Spectra integrated intensities, band shapes

Infrared and Raman spectra contain information about what compound(s) could be present in a sample and about the relative amounts of such constituents, as well as giving insights into the stmctures of compounds. Determination of rotation constants from high-resolution spectra of gases is described in Section 7.3.2, and derivation of force constants is discussed in Section 8.9. Absolute quantitative measurements of concentrations, such as can be obtained by integration of NMR spectra, are not possible for unknown species, because the intensity of each IR or Raman band for each compound is a specific property of that molecule. We have seen that the shapes and positions of bands vary depending on the phase of the sample, but even so the overall profile of absorption (or transmission) of a spectrum can be analyzed as a function of the relative concentrations of the components of the sample, if reference spectra for each of the components are... 

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