Near-field transmission spectra

Figure 3.3 Near-field transmission spectra and images of a single gold nanorod (length 510nm, diameter 20nm). The two transmission spectra were obtained at positions 1 and 2 indicated in the inset. Each image was obtained at the resonance peak wavelength. (Reproduced with permission from Royal Society of Chemist [10]).

Fig. 4.7 (a) Topography of a short gold nanorod (diameter 30 nm, length 180nm). (b) Near-field transmission spectrum taken at the cross point in (a). (c,d) Near-field transmission images taken at 532 and 780 nm, respectively. Scale bars 100nm... 

Fig. 4.8 (a) Near-field transmission spectrum of a long gold nanorod (diameter 20 nm, length 510 nm). Dotted lines indicate plasmon resonances, (b) Calculated density-of-states (DOS) spectrum of the gold nanorod... 

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... 

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... 

Figure 12 (A) A 3.1 x 3.1 pm shear force image of a thin polystyrene film deposited on a glass cover slip. The full-scale z-range is 62 nm. (B) Near-field IR transmission spectrum of a thin polystyrene film in the aromatic C-H stretching region. The inset is the laser output over the same spectral range in the absence of polystyrene absorption. Reproduced with permission of Stran-ick SJ, Richter LJ, Cavanagh RR and Michaels C, unpublished results.

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. 

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