internal transmittance symbols: $T_{\rm{i}}$, $\tau_{\rm{i}}$

Synonym: internal transmission
https://doi.org/10.1351/goldbook.08262
Transmittance fully corrected for surface effects and effects of the cell, such as reflection, scattering, luminescence, and vignetting losses.
Note:
If scattering and luminescence in the sample are negligible, \(\alpha_{\rm{i}} + Τ_{\rm{i}} = 1\), where \(\alpha_{\rm{i}}\) is internal absorptance.
Source:
PAC, 2021, 93, 647. 'Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)' on page 664 (https://doi.org/10.1515/pac-2019-0203)