DECAY OF THE DELAYED LIGHT IX ChlorcUa 



131 



nated through one of them is excited by flashing hght; the number of 

 flashes per second is given directly by an electronic tachometer. 

 Delaj'ed light emitted by the suspension, after passing through the 

 second shutter, falls on the photomultiplier. The signal thus obtained 

 is proportional to the intensity of the delayed light one half-period 

 after the flash. The results are complicated by the fact that the dark 

 time cannot be changed without changing the duration of the flash. 



1=100 



500 



toco 1500 



FLASHES/sec 



2000 



2500 



Fig. 4. The intensity of the delayed light as measured with the phosphoroscope 

 as a function of the number of flashes per second. Numbers on the curve are 

 relative exciting light intensities. 



Decay curves for the delayed light, at room temperature, between 

 0.05 and 6000 seconds are given in Fig. 1. The results are plotted on 

 logarithmic scales owing to the wide range covered both as to in- 

 tensity and time. 



There is one exception to the statement that no simple expression 

 has been found for the intensity of the delayed light as a function of 



