Pitarch-Ruiz J, Sánchez-Marin J, Velasco A M, Martin I
Institut de Ciència Molecular, Universitat de Valencia, Edifici d'Instituts Campus de Paterna, E-46980 Valencia, Spain.
J Chem Phys. 2008 Aug 7;129(5):054310. doi: 10.1063/1.2953584.
An all-electron full configuration interaction (FCI) calculation of the adiabatic potential energy curves of some of the lower states of BeH molecule is presented. A moderately large ANO basis set of atomic natural orbitals (ANO) augmented with Rydberg functions has been used in order to describe the valence and Rydberg states and their interactions. The Rydberg set of ANOs has been placed on the Be at all bond distances. So, the basis set can be described as 4s3p2d1f3s2p1d(BeH)+4s4p2d(Be). The dipole moments of several states and transition dipole strengths from the ground state are also reported as a function of the R(Be-H) distance. The position and the number of states involved in several avoided crossings present in this system have been discussed. Spectroscopic parameters have been calculated from a number of the vibrational states that result from the adiabatic curves except for some states in which this would be completely nonsense, as it is the case for the very distorted curves of the 3s and 3p (2)Sigma(+) states or the double-well potential of the 4p (2)Pi state. The so-called "D complex" at 54 050 cm(-1) (185.0 nm) is resolved into the three 3d substates ((2)Sigma(+),(2)Pi,(2)Delta). A diexcited valence state is calculated as the lowest state of (2)Sigma(-) symmetry and its spectroscopic parameters are reported, as well as those of the 2 (2)Delta (4d) state The adiabatic curve of the 4 (2)Sigma(+) state shows a swallow well at large distances (around 4.1 A) as a result of an avoided crossing with the 3 (2)Sigma(+) state. The probability that some vibrational levels of this well could be populated is discussed within an approached Landau-Zerner model and is found to be high. No evidence is found of the E(4ssigma) (2)Sigma(+) state in the region of the "D complex". Instead, the spectroscopic properties obtained from the (4ssigma) 6 (2)Sigma(+) adiabatic curve of the present work seem to agree with those of the experimental F(4psigma) (2)Sigma(+) state. The FCI calculations provide benchmark results for other correlation models for the open-shell BeH system and evidence both the limitations and capabilities of the basis set.
本文给出了对BeH分子一些低能态的绝热势能曲线的全电子全组态相互作用（FCI）计算。为了描述价态、里德堡态及其相互作用，使用了一个适度大的由原子自然轨道（ANO）组成并附加里德堡函数的基组。在所有键长下，里德堡ANO集都位于Be原子上。因此，该基组可描述为4s3p2d1f3s2p1d(BeH)+4s4p2d(Be)。还报道了几个态的偶极矩以及从基态出发的跃迁偶极强度随R(Be-H)距离的变化关系。讨论了该系统中几个避免交叉所涉及的态的位置和数量。除了某些态（如3s和3p (2)Σ⁺态的非常扭曲的曲线或4p (2)Π态的双阱势）的情况外，从绝热曲线得到的一些振动态计算了光谱参数，这些参数在这些情况下完全无意义。在54050 cm⁻¹（185.0 nm）处的所谓“D复合体”被解析为三个3d子态（(2)Σ⁺、(2)Π、(2)Δ）。计算出一个双激发价态为最低的(2)Σ⁻对称态，并报道了其光谱参数以及2 (2)Δ（4d）态的光谱参数。4 (2)Σ⁺态的绝热曲线在大距离（约4.1 Å）处由于与3 (2)Σ⁺态的避免交叉而显示出一个浅阱。在一个近似的朗道 - 泽纳模型中讨论了该阱中一些振动态可能被占据的概率，发现概率很高。在“D复合体”区域未发现E(4ssigma) (2)Σ⁺态的证据。相反，本工作从(4ssigma) 6 (2)Σ⁺绝热曲线得到的光谱性质似乎与实验得到的F(4psigma) (2)Σ⁺态的光谱性质一致。FCI计算为开壳层BeH系统的其他相关模型提供了基准结果，并证明了基组的局限性和能力。
