Theoretical studies on CuF+, CuF,CuF−, CuF2, and CuF2 −

Ab initio SCF studies were performed with Cu and F basis sets of near-Hartree-Fock (HF) limit quality to obtain accurate SCF results for the molecular ground state properties of CuF⁺, CuF, CuF^–, CuF₂, and CuF₂ ^–, as well as for the first two low-lying excited states of CuF₂. A study on the effects of electron correlation was carried out by Møller-Plesset (MP) and configuration interaction (Cl) calculations. The effect of relativity on the⁶³Cu nuclear quadrupole coupling in CuF was determined by use of a coupled HF procedure for a first-order spin-orbital-averaged Pauli operator. At the HF level the⁶³Cu coupling constant was found to be 35.8 MHz (in e²qQ h^–1), while allowing for relativity the value was reduced to 29.1 MHz, which is in better agreement with the experimental value of 22.0 MHz. The calculated molecular properties for CuF [r _e = 1.737 Å,D _e=4.38 eV, _e = 562 cm^–1 (MP4);r _e= 1.796 Å,D _e = 3.91 eV, _e=585 cm^–1 (CISD)] were in good agreement with experiment (r _e = 1.745 Å,D _e = 4.43 eV, _e=623 cm^–1). The adiabatic ground-state potential curve of CuF⁺ avoids crossing near the equilibrium distance between the two ionic potential curves Cu⁺-F and Cu²⁺-F^–. At the crossing point the Cu and F electric field gradients show a sharp discontinuity.     

Molecular constants for the 1Σ+ ground state of the ArH+ ion

From the near equilibrium PNO-CEPA potential and dipole moment curves the following molecular constants for the ¹⁺ ground state of the ArH⁺ ion have been calculated: r _e = 1.286Å, _e = 2723 cm^–1, _{e e} = 56 cm^–1, D ₀ = 3.89 eV and ₀ = 2.384 D. The rotationless radiative lifetimes of the five lowest vibrational states are predicted to be 2.28, 1.2, 0.85, 0.64, 0.46 for ArH⁺ and 9.09, 4.71, 3.27, 2.55 and 2.11 for ArD⁺, respectively (all values are in milliseconds and in ascending order of the vibrational levels).Dedicated to Prof. Hermann Hartmann on the occasion of his 65th birthday.     

Analysis of the 4800-Å absorption band of Cs2 by the classical method

The broad absorption band in Cs₂ having peak intensity near 4800 Å is analyzed through computational simulation of the experimental spectrum using the classical method. The absorption, which terminates in a weak satellite at 5223 Å, can be interpreted in terms of a single transition from the ground state (R_e = 4.65 Å, ω_e = 42 cm⁻¹) to an upper state having T_e = 20 470 cm⁻¹, ω_e = 33 cm⁻¹ and R_e = 5.28 Å. The absolute absorption strength is roughly consistent with published lifetime data, but its reliability is limited by thermodynamic uncertainties stemming from the remaining uncertainty in the Cs₂ ground state dissociation enegy. The paper includes a summary of diatomic radiation relations pertinent to the analysis of low-resolution spectra, and a brief discussion of the reduced potential method applied to the alkali dimer ground states.     

Test study on the excitation spectra of the N<Subscript>2</Subscript>–He van der Waals molecule

We have performed ab initio fourth-order Møller–Plesset perturbation theory calculations in the framework of the supermolecule approach on the vertical excitation spectra of the weakly bound van der Waals N₂–He dimer. They indicate a ``T-shaped' stablest ground N<sub>2</sub>(X<sup>1</sup><sub>g</sub><sup>+</sup>)–He(<sup>1</sup>S) electronic state with a well depth, D<sub>e</sub>, of 21.63 cm<sup>–1</sup> at a minimum distance, R<sub>e</sub>, of 3.44 Å and zero-point vibration correction, D<sub>o</sub>, of 7.07 cm<sup>–1</sup>. They also indicate a ``T-shaped' stablest excited conformer with R_e=3.25 Å, D_e=36.85 cm^–1 and D_o=17.06 cm^–1 for the N₂(B³_g)–He(¹S) triplet electronic level. In order to investigate the use of less-demanding correlation methods, test density functional theory calculations using the mPW1PW exchange–correlation functional are also presented for comparison.     

