ChemInform Abstract: THE MAGNETIC FIELD DEPENDENCE OF THE DELAYED FLUORESCENCE IN P‐TERPHENYL BETWEEN 130 AND 300 K

Singlet Fission

“…100 In a second study, a two-dimensional random walk model was used to fit the fluorescence decay. 101 The resulting rate constants were as follows: singlet fission, 5.8 × 10 9 s -1 ; in-plane hopping, 1.31 × 10 10 s -1 ; and out-of-plane hopping, 6 × 10 6 s -1 . The inplane diffusion constant was 5.3 × 10 -5 cm 2 s -1 .…”

“…In the process, the full complexity of the transformations implied by eq , possibly including coherences between the nine sublevels, may perhaps be revealed. An early harbinger can be seen in the observation of magnetic field-dependent quantum beats in the fluorescence decay of 2 . , It needs to be noted as well that the singlet fission rate constants obtained by direct transient absorption measurement refer to the rate at which triplet absorption appears, whereas those obtained earlier indirectly by fitting to kinetic models usually refer to the rate at which the initially formed triplet pair 1 (TT) dissociates. The latter rate could be substantially slower, and this may account for some of the disagreements.…”

“…This type of measurement provides additional information. Pulsed laser excitation with sub-ns resolution permitted the observation of quantum beats in the fluorescence decay of single crystals of 2 , , and they were attributed to the effect of spin evolution on geminate re-fusion of triplet pairs produced by singlet fission. The quantum beats were studied as a function of magnetic field orientation.…”

“…In one study of triplet−triplet interactions in 2 , they were found to be negligible for the conditions used . In a second study, a two-dimensional random walk model was used to fit the fluorescence decay . The resulting rate constants were as follows: singlet fission, 5.8 × 10 9 s −1 ; in-plane hopping, 1.31 × 10 10 s −1 ; and out-of-plane hopping, 6 × 10 6 s −1 .…”

“…cence decay of 2. 100,101 It needs to be noted as well that the singlet fission rate constants obtained by direct transient absorption measurement refer to the rate at which triplet absorption appears, whereas those obtained earlier indirectly by fitting to kinetic models usually refer to the rate at which the initially formed triplet pair 1 (TT) dissociates. The latter rate could be substantially slower, and this may account for some of the disagreements.…”