Light wavelengths

The primary photochemical act, subsequent to near-uv light (wavelengths <400 nm) absorption by Ti02 particles, is generation of electron—hole pairs where the separation (eq. 3) into conduction band electrons (e g ) and valence band holes (/lyB ) faciUtated by the electric field gradient in the space charge region. Chemically, the hole associated with valence band levels is constrained at... 

The existence of two separate but interacting photosystems in photosynthetic eukaryotes was demonstrated through analysis of the photochemical action spectrum of photosynthesis, in which the oxygen-evolving capacity as a function of light wavelength was determined (Figure 22.10). 

Molecules absorb light when the lights wavelength is just the right length to cause electrons in the molecule to vibrate in time with the light. The electrons resonate in the molecule. 

The a- and [3-isomers of endosulfan undergo photolysis in laboratory tests after irradiation in polar solvents and upon exposure to sunlight on plant leaves. The a-isomer also undergoes isomerization to the P-isomer, which is relatively more stable (Dureja and Mukerjee 1982). A photolytic half-life of about 7 days was reported for endosulfan by EPA (1982c). The primary photolysis product is endosulfan diol, which is subsequently photodegraded to endosulfan a-hydroxyether. Endosulfan sulfate is stable to direct photolysis at light wavelengths of >300 nm however, the compound reacts with hydroxy radicals, with an estimated atmospheric half-life of 1.23 hours (HSDB 1999). 

This process occurs only at the silver nanoparticles of which resonance wavelength is in accordance with the incident light wavelength. Therefore, size-specific dissolution is possible (processes bl-b3 in Figure 2). 

Figure 6. Difference extinction spectra of the silver nanoparticles on the rutile XiO2(100) single crystal after irradiation with monochromatic visible light (wavelength = 480 nm, light intensity 5.0mW cm , irradiation time = 30 min 550 nm, 5.0mW cm , 30min 600nm, 3.0mWcm , 60min (FWHM = lOmn)).

Fig. 3.11 Interstellar dust particles cause the extinction of starlight by the selective scattering of certain light wavelengths. Far IR is on the left, far UV on the right. Satellite data suggest that the extinction curve consists of three components ...

Ugnell H., Oberg P.A., The time variable photoplethysmographic signal. Its dependance on light wavelength and sample volume, Proc. SPIE vol.2331 89 (1994). 

Fig. 15.5 Cover penetration depth as a function of the effective refractive index. Using a substrate with RI less than the RI of the aqueous cover solution, the penetration depth into the aqueous cover can be tuned up to infinity. While using glass as a substrate with RI of 1.53 the probing depth has a maximum value around 180 nm, using a light wavelength of 633 nm...

Photolysis of nicotine (173) in the presence of oxygen and methylene blue with light wavelengths greater than 300 nm gave the pyrrolidone (174, 30%), nicotyrine (175, 23%) and TV-oxide (176, 7%). Under nitrogen, with eosin as photosensitizer, only nicotyrine (14%) was identified in the photodegraded mixture [112]. 

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