free induction decay 

Initialism: FID
https://doi.org/10.1351/goldbook.08249
Indication from a pulsed spectroscopy experiment that takes the form of damped sine waves arising from the excited system returning to equilibrium.
Note:
In nuclear magnetic resonance spectroscopy, the FID consists of sine waves oscillating at the Larmor frequency (ω) and dampened by net dephasing time relaxation (T2∗), sin⁡(ωt)exp⁡(−t/T2∗).
Source:
PAC, 2021, 93, 647. (Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)) on page 659 [Terms] [Paper]
Citation: 'free induction decay' 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.08249 RIS BibTex EndNote
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