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1.
The ground state of the van der Waals-type lanthanide dimer Yb2 has been studied by means of relativistic energy-consistent ab initio pseudopotentials using three different core definitions.
Electron correlation was treated by coupled-cluster theory, whereby core-valence correlation effects have been accounted for
either explicitly by correlating the energetically highest coreorbitals or implicitly by means of an effective core-polarization
potential. Results for the first and second atomic ionization potentials, the atomic dipole polarizability, and the spectroscopic
constants of the molecular ground state are reported. Low-lying excited states have been investigated with spin-orbit configuration
interaction calculations. It is also demonstrated for the whole lanthanide series that correlation effects due to the atomic-like,
possibly open 4f-shell in lanthanides can be modeled effectively by adding a core-polarization potential to pseudopotentials attributing the
4f-shell to the core.
Received: 3 April 1998 / Accepted: 27 July 1998 / Published online: 9 October 1998 相似文献
2.
3.
An implementation of analytic open-shell UHF-CCSD(T) second derivatives is presented. To demonstrate applicability and test
the accuracy of the UHF-CCSD(T) approach for the determination of spectroscopical parameters, vibration-rotation interaction
constants were calculated for the ground (12Π) and first electronically excited (12Σ) states of the NCO and NCS radicals. In addition, harmonic vibrational frequencies for both states, the Renner-Teller parameter
for the ground state, as well as the 12Π→12Σ excitation energy are reported. While the computed values are in good agreement with reliable experimental information for
NCO, most of the data presented for NCS are predictions of quantities not well known from experiment.
Received: 4 May 1998 / Accepted: 27 July 1998 / Published online: 12 October 1998 相似文献
4.
Contracted Gaussian-type function (CGTF) basis sets are reported for valence p orbitals of the six alkali and alkaline-earth atoms Li, Be, Na, Mg, K, and Ca for molecular applications. These sets are
constructed by Roothaan–Hartree–Fock calculations for the ns → np excited states of atoms, in which both linear and nonlinear parameters of CGTFs are variationally optimized. The present
CGTF sets reproduce well the numerical Hartree–Fock ns → np excitation energies: the largest error is 0.0009 hartrees for Li. New CGTFs are tested with diatomic Li2, Na2, K2, and MH molecules, where M = Li, Be, Na, Mg, K, and Ca, by self-consistent-field (SCF) and multiconfiguration SCF calculations.
The resultant spectroscopic constants compare well with those of more elaborate calculations and are sufficiently close to
experimental values, supporting the efficiency of the present set for the valence p orbitals.
Received: 9 July 1998 / Accepted: 17 September 1998 / Published online: 1 February 1999 相似文献
5.
Due to the publication of a number of contradictory assignments of the vibrational wave numbers of rotational isomers of Acrolein
in the ground electronic state, the analysis of their vibrational spectra is repeated based on the previously calculated scaled
ab initio force fields. With the use of the reported results that predicted the force fields of trans-acrolein in the 1(n,π*) and 3(n, π*) states at the CASSCF/cc-pVTZ level, the experimental vibrational bands are analyzed in these excited electronic states
based on well-established regularities. It is noted that in the assignment of the calculated vibrational wave numbers of the
molecule, the isotopic shifts in the ground and excited electronic states 1(n, π*) and 3(n, π*) are taken into account. The previously considered calculated potential curves of the internal rotation of acrolein in combination
with the data on the difference in the enthalpies (ΔH
0) of conformers allow a choice to be made in favor of one of the variants of the torsional vibration wave numbers that have
been reported in the literature. 相似文献
6.
Yukio Kawashima Tomohiro Hashimoto Haruyuki Nakano Kimihiko Hirao 《Theoretical chemistry accounts》1999,102(1-6):49-64
The valence π → π
* excited states of anthracene and naphthacene are studied with multireference perturbation theory with complete active space
self-consistent field reference functions. The predicted spectra provide a consistent assignment of all one- and two-photon
spectra and T-T spectra of low-lying valence π → π
* excited states of anthracene and naphthacene. The present theory predicts the valence π → π
* excitation energies with an accuracy of 0.15 eV for anthracene and of 0.25 eV or better for naphthacene. The excited states
of anthracene and naphthacene are compared with those of benzene and naphthalene studied previously. The present calculations
predict that, going from anthracene to naphthacene, there is a symmetry reversal of the two lowest singlet state transitions,
but not for the triplet, just as indicated by the experimental data. Some general trends of polyacene excited states are discussed
based on the calculated results for benzene to naphthacene. Conclusive results obtained for anthracene and naphthacene can
be used as a model for understanding the excited states of larger polyacenes.
