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.     

AlH~+离子5个Λ-S态和10个?态的光谱性质以及激光冷却的理论研究

利用考虑Davidson修正的内收缩多参考组态相互作用(icMRCI+Q)方法结合相关一致基组aug-ccpV6Z计算了AlH~+离子前两个离解极限对应的5个Λ-S态和10个?态的势能曲线.为了提高势能曲线的可靠性和精确性,计算中考虑了自旋轨道耦合效应、芯电子价电子相关和标量相对论修正以及将势能外推至完全基组极限.基于得到的势能曲线,获得了束缚和准束缚的4个Λ-S态和8个?态的光谱常数和振动能级,与已有的实验结果符合.计算了2(1/2)→X~2Σ_(1/2)~+和A~2Π_(3/2)→X~2Σ_(1/2)~+跃迁的跃迁偶极距.利用计算的精确的势能曲线和跃迁偶极矩,获得了2(1/2)~(第一势阱)(υ′=0, 1)→X~2Σ_(1/2)~+(υ′′)和A~2Π_(3/2)(υ′=0, 1)→X~2Σ_(1/2)~+(υ′′)跃迁的高度对角化分布的Franck-Condon因子(f_(00)和f_(11))和大的振动分支比;预测了2(1/2)~(第一势阱)(υ′=0, 1)和A~2Π_(3/2)(υ′=0, 1)态短的自发辐射寿命和窄的辐射宽度,这适合于AlH~+离子的快速激光致冷.所需的3束激光冷却波长都在紫外区域.这些结果表明了激光冷却AlH~+离子的可行性.此外,评估了自旋轨道耦合效应对光谱常数、振动能级和激光冷却AlH~+离子的影响.     

An Accurate Calculation of Potential Energy Curves and Transition Dipole Moment for Low-Lying Electronic States of CO

In this paper, potential energy curves for the X 1 Σ+ , a3 Π, a′3 Σ+ , d3 , A1 Π and I 1 Σ states of CO have been calculated using complete active space self-consistent field and multi-reference configuration interaction methods. The calculations have been performed at 108 nuclear separations from 0.7 to 4.0 A by the aug-cc-PV5Z basis set. Spectroscopic constants for the six low-lying electronic states are found in good agreement with experimental data. The vibrational states of the X1Σ+ and A1Π states are also calculated, which are reliable and accurate by comparison with the experimental data and the other theoretical values. The transition dipole moment (TDM) shows that the TDM of the two states (X1Σ + A1Π) are reduced strongly with increase of bond length.     

icMRCI+Q理论研究CF离子12个-S态和23个?态的光谱性质

采用考虑Davidson修正的内收缩多参考组态相互作用(icMRCI+Q)方法结合相关一致基组aug-ccpV5Z和aug-cc-pV6Z计算了CF~+离子第一离解极限C~+(~2p_u)+F(~2P_u)对应的12个∧-S态(X~l∑~+,a~3∏,1~3∑~+,1~3Δ,1~1∑~-,1~1∑~-,1~3∑~-,2~1∑~+,1~1∏,2~3∏,2~1∏和2~3∑~+)所产生的23个Ω态的势能曲线.计算中考虑了旋轨耦合效应、核价相关和标量相对论修正以及将参考能和相关能分别外推至完全基组极限.基于得到的势能曲线,获得了束缚和准束缚的9个∧-S态和16个Ω态的光谱常数,并且X~1∑~+,a~3∏~(势阱一)∧-S态的光谱常数与已有的实验结果非常符合.此外,计算了CF自由基X~2∏态到CF~+离子束缚和准束缚的9个∧-S态的垂直电离势和绝热电离势,并且CF~+(X~1∑~+)←CF(X~2∏)和CF~+(a~3∏(势阱一))←CF(X~2∏)的垂直电离势和绝热电离势与相应的实验结果也非常符合.由a~3∏,1~1∏态和其他激发∧-S态势能曲线的交叉现象,借助于计算的旋轨耦合矩阵元,分析了a~3∏~(势阱一),1~1∏~(势阱一)和2~1∑~+态的预解离机理.计算的23个Ω态离解极限处的相对能量与实验结果十分吻合.最后计算了(2)0+~(势阱一)(v'=0-5),(1)1~(势阱一)(v'=0-5)和(2)1~(势阱一)(v'=0)到X0~+态跃迁的Franck-Condon因子和辐射寿命.     

