Which of the following are the advantages for using the Michelson Interferometer

Question

Which of the following are the advantages for using the Michelson Interferometer and Fourier Transformation in an Infrared Spectrophotometer? Select ALL that apply A. Makes it cheaper. B. Allows for faster signal averaging, allowing great increase in S/N. C. Allows for greater instrument throughput using the entire spectrum (almost simultaneously), increasing S/N. D. Source never needs replacing. E. Allows instrument to used with UV/VIS wavelengths. F. More precision in the wavenumber selection of the optics. G. No need run reference sample.

Explanation / Answer

The advantages for using the Michelson Interferometer and Fourier Transformation (FTIR) in an Infrared (IR) Spectrophotometer are:

A. They are more expensive than the dispensive IR spectrometer for it uses diamond for attenuated total relectance (ATR). Diamond has excellent physical and chemical properties but is very expensive.

B. In FT-IR instrument more energies reach the sample for the instrument does not have slit to limit the individual frequency reach the sample and detector and also has fewer mirror surfaces to limit the reflection losses. Hence the signal-to-noise ratio of spectrum obtained by FTIR is significantly higher and you can acquire the spectra very quickly than the dispensive IR.

C. FTIR allows for greater instrument throughput using the entire spectrum almost simultaneously, thus increasing the signal-to-noise ratio and give high spectral accuracy.

D. The commonly used source of FTIR is a silicon carbide element heated to about 1200 K. This element will undergo gradual oxidation to form silica and carbon dioxide. Hence the source is not eternal and will require replacement.

E. The purpose of this instrument is to measure infrared induced stretching and bending infrared region between 1 m to 25 m (wavenumber range 10000 cm1 to 400 cm1) and does not allow the instrument to be used from with UV/VIS wavelengths.

F. FT-IR spectrometer uses lasers to control the velocity of the moving mirror and this laser is available as a source of wavelength calibration. Hence, FTIR provides more precision in the wavenumber selection of the optics than a dispensive IR. Accuracy and precision in IR spectra are much higher when collected on an FT-IR.

G. No need run reference sample. In FTIR, the sample used are usually neat without dilutions. Hence minimum or no sample preparation is required while other spectroscopy techniques such as uv-vis, NMR, etc. require reference sample. Note, chemists usually grind the solid sample to obtain spectrum with high intensity.

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