Configuration interaction calculations have been performed for the 62 electronic states of O2 arising from O atoms in the lowest 3P, 1D, and 1S states. The calculations used an extended one-particle basis set, and included internal and semi-internal electron correlation effects. Numerical values for potential curves are reported for all states. Detailed comparison with experiment and other calculations is made for the seven lowest bound states: X 3Σg−, a 1Δg, b 2Σg+, c 1Σu−, C 3Δu, A 3Σu+, and B 3Σu−. For these seven states the maximum error in the calculated spectroscopic constants Re, De, Te, and ωe are 0.04 Å, 0.4 eV, 0.2 eV, and 120 cm−1, respectively.

Configuration interaction (CI) calculations were performed for the X 2Σ, A 2Π, and B 2Σ states of NaAr. The A 2Π state is calculated to have a well depth of 492 cm−1 at an internuclear separation of 3.04 Å. Small wells of 55 and 32 cm−1 were found for the X 2Σ and B 2Σ states located at 5.01 and 6.80 Å, respectively. The spectra for A 2Π–X 2Σ emission in the limits of zero and infinite Ar pressure were calculated and compared with the experiment of York, Scheps, and Gallagher and the predictions using the pseudopotential curves of Pascale and Vandeplanque. The potentials from this work give spectra in much better agreement with experiment than the pseudopotential predictions. Total and differential cross sections for fine-structure changing transitions Na(2P1/2) +Ar→Na(2P3/2)+Ar−17.2 cm−1 were calculated by a quantum mechanical technique. The total cross sections are in excellent agreement with experimental results. The excited state differential cross sections exhibit prominent rainbow structure centered at τR=EΘR=5.5–6.0 eV deg.

This paper is dedicated to Professor Sigerzi Hzizinc~gc~ otz the occasion of his 65th birthdayROBERTA P. SAXON and MEGUMU YOSHIMINE. Can. J . Chem. 70, 572 (1992). Calculations designed to characterize the transition state and determine the barrier height for rearrangement of nitromethane to methyl nitrite are reported. Structures of CH,NO,, C H 3 0 N 0 , dissociation products, CH3 + NOz and CH,O + NO, and the transition state for nitro-nitrite rearrangement have been optimized at the MCSCF/4-31G level. The geometry of the transition state may be approximately described as separated CH3 and NO, species with extremely long C-N and C 4 bond lengths, 3.396 and 3.654 A, respectively. Energies have been obtained by large-scale multireference single-and double-excitation CI calculations (6-3 lG:+ basis). The transition state is calculated to lie 56.7 kcal/mol above nitromethane (with zero-point energy). A C-N bond dissociation energy of 51.7 kcal/mol is obtained. Results are compared with the infrared multiphoton dissociation experiment of Wodtke, Hintsa, and Lee.