The O + NO(v) Vibrational Relaxation Processes Revisited

Abstract

We have carried out a quasiclassical trajectory study of the O + NO( v) energy transfer process using DMBE potential energy surfaces for the ground-states of the A' andA″ manifolds. State-to-state vibrational relaxation rate constants have been computed over the temperature range 298 and 3000 K and initial vibrational states between v = 1 and 9. The momentum-Gaussian binning approach has been employed to calculate the probability of the vibrational transitions. A comparison of the calculated state-to-state rate coefficients with the results from experimental studies and previous theoretical calculations shows the relevance of the 1 A″ potential energy surface to the title vibrational relaxation process.

The N(4S) + O2(X3Σ−g) ↔ O(3P) + NO(X2Π) reaction: thermal and vibrational relaxation rates for the 2A′, 4A′ and 2A′′ states

“…As to compare with the more recent experiments 20 the individual contributions of the 2 A 0 , 4 A 0 , and 2 A 00 states towards vibrational relaxation of O + NO(n = 1) -O + NO(n = 0) were determined here. Additionally, the total rate is compared with previous theoretical 19,21 and experimental 3,20 results, see Fig. 7.…”

“…As has also been noted in previous work, there are a total of 36 states that can potentially participate in the vibrational relaxation dynamics. 21,62 However, only energetically low-lying states of 2 A 0 and 2 A 00 symmetry have attractive wells.…”

“…As the efficiency of vibrational relaxation depends on the contact time between the diatomic and the collision partner, only these two states are deemed to be relevant at the temperature considered in this section, which is T r 3000 K. Such a treatment is also consistent with previous investigations. 21,62 Nevertheless, simulations were also carried out for the 4 A 0 state. An early experiment 3 determined the rate for NO(n = 1) vibrational relaxation by O atoms at room temperature.…”

“…The rate for vibrational relaxation is k n=1-0 (T = 295 K) = 4.2 AE 0.7(10 À11 ) cm 3 s À1 which is an increase by 75% compared with the earlier results. 3 Later QCT simulations 21 based on the DIM PES for the 2 A 0 state 15 and a fitted DMBE PES based on 1681 MRCI/AVQZ calculations for the 2 A 00 state 17 report a value of k n=1-0 (T = 298 K) = 4.34 AE 0.7(10 À11 ) cm 3 s À1 . Another computational study 62 reported a value of k n=1-0 (T = 300 K) B 5(10 À11 ) cm 3 s À1 .…”

“…This experiment found a rate of k n=1-0 = 4.2 AE 0.7(10 À11 ) cm 3 s À1 at T = 295 K which is larger by 75% compared with the earlier experiments. 3 Quite recent QCT simulations using again the DIM-based PES 15 mentioned above reported a rate of k n=1-0 = 4.34 AE 0.7(10 À11 ) cm 3 s À1 at T = 298 K from QCT simulations 21 which used the empirical DIM PES for the 2 A 0 ground state 15 and a more recent, MRCI-based fitted PES for the 2 A 00 state. 17 Given the rather heterogeneous situation for the quality of the existing PESs for studying the N( 4 S) + O 2 (X 3 S À g ) reaction and the vibrational relaxation of NO, the present work determines fully dimensional PESs using a consistent methodology to represent the 3 lowest electronic states, 2,4 A 0 and 2 A 00 as well as to evaluate the cross sections for the (forward)…”