natural linewidth

https://doi.org/10.1351/goldbook.08641
Line width of a molecular spectral band that arises from the probability of spontaneous emission in the absence of radiation fields and interaction with other molecules or entities.
Notes:
  1. The natural linewidth, measured as the full width half maximum equals 1/(2πc0Δt), where Δt is the natural lifetime of the excited state.
  2. If the excited state n can only emit spontaneously to a single lower state m the natural linewidth is 1.86×10−38 ν~mn3⟨m|μ|n⟩2, when the transition wavenumber ν~mn is in cm−1 and the dipole moment μ is in Debye (1 D≈3.335E−30Cm). In the infrared, typical natural linewidths are approximately 10−7 cm−1.
Source:
PAC, 2021, 93, 647. (Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)) on page 755 [Terms] [Paper]
Citation: 'natural linewidth' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.08641 RIS BibTex EndNote
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