Optical reflectivity

The construction of a typical monochromator is shown in Figure 10.12. Radiation from the source enters the monochromator through an entrance slit. The radiation is collected by a collimating mirror, which reflects a parallel beam of radiation to a diffraction grating. The diffraction grating is an optically reflecting surface with... 

The other major source of noise is vibration from the environment. The entire measuring system is, of course, mounted on appropriate rubber isolation pads. However, these are not adequate for the level of accuracy required. The residual vibration is eliminated from the signal by mounting the lower part of the optical reflection system on a spring which is driven by servo electronics that detects its movement. An effective free period for the spring of up to 60 s can be achieved in this way, and virtually all environmental vibration is eliminated from the measured signal. 

FIG. 3. Absolute atomic concentrations in units of 10 al./cm. determined by ERD. RBS, and optical reflection and transmission spectroscopy, of (a) hydrogen, (b) carbon, and (c) silicon as a function of the carbon fraction. v. Results are presented for the series ASTI (filled circles), AST2 (filled triangles), ATLl (open circles), and ATL2 (open triangles). (From R. A. C. M. M. van Swaaij. Ph.D. Thesis, Universiteit Utrecht. Utrecht, the Netherlands, 1994. with permission.)... 

The charge transport and optical properties of the [Si(Pc)0]-(tos)y)n materials as y=0 -+ 0.67 are reminiscent of the [Si(Pc)0]-(BF4)y)n system, but with some noteworthy differences. Again there is an insulator-to-metal transition in the thermoelectric power near y 0.15-0.20. Beyond this doping stoichiometry, the tosylates also show a continuous evolution through a metallic phase with decreasing band-filling. However, the transition seems somewhat smoother than in the BF4 system for y)>0.40, possibly a consequence of a more disordered tosylate crystal structure. Both [Si(Pc)0]-(tos)y)n optical reflectance spectra and four-probe conductivities are also consistent with a transition to a metal at y 0.15-0.20. Repeated electrochemical cycling leads to considerably more decomposition than in the tetrafluoroborate system. 

Si(Pc)0] (S04)o.09)n> i-s limited by the oxidative stability of the sulfate anion. Thermoelectric power, optical reflectivity, magnetic susceptibility, and four-probe electrical conductivity measurements evidence behavior typical of an [Si(PcP+)0]n compound where p 0.20. That is, there is no evidence that the more concentrated counterion charge has induced significant localization of the band structure. 

Ahmad M., Narayanaswamy R., Fibre Optic Reflectance Sensor for the Determination of Aluminium (III) in Aqueous Environment, Anal. Chim. Acta 1994 291 255-260. 

See, for example, Philpott, M. R. "Optical Reflection Spectroscopy of Organic Solids," Ann Rev. Phys. Chem. 1980, 31,... 

In ideal situations, optical spectroscopy as a function of temperature for single crystals is employed to obtain the electronic spectrum of a SCO compound. Knowledge of positions and intensities of optical transitions is desirable and sometimes essential for LIESST experiments, particularly if optical measurements are applied to obtain relaxation kinetics (see Chap. 17). In many instances, however, it has been demonstrated that measurement of optical reflectivity suffices to study photo-excitation and relaxation of LIESST states in polycrystalline SCO compounds (cf. Chap. 18). 

The spin crossover characteristics of the corresponding Fe(II) compounds may be fine tuned by the systematic variation of the substituent at N-4 of the 1,2,4-triazole ring, as well as by changing the non-coordinated anionic groups. In this way, thermochromic Fe(II) materials showing a spin transition close to room temperature and accompanied by hysteresis have been obtained. As an example, the optical reflectivity measurements record-... 

Fig. 4 Optical reflectivity measurement (intensity vs temperature recorded at 1 K min-1) for [Fe(4-amino-1,2,4-triazole)3] (2-naphthalene sulfonate)2.xH20 (x=0, 2) ([31] (reproduced with permission of the Royal Society of Chemistry)...

Illumination is a relevant parameter in the electrochemistry of silicon because photogenerated carriers may initiate or contribute to the charge exchange at the electrolyte-silicon interface. If an electrode is illuminated, photogenerated electron-hole pairs are generated corresponding to the number of absorbed photons. This number depends on spectral distribution, total illumination intensity and losses due to optical reflection and transmission. The number of electron-hole... 

OP nickel complexes, 34 259 Optical reflectance spectroscopy, 34 277 Optical spectroscopy, 31 79-89, 259-261 Optical yields... 

J.H. Cho, P.J. Gemperline, P.K. Aldridge, S.S. Sekulic, Effective mass sampled by NIR fiber-optic reflectance probes in blending processes. Anal Chim. Acta, 348, 303-310 (1997). 

Optical reflection from a monomolecular film must be measured from the interface with a very small amount of material present. Therefore, in these methods, repeated interaction of the light beam with one or more identical films is generally employed. The simplest way to observe a light beam that has passed through several identical monolayers is to transfer portions of the layer to suitable transfer end plates, which are then stacked and examined in a conventional spectrophotometer. This method was used where monolayers of chlorophyll were deposited on glass slides by the LB method. Ferrodoxin and chlorophyll monolayers were investigated by measuring the spectra (550-750 nm) of these films at the interface. 

Carbon - The aerosol collected on the Tissuequartz filters was analyzed for total carbon by the nondestructive technique of proton-induced gamma-ray emissions (17) and graphitic carbon (soot) by calibrated optical reflectance at Washington University, St. Louis, Missouri. The estimated error in measurement of total carbon per filter was 5 yg or 20%, whichever was greater. The estimated error for soot was lyg or 20%, whichever was greater. 

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