Technical Note: A new mechanism of 15 μm emission in the mesosphere-lower thermosphere (MLT)
Atmospheric Chemistry and Physics Discussions
Accurate knowledge of the rate as well as the mechanism of excitation of the bending mode of CO<sub>2</sub> is necessary for reliable modeling of the mesosphere-lower thermosphere (MLT) region of the atmosphere. Assuming the excitation mechanism to be thermal collisions with atomic oxygen the rate coefficient derived from the observed 15 μm emission by space-based experiments differ from the laboratory measurements by a factor of 2–4. It is proposed that thermal collisions with
... with N<sub>2</sub>, mediated by a near-resonant rotation to vibration energy transfer process, excite bending mode of CO<sub>2</sub> by transferring energy from high rotational levels of thermal N<sub>2</sub>. Analogy with the excitation of the bending mode of CO<sub>2</sub> by H<sub>2</sub>O, a process important in CO<sub>2</sub> lasers, mediated by a near-resonant rotation-to vibration energy transfer process lends credibility to the hypothesis which has yet to be tested by direct calculations.