Vibrational relaxation of NO(v = 1) by oxygen atoms between 295 and 825 K

Abstract

[1] Vibrational excitation of ground-state NO through collisions with oxygen atoms produces NO(v = 1) in the lower thermosphere, representing a significant source of atmospheric cooling through the subsequent 5.3-mm radiative emission. A laser pumpprobe experiment has been used to measure the temperature dependence of the NO(v = 1)-O vibrational relaxation rate coefficient k O (v = 1) in the 295-825 K range, along with updated measurements of k O (v = 1,2) at room temperature. The experiment employed a continuous wave microwave source to form O atoms, combined with photolysis of a trace amount of added NO 2 to produce vibrationally excited NO. Oxygen atoms were detected through two-photon laser-induced fluorescence, cross-calibrated against a normalized O atom signal resulting from photolysis of a known concentration of NO 2 . No temperature dependence was observed for k O (v = 1) to within the uncertainty in the measurements. The measured room temperature value of k O (v = 1) = (4.2 ± 0.7) Â 10 À11 cm 2 s À1 is 75% larger than the value obtained previously in this laboratory, a significant difference at the 1s level. The present value is preferred owing to an improved experimental technique. The atmospherically relevant NO(v = 0)-O vibrational excitation rate coefficient can be derived from measured values of k O (v = 1) through detailed balance. The variable temperature measurements provide key information for aeronomic models of the lower thermospheric energy budget, infrared emission intensities, and neutral constituent densities.

The O + NO(v) Vibrational Relaxation Processes Revisited

“…At room temperature, one-quantum vibrational relaxation gets nearly twice as large as previously reported, thence in good agreement with the more recent and reliable experimental measurements. The temperature dependence of the v = 1 → 0 relaxation process is similar to the experimental results of Hwang et al, 16 with the QCT results lying within most of the reported experimental errors. Although modeling of Earths' thermosphere requires a value closer to the one reported by Fernando and Smith, 10 the QCT calculations point to a value 1.5× smaller at room temperature.…”

“…23 As the temperature raises, the energy content of the system becomes sufficiently high to overcome such topographical artifacts with the energy transfer being preferentially VT and VR (substantially less effective), but the number of isomerizations is still too small to be significant. Regarding the state-to-all rate constant, it is found to increase with the initial vibrational 20,23,26,48 and experimental measurements 10,16,18,19,49 and our previous result. 23 For clarity, some congested experimental data at v′ = 1 has been separated by 0.1. quantum state, a pattern similar to the one found for the 2 A′ dynamics, but now twice as large for low vibrational states.…”

The O + NO(v) Vibrational Relaxation Processes Revisited

“…At room temperature, one-quantum vibrational relaxation gets nearly twice as large as previously reported, thence in good agreement with the more recent and reliable experimental measurements. The temperature dependence of the v = 1 → 0 relaxation process is similar to the experimental results of Hwang et al, 16 with the QCT results lying within most of the reported experimental errors. Although modeling of Earths' thermosphere requires a value closer to the one reported by Fernando and Smith, 10 the QCT calculations point to a value 1.5× smaller at room temperature.…”

“…23 As the temperature raises, the energy content of the system becomes sufficiently high to overcome such topographical artifacts with the energy transfer being preferentially VT and VR (substantially less effective), but the number of isomerizations is still too small to be significant. Regarding the state-to-all rate constant, it is found to increase with the initial vibrational 20,23,26,48 and experimental measurements 10,16,18,19,49 and our previous result. 23 For clarity, some congested experimental data at v′ = 1 has been separated by 0.1. quantum state, a pattern similar to the one found for the 2 A′ dynamics, but now twice as large for low vibrational states.…”

Dynamics on Multiple Potential Energy Surfaces: Quantitative Studies of Elementary Processes Relevant to Hypersonics

“…Another computational study, 124 using a three-dimensional spline representation of energies from CASSCF/aug-cc-pVTZ calculations, reported a value of k ν=1→0 (T = 300 K) ∼ 5(10 −11 ) cm 3 s −1 . These relaxation rates agree quite favorably with experiment 122,128 but the T−dependence of the simulations using the DMBE PESs is too steep, in particular for the 2 A′′ state which leads to an underestimation of the vibrational relaxation at higher temperatures. More recent simulations based on RKHS-represented PESs at the MRCI/ aug-cc-pVTZ level of theory correctly describe both, the lowand high-T vibrational relaxation rates as observed experimentally.…”

The N( 4 S) + O 2 (X 3 Σ−g) ↔ O( 3 P) + NO(X 2 Π) reaction: thermal and vibrational relaxation rates for the 2 A′, 4 A′ and 2San Vicente Veliz, Koner, Schwilk et al. 2020Phys. Chem. Chem. Phys.

