Selected Topics in the Field of Luminescence: Report of the National Research Council. Committee on Luminescence

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National research council of the National academy of sciences, 1923 - 126 pages

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Page 6 - This paper is as important in the history of the theory of luminescence as was the work of Stokes or of Becquerel in the experimental study of the subject. in the Wiedemann theory as a chemical reaction in the ordinary sense. It seems not unlikely that we must admit the existence of several distinct types of luminescence, in some of which the phenomena are explainable in terms of electron dissociation alone, while in others chemical changes form the predominate factor. Experiments made with excitation...
Page 70 - ... In some cases, eg, calcite and the uranyl salts, the vanishing type of decay is shown with excitation by light and the persistent type when the same substance is excited by cathode rays. (1097; B 28, IV.) Among the cases studied by Lenard and Hausser there are a few where the linear relation holds throughout the greater part of the decay, but in the majority of cases the law is not even approximately correct. which electrons recombine with the active centers; and (2) that this rate of recombinations...
Page 5 - But if the temperature is raised, it becomes possible for the stored energy to be liberated and thermo-luminescence is observed. While the fundamental conception of the Wiedemann theory has been retained, it has been customary in recent years to make the hypothesis more definite by assuming that the change referred to as the reaction A to B consists in the expulsion of an electron from a molecule of the active substance, while the recombination of the ions thus formed constitutes the reverse reaction...
Page 25 - The formation in the light of dianthracene from anthracene with the slow reverse reaction in the dark (v' present in the temperature radiation) is given as another illustration. It should be pointed out that in both of these cases the experimental evidence is not complete, since the emission of radiation of frequency v during the reverse reaction has not been demonstrated. Thermo-luminescence is regarded by Perrin as an instance of the reversal of the photo-reaction due to excitation, the radiation...
Page 7 - ... been greatly extended and modified in its details as the result of the later investigations of Lenard and his co-workers. In the artificial preparation of phosphorescent substances the essential thing seems to be the bringing into intimate association of a small amount of one substance usually called the active substance and a large amount of some other substance, the latter acting as the solvent in the resulting solid solution. Wiedemann and Schmidt have accomplished this by evaporating...
Page 47 - ... materials will become luminescent under the action of the hydrogen flame which are capable of the proper sort of rapid reduction and subsequent oxidation already described and that the active range of temperatures in each case is that within which the above reaction occurs. SUMMARY AND CONCLUSIONS. 1. Flame excitation occurs when certain substances are brought into the zone of a hydrogen flame between the regions of reduction and oxidation. 2. It occurs, so far as known, in certain oxides and...
Page 116 - Sci. 3: 15-16. C. A. 11: 998 and 12:391. 1045. Bioluminescence, IV., V. and VI. Amer. J. Physiology 42: 318-341, 342-348, 349-358. CA 11: 1212. 1046. What Substance is the Source of the Light in the Firefly? Science 46: 241-243. C. A. 11:3059. 1047. Chemistry of Light Production in Luminous Organisms. Carnegie Irat.

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