Translation to vibration energy transfer in O + NH3 and O + CO2 collisions

Publisher Website
Google Scholar
Abstract
Vibrational excitation of NH3 and CO2 in collision with atomic oxygen is investigated for energies of 1–10 eV. A classical hard‐sphere model used previously for diatomic molecules is adopted. Four ``diatomic'' models of NH3, in which the H3 complex assumes the role of a single atom, are used to study excitation of the ν2 mode. The results for the four models are very similar despite the model differences. It is shown that excitation of the ν1 and ν2 modes of CO2 can be computed very accurately through construction of the appropriate diatomic molecules. The classical energy transfers for CO2 and NH3 are converted to excitation probabilities of specific quantum states by using the assumption that the time‐dependent interaction causing the excitation is a driving force independent of the oscillator coordinate. It is found that multiquantum excitation is important, the more so at higher energies. A scaling technique is used to estimate energy transfer for a more realistic atom‐atom interaction. This results in greatly reduced multiquantum excitation for energies less than 5 eV. Excitation of the stiffer modes is also investigated. It is found that while excitation of the NH3ν4 mode is comparable to that of the ν2 mode at higher energies, the other modes may be neglected for the entire energy range studied.