Teaching Raman Spectroscopy in Both the Undergraduate Classroom and the Laboratory with a Portable Raman Instrument

We have evaluated a small portable Raman instrument on loan from B&W Tek, Inc., and have determined that it can successfully be used in the classroom both as a visual aid for teaching the fundamentals of Raman spectroscopy and for a variety of undergraduate experiments as a normal component of an instrumental analysis class. Having portable Raman instrumentation would allow the instructor to demonstrate the principles of Raman spectroscopy, as well as the concepts of calibration curves, blank subtraction, detection limits, and regression analysis. Both qualitative and quantitative types of experiments were done for solid Tylenol tablets, aqueous solutions of isopropyl alcohol, dimethyl sulfoxide, methanol, and ethanol, and gaseous CO₂ and N₂O₄. Additionally, surface‐enhanced resonance Raman spectra of Rhodamine 6G were obtained using a chloride ion–activated silver colloid. Spectra from the B&W Tek, Inc., instrument were comparable to literature Raman spectra.     

Raman Spectroscopy for the Undergraduate Teaching Laboratory: Quantification of Ethanol Concentration in Consumer Alcoholic Beverages and Qualitative Identification of Marine Diesels Using a Miniature Raman Spectrometer

Raman spectroscopy has steadily gained popularity as a powerful tool in both the analytical lab and the undergraduate classroom. The technique is attractive because it allows for rapid, nondestructive qualitative or quantitative analyses of many analytes with little or no sample preparation requirements. The introduction of less expensive, smaller, and more powerful diode laser excitation sources and the recent availability of rugged, red‐sensitive, charge‐coupled device–based miniature modular spectrometers has prompted the integration of Raman spectroscopy into the undergraduate curriculum. We have evaluated the analytical utility of a small, portable Raman instrument for the qualitative and quantitative analyses of two “real” samples. The experiments in this paper were designed to be used as a laboratory component for undergraduate education and include the quantification of ethanol in consumer alcoholic beverages and the qualitative identification of marine diesel fuels that had been spilled on surface waters. In the case of the liquor samples, the ethanol concentration in colorless, odorless alcoholic beverages could be determined very rapidly, but colored and heavily scented liquors proved more difficult and required pretreatment with activated carbon to remove fluorescence that masked the Raman signal. Similarly, a high‐intensity fluorescence background was observed to mask characteristic Raman bands of the diesel fuels. Some reduction in the intensity of the fluorescence was observed after carbon pretreatment of the fuels. The set of undergraduate experiments described in this paper treat the concepts of quantitative and qualitative analysis using portable instrumentation, instrumental calibration by the standard addition and external curve methods, and method development for the analysis of real consumer and environmental samples.     

X‐Treme beamline at SLS: X‐ray magnetic circular and linear dichroism at high field and low temperature

X‐Treme is a soft X‐ray beamline recently built in the Swiss Light Source at the Paul Scherrer Institut in collaboration with École Polytechnique Fédérale de Lausanne. The beamline is dedicated to polarization‐dependent X‐ray absorption spectroscopy at high magnetic fields and low temperature. The source is an elliptically polarizing undulator. The end‐station has a superconducting 7 T–2 T vector magnet, with sample temperature down to 2 K and is equipped with an in situ sample preparation system for surface science. The beamline commissioning measurements, which show a resolving power of 8000 and a maximum flux at the sample of 4.7 × 10¹² photons s^?1, are presented. Scientific examples showing X‐ray magnetic circular and X‐ray magnetic linear dichroism measurements are also presented.     

