Monochromator performance characteristics

As a result of these differences in dependence on source intensity, fluorescence methods are generally one to three orders of magnitude more sensitive than methods based on absorption. Mercury arc lamps, xenon arc lamps, xenon-mercury arc lamps, and lasers are typical fluorescence sources. Monochromators and transducers are typically similar to those used in absorption spectrophotometers, except that photomultipliers are invariably used in high-sensitivity spectrofluorometers. Fluorometers and spectrofluorometers vary widely in sophistication, performance characteristics, and cost, as do absorption spectrophotometers. Generally, fluorescence instruments are more expensive than absorption instruments of corresponding quality. 

TABLE 7 1 Comparison of Performance Characteristics ol a Cof>veniional and an Echeile Monochromator... 

As shown in Figure 7-20b, the IMirow prism, which permits more compact monochromator designs, is a 30° prism with a mirrored back. Refraction in this type of prism takes place twice at the same interface so that the performance characteristics are similar to those of a 60° prism in a Bunsen mount. 

The slits of a monochromator play an important role in determining the monochromator s performance characteristics and quality. Slit jaws are formed by carefully... 

As with X-ray fluorescence, the characteristic X rays are analysed using wavelength dispersive spectrometers (WDS) based on the selective reflection of radiation by a monochromator crystal. The related analytical performance levels are ... 

This experimental system has enabled us to perform picosecond timc-resolvcd x-ray diffraction experiments. One of the earliest experi-ments consist of a Ge (HI) crystal bent for maximum reflection of 8 keV x-ray photons, ilai to a sensitive double-crystal monochromator. The x-ray diffraction spectra are recorded before excitation. This diffraction exhibiu the normal diffraction pattern characteristic of this surface. In... 

On the other hand, those characteristics of the laser that are important for its applications in spectroscopy are treated in more detail. Examples are the frequency spectmm of different types of lasers, their linewidths, amplitude and frequency stability, tunability, and tuning ranges. The optical components such as mirrors, prisms, and gratings, and the experimental equipment of spectroscopy, for example, monochromators, interferometers, photon detectors, etc., are discussed extensively because detailed knowledge of modem spectroscopic equipment may be cmcial for the successfiil performance of an experiment. 

In order to better compare the performances of various Echelle monochromator and slit configurations Smith and Harnly [136] introduced the term intrinsic mass . After the fashion of characteristic mass, intrinsic mass is the analyte mass required to produce an integrated absorbance of 0.0044 s per picometer of spectral bandwidth, calculated from the wavelength-integrated absorbance A (over nsam pixels) and the spectral bandwidth AA ... 

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