Near-field absorption

Already, several plasmonic effects have been explored within the contexts of thin-film silicon, dye-sensitized, and organic solar cells. The phenomena that have been observed and exploited - principally near-field absorption and light scattering -are described below. Together, these findings suggest strategies for further efficiency enhancements in water photoelectrolysis. 

One interesting new field in the area of optical spectroscopy is near-field scaiming optical microscopy, a teclmique that allows for the imaging of surfaces down to sub-micron resolution and for the detection and characterization of single molecules [, M]- Wlien applied to the study of surfaces, this approach is capable of identifying individual adsorbates, as in the case of oxazine molecules dispersed on a polymer film, illustrated in figure Bl.22,11 [82], Absorption and emission spectra of individual molecules can be obtamed with this teclmique as well, and time-dependent measurements can be used to follow the dynamics of surface processes. 

A nano-light-source generated on the metallic nano-tip induces a variety of optical phenomena in a nano-volume. Hence, nano-analysis, nano-identification and nanoimaging are achieved by combining the near-field technique with many kinds of spectroscopy. The use of a metallic nano-tip applied to nanoscale spectroscopy, for example, Raman spectroscopy [9], two-photon fluorescence spectroscopy [13] and infrared absorption spectroscopy [14], was reported in 1999. We have incorporated Raman spectroscopy with tip-enhanced near-field microscopy for the direct observation of molecules. In this section, we will give a brief introduction to Raman spectroscopy and demonstrate our experimental nano-Raman spectroscopy and imaging results. Furthermore, we will describe the improvement of spatial resolution... 

Photoluminescence from gold nanoplates induced by near-field two-photon absorption. Appl. Phys. Lett., 88, 023104 (3 pages). 

Osawa, M., Surface enhanced infrared absorption, In Near Field Optics and Plasmon Polar itons Kawata, S., Ed. Springer, Berlin, 2001, 163 187... 

In short fiber composites, energy absorption mechanisms, such as interfacial debonding and matrix cracking, most often occur at the fiber ends (Curtis et al., 1978). The damage model proposed by Bader et al. (1979) assumes that short fiber composites fail over a critical cross-section which has been weakened by the accumulation of cracks, since the short fibers bridging this critical zone are unable to carry the load. In fatigue loading, sudden fracture takes place as a direct result from the far-field effect of the composite, rather than due to the near field of the crack tip... 

Plane34-38 and Schlafer37,39 have argued that the photochemistry initiated by irradiation of the ligand field absorption bands of chro-mium(III) complexes in aqueous solutions near room temperature can... 

To date, a number of chemically selective near-field imaging methods have been demonstrated. Near-field contrast mechanisms that rely on electronic spectroscopy (UV-visible absorption and fluorescence),204 vibrational spectroscopy (IR absorption and Raman spectroscopies), dielectric spectroscopy (microwave dispersion), and nonlinear spectroscopy (second harmonic generation) have all been demonstrated at length scales well below the diffraction limit of light. 

Some of the most useful polarization-dependent NSOM methods, however, involve modulation of the polarization from the probe (see Figure 3.20),224 coupled with synchronous detection of the near-field signals. Such methods allow for multiple imaging modalities so that topography, absorption dichroism, and/or birefringence information can all be readily obtained. 

According to the formula (7) absorption spectrum for conductivity electrons in bulk metal should be a smooth curve down to co->0. Ag film in the near UV range demonstrates spectrum of such type. Appearance of a near UV absorption peak in a spectrum of M nanocrystal is caused by the surface charges that resulted from displacement of conductivity electrons under action of an external field. These charges create in a nanocrystal the internal field directed against external one [16]. For conductivity electrons this internal field plays a role of quasi-elastic bonds between valent electrons and cations in a crystal lattice. 

The Visible and Near Infrared Absorption Spectra of Some Trivalent Actinide and Lanthanide Elements in DCIO4 and in Molten Salts, W.T. Camall and P.R. Fields, Developments in Applied Spectroscopy 1, 233-247 (1962). 

Hazard-zone reduction can also be achieved by reducing the source emission strength using mass transfer, that is, chemical reaction and/or absorption. While dilution is effective in reducing near-field hazards, reducing source strength can be effective in reducing far-field hazards caused by toxic materials. 

Figure 18 contains the increase of the spin temperature Ts due to resonant absorptions and a nearly-field independent increase of Ts. Before going into a deeper discussion, we show in Fig. 19 the experimental confirmation of the linear evolution of the resonant field with frequency v = yBv as predicted from the inset of Fig. 17. The measured slope dWdS =yw 28.3 GHz/T yields a gyromagnetic ratio g-lhylfiB 2.02, a value close to the one obtained by Ajiro et al. [68] in single-crystal EPR measurements at 2.4 K (g 1.98).

Figure 20. Examples of the field dependence of Flts. The curves are obtained from the measured magnetization curves and Eq, 9, at 6 and 14 GHz, after subtraction of the nearly field independent non-resonant absorption background. The dots represent the fit of these curves using Eqs. 8 and 10 (Gaussian distributions) yielding

Spectroscopic studies of Co (II) derivatives of stellacyanin, plastocyanin, and azurin have established that the charge transfer interpretation is preferred (10, 11). Intense bands (c 2 X 103) that appear to be analogous to the 600-nm system of blue proteins are observed between 300 and 350 nm in the Co (II) derivatives. The shift in band position of about 16 kK [Cu(II) << Co (II)] accords well with expectation for an LMCT transition. The visible and near-infrared absorption, CD, and MCD spectra of Co (II) derivatives of stellacyanin, plastocyanin, and azurin have been interpreted (12) successfully in terms of the d-d transitions expected for distorted tetrahedral metal centers (Table I). Average ligand field parameters are the same for all three Co (II) proteins (Dq = 490, B = 730 cm"1), which strongly suggests that the donor atom... 

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