Enhanced reflection

Abstract The principles of coatings to either enhance reflectivity of mirrors or to enhance transmission of glass optics are described. Then the ion assisted deposition and ion beam sputtering techniques are addressed. Performances of these technique-sand their limitations are illustrated with the characteristics of the VIRGO mirrors coated at LMA. The importance of metrology is emphasized. 

Figure 17. Enhanced reflectance of an Al coating on a glass substrate, with one or several doublets of high Ti02) and low (Si02 or MgF2) index quarterwave layers.

The angle of incidence was 45°. At the clean sample surface a change in polarization of the probe pulse from p- to s-polarized led to a reduction in signal height due to enhanced reflection. No 2PPE signal was detected with s-polarization of the pump pulse since there was no component normal to the surface, i.e. parallel to the optical transition in the perylene chromophore [6] when oriented with the long axis perpendicular to the crystal surface (see Fig. 1). 

Figure 3. Rate constants of cis - -trans photoisomerization obtained from enhanced reflection measurements vs. surface pressure of mixed monolayers of the thioindigo TI and arachidic acid (AA), molar ratio TI AA = 1 3. Subphase bidistilled water, 22° C.

Figure 5. Enhanced reflection spectra of a monolayer of the diace-tylenecarboxylic acid DA before (curve 1) and after increasing exposure to UV radiation 5 min (2) 15 min (3) 30 min (4) 60 min (5) 90 min (6). Subphase 3x10- M CdCl2 and 5x10 M NaHCOj surface pressure 10 mN/m.

A hollow optical fiber (HOF) is a totally different type of optical fiber [42 16]. Figure 2.3A shows the structure of an HOF. An HOF is made of a glass tube with an inner coating of silver and a dielectric film, which enhances reflectivity. Matsuura et al. reported that the root mean square surface roughness of the silver film was 12 nm in their fabricated HOF [44]. 

Fig. 5. The reason why we considered that wedge-shaped contrast enhancement reflected a vascular lesion. We infused microspheres in the rat heart, and performed glomerular supervital staining with Alcian blue. In this rat, renal infarction was detected. This was the basis of the hypothesis that wedge-shaped lesions are related to vasoconstriction (p. 4)...

One other approach to metalated M21)-methyl corroles was reported by Johnson and coworkers in the early 1970s. In this instance, the A-methyl thiaph-lorin 2.206 was used as the starting material. It was heated in the presence of Pd(OAc)2 in acetic acid to give the metalated corrole derivative 2.233 directly (see Scheme 2.1.81). The rate of sulfur extrusion in the presence of the palladium(II) ions was found to be dramatically increased in comparison to that of the analogous metal-free system 2.206 or the N-unsubstituted thiaphlorins 2.102 (Scheme 2.1.22). It was proposed that this rate enhancement reflected the extra stabilization that... 

DMS reactions in the troposphere are believed to lead to enhanced reflectivity of marine clouds [171] and thus DMS emissions may have a cooling influence on the atmosphere. One of the best demonstrations of the link between the natural atmospheric sulfur cycle and the physical climate system are the observations that link the satellite derived stratus cloud optical depth and observed DMS derived cloud condensation nuclei (CCN) concentrations at Cape Grim, Australia [175]. Statistical evidence indicates that the optical depth of the clouds is correlated with the number of CCN in the atmosphere. Thus, any UV-related changes at the surface of the ocean that result in the alteration in DMS flux to the atmosphere and the subsequent formation of CCN would also alter the atmospheric radiation budget for the affected region. 

Let us next consider a metal hoUow-optical fiber with dielectric inner coating. When the coating thickness is properly designed, the dielectric layer enhances reflection in a specific wavelength range owing to the interference effect. Let us consider a metal surface coated with a dielectric film of thickness d as shown in Fig. 2. From Fresnel s formula, the reflection coefficient of the electric field on boundary I is expressed as... 

The nuclear Overhauser effect (NOE), caused by dipole-dipole crossrelaxation, has great potential in the elucidation of the molecular structure and conformation (Noggle and Shirmer, 1971 Hall and Sanders, 1980). A homonuclear NOE can theoretically be as large as 50%, but is usually much smaller, and depends on the inverse sixth power of the distance between the nuclei, so that the relative magnitudes of enhancements reflect the spatial relationships of the atoms involved. 

Emission spectra of the labeled melittin are shown in Fig. 9. Recall that only a small fraction of the melittin contains a NMA label. Hence, the emission spectra are mostly characteristic of tryptophan, with shoulders at 430 nm due to the NMA emission. In the presence of 2 M NaCl the NMA emission is enhanced, reflecting... 

During the last few years optical visualization techniques have also been introduced. Among them the total internal reflection fluorescence excitation (TIFR) microscopy [4] and optical interference-enhanced reflection microscopy [5] appear to be the most promising nonintrusive techniques. Their resolution, however, does not even approach the resolution of atomic force microscope and optical techniques may thus serve as an image survey of nanobubbles at 300 nm level (diameter) which is so far their resolution limit. 

X 10 " to 1,020-1,800 x 10 " esu). This substantial enhancement reflects a more efficient delocalization of the 7i-electron system in the closed forms favoring an efficient on/off switching of the NLO responses [71]. 

Calculations performed assuming the same contents in all tanks indicate that the reactivity of the tank next to the concrete reflector exceeds that of the other tanks. This is due to enhanced reflection of epithermal neutrons by the concrete. Solutions of U, which are more reactive in slab geometry than solutions of Pu or U, will only be placed into the new tanks located away from the concrete wall. (This prevents contamination of other tanks by radioactive decay daughters.) Calculations assuming that the two tanks closest to the wall are filled with Pu(N03)4 and that the two outer tanks are filled with U02(N03)2, yield keff = 0.8S8 0.006. This is about the same as when all tanks are Filled with Pu solution, and indicates that the reactivity of a polyethylene-reflected tank of solution docs not exceed the reactivity of a conciete-refleeted tank of Pu solution. Additional calculations show that the subcriticality of the four-tank grouping is not jeopardized by off-normal construction well beyond that to which control is readily achievable. 

The sharp onset of the very close near-field enhancement only at the shear-force distance indicates an abrupt start at a very close distance, and that is the reason why, despite the 1 pm wide illuminated area, a very good lateral optical resolution (<10nm) can be achieved with carefully pulled tips exhibiting around lOnm end radius. The enhanced reflection requires sharp tip radii of smaller than 20 mn. Blunt tips (e.g., etched ones with radii of 60 nm) or... 

Chemical contrast (imaging) Different sites on a surface provide different efficiencies of the enhanced reflection in the shear-force gap, giving the true optical contrast of the surface scan. 

Single-layer and multilayer coatings of oxides are also used to enhance reflectivity in the near IR. These coatings work because of optical interference effects and usually have a thickness about one-quarter of the wavelength of the radiation such that the primary wave reflected off the first interface is 180° out of phase with the secondary wave reflected from the second interface. The result is destructive interference of the two waves. Thin films of Ti02,... 

On enhanced images, FNH shows a homogeneous strong enhancement during arterial phase the degree of enhancement reflects the arterial hypervascularity and the homogeneous distribution is related to the uniform internal architecture of the tumor. The central scar, if present, remains hypodense during the arterial phase (Fig. 9.7a). 

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