Spectroscopy and molecule opacity investigation on excited states of SiS

The SiS molecule,which plays a significant role in space,has attracted a great deal of attention for many years.Due to complex interactions among its low-lying electronic states,precise information regarding the molecular structure of SiS is limited.To obtain accurate information about the structure of its excited states,the high-precision multireference configuration interaction(MRCI)method has been utilized.This method is used to calculate the potential energy curves(PECs)of the 18Λ–S states corresponding to the lowest dissociation limit of SiS.The core–valence correlation effect,Davidson’s correction and the scalar relativistic effect are also included to guarantee the precision of the MRCI calculation.Based on the calculated PECs,the spectroscopic constants of quasi-bound and bound electronic states are calculated and they are in accordance with previous experimental results.The transition dipole moments(TDMs)and dipole moments(DMs)are determined by the MRCI method.In addition,the abrupt variations of the DMs for the 1^(5)Σ^(+)and 2^(5)Σ^(+)states at the avoided crossing point are attributed to the variation of the electronic configuration.The opacity of SiS at a pressure of 100 atms is presented across a series of temperatures.With increasing temperature,the expanding population of excited states blurs the band boundaries.

ZnH分子激发态的电子结构和跃迁性质的理论计算

采用高精度的多参考组态相互作用方法计算了ZnH分子的能量最低四个离解限Zn(~1Sg)+H(~2Sg),Zn(~3P2u)+H(Sg),Zn^+(~2Sg)+H^-(~1Sg)和Zn(~1Pu)+H(~2Sg)对应的7个Λ-S态的势能曲线.计算中考虑了Davidson修正、标量相对论效应、自旋-轨道耦合效应和芯-价电子关联.基于计算的Λ-S和?态的势能曲线,数值求解一维径向Schr?dinger方程得到了束缚电子态的光谱常数,理论计算结果与之前的实验结果符合较好.计算得到了7个Λ-S态的电偶极矩随核间距的变化曲线,分析了电子组态成分变化对电偶极矩和成键性质的影响.计算结果表明,C^2Σ^+态是一个离子对态.进一步地,分析了避免交叉点附近?态的Λ-S态组成的变化规律,讨论了避免交叉现象对跃迁偶极矩的影响.基于计算的跃迁偶极矩、Franck-Condon因子和振动能级信息,给出了束缚激发态(2)1/2,(3)1/2,(4)1/2和(1)3/2的v′=0—2振动能级的自发发射寿命,结果与现有实验值相符合.

SO分子最低两个电子态振—转谱的显关联多参考组态相互作用计算

采用显关联多参考组态相互作用(explicitly correlated multi-reference configuration interaction method,MRCI-F12)方法和相关一致基组cc-p CVQZ-F12计算了双原子分子SO的基态X^3Σ^-和第一激发态a^1?的势能曲线,研究中考虑了Davidson修正,芯-价电子关联修正和标量相对论效应.通过对这两个束缚电子态势能曲线的拟合,给出了光谱常数并与其他理论和实验结果做了比较.进一步地,获得了这两个态的振-转能级信息.本文计算结果与实验的相对误差仅在千分之一量级,对将来的实验有重要的参考价值;同时也表明MRCI-F12方法可推广到小分子体系势能面的高效、精确计算研究中.

Molecular opacities of low-lying states of oxygen molecule

The X^3Σg^-,A^'3△u,A^3Σ^u+,1^3Πg,and B^3Σu^-electronic states of oxygen molecule(O2)are calculated by the multiconfiguration self-consisted filed(MRCI)+Q method with the scalar relativistic correction and core-valence correlation correction.The obtained spectroscopic constants of the low-lying bound states are in excellent agreement with measurements.Based on the accurately calculated structure parameters,the opacities of the oxygen molecule at the temperatures of 1000 K,2000 K,2500 K,and 5000 K under a pressure of 100 atm(1 atm=1.01325×10^5 Pa)and the partition functions between 10 K and 10^4 K are obtained.It is found that with the increase of temperature,the opacities for transitions in a long wavelength range are enlarged because of the larger population on excited electronic states at the higher temperatures.

