Peer-Reviewed Journal Details

Mandatory Fields

Nickel, B.,Borowicz, P.,Ruth*, A. A.,Troe, J.;

2004

July

Physical Chemistry Chemical Physics

Application of Smoluchowski's generalized theory to the kinetics of triplet-triplet annihilation of anthracene in viscous solution after long-pulse excitation

Validated

()

Optional Fields

6

13

3350

3363

The validity of Smoluchowski's theory is demonstrated by its application to the bimolecular triplet-triplet annihilation (TTA) T-1 + T-1 --> S-0+ S-1 in viscous solution. For that purpose the delayed S-1 --> S-0 fluorescence of anthracene in cis-1,3-dimethylcyclohexane/trans-1,4-dimethylcyclohexane (1:1) was measured after UV excitation with long laser pulses (similar to30 mus) in a temperature range where TTA is completely diffusion controlled. Through the adequate treatment of the kinetics of TTA upon spatially homogeneous and spatially periodic excitation (which is partially based on the results of previous publications) absolute values for the diffusion coefficients D of triplet molecules, for the effective annihilation distance R-A and for the Forster radius R-ST of heterogeneous annihilation S-1 + T-1 --> S-0 + T-n were determined. The temperature dependence of all three parameters (D, R-A and R-ST) is discussed. From the decrease of R-A with increasing temperature, the parameters A and L can be determined, which define the exponential distance dependence of the annihilation of a triplet pair in the kinetic model of Butler and Pilling (1977). Differences of the two models and applicability criteria are discussed.The validity of Smoluchowski's theory is demonstrated by its application to the bimolecular triplet-triplet annihilation (TTA) T-1 + T-1 --> S-0+ S-1 in viscous solution. For that purpose the delayed S-1 --> S-0 fluorescence of anthracene in cis-1,3-dimethylcyclohexane/trans-1,4-dimethylcyclohexane (1:1) was measured after UV excitation with long laser pulses (similar to30 mus) in a temperature range where TTA is completely diffusion controlled. Through the adequate treatment of the kinetics of TTA upon spatially homogeneous and spatially periodic excitation (which is partially based on the results of previous publications) absolute values for the diffusion coefficients D of triplet molecules, for the effective annihilation distance R-A and for the Forster radius R-ST of heterogeneous annihilation S-1 + T-1 --> S-0 + T-n were determined. The temperature dependence of all three parameters (D, R-A and R-ST) is discussed. From the decrease of R-A with increasing temperature, the parameters A and L can be determined, which define the exponential distance dependence of the annihilation of a triplet pair in the kinetic model of Butler and Pilling (1977). Differences of the two models and applicability criteria are discussed.

1463-90761463-9076

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