Inclusion of core-valence correlation effects in pseudopotential calculations. II. K2and KH lowest Σ+potential curves from valence-correlated wavefunctions

Full-Dimensional Ab Initio Potential Energy Surface and Vibrational Energy Levels of Li2H

We built a full-dimensional analytical potential energy surface of the ground electronic state of Li₂H from ca. 20,000 ab initio multi-reference configuration interaction calculations, including core–valence correlation effects. The surface is flexible enough to accurately describe the three dissociation channels: Li (2s ²S) + LiH (¹Σ⁺), Li₂ (¹Σ_g⁺) + H (1s ²S) and 2Li (2s ²S) + H (1s ²S). Using a local fit of this surface, we calculated pure (J = 0) vibrational states of Li₂H up to the barrier to linearity (ca. 3400 cm⁻¹ above the global minimum) using a vibrational self-consistent field/virtual state configuration interaction method. We found 18 vibrational states below this barrier, with a maximum of 6 quanta in the bending mode, which indicates that Li₂H could be spectroscopically observable. Moreover, we show that some of these vibrational states are highly correlated already ca. 1000 cm⁻¹ below the height of the barrier. We hope these calculations can help the assignment of experimental spectra. In addition, the first low-lying excited states of each B₁, B₂ and A₂ symmetry of Li₂H were characterized.

Spectroscopic study of the B (1)Pi state of (39)KH

The B (1)Pi excited electronic state of (39)KH has been observed for the first time by a pulsed fluorescence excitation spectroscopic technique. We have found only one vibrational level, in which seven e-parity and seven f-parity sublevels are identified. The Dunham-type coefficients A(00), A(01), and A(02) and the mean internuclear separation for the B (1)Pi state have been derived. Their numeric values are separately 27 682.64(1) cm(-1), 1.533(1) cm(-1), -0.001 25(2) cm(-1), and 3.345(1) A for the B (1)Pi(+) state; 27 682.66(2) cm(-1), 1.532(2) cm(-1), -0.001 20(3) cm(-1), and 3.347(2) A for the B (1)Pi(-) state. The dissociation energy D(0) is determined to be 131.4(7) cm(-1). The vibrational frequency and the dissociation energy for the B (1)Pi state have also been estimated and the results are compared with recent ab initio calculations.

Theoretical investigation of RbCs via two-component spin-orbit pseudopotentials: Spectroscopic constants and permanent dipole moment functions

Potential energy curves for the 28 lowest LambdaSigma states and 49 Omega states of RbCs are obtained from large-scale multireference configuration interaction calculations using both spin-averaged and two-component spin-orbit energy-consistent effective core potentials. Spectroscopic properties of all states are compared across available data in literature to date. Variations of the permanent dipole moments on the internuclear separation (R) for the (1)Sigma(+), (3)Sigma(+), (1)Pi, and (3)Pi states are evaluated over a wide range of R. The most important effects of the spin-orbit interaction on the dipole moment distribution are discussed.

Ground-state properties and static dipole polarizabilities of the alkali dimers from K2n to Fr2n(n=0,+1) from scalar relativistic pseudopotential coupled cluster and density functional studies

The newly adjusted energy-consistent nine-valence-electron pseudopotentials for K to Fr are used to calculate spectroscopic properties for the neutral and positively charged alkali dimers using coupled cluster and density functional theory. For the neutral dimers the static dipole polarizability was calculated. The coupled cluster results are all in excellent agreement with experimental values. The density functionals used can give quite different spectroscopic properties especially for the dipole polarizability, with the Perdew-Wang PW91 functional performing best.

Theoretical Study of the Electronic States of the Rb(2) Molecule

We have calculated the electronic states of Rb(2) by multireference configuration interactions using the averaged relativistic effective small-core potential and the core-polarization potential. The potential energy curves for a large number of states dissociating into from 5s+5s up to 7s+5s asymptotic limits are calculated and the spectroscopic constants are reported. The spin-orbit effects for the states dissociating into 5p+5s and 4d+5s are calculated using the effective spin-orbit potential. The results are compared with available experimental data and other theoretical works. Copyright 2001 Academic Press.