Question

Answer is A

For the process S_1 + Q S_0 + Q under continuous irradiation in different percentages of the quencher oxygen (% O_2) the Stern-Volmer linear fit was (I_f degree/I_f) = 1.00 + 0.09596 times (% O_2) Given k_f = 1.77 times 10^5 s^-1, calculate the fluorescence relaxation time tau_f #when a short pulse is applied on the same complex with 50% O_2 # present A) 9.74 times 10^-3 s B) 5.65 times 10^-6 S C) 1.84 times 10^6 S D) 9.74 times 10^-7 S E) 5.85 times 10^-7 S

Answer 1

There are two types of quenching mechanism. One is static and other is dynamic.

Oxygen is a dynamic quencher.

For dynamic quenching, lifetime varies

I_f⁰/I_f= t₀/t, where is the initial lifetime t₀ and is the t current lifetime.

Initial lifetime can be found from the fluorescence rate constant (t₀= 1/k_f) = 0.564 x 10^-5s.

And the

I_f⁰/I_f = 1+ 0.09596 (% O₂) at 50 % of O₂

I_f⁰/I_f= 5.798

Using this equation

I_f⁰/I_f= t₀/t

t= t₀/(I_f⁰/I_f) = 0.564 * 10^-5 / 5.798 = 0.097* 10^-5 or 9.7* 10^-3