Echelle emission spectrometer

D.C. Bankston. Processing data from the plasma echelle emission spectrometer. Amer. Lab., 31 (March, 1981). 

Both sequential and multichannel emission spectrometers are of iwo general types, one using a classical grating spectrometer and ihe other an echelle spectrometer, such as that shown in Figure 7-23. 

The measurements were performed using a Thermo Elemental IRIS Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES). A 2 kW crystal-controlled radio frequency (RF) generator operating at 27.12 MHz powers the plasma source. An Echelle optical system with a 381-mm focal length diffracts the light from the plasma source before it is focused onto the Charge Injected Device (CID) camera detector [4]. 

Figure 7.6 Schematic diagram of an emission spectrometer with an electrical discharge excitation source. The prism is meant only to illustrate a dispersive device a diffraction grating is used in all modem spectrometers with a single dispersive device. Echelle spectrometers use two dispersive devices, either a prism and a grating or two gratings.

PMTs and linear photodiode array detectors are discussed in detail in Chapter 5. This section will cover the 2D array detectors used in arc/spark and plasma emission spectrometers. In order to take advantage of the 2D dispersion of wavelengths from an Echelle spectrometer, a 2D detector is required. The detector should consist of multiple... 

A Charge-lnjectioii Device Instrumeat. A number of companies offer multichannel simultaneous spectrometers based on echelle spectrometers and two-dimensional array devices. This type of instrument has replaced other types of multichannel emission spectrometers in many applications. 

Several instrument manufacturers offer echelle-lype spectrometers for simultaneous determination of a multitude of elements by atomic emission spectroscopy. The optical designs of two of these instruments are shown in Figures 10-7,10-9, and 10-11. 

CCD detector consists of 224 linear photodetector arrays on a silicon chip with a surface area of 13 x 18 mm (Fig. 4.16). The array segments detect three or four analytical lines of high analytical sensitivity and large dynamic range and which are free from spectral interferences. Each subarray is comprised of pixels. The pixels are photosensitive areas of silicon and are positioned on the detector atx -y locations that correspond to the locations of the desired emission lines generated by an echelle spectrometer. The emission lines are detected by means of their location on the chip and more than one line may be measured simultaneously. The detector can then be electronically wiped clean and the next sample analysed. The advantages of such detectors are that they make available as many as ten lines per element, so lines which suffer from interferences can be identified and eliminated from the analysis. Compared with many PMTs, a CCD detector offers an improvement in quantum efficiency and a lower dark current. 

S. Euan, H. Pang and R. S. Houk, Application of generalized standard additions method to inductively coupled plasma atomic emission spectroscopy with an echelle spectrometer and segmented-array charge-coupled detectors, Spectrochim. Acta, Part B, 50(8), 1995, 791-801. 

Simultaneous Multielement Determinations by Atomic Absorption and Atomic Emission with a Computerized Echelle Spectrometer/Imaging Detector System... 

In the work reported here, the two-dimensional spectrum from the echelle spectrometer is displayed onto the active surface of a two-dimensional imaging detector that can monitor the different lines independently so that emission or absorption lines for multiple elements can be monitored simultaneously. 

These two-dimensional detectors [63] are ideally suited for coupling with an echelle spectrometer, which is state of the art in modem spectrometers for ICP atomic emission spectrometry as well as for atomic absorption spectrometers. As for CCDs the sensitivity is high and along with the signal-to-noise ratios achievable, they have become real alternatives to photomultipliers for optical atomic spectrometry (Table 3) and will replace them more and more. 

Figure 131 Emission lines of cadmium (X = 228.802 nm) and arsenic (X —228.812 nm) obtained by a plasma spectrometer equipped with a conventional (A) or echelle (B) monochromator...

The glow discharge (GD) is a reduced-pressure gas discharge generated between two electrodes in a tube filled with an inert gas such as argon. The sputtered atom cloud in a GD source consists of excited atoms, neutral atoms, and ions. The emission spectrum can be used for emission spectrometry in the technique of GD-OES, but the GD source can also be used for AAS, AFS, and MS. The source can be used with any of the types of spectrometers discussed for plasma emission sequential monochromator, Rowland circle polychromator, echelle spectrometer, or combination sequential-simultaneous designs. The detectors used are the same as described for plasma emission spectrometry PMTs, CCDs, or CIDs. 

Emission spectra measured using echelle spectrometer for the discharge ignited in Ar/C2H2 as well as in Ar/CH4 mixtures at different regions along the axis of tube indicates similar pattern. Measured spectra show characteristic emissions for the active sjjecies tike C, C2, CH, etc. which indicates the dissociation of precursors, and participation of hydrocarbon radicals in film deposition (figure 5). 

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