Light Absorption and Fluorescence. 3 



given by M + /iI, where n = 0, 1, 2, 3, etc. and I is the least 

 common multiple of the frequencies of a group of atoms 

 within the molecule. This may be called an intra-molecular 

 frequency. 



8. Each sub-group consists of a central line with series 

 of lines symmetrically arranged round it. If F be the fre- 

 quency of the central line, then the series of lines will have 

 frequencies given by Fdr9iA l5 F±?iA 2 , etc., where again 

 ^=0, 1, 2, 3, etc., and A T , A 2 , etc. are those atomic 

 frequencies the least common multiple of which is equal to I. 



The first question which arises is the meaning of the 

 characteristic atomic frequencies which are the fundamental 

 constants from which the whole system of frequencies shown 

 bv a molecule are derived. Presumably they are connected 

 with the shift of an electron from one stationary orbit to 

 another — a change which must require a definite amount 

 of energy depending upon the electromagnetic force field of 

 the atom. Indeed, it would seem that if the possibility be 

 allowed of the shift of an electron from one stationary 

 orbit to another, it becomes necessary at once to accept the 

 conclusion that a definite and fixed amount of energy is 

 evolved in the change. I therefore propose to start from 

 this assumption, that in any elementary atom it is possible 

 to shift an electron from one stationary orbit to another, 

 that a definite amount of energy is required to effect the 

 change, and that this fixed quantity of energy is connected 

 with the frequency by the relation 



Fixed Quantity of Energy -^ 



Constant ~ = ^^^'- 



This is readily to be understood if the constant involves a 

 function of the time taken in the actual operation, which is 

 the same for every atom and is a universal constant. 



This elementary quantum of energy involved in the 

 electron shift is, I believe, the basis of the whole energy 

 quantum hypothesis as applied to absorption and radiation ; 

 for I hope to show that the whole can be built up from the 

 original assumption of the elementary quantum as a specific 

 property of the atom. For the sake of convenience only 

 it will be necessary to make use of a value for the constant, 

 and the most recent value for this, based on Planck's theory, 

 is b''56 x 10 -27 . Using this value, the elementary quanta 

 already calculated — namely, those of hydrogen, oxygen, and 

 sulphur — lie between 5*25 x 10~ 16 and 1*65 x 10~ 15 erg, 

 corresponding with frequencies between 8*19 xlO 10 and 

 2-54 xlO 11 . 



B 2 



