Correlation dynamics in He. Upper panel: time-dependent correlation; middle panel: interelectronic distance, for a helium atom initially in the HF ground state; and lower panel: HF orbital population dynamics. The full line in the upper panel is an exact result, the dashed line corresponds to approximations to the HF ground state. Dotted line: correlation of the FCI ground state.
(Left) Minimal pump scheme for He to create an (approximate) HF state, from the correlated CISD ground state. He requires a very sophisticated scheme, with five excited states to be populated, which are not directly accessible via dipole transitions. Dashed lines: intermediate states. Dotted line: ionization potential. (Right) The same for Mg, which requires much less complicated pulses.
Time dependent correlation for neon and argon (left), and beryllium and magnesium (right), initially in their respective HF ground states. The full lines are exact results. For Ne, Be, and Ar the dashed lines correspond to approximations to the HF ground state. For Mg the dashed line corresponds to the correlation after the pump pulse. Horizontal dotted lines indicate the correlation in the CISD ground state.
Sliding gaussian average plot of the pulse spectrum to pump Mg from the correlated to the uncorrelated ground state, and the correlation during the pump process.
Time scale, on which the correlation reappears, as a function of the energy difference between the correlated ground state and the excited state with the highest contribution to the HF ground state. There is no simple connection between them. Calculations were done with the 6-31G* basis set, if not stated otherwise.
Time-dependence of the correlation for H2O, starting from the HF ground state. Line types have the same meaning as in previous figures.
List of correlation energies Ecorr and ionization potentials IP, for atoms considered in this paper. The correlation energies are given on the quantum chemical level used here, see text for details. The IPs are from Ref. 30 .
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