The relations between the fluorescence and absorption properties of organic molecules

Abstract Measurements have been made of the fluorescence spectra, lifetimes and quantum efficiencies and of the absorption spectra of several organic molecules in dilute solution. These have been used to test the validity of the theoretical relation between the radiative lifetime and the absorption intensity, and of the mirror-image relation between the fluorescence and absorption spectra. The former is found to be valid provided there is no major change in the nuclear configuration between the ground and excited states, but the latter is usually more sensitive to such changes. The effect of a change in nuclear configuration, which is particularly marked in the higher diphenylpolyenes, is to increase the radiative lifetime and to distort the spectral intensity distribution.