Two-electron ejection from helium by Compton scattering

Charge-State Distributions after Beta Decay of 6He to Form 6Li+

The shake-off processes and charge-state fractions of 6Li+, 6Li++, and 6Li3+ were studied following the beta decay of 6He in the 1s21S0, 1s2s1S0, and 1s2s3S1 initial states. The sudden approximation was used, together with fully correlated Hylleraas wave functions and pseudostates. A projection operator method was introduced to separate the charge-state fractions in the positive energy region of overlapping continua. The results show that 6Li++ (single-ionisation) remains dominant, even in the energy range E>0, where the formation of 6Li3+ (double-ionisation) is energetically allowed. The results reduce disagreements with the experiment for the fraction of 6Li3+ by nearly an order of magnitude, but substantial disagreements remain that are inconsistent with the sudden approximation widely used in other similar work.

Electron correlation dynamics in atoms and molecules

In this paper, we present quantum dynamical calculations on electron correlation dynamics in atoms and molecules using explicitly time-dependent ab initio configuration interaction theory. The goals are (i) to show that in which cases it is possible to switch off the electronic correlation by ultrashort laser pulses, and (ii) to understand the temporal evolution and the time scale on which it reappears. We characterize the appearance of correlation through electron-electron scattering when starting from an uncorrelated state, and we identify pathways for the preparation of a Hartree-Fock state from the correlated, true ground state. Exemplary results for noble gases, alkaline earth elements, and selected molecules are provided. For Mg we show that the uncorrelated state can be prepared using a shaped ultrashort laser pulse.