A photon counting device for the measurement of nanosecond and microsecond kinetics of light emission from biological systems

This paper describes the instrumentation and operation of a photon counting system which was constructed to measure the delayed light emission from the algae Scenedesmus. The functioning of the system was illustrated by a plot which compared data of the recorded delayed light emission with data of the system noise over the first 20-μsec interval after extinction of a modulated laser beam. We believe that this paper shows the utility of photon counting as a satisfactory method of measuring biological light emission, especially a very rapid process such as the delayed light emission from photosynthetic organisms.