FTIR Tutorial

Quiz 3 - Practical FTIR

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Question 1
What is the file extension for a sample single beam spectrum?
a. .smp
b. .bkg
c. .sbm
d. .sam
e. .abs

On the Mattson, sample single beam spectra are suffixed .sbm, backgrounds with .bkg.

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Question 2
What is the optimum pathlength for polymer samples in transmission mode?
a. 10 micrometers
b. 100 micrometers
c. 4 millimeteres
d. 40 micrometers

It's about 40 micrometers.

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Question 3
What are the units most commonly used to identify bands in FTIR spectroscopy?
a. Wavenumbers(cm-1)
b. Wavelength(m)
c. Frequency(Hz)
d. Wavelength(micrometres)

The most common unit is the wavenumber, cm-1.

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Question 4
What material did you obtain a spectrum of in the practical part of the course?
a. human hair
b. Polystyrene
c. Carbon Dioxide
d. PMMA

You should have got a spectrum of Poly(styrene).

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Question 5
What are interference fringes caused by?
a. Not putting the sample in properly
b. Gasses in the atmosphere that absorb infrared.
c. Reflection of infrared by the sample.
d. Impurities in the sample.

They're caused by internal reflection in your sample.

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Question 6
What is the correct way to display spectra?
a. In absorbance.
b. In transmission.
c. Either absorbance or transmission
d. As raw data.

You may display in absorbance or transmission.

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Question 7
How is the detector on the Mattson RS/1 FTIR spectrometer cooled?
a. With water
b. With liquid nitrogen
c. With a fan
d. By Peltier cooling
e. It's not.

The spectrometer has a room temperature detector.

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Question 8
Which infrared technique can measure two spectra at once?
a. FTIR spectroscopy
b. FTIR-ATR spectroscopy
c. Dispersive infrared spectroscopy
d. FTIR microscopy
e. none

Dispersive infrared measures 2 spectra (usually sample and background) at the same time.

It is a double-beam technique. FTIR is a single-beam technique.

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Question 9
If you measured a spectrum and it was saturated, what could you do to improve the spectrum?
a. Reduce the iris setting
b. Use a thinner sample.
c. Scan for a shorter period of time.
d. Increase iris setting
e. Reduce iris setting OR use a thinner sample

Either reducing the iris setting OR using a thinner sample would help.

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Question 10
What does the spectrum of Nitrogen(N2) look like?
a. The same as that of air
b. It has only p- and r- branches
c. The same as that of carbon monoxide
d. It doesn't have one!

Vibration of the nitrogen molecule does not cause a change in dipole change, therefore it has no spectrum.

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