Uv Luminance Spectroscopy

Question: 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: Option B

Explanation:

No answer description available for this question.

Question: 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: Option B

Explanation:

No answer description available for this question.

Question: Why must the radiation source for fluorescence spectrometry be more powerful than for absorption spectroscopy?
[A].

Because the magnitude of the output signal is proportional to the power of the incident radiation

[B].

Because the sample won’t fluoresce if the incident radiation is of low power

[C].

To allow for scattering by the sample

[D].

None of the above

Answer: Option A

Explanation:

No answer description available for this question.

Question: 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: Option C

Explanation:

No answer description available for this question.

Question: In the intersystem crossing
[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].

all of the above

Answer: Option A

Explanation:

No answer description available for this question.

Question: 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: Option C

Explanation:

No answer description available for this question.

Question: 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: Option B

Explanation:

No answer description available for this question.