The intensities of collision-induced emission of singlet oxygen O 2 (a 1 Δ) caused by the following two radiative processes-O 2 (a, ν = 0) + O 2 (a, ν = 0) → O 2 (X, ν = 0) + О 2 (X, ν = 0, 1) + hν and O 2 (a, ν = 0) + O 2 → O 2 (X, ν = 0) + O 2 + hν-are studied by emission spectroscopy. It is found that the rate constants of these radiative processes are (1.54 ± 0.23) × 10 -22 cm 3 s -1 and (2.74 ± 0.4) × 10 -23 cm 3 s -1 , respectively.