Photochemistry Photochemistry In chemistry, chromism is a process that induces a reversible change in the colors of compounds. In most cases, chromism is based on a change in the electron states of molecules, especially the π- or d-electron state, so this phenomenon is induced by various external stimuli which can alter the electron density of substances. It is known that there are many natural compounds that have chromism, and many artificial compounds with specific chromism have been synthesized to date. ...more on Wikipedia about "Chromism"
(Intersystem crossing) A photophysical process. An isoenergetic non-radiative transition between two electronic states having different multiplicities. It often results in a vibrationally excited molecular entity in the lower electronic state, which then usually deactivates to its lowest vibrational level. ...more on Wikipedia about "Intersystem crossing"
In chemistry, photocatalysis is the acceleration of a photoreaction in the presence of a catalyst. In catalysed photolysis, light is absorbed by an adsorbed substrate. In photogenerated catalysis the photocatalytic activity (PCA) depends on the ability of the catalyst to create electron-hole pairs, which generate free radicals able to undergo secondary reactions. Its comprehension has been made possible ever since the discovery of water hydrolysis by means of the titanium oxide. ...more on Wikipedia about "Photocatalysis"
A photochemical reaction is a chemical reaction which is induced by light. ...more on Wikipedia about "Photochemical reaction"
Photochemistry is the study of the interaction of light and chemicals. ...more on Wikipedia about "Photochemistry"
(Photochromism) Reversible photochromics (PC's) work by changing their chemical structure after absorbing UV light, usually from the sun or a UV light. The UV light causes the PC’s to absorb color (like a dye), and then change back to clear when the UV source is removed. They can cycle thousands of times depending upon the application. They can also change from one color to a different color by combination with a permanent pigment. ...more on Wikipedia about "Photochromism"
Photoexcitation is the mechanism of electron excitation by photon absorption, when the energy of the photon is too low to cause photoionization. ...more on Wikipedia about "Photoexcitation"
Photolysis refers to any chemical reaction in which a compound is broken down by light. The direct process is defined as the interaction of one photon interacting with one target molecule. ...more on Wikipedia about "Photolysis"
The Quantum Yield of a radiation-induced process is the number of times that a defined event (usually a chemical reaction step) occurs per photon absorbed by the system. Thus, the Quantum Yield is a measure of the efficiency with which absorbed light produces some effect. ...more on Wikipedia about "Quantum yield"
Radiolysis is the dissociation of molecules by radiation. It is the cleavage of one or several chemical bonds resulting from exposure to high-energy flux. For example water dissociates under alpha radiation into hydrogen and oxygen. The chemistry of concentrated solutions under ionizing radiation is extremely complex. Radiolysis can locally modify redox conditions, and therefore the speciation and the solubility of the compounds. Pulse radiolysis is a recent method of initiating fast reactions to study reactions occurring on a timescale faster than approximately one ten-thousandths of a second, when simple mixing of reagents is too slow and other methods of initiating reactions have to be used. ...more on Wikipedia about "Radiolysis"
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