BF分子X1Σ＋, A1P和B1Σ＋态的势能函数

使用SAC/SAC-CI和D95＋＋, 6-311＋＋g, 6-311＋＋g**及D95(d)基组, 分别对BF分子的基态X¹Σ^＋、第一简并激发态A¹Π和第二激发态B¹Σ^＋的平衡结构和谐振频率进行优化计算. 对所有计算结果进行比较, 得出6-311＋＋g**基组为最优基组. 运用6-311＋＋g**基组和SAC方法对基态X¹Σ^＋, SAC-CI方法对激发态A¹Π和B¹Σ^＋进行单点能扫描计算, 并用正规方程组拟合Murrell-Sorbie函数, 得到相应电子态的势能函数解析式, 由得到的势能函数计算了与X¹Σ^＋, A¹Π和B¹Σ^＋态相对应的光谱常数, 结果与实验数据较为一致.     

Electronic excitation spectra of radical anions of cyanoethylenes and cyanobenzenes: symmetry adapted cluster-configuration interaction study

Electronic excitation spectra of the radical anions of cyanoethylenes (trans-dicyanoethylene and tetracyanoethylene) and cyanobenzenes (1,2-dicyanobenzene: o-DCNB, 1,3-dicyanobenzene: m-DCNB, and 1,4-dicyanobenzene: p-DCNB) were studied by the symmetry adapted cluster-configuration interaction (SAC-CI) method. Theoretical calculations predicted positive electron affinities for all the molecules in good agreement with the experimental observations. Electronic excitation spectra of open-shell radicals is a topic that has not been studied as much as such spectra of closed-shell molecules, but this can be easily addressed using SAC-CI theory. The present paper systematically describes the calculation procedures for radical anions by investigating several basis sets, including anion diffuse and Rydberg functions. The calculated excitation energies were in good agreement with the experimental UV∕NIR (near infrared region) spectra, which had been observed by one of the present authors in 2-methyltetrahydrofuran matrix frozen to transparent glassy solids at 77 K. For p-DCNB, the SAC-CI theoretical spectrum agreed particularly well with the experimental spectrum. An extremely weak π*(SOMO) - π* excitation at 1.41 eV predicted in the present work, but had been overlooked in the previous experimental spectrum published in 1988, was confirmed to be real by a careful re-examination of the old spectrum.     

LiH分子X 1Σ+ 、A 1Σ+和B 1Π态的势能函数

The energies, equilibrium geometries and harmonic frequencies of the three electronic states (the ground state X 1Σ+, the first excitation state A 1Σ+ and the second excitation degenerate state B 1Π) of LiH molecule have been calculated by using the GSUM (Group Sum of Operators) method of SAC/ SAC-CI with the basis sets D95(d), 6-311G**, and cc-PVTZ. Comparing with the above-mentioned three basis sets, the conclusion is gained that the basis set D95(d) is the most suitable for the energy calculation of LiH molecule. The whole potential curves for these three electronic states are further scanned, using SAC/D95(d) method for the ground state and SAC-CI/D95(d) methods for the excited states. Murrell-Sorbie function were fitted using a least square and then the spectroscopy constants are calculated, which are in good agreement with the experimental data.     

Singly and doubly excited states of butadiene, acrolein, and glyoxal: Geometries and electronic spectra

Excited-state geometries and electronic spectra of butadiene, acrolein, and glyoxal have been investigated by the symmetry adapted cluster configuration interaction (SAC-CI) method in their s-trans conformation. Valence and Rydberg states below the ionization threshold have been precisely calculated with sufficiently flexible basis sets. Vertical and adiabatic excitation energies were well reproduced and the detailed assignments were given taking account of the second moments. The deviations of the vertical excitation energies from the experiment were less than 0.3 eV for all cases. The SAC-CI geometry optimization has been applied to some valence and Rydberg excited states of these molecules in the planar structure. The optimized ground- and excited-state geometries agree well with the available experimental values; deviations lie within 0.03 A and 0.7 degrees for the bond lengths and angles, respectively. The force acting on the nuclei caused by the excitations has been discussed in detail by calculating the SAC-CI electron density difference between the ground and excited states; the geometry relaxation was well interpreted with the electrostatic force theory. In Rydberg excitations, geometry changes were also noticed. Doubly excited states (so-called 2 (1)A(g) states) were investigated by the SAC-CI general-R method considering up to quadruple excitations. The characteristic geometrical changes and large energetic relaxations were predicted for these states.     

