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1.
Pilot calculations have been performed to study the effect of surrounding plasma on several doubly excited states for a few astrophysically important, highly stripped ions of helium isoelectronic sequence Al11+, Si12+, P13+, S14+, and Cl15+. The transitions from 1s2:1Se → 2s2:1Se, 2p2:1De, 2s2p:1Po, 2s3d:1De and 2p3d:1Fo are studied. The effect of the plasma background is taken care of using the Debye screening model which admits of a wide variety of plasma conditions. Transition energies as well as the analytical wave functions of the doubly excited states have been obtained from a study of the pole positions of the collective oscillation modes in the two‐electron charge cloud under a time‐dependent harmonic perturbation. The response properties of the system are analyzed from the linearized version of a suitably constructed variational functional. Most of the calculated data are new. Our results agree well with the relatively few existing experimental and theoretical data for the free ions. The general trend of the results show systematic behavior with respect to increased plasma strength, and the data may be useful from the astrophysical viewpoint. The doubly excited state wave functions have been used to calculate the Coulomb repulsion integrals to check their consistency and may be useful for evaluating other physical properties connected with transitions and also estimating the rate coefficients for dielectronic recombination processes, which play a major role in the diagnostic determination of high‐temperature plasmas. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005  相似文献   

2.
Summary Time-dependent coupled Hartree-Fock (TDCHF) scheme has been applied to study the behaviour of bound excited states embedded in the continuum for the negative ions Li, F, Na and Cl. The excited states have been obtained from the position of the poles of the dynamic polarizability values which are evaluated for all the ions within and beyond the normal dispersion region. Transition energies and dipole allowed oscillator strengths have been obtained for several transitions which lie in the continuum. Although the excited state functions are extremely diffuse, they show proper asymptotic behaviour and furnish correct number of nodes. Oscillator strengths are found to follow a different trend than observed in normal bound state calculations.  相似文献   

3.
The time‐dependent variation perturbation theory (TDVPT) was applied to estimate separately the effect of radial and angular correlations in the doubly excited states of two‐electron systems. Test calculations were performed for the transitions 1s2 : 1Se→2s2 : 1Se for H and 1s2 : 1Sens2 : 1Se (n=2,…,5) for He, Li+, Be2+, and B3+. Transition energies to various doubly excited states were estimated using radially correlated basis sets as well as with basis sets which take care of both radial and angular correlations. Angular correlation is taken care of by incorporating higher angular momentum basis sets in the expansion of the perturbed wave functions. The excitation energy is lower in all the cases, indicating the correct behavior. Overall improvement of the results is observed when angular correlation is included. The effect of angular correlation, however, diminishes rapidly with increase of the nuclear charge. This has been demonstrated explicitly for the lowest doubly excited transitions in the highly stripped ions Al11+, Si12+, P13+, S14+, and Cl15+. © 1999 John Wiley & Sons, Inc. Int J Quant Chem 76: 99–104, 2000  相似文献   

4.
In this paper a novel approach to study the formation and relaxation of excited states in solution is presented within the integral equation formalism version of the polarizable continuum model. Such an approach uses the excited state relaxed density matrix to correct the time dependent density functional theory excitation energies and it introduces a state-specific solvent response, which can be further generalized within a time dependent formalism. This generalization is based on the use of a complex dielectric permittivity as a function of the frequency, epsilonomega. The approach is here presented in its theoretical formulation and applied to the various steps involved in the formation and relaxation of electronic excited states in solvated molecules. In particular, vertical excitations (and emissions), as well as time dependent Stokes shift and complete relaxation from vertical excited states back to ground state, can be obtained as different applications of the same theory. Numerical results on two molecular systems are reported to better illustrate the features of the model.  相似文献   

5.
6.
A mechanism of energy transfer from highly excited triplet aromatic molecules has been developed, which involves a stage of formation of an exciplex between a highly excited energy-donor molecule and an unexcited energy-acceptor molecule. Interpretation of the experimental data on the shape and the intensity of triplet-triplet absorption bands and the energy transfer probability is presented. In this interpretation, the results of quantum-chemical calculations of the energies of highly excited triplet states of toluene and benzene molecules are used.  相似文献   

7.
The Auger decay widths of doubly-excited Rydberg states of He I and Ba I have been calculated by the multi-configuration Hartree-Fock procedure. The configuration mixing is crucial in obtaining the correct widths, while the energies seem to be relatively less sensitive to mixing. The usual mixing procedure is often unstable for doubly excited states and careful selection of configurations is required. An improved procedure for selecting the states for mixing is formulated, which seems to stabilize the calculation of both the energies and widths, with small numbers of configurations which are mixed. We apply the recipe to a selected set of doubly excited states of He and Ba. The long standing discrepancies in the widths for the series 7sns, 7snd, 8sns, and 8snd of Ba I withn > 11 may be explained by this procedure, except for the 7snd series. The calculated widths for the 7snd series are larger than the experimental values by a factor of 10–20. The difficulties of treating the states with both electrons in higher Rydberg orbitals are discussed.  相似文献   

8.
Accurate variational energies for even-parity core-excited 2Pe states in the lithium series (Li l-C IV) have been obtained by means of the superposition of correlated configurations (SCC) method. These energies can serve as a firm basis for the theoretical interpretation and proper assignments of several 2Pe2Po transitions in lithium-like ions.  相似文献   