“…7. In particular for low temperature the agreement with the more recent 20 experiments and the only high-temperature experiment (at 2700 K) 66 is noteworthy. The results from the simulations based on high-level, 2-dimensional PESs 16 for the 2 A 0 and 2 A 00 states are also in good agreement with the experiments and the present simulations.…”

The O + NO(v) Vibrational Relaxation Processes Revisited

“…At room temperature, one-quantum vibrational relaxation gets nearly twice as large as previously reported, thence in good agreement with the more recent and reliable experimental measurements. The temperature dependence of the v = 1 → 0 relaxation process is similar to the experimental results of Hwang et al, 16 with the QCT results lying within most of the reported experimental errors. Although modeling of Earths' thermosphere requires a value closer to the one reported by Fernando and Smith, 10 the QCT calculations point to a value 1.5× smaller at room temperature.…”

“…23 As the temperature raises, the energy content of the system becomes sufficiently high to overcome such topographical artifacts with the energy transfer being preferentially VT and VR (substantially less effective), but the number of isomerizations is still too small to be significant. Regarding the state-to-all rate constant, it is found to increase with the initial vibrational 20,23,26,48 and experimental measurements 10,16,18,19,49 and our previous result. 23 For clarity, some congested experimental data at v′ = 1 has been separated by 0.1. quantum state, a pattern similar to the one found for the 2 A′ dynamics, but now twice as large for low vibrational states.…”

Dynamics on Multiple Potential Energy Surfaces: Quantitative Studies of Elementary Processes Relevant to Hypersonics

“…Another computational study, 124 using a three-dimensional spline representation of energies from CASSCF/aug-cc-pVTZ calculations, reported a value of k ν=1→0 (T = 300 K) ∼ 5(10 −11 ) cm 3 s −1 . These relaxation rates agree quite favorably with experiment 122,128 but the T−dependence of the simulations using the DMBE PESs is too steep, in particular for the 2 A′′ state which leads to an underestimation of the vibrational relaxation at higher temperatures. More recent simulations based on RKHS-represented PESs at the MRCI/ aug-cc-pVTZ level of theory correctly describe both, the lowand high-T vibrational relaxation rates as observed experimentally.…”

The N( 4 S) + O 2 (X 3 Σ−g) ↔ O( 3 P) + NO(X 2 Π) reaction: thermal and vibrational relaxation rates for the 2 A′, 4 A′ and 2San Vicente Veliz, Koner, Schwilk et al. 2020Phys. Chem. Chem. Phys.

“…7. In particular for low temperature the agreement with the more recent 20 experiments and the only high-temperature experiment (at 2700 K) 66 is noteworthy. The results from the simulations based on high-level, 2-dimensional PESs 16 for the 2 A 0 and 2 A 00 states are also in good agreement with the experiments and the present simulations.…”

The O + NO(v) Vibrational Relaxation Processes Revisited

“…At room temperature, one-quantum vibrational relaxation gets nearly twice as large as previously reported, thence in good agreement with the more recent and reliable experimental measurements. The temperature dependence of the v = 1 → 0 relaxation process is similar to the experimental results of Hwang et al, 16 with the QCT results lying within most of the reported experimental errors. Although modeling of Earths' thermosphere requires a value closer to the one reported by Fernando and Smith, 10 the QCT calculations point to a value 1.5× smaller at room temperature.…”

“…23 As the temperature raises, the energy content of the system becomes sufficiently high to overcome such topographical artifacts with the energy transfer being preferentially VT and VR (substantially less effective), but the number of isomerizations is still too small to be significant. Regarding the state-to-all rate constant, it is found to increase with the initial vibrational 20,23,26,48 and experimental measurements 10,16,18,19,49 and our previous result. 23 For clarity, some congested experimental data at v′ = 1 has been separated by 0.1. quantum state, a pattern similar to the one found for the 2 A′ dynamics, but now twice as large for low vibrational states.…”

Dynamics on Multiple Potential Energy Surfaces: Quantitative Studies of Elementary Processes Relevant to Hypersonics

“…Another computational study, 124 using a three-dimensional spline representation of energies from CASSCF/aug-cc-pVTZ calculations, reported a value of k ν=1→0 (T = 300 K) ∼ 5(10 −11 ) cm 3 s −1 . These relaxation rates agree quite favorably with experiment 122,128 but the T−dependence of the simulations using the DMBE PESs is too steep, in particular for the 2 A′′ state which leads to an underestimation of the vibrational relaxation at higher temperatures. More recent simulations based on RKHS-represented PESs at the MRCI/ aug-cc-pVTZ level of theory correctly describe both, the lowand high-T vibrational relaxation rates as observed experimentally.…”

The N( 4 S) + O 2 (X 3 Σ−g) ↔ O( 3 P) + NO(X 2 Π) reaction: thermal and vibrational relaxation rates for the 2 A′, 4 A′ and 2San Vicente Veliz, Koner, Schwilk et al. 2020Phys. Chem. Chem. Phys.

“…7. In particular for low temperature the agreement with the more recent 20 experiments and the only high-temperature experiment (at 2700 K) 66 is noteworthy. The results from the simulations based on high-level, 2-dimensional PESs 16 for the 2 A 0 and 2 A 00 states are also in good agreement with the experiments and the present simulations.…”