252 



BIOCHEMISTRY OF BACTERIAL LUMINESCENCE 



directly into one in state D with complete conversion of the energy 



difiFerence into light. Similarly, let us indicate by hvi*, /iv2^ 



the 



energy absorbed when Ci*, Co 



are formed from state C. As 



seen from Fig. 17, the frequencies which are actually emitted are 



I'l = I'O + Vi* 



V2 = vo + P2*, etc. 



Fig. 17. 



■ V 



The i'*'s represent the contributions of the thermally activated inter- 

 mediate states to the quanta that are actually emitted, while I'o is the 

 contribution of the overall chemiluminescent reaction, C ^ D + light. 

 It is obvious that there must be some thermodynamic limit to the 

 increase in the energy of the emitted quantum above /iio that is ob- 

 tainable from the emission produced in this way by thermally acti- 

 vated intermediates. One might expect that the intensity of light 

 emitted at a frequency v, greater than lo, would decrease with increas- 

 ing frequency in proportion to exp( — h{i'—i'o)/kT), where T is the 

 temperature of the system. If vo corresponded to a wavelength of 

 5000 A, this means that the intensity should decrease by a factor of 10 

 for each 120-A decrease in the wavelength — which is a somewhat 

 sharper edge for an emission band than is usually observed with 

 luminous bacteria (Spruit-van der Burg, 1950). An exponential factor 

 of this kind must indeed operate, but as we shall now show, the upper 

 limit set by the laws of thermodynamics on the intensity is surprisingly 



