(d) The figure below shows the fluorescence intensity recorded for four porphyrin molecules (1-4), which each undergo single exponential decay. Fluorescence Decay 1.0 0.5 0.0 0 10 20 Time (ns) 30 1 2 3 A 4 O 40 (i) Using the data above and indicating the appropriate equations, estimate the lifetime of fluorescence for each porphyrin and calculate the rate constant in each case. (ii) Porphyrin fluorescence is quenched by molecular oxygen. If the diffusion coefficient (D) of O₂ in water at 25 °C is 2.5 x 10-5 cm² s1 estimate the distance travelled by an oxygen molecule during the lifetime of molecules 1 and 4 and comment on the relative likelihood of quenching.

(d) The figure below shows the fluorescence intensity recorded for four porphyrin molecules (1-4), which each undergo single exponential decay. Fluorescence Decay 1.0 0.5 0.0 0 10 20 Time (ns) 30 1 2 3 A 4 O 40 (i) Using the data above and indicating the appropriate equations, estimate the lifetime of fluorescence for each porphyrin and calculate the rate constant in each case. (ii) Porphyrin fluorescence is quenched by molecular oxygen. If the diffusion coefficient (D) of O₂ in water at 25 °C is 2.5 x 10-5 cm² s1 estimate the distance travelled by an oxygen molecule during the lifetime of molecules 1 and 4 and comment on the relative likelihood of quenching.