The first step in plant photosynthesis is absorption of light by chlorophyll molecules bound to proteins known as ‘light-harvesting complexes’, where the fluorescence of a chlorophyll molecule is quenched by other nearby chlorophyll molecules. Given that for a pair of chlorophyll a molecules R0 = 5.6 nm, by what distance should two chlorophyll a molecules be separated to shorten the fluorescence lifetime from 1 ns (a typical value for monomeric chlorophyll a in organic solvents) to 10 ps?

The first step in plant photosynthesis is absorption of light by chlorophyll molecules bound to proteins known as ‘light-harvesting complexes’, where the fluorescence of a chlorophyll molecule is quenched by other nearby chlorophyll molecules. Given that for a pair of chlorophyll a molecules R0 = 5.6 nm, by what distance should two chlorophyll a molecules be separated to shorten the fluorescence lifetime from 1 ns (a typical value for monomeric chlorophyll a in organic solvents) to 10 ps?

Principles of Modern Chemistry

8th Edition

ISBN:9781305079113

Author:David W. Oxtoby, H. Pat Gillis, Laurie J. Butler

Publisher:David W. Oxtoby, H. Pat Gillis, Laurie J. Butler

Chapter20: Molecular Spectroscopy And Photochemistry

Section: Chapter Questions

Problem 6P

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The first step in plant photosynthesis is absorption of light by chlorophyll molecules bound to proteins known as ‘light-harvesting complexes’, where the fluorescence of a chlorophyll molecule is quenched by other nearby chlorophyll molecules. Given that for a pair of chlorophyll a molecules R0 = 5.6 nm, by what distance should two chlorophyll a molecules be separated to shorten the fluorescence lifetime from 1 ns (a typical value for monomeric chlorophyll a in organic solvents) to 10 ps?
A substance has a fluorescence quantum yield of ϕF,0 = 0.16. In an experiment to measure the fluorescence lifetime of this substance, it was observed that the fluorescence emission decayed with a half-life of 1.5 ns. What is the fluorescence rate constant of this substance?
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Consider the chemical reaction described by 2A(aq) ⇌ D(aq)with rate constants k1 and k-1. If the reaction is subject to a temperature jump, derive the equation for d[D]/dt in terms of a relaxation constant t.
In an experiment to measure the quantum yield of a photochemical reaction, the absorbing substance was exposed to 320 nm radiation from an 87.5 W source for 28.0 min. The intensity of the transmitted radiation was 0.257 that of the incident radiation. As a result of irradiation, 0.324 mol of the absorbing substance decomposed. Evaluate the quantum yield.
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When benzophenone is exposed to ultraviolet radiation, 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 the solvent methanol, the phosphorescence intensity varied with amine concentration as shown below. [Q]/(mol·dm−3) 0.0010 0.0050 0.0100 If/(arbitrary units) 0.41 0.25 0.16 A time-resolved laser spectroscopy experiment had also shown that the half-life of the phosphorescence in the absence of a quencher is 38 µs. What is the value of kQ?
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The rate law v=(kr1[A][B])/(kr2 + kr3[B]1/2) was established in a series of experiments. Identify the conditions under which (i) an order with respect to A, (ii) an order with respect to B, and (iii) an overall order, can be assigned.
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