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Electronic structure

See which empty states a core electron can reach.

A K-edge excitation

Core electron and two possible excitation channelsTwo electrons occupy the deep 1s level. An incoming X-ray can promote one into an empty state. The continuum lies above the ionization threshold. The p-like dipole channel is allowed; the d-like channel needs mixing or a non-dipole transition. Level spacing is schematic.EnergyContinuumIonization thresholdp-like bandemptyd-like bandempty1s core levelX-ray photon hν
Level spacing and orbital shapes are schematic, not to scale. The core hole and electron interactions reshape real spectra. The d-like channel needs mixing or a non-dipole transition; no transition intensity is calculated.
The dipole channel can reach p character.
Orbital mixing and the quantum model

The paper’s active-space example

Choose which orbital groups to keep from Li4​Mn2​O. Each spatial orbital uses two system qubits.

18 spatial orbitals; 36 system qubits.

The paper uses all 18 orbitals and 22 electrons. This counts orbitals only; it does not build electronic integrals. The browser solver accepts at most six qubits.

0.35

O 2p share: 35%. This only redraws the sketch.

In a solid, p–d mixing can give a d-like state some dipole intensity. Quadrupole transitions can also contribute.

D=X0D = X_0 in the quantum page is a simple substitute for the X-ray kick. It acts on a small spin system.

Try time-domain spectroscopy