Molecular Opacity Calculations for Lithium Hydride at Low Temperature

The opacities of the lithium hydride molecule are calculated for temperatures of 300 K,1000 K,1500 K,and 2000 K,at a pressure of 10 atm,in which the contributions from the five low-lying electronic states are considered.The ab initio multi-reference single and double excitation configuration interaction(MRDCI)method is applied to compute the potential energy curves(PECs)of the 7 LiH,including four 1∑+states and one 1Πstate,as well as the corresponding transition dipole moments between these states.The ro-vibrational energy levels are calculated based on the PECs obtained,together with the spectroscopic constants.In addition,the partition functions are also computed,and are provided at temperatures ranging from 10 K to 2000 K for 7 LiH,7 LiD,6 LiH,and 6 LiD.

Explicitly correlated configuration interaction investigation on low-lying states of SiO^+ and SiO

SiO^+ and SiO, which play vital roles in astrophysics and astrochemistry, have long attracted considerable attention.However, accurate information about excited states of SiO^+ is still limited. In this work, the structures of 14 Λ–S states and 30? states of SiO^+ are computed with explicitly correlated configuration interaction method. On the basis of the calculated potential energy curves of those Λ–S states and ? states, the spectroscopic constants of bound states are evaluated, which are in good agreement with the latest experimental results. The predissociation mechanism of B^2Σ^+ state is illuminated with the aid of spin–orbit coupling matrix elements. On the basis of the calculated potential energy curves and transition dipole moments, the radiative lifetime for each of low-lying vibrational states B^2Σ^+and A^2Π is estimated. The laser cooling scheme of SiO^+ is proposed by employing B^2Σ^+–X^2Σ^+ transition. Finally, the vertical ionization energy values from SiO(X^1Σ^+) to ionic states: SiO^+ , X^2Σ^+, B^2Σ^+, and A^2Π are calculated, which agree well with experimental measurements.

Molecule opacities of X^2Σ^+, A^2Π, and B^2Σ^+ states of CS^+

Carbon sulfide cation(CS^+) plays a dominant role in some astrophysical atmosphere environments. In this work, the rovibrational transition lines are computed for the lowest three electronic states, in which the internally contracted multireference configuration interaction approach(MRCI) with Davison size-extensivity correction(+Q) is employed to calculate the potential curves and dipole moments, and then the vibrational energies and spectroscopic constants are extracted. The Frank–Condon factors are calculated for the bands of X^2^+Σ^+–A^2Π and X^2Σ^+–B^2Σ^+systems, and the band of X^2Σ^+–A^2Π is in good agreement with the available experimental results. Transition dipole moments and the radiative lifetimes of the low-lying three states are evaluated. The opacities of the CS^+ molecule are computed at different temperatures under the pressure of 100 atms. It is found that as temperature increases, the band systems associated with different transitions for the three states become dim because of the increased population on the vibrational states and excited electronic states at high temperature.

Molecule opacity study on low-lying states of CS

CS molecule, which plays a key role in atmospheric and astrophysical circumstances, has drawn great attention for long time. Owing to its large state density, the detailed information of the electronic structure of CS is still lacking. In this work, the high-level MRCI+Q method is used to compute the potential energy curves, dipole moments and transition dipole moments of singlet and triplet states correlated with the lowest dissociation limit of CS, based on which high accurate vibration-rotation levels and spectroscopic constants of bound states are evaluated. The opacity of CS relevant to atmospheric circumstance is computed at a pressure of 100 atms for different temperatures. With the increase of temperature,band systems from different transitions mingle with each other, and band boundaries become blurred, which are originated from the increased population on vibrational excited states and electronic excited states at high temperature.