We propose a spin-tensor (ST) version of the multireference first-order polarization propagator (PP) approximation (MRFOPPA) designed to produce precision-balanced approximations (PBA) of electronic transition energies, $\mathrm{\Delta }E$, to low-lying electronic states of selected multiplicity in small molecules in a wide range of their nuclear geometry. Comparing the STMRFOPPA $\mathrm{\Delta }E$ estimates with those obtained by the full configuration interaction (FCI) method and several multireference approximations on the example of transitions from the ground state of CH⁺ to its 25 excited states in the aug-cc-pVTZ basis set prompts the following conclusions: (i) STMRFOPPA provides PBA to the corresponding FCI results for the energies of transitions to the noted electronic states and the associated vibronic states and (ii) the accuracy of STMRFOPPA $\mathrm{\Delta }E$ estimates is higher than that of MRCIS and close to those of MRCISD and XMCQDPT2 that operate in spaces of higher dimensions. Additionally, Supplementary Material to the paper contains the FCI(frozen core)/aug-cc-pVTZ level data for potential energy curves of the 26 electronic states of CH⁺ that can be useful for future research groups.

我们提出了多参考一阶极化传播器（PP）逼近（MRFOPPA）的自旋张量（ST）版本，旨在产生电子跃迁能量的精确平衡逼近（PBA）， $\mathrm{\Delta }Ë$，在小范围内具有选定的多重性的低电子态，这些小分子具有广泛的核几何形状。比较STMRFOPPA$\mathrm{\Delta }Ë$用全配置相互作用（FCI）方法获得的估计值以及在aug-cc-pVTZ基集中从CH ⁺的基态到其25个激发态的跃迁示例的几个多参考近似值得出以下结论：（i ）STMRFOPPA为相应的FCI结果提供PBA，以获取跃迁到所述电子状态和相关的振动态的能量以及（ii）STMRFOPPA的准确性$\mathrm{\Delta }Ë$估计值比MRCIS高，并且接近于在较大空间中工作的MRCISD和XMCQDPT2。此外，该论文的补充材料还包含FCI（冻结核）/ aug-cc-pVTZ能级数据，用于CH ⁺的26个电子态的势能曲线，这可能对将来的研究小组有用。