Backscattering measurement

We have already discussed a number of applications of the SEM to materials characterization topographical (SE) imaging, Energy-Dispersive X-Ray analysis (EDS) and the use of backscattering measurements to determine the composition of binary alloy systems. We now shall briefly discuss applications that are, in part, spe-... 

Because of the complexity of sample preparation, backscatter measurement geometry (see Fig. 3.19) is the choice for an in situ planetary Mossbauer instrument [36, 47 9]. No sample preparation is required, because the instmment is simply presented to the sample for analysis. On MER, the MIMOS II SH is mounted on a robotic arm that places it in physical contact with the analysis target (e.g., rock or soil) [36, 37]. 

Saunders, M. J., 1970. Near-field backscattering measurements from a microscopic water droplet, J. Opt. Soc. Am., 60, 1359-1365. 

Best results are obtained when spatial variation is maximized. For that reason the recovered contrast is over 140 1 when the image reconstruction is based on transmission measurements, but only about 1.4 1 for contrast based on backscattered measurements. It is likely that even better results would be obtained in both image-guided Raman spectroscopy and Raman tomography if illumination and collection fibers were placed strategically around the specimen. 

Fig. 5.2. Cross section of the reconstructed image-guided Raman spectroscopic estimates of bone distribution using (a) backscattered collection using a ring/disk fiber optic probe and (b) transmission measurements using a rectangular array of collection fibers. The contrast between the bone and background from skin and tendons was more than 100-fold greater in the transmission measurements used than in the backscattered measurements (reprinted with permission from [26]. Copyright 2008 Optical Society of America)...

Sirotyuk (ref. 25) found that the complete removal of solid particles from a sample of water increased the tensile strength by at most 30 percent, indicating that most of the gas nuclei present in high purity water are not associated with solid particles. Bernd (ref. 15,16) observed that gas phases stabilized in crevices are not usually truly stable, but instead tend to dissolve slowly. This instability is due to imperfections in the geometry of the liquid/gas interface, which is almost never exactly flat (ref. 114). Medwin (ref. 31,32) attributed the excess ultrasonic attenuation and backscatter measured in his ocean experiments to free microbubbles rather than to particulate bodies this distinction was based on the fact that marine microbubbles in resonance, but prior to ultrasonic cavitation (ref. 4), have acoustical scattering and absorption cross sections that are several orders of magnitude greater than those of particulate bodies (see Section 1.1.2). 

Raman backscattering measurements were performed in the wave number range between 200 and 4300 cm. Besides the well known phonon modes that are located between 200 and 800 cm additional lines were observed at wave numbers ranging from 2800 to 3150 cm" (see spectrum (a) in Fig. 1). At higher wave numbers Raman lines were not observed. 

In summary, Raman backscattering measurements showed the presence of C-Hx and N-H local vibrational modes in single crystal ZnO. Heating the specimens to temperatures of up to 950 °C caused hydrogen out diffusion. After dehydrogenation the local vibrational modes disappeared indicating that they are related to the presence of H. From H effusion measurements the... 

Figure 3.6-9 Modification of the pulsed CARS set-up shown in Fig. 3.6-8 for backscattering measurements. Shown is only the modified sample area (Weippert et al., 1993).

Another big step ahead was the employment of the 180 ° configuration (see Sec. 6.3.3.2.2), enhancing sensitivity and therefore even allowing weakly scattering substances in aqueous solution to be measured (Hecht et al., 1989) Fig. 6.3-11 shows the optical arrangement of a ROA instrument employed for backscattering measurements (redrawn from Barron et al., 1992). 

Togkalidou, T. Tung, H.-H. Sun, Y. Andrews, A.T. Braatz, R.D. Parameter estimation and optimization of a loosely bound aggregating pharmaceutical crystallization using in situ infrared and laser backscattering measurements. Ind. Eng. Chem. Res. 2004, 43 (19), 6168-6181. 

During the two SIR-C/X-SAR missions in April and October, 1994, radar backscatter measurements were carried out with a 5-frequency/multi-polarisation scatterometer flown on a helicopter. This scatterometer, called HELISCAT, works at 1.25, 2.4, 5.3, 10.0, and 15.0 GHz (L-, S-, C-, X-, and Ku-band, respectively) and is capable of performing radar backscatter measurements at different incidence angles. 

In order to complement the results of the radar backscatter measurements on the open sea, laboratory measurements of the wave amplitude and slope and of the radar backscatter at X- and Ka-band were carried out in a wind-wave tank with mechanically generated gravity waves as well as with wind-generated waves on a slick-free and a slick-covered water surface. In this paper, we concentrate on the results of the radar measurements with wind-generated waves. For a full description of the obtained results the reader is referred to Gade et al. (1998c). 

Gas bubble formation and blistering effects have been widely observed in high-dose implantations of inert-gas ions. Backscattering measurements of depth distributions often show very low concentrations of implanted species in the nearsurface region. This indicates that the inert-gas atoms can escape from the material even without sputtering. In these cases, the simple model described in the previous sections does not apply. 

Ni forms a silicide and a carbide. Pai et al [98] performed MeV ion backscattering measurements for Ni vapour-deposited on chemically cleaned SiC substrates of unspecified lattice type. A Ni-rich silicide phase is observed after a 500 °C anneal which, at higher temperature, tends toward Ni2Si. By contrast, NiSi2 is the stable phase formed for Ni on bulk... 

Channelling only requires a goniometer to include the effect in the battery of MeV ion beam analysis techniques. It is not as commonly used as the conventional backscattering measurements because the lattice location of implanted atoms and the annealing characteristics of ion implanted materials is now reasonably well established [18]. Channelling is used to analyse epitaxial layers, but even then transmission electron microscopy is used to characterize the defects. 

As mentioned above, a more direct way of measuring particle orientation results from active, i.e. from lidar and radar based backscattering measurements. Figure 9 shows the size-distribution-averaged phase matrix elements at a visible non-absorbing wavelength in the backscattering direction as a... 

Pulse oximeter sensors consist of a pair of small and inexpensive red and infrared LEDs and a single, highly sensitive, silicon photodetector. These components are mounted inside a reusable rigid spring-loaded clip, a flexible probe, or a disposable adhesive wrap (Figure 6.6). The majority of the commercially available sensors are of the transmittance type in which the pulsatile arterial bed, for example, ear lobe, fingertip, or toe, is positioned between the LEDs and the photodetector. Other probes are available for reflectance (backscatter) measurement where both the LEDs and photodetectors are mounted side-by-side facing the skin [7,8]. 

Remarks on the Deconvolution of Multi-Wavelength Backscattering Measurements... 

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