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 (Re, De, D0, ωe, ωexe, ωeye, Be, αe, γe, Te, Dv) 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)­2u 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:0g+ and the excited states A:(1)­1u, B:(1)­0u+, C:(2)­1u, and B′:(1)­0u–] found in this work.本研究采用四分量相对论组态相互作用（Four-Component Relativistic COSCI）与多参考单双激发组态相互作用（MRCISD）方法，对溴分子（Br₂）的共价激发态与基态开展了理论探究。上述计算方法针对Ω(±)表象下的全部共价态进行了处理。本研究在四分量相对论组态相互作用水平下获得了计算势能曲线（PECs），并报道了束缚态的各项光谱学常数：平衡键长Rₑ、解离能Dₑ、零点能修正解离能D₀、基频振动频率ωₑ、一阶非简谐修正项ωₑxₑ、二阶非简谐修正项ωₑyₑ、转动常数Bₑ、转动修正项αₑ、离心畸变修正项γₑ、激发能Tₑ以及振动解离能Dᵥ。本文同时报道了COSCI、MRCISD以及MRCISD+Q能级下所有共价态的垂直激发能。此外，本研究还首次报道了两种此前文献未记载的弱束缚态A′:(¹)2ᵤ与B′:(¹)0–ᵤ的光谱学常数，并为本工作中确定的全部5种相对论分子束缚态——基态X:0g⁺以及激发态A:(¹)1ᵤ、B:(¹)0u⁺、C:(²)1ᵤ与B′:(¹)0u–——构建了高精度解析势能曲线。