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

Laboratory measurements of the quenching of CO2(nu(2)) 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 (nu(2)) modes. A significant fraction of the vibrationally excited CO2 relaxes through spontaneous 15-mu m 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(nu(2)) by O atoms, k(O)(nu(2)), is measured using transient diode laser absorption spectroscopy. A slight negative temperature dependence is observed for k(O)(v(2)), with values ranging from 2.7 (+/- 0.4) x 10(-12) cm(3) s(-1) at 142 K to 1.3 (+/- 0.2) x 10(-12) cm(3) s(-1) at 490 k.