The measured intensity must pass through the slits of the spectrometer: very narrow
slits introduce diffraction broadening, while wide slits reduce the
resolution. In general wide slits introduce a trapezoidall shape which
is then convoluted with the natural Voigt profile to produce the
lineshapes we typically observe in analytical spectrometers. The
trapezoidall shape itself is linked to the convolution the two
rectangular slits, entrance slit and exit slit respectively..
Instrumental lineshape FWHM ~50 pm
Different effects such as astigmatism may render the observed
For more details and a description of the equations used
see: R Payling and P L Larkins, in R Payling, D G Jones
and A Bengtson (Eds), Glow
Discharge Optical Emission Spectrometry, John Wiley &
Sons, Chichester (1997), pp 364-375.
Authors: Richard Payling and Thomas Nelis
First published on the web: 15 November 1999.