Calculation of Dyson orbitals using a symmetry-adapted-cluster configuration-interaction method for electron momentum spectroscopy: ${\mathrm{N}}_2$ and ${\mathrm{H}}_2$O

The symmetry-adapted-cluster (SAC) configuration-interaction (CI) theory was introduced to interpret the non-coplanar symmetric ($e$,$2e$) results. Dyson orbitals derived from the bench-marked SAC CI general-R method were utilized for computing the electron momentum distributions. The corresponding excitation energies and spectroscopic factors can be used to reproduce the ionization spectra. The implementation was demonstrated by examples of ${\mathrm{N}}_2$ and ${\mathrm{H}}_2$O. The electron momentum distributions calculated using SAC CI method were compared with recent experimental results, as well as the Hartree-Fock and density-functional-theory calculations. The SAC CI method gave the best performance on the description of the experimental momentum distributions. It was found that the electron momentum distributions of Dyson orbitals related to the satellite lines can be notably different from those of their parent orbitals due to the electron correlation in the initial target states. Present work demonstrated that the SAC CI theory is a very useful and accurate tool for interpreting high-resolution electron momentum spectroscopy results.

Figure 1

Comparison of experimental and theoretical binding energy spectra for ${\mathrm{N}}_2$ and ${\mathrm{H}}_2$O. (a) ($e$,$2e$) experimental binding energy spectrum of ${\mathrm{N}}_2$ taken from Ref. [40]. (b) ($e$,$2e$) experimental binding energy spectrum of ${\mathrm{H}}_2$O taken from Ref. [16]. (c) Simulated binding energy spectrum for ${\mathrm{N}}_2$ using the SAC CI general-R method. (d) Simulated binding energy spectrum for ${\mathrm{H}}_2$O using the SAC CI general-R method. See the text for details.

Figure 2

Comparisons of SAC CI, HF, and DFT predictions of three outer valence orbitals momentum distributions with experimental ones for ${\mathrm{N}}_2$ and ${\mathrm{H}}_2$O. Experimental data are taken from Refs. [40] and [16].

Figure 3

Momentum distributions of three well resolved Dyson orbitals in the inner valence region of ${\mathrm{N}}_2$ and ${\mathrm{H}}_2$O. Experimental data were taken from Refs. [40] and [16]

Figure 4

One-up and one-down mechanism for Dyson orbitals at 24.9 eV of ${\mathrm{N}}_{2.}$

Figure 5

Momentum distributions of summed satellite lines in the inner valence region of ${\mathrm{N}}_2$. Experimental data were taken from Ref. [40].

Figure 6

Momentum distributions of summed satellite lines in the inner valence region of ${\mathrm{H}}_2$O. Experimental data were taken from Ref. [16].