R. S. BECKER AND M. KASHA 35 



laboratory we have found an S'-T split of this same order of magni- 

 tude in metal phthallocyanines. We would expect the chlorophyll a 

 and chlorophyll b molecules also to exhibit a similar split. Since the 

 lowest frequency absorption of alcoholic solutions of these chloro- 

 phylls is at approximately 6500 to 6600 A, and the fluorescences at 

 approximately 6700 to 6800 A, the phosphorescences or triplet-singlet 

 emissions should occur at approximately 2500 cm"' lower in fre- 

 quency, which would be at about 8050 to 8200 A. 



Calvin and Dorough (1947) originally reported a phosphorescence 

 in a pure mixture of chlorophylls commencing at about 8000 A and 

 extending farther into the infrared. Later work by Calvin and Dorough 



(1948) on chromatographically separated chlorophyll a and chloro- 

 phyll h showed no phosphorescence in chlorophyll a and only a weak 

 phosphorescence in chlorophyll h, commencing at 8600 A and pro- 

 ceeding farther into the infrared. Further investigation by Livingston 



( 1949 ) failed to reveal any emission from either chlorophyll a or 

 chlorophyll h. Livingston believes that if a phosphorescence of chlo- 

 rophyll exists, it is at longer wavelengths than 9000 A or has a life- 

 time shorter than 0.01 second. It is obviously important that further 

 work clarify these contradictions of experiment. 



In our laboratory we have made preliminary observations on the 

 phosphorescence of chlorophyll a and chlorophyll h. In agreement 

 with Calvin and Dorough (1948), we found no phosphorescence for 

 chlorophyll a. Furthermore, in agreement with Calvin and Dorough 

 ( 1948 ) , we did get a very good photograph of the phosphorescence of 

 chlorophyll h. A small amount of chlorophyll a was present with the 

 fo-isomer; however, it is known that energy transfer will not take place 

 in dilute solutions as rigid glasses at low temperature. Our exposure 

 was sufficient to reveal one medium strong narrow band at 8650 A. 

 We believe there is no reasonable doubt as to the reality of this emis- 

 sion as a chlorophyll h phosphorescence. However, as discussion be- 

 low will reveal, we do not simply relate this state with the photosyn- 

 thetic step, contrary to the Calvin and Dorough (1947) hypothesis. 



The experimental conditions under which our observations were 

 made were as follows. We used a high-speed phosphoroscope having 

 a resolving time of 3 X 10 ~* second. The chlorophylls were dissolved 

 in a rigid glass solvent formed by supercooling the dilute solution 



