Luminescence and Intersystem Crossing Processes in Camphorquinone Crystals.
CALIFORNIA UNIV LOS ANGELES DEPT OF CHEMISTRY
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The use of phosphorescence microwave double resonance PMDR in detecting intersystem crossing ISC from higher excited singlet states is discussed. The method is then applied to camphorquinone for which such processes have been proposed to take place. The results of PMDR as well as other luminescence studies show no evidence to support such proposals. Theoretical aspects of the spin-orbit coupling interactions between n,pi states in cis-alpha-diketones are analyzed. The results indicate that while nonplanarity allows direct spin-orbit coupling between n,pi states of the same configuration, unlike in benzophenone, the one-center spin-orbit coupling terms vanish. Thus nonplanarity could only enhance spin-orbit coupling between n,pi states of different configurations. These selection rules predict inefficient S2 to T2 and S1 to T1 ISC in CQ and account for the luminescence properties of this compound.
- Atomic and Molecular Physics and Spectroscopy