Relativistic Four-Component Potential Energy Curves for the Lowest 23 Covalent States of Molecular Bromine (Br₂)

The covalent excited states and ground state of the Br₂ 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^(±). Calculated potential energy curves (PECs) were obtained at the four-component COSCI level, and spectroscopic constants (<i>R</i>_e, <i>D</i>_e, <i>D</i>₀, ω_e, ω_ex_e, ω_e<i>y</i>_e, <i>B</i>_e, α_e, γ_e, <i>T</i>_e, <i>D</i>_v) 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_u and B′:(1)­0^–_u) not yet reported in the literature, as well as accurate analytical curves for all five relativistic molecular bounded sates [the ground state X:0_g⁺ and the excited states A:(1)­1_u, B:(1)­0_u⁺, C:(2)­1_u, and B′:(1)­0_u^–] found in this work