Emission coefficient for a singly ionized uranium plasma: experimental and theoretical treatment

Absolute emission coefficient measurements on arc-generated singly ionized uranium (UII) in local thermodynamic equilibrium are described for a wavelength bandwidth of 1050 to 6000 A. Plasma temperature and uranium partial pressure at the arc centerline were approximately 8000/sup 0/K and 0.01 atm, respectively. The arc emission data compare favorably with experimental results obtained from UF/sub 6/ discharges, once allowance is made for the effects of cold-layer UF/sub 6/ photoabsorption on uranium plasma emission. Observed variation in the emission coefficient is well correlated with a composite of calculated oscillator-strength distribution for selected UII and UIII transition arrays. The theoretical treatment is based on a modified Hartree--Fock method for calculating the appropriate radial wave functions. Slater--Condon theory provides a detailed calculation of energy-level structures for both the upper and lower configuration of each transition array computed. However, the number of terms were truncated, when necessary, to accommodate size limitations of the matrices involved. With this theoretical approach, predictions are also offered as to the location of strong emission features for a hypothetical plasma dominated by doubly and triply ionized uranium. It is suggested that the capability now exists to predict successfully the location of major emission features of uranium and other complex systems for a substantial range of ionization stages

Laser-induced breakdown spectroscopy (LIBS): a new spectrochemical technique

We have used the breakdown spark from a focused laser beam to generate analytically useful emission spectra of minor constituents in air and other carrier gases. The medium was sampled directly. It was not necessary to reduce the sample to solution nor to introduce electrodes. The apparatus is particularly simple; a pulsed laser, spectrometer, and some method for time resolution. The latter is essential in laser-induced-breakdown spectroscopy (LIBS) because of the strong early continuum. High temperatures in the spark result in vaporization of small particles, dissociation of molecules, and excitation of atomic and ionic spectra, including species which are normally difficult to detect. In one application, we have monitored beryllium in air at conventrations below 1 ..mu..g/m/sup 3/, which is below 1 ppB (w/w). In another we have monitored chlorine and fluorine atoms in real time. LIBS has the potential for real-time direct sampling of contaminants in situ

CONTRIBUTIONS TO THE ARC SPECTRUM OF SILICON

Abstract not availabl

Method for spectrochemical analysis using time-resolved laser-induced breakdown. [Patent application]

A method for real-time elemental analysis using laser-induced breakdown of the material under investigation and spectroscopic analysis of the light emitted from the plasma consequently formed is described. By delaying the observation of the emitted radiation, the unwanted background continuum and line spectra from excited ionic species can be rendered unimportant relative to the excited atomic line spectra, thereby producing sharp, well-defined characteristic identifying atomic spectral features. These features provide the indicia for detailed elemental analyses of substances. The method is quite general in that it applies to gases, surfaces, and particulates entrained in gases. It requires no electrodes and can excite atomic species like fluorine and chlorine which are difficult to observe by more conventional analytical procedures

Real-time monitoring of airborne beryllium, at OSHA limit levels, by time-resolved laser-induced breakdown spectroscopy

Real-time detection of beryllium particulate is being investigated by the new technique of laser-induced breakdown spectroscopy. For beryllium detection we monitor the 313.1-nm feature of once ionized beryllium (Be II). Numerous publications describe the technique, our beryllium results, and other applications. Here we summarize the important points and describe our experiments with beryllium