FLUORESCENCE SPECTRUM OF CHLOROPHYLL 



743 



first fluorescence band is followed bj^ a second one, of lower intensity, situ- 

 ated in the far red, which is visible in figure 23. IB as well as in figure 23.2; 

 and by a third, weak one, situated in the near infrared, which is not re- 

 corded in these figures. 



In an earlier investigation of Zscheile (1935), an additional band was observed in the 

 fluorescence spectrum of chlorophyll b at 672.8 m^; but Dhere and Biermacher (1936) 

 and Biermacher (1936) ascribed it to contamination with chlorophyll a, and this ex- 

 planation was accepted by Zscheile and Harris (1943). 



According to Biermacher (1936), the fluorescence spectrum provides the most sensi-* 

 five test for the purity of chlorophyll b. A purification method based on this test was 

 described in chapter 21. 



100 



>- 



cn 



z 



UJ 



o 



z 



LD 



o 



(/) 

 Ijj 

 q: 

 o 



iij 

 > 



UJ 



— ^— Chlorophyll o 

 Chlorophyll b 



620 660 700 740 



WAVE LENGTH, m/i 



780 



Fig. 23.2. Fluorescence spectra of chlorophylls a and b in ether. Photo- 

 metric curves corrected for self-absorption (after Zscheile and Harris 1943). 



Table 23. lA shows the positions of the main fluorescence bands of the 

 two chlorophylls in ethyl ether, as found by several investigators, and 

 Table 23. IB, the positions of the same bands in various solvents. 



A spectrophotometric curve of the fluorescence of a benzine extract 

 from Brassica (containing both chlorophyll components) can be found in 

 a paper by Vermeulen, Wassink and Reman (1937). 



In Table 23.1, some values represent band maxima, Xj^^x., as determined 

 by photoelectric photometry, and others band axes, X, i. e., the arithmetic 

 means of the extension limits of the bands on spectrum photographs. 

 These limits depend strongly on the spectral sensitivity curves of the 

 photographic plates used, and on the length of the exposure. Biermacher 

 (1936) insisted, however, that, as long as only the peaks of the bands are 

 photographed, e. g., by using suitably short exposures, the axes coincide 



