Reciprocal of
wavelength of
electromagnetic radiation.
\(\sigma = 1/\lambda\).
Notes: - In spectroscopy, the unqualified term 'wavenumber' (sometimes referred to as "reciprocal centimetre" \(\pu{cm-1}\)) often means vacuum wavenumber, and symbol \(\sigma\) often means \(\tilde{\nu}\).
- SI unit: \(\pu{m-1}\). Common unit: \(\pu{cm-1}\).
Source:
PAC, 2021, 93, 647. 'Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)' on page 678 (https://doi.org/10.1515/pac-2019-0203)