Andrew T. Zander

Spectral Efficiency of the SpectraSpan III Echelle Grating Spectrometer

The efficiency of an echelle grating spectrometer incorporating prism cross-dispersion is empirically evaluated over a broad wavelength range incorporating a large number of orders. A derived parameter, the spectrometer efficiency, proportional to the spectrometer luminosity, conveniently gauges dynamic features of the echelle efficiency. Characteristics of efficiency over broad wavelengths suggested by earlier work are clearly observed. The shift of blaze wavelength with decreasing order of diffraction, predicted in a recent model of echelle grating efficiency, is experimentally documented.

Analytical characteristics of an inductively coupled plasma-mass spectrometer

Abstract A new instrument is described for inductively coupled plasma-mass spectrometry. The instrument has features which make it useful for both fundamental studies of plasmas and for analytical elemental analysis. Analytical characteristics of the instrument such as the background mass spectrum, the abundance sensitivity, presence of doubly charged and oxide ions, detection limits and analytical calibration curves are presented. Some interference effects commonly seen in atomic emission spectroscopy are evaluated, and comparisons are made between the performance of the new instrument and that of other inductively coupled plasma-mass spectrometers.

Examination of the Spectral Efficiency of an Echelle Grating Monochromator

The spectral efficiency of an echelle grating monochromator has been examined. The frequently cited advantage that “echelles are blazed at all wavelengths” is observed to be a result of the periodic character of the echelle efficiency as compared with the continually decreasing efficiency from the blaze wavelength for conventional gratings. The periodic character of the echelle efficiency may be also a disadvantage, particularly when regions near the ends of the orders are utilized, since the efficiency may drop significantly below the theoretical decrease of 50%. An awareness of the efficiency character of the echelle grating monochromator should facilitate the choice of wavelength region in which to work

Electron density spatial profiles of the DCP source

Abstract Electron densities are measured in the high current, analytical and intervening zones of a DCP whose operating parameters are systematically varied. Detailed N e distribution profiles are obtained for various sleeve flow, nebulizer flow, arc current and matrix concentration regimes. Flowing argon is found to establish a thermal pinch in the high current zone and to steepen gradients in plasmas employed for spectrochemical analysis. The distinctive electron density distributions in the DCP are more sensitive to modulation of gas flow variables than to changes in arc current. Magnetic pressure has no discernible role in pinch formation. Electron densities in spectroscopic regions are minimally affected by easily ionized or other matrix constituents at usual analytical concentrations.

Thermal pinch effect in the argon d.c. plasma

Abstract Creation and consequences of the marked thermal pinch in the analytical d.c. plasma (DCP) are investigated. The flowing plasma constricts due to interaction between forced convective cooling and electric current regulation of the low power arc. Distinctive visual, spectroscopic and operational features of the DCP are associated with the thermal pinch and the transport properties of hot argon. Response of modelled electron density to changes in cooling gas flow rates are compared to experimental data. Implications for non-local thermodynamic equilibrium (LTE) spectrochemical excitation are noted.