GeS分子基态和低激发态的势能曲线与光谱性质

本文以aug-cc-pv5Z为基组, 采用考虑Davidson修正的多参考组态相互作用方法(MRCI+Q)得到了GeS分子基态(X¹Σ⁺)和5个低激发态(1¹Σ, 1¹Δ, A¹Π, 1⁵Σ⁺, 2⁵Σ⁺)的势能曲线. 计算结果表明: 2⁵Σ⁺态为排斥态, 其余5个态为束缚态; 6个态有着共同的离解通道, 离解极限均为Ge(³P)+S(³P). 利用计算得到的势能曲线得了X¹Σ⁺, 1¹Σ^-, 1¹Δ, A¹Π和1⁵Σ⁺态的垂直跃迁能T_e, 平衡键长R_e, 离解能D_e, 谐振频率ω_e, 非谐性常数ω_ex_e及平衡位置的电偶极矩. X¹Σ⁺态的R_e 为2.034 Å, D_e 为5.728 eV, ω_e为571.73 cm^-1, ω_ex_e为1.6816 cm^-1, 平衡位置的电偶极矩为1.9593 Debye. 激发态1¹Σ, 1¹Δ, A¹Π, 1⁵Σ⁺的T_e 依次为25904.81, 26209.22, 32601.19, 43770.26 cm^-1; R_e依次为2.313, 2.322, 2.188, 2.8790 Å; D_e依次为2.524, 2.487, 1.694, 0.3036 eV, ω_e依次为358.90, 353.08, 376.32, 134.96 cm^-1; ω_ex_e依次为1.2421, 1.2151, 1.6608, 1.9095 cm^-1; 平衡位置的电偶极矩依次为1.3178, 1.4719, 1.5917, -1.9785 Debye. 通过求解核运动的薛定谔方程得到了J=0时X¹Σ⁺, 1¹Σ^-, 1¹Δ, A¹Π和1⁵Σ⁺态前30个振动态的振动能级G_v和分子常数B_v, 得到的结果和已有的实验值及其他理论值符合较好.     

BeC分子基态和低激发态光谱性质和解析势能函数

BeC是一个具有丰富低激发电子态的分子,本文基于动态权重完全活性空间自冾场方法获得的参考波函数,采用多参考组态相互作用方法对BeC分子进行高精度的从头计算,获得了BeC分子X~3Σ~-,A~3Π,b~1Δ,c~1Π和d~1Σ~+共5个电子态的势能曲线.为了获得精确的光谱结果,在计算中考虑了标量相对论效应修正,并把相互作用能外推至完全基组极限.在此基础上获得了这些态的光谱常数和偶极距,以及一些允许跃迁的跃迁偶极距、弗兰克-康登因子和辐射寿命.最后,通过扩展的Rydberg函数拟合获得了基态势能曲线精确的解析表达式.     

~6Li~(32)S双原子分子的光谱和辐射跃迁理论研究

在aug-cc-pV5Z/CASSCF/MRCI水平上讨论了~6Li~(32)S双原子分子的9个较低能量电子态(X~2∏,a~4△,B~2△,b~4△,A~2∑~+,C~2∏,F~2∑~-,E~2∑~+和D~2∏)的势能函数和光谱常数;其中基态平衡核间距、谐振频率、转动常数等均与实验值相符;b~4∏,C~2∏,D~2∏态的平衡核间距均超过了0.4 nm,并且离解能较小,不稳定.D~2∏态是离子对态,离解极限为Li~+(~1S_g)+S~-(~1S_g).预测了最低激发态A~2∑~+跃迁到基态X~2∏的电子跃迁偶极矩、爱因斯坦自发发射系数、弗兰克-康登因子和辐射寿命.     

