Depth resolution description

Raman spectroscopy is one of the most versatile spectroscopies for the characterization of solid catalyst surfaces and of surface species under reaction conditions. Banares and Mestl provide an in-depth description of catalytic reaction cells that allow recording of Raman spectra simultaneously with measurements of catalytic activities and selectivities. The authors discuss the advanced modem equipment and methodologies that permit the detection of Raman spectra at elevated pressures and temperatures (>1270 K) with good time resolution and spatial resolution (Raman microscopy). Measurements can be made during catalyst... 

Resolution the ratio m/Sm where m and m + Sm are the relative masses of the two ions that yield neighbouring peaks with a valley depth x % of the weakest peak s intensity. In the commercial description of mass spectrometers, x = 50 is normally used. However, 10 % valley has been largely used in the past. Another definition entails using for Sm the width of an isolated peak at x % of its maximum. 

If an analytical tree is not used, in addition to defining the system and clarifying the scope in terms of breadth (limits of resolution) and depth (indenture levels), a block diagram or other project description document may be required. 

Reflection of X-rays and neutrons from a surface responds to the variation of electron density and scattering-length density, respectively. Penetration depths can be several thousand angstroms and resolution 10A. Hence, in principle these techniques should be ideal for providing information on the nature, composition and size of polymer surfaces and interfaces. However, a direct description of the surface is not provided the predictions of a model have to be compared with literature data, and in many cases finding a unique solution may be difficult. Only neutron reflectometry is dealt with here, since this has been applied to a wider range of polymer systems than X-ray reflectometry. 

Several modes of operation are available in state-of-the-art confocal Raman microspectroscopy, including the measurement of samples with a spatial resolution of less than 1 pm, depth profiling, and line mapping. LaPlant and Ben-Amotz have given a detailed description of the design and construction of a confocal Raman microspectrometer [34] and a number of instruments are available commercially. 

However, this description omits some important limitations to the uses of ultrasound. Image quality is affected by body habitus, slim patients giving the best images because resolution deteriorates with depth as... 

These terms represent a bulk effect, a classical surface potential effect, and a surface field effect, respectively. Selection rules are stated through which these various contributions to the net photocurrent can be resolved. A complete theoretical description of photoemission, therefore, will enable resolution of each of these components as functions of the angles and j8), the available light intensity with depth, and the substrate epitaxy. This theory is discussed in detail in Ref. 51 note also Chapters 4 and 6 in this book. 

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