t2 

in two-dimensional nuclear magnetic resonance spectroscopy
Synonym: $t_2$ in 2-D NMR
https://doi.org/10.1351/goldbook.08430
Time domain in two-dimensional nuclear magnetic resonance spectroscopy arising from direct free induction decay detection.
Source:
PAC, 2021, 93, 647. 'Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)' on page 708 (https://doi.org/10.1515/pac-2019-0203)