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Gateway to Spectroscopy > Physical Background > Atomic Emission Lines Shapes > Instrumental Lineshape

Instrumental Lineshape

Gaussian line profileThe 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 lineshape asymmetric.

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.