Experimental Determination of the Useful Reflection Coefficient of Non-Cooperative Targets for a Time-of-Flight Laser Rangefinderx

An experimental verification of the reflection properties of non-cooperative targets for a time-of-flight laser rangefinder is proposed. Indeed, knowing the light scattering physical properties of usual targets is necessary to determine the optical power budget of such a device. The useful reflection coefficient (RC) is contained at between 0.6 and 0.7 at the wavelength λlD (=820 nm), polar diagrams presenting almost a lambertian shape for incident angles lower than 60°. The useful RC thus corresponds to the value of the lambertian RC increased by the contribution of the specular RC.Presented at the 7th International Workshop on Multiple Scattering Lidar/Light Experiments (MUSCLE7). July 21–23 1994, Chiba, Japan.     

Measurement techniques in high-enthalpy hypersonic facilities

Interest in hypersonic aerodynamic braking and aerospace planes has led to the development of new high-enthalpy hypersonic test facilities. This paper describes available techniques and future developments for making measurements in these facilities. Emphasis is on instrumentation for use with short-duration flows in free-piston shock tunnels. Issues of free-stream calibration, surface measurements on models, flow visualization, laser diagnostics, and accuracy are addressed, with references made to representative experimental studies. The paper concludes with a summary of future research needs.     

Plasma diagnostic through ion bernstein waves

Summary The effectiveness of a diagnostic method for both ion temperature and ion minority concentrations, based on propagation of Ion Bernstein Waves (IBW), is analysed theoretically and verified experimentally. The method is based on a comparison between wave vector measurements, obtained with an interferometric system, and theoretical dispersion relations.     

Integral imager: Prototype scientific performances

Summary The Imager proposed for the gamma-ray satellite project INTEGRAL is based on a multilayer two-dimensional array of CsI(TI) elements viewed by Si photodiodes. The total active area is ≈2500 cm². The operative energy interval ranges from 0.05 to 10 MeV. A prototype version of this instrument, ready to be tested on a ballon-borne experiment, has been realized. In this article the expected performances of the instrument are presented, toghether with the first calibration results of the prototype. Paper presented at the 6th Cosmic Physics National Conference, Palermo, 3–7 November 1992.     

In‐situ analysis of planetary surfaces by Mössbauer spectroscopy

Iron is one of the key elements in the evolution of the solar system and is highly abundant in terrestrial planets. Its oxidation state reflects the history of the oxidation–reduction reactions on planetary surfaces. The identification of iron mineralogies and the relative abundance of iron oxidation states (2+ and 3+) will contribute to a much deeper understanding of the evolution of planetary bodies and their surfaces. Miniaturized Mössbauer spectrometers are under development primarily for missions to the planet Mars and the Moon, but there is also an interest on using such an instrument for space missions to the planet Venus, comets and asteroids. The instrument MIMOS II developed at TU Darmstadt meets the requirements for space application as low mass (about 500 g), small volume, and low power consumption (about 1 W). The instrument has been tested extensively in the laboratory but also recently in the field mounted on the robotic arm of a prototype Martian Rover under development at JPL/NASA, United States.     

Polarization change of high-frequency electromagnetic waves in magnetically sheared plasmas

Summary The polarization change of an electromagnetic wave passing through a magnetized plasma turns out to be of renewed interest because of the possibility, offered by polarimetry measurements in the infrared range of frequencies, of determining the current density profile for a tokamak plasma. Because of magnetic shear, acting as a coupling parameter between the characteristic modes, the fraction of energy in each mode is not a constant, and a non-WKB treatment is necessary in order to describe the evolution of the wave polarization. The present work shows that this evolution, together with the one of the mode energy, is described by a set of four first-order differential equations. The solutions of this system are discussed in the general case, and in significant limiting cases. Work performed under JET Contract     

Molecular diffusivity of sample solutes in a number of eluents and the implications with regard to the design of capillary chromatographic systems

The properties of sample solutes and eluents injected into capillary tubes were studied in order to develop improved chromatographic instrumentation technology. Use of a new apparatus to determine molecular diffusion coefficients (D) of solutes in both aqueous and organic eluents under laminar flow conditions provided results more rapidly than older methods. The experimental results obtained were in agreement with theoretical predictions and will be useful in the design of chromatographic systems.