I 



INTERFERENCE OF EJ,1ISSI0N CliANCES MTH FAST ABSORPTION CHANCES 

 IN THE FLASH SPECTROSCOPY OF ALGAE 



Edgar Inselberg and J. L. Rosenberg 



Many significant findings have emerged in recent years from 

 the flash spectroscopy of algae, notably from 7/itt's and Kok's 

 laboratories. 



Our own group constructed a flash apparatus at a later stage 

 and studied some aspects of the 5l5 mn change found by Witt and 

 Moraw (6). As interest shifted to changes in the 700 m^i region, 

 first reported by Kok (2)^ we modified our apparatus for measure- 

 ments in the far-red region. 



EXPERBENTAL 



The apparatus is illustrated in Fig. 1. The monochromatic beam 



2 3 2—1 

 (10 - 10 erg cm sec in intensity, depending on the experi- 

 ment) is focused into the sample, and then the transmitted frac- 

 tion of the beam is detected by a red-sensitive multiplier photo- 

 tube (RCA 7102). At ri^t angle to the monochromatic beam, the 

 sample is excited by short flashes from a General Electric FT-230 

 fLashtube (18. $ joules input per flash). Filter F-j^ determines the 

 spectral region of excitation, while F2 excludes all but a small 

 fraction of the actinic li^t from the phototube. The output of 

 the phototube, corresponding to single flashes, is displayed on 

 an oscilloscope screen. 



flash tube 



Q 



' Fj multiplier 



phototube 



monochrDmotor r''lQl-^--lX^~IIi:] 



^^^^® oscilloscope 



Fig. 1. Top view of the flash apparatus. 



717 



