Based on the ab initio potential energy, spin-orbit coupling, electronic transition dipole moment, and radial nonadiabatic coupling functions, the energy level positions, lifetimes, and radiative transition probabilities (Einstein A coefficients) have been determined for the lowest electronic states of NO2+ using the log-amplitude-phase, stabilization, and complex-scaling methods. The calculated characteristics are in reasonable agreement to the available experimental data, thus, evidencing the reliability of the theoretical predictions for the characteristics unobserved to date. With the exception of the v

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Radiative transition probabilities (Einstein A coefficients),Franck-Condon factors, and radiative lifetimes have been determined for the X 3 , 3 − , a 1 + , 1 , c 1 , and A 3 + states of the CO 2+ dication using ab initio potential energy, spin-orbit coupling, electric dipole and electronic transition moment functions, and the standard complex-scaling method. The calculated radiative lifetimes of the upper electronic states of the spin-allowed A 3 + -X 3 and b 1 -a 1 + transitions are generally longer than their predissociating lifetimes, explaining thus the failure of the attempts made so far to observe CO 2+ in the optical spectral region in a convincing fashion.

We introduce an accurate and efficient algebraic technique for the computation of the vibrational spectra of triatomic molecules, of both linear and bent equilibrium geometry. The full three-dimensional potential energy surface (PES), which can be based on entirely ab initio data, is parametrized as a product Morse-cosine expansion, expressed in bond angle internal coordinates, and includes explicit interactions among the local modes. We describe the stretching degrees of freedom in the framework of a Morse-type expansion on a suitable algebraic basis, which provides exact analytical expressions for the elements of a sparse Hamiltonian matrix. Likewise, we use a cosine power expansion on a spherical harmonics basis for the bending degree of freedom. The resulting matrix representation in the product space is very sparse, and vibrational levels and eigenfunctions can be obtained by efficient diagonalization techniques. We apply this method to carbonyl sulfide, hydrogen cyanide, water, and nitrogen dioxide. When we base our calculations on high-quality PESs tuned to the experimental data, the computed spectra are in very good agreement with the observed band origins.