Received: 22 April 1998 / Accepted: 6 July 1998 / Published online: 28 September 1998 相似文献
7.
Quantum control spectroscopy (QCS) is used as a tool to study, address selectively and enhance vibrational wavepacket motion in large solvated molecules. By contrasting the application of Fourier-limited and phase-modulated excitation on different electronic states, the interplay between the controllability of vibrational coherence and electronic resonance is revealed. We contrast control on electronic ground and excited state by introducing an additional pump beam prior to a DFWM-sequence (Pump-DFWM). Via phase modulation of this initial pump pulse, coherent control is extended to structural evolution on the vibrationally hot ground state (hot-S0) and lowest lying excited state (S1) of β-carotene. In an open loop setup, the control scenarios for these different electronic states are compared in their effectiveness and mechanism. 相似文献
8.
The repulsive ground electronic state X2Σ+ of HeH is strongly coupled to the Rydberg states at small interatomic distances. Such large couplings also occur between
some of the Rydberg states. HeH+ ions that capture an electron in a Rydberg state end up in separated He and H atoms by indirect predissociation. This paper
presents a study of potential functions and pertinent matrix elements involving the lowest electronic states: the 2Σ+ states, X, A, C, and D, and the 2Π states B and E. Individual transition rates as well as total radiative and non-radiative lifetimes have been computed for
the lowest vibrational and rotational levels.
Received: 22 June 1998 / Accepted: 21 August 1998 / Published online: 12 October 1998 相似文献
9.
Tatiana Korona Bogumil Jeziorski Robert Moszynski Geerd H. F. Diercksen 《Theoretical chemistry accounts》1999,101(4):282-291
Symmetry-adapted perturbation theory is extended to the (quasi) degenerate, open-shell case. The new formalism is tested
in calculations of the interaction energies for a helium atom in the ground state interacting with an excited hydrogen atom.
It is shown that the method gives satisfactory results if the coupling with higher Rydberg states of the dimer is small, as
is the case for the A2Σ+,B2Π,E2Π,32Π, and 12Δ states of HeH. For the C2Σ+ state convergence of the method is very slow, but it can be improved by including the n=3 states in the model space.
Received: 3 June 1998 / Accepted: 9 September 1998 / Published online: 7 December 1998 相似文献
10.
Potential-energy curves for the ground state and lower excited states of the Cd2 dimer have been calculated. They are obtained using a multireference doubles excitation configuration interaction procedure
and employing Slater basis sets, previously optimized at the self-consistent-field level for excited states of the Cd atom.
The spectroscopic constants and excitation energies for the bound states of Cd2 have been compared with experimental as well as other theoretical results. The ground state of Cd2 is essentially repulsive and presents a shallow van der Waals minimum. The computed adiabatic electronic transitions are
in good agreement with the experimental ones.
Received: 16 September 1999 / Accepted: 3 February 2000 / Published online: 2 May 2000 相似文献
11.
We present pseudo-potential calculations of geometrical structures of stable isomers of LiAr
n
clusters with both an electronic ground state and excited states of the lithium atom. The Li atom is perturbed by argon atoms
in LiAr
n
clusters. Its electronic structure obtained as the eigenfunctions of a single-electron operator describing the electron in
the field of a Li+Ar
n
core, the Li+ and Ar atoms are replaced by pseudo-potentials. These pseudo-potentials include core-polarization operators to account for
the polarization and correlation of the inert core with the valence Lithium electron [J Chem Phys 116, 1839 1]. The geometry optimization of the ground and excited states of LiAr
n
(n = 1–12) clusters is carried out via the Basin-Hopping method of Wales et al. [J Phys Chem 101, 5111 2; J Chem Phys 285, 1368 3]. The geometries of the ground and ionic states of LiAr
n
clusters were used to determine the energy of the high excited states of the neutral LiAr
n
clusters. The variation of the excited state energies of LiAr
n
clusters as a function of the number of argon atoms shows an approximate Rydberg character, corresponding to the picture
of an excited electron surrounding an ionic cluster core, is already reached for the 3s state. The result of optical transitions calculations shows that the absorption spectral features are sensitive to isomer
structure. It is clearly the case for transitions close to the 2p levels of Li which are distorted by the cluster environment. 相似文献
12.
