Spectrum of a material under the influence of an applied external perturbation represented by a variable
\(\tau\), relative to a reference spectrum.
Note:
The reference spectrum may be chosen in many ways; e.g., it may be the average over \(\tau\), of the observed spectrum, or it may be zero.
See also: two-dimensional correlation spectroscopy, two-dimensional correlation spectrum
Source:
PAC, 2021, 93, 647. 'Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)' on page 744 (https://doi.org/10.1515/pac-2019-0203)