Many-body multipartitioning perturbation theory ͑MPPT͒ was applied to calculate the potential energy of 11 lowest electronic states of the NaRb molecule, A,⌸ transition dipole moments, as well as nonadiabatic L-uncoupling matrix elements between the examined 1 ⌸ and four lowest 1 ⌺ ϩ states for both 23 Na 85 Rb and 23 Na 87 Rb isotopomers. The relevant MPPT ab initio matrix elements and energy curves were converted by means of the approximate sum rule to radiative lifetimes and ⌳-doubling constants (q factors͒ for the particular rovibronic levels of the B 1 ⌸ and D 1 ⌸ states. The theoretical lifetimes agree well with their experimental counterparts for both B 1 ⌸ and D 1 ⌸ states. The q factor estimates obtained in the singlet-singlet approximation are in good agreement with the experimental ones for the D 1 ⌸(1рvЈр12;7рJЈр50) levels, exhibiting a pronounced difference for the B 1 ⌸ state. Considerably better agreement was achieved by accounting for the spin-orbit perturbation effect caused by the near-lying c 3 ⌺ ϩ state. Relative intensity distributions in the D 1 ⌸→X 1 ⌺ ϩ dispersed fluorescence spectra excited by fixed Ar ϩ laser lines were measured for vЈ(JЈ)ϭ0 (44), 1(104), 4(25), 6(44,120), 10(36), and 12(50) D 1 ⌸ levels. The experimental intensities and term values were simultaneously embedded in the nonlinear least-square fitting procedure to refine the D 1 ⌸ potential.

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The multipartitioning form of the second-order many-body perturbation theory for state-selective effective Hamiltonians is adapted to stabilization calculations of temporary molecular anionic states. We restrict our attention to the simplest case of a system composed of a closed-shell-like molecule and an electron. Pilot applications to the description of the 2 g state of the nitrogen molecular anion and the 2 state of CO − are reported.

Present-day computational techniques provide a possibility of evaluating properties of macrosystems using ab initio quantum chemistry and theories of elementary processes. Physical and chemical phenomena on very different timescales have to be taken into account (excitation, emission, chemical reactions, diffusion) at different levels of refining. This refining covers a very wide region of parameters starting from the structure of species up to the macro chemical mechanism of their conversion. This multilevel approach is described in detail in the paper and includes interaction and data transfer between different levels of phenomena description. In the framework of the approach, unknown properties of molecules, ions and atoms (structure, potential energy curves, transition dipole moments) are calculated based on quantum-chemical methods. The calculation results are used to evaluate rate characteristics of physical and chemical processes. The developed kinetic state-to-state scheme is then used to calculate the macro properties of the system under investigation. As an example of the multilevel approach, the emission properties of the Ar–GaI3 positive column discharge plasma were calculated using the Chemical Work Bench computational environment. The calculations yield the electron energy balance and emission efficiency as functions of plasma parameters.

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