Bourdon F. Scribner

The plasma jet as a spectroscopic source

Abstract The plasma jet utilizes electromagnetic and thermal pinch effects to form an arc plasma into a flame-like cone of high energy. The plasma produced in the discharge chamber is constricted and carried through a circular opening in the cathode by a stream of fluid such as helium; resulting in a jet of hot partially ionized gas. For application as a spectroscopic excitation source, a plasma jet was designed to operate with moderate currents (15–20 A) from a conventional d.c. arc power supply and to include an atomizer to spray a solution through the anode into the discharge. The source excites spark-lute spectra, indicating a high excitation temperature. Applied to the spectrographic analysis of stainless steel for iron, chromium and nickel, the results exhibited a coefficient of variation of about 2 per cent, including the photometric error. The plasma jet offers promise as a reproducible means of high energy excitation of solutions and of liquids in general.

Laser probe excitation in spectrochemical analysis.I: characteristics of the source.

A modified laser probe for spectrochemical analysis is described. A high energy laser beam is focused onto a specimen to vaporize a sample from a small area, and the vapor thus formed is further excited by a spark discharge. The characteristics of emission spectra with and without auxiliary spark excitation are compared. Spectrograph illuminating systems for qualitative and quantitative analysis were investigated. Some difficulties were encountered with the laser probe, and modifications were made to the instrument to alleviate some of these problems. Some typical analytical applications are discussed.

Laser Probe Excitation in Spectrochemical Analysis. II: Investigation of Quantitative Aspects

A study has been made of quantitative analysis by a laser probe with spark excitation of the sample vapor. Random errors come largely from variations in laser energy and from photometric errors. The parameters of the spark circuit affect the line intensities; however, these factors are well controlled. Correlations have been established between the energy of the laser beam, the size of the pit formed, and spectral intensities. For most purposes, single-spike laser operation has been found to be preferable to multiple-spike operation. At present, the coefficients of variation for analysis are 15% to 40%.

Simple Arc Devices for Spectral Excitation in Controlled Atmospheres

The replacement of air around a carbon arc by other gases has been shown to have several effects in the excitation of spectra, the most obvious being the elimination of cyanogen bands when the atmosphere surrounding the arc contains no nitrogen. Although the effects of controlled atmospheres have been applied in spectrographic analysis, work along these lines has been limited by the practical difficulties involved. These difficulties include delays in changing electrodes between samples, the need for flushing the chamber before excitation can be started, and clouding of chamber windows by deposits of sample and electrode vapors.

RELATIVE INTENSITIES FOR THE ARC SPECTRA OF SEVENTY ELEMENTS

Abstract The relative intensities, or radiant powers, of 39,000 spectral lines with wavelengths between 2000 and 9000 A have been determined on a uniform energy scale for seventy chemical elements. This was done by mixing 0·1 at. per cent of each element in powdered copper, pressing the powder mixture to form solid electrodes which were burned in a 10-A, 220-V d.c. arc, and photographing the spectra with a stigmatic concave grating while a step-sector was rotating in front of the slit. The sectored spectrograms facilitated the estimation of intensities of all element lines relative to copper lines which were then calibrated on an energy scale provided by standardized lamps, and all estimated line intensities were finally adjusted to fit this calibration. Comparisons with other intensity measurements in individual spectra indicate that the spectralline intensities may have errors of 20 per cent, but they first of all provide uniform quantitative values for the seventy chemical elements commonly determined by spectrochemists. The complete data are being published as a National Bureau of Standards Monograph. About 1100 of the lines are presented in this paper as a list of the strong lines of each element. Energy levels and term combinations are given for each classified line.

