GeCl分子激发态的势能曲线和辐射寿命的理论研究

采用考虑Davidson校正、标量相对论效应、芯-价电子关联和自旋-轨道耦合效应高精度的多参考组态相互作用方法计算了GeCl分子的最低解离极限Ge(3Pg)+Cl(2Pu)对应的12个Λ-S电子态的势能曲线. 基于计算得到的势能曲线, 求解一维核运动的Sch?rdinger方程得出束缚态的光谱常数, 这些光谱常数与实验值符合较好. 本文计算了12个Λ-S态的电偶极矩随核间距的变化, 分析了电子态组态成分的变化对电偶极矩的影响. 本文还研究了GeCl分子的辐射跃迁性质, 给出了激发态到基态之间和低激发态之间的跃迁偶极矩和电子态之间的Franck-Condon因子, 并根据计算得到的跃迁偶极矩和Franck-Condon因子计算出了束缚激发态低振动能级的辐射寿命.     

MRCI计算研究B2+分子的结构和解析势能函数

采用从头计算的多参考组态CI方法(MRCI) 和B原子Dunnings相关调和基函数含扩散基的大基组aug-cc-pVQZ对B+2分子的基态和低激发态的势能曲线进行计算 .利用Huxley函数、Murrell-Sorbie函数和最小二乘法拟合出了解析势能函数,并以此为基础计算出光谱常数.通过比较发现:Huxley 函数比MS函数的拟合方差更小,能更好地再现分子中原子间相互作用.采用两种函数所得解析势能函数与从头计算势能曲线间的误差RMS 均远小于化学精度4.184 kJ/mol的要求,表明所得解析势能函数很好地再现了这些态中原子间的相互作用情况,可用于更广泛的研究.     

BeCl分子电子激发态的多参考组态相互作用计算

运用含Davidson修正的多参考组态相互作用方法,在aug-cc-pVTZ基组水平上,对BeCl分子基态和相同多重度的几个低电子激发态进行了势能扫描计算.通过群论原理确定各电子态对称性及离解极限.将其中基态(X²Σ⁺)和第一激发态(A²Π})对应的势能曲线拟合到Murrell-Sorbie解析势能函数形式,得到基态(X²Σ⁺)的离解能及主要光谱常数(括号中为文献[6]提供的实验值)为D_e=3.74eV,R_e=0.18173nm(0.17970),w_e=857.4cm¹(847.2),w_ex_e=5.03cm^-1(5.14),B_e=0.7103cm^-1(0.7285),α_e=0.0059cm^-1(0.0069),第一激发态(A²Π)的D_e=3.02eV,R_e=0.18369nm(0.18211),w_e=832.7cm^-1(822.1),w_ex_e=5.93cm^-1(5.24),B_e=0.6953cm^-1(0.7094),α_e=0.0065cm^-1(0.0068),计算结果与实验值符合得较好.另外,通过Level程序求解双原子径向核运动的Schrödinger方程得到J=0时BeCl分子这两个电子态的全部振动能级.     

AlCl分子低激发态光谱性质的从头计算研究

AlCl 分子在天体物理、化学领域以及激光冷却方面发挥着重要作用。 本文使用高精度多参考组态相互作用方法(MRCI+Q)对 AlCl 分子低激发态进行研究。 基于获得的势能曲线(PECs)拟合电子态的光谱常数,与实验值吻合较好。 计算了电子态的偶极矩(DMs)以及自旋轨道(SO)矩阵元随核间距变化的曲线。 同时还计算了 AlCl 分子的跃迁性质,包括跃迁偶极距(TDMs)和 Franck-Condon 因子(FCFs)以及辐射寿命。 AlCl 分子的 1¹Π-1¹Σ⁺跃迁 FCFs 高度对角化,有作为激光冷却光循环的潜力。计算结果对 AlCl 分子电子结构性质后续的实验研究具有一定的参考价值。     

从头计算研究BCl+基态和激发态的势能曲线和光谱性质

基于相关一致极化4zeta(aug-cc-pVQZ)基组, 应用量子化学从头计算中高水平的多参考组态相互作用方法计算了BCl⁺ 两个离解极限B⁺(¹S_g)+Cl(²P_u)和B (²P_u)+Cl⁺ (³P_g)的14个Λ-S态势能曲线. 在计算中考虑了Davidson修正(+Q)和标量相对论效应, 并首次在计算中考虑了BCl⁺ 的旋轨耦合效应, 获得了由能量最低的4个Λ-S态分裂出的7个Ω 态. 计算结果表明相同对称性的Ω 态的势能曲线存在着非常明显的避免交叉. 通过分析Λ-S态的电子结构, 得到了各态的电子跃迁特性, 并确认了电子态的多组态性质. 使用LEVEL程序通过求解径向的Schrödinger方程得到了束缚Λ-S 和Ω态的光谱参数D_e, R_e, T_e, ω_e, ω_eχ_e和B_e. 通过和已有的Λ-S态X²∑⁺ 的实验数据进行对比发现, 本文所得的计算结果与实验结果非常一致. 而文中其他电子态的光谱参数均为首次报道. 关键词： 势能曲线 光谱参数 多参考组态相互作用方法 旋轨耦合     

