Incident light effect

Figure Al.6.15. Schematic diagram, showing the time-energy uncertainty principle operative in resonance Raman scattering. If the incident light is detuned from resonance by an amount Aco, the effective lifetime on the excited-state is i 1/Aco (adapted from [15]).

Interference effects, which arise because of the extraordinary uniformity of thickness of the film over the spectrometer sample beam, superimposed on the absorption of incident light by parylene films, can be observed. Experimentally, a sinusoidal undulation of the baseline of the spectmm is seen, particularly in the spectral regions where there is Htde absorption by the sample. These so-called "interference fringe" excursions can amount to some... 

FTR is an effective method for film thickness measurement in mixed lubrication. If the strength of incident light is properly adjusted, the resolution of film thickness by the FTR method can be limited within 5 nm. Theoretically, if the typical height of the surface asperities is less than the penetrating depth, the FTR method can be successfully used. In the tests, it is found that if Ra is greater than 0.15 /rm, a con-... 

The comparison of the light effect on carotenoids in foods is very difficult to carry out because different foods with different isomer compositions are employed at the beginnings of experiments. The presence of large molecules offers some photoprotection to carotenoids in food systems, either by complexation with proteins as found in carrots or acting as a filter to reduce the light incidence. Different storage conditions are often found because different light intensities are used or sometimes they are not even reported and experiments are carried out under air, N2, or in a vacuum. 

Most dyes and pigments owe their colour to the selective absorption of incident light. In some compounds, colour can also be observed as a result of the emission of visible light of specific wavelengths. These compounds are referred to as luminescent. The most commonly encountered luminescent effects are fluorescence and phosphorescence. The transitions which can occur in a molecule exhibiting either fluorescence... 

Pearlescent pigments give rise to a white pearl effect often accompanied by a coloured iridescence. The most important pearlescent pigments consist of thin platelets of mica coated with titanium dioxide which partly reflect and partly transmit incident light. Simultaneous reflection from many layers of oriented platelets creates the sense of depth which is characteristic of pearlescent lustre and, where the particles are of an appropriate thickness, colours are produced by interference phenomena. Pearlescent pigments are used in automotive finishes, plastics and cosmetics. 

Finally, some liquid-crystalline elastomers exhibit interesting photonic effects [200,201]. Of particular importance are non-linear optical properties. These involve interactions of light with the elastomer in a way that some of the characteristics of the incident light change, specifically its phase or frequency (including frequency doubling or frequency mixing) [202,203]. 

The presence of mica in pearlescent pigments only partly accounts for the appearance of the pigment. A very thin layer of the inorganic oxide titanium dioxide (TiC>2) or iron oxide (Fe2C>3) or both is coated on the mica platelets. The various colors and pearlescent effects are created as light is both refracted and reflected from the titanium dioxide layers. The very thin platelets are highly reflective and transparent. With their plate-like shape, the platelets are easily oriented into parallel layers as the paint medium is applied. Some of the incident light is reflected... 

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