Vibrational relaxation of CO₂(ν₂) by O(³P) in the 142–490 K temperature range

[1] Laboratory measurements of the quenching of CO₂(ν₂) by O atoms are presented over the 142–490 K temperature range relevant to the 75–120 km altitude region of the terrestrial atmosphere. The primary cooling mechanism in this region occurs when CO₂ is efficiently excited through collisions with ambient O atoms, populating the bending vibrational (ν₂) modes. A significant fraction of the vibrationally excited CO₂ relaxes through spontaneous 15-μm emission that escapes into space, thereby removing kinetic energy from this region of the atmosphere and generating a local cooling effect. The rate coefficient for the vibrational relaxation of CO₂(ν₂) by O atoms, k_O(ν₂), is measured using transient diode laser absorption spectroscopy. A slight negative temperature dependence is observed for k_O(ν₂), with values ranging from 2.7 (±0.4) × 10⁻¹² cm³ s⁻¹ at 142 K to 1.3 (±0.2) × 10⁻¹² cm³ s⁻¹ at 490 K.