The state-resolved differential cross sections for both the 1s 2 1 S 0 → 1s2s 1 S 0 monopolar transition and the 1s 2 1 S 0 → 1s2p 1 P 1 dipolar transition of atomic helium had been measured over a large momentum transfer region by high-resolution inelastic x-ray scattering (IXS). The almost-perfect match of the present measurement with the theoretical calculations gives a stringent test of the theoretical method and the calculated wave functions. Our results demonstrate that high-resolution IXS is a powerful tool for studying the excitations in atoms and molecules.
The x-ray energies and transition rates associated with single and double electron radiative transitions from the double K hole state 2s2p to the 1s2s and 1s 2 configurations of 11 He-like ions (10 ≤ Z ≤ 47) are evaluated using the fully relativistic multi-configuration Dirac-Fock method. An appropriate electron correlation model is constructed with the aid of the active space method, which allows the electron correlation effects to be studied efficiently. The contributions of electron correlation and the Breit interaction to the transition properties are analyzed in detail. It is found that the two-electron one-photon (TEOP) transition is correlation sensitive. The Breit interaction and electron correlation both contribute significantly to the radiative transition properties of the double K hole state of He-like ions. Good agreement between the present calculation and previous work is achieved. The calculated data will be helpful to future investigations on double K hole decay processes of He-like ions.
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