从头计算研究BP分子的势能曲线和光谱性质

利用高精度的量子化学从头计算MRCI+Q方法结合相关一致aug-cc-pVQZ基组计算了磷化硼分子X3Π,3Σ-,5Π和5Σ-态的势能曲线,计算所得的电子态在大键长位置处收敛于同一个离解极限B(2Pu)+P(4Su).为了得到更精确的结果,计算中首次纳入了旋轨耦合(SOC)效应,使得BP分子的4个Λ-S态分裂成为15个Ω态,其中3Π0+态被确定为基态.此外,SOC效应还使两个三重态X3Π和3Σ-分裂出的0+和1态的势能曲线产生了避免交叉,表明在当前的计算中考虑SOC效应是非常必要的.利用LEVEL8.0程序对计算所得的Λ-S态和Ω态的势能曲线进行拟合,得到了相应的光谱常数,通过与其他理论和实验工作进行比较,可知我们的结果更加精确、完整,可以为实验和理论方面进一步研究BP分子的光谱性质提供可靠的参考.     

Ab initio study on the electronic states and laser cooling of AlCl and AlBr

We investigate whether AlCl and AlBr are promising candidates for laser cooling. We report new ab initio calculations on the ground state X~1Σ~+ and two low-lying states(A~1Π and a~3Π) of AlCl and AlBr. The calculated spectroscopic constants show good agreement with available theoretical and experimental results. We also obtain the permanent dipole moments(PDMs) curve at multi-reference configuration interaction(MRCI) level of theory. The transition properties of A~1Π and a~3Π states are predicted, including the transition dipole moments(TDMs), Franck–Condon factors(FCFs), radiative times and radiative width. The calculated radiative lifetimes are of the order of a nanosecond, implying that they are sufficiently short for rapid laser cooling. Both AlCl and AlBr have highly diagonally distributed FCFs which are crucial requirement for molecular laser cooling. The results demonstrate the feasibility of laser cooling AlCl and AlBr, and we propose laser cooling schemes for AlCl and AlBr.     

Potential energy curves,transition dipole moments,and radiative lifetimes of KBe molecule

An ab initio calculations on the ground and low-lying excited states(X~2Σ+, 2~2Σ+, 3~2Σ+, 1~4Π, 2~4Π, 1~4Σ~+, 2~4Σ~+,and 3~4Σ~+) of KBe molecule have been performed using multireference configuration interaction(MRCI) plus Davidson corrections(MRCI+Q) approach with all electron basis set aug-cc-p CV5Z-DK for Be and def2-AQZVPP-JKFI for K.The 3~2Σ+, 1~4Π, 2~4Π, 1~4Σ~+, 2~4Σ~+, and 3~4Σ~+states are investigated for the first time. Inner shell electron correlations are computed on the potential energy curves(PECs) calculations. The spectroscopic and molecular parameters are also predicted. In addition, The transition properties including transition dipole moment, Franck–Condon factors qv'v', Einstein coefficients Av'v', and the radiative lifetimes τυ for the 2~2Σ~+–X~2Σ~+, 3~2Σ~+–X~2Σ~+, and 2~4Π–1~4Π transitions are predicted at the same time.     

Absorption spectra and isotope shifts of the(2, 0),(3, 1), and(8, 5) bands of the A~2Π_u-X~2Σ_g~+ system of ~(15)N_2~+ in near infrared

The high-resolution absorption spectra of the(2, 0),(3, 1), and(8, 5) bands of the A~2Π_u–X~2Σ_g~+system of~(15) N_2~+ have been recorded by using velocity modulation spectroscopy technique in the near infrared region. The rotational constants of the X~2Σ_g~+and A~2Π_u states of~(15) N_2~+ were derived from the spectroscopic data. The isotope shifts of these bands of the A~2Π_u–X~2Σ_g~+system of~(14) N_2~+ and~(15) N_2~+ were also analyzed and discussed.     