Theoretical study of the low-lying electronic states of ZnO and ZnS

Theoretical spectroscopic constants (r_e, D_e) and dipole moments (μ, ∂μ/∂r) are determined for the ¹σ⁺, ^1,3Π and ³σ⁺ states of ZnO and ZnS, using extended Gaussian basis sets and incorporating correlation using both configuration- interaction and coupled pair (CPF) methods. Relativistic corrections (Darwin plus mass velocity), included using first-order perturbation theory, are relatively small. At the CPF level, both ZnO and ZnS have ¹Σ⁺ ground states, with the ³Π state lying 209 and 2075 cm⁻¹ higher, respectively. The ³σ⁺ state lies about 1.5 eV higher in ZnO and 2.1 eV higher in ZnS. The ^1,3Π states are relatively close together since the exchange splitting is small with the σ electron localized on Zn and the π electron on oxygen (or sulfur).     

Resonance Raman spectroscopy of mass selected Al2 in an argon matrix

In an excitation range of 620–760 nm, resonance Raman spectra of aluminum dimers (Al₂) in an argon matrix have been obtained for the first time. Temperature annealing experiments were performed to remove Raman lines attributed site effects caused by the Al₂/Ar matrix. We observe a single fundamental at 293.3 (5) cm⁻¹ along with a progression up to 1149 (1) cm⁻¹. Taking successive differences of band centers we obtain spectroscopic constants for the ground state fundamental, ω_e=297.5 (5) cm⁻¹, the anharmonicity, ω_ex_e=1.68 (8) cm⁻¹. Our results are in close agreement with previous experimental results for Al₂ which designate the ground state as a ³Π_u state, and may be considered as confirmation of this assignment.     

Ni + B2H6: Spectroscopic observations on NiB and NiH

An electronic spectrum of the nickel monoboride radical has been observed for the first time, in a reaction between a nickel plasma and diborane. Numerous bands of ⁵⁸Ni¹⁰B and ⁵⁸Ni¹¹B have been recorded between 442 and 503 nm in laser-induced fluorescence (LIF). Dispersed fluorescence experiments have also been performed. The LIF spectrum is dominated by a strong progression of bands of a [19.7]²Σ⁺–X²Σ⁺ transition. Analyses have been carried out to yield the following ⁵⁸Ni¹¹B ground state parameters: r₀ = 0.1698 nm, ω_e = 778 cm⁻¹, ω_ex_e = 4.9 cm⁻¹. Strong signals from NiH have also been observed.     

Spectroscopic investigations on AsH(XΣ) radical using CCSD(T) theory in combination with correlation-consistent quintuple basis set

The equilibrium internuclear separations, harmonic frequencies and potential energy curves of the AsH(X³Σ⁻) radical have been calculated using the coupled-cluster singles–doubles–approximate-triples [CCSD(T)] theory in combination with the series of correlation-consistent basis sets in the valence range. The potential energy curves are all fitted to the Murrell–Sorbie function, which are used to reproduce the spectroscopic parameters such as D_e, ω_eχ_e, α_e, B_e and D₀. The present D₀, D_e, R_e, ω_e, ω_eχ_e, α_e and B_e obtained at the cc-pV5Z basis set are of 2.8004 eV, 2.9351 eV, 0.15137 nm, 2194.341 cm⁻¹, 43.1235 cm⁻¹, 0.2031 cm⁻¹ and 7.3980 cm⁻¹, respectively, which almost perfectly conform to the measurements. With the potential obtained at the UCCSD(T)/cc-pV5Z level of theory, a total of 18 vibrational states is predicted when the rotational quantum number J is set to equal zero (J = 0) by numerically solving the radial Schrödinger equation of nuclear motion. The complete vibrational levels, classical turning points, inertial rotation and centrifugal distortion constants are determined when J = 0 for the first time, which are in excellent agreement with the experiments.     

