Interval between the two points across a section of a
spectrum where the ordinate is equal to half the maximum ordinate of the section.
Notes: - \(W\) is a measure of line or band width.
- FWHM has units of wavelength, wavenumber, frequency, or energy.
- For infrared absorption spectra, the FWHM must be measured from a spectrum that is plotted linear in absorbance.
- In Raman spectra, the FWHM can be measured directly from the spectrum of scattered light intensity unless the instrument response function varies significantly across the band.
- Inclusion of "full" distinguishes FWHM from half-width at half maximum.
Source:
PAC, 2021, 93, 647. 'Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)' on page 660 (https://doi.org/10.1515/pac-2019-0203)