Detailed Subject Index

Absorption, of atomic radiation, 2764, 3389 Abstracts, of 1945 literature, 2514 of 1940 to 1945 literature, 2776, 2805 Accuracy (see also Precision) contribution of source unit to —, 3568 effect of microstructure of electrodes on —, 2988 effect of photographic plate on —, 2784 factors affecting —, 2950 improvements in —, 3377, 3378 in flame photometry, 2977 in photographic photometry, 2920 of plate calibration, 3014, 3016 of steel anal., 2780, 2851, 3341 statistical fluctuations in anal., 2893 Air, detection of Pb in — by Geiger counter, 3200 detn. of Be in dust from —, 3513 detn. of Pb in —, 3079, 3451 Albite, anal, of —, 2998 Alkali salts, detn. of Li in —, 2420b Alkaline earths, detn. of Li in —, 2420b Alum, detn. of Ca in —, 3537 detn. of Mg hi —, 3183 Alumina (see also Bauxite) anal, of —, 3550 Aluminum, anal, of — at University of Ghent, 2672 anal, of — by solns., 221 la detn. of Al, Cu, Fe, Mg hi —, 2651 detn. of Be hi — by soln. method, 3495 detn. of Cd, Ni, Pb, Sn hi recast —, 3019 detn. of Cu, Fe, Mg, Mn, Si hi — with unproved excitation source, 2626 detn. of Cu, Fe, Si, Zn hi —, 2876, 3469 detn. of Fe, Mg, Si hi —, 2549 detn. of Fe, Si hi —, 2674, 2894 detn. of Ga hi —, 3252, 3380 detn. of Mg hi — by line-width method, 2491 detn. of Mn hi — by line-width method, 1990a,1990b detn. of Mn, Ni hi —, 2817 detn. of Na hi —, 2556, 2975 detn. of Na hi — by flame photometer, 3340 detn. of Si hi —, 2554 detn. of Zn hi —, 2877, 3373 effect of circuit hi anal, of —, 2170b effect of sample treatment hi detn. of Si hi—,2554 Aluminum alloys (see also Duralumin, Silumin) anal, by photoelectric spectrometer, 2621, 3357 anal, of — with intermittent a-c arc, 3224 calibration of standard samples of —, 3221 conditions for anal, of —, 2l70c control of — by photoelectric method, 2867 detn. of Al, Fe, Mg, Mn, Si, Zn hi —, 3334 detn. of Be hi —, 3161 detn. of Cr, Cu, Fe, Mg, Mn, Ni, Pb, Si, Sn, Ti, Zn hi —, 2824 detn. of Cr, Cu, Fe, Mg, Mn, Ti, Zn hi —, 3238 detn. of Cu hi —, 2534, 2809 detn. of Cu, Fe, Mg, Mn hi —, 2826 detn. of Cu, Fe, Mg, Mn, Si hi —, 3230 detn. of Cu, Fe, Mg, Mn, Si, Ti, Zn hi —, 2216b, 2569 detn. of Fe, Mg, Mn, Si hi — with phototubes, 2895 detn. of Mg hi —, 3572 detn. of Mg hi — by self-reversal, 2769 detn. of Mg, Zn hi —, 3042 effect of alloying components on spectra of—,3308 effect of background on detn. of Cu hi —, 3523 effect of heat treatment hi anal, of —, 2570, 3314a effect of heat treatment of electrodes on intensities, 3005 effect of microstructure on anal, of —, 2763 effect of pre-spark on anal, of —, 2570 effect of Si content in anal, of Al-Si —, 3536 effect of microstructure on anal, of —, 2763 prepn. of standard samples for —, 2732 sampling of —, 2733 semiquant. anal, of — scrap, 2731 study of diffusion hi —, 2919 visual anal, of —, 3047 visual sorting of —, 2791, 2797 Aluminum and alloys, anal, of —, 3110 British Aluminum Co. methods for anal. of—,2102a detn. of Cr, Cu, Fe, Mg, Mn, Ni, Pb, Si, Sn, Ti, Zn hi —, 2813 detn. of Mg, Si hi — by two-line method, 2962 review of anal, of —, 2756a