Accurate analytic potential energy function and spectroscopic study for CH(XΠ) radical using coupled-cluster theory in combination with the correlation-consistent quintuple basis set

The coupled-cluster singles-doubles-approximate-triples [CCSD(T)] theory in combination with the correlation-consistent quintuple basis set (aug-cc-pV5Z) is used to investigate the spectroscopic properties of the CH(X²Π) radical. The accurate adiabatic potential energy curve is calculated over the internuclear separation ranging from 0.07 to 2.45 nm and is fitted to the analytic Murrell–Sorbie function, which is employed to determine the spectroscopic parameters, ω_eχ_e, α_e and B_e. The present D_e, R_e, ω_e, ω_eχ_e, α_e and B_e values are of 3.6261 eV, 0.11199 nm, 2856.312 cm⁻¹, 64.9321 cm⁻¹, 0.5452 cm⁻¹ and 14.457 cm⁻¹, respectively. Excellent agreement is obtained when they are compared with the available measurements. With the potential obtained at the CCSD(T)/aug-cc-pV5Z level of theory, a total of 18 vibrational states is predicted when J = 0 by numerically solving the radial Schrödinger equation of nuclear motion. The complete vibrational levels, classical turning points, inertial rotation and centrifugal distortion constants are reproduced for the CH(X²Π) radical when J = 0 for the first time, which are in good agreement with the available RKR data.     

Nonadiabatic dissociation dynamics of ClHD van der Waals complex initiated by electron detachment of Cl–HD

Nuclear dynamics following the electron detachment of the Cl⁻–HD anion is investigated by a time-dependent wave packet propagation approach. Photodetachment of Cl⁻–HD promotes it to the van der Waals well region of the reactive ClHD potential energy surface. The latter is a manifold of three electronic states coupled by the electronic and (relativistic) spin-orbit coupling. Among the three surfaces, the electronic ground one is of ²Σ_1/2 type and yields products in their electronic ground state. The remaining two, ²Π_3/2 and ²Π_1/2, on the other hand, yield products in their excited electronic states. However, these two can yield products in their electronic ground state via nonadiabatic transitions to the ²Σ_1/2 state. The channel specific, HCl + D or DCl + H or Cl + HD, dissociation probabilities on this latter state are calculated both in the uncoupled and coupled surface situations. Separate initial transitions (via, photodetachment) to the ²Σ_1/2, ²Π_3/2 and ²Π_1/2 adiabatic electronic states of ClHD are considered in order to elucidate the nonadiabatic coupling effects on this important class of chemical reactions initiated by an electron detachment.     

Spectroscopic properties and potential energy curves of some low-lying electronic states of AlO,AlO+, LaO,and LaO+: An ab initio CASSCF study

Results of CASSCF state-averaged calculations on the lowest electronic states of LaO and LaO⁺ are reported in this work. For comparison, some low-lying electronic states of AlO and AlO⁺ are also reported. The ground state of LaO was found to be the X²Σ⁺ (R_e = 1.987 Å, ω_e = 794 cm^?1) with a low-lying A²Δ excited state. Five more excited states below 26000 cm^?1 were found. The first ionization potential (IP ) is found at 5.16 eV, resulting in an X¹Σ⁺ ground state for the LaO⁺ diatom, in opposition to AlO⁺ for which an X³ Π ground state has been found. Analysis of the wave functions, dipole moments, and Mulliken populations reveal that the bonding is quite ionic in both systems. © 1994 John Wiley & Sons, Inc.     

Investigation of solvatochromism in the low-lying singlet states of dithienyl polyenes

To understand the low-lying singlet states of dithienyl polyenes, we investigated the solvatochromism of a series of α,ω-di(2-dithienyl 3,4-butyl) polyenes having n=1–5 double bonds. Absorption and emission spectra were collected in a series of aprotic solvents. The absorption energy dispersion effect sensitivity increased smoothly with n, reaching asymptotic behavior as n approached 5. The emission energy had less solvent sensitivity. The trends gave evidence for the existence of a ¹B^*_u absorbing state and a ¹A^*_g emitting state. We observed sensitivity of the absorbing and emitting states to solute–solvent electrostatic interactions, suggesting the dithienyl polyenes had a polar ground state conformation.     

