Measure of the energy difference between the source (

) and the
absorber (

) transition. The measured Doppler velocity shift,

, is related to the energy difference by
where

is the Mössbauer gamma energy and

is the speed of light in vacuum.
Source:
PAC, 1976, 45, 211
(Nomenclature and Conventions for Reporting Mossbauer Spectroscopic Data)
on page 214
Cite as:
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A.Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8.
doi:10.1351/goldbook.