Optics: measuring and testing – By dispersed light spectroscopy – With sample excitation
Patent
1987-12-22
1989-05-16
McGraw, Vincent P.
Optics: measuring and testing
By dispersed light spectroscopy
With sample excitation
313619, 356314, H01J 188, G01N 2166
Patent
active
048304921
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a glow-discharge lamp made of insulated material provided with at least one gas supply means and evacuation openings means; an anode in said chamber body; a gas inner chamber which expands toward the anode and which is defined by sides of inner walls of the chamber body and whose diameter is largest at approximately the level of the anode and whose smallest diameter corresponds to an examination sector of the sample to be examined; a cathode adjacent one end of the chamber body; a sample placed at the cathode end of the chamber body and an end section in the form of a window means arranged at one end of the chamber body and wherein the glow-discharge lamp is used for atom absorption spectroscopy (AAS), optical emission spectroscopy processes (OES), atom fluoresence spectroscopy (AFS) and optogalvanic process (LEI).
STATE OF THE ART
Glow-discharge lamps have found wide use in the analysis of metals by means of atom emission spectroscopy (AES), in which a conductive sample to be examined is connected to a cathode and the region between the cathode and the anode is filled with a gas capable of glow discharge, preferably an inert gas under low pressure. The glow discharge depends on the relationship between the voltage during conduction, the current and the gas pressure between the cathode and the anode. The radiation of the glow discharge is observed through the customary window situated above the anode and from its spectral analysis inforamtion is gained about the content of specific elements in the sample.
A glow-discharge lamp is known from the German Patent Application 34 29 765, in which a carrier gas passes through an inner gas chamber and a glow discharge is excited by applying voltage between the anode and the cathode. The sample is connected as a part of the cathode, whereby a transparent part of the housing is used for the spectral analysis of the glow-discharge light. The anode is partially embedded in a fixed non-conducting body and has high voltage potential, whereas the sample--as the cathode--has zero potential.
The embedding of the anode in a fixed non-conducting body ensures, in a most simple manner, the short circuit resistancy of the housing. Furthermore, this prior art technique permits applying high voltage to the anode while the cathode is at zero potential, by which means it is possiblee to easily and safely replace the samples. The non-conductive material of the gas chamber also makes it possible that the walls of the discharge chamber rapidly adjust to the temperature in the gas chamber as non-conductive material usually has poor thermal conductive properties. This known arrangement ensures rapid establishment of constant measuring conditions and reproduceable results.
Although the apparatus known from P 34 29 765 is major progress compared to known glow-discharge lamps, nonetheless conventional glow-discharge lamps are only suited for the customary application in atom emission spectroscopy.
BRIEF DESCRIPTION OF THE INVENTION
The object of the present invention is, therefore, to improve known glow-discharge lamps while lowering the detection limit in the atom emission spectropscopy in such a manner that also permits applying other spectroscopic methods, with which excited atoms, like those present in a glow discharge, can be examined.
Said object is carried out in accordance with the present invention and its embodiments as set forth in the appended claims.
A fundamental thought underlying the present invention is the observation of the glow discharge through a side window. By this means, which in contrast to previously known glow-discharge lamps, for the first time provides lateral observation of the glow light, if necessary, following optical excitement from incident radiation. The glow-discharge lamp can thus be used for other spectroscopic processes such as, by way of illustration, atom fluorescence spectroscopy or similar processes. It is also possible to link up a light guide or similar devices to the side windo
REFERENCES:
Williamson et al. "Glow-Discharge Optical Spectroscopy Measurement of B-, Ge, & Mg-Implanted GaAs" Jour. of Applied Physics 50(12) Dec. 1979 pp. 8019-8024.
Gesellschaft zur Forderung der Spektrochemie und angewandten
McGraw Vincent P.
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