In this work, we present a thorough theoretical structure and spectroscopic study of the ground and low lying excited states of RbBa molecule. High-level ab-initio calculations are performed, using MCSCF/MRCI+Q level of method, based on the effective core potential (ECP) and core-polarization potential (CPP) approach. The potential energy curves, spectroscopic parameters, vibrationnel energy levels of the 16(^2,4Σ⁺,^2,4Π,^2,4Δ) first electronic states, with respect to the lowest five dissociation limits were calculated. The comparison of the spectroscopic constants of the ground state X²Σ⁺ with the available theoretical work, are in good agreement. The study of all the excited states is performed in this work for the first time. Afterwards, the spin-orbit operator is incorporated in valence MRCI calculation using optimized relativistic spin-orbit pseudo-potentials and 33 Ω states are generated and split into Λ-S states. In addition, both relativistic and non relativistic calculations of permanent and transition dipole moments are presented and discussed. Stimulated black body (T= 300 K) and spontaneous transition rates of vibrational states of X²Σ⁺ state were evaluated. The related vibrational lifetimes for RbBa are found to be in order of 10³ s which is sufficiently large for ultracold experiments. Moreover, the vibrational life-time for the A²Σ⁺(v’) and A²П (v”) states are measured and the possibility of Laser Cooling for the RbBa molecule is discussed based on Franck–Condon factors calculation of A²Σ⁺ (v’)→ X²Σ⁺(v) and A²П(v”) → X²Σ⁺(v) transition. This work represents a significant contribution for experimentalists as it provides efficient information in order to form cold alkali and alkaline-earth RbBa molecules.

在这项工作中，我们介绍了RbBa分子的基态和低位激发态的透彻理论结构和光谱研究。基于有效磁芯电势（ECP）和磁芯极化电势（CPP）方法，使用MCSCF / MRCI + Q级别的方法执行高级从头计算。势能曲线，光谱参数时，16的vibrationnel能级（^2,4- Σ ⁺，^2,4- Π，^2,4- Δ）第一电子态，相对于最低的5个离解极限进行了计算。基态的光谱常数的比较X ² Σ ⁺与现有的理论工作相吻合。这项工作是第一次进行所有激发态的研究。然后，使用优化的相对论自旋轨道伪势将自旋轨道算子纳入价MRCI计算中，并生成33Ω状态并将其拆分为Λ-S状态。此外，介绍并讨论了永久偶极矩和过渡偶极矩的相对论和非相对论计算。刺激黑体（Ť = 300K）和X的振动状态的自发跃迁率² Σ ⁺状态进行了评价。发现RbBa的相关振动寿命约为10 ³ 对于超冷实验而言足够大。此外，振动寿命时间为A ² Σ ⁺（V”）和A ² П（V”状态被测量）和激光的冷却为RbBa分子的可能性是基于讨论弗兰克-康登因子A的计算² Σ ⁺（ v”）→X ² Σ ⁺（v）和A ² П（v”）→X ² Σ ⁺（v） 过渡。这项工作为实验人员做出了重大贡献，因为它提供了有效的信息以形成冷碱和碱土RbBa分子。