Experimental rate constants for the transfer of electronic excitation energy from naphthalene, phenanthrene and chrysene to biacetyl were obtained in hexadecane, from the measured quenching coefficients and the directly measured lifetimes. These rate constants were compared with rate constants calculated from the Smoluchowski equation using measured diffusion coefficients and assuming that the transfer radii are of similar magnitude as the kinetic radii. Diffusion coefficients for biphenyl, acetone, methyl ethyl ketone and diethyl ketone were also measured in hexadecane at 30°C and compared with values estimated by various theoretical and semi-empirical relations.

The technique of energy transfer has been used in an attempt to establish the photoreactive state of acridine in solution. It is shown that the lowest-lying triplet of acridine, the ππ* triplet, is not the reactive species and that the reaction originates, at least in part, through the nπ* triplet. In the course of this work, the transfer of triplet-state energy from biacetyl to acridine, phenazine, anthracene, 1,2-benzanthracene, pyrene, 1,2-benzpyrene and 3,4-benzpyrene has been studied by an intensity method.

The transfer of electronic excitation energy from the lowest excited singlet and triplet states of a number of aromatic hydrocarbons and ketones to the lowest excited singlet and triplet state of biacetyl has been studied in hexane and benzene solution at room temperature by the spectrophotofluorometric method. Singlet-state lifetimes for benzene, toluene, diphenyl, and acetone are reported and triplet-state lifetimes for diphenyl, naphthalene, acetophenone, and acetone are also obtained. Useful information concerning the triplet states of other donors is also obtained by comparing the phosphorescence to fluorescence ratio of biacetyl when biacetyl alone is irradiated with the ratio obtained when a mixture of biacetyl and the donor is excited at wavelengths absorbed by the donor.

Quenching of the fluorescence of acridine in ethanol solution by iodide ions takes place with unit collisional efficiency converting the excited singlet state to the triplet state. The photoreduction of acridine in the presence of iodide ions is descreased by an amount corresponding to the decrease in fluorescence, illustrating that the reactive state is a singlet-state probably (π, π*)1 in nature.

Generalized oscillator strength for the first singlet-singlet transition in pdifluorobenzene and the cross section for energy transfer to acetone J. Chem. Phys. 68, 3511 (1978); 10.1063/1.436260 Erratum: ''Singlet-singlet electronic energy transfer: Dipole-dipole and exchange contributions''