﻿Light Absorption and Fluorescence. 



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and the latter also by Goldstein. The fundamental frequencies 

 of these compounds are 405 and 258 respectively. The 

 simplest method of calculation is to find whether the phos- 

 phorescence maxima can be arranged in each case with 

 reference to a multiple of the fundamental frequency, due 

 regard being paid to the fact that the phosphorescence 

 maxima are certain to be moved towards the red. The 

 accuracy of measurement reached by v. Kowalski and 

 Goldstein is only about 25 Angstroms, and therefore the 

 frequencies are only expressed in three figures. But in 

 spite of this, it is clear that the same relation holds good 

 here also. 



Thus in benzene the frequencies of the phosphorescence 

 maxima can be arranged symmetrically with respect to 

 l/\ = 242, as shown in Table XIV., together with the cor- 

 responding values of v x (in brackets) found in the absorption 

 band. 



Table XIY. — Benzene phosphorescence 

 (v. Kowalski). 



1/X. 



Vx. 



230 



12 (12-7) 



233 



9 (9-2) 



239 



3 



242 







249 



7 (7-7) 



252 



10 (10-2) 



260 



18 (18-4) 



263 



21 (20 8) 



270 



28 



274 



32 (31-8) 



280 



38 



284 



42 (40-5) 



289 



47 



295 



53 



It may be pointed out that the frequency difference of 47 

 corresponds very nearly with the infra-red band at 2*18//, 

 (1/X -=46). 



I „We thus have for the fundamental frequency of benzene 

 the following values : — 



Phosphorescence . . 6 X 403'3 

 Fluorescence . . . 9 x 405 

 Absorption .... 10x405 



