Near-Field Transmission Measurements

In far-fleld measurements, the transmission spectrum is defined as the intensity spectrum for the sample /(A) divided by the intensity spectrum of the reference 7o(A). Instead, the near-held transmission spectrum is obtained by (7-/o)//o, where 7 and lo represent the intensity spectrum taken at the sample locahon and that at the bare substrate, respectively. 

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Near-Field Transmission Measurement of Spherical Gold Nanoparticles [67]... 

The resonance energy and the wave vector of the plasmon can be obtained from the extinction peak wavelength of the transmission spectrum and the spatial oscillation period of the image of the nanorod, respectively. By plotting the wave vector of the plasmon vs. the resonance photon energy, the dispersion relation of the plasmon in the nanorod can be determined. Figure 4.10 shows the dispersion relation determined from near-field transmission measurements of various nanorods with... 

We usually use white light from a Xe discharge arc lamp for the measurement of near-field transmission images and spectra [9]. The spectrum of transmitted light... 

Imura, K and Okamoto, H. (2006) Redprodty in scanning near-field optical microscopy illumination and collection modes of transmission measurements. Opt. Lett., 31, 1474-1476. 

The use of electrically conductive diamond as an optically transparent electrode is a new field of research [50,52,117,118]. Diamond possesses attractive qualities as both an electrode and an optically transparent material, making it an obvious choice for use as an OTE in spectroelectro-chemical measurements. Diamond OTEs exhibit several technologically useful properties (1) the possibility of transmission measurements from the near-UV to the far-IR (0.225-100 pm) (2) low background current (3) wide working potential window (4) good responsiveness for many... 

We wrote earlier that the use of an aperture for SNOM was essentially precluded because of the extremely low transmission of narrow metalized glass fibers caused by the waveguide cutoff effect. Several workers recognized the potential of achieving better resolution by using a small scatterer instead of a small aperture [12-16] because an illuminated particle can exhibit enhanced optical fields in its neighborhood that is in turn modified by the presence of a sample. As a result of this near-field interaction, scattered light that is measured in the far field contains... 

Makela et al. [875] carried out detailed studies of the EMI-SE properties of 1 to 30 /im thick camphor-sulfonic-acid-doped P(ANi) films having conductivities in the 10 to 100 S/cm region. Measurements were carried out in the near-field with a dual chamber, and in the far-field using a transmission line method, in 0.1 MHz to 1 GHz region. A strong correlation with surface film resistivity was found. Multi-layered structures were found to enhance shielding considerably, up to 40 dB at 100 MHz to 1 GHz. Fig. 19-3 summarizes some of their results in the near and far field. 

The vibrational spectrum of benzene around 1000 cnf has also been measured. IQ. Benzene was physisorbed on a cooled copper substrate in the vacuum chamber. Figure 19 shows the transmission for several thicknesses of benzene and a prism separation of 3 cm. The thickness was determined from the measured transmission in transparent regions using Eg. (7). The solid curves were calculated from Eqs. (5) and (6) using optical constants for benzene obtained from an ordinary transmission experiment.il The benzene film was assumed to be isotropic. Of the two absorption lines seen, one belongs to an in-plane vibrational mode, and one to an out-of-plane vibration. Since the electric field of the SEW is primarily perpendicular to the surface, the benzene molecules are clearly not all parallel or all perpendicular to the copper surface. Also it should be noted that the frequencies are the same (within the experimental resolution) as those of solid benzene22 and of nearly the same width. These features indicate that the benzene interacts only weakly with the copper surface, as would be expected for physisorbed molecules. 

Until 1979, there was no evidence associating extremely low frequency (ELF) EMFs with cancer. That year, Wertheimer and Leeper reported a substantial excess of high-current electrical wiring configurations near the homes of children in Denver, Colorado, who had died of brain cancer and leukemia. This association was not based on actual measurements of ELF fields, but rather, wiring codes were used as a surrogate indicator of magnetic fields from the power transmissions lines and lines... 

Herres [182] has described a comparison of various spectroscopic methods (ATR-FTIR, PA-FTIR and LR-NMR) for the quantitation of plasticiser concentration in 0.2 mm thick PVC containing 9 wt.% Ti02 and 15-20 wt.% plasticiser. Sample sizes were in the range of g (LR-NMR), 100 mg (ATR-FTIR) and 5 mg (PA-FTIR). Quantitative analysis in normal transmission IR is limited for highly filled materials. For those cases the surface techniques ATR-FTIR and PA-FTIR may be applied. These FTIR methods yield information about migration and accumulation of low-MW species near the surface. ATR spectroscopy is well suited for quantitative analysis provided contact between the specimen and ATR crystal is reproducible. PA-FTIR samples some 8-15 /xm, Le. considerably more than the ATR technique (<2 /xm). The indirect detection method of PAS does not reach the sensitivity of normal FTIR measurements. Quantitative analysis of plasticisers in polymers by means of LR-NMR uses the fact that relaxation of protons in a magnetic field depends on the molecular environment. As shown in Table 6.38, LR-NMR is most precise and fast (0.5 min) in comparison to ATR-FTIR (2 min) and PA-FTIR (5 min). 

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