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PHOSPHORESCENCE ENHANCEMENT DUE TO EXCITON SPLITTING IN HYDROGEN BONDED 7-AZAINDOLE DIMER.

M. Ashraf El‐Bayoumi,A.G. Taylor,Michael Kasha-1967-01-01-The Knowledge Bank (The Ohio State University)
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splits as a result of dimerization. This is a manifestation of the exchange of excitation energy between the two molecules forming the dimer due to exciton interaction. Since the $S_{2}\leftarrow S_{0}$ transition in 7-azaindole is long axis polarized, the high energy exciton state is predicted to be allowed, and the low energy component is predicted to be forbidden in a first order approximation. The coupling of the two exciton states via intramolecular vibrational modes qualitatively accounts for the appearance of the forbidden lower exciton state. Lowest triplet exciton states remain essentially degenerate since spin exchange and dipole-dipole interactions are both small. After excitation to the upper allowed singlet exciton state, rapid internal conversion (I.C.) occurs to the lower forbidden singlet exciton state. The lifetime of this state is expected to be in the millisecond range, due to its small transition probability. Consequently the radiationless intersystem crossing (I.S.

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splits as a result of dimerization. This is a manifestation of the exchange of excitation energy between the two molecules forming the dimer due to exciton interaction. Since the $S_{2}\leftarrow S_{0}$ transition in 7-azaindole is long axis polarized, the high energy exciton state is predicted to be allowed, and the low energy component is predicted to be forbidden in a first order approximation. The coupling of the two exciton states via intramolecular vibrational modes qualitatively accounts for the appearance of the forbidden lower exciton state. Lowest triplet exciton states remain essentially degenerate since spin exchange and dipole-dipole interactions are both small. After excitation to the upper allowed singlet exciton state, rapid internal conversion (I.C.) occurs to the lower forbidden singlet exciton state. The lifetime of this state is expected to be in the millisecond range, due to its small transition probability. Consequently the radiationless intersystem crossing (I.S.

Keywords

ExcitonPhosphorescenceIntersystem crossingSinglet stateChemistryTriplet stateAtomic physicsExcitation

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