Correlation effects in the excited states of atoms the 1s22sn2pm configuration of carbon, nitrogen, and oxygen (original) (raw)
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Correlation Energy of Atomic Nitrogen
Physical review, 1972
The Brueckner-Goldstone many-body perturbation theory is applied to stu the electronic structure of the atomic nitrogen in its ground 4$ state. A complete orthonormal set of the V" single-particle states with angular symmetry up to) = 5 is explicitly used to calculate the correlationmnergy diagrams. The contribution from higher l (& 5) is estimated by a hydrogenic approximation of the continuum wave functions. Our final correlation energy is-0.1895 + 0.003 a.u. , as compared with-0.1886+ 0.0094 a.u. from the semiempirical estimate made by Veillard and Clementi. The sum of the exchange-core-polarization and pair-correlationenergy diagrams give a total of-Q. 207 28 a.u. , which is 110% of the semiempirical estimate. This contains a contribution of-0.00610 a.u. (3.2 %} from L &3 states and-0.05825 a.u. (31 %) from the excitations into the valence 2p orbitals, the latter arising from the open-shell nature of the nitrogen atom. The overestimate (10 %) of the correlation energy is remedied by the pair-pair correlation of 0. 01137 a. u. (6%) and the many-electron (three and four) effect of 0.00642 a.u. (3.4 %). A comparison with earlier configuration-interaction results is also made.
Estimation of correlation energy for excited-states of atoms
The correlation energies of various atoms in their excited-states are estimated by modelling the Coulomb hole following the previous work by Chakravorty and Clementi. The parameter in the model is fixed by making the corresponding Coulomb hole to satisfy the exact constraint of charge neutrality.
Pair-correlated atoms with a twist
Physical Review A, 2007
We present an analysis of the quantum state resulting from the dissociation of diatomic molecules prepared in a condensate vortex state. The many-body state preserves the rotational symmetry of the system in quantum correlated states by having two equally populated components with angular momentum adding to unity. A simple two-mode analysis and a full quantum field analysis is presented for the case of non-interacting atoms and weak depletion of the molecular condensate.
The Journal of Chemical Physics, 2010
The parent state-specific multireference coupled-cluster (SS-MRCC) theory proposed by Mukherjee et al. [J. Chem. Phys. 110, 6171 (1999)], though rigorously size-extensive and also size-consistent with localized orbitals, has some deficiencies in the minimal truncation scheme, viz. at the singles and doubles (SD) level (SS-MRCCSD). SS-MRCCSD does not involve the direct coupling of all the model functions with a given virtual function belonging to the uncontracted multiconfiguration CISD space. It also does not involve, even in the linear power of a cluster operator T μ , the direct coupling of the virtual functions χ l μ , which are up to doubly excited with respect to a model function φ μ to the other virtual functions of the MRCISD space which can be generated by triple and quadruple excitations from φ μ . We argue that inclusion of a selection of triples and quadruples involving at most two inactive orbital excitations from every φ μ would ameliorate the shortcoming of the incomplete coupling of the triply and quadruply excited virtual functions which can couple with the singly and doubly excited ones. This extended ansatz for our SS-MRCC theory, to be called SS-MRCCSDtq by us, would still miss the direct coupling of the manifold of the model functions {φ λ , λ = μ} to singly and doubly excited virtual functions. However, this effect is expected to be less significant than the lack of the more complete virtual space couplings, these functions being many more numerous, suggesting the new methods to be significantly improved schemes. Excellent results on the potential energy surfaces of small molecules involving single, double, and triple bond dissociation bear out our expectations fully.
We present nonrelativistic frozen-core and fully-correlated configuration interaction calculations for the ground and the lowest excited terms of N + (3 P and 1 D), and N(4 S o and 2 D o) belonging to the configuration 2s 2 2p n with n=2 and n=3 for N + and N, respectively. Both the a priori selected configuration interaction with truncation energy error and configuration interaction by parts techniques are employed to manage the wave function expansion and to handle the configuration interaction eigenvalue problem, respectively. Systematic comparisons between frozen-core and fully-correlated CI energies and the corresponding excitation energies and the related ionization potential convergence with respect to the CI excitation level are reported. A comparison of our results for the total nonrelativistic energies, excitation energies, and ionization potential displays good improvement over previous theoretical results and very good agreement with the experiment.
Short-range correlations in low-lying nuclear excited states
Physical Review C, 2000
The electromagnetic transitions to various low-lying excited states of 16 O, 48 Ca and 208 Pb are calculated within a model which considers the short-range correlations. In general the effects of the correlations are small and do not explain the required quenching to describe the data.
2007
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Correlation energies of light atoms related to pairing between antiparallel spin electrons
Journal of Physics B: Atomic, Molecular and Optical Physics, 2003
Early theoretical work emphasized the gross trend of the total correlation energy of neutral atoms with atomic number Z . This was later improved quantitatively, by focusing on the number of pairings between antiparallel-spin electrons in the same main shell (i.e., K, L, M . . . shells). Here, this viewpoint is pressed, and correlation energies associated with s-s, s-p and p-p pairings are extracted. The s-s energy turns out to be rather insensitive to a change from K to L shells, but a small increase is found to occur in the M shell. Also, the s-p and p-p pairing energies show a small increase from the L to the M shells. The s-s and s-p energies are ≈1 eV, the s-s contribution being the larger. The p-p energy is ≈1/3 eV. The effect of removing or adding one electron to the neutral atom has also been analysed. Wavefunction overlap and wavefunction localization appear to control the values of the pairing energies.
Geometrical Correlation Effects for Excited States of a Helium Atom
Doklady Physical Chemistry, 2004
Multielectron correlation effects have attracted the attention of researchers since the development of quantum mechanics. Many important effects cannot be adequately described without the consideration of electron interaction. Of particular importance are the correlation effects related to the positions and geometry of nodal manifolds of the multielectron wavefunction. In particular, the Fermi correlation of electrons with parallel spins, which is due to the Pauli principle, necessarily results in the occurrence of some nodal surfaces in the configuration space . Therefore, the study of nodal manifolds is of interest both for quantum Monte Carlo methods and for an understanding of the form of the wavefunctions .