Model of Odd N in the Terrestrial Thermosphere: 1. A First Principles Calculation of the NO2 Potential Energy Surfaces Relevant to the Production of NO via the N(2D)+O2 Reaction.

Details Model of Odd N in the Terrestrial Thermosphere: 1. A First Principles Calculation of the NO2 Potential Energy Surfaces Relevant to the Production of NO via the N(2D)+O2 Reaction. Model of Odd N in the Terrestrial Thermosphere: 1. A First Principles Calculation of the NO2 Potential Energy Surfaces Relevant to the Production of NO via the N(2D)+O2 Reaction.

Dec 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agufmsa22a0718d&link_type=abstract

American Geophysical Union, Fall Meeting 2001, abstract #SA22A-0718

Physics

0310 Airglow And Aurora, 0317 Chemical Kinetic And Photochemical Properties, 0355 Thermosphere: Composition And Chemistry

Scientific paper

The daytime observation of 5.3 μ m thermospheric emission from the NO fundamental vibration-rotation band by the interferometer aboard the cryogenic infrared radiance instrumentation for shuttle (CIRRIS 1A) has provided important insight into the phenomenology of NO formation. The four major mechanisms to the 5.3 μ m emission considered by previous modeling are solar pumping, inelastic collisions of O with NO(v=0), the reactions of N(2D) with O2, and the reactions of N(4S) with O2. It has previously been shown that the reaction of N(4S) with O2 is consistent with rotationally nonthermal 5.3 μ m emission, while the N(2D)+O2 reaction has been assumed to contribute to rotationally thermal emission. The assumption of a thermal rotational distribution from the N(2D)+O2 reaction cannot be confirmed by the CIRRIS 1A data. The existence of a significant fraction of nonthermal atoms in the tail of the N(2D) energy distribution function (EDF) in the daylit thermosphere was demonstrated earlier (AGU Spring 2001). Therefore the investigation of possible nonthermal behavior in NO formation via the N(2D)+O2 reaction in the daylit and aurorally dosed thermosphere requires energy dependent cross sections for the reaction between N(2D) and O2. To calculate the N(2D)+O2 cross sections, potential energy surfaces (PES) of the NO2 system are required. The output of these calculations include the energy dependent cross sections and the vibrational and rotational distribution of the nascent NO needed for accurate calculation of the cooling rates due to 5.3 μ m emission. This work concentrates on the first step towards the calculation of such cross sections, the ab initio calculations of the NO2 PES. Previous existing PES, using different basis sets and electron correlation levels, have shown disagreements in the magnitude of the barriers for the lowest lying doublet surfaces in the reaction entrance channel. Comparative results from our calculations are presented here, showing PES computed with gaussian basis sets including 6-311G, Dunning triple ζ , and quadruple ζ sets, at the CASSCF (Complete Active Space Self Consistent Field), CASSCF/MP2 (2nd order Moller-Plesset perturbation), and CI (Configuration Interaction) levels of electron correlation. Our results indicate that as the basis set size and the correlation levels are increased, the barriers of the lowest lying doublet NO2 surfaces gradually become nonexistent, consistent with the low temperature measurements of the rate coefficients of the N(2D)+O2 reaction.

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