thermal diffusion depth

symbols: $L$, $\mu_{\rm{s}}$, units: $\pu{m}$, $\pu{\upmu\!m}$
synonym: thermal wave decay length
https://doi.org/10.1351/goldbook.08696
In photoacoustic spectroscopy, \(L = \sqrt{(D/\pi f)}\), where \(D\) is thermal diffusivity and \(f\) is modulation frequency of the electromagnetic radiation.
Notes:
  1. SI unit: \(\pu{m}\). Common unit: \(\pu{\upmu\!m}\).
  2. \(\pu{63 \%}\) of the PAS signal originates within the thermal diffusion depth.
Source:
PAC, 2021, 93, 647. (Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)) on page 766 [Terms] [Paper]
Citation: 'thermal diffusion depth' 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.08696 RIS BibTex EndNote
Div. VTextXMLJSON