMorris, W. F.; Worden, E. F.
doi: 10.1366/000370275774456058pmid: N/A
Arc temperatures have been measured, and relative electron densities have been estimated for dc arcs in Ar, Ar-CO, He, and He-CO. Two temperatures were measured: the excitation temperature, Tcxc, by means of the zinc two-line intensity ratio method, and the rotational temperature, Tr, by the C2 band method. Relative electron densities were estimated by comparing Ha line widths in each of the four arc atmospheres. These measurements were performed to gain some understanding of the influence of small amounts of CO on the excitation characteristics of low amperage arcs in argon and helium. The resulting temperatures and electron density estimates indicate that only the c in argon with CO present approaches local thermodynamic equilibrium. Tables of the measured temperatures and plots of the Hα line widths for the estimation of electron densities are given. Implications with regard to the excitation of metal impurities vaporized into these arcs are discussed.