Spectrometer general requirements

Electron spectrometers arc made up of components whose functions are analogous to those encountered in optical spectroscopic instruments. These components include (1) a source (2) a sample holder (3) an analyzer, which has the same function as a monochromator (4) a detector and (. ) a signal processor and readout. Figure 21-4 shows a typical arrangement of these components. Electron spectrometers generally require elaborate vacuum systems to reduce the pressure in all of the components to as low as lO" to 10 lorr. ... 

In principle, a resonance frequency or difference in frequencies can be employed to perform NMR thermometry. The accuracy of temperature measurement depends on the accuracy of the thermocouple (0.2°C) in the NMR spectrometer. Generally, a precision of better than 0.2°C has been reported with these NMR thermometry measurements. Individual calibration plots may not be required when using aqueous buffers. Proper calibration procedures should be adopted with nonaqueous buffers and in the presence of organic modifiers. 

Blood Gas Analysis Cell. The blood gases enter the mass spectrometer by permeation through a thin Teflon membrane enclosed in the blood gas cell (BGC). The design of the stirred BGC was determined by the following general requirements and constraints ... 

The use of cylindrical internal reflectance cells for HP-IR was pioneered by Moser and further modified by others.This method involves the use of an optically transparent internal reflectance crystal (typically ZnS, ZnSe, sapphire). Due to the inherently short path length, the method is not as sensitive as transmission-based IR, and a Fourier transform infrared (FTIR) spectrometer is therefore generally required. In addition, the type of crystal may need to be changed depending on the reaction of interest, as the optics may be corroded by some reagents or catalysts. However, as the path length is fixed regardless of conditions, it is much easier to quantify catalyst species, and unlike transmission systems the cells can also be used for the study of liquid-solid and gas-liquid-solid mixtures. ... 

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