BH分子X 1Σ+、A 1Π和B 1Σ+ 态的势能函数

利用SAC/SAC-CI方法，使用D95++、6-311++g及cc-PVTZ等基组，对BH分子的基态(X ¹Σ⁺)、第一简并激发态(A ¹Π)及第二激发态(B ¹Σ⁺)的平衡结构和谐振频率进行了优化计算． 通过对三个基组计算结果的比较，得出了cc-PVTZ基组为三个基组中的最优基组的结论；使用cc-PVTZ基组，利用SAC的GSUM(group sum of operators)方法对基态(X ¹Σ⁺)， SAC-CI的GSUM方法对激发态(A ¹Π 和B ¹Σ⁺)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(X ¹Σ⁺)、第一简并的激发态(A ¹Π)和第二激发态(X ¹Σ⁺)相对应的光谱常数(Be、αe、ωe 和ωeχe)，结果与实验数据较为一致． 其中基态、第一激发态与实验数据吻合得较好．     

He2+和He2++分子离子基态和激发态的特性研究

采用SAC/SAC-CI方法在CC-PV5Z基组下, 计算研究了He2+、He2++的基态及低激发态的分子特性, 给出了其基态和一些激发态的势能函数和光谱数据(Be、αe、ωe和ωeχe). 从群论出发推导了相应状态的离解极限；与已有实验结果的He2+(X2Σu+)相比, 计算结果令人满意. 还计算了激发态2Πu、4Σu+和4Πg的结构与光谱数据. 对于He2++, 计算的九个电子态中只有三个态(X1Σg+、1Σg+和1Σu+)属束缚态, 并得到了其光谱常数. 用价键理论模型的不相交规则对He2++基态的势能曲线极大点产生的原因做了较好的分析.     

Excited states and electronic spectra of extended tetraazaporphyrins

Electronic excited states, electronic absorption, and magnetic circular dichroism (MCD) spectra of free-base tetraazaporphyrin (TAP), phthalocyanine (Pc), naphthalocyanine (Nc), and anthracocyanine (Ac) were studied by quantum chemical calculations using the symmetry-adapted cluster-configuration interaction (SAC-CI) method. Not only optically allowed states including the Q- and B-bands but also optically forbidden states were calculated for transitions whose excitation energies were lower than 4.5 eV. The present SAC-CI calculations consistently assigned the absorption and MCD peaks as optically allowed π→π(?) excitations, although these calculations using double-zeta basis limit quantitative agreement and discussion. For Nc and Ac, excited states beyond the four-orbital model appeared in the low-energy region. The low-energy shifts of the Q-bands with the extension of molecular size were explained by the orbital energies. The splitting of the Q-bands decreases with extension of the molecular size. This feature was reproduced by the SAC-CI calculations but the configuration interaction with single excitations and time-dependent density functional theory calculations failed to reproduce this trend. Electron correlation in the excited states is important in reproducing this splitting of the Q-bands and in describing the energy difference between the B(2u) and B(3u) states of free-base porphyrins.     

Theoretical study of valance photoelectron spectra of hypoxanthine, xanthine, and caffeine using direct symmetry-adapted cluster/configuration interaction methodology

UV photoelectron spectra of hypoxanthine, xanthine, and caffeine, up to 20 eV, were calculated and compared with the experimental spectra reported in literature. The calculations were performed using a novel version of the quantum mechanical symmetry-adapted cluster/configuration interaction (SAC-CI) method termed, direct SAC-CI. The Duning/Huzinaga valance double-zeta D95+(d,p) Gaussian basis set was also employed with this method. The ionization energies and intensities were calculated, and the corresponding spectral bands were assigned. Natural bonding orbital (NBO) calculations were employed for better spectral band assignment. The calculated ionization energies and intensities reasonably produced the experimental photoelectron spectra.     

Excited and ionized states of RuO4 and OsO4 studied by SAC and SAC-CI theories

The excitation and ionization spectra of RuO₄ and OsO₄ are studied theoretically by the symmetry-adapted cluster (SAC ) and SAC-CI theories. This is the attempt to assign whole of the spectra by ab initio calculations including electron correlations. In the ground state, electron correlations work to reduce the polarity of the M–O bond overestimated in the Hartree–Fock calculation. The Os–O bond is stronger than is the Ru–O bond, which is reflected in the differences of the excitation and ionization spectra of RuO₄ and OsO₄. The excitation energies of the experimental spectra are well reproduced by the SAC-CI theory, though the calculated intensities of some peaks are very small in comparison with the experiments. The outer-valence ionization spectra calculated by the SAC-CI theory agree well with the experimental photoelectron spectra. Some shake-up peaks that are accompanied with an electron-transfers from oxygen to metal are also calculated.     