Structure of nm-sized InSb clusters formed by spontaneous alloying

The negative ion photoelectron spectrum of⁷Li ₂ ^– is reported at 488 nm (2.540 eV). Three electronic bands are observed in this spectrum and are assigned to the following photodetachment transitions:⁷Li₂,X ¹ _g ⁺ +e ^{– 7}Li ₂ ^– ,X ² _u ⁺ ;⁷Li₂,a ³ _u ⁺ +e ^{– 7}Li ₂ ^– ,X ² _u ⁺ ; and⁷Li₂,A ¹ _u ⁺ +e ^{– 7}Li ₂ ^– ,X ² _u ⁺ . The electron affinity of⁷Li₂ is determined to be 0.437±0.009 eV, leading to an anion dissociation energy,D ₀, of 0.865±0.022 eV for the ground state of⁷Li ₂ ^– . A Franck-Condon analysis of the⁷Li₂,X ¹ _g ⁺ +e ^{– 7}Li ₂ ^– ,X ² _u ⁺ band yields the following spectroscopic constants for the ground state of⁷Li ₂ ^– :B _e =0.502±0.005 cm^–1,r _e =3.094±0.015 Å, and _e =232±35 cm^–1.     

Ab initio investigation of the HCO and COH molecule-ions: Structure and potential surfaces for dissociation in ground and excited states

Ab initio SCF calculations are reported for the potential surfaces of the HCO⁺ and COH⁺ molecular ions in both ground and low-lying excited states. An analysis of the bonding characteristics of the two systems is undertaken, from which it is noted that the 5σ and 1π orbital energy levels in HCO⁺ are inverted relative to the order found in both COH⁺ and also in CO itself. This fact leads to a situation in which the (1π, 2π) excited states of HCO⁺ as well as the ground state are more stable than their COH⁺ counterparts, whereas the opposite relationship is observed for (5σ, 2π) species. In addition it is pointed out that those states which populate the 7a' in-plane component of the 2π MO in either molecule-ion are characterized both by bent equilibrium structures and also by dissociation into CO⁺ + H, whereas all other low-lying species, including the ground state, prefer linear structures which dissociate via a CO + H⁺ channel.     

Ab initio computation of the interaction energy curves for some low-lying states of CO which dissociate to ground-state3 P O and3 P C atoms

Summary We investigate the molecular electronic structure of the quintet states of CO which correspond to the C(³ P)+O(³ P) interaction at several levels of theory. We find the 1⁵⁺ state to be relatively deeply bound (D _e ca. 587 cm^–1) while the other quintets have relatively shallow potential wells (D _e<40 cm^–1) according to our multireference configuration interaction calculations which are counterpoise corrected for basis set superposition effects. Our results are in qualitative accord with the recent semiempirical estimates of Bussery and co-workers [(1989) Chem. Phys. 134:7].National Academy of Sciences, National Research Council, Air Force Astronautics Laboratory, Resident Research Associate 1987–89     

Electronic spectra of the linear magnesium-containing carbon chains MgC2nH (n = 1–5): A CASPT2 study

Complete active space self-consistent-field (CASSCF) approach has been used for the geometry optimization of the X²Σ⁺ and A²Π electronic states for the linear magnesium-containing carbon chains MgC_2nH (n = 1–5). Multireference second-order perturbation theory (CASPT2) has been used to calculate the vertical excitation energies from the ground to selected seven excited states, as well as the potential energy curves of two ²Σ⁺ and two ²Π electronic states. The studies indicate that the vertical excitation energies of the A²Π ← X²Σ⁺ transition for MgC_2nH (n = 1–5) are 2.837, 2.793, 2.767, 2.714, and 2.669 eV, respectively, showing remarkable linear size dependence. Compared with the previous TD-DFT and RCCSD(T) results, our estimates for MgC_2nH (n = 1–3) are in the best agreement with the available observed data of 2.83, 2.78, and 2.74 eV, respectively. In addition, the dissociation energies in MgC_2nH (n = 1–5) are also been evaluated.     