BH分子基态和激发态解析势能函数和光谱性质

运用多参考组态相互作用的方法和Dunning’s相关调和基函数并含扩散基的大基组aug-cc-pV5Z,获得了BH分子基态（X¹Σ⁺）和6个电子激发态（a³П, A¹П, B¹Σ⁺, b³Σ⁺, b³ 关键词： 势能曲线 解析势能函数 多参考组态相互作用方法 光谱常数     

多参考组态相互作用方法计算研究XOn(X=S,Cl; n=0,±1)的解析势能函数和光谱常数

采用从头计算的多参考组态相互作用方法和含扩散基的3个基组aug-cc-PVXZ(X=D,T,Q)计算了SO和ClO分子及其分子离子的势能曲线,确定了平衡几何结构、离解能,并采用Feller拟合递推方法得到了基函数为无穷大计算水平值.确定了SO-,ClO ,ClO-分子离子的基态.通过Murrell-Sorbie势能函数和最小二乘法拟合得到了解析势能函数.基于所得的势能函数,通过解核运动的薛定谔方程得到振动能级,精确计算了相应的光谱常数,并与现有的理论值和实验值进行了比较.     

B_2分子X~3Σ_g~-和A~3Σ_u~-态的势能函数

使用SAC/SAC-CI方法,利用D95(d),6-311g**以及cc-PVTZ等基组,对B2分子的基态(X3Σg-)和第一激发态(A3Σu-)的平衡结构和谐振频率进行了优化计算.通过对3个基组的计算结果的比较,得出了D95(d)基组为3个基组中的最优基组的结论;使用D95(d)基组,利用SAC的GSUM(Group Sum of Operators)方法对基态(X3Σg-),SAC-CI的GSUM方法对激发态(A3Σu-)进行单点能扫描计算,用正规方程组拟合Murrell-Sorbie函数,得到了相应电子态的完整势能函数;从得到的势能函数计算了与基态(X3Σg-)和第一激发态(A3Σu-)相对应的光谱常数(Be,αe,ωe和ωeχe),结果与实验数据吻合.     

多参考组态相互作用方法计算研究XOn(X=S,Cl；n=0,±1)的解析势能函数和光谱常数

采用从头计算的多参考组态相互作用方法和含扩散基的3个基组aug-cc-PVXZ (X=D,T,Q) 计算了SO和ClO分子及其分子离子的势能曲线，确定了平衡几何结构、离解能，并采用Feller拟合递推方法得到了基函数为无穷大计算水平值. 确定了SO^－，ClO⁺，ClO^-分子离子的基态. 通过Murrell-Sorbie势能函数和最小二乘法拟合得到了解析势能函数. 基于所得的势能函数，通过解核运动的薛定谔方程得到振 关键词： 多参考组态相互作用 势能曲线 解析势能函数 光谱常数     

N2同位素分子X1Σ+g态的光谱常数与分子常数

利用内收缩多参考组态相互作用方法和核价相关一致极化基aug-cc-pCV5Z在0.04-0.54 nm的核间距范围内计算了N2分子X1Σ+g态的势能曲线. 利用这一势能曲线并在同位素质量识别的基础上, 拟合出了同位素分子14N2(X1Σg+), 15N2(X1Σg+)和14N15N(X1Σg+)的光谱常数(D0, De, Re, ωe, ωexe, αe和Be)和无转动时的振动能级G(υ)、惯性转动常数Bυ和离心畸变常数Dυ等分子常数. 这些结果与已有的实验值十分一致.     