Observation of L uncoupling in the 5 1Deltag Rydberg state of Na2

The phenomenon of electronic orbital angular momentum L uncoupled from its internuclear axis has been observed in the sodium dimer using high-resolution cw optical-optical double-resonance spectroscopy. When L uncoupling occurs, the degeneracy of Lambda doubling is removed. In our experiment, the intermediate B (1)Pi(u) state of Na(2) is excited from the thermally populated ground X (1)Sigma(g) (+) state by a single-line Ar(+) laser. Then, a single-mode dye laser is used to probe the Rydberg states from the intermediate state. The signals are detected by monitoring the UV fluorescence from the triplet gerade states back to the a (3)Sigma(u) (+) state via collision energy transfer. Under our experimental resolution, the splitting of Lambda doubling in the 5 (1)Delta(g) state of Na(2) can be measured. A total of 136 rovibronic levels with ef parities have been assigned to the 5 (1)Delta(g) state. The Lambda-splitting constants deduced from these data are q(0)=0.376(90)x10(-4) cm(-1), q(v)=0.114(6)x10(-4) cm(-1), and mu=0.76(33)x10(-8) cm(-1). In general, the Lambda splitting of the Delta states is considerably smaller than that of the Pi states. However, the first-order splitting constants q(0) and q(v) reported here are larger than those in the B (1)Pi(u) state. This is due to the L uncoupling of the Rydberg states.     

Two-color resonance-enhanced multiphoton ionization study of the lowest Rydberg p state of bis(eta6-benzene)chromium and its deuterated derivatives

Two-color resonance-enhanced multiphoton ionization (REMPI) spectra of jet-cooled (eta(6)-C(6)H(6))(2)Cr(1), (eta(6)-C(6)D(6))(2)Cr(2), and (eta(6)-C(6)D(6))(eta(6)-C(6)D(5)H)Cr(3) have been measured with use of the 3d(z)2-->R4p(x,y) Rydberg transition as the first step of the electronic excitation. The 0(0) (0) Rydberg component shifts by 59 and 54 cm(-1) to red when one goes from 1 to 2 and 3, respectively. Surprisingly, the REMPI spectra of 1-3 show very rich vibronic structures revealing both totally symmetric vibrations and degenerate vibrational modes. Presence of intense peaks corresponding to the e(2g) modes in the spectra of 1 and 2 is indicative of Jahn-Teller coupling in the R4p(x,y) Rydberg state. Additional REMPI resonances appear on going from 1 and 2 to 3 as a result of the symmetry reduction. The vibronic components in the spectra of 1-3 were assigned on the basis of the selection rules and comparison with the vibrational frequencies of the 1 and 2 ground-state molecules. The frequencies of over 10 normal vibrations have been determined for the gas-phase 1-3 Rydberg-state molecules from the REMPI experiment. The wavenumber corresponding to the lowest-energy mode (the ring torsion vibration) appears to be 40 cm(-1) in 1 and 35 cm(-1) in the deuterated complexes. The REMPI peaks are homogeneously broadened. The lower lifetime limits for the upper-state components increase on going from the vibrationless level to higher-lying vibronic states and on going from 1 to the deuterated derivatives.     

Symmetry-adapted-cluster/symmetry-adapted-cluster configuration interaction methodology extended to giant molecular systems: ring molecular crystals

The symmetry adapted cluster (SAC)/symmetry adapted cluster configuration interaction (SAC-CI) methodology for the ground, excited, ionized, and electron-attached states of molecules was extended to giant molecular systems. The size extensivity of energy and the size intensivity of excitation energy are very important for doing quantitative chemical studies of giant molecular systems and are designed to be satisfied in the present giant SAC/SAC-CI method. The first extension was made to giant molecular crystals composed of the same molecular species. The reference wave function was defined by introducing monomer-localized canonical molecular orbitals (ml-CMO's), which were obtained from the Hartree-Fock orbitals of a tetramer or a larger oligomer within the electrostatic field of the other part of the crystal. In the SAC/SAC-CI calculations, all the necessary integrals were obtained after the integral transformation with the ml-CMO's of the neighboring dimer. Only singles and doubles excitations within each neighboring dimer were considered as linked operators, and perturbation selection was done to choose only important operators. Almost all the important unlinked terms generated from the selected linked operators were included: the unlinked terms are important for keeping size extensivity and size intensivity. Some test calculations were carried out for the ring crystals of up to 10 000-mer, confirming the size extensivity and size intensivity of the calculated results and the efficiency of the giant method in comparison with the standard method available in GAUSSIAN 03. Then, the method was applied to the ring crystals of ethylene and water 50-mers, and formaldehyde 50-, 100-, and 500-mers. The potential energy curves of the ground state and the polarization and electron-transfer-type excited states were calculated for the intermonomer distances of 2.8-100 A. Several interesting behaviors were reported, showing the potentiality of the present giant SAC/SAC-CI method for molecular engineering.     

