A Theoretical Study of Rate Coefficients for the O + NO Vibrational Relaxation

Abstract

Quasi-classical trajectories have been integrated to study the vibrational relaxation of the O + NO(V) process as a function of the initial vibrational quantum number for T ) 298 K, 1500 K, and 3000 K. Two reliable potential energy surfaces have been employed for the A′ and A′′ doublet states of NO 2 . The calculated vibrational relaxation rate constants show a nearly V-independent behavior at room temperature and a moderate increase with V for higher temperatures. Although deviating significantly from the recommended values, good agreement with recent experimental results has been obtained. The importance of multi-quantum transitions is also analyzed.

The O + NO(v) Vibrational Relaxation Processes Revisited

“…A set of experiments have been carried out by Dood’s , group using the laser photolysis-laser probe technique, where vibrationally excited NO and O atoms are formed in a dilute mixture of NO 2 in argon and monitored by laser-induced fluorescence (LIF). The reported , values k v ′=1→0 = (2.4 ± 0.5) × 10 –11 cm 3 s –1 , k v ′=1→all = (2.2 ± 0.2) × 10 –11 cm 3 s –1 , and k v ′=1→all = (2.5 ± 0.3) × 10 –11 cm 3 s –1 are nearly twice as small as the QCT ones here reported, although in good agreement with our previous QCT results and other theoretical predictions. , Such experiments , have been revisited by Hwang et al using microwave discharge rather than relying on the 355 nm laser photolysis of NO 2 . As they have noted, their previous technique produced atoms that evolved on the same time scale as the NO­( v ) population decay and masked the signals of the detector.…”

“…The discrepant values obtained from different experiments created unrealistic interpretations of the global mean model temperature and density structure of the upper atmosphere using the MSIS model as a benchmark. The first measurement has been carried out by Fernando and Smith 10 in 1979 using laser-induced infrared fluorescence techniques, who have reported a value of (6.5 ± 0.7) × 10 −11 cm 3 s −1 at (296 ± 3) K. Lilenfeld 49 17,19 values k v′=1→0 = (2.4 ± 0.5) × 10 −11 cm 3 s −1 , k v′=1→all = (2.2 ± 0.2) × 10 −11 cm 3 s −1 , and k v′=1→all = (2.5 ± 0.3) × 10 −11 cm 3 s −1 are nearly twice as small as the QCT ones here reported, although in good agreement with our previous QCT results 23 and other theoretical predictions. 20,26 Such experiments 17,19 have been revisited by Hwang et al 16 using microwave discharge rather than relying on the 355 nm laser photolysis of NO 2 .…”

“…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. As the temperature raises the rate constant tends to diminish due to the above-mentioned change of mechanism.…”

“…For the one-quantum vibrational relaxation, the isomerization channel is nearly twice as large than the direct process for all temperatures while, for larger NO initial vibrational quantum states, energy transfer is dominated by the direct channel. The reason for such an apparent change in the energy transfer mechanism may be due to multiquantum transitions that are observed for high initial vibrational states, a trend already seen in previous studies; e.g., the ratio for v ′ = 10 → 0 at T = 298 K is 11% in isomerization, with a nearly constant value (within the statistical error) for all final quantum states. This can be seen from panel b where the state-to-all vibrational relaxation rate constant is shown: the dominant channel arises from isomerizing trajectories.…”

“…A detailed analysis of the role of the initial vibrational quantum state for temperature regimes of relevance in atmospheric modeling has also been presented. The calculated reaction attributes were found to differ substantially from the ones reported previously using a MBE form fitted to CASPT2 ab initio data for the 1 2 A″ state. If the DMBE potential energy surface is employed for this state, the vibrational energy transfer contribution to the total rate constant is found to be similar to that of the 1 2 A′ state, thus revealing the effect of its distinct topography on the energy transfer process when the trajectory samples the regions of the global and local minima.…”

The O + NO(v) Vibrational Relaxation Processes Revisited

“…A set of experiments have been carried out by Dood’s , group using the laser photolysis-laser probe technique, where vibrationally excited NO and O atoms are formed in a dilute mixture of NO 2 in argon and monitored by laser-induced fluorescence (LIF). The reported , values k v ′=1→0 = (2.4 ± 0.5) × 10 –11 cm 3 s –1 , k v ′=1→all = (2.2 ± 0.2) × 10 –11 cm 3 s –1 , and k v ′=1→all = (2.5 ± 0.3) × 10 –11 cm 3 s –1 are nearly twice as small as the QCT ones here reported, although in good agreement with our previous QCT results and other theoretical predictions. , Such experiments , have been revisited by Hwang et al using microwave discharge rather than relying on the 355 nm laser photolysis of NO 2 . As they have noted, their previous technique produced atoms that evolved on the same time scale as the NO­( v ) population decay and masked the signals of the detector.…”

