MELVIN CALVIN 



349 



z 



o 



z 



UJ 



o 



UJ 

 IT 



o 



3 



600 



700 



mp 



Fig. 28. Fluorescence spectra of Chlorella at room temperature (crosses) and 

 — 193°C (open circles). The fluorescence intensities indicated are tlie same for botli 

 cur\es. 1 he decrease in fluorescence yield at 690m/x is probably due to the in- 

 creased scattering of the exciting and fluorescent light. 



the two absorption peaks. This means that there is a new state emit- 

 ting, and quite different from the one producing fluorescence emis- 

 sion at 6900 A. The triplet emission is out still further, at around 

 7600 A, and this has been observed in pure chlorophyll samples. 

 Krody has seen the 7180 A peak both in whole Chlorella as well as 

 in concentrated chlorophyll solutions, and he believes this to be the 

 emission of a state of aggregated chlorophyll and quite different from 

 the triplet emission but corresponding to something which exists 

 in the li\ing organism. Another possibility is that it may be the 

 lowest ii,7r* state as distinct from the more readily reached tt.tt* state. 

 One can presume, now, that excitation to such a state as this is 



