Investigating properties of Cl${}^{-}$ and Au${}^{-}$ ions using relativistic many-body methods

We investigate ground state properties of singly charged chlorine (Cl${}^{-}$) and gold (Au${}^{-}$) negative ions by employing four-component relativistic many-body methods. In our approach, we attach an electron to the respective outer orbitals of chlorine (Cl) and gold (Au) atoms to determine the Dirac-Fock (DF) wave functions of the ground state configurations of Cl${}^{-}$ and Au${}^{-}$, respectively. As a result, all the single-particle orbitals see the correlation effects due to the appended electron of the negative ion. After obtaining the DF wave functions, lower-order many-body perturbation methods, random-phase approximation, and coupled-cluster (CC) theory in the singles and doubles approximation are applied to obtain the ground state wave functions of both Cl${}^{-}$ and Au${}^{-}$ ions. Then, we adopt two different approaches to the CC theory – a perturbative approach due to the dipole operator to determine electric dipole polarizability and an electron detachment approach in the Fock-space framework to estimate ionization potential. Our calculations are compared with the available experimental and other theoretical results.