Spektrochemische analysen mit einer glimmentladungslampe als lichtquelle—I: Elektrische eigenschaften, probenabbau und spektraler charakter

Abstract

The Grimm glow discharge lamp is a new type of spectrochemical light source that is distinguished from other types of light sources in several ways. Therefore the more important physical properties of the source were initially investigated. The electrical behaviour of the discharge, characterized by the voltage-current parameters, depends on the type of discharge gas and its pressure as well as on the composition of the sample. The rate of erosion by cathode sputtering differs with samples of different composition and structure, and also depends upon the electrical parameters of the discharge gas and its pressure. The spectral nature of the discharge is due to the fact that no thermal equilibrium exists between atoms, ions, and electrons in the source. The higher the ionization energy of the discharge gas is, the stronger are the ion line intensities of the sample. For the discharge in a pure noble gas alone, the background is a continuum, but the spectral distribution differs for the various gases. From these observations, and from further investigations on the dependence of atom lines, ion lines, and background on the discharge parameters, conclusions could be drawn of the suitability of the source for qualitative and quantitative analysis. Side-on observations of the source indicate that the radiating layer of the source is very thin, and at low power densities is only about 1–2 mm. When such a discharge is observed normal to the sample (i.e. end-on) then inhomogeneities in the sample can be observed by the suitable illumination of a spectrograph.