Near-resonant energy transfer from vibrationally excited OH(v),v= 9, 8, 1 to CO2

Abstract

[1] The transfer of vibrational energy from chemiluminescent OH, produced predominately by the H + O3 → OH (v) + O2 reaction, is of importance in modeling the airglow from the atmospheres of Earth, Mars, and Venus. We have calculated the energy transfer probability per collision as function of temperature for the near-resonant processes OH (v) + CO2 (00001) → OH(v − 1) +CO2 (mnpqr) for v = 1, 8, and 9 in the 100 – 350 K temperature range. We show that the measured room temperature values of the removal rate coefficient of OH(v = 9, 8) and OH(v = 1) by CO2, are in agreement with the ones calculated for the vibration-to-vibration (VV) energy transfer (ET) processes OH (v) + CO2 (00001) → OH (v − 1) + CO2 (00011) and OH (1) + CO2 (00001) → OH (0) + CO2 (1001 n) n =1, 2, respectively. The emission from the latter levels of CO2 in the terrestrial mesosphere is not self-absorbed leading to the possibility that these levels may be important contributors to the 4.3 μm emission. Our calculation favors the “Collisional Cascade” model of vibrational energy transfer from OH to CO2 that predicts about 50 times more radiation in the Martian Meinel bands over that predicted by the “Sudden Death” model. These two models of Martian atmosphere predict vastly different steady-state populations of the vibrational levels of OH and should, because of the chemical reactions, of other trace species, e.g., H, O, and CO, as well.