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Questions and Answers
What is the process known as the emission of light from any substance?
What is the process known as the emission of light from any substance?
- Phosphorescence
- Luminescence (correct)
- Stokes shift
- Fluorescence
What is typically observed at lower energies or longer wavelengths in fluorescence?
What is typically observed at lower energies or longer wavelengths in fluorescence?
- Internal conversion
- Excited-state reactions
- Stokes shift (correct)
- Energy transfer
What principle states that the same fluorescence spectrum is generally observed irrespective of the excitation wavelength?
What principle states that the same fluorescence spectrum is generally observed irrespective of the excitation wavelength?
- Solvent effects
- Kasha’s Rule (correct)
- Complex formation
- The Franck-Condon Principle
What is plotted as fluorescence intensity versus wavelength or wavenumber?
What is plotted as fluorescence intensity versus wavelength or wavenumber?
What occurs when the nuclei does not have time to adjust after an energetic transition?
What occurs when the nuclei does not have time to adjust after an energetic transition?
What is the decay to higher vibrational energy levels of S0 called?
What is the decay to higher vibrational energy levels of S0 called?
What is the process of emission of light from any substance other than fluorescence?
What is the process of emission of light from any substance other than fluorescence?
What is fluorescence anisotropy based on?
What is fluorescence anisotropy based on?
What decreases measured anisotropy in fluorescence anisotropy measurements?
What decreases measured anisotropy in fluorescence anisotropy measurements?
What is resonance energy transfer (RET) based on?
What is resonance energy transfer (RET) based on?
What is steady-state fluorescence measurement performed with?
What is steady-state fluorescence measurement performed with?
What is lost in the time averaging process in time-resolved fluorescence?
What is lost in the time averaging process in time-resolved fluorescence?
What does the Perrin equation relate to in fluorescence measurements?
What does the Perrin equation relate to in fluorescence measurements?
What is the Förster distance (R0) related to in resonance energy transfer (RET)?
What is the Förster distance (R0) related to in resonance energy transfer (RET)?
What are intrinsic fluorophores?
What are intrinsic fluorophores?
What is fluorescence correlation spectroscopy (FCS) based on?
What is fluorescence correlation spectroscopy (FCS) based on?
What does fluorescence polarization or anisotropy indicate?
What does fluorescence polarization or anisotropy indicate?
What does quenching of fluorescence reveal?
What does quenching of fluorescence reveal?
What is the main characteristic of single molecule detection (SMD)?
What is the main characteristic of single molecule detection (SMD)?
What is the main principle of resonance energy transfer (RET)?
What is the main principle of resonance energy transfer (RET)?
What are extrinsic fluorophores?
What are extrinsic fluorophores?
What is the main purpose of emission spectra and the Stokes shift in fluorescence?
What is the main purpose of emission spectra and the Stokes shift in fluorescence?
What characteristic indicates whether a fluorophore is suitable for a sample being studied?
What characteristic indicates whether a fluorophore is suitable for a sample being studied?
According to Kasha’s Rule, from which level do molecules emit?
According to Kasha’s Rule, from which level do molecules emit?
What determines the emitted photons and interaction time for a fluorophore?
What determines the emitted photons and interaction time for a fluorophore?
What type of quenching decreases intensity and can be collisional or static?
What type of quenching decreases intensity and can be collisional or static?
Which principle explains fast absorption and longer emission timescales?
Which principle explains fast absorption and longer emission timescales?
What provides information on dynamic processes in solution or macromolecules?
What provides information on dynamic processes in solution or macromolecules?
What is directionally dependent and differs from isotropy?
What is directionally dependent and differs from isotropy?
Which of the following is a common quencher for fluorescence?
Which of the following is a common quencher for fluorescence?
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Study Notes
Fluorescence and Quenching in Molecular Processes
- Fluorophores exist in two ionization states with different absorption and emission spectra
- Kasha’s Rule states that molecules emit from the S2 level
- Symmetry of absorbance and emission spectra is due to similar transitions and vibrational energy levels of S0 and S1
- Quantum yield and lifetime determine emitted photons and interaction time for the fluorophore
- Fluorescence quenching decreases intensity and can be collisional or static
- Stern-Volmer equation includes constants and quencher concentration
- Common quenchers include O2, halogens, amines, and electron-deficient molecules
- Quenching provides information on dynamic processes in solution or macromolecules
- Franck-Condon principle explains fast absorption and longer emission timescales
- Fluorescence anisotropy is directionally dependent and differs from isotropy
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