when using an FTIR,which utilizes an inferometer, why do we need a fourier transform to obtain the actual spectrum
Solution
Fourier-transform infrared spectroscopy is based on the certainty that a Fourier transform (a mathematical procedure) is needed to turn the raw data into the actual spectrum.
In the experiment an Interferometer is used which is adapted for FTIR, light from the polychromatic infrared source is collimated or made parallel and directed to a beam splitter.
Interferogram is termed as the signal format acquired by an FT-IR spectrometer.
The interferogram needs to be measured from zero path difference to a maximum length which relies on the resolution needed.
Practically, the scan can be on either side of zero resulting in a double-sided interferogram.
The interferogram is converted to a spectrum by Fourier transformation. This requires it to be stored in digital form as a series of values at equal intervals of the path difference between the two beams.
The result of Fourier transformation is a spectrum of the signal at a series of discrete wavelengths. The range of wavelengths that can be used in the calculation is limited by the separation of the data points in the interferogram. The shortest wavelength that can be identified is twice the separation between these data points.
The interferogram is present in the length dimension. Fourier transform (FT) inverts the dimension, so the FT of the interferogram belongs in the reciprocal length dimension([L?1]), that is the dimension of wavenumber. The spectral resolution in cm?1 is same as the reciprocal of the maximal retardation in cm. A really higher resolution can be gained by increasing the maximum retardation.
The interferogram in working comprises of a set of intensities measured for discrete values of retardation. The difference between consecutive retardation values is same. Therefore, a discrete Fourier transform is of extremely necessary. The fast Fourier transform (FFT) algo is hence utilized.
The above clearly states the importance of a fourier transform in FTIR.
.
when using an FTIR-which utilizes an inferometer- why do we need a fou.docx
1. when using an FTIR,which utilizes an inferometer, why do we need a fourier transform to obtain
the actual spectrum
Solution
Fourier-transform infrared spectroscopy is based on the certainty that a Fourier transform (a
mathematical procedure) is needed to turn the raw data into the actual spectrum.
In the experiment an Interferometer is used which is adapted for FTIR, light from the
polychromatic infrared source is collimated or made parallel and directed to a beam splitter.
Interferogram is termed as the signal format acquired by an FT-IR spectrometer.
The interferogram needs to be measured from zero path difference to a maximum length which
relies on the resolution needed.
Practically, the scan can be on either side of zero resulting in a double-sided interferogram.
The interferogram is converted to a spectrum by Fourier transformation. This requires it to be
stored in digital form as a series of values at equal intervals of the path difference between the
two beams.
The result of Fourier transformation is a spectrum of the signal at a series of discrete
wavelengths. The range of wavelengths that can be used in the calculation is limited by the
separation of the data points in the interferogram. The shortest wavelength that can be identified
is twice the separation between these data points.
The interferogram is present in the length dimension. Fourier transform (FT) inverts the
dimension, so the FT of the interferogram belongs in the reciprocal length dimension([L?1]), that
is the dimension of wavenumber. The spectral resolution in cm?1 is same as the reciprocal of the
maximal retardation in cm. A really higher resolution can be gained by increasing the maximum
retardation.
The interferogram in working comprises of a set of intensities measured for discrete values of
retardation. The difference between consecutive retardation values is same. Therefore, a discrete
Fourier transform is of extremely necessary. The fast Fourier transform (FFT) algo is hence
utilized.
2. The above clearly states the importance of a fourier transform in FTIR.
![when using an FTIR,which utilizes an inferometer, why do we need a fourier transform to obtain
the actual spectrum
Solution
Fourier-transform infrared spectroscopy is based on the certainty that a Fourier transform (a
mathematical procedure) is needed to turn the raw data into the actual spectrum.
In the experiment an Interferometer is used which is adapted for FTIR, light from the
polychromatic infrared source is collimated or made parallel and directed to a beam splitter.
Interferogram is termed as the signal format acquired by an FT-IR spectrometer.
The interferogram needs to be measured from zero path difference to a maximum length which
relies on the resolution needed.
Practically, the scan can be on either side of zero resulting in a double-sided interferogram.
The interferogram is converted to a spectrum by Fourier transformation. This requires it to be
stored in digital form as a series of values at equal intervals of the path difference between the
two beams.
The result of Fourier transformation is a spectrum of the signal at a series of discrete
wavelengths. The range of wavelengths that can be used in the calculation is limited by the
separation of the data points in the interferogram. The shortest wavelength that can be identified
is twice the separation between these data points.
The interferogram is present in the length dimension. Fourier transform (FT) inverts the
dimension, so the FT of the interferogram belongs in the reciprocal length dimension([L?1]), that
is the dimension of wavenumber. The spectral resolution in cm?1 is same as the reciprocal of the
maximal retardation in cm. A really higher resolution can be gained by increasing the maximum
retardation.
The interferogram in working comprises of a set of intensities measured for discrete values of
retardation. The difference between consecutive retardation values is same. Therefore, a discrete
Fourier transform is of extremely necessary. The fast Fourier transform (FFT) algo is hence
utilized.](https://image.slidesharecdn.com/whenusinganftir-whichutilizesaninferometer-whydoweneedafou-230209234059-52974120/85/when-using-an-FTIR-which-utilizes-an-inferometer-why-do-we-need-a-fou-docx-1-320.jpg)
