Electronic structure and dynamics of O(3P)+CO(1Σ+) collisions

Abstract

Electronic to vibrational and rotational energy transfer in S ( 1 D)+ CO quenching reaction: Ab initio MO and surface hopping trajectory studies A new He-CO interaction energy surface with vibrational coordinate dependence. II. The vibrational deactivation of CO (v=1) by inelastic collisions with 3 He and 4 He The potential energy surfaces of the three lowest electronic triplet states of CO 2 which lead to O( 3 P)ϩCO( 1 ⌺ ϩ ), 3 AЈ, 1 3 AЉ, and 2 3 AЉ, have been computed at the completeactive-space-self-consistent-field plus second-order perturbation theory ͑CASSCF-MP2͒ level with a modest 631ϩG(d) basis. Potential energy surfaces are fit with a global functional form. The 3 AЈ state has a well 0.9 eV deep and the 1 3 AЉ state has a 0.2 eV well with respect to the O( 3 P) ϩCO( 1 ⌺ ϩ ) dissociation threshold. The 3 AЈ and 1 3 AЉ states are both bent at their minima and have a barrier at 0.2 eV and 0.3 eV above threshold, respectively. The 2 3 AЉ state is mostly repulsive, and has a saddle at C 2v geometries. We have run classical trajectory calculations for O( 3 P) ϩCO( 1 ⌺ ϩ ) collisions using these surfaces. Results agree well with available vibrational relaxation and oxygen atom exchange measurements except at low temperature. Comparisons are also made with measured vibrational excitation cross sections and infrared emission spectra of the nascent CO products at 3.4 eV collision energy. These results show a high degree of vibrational and rotational excitation with a nearly statistical population which is evident in a distinct spectral ''bandhead'' signature. Analysis of the trajectories show that almost all collisions which lead to oxygen atom exchange and/or vibrational energy transfer occur when the O( 3 P) approaches the CO at OCO angles between 80°and 140°, passes over the barrier and through the wells of the 3 AЈ and 1 3 AЉ states, and interacts with the repulsive wall of the carbon end of the CO nearly perpendicular to the CO bond.

Spin-orbit coupling and dissociation of CO2 molecules

“…Comparison with other works calculating the low lying СО 2 states showed that energies agree well with the results of [2][3][4][5] given in Table 2. The values of obtained by us for the 3 B 2 and 3 A 2 electronic states are close to the data of [2], while our results for 1 A 2 are close to those of [4].…”

“…The electronic states (both ground and excited) of the СО 2 molecule were the subjects of previous studies [1][2][3][4][5][6]. However, the authors of many calculations per formed using quantum chemistry methods frequently use experimental data mainly for comparing the min ima of calculated potential energy surfaces (PESs) and the vibrational frequencies of different modes.…”

The potential energy surfaces of the ground and excited states of carbon dioxide molecule

“…The dissociation energy for 1 B 2 state is 2.01 eV which also agrees with the experiment value 1.73 eV within range of error. About the dissociation energy for 3 B 2 state, our result is 0.94 eV, which is sup ported by Braunstein and Duff's theoretical result [24] of 0.94 eV.…”

“…The adiabatic excitation energy of 3 B 2 , 3 A 2 , 1 A 2 , and 1 B 2 states had been reported by many experimen tal and theoretical researchers [16,17,23,24]. How ever, as a result of the limitation of conditions of experiment and calculation, the results are not very accurate.…”

Tunnelling in the O + CO reaction

“…To calculate the tunnelling probability for the O( 3 P) + CO reaction we started with the analytical PES of Braunstein & Duff (2000) based on CASPT2 calculations on the lowest 3 A′ electronic state. However, this PES has an artificially deep van der Waals well (1440 K) at the wrong (non‐linear) geometry, which is probably an artefact of the fitting.…”