Glow discharge (GD) is a highly specialised source that especially meets the requirements for accuracy, simplicity and speed for content depth profiling and bulk analysis in both optical emission (OES) and mass spectrometry (MS). The pulsed radio frequency GD source has the potential for both elemental and molecular analysis of conductive and non-conductive materials. To exploit the information delivered by pulsed radio frequency (r.f.)-GD sources, fast sampling is required, and is available only through timeof-flight mass spectrometry (ToF-MS). Compared to optical glow discharge (GD-OES) instrumentation, a GD-ToF-MS system shows much simpler spectra, lower background signals and lower detection limits. The presented new r.f.-GD-ToF-MS system is a successful combination of a commercial high-end glow discharge instrument and an extremely fast and high-resolution time-of-flight mass spectrometer. This new instrument was applied to analyse conductive and non-conductive materials like anodic thin films. We could resolve 2-nm Cr makers in aluminium oxide layers and measure trace elements in ultra thin titanium oxide films. Furthermore, we show the potential of the pulsed mode to separate analyte species from elements originating from residual gas.
A global deperturbation is presented for all electronic states of NiH with To values below 0.3 eV. These states form an isolated group and are treated as components of a molecular "supermultiplet" which is derived from a nickel-centered 3d 9 electron configuration such as that found in the 2 D term of Ni + . Observed term energies for all low-lying states, including some vibrationally excited levels, are used in a least squares fit to the supermultiplet model. A crucial feature of the supermultiplet model is its employment, wherever possible, of atomic angular (e.g., L± ILA) = [L(L + 1) -A(A ± 1)] 1I21LA ± 1» and radial (e.g., spin-orbit coupling constants) matrix elements to define and constrain the molecular effective Hamiltonian. A relatively small number of adjustable parameters are required to represent the v = 0 and 1, J = 0.5-11.5 term values in the supermultiplet picture and accurately describe a variety of observations, which include large 0 doublings, unusually large and J, 0, elfdependent Zeemang values, and a symmetry-forbidden (~A = 2) rotational pertubation. The number of independently adjustable parameters required by the supermultiplet model is significantly smaller than a standard 2~, 2IT, 2~ + deperturbation model. In addition, the fitted de perturbed (i.e., nonrelativistic and nonrotating) molecular constants for the 2~, 2IT, 2~ + components of the NiH supermultiplet are in better agreement with theoretical descriptions than previous empirical constants taken directly, without deperturbation, from spectra. The fit model also yields an empirical value of the (3d9)(T~ 3d 10 configuration mixing coefficient, which is relevant to a global understanding of the d 9 and d 10 states in the homologous NiH, PdH, PtH series of molecules. 7164
This review paper describes the evolution of the quantification procedure for compositional depth profiling (CDP) in glow discharge optical emission spectrometry (GD-OES), based on the constant emission yield concept. The concept of emission yield (EY) is defined and ways of measuring it experimentally are discussed. The history of the development of quantitative CDP is reviewed, which shows that all of the different approaches depend on the assumption that the EY is essentially a matrix-independent quantity. Particular emphasis is placed on the dependence of the EY on the plasma parameters of current, voltage, power and pressure. In short, impedance changes (current voltage) can significantly affect the emission yield and should either be corrected mathematically or the impedance should be kept constant by pressure regulation in order to obtain reliable results from GDOES CDP. On the other hand, the effect of varying the pressure on the emission yield can be considered to be minor within the limits of practical operating conditions for most CDP applications. It is worth, however, bearing in mind that varying the discharge pressure has a significant effect on the plasma processes, and does affect the emission yield when these variations are large. The experimental results obtained for the emission yield are related to the results from theoretical model calculations published on the subject.
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