“…The discrepant values obtained from different experiments created unrealistic interpretations of the global mean model temperature and density structure of the upper atmosphere using the MSIS model as a benchmark. The first measurement has been carried out by Fernando and Smith 10 in 1979 using laser-induced infrared fluorescence techniques, who have reported a value of (6.5 ± 0.7) × 10 −11 cm 3 s −1 at (296 ± 3) K. Lilenfeld 49 17,19 values k v′=1→0 = (2.4 ± 0.5) × 10 −11 cm 3 s −1 , k v′=1→all = (2.2 ± 0.2) × 10 −11 cm 3 s −1 , and k v′=1→all = (2.5 ± 0.3) × 10 −11 cm 3 s −1 are nearly twice as small as the QCT ones here reported, although in good agreement with our previous QCT results 23 and other theoretical predictions. 20,26 Such experiments 17,19 have been revisited by Hwang et al 16 using microwave discharge rather than relying on the 355 nm laser photolysis of NO 2 .…”

“…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. As the temperature raises the rate constant tends to diminish due to the above-mentioned change of mechanism.…”

“…For the one-quantum vibrational relaxation, the isomerization channel is nearly twice as large than the direct process for all temperatures while, for larger NO initial vibrational quantum states, energy transfer is dominated by the direct channel. The reason for such an apparent change in the energy transfer mechanism may be due to multiquantum transitions that are observed for high initial vibrational states, a trend already seen in previous studies; e.g., the ratio for v ′ = 10 → 0 at T = 298 K is 11% in isomerization, with a nearly constant value (within the statistical error) for all final quantum states. This can be seen from panel b where the state-to-all vibrational relaxation rate constant is shown: the dominant channel arises from isomerizing trajectories.…”

“…A detailed analysis of the role of the initial vibrational quantum state for temperature regimes of relevance in atmospheric modeling has also been presented. The calculated reaction attributes were found to differ substantially from the ones reported previously using a MBE form fitted to CASPT2 ab initio data for the 1 2 A″ state. If the DMBE potential energy surface is employed for this state, the vibrational energy transfer contribution to the total rate constant is found to be similar to that of the 1 2 A′ state, thus revealing the effect of its distinct topography on the energy transfer process when the trajectory samples the regions of the global and local minima.…”

The O + NO(v) Vibrational Relaxation Processes Revisited

“…A set of experiments have been carried out by Dood’s , group using the laser photolysis-laser probe technique, where vibrationally excited NO and O atoms are formed in a dilute mixture of NO 2 in argon and monitored by laser-induced fluorescence (LIF). The reported , values k v ′=1→0 = (2.4 ± 0.5) × 10 –11 cm 3 s –1 , k v ′=1→all = (2.2 ± 0.2) × 10 –11 cm 3 s –1 , and k v ′=1→all = (2.5 ± 0.3) × 10 –11 cm 3 s –1 are nearly twice as small as the QCT ones here reported, although in good agreement with our previous QCT results and other theoretical predictions. , Such experiments , have been revisited by Hwang et al using microwave discharge rather than relying on the 355 nm laser photolysis of NO 2 . As they have noted, their previous technique produced atoms that evolved on the same time scale as the NO­( v ) population decay and masked the signals of the detector.…”

“…The discrepant values obtained from different experiments created unrealistic interpretations of the global mean model temperature and density structure of the upper atmosphere using the MSIS model as a benchmark. The first measurement has been carried out by Fernando and Smith 10 in 1979 using laser-induced infrared fluorescence techniques, who have reported a value of (6.5 ± 0.7) × 10 −11 cm 3 s −1 at (296 ± 3) K. Lilenfeld 49 17,19 values k v′=1→0 = (2.4 ± 0.5) × 10 −11 cm 3 s −1 , k v′=1→all = (2.2 ± 0.2) × 10 −11 cm 3 s −1 , and k v′=1→all = (2.5 ± 0.3) × 10 −11 cm 3 s −1 are nearly twice as small as the QCT ones here reported, although in good agreement with our previous QCT results 23 and other theoretical predictions. 20,26 Such experiments 17,19 have been revisited by Hwang et al 16 using microwave discharge rather than relying on the 355 nm laser photolysis of NO 2 .…”

