Direct optical excitation of singlet oxygen in organic solvents

Efficient excitation of singlet oxygen is demonstrated for several organic solvents (CS2, CCl4, and C6F14) that are irradiated using LED in the visible spectral range in the absorption bands of the O2-O2 collision complexes at the corresponding cooperative transitions. It is shown that the two-photon interaction of the pumping radiation in the Herzberg I band of molecular oxygen with its excitation to the 3Σ + state and the subsequent collisional relaxation to the 1Σ g and 1Δ g singlet states contributes to the excitation of singlet oxygen.