Abstract Quantitative measurements of the steady state vibrational population of O 2( 1Σ + g) υ = 0,1,2 from the energy pooling reaction: 2O 2( 1Δ g) → O 2( 3Σ − g) + O 2 ( 1Σ + g), in the presence of strong electronic quenchers of the 1Σ + g state indicate that this reaction produces O 2( 1Σ + g) preferentially with two quanta of vibrational excitation. The relative probabilities for the products O 2( 1Σ + g) υ = 0 and O 2( 1Σ + g) υ = 1 are lower by roughly a factor of two, and by at least a factor of 17, respectively. The rate constant for vibrational relaxation of O 2 ( 1Σ + g) υ = 2 by molecular oxygen, directly to O 2( 1Σ + g) υ = 0, is found to be (9 ± 1) × 10 −13 cm 3 molecule −1 s −1, this value being based on rate constants for electronic quenching of O 2( 1Σ + g), assumed to be independent of vibrational excitation. This rapid process provides for an extremely efficient vibrational equilibration of O 2 ( 1Σ + g) υ in discharged oxygen. The gases NH 3, H 2 and CO 2 are found to act predominantly as electronic quenchers of O 2( 1Σ + g) υ, while CH 4 and C 2H 2 contribute measurably to its vibrational relaxation.