Fluorescence of Dyes on Wave-Length of Exciting Light. 309 



of: probability. The experimental curve of absorption is 

 therefore a probability curve, enclosing the family of theo- 

 retical curves with a A^ariable parameter — its frequency. 

 For an explanation of the experimental curves from the 

 standpoint of this hypothesis it was unfortunately necessary 

 to suppose at least two types of resonators. Therefore in 

 this theory the absorption-band of dyes is also a complex one. 



Many experimental facts and theoretical consequences 

 necessitate a fundamental revision of the classical theory of 

 dispersion and absorption. This is required by a consequent 

 quantum theory, by a complete vagueness of the problem of 

 the nature of damping constant, etc. Still w T e consider that 

 the question of the physical simplicity or complexity of 

 an absorption-band can.be solved independently of this or 

 other modification of the theory of absorption. The way 

 of solution is already indicated; it is an experimental deter- 

 mination of coefficients characterizing the secondary pro- 

 cesses of absorption inside the considered band. 



Einstein's theoiy of the simplest photochemical reactions * 

 leads to the result that the coefficient of the velocity of 

 reaction must be inversely proportional to the frequency of 

 the active light. Considering in accordance with modern 

 theories the fluorescence as a production of light accompanying 

 the simple reaction of dissociation, we can hypothetically apply 

 this conclusion to fluorescence. Therefore we can expect the 

 following dependence of /c upon X inside a simple absorption- 

 band : 



K = a . X, 



where a is a constant. For a complex band, k must be a 

 totally different function of X. 



Thus we can interpret the experimental results of com- 

 putation of k on the following lines : — 



(a) If tc = <l>{\), (3) 



where is a more or less complicated function of X, the 

 absorption-band is a physically complex one. 



■(b) If K = a.\, (4) 



the band is a simple one and the theory of Einstein is true. 

 (c) If k, = const., (5) 



the band is a simple one and the theory of Einstein is not 

 true. 



* A. Einstein, Journ. d. Phys. V. iii. p. 277 (1913). 



