Sunlight, wavelength separation

A FIGURE 1.7 Wavelength separation of sunlight reveals absorptions at certain wavelengths. 

In the atmospheric gas phase the main reactive species are OH, N03, 03, and sunlight itself which can be involved in direct photolysis processes. In the latter case a sunlight-absorbing molecule reaches an electronically and vibra-tionally excited state after absorption of a photon of appropriate wavelength. The surplus energy can be dissipated by vibrational relaxation (i.e., thermally lost), fluorescence, phosphorescence, or chemical reactivity. The latter is often in the form of bond breaking (photolysis), induced by the excess of vibrational energy that can sometimes increase vibration amplitude beyond the threshold where the atoms involved in the bond (B and C in Equation 17.1) are permanently separated [7]. 

Table III lists the sunlight quantum yields determined In this manner for the six test compounds Quantum yields approach or exceed unity for several Indoles, Indicating that the photolysis rates used for the indoles Include an element of autocatalysis that Is difficult to separate from the overall process. The results show that Indoles are much more efficiently photolyzed than carbazole as evidenced by their higher quantum yields. In spite of their high quantum yields, the sunlight photolysis rates of Indoles are slower than those of carbazole. This result Is explained by the very weak absorbance of Indoles In the solar wavelength region as opposed to the strong absorbance of carbazole In this region.

White light is actually made from a bundle of colored components, which together blend into a white color. A rainbow occurs when sunlight passes via droplets of water, which refract (change direction) and reflect the light, such that its colored components separate according to their different wavelengths and thereby... 

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