BH~+离子基态及激发态的势能曲线和跃迁性质的研究

利用高精度的多组态相互作用及Davidson修正方法 (MRCI+Q),采用ACV5Z-DK全电子基组计算了BH~+离子的前4个离解通道B~+(~1S_g)+H(~2S_g),B~+(~3Pu)+H(~2S_g),B(~2P_u)+H~+(~1Sg)和B~+(~1Pu)+H(~2Sg)的9个Λ—S态的势能曲线.X~2Σ~+,A~2Π和B~2Σ~+态的光谱常数和已有实验值符合得很好,其中b~4Σ~+,3~2Σ~+,3~2Π和4~2Σ~+态的光谱常数为首次报道,3~2Π和4~2Σ~+态具有双势阱结构.预测了A~2Π和B~2Σ~+态的辐射寿命:τ(A~2Π)=239.2 ns和τ(B~2Σ~+)=431.2 ns.最后在考虑自旋轨道耦合效应下讨论了B~2Σ~+与A~2Π态的势能曲线的相交对激光冷却BH~+离子的影响.     

MRSDCI study on potential energy curves and ro-vibrational spectra of the BBr molecule

Four low-lying electronic states of the BBr molecule, including Σ⁺ symmetry and Π symmetry with singlet and triplet spin multiplicities, have been studied using the complete active space self-consistent-field method followed by multi-reference single and double excitation configuration interaction calculation. For the ground state, four isotopes (¹¹B⁷⁹Br, ¹¹B⁸¹, ¹⁰B⁷⁹Br, ¹⁰B⁸¹Br) of the BBr molecule have been studied, since their experimental spectroscopic constants and ro-vibrational energy levels are abundant. For the three excited states, just the most natural abundance isotope–¹¹B⁷⁹Br–is investigated. The spin–orbital coupling effect for the a³Π state is also considered. Finally, the analytical potential energy functions of these states are fitted except for the ³Σ⁺ state because its potential well is too shallow to be fitted with available functions. These results have been compared in detail with those of the investigations reported in the literature.     

TiN分子基态(X2Σ)结构和势能函数

应用群论及原子分子反应静力学方法推导了TiN分子基态(X²Σ)的离解极限. 采用不同的密度泛函方法,包括BP86, B3P86, B3LYP, B3PW91, 分别选用不同的基组对TiN分子基态进行结构优化计算.通过比较得出使用BP86方法, 对N原子使用D95V++(d,P)基组和Ti原子使用6-311++G^**基组时,计算得到的平衡几何结构、分子离解能和谐振频率与实验值符合得最好. 并采用最小二乘法拟合改进的Murrell-Sorbie函数得到了相应电子态的完整势能函数. 计算得到的光谱常数与实验光谱数据符合得很好. 关键词： BP86 TiN分子基态 势能函数 光谱常数     

Li2分子自旋一致激发态a3Σ+u和b3Πu的分析势能函数的从头算

使用对称性匹配簇-组态相互作用方法首次计算了Li₂分子自旋一致激发态a³Σ⁺_u和b³Π_u的离解能、平衡几何及其谐振频率。使用最小二乘法、利用Murrell-Sorbie函数形式拟合出了Li₂分子三重态的第一激发态a³Σ⁺_u 和第二激发态b³Π_u的完整势能函数，并计算了这两个态的光谱常数 (B_e, α_e, ω_e 和 ω_eχ_e) 和力常数 (f₂, f₃和f₄)。得到了Murrell-Sorbie函数形式既适用于基态、又适用于激发态的结论。将计算得到的激发态（a³Σ⁺_u和b³Π_u）的离解能、平衡几何及其谐振频率与实验结果及其它理论计算结果进行了比较。从比较的结果中可以清楚地看出，本文的计算结果在计算精度方面有很大的改进。     

Ab initio calculation of the ground and first excited states of the lithium dimer

Based on a high level ab initio calculation which is carried out with the multireference configuration interaction method under the aug-cc-pVXZ (AVXZ) basis sets, X=T, Q, 5, the accurate potential energy curves (PECs) of the ground state ${\rm{X}}{}^{{\rm{1}}}{\rm{\Sigma }}_{g}^{+}$ and the first excited state ${\rm{A}}{}^{{\rm{1}}}{\rm{\Sigma }}_{u}^{+}$ of Li₂ are constructed. By fitting the ab initio potential energy points with the Murrell–Sorbie potential function, the analytic potential energy functions (APEFs) are obtained. The molecular bond length at the equilibrium (R_e), the potential well depth (D_e), and the spectroscopic constants (B_e, ω_e, α_e, and ω_eχ_e) for the ${\rm{X}}{}^{{\rm{1}}}{\rm{\Sigma }}_{g}^{+}$ state and the ${\rm{A}}{}^{{\rm{1}}}{\rm{\Sigma }}_{u}^{+}$ state are deduced from the APEFs. The vibrational energy levels of the two electronic states are obtained by solving the time-independent Schrödinger equation with the Fourier grid Hamiltonian method. All the spectroscopic constants and the vibrational levels agree well with the experimental results. The Franck–Condon factors (FCFs) corresponding to the transitions from the vibrational level (v′=0) of the ground state to the vibrational levels (v″=0–74) of the first excited state have been calculated. The FCF for the vibronic transition of ${\rm{A}}{}^{{\rm{1}}}{\rm{\Sigma }}_{u}^{+}$(v″=0) ←${\rm{X}}{}^{{\rm{1}}}{\rm{\Sigma }}_{g}^{+}$(v′=0) is the strongest. These PECs and corresponding spectroscopic constants provide reliable theoretical references to both the spectroscopic and the molecular dynamic studies of the Li₂ dimer.     

