Wissensfundus

What is the spectral resolution?

Spectral resolution is the ability of a spectroscopic system to separate adjacent peaks.
Confocal Raman systems have a spectral resolution which is primarily defined by:

  • The focal length of the spectrometer (the longer the focal length, the higher the spectral resolution)
  • The grating (the higher the groove density, the higher the spectral resolution)
  • The pixel size on the CCD camera (the smaller the pixels, the higher the spectral resolution)
  • The entrance slit or pinhole (the smaller the slit/pinhole the higher the spectral resolution)
  • The line shape preservation (=imaging quality) of the spectrometer

The spectral resolution can be experimentally determined e.g. by measuring the peak resolution on known reference samples. An established sample used to demonstrate spectral resolution is for example CCl4.

With few exceptions the natural linewidths of Raman lines are typically larger than 3 cm-1. Therefore a spectral resolution in the range of 1 cm-1 is sufficient for the majority of samples.