Emission of light, and

The three unimolecular physical processes that originate from SI are internal conversion to emission of lights and transformation of Sx into Tx. If IC occurs, the net change resulting from electronic excitation is heat transference to the solvent. The other two processes are considerably more interesting. 

In the final stages of the reaction, under favourable initial reaction conditions, a sudden temporsiry acceleration of the reaction is observed. This phenomenon, known as the pic d arret , was first observed by Lucquin in the low temperature slow oxidation of n-pentane [142] and subsequently in the high temperature oxidation of other hydrocarbons, e.g. refs. 143, 144. The pic d arret manifests itself as a sudden increase in the intensity (/) of the emission of light and as a peak on the recording of the derivative of the pressure change (IV) against time as shown in Fig. 15 [145]. 

Gravitational contraction of the stars causes increase of temperature associated with the emission of light and other kinds of electromagnetic radiation. 

The oxidation reactions of 2,4,5-triphenylimidazole (lophine) have received considerable attention. With chromic acid it gives benzamide and benzanilide, but even more interest has centred on its involvement in the phenomenon of chemiluminescence. Some of this material has been discussed earlier (Sections 4.06.3.6, 4.07.1.2.1 and 4.07.1.2.3). The oxidative decomposition of lophine in the presence of air is accompanied by the emission of light, and it is the excited singlet state of the diaroylarylamidine (12 Scheme 2) which is the light emitter. The radical (46) derived from oxidation of lophine with aqueous ferricyanide and ethanolic KOH forms a hydroperoxide with hydrogen peroxide with consequent luminescence. When 2,4,5-tri- and 1,2,4,5-tetra-phenylimidazoles are oxidized in dilute methanol solution in the presence of methylene blue, the dibenzoylbenzamidine is also formed under circumstances in which hydroperoxides cannot be intermediates (B-76MI40701). 

Descartes described the sunspots discovered by Galileo as an accumulation of coarse material, which could eventually prevent emission of light and collapse of the vortex into a planet, to be captured into a neighbouring stellar vortex. 

To identify a chemical reaction, determine whether one or more of the initial substances changed into a different substance. If so, a chemical reaction occurred. One or more of the following often accompanies a chemical reaction a color change the formation of a solid or precipitate the formahon of a gas the emission of light and the emission or absorption of heat. 

Herschel W (1801) Observations tending to investigate the nature of the Sun, in order to find the causes or symptoms of its variable emission of light and heat with remarks on the use that may possibly be drawn from solar observations. Phil Trans R Soc Lond 91 265-318... 

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