Knowledge Bank

It has recently become evident that the fluorescence yields of many molecules depend on which electronic state of the molecule is initially $excited.1,2$ Such an effect may be due to a variety of causes although the most attractive of these involves intersystem-crossing between upper electronic states. Work is underway to examine the phosphorescence yield as a function of the exciting light energy and polarization for a few of these anomolous cases. Data on some aryl-ethylene derivatives, anthracenic compounds and tetracene will be presented.