Reciprocal of the
vacuum wavelength of
electromagnetic radiation.
\(\tilde{\nu} = 1/\lambda_{0}\).
Notes: - Wavenumber is related to the energy change, \(\Delta E\), induced when the radiation is absorbed by \(\Delta E = hc_{0}\tilde{\nu}\), where \(h\) is the Planck constant and \(c_{0}\) the speed of the radiation.
- Wavenumber should only be used when no confusion with frequency is possible.
- The symbol \(\nu\) is often used instead of \(\tilde{\nu}\); this usage should be discouraged.
- 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)