Abstract—A new spectroscopic method has been developed in our laboratory for perturbation of singlet‐triplet transitions in organic molecules by O2. A dilute solution (10‐2‐10‐4M) of the molecule to be studied in various solvents is pressurized in a bomb with O2at 100 atm (10MPa) for 3–10h. The pressure is released, the solution pipetted into a sample tube, sealed, and frozen to a rigid glass state at 77 K. Then the luminescence spectra and excitation spectra of the sample are scanned.For benzene‐O2we have evidence for a weak complex with a mild perturbation and a strong complex, with various new combination states. For the strong complex, the T1→ S emission and excitation spectrum is observed, and also the T2← S excitation spectrum. The T1→ S emission for the benzene‐O2complex is seen as a highly resolved emission at 77 K in the glass solvent, but also at 298 K as a poorly resolved emission (induced triplet–triplet fluorescence in the complex). Variousupconversion simultaneous transitionsanddownconversion simultaneous transitionsare observed, e.g. (3Blu+1Σ+g), (3Blu+1Δg)upconversions, and the (3Blu+1Σ+g), (3Blu+1Δg)downconversions; thus, in the latter, the third π, π* triplet is revealed for the first time. A novel structure for the benzene–O2strong complex is proposed as ananf jamelmodel.Forpyridine–O2andperdeuteropyridine–O2we observe the T1→ S emission for the first time; it is π,