Relativistic Four-Component Potential Energy Curves for the Lowest 23 Covalent States of Molecular Bromine (Br<sub>2</sub>)

The covalent excited states and ground state of the Br<sub>2</sub> molecule has been investigated by using four-component relativistic COSCI and MRCISD methods. These methods were performed for all covalent states in the representation Ω<sup>(±)</sup>. Calculated potential energy curves (PECs) were obtained at the four-component COSCI level, and spectroscopic constants (<i>R</i><sub>e</sub>, <i>D</i><sub>e</sub>, <i>D</i><sub>0</sub>, ω<sub>e</sub>, ω<sub>e</sub>x<sub>e</sub>, ω<sub>e</sub><i>y</i><sub>e</sub>, <i>B</i><sub>e</sub>, α<sub>e</sub>, γ<sub>e</sub>, <i>T</i><sub>e</sub>, <i>D</i><sub>v</sub>) for bounded states are reported. The vertical excitations for all covalent states are reported at COSCI, MRCISD, and MRCISD+Q levels. We also present spectroscopic constants for two weakly bounded states (A′:(1)­2<sub>u</sub> and B′:(1)­0<sup>–</sup><sub>u</sub>) not yet reported in the literature, as well as accurate analytical curves for all five relativistic molecular bounded sates [the ground state X:0<sub>g</sub><sup>+</sup> and the excited states A:(1)­1<sub>u</sub>, B:(1)­0<sub>u</sub><sup>+</sup>, C:(2)­1<sub>u</sub>, and B′:(1)­0<sub>u</sub><sup>–</sup>] found in this work.