Ab initio spectroscopic study for the NaRb molecule in ground and excited states

A wide adiabatic study is performed for NaRb molecule, involving 15¹Σ⁺ electronic states including the ionic state Na^?Rb⁺, as well as 14³Σ⁺, 1–9^1,3Π, and 1–5^1,3Δ states. This investigation is performed using an ab initio approach which involves the effective core potential, the core polarization potential with l‐dependent cut‐off functions. The NaRb system has been treated as a two‐electron system and the full valence configuration interaction is easily achieved. The spectroscopic constants R_e, D_e, T_e, ω_e, ω_ex_e, B_e, and D₀ for all these states are derived. We have also computed the vibrational levels as well their spacing for different values of J. In addition, permanent and transition dipole moments are determined and analyzed. The Dunham coefficients have been used to perform experimental spacing to compare directly with our results. The present calculations on NaRb extend previous theoretical works to numerous electronic excited states in the various symmetries. © 2014 Wiley Periodicals, Inc.     

OH自由基的高精度量子化学研究

采用内收缩MRCI方法(Internally Contracted Multiconfiguration-Reference Configuration Interaction)研究了OH自由基, 计算得到其基态稳定构型的键长是0.09708 nm, 对应的实验值是0.096966 nm, 第一激发态的键长是0.10137 nm,实验值是0.10121 nm. 同时得到势能曲线PECs (Potential Energy Curve), 再分别由Murrell-Sorbie势能函数拟合计算和POLFIT程序计算得到OH自由基在基态X²Π和第一激发态A²Σ⁺时的光谱数据：平衡振动频率ω_e, 非谐性常数ω_eχ_e以及高阶修正ω_eY_e, 平衡转动常数B_e, 振转耦合系数α_e, 解离能D₀和垂直跃迁能量ν₀₀. 这些理论计算结果与最新的实验值非常吻合, 精确度比前人也有很大提高. 其中我们计算得到基态OH(X²Π)的解离能D₀＝35568.86 cm^－1, 第一激发态OH (A²Σ⁺)的解离能D₀＝18953.93 cm^－1, 从第一激发态A²Σ⁺ (ν＝0)到基态X²Π (v＝0)的垂直跃迁能ν₀₀＝32496.42 cm^－1.     

Potential energy surfaces of OsCO

Potential energy surfaces for the low-lying states of osmium carbon monoxide (OsCO) have been studied using the complete active space multi-configuration self-consistent field (CAS-MCSCF) followed by multireference singles+doubles configuration interaction (MRSDCI). Additionally, spin–orbit effects were included through the relativistic configuration interaction method. It is found that the ground state of OsCO is an 0⁺ spin–orbit state which is a mixture of ³Σ⁻ and ¹Σ⁺. Spin–orbit coupling not only splits the various electronic states of OsCO but also mixes different electronic states.     

An ab initio study of electronic spectra and excited-state properties of 7-azaindole in vapour phase and aqueous solution

The geometries of 7-azaindole (7AI), its tautomer (7AT), and 7AI–H₂O and 7AT–H₂O complexes were optimised in the ground state and some low-lying singlet excited states using the 3-21G basis set. Differences of total energies of the optimised ground and excited states and the vertical excitation energies of these systems were used to explain the observed electronic spectra. Effect of solvation of these systems in bulk water was studied using the polarized continuum model (PCM). The mode of binding of a water molecule in the S₂(n–π^*) excited state of 7AI was found to be quite different from those in its ground and π–π^* excited states. It is shown that crossing of the lowest two singlet excited-state potential surfaces S₁(π–π^*) and S₂(n–π^*) of 7AI occurs in the vapour phase under geometry relaxation while on interaction with water, the S₂(n–π^*) excited state is raised up appreciably going even above the S₃(π–π^*) excited state. Ground- and excited-state molecular electrostatic potential mapping was carried out, which led to valuable information regarding the nature of excited states of the above-mentioned systems.