Vibrational relaxation of CO2 by O atoms

Abstract

The vibrational relaxation in CO2–Ar, CO2–O2–Ar, and CO2–O–O2–Ar mixtures was studied over the temperature range 2000–4000°K. Infrared emission measurements were made of the 4.3 μ asymmetric stretch mode and the 2.7 μ combination bands. Since all the modes of CO2 have been shown to exhibit the same relaxation time, the present measurements could be directly related to the relaxation rate for the translation-vibration excitation excitation of the bending mode. The experimental results indicate that O-atoms are approximately an order of magnitude more efficient than Ar in the relaxation of the bending mode with a collisional probability of the order of 10−2 at 3000°K.

Plasma activation of N2, CH4and CO2: an assessment of the vibrational non-equilibrium time window

“…Dissociation products in CO 2 plasma may shorten effective VT times, similar as was discussed for CH 4 and N 2 . Atomic oxygen is approximately an order of magnitude more potent in quenching vibrations than CO 2 itself [38]. Still, a dissociation fraction of ∼10% is required to decrease the effective VT times sufficiently to correctly predict the measured gas temperatures.…”

“…Vibrational energy transfer in these molecules has been studied extensively. For N 2 and CO 2 , this was mainly in the context of the CO 2 laser [16,[37][38][39]. The CO 2 laser operates on population inversion between the first excited asymmetric stretch vibrational level and the first Fermi resonant levels.…”

Rate constant for quenching of CO2(010( by atomic oxygen

“…(2) as measured (a) in a shock tube at high temperatures [Center 1973 Theoretical temperature dependence of k• Vibrational relaxation by collision with closed-shell species normally occurs by an impulsive (Landau-Teller) mechanism, which may be enhanced by the presence of an attractive interaction between the colliding species. Our trajectory calculations for such a mechanism, using the WKB energy-tr•sfer probabilities given by Shin [1976], indicate that the large room-temperature value found for k2 cannot be understood in terms of the Landau-Teller mechanism.…”

Vibrational quenching of CO2(010) by collisions with O(P3) at thermal energies: A quantum-mechanical study

“…2 In addition, the temperature dependence of k is not well known in the atmospheric temperature range ͑150-550 K͒. Taylor, 3 based on high-temperature ͑1975-3840 K͒ shock-tube measurements by Center, 4 reported an expression for k͑T͒ with a Landau-Teller temperature dependence, A exp͑−BT −3 ͒, which gives a roomtemperature value of 2.4ϫ 10 −14 cm 3 s −1 . On the other hand, using field-based data of atmospheric 15 m radiance, Sharma and Wintersteiner 5 recommended a value of 6͑±3͒ ϫ 10 −12 cm 3 s −1 of k at 300 K, i.e., a factor of about 250 larger than Taylor's extrapolation.…”