Structural,Spectroscopic and Vibrational Properties for Low-Lying Electronic States of LiCl

A multireference configuration interaction (MRCI) study has been carried out on the LiCl molecule. The potential energy has been calculated over a wide range of internuclear separation for the 21 low-lying electronic states of the LiCl molecule dissociating into Li (²S, ²P, ³S)+Cl(²P). The (4)¹Σ⁺, (3)¹Π, 1-3³Σ⁺, 1-3³Π, ^1,3Δ, ^1,3Σ^-, (5)¹Σ⁺, (4)³Σ⁺, (4)¹Π, (4)³Π excited states are studied for the first time in theory. Molecular spectroscopic constants (R_e, D_e, ω_e, ω_eχ_e, B_e and α_e) have been derived for the 9 bound states (X¹Σ⁺, (3)¹Σ⁺, (2)¹Σ⁺, ^1,3Δ, ^1,3Σ^-, (4)¹Π, (4)³Π) with a regular shape, and the spectroscopic constants of ground states X¹Σ⁺ are in good agreement with available experimental and theoretical values. The relative differences between experimental values and our values for R_e, D_e, ω_e, ω_eχ_e, B_e and α_e are 1.02%, 0.60%, 1.72%, 9.46%, 2.0%, and 0.75%, respectively. Moreover, vibrational levels of 9 bound states, which have not been investigated experimentally, are computed.     

用于α和μ常数变化测量的碘离子光谱研究

分子离子I_2~+的禁戒跃迁光谱有可能用于测量α和μ常数的变化,并且具有增强的灵敏度.通过分析I_2~+在11860—13100 cm~(-1)范围内的转动光谱,拟合了A~2Π_(3/2)-X~2Π_(3/2)系统31个振转带的5759根吸收谱线,得到5个属于X~2Π_(3/2)态和9个属于A~2Π_(3/2)态的振动能级准确的转动光谱常数.在量子噪声极限和1 Hz跃迁线宽的条件下,计算得到X~2Π_(3/2)和X~2Π_(1/2)之间的禁戒跃迁对α和μ常数变化测量的灵敏度为δ_(α/α)≈2.37×10~(-19)a~(-1)和δ_(μ/μ)≈1.18×10~(-18)a~(-1).     

Differential cross sections for electron impact excitation of molecular hydrogen using the momentum-space multichannel optical method

In the present work, the momentum-space multichannel optical method is employed in four-state close-coupling calculations to study the electronic excitation of H_2 molecules by electron-impact. Particularly, differential cross sections for the X~1Σ_g~+→ b~3Σ_u~+, X~1Σ_g~+→ aΣ_g~+, and X~1Σ_g~+→ c~3Π_u transitions are reported. Comparison is made with the available experimental and theoretical results.     

Superconductivity in Alkali-Doped C60

There ark three kinds of effective attractive interaction between C₆₀^2- and "nearly free" electron in A₃C₆₀: 1) the strong short-range attraction between the low energy unoccupied orbital of C₆₀^2- ions and the "nearly free" electrons; 2) the potential barrier due to large angular momentum of t_1u orbital; 3) the A⁺ crystal field forced "nearly free" electrons in C₆₀^2- neighborhood. All effective attraction coupling with the A⁺ optical modes and the vibration modes of C₆₀ mass center produces a strong electron-phonon interaction. It plays a principal role for A₃C₆₀ superconductivity. Based upon this mechanism critical temperature and other properties of superconductivity state can be explained by means of the BCS theory.     

基于ab initio的BD~+离子激光冷却理论研究

基于相关一致基组aug-cc-pV5Z,采用内收缩多参考组态相互作用方法计算了BD~+离子两个最低解离极限B~+(~1Sg)+D(~2Sg)和B+(~3Pu)+D(~2Sg)对应的5个Λ—S态(X~2Σ~+,A~2Π,B~2Σ+,a~4Π和b~4Σ~+)的势能曲线和跃迁偶极矩.根据计算结果,求解核运动的径向薛定谔方程得到相应电子态的振-转光谱常数、Franck-Condon(F-C)因子和振动能级辐射寿命.其中A~2Π—X~2Σ~+的F-C因子(f_(00)=0.923)、辐射寿命(τ=235 ns)满足激光直接冷却的条件.因此,我们基于分子转动跃迁提出了一个可实现Doppler激光冷却的光循环方案:A~2Π_(1/2)(υ′=0)—X~2Σ+(υ′′=0,1),其中υ′=0中包含2个转动能级,υ′′=0和υ′′=1中分别包含6个和4个转动能级.根据方案,模拟了激光冷却过程中的分子布居数动力学变化过程,并计算了初速度为100 m/s的BD~+,历经5.4 ms散射1150个光子可减速到4.6 m/s、温度为13 mK.     

