308 Mr. S. I. Vavilov on Dependence of the Intensity of ' 



the most probable supposition that such secondary processes 

 as fluorescence and photochemical effect are conditioned 

 exclusively by the intrinsic energy of the resonator and its 

 constant mechanism, the value of k must be constant for the 

 whole region of absorption : i. e., for a physically simple 

 absorption-band. Such a conclusion is maintained by the 

 old resonance theory of fluorescence of Lommel * and the 

 modern theories which consider this phenomenon as a tertiary 

 process of lighting which accompanies this or that process of 

 dissociation of molecules t- A somewhat different result is 

 given by the theory of Einstein, which will be mentioned 

 later on. 



From our standpoint, the inconstancy of k inside an ab- 

 sorption-band is an indication of its physical complexity. 

 Such a band is a result of a superposition of several bands 

 belonging to resonators of different types : i. e., with a 

 different k. 



The classical theory of dispersion and absorption in all its 

 modifications is forced to apply broadly the sign X in the 

 explanation of absorption- and dispersion-bands of liquid and 

 solid bodies J, which allows us to introduce any number of 

 new empirical constants. The liberty in this operation is 

 practically unlimited. It is essential that none of the expe- 

 rimental curves can be considered from this standpoint as a 

 physically simple one. In all these cases we can, therefore, 

 expect a variability of k. As a criterion can be used also 

 another secondary process accompanying the absorption of 

 light — the photochemical effect, as was shown by Lasareff§. 

 Therefore the experimental result of Nichols and Merritt is 

 an argument in favour of the classical theory of dispersion 

 and absorption. 



Another supposition about the nature of broad absorption- 

 bands was proposed by Kravec || and qualitatively by 

 Webster %. Their supposition consists in that occasional 

 influence of fields of surrounding moving molecules (or 

 parts of the same molecule) can in some way modify the 

 frequency of a resonator towards both sides. The molecules 

 will be distributed along the frequencies following the law 



* E. Lommel, Wied. Ann. iii. p. 251, § 19 (1878). 



t E. Merritt, he. cit. 



X Cf. H. Kayser, Handbuch der Spectroscopic, Bd. iv. p. 457 ff. B. J. 

 van der Plaats, Ann. d. Phys. xlvii. p. 429 (1915). 



§ P. Lasaretf, Ann. d. Phys. xxiv. p. 661 (1907). 



|j T. R. Kravec, ' The Absorption of Light in Solutions of Dves," 

 Moscow, 1912, p. 106. 



^ D. L. Webster, Phys. Rev. II. iv. p. 177(1914). 



