Irradiation optical properties

Several gemstone species occur in various colors, depending on the presence of impurities or irradiation-induced color centers. Examples are the beryl, comndum, and quart2 families. Quart2 has poor optical properties (RI = 1.55, DISP = 0.013), but becomes of gemological interest when it exhibits attractive colors. Any material can have its color modified by the addition of various impurities synthetic mby, sapphires, and spinel are produced commercially in over 100 colors (2). Synthetic cubic 2irconia has been made in essentially all colors of the spectmm (11), but only the colorless diamond imitation is produced commercially in any quantity. 

Thus, the process of PAN transformation under the effect of IR radiation proceeds with considerable self-acceleration. The irradiation of uniaxially oriented PAN films gives a polymer with a distinct anisotropy of optical properties, dichroism in the visible spectral region in particular. Figure 8 presents dichroism curves [D =/(X)] at various angles (ip) between the polarization plane and the orientation axis. The same figure shows the dependence D =f(uniaxially oriented film. 

The term nonlinear optical property refers to an optical property, which can be modified by exposing the material to intense light irradiation. In this section, we focus on the cascaded first- (/ 1 ) and third-order ( / ) susceptibilities describing nonlinear absorption (ESA and 2PA) and nonlinear refraction (n2) processes. Z-scan, pump-probe, and two-photon upconverted fluorescence techniques are among the most used experimental methods for determining optical nonlinearities. 

Optical properties of dendrimers bearing eight chromophores have been examined by single molecule spectroscopy techniques. It is especially exciting that variations in the spectra are recorded if one of these dendrimers is observed for a period of time under continuous irradiation.1481 The fluorescence intensity of the dendrimer nanoparticle also jumps between discrete emissive levels. All these findings suggest the existence of strong electronic interactions between several perylene imide chromophores within one dendrimer and provide new... 

SnC>2 nanoparticles have been successfully synthesized by chemical co-precipitation method using ethanol, acetone, tetrahydrofuran (THF) and ether as solvents. X-ray Diffraction (XRD), Field Emission Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM) have been used to study the crystallographic and morphological properties of synthesized SnC>2 nanoparticles, while their optical properties have been studied by UV-Visible absorption spectroscopy. UV-Vis absorption spectra shows a weak quantum confinement in all the synthesized SnCL samples. The photo-catalytic activity of as-synthesized SnC>2 nanoparticles under UV irradiation has been evaluated using Methylene Blue (MB) dye as a test contaminant in water. The results showed that solvents played a key role to control the morphology and photo-catalytic activity of SnCE nanoparticles. 

Nonhnear absorption is the key mechanism responsible for 3D structuring of materials, including photoresists and photosensitive resins. Optical nonhn-earities take place when intensity of the irradiating electrical approaches that of molecular couphng, which occurs at the levels of approximately 10 ° V/m or 100 GW/cm. Detailed description of optical properties of polymers can be foimd in the literature [8]. Among the optical nonhnearities, multipho-... 

Rare earth doped alkali sulphates are of interest because of their optical properties. EPR spectra of y-irradiated Ce and Ce-U doped KjNa(S04)2 exhibited signals characteristic of a S04T SOjT radical pair.34 The dipolar splitting (32 G) corresponds to r = 9.8 A. The radical pairs create deep traps, apparently assisted by dopants. 

According to Patry [22] fulminate darkens under the influence of irradiation by a mercury arc. After a month test samples become almost black and the mercury content increases from 70.8 to 71.3. As on heating, the crystalline structure remains unchanged but the optical properties of the crystals undergo alteration. 

The more recent expts involving UV and X-ray irradiations were performed by Wiegand (Ref 226) who determined the changes in the optical properties of Pb and thallous azides. The same type of extinction due to colloidal metal was caused by both types of radiation and is increased in magnitude with decreasing wavelength to the band edge... 

Rodriguez-Zuniga, U. F., Milori, D. M. B. P., da Silva, W.T. L., Martin-Neto, L., Oliveira, L. C., and Rocha, J. C. (2008). Changes in optical properties caused by UV-irradiation of aquatic humic substances from the Amazon River basin Seasonal variability evaluation. Environ. Sci. Technol. 42(6), 1948-1953. 

The coloration and bleaching processes consist of irradiation with UV light and a 632.8-nm laser, respectively. After five hundred written-erased cycles on the photochromic disk sample, there was no change that could be observed in the photosensitivity and other properties of the disk. The sample was stored at ambient conditions for over 5 years with its optical properties well preserved. 

Irradiation of the crystal by electrons or neutrons is the simplest way of introducing the defects by controlled means. Optical properties of organic conductors are sensitive to changes in the electron distribution induced by irradiation defects (i.e., their spectra are sensitive to the localization of the carriers, due to random potentials in the environment of the defects). The electronic absorption spectra give information on the density of charge carriers and their localizations as well as on the electronic energy levels. 

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