LiGd(W_yMo_(1-y))_2O_(8-x/2)F_x∶Eu~(3+)红色荧光粉的制备和发光特性

采用高温固相法制备了LiGd(W_yMo_(1-y))_2O_(8-x/2)F_x∶0.4Eu~(3+)(x=0~1,y=0~1)系列白光LED用红色荧光粉。通过扫描电子显微镜、X射线衍射仪、红外光谱仪、荧光光谱仪对荧光粉的形貌、结构、光学性能进行了表征。结果表明,Eu~(3+)、F-和WO_4~(2-)的掺杂没有改变LiGd(MoO_4)_2的四方晶系白钨矿结构;F~-和WO_4~(2-)最佳掺杂量分别为x=0.6,y=0.4。在396 nm激发下,LiGd(W_(0.4)Mo_(0.6))_2O_(7.7)F_(0.6)∶0.4Eu~(3+)的发光强度比未掺杂样品提高了60%,量子效率可达66.23%。当温度升高至100℃时,样品的发射强度降为25℃时的76.6%。在460 nm激发下,样品的最强窄带发射峰位于617 nm处,归属于~5D_0→~7F_2跃迁,色坐标为(0.649 9,0.346 3)。5D0能级的荧光寿命曲线遵循单指数规律衰减,随着F-掺杂浓度的增加,5D0能级的荧光寿命不断增加,归因于低声子能量的F-掺入有效减小了能量的无辐射跃迁概率。所制备的LiGd(W_(0.4)Mo_(0.6))_2O_(7.7)F_(0.6)∶0.4Eu~(3+)荧光粉有望应用于白光LED。     

Pressure-broadened atomic Li(2s-2p) line perturbed by ground neon atoms in the spectral wings and core

Full quantum calculations are performed to investigate the broadening profiles of the atomic lithium Li(2s-2p) resonance line induced by interactions with ground Ne(2s~22p~6) perturbers in the spectral wings and core. The X~2Σ~+, A~2Π,and B~2Σ~+ potential-energy curves of the two first low lying Li Ne molecular states, as well as the corresponding transition dipole moments, are determined with ab initio methods based on the SA-CASSCF-MRCI calculations. The emission and absorption coefficients in the wavelength range 550-800 nm and the line-core width and shift are investigated theoretically for temperatures ranging from 130 K to 3000 K. Their temperature dependence is analyzed, and the obtained results are compared with the previous experimental measurements and theoretical works.     

SiCl自由基X2Π和A2Σ+态的光谱性质

采用内收缩多参考组态相互作用(ic MRCI)方法结合Dunning等相关一致基,计算Si Cl自由基X²Π和A²Σ⁺态的势能曲线.讨论参考能和相关能外推对X²Π和A²Σ⁺态光谱的影响.对势能进行相对论修正及核价修正计算.拟合势能曲线得到X²Π和A²Σ⁺态的光谱常数.它们与实验结果一致.利用Breit-Pauli算符,计算旋轨耦合效应,得到X²Π_1/2和X²Π_3/2的势能曲线、并计算它们的光谱常数.求解双原子分子核运动的径向SchrÖdinger方程,获得无转动SiCl自由基2个Λ-S态及X²Π态的耦合分裂态的全部振动态.得到J=0时X²Π态的自旋-轨道耦合常数、较高振动态的惯性转动常数以及X²Π_1/2和X²Π_3/2的振动能级等分子常数.     

Theoretical study of potential energy curves,spectroscopic constants,and radiative lifetimes of low-lying states in SeO molecule

The low-lying potential energy curves of SeO molecule are computed by means of ab initio multireference configuration interaction technique, taking into account relativistic (scalar plus spin-orbit coupling) effects. The spectroscopic constants of Ω states for X³Σ^-, a¹Δ, b¹Σ⁺, A³Π, A'³Δ, and A"³Σ⁺ states are obtained, and they are in good accordance with available experimental values. The Franck-Condon factors and transition dipole moments to the ground state are computed, and the natural radiative lifetimes of low-lying Ω states are theoretically obtained. Comparisons of the natural lifetimes of Ω states with previous experimental results and those of isovalent TeO molecule are made.