Exercise: Uv Luminance Spectroscopy

Questions for: Uv Luminance Spectroscopy

Fluorescence occurs when
A:
a molecule returns to the electronic ground state from an excited triplet state by losing it's excess energy as a photon
B:
a molecule returns to the electronic ground state from an excited singlet state by losing it's excess energy as a photon
C:
a molecule lowers its vibrational energy by losing it's excess energy as a photon
D:
none of the above
Answer: B
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Why phosphorescence measurements are usually made at a low temperature?
A:
To prevent thermal degradation of the phosphorescent species
B:
To promote phosphorescence by slowing the rate of radiationless transfer processes
C:
To increase the efficiency of the detector
D:
To decease the efficiency of detector
Answer: B
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Internal conversion is where
A:
the spin of an excited electron reverses, changing the state of the molecule (from singlet state to triplet state or vice versa)
B:
A molecule converts its excess energy to light, and emits a photon
C:
A molecule converts excess electronic energy to vibrational energy
D:
none of the above
Answer: C
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For a molecule to absorb IR, why must the molecule's vibrations cause fluctuations in the dipole moment of the molecule?
A:
Because a change in dipole moment lowers the energy required for electronic transitions
B:
Because for absorption to occur, the radiation must interact with the electric field caused by changing dipole moment
C:
Because fluctuations in the dipole moment allow the molecule to deform by bending and stretching
D:
All of the above
Answer: B
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Why do fluorescence spectrometers often use double-beam optics?
A:
So a reference solution can be used
B:
To compensate for beam attenuation by the monochromator
C:
To compensate for power fluctuations in the radiation source
D:
All of the above
Answer: C
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