Low-resolution scans

Figure 9.6 (a) High-resolution and (b) low-resolution scanning electron micrographs... 

Figure 4 (a) Low-resolution scanning transmission electron microscopy (STEM) image of a thin sol-gel film (1 -2 layers) containing 5 nm CdSe NCs. The NCs appear in white, and the dark areas are pores, (h) Linear absorption (solid line) and PL (dashed line) spectra of as-prepared CdSe NCs (r = 2.5 nm) in a hexane solution (the arrow marks the lowest IS absorption resonance), (c) Absorption and PL spectra of the same NCs after their incorporation into titania... 

Particularly in quadrupole systems spectral interferences may limit the power of detection as well as the analytical accuracy. This is shown by a comparison of a high- and a low-resolution scan of a mass spectrum (Fig. 123) [609, 610], In the first scan (A), the signals of 56Fe2+, 28Si+, 12C160+ and 2N are clearly separated, which is not, however the case in the quadrupole mass spectra. In the latter scan, interferences can be recognized from comparisons of the isotopic abundances. Also physical means such as the use of neon as an alternative discharge gas [611] can be used to overcome the spectral interference problem. 

Figure 4 (a) Low-resolution scanning transmission eiectron micro-... 

The two predominant cleavage products occur at m/e 58, which corresponds to CH2N(CH3)2, and m/e 195, corresponding to the trimethoxybenzoyl moiety. Other characteristic masses appearing in the spectrum are m/e 330, which corresponds to the loss of CH2N(CH3)2 from the molecular ion, and m/e 317 corresponding to the loss of C HgN from the parent mass. The high resolution spectrum fully confirmed the results of the low resolution scan (5). 

Low resolution scans are certainly less sensitive to these form factors and provide extremely useful morphology information. 

X-ray photoelectron spectroscopy (XPS) XPS is a surface analysis technique that can be used to ascertain surface elemental composition and types of bonds present on the surface. It is also a straightforward, easy, and non-destructive characterization technique. In XPS, different scan resolutions lead to different information. On the one hand, a low-resolution scan can provide the percent of each element, as well as their atomic concentrations. On the other hand, a high-resolution scan can give the types of bonds and concentrations on the surface. Take carbon (Cis) as an example, its high resolution scans can be divided into four components peaks around 285.0, 286.5, 228.0, and 289.5 eV. These subpeaks are Cl (C-C or C-H), C2 (C-OH), C3 (O-C-O or C=0), and C4 (0-C=0), respectively. XPS has frequently been applied to confirm the chemical changes of polymer or fiber after treatment. In addition. XPS can be used to verify the occurrence of surface... 

Detailed vibronic structure is seen in the low-resolution scan of the ZEKE spectrum of benzene, recorded via the 6 vibrational level in the state of the neutral. Bands with fundamental frequencies characteristic of the and vibrational... 

Since interferogram data points are obtained at evenly spaced intervals, high-resolution scans require more data points and hence greater optical path differences than low-resolution scans. Thus there is a relationship between resolution and optical path difference as follows ... 

Recall that each high-resolution scan involves a larger optical path difference than each low-resolution scan. Literally, it takes more time to move the mirror a long distance than a short distance. As a result, high-resolution scans take more time than low-resolution scans, as summarized in Equation 2.14. 

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