Adiabatic potential curves for the ground state and several low-lying excited states of the barium atom interacting with
Ne, Ar, Kr and Xe have been obtained from valence ab initio configuration-interaction calculations. Atomic cores are replaced
by scalar-relativistic l-dependent pseudopotentials, while core-polarization potentials are used for describing correlation contributions of the rare-gas
atoms and the Ba2+ cores. Implications of the resulting potential curves for the interpretation of experimental data are discussed, together
with first applications of the curves for calculating absorption profiles of the (6s
2)1S→(6p)1P Ba transition.
Received: 7 April 1998 / Accepted: 27 July 1998 / Published online: 12 October 1998 相似文献
13.
Ab initio calculations have been performed to investigate the state transition in photoinduced electron transfer reactions
between tetracyanoethylene and biphenyl as well as naphthalene. Face-to-face conformations of electron donor–acceptor (EDA)
complexes were selected for this purpose. The geometries of the EDA complexes were determined by using the isolated optimized
geometries of the donor and the acceptor to search for the maximum stabilization energy along the center-to-center distance.
The correction of interaction energies for basis set superposition error was considered by using counterpoise methods. The
ground and excited states of the EDA complexes were optimized with complete-active-space self-consistent-field calculations.
The theoretical study of the ground state and excited states of the EDA complex in this work reveals that the S1 and S2 states of the EDA complexes are charge–transfer (CT) excited states, and CT absorption which corresponds to the S0→S1 and S0→S2 transitions arise from π−π* excitation. On the basis of an Onsager model, CT absorption in dichloromethane was investigated by considering the solvent
reorganization energy. Detailed discussions on the excited state and on the CT absorptions were made.
Received: 30 April 2001 / Accepted: 18 October 2001 / Published online: 9 January 2002 相似文献
14.
Stuart Carter Joel M. Bowman Nicholas C. Handy 《Theoretical chemistry accounts》1998,100(1-4):191-198
We describe extensions and tests of the code “multimode” which does vibrational self-consistent field method (VSCF) and two
types of state-mixing (denoted VSCF-CI and V-CI) for rovibrational energies of many-mode systems. The extensions include an
exact treatment of rotation, flexible approaches to perform the CI calculations, and the inclusion of a Davidson diagonalization
routine to find low-lying eigenvalues of large matrices. The code is tested against previous exact variational calculations
for non-rotating H2CN, and J=0 and J=1 rovibrational states of H2CS. The code represents the full potential by a hierarchical n-mode representation, where n is the number of normal coordinates that are coupled together. Tests are presented for the convergence and accuracy of this
representation for n equal to 3 and 4, where 4 is the current maximum value. These tests are done at the VSCF and V-CI level, with very encouraging
results.
Received: 8 June 1998 / Accepted: 11 August 1998 / Published online: 19 October 1998 相似文献
15.
Kouichi Takeshita 《Theoretical chemistry accounts》1999,103(1):64-69
Ab initio calculations have been performed to study the second band of the photoelectron spectrum of benzene with analysis
of the vibrational structure. The 2E2
g
and 2A2
u
states contribute to this band. In this study each contribution to the band is discussed. We propose that the onset of the
band should be assigned to the 0-0 transition of the 2A2
u
state.
Received: 20 August 1998 / Accepted: 15 January 1999 / Published online: 7 June 1999 相似文献
16.
The ground state and several low-lying excited states of the Mg2 dimer have been studied by means of a combination of the complete-active-space multiconfiguration self-consistent-field (CASSCF)/CAS
multireference second-order perturbation theory (CASPT2) method and coupled-cluster with single and double excitations and
perturbative contribution of connected triple excitations [CCSD(T)] scheme. Reasonably good agreement with experiment has
been obtained for the CCSD(T) ground-state potential curve but the dissociation energy of the only experimentally known A1Σ
u
+ excited state of Mg2 is somewhat overestimated at the CASSCF/CASPT2 level. The spectroscopic constants D
e, R
e and ωe deduced from the calculated potential curves for other states are also reported. In addition, some spin–orbit matrix elements
between the excited singlet and triplet states of Mg2 have been evaluated as a function of internuclear separation.
Received: 10 May 2001 / Accepted: 15 August 2001 / Published online: 30 October 2001 相似文献
17.
