Microwave-induced delayed phosphorescence studies of the total and radiationless decay processes of 3 &pgr;&pgr;* aromatic carbonyls

Author： Harrigan Edward Hirota Noboru

Publisher： Taylor & Francis Ltd

ISSN： 1362-3028

Source： Molecular Physics, Vol.31, Iss.3, 1976-03, pp. : 663-680

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Abstract

We have investigated the details of the radiationless decay processes of 3 &pgr;&pgr;* aromatic carbonyls of benzaldehyde type using microwave-induced delayed phosphorescence (MIDP) technique. Correlations between the decay rates from the spin sublevels and the energy separations between the 3 &pgr;&pgr;* and 3 n&pgr;* state (Δ E TT ) and those between the 3 &pgr;&pgr;* and 1 &pgr;&pgr;* states (Δ E ST ) were examined in detail for a series of systems. It is shown that the decay rates from the z and x sublevels depend on both Δ E TT and Δ E ST strongly, but the y sublevel decay is independent of them. An empirical model to explain the correlations among the decay rates, ZFS, Δ E TT and Δ E ST is presented. It is shown that the decays from the z and x sublevels of the 3 &pgr;&pgr;* aromatic carbonyls are dominantly radiationless and are primarily determined by the mixing with the 1 n&pgr;* states unless Δ E TT is very small. On the other hand, the radiationless decay from the y sublevel is likely due to the mixing with the 1 &sgr;&pgr;* ( 1 &pgr;&sgr;*) states. The mechanism for the radiationless decay from each spin sublevel is discussed in view of the results obtained.