China
Africa
Explore chapters and articles related to this topic
Inductively Coupled Plasma Optical Emission Spectrometry
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
Echelle grating-based ICP-OES instruments have become very popular with the manufacturers and the ICP spectroscopists in recent years. It has been shown that some advantages may be taken of if the characteristics of two dispersing devices, such as that of a diffraction grating and a prism are combined. The two optical devices are placed perpendicular to each other in this configuration. One of the dispersing devices is the Echelle grating which is a coarsely ruled grating, with rulings ranging between 8 and 300 grooves/mm (compared with diffraction grating with rulings ranging from 600 to 4200 grooves/mm). The function of the Echelle grating is to separate the polychromatic radiation from the ICP by wavelengths and produce multiple, overlapping spectral orders. The second optical device, the prism, sorts or cross-disperses the overlapping orders to produce a 2D array of wavelengths on the focal plane of the spectrometer. In the 2D array, the wavelengths are in one direction, and the spectral orders are in the other. A typical optical arrangement for an Echelle grating-based ICP-OES spectrometer is illustrated in Figure 3.12.
Diffraction Gratings
Published in Roshan L. Aggarwal, Kambiz Alavi, Introduction to Optical Components, 2018
Roshan L. Aggarwal, Kambiz Alavi
Echelle gratings are used for high-resolution spectroscopy. They are coarsely ruled (large d) blazed gratings with a large blaze angle. The resolving power of an echelle grating used in the Littrow mode at the blaze angle is proportional to the tangent of the large blaze angle. Echelle gratings are generally used with a second grating, or prism, to separate the overlapping diffraction orders. Albert Michelson, who referred to them as echelons, discovered echelle gratings in 1898. The resolving power of an echelle grating relative to that of a conventional blazed grating in the Littrow mode is given by () (λ/Δλ)E(λ/Δλ)C=tanθEtanθC
Recent Trends in Plasma Chemistry and Spectroscopy Diagnostics
Published in Tanmoy Chakraborty, Lalita Ledwani, Research Methodology in Chemical Sciences, 2017
For line monitoring, which means following the temporal behavior of a particular emission line, pocket size spectrometers are suitable although they have a poor spectral resolution Δλ ≈ 1–2 nm. A spectrometer/spectrograph with a focal length of 0.5–1 m (Δλ ≈ 40 pm) having a grating of 1200 lines/mm and a 2-D CCD array gives a good choice for spectral and temporal resolutions. An Echelle spectrometer35 provides an excellent spectral resolution (Δλ ≈ 1–2 pm) by making use of the higher orders of diffraction provided by the special Echelle grating. They are an excellent tool for the measurement of line profiles and line shifts.
Compact cross-dispersion device based on a prism and a plane transmission grating
Published in Journal of Modern Optics, 2018
An early echelle spectrometer uses two planar reflection gratings operating in two perpendicular planes so that the incident light is first diffracted by an echelle grating into a high diffraction order in one plane, then diffracted by a second reflection grating in a perpendicular plane (3). The resulting dispersion spreads the spectrum out on the detector plane in two dimensions to produce a two-dimensional spectrogram including several lines side by side that correspond to different diffraction orders, namely, several diffraction-order lines side by side with the wavelength varying with its position along each line. However, if large spectral range or high resolving power or both are required, the diffraction-order lines would become crowded near one end of the spectrogram, which tend to make the spectral lines within the order lines indistinguishable.