The theoretical study on the potential energy curve for X~3△ state of TiO molecule

This paper applies the density functional theory method to optimise the structure for X ³Δ state of TiO molecule with the basis sets 6-31G, 6-31++G and 6-311G^**. Comparing the attained results with the experiments, it obtains the conclusion that the basis set 6-31++G is most suitable for the optimal structure calculations of X ³Δ state of TiO molecule. The whole potential energy curve for the electronic state is further scanned by using B3P86/6-31++G method for the ground state, then it uses a least square fitted to Murrell--Sorbie functions, at last it calculates the spectroscopic constants and force constants, which are in better agreement with the experimental data.     

Multireference configuration interaction potential curve and analytical potential energy function of the ground and low-lying excited states of CdSe

The potential energy curves (PECs) of the ground state ($^{3}\Pi )$ and three low-lying excited states ($^{1}\Sigma $, $^{3}\Sigma $,$^{ 1}\Pi )$ of CdSe dimer have been studied by employing quasirelativistic effective core potentials on the basis of the complete active space self-consistent field method followed by multireference configuration interaction calculation. The four PECs are fitted to analytical potential energy functions using the Murrel--Sorbie potential function. Based on the PECs, the vibrational levels of the four states are determined by solving the Schr\"{o}dinger equation of nuclear motion, and corresponding spectroscopic constants are accurately calculated. The equilibrium positions as well as the spectroscopic constants and the vibrational levels are reported. By our analysis, the $^{3}\Pi $ state, of which the dissociation asymptote is Cd($^{1}$S) + Se($^{3}$P), is identified as a ground state of CdSe dimer, and the corresponding dissociation energy is estimated to be 0.39\,eV. However, the first excited state is only 1132.49\,cm$^{ - 1}$ above the ground state and the $^{3}\Sigma $ state is the highest in the four calculated states.     

Ab initio calculations on the α^3∑u^＋ state properties of dimer ^7Li2

The comparison between single-point energy scanning （SPES） and geometry optimization （OPT） in determining the equilibrium geometry of the α^3∑u^＋ state for ^7Li2 is made at numerous basis sets such as 6-311＋＋G（2df）, cc-PVTZ, 6-311＋＋G（2df, p）, 6-311G（3df,3pd）, 6-311＋＋G（2df,2pd）, D95（3df,3pd）, 6-311＋＋G, DGDZVP, 6-311＋＋G（3df,2pd）, 6-311G（2df,2pd）, D95V＋＋, CEP-121G, 6-311＋＋G（d,p）, 6-311＋＋G（2df, pd） and 6-311＋＋G（3df,3pd） in full active space using a symmetry-adapted-cluster/ symmetry-adapted-cluster configuration-interaction （SAC/SAC=CI） method presented in Gaussian03 program package. The difference of the equilibrium geometries obtained by SPES and by OPT is reported. Analyses show that the results obtained by SPES are more reasonable than those obtained by OPT. We have calculated the complete potential energy curves at those sets over a wide internuclear distance range from about 3.0α0 to 37.0α0, and the conclusion is that the basis set cc-PVTZ is the most suitable one. With the potential obtained at ccopVTZ, the spectroscopic data （Te, De, D0, ωe,ωeХe, αe and Be） are computed and they are 1.006 eV, 338.71 cm^-1, 307.12 cm^-1, 64.88 cm^-1, 3.41 cm^-1, 0.0187 cm^-1 and 0.279 cm^-1, respectively, which are in good agreement with recent measurements. The total 11 vibrational states are found at J=0. Their corresponding vibrational levels and classical turning points are computed and compared with available RKR data, and good agreement is found. One inertial rotation constant （By） and six centrifugal distortion constants （Dr Hv, Lv, My, Nv, and Ov） are calculated. The scattering length is calculated to be -27.138α0, which is in good accord with the experimental data.