Observation of collision-induced near-IR emission of singlet oxygen O2 a1Δg generated by visible light excitation of gaseous O2 dimol

The dimol absorption of O2 at 630 nm was performed to generate O2 a1Δg in the gas phase. The pure collision-induced phosphorescence spectrum was recorded around 1260 nm at the O2 pressure of 130 atm. The excitation spectrum, recorded by measuring the near-IR emission intensity, had the same spectral shape as that of the dimol absorption spectrum in 620–640 nm. The quadratic pressure dependence of the phosphorescence intensity evidenced that the emission was induced by collision. The self-quenching rate constant of O2 a1Δg has been estimated to be (1.7 ± 0.2) × 10−18 cm3 molecule−1 s−1.