The Spectroscopy Net
Gateway to Spectroscopy > Spectrometers > Spectrometer Resolution > Resolution


As stated above spectral resolution expresses the ability, for an optical system, to resolve near lines, for example an analytical line and a line of the matrix. To carry out an analysis without the need for numerous inter-element corrections, adequate resolution is necessary, hence a grating with a large number of lines.


Spectral resolution can be improved by reducing the width of the spectral slits, but signal strength (luminosity) is also reduced.

For a given grating and in a given order, the spectral resolving power is proportional to the focal length of the optical system and to the reciprocal of the entrance and exit slit widths. It is exactly the opposite for system brightness.


To achieve the resolution necessary for analyses, one can increase either the focal length of the system for a given grating, or the number of lines of the grating for a given focal length.

However, when the system's focal length is increased, its mechanical stability may be impaired and, for the same grating, brightness is reduced. Stability is a critical characteristic for equipment which must retain its calibration characteristics over a long period of time. Further, brightness is invaluable as it is synonymous with good detection limits

Author: Jean Charles Lefebvre, Horiba Jobin-Yvon

First published on the web: 15 November 1999.