626 Applications of Theory of Electrons to Phosphorescence. 



temperature at which the initial intensity of the phosphores- 

 cence will be a maximum, and another temperature, which 

 need not necessarily be the same as the first, at which the 

 decrense in intensity will be slowest. These conclusions are 

 confirmed by the experiments of Lenard and Klatt. 



An upper limit of temperature for the existence of the 

 phenomenon of phosphorescence may likewise be explained 

 by analogous considerations. A sudden elevation of the 

 temperature of a phosphorescent body excited at a rather low 

 temperature, will diminish the constant B and hence the- 

 intensity of the light ought to increase ; still another fact 

 confirmed by experience. 



The spectrum of extinction discovered by E. Becquerel 

 and studied by H. Becquerel, would be explained, according 

 to my theory, by the following considerations: — Experiments 

 on the ionization produced by bodies exposed to light, show 

 us that certain regions of the spectrum possess the power of 

 exciting secondary rays in a higher degree than other regions. 

 If then the luminophorous system of the phosphorescent body 

 increases its electronogenous properties in the infra-red region 

 of the spectrum, the excitation of the phosphorescent body by 

 the spectrum will accelerate the emission of the electrons of 

 the luminophorous system. Thus its energy will rapidly fall 

 beneath the critical value. 



Y. — According to my theory, the phosphorescence produced 

 by the cathode rays, discovered by Sir William Crookes, 

 would be a rather complex phenomenon. It would be due in 

 part to the electrons which come directly from the cathode 

 rays and traverse the luminophorous system, and in part to 

 the electrons which are emitted by the secondary rays. A 

 course of reasoning analogous to that given by Prof. J. J.. 

 Thomson to explain the two spectra of argon, permits me 

 likewise to explain certain peculiarities in the experiments, 

 particularly the differences in the phosphorescent spectra of 

 europium when it is diluted with lime, and with gadolinia. 



It is quite evident that an atom which is able to contain 

 several distinct luminophorous systems may present different 

 spectra when treated with the same solvent. 



It is impossible for me to mention in this note all the 

 phenomena of phosphorescence and fluorescence which con- 

 firm my theory. I do not think that it is complete, but I 

 believe it presents a good working hypothesis that might give 

 an impulse to investigations along these lines and serve as a 

 guide in new experimental researches. 



Physical Institute, 



Fribourg, Switzerland. 



