Absolute Spectral Sensitivity of Phototubes and the Application to the Measurement of the Absolute Quantum Yields of Chemiluminescence and Bioluminescence*

Methods for the absolute measurement of the spectral sensitivity of phototubes are reviewed in detail. Several experimental arrangements are described for the independent determination of these values to insure the elimination of systematic error. On the basis of these measurements a rapid, simple technique is described for measuring the average absolute spectral sensitivity of a phototube over a defined emission spectrum, thus obviating the original tedious point‐by‐point methods and allowing frequent re‐Standardization. The application of these standardized phototubes to the measurement of the absolute quantum yields of the chemiluminescence of luminol and the bioluminescence of luminous bacteria and the firefly is described. An absolute low‐level light emission standard in the form of the luminol chemiluminescence reaction, either in aqueous or in the non‐aqueous solvent dimethylsulfoxide is proposed for general use and the conditions for its use are described in detail. It should therefore be possible for any researcher to obtain an absolute calibration, in his own experimental geometry, in the blue region of the spectrum.