“…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. As the temperature raises the rate constant tends to diminish due to the above-mentioned change of mechanism.…”

“…For the one-quantum vibrational relaxation, the isomerization channel is nearly twice as large than the direct process for all temperatures while, for larger NO initial vibrational quantum states, energy transfer is dominated by the direct channel. The reason for such an apparent change in the energy transfer mechanism may be due to multiquantum transitions that are observed for high initial vibrational states, a trend already seen in previous studies; e.g., the ratio for v ′ = 10 → 0 at T = 298 K is 11% in isomerization, with a nearly constant value (within the statistical error) for all final quantum states. This can be seen from panel b where the state-to-all vibrational relaxation rate constant is shown: the dominant channel arises from isomerizing trajectories.…”

“…A detailed analysis of the role of the initial vibrational quantum state for temperature regimes of relevance in atmospheric modeling has also been presented. The calculated reaction attributes were found to differ substantially from the ones reported previously using a MBE form fitted to CASPT2 ab initio data for the 1 2 A″ state. If the DMBE potential energy surface is employed for this state, the vibrational energy transfer contribution to the total rate constant is found to be similar to that of the 1 2 A′ state, thus revealing the effect of its distinct topography on the energy transfer process when the trajectory samples the regions of the global and local minima.…”

The O + NO(v) Vibrational Relaxation Processes Revisited

“…A set of experiments have been carried out by Dood’s , group using the laser photolysis-laser probe technique, where vibrationally excited NO and O atoms are formed in a dilute mixture of NO 2 in argon and monitored by laser-induced fluorescence (LIF). The reported , values k v ′=1→0 = (2.4 ± 0.5) × 10 –11 cm 3 s –1 , k v ′=1→all = (2.2 ± 0.2) × 10 –11 cm 3 s –1 , and k v ′=1→all = (2.5 ± 0.3) × 10 –11 cm 3 s –1 are nearly twice as small as the QCT ones here reported, although in good agreement with our previous QCT results and other theoretical predictions. , Such experiments , have been revisited by Hwang et al using microwave discharge rather than relying on the 355 nm laser photolysis of NO 2 . As they have noted, their previous technique produced atoms that evolved on the same time scale as the NO­( v ) population decay and masked the signals of the detector.…”

“…The discrepant values obtained from different experiments created unrealistic interpretations of the global mean model temperature and density structure of the upper atmosphere using the MSIS model as a benchmark. The first measurement has been carried out by Fernando and Smith 10 in 1979 using laser-induced infrared fluorescence techniques, who have reported a value of (6.5 ± 0.7) × 10 −11 cm 3 s −1 at (296 ± 3) K. Lilenfeld 49 17,19 values k v′=1→0 = (2.4 ± 0.5) × 10 −11 cm 3 s −1 , k v′=1→all = (2.2 ± 0.2) × 10 −11 cm 3 s −1 , and k v′=1→all = (2.5 ± 0.3) × 10 −11 cm 3 s −1 are nearly twice as small as the QCT ones here reported, although in good agreement with our previous QCT results 23 and other theoretical predictions. 20,26 Such experiments 17,19 have been revisited by Hwang et al 16 using microwave discharge rather than relying on the 355 nm laser photolysis of NO 2 .…”

“…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. As the temperature raises the rate constant tends to diminish due to the above-mentioned change of mechanism.…”

“…For the one-quantum vibrational relaxation, the isomerization channel is nearly twice as large than the direct process for all temperatures while, for larger NO initial vibrational quantum states, energy transfer is dominated by the direct channel. The reason for such an apparent change in the energy transfer mechanism may be due to multiquantum transitions that are observed for high initial vibrational states, a trend already seen in previous studies; e.g., the ratio for v ′ = 10 → 0 at T = 298 K is 11% in isomerization, with a nearly constant value (within the statistical error) for all final quantum states. This can be seen from panel b where the state-to-all vibrational relaxation rate constant is shown: the dominant channel arises from isomerizing trajectories.…”

“…A detailed analysis of the role of the initial vibrational quantum state for temperature regimes of relevance in atmospheric modeling has also been presented. The calculated reaction attributes were found to differ substantially from the ones reported previously using a MBE form fitted to CASPT2 ab initio data for the 1 2 A″ state. If the DMBE potential energy surface is employed for this state, the vibrational energy transfer contribution to the total rate constant is found to be similar to that of the 1 2 A′ state, thus revealing the effect of its distinct topography on the energy transfer process when the trajectory samples the regions of the global and local minima.…”