Cheng Qianyi, DeYonker Nathan J
Department of Chemistry, University of Memphis, Memphis, Tennessee 38152, USA.
J Chem Phys. 2019 Jun 21;150(23):234304. doi: 10.1063/1.5096519.
Both FeH and FeH are predicted to be abundant in cool stellar atmospheres and proposed to be molecular components of the gas phase interstellar medium (ISM). However, experimental and simulated data for both species are lacking, which have hindered astronomical detection. There are no published laboratory data for the spectroscopy of FeH in any frequency regime. It is also not established if FeH possesses salient multireference character, which would pose significant challenges for ab initio modeling of geometric and spectroscopic properties. With a set of high-level coupled cluster and multireference configuration interaction computations, a study of the electronic structure of the ground state and seven excited states of FeH was carried out. An XΔ electronic ground state of FeH is found, in agreement with previous theoretical studies. Including corrections for spin-orbit coupling and anharmonic vibrational effects, the Ω = 3, ν = 0 spin ladder of the AΠ electronic state lies 872 cm higher in energy than the Ω = 4, ν = 0 spin ladder of the ground state. Combined with previous work in our laboratory, the ionization energy of FeH is computed to be 7.4851 eV. With modern multireference configuration interaction and coupled cluster methods, spectroscopic constants (r, B, ω, ωx, α, and D¯) for several bound excited states (AΠ, B Σ , a Σ , bΦ, cΠ, dΔ, and Σ) were characterized. This study will lead efforts to identify FeH in the ISM and help solve important remaining questions in quantifying metal-hydride bonding.
预计FeH和FeH在低温恒星大气中含量丰富，并被认为是气相星际介质（ISM）的分子成分。然而，这两种物质的实验和模拟数据都很缺乏，这阻碍了天文探测。在任何频率范围内，都没有关于FeH光谱的已发表实验室数据。FeH是否具有显著的多参考特征也尚未确定，这将给几何和光谱性质的从头算建模带来重大挑战。通过一组高水平的耦合簇和多参考组态相互作用计算，对FeH基态和七个激发态的电子结构进行了研究。发现FeH的基态为XΔ，与先前的理论研究一致。包括自旋轨道耦合和非谐振动效应的校正后，AΠ电子态的Ω = 3、ν = 0自旋梯比基态的Ω = 4、ν = 0自旋梯能量高872 cm。结合我们实验室之前的工作，计算出FeH的电离能为7.4851 eV。利用现代多参考组态相互作用和耦合簇方法，对几个束缚激发态（AΠ、B Σ 、a Σ 、bΦ、cΠ、dΔ和Σ）的光谱常数（r、B、ω、ωx、α和D¯）进行了表征。这项研究将推动在ISM中识别FeH的工作，并有助于解决量化金属氢化物键合方面剩余的重要问题。