Excitation and circular dichroism spectra of (-)-(3aS, 7aS)-2-chalcogena-trans-hydrindans(Ch = S, Se, Te): SAC and SAC-CI calculations

The ground and several electronic excited states of (3aS,7aS)-2-chalcogena-trans-hydrindans were calculated by the symmetry adapted cluster (SAC) and SAC-configuration interaction (SAC-CI) methods. Theoretical electronic excitation spectra and natural circular dichroism (CD) spectra were obtained for these compounds, and the calculated spectra showed good agreement with the experimental ones reported by Laur (Proceedings of the Third International Symposium on Organic Selenium and Tellurium compounds, Metz, France, 1979, pp. 219-299). For all the chalcogen compounds, the first singlet excited states are assigned to n-sigma* and the other states are assigned to n-Rydberg in our calculations. It indicates that the spectra for the sulfide, selenide, and telluride are almost regarded as the analogues except for the red shifts of the band positions from the sulfide to the telluride. For the telluride, however, the experimental spectra have shapes that cannot be interpreted by the singlet excitations solely. Our calculations predict the triplet states that account for the spectral shapes, indicating importance of the spin-orbit interaction effects for the accurate reproduction of the experimental spectra of the telluride.     

Theoretical prediction of valence and Rydberg excited states: Minnesota exchange-correlation functionals vs symmetry adapted cluster-configuration interaction

During this contribution, we present a benchmark investigation on the applicability of several Minnesota functionals from various classes like local meta-generalized and meta-nonseparable gradient approximations, hybrids, and range-separated hybrids for describing the valence and Rydberg excitation energies of some organic compounds from different categories. Furthermore, the performances of Minnesota density functionals from density functional theory are also assessed against a wave function theory based approach in the context of excite states calculations, symmetry adapted cluster-configuration interaction (SAC-CI) method. Pragmatically, the singles and doubles linked excitation operators are considered in the SAC-CI wave functions. With more or less different accountabilities of the considered methods, it is shown that the M06-2X, M05-2X, and M11 functionals have the best performances for valence excited states. On the other hand, for Rydberg excited states although the SAC-CI method outperforms others, the statistical analyses reveal that the efficiency of some Minnesota functionals is also respectable.     

Theoretical and experimental investigations of the electronic Rydberg states of diazomethane: assignments and state interactions

The electronic states of diazomethane in the region 3.00-8.00 eV have been characterized by ab initio calculations, and electronic transitions in the region 6.32-7.30 eV have been examined experimentally using a combination of 2 + 1 REMPI spectroscopy and photoelectron imaging in a molecular beam. In the examined region, three Rydberg states of 3p character contribute to the transitions, 2(1)A2(3p(y) <-- pi), 2(1)B1(3p(z) <-- pi), and 3(1)A1(3p(x) <-- pi). The former two states are of mostly pure Rydberg character and exhibit a resolved K structure, whereas the 3(1)A1(3p(x) <-- pi) state is mixed with the valence 2(1)A1(pi* <-- pi) state, which is unbound and is strongly predissociative. Analyses of photoelectron kinetic energy distributions indicate that the ground vibrational level of the 2(1)B1(3p(z)) state is mixed with the 2(1)A2(3p(y)) nu(9) level, which is of B1 vibronic symmetry. The other 2(1)A2(3p(y)) vibronic states exhibit pure Rydberg character, generating ions in single vibrational levels. The photoelectron spectra of the 3(1)A1(3p(x) <-- pi) state, on the other hand, give rise to many states of the ion as a result of strong mixing with the valence state, as evidenced also in the ab initio calculations. The equilibrium geometries of the electronic states of neutral diazomethane were calculated by CCSD(T), using the cc-pVTZ basis, and by B3LYP, using the 6-311G(2df,p) basis. Geometry and frequencies of the ground state of the cation were calculated by CCSD(T)/cc-pVTZ, using the unrestricted (UHF) reference. Vertical excitation energies were calculated using EOM-CCSD/6-311(3+,+)G* at the B3LYP optimized geometry. The theoretical results show that the 2(1)A2(3p(y) <-- pi) and 2(1)B1(3p(z) <-- pi) states have geometries similar to the ion, which has C(2v) symmetry, with slight differences due to the interactions of the electron in the 3p orbital with the nuclei charge distributions. The geometry of the 3(1)A1(3p(x) <-- pi) state is quite different and has Cs symmetry. The experimental and theoretical results agree very well, both in regard to excitation energies and to vibrational modes of the ion.     

