Prediction of metastable ${\mathbf{AlS}}^{2+}$ dications in the gas phase

Using ab initio methodologies, we investigate the lowest electronic states of ${\mathrm{AlS}}^{2+}$ dications. These computations are performed using standard and explicitly correlated methods. Here we predict the metastability of this particular dication, where several potential wells are located. For the bound states, we report equilibrium distances and vibrational and rotational spectroscopic parameters. These computations show that the ground state of ${\mathrm{AlS}}^{2+}$ is of ${}^2{\mathrm{\Sigma }}^{-}$ space symmetry. We also derive vertical and adiabatic charge-stripping energies of ${\mathrm{AlS}}^{+}$ and vertical and adiabatic double-ionization energies of AlS. A comparison with the isovalent molecular species is carried out. Also, we show that the electronic properties of sulfur-containing dications cannot be predicted from those of the corresponding oxygenated dications.

Figure 1

Potential energy curves (PECs) of the lowest electronic states of ${\mathrm{AlS}}^{2+}$ computed using mrci and mrci-f12 and extrapolated to the CBS limit. The reference energy is chosen to be the energy of ${\mathrm{AlS}}^{2+}\left(X{}^2{\mathrm{\Sigma }}^{-}\right)$ at equilibrium.

Figure 2

Outermost MOs of AlS derived using the CASSCF/aug-cc-pVDZ method. We give the evolution of their energies along the internuclear separation.

Figure 3

mrci/aug-cc-pV(5+$d)\text{Z}$ potential energy curves of ${\mathrm{AlS}}^{2+}$ along the internuclear separation $\left(r\right)$. The reference energy is chosen to be the energy of ${\mathrm{AlS}}^{2+}\left(X{}^2{\mathrm{\Sigma }}^{-}\right)$ at equilibrium.