absorption which takes place with the transition from the singlet ground state of the molecule to triplet states (S 0 → T n) and results in the singlet-triplet absorption spectrum.
Source:
PAC, 1984, 56, 231. 'Nomenclature, symbols, units and their usage in spectrochemical analysis-Part VI: molecular luminescence spectroscopy' on page 234 (https://doi.org/10.1351/pac198456020231)