Search for long-lived doubly charged negative atomic ions

Hartree-Fock Stability and Broken Symmetry Solutions of O2- and S2- Anions in External Confinement

We study the effect of a confining potential on systems that exhibit Hartree-Fock (HF) instabilities, and thus admit broken symmetry (BS) HF solutions, by relying on the O2- and S2- doubly-charged anions as model systems. We find that with the increasing strength of the external harmonic confinement potential, W(r) = 1/2(ωr)2 (with 0.0 ≤ ω < 0.2), the BS solutions are systematically eliminated. We use extended, diffuse, doubly-augmented Gaussian basis sets up to and including d-aug-cc-pV6Z, and find that the number and the character of BS solutions exhibit significant basis set effects. These basis sets were further extended by additional ghost basis functions, located away from the atomic center. The role of the electron correlation effects for the BS HF solutions was examined by the CCSD(T) method. In addition to modelling the confinement by the harmonic-like potential W(r), we also examined a more realistic "confinement", realized by a grid of point charges modelling the crystal structure of MgO. Again, we find that the HF instabilities and the implied BS solutions disappear with the increasing magnitude of the model charges simulating the crystal environment. At the same time, the O2- anion is energetically stabilized with respect to both the O- anion and the neutral oxygen atom.

New stable multiply charged negative atomic ions in linearly polarized superintense laser fields

Singly charged negative atomic ions exist in the gas phase and are of fundamental importance in atomic and molecular physics. However, theoretical calculations and experimental results clearly exclude the existence of any stable doubly-negatively-charged atomic ion in the gas phase, only one electron can be added to a free atom in the gas phase. In this report, using the high-frequency Floquet theory, we predict that in a linear superintense laser field one can stabilize multiply charged negative atomic ions in the gas phase. We present self-consistent field calculations for the linear superintense laser fields needed to bind extra one and two electrons to form He-, He2-, and Li2-, with detachment energies dependent on the laser intensity and maximal values of 1.2, 0.12, and 0.13 eV, respectively. The fields and frequencies needed for binding extra electrons are within experimental reach. This method of stabilization is general and can be used to predict stability of larger multiply charged negative atomic ions.