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physics.atom-ph2015★ 72 cited
First-principles nonequilibrium Green's function approach to transient photoabsorption: Application to atoms
E. Perfetto, A. -M. Uimonen, R. van Leeuwen +1
We put forward a first-principle NonEquilibrium Green's Function (NEGF) approach to calculate the transient photoabsorption spectrum of optically thin samples. The method can deal…
physics.atom-ph2013★ 25 cited
Long-range interactions and the sign of natural amplitudes in two-electron systems
Klaas J. H. Giesbertz, Robert van Leeuwen
In singlet two-electron systems the natural occupation numbers of the one-particle reduced density matrix are given as squares of the natural amplitudes which are defined as the ex…
physics.atom-ph2013★ 38 cited
Natural occupation numbers: When do they vanish?
K. J. H. Giesbertz, R. van Leeuwen
The non-vanishing of the natural orbital occupation numbers of the one-particle density matrix of many-body systems has important consequences for the existence of a density matrix…