Photoelectron spectrum of NO2−: SAC-CI gradient study of vibrational-rotational structures

Three-dimensional accurate potential energy surfaces around the local minima of NO₂⁻ and NO₂ were calculated with the SAC/SAC-CI analytical energy gradient method. Therefrom, the ionization photoelectron spectra of NO₂⁻, the equilibrium geometries and adiabatic electron affinity of NO₂, and the vibrational frequencies including harmonicity and anharmonicity of NO₂⁻ and NO₂ were obtained. The calculated electron affinity was in reasonable agreement with the experimental value. The SAC-CI photoelectron spectra of NO₂⁻ at 350 K and 700 K including the rotational effects were calculated using the Franck–Condon approximation. The theoretical spectra reproduced well the fine experimental photoelectron spectra observed by Ervin et al. (J. Phys. Chem. 1988, 92, 5405). The results showed that the ionizations from many vibrational excited states as well as the vibrational ground state are included in the experimental photoelectron spectra especially at 700 K and that the rotational effects are important to reproduce the experimental photoelectron spectra of both temperatures. The SAC/SAC-CI theoretical results supported the analyses of the spectra by Ervin et al., except that we could show some small contributions from the asymmetric-stretching mode of NO₂⁻. © 2018 Wiley Periodicals, Inc.     

Inner-shell ionizations and satellites studied by the open-shell reference symmetry-adapted cluster/symmetry-adapted cluster configuration-interaction method

Open-shell reference version of the symmetry-adapted cluster (SAC) and SAC-configuration-interaction (CI) methods, termed open-shell reference (OR)-SAC and OR-SAC-CI methods, are developed and applied to inner-shell ionizations of CH4, NH3, H2O, and HF. The inner-shell ionization potentials and spectra calculated by the OR-SAC and OR-SAC-CI methods are in excellent agreement with the experimental data. Including both of the electron correlation and orbital relaxation is important for quantitative agreements. Timing comparisons with the SAC-CI general-R calculations that give similar high accuracies show an efficiency of the present OR-SAC and OR-SAC-CI methods.     

A theoretical investigation of the excited states of OCLO radical, cation, and anion using the CASSCF/CASPT2 method

Using the complete active space self-consistent field method with a large atomic natural orbital basis set, 10, 13, and 9 electronic states of the OClO radical, OClO(+) cation, and OClO(-) anion were calculated, respectively. Taking the further correlation effects into account, the second-order perturbation (CASPT2) calculations were carried out for the energetic calibration. The photoelectron spectroscopy of the OClO radical and OClO(-) anion were extensively studied in the both case of the adiabatic and vertical ionization energies. The calculated results presented the relatively complete assignment of the photoelectron bands of the experiments for OClO and its anion. Furthermore, the Rydberg states of the OClO radical were investigated by using multiconfigurational CASPT2 (MS-CASPT2) theory under the basis set of large atomic natural orbital functions augmented with an adapted 1s1p1d Rydberg functions that have specially been built for this study. Sixteen Rydberg states were obtained and the results were consistent with the experimental results.     

Insight into the Rydberg states of CH

Ab initio electronic structure calculations of a relatively large number of Rydberg states of the CH radical were carried out employing the multireference single and double excitation configuration interaction (MRD-CI) method. A Gaussian basis set of cc-pV5Z quality augmented with 12 diffuse functions was used together with an extensive treatment of electron correlation. The main focus of this contribution is to investigate the 3d Rydberg complex assigned by Watson [Astrophys. J. 555, 472 (2001)] to three unidentified interstellar bands. The authors' calculations reproduce quite well the absolute excitation energies of the three components of the 3d complex, i.e., 2Sigma+(3dsigma), 2Pi(3dpi), and 2Delta(3ddelta), but not the energy ordering inferred from a rotational assignment of the 3d<--X 2Pi laboratory spectrum. The computation of the 4d complex is reported for the first time along with a number of other higher lying Rydberg species with an X 1Sigma+ core. The lowest Rydberg states belonging to series converging to the a 3Pi and A 1Pi excited states of CH+ are also calculated.