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

Abstract

The rate of quenching of CO2(010) by O(3p) has been measured at room temperature by a temperature-jump method. The rate constant value obtained is in good agreement with a previous room-temperature measurement based on steady-state analysis of a hollow-cathode discharge in CO2. The results of fitting the room-temperature result to trajectory calculations with a curve-crossing (Nikitin) energytransfer mechanism lead to the conclusion that the quenching rate constant should increase only slowly with increasing temperature.

Cooling Mechanisms of the Planetary Thermospheres: The Key Role of O Atom Vibrational Excitation of CO2 and NO

“…After a closer examination of the data, Sharma [12] revised the low temperature value of this rate coefficient still upward by a factor of about seven to 2 Â 10 À13 T 1/2 -in all, a factor of about 140 larger than the value recommended by Taylor at 300 K. After a thorough examination of the model atmospheres used in calculating the 15 mm emission, Sharma and Wintersteiner [13] recommended an expression, Equation (1), for the temperature range of interest, with a value of 6(AE 3) Â 10 À12 cm 3 s À1 at 300 K. This value of the rate coefficient was arrived at solely by modeling the 15 mm emission observed by SPIRE and has since been supported by analysis of other space-based measurements of Earth and Mars. [14±17] The planetary modeling community until recently has used the low end of the suggested value in their models, (3 ± 4) Â 10 À12 cm 3 s À1 at 300 K. Two sets of experiments [18,19] have however recommended an even lower room temperature value of (1 ± 1.5) Â 10 À12 cm 3 s À1 . k c 3.5(AE 1.8)Â 10 À13 T 1/2 2.32Â 10 À9 exp(À76.75/T 1/3 ) cm 3 s À1 (1)…”

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

“…In order to account for this discrepancy, they proposed an expression for k͑T͒ in which a low-temperature, CT 1/2 , term is added to the Landau-Teller term. During the last decade, laboratory determinations of the relaxation rate have been reported at room temperature, [6][7][8][9] providing values in the ͑1 -1.5͒ ϫ 10 −12 cm 3 s −1 range. Nevertheless, the value of k required by the atmospheric models is about a factor of 4 larger than the measured values.…”

Extending MGS-TES temperature retrievals in the martian atmosphere up to 90km: Retrieval approach and results

“…Changing k VT {CO 2 -O} to 1.5 Â 10 À12 cm 3 s À1 , the value obtained in laboratory measurements (Pollock et al, 1993;Khvorostovskaya et al, 2002;Castle et al, 2006;Huestis et al, 2008) modifies the retrieved profile in the entire range of the retrieval. This is explained by the non-LTE effects in CO 2 : reducing the collisional rate coefficient leads to less efficient thermalizing of the vibrational levels that become more populated by radiance coming from the warmer and denser layers below.…”