Question

*The quenching of tryptophan fluorescence by dissolved O₂ gas was monitored by measuring emission lifetimes at 348 nm in aqueous solution. Determine the quenching rate constant for this process from the following data.

[O2] (10-2mol dm-3)	0	2.3	5.5	8	10.8
T/ns	2.6	1.5	0.92	0.71	0.57

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When benzophenone is illuminated with ultraviolet light, it is excited into a singlet state. This singlet changes rapidly into a triplet, which phosphoresces. Triethylamine acts as a quencher for the triplet. In an experiment in methanol as solvent, the     phosphoresces intensity varied with amine concentration as shown below. A time-resolved laser spectroscopy experiment had also shown that the half-life of the fluorescence in the absence of quencher is 29μs. What is the value of K_Q?

[Q] (mol dm-3)	0.0010	0.0050	0.0100
If/(arbitrary units)	0.41	0.25	0.16

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Answer 1

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