 Solution

ID: past-exam-of-the-chemistry-course-of-the-year-3-of-the-natural-sciences-course-of-the-university-of-cambridge/2021/paper-2a/section-b/22/b/v/solution

$k_{Q} = 9.9 \times 1 0^{4} d m^{3} mo l^{- 1} s^{- 1}$ . The unquenched triplet lifetime is

τ_{0} = \frac{1}{180 + 18} = 5.05 \times 1 0^{- 3} s .

Since the slope is

k_{Q} τ_{0}

, the bimolecular rate constant is

k_{Q} = (5.0 \times 1 0^{2}) (198) = 9.90 \times 1 0^{4} d m^{3} mo l^{- 1} s^{- 1} .

For comparison, the unquenched phosphorescence yield in the unit-triplet-yield approximation is

180/198 = 0.909

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