9.
An efficient computational scheme for calculating highly excited vibrational eigenstates is proposed, combining a Richardson-Leja spectral filter with a novel version of the Davidson method [J. Comput. Phys. 17, 87 (1975)]. Highly excited eigenstates of the Rb2 and H2O molecules are computed to test and verify the method. On the average less than 2.5 outer recursions per eigenstate are needed. For each outer Davidson recursion, less than 20 inner filter recursions per eigenstate are needed on the average.  相似文献   

10.
A nonlinear conjugate gradient optimization scheme is used to obtain excitation energies within the random phase approximation (RPA). The solutions to the RPA eigenvalue equation are located through a variational characterization using a modified Thouless functional, which is based upon an asymmetric Rayleigh quotient, in an orthogonalized atomic orbital representation. In this way, the computational bottleneck of calculating molecular orbitals is avoided. The variational space is reduced to the physically-relevant transitions by projections. The feasibility of an RPA implementation scaling linearly with system size N is investigated by monitoring convergence behavior with respect to the quality of initial guess and sensitivity to noise under thresholding, both for well- and ill-conditioned problems. The molecular-orbital-free algorithm is found to be robust and computationally efficient, providing a first step toward large-scale, reduced complexity calculations of time-dependent optical properties and linear response. The algorithm is extensible to other forms of time-dependent perturbation theory including, but not limited to, time-dependent density functional theory.  相似文献   

11.
12.
Excited states of two 7-aminocoumarin derivatives, coumarin 120 (7-amino-4-methylcoumarin) and coumarin 151 (7-amino-4-trifluoromethylcoumarin), were investigated using generalized multiconfigurational quasidegenerate perturbation theory (GMC-QDPT), multiconfigurational quasidegenerate perturbation theory (MC-QDPT) and time-dependent density functional theory (TDDFT) with the B3LYP and CAM-B3LYP functionals. The absorption and fluorescence spectra of C120 and C151 were calculated. We elucidated the characters of the low-lying states of C120 and C151. The absorption spectra calculated with GMC-QDPT and TDDFT B3LYP agreed well with the experimental data, while for the fluorescence spectra, the TDDFT calculations overestimated the fluorescence spectra compared to GMC-QDPT calculations. Utilizing active spaces with large numbers of electrons and orbitals for reference functions, GMC-QDPT showed a better performance than MC-QDPT with a complete active space self-consistent field (CASSCF) reference of active space with smaller number of electrons and orbitals. In our gas phase calculation, we found that the optimized structures for the first excited states have a planar amino group with a CN single bond, while the amino group is pyramidal in the ground state.  相似文献   

13.
《Chemical physics letters》1987,139(6):503-506
The rotational structure of the D 2Σ+ →A2Σ+ transition of 4HeD is highly perturbed, and this is caused by the near degeneracy of the D, ν=0 and C, ν=3 vibrational levels. A perturbation analysis is presented which yields the spectroscopic constants for both of the perturbing levels, yielding the first experimental information on a vibrationally excited state of HeH.  相似文献   

14.
We consider the criteria that should be met by the perturbation theory for excited states to preserve the advantages of the Möller-Plesset version for the ground state. A few zero-approximation Hamiltonians are proposed and discussed. Expressions for the first-order corrections to the wave function and for the second-order corrections to the energy of excited states are obtained. The expressions are consistent with the conditions of orthogonality of states with the same symmetry. It is shown that the perturbation theory for excited states proposed in this work is identical to the Möller-Plesset perturbation theory for the ground state.  相似文献   

15.
The intermolecular interaction energy for binary systems in the ground and excited electronic states was partitioned into the Coulomb, exchange-repulsion, induction, dispersion and charge-transfer interaction terms by the perturbation expansion method. The various interaction terms were evaluated for the hydrogen bondings in (HF)2, (H2O)2, (CH3OH)2, (RCOOH)2, and HF·H2O in various geometrical configurations. It has been found that the Coulombic interaction plays a dominant role in the stability of these hydrogen bonded systems. The method was further applied to the HCOOH·H2O codimer in both the ground and excited singlet electronic states. The results were in accord with the well-known water solvent effects on the shifts of absorption spectral bands.  相似文献   

16.
We investigate the laser induced recombination of electrons to excited states of hydrogen-like ions. The time integration and averaging over incidente energies are performed analytically for a model Hamiltonian, which takes into account the degeneracy of the states and possible resonant transitions to lower lying states. The range of validity of the model assumptions is determined by comparison with numerical calculations using the exact Hamiltonian. For an arrangement of merged laser, ion and electron beams we calculated the recombination yields as a function of the laser pulse energy to then=5 to 20 states of hydrogen like ions with nuclear charges fromZ=1 to 4.  相似文献   

17.
A variant of statement of the problem on highly excited states of an electron (Rydberg states in the limit) in the field of nuclei has been considered. It has been shown that this problem can be reduced to the one-center problem with a variable positive charge. The general solution can be found as a linear combination of basis functions corresponding to the stationary states of the single-center model.  相似文献   

18.
19.
Lifetimes of Rydberg states of the triplet-series 5s ns 3 S 1 withn = 19–23, 35 and 5s nd 3 D 3 withn = 18–20, 23–28 in the spectrum of neutral strontium have been determined. Observation of the exponential decay after excitation by a pulsed laser in a fast atomic beam and subsequent state-selective field ionization was employed. The lifetimes of the states of the3 S 1-series show the expectedn*3 dependence on the effective principal quantum number, while the3 D 3-series is disturbed by configuration mixing. Furthermore, state re-populations induced by black-body radiation have been observed.  相似文献   

20.
Highly excited autoionizing levels of atomic sodium are calculated via an effective two electron-model. The results obtained are in good agreement with experimental data, proving the model to be valid.  相似文献   

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