Unsymmetrical Peak Shapes

Fig. 14. Molecular weight characteristics of novolac resins. Shown is the size-exclusion chromatogram for a typical commercial novolac polymer. The unsymmetrical peak shape reflects the multimodal molecular weight distribution of the polymer.

An unsymmetrical peak shape indicates that the sample size is too large. 

Loss peaks obtained for solid polymers are generally much broader than a Debye process, and indeed broader than is the case for many relaxations in solution. In many cases they are grossly unsymmetrical and even show structural features. For broad and even unsymmetrical loss peaks their shapes are often analysed in terms of a standard distribution function as described on p. 106. It should be stressed, however, that anomalous peak shapes can result from an artifact in data analysis when relaxations occur at low frequencies (10 to 10 Hz). The conventional technique for this frequency range is to measure the decay current (or less commonly, the... 

In contrast with graphite and diamond with a crystalline structure that is connected with Raman lines, amorphous carbon reveals broad bands caused by the structural disorder with an unsymmetrical Raman band in the wavenumber region between 900 and 1800 cm. Its shape is formed by two more or less significant features, originating from the graphite G line at about 1580 cm" and the D line near 1350 cm Analyzing the intensity relation 1 /1, the peak position, and their FWHM, one gets information about the diamond-likeness of the films. 

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