Suppression of Disturbing Light Signals in Rapid Flash Kinetic Measurements

Abstract

IN the flash kinetic method for investigating rapid photochemical reactions¹, a reaction is initiated by a short flash of light and measured by a rapid-response photometer. Improvements of this method (refs. 2–5), particularly by the use of repetitive excitation followed by signal averaging, have increased the sensitivity of the method by a factor of about 100. Although the repetitive procedure eliminates the disturbance caused by statistically random signals, it does not remove disturbing signals related by a fixed phase to the flash sequence. In the study of the primary processes of photosynthesis such a false signal is caused by the fluorescence of chlorophyll, excited by the flashes, which interferes with a photometer signal in the same spectral range. This strong interference can be reduced by restricting the aperture and by electric compensation^6,7. The rejection ratio which results, however, limits the sensitivity to a level far above that which might be normally obtained by repetitive signal evaluation⁵.