The singlet states of methyl cinnamate and methyl indenoate

Abstract The fluorescence lifetimes of methyl cinnamate and methyl indenoate have been investigated by means of picosecond laser spectroscopy. Values of * singlet state and its internal conversion to a lowest n,π * singlet state. The efficiency of isomerization is independent of solvent, but dependent upon temperature and excitation wavelength. Comparison of the quantum yields for direct and triplet-sensitized dimerization indicates that intersystem crossing is highly inefficient. Thus the isomerization which occurs upon direct irradiation occurs predominantly from the singlet manifold.