spectral resolution symbols: $\delta \tilde{\nu}$, $\delta \nu$, $\delta \lambda$

of an instrument
Synonym: resolution
https://doi.org/10.1351/goldbook.08289
Smallest difference between wavenumbers (or wavelengths or frequencies) at which different spectral properties may be distinguished, measured as the full width at half maximum.
Notes:
  1. An equivalent definition is the minimum separation of two infinitely sharp lines of equal intensity of radiation that allows the presence of two lines to be seen in the measured spectrum.
  2. Resolution depends strongly on the instrument line shape "function" of the spectrometer and on the natural line width.
See also: nominal spectral resolution
Source:
PAC, 2021, 93, 647. 'Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)' on page 674 (https://doi.org/10.1515/pac-2019-0203)