348 



LIGHT AND LIFE 



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o ACTION SPECTRUM 



'EMISSION SPECTRUM 

 25°C 



• EMISSION SPECTRUM 

 25°C (THICK FILM) 



° EMISSION SPECTRUM 

 -45°C (THICK FILM) 



• EMISSION SPECTRUM 

 -70°C (THICK FILM) 



o ACTION SPECTRUM 



"EMISSION SPECTRUM 



25°C 

 o FLUORESCENCE 



SPECTRUM 

 (AFTER DUYSENS) 



o ACTION SPECTRUM 



• EMISSION SPECTRUM 

 25°C (THICK FILM) 



Fig. 



""9to 



X (mp) 



27. Action, cmi.ssion, and fluorescence spectra of spinach chloroplasls, 

 ChlorelUi, and Xostoc. 



observed for long-lived emission. The peak is at 6800 A, but there 

 is a very prominent shoulder at 7200 A. This was originally inter- 

 preted as due to self-absorption of the ordinary fluorescence. How- 

 ever, the fact that this is such an asymmetric curve now seems to 

 suggest that there may be another emission band somewhere beyond 

 7000 A. 



A better experiment was performed by Brody (11), in which he 

 found exactly that: a very pronounced emission with a peak at 

 7180 A (Fig. 28). The ordinary fluorescence spectrum of Chlorella 

 has a peak at around 6900 A, but if one cools the Chlorella to — 190°C 

 a strong emission at 7180 A aj^jiears. This cannot be a self-absorption 

 effect, because if it were, there would not be a minimum between 



