Question 1

What is the relationship between wavelength and wave number?

Accepted Answer

Wavenumber = 1 / wavelength in centimeters

Question 2

Why must the radiation source for fluorescence spectrometry be more powerful than for absorption spectroscopy?

Accepted Answer

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

Question 3

Why phosphorescence measurements are usually made at a low temperature?

Accepted Answer

To promote phosphorescence by slowing the rate of radiationless transfer processes

Question 4

In the intersystem crossing

Accepted Answer

the spin of an excited electron reverses, changing the state of the molecule (from singlet state to triplet state or vice versa)

Question 5

For a molecule to absorb IR, why must the molecule's vibrations cause fluctuations in the dipole moment of the molecule?

Accepted Answer

Because for absorption to occur, the radiation must interact with the electric field caused by changing dipole moment

Question 6

Why do fluorescence spectrometers often use double-beam optics?

Accepted Answer

To compensate for power fluctuations in the radiation source

Question 7

Fluorescence occurs when

Accepted Answer

a molecule returns to the electronic ground state from an excited singlet state by losing it's excess energy as a photon

Question 8

Internal conversion is where

Accepted Answer

A molecule converts excess electronic energy to vibrational energy

UV Luminance Spectroscopy Questions