Aishui Yu Naoaki Kumagai Zhaolin Liu Jim Y. Lee 《Journal of Solid State Electrochemistry》1998,2(6):394-400
Hexagonal and monoclinic tungsten trioxides WO3 and hexagonal lithium tungstates Li
x
WO3+
x
/2 (x = 0.10–0.42) from a soft chemistry route were used as the active cathode material in secondary lithium batteries. The hexagonal
structures, regardless of their being an oxide or a tungstate, showed higher specific capacities and better cycling behavior
in Li+ intercalation reactions than the monoclinic form. The presence of pre-allocated lithium (as Li2O) in hexagonal tungstates decreased the capacity for lithium intercalation. Additionally, the plot of open-circuit voltage
(OCV) against the depth of intercalation (n) for anhydrous tungstates showed two straight lines with different slopes that can be related to the structural changes in
lithium intercalation. The effective diffusion coefficients of lithium insertion into the host structure, D˜, were also found to be dependent on the structure and the composition of these compounds.
Received: 28 November 1997 / Accepted: 6 March 1998 相似文献
18.
《Journal of Chemical Sciences》1991,103(3):417-428
Visible and ultraviolet fluorescence of I2, following excitation by ArF/193nm excimer laser pulses, was recorded for different pressures of argon buffer gas in a flow
system. Dispersed fluorescence spectra due to the transitionsD’(2g) → A’(2y andD(0
n
+
)→X0
g
+
) were analysed by inversion and spectral simulations. Thus vibrational distributions in the emitting states were obtained
as a function of pressure to determine the mechanism of relaxation to populate the lowest quantum levels of theD’ state, which are the emitting states in the iodine laser. Fast intersystem crossing is found to occur from initially populated
vibrational levels of theD state to other ion-pair states correlating with the ground state ions, followed by rapid relaxation, involving both direct
vibrational relaxation within individual states and intersystem crossing between states. 相似文献
19.
Moss CL Liang W Li X Tureček F 《Journal of the American Society for Mass Spectrometry》2012,23(3):446-459
We report a new approach to investigating the mechanisms of fast peptide cation-radical dissociations based on an analysis
of time-resolved reaction progress by Ehrenfest dynamics, as applied to an Ala-Arg cation-radical model system. Calculations
of stationary points on the ground electronic state that were carried out with effective CCSD(T)/6-311++G(3df,2p) could not
explain the experimental branching ratios for loss of a hydrogen atom, ammonia, and N–Cα bond dissociation in (AR + 2H)+●. The Ehrenfest dynamics results indicate that the ground and low-lying excited electronic states of (AR + 2H)+● follow different reaction courses in the first 330 femtoseconds after electron attachment. The ground (X) state undergoes competing loss of N-terminal ammonia and isomerization to an aminoketyl radical intermediate that depend
on the vibrational energy of the charge-reduced ion. The A and B excited states involve electron capture in the Arg guanidine and carboxyl groups and are non-reactive on the short time scale.
The C state is dissociative and progresses to a fast loss of an H atom from the Arg guanidine group. Analogous results were obtained
by using the B3LYP and CAM-B3LYP density functionals for the excited state dynamics and including the universal M06-2X functional
for ground electronic state calculations. The results of this Ehrenfest dynamics study indicate that reaction pathway branching
into the various dissociation channels occurs in the early stages of electron attachment and is primarily determined by the
electronic states being accessed. This represents a new paradigm for the discussion of peptide dissociations in electron based
methods of mass spectrometry. 相似文献
20.
Kazunari Naka Hirofumi Sato Akihiro Morita Fumio Hirata Shigeki Kato 《Theoretical chemistry accounts》1999,102(1-6):165-169
The free-energy profile for the Menshutkin-type reaction NH3 + CH3Cl → NH3CH3
+ + Cl− in aqueous solution is studied using the RISM-SCF method. The effect of electron correlation on the free-energy profile is
estimated by the RISM-MP2 method at the HF optimized geometries along the reaction coordinate. Solvation was found to have
a large influence on the vibrational frequencies at the reactant, transition state and product; these vibrational frequencies
are utilized to calculate the zero-point energy correction of the free-energy profile. The computed barrier height and reaction
exothermicity are in reasonable agreement with those of experiment and previous calculations. The change of solvation structure
along the reaction path is represented by radial distribution functions between solute-solvent atomic sites. The mechanisms
of the reaction are discussed from the view points of solute electronic and solvation structures.
Received: 26 June 1998/Accepted: 28 August 1998 / Published online: 2 November 1998 相似文献