The electronic states of OsSi are calculated by multi-state N-electron valence state second order perturbation theory (MS-NEVPT2) with all-electron basis sets. The relativistic effects are considered comprehensively that allows us to identify the X3Σ0+– ground state. The theoretical equilibrium bond length 2.103 Å is close to the experimental measurement of 2.1207 Å while the vibrational frequency 466 cm–1 is smaller than the experimental value of 516 cm–1. Two excited states, namely 3Π1(I) and 3Π1(II), are located at 15568 and 18316 cm–1 above the ground state, respectively. The 3Π1(I) ← X3Σ0+– transition has been assigned to the experimental spectra at 15729 cm–1 and 3Π1(II) ← X3Σ0+– may produce the bands near 18469 cm–1. Although the latter transition energy is in accord with the experimental spectra, theoretical calculations give too small oscillator strength. Moreover, plenty of excited states with considerable oscillator strengths are located that could serve as reference data in future experiments. The four low-lying states of OsC are also calculated for comparison.

中文翻译：

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包含相对论效应的MS-NEVPT2计算的OsSi电子结构

OsSi的电子态是通过具有全电子基集的多态N电子价态二阶摄动理论（MS-NEVPT2）来计算的。相对论效应综合考虑，使我们能够识别X 3 Σ 0 + -基态。理论平衡键长2.103Å接近于2.1207Å的实验测量值，而振动频率466 cm –1小于516 cm –1的实验值。两个激发态，即3 Π 1（I）和3 Π 1（II），位于15568和18316厘米-1以上的基态时，分别。这3 Π 1（I）←X 3 Σ 0 + -过渡已经被分配给该实验谱在15729厘米-1和3 Π 1（II）←X 3 Σ 0 + -可产生近18469厘米频带-1。尽管后者的跃迁能量与实验光谱一致，但理论计算得出的振荡器强度太小。而且，找到了具有相当大的振荡器强度的大量激发态，这些激发态可以在将来的实验中用作参考数据。还计算了OsC的四个低位状态以进行比较。